Powder Actuated Tool

Abstract

A captive piston type of powder actuated tool is provided with a barrel pivotally engaged by the forward end of the tool housing so that the breech end of the barrel can be upraised into a loading position. A piston retractor is slidably carried on the barrel and includes a member extending through a slot in the barrel for engaging the head of the piston used for moving of a piston into a firing position. The barrel may be pivotally returned to firing position only after the piston retractor has been moved forwardly and out of the way of piston movement in the subsequent firing of the tool.

Description

BACKGROUND OF THE INVENTION

Piston type explosively actuated tools, e.g. for driving fastener devices into concrete or masonry walls, conventionally employ a blank cartridge for providing the explosive gases applied to drive the fastener device. Such a tool is cocked by pressure of the muzzle against a workpiece or wall, resulting in movement of the tool's breechblock into a firing position. A cartridge may then be fired to force the captive piston through the barrel and drive the fastener device. After firing, the barrel and the breechblock are conventionally separated so that a new cartridge or power load may be inserted, and the captive piston must be returned to its firing position. Various constructions have been employed heretofore to facilitate the loading and piston return operations. The barrel may be rotated laterally to the side of the tool facilitating the removal of the captive piston to a firing position and insertion of a new load. Alternatively, the barrel may be movable longitudinally forward of the tool for retraction of the piston and reloading. In the case of these constructions and other similar arrangements, the tool mechanism is apt to be quite complex and/or somewhat unbalanced.

SUMMARY OF THE INVENTION

According to the present invention a powder actuated tool comprises a housing including a rearward breech portion and a forward barrel portion. The tool's barrel is cradled by the barrel portion when the barrel is in a first position in substantial alignment with the tool's breechblock. The barrel is pivotally engaged by the barrel portion at a forward location so that the breech end of the barrel can be pivotally upraised away from the breechblock into a loading position. The tool further includes a piston retractor slidably carried by the barrel, which retractor includes a member for engaging the piston, and a handle portion which is manually engageable for moving the piston retractor. The piston may be moved thereby to a firing position toward the breech end of the barrel. The retractor and housing construction prevent the barrel from being pivotable back into firing position in alignment with the breechblock until such retractor is moved forwardly out of the way of the captive piston, allowing firing of the tool. The tool is compact, and movement of component parts thereof is reduced to a minimum.

It is accordingly an object of the present invention to provide an improved powder actuated tool of the captive piston type which is better balanced, more compact, and more easily manufactured.

It is a further object of the present invention to provide an improved powder actuated tool of the captive piston type wherein movement of component parts of the tool relative to the housing thereof is minimized.

It is another object of the present invention to provide an improved powder actuated tool of the captive piston type which is quiet in operation.

It is another object of the present invention to provide an improved powder actuated tool of the captive piston type which is easy to operate.

The subject matter which I regard as my invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. The invention, however, both as to organization and method of operation, together with further advantages and objects thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings wherein like reference characters refer to like element.

DRAWINGS

FIG. 1 is a longitudinal cross section of a powder actuated tool according to the present invention;

FIG. 2 is a lateral cross section of the FIG. 1 tool taken at 2-2 in FIG. 1;

FIG. 3 is a lateral view of the cross section of the FIG. 1 tool taken at 3-3 in FIG. 1;

FIG. 4 is a top view partially broken away in horizontal cross section of the FIG. 1 tool; and

FIG. 5 is a side view of the FIG. 1 tool in a loading position thereof.

DETAILED DESCRIPTION

Referring to the drawings, an explosively operated tool includes a housing generally indicated at 10 including a forward portion 12 which may be designated as a barrel portion and a rearward portion 13 which may be designated as a breech portion. Rearward portion 13 includes a handle portion or grip 118. Barrel portion 12 is semicircular in cross section and cradles barrel 14 in a first position thereof wherein the barrel is aligned with the breechblock 16 positioned in the breech portion of the housing. Barrel 14 extends from muzzle 15 rearwardly to a power plug 18 received in the breech end of the barrel. The barrel is provided with an inner bore 20 within which a captive piston 22 is slidable, such piston having an enlarged piston head 24 which slides within inner bore 20 and a ram or plunger 26 adapted to contact and drive the head of a fastener device (not shown) into a workpiece at the left end of muzzle 15. Enlarged head 24 of the captive piston includes a rearward head portion 25 and a forward head portion 27 slidably engaged with the inside of the barrel bore. Head portion 25 is suitably provided with a piston ring or seal 32 therearound to prevent excessive escape of gas past head 24.

