US2869127A

US2869127A - Tool for driving powder-actuated fasteners

Info

Publication number: US2869127A
Application number: US244845A
Authority: US
Inventors: Jesse E Williams
Original assignee: Olin Corp
Current assignee: Olin Corp
Priority date: 1951-09-01
Filing date: 1951-09-01
Publication date: 1959-01-20
Anticipated expiration: 1976-01-20
Also published as: FR1058870A; CH301078A; BE510186A; GB722109A; DE1095217B; LU31350A1

Description

Jan. 20, 1959 J. E. wlLLlAMs 2,869,127

TOOL FOR DRIVING `POWDERACTUATED FASTENERS Filed Sept. 1. 1951 4 shets-sheet 1 INVENTOR.

Te-.rse E. WILL/AM:

BY A @Mmw y Arran/vs YJ n 2,869,127 Toor. Fon DRIVING PowDER-AcTuATED FAsTr-:NERS

Filed sape. 1, 1951 Jan. 20, 1959 J. E. WILLIAMS 4 Sheets-Sheet 2 @El W www QTY n l C. 1 Hm n mi IL@ o* Jan. 20, 1959 J. E. WILLIAMS TOOL FOR DRIVING POWDER-ACTUATED FASTENERS Filed Sept. 1, 1951 4 Sheets-Sheet 5 lmw Alm,

Jan. 20, 1959 J. E. WILLIAMS 2,869,127

`TOOL FOR DRIVING POWDER-ACTUATED FASTENERS Filed Sepl' 1. 1951 4 Sheets-Sheet 4 INVENToiz. 7475555 El vV/L/Ams to discharge the tool.

seam

' G PWDER-U' FASTENERS T091. FR D. i

This invention relates to tools and more particularly to tools for driving powder-actuated fasteners, such as studs, pins, etc.

One of the objects of the present invention is to provide in a tool of the type described certain safety features toprevent accidental discharge of the tool. n Another object of the present invention is to provide in a tool of the type described a safety feature to prevent discharge of the tool whenever the flash shield forms an angle greater than substantially 7-14 degrees with the surface of the workpiece.

Another object of the present invention is to provide in a tool of the type described a safety feature to prevent discharge of the tool whenever the barrel muzzle is not ield against the workpiece.

Another object of the present invention is to provide in a tool of the type described a safety feature to prevent accidental discharge if the tool is dropped.

Another object of the present invention is to provide in a tool of the type described a safety feature to prevent accidental discharge of the tool by requiring the operator to move the tool actuator in two diiferent directions before the tool will ire the powder charge and drive the fastener. When the actuator is moved in the first direction, the firing pin is moved from the safety position to the ready-to-lire position, and when the actuator is moved in the second direction, the tiring pin is moved from the ready-to-re position to the firing position.

Another object of the present invention is to provide in a tool for driving powder-actuated fasteners of the type described dual-action means for discharging the tool by either turn ring or tap tiring. ln turn firing, the tool actuator or handle is rotated counterclockwise to move the firing pin from the safety position to the ready-indire position and then is turned clockwise to move the tiring pin from the ready-to-iire position to the tiring position in tap firing, the tool actuator is moved counterclockwise to move the firing pin from the safety position to the ready-to-iire position, and then the tool actuator is struck a sharp blow to move the tiring pin from the ready-to-rre position to the ring position to discharge the tool.

Another object of the present invention is to provide in a tool of the type described an index plate to enable the tool operator to drive the fasteners either any given distance apart or any given distance from a reference surface. The index plate is graduated for the range of distances available.

Another object of the present invention is to provide in a tool of the type described a threaded barrel muzzle for mounting a barrel extension, a thread protector, a disk adapter, or a fixture or device to facilitate the use or the tool.

Other features of this invention reside in the arrangement and design of parts for carrying out their appropriate functions.

Other objects and advantages of this invention will be apparent from the accompanying drawings and description Fatented dan. ZU, ifil and the essential features will be set forth in the appended claims.

ln `the drawings,

Fig. l is an elevational View of the tool of this invention with parts broken away to more clearly show the construction, with the parts assembled for turn tiring, and with the tiring pin and other parts in the safety position;

2 is longitudinal sectional view taken on line 2 2 of Fig. 1;

Fig. 3 is a longitudinal sectional view similar to Fig. 2 but showing the firing pin and associated tool parts in the ready-to-f1re position;

Figs. 4 and 5 are cross sectional views taken through the slot and screw head for controlling relative motion of some of the parts and through the tip of the firing pin on the lines i-d and 5 5 respectively of Fig. 2 with the parts assembled for turn firing and being in the safety position;

Figs. 6 and 7 are cross sectional views corresponding to Figs. 4 and 5 and taken on the lines 6-6 and 7-7 respectively of Fig. 3 with the parts in the ready to lire position;

Fig. 8 is a cross sectional View similar to Figs. 4 and 6 but showing the firing pin in the'ring position when the explosive charge is discharged;

Fig. 9 is a cross sectional view similar to Figs. 5 and 7 but showing the same position of the parts shown in Fig. 8;

Fig. 10 is a cross sectional view on the line litilil of Fig. 2;

Fig. 1l is a longitudinal sectional View similar to Fig. 2 but showing the firing pin advanced to its normal firing position but being inoperative to explode the powder charge since the ash shield forms an angle greater than Substantially seven degrees with the surface of the workpiece with the parts in the position shown;

Fig. l2 is a cross sectional view taken on the line 12--112 of Fig. 2 and showing the flash shield and index plate;

Fig. 13 is an end view taken from the left of Fig. 2;

Fig. 14 is a sectional view taken on the line lll-14 of Fig. l2;

Fig. l5 is a fragmentary longitudinal sectional View similar to the right-hand side ofFig. 2 after the necessary changes have been made to convert the tool from turn tiring to tap tiring;

Figs. 16 and 17 are cross sectional views taken through the slot and screw head for controlling relative motion of some of the parts and through the tip of the tiring pin `on the lines 16-16 and 17-17 respectively of Fig. 15 with the parts assembled for tap ring and being in the safety position;

Fig. 18 is a fragmentary longitudinal sectional View similar to Fig. 15 but showing the firing pin in its readyto-ire position;

Figs. 19 and 20 are cross sectional views taken on the lines 1 9--19 and 22 respectively of Fig. 18;

Fig. 2l is an elevational View taken on the line 2li-2l of Fig. 19 with parts broken away to more clearly show the construction; while Fig; 22 is a cross sectional View taken on the line 22-22 of Fig. 19.

Before the tool here illustrated is specifically described, it is to be understood that the invention here involved is not limited to the structural details or arrangement of parts here shown, as tools embodying the present invention may take various forms. lt is also to be understood that the phraseology or terminology herein employed is for purposes of description andnot of limitation, the scope of the present invention being denoted by the appended claims.

