US2890685A - Cartridge-powered piston type tool - Google Patents

Description

June 9 P. R. HASKELL ETAL 2,890,635

CARTRIDGE-POWERED PISTON TYPE TOOL Original Filed May 10, 1955 3 Sheets-Sheet 2 m m INVENTORS.

PHILIP/P. HAsKELL. 3 RICHARD E. EVA/V5.

y w. A. KETCHPEQJIF;

LYLE 5. Cam/v0? June 16, 1959 P. R; HASKELL ETAL 2,890,685

CARTRIDGE-POWERED PISTON TYPE TOOL Original Filed May lo, 1955 3 Sheets-She avo7 l u //A INVENTORS PHIL/PE, HAsKELL. RICHAED E. EVA rvs. y PAUL A. KETCHPEL JR. LYLE B. Gav/VOA MM Mr/mm 14/ ATTORNEYS.

Unite States CARTRIDGE-POWERED PISTON TYPE TOOL Philip R. Haskell, Fairfield, and Richard E. Evans, South= port, Conn, Paul A. Ketchpel, Jr., West Englewood, N.J., and Lyle B. Connor, .luno, Fla., assignors to Remington Arms Company, Inc., Bridgeport, Conn, a corporation of Delaware Original application May 10, 1955, Serial No. 507,281. Divided and this application July 26, 1957, Serial No. 674,536

Claims. (Cl. 12324) This invention pertains to improvements in explosively actuated or cartridge powered tools, and provides a tool of this type of unique construction which is characterized by extreme compactness, lightness in weight and ease of manipulation with a minimum of effort, and which furthermore is substantially foolproof.

This application is a division of our copending application Serial No. 507,231, filed May 10, 1955.

In its various modifications the tool of the invention is adapted for performing a wide variety of work functions, such as the cutting of conduit, bar stock and heavy cable, etc., the punching of holes, riveting, the swaging of terminals or sleeves on electrical cables for terminating or uniting the same, the uniting of electrical conduit sections by means of an interposed coupling member, as well as the securing of threaded members on electrical conduit terminations, etc.

The tool of the invention comprises in its essentials and in accordance with a preferred modification, an elongated frame member of steel comprising a tubular or barrel section terminating at one end in a hook-like retainer arm of substantially G-shaped configuration for mounting a work piece to be operated upon. Within the barrel section is slidably displaceable a piston which mounts on its forward end a work tool, such as a cutter blade, hole puncher, cable swager, riveting plunger, etc. The tubular section of the frame is of reduced aperture at its muzzle end to provide a shouldered impact face for arresting forward motion of the piston thereat. The muzzle end is, in addition, appropriately apertured for passage of the work tool therethrough to work engaging position with a work piece held in the retainer arm.

One of the most important of the tools of the invention to which this divisional application is directed, is a novel shock absorbing assembly mounted on the piston for preventing injury to the equipment on impact of the piston with the impact face of the frame, particularly if the tool is fired inadvertently with no workpiece mounted in the retainer arm. This shock absorbing mechanism comprises an elastically deformable member which is adapted to absorb the excess kinetic energy for stopping the piston at the impact face after the work tool has performed its function. The other is a plastically deformable member for absorbing such excess kinetic energy as cannot be taken up by the elastically deformable unit, and which comes into play particularly if the tool is fired with no workpiece mounted in the retainer arm. These two units are mounted in axial alignment on the piston so that the elastically deformable shock absorber absorbs the initial impact to its maximum extent whereupon the residue is absorbed by the plastically deformable component. The elastically deformable unit is of laminated construction and in its preferred embodiment, comprises an axially aligned assemblage of metal rings, preferably of steel, interleaved with which are other rings formed offibrous material impregnated with an elastic polymer, preferably woven nylon fabric impregnated with neoprene.

Having thus described the invention in general terms,

reference will now be had for a more detailed description of the construction and additional novel features of the invention, to the accompanying drawings wherein:

Figure 1 is a longitudinal sectional elevation through the entire tool assembly showing the tool in condition for firing.