Power plug 18 is slidably positioned in the breech end of barrel bore 20 wherein the bore 20 is substantially smooth. The outer circumference of power plug 18 is grooved and provided with a spring retainer 34 which releasably secures the power plug at the end of the barrel. Power plug 18 includes a chamber 36 for the receiving a power charge or cartridge.

Breechblock 16 is longitudinally slidable within breech portion 13 of the housing and is recessed at 38 to receive power plug 18 in the firing position thereof. Breechblock 16 slidably carries firing pin holder 40 in turn carrying a tapered firing pin 42. The firing pin holder is normally held in a retracted position relative to breechblock 16 by sear 44 which is urged at this time by spring 46 to a location adjacent an edge 48 of the breechblock. When the tool is cocked and the breechblock is forced to the right into a cocked position against the spring bias of springs 50 and 52, sear 44 will be aligned with trigger bar 54 and can be moved upwardly by trigger bar 54. When breechblock 16 is in such cocked position, firing pin spring 56 is compressed, and upward movement of the sear 44 causes tapered firing pin 42 to be driven by spring 56 into tapered bore 58 in the breechblock 16. The firing pin 42 is adapted to project through tapered bore 58 and strike a rim fire power load or the like positioned in chamber 36. To fire the tool, trigger 60 is compressed against spring 62 moving trigger bar 54 upward into contact with sear 44, providing the latter is in cocked position. Trigger bar 54 is carried in a vertical slot in the trigger and is pivoted at 57, being maintained in alignment with the trigger by internal spring 59. This mechanism permits the trigger bar 54 to turn in a clockwise manner without damage in the event that the tool is cocked with the trigger compressed. In this event, trigger bar 54 will merely rotate in a clockwise sense as the side of sear 44 contacts the same. The tool may then not be fired until the trigger is released and compressed again.

The barrel portion 12 of the housing, being semicircular in cross section, is substantially channel-shaped and open upwardly where it receives or cradles cylindrical barrel 14 in the first position of the barrel in alignment with breechblock 16. The barrel 14 is pivotally engaged by the barrel portion 12 of the housing at a location towards the muzzle end of the barrel so that the breech end of the barrel can be upraised away from the breechblock into loading position. A substantially horizontal pin member 64 is carried by the barrel portion of the housing at the aforementioned location toward the muzzle end of the barrel, pin member 64 being positioned at the lower side of the barrel and extending transversely of the tool. A pin-matching longitudinal and transverse slot 66 is located on the underside of barrel 14 through which pin member 64 extends. Slot 66 has longitudinal length along the barrel permitting longitudinal sliding movement of the barrel for full engagement of power plug 18 within recess 38 of breechblock 16, as well as movement of the breechblock 16 within breech portion 13 of the housing into the aforementioned cocked position. Thus, in FIG. 1, dimension X substantially corresponds at least to the depth of penetration of power plug 18 within recess 38, and dimension Y corresponds to the movement of breechblock 16 further to the right to the cocked position wherein sear 44 is above trigger bar 54. Thus, barrel 14, when moved to the left by the distance X, will clear power plug 18 from breechblock 16, and when moved to the right by the distance Y, will compress breechblock 16 against the bias of springs 50 and 52 until sear 44 is over trigger bar 54.

The barrel portion 12 is provided with an arched barrel retaining member 68 proximate and above the location of pin member 64. The arched barrel retaining member 68 has an inner surface 70 semicircular in cross section which substantially matches the cylindrical barrel 14, but which is angled upwardly and to the right in FIG. 1. It will be apparent that barrel 14 may be moved to the left by a distance X whereby power plug 18 clears breechblock 16, and then the breech end of the barrel may be moved upwardly into a loading position, with the barrel pivoting substantially around pin member 64. At this time, arched barred retaining member 68 limits the upward movement of the barrel, and when barrel 14 is upraised as far as it will go, the inner surface 70 of the retaining member substantially matches or cradles the upper side of barrel 14. Retaining member 68 prevents the barrel from moving away from pin member 64 by a distance as great as the diameter of pin member 64 so that the barrel pivots substantially around pin member 64.

