US3905535A

US3905535A - Fastener driving tool

Info

Publication number: US3905535A
Application number: US396878A
Authority: US
Inventors: Raymond F Novak; Howard B Ramspeck; Bernard W Geist; Frank R Potucek
Original assignee: Duo Fast Corp
Current assignee: Duo Fast Corp
Priority date: 1973-09-13
Filing date: 1973-09-13
Publication date: 1975-09-16
Anticipated expiration: 1992-09-16
Also published as: CA1020701A

Abstract

A pneumatic stapler includes a housing in which is mounted for limited sliding movement a drive cylinder containing a piston coupled to a driver blade. A nosepiece structure on the housing contains a drive track slidably receiving the blade and supporting an annular or cylindrical member aligned with the lower end of the cylinder and carrying a valve seat. A main valve engages the top of the cylinder and forces the cylinder downwardly to seat on the valve seat in the normal condition of the tool. When the main valve moves upwardly, it closes an upper cylinder exhaust valve, and the cylinder follows through its limited travel to move out of engagement with the valve seat and exhausts the lower end of the drive cylinder. Further upward movement of the main valve admits compressed air to move the drive piston downwardly through a power stroke. A cycle valve receiving air from the cylinder at the end of the power stroke controls the main valve to move downwardly and not only seat the cylinder lower end on the valve seat, but also exhaust the upper end of the cylinder interior. A return valve senses this condition and supplies compressed air through the nosepiece within the annular member to return the drive piston and to supply compressed air to the cycle valve to prevent a premature opening of the main valve. The completion of the return stroke of the piston releases the return valve. A magazine includes a biased staple strip pusher with a pair of rigid legs pivoting in the planes of the staple legs to facilitate loading the staple strips.

Description

United States Patent [191 Novak et a1.

[ FASTENER DRIVING TOOL [75] lnventors: Raymond F. Novak, Schiller Park;

Howard B. Ramspecl-t, Chicago; Bernard W. Geist, Melrose Park; Frank R. Potucek, Des Plaines, all

[731 Assignee: Duo-Fast Corporation, Franklin Park, 111.

[22] Filed: Sept. 13, 1973 21 1 Appl. No.1 396,878

Primary Examiner-Granville Y. Custer, Jr. Allurm'y, Agent, or Firm-Mason, Kolehmainen, Rathburn & Wyss [57] ABSTRACT A pneumatic stapler includes a housing in which is [451 Sept. 16, 1975 mounted for limited sliding movement a drive cylinder containing a piston coupled to a driver blade. A nosepiece structure on the housing contains a drive track slidably receiving the blade and supporting an annular or cylindrical member aligned with the lower end of the cylinder and carrying a valve seat. A main valve engages the top of the cylinder and forces the cylinder downwardly to seat on the valve seat in the normal condition of the tool. When the main valve moves upwardly, it closes an upper cylinder exhaust valve, and the cylinder follows through its limited travel to move out of engagement with the valve seat and exhausts the lower end of the drive cylinder. Further upward movement of the main valve admits compressed air to move the drive piston downwardly through a power stroke. A cycle valve receiving air from the cylinder at the end of the power stroke controls the main valve to move downwardly and not only seat the cylinder lower end on the valve seat, but also exhaust the upper end of the cylinder interior. A return valve senses this condition and supplies compressed air through the nosepiece within the annular member to return the drive piston and to supply compressed air to the cycle valve to prevent a premature opening of the main valve. The completion of the return stroke of the piston releases the return valve. A magazine includes a biased staple strip pusher with a pair of rigid legs pivoting in the planes of the staple legs to facilitate loading the staple strips.

16 Claims, 13 Drawing Figures PATENHQ SEP 1 6 i9?5 seam 1 0 7 mm QR $6 NQN J TQM mm mm Wmw mm v9 1% mm mm m\ wGm Y mm m m mm m mm mm mm Qm N Qm WNN PATENTEQ SEP 1 61975 SHEET 5 BF RWDTIXW WE? mm FASTENER DRIVING TOOL This invention relates to a fastener driving tool and, more particularly, to a fastener driving tool including new and improved fastener driving and feeding means.

There is a growing tendency to extend the applications in which power driven fasteners, such as staples and nails, are used. This extension frequently involves driving fasteners of larger sizes with the result that the power required of the driving tools must be increased. However, this increase in driving power must be obtained within the limits imposed by the pressures and quantities of compressed air available in most manufacturing and fabricating locations and by weight that can be conveniently manipulated by an operator. In general, this requires the design of more efficient tools. tools that are more efficient in the utilization of power available from existing compressed air sources, and tools that are more efficient in the quantity of air consumed. Included in any consideration of the efficiency of use by the operator are the ease of replenishing the supply of fasteners and, in the case of multifire tools, the assurance by the operator that a fastener will be driven in each successive power stroke of the tool.

Accordingly, one object of the present invention is to provide a new and improved fastener driving too].

A further object is to provide a fastener driving tool including a new and improved drive system.

A further object is to provide a fastener driving tool including a new and improved piston drive and return system.

A further object is to provide a fastener driving tool including a shiftable cylinder for venting the lower end of the cylinder prior to the power stroke of a drive piston and new and improved means for effecting the return of the drive piston.

A further object is to provide a fastener driving tool using a cycle valve for effecting an automatic sequence of power and return strokes and a controlled source of pressurized fluid for insuring that each return stroke is completed before the initiation of the following power stroke.

A further object is to provide a fastener driving tool including a new and improved magazine for feeding fasteners to a drive track.

In accordance with these and many other objects, an embodiment of the present invention includes a pneumatic fastener or staple driving or applying tool having a housing containing a drive cylinder mounted for limited vertical reciprocation. A main valve movable into and out of engagement with the upper end of the cylinder normally holds the lower end of the cylinder seated on a cylindrical member upstanding from the housing at its lower end to close off communication between the cylinder and the atmosphere. When the main valve is elevated, the cylinder moves with the main valve through its limited travel so that the upper cylinder exhaust valve is first closed and the lower end of the cylinder moves out of engagement with the valve seat defined by the cylindrical member, thereby connecting the lower interior of the cylinder to the atmosphere. 'Ihe main valve then moves out of engagement with the top of the cylinder to admit compressed air for driving a piston slidably mounted in the cylinder and a connected driver blade through a power stroke.

A cycle valve assembly senses the arrival of the piston at the end of its power stroke and controls a cycle (all valve in the control valve assembly to effect reclosure of the main valve. Closure of the main valve moves the cylinder downwardly so that its lower end seats on the cylindrical valve seat and closes off communication between the atmosphere and the lower interior of the cylinder. This movement of the main valve also vents the upper interior of the cylinder which is detected by a return valve assembly. The return valve assembly supplies compressed air to the lower interior of the cylinder beneath the piston through a system of passageways extending to a point inside of the cylindrical lower valve. This compressed air elevates the piston to its normal position and also provides a supplemental signal or bias for retaining the cycle valve in its prior position. When the drive piston returns to its normal position, this condition is sensed by the return valve, and the supply of pressurized fluid below the piston is terminated to terminate one cycle of operation of the tool. When the pressurized fluid beneath the drive piston and the cycle valve leaks to the atmosphere, the cycle valve returns to its alternate state, and an additional cycle of operation of the tool is initiated.

A magazine assembly is provided for feeding successive staples into the drive track in the nosepiece structure beneath the driver blade. This magazine assembly includes a resiliently biased pusher having a pair of rigid arms pivotally mounted in the planes of the staple legs. When staple strips are inserted into the magazine behind the pusher, rearward movement of the pusher pivots the legs upwardly to a position clearing their crowns from which they are returned to a position engaging the legs of the last staple in the strip by a resilient bias.

Many other objects and advantages of the present invention will become apparent from considering the following detailed description in conjunction with the drawings in which:

FIG. 1 is a side elevational view of a pneumatically operated fastener driving tool embodying the present invention;

FIG. 2 is an end elevational view of the tool shown in FIG. 1;

FIG. 3 is an enlarged fragmentary sectional view taken along line 3-3 in FIG. 2;

FIG. 4 is a sectional view taken along line 44 in FIG. 3;

FIG. 5 is a fragmentary sectional view similar to FIG. 3 illustrating the tool after the opening of a main valve assembly but prior to the initiation of a power stroke of the tool;

FIG. 6 is an exploded perspective view of a structure for closing the lower end ofa drive cylinder in the tool;

FIG. 7 is a fragmentary sectional view illustrating the tool at the end of a power stroke and portions of the magazine assembly;

FIG. 8 is a sectional view taken along line 8-8 in FIG. 7;

FIG. 9 is a sectional view taken along line 99 in FIG. 7'.

FIG. I0 is an enlarged fragmentary sectional view taken in the direction of line l0 10 in FIG. 8;

FIG. II is a sectional view of a control valve assembly for the tool shown in a normal state;

FIG. I2 is a sectional view similar to FIG. ll illustrating the control valve assembly at the conclusion of a power stroke of the tool; and

FIG. 13 is a schematic diagram illustrating the control functions performed by the control valve assembly shown in FIGS. 11 and 12.

