US2898893A - Impact tool - Google Patents

Description

Aug. 11, 1959 D. `P. RoHRER ETAL IMPACT TOOL 4 sheets-sheet 1 Filed April 1l. 1958 QON . R OEI- o TRI- I- MHP. B VOH NRC IBF. m H NS N O n Mm. M 3Q b wm aF m v QN mw U C O Y N.. l @w D B R l 1 o lwwm H QN\\ w w o P uw U I II G J l B .l|| zo e QJN ovm m l will w ww ww NS v \\Qw %k\ w@ m. om mm .Qwv I www r\ w IUI l O a n a Non ||\1||f\ H|| R wk IJ vv ||1| l l m www mw .O-u mm 4 Sheets-SheerI 2 Aug. 11, 1.959

D. P. ROHRER ET AL IMPACT TOOL Filed April ll. 1958 AU8- 1.1 1959 D. P. ROHRER ETAL 2,898,893

IMPAC'I*` TOOL 4 Sheets-Sheet 3 Filed April 1l, 1958 Om. N mwN NNN ATTORNEYS' IMPACT TOOL Filed April 1l. 1958 4 Sheets-Sheet 4 Unite@ IMPACT TooL Application April 11, 1958, Serial No. 727,856

11 Claims. (Cl. 12S- 7) This invention relates to an impact tool and more particularly kto a tool actuated by the explosion of a charge of fuel and air in which tool each explosion is separately manually initiated by a trigger mechanism and the tool is thereafter automatically brought to a condition in which it is again ready to [be -fred by a manual actuation of Vthe trigger mechanism. i

The tool of the present invention constitutes an improvement over the impact tool disclosed in the copending application of Carleton S. Marden and William l. J. Gordon, Serial No. 641,190 filed February 19, 1957. Tools of the type described in such application are in fact internal combustion engines operating at all times under starting conditions. In normal use of such tools, the time intervals between explosions are suiciently long vthat the walls -of the explosion chamber are not heated to any substantial extent Iby previous use of the tool. The result is that the fuel vapors condense on the walls of the explosion chamber and a correctly proportioned charge exists only momentarily. Unless there is proper coordination between the charge forming mechanism and the ignition mechanism, the tool will not consistently lire. The specic tool disclosed in the copending application referred to above provides one solution of the problem. In such tool a piston is manually moved from one end of a cylinder to an intermediate position against the action of a spring while drawing in a charge of fuel and air, and such manually actuated mechanism also causes ignition of the charge as soon as the piston reaches such intermediate position.

The present tool includes a manually controlled power operated mechanism for moving the piston from one end of the cylinder to an intermediate position which mechanism is operated lby power stored from the previous explosion. The -tool also includes an improved charge forming device which is simple in structure and which consistently results in the introduction of a proper charge of air and fuel into the explosion chamber at the right time to be fired. In the specific tool disclosed, the charge is formed by spraying a small amount of liquid fuel upon surfaces immediately adjacent an inlet valve leading into the explxosion chamber so that such fuel is contacted by air drawn into such explosion chamber. The fuel is sprayed by an adjustable pump actuated lby the trigger of the tool and occurs just prior to opening of the inlet valve. The inlet valve is opened by the vacuum produced as a result of the movement of the piston referred to above and the air drawn into the explosion chamber thereby provided results in the forming of a correctly proportioned charge of air and fuel yvapor in the explosion chamber. The vapor in such charge will, however, rapidly condense upon the unheated surfaces of the explosion chamber. In the present tool, the charge is ignited immediately upon its entrance into .the explosion chamber -by an ignition system under control of the mechanism which moves the piston from one end of the cylinder to an intermediate position therein. Thus the charge is ignited as soon `as the piston reaches its inter- States KPatent mediate position. The tool of the present application is also more compact and of simpler construction than that disclosed in the copending applictaion referred to above.

It is therefore an object of the present invention to provide an improved impact tool in which charges of a 'mixture of fuel and air fare exploded in a cylinder to product impacts and the exposions are each separately manually initiated.

Another object of the invention is to provide an impact "tool actuated by manually initiated explosions of mixtures of fuel and air in the cylinder in which tool a piston is automatically moved from a rest position at one end of the cylinder to an intermediate position to yprovide an explosion chamber when a trigger 'mechanism is actuated, and in which tool a charge of fuel and -air is introduced into such combustion chamber and ignited as soon as formed in such explosion chamber.

A further object of the invention is to provide an improved impact `tool actuated -by explosions of air and fuel in a cylinder in which tool there is storage of power from a previous explosion for moving the piston through an intake stroke initiated by manual actuation of a manually controlled element and in which tool a charge of fuel and air is introduced into the resulting explosion chamber during such inlet stroke and iired as soon as the charge is introduced.

A still further object of the invention is to provide an improved charge forming device for forming a charge of fuel and air and introducing the same into an explosion chamber in an impact tool of the type which produces impacts by explosions of such charges, each of which explosion is separately manually initiated.

Other objects and advantages of the invention will appear in the following description of the preferred embodiment shown in the attached drawing of which:

Fig. 1 is a side elevation of a tool in accordance with the present invention showing one side of the tool;

Fig. 2 is a partial side elevation of the tool of Fig. 1 showing the other side of the tool;

Fig. 3 is a plan View of the -tool of Figs. 1 and 2 with 4parts broken away to show internal structure;

Fig. 4 is a rear elevation of the tool of Figs. 1 to 3;

Fig. 5 is a partial longitudinal vertical section on an enlarged scale taken on the line 5 5 of Fig. 3;

Fig. 6 is a view partly in side elevation and partly in longitudinal vertical section on such enlarged scale, showing `certain of the parts in a different position from that of Fig. 5; l

Fig. 7 is a fragmentary longitudinal vertical section on a still further enlarged scale through the fuel pump mechanism of the tool;

Fig. 8 is a fragmentary end elevation on such further enlarged scale of the fuel pump adjusting means, taken in the direction of the arrows 8-8 of Fig. 5;

Fig. 9 is a rear elevation of the inlet valve mechanism looking in the direction of the arrows 9 9' of Fig. 7;

Fig. 10 is a fragmentary cross section through the fuel pump on a still further enlarged scale, taken on the line lll-10 of Fig. 7;

Fig. 11 is a fragmentary plan view on an enlarged scale of the manually actuated cooking member, looking in the direction of the arrows 11-11 of Fig. 5;

Fig. 12 is a fragmentary transverse vertical section through the fuel tank on an enlarged scale taken on the line 12-12 of Fig. 5; and

Fig. 13 is a schematic diagram of an ignition system of the tool of Figs. l to 12;-and v Fig. 14 is a view partly inside elevation and partly in longitudinal vertical section showing a modified tool having a limb cutting adapter.

