US2215470A - Automatic firearm - Google Patents

Description

Sept. 24, Jil- M. M. JOHNSON, JR

AUTOMATIC FIREARM Filed March 14, 1958 4 Sheets-Sheet l Sept. 24, M. M, JOHNSON, JR

AUTOMAT I C FIREARM 4 Sheets-Sheet 2 Filed March 14, 1958 ww w.

www NN Sept 24, 1940- M. M. JOHNSON, JR 2,215,470

AUTOMATIC FIREARM Filed March l4 1938 4 Sheets-Sheet 3 ma myd' M. M. JOHNSON. JR

AUT OMAT I C F IREARM Filed March 14, 1938 4 Sheets-Sheet 4 @mY V AUTOMATIC FIREARM Melvin M. Johnson, Jr.,

Brookline, Mass., assignor to Melvin M. Johnson, Brookline, Mass., Edward E. Rice, Boston, Mass., and himself, as trustees of Johnson Patent Trust Application Maren 14, 193s, serial No. 195,781

5 Claims.

This invention relates to rearms of the type disclosed in my prior Patent No. 2,094,156, granted September 28, 1937, in which the barrel has a short recoil movement, the bolt has locking lugs interlocking with abutments on theV barrel, the bolt has a long reciprocatory movement to and from open positiomand at least the partvof the bolt carrying the locking lugs has rotary movement into and out of locking position at the forward end of its reciprocatory movement. Automatic unlocking is eiected by a cam behind a cam surface on the bolt which-imparts td the bolt a spiral motion while the bolt and barrel are recoiling together. 'I'he barrel is preferably returned to forward position, by an auxiliary spring before the bolt returns to forward position, and the closing movement of the bolt preferably comprises forward reciprocation, at the end of which the locking lugs pass between the abutments on the barrel, followed by pure rotation (not a spiral movement) to bring the locking lugs in front of said abutments.

Objects of the present invention are to provide. firearms of the aforesaid type capable of firing high-power'ammunition (such as army riiie-or machine-gun cartridges) in which the barrel does not pound heavily on the receiver at the end of barrel recoil, in which the bolt, after being unlocked from the barrel has sufficient 'energy to retract fully and to eiect extraction and reloading reliably throughout variations in the power of successive cartridges, in which the residual gas pressure at the moment of extraction is not excessive, which does not require lubrication of the cartridges to effect extraction, which is simple and economical in construction', quick andeasy to assemble and disassemble, and which is reliable and durable in action. 'Another object of the invention is positively to preventfiring until the breech-closing mechanism is in ring position. Other objects will be evident from the following description and the accompanying drawing I n one aspect the invention involves dividing the short 'recoilmovement (in firearms of the aforesaid., type) into two stages, a primary stage in which the bolt and barrel recoil together without rotation of the boltand a secondary stage in which, while the bolt and barrel continue to recoil, the bolt rotates into unlocked position. The primary stage is preferably Vlong enough to permit the projectile to leave the barrel so that when the bolt starts'to rotate.only residual pressure remains in the barrel. Thus the frictional resistance between locking lugs Furthermore the residual pressure drops rapidly during the secondary stage. Consequently little pounding results at-the end `of the secondary stage when the barrel reaches the end f its recoil movement.

By thus dividing the short recoil movement into two stages the angle of the unlocking cam can be reduced in relation tothe direction of thereby increasing the cirbolt reciprocation, cumferential component of pressure between said c am and cam surface in relation to the axial component, and reducing,- deceleration of the bolt by the cam. Furthermore, the sliding movement of the locking lugs against the abutments on the barrel is initiated more eectively by the impact between the cam and cam surface after the bolt has acquired momentum during the primary stage than in the case where thelocking lugs, pressed against the barrel abutments under very high pressure, must be started from restto slide over the ,barrel abutments.

