US2429650A

US2429650A - Front sear for rifles

Info

Publication number: US2429650A
Application number: US666938A
Authority: US
Inventors: Schiff Sigmund
Original assignee: Individual
Current assignee: Individual
Priority date: 1946-05-03
Filing date: 1946-05-03
Publication date: 1947-10-28
Anticipated expiration: 1964-10-28

Description

S. SCHIFF FRONT SEAR FOR RIFLES 0a. z8, y 1947-.

Filed May 5, 194e 5 Sheets-sheet 1 Oct. 28, 1947. s. scHlFF FRONT SEAR FOR RIFLES Filed May 5, 1946 5 Sheets-Sheet 2 3 Shets-Sheet 5 s. sci-UFF FRONT SEAR FOR RIFLES oct. A28, 1947.

Filed May 5, 1946 Nm mw mw Patented Oct. 28, 1947 UNITED STATES PATENT OFFICE FRONT SEAR FOR RIFLES Sigmund Schiff, Cincinnati, Ohio, assignor to the United States of America, as represented by the Secretary vof War (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to a breech block assembly for use with an automatic gun of the type of the 20 mm. aircraft Weapon.

An object of the invention is to provide asturdy block of comparatively few parts and these so formed and arranged and cooperating to reduce to a minimum the likelihood of malfunctioning and adding to thelife of the gun and the facility of its operation.

The `block of the gun of the type mentioned is operated partly by gas recoil means and partly by blowback means, that is to say, by a modicum of gas derived by the bore of the gun when the round is ired and blowback force of the round when the round is exploded.

The block comprises a main body portion and a slide slidably related thereto. The body portion is normally locked in battery position and recoils in response to the blowback force of the explosion of the round of ammunition for the purpose of extracting ejecting and feeding ammunition after having been unlocked from battery position by the slide `in its initial rearward movement responsive to the gas derived from the bore `of the gun when the gun is fired, the slide also operating to cock the firing pin against its spring upon such initial rearward movement, and to compress the slide returning springs preparatory to returning the slide to battery position wherein the firing pin is in position to be projected to re the round to inaugurate another cycle, or cycles.

The improvements about to be described reside particularly in the sear and ring pin, their construction and location relative to each other and to the slide element and in the modification of the slide and main body of the block for coaction with the sear and ring pin, and in the provision of a spring for the ring pin independent of the recoil and counterrecoil or drive spring, `assuring uniform extent of movement and uniform impact strength of the pin with respect to the round ,in the gun, thus eliminating the likelihood of misre and incident malfunctioning of the gun.

Ordinarily the sear is a spring-backed element engaging a notch in a hammer or iiring pin and released by a trigger to fire the round, there being no other function of the sear. In the present instance the sear and firing pin are so constructed that they cooperate with each other and with the slide and main body portion of the block in a radically novel manner, so far as I` am aware.

The sear may be described as a floating element, that is to say, it is not attached to any other portion and is free to be rocked and/or depressed and caused in its movements to assume successively, several positions relative to the firing pin and slide, notably among which is Where the sear, after being released from the notch in the ring pin, is depressed by the pin in its forward movement to unlock the slide to permit it to be moved rearwardly to unlock the main body portion. The sear not only performs the oilice of a sear but serves as a lock to prevent the rebound of the slide relative to the main body portion of the block when the block returns to lbattery position, thus preventing the slide from prematurely unlocking the body portion of the block at the time of firing.

As stated at the outset, the block compresses two main portions. These will hereinafter be designated as the body portion which is the part that carries the sear, sear spring, firing pin, ring pin spring, recoil 4and counterrecoil spring, and the sear releasing cam and extractor, some of which are constructed and arranged to coact intimately with parts carried by the other main part of the block which will be designated as the slide.

The receiver will be internally shaped to accommodate, guide and support the block in its reciprocations therein and to prevent lateral movement of the block, all as is customary in such structures. It is closed at its front end with exception of a threaded opening for the reception of the threaded portion of the gun barrel, and at its rear end it is provided with the usual buffer device.

Other objects and advantages of the invention other than those stated will become apparent from the following description.