The barrel 14 is provided with a longitudinal slot 72 on the underside thereof or the side adjacent barrel portion 12 of the housing. This longitudinal slot does not extend the full length of the barrel, but stops short of the breech and muzzle ends thereof as illustrated. Thus, ring 32 on piston head 24 is located a predetermined distance toward power plug 18 from the breech end of slot 72 in the firing position of the piston. Also, the muzzle end of slot 72 is proximate an insert or stop 74 located at the left end or muzzle end of barrel 14.

The tool is provided with a piston retractor 76 carried by the barrel. This piston retractor comprises a ring slidably mounted on the exterior of the cylindrical barrel and fitted on the outside of the barrel for easy slidable movement therealong. The retractor 76 is provided with a pair of horizontal handles 78 and 80 extending horizontally outwardly from the retractor and just above the upper edges of barrel portion 12 of the housing toward the muzzle end thereof adjacent retaining member 68. Retractor 76 includes a member 82 for engaging piston head portion 27 as when the piston 22 has moved toward the muzzle end of the barrel. As illustrated in FIG. 5, barrel 14 may be upraised by pivoting around pin member 64, after which either of the handles 78 or 80 may then be grasped to move retractor 76 to the right. Member 82 engages head portion 27 as retractor 76 is moved to the right, bringing with it piston 22 until the piston is returned to the right end or breech end of barrel 14. Then, retractor 76 is moved to the left-hand position illustrated in the drawings, and indeed must be before barrel 14 can be returned to a position in alignment with breechblock 16. The barrel portion 12 of the housing is cut down at 90 to receive handles 78 and 80 only when retractor 76 is in its forwardmost position. Moreover, the barrel portion of the housing includes wedge-shaped recess 92 for receiving a lower wedge-shaped portion 94 of the retractor only when the retractor is returned to its left-hand position. Therefore, the retractor 76 is removed out of the way of the movement of piston 22 when the tool is in firing position, thereby avoiding danger to the operator of the tool from undesired movement of retractor 76 when the tool is fired.

Lower wedge-shaped portion 94 of retractor 76 carries member 82 in a vertical slot 96 at the middle thereof, with the L-shaped member 82 being pivotally secured in the slot at its rearward end by means of horizontal pin 98. A setscrew 100 in wedge-shaped portion 94 of the retractor normally maintains member 82 in its operating position shown. However, for disassembly of the tool, the retractor 76 is moved rearwardly toward the breech end of the upraised barrel (as illustrated in FIG. 5) and the setscrew 100 may be loosened whereby member 82 can be pivoted out of engagement with slot 72 in the barrel. This allows the retractor 76 to be slid off the barrel.

Piston 22 is provided with an ejector 86 which may protrude into chamber 36 for ejecting power load or cartridge 88. The ejector 86 is tapered at its rearwardmost end where it may extend into chamber 36. This tapered configuration acts to guide explosion gases along the chamber with minimum lateral deflection of such gases during firing of the tool to prevent chamber erosion. This construction is more fully described in the copending application of Yung Shing Hsu entitled, "Chamber Erosion Preventing Powder Actuated Tool," Ser. No. 675,140, filed Oct. 13, 1967, and assigned to the assignee of the present invention.

In barrel portion 12 of the housing underneath barrel 14 and between recess 92 and breechblock 16 there is located a muffler recess 102 extending longitudinally of the barrel portion of the housing. This muffler recess 102 is closed at the top by liner 104, forming a part of the barrel portion of the housing, and secured by screw 106, except for longitudinal slot 108 substantially matching slot 72 in the barrel. Muffler recess 102 is desirably provided with an internal muffler 110 here comprising a loosely coiled roll of sheet metal. The axis of the roll of sheet metal is disposed in recess 102 in a direction longitudinal of the tool, and the outer end of the roll of sheet metal is oriented upwardly toward slot 108, so the outer entrance of the passage between convolutions of the roll opens toward such slot to receive the explosion gases. The explosion gases tend to take a path between convolutions of the roll, this circuitous path tending to dissipate the energy thereof.

As the tool is fired, a power load explodes and combustion explosion gases enter bore 20 of barrel 14 forcing piston 22 to the left. As head portion 25 moves past the breech end of slot 72, these gases are vented along slot 72 and leave around retractor 76. However, to diminish the report of the tool when fired, these gases also expand into recess 102 and through the muffler convolutions. Such gases enter and eventually leave recess 102 through slot 108.

