US2748661A - Firing rate reducer for automatic firearms - Google Patents

Description

J1me 1956 c. E. SIMPSON 2,74

FIRING RATE REDUCEZR FOR AUTOMATIC FIREARMS Filed Dec. 10, 1952 INVENTOR. Elurence E- 51m sun ATTORNEYS FIRING RATE REDUER FOR AUTOMATIC FIREARMS Clarence E. Simpson, Wilbraham, Mass., assignor to the United States of America as represented by the Secretary of the Army Application December 10, 1952, Serial No. 325,239

6 Claims. (Cl. 89-130) (Granted under Title 35, U. S. Code (1.952), sec. 265) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.

This invention relates to a fire control mechanism for automatic firearms and particularly to a mechanism for delaying the rate of fire of the firearm.

Modern warfare demands a large volume of fire from automatic firearms at a rapid rate. However in the attempt to design firearms of lesser weight, the cyclic rate of the firearm increased as the weight of the reciprocating parts decreased. Thus while a larger volume of fire at a high rate was capable of'being produced by such firearms, the rate of firing was excessively fast so that such a high rate of fire wore out the barrels unduly fast. Another drawback to such high rate of fire was the inability of the shooter to accurately concentrate his fire on a target.

In order to slow down the rate of fire of such firearms various rate reducing devices have been resorted to. Unfortunately the shape, size, and operation of many prior art rate reducing devices preclude their use in modern design of firearms. This is particularly true when such a mechanism must be located in the pistol grip of the firearm and combined with the fire control mechanism thereof.

Accordingly, it is an object of this invention to provide a fire control mechanism for an automatic firearm having a delaying mechanism whereby a reduced rate of automatic fire can be obtained.

Another object of this invention is to provide a fire control mechanism having full automatic fire and semiautomatic fire control.

A further object of this invention is to provide a delaying device for a fire control mechanism which is simple and positive in action.

Still another object of this invention is to provide a fire control and rate reducing mechanism for an automatic firearm capable of being contained in the pistol grip of a firearm.

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 fragmentary longitudinal sectional view of the trigger guard of a firearm embodying this invention;

Fig. 2 is an exterior left side view of the trigger guard; and

Fig. 3 is a cross-sectional view taken along the line 33 of Fig. 1.

The fire control mechanism of this invention is contained in a trigger housing 10. Such housing is arranged to be secured to a firearm (not shown) and comprises a trigger guard 11 and apistol grip 12. Trigger housing is recessed at 13 so that the elements .of this invention can be mounted in such recess. A trigger 14 is mounted in the forward end of recess 13 and is pivotally secured to housing 10 by a transverse pin 15. Trigger 14 has a finger portion 16 of conventional construction.

nited t e Patent The upper end of trigger 14 is bifurcated as shown at 17 and a button 18 is mounted within such bifurcation for transverse slidable movement. Button or block 18 is cylindrical and is provided with a reduced diameter end portion 24 for a purpose as will later appear. Such button is mounted on a pin 19 provided with a head 20. The head 24) of pin 19 has a conical shaped end 21 which is engageable by'a screw 22 transversely secured in the trigger housing 10. Such screw is provided with an end 23 having a sloped surface corresponding to the sloped end 21 of pin 19. Screw 22 cooperates with pin 19 to movebutton 18 as will be later described.

A washer-like spring 25 is provided within bifurcation 17 surrounding pin 19 to normally bias button 18 to the right asshown in Fig. 3. Head 20 of pin 19 is constructed to contact the reduced diameter end of button 13 at all times so that button 18 may be forced to the left against the bias of spring 25 when the conical head 20 of pin 19 contacts the correspondingly shaped end of screw 22, as will be later described. A third pin 26 is transversely mounted at the top of trigger 14 as shown in Figs. 1 and 3.

A sear 27 is pivotally mounted within recess 13 of trigger housing 19 by a transverse pin 28. Such sear is mounted substantially above trigger 14 and sear 27 is provided with a forwardly projecting end 29 having a sloped surface 30 thereon. The forward end 29 of sear 27 rests on button 18 while the sloped end 30 thereof is engageable with pin 26 as will be later described. The other end 31 of sear 27 is provided with a squared end 32 which is engageable with a scar notch 33 provided on the underside of a bolt 34 shown in outline horizontally disposed above the trigger housing 10 in Fig. l.