In the drawings illustrating the invention:

Figure 1 is a longitudinal vertical section of the receiver and rear portion of the gun barrel, the block being shown in side elevation and in locked battery position, the ring pin being cocked;

Figure 2 is a longitudinal section of the receiver showing a portion of the gun barrel with the slide portion of the block removed, the lower part of the block and parts carried thereby or closely associated therewith, in plan;

Figure 3 is a view like Figure 1, with the body and slide in longitudinal vertical central section showing the parts in battery position with the ring pin cocked;

Figure 4 is a fragmentary view of the forward end of the receiver and the rear end of the barrel, the block parts and sear being in section and in the position they occupy at the time of firing;

Figure 5 Iis a View substantially like Figure 3, with the parts being in initial recoil position;

Figure 6 is a transverse vertical section of the receiver and block about on the line 5 6 of Figure 1;

Figure 7 is a view on the line 'I-'I of Figure 1;

Figure 8 is a perspective view of the sear;

Figure 9 is a side elevation of the slide partly broken away to show the relation of the slide return springs (of which there are two) and movable block yieldingly connecting the slide with the body portion of the block in their sliding movement relative to each other.

Figure 10 is a similar view of the body portion of the block, the sear being-in section;

Figure 11 is a frontend view of Figure 9;

Figure 12 is a front end View of Figure 10;

Figure 13 is a fragmentary section of the forward end of the block showing the sear released and in position to be depressed by the ring pin in its forward movement under the influence of the ring pin spring;

Figure 14 is a similar view showing the parts in firing position, the firing pin in its forward movement having levelled up the sear;

Figure 15 is a view similar tofFigure 14, the parts being in recoil position and the sear in position to engage the sear notch to cock the pin;

Figure 16 is a similar view showing the firing pin cocked and in battery position;

Figure 1'7 is an inverted perspective View of the ring pin;

Figure 18 is a perspective View of the Sear spring;

Figure 19 is a detail perspective VView of the sear operating cam and a portion of the sear showing the formation of the cam whereby the lateral movement of the cam produces a downward movement of the sear.

Referring to the drawings, the receiver is generally indicated by the numeral I, which, as stated, is of usual construction, open at its top and bottom and having parallel side walls 2 and longitudinally extending internal top flanges 3 which embrace and guide .the upper portion pf the breech block, and inwardly extending rails 4, the latter for supporting the block assembly in its reciprocations in the receiver, as best shown in Figures 6 and 7.

Spanning the space between the side walls of the receiver and forming a portion thereof, is a key 5 which cooperates with a block lock, both of which will be presently described in detail together with the manner of their cooperation with other parts of the assembly.

At the front of the receiver is a block 6 which threadedly receives the barrel 'I provided with the usual cartridge chamber 8. The block 6 is formed with a central lug 9 into which is threaded the rear end of a short guide rod I9 who-se front end extends into the gas cylinder sleeve II carried by the gun barrel. The rear end of the gas cylinder carries a yoke I2 whose arms straddle the breech portion of the barrel and carry rearwardly extending push rods I3 whose rear ends engage the forward end of the block slide to impart rearward movement thereto upon the rearward movement of the sleeve II, the sleeve being actuated by gas from a port (not shown) in the gun barrel upon the firing of the round, all as usual in guns of this type.