In another aspect "the invention involves means associated with the 4breech-closing' mechanism to obstruct movement of the nring mechanism toward firing position until the breechclosing vmechanism is in ring position. This means preferably comprises a stop associated with the hammer or other part of the ring mechanism and a stop associated with the bolt pusher or other part of the breech-closing mechanism. vIn the preferred embodiments of the invention onek of the stops has a substantialdimension along the path of movement of the stop associated with the breech-closing mechanism, whether the path be straight, spiral or otherwise, so that the iiring mechanism may be obstructed in any' position of the breech-closing mechanism throughout a substantial portion of its closingmovement, the stop associated with the ring mechanism sliding oi the other stop when the breech-closing mechanism reaches ring position.v The aforesaid stops preferably comprise a shoulder on one side of the hammer and al-shoulder on the breech-closing mechanism extending along the path of movement of the mechanism and, when the mechanism is in firing position, terminating at its rear end imcatory rebound may be counteracted by a detent end of the receiver.

which automatically moves behind a shoulder on the breech mechanism when the mechanism reaches forward position. In the preferred embodiment the aforesaid hammer stop serves both to prevent reciprocatory rebound and also to prevent premature firing. The rotary rebound is preferably counteracted by a spring Ydetent which snaps'behind a circumferentially facing shoulder on the rotary part of the breech mechanism, the forward end of the shoulder passing to the rear of the detent in the initial reciprocatory recoil of the breech mechanism to permit the rotary part to rotate out of locked position.

OtherA aspects of the invention ,will be evident from the following description and the accompanying drawings in which:

Fig. 1 is a side elevation of a typical embodiment of the invention;

Fig. 2 is a vertical longitudinal central section' showing the hammer part and the breech mechanism moving toward closed position, as indicated by the arrow;

Fig. 3 is a similar view showing the hammer disengaged from the'hammer sear and the breech mechanism almost in firing position;

Fig. 4 is a similar view at the instant of ring;

Fig. 5 is a similar view during recoil of the breech mechanism;

Fig. 6 is a top plan view of the bolt and bolt pusher showing the bolt rotated out of locked position;

Fig. 7 is a top plan view with the cover removed from the receiver;

Fig. 8 is a rear elevation of the receiver;

Fig. 9 is a section on line 9-9 of Fig. 7;

Fig. 10 is a section on line IIJ-II of Fig. '7 showing the bolt in forward position but not rotated into locked position; and

Fig. 11 is a similar view after the bolt has rotated into locked position;

The particular embodiment of the invention chosen for the purpose of illustration is of the reciprocatory barrel type, comprising a barrel I, a receiver 2, a cover 3 for the receiver, a detentA 4 for holding the cover 3 in position, the detent also serving to close the rear end of the receiver, a bolt 5, a bolt pusher 6, a hammer 1, a hammer sear 8, a bolt sear 9, a trigger I0, a recoil spring II, an extractor I2 and a firing pin I3. Threaded on the rear end of the barrel I is a locking sleeve I4 having a series of locking abutments I5 for cooperation with corresponding locking lugs I6 on the forward end of the bolt. The barrel is free to recoil until the rear end of the sleeve I4 engages the annular shoulder I1 at the forward 'I'he abutting surfaces of abutments I5 and lugs IB are preferably perpendicular to the axis of the barrel.

'Ihe bolt 5 has an-annular recess I8 immediately behind the locking abutments I6 to accommodate the locking abutments I5 on the barrel sleeve I4 when the bolt is rotated into locking position with the lugs I6 in front of the abutments I5, the lugs I9 passing between the abutments I5 as the bolt moves toward and from its forward position. The extractor I2 is mounted in a recess in the right-hand side of the bolt by means of the bolt handle I9 as described in my copending application Serial No. 190,009, filed February 11, 1938. On the left-hand side the bolt is provided with an ejector recess (Figs. 10 and 11). f Projecting upwardly from the top of the bolt is a lug 2| having cam surfaces 22 and 23 (Fig. 6) for rotating the bolt into and out of locked position, an anti-friction roller 24 being mounted in a recess in the lug 2| to hold the bolt against rotation, by engagement with the edges 25 (Fig. 7) of a slot in the top of the receiver, except when the bolt is at or near the forward end of its reciprocatory path of movement. Immediately in front of the roller 24 is a rib or 1in 35 the upper end of which slopes upwardly from front to rear. As shown in Fig. 7 the forward end of the slot 25 is widened on the' right-hand side to permit the bolt to rotate ina clockwise direction into locked position, the wider portion of the slot joining the narrower portion along an inclined surface 26 for engagement with the cam surface 23 to rotate the bolt out of locked position at the end of the recoiling movement of the .bolt and barrel together. After the barrel is unlocked from the bolt the barrel is preferably returned to its forward position by a spring (not shown) as disclosed in the aforesaid patent.