A toggle 35 is pivotally secured to end 31 of sear 27 by a transverse pin 36. Such toggle is provided with an upwardly projecting heel 37 which is engageable with the underside of bolt 34. A rearwardly and downwardly projecting toe 38 is provided on toggle 35 which contacts a sear actuator 39 for a purpose to be later described. On the underside of sear 27 there is provided a downwardly projecting cylindrical boss 40 which serves as a seat for one end of a spring 41. A corresponding and oppositely disposed boss 42 is provided on the upper side of trigger 14 on which the other end of spring 41 is mounted.

Actuator 39 comprises a substantially cylindrical bar provided with an integral axially disposed spring guide 43 on the bottom end thereof. Actuator 39 is slidably contained within a tubular housing 44 which in turn is contained within pistol grip 12. Such housing is substantially vertically disposed therein and also contains a spring 45, one end of which abuts the bottom of actuator 39 cooperating with spring guide 43 to retain such spring thereon. An annular groove 46 is provided'on actuator 39 and a latch 47 projects through an opening 48 in tubular housing 44 for engagement with groove 46. Latch 47 is maintained out of engagement with groove 46 by a knob or handle 49 attached to latch 47. Any suitable detent means may be provided to yieldingly secure handle 49 in either of two positions whereby latch 47 is maintained out of engagement with groove 46 or maintained in engagement therewith. Latch 47 is utilized to hold or to secure actuator 39 in a depressed position for semi-automatic fire as will be later described.

I A selector 50 is transversely mounted within recess 13 of trigger housing 10 directly underneath sear mounting pin 28. Selector 50 is provided with two flat surfaces 51 is provided to rotate selector 50 to the desired position and is held therein by any suitable detent means. By the use of selector 50 either full automatic fire or reduced rate automatic fire may be readily obtained as will now be described.

Operation The fire control mechanism of this invention is preferably utilized with a firearm adapted to shoot from the open bolt position. In Fig. 1 bolt 34 is shown in the retracted position and held thereby sear end 32 being in engagement with the shoulder produced by notch 33 in bolt 34. With the selector set in the position shown in Fig. 1 so that the flat surface 51 faces lug 53, the fire control mechanism is set for full automatic fire.

In the position of the parts shown in Fig. l sear nose 29 rests on top of the larger diameter portion of button 18. Thus when trigger 14 is pulled rearwardly such trigger pivots about pin 1.5 in a clockwise direction carrying therewith button 18. Nose 29 of scar 27 is thus forced upwardly and in a counter-clockwise direction thereby forcing end 32 of scar 27 out of engagement with notch 33 whereupon bolt 34 moves forwardly to the battery position. Sear 27 is held out of engagement with bolt 34 as long as trigger 14 is depressed. With sear 27 thus held down, toggle 35 is likewise held downwardly and in contact with actuator 39. In this setting of the fire control mechanism the actuator has no effect on toggle 35 as such toggle is maintained in contact with the actuator by sear 27. The rate of fire of the firearm with the fire control mechanism set for full automatic fire as just described will be the normal cyclic rate obtainable without any delay or impedance in the firing of the cartridge. Full automatic fire may be stopped by releasing trigger 14.

When such trigger is released, sloped end of sear 27 is raised into contact with pin 26 on trigger 14 of the recoil stroke of bolt 34. On such stroke of the bolt a lug 54 thereon contacts a cam 55 of sear 27 thereby sharply depressing sear end 32 and toggle 35. Toe 38 of toggle then strikes actuator 39 smartly driving such actuator downwardly. Meanwhile spring 41 biases sear end 32 into notch 33 as bolt 34 starts forwardly whereby such bolt is retained in the open position. Shortly after such action has taken place actuator 39 has been biased upwardly by spring to strike toe 38 of toggle 35 thereby tending to pivot such toggle about heel 37 and to disengage sear 27 from bolt 34.

However as pin 26 is engaging sloped end 30 of scar 27 such is not possible. The reason therefore is due to the bias of trigger spring 41 being greater than the force with which actuator 39 strikes toggle 35 coupled with the fact that the leverage advantage of trigger 14 about its pivot point is substantially greater than that of toggle 35. Thus the rate reducing device is retained relatively inoperative when the trigger is released in order to cease firing.