Figures 2 and 3 are views similar to Figure l, but subsequent to firing and showing the advance of the piston and cutter assembly in successive stages to the cutting position.

Figure 4 is a partial showing, similar to Figure 1, but illustrating the tool in the cartridge ejecting or loading condition.

Figure 5 is an enlarged longitudinal sectional view'of the piston assembly showing in detail the shock absorbing and safety feature construction; while Figure 6 is an enlarged fragmentary sectional detail showing two of the steel shim laminae and interposed neoprene-impregnated nylon fabric laminae of the shock absorbing assembly of Figure 5.

Figure 7 is a graph idealizing the load-compression characteristics of the shock absorbing constructions of'the Figures 17 and 18 showings.

Figure 8 is a fragmentary, axial sectional elevation of a modified form of the piston and frame assembly 'illustrating the action of the safety feature of the shock absorbing assembly in disabling the tool when fired in the absence of a workpiece.

Figure 9 is a longitudinal sectional elevation of the breech end of the tool, similar to Figure 4, but showing a modification of the cartridge chamber for varying the explosive action from a standard cartridge.

Referring to Figs. 1-4, inc., of the drawings, the conduit-cutting modification of the invention shown comprises a frame, identified generally by numeral 1, consisting of a tubular frame portion 2 extending from the breech end at the left to the muzzle end at the right, and a 0 frame extension comprising a Work support 3 in general longitudinal alignment with the frame portion 2 and connected therewith by a curved shank 3a. The breech end of the frame portion is of slightly enlarged bore as compared to the muzzle end of the frame portion 2 and thus provides a shoulder at 4, against which a rela tively short sleeve barrel 5 is held by means of a barrel plug 6 inserted in the breech endof the frame. In a modified form of the construction shown in Fig. 8, the forward end of the barrel sleeve 5 supplies a forwardly facing shoulder for a purpose to be described below with reference to said Fig. 8. The barrel plug is locked in the position shown by a cylindrical cartridge chamber plug 7, which extends transversely of the barrel axis through suitable holes 8, 9 drilled in the barrel plug and the breech end of the frame portion 2, respectively. The cartridge chamber plug 7 is provided with an enlarged head ltl which seats in a counterbore 11 of the barrel plug, thus to maintain the assembly locked in position as shown in Fig. 1.

The mouth of the chamber plug is radially slotted to receive an ejector (to be described), and to locate chamber plug 7 in proper longitudinal and radial'positio'n'in the bores 8, 9, the cylindrical wall'of the plug is notched for reception of a pin 12;, backed by a small compression spring 13, mounted in an axial bore 13a of the barrel plug 6.

In the firing position shown in Fig. 1, a piston "14 is slidably disposed in'the sleeve barrel 5, and to. which is secured a cutter blade 15 'positioned'in advance of the piston in the frame portion of smaller inside diameter. The cutter blade is slidable in grooves-16, 17 extending along the upper and lower portions of the framebarrel, these grooves being formed as explainedbelow.

The cutter assembly 15 shown as a cutter blade is secured to or formed integral with a shank 18, which extends thIOugh a central sleeve member 18b of the piston 14 and is secured to the piston by means of a piston cap 19 threaded onto the breech end of the shank 18. This piston and cutter assembly will be described more in detail, infra.

For purposes above noted, to be explained in detail below, and as shown in Fig. l, the breech end of the piston cap 19 terminates in a protuberant extension 20 of considerably smaller diameter than the piston 14, which extension in the action or firing position, rests in a conforming bore 20a drilled in the inner end of the barrel plug 6.

Also in the action or firing position of Fig. 1, the piston and cutter blade assembly 14, 15, is resiliently held in place by means of a resiliently mounted detent 26b which engages the upper edge of the cutter blade as shown.