When the bolt is closed and locked there is a gap between the unlocking cam surfaces 23 and 26 on the bolt and receiver respectively, as shown in Fig. 7. The recoil movement of the barrel and bolt is thus divided into two phases, a primary phase during which the parts recoil to close the aforesaid gap and a secondary phase during which the bolt is rotated into unlocked position. In an army rifle, for example, having a barrel about one pound, the recoil during the primary phase may be of the order of 1,4," to `and the recoil during the secondary phase may be about 1A", the angle of bolt rotation may be 20 and the pitch of the cam 26 (measured from a line extending longitudinally of the receiver) may be in the neighborhood of 40.

'I'he bolt pusher 6, which is interposed between the bolt 5 and the recoil spring I I, comprises a cylindrical central portion-having the same diameter as the bolt, a cylindrical forward portion 21 of reduced diameter telescoping into an axial recess 28 in the rearward end of the bolt, and a tubular rear portion 80 extending into'the recoil spring.A Projecting upwardly from the top of the forward portion 21 is an integral lug 29 having a forwardly facing cam surface 30 for engagement with the cam surface 22 on the bolt for rotating the bolt into locked position at the forward end of the reciprocatory movement of the bolt. Mounted in a recess in the rearward end of the lug 29 is a roller 3| for engagement with the edges of the slot 25 in the receiver. The central part of the pusher 6 is provided with a vertical slot 32 to permit the hammer 1 to swing from the position shown in Fig. 2 to the firing position shown in Fig. 4, and an opening 3| to permit insertion of the firing pin from the rear. Along the left-hand edge of the slot 32 is an upstanding integral iin 33 for engagementwith the lug 34 projecting from the left-hand side of the hammer 1 to prevent the hammer from reaching firing position until the bolt is fully closed and locked. 'I'he pusher`6 is also provided with an integral part 38 projecting upwardly and forwardly from the forward end of the larger central part of the pusher, the part 36 being provided with a cam surface 31 for engagement with an arm 38 depending from the hammer sear 3, whereby the slides downwardly into the receiver from the top,

being held in position by a plunger 33 pressed rearwardly by the recoil spring ll. To open the receiver the plunger 33 is pressed forwardly and the detent 4 is slipped upwardly out of the receiver, whereupon the cover 3 may be slipped o the receiver to the rear. The bolt, bolt pusher and recoil spring may be removed either before removing the cover or along with the cover.

Intermediate its ends the cover 3 is provided with an integral raised portion 40 constituting a housing for the hammer mechanism, the hamm'er and hammer sear being pivotally mounted in the housing by means of pins 4I and 42 respectively, and the arm 38 being guided by a pin 43 extending across the housing through a slot in the arm. The arm 38 is pivotally connected to the sear 8 at* 44 and is pressed downwardly by means of a spring 45, The hammer is urged in a counterclockwise direction (Figs. 3, 4 and 5) by means of a compression spring 46 acting on a-rod 41 pivotally connected to the hammer at 48. To prevent rotary rebound of the bolt when it is rotated into locked position the receiver Acarries a spring pressed plunger 5I) in a housing 5I for engagement with the forward end of the n 35. In the closing movement of the breech mechanism the fin 35 reciprocates forwardly on the left-hand side oi' the detent 5l) and, when the bolt is then rotated in clockwise direction by the cam surfaces 22 and 3l), the plunger 5I) snaps down along the left-hand side of the fin to prevent rotary rebound in a counterclockwise direction. In the opening movement of the breech mechanism the initial movement, until the cam surface 23 engages the cam surface 26, is a straight line movement and during this initial movement (the aforesaid primary phase) the fin 35 moves out of engagement with the detent 5l) so that the bolt is free to rotate in a counterclocl'swise direction when the cam surface 23 engages the surface 26.

