US 3822816 A
An apparatus for fastening metal studs to drywall panels use staples driven against anvil surfaces formed integral with the metal studs so that the staple crowns overlie the studs with the legs curled into the drywall panels from the backside. Since staples are driven from the back of the panel and do not project through the other side, the usual need for covering the fasteners or their heads is avoided. The nosepiece of the staple driving tool is recessed to accept the metal stud, and the drive track in which the staple driver is reciprocated is outwardly open or flared adjacent the received stud to control the curling of the staple legs within the panel. The tool is provided with stabilizers to insure balanced penetration of the workpiece by the staple legs, and the relative positions of the anvil surfaces on the stud and the various portions of the drive track are controlled in dependence on the staple used so as to obtain predictable controlled curling of the legs within the drywall panel. A safety prevents operation of the tool when it is placed against the panel unless and until the stud is also disposed in the recess in the nosepiece.
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llnited States Patent 1191 Doyle 1 APPARATUS FOR DRIVING STAPLES  Inventor: Richard H. Doyle, 104 S. Albert St.,
Mount Prospect, 111. 60056 22 Filed: Apr. 17, 1972 [21 Appl. No.: 244,746
 US. Cl. 227/83, 227/119 [51,] int. Cl. B25c 5/02  Field of Search 227/8, 83, 110, 119, 120,
 References Cited UNITED STATES PATENTS 2,237,438 4/1941 James ..1 227/83 2,341,530 2/1944 Crosby 227/128 2,418,118 4/1947 Hamilton et al. 227/127 X 2,746,043 5/1956 Heller 227/132 2,754,515 7/1956 King 227/132 2,997,713 8/1961 Anuteft 227/110 X 3,152,335 10/1964 Wandel et al 227/83 3,417,908 12/1968 Treat man 227/128 X Primary ExaminerGranville Y. Custer, Jr. Attorney, Agent, or Firm--Mason, Kolehmainen, Rathburn & Wyss [451 July 9, 1974 [5 7] ABSTRACT An apparatus for fastening metal studs to drywall panels use staples driven against anvil surfaces formed integral with the metal studs so that the staple crowns overlie the studs with the legs curled into the drywall panels from the backside. Since staples are driven from the back of the panel and do not project through the other side, the usual need for covering the fasteners or their heads is avoided. The nosepiece of the staple driving tool is recessed to accept the metal stud,
,and the drive track in which the staple driver is reciprocated is outwardly open or flared adjacent the received stud to control the curling of the staple legs withinthe panel. The tool is provided with stabilizers to insure balanced penetration of the workpiece by the staple legs, and the relative positions of the anvil surfaces on the stud and the various portions of the drive track are controlled in dependence on the staple used so as to obtain predictable controlled curling of the legs within the drywall panel. A safety prevents operation of the tool when it is placed against the panel unless and until the stud is also disposed in the recess in the nosepiece.
10 Claims, 7 Drawing Figures t 11 APPARATUS FOR DRIVING STAPLES This invention relates to an apparatus for stapling articles to workpieces and, more particularly, to a new and improved staple driving tool for stapling metal studs to drywall panels.
In an attempt to improve the methods and structures previously used to mount or install drywall panels in dwellings, it has been proposed to use metal studs or joices having integrally formed anvil surfaces. When staples are driven with the crowns overlying the studs, the staple legs straddle the stud and engage and are deflected by oppositely positioned anvil surfaces on the stud so as to penetrate the back of the panel. A series of such staples spaced along the length of the stud securely connect the stud and the drywall panel to support the panel in its desired position on a wall or ceiling. Since the stud is located on the back or blind surface of the panel and since the staples enter this panel from the back, the fasteners are completely concealed, and the time usually required to cover the heads of prior fasteners, frequently nails, is avoided. Further, the possibility of nail pops" is avoided.