This invention relates to a tool for driving powdervactuated fasteners and more particularly to a dual-action tool for either turn or tap firing.

assale? The general operation of the tool may best be understood by examining Fig. 3. A barrel 10 is provided with a muzzle end and a breech end. The projectile type fastener 11 is driven through vthe barrel by an explosive charge and primer 12 after the primer has been struck by a iirlng pin 13. The primer ignites the explosive charge and pressure is built up to drive the projectile type fastener out of the tool barrel and into the workpiece to the left of the muzzle. The barrel muzzle normally engages the workpiece while the fastener is being driven and the firing pin is moved in step sequence by the handle or actuator at the right hand side of Fig. 2 from a normal safety position, as seen in Fig. 2, to a ready-to-fre positlon. as seen in Fig. 3, and then to a firing position Awith the firing pin 13 striking the primer. Figs. 2 land 3 illu."-

trate the first two mentioned positions for the tool parts during turn firing while Figs. 15 and 18 illustrate the same respective posltions during tap tiring. This dual-action feature 1s advantageous since the tool frequently has to be used in work places having close clearances where one of l the tiring methods, either turn or tap, cannot be used.

Figs. l t 14 inclusive disclose the relation of parts in the tool when it is set up for turn tiring. I

A means is provided to hold the fastener, charge, and primer in the breech of the barrel. A cylindrical breech block. 16. having a rear surface 16a, is threaded onto the breech of the barrel 10. Right hand screw threads connect the breech block 16 and the barrel 10 and permit the barrel to be unscrewed and separated from the breech block for loading and unloading the tool. A breech nlug ts into the counter bore chamber in the breech of the barrel 10 and in the breech block 16. This breech nlug 15 may be removed from the breech of the barrel to irisert the fastener 11 either into the barrel or into the bore of the breechnlug and to also insert or load an explosive charge or primer 12 into the bore of the breech plug. lt should be noted in Fig. 10 that the rear flange of the breech nlug 15 has a hexagonal shape which corresponds to the hexagonal bore in the breech block adapted to receive it. These mating hexagonal shanes prevent relative rotation between the breech block 16. explosive charge and primer 12, and breech nlug 1S when barrel 10 is being screwed into the breech block 16 while the tool. is beiney loaded. There is less danger of the charge being set oif if a piece of grit or the like is caught between the primer and the breech block 16 if the breech plug 15 land the breech block 16 cannot rotate relative to each other. The breech block 16 has a longitudinal bore 17 into which the firing pin 13 may travel to strike the primer and set oil the charge. This bore 17 is eccentric or olf center and is not coaxial with the longitudinal bore of the breech block 16` as shown in Figs. 2 and 5.

A housing 18 surrounds the breech of the barrel and the barrel projects from the front of this housing. as seen in Fig. 2. As seen in Fig. 3, the housing has a bore surrounding and telescopically mounted over the breech block 16. The housing 18 has a shoulder or stop 18a at tits Ifront end and a cam slot 2l). as seen in Fig. 1, intermediate its ends. The cam slot 20 comprises two. spaced apart, non-aligned, longitudinal slots 20a and 2Gb, one being in advance of the other and an intermediate cam zslot 20c joining the front end of the longitudinal slots 20a and 2012. vA guide screw 19 4is threaded into the breech block 16 and has its head 19altravelling in cam )slot 20 so that breech block 16 has a limited relative 4 rounds the housing 18. It has a kuurled outer surface, as seen in Fig. 1, so that it may be rmly gripped by the tool operator during the firing of the tool. This tube also has a longitudinal slot 23a, as seen in Fig. 3, in which yguide screw head 19a may travel.

The rear of the housing has a firing pin assembly, as clearly seen in Fig. 2. The cylindrical ring pin carrier tor iring pin housing 25 is mounted in the housing bore previously described. The carrier 25 has a longitudinal bore 25a eccentric to or offset from its longitudinal axis, as seen in Figs. 2 and 4.l Two tapped or threaded holes 26 an-d 27, as seen in Fig. 4 extended into the longitudinal bore of the carrier from its outer surface. Since the bore 25a is off center, threaded hole 26 is longer than the threaded hole 27. The first hole 26 is used in turn ring while the second hole 27 is used in tap firing, the latter will be described in more detail later. The firing pin 13 is mounted in the off center longitudinal bore 25a for limited longitudinal movement relative to the bore. The firing pin 13 has a shoulder 13a near its primer striking joint and has a shoulder 13b normally biased against a shoulder 25h of the firing pin carrier 25, as shown in Fig. 2, by a firing pin spring or resilient means 29. This firing pin spring 29 is located in a blind hole in the ring pin 13 and acts against firing pin plug 30, removably held in bore 25a, to normally bias the tiring pin toa forward position. A tool actuator or handle 31, at the right of Fig. 2, is made up as a metal core 31a coated with a covering 31h of Neoprene or the like. A set screw 32 is threaded into the metal core and engages the rear of the plug 30. After the handle 31 is screwed onto the threaded portion at the rear of the firing pin carrier 25, the set screw 32 is tightened to lock the handle in position. A safety tube cap 33 is screwed onto the threaded portion at the rear of the housing 18 to retain the safety release tube 23 between the front stop shoulder 18a and the cap 33. Flange 33b of the cap 33 engages ou outer shoulder 25C of the firing pin carrier 25. A slot 33a is provided in the cap 33 so that cap 33 may be rotated to permit guide screw 35 to be screwed into the threaded hole provided in the firing pin carrier. In turn firing, the guide screw head 35a travels in the circumferential slot 21 of housing 18, as seen in Figs. 1 and 2 so that the firing pin carrier has limited relative rotatable movement with respect to the housing 18. This angular rotatable movement is approximately 36 degrees. A safety spring or resilient means 38 normally urges the tiring pin away from the primer of the explosive charge 12. This spring, bearing against the left face of the tiring pin carrier 25 that is prevented from moving toward the right by flange 3311, urges the breech block 16 to the left toward the front of the housing with guide screw head 19a in the front of slot 20a to place the firing pin in a normal safety position as seen in Fig. 2.

In using the tool, the muzzle thereof is pressed against the work piece, and the tool operator moves the ring pin in step sequence from the safety position shown in Fig. 2 to the ready-to-re position shown in Fig. 3 and then to the tiring position to set olf the explosive charge 12.

The operation of the tool during turn firing will now be described. The tool is loaded by first unscrewing the breech block 16 from the barrel 10. It should be understood that the breech block 16, housing 18. firing' pin 13, handle 31 and their associated parts to the right of breech block 16 in Fig. 2 are removed as a unit and separated from the barrel and its associated parts. The breech plug 15 is then lifted from the barrel and a fastener 11 is either dropped into the barrel or inserted in the breech plug 15. Ias shown in Fig. 3. A cartridge or explosive charge and primer 12 are inserted in the breech plug 15, the breech plug 15 is replaced in the barrel 10, and then the breech block 16 and its associated parts are screwed onto the barrel 10.