Referring to Figs. 1 to 4 of the drawings, the tool of the present invention includes a cast body member 20, having an integral downwardly projecting handle portion 21. A cylinder 22 is secured to the forward end of the body member 20 and has secured to its forward end a plunger guiding member 24 which in turn has secured to its forward end a casing 26 for au operating instrumentality such as a stud driving device actuated by the tool. The body member 20 and plunger guiding member 24 form the rear and front cylinder heads respectively for the cylinder 22, as shown most clearly in Fig. 5, and are secured thereto by spring keys 27. A piston 28 is positioned within the cylinder 22 for reciprocation therein. As described below, the body member 20 also encloses a mechanism for moving the piston from one end of the cylinder to an intermediate ring position, a fuel pump for supplying a charge of liquid fuel, a fuel supply tank and the elements of an ignition system and also supports a trigger mechanism for ring the tool.

Piston and cylinder structure The piston 28 is provided with a piston ring 30 (Fig. 5). The ends of the cylinder are sealed to the body member 20 and plunger guiding member 24 by O-rings 31. The O-rings may be of rubber or similar material as the tool does not become heated in operation much above ambient temperature. rl`he piston 28 is secured to the rearward end of a plunger 32 which extends forwardly through the plunger guiding member 24 and is guided therein by a bushing 34 (Fig. 3) positioned in the forward end of the plunger guiding member 24. A coiled compression spring 36 surrounds the plunger 32 and has its rear end bearing against the piston 28 and its forward end received in an enlarged bore 38 in the plunger guiding member 24 and bearing against the bushing 34. It will be apparent that the spring 36 urges the piston 28 toward a rest position at the end of the cylinder closed by the body member 20.

As described more in detail below, for each operation of the tool the piston 28 is initially moved from the position shown in Fig. to the intermediate position shown in Fig. 6. During this movement, a charge of air and fuel is introduced into the explosion chamber 40 thus provided. Ingition of such charge causes the piston to be further moved by the resulting explosion to the position indicated by the dotted lines 42 in Fig. 6. In such position of the piston 28, the spent exhaust gases are exhausted through ports 44 in the walls of the cylinder and the piston is cushioned by air trapped between the piston and the plunger guiding member 24.

Stud driving adapter vThe plunger 32 is driven forwardly of the tool by the explosion acting on the piston to provide an impact. Such impact is imparted to a work piece through an operating instrumentality which is shown in Fig. 3 as a pin or stud driving plunger 46 having its rear end secured to the forward end of the plunger 32, for example, by a threaded connection 48. The forward end of the plunger 46 is guided in a bore 50 of reduced diameter in the casing 26. A stud or pin S2 having an enlarged head and a friction retainer 54 on its body portion may be positioned in the forward end of the bore 50 so as to be struck by the pin driving plunger 46. It will be appreciated that the length of the casing 26 will be such that the pin driving plunger 46 will have its forward end just slightly protruding from the end of the casing Z6 when the piston is at the extreme of its travel to the right in Figs. 3 and 6. The pin 52 may be driven into concrete or steel by one or more impacts from the piston 28.

Piston moving mechanism The mechanism for moving the piston 28 from the rest position shown in Fig. 5 to the intermediate or firing position shown in Fig. 6 against the force of the spring 36 is shown most clearly in Figs. 5 and 6. Such mechanism includes an auxiliary piston 56 of smaller diameter than the main piston 28 mounted in and reeiprocable in a liner 58 secured in the forward end of a bore 60 inthe body member 20'. The liner 58 and piston 56 are concentrically disposed with respect to the interior of the cylinder 22 and the forward end of the piston 5,6 is aligned with a rearwardly extending concentric circular portion 61 on the piston 28 of smaller diameter than the piston 28. The auxiliary piston 56 is urged forwardly by a coiled compression spring 62 having its rear end bearing against the rear surface of the bore 60 and its forward end bearing against the piston 56. The bore 60 has a vent port 63 to prevent trapping of air behind the piston 56. The piston 56 has an integral rearwardly extending plunger 64 which extends through the spring 62 and is guided in a bushing 66 positioned in a bore 68 of smaller diameter than the bore 60. The bore 68 extends concentrically from the interior of the bore 60 into an open-topped cavity 70 in the body member 20 of the tool. The body member has a longitudinally extending slot 71 (Fig. l) in one side opening into the cavity 70. The rearward end of the plunger 64 has secured thereto a stop member 72 which has a manually actuatable cocking element 73 secured thereto and extending laterally outwardly through the slot 71. The stop member 72 limits the forward travel of the auxiliary piston 56 to the position shown in Fig. 6, the rearward travel of such piston being limited by the engagement of the stop member 72 against the rear surface of cavity 70 in the body member 20. The spring 62 is of suicient strength that it can move the pistons 56 and 28 against the force of the spring 36 so as to move the piston 28 to the intermediate position shown in Fig. 6. The piston 56 can be manually moved to its rear position shown in Fig. 5 by manually moving the cocking element 73 rearwardly.

In the cocked or rearward position of the pistons 56 and 28 shown in Fig. 5, the piston 56 is locked in its rearward position by engagement between the rear end of a pivoted locking member 74 with a projection 76 extending downwardly from the stop member 72. The locking member 74 is positioned in a slot 77 in the body member 20 extending downwardly from the cavity 70 and is pivoted intermediate its ends on a pivot pin 78. The locking member has its rear end urged toward the stop member '72 by a coiled compression spring 80 having its ends positioned in suitable seats in the rear end of the locking member 74 and in the lower surface of the slot 77. It will be apparent that the locking member 74 will hold the plunger 64 and piston 56 in the position shown in Fig. 5 against the force of the spring 62 and that under these conditions, the spring 36 will hold the piston 23 in the rest position shown in Fig. 5 against the forward end of the body member 2t). Upon release of the locking member 74 from the stop member 76, the spring 62 will move the piston 56 from its rearward position shown in Fig. 5 to its forward position shown in Fig. 6 to thereby move the piston 28 from its rearward position shown in Fig. 5 to the intermediate position shown in Fig. 6. ln the rearward position of the piston S6, such piston uncovers an exhaust port 81 (Figs. 5, 6 and 2) extending through the liner 58 to the exterior of the tool from the interior of the explosion chamber 40 (Fig. 6). When such piston is in its forward position shown in Fig. 6, it seals the exhaust port 81.