Reference is made particularly to Figures 9 and 10 in which I4 designates the main body of the block, and I5 the slide, the relative positions of the parts being such'that they would t accurately together if assembled. The general cross-sectional shape of the body portion and the slide are shown in Figures 11 and 12 which are end elevations of those parts. The body portion I4 is formed with a central, longitudinal semi-circular driving spring groove I6 on each side of which is a track I 'I for sliding engagement with the downwardly facing track I8 of the slide I5. The groove extends throughout substantially the full length of the body portion, but is interrupted near its front end by a transverse recess I9, Figure 2, for the reception ci the novelly-shaped and noVelly-arranged sear 29, shown best in Figures 2, 8 and 19. The front end of the body portion I4 terminates in an upstanding wall 2l at the rear of which is a continuation of the groove I6 and the tracks I'I, Figure 2. This continuation is of smaller radius than the groove I5 as indicated b-y I6 to conform to the radius of the front portion of the ring pin. TheV wall 2l is apertured centrally as at 22 for the passage of the striker 23 ora firing pin 24 appearing in most 0f the views, and in inverted perspective in Figure 1'7. Numeral 25 designates the Sear spring shown in its entirety in Figure 18. The spring is of the leaf variety and formed with a base piece 25 bent to form an upwardly and rearwardly extending lip 21, the base piece being secured in the bottom of the recess I9. The slightly curved free end of the spring engages the underside of the sear and urges it bodily upward, but as will presently clearly appear, allows the sear to rock in the recess with the spring as a fulcrum, for cooperating with the firing pin 24 and slide I5. The sear has formed integrally at each corner, an upwardly extending lug 28 bevelled forwardly and downwardly as at 28' and adapted tov enter the oppositely disposed notches 29, also bevelled as at 29', Figures 1 and 9, for proper cooperating with said lugs, for a purpose that will appear.

There is a central recess 39 in the front edge ofthe sear presenting a shoulder for engagement with a specially formed part of the firing pin. The sear is further provided with side extensions 3I, Figures 2, 8 and 19, provided with cam surfaces 32 for cooperating with cam surfaces 33 of a spring-backed sear operating lever or trigger 34 pivotally mounted at 35 in a vertical recess 36, Figure 2, in the side wall of the body portion I4, the extensions 3| extending rearwardly to position to be engaged by the cam when actuated to release the sear. The rear of the sear body terminates in a sharp edge 31 which is bevelled downwardly and forwardly between the extensions 3| for engagement with the sear notch in the firing pin. The front edge of the sear is denitely bevelled as indicated at 38, Figure 8, to conform to the bevelled surfaces 39 of the inner wall of the recess I9, Figures 13 and 14. There is an abutment 40 in the groove I6 between which and the cylindrical rear end 4I of the firing pin is the ring pin spring 42 which is independent of a recoil and counterrecoil or driving spring 43 which is also seated in the groove and contains a guide plunger 44 whose forward end engages the abutment 40, and which, with the spring 43, extends through the tubular portion 45 of the body portion I4, the plunger rod extending into the guide sleeve 44' which extends to the usual buffer mechanism (not shown) at the rear of'the receiver.

'Ihe firing pin 24 is shaped to form a flat bearing surface 46 on its underside terminating at its forward end in a sear notch 41 preferably vinolining slightly downwardly and forwardly for engagement at times 4with the edge 31 of the sear. The rear end 4I off the firing pin is cylindrical and has an easy sliding fit in the groove I 6, Vibut from 'a point just forward of the sear notch the pin is reduced `in diameter to form 'a forwardly facing important shoulder 4'8 which cooperates with the slide in its rearward movement tocock the pin. The forward reduced 'end of the pin presents a definite rearwardly facing Vshoulder 49V which engages the notch 3B in ythe front edge `of the sear, the space between the sear notch and the shoulder 49 being enough to allow the firing pin 'to be moved backward far enough to let the rear edge of the sear engage the notch in the pin.

The mechanism for locking the body portion I4 in battery position is characteristic of the 20 mm. type of gun. It 'comprises a transverse recess 5i! in whose front wall there is a transverse semi-circular groove 5I in which is rockably received the semi-circular end of a block lock 52 that ffolds into the recess to unlock the block (Figure 5) and permits it to move rearwardly, but arranged to engage 'the notch 53 in the key 5 (Figures 1 and 3) t'o lock the body portion `I4 in battery position.

The lock 52 is provided with two oppositely disposed upwardly and forwardly inclined projections 54 which are arranged to engage upwardly and forwardly yfacing inclined cam faces 55 made in the opposite side walls of the rear end of the slide,the projections cooperating with the cam faces to cam the lock 52 upwardly and out of engagement with the notches 53 of the key 5, so that the lock clear the key to unlock the body portion VI4 and permit it to be moved rearwardly by blowback pressure.

