US2742822A - Firing mechanism for automatic and semi-automatic firearms - Google Patents

Description

April 24, 1956 E. M. HARVEY FIRING MECHANISM FOR AUTOMATIC AND SEMI-AUTOMATIC FIREARMS I5 Sheets-Sheet l a. k\/// Z!I Original Filed Feb. 11, 1949 I EurleM-Hurve r fi)-W%/%% April 24, 1956 E. M. HARVEY FIRING MECHANISM FOR AUTOMATIC AND SEMI-AUTOMATIC FIREARMS 5 Sheets-Sheet 2 Original Filed Feb. 11, 1949 April 24, 1956 M HARVEY 2,742,822

FIRING MECHANISM FOR AUTOMATIC AND SEMI-AUTOMATIC FIREARMS Original Filed Feb. 11; 1949 3 Sheets-Sheet 3 grwcm lom M g w ww 1 United States ate-n t O FIRING MECHANISM FOR AUTOMATIC AND SEMI-AUTOMATIC FIREARMS Earle M. Harvey, Agawam, Mass, assignor to the United States of America as represented by the Secretary of War I 7 Claims. (Cl. 89-140) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described in the specification and claims may be used by or for the Government for governmental purposes without the payment of any royalty thereon.

This invention relates to those firearms arranged to be selectively operated in either semi-automatic or full automatic fire at the option of the user and relates more specifically to an improved firing mechanism therefor.

The present application constitutes a division of my copending application Serial No. 75,921 filed February 11, 1949, now Patent No. 2,714,334.

One of the objects of this invention is to provide in an automatic and semi-automatic firearm simple and reliable selector means adaptedto be readily manipulated from one position to the other in either the open or closed position of the bolt.

Another object of the present invention is to provide manual selector means for converting the operation of a firearm from semi-automatic to automatic fire or vice versa which when once set in either of its two positions will be positively yet releasably locked against accidental displacement.

A further object of this invention is to provide in a firearm an improved fire control mechanism having latchmeans associated therewith for retaining the bolt in the open recoiled position upon the cessation of automatic fire.

Still another object of this invention resides in the provision of an improved firing mechanism for an automatic and semi-automatic firearm wherein the bolt must be fully locked in battery position before the firing pin can be actuated to discharge a cartridge.

A specific object of this invention is to provide in an automatic and semi-automatic firearm an improved firing mechanism wherein the parts are so arranged that a single spring provides the functions of the conventional harnmer, trigger, and sear springs.

. The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which:

Fig. 1 is a right side fragmentary view of the firearm showing the selector set for semi-automatic fire, the stock being cut away to reveal the firing mechanism of the present invention in a cocked position preparatory to pulling of the trigger;

- Fig. 2 is an enlarged longitudinal sectional view of Fig. l but showing the selector set for full automatic fire;

--Fig. 3 is a cross-sectional longitudinal view showing the bolt and locking block at the beginning of recoil;

Fig. 4 is a longitudinal sectional view showing the firing mechanism set for full automatic fire and the bolt assembly at the beginning of counter-recoil movement about to be engaged by the bolt latch;

Fig. 5 is a perspective view of the trigger;

Fig. 6 is a perspective view of the selector;

Fig. 7 is a perspective view of the bolt latch;

Fig. 8 is a fragmentary detail view showing the hammer held in the cocked position by the sear during semiautomatic fire;

Fig. 9 is a fragmentary detail view showing the hammer held in the cocked position by the trigger and showing the selector cam set for semi-automatic fire;

Fig. 10 is a view similar to Fig. 9 but showing the selector cam set for full automatic fire;

Fig. 11 is a fragmentary detail view showing a moditied form of the selector cam; and

I Fig. 12 is a cross-sectional view taken along theline 1212 in Fig. 1 showing the details of the selector and bolt latch mechanisms.

The firearm illustrated in Figs. 1 and 2 essentially comprises a receiver 5, a barrel 6 threadably secured to the forward end thereof, a reciprocating bolt 7 having a locking block 8 associated therewith in a manner more fully described in my aforementioned copending application, and a trigger housing 9 suitably secured to the underside of receiver 5.