The use of this building structure is dependent on or is facilitated by the ability of the staple driving too] to properly locate the staples relative to the stud and to drive the staples in such a manner that the holding power is made as great as possible while insuring that the staple legs do not protrude through the front or finish side of the drywall panel. This requires a control over the relative positions of the tool, the stud, and the panel or workpiece as well as the provision of a staple driving tool or assembly capable of producing predictable penetration of the workpiece by the staple legs.
Accordingly, one object of the present invention is to provide a new and improved staple driving tool.
. A further object is to provide a new and improved tool for driving staples including a nosepiece structure for locating the tool relative to a stud and stabilizers for locating the tool relative to the workpiece or panel.
Another object is to provide a tool including a new and improved nosepiece structure which locates a drive track therein relative to' an elongated article having anvil surfaces and in which the drive track is formed and positioned relative to the anvil surfaces so as to obtain predictable controlled penetration or curling of the staple legs straddling the element as they enter a workpiece to which the article is to be secured.
A further object is to provide a new and improved tool for joining an anvil-bearing element to a workpiece in which a staple leg bending surface or edge on a staple driving tool is disposed in a given relation to the anvil before the staple is driven to insure proper curling of the staple legs as they enter the workpiece.
Another object is toprovide an improved fastener driving tool in which the workpiece engaging surface of a nosepiece structure includes an article locating recess and in which a safety assembly prevents operation of the tool unless the article is located in the recess.
An embodiment of the present invention uses a fastener or staple driving tool to secure metal studs or supporting elements to the back surface of a wall panel such as a sheet of drywall material by driving a series of staples with their legs straddling the stud in the back surface of the panel. The stud is formed with a pair of outwardly inclined or flared side walls which provide an anvil against which the free ends of the staples are driven to deflect orcurl these legsinto the drywall panels so as to secure maximum holding power without marring the finish side of the panel by protrusion the rethrough.
In accordance with the present invention, the nosepiece structure is provided with locating recesses in the workpiece engaging end or portion thereof for removably receiving the anvil so as to provide means for locating the anvil relative to a drive track in the nosepiece. The drive track is completely enclosed by rigid walls for guiding thestaple and the reciprocating movement of a driver blade except for a lower portion disposed immediately adjacent the anvil which is outwardly flared or open to provide a staple leg bending or curling edge or surface. When a staple is driven, this edge cooperates with the anvil engaging the free end of the staple leg to impart a predictable controlled curl to the staple leg as it enters the workpiece, thereby to achieve maximum holding power while insuring that the staple does not project through the finish side of the drywall panel. by suitably proportioning the relative positions of these components in terms of the thickness of the staple used, it is possible to control curling of the staple legs to obtain the desired result.
Further, so as to insure that the staple driving tool is maintained in a relationship generally perpendicular to the drywall panel, the fastener driving tool includes a spaced stabilizing unit providing supporting contact for the tool spaced on opposite sides of the stud which generally underlies the magazine of the tool. This stabilization of the tool in a perpendicular position relative to the panel is desirable because the operation of the tool in a skewed position can result in driving one of the legs of the staple through the panel so that the finish surface thereof is marred. In this connection, the tool also includes a safety assembly for disabling operation of the tool, unless the stud is disposed within the locating recesses formed in the nosepiece structure.
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. l is a front elevational view in partial section illustrating a fastener driving tool embodying the present invention in conjunction with anassembly of a supporting stud and a drywall panel;
FIG. 2 is a fragmentary sectional view taken along line 2-2 in FIG. 1;
FIG. 3 is a fragmentary front elevational view in partial section illustrating the fastener driving tool in an assembled relation with the stud and panel in condition for operation;
FIG. 4 is a view similar to FIG. 2 illustrating the fastener driving too] at the end of a drive stroke;
FIG. 5 is a sectional view taken along line 5-5 in FIG. 4;
FIG. 6 is afragmentary perspective view of another embodiment of a stabilizing unit used with the tool shown in FIG. 1; and
FIG. 7 is an enlarged fragmentary sectional view similar to FIG. 4 illustrating the relative dimensions and positions of certain components of the fastener driving tool, staple, stud, and the drywall panel.