The tool normally assumes its safety position, as seen in Fig. 2, under the influence of safety spring 38. lf the .gun should accidentally .be dropped in this ,positionand drive the'barrel into the housing, the charge 12 would-not Iaccidentally be set off. The guide screw head 19a-would move yfrom its safety position, as seen in Fig. l, back against the rear end of slot 26a but it would not travel over into slot Zilli (the position it normally occupies while lthe firing pin 13 is in its ready-to-iire and firing position) since housing 18 was not rotated with respect to thebarrel 10. The lip at the upper rear edge of slot Ztla prevents the guide screw head 19a from moving up into the slot Zibb when the barrel is pushed to the rear and into the housing.

The ring pin 13 is then longitudinally moved from its safety position in Fig. 2 to its ready-to-re position in Fig. 3. The tool operator grasps the outer knurled sur face of safety release tube 23 in one hand to prevent it from turning and handle 31 in the other. He then turns the tool actuator or handle 31 counterclockwise, which in turn also turns the tiring pin carrier 25 in which is threaded the screw 35. The guide screw head 35a engages the left side of slot 21, as seen in Fig. 4, and rotates the housing 1S counterclockwise to the position shown in Fig. 6. This rotation of housing 18 moves slot 20a away from guide screw head 19a, which is held against rotation by longitudinal slot 23a in safety release tube 23. -Since the muzzle of the barrel is pushed up against the workpiece as the handle is turned, the housing, firing pin 13 and handle 31 will move forward to the ready-to-re position or toward the left closer to the workpiece, as seen in Fig. 3, as the cam slot in housing 1S engages the guide screw head 19a successively from slot 20a along slot 20c to slot 2Gb. Since the longitudinal bore 17 in the breech kblock 16 and the longitudinal bore 25a in the firing pin carrier are eccentric or offset with respect to the bore of the housing, this turning movement of the handle and the firing pin carrier 2.5 moves the tiring pin 13 relative to breech block bore 17 into a position out of alignment with the bore, as seen in Fig. 7. The ring pin is eccentric or in non-registering or non-coaxial position with the bore. The shoulder 13a of the ring pin engages the rear surface 16a of the breech block land preventsthe ring pin 13 from reaching the primer even though the ring pin 13 is in the breech block bore.

Since the tool operator firmly grips tube 23 to prevent its turning, longitudinal slot 23a in the safety release tube `23 guides the guide screw head 19a in a longitudinal path during the advance of the firing pin and prevents any tendency to unscrew the barrel 1@ from the breech block 16. The safety release tube 23 also presents a knurled exterior surface easily grasped by the operator and free lfrom the moving parts within the housing. After the shoulder 13a of the tiring pin engages the rear surface 16a of the breech block, the firing pin 13 will not move any vfurther to the left in Fig. 3 since the barrel 1t) is abutted rmly against the work. Any continued longitudinal movement of the housing and tiring pin carrier 2S to the left in Fig. 3 will compress the firing pin spring Z9 and move the firing pin carrier shoulder 2517 out of contact with the tiring pin shoulder 13b to load the firing pin spring 29, as seen in Fig.- 3.

When the tool operator turns the handle 31 clockwise and thus rotates the tiring pin carrier 25 and screw 35 from the position shown in Fig. 6 to the position shown in Fig. 8, the firing pin 13 moves from the ready-tod're position of Fig. 3 to the iiring position of Figs. 8 and 9 in which the forward tip of the firing pin strikes the primer, sets olf the charge 12 and drives the fastener 11 into the workpiece. When the handle is rotated clockwise, the guide screw head 35a moves from the left end of the slot 21 in Fig. 6 to the right end of the slot 21 in Fig. 8. The firing pin 13 moves into a registering, co-axial, concentric position with the longitudinal bore 17 in the breech block 16, as seen in Fig. 9, and in so moving shoulder 13a is released from the rear surface 16a of the breech block 16.

.The tiringL pin spring 29, previously having been conrpressed, now forces the firing pin 13 forward until ;it strikes the primer.

The above sequence of steps required to fire the tool provides the tool with another safety feature. Since the actuator or handle 31 must be irst rotated or turned counterclockwise and then turned clockwise before the tool will discharge, there is little likelihood that the tool will be discharged either by dropping it or by careless handling of the tool.

The tool hasy still another safety feature. The muzzle of the barrel must be firmly held against the workpiece for two reasons. First, it protects the tool operator from ricochets. Second, it is necessary in order to move the firing pin 13 from the normal safety position to the readyto-re position. A means is provided to render the firing reans or firing pin 14 inoperative whenever the flash shield 411 forms an angle greater than substantially 7-14 degrees-with the surface of the workpiece as well as whenever the barrel muzzle is not held against or in contact with the workpiece. The ilash shield 4t) surrounds the muzzle of the barrel `and has a flash shield pad 49a made of resilient material normally contacting the surface of the. workpiece, as seen in Fig. 2. The Hash shield protects the tool operator from flying objects and ricochets. The ash shield 461 has a sleeve 41 attached to its rear surface and these members are mounted for limited relative longitudinal movement with respect to the barrel. The rear end of the sleeve 41 has a stop 41a while the front end of the sleeve has a plate41b welded thereto. Plate 41h has a non-circular hole surrounding the noncircular cross section of the barrel 1d near the muzzle, as seen in Fig. l2, with this non-circular hole mounting the sleeve 41 and the ilash shield for longitudinal but non-rotatable movement with respect to the barrel front section 10b. It should be noted that the barrel Titi is not a solid barrel but consists of a rear section lim and a front section 10b threaded together. A barrel sleeve 46, .having a stop shoulder 46h, is telcscopicaliy mounted around the barrel 10 and is mounted for relative longitudinal movement thereto by a stud or set screw 47 screwed into a threaded hole in the barrel sleeve and having its lower end slidably mounted in an elongated slot 142e in the surface of the barrel. This mounting permits the barrel sleeve 46 to have limited relative longitudinal movement with respect to the barrel but prevents any relative rotatable movement. A guide screw 43 threaded into the barrel sleeve 46 has a head 48a adapted to slide in the longitudinal slot 42 of the sleeve 41. This mounting permits relative longitudinal movement between sleeve 41 and barrel sleeve 46 but prevents any relative rotatable movementbetween them. Hole 43 in Sleeve 41 is provided sothat the tool user may reach set screw 47 and guide screw 48 to remove them, if desired. A ring 4S yis weldedto the front of the barrel 1i) and serves as a front end stop engaging plate 41h as the barrel spring or resilient means 44 acts against the front shoulder 4&1 of the barrel sleeve 46 and normally biases the ilash shield forward into its normal position wherein it is coplanar with the muzzle of the barrel, as seen in Fig. 2. Barrel spring 44 is weaker than the previously mentioned safety spring 38.

