US3155980A

US3155980A - Powder actuated tool

Info

Publication number: US3155980A
Application number: US167402A
Authority: US
Inventors: Lester F Mulno; Richard H Maynard; William A Eager
Original assignee: Star Expansion Industries Corp
Current assignee: Star Expansion Industries Corp
Priority date: 1962-01-19
Filing date: 1962-01-19
Publication date: 1964-11-10
Anticipated expiration: 1981-11-10

Description

Nov. 10, 1964 L. F. MuLNo ETAL POWDER ACTUATED TOOL 2 Sheets-'Sheet 1 Filed Jan. 19, 1962 a D MMR TONE WWYG VUAMHN. mM HA l E Q`N| RWM W/ UI: .EAM Qf/ HL wm l LRW w their ATTORNEYS L. F. MuLNo ETAL 3,155,980

POWDER `ACTUATED TOOL Nov. 10, 1964 2 Sheets-Sheet 2 Filed Jan. 19, 1962 INVENTORS. LESTER E MuLNo, RlcHARD H. MAYNARD a Y WILLIAM A. EAGER B e @MMM /ggr ATTORNEYS United States Patent Oce 3,155,980 Patented Nov. 10, 1964 3,155,980 POWDER ACTUATED TOOL Lester F. Mulno aud Richard H. Maynard, Newburgh, and William A.. Eager, Cornwall on the Hudson, NY., assignors to Star Expansion Industries Corporation, Mountainville, NX., a corporation of Delaware Filed dan. 19, 1962, Ser. No. 167,4t2 4 Claims. (Cl. 1-44.5)

This invention relates to powder actuated tools, and more particularly, a new and improved powder actuated tool for driving fasteners characterized by its simple construction and safe operation.

Heretofore, powder-actuated tools for driving studs, bolts and other types of fasteners into masonry or the like have been basically complex in structure and difficult to disassemble and reassemble. Moreover, the various safety features required by law or common sense have further contributed to their complexity of construction.

Accordingly, a primary object of this invention is to provide an improved powder actuated fastener driving tool consisting of a minimum number of parts arranged for particular ease of assembly and disassembly.

Another object of this invention is to provide a new and improved powder actuated fastener driving tool having highly effective safety features.

These and other objects of the invention are attained by providing in a powder actuated tool, a trigger arranged to lock the firing pin in an inoperative position until the trigger is actuated and which, in turn, cannot be operated until the tool is cocked by pressure against a work surface while, at the same time preventing the tool from being cocked while the trigger is in the actuated position. Safety in loading and unloading cartridges is increased by an arrangement between the barrel assembly and tiring action which permits the barrel assembly to pivot only when withdrawn a maximum distance from the firing assembly. As a further safety feature, the tool includes a device to prevent cocking unless the breech is fully locked.

The foregoing and other objects and advantages of the present invention will become more apparent from the following detailed description thereof, when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a View in longitudinal section illustrating a representative embodiment of the tool of the invention in the uncocked condition.

FIG. 2 is a cross-sectional View of the tool taken along the line 2-2 of FIG. l and looking in the direction of the arrows;

FIG. 3 is a view similar to that of FIG. 1, illustrating the tool in the cocked condition;

FIG. 4 is a fragmentary view of the tool illustrating the breech in the locked and open positions; and

FIG. 5 is a cross-sectional view taken on the line 5 5 of FIG. 3 and looking in the direction of the arrows.

Referring lirst to FIG. 1 of the drawings, a typical tool arranged according to the present invention, comprises a handle conveniently of the piston grip configuration, a breech housing 11, and a barrel housing 12. As shown, the breech housing and barrel housing are of generally cylindrical shape, although any suitable configuration may be used. A safety shield 13 is provided at the muzzle end of the tool. Within the barrel housing 12 there is a barrel 14 having a bore 15 for discharging a fastener while the breech housing 11 encloses a fronty breech block 16, which is of generally cylindrical configuration. The front breech block 16 is rigidly fastened about the breech or rearward end 17 of the barrel 14 and this front breech block is arranged to be mated with and releasably locked to the rear breech block 18, making a complete breech enclosure. In the breech end of the barrel 14 there is a removable breech plug 19 for receiving a powder charge which may, for example, be a blank cartridge (not shown). The breech plug may be slipped from the breech end of the barrel 17 when the tool is in the broken open position.