Referring now more specifically to FIG. ll of the drawings, therein is illustrated a fastener driving tool which isindicated generally as 10 and which embodies the present invention. The tool 10 is designedfor driving a series of individual fasteners or staples 12 into the back of a drywall panel 14 to secure this panel to a metal stud 16. The stud 16, in turn, can be secured to a framing element, such as a wooden stud or joice 18, so that the connection of the drywall panel 14 to the stud 16 mounts the panel in an assembled relation in a building structure. Since the staples 12 are driven into the back surface of the panel 14 and do not protrude through a finish or front surface 14A thereof, the structural assembly does not produce mars in thc finish surface 14A and reduces the time and expense of decorating the dwelling.
The tool is so designed as to secure predictable controlled penetration or curling of the legs of the staples 12 within the panel 14 so as to provide maximum holding power without the possibility of marring the finish surface 14A of the panel 14. To this end the tool 10 includes novel means for controlling the curling or driving of the staples 12. In addition, thetool 10 includes new and improved means for insuring the proper positioning of the tool 10 on the stud 16 before the tool can be operated, as well as means for stabilizing the position of the tool 10 in a proper relation to the panel 14 so as to further the control over proper setting or driving of the staples 12.
The tool 10 can be of any of a number of constructions that are well known in the art such as those shown in U.S. Pat. Nos. 3,043,272 and 3,056,l37, for instance. In general, the tool 10 includes'a housing indicated generally as 20 having a generally vertically extending head portion 20A in which is located a power unit or a pneumatically actuated piston assembly for reciprocating a fastener driving element or blade 22 (FIG. 2). A magazine assembly indicated generally as 24 extends rearwardly from the lower end of the head portion 20A and is secured adjacent its rear end to a depending portion of a rearwardly extending handle portion 208 of the housing 20. The magazine 24 is of conventional construction and successively feeds staples 12 from a stick or supply thereof to a drive track 26 formed in a nosepiece structure or assembly which is indicated generally as 28 and which is secured to the forward end of the magazine assembly 24 and the lower end of the head portion 20A in the usual manner.
The operation ofthe tool 10 is controlled by a manual valve assembly actuated by a trigger 30 which is pivotally mounted on the housing 20 and a safety assembly which is indicated generally as 32. The safety assembly 32 can include valve means operating in conjunction with the valve controlled by the trigger 30 to insure that the power unit in the head portion 20A for driving the fastener driving blade 22 cannot be operated unless both the trigger 30 is depressed and the safety assembly 32 is actuated. In accordance with the present invention, the safety assembly 32 is so constructed and arranged that it is not actuated to a position permitting operation of the tool 10 unless the tool 10 is properly located with respect to the metal stud 16.
The metal stud 16 comprises an elongated inverted channel with a central portion 16A disposed generally parallel to the back surface of the panel 14 and connecting a pair of outwardly inclined or flared side walls 16B providing anvil portions formed integral with the stud 16 (FIG. 2). The interior angle formed by the inclined walls 168 with the adjacent surface of the panel 14 is around 40 plus or minus five degrees in one embodiment found suitable in carrying out the present invention. The ends of the stud 16 can be provided with offset portions 16C which are connected to the structural elements 18. If desired, the stud 16 can be provided with one or more laterally extending webs at the free ends of the walls 168 extending generally parallel to and in contact with the adjacent surface of the panel 14 and provided with spaced apertures or openings for receiving the legs of the staple 12.