The gun is cocked with the bolt in retracted position by means of the sear 9 engaging behind the shoulder 60 on the bolt, the sear being pivotally mounted on the receiver by means of a pin 6IA and continuously urged in a clockwise direction (Fig. 2) by means of a spring 62. The trigger I 8 is pivotally mounted o nthe receiver at 63 and is provided with a forwardly' projecting nose 64 for engagement with the sear 9 to disengage the sear fromthe bolt. A stop 84 is pro- Y vided to limit the movement of the trigger and sear in response to spring 62.

'I'he 'operation of the illustrative embodiment of the invention is as follows: Upon pulling the trigger the bolt is released from the sear 9 and at the end of the forward movement of the bolt,

while the bolt is rotating into locked position and the pusher is still advancing, the arm 38 is lifted by the cam 3B thereby to disengage the sear 8 from the hammer.A 'Ihe parts are so timed that the lug 34 on the hammer engages the iin 33 on the pusher, thereby arresting the movement of mer is swung in a clockwise direction (Figs. 2, 3, 4 and 5) by engagement with the forward end of the slot 32 and the cam 31 until the hammer is reengaged by the sear 8, the lug 34 passing in front of the n 33. The lower end of the arm `38 is provided with a slot 10 (Fig. 2) through which the fin 35 passes Without engagement with the arm. The iin 35 serves not only as a stop for cooperation with the detent 50 but also to prevent the hammer from 4accidentally catching in front of the lug 2l in the event that the hammer'should accidentally be disengaged from its sear while the bolt is in retracted position.

It should be understood that the presenty disclosure kis for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

I claim: A

1. An automaticuiirearm comprising breechclosing mechanism including a reciprocatory bolt part which rotates into locked position at the cur. As the breach mechanism recoils, the hamwhich snaps behind the latter shoulder at the end of the locking movement of the bolt part to prevent circumferential rebound of said part, the forward end of the latter shoulder passing to the rear of said spring detent during said short reciprocating movement to permit said rotary movement.

2.V An automatic rearm comprising a reciprocatory bolt part which rotates into locked posi- ,tion at the forward end of its closing movement and which, in its opening movement. has first a short reciprocatory movement and then a rotary movement out of locked position, a circumferentially facing shoulder on said part, and a spring detent which lsnaps behind said shoulder at the end of the locking movement of the bolt part to prevent rebound of said part, the forward end of the shoulder passing to the rear of the detent during said short reciprocatory movement t permit said rotary movement.

3. A firearm of the type having a. short recoil movement of the barrel, a bolt having locking lugs, locking abutments on the barrel interlocking with said lugs, said short recoil movement comprising primary 'and secondary stages, `means for guiding the bolt and barrelv along a substantially straight path without rotation during said primary stage, the bolt having a cam surface, a cam on the firearm in the path of said surface for rotating the'bolt' into unlocked position during said secondary stage, and a pusher having a cam for rotating the bolt into locked position at the end of its forward movement.

4. A rearm of the type having a short :recoil movement of the barrel, a bolt having a cam surface, cooperating means on the bolt and barrel for locking the bolt to the barrel in response to a rotary movement of the bolt relatively to the barrel, a cam on the rearm in the path of said cam surface to rotate the bolt to unlocked position during recoil of the barrel, and means for rotating the bolt into locked position after it reaches the end of its forward movement, said cam and surface being spaced apart longitudinally 'of the firearm when the parts are in ring position so that the barrel and bolt recoil together a substantial distance before the bolt starts to rotate into unlocked position, whereby unlocking movenient is initiated by an impact between said cam and surface after the bolt has attained considerable momentum.

' 5. A firearm of the type having a short recoil movement of the' barrel, a bolt having locking lugs, locking abutmentson the barrel engageable ing the bolt into unlocked position during recoil of the barrel, and means for rotating the bolt into locked position after it reaches the end of its forward movement, said cam and surface being spaced apart longitudinally of the rearm when the parts are in firing position so that the barrel and bolt recoil together a substantial distance before the bolt starts to unlock and said cam being inclined more than 45 to a plane perpendicular to said axis so that the circumferential component of pressure between said cam and surface is greater than the axial component, thereby to overcome the friction between said perpendicular surfaces resulting from the residual gas pressure remaining during the unlocking movement of the bolt relative to the barrel.

MELVIN M. JOHNSON, JR.

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