The captive piston 22 is tapered between head 24 and ram or plunger 26, and this tapered portion and head 24 have a low hardness and high ductility as compared with a high hardness and little or no ductility of stop 74. The hard metal stop 74 includes a long cylindrical entrance bore 114 and a frustoconical die portion 116. The bore 114 serves to slidably receive the muzzle end of the piston head 24, to the left of head portion 25, should the captive piston 22 be overdriven so that ram 26 extends outwardly at the left of muzzle 15. Should the piston thus be overdriven, piston energy is dissipated by extruding, by frustoconical die portion 116, the tapered portion of the captive piston 22. The construction allows the dissipation of energy of an overdriven piston without damage to the captive piston inasmuch as bore 114 laterally supports the captive piston during overdriving so as to prevent bending of the head portion of the piston. This energy-dissipating mechanism is further described and claimed in the copending application of Yung Shing Hsu and Raymond V. Pomeroy, Ser. No. 796,980, filed Feb. 6, 1969.

In the general operation of the tool according to the present invention, a fastener device is inserted in muzzle 15 and the user grasps a handle portion or grip 118 and forces the fastener device against a workpiece such as a masonry wall or the like. Urging the tool against a workpiece brings about full contact between power plug 18 and breechblock 16, and further urges the breechblock rearwardly of the tool into a cocked position, i.e. placing sear 44 above trigger bar 54. The trigger 60 may now be compressed raising sear 44 such that firing pin 42 is driven to the left exploding a cartridge or power load in chamber 36. Explosive gases enter the inner bore of barrel 14 behind the head 24 of the captive piston driving the captive piston to the left and forcing the fastener device into the workpiece. As hereinbefore mentioned, explosive gases leave through slot 72 as the head portion 25 passes the breech end of slot 72 from what may be considered a combustion chamber inside the barrel to the right of slot 72 in FIG. 1. These gases leave directly through the length of slot 72, but muffler recess 102 provides an expansion chamber for these gases which pass through muffler 110 whereby the noise of the explosion is reduced. The muffler breaks up the gas to muffle the sound.

To reload the tool, and return the captive piston to firing position, the barrel is moved to the left in FIG. 1 by a distance, X, and the breech end thereof is pivoted upwardly around horizontal pin member 64. In practice, the tool may be grasped by means of grip 118 and snapped in a downward direction causing the barrel 14 to lower and pivot around horizontal pin member 64 so that the breech end of the barrel including power plug 18 tilts away from the breechblock. With the barrel in the out-tilted position, a handle 78 or 80 of the retractor 76 is grasped and pulled rearwardly. As a result, member 82 engages the outer edge of head portion 27 pulling the piston 22 to the right, back to a firing position. The movement of the piston, as head portion 25 reaches the breech end of slot 72, may force shell or power load 88 from chamber 36. If ejection is not accomplished by air pressure, the ejector contacts the cartridge for forcibly removing the same. The retractor is then returned to its forwardmost position by means of handles 78 or 80, and a new cartridge or power load is inserted in chamber 36. The barrel 14 is then pivoted back into alignment with breechblock 16 for the next operation. It is thus seen that the operation of the tool according to the present invention is simple and construction thereof is compact. The tool retains a compact and balanced construction, and, since the weight of the tool is well balanced, the tool is easy to handle.

It should be noted that when the tool is urged against a workpiece, retractor 76 is automatically urged to the rear of wedge-shaped recess 92, assuming the retractor is not already in such position. With the tool forced against a workpiece, the retractor 76 is held in position between the breech end of recess 92 and the muzzle end of slot 72. The muzzle end of slot 72 engages the inwardly extending portion of member 82. Therefore, when the tool is fired, no undesired movement of retractor 76 will take place. It should be noted that even if the piston 22 should be overdriven into stop 74, the edge of head portion 27 will not strike or move member 82 with the retractor 76 in its locked position between the edges of recess 92 and slot 72.

While I have shown and described a preferred embodiment of my invention, it will be apparent to those skilled in the art that many changes and modifications may be made without departing from my invention in its broader aspects. I therefore intend the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

Claims

I claim:

1. A powder actuated tool comprising:

a housing including a rearward breech portion and a forward barrel portion;

a breechblock carried by said breech portion;

a barrel cradled by said barrel portion when said barrel is in a first position in substantial alignment with said breechblock;

said barrel being pivotally engaged by the barrel portion of said housing at a location toward the muzzle end of said barrel so that the breech end of said barrel can be upraised away from said breechblock into a loading position;

a captive piston longitudinally slidable within said barrel and movable in response to explosion of a power load for driving a fastener element into a workpiece at the muzzle end of said barrel; and

a piston retractor slidably carried by said barrel, said retractor including a member extending into said barrel for engaging said piston and a handle portion which is manually engageable for moving said piston retractor and said piston to a firing position toward the breech end of said barrel.