The operation will now be describedof the means to render the firing pin 13 inoperative either whenever the flash shield 40 forms an angle greater than substantially 7-14 degrees with the surface of the workpiece or whenever tne barrel muzzle is not held against or in contact with the workpiece. When the barrel is in its outward or normal safety position (Fig. 2) stop 41a is forward from stopfiob and neither hit the stopshoulder 13a. Both stops41a and 46b abut against the shoulder stoprla in Fig. 3 when the barrel is in its inward,,ready-to-fire` or ring position. However, when the flash shield4 forms an .angle .greater than substantially 744 degrees with the `surface of the workpiece, vas seen in Fig.l il, .the tiring 7 pin 13 cannot reach the primer to set off the charge 12. Even though stops 41a on sleeve 41 and 4Gb on lbarrel sleeve 46 engage the stop shoulder 18a of housing 18 in the tiring position in Fig. ll, the tiring pin 13 cannot reach the primer since the barrel 10 is forced forwardly to the left by the stronger safety spring 38. The critical angle is substantially 7 degrees when the barrel is in the slot 40h in the flash shield at its farthest position from reference edge 54, as shown in Figs. ll to 13. The critical angle is substantially 14 degrees when the barrel is at the opposite end of slot 40h closest to edge 54.

The aforementioned operation of the means to render the tiring pin inoperative, also called angle fire control, may be described in another way. Fig. 3 shows the muzzle of barrel 1li and the workpiece engaging face of flash shield 4C, each in workpieceengagement and located in a ready-to-fire muzzle plane extending perpendicular' to the bore of said barrel l@ and located axially a given distance to the left of housing 1S. If the tool is to fire,

both the barrel muzzle and liash shield face must be,lo

cated substantially in this plane, as shown in Fig. 3. If only the flash shield face is so located but the barrel muzzle is ahead of this plane (ahead with respect to the tool operator located at handle 31), .as shown by the Fig. ll position, the tool will not i re. However, when the tool is removed from the workpiece and is in the Fig. 2 position, both the barrel muzzle and flash shield face are then located ahead of this plane with respect to the operator at handle 3l because this plane moves with housing 1S and is located a fixed axial distance in front of it. For example, if one would measure by dividers the axial distance from a given point on housing 18 to the tool engagement surface on the workpiece in Fig. 3, he will establish the location of the ready-to-re muzzle plane relative to the housing. If he then transfers this distance to Figs. 2 and ll, he will find that the workpiece engagement face of the flash shield and the barrel muzzle are forward of this plane in Fig. 2, and that the shield face is in the plane in Fig. ll but the barrel muzzle is ahead of the plane.

Ofv course, the tool caribe discharged when the barrel muzzle moves only a slight distance to the left f its normal coplanar relationship with the work engaging face of the flash shield so that the tool may be discharged when used on rough work such as concrete. flash shield would touch only the high spots of the concrete and the front section b of the barrel and the muzzle thereof could enter a low spot and still enable the tool to be discharged.

It should be noted that the construction of the tool permits it to be disassembled into three distinct units. When the barrel lll is unscrewed from the breech block 16, the breech block i6 and the housing l and all the parts associated therein to the right of the barrel breech in Fig. 2 may be removed as one unit. When the barrel in the other unit is pushed forward to compress `barrel spring d4, the head 43a of guide screw 48 is exposed in the hole -t-Zt in sleeve 4l so that the screw 48 may be removed therefrom. Then, the rear section of the barrel 10a may be unscrewed from the front section 10b and separated from the front section. The barrel sleeve 46 remains attached to the rear section of the barrel 10a.

The flash shield has a means for spacing the fasteners any given distance apart or in a line any given distance from' a locating surface. T he round disk type index plate 51 is attached to the sleeve 41 so that the index plate 5l. is non-rotatable with respect to the barrel. The flash shield lil is pivoted to the index plate 5l at 5t), as seen in Figs. 2, l2, and l3. This pivot point 50 is eccentric or off center with respect to the barrel bore. The index plate 5l, as seen -in Fig. l2 has a series of graduations 52 around its outer edge and each graduation has an aligned notch adjacent thereto. A reference point 53 may be aligned with any of the graduations 52 as the index plate 51 is ,rotated with respect to flash shield 40 Then, the

' assale? at pivot point 50. The graduation 52 aligned with the reference mark 53 indicates the distance from the barrel muzzle to the reference edge Sil of the `flash shield 40. Quadrant marks 55 are also provided on the flash shield zl0 yand may be used in aligning the barrel with layout marks on the workpiece. Flash shield 40 has a slot 40b through which the barrel muzzle protrudes and this slot permits the flashv shield lll to be rotated with respect to the index plate S1 without interfering with the firing of the fastener.

A locking means is provided for locking the flash shield 40 to the index plate 51 to prevent relative movement between them and to keep any given graduation .aligned with the reference mark 53. Stud 56 has a knurled head and is screwed into the threaded hole in flash shield 4), as seen -inFig. 14. The stud has a shoulder57adapted to lit in any one of the notches opposite the graduations 52. ln the drawing, the locking means stud 56 serves as the reference mark 53 previously described.

This index plate is particularly useful when a series of fasteners are to be driven a fixed distance from a wall or the like. Then, the desired graduation 52 is set opposite the reference rnark 53 andv the knurled knob or stud 56 is tightened. Reference edge 54 of the flash shield is then held against the wall so that the fastener will be driven a given distance from it. The reference edge S4, if desired, may also engage or be aligned With a previously driven fastener so that the fastener to be driven will be driven into the workpiece a given distance from the previously driven fastener.

The muzzle of the barrel may also be threaded as shown at S8. A thread protector cap 59 is shown screwed thereon in Figs. 2 and 3. This cap protects the threads 58 when the muzzle of the barrelcontacts the workpiece. It has a bo-re at least as large as the bore of the barrel and is longitudinally aligned with the barrel bore. This cap 58, or other Suitable collar in the zone of the muzzle, will serve as an end stop for shield movement by spring 44.

The threaded portion 58 may also be used to mount a disk adapter (not shown) which resembles cap 59 but has a larger bore. A mild steel, thin disk is inserted into the bore of the disk adapter. The driven fastener lcarries the disk ahead of it and pierces its center, and then a portion of the fastener travels through the disk as the disk engages thesurface of the workpiece. This washer shaped disk provides an increased holding surface and helps to control penetration of the fastener in mortar joints and other soft materials and reduces spalling of the workpiece.