The locking arrangement between the rear breech block 18 and the front breech block 16 may be any suitable type, but preferably, it is of the interrupted-thread type known in the prior art. In this arrangement, segments of mating threads, indicated at 20 in FIG. 1 are cut on the interior surface of the rear breech block 1S and cut on the exterior surface of the front breech block 16 so that rotation of the front breech block with respect to the rear breech block is required to bring the thread segments into locked relationship.

Also mounted within the breech housing 11 is a tiring pin retainer 21 which, as best seen in FIG. 5, is affixed to the rear breech block 18 by two screws 21a. Outside the breech housing, bolt 22, threaded into the firing pin retainer and passing through a breech housing lug 23 and the breech housing 11, fastens the firing pin retainer in place accurately with respect to the breech housing.

A trigger 24 is pivoted through a longitudinal slot 25 in the breech housing lug 23 on a trigger pivot pin 26 extending transversely through the breech housing lug and trigger. The trigger 24 is made with two projections 27 and 28 on its uppermost edge, which projections can be extended rinto the breech housing as will be hereinafter described. A trigger spring 29, carried on a trigger spring screw 30 which is threaded into a screw retainer 77 rotatably supported in the trigger, normally draws the trigger toward a forward position in which the projection 2S is withdrawn from the housing as shown in FIG. 1 and returns the trigger to the same position after it has been released. t

Slidably received in the breech block 18 and above the uppermost surface of a rear cocking rod 31 is a ring pin assembly 32. A firing pin spring 33, supported on a firing pin spring guide 34 which extends into a longitudinal bore in the tiring pin retainer 21 through a slot 35 in fthe rear breach block 18 and into a recess 36 in the firing pin assembly, urges the firing pin assembly toward the rear face 37 of the rear breech block 18. With the trigger in its normal position shown in FIG. 1, however, the forward motion of the firing pin assembly is limited by the projection 27 on the forward edge of the trigger thereby preventing the firing pin from reaching a cartridge in the breech plug 19. Moreover, it will be noted that the rear cocking rod 31, in the uncooked condition shown in FIG. 1 blocks the projection 28 so that the trigger cannot be actuated.

Within the firing pin :assembly 32 a sear 38, loaded by a sear spring 39, 'and restricted in movement by a sear retaining pin 40, normally projects downwardly out of the bottom of fthe assembly just above the rear cocking rod 31. During cocking, as the breech housing 11 and rear breech block 18 are pushed forward in the manner described hereinafter, a shoulder 41 on the rear cocking rod 31 engages |the lower forward edge of the projecting part of the sear 38, holding the entire tiring pin assembly 32 stationary while the lforward movement of the breech housing compresses the tiring pin spring 33 and disengages the trigger projection 27 from the firing pin assembly 32. This relative motion of the housing 11 and trigger 24 with respect to the rear cocking rod 31 aligns the trigger projection 28 with -a sear release aperture 43 in the rear cocking rod 31 and also with the sear 38 which is just above this aperture. f

In the uncooked condition the rear cocking rod 31 is urged forwardly toward a lug 44 on a swivel band 81 which is rotatably supported on the barrel housing 12 by the action of a rear cocking rod spring 45 guided by a rear cooking rod spring guide 46. The rear cooking rod spring 45 forces the rear cooking rod 31 against an abutting shoulder of the swivel band lug 44 when the breech is closed as shown in FIG. l and against the trigger projection 27 when the breech is open. In this position of the rear cooking rod 31 the projection 28 on the rearward edge of the trigger is prevented from engaging the sear 38 since it is out of line with both the sear and the aperture 43. Thus, only limited movement of the trigger is possible with the tool in the uncooked condition and the projection 27 on the forward edge of the trigger cannot be pivoted out of the way of the tiring pin assembly 32 while the tool is uncooked because ofthe restricted movement of the trigger. In this manner a valuable positive safety device is incorporated into the tiring action of this tool, making the tool safe for rough handling during construction work.