Referring now more specifically to FIGS. 1-3 of the drawings, therein is illustrated a fastener driving tool which is indicated generally as 20 and which embodies the present invention. The tool 20 includes a housing shown generally as 22 including a vertically extending forward head portion 22A and a rearwardly extending hollow handle portion 22B. The cavity defined by the head portion 22A and the hollow handle portion 228 provide a reservoir 24 of pressurized fluid or compressed air for operating the tool 20. Slidably mounted within the head portion 22A for limited movement is a drive cylinder 26 normally engaged at its upper end by a main valve assembly indicated generally as 28 for selectively connecting the upper interior of the cylinder 26 to the atmosphere or to the pressurized fluid in the reservoir 24. A lower cylinder exhaust valve assembly indicated generally as 30 selectively connects the lower interior of the cylinder 26 to the atmosphere prior to and during the power stroke to improve the efi'iciency of drive of the tool 20. A piston 32 slidably mounted within the cylinder 26 is secured to the upper end of a fastener driving blade or element 34, the lower end of which is slidably received within a drive track 36 formed in a nosepiece assembly indicated generally as 38. On each power stroke of the piston 32, the driver blade 34 engages and drives a staple 40 supplied to the drive track 36 by a magazine assembly indicated generally as 42. The power and return strokes of the piston 32 are controlled by a control valve assembly indicated generally as 44.

Nosepiece Assembly 38 and Magazine 42 The magazine assembly 42 is secured at its forward end to and supported by the nosepiece assembly 38 and feeds successive staples 40 from a strip thereof into the drive track 36 defined by the nosepiece assembly 38. This assembly also includes a quick release assembly indicated generally as 46 (FIG. 1) for obtaining access to the drive track 36.

The nosepiece assembly 38 is carried out on a laminated plate assembly indicated generally as 48 which closes the lower open end of the head portion 22A of the housing and which is secured thereto by a plurality of nuts 50 threaded on inserts 52, the upper ends of which are threaded within tapped openings 54 (FIG. 6) at the lower end of the head portion 22A. A nose insert 56 (FIGS. 1-3 and is disposed within aligned openings 58 (FIG. 6) in the plate assembly 48 and welded thereto. The rear wall of the nose insert 56 provides the front wall of the upper portion of the drive track 36.

The nosepiece assembly 38 further includes a multiplate or welded, laminated, and generally T-shaped structure 60 including depending side walls 60A and spaced transverse cross members 608 which are secured to and are on opposite sides of the nose insert 56 by suitable fasteners 62, such as a bolt carrying a nut. A shear block 64 (FIG. 3) is secured between depending leg portions 60A of the structure 60 and defines a substantial portion of the back wall of the drive track 36 as well as defining a generally U-shaped opening through which the staples 40 pass into the drive track 36.

A substantial portion of the front wall of the drive track 36 is defined by the assembly 46. This assembly includes a removable front plate 66 fitting within the recess defined between the spaced depending legs A of the structure 60 with longitudinally extending flanged edges overlying the front walls of the legs 60A. The rear wall surface of the plate 66 is recessed in accordance with the desired configuration of the drive track 36.

To provide means for detachably mounting the front plate 66 on the nosepiece assembly 38, there is provided a generally U-shaped bail 68 (FIGS. 1 and 2), a bight portion 68A of which passes around the front wall of the nosepiece structure 38 to be received within an indentation 66A in the front wall of the plate 66. The free ends of the rearwardly extending legs 68B of the bail 68 are slidably received within two angled and elongated slots 70 formed in a lever 72. The lever 72 is pivotally mounted on a rearwardly extending portion of the shear block 64 by a pivot pin 74 which passes through an elongated opening 76 in the lower rearwardly disposed portion of the shear block 64 adjacent a resilient body 77 (FIGS. 3 and 5 The bail 68 and the lever 72 provide an over-center linkage for clamping the front plate 66 in its desired position. When the plate 66 is to be removed, the lever 72 is pivoted about the pivot pin 74 in a clockwise direction (FIG. I) to displace the bail 68 sufficiently to permit the plate 66 to be removed. When the plate 66 has been reassembled following, for example, the removal of a jammed staple from the drive track 36, the bight portion 68A of the bail 68 is placed in the recess 66A, and the lever 72 is pivoted in a counterclockwise direction to the position shown in FIG. 1.

The magazine assembly 42 comprises a generally U- shaped magazine housing indicated generally as 80 which is open at its top and closed at its bottom by a bottom wall 80A (FIG. 4) to define a narrow recess approximately the size of a strip of staples 40. At its forward end, the lower wall 80A of the housing 80 is secured, as by a plurality of machine screws 82, to a rearwardly extending portion of the shear block 64 (FIGS. 3 and 4). At its upper end. the magazine is secured to and within the outer lamina of the cross pieces 60B of the nosepiece structure 60 by a plurality of machine screws 84 (FIG. 4).

To provide means for slidably supporting a strip of staples 40 within the cavity in the housing 80, there is provided a staple rail 86 which is generally U-shaped in configuration and mounted within the housing 80 so that a wall 86A defining the bight portion of the rail 86 faces upwardly to provide a support for the crown portions 40A of the staples 40 (FIGS. 3 and 4). At its forward end indicated as 86B (FIG. 3), the rail 86 is closed to encircle a rearwardly extending portion 64A of the shear block 64. A compression spring 88 biases the lower wall of the closed portion 868 of the rail 86 against the adjacent structure 64A to retain the rail 86 in position. This interfitting resiliently biased connection of the front end of the rail 86 to the shear block 64 aids in controlling manufacturing tolerances and prevents wear which might result in eccentric or misaligned positioning of the rail 86 relative to the shear block 64 and the structures defining the drive track 36. The rear end of the rail 86 is secured to the housing 80 in any suitable manner such as by a member 90 which is secured to the housing 88 by machine screws 92 (FIG. I and which interfits with the rear end of the rail 86.

Strips of staples 40 can be inserted into the magazine 42 to be supported on the rail 86 through the open top of the housing 80. A plate-like extension 90A on the member 90 (FIGS. 1 and 8) extends forwardly between the housing side walls and includes two downwardly inclined legs 90B (FIGS. 1, 8, and 10) straddling the U- shaped rail 86 and disposed immediately adjacent depending opposite side walls 86C of the rail. The pointed ends at the lower end of the legs 40B of the staples 40 in a strip can be placed in engagement with the downwardly inclined legs 908 to guide a strip into the magazine 42 to a position in which the legs 40B of the staples in the strip are disposed immediately adjacent and extending generally parallel to the rail side walls 86C with the crown portions 40A of the staples resting on the upper wall 86A of the rail 86.

To provide means for resiliently biasing or feeding a strip of staples 40 toward the drive track 36 in the nosepiece assembly 38, there is provided a pusher assembly indicated generally as 96. The pusher assembly 96 is movably mounted on the housing 80 within a pair of aligned and opposed grooves 99 (FIG. 9) formed in enlarged upper end portions 808 of the side walls of the housing 80. The grooves or slots 99 slidably receive the side edges ofa supporting plate 100 to mount this plate in a position spaced above the wall 86A of the staple supporting rail 86. A generally U-shaped bracket 102 having a pair of spaced upstanding side walls 102A is mounted on the upper surface of the plate 100 with the lower end portion of a handle 104 for the pusher assembly 96 disposed between the walls 102A. The handle 104 and the bracket 102 are secured to the plate 100 by a suitable fastener 106. To provide means for engaging the staples 40, the pusher assembly 96 includes a generally U-shaped pusher member 108 pivoted at one end to the side walls 102A of the bracket 102 by a pivot pin 110. The opposite end of the member 108 is provided with two downwardly inclined legs 108A having staple leg engaging portions 108B generally disposed parallel to and in immediate proximity to the side walls 86C of the staple rail 86. To provide means for resiliently biasing the staple legs 108A to the position shown in FIG. 10, a torsion spring 112 is pro vided having a cylindrical center portion which is mounted on the pivot pin 110 between the side walls 102A with the outer free ends bearing against the plate 100. An end portion 112A of the torsion spring 112 bears against a bight portion 108C to pivot the pusher element 108 in a counterclockwise direction about the pivot pin 1 10 to the normal position shown in FIG. 10. This position is determined by engagement of the pusher 108 with the top surface of the plate 100.

To provide means for biasing the pusher assembly 96 toward the nosepiecc assembly 38, there is provided a constant force spring 114, one end portion 114A of which is hooked or clamped between the bight of the bracket 102 and the lower wall of the handle 104 to secure the constant force spring 114 to the pusher assembly 96. The other end of the constant force spring 114 (FIG. 3) is coiled about a spool 116 (FIGv 3) rotatably mounted within an enclosure indicated generally 118 by a shaft or a pin 120. The constant force spring 114 tends to return to the coiled position whenever it is extended by moving the pusher assembly 96 to the right. This tendency to return to a coiled position pro vides a resilient bias forcing the pusher assembly 96 to the left as shown in the drawings, and thus forcing the staple leg engaging portions 1088 on the pusher legs 108A into engagement with the leg 40B of the last staple 40 in the strip. The withdrawn portion of the constant force spring 114 extending between the spool 116 and the pusher assembly 96 is narrower than the upper opening in the magazine housing and is spaced above to overlie the crowns 40A of the staples 40 in a strip disposed within the magazine assembly 42. The spring 114 passes between the pusher legs 108A.