Bolt 7 as illustrated in Fig. 3 is provided with a longitudinal axial hole 10 having a counterbored portion 11 at the rear end thereof. A firing pin 12 is slidably mounted in hole 10 and is provided with an enlarged cylindrical rear end 13 arranged to fit in counterbore 11. A pin 14 extends transversely through the rear end of bolt 7 and through a cutaway portion 15 on the underside of the rear end 13 of firing pin 12 thereby permitting limited longitudinal reciprocation thereof in bolt 7. A helical coil spring 16 is retained within counterbore 11 between the front wall thereof and the shoulder formed by firing pin cylindrical rear end 13. Spring 16 normally biases firing pin 12 rearwardly in bolt 7.

The forward end of locking block 8 terminates in a cylindrical portion 17 arrangedto be pivotally retained in a suitable mating cut 18 formed in bolt 7. The underside of block 8 is cut away adjacent its rear end to'form a pair of spaced-apart locking shoulders 91, a side view of one shoulder being shown in Figs. 2 and 3. A hole 19 is obliquely disposed in block 8 and extends forwardly therethrough to terminate in a rectangular slot 20. A striker 21 is slidably disposed in hole 19 and is provided with a rectangular front end 22 arranged to fit in slot 20. The upper and lower forward edges of rectangular striker end 22 are beveled as shown at 23 and the lower beveled edge is arranged to be contacted by a similarly inclined shoulder 24 formed transversely across the rear end of bolt 7 for a purpose to be explained.

A camming lug 25' projecting laterally from a reciprocable operating slide 26 is arranged to actuate locking block 8 between a raised locked position wherein rearward movement is prevented by a locking shoulder 27 provided in receiver 5 and an unlocked position wherein block 8 is longitudinally aligned with bolt 7 for reciproeating movement in receiver 5. In the full locked position of Fig. 2, firing pin 12 and striker 21 are in longitudinal alignment while in the unlocked position of Fig. 3, striker 21 is angularly inclineclwith respect to the longitudinal axis of firing pin 12. It can therefore be readily seen that as long as locking block 8 is not fully locked when in battery position, it is impossible to actuate firing pin 12 to discharge a chambered cartridge 84.

A trigger 28 is pivotally mounted in housing 9 substantially midway therealong by means of a transverse pin 29 and comprises a conventional arcuate finger piece 30 and an upwardly projecting body 31. The upper portion of trigger body 31 is offset to the right as best shown at 32 in Fig. 5 and terminates at its upper end in a wedgeshaped lug 33 projecting outwardly to the left for a pur- I pose to be hereinafter explained.

A second transverse "pin 34 of slightly larger diameter than trigger pin '29 extends through the forward-end portion of trigger housing 9 and'serves to pivotally mount a hammer thereto. It will be noted that the pivot point of such hammer 35 lies in a higher elevation than the previously mentioned pivot point of trigger 28 for a reason which will later be more apparent. Hammer 35 comprises abody portion 36 and an integral arm 37 projecting rearwardly from the upper 'end'thereof. Arm 37 terminates in oppositely disposed lugs 38 and 39 as best shown by the dotted outline appearing in Fig. 3. The lower end of hammer body portion36 terminates in a downwardly depending extension 40 extending beyond hammer pin 34. A lug 42 formed on theright side of hammer 35 is arranged to lie in'abutment with a hammer lock mechanism, designated generally bythe numeral 43, until such time asoperating slide26 completes its counterreco1l movement as is fully described and explained in a second copending application Serial No. 153,952, filed trigger 28 is in its pulled position during'semiautomatic,

fire as will be later shown in more detail. A forwardly projecting arcuate portion 44 on sear 45 is arranged to extend into a rectangular opening 46 formed through trigger body 31 below the pivot point of trigger 28. A transverse pin '47 extends through the walls of opening 46 and sear arcuate portion 44 and thereby serves to pivotally secure sear 45 to trigger 28. The upper end of sear 45 is provided with a forwardly projecting nose 48 arranged to retain hammer 35 in its cocked position by engaging'over lug 38 thereon as will be hereinafter more fully described. An arm 83 is arranged to project laterally -from the right side of scar 45 for a purpose to be later shown.