When selector 5!) is rotated so that flat surface 52 is disposed opposite lug 53 on trigger 14, the control mechanism is then set for reduced rate of automatic fire. In such position of the selector, trigger 14 may now be pulled rearwardly a greater distance than for full automatic fire. Hence as trigger 14 is pulled rearwardly nearly to the limit of its movement as governed by lug 53, the head portion 20 of pin 19 engages screw 22. The sloped end of such screw and head portion 20 of such pin cooperate to force pin 19 to the left from the position as shown in Fig. 3 against the bias of spring 25 whereupon the larger diameter of button 18 is moved away from sear 27, thus sear 27 is relatively free to pivot about pin 28 without restraint from button 18.

Initially when the trigger is pulled rearwardly the nose 29 of scar 27 resting on the large diameter portion of button 18 forces such end upwardly in the same manner as described for automatic fire. Thus end 32 of sear 27 is rotated out of engagement with notch 33 of bolt 34 allowing such bolt to go into battery position. The trigger meanwhile has been pulled to the extreme rear position whereupon button 18 has been cammed to one side so that sear nose 29 no longer rests thereon as above described. On the recoil stroke of bolt 34, lug 54 provided on the underside thereof and rearwardly of notch 33, strikes end 32 of scar 27 thereby depressing such sear and simultaneously driving toggle 35 downwardly against actuator 39 whereupon the impact from such blow forces actuator 39 downwardly within tubular housing 44.

As soon as notch 33 of bolt 34 comes opposite end 32 of sear 27 on the counter-recoil stroke of bolt 34, spring 41 biases sear end 32 upwardly into engagement with sear notch 33 thereby holding bolt 34 in the open position. Meanwhile, however, actuator 39 is still moving downwardly in tubular housing 44 and at the end of such movement spring 45 returns such actuator upwardly. The bias of such spring however is sufficiently great to impart considerable momentum to actuator 39 and such actuator therefore strikes toe 38 of toggle 35 a smart blow whereupon end 32 of scar 27 is forced out of engagement with notch 33. This arrangement is possible because heel 37 of toggle 35 acts as a fulcrum and when a force is exerted on toe 38 of toggle 35 the other end of such toggle being pivotally secured to sear end 32 by pin 36, forces end 32 of sear 27 out of engagement with notch 33 whereupon bolt 34 is permitted to go forwardly again to the battery position. This cycle will be repeated as long as the trigger is held rearwardly or until the ammunition is consumed. Release of trigger 14 at any time stops the firing in the same manner as described for full automatic fire.

It should therefore be readily apparent that the delay introduced by the length of time it takes the actuator to travel from the position shown in Fig. l to the bottom of housing 44 and up again is appreciable, thus there is introduced a delay period before the sear 27 is released, which materially slows down the firing rate of the firearm.

The device is readily set for semi-automatic fire when the selector is positioned to produce a reduced rate of automatic fire. Latch 47 is rotated into engagement with actuator 39 when such actuator is manually depressed by knob 59 so that such latch can engage groove 46 to hold actuator 39 in such depressed position. Slots 58 in housing 10 permit knob 59, attached to actuator 39, to depress such actuator downwardly. Thus toggle 35 cannot act on actuator 39 and hence such actuator will be ineffective to trip sear end 32 out of engagement with notch 33. Thus semi-automatic fire is also obtained with this fire control mechanism.

From the foregoing description it is clearly apparent to those skilled in the art that there is here provided a compact arrangement of elements for a fire control mechanism that are readily contained in the pistol grip of the trigger housing. Not only does the fire control mechanism of this invention provide for full automatic fire and semi-automatic fire but also a reduced rate of fire. The means utilized for delaying the firing rate of the firearm with which this fire control mechanism is employed is not only unique in arrangement but simple and positive in operation. The various elements of this invention are of simple and rugged construction thereby producing a dependable and positive fire control mechainsm.