Assuming that a partially consumed strip of staples 40 is disposed within the magazine assembly 42 and an additional strip of staples 40 is placed on the rail 86 disposed to the right of the pusher assembly 96 (FIG. 10), the handle 104 is grasped by the operator, and the pusher assembly 46 is moved to the right. As the pusher assembly 96 moves to the right, the inclined right-hand edges 108B of the two pusher legs 108A engage the first staple 40 in the strip to be added, and the pusher element 108 may either be pivoted in a clockwise direction about the pivot pin 110 to the position shown in dot and dash outline in FIG. 10 or engage the first staple 40 in the strip and move the strip rearwardly until the last staple engages legs B whereupon the pusher element 108 is pivoted in the manner described. When the lower ends of the pusher legs 108A clear the last staple 40 in the strip to be added, the torsion spring 112 pivots the pusher element 108 in a counterclockwise direction about the pivot pin 1 10 so that the staple leg engaging portions 10813 of the pusher legs 108A and slide down legs 90B and engage the legs 40B of the last staple 40 in the strip to be added. If the handle 104 is released, the extended constant force spring 114 biases the pusher assembly 96 to the left (FIG. 10) to move the first staple 40 in the strip to be added into en gagement with the last staple 40 in the strip previously disposed in the magazine assembly 42, and the pusher assembly 96 thereafter advances successive staples 40 into the drive track 36 as they are driven.

To provide means for limiting movement of the pusher assembly 96 to the left so that the pusher legs 108A cannot enter the drive track 36, a drive or roll pin 122 extends through the side walls 102A and the lower portion of the handle 104 (FIG. 8) so that the ends of the pin 122 extend substantially beyond the side walls 102A. When the pusher assembly 96 reaches the position at which the staple engaging portions 108B on the pusher legs 108A are disposed immediately adjacent the entrance to the drive track 36, the projecting ends of the pin 122 engage the end surfaces of a pair of plates 124 which are mounted within relieved portions along the inner surface of the side walls of the housing 80 and secured therein by the machine screws 84. The engagement of the ends of the pin 122 with the plates 124 provides a positive stop for limiting movement of the pusher assembly 96 to the left. as shown in the drawings.

If the pusher 96 is pulled to an extreme righthand position (FIGS. 8 and 10). the inclined right-hand edges of the pusher legs 108A come into contact with the downwardly inclined legs 90B. This cams the pusher element 108 in a clockwise direction against the bias of the torsion spring 1 12 to permit the pusher 108 to be manually grasped. The pusher assembly 96 can then be permitted to move to the left with the pusher element 108 elevated. In this way, by tipping the maga- Zinc 46, strips of staples 40 can be removed from the rail 86 within the magazine housing 80.

Drive System The drive system for controlling the reciprocation of the piston 32 within the slidably mounted cylinder 26 includes the main valve assembly 28 which selectively connects the upper interior of the cylinder 26 to the atmosphere or to the compressed air in the reservoir 24 as well as controlling the shifting movement of the cylinder 26 to open and close the exhaust valve assembly 30. The exhaust valve assembly 30 opens the lower in' terior of the cylinder 26 prior to and during a power stroke of the piston 32 and seals the lower interior of the cylinder 26 during a return stroke to permit the piston 32 to be pneumatically returned to its normal position.

To provide for slidably mounting the cylinder 26 within the head portion 22A, this head portion 22A includes an annular or cylindrical portion 22C (FIGS. 3-5) formed integral with the housing 22 within which is mounted a sleeve I30 sealed by the illustrated rings. The cylinder 26 is slidably mounted within the cylindrical sleeve 130, and a similar cylindrical portion 22D formed in the housing 22. To provide means for limiting the movement of the cylinder 26, the cylinder carries an annular ring 132 sealed by the illustrated 0- rings and bearing against a shoulder on the cylinder 26. A space 134 between the ring 132 and the sleeve I30 is continuously vented to the atmosphere. Upward movement of the cylinder 26 relative to the housing 22 is limited by engagement of the ring 132 with the lower surface of the sleeve 130 (FIG. The exposed lower surface of the ring 132 provides a continuous upwardly directed pneumatic bias tending to shift the cylinder 26 to the elevated position shown in FIG. 5. The selective movement of the cylinder between the upper position shown in FIG. 5 and the lower position shown in FIG. 3 is controlled by the main valve assembly 28.

More specifically. the main valve assembly 28 includes an annular main valve member 136, an upper annular piston portion 136A of which is slidably mounted within an annular chamber 138 formed in a closure cap 140 and surrounding a central hollow post 140A on the closure cap 140. A plurality of depending lugs 1408 on the cap bear against the upper end of the sleeve 130 to mechanically hold the sleeve I30 in position. A circular exhaust valve member 142 secured to the cap by a fastener 144 is disposed within a central opening in the annular valve 136. A plurality of compression springs 148 interposed between the cap 140 and the upper surface of the main valve element 136 together with the pressurized fluid normally supplied to the chamber I38 above the piston portion 136A normally hold the main valve element 136 in the position shown in FIG. 3 in which a resilient valve element I50 engages the upper end of the cylinder 26 to hold this cylinder in the position shown in FIG. 3. The resilient valve element 150 closes off communication between the upper interior of the cylinder 26 and the compressed air contained in the surrounding reservoir 24. In this position, the interior surfaces of the annular valve I36 are spaced from the exhaust valve member I42 so that the upper interior of the cylinder 26 is connected to the atmosphere through a plurality of passageways 152 in the closure cap I40.

To provide means for controlling the shifting movement of the annular main valve element 136, there is provided a dump valve assembly indicated generally as 154. The dump valve assembly 154 includes a plural diameter valve element 156 carrying the illustrated sealing O-rings and slidably disposed within a cylinder 158 formed in the cap 140. A compression spring 160 continuously biases the valve element to the left-hand position shown in FIG. 3. The bias provided by the spring 160 is supplemented by pressurized fluid supplied to the right-hand end of the cylinder 158 over a passageway 162 in the closure cap which is placed in communication with the control valve assembly 44 by a conduit I64 (FIGS. 3S). In the normal condition of the tool, pressurized fluid is supplied to the conduit or duct 164 by the control valve assembly 44. This pressurized fluid in the right-hand end of the cylinder 158 coupled with the resilient bias of the spring forces the valve piston 156 to the position shown in FIG. 3. In this position, the pressurized fluid from the reservoir 24 passes from a passageway I66 in the closure cap into the chamber 138 through a passageway 168.

When the main valve assembly 28 is to be operated, the conduit 164 is connected to the atmosphere by the control valve assembly 44, and the pressurized fluid supplied through the passageway I66 acts on the enlarged right-hand portion of the valve piston I56 to shift this valve piston against the bias of the compression spring 160 to the position shown in FIG. 5. In this position, the passageway 168 is cut off from communication with the passage I66, and pressurized fluid from the reservoir 24 can no longer be supplied to the chamber 138. Further, the passageway I68 and an additional passageway 170 are connected to the atmosphere through the passageways 152 by means of a port 172 that is now opened by the displacement of the valve piston 156.

When the dump valve assembly moves to the position shown in FIG. 5, pressurized fluid in the chamber 138 above the piston portion 136A on the annular main valve I36 is exhausted to the atmosphere through the passageways 168 and 170, the port 172, and the passageways I52. The pressurized fluid in the reservoir acts on the lower effective surfaces of the main valve 136 to move this valve upwardly toward the position shown in FIG. 5 against the resilient bias of the compression Springs 148. During the first portion of this movement. the cylinder 26, because of the continuous upwardly directed bias applied to the ring 132, moves with the main valve 136, and the resilient element 150 remains seated on the upper end of the cylinder 26. When the upper surface of the ring I32 bears against the lower surface of the sleeve 130, the cylinder 26 can no longer move upwardly. During further movement of the main valve element I36, an O-ring I74 carried on the inner surface of the annular main valve element I36 seats on the outer periphery of the exhaust valve member 142 to close off communication between the upper interior of the cylinder 26 and the exhaust passageways 152 in the cap. Further upward movement of the main valve I36 moves the resilient element I50 completely out of engagement with the now stationary cylinder 26 so as to connect the upper interior of the cylinder 26 to the reservoir 24 of pressurized fluid. This initiates a power stroke of the piston 32 and the connected driver blade 34.

When the main valve assembly 28 is to be closed, the control valve assembly 44 again supplies pressurized fluid over the conduit I64 and the passageway 162 to the right-hand end of the cylinder 158. This pneumatic bias coupled with the bias of the compression spring 160 shifts the valve piston 156 from the position shown in FIG. to the position shown in FIG. 3. In this position. the port 172 is closed, and the

passageways

166 and 168 are placed in communication so that pressurized fluid again flows into the chamber 138 above the piston portion 136A of the main valve element 136. This pneumatic bias coupled with the resilient bias pro-- vided by the compression springs 148 initiates downward movement of the main valve element 136 from the position shown in FIG. 5 to the position shown in FIG. 3. During the initial movement, the resilient O- ring 150 seats on the upper end of the cylinder 26 so that the upper interior of the cylinder 26 is cut off from communication with the pressurized fluid in the reser voir 24. During subsequent movement, the O-ring 174 is moved downwardly enough to place the cylinder 26 in communication with the exhaust passageways 152 to exhaust the upper end of the cylinder. Continuing downward movement of the annular main valve 136 moves the cylinder 26 downwardly from the position shown in FIG. 5 to the position shown in FIG. 3. In this position, the piston 32 and the driver blade 34 can be moved through a return stroke to restore the drive system to its normal condition.