It will be readily apparent that, when the breech is opened, the breech assembly can be completely disassembled by rst removing a hanger retaining bolt 47 and a hanger 48 which disconnects the grip 10 from the breech housing lug 23. The trigger is then removed by unscrewing the trigger spring screw 30 and expelling the trigger pivot pin 26 from its recess. Upon removal of the trigger from the breech housing lug 23 the `trigger spring screw retainer 77 can be slipped out of a transverse recess in the trigger. The rear cooking rod 31, rear cooking rod spring 45 and rear cocking rod spring guide 46 can bf removed from ya recess in the breech housing lug. Un screwing the bolt 22 in the breech housing lug permits the rear breech block 18, firing pin assembly 32 and firing pin retainer 21 to be withdrawn from the breech housing 11. The tiring pin retainer 21 is unbolted from the rea] breech block 18 by unscrewing the two tiring pin retainer screws 21a. On disengaging the firing pin retainer from the rear breech block the firing pin spring 33, ring pin spring guide 34 and ring pin assembly 32 can be slipped out of the rear breech block and separated from each other. The scar 38 can then be removed from the firing pin assembly by driving the sear retaining pin 40 out of the firing pin and permitting the sear spring 39 to push the sear 38 out of the sear recess.

Upon reassembly, it is necessary only to replace each part in its proper position in the order opposite to that in which :the tiring action was disassembled. Accordingly the breech assembly may be completely disassembled and reassembled with a minimum of manual dexterity and effort. It will also be noted that a minimum number of parts are used in the breech assembly which thus contributes to ease of manufacture and freedom from breakdown problems.

The shield assembly 13, best shown in FIG. l, comprises a chamber-defining portion 49 and a shield sleeve t) rigidly fastened thereto by welding or the like. For convenience, the chamber-defining portion 49 illustrated in the drawings is a metal shell of rectangular cross-section in a plane perpendicular to the barrel axis, but it will be understood that the shield can have other suitable shapes. In the assembled condition, the shield sleeve 50 engages the outer surface of a middle cooking sleeve 51 which surrounds the barrel 14 and is slidable axially thereon, the cooking sleeve being slidable in the shield sleeve but being retained therein by a rivet 52 engaging a slot 53 in the middle cooking sleeve 51. The outer surface of the muzzle end of the barrel 54 is threaded to receive a barrel nut 55, which has an inner forward shoulder abutting against the muzzle 56 ofthe barrel and a rearward outer shoulder 57 abutting against an inner shoulder on a front cooking sleeve 58, the barrel and barrel nut being free to` slide axially within the front cooking sleeve. The forward edge of the front cooking sleeve is provided with a series of semicircular ports 59 to permit the escape of gases evolving from the firing of a cartridge (not shown) in the chamber bushing 19 and a shoulder formed at approximately the center of the outer surface of the front cock- It ing sleeve 5S abuts the forward end of the shield sleeve 50. Also, the rearward end of the front cooking sleeve abuts the forward end of the middle cooking sleeve.

On the outer surface of the shield sleeve 50 there are a plurality of angularly disposed longitudinal grooves 60 which cooperate with a spring-biased ball detent 61 mounted in a projection 62 on the barrel housing 12. Consequently, the shield assembly 13 may be rotated about the barrel axis and releasably retained by the groove and detent arrangement 60 and 61 at any of a plurality of angular orientations which may be dictated by the shape of the chamber-deinng portion 49 and the contour of the work surface against which the tool is used.

The shield assembly 13 is normally maintained in its forward, `uncooked position as illustrated in FIG. l by the force of a guard action spring 63 which abuts at its forward end against the rearward edge of the shield sleeve 50. The rearward end of the guard action spring 63 abuts against a guard action spring washer 64 which is retained in place by a shoulder 65 on the inner surface of the barrel housing.

The rearward edge of the middle cooking sleeve 51 abuts the forward end of a rear cooking sleeve 66 provided with an interior shoulder 67 which limits the forward axial movement of this cooking sleeve. Extending between the front breech block 16 and the rear cooking sleeve 66 is a rear cooking sleeve spring 68 which urges all three cooking sleeves forwardly against the shoulder 57 of the muzzle nut 5S, the rear cooking sleeve 66 being slidably mounted over the barrel 14 so that the barrel can move axially relative thereto. The barrel housing 12 encloses the entire rear cooking sleeve assembly and abuts against a shoulder 69 on the front breech block 16 which is joined to the barrel by a set screw 70, which is accessible through a hole in the swivel band 81. As shown in FIG. 2, the barrel housing 12 is connected to the front breech block 16 by two pins 71 and 71a which are accessible through two openings 71b and 71C in the swivel band 81 when that band is in either of its two extreme positions. Consequently, when the breech housing 11, the handle 10, and the swivel band 81 are turned relative to the barrel housing 12, the forward breech block 16 and the barrel 14 remain stationary.