I claim:

1. In a firearm, a reciprocating bolt mounted therein for movement between a battery and recoil position, said bolt having a scar engaging notch with a camming surface rearwardly thereof and a flat surface therebetween, a trigger guard mounted to said firearm, a trigger pivotally mounted in said trigger guard and operable to a first and second pulled position, a sear pivotally mounted in said trigger guard and movable into and out of engagement with said bolt, a selector rotatably mounted in said trigger guard and having a first and second flat surface disposed at an obtuse angle to each other, an upstanding lug on said trigger arranged for cooperation with said selector whereby the degree of movement of said trigger to said first pulled position is limited by said first surface of said selector and the degree of movement of said trigger to said second pulled position is limitedby said second surface of said selector, blocking means slidably mounted on said trigger and movable therewith for pivoting said sear to a disengaged position when said trigger is pulled to said first position, cam means adjustably mounted in said trigger guard for moving said blocking means to an inoperative position when said trigger is pulled to said second position whereby said sear is permitted to reengage said notch at the recoil position during reciprocation of said bolt, a toggle pivotally secured to the rear end of said sear, said toggle having a downwardly depending toe portion and an upwardlyextending heel portion for cooperation with said flat surface of said bolt, an actuator slidably mounted in said trigger guard provided with spring means for urging said actuator upwardly against said toe of said toggle, spring means on said trigger for biasing said sear to an engaged position, said spring means operative in said second position of said trigger for moving said sear to an engaged position and whereby reciprocating movement of said camming surface on said bolt in the recoil position cams said toe of said toggle downwardly thereby deflecting said actuator downwardly and whereby recovery of said actuator forces said toggle upwardly in a clockwise direction thereby disengaging said sear from said notch of said bolt when said heel portion of said toggle contacts said flat surface of said bolt.

2. In an automatic firearm having a receiver, a trigger housing depending therefrom, and a longitudinally reciprocal bolt slidable between a battery and a retracted position, the combination of a pivotal sear for holding the bolt in the retracted position, a trigger pivotally mounted at a point forwardly of and below the pivot point of said sear, a cylindrical member transversely mounted for slidable movement on said trigger and in contact with the underside of said sear whereby actuation of said trigger lifts said cylindrical member to pivot said sear out of engagement with the bolt, a spring intermediate said trigger and said sear rearwardly of the respective pivot points thereof for urging said sear into engagement with the bolt and simultaneously urging said trigger to the released position, said cylindrical member having an end portion of reduced diameter, cam-means in the trigger housing for imparting a transverse movement to said cylindrical member after release of said sear from the bolt but during the continued actuation of said trigger whereby said reduced diameter portion of said cylindrical member is vertically aligned with the front end of said sear to permit a return thereof into engagement with the bolt under the bias of said sear spring, a toggle pivotally secured to the rear end of said sear, a spring-biased actuator slidably mounted in the trigger housing for substantially vertical movement from and toward contact with the underside of said toggle, and an inclined cam surface on the underside of the bolt for actuating said toggle to depress said actuator whereby the upward recovery movement thereof pivots said toggle to simultaneously pivot said sear out of engagement with the bolt whereby the interval of engagement between said scar and the bolt serves to retard each cycle of automatic fire.

3. In an automatic firearm having a receiver, a trigger housing depending therefrom, a trigger guard and pistol grip included in the trigger housing, and a longitudinally reciprocable bolt slidable between a battery and a retracted position, a pivotal sear for holding the bolt in the retracted position, a trigger pivotally mounted at a point forwardly of and below the pivot point of said sear, a spring intermediate said sear and said trigger rearwardly of the respective pivot points thereof for urging said sear to pivot in a clockwise direction into engagement with the bolt and simultaneously urging said trigger in a counterclockwise direction toward the released position thereof, said trigger having anupper bifurcated portion, a transverse pin slidably mounted in said bifurcated portion, said pin having an enlarged head portion projecting from the side of said bifurcated trigger portion, a cylindrical member slidably mounted on said transverse pin and having a reduced diameter portion on one end thereof, spring means normally biasing said cylindrical member against said enlarged head portion of said transverse pin and against the side of said bifurcated portion of said trigger whereby clockwise pivotal movement of said trigger lifts said cylindrical member to pivot said sear in a counterclockwise direction out of engagement with the bolt, a cam stud fixedly mounted in the trigger housing to contact said enlarged head portion of said transverse pin during clockwise pivoting of said trigger and thereby impart transverse movement to said cylindrical member after release of said sear from the bolt whereby said reduced diameter end of said cylindrical member is vertically aligned with the front end of said sear to permit reengagement thereof with the bolt under the bias of said sear spring, a toggle pivotally secured to the rear end of said sear, said toggle having an upwardly projecting heel portion and a downwardly projecting toe portion, a spring-biased actuator slidably mounted in the pistol grip portion of the trigger housing for reciprocal vertical movement from and toward contact with said toe portion on said toggle, an inclined cam surface on theunderside of the bolt for contacting said heel portion on said toggle during recoil movement and thereby pivoting said toggle to depress said actuator, said toggle being arranged to pivot said sear in a counterclockwise direction out of engagement with the bolt in response to the clockwise pivotal movement imparted to said toggle by the upward recovery movement of said actuator whereby the interval of engagement between said sear and the bolt serves to retard each cycle of bolt operation during movement thereof into battery position, and selector means for limiting the clockwise pivotal movement of said trigger to prevent contact of said fixed stud in the trigger housing with said enlarged head portion on said transverse pin whereby said sear is continuously held out of engagement with the bolt to eifect unretarded automatic fire while said trigger is held in the pivoted position.