Associated with the sliding cylinder 26 and the main valve assembly 28 is an assembly for providing the control valve assembly 44 with signals representing the position of the piston 32. More specifically, the cylindrical portion 22C of the housing is provided with a hollow projection 176 (FIGS. 35) communicating with the control valve assembly 44 over a duct or conduit 178. A plug 180 (FIG. 4) with a restricted orifice therethrough places a chamber 182 in communication with the pressurized fluid in the reservoir 24. The chamber I82 is placed in communication with the exterior of the sleeve 130 (FIGS. 3 and 5) through an opening or port 184 (FIG. 4). The outer surface of the sleeve 130 (FIGS. 3 and 5) is, in turn. placed in communication with a port or passageway 186 through the upper end of the cylinder 26 by means of a passageway 187 through the sleeve 130. These passageways are sealed by the illustrated O-rings.

When the piston 32 occupies the normal position shown in FIG. 3, the two illustrated O-rings on the piston 32 seal the

passageways

186 and 187 so that the chamber 182 (FIG. 4) and thus the conduit 178 extending to the control valve assembly 44 becomes pressurized to the pressure of the compressed air in the res ervoir 24. This signal indicates that the piston 32 is in its normal home position. Alternatively. when the piston 32 is displaced from its normal position through a power stroke and the main valve assembly 28 has again been closed at the termination of this power stroke, the upper interior of the cylinder 26 is placed at atmo spheric pressure in the manner described above. At this time. the passageways I86 and I87 and the port 184 vent the chamber 182 and the duct 178 to the atmosphere because these passageways exhaust pressurized air faster than it can be supplied through the restricted orifice in the plug 180. Thus. when the main valve assembly 28 is closed and the piston 32 is not in a normal home position, the conduit 178 provides an exhaust signal to the control valve assembly 44. When the piston 32 is returned to its normal position. the port 186 is again sealed, and the restricted orifice in the plug I80 (FIG. 4) again pressurizes the chamber 182 and the conduit 178 to advise the control valve assembly 44 that the piston 32 has been returned to its normal home position.

To provide the exhaust valve assembly is for selectively sealing or opening to the atmosphere the lower interior of the cylinder 26, there is provided an annular or cylindrical member 188 (FIGS. 3, 5, and 6) whose lower end is welded or otherwise permanently secured to an uppermost plate 48A in the four laminated plates 48A-48D in the plate assembly 48. The annular memher 188 includes an enlarged upper end portion 188A having a recess in which is disposed a resilient O-ring 190 providing an exhaust valve seal. The element 190 is aligned with the lower end of the cylinder 26.

In the normal condition of the tool 20 (FIG. 3), the engagement of the upper end of the cylinder 26 by the main valve 136 or the resilient element thereon seats the lower end of the cylinder 26 on the resilient element to close off communication between the lower interior of the cylinder 26 and the atmosphere through, for example, a plurality of spaced ports or openings 192 (FIGS. 3, 5, and 6). When, however, the main valve assembly 28 is opened (FIG. 5), the cylinder 26 is moved upwardly in the manner described above, and the lower end of the cylinder 26 is spaced from the resilient element 190. This places the lower interior of the cylinder 26 beneath the piston 32 in communication with the atmosphere through the openings 192. The entire lower end of the cylinder 26 is vented through the large area openings I92, and thus no back pressure is encountered by the piston 32 during its driving stroke. This substantially improves the efficiency of the drive system for the tool 20.

Associated with the exhaust valve assembly 30 is a unique fluid conveying means controlled by the control valve assembly for supplying pressurized fluid to the lower interior of the cylinder 26 to move the piston 32 through a return stroke. More specifically, this pressurized fluid is supplied by the control valve assembly 44 to a passageway 194 (FIGS. 4, 6, and 8), which passageway extends through a depending portion of the head portion 22A of the housing 22 immediately adjacent one of the tapped openings 54 used to secure the plate assembly 48 to the head portion 22A. This pas sageway 194 is aligned with an opening 196 in the uppermost plate 48A, and the port or passageway 196 is, in turn. aligned with a pair of elongated passageways 198 in the

plates

48B and 48C at the right-hand end thereof. The elongated slots 198 extend through the

plates

48B and 48C to a point underlying an opening 200 (FIGS. 6 and 8) in the uppermost plate 48A. The opening 200 extends through the plate 48A to discharge air within the annular member 188.

A resilient or elastomeric bumper or cushion 202 is disposed within and held in position by the annular member 188 in a position to cushion or terminate the power stroke of the piston 32. The bumper 202 includes a plurality of radially extending, tapered ribs 202A terminating above the plate 48A so that pressurized fluid supplied through the opening 200 can be dispersed around the periphery of the bumper 202 through a passage 203 and then pass downwardly through the passageways defined by the ribs 202A to be applied to the lower surface of the piston 32 when this piston is in its lower position (FIG. 7). The pressurized return air supplied through the opening 200, in passing through the passageways defined by the ribs 202A, cools the bumper 202 to prevent deterioration an! overheating thereof. By thus supplying piston return air over the system of

passageways

194 and 196 and 198 and 200, and then dispersing this air around the exte rior surface of the bumper 202, the piston return air not only is supplied directly beneath the piston 32 without passing through the side walls of the cylinder 26, but is also used to effect cooling of the bumper 202. Further, the use of the laminated plate assembly 48 facilitates the formation of the passageways in a construction of welded or brazed individual plates which are capable of absorbing the impact shocks arising from terminating the power stroke of the piston 32.

Associated with the exhaust valve assembly 30 is an improved arrangement for supplying a signal to the control valve assembly 44 indicating that the piston 32 has completed its power stroke. This arrangement is best illustrated in FIG. 7 of the drawings. More specifi cally, when the piston 32 reaches the end of its power stroke, as determined by engagement with the bumper 202, pressurized fluid from above the piston 32 flows out of the cylinder through a plurality of spaced ports 204 to an area in the interface between the cylinder 26 and the portion 22D of the head 22A of the housing. A passageway through the portion 22D of the head 22A supplies this pressurized signal to the control valve assembly 44. In the past, there has been a tendency for this end of power stroke signal of pressurized fluid to become dissipated when the interior of the cylinder 26 above the piston 32 is exhausted by closing the main valve to start the return stroke of the piston 32.

However, in the present arrangement, as soon as the signal supplied through the ports 204 controls the control valve assembly 44 to effect the closing of the main valve, the cylinder 26 is moved downwardly from the position shown in FIG. 7 to the position shown in FIG. 3 in which the lower end of the cylinder 26 seats on the exhaust valve seat 190. When this happens, the ports 204 are moved to a position bounded on opposite sides by the two O-rings carried on the piston 32. The pressurized signal supplied through the ports 204 is thus sealed off from communication with either the upper or lower interior of the cylinder 26. Further, when compressed air is supplied through the opening 200 be neath the piston 32 to start the return stroke of the piston 32, this pressurized fluid also passes through the ports 204 to supplement the cycle valve bias previously supplied from the pressurized fluid above the piston 32 which may now have been exhausted to the atmosphere by the closure of the main valve assembly 28.

Control Valve Assembly 44 The control valve assembly 44 is controlled by a manually actuated trigger 206 and a conventional workpiece engaging assembly indicated generally as 208 to operate the fastener driving tool through one or a number of automatically effected cycles of power and return strokes of the piston 32. The mechanical construction ofthe control valve assembly 44 can be of any suitable type and can, for example, be of the gen eral nature disclosed and described in US. Pat. No. 3,685,396. In general, the control valve assembly is carried in a housing 210 as an integral subassembly which can be secured to a wall of the head portion 22A of the housing 22 by suitable fasteners, such as machine bolts or screws 212 (FIG. 4). The passages in the valve housing 210 communicating with the various control components of the assembly 44 are coupled to ports terminating related passageways formed in the housing 22. The valve housing 210 is provided with a pair of spaced supporting lugs 210A between which the trigger 206 is pivotally mounted on a pivot pin 214 (FIGS. 1 and 4).

The workpiece engaging assembly or means 208 which is actuated when the tool 20 is placed adjacent a workpiece can be of any suitable well known construction, such as that shown in US. Pat. No. 3,615,049. In general, the assembly 208 includes a linkage 216 mounted on the housing 22 and the nosepiece assembly 38 and resiliently biased to a position in which a workpiece engaging portion 216A of the mechanism projects downwardly below the lower end of the nosepiece assembly 38. An upper portion 2168 is coupled by a lost motion arrangement to the lower end of a safety valve stem 218 (FIG. 3) forming a part of the control valve assembly 44. When the tool 20 is placed adjacent a workpiece, the lower end portion 216A engages the workpiece and moves the mechanism 216 upwardly. After the lost motion has been taken up, the portion 2168 of the linkage 216 moves the safety valve stem 218 upwardly from a normal position shown in FIG. 11 to an actuated position shown in FIG. 12. When the tool 20 is moved away from the workpiece, resilient biasing means 220 (FIG. 1 moves the linkage 216 downwardly so that after the lost motion is taken up, a portion 216B moves the valve stem 218 downwardly from the actuated position shown in FIG. 12 to the normal position shown in FIG. 11.