-A'slot 49 is transversely formed through the lower rearportion of sear 45 and serves to engage the rear loop 50 of a hammer spring 51. The front loop 93 of spring 51 is similarly engaged in a slot 41 provided through the forward portion of hammer extension 40., Such arrangement places hammer spring 51 in tension which therefore not only biases hammer 35 in a clockwise direction but serves to return trigger 28 to a'pre-pulled position when released by the operator. Moreover, hammer spring 51 normally urges sear 45 forwardly against the rear surface of trigger body 31 so as to be in position to engagehammer lug 38 when 'trigger28 is in its pulled position. Sear 45 can, of course, be pivoted rearwardly about pin 47 against the'bias' of hammer spring 51 as will be clearly shown during the description of full automatic firing. Furthermore, since hammer spring 51 engages hammer 35 substantially below the fulcrum thereof, the resulting lever armprovided by hammerbody. portion 36 isrelatively greater than that of conventional constructions wherein -a hammer spring is arranged to bear against a hammer above its point of rotation and be compressed during the cocking movement thereof.

A U-shaped bolt retainer 52 is fixedly secured'at its rear end to the rear end of trigger housing 9 and at its front end to receiver 5 thereby serving as a track for the underside of bolt 7 and locking block 8. A-selec'tor 53 is' rotatably mounted to the right side of retainer'52 by means of a transversepin member 61 and essentially comprises a substantially rectangular body 54 and a finger piece 55 projecting laterally therefrom adjacent the top portion thereof as best shown in Figs. 6 and 12. Selector body 54 is provided with a hole 56 extending upwardly therein and arranged to accommodate a spring 57 and a detent plunger 58. A vertical slot 59 is also formed transversely through body 54 so as to intersect hole 56. One end of pin 61 is slabbed on both sides as shown at 60 in'Fig. 12, while the other end terminates in a depending lug 65. The slabbed portion 60-of pin 61 fits within vertical slot 59 and the adjacent cylindrical portion'63 is rotatably mounted in a suitablehole 64provided trans- '4 versely through the right side wall of retainer 52. Thus lug 65 isarranged to lie adjacent the inner side of retainer 52. A suitable recess 62 is provided in the top surface of slabbed portion 60 of pin 61 and is arranged to receive the detent end of plunger 58. As a result of such construction, selector 53 is releasably secured to selector pin 61 so'that rotation of the former effects similar rotation of the latter. The portion of selector body 54 which projects upwardly beyond finger piece 55 is arranged to extend into a suitablearcuate slit 67 provided in the underside of receiver 5.

Disassembly of selector 53 is achieved by inserting a drift 01" other suitable tool up into vertical hole 56in selector body 54 and through a vertical slot 66 formed along one side of slabbed portion 60 so that'such tool contacts the bottom of plunger 58. Then by depressing plunger 58 against the bias of spring 57 and out of en gagement with recess 62, selector 53 is thereby permitted to be removed from pin 61.

The side of selector body 54 which lies adjacent the outer wall surface of bolt retainer 52 is provided with a substantially rectangular recess 68. The opposite lower corners thereof are arcuately extended. as best shown at 69 in Fig. 6 so as to the receive the protruding reduced end 70 of a transverse cylindrical pin 71 rotatably mounted in retainer 52.

Thus there is here provided positive means for releasably securing selector 53 in either of the two positions corresponding to the particular one of corners 69 in which pin 71 is engaged. To change selector 53 from one position to the other, it is merely necessary to depress selector body 54 against the bias of spring 57 by pressing down on finger piece 55. Since vertical slot 59 in body 54 is of greater height thanthe slabbed endportion 60 of pin 61, selector 53 will be depressed sufficiently so that protruding end 70 of pin 71 will, disengage from one of arcuate corners 69 in rectangular recess 68. Then selector 53 can be rotatedto the position desired and upon release thereof pin end 70 will be automatically engaged with the other of corners 69'through the bias of spring 57.