2. The tool according to claim 1 wherein said barrel is provided with a longitudinal slot ending short of the breech and muzzle ends of said barrel, and wherein said member for engaging said piston extends through said longitudinal slot in said barrel for engaging the head of said piston at the muzzle end thereof.

3. The tool according to claim 2 wherein the head of the piston is provided with an ejector extending from the breech end of the head.

4. The tool according to claim 2 wherein said barrel portion of the housing is channel-shaped and open upwardly, said slot in said barrel being located on the lower side of said barrel toward said barrel portion of the housing.

5. The tool according to claim 1 including a power plug received in the breech end of said barrel for receiving a power load cartridge, with the breechblock being movable rearwardly within said breech portion of said housing from an uncocked to a fully cocked or triggerable position, and wherein the barrel, in addition to being pivotally engaged by the barrel portion of said housing, is also slidable with respect to the barrel portion of said housing into full engagement with said breechblock and is further rearwardly slidable for urging said breechblock into a cocked position in response to pressure of the muzzle end of the barrel against a workpiece.

6. The tool according to claim 5 wherein said captive piston includes a head provided with an ejector extending from the breech end of said head for ejecting a cartridge from the power plug when said piston retractor moves the captive piston to the firing position.

7. The tool according to claim 5 including a substantially horizontal pin member carried by said barrel portion of said housing at said location toward the muzzle end of said barrel, said pin member being positioned at the lower side of said barrel, and a matching slot in the underside of said barrel through which said pin member extends, said last mentioned slot having a longitudinal length along said barrel permitting longitudinal sliding movement of the barrel for full engagement with the breechblock plus movement of the breechblock into a cocked position.

8. The tool according to claim 1 wherein the barrel portion of the housing is substantially semicircular in cross section for cradling a cylindrical barrel, and is provided with an arched barrel-retaining member proximate said location toward the muzzle end of the barrel for substantially enclosing the upper side of the barrel at such location, said arched barrel-retaining member having an inner semicircular surface for substantially matching the cylindrical barrel in an upraised position thereof and for limiting the upward movement of the barrel.

9. The tool according to claim 8 including a substantially horizontal pin member carried by said barrel portion of said housing at said location toward the muzzle end of the barrel, and at the lower side of said barrel, and a matching slot in the underside of said barrel through which said pin member extends, said last mentioned slot having a longitudinal length along said barrel for permitting longitudinal slidable movement of the barrel for full engagement with the breechblock plus movement of the breechblock into a cocked position.

10. A powder actuated tool comprising:

a housing including a rearward breech portion and a forward barrel portion;

a breechblock carried by said breech portion;

a barrel cradled by said barrel portion when said barrel is in a first position in substantial alignment with said breechblock;

said barrel being pivotally engaged by the barrel portion of said housing at a location toward the muzzle end of said barrel so that the breech end of said barrel can be upraised away from said breechblock into a loading position;

a captive piston longitudinally slidable within said barrel and movable in response to explosion of a power load for driving a fastener element into a workpiece at the muzzle end of said barrel;

and a piston retractor ring slidably carried on said barrel, said ring carrying a member for engaging the head of said captive piston by engaging the head of said piston on the muzzle end thereof;

handle means extending outwardly from either side of said ring for moving said ring and said piston to a firing position toward the breech end of said barrel; and

said barrel being provided with a longitudinal slot ending short of the breech and muzzle ends of said barrel, wherein said member for engaging the head of said captive piston extends through said longitudinal slot in said barrel.

11. The tool according to claim 1 wherein said barrel portion of said housing matingly receives said piston retractor allowing location of said barrel in said first position only when said piston retractor is located far enough toward the muzzle end of said barrel so that said member for engaging the captive piston does not interfere with the movement of the captive piston in driving said fastener element.