An inward projection or follower 72 at the forward end of the front cooking rod 42 passes through an L- shaped slot 73 on the barrel housing and fits into a hole drilled transversely through the shoulder 67 of the rear cooking sleeve 66. Thus, the L-shaped slot 73 on the barrel housing limits the motion of the breech housing 11, handle 10, and swivel band 81 with respect to the barrel housing, front breech block 16 and barrel to a selected angular rotation and length of axial travel, the rear cooking sleeve being rotated with the swivel band and the front cooking rod. The slot 73 on the barrel housing is provided with two detent recesses 74 and 75 in its forward edge and the projection 72 is urged against this edge or into one or the other of the detent recesses by the rear cooking sleeve spring 68 acting between the rear cooking sleeve 66 and the front breech block 16. One detent recess 74 releasably retains the projection 72 in a position wherein the barrel housing 12, front breech block 16, and barrel 15 are at an angular orientation relative to the breech assembly 11 at which the interrupted threads 20 on the front and rear breech blocks 16 and 18 are in an unlocked, disengaged relationship with each other as illustrated in FIG. 4. Inasmuch as there is no axial extension at the end of the slot adjacent to the detent recess 74, the tool cannot be cocked in this condition. Rotating the barrel housing 12 through the full angular component of the motion described by the slot 73 moves the projection 72 into the second detent recess 75 so that the segments of the interrupted thread 20 of the front andrear breech blocks are in the fully mated and interlocked relationship shown in FIG. 1. This closes the breech securely so that the tool can be operated. As

illustrated in FIG. 1, when the breech housing 11 and the barrel housing 12 are in the latter orientation, the projection 72 can move in the axial portion of the L-shaped slot 73, permitting the tool to be cocked for ring. Thus, it can be seen that the breech must be locked fully closed and the tool pressed against the work surface before the device can be tired. This is a valuable safety feature permitting the tool to be used under all conditions to be encountered during building construction work.

To permit easy loading and unloading of the tool, a keyhole shaped slot 78 is cut in the swivel band lug 44 and a pivot pin 79 having flat portions on opposite sides is mounted in the handle so as to pass through the slot 78 with the flats engaging the sides thereof when the breech is closed, as shown in FIG. 1. The enlarged end of the keyhole slot is large enough to permit rotation of the pin 79 therein when the breech housing has been withdrawn axially from the barrel housing but it will be noted that, after the pin 79 has been rotated in this manner, it cannot re-enter the narrower portion of the slot until the two housings have been realigned. The swivel band 81 also carries an ejector pin 80 to assist in removing spent cartridges from the breech plug 19.

In operation, the tool is loaded by rotating the handle 10 and breech housing 11 with respect to the barrel housing 12 and then separating the two housings axially and pivoting them about the pin 79 in the manner just described. The breech plug 19 is removed and an appropriate fastener (not shown) inserted into the barrel bore after which the breech plug is loaded with a blank cartridge (not shown) and reinserted in the barrel breech. After the breech has been closed and locked by relative motion of the two housings, the tool is placed against a wall or the like in which the fastener is to be driven and the handle 10 and housing 11 and 12 are pressed forwardly against the shield 13 in the manner shown in FIG. 3.

As the tool is pressed against the work surface the barrel housing 12, front breech look 16, barrel 14 and rear breech block 13, move forwardly toward the working surface while the front cooking sleeve 58, middle cooking sleeve 51, rear cooking sleeve 66, front cooking rod 42 and rear cooking rod 31 al1 remain stationary, the shield 13 being held against the workpiece by the spring 63. The forward motion of the barrel housing is arrested when the forward edge of the barrel housing 12 abuts against the shield assembly 13. The axial opening in the L- shaped slot 73 permits the housing 12 to move with respect to the projection 72 on the front cooking rod 42, so that the rear cooking rod 31 is held stationary as the rear breech block 18 moves forward toward the work surface and the shoulder 41 on the rear cooking rod 31 engages the forward edge of the scar 38, compressing the iiring pin spring 33 to cock the tool.