Pin 71 also serves to rotatably mount a bolt latch 72 which comprises a substantially H-shaped member having legs'73 and 74 connected'by a cross bar 75. The forward end of leg 74 is provided with an'offset depending lug 76 having'a wedge-likelowerend 77 as best illustrated in Fig. 7. Legs 73 and 74 are each provided with a transverse hole 78in axial alignment with one another for passage therethrough of pin'71. The top of cross bar is provided with'a shallow arcuate cut 79 which permits passagefor the underside of-locking block s. A coil spring 80 surrounds pin 71 and one end thereof bears up against the underside of cross piece 75 adjacent leg 74 of latch 72 while the other end of spring 80 is engaged in a slot '81 formed transversely through the left side wall of bolt retainer 52. Consequently, spring '80 biases the rear ends of latch legs 73 and74 upwardly in a clockwise direction so as to engage in front of locking shoulders 91 and obstruct counterrecoil'movement-of locking block 8 and therefore of bolt 7 as well. However, when trigger 28 is pulled, a stud 82projecting from the right side thereof engages wedge-likejend 77 of latch lug 76 and rotates latch'72 in the opposite direction against the bias of spring 80 whereupon-bolt 7 and locking block 8 are free to counterrecoil.

Referring now to Fig. 1 there is shown the firing mechanism of this invention in position to effect semi-automatic fire. Bolt 7 is in full battery position and locking block 8 has been cammed upwardly to project in front of locking shoulder 27 on receiver 5. Manual retraction of operating slide 26 has broughtabout the cocked position of hammer 35 which is then held cocked by engagement of lug39 thereon with lug33 on trigger 28. Selector 53 has been rotated to the semi-automatic position wherein selector lug 65 thereon is outof engagement with projecting arm'83 on sear 45.

mess-t natecartridge 84.

Operating slide 26 is driven to the rear in a manner conventional to gas operated firearms. The initial recoil movement of slide 26 causes camming lug 25 thereon to unlockblock 8 from in front of receiver shoulder 27. During this unlocking movement, the lower beveled edge 23 of striker front end 22 contacts transverse shoulder 24 on the rear face of bolt 7 thereby causing striker 21 to be cammed rearwardly in locking block 8 to the limit pemitted by the depth-of rectangular slot 20. At the same time, spring 16 biases firing pin 12 rear wardly to its cocked position, Thus the rear end of striker 21 protrudes sufliciently to be struck by hammer 35 during the next cycle of operation. 1 h

The continuing recoil movement of slide 26 carries .locking block 8' and bolt 7 rearwardly until the former :is arrested by a suitable buffer 85 provided inthe rear end of receiver 5. During this recoil travel of locking 'block 8, the underside thereof cams hammer 35 in a counter-clockwise direction whereupon hammer lug 38 :is forced past sear nose 48 so as to pivot sear 45 rearwardly about pin 47. This counter-clockwise movement of hammer 35 is finally halted by contact with an upwardly projectingaabutment 86 formed on the right side of trigger housing 9.

With trigger 28 still held in the pulled position due to the rapidity with which the recoiling parts function, locking block 8 moves forwardly in counter-recoil to ride off of hammer 35 which consequently begins to rotate in the clockwise direction. Thereupon hammer lug 38 engages under sear nose 48 so that sear 45 holds hammer 35 in the cocked position of Fig. 8. When trigger 28 is finally released by the operator of the firearm, sear nose 48 rides off of hammer lug 38 thereby permitting lug 39 to engage beneath trigger lug 33 thus continuing to hold the hammer cocked but this timeby trigger 28 as shown in Fig. 9. Then by pulling-trigger 28 again, another cycle of operation is initiated and the firearm will operate semiautomatically as long as cartridges 84 remain in magazine 88.

An alternative construction wherein bolt latch 72 is pivoted out of the path of locking shoulder 91 on locking block 8 lies in the provision of a depending lug 94 similar to lug 65'but' having a cam' portion 92 thereon. When selector 53 is moved to the semi-automatic position, cam portion 92 will engage wedge-like end 77 of bolt latch 72 and pivot such latch in a counterclockwise direction against the bias of spring 80. As a result of this construction, stud 82 on trigger 28 will not be in contact with depending lug 76 of latch 72 thereby introducing a desirable decrease in the amount of pull required to actuate trigger 28.