12. A powder actuated tool comprising:

a housing including a rearward breech portion and a forward barrel portion;

a breechblock carried by said breech portion;

a barrel cradled by said barrel portion when said barrel is in a first angular position in substantial alignment with said breechblock;

said barrel being pivotally engaged by the barrel portion of said housing at a location toward the muzzle end of said barrel so that the breech end of said barrel can be upraised away from said breechblock into a loading position;

said barrel also being slidable with respect to the barrel portion of said housing in and out of cocked position;

a captive piston longitudinally slidable within said barrel and movable in response to explosion of a power load for driving a fastener element into a workpiece at the muzzle end of said barrel;

a piston retractor slidably carried by said barrel, said retractor including a member for engaging said piston for moving said piston to a firing position toward the breech end of said barrel; and

said barrel portion of said housing including a recess for receiving a portion of said piston retractor toward the muzzle end of the barrel portion of the housing when said barrel is in said first angular position, the piston retractor being restrained between a portion of said barrel and said recess in the barrel portion of said housing when said barrel is in its cocked position so that said piston retractor will not be struck by movement of said piston in response to explosion of the power load.

13. The tool according to claim 2 including a power plug received in the breech end of said barrel for holding a power load, said breechblock being movable within said breech portion of said housing from an uncocked to a fully cocked or triggerable position, wherein the barrel, in addition to being pivotally engaged by the barrel portion of said housing, is also rearwardly slidable with respect to the barrel portion of said housing into full engagement with said breechblock and is further rearwardly slidable for urging said breechblock into a cocked position in response to pressure of the muzzle end of the barrel against a workpiece, and wherein said barrel portion of said housing includes a recess for receiving said piston retractor toward the muzzle end of the barrel portion of the housing when said barrel is in said first position, the piston retractor being restrained between the muzzle end of the slot in the barrel and the rearward end of the recess in the barrel portion of the housing when the barrel is in a cocked position.

14. The tool according to claim 1 including a power plug received in the breech end of said barrel for receiving a power load, said barrel having a substantially smooth inner bore at the breech end thereof, with said power plug being slidably received therewithin and yieldably retained within said inner bore.

15. The tool according to claim 14 wherein said power plug includes a circumferential groove, and spring retaining means mounted within said groove for bearing against the inner bore of said barrel.

16. A powder actuated tool comprising:

a housing including a rearward breech portion and a forward barrel portion;

a breechblock carried by said breech portion;

a barrel cradled by said barrel portion when said barrel is in a first position in substantial alignment with said breechblock;

said barrel being pivotally engaged by the barrel portion of said housing at a location toward the muzzle end of said barrel so that the breech end of said barrel can be upraised away from said breechblock into a loading position;

a captive piston longitudinally slidable within said barrel and movable in response to explosion of a power load for driving a fastener element into a workpiece at the muzzle end of said barrel;

a piston retractor slidably carried by said barrel, said retractor including a member for engaging said piston and a handle portion which is manually engageable for moving said piston retractor and said piston to a firing position toward the breech end of said barrel; and

said tool further including a slot in said barrel at least adjacent the breech end of said barrel, said barrel portion of said housing including a muffler recess communicating with said slot in said barrel when said barrel is in said first position.

17. A powder actuated tool comprising:

a housing including a rearward breech portion and a forward barrel portion;

a breechblock carried by said breech portion;

a barrel cradled by said barrel portion when said barrel is in a first position in substantial alignment with said breechblock;

said barrel being pivotally engaged by the barrel portion of said housing at a location toward the muzzle end of said barrel so that the breech end of said barrel can be upraised away from said breechblock into a loading position;

a captive piston longitudinally slidable within said barrel and movable in response to explosion of a power load for driving a fastener element into a workpiece at the muzzle end of said barrel;

a piston retractor slidably carried by said barrel, said retractor including a member for engaging said piston and a handle portion which is manually engageable for moving said piston retractor and said piston to a firing position toward the breech end of said barrel;

said barrel being provided with a longitudinal slot ending short of the breech and muzzle ends of said barrel, and wherein said member for engaging said piston extends through said longitudinal slot in said barrel for engaging the head of said piston at the muzzle end thereof; and

said barrel portion of said housing including a muffler recess communicating with said longitudinal slot in said barrel when said barrel is in said first position, wherein explosive gases from said barrel travel through said slot and into said recess as the head of said captive piston moves past the breech end of said longitudinal slot, said gases further passing along said longitudinal slot toward the muzzle end of said barrel, and a muffler in said muffler recess.