The cartridge chamber 7 has formed in the upper portion thereof a bore 21 for insertion of a blank cartridge, as at 22, the cavity below the cartridge forming an explosion chamber which has access through aligned openings in the sidewall of the chamber plug and the forward end of the barrel plug, as at 2211, 23, to the bore 20a of the barrel plug.

Thus when the cartridge is fired, the piston and cutter assembly 14, 15, is impelled progressively forward as illustrated in Figs. 2 and 3, until the pointed end of the cutter blade has advanced to the position shown in Fig. 3 to sever the conduit as discussed, post. The piston and cutter assembly is thereupon brought to rest by engagement of the forward end of the piston 14 with a shouldered impact face 24 of conforming configuration formed at the muzzle end of the tubular frame section 2, at which the bore is tapered to an outlet passage 25 of relatively small bore through which the explosion gases escape as explained below. The muzzle end of the frame is also vertically slotted to permit advance therethrough of the cutter blade to the conduit cutting position of Fig. 3.

The tubular frame section 2 is longitudinally slotted through its upper surface. Mounted in this slot and partially closing the same is an insert member 38, Fig. 1, which is positioned in engagement with one side of the slot as shown. This insert member is secured to the frame by means of screws as at 39, which extend through holes in the sidewall of frame 2 and into threaded engagement with the insert member 38, thereby clamping the insert member to the frame.

Mounted on the breech end of the cover is the firing unit 55, Fig. l. Mounted adjacent thereto is the cross slide protective device 56 which is transversely adjustable to locking, ejecting and firing positions, and which prevents firing except when adjusted to the position last mentioned. Resiliently mounted on the muzzle end of the cover is a clamping device 57 which clamps the conduit to be cut in the C terminus or work support 3 of the frame when the cover is longitudinally positioned with respect to the frame as shown in Fig. 1.

For limiting the forward displacement of the cover 50 with respect to the frame 1, the insert 38 is provided with a raised portion or shoulder 60 at the muzzle end of the frame section 2, Fig. 1. When the cover is advanced to the position of Fig. 1, this shoulder is engaged by a pin 61 extending transversely along the under side of the cover 50, and mounted in a bore 62, Fig. 1, drilled through the sidewalls of the cover.

For returning the piston 14 from the impact face 24 of the frame barrel 2, against which the piston rests after firing as above explained, a piston return bolt 63 is tapped vertically through the cover as shown in Figs. 1 and 2, with the lower end of this bolt projecting into the slot of the frame for a sufiieient depth as shown in Figs. 2 and 4, to engage the piston as the cover 50 is displaced to the left from the firing position of Fig. 1, to

the cartridge ejecting position of Fig. 4. It will be noted, referring to Fig. 1, that the frame slot extends at the muzzle end of the frame barrel 2, beyond the piston impact face 24, and is thus protected from impact by the piston even if the shoulder 24 is set back by repeated impact.

Referring more particularly to Fig. 6, a shallow axially extending slot 65, is provided in the upper face of the frame section 2 near the breech end, in which is mounted an elongated cartridge ejector 66, which pivots on a pin 67 retained in a transverse bore 68 of the frame. The ejector 66 is actuated by displacement of the cover 50 as follows: As the cover is retracted from the firing position of Fig. 1 to the cartridge ejecting position of Fig. 4, the pin 61 mounted on the under side of the cover, engages a concave cam face 69 of the ejector and rotates it clockwise to the canted position shown in Fig. 4, to eject the cartridge shell 22, through an opening formed in the cover of the cross slide 56. The under face of the frame cover 50 is provided with a sloping ramp, as at 71, to permit of this actuation of the ejector. With the cover in the position of Fig. 4, a new cartridge may be inserted through the cross slide opening, until the rim thereof engages the cartridge ejector end 72 of the ejector, whereupon the frame cover 50 is returned to the position of Fig. 1. As the cover is thus moved into position a second sloping ramp provided on the opposite under side of the cover, as at 73, engages the rim of the cartridge and seats it in the cartridge chamber cavity 28 with the shell rim flush with the upper edge of the cavity as shown in Fig. 1, while at the same time returning the ejector 66 to the cartridge seating position of Fig. 1 as the frame cover pin 61 rides off the cam face 69. In order to provide for seating of both the cartridge shell 22 and the ejector 66 flush with the upper surface of the chamber plug 7, this surface is periperally recessed, as at 70a and radially slotted, as at 70b, Fig. l, appropriately to seat the shell rim and ejector, respectively.