The trigger is kept in its normal position by the force of the trigger spring 29 on the .trigger spring screw 34D which is .threadedly engaged with the trigger spring screw retainer 77. To release the tiring pin assembly 32 from the cocked position shown in FIG. 3, the trigger 24 is moved counter-clockwise as viewed in FIG. 3, pivoting the projection on the forward edge of the trigger 27 out of the path of the tiring pin assembly and pivoting the projection on the rearward edge of the trigger 2S up through the aperture 43 in the rear cooking rod 31. This projection contacts the bottom surface of the sear 3S, raising it above the shoulder of the rear cooking rod 41, thereby allowing the energy stored in the compressed firing pin spring 33 to drive the firing pin into the opening in the rear breech -block 1S to detonate the blank cartridge.

After firing, the trigger is released and the tool is withdrawn from the work surface so that the forward trigger projection 27, under the influence of the trigger spring 29, pivots up into the path of the firing pin assembly 32, separating the ring pin from the rear face 37 of the rear breech block by slightly compressing the now relaxed firing pin spring 33. On removing the tool from the work surface, the barrel housing, front and rear breech blocks and barrel return to the fully uncooked position under the action of the guard action spring 63. The L-shaped slot 73 also slides axially along the projection 72, returning the projection .to the detent recess 75. The barrel housing may now be rotated about its axis through the angle described by the angular component of the slot 73 to permit opening ofthe breech to remove `the spent cartridge from the breech plug 19.

As is apparent from the foregoing, the structure of the present invention provides a fastener driving tool which is extremely simple in construction, providing ease of maintenance and repair. The improved safety features render improper ring of the tool virtually impossible; the tool being incapable of being fired in the uncooked position, or with the breech not fully locked.

While a representative embodiment of the present invention has been shown and described for purposes of illustration, various changes and modifications may be made therein by those skilled in the art without departing from the principles of this invention. Therefore, all such changes and modications are included within the intended scope of the invention as defined by the following claims.

We claim:

l. A powder actuated tool comprising a housing, a barrel having a breech end Within the housing adapted to receive a powder charge, firing pin means movably supported within the housing, means for urging the firing pin means toward the breech end of lthe barrel, and trigger means pivotally supported with respect to the housing having a projection normally interposed between the firing pin means and the breech end of the barrel to prevent the ring pin means from coming into contact with the powder charge, and means urging the trigger means projection into interposing relation with the tiring pin means.

2. A powder actuated tool according to claim 1 including cooking means for moving the firing pin means away from the breech end ofthe barrel against the force of the urging means to a cocked position, including means interposed between the pivotally urged trigger means and the firing pin means and wherein the firing pin cooking means is effective to prevent the trigger means from being pivoted so as to remove the normally interposed projection when the tiring pin is not cocked.

3. A powder actuated tool according to claim 2 including movable sear means interposed between the cocking means and the firing pin means and wherein the trigger means includes a tiring pin release element engageable with the sear means when .the iiring pin means is in the cocked position upon actuation of the trigger means to release the ring pin means.

4. A powder actuated tool for driving a fastener into a workpiece comprising a barrel housing, a breech block housing, a barrel rigidly supported in the barrel housing having a breech end receivable within the breech block housing adapted to receive a powder charge, a breech block rigidly mounted within the breech block housing and engageable with the breech end of the barrel means by relative axial and rotational motion therebetween, iiring pin means supported for motion within the breech housing between a cooked position and a ring pin position, means for urging the ring pin means toward the tiring position adjacent to the breech end of lthe barrel, ring pin cooking means engageable with the workpiece and movable axially with respect to the housings to move the tiring pin means to the cocked position against the force of the urging means, sear means interposed between the firing pin means and the cooking means and movable to release the tiring pin means from the cookingr means, trigger means pivotally supported with respect to the breech block housing having a projection normally interposed between the firing pin means and the breech end 7 of the barrel to prevent the firing pin means from contacting the powder charge but movable out of the interposed position upon actuation ofthe trigger means, means urging the trigger means projection into interposing relation with the tiring pin means, a sear release element on the trigger means engageable with the sear means upon actuation of the trigger when the ring pin means is in the cocked position, means on the cockng means preventing actuation of the trigger means when the cooking means is away from the ring pin cooking position, a sleeve member rotatably mounted on one of the housings supporting the other housing for relative rotary motion with respect thereto, pin and slot means connecting said other housing to the sleeve member permitting limited relative axial motion of the housings and preventing relative pivotal motion therebetween except at one extreme of relative axial motion, second slot means formed in one of the housings having a shape corresponding to the rela- CitA 8 tive rotary motion orf-the housings and axial motion of the cocking means and including detent recess means at each end of the portion corresponding to relative rotary motion of the housings, follower means associated with the cocking means and movable within the second slot means, and spring means urging the follower means into the detent recess means thereby releasably retaining the housings in their corresponding relative angular positions.