A barrel extension may also be threaded onto the threaded portion 58 of the barrel lll. This barrel extension (not shown) is used for accurately driving fasteners down into the bottom of a hole in a workpiece. The ba-rrel extension extends somewhat tothe left of the front of the flash shield in Fig. 3 and into the hole in the workpiece so that the driven fastener Iis accurately guided in its travel down to the bottom of the hole while the flash shield 4G securely engages the top surface of the workpiece and insures the workman against any danger from flying particles.

Figs. l5 to 22 inclusive disclose the tool arranged for tap firing. The tool parts used in tap ring are identical to the parts used in turn firing and are arranged in the same relationship except that the turn firing handle 3l in Fig. 2v is replaced by a tap firing, safety release grip or knob 60, as seen in Fig. l5, and guide screw 35 is screwed into the shorter threaded hole 27, as seen in Fig. 16, instead of into the longer threaded hole 26, as seen in Fig. 4 of the tiring pin carrier 25. Although Figs. l5 to 22 inclusive do not show the left and central portions of the tool .shown in Fig. 2, it should be clearly underv stood that the parts in these portions are included.

The user of the tool may easily convert it from turn firing to tap tiring. Setscrew 32 is loosened and then .is screwed into hole 27 in the firing pin carrier 255'.

turn -ring handle 31 is unscrewed from the rear of the iring pin carrier 2S. Cap or tool actuator 60 is screwed onto .the ring pin carrier .f5 and the set screw 61 is tightened. The knob 60 also has a metal core 60a and a covering 60h of Neoprene or the like. The safety tube cap 33 is then unscrewed while the safety release tube 23 is held until slot 33a of Fig. l aligns with the set screw 35, and then the set screw is removed. Cap 33 is then completely unscrewed from the end of the safety tube 1S and the knob 60, cap 33, tiring pin 13, tiring pin carrier 25, ring pin plug 36, and tiring .pin spring are removed as a unit from the housing. Then, set screw 35 The 'firing pin 13 is then depressed, and the set screw 35 is tightened so that the reduced end of the set screw engages the shoulder l13b of the firing pin 13 to keep the ring pin in the retracted position shown in Figs. l5, i8, and 22. When the parts are reassembled on the back of the housing, set screw head 35a is engaged into tl e longitudinal slot '22, as seen in Fig. 21 in the safety tube 13 and the cap 33 is screwed onto the rear end of the safety tube.

'The engagement of the set screwhead 35a in the longitudinal slot '22 permits longitudinal movement of the ring pin 13, firing pin housing 2S, and knob da as a unit and prevents relative rotation of firing pin housing 2S and the safety tube 18.

The tap ring operation of the tool is somewhat similar to the turn tiring operation previously described. The tool is rst loaded with a fastener 11 and an explosive charge 12 as previously described, and then the tiring pin 13 is moved in step sequence from its normal safety position longitudinally forward to its ready-to-re position and then its tiring position. Each step brings the 'firing pin 13 closer to the primer and charge 12. The parts of the tool in the safety position function substantially the same as they did in the turn tiring description.

After the muzzle ofthe barrel is pushed up against the workpiece to receive the fastener, the tool operator grasps the outer knurled surface of safety release tube 23 in one hand to prevent it from turning and knob d in the other hand. Hethen turns knob or tool actuator 60 counterclockwise from the position in Figs. 16 and l7 to the positions in Figs. 19 and 2O and to move the firing pin 13 fromthe normal safety position in Fig. l5 to the ready-to-re position in Fig. 18. lt should be noted that in the normal safety position, the firing pin 13 is not in coaxial. relationship with the longitudinal bore 17 in the breech block 16. The firing pin is eccentric to the center line of the bore and does not register with it, as shown in Fig. 17. However, when the knob or actuator 60 is turned counterclockwise the ring pin is moved into registering, concentric, coaxial relationship with the bore 17, as seen in Fig. 20. This rotating movement displaces the cam slot from engagement with guide screw head 19a in safety slot 20a to engagement with the guide screw head .in slot 20h since screw head 35a rotates the safety tube 18 by engaging the longitudinal slot 22 therein.

The firing pin 13 is longitudinally moved forwardly from the ready-to-re position in Fig. 18 to the firing position by striking knob or actuator 60 a sharp blow to overcome the rearward force of spring 3S. Then, firing pin 13 strikes the primer and sets oi the explosive charge to propel the fastener 11 through the barrel into the workpiece. The screw head a moves longitudinally in the longitudinal slot 22 during this movement of the firing pin from the ready-to-ire to firing position. lt should be noted that in tap firing the actuator or knob must be first turned counterclockwise and then pushed longitudinally to set olf the charge 12. This complex motion of the actuator assures that the tool will not be yaccidentally discharged either by dropping or by careless handling.

There is a small space 62 provided between the rear of the tiring pin 13 and the head of the firing pin plug dit, as seeniu Fig. 18, so that a sharp blow is necessary to detonate or set off explosive charge 12. If the-firing pin 13'were held tightly against the plug 30 and the actuator or knob 6i) were pushed slowly toward the cartridge or charge 12, the charge might not be detonated but the firing pin would dent the cartridge and prevent the detonationrof the cartridge later even though the knob 60 was then struck a sharp rblow. The space 62 assures that the cartridge will not be dented if theactuator or knob 60 is pushed slowly since the firing pin spring 29 will permit the knob 60 to move forward relative to'the firing pin 13. However, the ring spring 29 does not interfere with the operation of the firing pin 13 if the knob 60 is struck a sharp blow.

Although the form yof tool actuator is illustrated by handle 31 in Fig. 2 for turn ring and'by knob 60 in Fig. l5 for tap firing,v it should be understood that the tool .actuator need not take the form shown in the drawings. For example, knobl 60 could be used in turn firing, if desired.

It should now be clear that the tool of this invention is a dual-action tool, easily fired by either the turn firing method or the tap firing method. The tool also has a plurality of safety features to prevent accidental discharge.

Various changes in details and arrangement of parts can be made by one skilled in the art without departing from the spirit of this invention or the scope of the appended claims.

What is claimed is:

l. A tool' for driving a .powder-actuated fastener comprising a barrel having breech and muzzle ends, means to hold 4a fastener and an explosive charge with a pr'mier in the breech end of said barrel, said means including a breech block having a longitudinal bore, a tiring pin longitudinally movable relative to said bore in step sequence from a normal safety position to a ready-to-fire position to a discharge position wherein said firing pin strikes said primer and sets off said charge, means for moving longitudinally said firing pin from the normal safety position to the ready-to-iire position, means for moving said firing pin between positions consisting of non-registering and registering positions with said bore, and means for moving said firing pin longitudinally in said registering position from said ready-to-fire to firing position, whereby said firing pin when in registering position with said bore may be pushed forward to firing position.