The nosepiece structure 28 is formed by a front wall member 34 and a rear wall member 36, the upper ends of which are secured to the lower end of the head portion 20A of the housing 20. The back or rear nosepiece member 36 is secured as by a pair of machine bolts 38 to the front wall of a housing 24A for the magazine assembly 24. The wall member 36 is provided with a centrally disposed recess defining the front and both side walls of the drive track 26. The front wall member 34 includes a flat inner wall surface which is secured against the front wall of the member 36 as by a pair of machine bolts 40 so that the member 34 completes the definition of the drive track 26 bylproviding the front wall thereof. To provide means for feeding staples 12 from the magazine assembly 24 into the drive track 26 below the lower end of the driver 22, the nosepiece member 36 includes a generally U-shaped opening 36A (FIG. 2) providing a passageway between the drive track 26 and the interior of the staple magazine 24.
To provide means for accurately locating the stud 16 relative to the tool 10 and more specifically to the drive track 26 and the staple 12 disposed therein, each of the nosepiece members 34, 36 includes a lower workpiece engaging portion or end such as the workpiece engaging portion 36B on the member 36 shown in FIG. 2. This portion and the lower surface thereof is adapted to be moved into engagement with the panel 14 when the tool 10 is in position for driving a staple 12. A stud locating recess or notch 36C is formed in the work engaging portion 368 so located with respect to the nosepiece structure 28 that when a stud 16 is disposed in the recess 36C, it is positioned directly beneath the staple 12 in the drive track 26 with the free ends of the legs 12A of the staple disposed immediately above the upper portions of the inclined walls 16B on the stud (see FIGS. 2 and 7). A similar notch is formed in the from member 34 of the nosepiece assembly 28 aligned with the illustrated recess 36C so that the tool 10 is disposed in a generally parallel relation to the stud with the magazine assembly 24 overlying the stud 16. When so disposed, a crown portion 12B on the staple 12 in the drive track 26 overlies the flat upper wall 16A of the stud.
To provide means for controlling the curling of the legs 12A of the staple 12 when the staple 12 is driven downwardly through the drive track 26 by the driver blade 22, the drive track 26 is provided with an outwardly flared or opened portion indicated generally as 26A in an area disposed immediately above and in proximity to a stud 16 located in the recesses 36C (FIGS. 2 and 4). This outwardly opened or flared portion 26A is defined by removing the material on front wall of the nosepiece member 36 at its lower end so that, in effect, there is defined a transversely extending slot or opening 36D (FIGS. 2-4) separating the lower end or workpiece engaging portions of the nosepiece members 34 and 36. A pair of bending edges or fulcrum surfaces indicated as 36E are provided in the transitional-area connecting the drive track 26 to the slot 361). These fulcrum edges cooperate with the outer surfaces of the staple legs 12A when the staple 12 is driven downwardly so that its free ends engage the anvil portion 168 to control the deflection or curling of 5 these staple legs as they are driven into the back surface of the drywall panel 14.
It has been determined that if the tool is mounted on the panel 14 in a skewed or nonperpendicular relation with respect to the back surface of the panel 14 when the staple 12 is driven, there is a likelihood that one of the staple legs 12A will not be sufficiently or properly curled during the driving operation with the result that this leg will penetrate the finish surface 14A of the panel 14. To prevent this and insure that the tool 10 is disposed in substantially a perpendicular relation with respect to the adjacent surface of the panel 14, the tool 10 is provided with a pair of rearwardly spaced stabilizer assemblies indicated generally as 42. These sta bilizer assemblies include generally U-shaped and downwardly open elements whose bight portions are welded or otherwise secured to the lower wall of the housing 24A of the magazine assembly 24 at points spaced rearwardly of the head portion A. The free ends of the depending legs 42A formed on the stabilizer assembly are adapted to engage the panel 14 and maintain the tool 10 against tipping in either direction relative to a perpendicular or upright position. -In a preferred embodiment, the lower ends of the legs 42A engage the adjacent surface of the panel 14 when the stud l6 isfully inserted in or received within the aligning openings or recesses 36C (FIG. 4).