References Cited in the file of this patent UNITED STATES PATENTS v su

Claims

4. A POWDER ACTUATED TOOL FOR DRIVING A FASTENER INTO A WORKPIECE COMPRISING A BARREL HOUSING, A BREECH BLOCK HOUSING, A BARREL RIGIDLY SUPPORTED IN THE BARREL HOUSING HAVING A BREECH END RECEIVABLE WITHIN THE BREECH BLOCK HOUSING ADAPTED TO RECEIVE A POWDER CHARGE, A BREECH BLOCK RIGIDLY MOUNTED WITHIN THE BREECH BLOCK HOUSING AND ENGAGEABLE WITH THE BREECH END OF THE BARREL MEANS BY RELATIVE AXIAL AND ROTATIONAL MOTION THEREBETWEEN, FIRING PIN MEANS SUPPORTED FOR MOTION WITHIN THE BREECH HOUSING BETWEEN A COCKED POSITION AND A FIRING PIN POSITION, MEANS FOR URGING THE FIRING PIN MEANS TOWARD THE FIRING POSITION ADJACENT TO THE BREECH END OF THE BREECH FIRING PIN COCKING MEANS ENGAGEABLE WITH THE WORKPIECE AND MOVABLE AXIALLY WITH RESPECT TO THE HOUSINGS TO MOVE THE FIRING PIN MEANS TO THE COCKED POSITION AGAINST THE FORCE OF THE URGING MEANS, SEAR MEANS INTERPOSED BETWEEN THE FIRING PIN MEANS AND THE COCKING MEANS AND MOVABLE TO RELEASE THE FIRING PIN MEANS FROM THE COCKING MEANS, TRIGGER MEANS PIVOTALLY SUPPORTED WITH RESPECT TO THE BREECH BLOCK HOUSING HAVING A PROJECTION NORMALLY INTERPOSED BETWEEN THE FIRING PIN MEANS AND THE BREECH END OF THE BARREL TO PREVENT THE FIRING PIN MEANS FROM CONTACTING THE POWDER CHARGE BUT MOVABLE OUT OF THE INTERPOSED POSITION UPON ACTUATION OF THE TRIGGER MEANS, MEANS URGING THE TRIGGER MEANS PROJECTION INTO INTERPOSING RELATION WITH THE FIRING PIN MEANS, A SEAR MEANS UPON THE TRIGGER MEANS ENGAGEABLE WITH THE SEAR MEANS UPON ACTUATION OF THE TRIGGER WHEN THE FIRING PIN MEANS IS IN THE COCKED POSITION, MEANS ON THE COCKING MEANS PREVENTING ACTUATION OF THE TRIGGER MEANS WHEN THE COCKING MEANS IS AWAY FROM THE FIRING PIN COCKING POSITION, A SLEEVE MEMBER ROTATABLY MOUNTED ON ONE OF THE HOUSING SUPPORTING THE OTHER HOUSING FOR RELATIVE ROTARY MOTION WITH RESPECT THERETO, PIN AND SLOT MEANS CONNECTING SAID OTHER HOUSING TO THE SLEEVE MEMBER PERMITTING LIMITED RELATIVE AXIAL MOTION OF THE HOUSINGS AND PREVENTING RELATIVE PIVOTAL MOTION THEREBETWEEN EXCEPT AT ONE EXTREME OF RELATIVE AXIAL MOTION, SECOND SLOT MEANS FORMED IN ONE OF THE HOUSINGS HAVING A SHAPE CORRESPONDING TO THE RELATIVE ROTARY MOTION OF THE HOUSINGS AND AXIAL MOTION OF THE COCKING MEANS AND INCLUDING DETENT RECESS MEANS AT EACH END OF THE PORTION CORRESPONDING TO RELATIVE ROTARY MOTION OF THE HOUSINGS, FOLLOWER MEANS ASSOCIATED WITH THE COCKING MEANS AND MOVABLE WITHIN THE SECOND SLOT MEANS, AND SPRING MEANS URGING THE FOLLOWER MEANS INTO THE DETENT RECESS MEANS THEREBY RELEASABLY RETAINING THE HOUSINGS IN THEIR CORRESPONDING RELATIVE ANGULAR POSITIONS.