2. A tool for driving a powder-actuated fastener comprising a barrel having breech and muzzle ends, means to hold a fastener and an explosive charge with a primer in the breech end of said barrel, said means including a breech block having a longitudinal bore, a firing pin longitudinally movable relative to said bore in step sequence from a normal safety position 4to a rea-dy-to-re position to a discharge position wherein said firing pin strikes said primer and sets off said charge, means for moving longitudinally said firing pin from the normal safety position to the ready-to-ire position, means for moving said firing pin between positions comprising registering and non-registering positions with said bore, and means for moving said ring pin longitudinally in said registering position from sai-d ready-to-re to firing position, whereby said firing pin moves ,between said nonregistering and registering positions with said bore vby a turn type firing movement after which said firing pin moves to firing position.

3. A tool for driving a powder-actuated fastener comprising a barrel having breech and muzzle ends, means to hold a fastener and an explosive charge with `a primer in the breech end of said barrel, said means including a breech block having a longitudinal bore, a firing'pin longitudinally movable relative to said bore in step sequence from a normal safety position to a ready-to-fire position to a discharge position wherein said tiring pin strikes said primer and sets off said charge, means for moving longitudinally said firing pin from the normal safety position to the ready-to-re position, means for moving said firing pin between positions consisting of concentric and eccen* tric positions with said bore, and means for moving said firing pin longitudinally in said concentric position from said ready-to-fire to firing position, whereby said firing pin when in concentric position with said bore may be pushed forward to ring position.

4. A tool for driving a powder-actuated fastener ccmprising a barrel having breech and muzzle ends, means to holda fastener and an explosive charge with a primer in the breech end of said barrel', said means including a breech block having a longitudinal bore, a ring pin longitudinally movable relative to said bore in step sequence from a normal safety position toa ready-to-fire pesi to a discharge position wherein said firing pin strikes primer and sets yoil said charge, means for moving longitudinally said tiring pin from the normal safety position to the ready-to-re position, means for moving said firing pin between positions comprising concentric and eccentric positions with said bore, and means for moving said firing pin longitudinally from said ready-to-iire position, whereby said firing pin when in eccentric position with said bore moves between said eccentric and concentric positions with said bore by a turn type firing movement after which said firing pin moves to a firing position.

5. A tool for driving a powder-actuated fastener comprising a barrel having breech and muzzle ends, means to hold an explosive charge and a fastener in the breech end of said barrel, a movable tiring pin adapted to contact and vexplode said charge but normally spaced a predetermined distance therefrom, and means rotatable by a tool operator in one direction to move said ring pin a given portion of said predetermined distance to place said tiring pin in a ready-to-re position, with continuance of such movement being ineffective to move the firing pin the remaining part of such predetermined distance, and said means also being movable by the operator in a different direction to move the firing pin the remaining distance toward said charge into firing position.

6. A tool for driving a powder-actuated fastener comprising a barrel having breech and muzzle ends, means to.

hold a fastener and an explosive charge with a primer in the breech end of said barrel wherein said means includes a cylindrical breech block having a longitudinal bore offset from its longitudinal axis, a cylindrical housing having a bore surrounding said block and arranged for limited helical movement relative thereto, a cylindrical firing pin carrier mounted in said housing bore and arranged for limited movement relative to said housing, said tiring pin carrier having a longitudinal bore offset from its longitudinal axis, a firing pin mounted rearward of said breech block in said firing pin carrier bore for limited longitudinal relative movement, a resilient means normally biasing said tiring pin toward said primer, an operator actuat able member connected to said carrier for longitudinalhI moving said carrier relative to said breech block and for moving said firing pin either to a registering position with said firing pin coaxial with said breech block bore or to a non-registering, non-coaxial position, and means operatively connecting said housing, said carrier and said breech block so that said tiring pin is longitudinally movable from a normal safety position with said tiring pin spaced from said breech block to a ready-tof1re position with said firing pin in said breech block bore to a firing position with said ring pin engaging said primer.

7. A turn tiring tool for driving a powder actuated fastener comprising a barrel having breech and muzzle ends, means to hold a fastener and an explosive charge with a primer in the breech end of said barrel wherein said means includes a cylindrical breech block having a longitudinal bore offset from its longitudinal axisa cylindrical housing having a bore surrounding said block and arranged 12 for limited helical movement relative thereto, a cylindrical firing pin carrier mounted in said housing bore and arranged for limited rotatable movement relative to said housing, said firing pin carrier having a longitudinal bore offset from its longitudinal axis, a firing pin mounted rearward of said breech block in said firing pin carrier bore for limited longitudinal relative movement, a resilient means normally biasing said firing pin toward said primer, said firing pin having a laterally projecting shoulder, said firing pin being movable from a normal safety position spaced rearwardly of said breech block to a ready- .to-fire position with said firing pin being out of axial alignment with the breech block bore and with said ring pin shoulder engaging the rear surface of said breech block fer preventing said firing pin from contacting said primer and with said firing pin moved rearwardly relative to said carrier to load said resilient means and then to a firing position with said ring pin being coaxial with said breech block bore and engaging said primer, an operator actuatable member attached to said carrier, and means operatively connecting said operator a-ctuatable member, said housing and said carrier, said operator actuatable member being rotatable in one direction to advance said tiring pin from sai-d safety position to said ready-to-re position and being rotatable in an opposite direction to move said ring pin in to firing position in coaxial alignment with said breech block bore to explode said charge and drive said fastener into a workpiece.

8. A tap tiring tool for driving a powder-actuated fastener comprising a barrel having breech and muzzle ends, means to hold a fastener and an explosive charge with a primer in the' breech end of said barrel, a tiring pin carrier, a housing operatively connecting said carrier to said means, said housing being arranged fo-r relative longitudinal movement with respect to said carrier and for relative helical movement with respect to said means, an operator actuatable member and a tiring pin being operatively connected to said carrier, said firing pin being movable longitudinally from a normal safety position spaced rearwardly of said means to a ready-to-re position closer to said primer and then to a firing position in contact with sai-d primer, said operator a-ctuatable member being ro tatable in one direction to longitudinally advance said liring pin into said ready-tofire position and then being longitudinally movable to longitudinally advance said firing pin into said firing position to explode said charge and drive said fastener into a workpiece.