Trigger mechanism The locking member 74 is actuated to release the stop member 72 by a sliding trigger 82 acting through a sliding member 84 most clearly shown in Figs. 7 and l0, which sliding member forms part of a fuel pump described more in detail below. The sliding member 84 is mounted for reciprocation in a bore 85, an elongated tubular casing 86 for the fuel pump and has upper and lower projections 88 and 90, respectively. The upper projection 88 projects upwardly .finto a .slot 92 yin thecasling r86'rand the Ilower projection 90 :projects downwardly vthrough a slot 94 in such casing. The .upper projection T88 has a Vrearwardly facing :inclined surface Vfor engagement with a cooperating inclined surface on a pivoted element 96 journaled on a pivot pin '98 through the bifurcated forward end ofthe vlocking member 74. The pivoted element 96 is resiliently urged in a rclockwise vdirection kabout the pivot pin 48 by a spring 100 coiled about the pivot pin 98 so that the spring 100 normally holds the pivoted element '96 in the position shown in Figs. and 6. It will be apparent that rearward sliding of the sliding member 84 will cause the upper projection 88 on such sliding `member Ito engage the pivoted member 96 so as to raise the forward end lof the locking member 74 and to depress the rear iend of the locking members 74. This will release the vlocking member from the projection 76 on the stop-member 72 `on ythe plunger 64 to enable the piston 56 to move the piston 28 from the position shown in Fig. 5 to the position shown in Fig. 6. Upon return or forward sliding motion of the sliding `member 84, the upper projection 88 will cam the pivoted element 96 out of its path by rotating such pivoted elemen-t about the pivot pin 98 against the action of the :spring 100. It will be understood that the spring 80 for the locking member 74 will have sufficient spring force so ythat the locking member 74 remains in its locking position shown in Fig. 5 when the .projection 88 on the sliding member 84 moves forwardly beneath the pivoted element 96.

The trigger 82 is mounted vfor sliding motion in a trigger support member 102 suitably secured to the lower side of the body member 20 forward of the handle'21. As shown most clearly in Fig. l0, the trigger 82 is in the form of a T having an upper cross member 104 resting on the top of the trigger support member 102 and a downwardly projecting central member guided in a slot 108 in the trigger support member. The cross member 104 and downwardly projecting portion 106 are of substantial length longitudinally of the tool so that the trigger 82 is guided for reciprocation in the slot 108. The upper surface of the cross member 104 bears against the side portions of the fuel pump casing 86 so as to be guided between vertically spaced longitudinally extending surfaces on such side portions and on the trigger support member 102. The cross member 104 has a lat* erally extending slot 110 in its upper surface and intermediate its ends into which the lower projection 90 on the sliding member 84 projects.

It will be apparent that rearward motion of the trigger 82 from the position shown in Fig. 5 will cause movement of the sliding member84 from theposition shown in Figs. 5 and 7 to the position shown in Fig. 6. During such movement, the upper projection 88 on the sliding member 84 will pass under lthe pivoted element 96 on the locking member 74 to release the stop member '72 and allow the spring 62 and .piston 56 to move the piston 28 from the position shown in Fig. 5 to the position shown in Fig. 6. As soon as the projection v88 passes under the pivotal element 96, the locking member 74 is returned to its locking position by the spring 80 so as to be conditioned to again lock the stop member '72 in its vrearward position. When the trigger 82 is released, a coiled compression spring 112, shown in Figs. 6 and 8,

as bearing against the rearward end of the sliding member 84 moves the sliding member 84 forwardly -to carry the upper projection 88 Vthereon beneath the pivoted element 96. Such pivoted element pivots out of the way, as described above, without causing pivoting of the locking element 74.

F nel pump Rearward movement of the trigger S82 also actuates 'the fuel pump of which the casing 86 and the sliding mem- -ber 84constitute parts. The details of the fuel pump are Arnost clearly shown in Fig. 7. The casing 86 is a-tubular .sleeve member which is inserted in and :fits the interior 'of 'a 'longitudinally extending bore 114 in :the body :member 20. Such borer v114 has .an venlarged concentric por tion 116 adjacent its yrearward -end which iextends to the rearward surface of the body .member 20. The 'fuel pump casing V86 has an enlarged head 118 at tits rear end abutting against the shoulder formed lbetween the bore 114 and its enlarged continuation 116 and such casing 86 is held in position in the bore by a bushing 120 secured in position by screws `12'2 (Fig. 4) and "forming a guide for a manually actuatable'fuel pump plunger 124. The casing 86 is prevented from rotating in the `bore -114 by engagement with the cross member 104 of the trigger 82. The manually actuatable fuel pump plunger 11'24 lis held in position in the bore y in the casing 84 by means of a cross pin 126 extending through opposed apertures in the walls of the casing 86 and through .a vertically extending longitudinal slot 128 in the plunger 124. fIt will be apparent that the slot 128 and bushing 120 :permit longitudinal reciprocation of the plunger 124 -forwardly from the position shown `in Fig. 7.

The plunger 124 has a reduced portion 130 at its forward end which is received in a bore in the rear endof 4a rear pump plunger 132 'and is secured in such bore by a cross pin 134. An C-ring 136 surrounds the .plunger 124 at the rear end of the rear pump plunger 132 so as to seal the rear plunger with respect to the bore 85 in the casing 86. A similar O-Iing 138 surrounds the rear pump plunger 132 at a point spaced from the 0-ring 136. The rear portion of the rear pump plunger 132 between the O-rings 136 and 138 is reduced in diameter so as to provide an annular duct 140 within Vthe bore 85 and surrounding the rear pump plunger 132, the duct 140 eX- tending a substantial distance longitudinally of such plunger. Such annular duct 140 communicates in all positions of the rear pump `plunger 132 with -a duct 142 extending radially outwardly through fthe wall `of the casing 86 into communication with an annular .groove 144 in the body member 20, which annular groove 144 in turn communicates with a duct 146 leading to the fuel tank described below.