Referring to Fig. 1, the firing unit 55 comprises a housing 74, secured to the frame cover 50, by means of screws. The housing is drilled for axially displaceable reception of a firing bolt or hammer having an intermediate portion 76 of enlarged diameter which is slidably displaceable in the frame bore 76a and from one end of which extends a hammer terminus 77 of smaller diameter, sleeved through a hammer spring 78, housed in an open-ended sleeve-like retainer 79, the inner end of which is threaded to the housing.

From the opposite end of the enlarged hammer portion 76, there extends a second hammer terminus 80 having a flat under face 81 which terminates adjacent the enlarged hammer portion 76, in a stepped cam face 82 for actuating a firing pin 83. interposed in the housing bore between the end of the shank 80 and the bore terminus, is a relatively light spring 84 which is compressed in the firing movement of the hammer and thereafter returns the hammer to normal uncocked position with the shouldered end of hammer enlargement 76 contacting the spring 78 at the housing abutment 790, as seen in Fig. 1.

As shown in Fig. 1, the flat under face 81 of the terminus 80, normally bears against the enlarged head of the firing pin 83, which latter is positioned in a bore extending through the housing 74 and into the frame cover 50. The lower end of the firing pin is of reduced diameter as shown and sleeves through a firing pin spring 85, which is retained in position between the enlarged head of the firing pin and the reduced diameter base of the frame cover aperture, through which the tapered lower end of the firing pin extends into engagement with the rim of the cartridge 22, when the tool is loaded in the manner illustrated.

Referring more particularly to Fig. l, the conduit to be cut, is positioned in the hook-like retainer arm 3 of the tool frame, and against a pair of arcuate bushings 151, 152, these bushings being secured to the rear of the retainer arm by means of a pair of bolts 153, 154, which extend through the rear of the retainer arm and thread into the bushings. These bushings are spaced apart slightly in excess of the width of the cutter blade and the retainer arm or work support 3 of the frame is centrally slotted for passage of the cutter blade in severing the conduit to the position illustrated in Fig. 3. This slot 155 terminates at the rear end of the retainer arm 3 in a vertical bore 156 from which the chips resulting from the severing of the conduit may be dumped by inverting the tool.

As above stated, there is resiliently mounted on the frame cover 50 at the muzzle end thereof, a clamping assembly 57, which includes a metal clamping member 157 of substantially U-shaped configuration viewed in end elevation, and which spans the frame cover 50 and is formed at its opposite ends with turned down or depending arms 153, 159. These arms have the configuration, viewed in side elevation, best shown in Fig. 1, and are provided with arcuately curved lower front edges, as at 16%, adapted to engage the surface of the conduit 150 and thereby force the same against the bush ings 151, 152. The clamping member 157 is loosely secured to the frame cover 5G by means of a guard screw 161 which passes through an overs'me central aperture of the clamping member, and is threaded into the frame 50. Adjacent the guard screw the clamping element is provided with a struck-up, apertured portion, as at 162, in which is mounted a resilient cushioning element 163 of rubber or equivalent, which rests on the top of the frame cover 50, and thus resiliently supports the clamping member 157 in spaced relation to the frame cover 50. As the frame cover is moved to the firing position of Fig. 1, the arcuate edges lot} of the clamping element arms 158, 159, engage the conduit 150 and force the same against the bushings 151, 152, and in so doing rotate the clamping element 157 clockwise about the axis of support provided by the guard screw 161, whereby the cushioning element 163 is flattened somewhat from the position of Fig. l to that of Fig. 3, thus resiliently clamping the conduit 150 in position in the manner shown in Fig. 3.