FIG. 6 of the drawings illustrates another embodiment of a stabilizermeans 44 that can be used with the tool 10 in accordance with the present invention. The stabilizer means or element 44 is adapted to be secured toa lower wall of the housing 24A for the magazine assembly 24 in substantially the same position on the tool 10 as the stabilizer unit 42. Each of the stabilizer elements 44 comprises a generally flat or plate-like element having a lug 44A at its upper end for attachment to a lower wall of the housing 24A. The opposite ends of the lower edge of the plate 44 are provided with two workpiece engaging portions 44B adapted to engage the panel 44 at points spaced outwardly and on opposite sides of the stud 16.
In these respects, the functions performed by the stabilizer units 44 are the same as those performed by the units 42. However, each of the stabilizer units or plates 44 includes a generally centrally disposed locating opening or recess 44C along its lower edge. The configuration of the recess 44C matches the cross-section of the stud 16. Thus, when the tool 10 is placed on anassembled stud l6 and'panel 14, the stud 16 is received in the locating openings 44C which are spaced rearwardly from but aligned with the-locating openings 36C to provide more accurate orientation of the tool 10 relative to the stud 16.
As set forth above. the tool 10 includes a new and improved safety assembly by which operation of the tool 10 is disabled unless the stud 16 is disposed within the locating openings similar to the opening 36C in the nosepiece assembly 28. More specifically, the safety assembly 32 is in large part one of the type long known in the art in including a valve operating stem or member 46 that is pneumatically biased to the normal position shown in FIG. I by compressed air within the hous- 6 ing 20 of the tool. The bight of a generally U-shaped operator 48 is secured to the stem 46 with two depending leg portions 48A disposed at opposite sides of the head portion 20A and the nosepiece assembly 28. These legs 48A are provided with slots opening toward the front of the tool 10 in which are received two outwardly projecting ears D (FIGS. 1 and 2) on a workpiece engaging yoke indicated generally as 50.
The yoke 50 is generally U-shaped in including two upstanding side wall portions 50A joined at their lower rear ends by a transversely extending bight portion 50B. The side walls 50A are provided with indented or struck out portions 50C (FIG. 5) which are slidably received within vertically extending grooves ,52 (FIGS. 1 and 3) formed in opposite edgesof the back member 36 of the nosepiece assembly 28. The cooperation of the struck out portions 50C with the grooves or slots 52 mounts the actuating yoke 50 on the nosepiece assem- In the normal position of the tool 10, the pneumatic bias applied to the stem 46 is coupled through the operating member 48 to the yoke 50 to hold the yoke in the position shown in FIGS. 1 and 2. When the tool 10 is moved into an assembled relation with the stud 16 to prepare the tool 10 for operation, the lower edge of the connecting portion 50B (FIG. 2) of the yoke 50 engages the upper wall 16A of the stud 16. As the tool housing 20 is moved downwardly to the position shown in FIG. 4, the stud engaging portion 508 is moved upwardly to the position shown in FIGS. 3 and 4 with the result that the elements 46, 48, and 50 are moved to the upper or operated position shown in FIG. 3. In this position, the assembly 32 releases the tool 10 for operation under the control of the manual valve assembly actuated by the trigger 30 in the manner described in the above-identified patent. In this connection, it should be noted that since the lower edge of the connecting portion 50B of the operating yoke 50 occupies a normal position in which it is substantially flush with the lower surface of the workpiece engaging portions, such as the portion 36B of the nosepiece assembly 28, the tool 10 cannot be conditioned for operation by placing this tool'against a panel I4. The operating yoke 50is elevated to the position necessary to release the tool for operation only if a stud 16 is disposed within the locating recesses 36C or 36C and 44C. The operating yoke 50 is restored to the normal position shown in FIGS. 1 and 2 by the pneumatic pressure applied to the stem 46 when the tool 10 is lifted from the workpiece.