Upon expenditure of the last round in magazine 88, a bolt stop lug 89 on a magazine follower 90 will spring up in front of bolt 7 thereby holding it in the open position. When magazine 88 is removed from the firearm, bolt 7 and locking block 8 move forwardly slightly into engagement with bolt latch 72. Operating slide 26 must then be retracted slightly and trigger 28 pulled so that upon release of slide 26, bolt 7 and locking block 8 will move into locked battery position as previously explained, and upon release of trigger 28, hammer 35 will engage therewith and be held in the cocked position. Pulling of trigger 28 then serves to initiate the semi-automatic firing cycle as outlined above.

When it is desired that the firearm operate as a fully automatic weapon, i. e., continue to fire as long as trigger 28 is held in the pulled'position and cartridges 84 are present in magazine 88, selector 53 is rotated to the position of Fig. 2 through the procedure previously discussed. Consequently, depending lug is rotated to engage sear arm 83 thereby preventing clockwise movement thereof when trigger 28 is pulled. Thus when hammer 35 is rotated toward the cocked position by recoiling locking block 8, sear 45 will be rendered inoperative and will not engage hammer lug 38 asin semi-automatic fire. Instead, hammer lock mechanism 43 holds hammer 35 cocked by engaging lug 42 thereon until such time as operating slide 26 has attained its battery position.

Upon release of trigger 28, bolt latch 72 will rotate to obstruct the path of movement of locking block 8 and consequently engage locking shoulders 91 thereon to hold bolt 7 in the open position. When trigger 28 is again pulled, bolt latch 72 will be pivoted to release locking block 8 and hammer lock mechanism 43 will release hammer 35 to initiate another burst of automatic fire.

It can thus be readily appreciated by those skilled in the art that there is here provided a simple, compact and reliable selector mechanism which can be readily manipulated from either one of its two positions to the other regardless of whether the bolt is in the open or closed position. This feature is highly desirable in present day military tactics inasmuch as the selector can be changed from automatic to semi-automatic fire control during the open bolt position of the firearm thereby eliminating the usual loss of time involved in manually charging the gun for the initial shot.

in addition, the simple and positive means for rotatably mounting the selector mechanism to the firearm is also used to mount a boltlatch thereby utilizing a minimum number of parts in the firearm.

An additional reduction in the number of conventional parts normally required in the type of firing mechanism herewith concerned is accomplished by the unique arrangement of this'invention wherein the hammer spring serves not only tofunction the hammer but the trigger and sear as well. As a result, the conventional sear and trigger springs are not here required. Moreover, by attaching the hammer spn'ng below the pivot point of the hammer, a far more rapid fall thereof is effected as previously explained. Thus, by increasing the speed with which the hammer can operate, a desirable increase in the rate of tire of the weapon can be readily obtained without the necessity for providing a stronger hammer spring which in itself would serve to detract from the maximum rate of fire attainable by increasing the time required for bolt recoil.

- Iclaim:

1. In an automatic and semi-automatic firearm having a reciprocating bolt and a locking block pivotally secured thereto for movement therewith, a pivotal hammer mounted for movement between a cocked position and a firing position, a pivotally mounted trigger arranged to engage and hold said hammer in its cocked position, a scar pivotally secured to said trigger and arranged to engage and hold said hammer in its cocked position during such time as said trigger is in a pulled position, a hammer spring arranged to be in tension when said hammer is engaged by either said sear or said trigger, selector means for pivoting said sear out of position to engage said hammer thereby producing automatic fire when said trigger is pulled, pivotally mounted latch means for engaging the locking block during the initial forward movement thereof and thereby holding the bolt in an open position, said selector means arranged to be shifted between automatic and semi-automatic positions in either the closed or open I portion having a vertical slot there'through, a. cylindrical I selector pin rotatably secured in the firearm, said pin having asIabbed endportion extending outwardly of the-firearrnand arranged tobe engaged insaid selector vertical slot, a detent slidably mounted in said selector'body portion and arranged to be releasably engaged. with said slabbe'd end portion of saids'elector pin whereby rotation of said selector effectscorresponding rotation of said pin, a spring'arrangedto bias said detent. into said selector pin engagement, a depending'lugon' the other end'of said pin arranged-tomove'into and out of engagement with the sear'to effect'pivoting' thereofas'said selector is rotated, means'for 'releasably locking said selector and thereby said depending lug in either a sear engaging or searjnonengaging position for respectively effecting automatic ,or semiautoinatic fire, a bolt latchrotatably mounted in the firearm, spring means urging said'bolt latch into operative position, and stud'me'ans onthe trigger for rotating saidlatch against the bias of said spring means and out of operativeposition when the trigger is pulled;