To further assist in the supporting and clamping of the conduit, there is mounted at the base of the frame arm 3, an arcuately surfaced segment member 164, held in position by a bolt 165 threading into the base of the frame arm 3, this segment being centrally slotted to provide passage of the cutter blade past the same. The arcuate face 167 of this segment supports the underside of the conduit in the manner best illustrated in Fig. 1. After the conduit is severed by the cutter blade in the manner illustrated in Fig. 3, retraction of the frame cover 5th of course, retracts the clamping element 157 along with it, thus to permit of inserting a new conduit section in the frame arm 3 to be cut.

Referring to Fig. 1, it will be observed that when the cover 50 is advanced to the firing position, the forward end of the cover covers the open 0 of the hooklike retainer arm 3, so that the cover is thus in this closure position whenever the conduit is to be severed. As thus closed the cover insures that the conduit cannot be half-in and half-out of the die bushings 151, 152, when the tool is fired. The frame cover 50 as thus closed automatically and safely covers the region into which the shear cutout conduit chips are thrown, and permits them to be dumped out when the cover is open. The operator is thus shielded against flying chips of metal.

To insure that the work is out completely through, it is necessary to impart to the piston and blade assembly an excess of say 25% of the energy actually required to sever the work or to perform other operations heretofore outlined, and, to stop the movement of the piston and tool assembly after its work is completed, a buffer 6 is associated with this assembly. In a preferred form of the invention, this buffer comprises two elements, the first being a stack of radially elastically deformable members and the second a ring spring type of assembly comprising one or more members which are radially elastically deformed and under excessive stress undergo a plastic deformation. Such excessive stress may be applied when the tool is inadvertently fired without a workpiece in place. Under these conditions the buffer assembly must absorb the entire kinetic energy of the piston and blade assembly, there being no other resistance to the forward movement of this assembly. The construction of the tool may be such that plastic deformation of the ring spring disables the tool, in a manner to be described, both indicating that the tool has been fired without a workpiece in place and necessitating replacement of the plastically deformable ring. As particularly shown in Fig. 5, the elastically deformable shock absorbing component is identified generally by numeral 179 and the elastically and plastically deformable member by numeral 180. The function of the elastically deformable shock absorbing component 179 is to absorb the excess kinetic energy of the piston, over and above that required to sever the conduit when the tool is fired and the piston impelled thereafter against the impact surface 24 of the frame. The function of the plastically deformable member 180 is to absorb the excess kinetic energy of the piston on firing, which is not taken up in severing the conduit, and in elastic deformation of the shock absorbing member 179, such as occurs, for example, if the tool is inadvertently fired with no conduit in the retainer arm.

In order for the elastically deformable shock absorbing component 17 9 satisfactorily to perform its function above stated, it must be designed to meet two rigid requirements. First, the compression modulus of elasticity of this member must be such as to decelerate the piston without exceeding the tensile strength of the blade. In this connection it will be observed that upon impact of the piston against the frame impact face 24, tending abruptly to stop the piston, the inertia of the blade places the same under tension so that if the piston is stopped too abruptly, the cutter blade will fail in tension. Therefore the shock absorbing component 179 must have a modulus of elasticity which is sufliciently low as to decelerate the piston at a rate sufficiently low that the tensile strength of the cutter blade is not exceeded. The second requirement which the shock absorbing component 179 must meet is that it must be capable of sup porting a compression load equal to the tensile strength of the blade. This is explainable as follows: As the front face of the piston impacts the frame impact face 24, the shock absorbing component becomes analogous to a compression spring, the rear end of which is connected to, and compressed by, the piston cap 19 threaded onto the terminus of the blade shank 18. The momentum of the blade is thus resisted by the force exerted by the spring as it is compressed. If this spring has too high a compression modulus, the blade will fail in tension. Metal springs, even in coiled forms of low modulus, have nevertheless too high a compression modulus, and, being made of metal, a shock wave is built up that outraces the load velocity and sets the spring. On the other hand, solid plastics have too high a compression modulus, and, in addition, cannot withstand the compressive forces which their high modulus quickly produces. For example, leather approximates a satisfactory modulus, but fails in compression loading during repeated cycles, because its outer tough fibers break loose from their supporting matrix. Rubber and rubber-like material, including the synthetic rubbers such as neoprene, display a compression modulus somewhat under that of leather, so that considerably more stroke is required to store the same energy. While rubber and equivalent materials can withinstand heavy loading with elastic recovery, they require support within a container both to raise their natural modulus and to prevent shredding failure under load. As thus compressed in a container, for example, in a steel sleeve, rubber behaves like an incompressible fluid, exerting tremendous hydraulic pressure on the surrounding container. The strength of the retainer thus required cannot be provided in a tool of reasonable size.