4. In an automatic firearm having a receiver, a trigger housing depending therefrom to terminate in a pistol grip portion, a bolt having a sear notch in the underside thereof and slidably mounted in the receiver for longitudinal recoil and counterrecoil movement, a pivotal sear having spring means normally urging the rear end thereof into engagement with the sear notch to hold the bolt in a retracted position, and a pivotal trigger having means for imparting counterclockwise movement to the sear to release the bolt from the retracted position thereof, a rate reducing mechanism comprising means operative during the completion of the firing movement of the trigger for disconnecting the sear therefrom to permit reengagement thereof with the sear notch of the bolt during the counterrecoil movement thereof, an actuator slidably mounted in the pistol grip for movement toward and away from the underside of the bolt, a toggle member pivotally secured to the rear end of the scar and having an upwardly projecting heel portion and a downwardly extending toe portion, a spring normally urging said actuator upwardly to contact said toe portion on said toggle member and force said heel portion thereof against the underside of the bolt, and cam means on the underside of the bolt rearwardly of the sear notch therein for pivoting the sear in a counterclockwise direction during recoil movement of the bolt and thereby imparting a corresponding movement to said toe portion of said toggle member for depressing said actuator against the bias of said spring whereby the recovery movement thereof pivots said toggle member in a clockwise direction about said heel portion as a fulcrum to simultaneously withdraw the sear out of engagement with the sear notch of the bolt to permit completion of the counterreeoil movement thereof.

5. The combination defined in claim 4 wherein the rear end of the bolt is of reduced diameter and wherein said cam means comprises an upwardly and rearwardly inclined surface on the underside of the bolt between the larger and smaller diameter portions.

6. in a firearm having a reciprocal bolt, a spring-biased pivotal sear for holding the bolt in a retracted position, and a pivotal trigger for actuating the sear to release the bolt, the combination of means for disconnecting the sear from the trigger during the firing movement thereof subsequent to the release of the bolt to free the sear from rcengaging the bolt during the counterrecoil movement thereof, a rotatable selector having a first stop surface for halting the firing movement of the trigger prior to the disconnecting of the sear therefrom whereby the sear is held out of engagement with the bolt to provide automatic fire until the trigger is returned to the prefired position thereof, said selector having a second stop surface for halting the firing movement of the trigger subsequent to the disconnecting of the sear therefrom whereby the sear reengages the bolt during counterrecoil thereof, a toggle member pivotally secured to the rear end of the sear, an upwardly biased actuator engageable with the free end of said toggle member, cam means on the underside of the bolt for pivoting the sear in a counterclockwise direction during recoil movement of the bolt to impart a corresponding movement to said toggle member and depress said actuator whereby the recovery movement thereof pivots said toggle member against the underside of the bolt to simultaneously withdraw the sear out of engagement with the bolt and thereby provide a reduced rate of automatic fire when the firing movement of the trigger is halted by said second stop surface on said selector, means for manually depressing said actuator, and latch means for retaining said actuator in the manually depressed position thereof out of contact with said toggle member whereby the sear engages the bolt until the trigger is returned to the prefired position thereof and again retracted thereby providing semiautomatic operation.

References Citcd'in the file of this patent UNITED STATES PATENTS 1,318,214 Logan Oct. 7, 1919 1,518,355 Reibel Dec. 9, 1924 2,384,832 Gilligan Sept. 18, 1945 2,384,854 Simpson Sept. 18, 1945 FOREIGN PATENTS 579,096 Germany June 21, 1933 999,340 France Oct. 3, 1951

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