Referring now more specifically to the valving arrangement included in the control valve assembly 44, the assembly 44 is shown in normal position in FIG. 11 and in an operated position in FIG. 12. The control valve assembly includes a return air valve assembly in dicated generally as 222, a combined manual-safety valve assembly indicated generally as 224, and a cycle valve assembly indicated generally 226. To provide a master source of pressurized fluid or compressed air for use by the control valve assembly 44, there is provided a port or passageway 228 extending from the reservoir 24 through a wall of the housing 22 and the back wall of the housing 210 to the control valve assembly 44 to open into a valve cylinder 230 forming a part of the return valve assembly 222. A passageway 232 forwards this pressurized fluid to a valve cylinder 234 forming a part of the manual valve assembly 224. A further passageway 236 forwards this pressurized air to a valve cylinder 238 forming a part of the cycle valve assembly 226.

The manual-trigger valve assembly 224 is actuated by the trigger 206 and the workpiece engaging assembly 208 to selectively connect a passageway 240 coupled to the cycle valve assembly 226 to a source of pressurized fluid when the control valve assembly 44 is in its normal position and to connect the passageway 240 to the atmosphere when the assembly 224 has been properly actuated by the trigger 206 and the workpiece engaging assembly 208. The manual valve assembly 224 includes the safety valve stem 218 having therein a valve chamber 242 open at its upper end to the atmo sphere. Slidably disposed within the valve chamber or cylinder 242 is a valve element or stem 244 with an en larged upper end portion 244A. A compression spring 245 interposed between the lower end of the valve stem 244 and the lower wall of the valve chamber 242 normally biases the valve stem 244 to the position shown in FIG. 11. The pressurized fluid admitted to the interior of the chamber 242 through a plurality of passageways 246 from the valve cylinder 234 and the passageway 232 also acts on the enlarged portion 244A to aid the bias of the spring 245 and normally seat this enlarged portion 244A on an exhaust valve O-ring 248. The spring bias insures that the tool will not fire when first coupled to pressurized air. This pressurized fluid also passes outwardly from the chamber 242 through a plurality of ports or passageways 250 and the portion of the valve chamber 234 bounded by the illustrated O-rings to be conveyed over the passageway 240 to the cycle valve assembly 226.

When the valve stem 218 is moved upwardly to its actuated position determined by engagement of the upper stem 218 with a shoulder formed in the valve cylinder 234 (FIG. 12) and when the trigger 206 is pivoted in a counterclockwise direction about the pivot pin 214 to the position shown in FIG. 5, the indicated portion of the trigger 206 moves downwardly into engagement with the upper end of the valve stem 244 and shifts this valve stem to the position shown in FIG. 12. In this position, an O-ring 252 seats on the inner wall of the valve chamber 242 to close off communication between the ports or

passageways

246 and 250 to terminate the supply of pressurized fluid to the passageway 240. At the same time. the enlarged upper end portion 244A of the valve element 244 moves out of engagement with the O-ring 248 to connect the passageway 240 to the atmosphere. The valve means 244 cannot be moved to the position shown in FIG. [2 unless both the safety valve stem 218 is elevated to the position shown and the trigger 206 is depressed to the position shown. Thus, the manual-safety valve assembly 224 cannot be operated to connect the passageway 240 to the atmosphere unless both the trigger 206 and the workpiece engaging assembly 208 are actuated. The release of these elements restores the manual valve assembly 224 to its normal position shown in FIG. ll so that pressurized fluid is reapplied to the passageway 240 and its communication with the atmosphere is interrupted.

The return air valve assembly 222 is controlled by the pressure in the upper interior of the drive cylinder 26 to selectively supply return air to the lower end of the cylinder 26 at the end of a power stroke and to terminate this supply of return air when the piston 32 is re stored to its normal position. In addition. the return air valve assembly 222 supplies a supplemental source of pressurized air for preventing premature operation of the cycle valve assembly 226. The return air valve assembly 222 includes a valve piston 254 slidably mounted in the valve chamber 230 and having an upper greater area piston portion 254A and a lower smaller area piston portion 2548 providing a bias oppositely directed to that provided by the piston portion 254A. The pressurized fluid normally supplied through the conveying means 178 in the manner described above acts on the piston portion 254A to provide a greater magnitude downwardly directed bias acting on the valve piston 254 than is provided by the pressurized fluid supplied by the passageway 228 to the valve chamber 230 which provides an upwardly directed bias acting on the piston portion 254B. Thus, the valve piston 254 normally occupies the position shown in FIG.

11 in which its lower end seats on a resilient O-ring 256.

When the drive piston 32 reaches the end of its power stroke and the main valve assembly 28 is closed to exhaust the upper interior of the cylinder 26, the conduit 178 is placed at atmospheric pressure, and the bias is removed from the large piston portion 254A on the valve piston 254. At this time the pressurized fluid supplied to the lower end of the valve cylinder 230 by the passageway 228 acts on the small area piston portion 254B to move the valve piston 254 upwardly to the position shown in FIG. 12. At this time, the lower end of the valve piston 254 moves out of engagement with the valve seat 256, and pressurized fluid from the passageway 228 and the valve cylinder 230 enters a passageway 258 to be forwarded through a port 260 to the passageway 194 (FIGS. 4 and 8) to be supplied in turn through the opening 200 to the lower end of the cylinder 26. In addition, pressurized fluid from the passageway 258 is forwarded over another passageway 262 to be supplied to the lower end of the valve chamber 238 for the cycle valve assembly 226. The pressurized fluid supplied by the passageway 262 is used to avoid a pre mature change in the state of the cycle valve 226.

When the drive piston 32 has been restored to its normal position in the manner described above. the conduit 178 is again pressurized, and the greater bias applied by the large piston portion 254A returns the valve piston 254 to the normal position shown in FlG. 11 so that the supply of pressurized fluid to the passageway 258 is terminated. The pressurized fluid trapped in the

passageways

258, 260, and 262 is discharged to the atmosphere over the connection through the opening 200 to the lower end of the interior of the cylinder 26. From the closed cylinder, trapped fluid can leak to the atmosphere through clearances along the driver blade 34.

The cycle valve assembly 226 illustrated in FIGS. 1] and I2 is one that automatically and successively cycles the main valve assembly 28 between open and closed conditions after the manual valve assembly 224 has been operated to produce a sequence of power and re turn strokes of the piston 32 and the driver blade 34. To accomplish this, the control valve assembly 226 in cludes a valve piston 264 movable to a position causing opening of the main valve 28 by a continuous bias and movable to an alternate position closing the main valve assembly 28 in accordance with the high pressure signal received through the ports 204 (FIG. 7) and 280 (FIG. II) when the piston 32 has reached the end of its power stroke. A control piston 266 slidabl y mounted within the valve cylinder 238 for the cycle valve assembly 226 also forms a part of this assembly and is con trolled by the return air valve assembly 222 to prevent premature return of the valve piston 264 to its setting effecting opening of the main valve 28.

More specifically, the cycle valve piston 264 which is slidably mounted within the valve cylinder 238 includes a small area piston portion 264A slidably mounted within a reduced diameter cylinder 268 formed in a plug'270 that is carried within an opening 272 in the housing 22B immediately above and in alignment with the valve chamber 238 in the valve housing 210. The chamber 268 is continuously supplied with pressurized fluid from the reservoir 24 through a restricted orifice 274 formed in the plug 270. This pressurized fluid acts on the small diameter portion 264A to continuously bias the cycle valve piston 264 to the normal position shown in FIG. 11.

In this position, pressurized fluid normally supplied by the manual valve assembly 224 over the passageway 240 passes around an O-ring 276 in an enlarged portion 238A of the valve chamber to be forwarded over a passageway 278 to one end of the conduit 164. As described above, the conduit 164 extends to the dump valve assembly 154 (FIG. 3) in the closure cap 140 for the tool and holds the main valve assembly 28 in a position closing the open upper end of the cylinder 26. When the manual-safety valve assembly 224 is operated in the manner described above to connect the passageway 240 to the atmosphere, the conduit I64 and the passageway 278 are also connected to the atmosphere to effect opening of the main valve assembly 28 in the manner described above. In this operation, the lower exhaust valve assembly opens first, the exhaust passageways I52 are then closed, and finally compressed air is admitted to the top of the cylinder 26.