9. A tool for driving a powder-actuated fastener comprising a housing, a barrel having muzzle and breech ends and projecting from the front end of said housing, said housing and said barrel being mounted for limited longitudinal relative movement between an inward tiring position and outward normal position of said barrel relative to said housing, a flash shield associated with said barrel for relative' longitudinal movement thereto, said muzzle end of the barrel and said flash shield adapted to engage the workpiece to receive the fastener, means to hold an explosive charge and fastener in the breech end of said barrel, means to fire said charge when said barrel is in said inward position, and means to render said firing means inoperative either whenever the flash shield forms an angle greater than substantially 7-14 degrees with the surface of the workpiece or whenever the barrel muzzle end is not held in contact with said workpiece.

l0. A tool foi driving a powder-actuated fastener comprising a housing, a barrel having muzzle and breech ends and projecting from the front end of said housing, said housing and said barrel being mounted for limited longitudinal relative movement between an inward tiring -position and outward normal position of said barrel relative to said housing, a flash shield associated with said barrel for relative longitudinal movement thereto, said muzzle end of the barrel and said ash shield adapted to engage the workpiece to receive the fastener, means to hold an explosive charge and fastener in the breech end of said barrel, means to re said charge when said barrel is in .said inward position, and means to render said firing means inoperative either whenever the ash shield forms an angle greater than substantially 7-14 degrees with the .surface of the workpiece or whenever the barrel muzzle end` is not held in contact with said workpiece, said last mentioned means comprising a resilient means in said housing engaging said breech end and normally biasing the barrel to said outward normal position to render said firing means inoperative.

`ll. A tool for driving a powder-actuated fastener comprising a housing, a barrel having muzzle and breech ends and projecting from the front end of said housing, said barrel being mounted for limited longitudinal movement between an inward firing position and outward normal position relative to said housing, a` flash shield associated with said barrel for relative longitudinal movement thereto, said muzzle end of the barrel and. said flash shield adapted to engage the workpiece to receive the fastener, means to hold an explosive charge and fastener in the breech end of said barrel, means to fire said charge when said barrel is in said inward position, means to render said firing means inoperative either whenever the hash shield forms an angle greater than substantially 7-14 degrees with the surface of the workpiece or whenever the barrel muzzle end is not held in contact with said workpiece, said last mentioned means comprising a resilient means in said housing engaging said breechend and normally biasing the barrel to said outward normal position to renderV said firing means inoperative, and stop means operatively connected with said barrel for abutting the front end of said housing when said barrel is in said inward position` 112. A tool for driving a powder-actuated fastener comprising a housing, a barrel having muzzle and breech ends and projecting from the front end of said housing, said housing and said barrel being mounted for limited longitudinal relative movement between a ring position and a normal barrel projected position relative to said housing, a ash shield associated with said barrel for relative longitudinal movement thereto, said muzzle end of the barrel and said ilash shield adapted t0 engage the workpiece to receive the fastener, means to hold an explosive charge and a fastener in the breech end of said barrel, means to fire said charge only when said barrel .is in said ring position, means to render said firing means inoperative either whenever the flash shield forms an angle greater than substantially 7-14 degrees with the surface of the workpiece or whenever the barrel muzzle end is not held in contact with said workpiece, said last mentioned means comprising a resilient vmeans in said housing engaging said breech end and normally biasing the barrel to said normal projected position to render said ring means inoperative, and a resilient means operatively connected between said barrel and said ash shield to bias said ash shield against said workpiece as the operator presses the tool against the workpiece.

13. A tool for driving a powder-actuated fastener comprising a housing, a barrel having muzzle and breech Vends and projecting from the front end of said housing,

said housing and said barrel being mounted for limited Vlongitudinal relative movement between a tiring position and a normal barrel projecting position from said housing, a flash shield associated with said barrel for relative longitudinal movement thereto, said muzzle end of the barrel and said ash shield adapted to engage the workpiece to receive the fastener, means to hold an explosive charge and a fastener in the breech end of said barrel, means to re said charge only when said barrel is in said firing position, means to render said firing means inoperative either whenever the ash shield forms an angle greater than substantially 7-14 degrees with the surface of the workpiece or whenever the barrel muzzle end is not` held in contact with said workpiece, said last mentioned means comprising a resilient means in said housing engaging said breech end and normally biasing the barrel to said normal projected position to render said tiring means inoperative, stop means operatively connected with said barrel for limited relative longitudinal movement with said barrel and said iiash shield, said stop means abutting the front end of said housing when said barrel is in its firing position, a resilient means operatively connected between said longitudinally movable stop means and said flash shield to normally bias said flash shield into coplanar relationship with said muzzle end, and a stop means on said ash shield abutting the front end of said housing when said barrel is in its firing position.

14. A tool for driving a powder-actuated fastener comprising a housing, a barrel having muzzle and breech ends and projecting from the front end of said housing, said housing and said barrel being mounted for limited longitudinal relative movement between a tiring position and a normal barrel projected position from said housing, a flash shield associated with said barrel for relative longitudinal movement thereto, said muzzle end of the barrel and said flash shield adapted to engage the workpiece to receive the fastener, means to hold an explosive charge and a fastener in the breech end of said barrel, means to iire said charge only when said barrel is in said firing position, and means tov render said firing means inoperative either whenever the flash shield forms an angle greater than substantially 7-14 degrees with the surface of the workpiece or whenever the barrel muzzle end is not held in contact wtih said workpiece, said last mentioned means comprising a resilient means in said housing engaging said breech end and normally biasing the barrel to said normal projected position to render said firing means inoperative, stop means operatively -connected with said barrel for limited relative longitudinal movement with said barrel and said llash shield, said stop means abutting the front end of said housing when said barrel is in its tiring position, a resilient means operatively connected between said longitudinally movable stop means and said flash shield to normally bias said flash shield into coplanar relationship with said muzzle end and said stop means into its most rearward position on said barrel, and a stop means on said hash shield abutting the front end of said housing when said barrel is in its firing position, said last mentioned stop means being located farther from the front end of said housing than said first mentioned stop means when said barrel is in said normal projected position.

l5. A tool for driving a powder-actuated fastener comprising a barrel having breech and muzzle ends, means to hold an explosive charge and a fastener in the breech end of said barrel, means to lire said explosive charge, a sleeve telescopically related to said barrel, a flash shield on said sleeve adjacent the muzzle end of said barrel, a threaded portion on said muzzle end. and a thread protector cap threaded onto said threaded portion to protect the threads when said muzzle end contacts the workpiece to receive the fastener, said thread protector cap having a longitudinal bore `aligned with the bore of the barrel and being at least as large as said barrel bore.

16. A safety structure for a tool having a barrel through which a powder-actuated fastener may be driven into a workpiece and also having abutment means externally of said barrel, said safety structure comprising in combination a sleeve supported coaxially with the barrel for reciprocation on the muzzle end of the barrel and a shield forming a box-like structure of penetration rcsistant material defined by an open bottom, by a substantially continuous side wall, and by a top plate, said shield being mounted on said sleeve with said barrel extending through the top plate into said shield whereby the edge of the side wall defining the open bottom of the shield is in engagement with the surface surrounding the Apoint on the workpiece into which the fastener is driven l and the shield forms a substantially closed chamber with said workpiece to coniine substantially completely Within the box-like structure any material displaced by fastener driving and to receive the combustion gases discharged from the barrel muzzle, and compression spring means interposed between said abutment means and the top plate of said shield yieldingly urging the shield away from said abutment means to maintain the edge of the shield in engagement with the workpiece surface and maintain connement of material displaced from the workpiece within said chamber during normal recoil of the barrel away from said workpiece incident to driving of the fastener.