The foregoing description has been Vvfor the most part of the lower body portion I4 of the block, and the parts carried thereby. VReference is now made tothe Figures9 and 11. The roof 56 of the 'slide I5 is provided with a central semicircular groove 51 between 'the tracks I8 which match with the groove I6 in the body `I4 for the greater part of the length of said, groove I6, so that when the block is assembled there is formed a cylindrical bore :for the reception of the upper portion of the driving spring 43, abutment 4B, firing spring Y42 and a portion of the firing pin 24. The groove 51 is reduced in radius at its forward end to form a short groove 51 corresponding with the groove II in the lower body portion of the block. This reduction in the radius of the groove shoulder 51" against which the front end of the firing pin engages at times, for a purpose that will later appear.

Just in advance of the cam faces 55 in Figure 1, in the side walls oi the slide, there are two oppositely disposed elongated recesses 58, Figures 1 and 6, in which are slidably mounted oppositely disposed downwardly extending lugs 55 to each of which is attached a guide rod 59 within thel coils of slide return springs 5I with one end abutting against a lug 59 and the other against an abutment in its recess, the rearward movement of the lugs being limited by the rear ends of the recesses.

A plate, such as 62, Figures 1, 6, 9 and 11, is sein the slide forms a definite lliV cured Vto each side of the wall of the slide, as for instance, by screws 63. The lower side of the plates are bent inwardlyto form iianges 53' which extend for about one half of the length of the recesses to completely house the guide rods and return springs, but are cutaway for a suitable distance in advance of the lugs 59 for the passage of thelugs and to permit them to have the necessary sliding movement in their recesses in performing their functions in cooperation with two oppositely disposed notches 64, Figure 10, in the body portion I4, their functions being to compress the spring EI on the rearward stroke of the slide under the influence of the push rods actuated by gas from the gun barrel, and the return of the slide to its normal position.

The angle of the bevel 25' of the notches `29 in theslide I5 is such with respect to the bevel 28 of the sear lugs 2B that the tendency of the slide to rebound upon reaching battery position will not be sufficient to disengage the lugs from the notches, but upon the application of sufficient manual force exerted upon the slide, these lugs may be retracted as becomes necessary to initiate ammunition feed.

As shown in Figures 3 and 4, there is the usual extractor 55 rockably mounted on the body -portion I4, there being the usual extractor spring 66 tending to hold the upper ends of the extractor elevated.

Operation-Reference is made to Figures 1, 2 and 3, and more particularly to Figures 13, 14, 15 and 16, which latter gures are somewhat enlarged fragmentary sections of the block in the neighborhood of the sear, firing pin and sear spring, showing various positions the sear, firing pin and slide assume at dilerent stages of the cycle of operation of the block. In Figure 16 the firing pin is cocked and the gun ready to be red with the edge 31 of the sear in the sear notch 41. The trigger 34, Figures 2 and 19, is rocked inwardly either manually or otherwise so that its cam 33 engages the cam surface 32 of the sear depressing its rear portion, Figure 13, the sear meanwhile fulcruming on its spring 25 and smoothly riding against the correspondingly shaped rear ends 39 of the short track sections flanking the short groove I6 in the body portion I4 of the block. The depression of the rear portion of the sear to the positions shown in Figure 13 `permits the flattened portion 46 of the firing pin, under the influence of its spring 42, to ride upon and atten out the sear and simultaneously withdrawing the sear lugs 2S from the notches 23 in the slide, the pin continuing its movement to the iiring position shown in Figure 14. Upon ring a round the gas from the gun barrel causes the push rods I3, Figures 1 and 3, to move the slide rearwardly. The slide in moving rearwardly brings the shoulder 51 of the slide into engagement with the shoulder 48 of the firing pin, carrying the pin back with the slide to the recoil position shown in Figure 15 wherein the sear spring 21 acts to bodily elevate the sear to position to enter the notch in the firing pin counterrecoil. During the initial rearward movement of the slide the body portion I4 can not move and is momentarily held in battery position being locked by the block lock 52 in engagement with the key 5, Figures 1 and 5. However, when the forwardly facing cam surfaces of the projections 54 of the lock engage the rearwardly facing cams 55 of the slide block lock, the lock will be cammed upwardly into its recess, clearing the key 5 and unlocking the body portion of the block from the 7 receiver.` The slide and body portion are now free to move rearwardly together on recoil responsive to the blowback force of the explosion of the round, against the restraint of the driving or recoil. and counterrecoil spring G3, which With the buffer spring (not shown) returns them together to battery position, when the lugs 28 of the sear enter the notches 29 in the slide and prevent the rebound of the slide against the then released slide return spring 6l when the slide and bolt reach battery position.