When the tool 10 is to be used to fasten the stud 16 to the panel 14, these components being in their properly assembled relation, the tool 10 is placed above the stud 16 with the locating openings 36C or 36C and 44C aligned with this stud. The tool 10 is then moved downwardly so that the upper wall 16A of the stud engages a lower edge of the bight portion 508 of the operating yoke 50 for the safety means 32. As the tool 10 is moved toward the adjacent surface of the panel 14, the operating yoke 50 is elevated in the manner described above, and the safety assembly 32 is moved from the normal or inoperative position shown in FIG. I to the actuated or operative position shown in FIG. 3. In this position, the stud I6 is received within the locating openings 36C, 44C, and either the legs 42A or the workpiece engaging portion 44B engage the back surface of the panel 14 to hold the tool 10 in a perpendicular relation thereto as illustrated in FIG. 4. The tool can then be operated to drive the first fastener or staple 12.
More specifically, the tool operator then pivots the trigger 30 in a counterclockwise direction from the position shown in FIG. 1 to the position shown in FIG. 3 to actuate the manual valve so that the power unit initiates downward movement of the staple driving blade 22 from its normal position shown in FIG. 2 toward its final position shown in FIG. 4. During the initial downward movement of the blade 22, its lower edge engages the crown 12B of the staple 12 disposed in the drive track 26 and moves this staple downwardly to an intermediate position shown in FIG. 7 in which the lower ends of the legs 12A of the staple 12 engage the inclined walls or anvil portions 168 of the stud l6 immediately adjacent the top wall 16A. The staple legs 12A are shown as being provided with a point which forms a preferred embodiment of the staple 12 to be used in the present invention. As the driver blade moves downwardly to the position shown in FIG. 7, the lower free ends of the staple legs 12A are cammed outwardly as they slide along the walls 168. During this movement, the outer surfaces or edges of the staple legs 12A are deflected somewhat outwardly into engagement with the curling or bending edges or surfaces 36E to impart a curl to these legs during continuing movement of the driver blade. The driver blade 22 reaches the fully driven position shown in solid outline in FIG. 4 and dashed outline in FIG. 7. The legs 12A of the staple 12 are driven into the panel 14 with sufficient curl that the free ends do not penetrate the finish surface 14. In this position, the crown 12B of the staple overlies the wall 16A of the stud 16 with the legs 12A of the staple straddling the inclined side walls or anvil portions 168.
When the trigger 30 is released, the driver blade 22 is retracted by the power unit, and the the tool 10 can be advanced along the stud 16 to the next position at which a staple 12 is to be driven. If the tool 10 is held in engagement with the stud during this relative movement, the tool 10 can be reoperated merely by depressing the trigger 30. Alternatively, if the tool 10 is lifted from the stud 16 so that the safety assembly 32 is released, the tool 10 must again be properly located on the stud 16 as described above before operation of the trigger 30 will result in operation of the tool 10.
In the illustrated embodiment of the invention, it is necessary to manually actuate the trigger 30 each time that a staple 12 is to be driven. As shown in the drawings, it is desirable to provide a series of staples 12 spaced along the length of the stud 16. This can be easily and automatically accomplished by coupling the valve mechanism actuated by the trigger 30 to one of the actuating mechanisms shown in U.S. Pat. No. 2,9 I 5,754 so that the tool 10 is operated automatically in response to fixed increments of relative movement between the tool 10 and the workpiece 14. With this arrangement, the staples 12 are automatically driven at fixed predetermined distances from each other.
In assembling studs 16 with panels 14 using tools 10 embodying the present invention, what appears to be a relationship between the sizes or dimensions of certain of the components and the controlled predictable'curling ofthe staple legs 12A within the panel 14 has been determined. Certain of these dimensions are illustrated in FIG. 7 of the drawings. More specifically, it has been determined that curling of the staple legs 12A within the panel 14 usually results if the relationships set forth in the following paragraph are followed.
The space T (FIG. 7) between the bending edge or surface 36E at the lower end of the drive track 26 and the point of initial contact of the lower free ends of the staple leg 12A with the anvil or inclined wall surface 168 should be in the range from 4! to 7! where t is the thickness of the staple leg 12A. A preferred value for the distance T lies midway within this range and is around 5.5!. Further, the distance C between the surface of the panel 14 and the point of initial contact of the lower free end of the staple leg 12A with the inclined wall 168 should be around 2!. In addition, the length of the staple leg 12A measured from its lower free end to the top of the crown portion 12B should be around 2H where H is the thickness of the wallboard.