18. A powder actuated tool comprising:

a housing including a rearward breech portion and a forward barrel portion;

a breechblock carried by said breech portion and movable within said breech portion of said housing from an uncocked to a fully cocked or triggerable position;

said breechblock also carrying a triggerable firing pin;

trigger means for operating said firing pin when said breechblock is in a cocked position;

a barrel cradled by said barrel portion of said housing, when said barrel is in a first position in substantial alignment with said breechblock;

a substantially horizontal pin member carried by said barrel portion of said housing at a location toward the muzzle end of said barrel, said horizontal pin member being positioned at the lower side of said barrel;

a power plug positioned at the breech end of said barrel having a chamber communicating with said barrel for receiving a power load adapted to be fired by said firing pin;

a matching first slot in the underside of said barrel through which said horizontal pin member extends, said first slot having a longitudinal length along such barrel permitting longitudinal sliding movement of the barrel for full engagement of the power plug with the breechblock plus movement of the breechblock into a cocked position as the barrel is urged toward a workpiece;

said barrel being pivotable about horizontal pin member so that the breech end of said barrel including said power plug can be upraised away from said breechblock into a loading position when the barrel carrying the power plug is withdrawn from engagement with said breechblock;

said barrel portion of said housing being provided with an arched barrel retaining member proximate and above the location of said horizontal pin member for substantially enclosing the upper side of the barrel proximate said location, said arched barrel retaining member having an inner surface semicircular in cross section for substantially matching the upper side of the barrel in an upraised position of the barrel for limiting the upward movement of the barrel;

said barrel having a longitudinal second slot on the underside of the barrel ending short of the breech and muzzle ends of said barrel;

a captive piston longitudinally slidable within said barrel and movable in response to an explosion of the power load in the power plug for driving a fastener element;

a ring-shaped piston retractor slidably carried on the exterior of said barrel, said retractor including a member for engaging said piston through a longitudinal second slot in the barrel and a handle portion which is manually engageable for moving said piston retractor and said piston to a firing position toward the breech end of said barrel; and

said barrel portion of said housing including a recess for receiving said piston retractor toward the muzzle end of the barrel portion when the barrel is in a position of alignment with the breechblock such that said piston retractor does not interfere with the movement of said captive piston in response to explosion of the power load.

19. The tool according to claim 1 further including means for preventing movement of said barrel into said first position until said piston retractor is positioned far enough toward the muzzle end of said barrel so that said member for engaging said piston does not interfere with the movement of said piston in driving said fastener element.

20. A powder actuated tool comprising:

a housing including a rearward breech portion and a forward barrel portion;

a breechblock carried by said breech portion;

a barrel carried by said barrel portion and provided with a longitudinal slot ending short of the breech and muzzle ends of said barrel and through which explosive gases may escape from said barrel;

a captive piston longitudinally slidable within said barrel and movable in response to explosion of a power load for driving a fastener element into a workpiece at the muzzle end of said barrel;

said barrel portion of said housing being provided with a muffler recess communicating with said slot near the breech end thereof for receiving expansion of explosive gases from said barrel as the head of the captive piston passes the breech end of said longitudinal slot; and

a muffler in said muffler recess, wherein said muffler comprises a roll of sheet metal located in said muffler recess.

21. A powder actuated tool comprising:

a housing including a rearward breech portion and a forward barrel portion;

a breechblock carried by said breech portion;

a barrel carried by said barrel portion and provided with a longitudinal slot ending short of the breech and muzzle ends of said barrel and through which explosive gases may escape from said barrel;

a captive piston longitudinally slidable within said barrel and movable in response to explosion of a power load for driving a fastener element into a workpiece at the muzzle end of said barrel;

said barrel portion of said housing being provided with a muffler recess communicating with said slot near the breech end thereof for receiving expansion of explosive gases from said barrel as the head of the captive piston passes the breech end of said longitudinal slot;

a muffler in said recess; and

wherein said barrel portion of said housing includes a longitudinal slot matching the breech end portion of said longitudinal slot in said barrel, said muffler recess being closed except for the longitudinal slot in the barrel portion of the housing communicating therewith.

22. The tool according to claim 21 wherein said muffler comprises a loosely coiled roll of sheet metal disposed in said recess with the axis of the roll in a direction longitudinal of said tool.

23. The tool according to claim 22 wherein an outer end of said roll is oriented upwardly so the outer entrance of the passage between the convolutions of the roll opens toward said first mentioned longitudinal slot.