The rear end of the rear pump plunger 132 has a cross duct 148 therein which is in communication with the annular duct 140 and leads to a check valve 150 including a ball and a spring 152. The easing 86 is sealed to the interior surfaces ofthe bore 114 in the body member 20 on opposite sides of the annular groove 144 by O-rings 154 positioned in annular grooves in the casing 86. The check valve provides one-way communication between the fuel tank and a longitudinal duct 156 extending longitudinally through the center ofthe rear pump pllunger 132 into the pumping chamber provided by a bore 158 in the sliding member 84.

The intermediate and forward portions of the rear ptunp plunger 132 are of reduced diameter and provide a guide lfor the spring 112 which urges the sliding member 84 toward its fonward position in the casing 86. The spring 112 also urges 4the rear pump plunger 132 and the manually actuated pump plunger 124 connected .thereto toward their rearward position in the casing 86. The forward end of the rear pump plunger 132 is received i'n the bore 158 in the sliding member 84 and has an'O- ring 160 positioned in an annular groove y-in its forward end and engaging the internal sunfalces of the bore -158 to provide a seal. The bore 158 provides a variable voltune pumping chamber as described below.

The forward end of the sliding member 84 also .has a bore 162 therein which -is of somewhat smaller diameter than the lbore 158 and which is concentric with the bore 158. The bore 162 `receives the rearward endof astationary member 164 which has an O-ring 1'66 positioned in an annular groove in its rearward end, the O-r-ing 166 engaging the internal Surface of the bore 162 to provide a seal. The stationary `member is secured in position in the forward end of the casing 86 by an arcuate -key `:16,8

received in aligned grooves in the stationary member and casing. The stationary member has a duct 170 extending longitudinally therethrough providing communication between the bore 158 in the sliding member 84 and a nozzle orifice 172 through a ball check valve 174 including a spring 176. The nozzle orifice 172 and check valve are positioned in a nozzle member 178 screw-threaded into a bore in the forward end of the stationary member 164.

It will be apparent that a manual pumping action can be effected by reciprocating the manually actuatable plunger 124 to reciprocate the plunger 132. Such manual actuation can be employed to initially fill the pump mechanism with fuel from the fuel tank. On moving the plunger 124 forwardly to move the pump plunger 132 forwardly, `the forward end of the pump plunger 132 is moved into the bore 158 in the sliding member 84 to reduce the volume of the pumping chamber provided by such bore. Air or fuel present in the chamber is forced through the duct 170 to open the check valve 174 and such air or fuel is then forced out of the nozzle orifice 172. Return of the plunger 124 and plunger 132 rearwardly of the tool will cause the check valve 174 to close and cause fuel to be introduced into the bore 158 through the check valve 150 from the fuel tank. The plunger 124 can then again be moved forwardly of the tool to again force air or fuel out of the nozzle orice 172. When the pump mechanism has thereby been filled with fuel, actuation of the trigger will supply a charge of fuel to the inlet of the cylinder. Movement of `the sliding member 84 rearwardly by the trigger 82 as described above will also decrease the volume of the pumping chamber provided by the bore 158 in the sliding member 84 to force fuel through the check valve 174 and nozzle orifice 172. Rearward motion of the trigger 82, therefore, projects a charge of fuel out of the nozzle orifice 172 and the amount of such fuel is determined by the travel of the trigger 82.

Fuel pump adjustment In order to adjust the travel of the trigger 82 and the sliding member 84, a threaded member 180 is screwthreaded into an inclined bore 182 in the trigger supporting structure 102 so that its rearward end engages the forward surface of the trigger 82. The forward end of the threaded member 180 extends concentrically through a bore in an adjusting knob 184. The knob 184 has an enlarged knurled portion received in a slot 186 in the trigger support structure 102. The threaded member has a sliding t in such knob and has a pin 188 (Fig. 8) extending through its forward end and received in a diametrically extending slot 190 in the bore in the knob 184. It will be apparent that rotation of the knob 184 will rotate the threaded member 180 to move such threaded member either toward the trigger 82 or away from such trigger so as to vary the stroke of the trigger. That is to say, the rearward motion of the trigger is limited by engagement of the trigger with the rear end of the slot 108 and its forward motion is limited by engagement with the rear end of the threaded member 180. Adjusting the stroke of the trigger 82 will also adjust the stroke of the sliding member 84 to thereby vary the stroke of the fuel pump and the amount of fuel charge jetted through the nozzle orifice 172 for one stroke of the trigger.

Charge forming and fuel inlet structure In order to deliver fuel to the inlet of the explosion chamber 40 of Fig. 6, the forward end of the pump casing 86 and the nozzle member 178 project into a slot 192 in the lower forward portion of the body member 20. The nozzle orifice 172 as shown in Fig. 7 is aligned with and positioned concentrically with a valve seat member 194 positioned in the forward portion of the body member in front of the slot 192 in the portion of such body member which forms the rear head for the cylinder member 22. Such valve seat member is secured in a bore 196 in the body member 20 which extends from the slot 192 into the interior of the cylinder member 22. The valve seat member 194 has a spider portion 198 shown most clearly in Fig. 9 which has a bore receiving and guiding the stem 200 of an inlet valve 202 which is spring-urged to closed position by a coiled compression spring 204 surrounding the valve stem 200 and extending between a spring retainer washer on the valve stem and the spider portion 198 of the valve seat member. The nozzle orice 172 jets fuel into the interior of the valve seat member 194 and onto the surfaces of the spider member 198, the valve stem 200 and the spring 204. A very small amount of fuel, for example, four or five drops is involved in each fuel feeding operation. Upon subsequent movement of the piston 28 in the cylinder member 22 from the position shown in Fig. 5 to the position shown in Fig. 6 as described above, the inlet valve 202 opens by reason of reduction of pressure in the explosion chamber 40 and air is drawn through the valve seat member 194 from the slot 192. Such opening of the valve 202 occurs immediately after the jetting of the fuel into the valve seat member 194, since motion of the trigger 82 causes the jetting of the fuel and continued motion of the trigger 82 actuates the locking member 74 to release the stop member 72 and thereby allow the piston 56 to move the piston 28 to its intermediate position.