When the piston 32 reaches the end of its power stroke (FIG. 7), pressurized fluid is supplied through the ports 204. This pressurized fluid is conveyed through a passageway 280 extending through the portion 22D of the head portion 22A and the back wall of the housing 210 for the valve assembly 44 to supply this fluid below a large area piston portion 26413 on the cycle valve piston 264. This fluid is supplied above the upper surface of the control piston 266. The pressurized fluid supplied through the passageway 280 pro vides a greater upwardly directed bias than the pressurized fluid acting on the small area piston portion 264A. Thus, the cycle valve piston 264 is moved upwardly from the position shown in FIG. 11 to the position shown in FIG. 12. When the piston 264 moves to the position shown in FIG. 12, the O-ring 276 closes off communication between the

passageways

240 and 278 so that the conduit I64 is no longer connected to the atmosphere. In addition, an O-ring 282 moves into the enlarged portion 232A of the valve cylinder 238 and places the passageway 278 in communication with the pressurized fluid supplied to the valve chamber 238 by the passageway 236. When the conduit 164 is again pressurized, the main valve assembly 28 is closed to terminate the supply of pressurized fluid above the piston 32 and then to connect the upper interior of the cylinder 26 to the atmosphere. Further, when the main valve assembly 28 is closed, the cylinder 26 is then moved downwardly to close the lower end exhaust valve assembly 30 (FIG. 3). In this position, the O-rings on the piston 32 seal the ports 204 so that the pressurized fluid applied to the piston portion 264B cannot be dissipated. This aids in holding the cycle valve piston 264 in the elevated position shown in FIG. 12.

When the pressure within the upper interior of the cylinder 26 becomes sufficiently dissipated, the return air valve assembly 222 is opened, as shown in FIG. 12, and pressurized fluid is applied over the

passageways

258 and 262 to the extreme lower end of the cycle valve cylinder 238. This pressurized fluid, in being sup plied directly from the reservoir 24 without appreciable throttling, is of greater pressure than that trapped above this control piston and supplied through the signal passageway 280. Accordingly. the control piston 266 moves upwardly to the position shown in FIG. I2. The piston 266 may not physically engage the large pis ton portion 2648 of the cycle valve piston 264 under certain conditions where the pressure supplied by the port 280 is great enough. In any event, the control piston 266 provides an additional bias urging the piston 264 upwardly to the position shown in FIG. 12 against the bias applied to the small area piston portion 264A with the result that the cycle valve piston 264 cannot be prematurely restored to its alternate setting shown in FIG. 11.

The opening of the return air valve assembly 222 also supplies pressurized fluid in the manner described above to the lower interior of the cylinder 26 so that the piston 32 is elevated toward its normal position. As the piston 32 clears the ports 204 (FIG. 7), the signal air supplied to the large piston portion 264B begins to dissipate over the passageway 280 due to expansion of air within the lower interior of the cylinder 26. However, the pressure of this air is supplemented by that supplied by the return valve assembly 222 so that a substantial bias remains applied to the large piston portion 2648. In addition, the control piston 266 provides a continuing bias acting on the large piston portion 2648 to prevent any movement of the cycle valve piston 264 at this time.

When the piston 32 is returned to its normal home position, the conduit 178 is pressurized, and the return valve assembly 222 is moved to the closed position shown in FIG. 1 1. This terminates the supply of return air beneath the piston 32 and beneath the control piston 266. The air acting on the piston 266 becomes dissipated primarily by leakage around the driver blade 34, and the bias resulting from the pressurized fluid within the chamber 268 acting on the small piston portion 264A is now effective to move the cycle valve piston 264 to the normal position shown in FIG. 11 along with the control piston 266. When the cycle valve piston 264 reaches the position shown in FIG. 11, the O- ring 282 closes oi? communication between the passageway 278 and the fluid pressure supplying passageway 236. The O-ring 276 in moving into the enlarged portion 238A connects the passageway 278 to the exhaust passageway 240 so that the main valve 28 is again opened. This initiates another cycle of operation of the drive system for the tool 20. This operation continues, providing successive cycles of alternate power and return strokes until such time as the manualsafety valve assembly 224 is released.

The cycle valve assembly 226 can also easily be modified to provide single cycle rather than autoflre operation. The only change that is required is to replace the plug 270 with another plug of identical configuration except that the passageway 274 instead of extending axially within the opening 272 to place the chamber 268 in communication with the reservoir 24 extends laterally through the plug 270 to communicate with a passageway 290 leading to the atmosphere. This, in effect, removes the autofire bias applied to the small area piston portion 264A. With this modification, a small area piston portion 264C is effective when the passageway 240 is pressurized to hold the piston 264 for the cycle valve assembly 226 in the normal position shown in FIG. 11. However, when the valve piston 264 is shifted to its elevated position shown in FIG. 12 in precisely the manner described above, the piston portion 264C is connected to the atmosphere over the passageway 240, and no bias exists for returning the piston 264 to the normal position shown in FIG. 1] until such time as the manual-safety trigger assembly 224 is released to repressurize the passageway 240. With this modification, the cycle valve assembly 226 operates the tool 20 through a single power and return stroke, and further power strokes cannot be initiated until the manualsafety valve assembly 224 is released.

Referring now more specifically to FIG. 13 of the drawings, therein is illustrated a schematic diagram of the control valve assembly 44 for effecting autofire operation of the tool 20. The main valve assembly 28, in its schematic form shown in FlG.. 13, includes the dump valve assembly 154. A small effective area piston portion 28A shown in FIG. 13 represents the lower area of the main valve element 136 tending to open this valve. A large effective area piston portion shown as 288 in FIG. 13 represents the upper effective area of the piston portion 136A as well as the bias applied by the compression springs 148. Since the bias provided by the large area piston portion 28B overcomes the bias provided by the piston portion 28A, the main valve 28 in its normal position connects the upper interior of the cylinder 26 to the atmosphere. The large area piston portion 283 is normally connected to pressurized fluid over the

passageways

164, 240, the cycle valve 226, and the manual-safety valve assembly 224.

When the tool 20 is to be operated, and both the trigger 206 and the workpiece engaging assembly 208 are operated, the manual-safety valve assembly 224 is operated to its alternate setting, and the

lines

164 and 240 connect the large piston portion 288 on the main valve assembly 28 to the atmosphere. The continuous bias applied to the small area piston portion 28A shifts the main valve assembly 28 to its open position so that the lower exhaust valve assembly 30 is first opened, the exhaust passages 152 are next closed, and finally pressurized fluid is applied to the upper interior of the cylinder 26. This moves the piston 32 and the driver blade 34 through a power stroke to drive a staple 40 supplied to the drive track 36. At the end of the power stroke of the piston 32, pressurized fluid collected through the ports 204 is supplied over the passageway 280 to pressurize the large piston portion 26413 of the cycle valve assembly 226.

The force applied by the large area piston portion 264B overcomes the continuous bias applied to the small area piston portion 264A, and the cycle valve 226 shifts to its alternate setting so that even though the line 240 remains at atmospheric pressure, the passageway 164 is again pressurized, and the large area piston portion 288 shifts the main valve assembly to its normal setting shown in FIG. 13. Incident to this, the exhaust valve assembly 30 for the lower interior of the cylinder 26 is closed.

When the upper interior of the cylinder 26 approaches atmospheric pressure, the port 186 exhausts the passageway or conduit 178 faster than pressurized fluid can be supplied through the restricted orifice in the plug [80, and the large area piston portion 254A of the return air valve assembly 222 becomes substantially depressurized. At this time, the continuous pneumatic bias applied to the small area piston portion 2548 is effective to operate the return air valve assembly 222 to its alternate setting. When this happens, the line 258 is pressurized to supply fluid pressure over the passageway 262 to the control piston 266. The control piston mechanically biases the cycle valve assembly 226 toward its alternate setting to supplement the pneumatic bias applied by the large piston portion 2643.

The pressurized fluid supplied to the passageway 258 is also supplied to the opening 200 below the piston 32 in the cylinder 26 over a system of passageways and ports including the

components

194, 196, 198, and 200. This pressurized fluid moves the piston 32 upwardly through a return stroke toward its normal position. As the piston 32 clears the ports 204, pressurized fluid from the opening 200 also passes out of the cylinder 26 through the ports 204 to be applied over the passageway 280 to supplement the bias applied to the large area piston portion 2648 on the cycle valve 226. When the piston 32 reaches its normal home position, the ports 186 are sealed from communication with the atmosphere by the O-rings carried on the piston.

The orifice in the plug then begins to pressurize the passageway 178. When this becomes sufficiently pressurized, the bias applied to the large piston portion 254A on the air return valve 222 shifts this valve to the normal position shown in FIG. 13 against the continuous bias applied to the small area piston portion 254B. When this happens, the passageway 258 and the passageways connected thereto tend toward atmospheric pressure along with the passageway 280, by, for example, leakage of air from the bottom of the cylinder 26 along the sides of the driver blade 34. When this pressure drop becomes great enough, the continuous bias applied to the small area piston portion 264A of the cycle valve assembly 226 shifts this cycle valve back to its normal position shown in FIG. 13 and restores the control piston 266 to its normal position.

With the cycle valve 226 in its normal position, the passageway or conduit 164 is again connected to atmosphere over the passageway 240 and the operated valve assembly 224. This opens the main valve assembly 28 in the manner described above. This cyclic operation continues until such time as the manual-safety valve assembly 224 is released. At this time, the control components of the control valve assembly 44 are restored to the normal position shown in FIG. 13.

Although the present invention has been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this invention.