In accordance with one aspect of the present invention, this problem is successfully solved in a compact structure by making the elastically deformable component 179 of a laminated construction and consisting of a series of axially aligned metal rings 181, such as steel shims, which are inter-leaved with other rings 182 formed of woven fabric, preferably woven nylon fibers, which are impregnated with an elastic polymer, preferably neoprene. This laminated arrangement is assembled, in axial alignment as shown, on a steel assembly tube 18b between an impact plate 184 mounted on the forward end of the assembly tube and an annular spacer member 185 assembled on the rear end of the assembly tube. To facilitate this assembly, the assembly tube is formed with a flanged terminus 186 at its rear or left end in the drawing and the spacer member 185 is formed with a conforming axial counterbore, which seats against this shoulder. The assembly tube at its opposite end is crimped up against the impact plate 183 as at 187, thus to lock the entire assembly together.

In this assembly, in the elastic polymer-impregnated fabric rings 182, such as the neoprene impregnated woven nylon fibers, the fibers act as stay bolts to hold the elastic polymer or neoprene from expanding, and thus absorb the lateral strain on these rings resulting from impact of the piston against the frame impact face 24. Neoprene has been found to be a convenient elastic binder for nylon fibers, and thus facilitates the establishment of a synthetic modulus of elasticity which neither the nylon alone nor the neoprene alone can possess. The surface of the steel shims separating the layers of impregnated fabric are preferably roughened, as by sandblasting. These shims frictionally support the fabric layers, giving added strength and retarding radial expansion; their friction against the fabric also dissipates a substantial amount of energy. When, as illustrated, the ring spring is used in conjunction with the stack, the stack is of such length and construction as to sustain without plastic flow a compression substantially equal to that which will initiate elastic deformation of the ring 180.

Referring to Fig. 7, by appropriately dimensioning the elastic polymer impregnated fabric rings 182 in relation to the metal rings 181, the modulus of elasticity 188 of the plastically deformable member 180 may be sloped as desired within limits, thus to adjust the deceleration of the piston in accordance with the requirements above stated.

Because of the requirement that the piston weight be minimized, the amount of elastic shock absorption that can be built into the shock absorbing component 179, is limited, and the excess must be taken up by the plastically deformable member 180, both as regards excess kinetic energy resulting from the conduit severing operation, and more particularly as regards the excess kinetic energy resulting from inadvertent firing of the tool with no conduit mounted in the retaining arm. This latter is strictly a protective feature to prevent injury to the cutting blade, piston and the tool itself resulting from such inadvertent firing. To this end the plastically deformable member 180 comprises a ring made of a malleable metal like aluminum or an aluminum alloy of such dimensions that it will fail in compression before the other tool components will fail in tension. That is to say, the compression strength of the plastically deformable member 18!} must be substantially less than the tensile strength of the tool frame, cutting element and piston. It will be noted in this connection that when the piston impacts the frame impact face 24, the tubular portion of the frame is placed under tension. Likewise, as above explained, the cutting element is placed under tension due to its inertia. As shown in Fig. 5, the plastically deformable member of malleable metal is of trapezium configuration, as viewed in axial section, and is mounted between the spacer member and the piston cap 19, both of which are made of a metal having a high elastic limit, such as steel. The abutting surfaces 190, 191, between the plastically deformable member 180 and the adjacent steel spacer and piston cap members 185, 19, are preferably sloped in accordance with the minimum slope or friction angle of the contiguous metals, i.e., aluminum vs. steel in the preferred modification as above mentioned, thus to enhance the energy absorption by the malleable metal plastically deformable member 180 as the latter is plastically deformed, and squeezed from the full line sectional area 180 to that of the dotted line 180a.