Fuel supply tank As shown in Fig. 5, a fuel supply tank is provided by a cavity 206 in the handle 21 of the body member 2O of the tool. Such cavity may be closed at its lower end by a screw plug 208 threaded into an opening at the lower end of the handle to constitute a filler plug. The upper end of the cavity 206 has a threaded bore 210 communicating with the duct 146 leading to the fuel pump. The upper end of a fuel supply tube fitting 212 is threaded into the bore 210. A fuel supply tube 214, also shown in Fig. 12, is secured to the lower end of the fitting 212 and has a plurality of perforations 216 spaced along its length for entrance of liquid fuel into the tube 214. The open lower end of the tube 214 as well as the portion of the tube containing the perforations 216 surrounded by a tubular screen or gauze member 218 and the resulting assembly including the lower end of the fitting 212, the tube 214 and the gauze member 218 is positioned between two layers of felt 220. The felt layers are held in position by a pair of metal plates 222 engaging the exterior surfaces of the felt layer and secured together by screws 224 extending through the plates and the felt layers. The metal plates have longitudinally extending arcuate center portions 225 forming an enlarged center chamber between the plates for receiving the gauze member. The felt layers 220 extend substantially the entire vertical length of the cavity 206 and also extend across such cavity so as to be in contact with any liquid fuel in the cavity in any position of the tool. The fuel employed is usually ordinary gasoline and upon reduction of pressure in the pumping chamber formed by the bore 158 in the sliding member 84 of Fig. 7, fuel is drawn into the pump mechanism. The felts 220 maintain a supply of fuel immediately adjacent the tube 214 so that fuel is supplied to the tool by the fuel pump in any position of the tool. The cavity 206 may be filled with fuel by inverting the tool and removing the filler plug 208 in the lower end of the handle.

Ignition system As shown most clearly in Fig. 5, the open top of the cavity 70 in which the stop member 72 and plunger 64 attached to the cylinder 56 reciprocate is closed by a cover plate 226. The upper portion of the rear end of the body member 20 has an upwardly projecting lpoi'tion- 227" forming the rear wall of la casing for receiving an ignition=battery`228g which, for example, may be a 45 volt battery ofthe type employed in hearing aids. Thebody member also has an upwardly projecting portion 229 adjacent its forward end forming the forward wall' ofl such receptacle. An iginition switch 230 is secured in position in suchreceptable forwardly of the battery'228 by a bracket 232 which is suitably secured to the switchand to-the portion 229 of the body member 20. Such bracket also supports a terminal member 234 of'insulatingmaterialhaving terminals for making connection to thebattery. 228. rEhe switch 230-may be of the single pole double throw type actuated by a spring lever 236 having |a roller 238 positioned in the path of an inclined surface on the upper portion ofthe stop member '72 carriedlby the plunger 64 attached to-the piston 56. When the piston 56 moves from the position shown in Fig. 5 to that shown inI Fig. 6, the stop member 72 cams the roller 238 upwardly to actuate the switch 230.

Thebattery 228 and switch 230 are covered` by a removable cover plate 240 having top and side portions extending between the upwardly projecting portion 227 at the rear of the body member 20 and the upwardly projecting portion 229 of the body member adjacent the front ofY thebody member. The portion 229 has alaterally extendingbore 244 for receiving a capacitor 246 forming part of the iginition system and also a larger laterally extending bore 248 for receiving an ignition coil 256. The ignition system including the parts just described, furnishes high voltage electrical energy to a spark plug 252, shown in Figs. 2, 4 and 6. rl`=he spark plug extends through the portion of the body member 2t) which forms the rear head for the cylinder member 22. It will be apparent from the position of the spark plug 252 shown in'Fig. 4 that the electrodes thereof are radially displaced from the rearwardly projecting portion 61 of the piston-28.

The bores 244` and 248 for securing the capacitor 246 and coil 250 respectively, open through one side of the portion 229 of the body member 2)` and such openings are closedy by a cover plate 256 (Figs. 2 and 4) througl which the conductor 258 from the ignition coil 250- to the lspark plug 252 extends. It will be understood that suitable bores will be provided in the portion 229 of the body member 26 containing the capacitor 246 and ignition coil 250 for conductors connecting such elements to the switch 230 and battery 228. A single pole double throw manually actuable switch 260if may also form part of the iginition system and may, for example, be mounted in the cover plate 240 for the battery 228 and switch 230. Such switch constitutesa safety switch for the tool and also completely disconnects the battery to prevent any leakage of current through the capacitor' 246 from discharging the battery when the tool is not in use.

A schematic diagram of the ignition systemy is given in Fig; 13 including the battery 228, capacitor 246, ignition coil 250, switch 230 and spark plug 252. The switch 230` actuated by the stop member 72 is in the position shown in Fig. 134 when the stop member isin itsrearmost position shown in Fig. 5. The manually actuatable safety switch 260 is closed Whe-n the tool is in condition, for firing. Under these conditions, the capacitor 246 is charged from the battery 228 through the current limiting resistor 262. When the stop member 72 moves to the position shown in Fig. 6 upon being released from the locking member 74 by -the actuation of the trigger 82, thev switch- 2302 is actuatedy to disconnect the capacitor 246 from the batteryv 2283 and connect it to the primary of the coil 250?. This discharges the capacitor through the primary of the coil and delivers a high voltage pulse from` the secondary to the spark plug 2'52 to tire the charge-in the explosion chamber. With the circuit shown, acommercially available 45-' volt battery designed for hearing aids will provide many. hours of operation. The

i capacitor 246- may be of theelectrolytietype and Whel the switchr 2601is in the open position or. oi" position, the capacitor 246.. is isolated from the battery. 228. 'Flic ignition coil 250 may be a commerciallyY available, coil of the type employed in electronic flash devices: for photography or in ignition systems for model airplanes.

Limb cutting adapter In Figs. 1 to 3, the tool of the present invention` is shown as being equipped with- .an adapter for driving studs of the general type shown at 52. Such adapter includes the casing 26 and the plunger 46 securedto the plunger 32 which is attached to the piston 28.. To illustrate that the tool of the present inventiony may be employed to actuate other devices, a device forcutting brush or cutting olf tree limbs is shown inl Fig. 14. In such structure, a modified form of casing 264- is. atttachedy to the plunger guiding memberv 24 of the tool. t0 form a guide for a blade operating plunger 266.- The plunger 266 has its rearward end normally in contact` with an anvil member 268 secured to the forwardv endi of the plunger 32 `driven by the piston 28- of -the toolr, The casing 264 has a limb holding forked member 270= suitably secured to its forward en'd, such holding member providing a guide for a. knife member 272l mounted on the forward end of the plunger 266 and havinga bifurf cated hooked portion 274 for holding a limb 276I to be cut olf. The plunger 266: has a collar portion 278 positioned in an enlarged bore 280 in Ithe casing,- 264 -so as to be guided in such bore and the plunger 266 is urged -to a rearward position to engage the anvil member 268 by a coiled compression spring 282 positioned in the bore 280 and having its ends bearingagainst. the collar member 278 .and the limb holder 270. It will. be apparent that driving of the knife 272 forwardly bythe piston of the tool will cause it to cut off the limb 27.6. In case a single impact is not suicicnarepeated impacts may be employed. If the knife 272 wedges in the limb 276 so as to be retained in its forward position, the plunger 32 of the tool is nevertheless returned toits normal position by the spring 36 so as to enable the tool to continue operation to furnish impacts, each of which is controlled by the operator of the tool.