Although the present invention has been described with regard 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 which will fall within the spirit and scope of the principles of this invention.
What is claimed as new and desired to be secured by Letters Patent of the United States is:
1. In combination, a staple driving tool and an elongated element,
said tool comprising a housing for a staple driving means including a reciprocable driver element;
a nosepiece structure carried on the housing and defining a drive track for slidably receiving the driver element, said nosepiece structure including front and back walls defining the drive track and each having a recess at its lower end for receiving the elongated element disposed generally transverse to the driver element, said drive track having an outwardly enlarged portion at its lower end,
and a magazine assembly coupled to the nosepiece structure for successively feeding staples into the drive track above the outwardly enlarged portion of the drive track, said staples having a crown portion and depending leg portions having a thickness t, said drive track being disposed relative to the recesses receiving the elongated element such that the crown portion of a staple in the drive track overlies the elongated element disposed in said recess,
said elongated element comprising an anvil portion engaged by the staple legs directing the free ends of the staple legs outwardly;
said nosepiece structure including staple leg curling edges engaging'the legs of the staple adjacent the outwardly enlarged portion of the drive track, said curling edges being spaced above the point of contact of the free ends of the legs with the anvil portion of said elongated element a distance T in a general range of 4! to 7!.
2. The combination set forth in claim 1 in which the distance T is 5.5t.
3. The combination set forth in claim 1 in which the point of contact between the free ends of the staple legs and the anvil is spaced above the workpiece a distance of around 2t.
4. The combination set forth in claim 1 in which the workpiece has a thickness H, and in which the legs of the staples have a length around 2H.
5. A staple driving tool for securing an elongated anvil element with inclined walls to a workpiece using staples with depending legs joined by a crown comprising housing means including a head portion containing a reciprocable fastener driving element,
a nosepiece structure carried on the housing and defining a drive track for slidably receiving the driving element, said structure having a lower surface adapted to be disposed adjacent the workpiece and said lower surface having a recess to receive said anvil element, the drive track in said structure being aligned with the recess and being generally closed throughout its length and having a first width measured in a direction transverse to the direction of elongation of the anvil element that generally corresponds to the width of the crown of the staple, said drive track opening outwardly at its lower end adjacent the recess to a width greater than the width of the crown of the staple, said drive track having a substantially uniform second width throughout its length measured in a direction parallel to the direction of elongation of the anvil element,
and a magazine assembly for feeding successive staples into the drive track above said recess.
6. The staple driving tool set forth in claim in which the nosepiece structure provides a bending surface adjacent the point at which the drive track opens outwardly, the legs of the staples are disposed above and are adapted to initially engage the inclined walls of the anvil element at given points thereon, and the distance between the bending surface and said given points is in the range of 4! to 71 where t is the thickness of the staple leg. 7 7. In a fastener driving too] of the type having a power unit for driving fasteners to secure an article to a workpiece,
a housing for the power unit,
, 10' v a nosepiece structure on the housing defining a drive track and having a lower workpiece engaging portion, said lower portion having an article locating recess therein, a fastener driving element slidable in said drive track and operable by said power unit, manually actuated means and safety means on said housing for controlling the operation of the power unit when both said manually actuated means and said safety means are operated,
and actuating means coupled to the safety means and including an article engaging portion, said actuat ing means operating said safety means only when an article is disposed in said article locating recess in said nosepiece structure and is engaged by said into said article locating recess, said article engaging portion being moved by engagement with an article inserted into said article locating recess. 10. The fastener driving tool set forth in claim 7 in which the housing includes stabilizing means with spaced workpiece engaging portions adapted to engage the workpiece and maintaining the tool in a predetermined position relative to the workpiece when the safety means is actuated.
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