Thus the camming angles of the sloped surfaces 190, 191, approximate the friction angles between the contacting metal surfaces, so that the yield strength of the plastically deformable member 180, is mechanically increased by the friction. The plastically deformable member 180 shown, approximates a rectangular stress-strain diagram for maximum etficiency of energy dissipation as a function of piston stroke. The maximum force developed thereon accordingly never exceeds a value exceeding the tensile strength of the cutter blade and shank.

Referring again to Fig. 7, the plastic deformation of the member 180 may be designated to occur at any given load level such as 192. As a result, therefore, of the composite assembly comprising the elastically deformable shock absorbing component 179 and the plastically deformable energy absorption member 180, the composite load compression graph thereof will be approximately as indicated at 188, 192 of Fig. 7. That is to say, as the piston impacts the frame shoulder, the impact of the piston against the shoulder will at first be gradually absorbed by elastic deformation of the shock absorbing member 179, along the line 188, until a load corresponding to the level 192 is reached, whereupon the additional load will be assumed by plastic deformation of the plastically deformable member 180 which holds the load substantially constant thereafter at the level 192 as shown in Fig. 7.

It should be noted that in the ordinary usage of the tool the plastically deformable member 180 is not deformed beyond its elastic limit and that it is only in the event that the tool is operated without a workpiece in place that the stress applied to this ring is suflicient to plastically and permanently deform it. Under some conditions, it is desirable that such permanent deformation of the plastically deformable member 180 be indicated and disable the tool until the ring is replaced. This can be accomplished by providing that permanent deformation of the plastically deformable member 180 increases its diameter beyond the bore diameter of the barrel sleeve 5 in the manner illustrated in Fig. 8. In this condition, when an attempt is made to retract the piston to firing position, the margin of plastically deformable member 180 engages the end of the barrel sleeve 5, preventing complete retraction of the piston.

Reverting to Figs. 5 and 6, While the elastically deformable component 179 is a buffer and preferably comprises layers of impregnated fabric alternating with metal shims, under some conditions it is possible to omit the shims and place successive layers of impregnated fabric in face-to face relation. It is essential, however, that the bufiier comprise a plurality of rings or disks of fibrous material held in an elastic impregnating medium, such that the transversely disposed elastic fibers and the elastic impregnant interact to oppose radial deformation while enabling the required longitudinal deformation.

The piston impact plate 184 is likewise preferably made of a malleable metal like aluminum or an aluminum alloy, having a compression strength substantially below that of the metal of the frame 11, which latter is made of steel. The purpose of this is to assure that the impact plate will fail through compression before the steel frame is broken under tension, this being an additional safety precaution in the piston construction. Moreover, the stress incident to stopping the piston assembly, either in normal usage or in firing without a workpiece, is received by the main frame 2, and not by the work support .3, thus avoiding any bending stress in the curving connecting shank 3a.

Reverting to Fig. 1, the tool is provided with a handle 2&0 of wood, hard rubber or equivalent, which is assembled on the under side of the tubular frame section 2, by means of bolts, as at 201, 202, threaded into the frame.

What is claimed is:

1. A powder actuated device comprising a frame having therein a barrel bore of two diameters joined by a shoulder, a piston assembly in said bore adapted for movement from a normal retracted position through a Working stroke and return to normal position, said piston assembly including a buffer, said buffer comprising a plastically deformable element which passes said shoulder in the forward and return movements of said tool assembly, said plastically deformable element being adapted for radial deformation under excessive stress to a diameter such that it engages said shoulder and blocks the return of said piston assembly to said normal position.