Operation The operation of the tool shown in the various drawings should be apparent from the above description. The normal position of the parts of the tool. whenready for operation is illustrated in Figs. 5 and 7. In such position of the parts, the auxiliary piston 56 and asso.- ciated plunger 64 and stop member 72 are in their rear position and are held in such position by the pivoted locking member 74. If, for any reason, the piston 56 is in itsV forward position shown inv Fig. 6 it may be manually moved to its rear position by the operator grasping the external projecting portion of the manual cocking member 73 (Figs. 1, 3, 4, and l1.) and moving` such member rearwardly. The locking member 74 (Fig. 5') is napped into position by the spring to engage the projection 76 on the stop member 72 to retain 'the piston 56 in its rearmcst position. Under these conditions the pistonV 28 is in its rear position shown in Fig. 5.

If the tool has been out of use for a period of time., the manually actuatable plunger 124 of the fuel` pump mechanism may be moved forwardly by the operator and allowed to return under action of the spring 112 to prime the fuel pump and insure that there is a supply of gasoline in the pumpingv chamberl 158. Such. manual actuation of the plunger 124 may be repeated until a small amount of gasoline is jetted from the nozzle orifice 172 into the valve seat member 194. The fuel pump under these conditions Works as an ordinary piston pump. The pump plunger 132 is rigidly connected -to the plunger 124` and has its forward end received in `the bore 158 (Fig. 7) forming a pumping chamber in the sliding mem` 'Der 84. The two check valves 150 and 174 in the rear pump plunger 132 and stationary member 164, respectively, act as inlet .and outlet valves, respectively. The pump thus draws liquid fuel from the cavity 206 in the handle 21 through the tube 214 (Fig. 5), fitting 212, duct 146, annular groove 144, annular duct 142 (Fig. 7) and duct 148 leading to the check valve 150. When any air has been cleared from the pump mechanism so that the pump cylinder 158 is full of fuel, the manually controlled ignition switch 260 (Figs. 2, 4 and 14) is mofved from the olf position to the on position to condition the ignition system for operation and the tool is ready for tiring.

To fire the tool the trigger 82 is manually moved by the linger of the operator from the forward position shown in Fig. 5 to the rear position shown in Fig. 6. The rearward motion of the trigger 82 first moves the sliding member 84 of the fuel pump (Fig. 7) rearwardly with respect to the rear pump plunger 132 which is held stationary in the casing 86 by the pin 126 and the'plunger 124. The sliding member 84 also moves rearwardly with respect to the stationary member 162 which is held stationary in the casing 86 by the key 168. The differential piston areas provided by the ends of the plunger 132 and of the stationary members 164 which form the end walls of the pumping chamber in the bore 158, produce a decrease in the volume of such chamber and cause jetting of fuel through the nozzle orifice 172 into the interior of the valve seat member 194. The amount of such fuel is determined by the stroke of the sliding member 84 and such stroke may be `adjusted by adjusting the stroke of the trigger 82 by turning the threaded member 180 by the knob 184. Actuating of the trigger thus introduces a measured amount of liquid fuel into the valve seat member 194 adjacent the path of a stream of air -immediately thereafter drawn into the explosion chamber 40 in the cylinder 22.

Continued motion of the trigger carries the upper projection 88 of the sliding member 84 to engage the pivoted element 96 on the locking member 74 to pivot such locking member in a counterclockwise direction and release its rear end from the projection 76 on stop member 72. The spring 62 positioned in the bore 60 then moves the piston 56 and associated plunger 64 and stop member 72 forwardly against the action of the spring 36 from the position shown in Fig. 5 to the position shown in Fig. 6. During this motion, the gas pressure is reduced in the explosion chamber 40 so that the spring loaded air inlet valve 202 opens to allow air to enter the explosion chamber from the slot 192 through the valve seat member 194. The fuel previously jetted into the valve seat member 194 is evaporated into the air entering the explosion chamber 40 so that an explosive charge of air and fuel is produced in the explosion chamber. It has been found that the amount of fuel jetted into the 'air passage immediately adjacent the inlet valve 202 is not critical so long as enough fuel is supplied, although there is, of course, no useful purpose served in furnishing a large excess of such fuel. lt has also been found, for example, that an amount of liquid fuel equal to four or five drops is sufficient for a tool providing an explosion chamber of approximately 30 cubic inches. Such manner of forming the explosive charge has been found to be effective and reliable in operation.

As soon as the pistons 56 and 28 approach the position shown in Fig. 6, the stop member 72 attached to the piston 56 engages the roller 238 of the switch 230 to cam it toward the body of such switch. This actuates such switch to connect the charged capacitor 246 to the primary of the ignition coil 250. A spark is thereby pro duced at the electrodes of the spark` plug 252 to fire the charge. By actuating the ignition switch by the member which moves the piston 28 to its firing position, the charge is tired immediately upon its formation in the explosion chamber and before the fuel vapors of such charge have had an opportunity to condense out on the walls of the explosion chamber 40 to render the charge nonexplosive. Such condensation will take place rapidly, since the walls of such explosion chamber remain relatively cool even though the tool is fired manually as rapidly as possible. That is to say, the time required for the various parts to return to their initial position and for the capacitor 246 to be charged and the trigger to be again manually actuated, provides sufficient time for the cylinder walls to cool after each explosion.

As the result of the explosion in the explosion chamber 40, the piston 28 is driven farther forwardly in the cylinder member 22 from the position shown in Fig. 6 to cause the plunger 32 to deliver an impact against or through any operating instrumentality connected to the tool. During movement of the piston 28 forwardly of the cylinder member, air in the forward end of the cylinder member 22 is exhausted through the ports 44 until such ports are closed by the piston 28. As soon as the piston 28 closes or passes such ports 44, air is entrapped in the forward end of the cylinder member 22 to cushion the stopping of the piston 28. The explosion will ordinarily drive the piston 28 past the ports 44 to the dotted line position indicated at 42 so that exhaust gases are exhausted through the ports 44 to reduce the pressure in the cylinder member 22 at the rear of the piston 28.