When the gun is fired by remote control, a solenoid arrangement may be employed such as is indicated by the numeral 65, suitably attached to the outer wall of the receiver. In the present case the trigger 34 ywould be operated by the solenoid plunger 66 whose operation is the reverse of the ordinary plunger in that the plunger is projected or pushed against the trigger rather than being pulled to release the sear.

I claim:

1. A breech block reciprocable in recoil and counterrecoil and for use in automatic machine guns, comprising a body portion and a slide mounted on said body portion and associated therewith for joint and independent relative movement, means for initiating recoil of said body portion and slide, means for locking the body portion in lbattery position at the time of firing, said slide being constructed and arranged to unlock the body portion upon initial rearward movement of said slide, a sear in said body portion, means carried partly by the sear and partly by the slide cooperating to lock the slide in battery position along with said body portion when in :dring position, a spring-backed ring pin controll-ed by the sear, means for operating the sear to release the firing Din and at the same time unlock the slide from said body portion to permit the slide to move rearwardly independently of said body portion. Y

2. A breech block reciprocable in recoil and counterrecoil and for use in automatic machine guns, comprising a body` portion and a slide mounted on said body portion for joint` and independent movement, means for initiating recoil oi said body portion and slide, means for locking the body portion in battery-position at the time of firing, said slide constructed and arranged to unlock said body portion upon` initial rearward movement of the slide, va transverse recess adjacent the iorward end of said body portion, a sear in said recess, a sear spring in said recess supporting said sear and serving as a ful- Crum for the operative movements of the sear,

means carried partly by the sear and partly by the slide for cooperating to lock the slide in bat-' tery position along with the body portion, a

spring-backed ring pin controlled by the sear, and means for operating the sear to release the iiring pin and at the same time unlock the body portion from the slide to permit the slide to move rearwardly independently of said body portion.

3. A breech block reciprocable in recoil and counterrecoil and for use in automatic machine guns, comprising a body portion and a slide mounted for joint independent relative movement, means for initiatingvrecoil of said body portionv and slide, means for locking the body portion in battery position at the time of ring, said slide being constructed and arranged to unlock said body portion upon the initial rearward movement of the slide, a transverse recess adjacent the forward end of the body portion, a sear in said recess, a sear spring in said recess supporting the sear and serving as a fulcrum for the sear in its operative movements, lugs carried by the sear, means carried by the slide cooper-ating with the lugs to lock the slide in battery position along with said body portion at the time of ring, a firing pin slidable between said body portion and slide and spanning said recess and overhanging the sear, said firing pin being formed with an undercut portion having a notch therein engaged lby the sear, said firing pin being further provided with a shoulder arranged to be engaged by the slide upon its initial rearward movement to cock the firing pin, a spring carried by said body portion in engagement with the ring pin and independent of the recoil and counterrecoil springs of the weapon, and means for operating the sear to release it from the ring pin and to simultaneously unlock said body portion from the slide to permit the rearward movement of the slide independently of said body portion. v

4. The invention of claim 3 characterized in that the means carried by the slide cooperating with the lugs on the sear comprises oppositely disposed recesses in the slide entered by said lugs, and that the sear is provided with a rearward extension having a cam surface thereon, and that the means for operating the sear to release the iiring pin and unlock the body portion of the block comprises a trigger pivoted to said body portion and provided with a cam surface cooperating with the cam vsurface of the sear extension to depress the sear upon the inward movement of the trigger.

SIGMUND SCHIFF.