What is claimed and desired to be secured by Letters Patent of the United States is:

l. A tool for driving fasteners into a workpiece comprising a powered fastener driving assembly including a driver element actuated by a drive piston slidable within a drive cylinder,

:1 fluid controlled main valve means opened to supply pressurized fluid to and closed to exhaust fluid from the cylinder to move the piston through power and return strokes,

a cycle valve coupled to the main valve means and operable to alternate positions to open and close the main valve means, said cycle valve being biased to a position to close the main valve means, said cycle valve also including valve piston means,

passage means coupling the valve piston means to the drive cylinder to receive pressurized fluid for biasing the cycle valve to a position to close the main valve means,

return valve means responsive to the exhaust of the drive cylinder above the drive piston for supplying pressurized fluid into the drive cylinder below the drive piston to move the drive piston through a re turn stroke, the pressurized fluid below the drive piston being supplied to the valve piston means to bias the cycle valve to a position to close the main valve means,

and means responsive to the completion of the return stroke of the drive piston for controlling the return valve means to terminate the supply of pressurized fluid to the drive cylinder below the piston means and thus to the valve piston means.

2. A tool as set forth in claim 1 including a bias piston movable into engagement with the valve piston means,

and means coupling the bias piston to the return valve means to receive pressurized fluid from the return valve means,

3. A tool as set forth in claim 1 including a valve seat adjacent the lower end of the drive cylinder communicating with the atmosphere,

and means movably mounting the drive cylinder for movement into engagement with the valve seat when the main valve means is closed and out of engagement with the valve seat when the main valve means is opened to exhaust the drive cylinder below the piston.

4. A tool as set forth in claim 3 including port means in the cylinder forming a part of said passage means, said port means being opened to pressurized fluid in the drive cylinder above the drive piston when the cylinder is out of said engagement with the valve seat and the drive piston is at the end of its power stroke, said port means being closed by said drive piston when the drive cylinder engages said valve seat and the drive piston is at the end of its power stroke.

5. A tool for driving fasteners into a workpiece comprising a housing,

a cylinder slidably mounted in the housing and slidably receiving a piston movable through power and return strokes,

fastenerdriving blade actuated by the piston,

a main valve means opened to supply a pressurized fluid to the top of the cylinder and closed to exhaust fluid from the top of the cylinder, said main valve means including means engaging the cylinder to move the cylinder down when the main valve means is closed and permitting upward movement of the cylinder when the main valve means is opened,

a nosepiece structure on the housing adjacent the lower end of the cylinder and having a drive track through which the fastener driving blade extends,

a cylindrical valve seat engaged by the lower end of the cylinder when the main valve means is closed and spaced below the lower end of the cylinder when the cylinder moves upwardly as the main valve means is opened, the space between the valve seat and the lower end of the cylinder exhausting the lower interior of the cylinder,

a fluid actuated cycle valve means coupled to the main valve means and automatically operable through a sequence of two spaced positions to open and close the main valve means, said cycle valve means including means responsive to pressurized fluid from the lower end of the cylinder to effect closure of the main valve means,

a fluid controlled return valve means responsive to the closure of the main valve means for supplying pressurized fluid to the cycle valve means to hold the main valve means closed and to the lower end of the cylinder below the piston to move the piston through a return stroke, said fluid controlled return valve means being released to terminate the supply of pressurized fluid when the piston completes its return stroke,

and control means for initiating movement of the cycle valve means to start a power stroke of the piston.

6. A tool as set forth in claim 5 in which the cylindrical valve seat is fixedly secured to and projects upwardly from the nosepiece structure,

and the return valve means is carried on the housing and includes passage means through the housing and nosepiece structure terminating in a discharge port disposed within the cylindrical valve seat.

7. A tool for driving fasteners into a workpiece comprising a housing defining a chamber,

a cylinder slidably mounted within the chamber for limited movement,

a fluid actuated main valve assembly movable into and out of engagement with the top portion of the cylinder, said cylinder being fluid biased toward the main valve assembly and movable over a limited travel with the main valve assembly before separation of the top portion of the cylinder and the main valve assembly,

a piston slidable within the cylinder,

a fastener driving blade actuated by the piston,

a nosepiece structure on the housing adjacent the lower end of the cylinder and defining a drive track slidably receiving the fastener driving blade,

an annular member fixedly secured to the nosepiece structure encircling the fastener driving blade and aligned with the lower portion of the cylinder,

a resilient sealing element carried on the annular member adapted to be engaged by the lower portion of the cylinder when the main valve means is moved into engagement with the top of the cylinder to move the cylinder down into seating engagement with the sealing element, said sealing element being spaced from the lower portion of the cylinder when the main valve assembly is moved upwardly out of engagement with the cylinder to permit limited upward movement of the cylinder away from the sealing element,

a fluid passage passing through the housing and the nosepiece structure and having a port in the nose piece structure within the annular member,

and fluid control means coupled to the main valve assembly and to the fluid passage to move the main valve assembly into and out of engagement with the top portion of the cylinder and to supply fluid to the fluid passage.

8. A tool for driving fasteners comprising a tool housing with a nosepiece structure including a drive track,

power actuated fastener driving means on the tool housing including a driver element movable in said drive track,

a magazine housing with an open top coupled to the nosepiece structure and having a fastener supporting structure disposed below said open top for supporting and feeding a series of fasteners-into the drive track,

a pusher carriage mounted on said housing for movement toward and away from the drive track along an elongated path,

a rigid fastener engaging pusher element for engaging fasteners on said fastener supporting structure,

pivot structure coupling the pusher carriage and the pusher element to mount the rigid pusher element for pivotal movement into and out of the open top of the magazine about an axis extending transverse to the direction of the elongated path of movement of the pusher carriage,

and resilient means coupled to the pusher carriage to resiliently bias the pusher carriage for movement toward the drive track.

9. The tool set forth in claim 8 in which the resilient means includes an extensible elongated flat spring means coupled between the tool housing and the pusher carriage and disposed at the open end of the magazine housing overlying the fasteners on the fastener supporting structure.

10. The tool set forth in claim 9 for use with U- shaped fasteners with spaced legs in which driver for driving generally U-shaped fasteners successively supplied to a drive track,

a magazine housing communicating at one end with the drive track and having an open top,

a support disposed within the housing for supporting a strip of U-shaped fasteners,

a carriage slidably mounted on the housing adjacent its open end for movement toward and away from the drive track,

flat spring means connected between the tool and the carriage and overlying the portion of the strip and the support that is disposed between the carriage and the drive track, said flat spring means biasing the carriage toward the drive track,

pusher means with at least one rigid pusher arm piv' otally mounted on the carriage for movement into and out of the open top of the housing and adapted to engage the U-shaped fasteners when disposed within the magazine housing, the flat spring means being provided with a clearance to permit the pusher arm to move past the flat spring in moving into and out of the open end of the magazine housing and biasing means normally biasing the pusher arm into the open top of the magazine housing to a position for engaging a Ushaped fastener.

12. The tool set forth in claim ll in which the pusher means includes a pair of rigid pusher arms connected for joint movement and normally disposed within the magazine housing on opposite sides of the support,

said pair of pusher arms being spaced a given dis tance apart, and the flat spring means having a width less than said given distance .in the portion of the length of the flat spring means adjacent the pusher arm so as to permit the pair of pusher arms to move into and out of the open top of the magazine housing.

13. A: tool for driving fasteners comprising a housing having a cylinder means closed at its lower end by a lower wall structure,

a power actuated drive means in the housing including a coupled piston and driver blade movable within the cylinder means,

valve means for selectively connecting the cylinder means to pressurized fluid to move the piston and driver blade through a power stroke,

a bumper on said lower wall structure and cooperating with the cylinder means and the lower wall structure to provide a peripheral passage around the bumper adjacent the lower wall structure communicating with a plurality of upwardly extending passages spaced circumferentially around the outer surface of the bumper.

and means for supplying pressurized fluid to the peripheral passage to be conveyed over said periprr era] and upwardly extending passages to the interior of the cylinder means to move said piston and driver blade through a return stroke,

said means including a source of pressurized fluid and control means responsive to said drive stroke for interconnecting said source with said peripheral and upwardly extending passages.

14. A tool for driving fasteners into a workpiece comprising a housing.

a powered fastener driving assembly in said housing including a driver element actuated by a drive piston slidablc within a movable drive cylinder,

fluid controlled main valve means opened to supply pressurized fluid to and closed to exhaust fluid from the cylinder to move the piston through power and return strokes.

said main valve means including passageways ex hausting said main valve means, and valve means movable to open and close said passageways,

said drive cylinder being movable with said passage way valve means, and

control means for controlling the main valve assembly, said control means actuating said valve means to close said passageways prior to supplying pres surized fluid to said cylinder to drive said piston and opening said passageways prior to the return stroke of said piston.

15. The tool set forth in claim l4 further comprising a lower wall structure closing said cylinder at its lower end means for exhausting the portion of said housing be neath said drive piston, and said control means controlling the movement of said cylinder from its closed position with said lower wall structure to an open position communicating said cylinder with said exhaust means.

If). The tool set forth in claim 14 further comprising a bumper on said lower wall structure cooperating with said cylinder and said lower wall structure to provide a peripheral passage around the bumper adjacent the lower wall structure communicating with a plurality of upwardly extending passages 23 24 spaced circumferentially around the outer surface blade through a return stroke, and of the bumper, said means including a source of pressurized fluid means for supplying pressurized fluid to the periphand control means responsive to said drive stroke era] passage to be conveyed over said peripheral for interconnecting said source with said peripheral and upwardly extending passages to the interior of and upwardly extending passages.