Another result of the explosion in the explosion chamber 40 is to drive the piston 56 rearwardly from the position shown in Fig. 6 to the position shown in Fig. 5. The piston 56 arrives at its rearmost position at about the 'same time as the piston 28 arrives at its most forward position. ln the rearmost position of the piston 56, the exhaust port 81 is uncovered so that exhaust gases are exhausted from the explosion chamber 40 as the piston 28 is returned rearwardly of the tool by the spring 36. Even if the forward movement of the piston 28 past the ports 44 is prevented by resistance to travel of the plunger 32 by an operating instrumentality connected thereto, the gases trapped in the explosion chamber 40 will be exhausted through the port 81 so that the piston 28 can be returned to its initial or normal position shown in Fig. 5 by the spring 36. Movement of the piston 56 in the bore 60 in the body member 20 of the tool is facilitated by the vent port 63 and such port may be a size causing it to act as a metering port to regulate the speed of travel of the piston S6 and cushion its stopping.

When the piston 56 is thus driven rearwardly, it is held in its rearward position by the locking member 74 irrespective of whether the trigger 82 is immediately released by the operator of the tool. The upward projection 88 on the sliding member 84 passes beneath the pivoted element 96 when the trigger is actuated. When the trigger is released, the sliding member is returned to its forward position by the spring 112. The upper projection 88 on the sliding member cams the pivoted element 96 upwardly so that the stop member 72 is not again released until the trigger 82 is again moved rearwardly of the tool. Forward movement of the trigger 82 replenishes the fuel in the pumping chamber provided by the bore 158. Also rearward movement of the stop member 72, as the result of the explosion in the explosion chamber 40, again restores the switch 230 to its position shown in Fig. 13. The capacitor 246 is again charged from the battery 228 and the tool is again in condition to be fired.

If the tool should misfire, at any time it can be manually cocked by moving the manual cocking member 73 rearwardly to return the stop member 76 and piston 56 to its rearmost position. If the failure to re is due to a lack of fuel, the manual actuatable pump plunger 124 can be operated to replenish the supply of fuel in the fuel pumping chamber in the bore 158 in the sliding member 84 and it will be apparent that additional fuel may be introduced into the fuel supply tank in the handle 21 of the tool at any time by removing the filler plug 208 therein. The cavity or reservoir 206 inV such handle fwill contain enough fuel for several hours of operation under normal operating conditions. The cost of fuel for each impact is a very small fraction of a cent. The preferred fuel `is a straight run gasoline having aV low octane number as a detonating explosion is advantageous. yPreferably a small amount of lubricating oil is mixed with the fuel in order to lubricate the interior of the cylinder member 22 and, in general, such oilwill' reach the other moving parts of the tool. The proportion of oil to fuel is considerably lower than that required in ordinary rotary two-cycle engines, since the tool runs at a sufficiently low temperature thatthe oil is not burned.

The impact produced by the tool can be employed for any of numerous purposes including the driving of studs with the type of adapter shown in Figs. l to 3, or cutting off limbs or brush with the device shown in Fig. 14.

While we have disclosed the preferred embodiment of our invention, it is to be understood that the details may be varied and that the scope of the invention is to be determined by the following claims.

We claim:

1. An impact tool for delivering impacts each of which is separately manually initiated comprising a cylinder, a piston reciprocable in said cylinder, first meansurging said piston toward one end of said cylinder, second means for moving said piston against the action of said first means away from said end to an` intermediate position in said cylinder to provide an explosion chamber, locking means for locking said second means in inactive position to enable said first means to move said piston to said end, manually controlled means for releasing said locking means to enable said second means to cause movement of said piston to said intermediate position, means for introducing a charge of air and fuel into said chamber during said movementof said piston, and means for igniting said charge when said piston reaches said intermediate position to cause an explosion of said charge and further movement of said piston to provide an impact.

2. An impact tool for delivering impacts each of which is separately manually initiated comprising a cylinder, a piston reciprocable in said cylinder, first resilient means urging said piston toward one end of said cylinder, second resilient means providing a greater force than said first means for moving said piston against' the action of said first means away fromy said end to an intermediate position in said cylinder to provide an explosion chamber, locking means for locking said second means in. inactive position to enable said first means to move said piston to said end, manually controlled means for releasing said locking means to enable said second means to cause movement of said piston to said intermediate position, means for introducing a charge of air and fuel into said chamber during said movement of said piston, and means for igniting said charge when said piston reaches said intermediate position to cause an explosion of said chargeand further movement of said piston to provide an impact.

3. An impact tool for delivering impacts each of which is separately manually initiated comprising a cylinder, a piston reciprocable in said cylinder, first means urging said piston toward one end of said cylinder, second means for moving said piston against the action of said first means away from said end to an intermediate position in said cylinder to provide an explosionchamber, locking means for locking said second means in inactive position to enable said first means to move said piston to said end, manually controlled means for releasing said locking means to enable said second means to cause movement of said piston to said intermediate position, means including a liquid fuel pump actuated by said manually controlled means for introducing a charge of air and fuel into said chamber during said movement of i4 said piston, and means actuated by said second means for igniting said charge when said piston reaches said intermediate position to cause an explosion of said charge and further -movement of said pist-on to provide an impact.

4. An impact tool for delivering impacts ecah of which is separately manually initiated comprising a cylinder, ar piston reciprocable in said cylinder, first means urging said piston toward one end of said cylinder, second means for moving said piston against the action of said first means away from said end to an intermediate position in said cylinder to provide an explosion chamber, locking means for locking said second means in inactive position to enable said first means to move said piston to said end, manually controlled means for releasing said locking means to enable said second means to cause movement of said piston to said intermediate position, means for introducing a charge of air and fuel into said chamber during said movement of said piston, means for igniting said charge when said piston reaches said intermediate position to cause an explosion of said charge and further movement of said piston to provide an imp-act, and means operating as a result of said explosion to return said second meansV to said inactive position.