"5 The construction'define'din claim 4 wherein said means for releasably locking said selector in either of its two'positions comprises, atransverse cylindrical pin fixedly secured in the firearmand "having-a protruding end of smaller diameter, said selector having a rectan-' gular recess in the side thereof adjacent the firearm,'the lower corners of said recess being arcuately formed "to engage said protruding end of said cylindrical "pin, said detent spring being arranged to bias said selector upwardly to maintain said cylindrical pin engagement, said cylindrical pin-also being arranged to rotatably mount said bolt latch. 1

6. In combination with a firearm having a triggerhousin g,-a trigger pivotally mounted in the housing for movement'b'et-weena pulled and'arreleasedposition, a hammer-rotatably mounted in the housing at a point forwardly of: and inhigher elevation than the point of trigger'pivot for movement between-a cocked and a firing position said hammer having an integral footportion projecting beyond the point of hammer rotation, a sear pivotally mounted to said trigger below the pivot point thereof for movement between a -hammer-retaining and mm lea n rpp tinn a d a hammer tinsh ns- 1 0 we t saiflha n m POFF and. theother end connected to said sear above the pivot point thereof but below the pivot point of .said trigger, said spring being thereby mounted in tension for'urging said sear to pivot into cocking engagement with said hammer and for simultaneously urging said hammer to rotate toward the firing position thereof while at the same time resisting pivotal movement of said trigger to the pulled position'thereof.

7. In combination with a firearm having a triggerrousing, a trigger pivotally mounted in the ,housing for movement between a pulled and a released position, said trigger having a substantially rectangular opening therethrough below the pivot point thereof, ahammer rotatably mounted in the housing ata point forwardly of and in higher elevation than the point of trigger pivot for movement between a cocked and a firing position, saidhammer having an integral foot portion projecting beyond the point of hammer rotation to jforrn an angle with the longitudinal axis of said hammena sear having a forwardly projecting 'arcuate'base portion and an upwardly extending hammer-engaging portion, said arcuate base being pivotally secured in said rectangular opening of said trigger with said upwardly extending seat portion disposed behind said trigger for pivotal movement into and out of cocking-engagement with said hammer, and a hammer spring having a forwardly projecting loop portion connectedto said hammerfoot portion and a rearwardly projecting loop portion connected to said sear between the pivot point thereof and that of said trigger, said spring being ,mounted under tension for urging said hammer to rotate toward the firing position and simultaneously'urging said'sear to pivot intohammer-engaging position while at the same time resisting the pulling of said trigger to efiect the return thereof to the pre-fired position when released.

References Cited in thefile of this patent UNITED STATES PATENTS 1,067,054 Nardin 'July 8, 1913 1,743,472 Meyer Jan. '14, 1930 2,098,727 Lahti Nov.,9,, 1937 2,308,598 Ferrel Jan. 19, 1943 2,448,810 Kouckeyet a1. Sept. 7, 1948 2,464,418 Sefried Mar. 15, 1949 2,479,419 Sefried Aug. 16, 1949 2,522,628 Maillard Sept. 19,, --1950 2,539,447 Lochhead Jan. 30, 1951 2,597,089 Everett May.;20, -1952 FOREIGN PATENTS 184,191 Germany Apr ll, 1907 361,022 Italy July 11, 1938

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