I. l I! the cylinder means to move said piston and drive

Claims

1. A tool for driving fasteners into a workpiece comprising a powered fastener driving assembly including a driver element actuated by a drive piston slidable within a drive cylinder, a fluid controlled main valve means opened to supply pressurized fluid to and closed to exhaust fluid from the cylinder to move the piston through power and return strokes, a cycle valve coupled to the main valve means and operable to alternate positions to open and close the main valve means, said cycle valve being biased to a position to close the main valve means, said cycle valve also including valve piston means, passage means coupling the valve piston means to the drive cylinder to receive pressurized fluid for biasing the cycle valve to a position to close the main valve means, return valve means responsive to the exhaust of the drive cylinder above the drive piston for supplying pressurized fluid into the drive cylinder below the drive piston to move the drive piston through a return stroke, the pressurized fluid below the drive piston being supplied to the valve piston means to bias the cycle valve to a position to close the main valve means, and means responsive to the completion of the return stroke of the drive piston for controlling the return valve means to terminate the supply of pressurized fluid to the drive cylinder below the piston means and thus to the valve piston means.

2. A tool as set forth in claim 1 including a bias piston movable into engagement with the valve piston means, and means coupling the bias piston to the return valve means to receive pressurized fluid from the return valve means.

3. A tool as set forth in claim 1 including a valve seat adjacent the lower end of the drive cylinder communicating with the atmosphere, and means movably mounting the drive cylinder for movement into engagement with the valve seat when the main valve means is closed and out of engagement with the valve seat when the main valve means is opened to exhaust the drive cylinder below the piston.

5. A tool for driving fasteners into a workpiece comprising a housing, a cylinder slidably mounted in the housing and slidably receiving a piston movable through power and return strokes, a fastener driving blade actuated by the piston, a main valve means opened to supply a pressurized fluid to the top of the cylinder and closed to exhaust fluid from the top of the cylinder, said main valve means including means engaging the cylinder to move the cylinder down when the main valve means is closed and permitting upward movement of the cylinder when the main valve means is opened, a nosepiece structure on the housing adjacent the lower end of the cylinder and having a drive track through which the fastener driving blade extends, a cylindrical valve seat engaged by the lower end of the cylinder when the main valve means is closed and spaced below the lower end of the cylinder when the cylinder moves upwardly as the main valve means is opened, the space between the valve seat and the lower end of the cylinder exhausting the lower interior of the cylinder, a fluid actuated cycle valve means coupled to the main valve means and automatically operable through a sequence of two spaced positions to oPen and close the main valve means, said cycle valve means including means responsive to pressurized fluid from the lower end of the cylinder to effect closure of the main valve means, a fluid controlled return valve means responsive to the closure of the main valve means for supplying pressurized fluid to the cycle valve means to hold the main valve means closed and to the lower end of the cylinder below the piston to move the piston through a return stroke, said fluid controlled return valve means being released to terminate the supply of pressurized fluid when the piston completes its return stroke, and control means for initiating movement of the cycle valve means to start a power stroke of the piston.

6. A tool as set forth in claim 5 in which the cylindrical valve seat is fixedly secured to and projects upwardly from the nosepiece structure, and the return valve means is carried on the housing and includes passage means through the housing and nosepiece structure terminating in a discharge port disposed within the cylindrical valve seat.

7. A tool for driving fasteners into a workpiece comprising a housing defining a chamber, a cylinder slidably mounted within the chamber for limited movement, a fluid actuated main valve assembly movable into and out of engagement with the top portion of the cylinder, said cylinder being fluid biased toward the main valve assembly and movable over a limited travel with the main valve assembly before separation of the top portion of the cylinder and the main valve assembly, a piston slidable within the cylinder, a fastener driving blade actuated by the piston, a nosepiece structure on the housing adjacent the lower end of the cylinder and defining a drive track slidably receiving the fastener driving blade, an annular member fixedly secured to the nosepiece structure encircling the fastener driving blade and aligned with the lower portion of the cylinder, a resilient sealing element carried on the annular member adapted to be engaged by the lower portion of the cylinder when the main valve means is moved into engagement with the top of the cylinder to move the cylinder down into seating engagement with the sealing element, said sealing element being spaced from the lower portion of the cylinder when the main valve assembly is moved upwardly out of engagement with the cylinder to permit limited upward movement of the cylinder away from the sealing element, a fluid passage passing through the housing and the nosepiece structure and having a port in the nosepiece structure within the annular member, and fluid control means coupled to the main valve assembly and to the fluid passage to move the main valve assembly into and out of engagement with the top portion of the cylinder and to supply fluid to the fluid passage.

8. A tool for driving fasteners comprising a tool housing with a nosepiece structure including a drive track, power actuated fastener driving means on the tool housing including a driver element movable in said drive track, a magazine housing with an open top coupled to the nosepiece structure and having a fastener supporting structure disposed below said open top for supporting and feeding a series of fasteners into the drive track, a pusher carriage mounted on said housing for movement toward and away from the drive track along an elongated path, a rigid fastener engaging pusher element for engaging fasteners on said fastener supporting structure, pivot structure coupling the pusher carriage and the pusher element to mount the rigid pusher element for pivotal movement into and out of the open top of the magazine about an axis extending transverse to the direction of the elongated path of movement of the pusher carriage, and resilient means coupled to the pusher carriage to resiliently bias the pusher carriage for movement toward the drive track.

10. The tool set forth in claim 9 for use with U-shaped fasteners with spaced legs in which a pair of rigid pusher elements are pivotally mounted on the pusher carriage and spaced from each other in the direction of said axis to engage the spaced legs of the U-shaped fasteners, and the flat spring means includes a portion disposed between the spaced pair of pusher legs.

11. In a fastener driving tool having a reciprocable driver for driving generally U-shaped fasteners successively supplied to a drive track, a magazine housing communicating at one end with the drive track and having an open top, a support disposed within the housing for supporting a strip of U-shaped fasteners, a carriage slidably mounted on the housing adjacent its open end for movement toward and away from the drive track, flat spring means connected between the tool and the carriage and overlying the portion of the strip and the support that is disposed between the carriage and the drive track, said flat spring means biasing the carriage toward the drive track, pusher means with at least one rigid pusher arm pivotally mounted on the carriage for movement into and out of the open top of the housing and adapted to engage the U-shaped fasteners when disposed within the magazine housing, the flat spring means being provided with a clearance to permit the pusher arm to move past the flat spring in moving into and out of the open end of the magazine housing, and biasing means normally biasing the pusher arm into the open top of the magazine housing to a position for engaging a U-shaped fastener.

12. The tool set forth in claim 11 in which the pusher means includes a pair of rigid pusher arms connected for joint movement and normally disposed within the magazine housing on opposite sides of the support, said pair of pusher arms being spaced a given distance apart, and the flat spring means having a width less than said given distance in the portion of the length of the flat spring means adjacent the pusher arm so as to permit the pair of pusher arms to move into and out of the open top of the magazine housing.

13. A tool for driving fasteners comprising a housing having a cylinder means closed at its lower end by a lower wall structure, a power actuated drive means in the housing including a coupled piston and driver blade movable within the cylinder means, valve means for selectively connecting the cylinder means to pressurized fluid to move the piston and driver blade through a power stroke, a bumper on said lower wall structure and cooperating with the cylinder means and the lower wall structure to provide a peripheral passage around the bumper adjacent the lower wall structure communicating with a plurality of upwardly extending passages spaced circumferentially around the outer surface of the bumper, and means for supplying pressurized fluid to the peripheral passage to be conveyed over said peripheral and upwardly extending passages to the interior of the cylinder means to move said piston and driver blade through a return stroke, said means including a source of pressurized fluid and control means responsive to said drive stroke for interconnecting said source with said peripheral and upwardly extending passages.

14. A tool for driving fasteners into a workpiece comprising a housing, a powered fastener driving assembly in said housing including a driver element actuated by a drive piston slidable within a movable drive cylinder, fluid controlled main valve means opened to supply pressurized fluid to and closed to exhaust fluid from the cylinder to move the piston through power and return strokes, said main valve means including passageways exhausTing said main valve means, and valve means movable to open and close said passageways, said drive cylinder being movable with said passageway valve means, and control means for controlling the main valve assembly, said control means actuating said valve means to close said passageways prior to supplying pressurized fluid to said cylinder to drive said piston and opening said passageways prior to the return stroke of said piston.

15. The tool set forth in claim 14 further comprising a lower wall structure closing said cylinder at its lower end, means for exhausting the portion of said housing beneath said drive piston, and said control means controlling the movement of said cylinder from its closed position with said lower wall structure to an open position communicating said cylinder with said exhaust means.

16. The tool set forth in claim 14 further comprising a bumper on said lower wall structure cooperating with said cylinder and said lower wall structure to provide a peripheral passage around the bumper adjacent the lower wall structure communicating with a plurality of upwardly extending passages spaced circumferentially around the outer surface of the bumper, means for supplying pressurized fluid to the peripheral passage to be conveyed over said peripheral and upwardly extending passages to the interior of the cylinder means to move said piston and drive blade through a return stroke, and said means including a source of pressurized fluid and control means responsive to said drive stroke for interconnecting said source with said peripheral and upwardly extending passages.