5. An impact tool for delivering impacts each of which is separately manually initiated comprising a cylinder, a piston reciprocable in said cylinder, first resilient means urging said piston toward one end of said cylinder, second resilient means for moving said piston against the action of said first means away from said end to an intermediate position in said cylinder to provide an explosion chamber, locking means for locking said second means in inactive position to enable said first means to move said piston to said end, manually controlled means for releasing said locking means to enable said second means toy cause movement of said piston to said intermediate position, charge forming means for including an inlet valve for introducing a charge of air and fuel into said chamber during said movement of said piston, said charge forming means also including means for delivering a measured amount of liquid fuel to said inlet valve, means for igniting said charge when said piston reaches said intermediate position to cause an explosion of said charge and further movement of said piston to provide an impact, and means operating as a result of said explosion to return said second means to said inactive position.

6. An impact tool for delivering impacts each of which is separately manually initiated comprising a cylinder, a piston reciprocable in said cylinder, first resilient means urging said piston toward one end of said cylinder, second resilient means for moving said piston against the action of said first resilient means away from said end to an intermediate position in said cylinder to provide an explosion chamber, locking means for locking said second means in inactive position to enable said first means to move said piston to said end, manually controlled means for releasing said locking means to enable said second means to cause movement of said piston to said intermediate position, means for introducing a charge of air and fuel into said chamber during said movement, means actuated by said second means for igniting said charge when said piston reaches said intermediate position to cause an explosion of said charge and thereby cause further movement of said piston to provide an impact, and second piston means operating as a result of said explosion to return saidsecond resilient means to said inactive position.

7. An impact tool for delivering impacts each of which is separately manually initiated comprising a first cylinder, a first piston reciprocable in said cylinder, first resilient means urging said piston toward one end of said cylinder, a second cylinder of smaller diameter than said first cylinder and communicating with said first cylinder, a second piston reciprocable in said second cylinder and having a portion engaging said first piston, second resilient means urging said second piston toward said first piston to move said first piston against the action of said first resilient means away from said end to an intermediate position in said cylinder to provide an explosion chamber, locking means for locking said second piston in inactive position to enable said first resilient means to move said piston to said end, manually controlled means for releasing said locking means to enable said second resilient means to move said second piston and cause movement of said first piston to said intermediate position, means for introducing a charge of air and fuel into said chamber during said movement, means actuated by said second piston for igniting said charge when said first piston reaches said intermediate position to cause an explosion of said charge and thereby cause further movement of said first piston to provide an impact, said explosion also returning said second piston to said inactive position.

S. An impact tool for delivering impacts each of which is separately manually initiated, said tool comprising a cylinder, a piston reciprocable in said cylinder, first resilient means urging said piston toward one end of said cylinder, second resilient means having a movable member for causing movement of said piston away from said one end against the action of said resilient means to an intermediate position in said cylinder to provide an explosion chamber, means for locking said second means in inoperative position, manually controlled means for releasing said second means to cause said movement of said piston, charge forming means for forming an explosive charge of air and fuel in said chamber, said charge forming means including a spring closed inlet valve opened by a drop in pressure in said explosion chamber during said movement of said piston, an air inlet passage leading to said inlet valve, and a fuel purnp actuated by said manually controlled means for spraying a measured amount of liquid fuel into said passage immediately adjacent said valve just prior to the initiation of said movement of said piston, said tool also having means for igniting said charge when said piston reaches said intermediate position for causing an explosion of said charge to thereby cause further movement of said piston away from said end to provide an impact.

9. An impact tool for delivering impacts each of which is separately manually initiated comprising a cylinder,

a piston reciprocable in said cylinder, first means urging i said piston toward one end of said cylinder, second means for moving said piston against the action of said first means away from said end to an intermediate position in said cylinder to provide an explosion chamber, locking means for locking said second means in inactive position to enable said first means to move said piston to said end, manually controlled means for releasing said locking means to enable said second means to cause movement of said piston to said intermediate position, charge forming means for introducing a charge of air and fuel into said chamber during said movement of said piston, said charge forming means including an inlet valve and having an air passage leading to said inlet valve, said valve being opened during said movement of said piston to said intermediate position `to admit a current of air into said chamber through said passage, said charge forming means also having means providing a surface in said passage wetted with liquid vaporizable fuel and positioned to be contacted by said current of air to form said charge, and means for igniting said charge when said piston reaches said intermediate position to cause an explosion of said charge and further movement of said piston to provide an impact.

10. An impact tool for delivering impacts each of which is separately manually initiated comprising a cylinder, a piston reciprocable in said cylinder, first resilient means urging said piston toward one end of said cylinder, second resilient means providing a greater force than said first means for moving said piston against the action of said first means away from said end to an intermediate position in said cylinder to provide an explosion chamber, locking means for locking said second means in inactive position to enable said first means to move said piston to said end, manually controlled means for releasing said locking means to enable said second means to cause movement of said piston to said intermediate position, charge forming means for introducing a charge of air and fuel into said chamber during said movement of said piston, said charge forming means including a spring closed inlet valve opened as a result of a drop in pressure in said chamber during said movement of said piston to said intermediate position to admit a current of air into said chamber and having an air inlet passage leading to said valve for said current of air, said charge forming means also having means providing a surface in said passage wetted with liquid vaporizable fuel and positioned to be contacted by said current of air to form said charge, and means for igniting said charge when said piston reaches said intermediate position to cause an explosion of said charge and further movmeent of said piston to provide an impact.

1l. An impact tool for delivering impacts each of which is separately manually initiated comprising a cylinder, a piston reciprocable in said cylinder, first means urging said piston toward one end of said cylinder, second means for moving said piston against the action of said first means away from said end to an intermediate position in said cylinder to provide an explosion chamber, locking means for locking said second means in inactive position to enable said first means to move said piston to said end, manually controlled means for releasing said locking means to enable said second means to cause movement of said piston to said intermediate position, charge forming means for introducing a charge of air and fuel into said chamber during said movement of said piston, said charge forming means including an inlet valve and having an air passage leading to said inlet valve, said valve being openend during said movement of said piston to said intermediate position to admit a current of air into said chamber through said passage, said charge forming means also having means providing a surface in said passage wetted with liquid vaporizable fuel and positioned to be contacted by said current of air to form said charge, means for igniting said charge when said piston reaches said intermediate position to cause an explosion of said charge and further movement of said piston to provide an impact, and means operating as a result of said explosion to return said second means to said inactive position.

References Cited in the file of this patent UNITED STATES PATENTS 1,802,848 Summers Apr. 28, 1931 2,009,929 Johnson July 30, 1935 2,522,456 Mallory Sept. 12, 1950 2,821,372 Nystrom et al. Jan. 28. 1958

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