17. A safety structure for a tool, as set forth in claim 16, including a resilient impact resistant pad carried by said shield within said closed chamber to absorb impact of said displaced material.

18. A shield for a tool having a barrel and a sleeve surrounding said barrel and also having abutment means externally of said barrel, said tool being adapted for powder-actuated driving of a fastener through said barrel and into a workpiece, said shield forming a box-like structure of penetration resistant material having one open side,

interengaging means on said sleeve and on said shield by which said shield is supported on said sleeve for reciprocation parallel to the axis of said barrel and with the open side facing in the same direction as the muzzle of said barrel, said shield being of such dimensions that the shield, together with the surface of the workpiece against which said tool and shield are held, form a substantially closed chamber in the box-like structure substantially enclosing the muzzle of the barrel and adapted to receive combustion gases discharged therefrom and other material displaced by the driving of the fastener into the workpiece, and compression spring means interposed between said abutment means and said shield yieldingly urging the open side of said shield to project forwardly and thereby tend to maintain contact between said shield and the workpiece surface during normal recoil of the tool incident to tiring.

19. A shield for a tool having a barrel and a sleeve surrounding said barrel and reciprocable relative thereto and also having abutment means externally of said barrel, said tool being adapted for powder-actuated driving of a fastener through said barrel and into'a workpiece surface, said shield being of penetration resistant material having one open side, interengaging means on said sleeve and on said shield by which said shield is supported on said sleeve for reciprocation thereon along a line parallel to the axis of the barrel and with the open side facing in the same direction as the muzzle of said barrel, said shield being of such dimensions that the shield, together with the workpiece surface against which said tool and said sleeve are held, form a substantially closed chamber enclosing the muzzle of said barrel and adapted to receive combustion gases discharged from said barrel and other material displaced incident to the driving of the fastener into the workpiece surface, and compression spring means interposed between said abutment means and said shield urging the open side of said shield to project forwardly to maintain contact between said shield and the workpiece surface during normal recoil of the tool incident to tiring.

20. A tool for driving a powder-actuated fastener, comprising a barrel with a fastener driving bore and a barrel muzzle, a Hash shield, means telescopically mounting said flash shield over said barrel near the muzzle for relative movement, and coacting stop means on said barrel and shield for limiting relative movement therebetween.

2l. A tool for driving a powder-actuated fastener, comprising a barrel with a fastener driving bore and a barrel muzzle, a ash shield, means telescopically mounting said flash shield over said barrel near the muzzle for axial relative movement, and coacting stop means on said barrel and shield for limiting relative movement there- 16 between, said coacting stop means including a collar on said barrel in the zone of the muzzle for limiting` axial movement in one direction.

22. A tool for driving a powder-actuated fastener, cornprising a housing, a barrel mounted in said housing and having a fastener driving bore and a barrel muzzle, a ash shield, means telescopically mounting said Viash shield over said barrel near the muzzle for axial relative movement, and coacting stop means on said barrel and shield for limiting relative movement therebetween, said coacting stop means including means carried by said shield adapted to abut gaainst said housing to limit axial movement in one direction. t

23. A tool for driving a powder-actuated fastener, cornprising a barrel with a fastener driving bore `and a barrel muzzle, a flash shield, means telescopically mounting said flash shield over said barrel near the muzzle for axial relative movement, and coacting stop means on said barrel and shield for limiting relative movement therebetween, said coacting stop means including keying parts preventing rotative movement therebetween so as to restrain the relative movement to the axial direction.

24. A tool for driving a powder-actuated fastener, comprising a housing, a barrel mounted in said housing and having a fastener driving bore and a barrel muzzle, a

vflash shield, means telescopically mounting said flash shield over said barrel near the muzzle for axial relative movement, coacting stop means on said barrel and shield for limiting relative movement therebetween, said coacting stop means including 'a collar on said barrel in the zone of the muzzle for limitingaxial movement in one direction away from said housing, including means carried by said shield adapted to abut against said housing to limit axial movement in the opposite direction, and including keying parts preventing rotative movement therebetween so as to limit the relative movement to the axial direction, and a compression spring telescoped over the barrel for biasing said shield toward said muzzle and against said collar.

2S. A tool for driving a powder-actuated fastener, comprising a firing means for the powder, a housing carrying said firing means, a barrel having a'bore and a barrel muzzle, means operatively connecting together said barrel and housing, with said housing and at least the muzzle of said barrel mounted for axial relative movement between a rst position with said housing spaced farther from the muzzle and a second position with said housing spaced closer to said muzzle, means responsive to movement from said first to second positions for moving said firing means from aV safety to a ready-to-fire position, a ash shield having workpiece engageable portions, means telescopically mounting said flash shield over said barrel near the muzzle for axial relative movement between said shield, said barrel and said housing, with said workpiece engageable portions extending laterally from the barrel bore axis, and means for stopping relative movement of said housingy and said shield during movement from said rst to second positions, with said workpiece engageable shield portions generally flush with said muzzle in said second and ready-to-re positions with the tool barrel bore generally perpendicular to the shield engaging surface of the workpiece, whereby substantial tilt from the perpendicular prevents movement to said ready-to-iire position and tool tiring.

26. A tool for driving a powder-actuated fastener, comprising a firing means for the powder, a housing carrying said firing means, a member extending in the direction of the axial path of fastener drive with one end remote from said housing adapted to engage the workpiece, means operatively connecting together said member and housing, with said housing and at least said one end of said member mounted for axial relative movement along the direction of fastener drive between a first position with said housing spaced farther from said one end and a second position with said housing spaced closer to said one end.

1.? means responsive to movement from said irst to second positions for moving said tiring means from a safety to a ready-to-iire position, a ash shield having workpiece engageable portions, means mounting said flash shield and said member for axial relative movement between said shield, said member and said housing, with said workpiece engageable portions extending laterally from said one end, and means for stopping relative movement of said housing and said shield during movement from said rst to second positions with said workpiece engageable shield portions generally ush with said one end in said second and ready-to-ire positions with the axis of fastener drive generally perpendicular to the shield engaging sur- 18 face of the workpiece, whereby substantial tilt from the perpendicular prevents movement to said ready-to-re position and tool firing.

References Cited in the file of this patent UNITED STATES PATENTS 2,045,333 Pipes June 23, 1936 2,501,362 Temple Mar. 21, 1950 2,533,851 Temple Dec. 12, 1950 2,645,772 Walker July 21, 1953 2,679,645 Erickson June 1, 1954 2,785,401 Henning Mar. l0, 1957