2. An explosively actuated tool including: a barrel extending from breech to muzzle thereof, said barrel being of one diameter over a portion thereof adjacent said breech and of larger diameter over the remaining portion thereof extending to said muzzle, said two diameters being joined by a shoulder portion, a piston in said barrel adapted for movement from a normal retracted position adjacent said breech through a working stroke to engagement with a stop adjacent said muzzle and return to said breech, said piston mounting a buffer comprising an elastically deformable shock absorbing member and a plastically deformable shock absorbing member mounted in axial alignment on said piston, said plastically deformable member being adapted for permanent radial deformation under excessive stress to a diameter such as to engage said shoulder and block the return of said piston assembly to said normal position.

3. An explosively actuated tool including: a barrel extending from breech to muzzle thereof, said barrel being of one diameter over a portion thereof adjacent said breech and of larger diameter over the remaining portion thereof extending to said muzzle, said two diameters being joined by a shoulder portion, a piston in said barrel adapted for movement from a normal retracted position adjacent said breech through a working stroke to engagement with a stop adjacent said muzzle and return to said breech, said piston mounting a buffer comprising an elastically deformable shock absorbing member and a plas tically deformable shock absorbing member mounted in axial alignment on said piston assembly, said plastically deformable member being adapted for permanent radial deformation under excessive stress to a diameter such as to engage said shoulder and block the return of said piston assembly to said normal position, said plastically deformable member comprising a relatively thick ring of 10 a malleable metal interposed in axial alignment on said piston between backing members of a stronger metal which is resiliently deformable beyond the stress which produces permanent plastic deformation of said ring.

4. A powder power actuated tool including a barrel extending from breech to muzzle thereof, said barrel being of one diameter over a portion thereof adjacent said breech and of larger diameter over the remaining portion thereof extending to said muzzle, said two diameters being joined by a shoulder portion, a piston in said barrel adapted for movement from a normal retracted position adjacent said breech through a working stroke to engagement with a stop adjacent said muzzle and return to said breech, said piston mounting a buffer comprising an elastically deformable shock absorbing member and a plastically deformable shock absorbing member mounted in axial alignment on said piston, said plastically deform able member being adapted for permanent radial deformation under excessive stress to a diameter such as to engage said shoulder and block the return of said piston assembly to said normal position, said plastically deformable member comprising a relatively thick ring of a malleable metal interposed in axial alignment on said piston ibetween backing members of a stronger metal which is resiliently deformable beyond the stress which produces permanent plastic deformation of said ring, said ring abutting said backing members along radially inclined surfaces of greater axial spacing adjacent the outer than adjacent the inner periphery of said ring.

5. A powder power actuated tool including a barrel extending from breech to muzzle thereof, said barrel being of one diameter over a portion thereof adjacent said breech and of larger diameter over the remaining portion thereof extending to said muzzle, said two diameters being joined by a shoulder portion, a piston in said barrel adapted for movement from a normal retracted position adjacent said breech through a working stroke to engagement with a stop adjacent said muzzle and return to said breech, said piston mounting a buffer comprising an elastically deformable shock absorbing member and a plastically deformable shock absorbing member mounted in axial alignment on said piston assembly, said plastically deformable member being adapted for permanent radial deformation under excessive stress to a diameter such as to engage said shoulder and block the return of said piston assembly to said normal position, said plastically deformable member comprising a relatively thick ring of a malleable metal interposed in axial alignment on said piston between backing members of a stronger metal which is resiliently deformable beyond the stress which produces permanent plastic deformation of said ring, said ring abutting said backing members along radially inclined surfaces of greater axial spacing adjacent the outer than adjacent the inner periphery of said ring, said surfaces being inclined substantially in accordance with the minimum friction angle between said ring and backing members.

Switzerland Sept. 1, 1934 Great Britain Sept. 1, 1954

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