US 3345914 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
at w, 1967 F. N. NEWCOMB ETAL 7 3 TWO ROUND BURST MECHANISM MECHANICAL AUTOMATIC RIFLE 2 Sheets-Sheet 1 Filed March 31, 1966 INVENTORS, Fred N. Newcom b Edsel H. Spa/Imam.
fl l I BY w J-W M ATTORNEYS.
Oct. 10, 1%? F. N. NEWCOMB ETAL 3,345,914
TWO ROUND BURST MECHANISM MECHANICAL AUTOMATIC RIFLE Filed March 31 1966 2 Sheets-Sheet 2 INVENTORS Fred N/Vewcomb fa/ie/ ASpaZ/mam m N R m A 3,3453% Patented Oct. 10, 1967 3,345,914 TWO ROUND BURST MECHANISM MEHANL CAL AUTOMATIC RIFLE Fred N. Newcomb, Kingsville, and Edsel A. Spellman,
Abingdon, Md., assignors to the United States of America as represented by the Secretary of the Army Filed Mar. 31, 1966, Ser. No. 540,156 9 Claims. (Cl. 89-129) ABSTRACT 6F THE DISCLGSURE A rifle having selective semiautomatic, full automatic and two round burst firing cycles. The two round burst cycle is eifected by an auxiliary mechanism activated by the rifles bolt and includes a cam progressively rotatable thereby and which intermittently rocks a lever contacting the rifles disconnector into a selected number of positions relative to the trigger. The cam is also capable of rotation by a hand lever to return the trigger mechanism to a position for semiautomatic or full automatic firing.
This invention relates to a two round burst, mechanical, automatic rifle, and more particularly to a mechanism by which a rifle originally designed for semiautomatic and/ or automatic fire may also deliver an automatic burst of two rounds per trigger pull, thereby providing controlled firepower resulting in economy of ammunition and in greater hit probability.
Semiautomatic and automatic rifles usually have a spring biased hammer having a disconnector thereon to hold the hammer upon recoil of the bolt after a single round has been fired, so that the trigger must be pulled again to fire again. This is for intermittent fire. When automatic fire is desired, a selector arm is turned to position the disconnector so that the hammer is free to follow the bolt in its travel to fire the weapon. As long as the trigger is pulled, the weapon will fire continuously to exhaust the ammunition. When it is desired to stop the firing, the trigger is released so that the disconnector will again engage the hammer.
In most automatic fire weapons, many rounds are fired even with a short pull of the trigger and results in waste of valuable ammunition.
The present invention provides an auxiliary mechanism to cause the weapon to fire two bursts (or more) as desired.
In operation, the auxiliary mechanism provides a means to hold the disconnector out of contact with the hammer on alternate rearward excursions thereof, the result being the eflect of firing a first round as if in the automatic firing mode, while the second round will cause the hammer to remain in its rearward position as being held in the semiautomatic firing mode.
It is therefore a primary object of this invention to provide a mechanism for permitting a two round burst of ammunition in a semiautomatic and/or automatic weapon.
It is another object to permit a two round 'burst of ammunition in a weapon with a single pull on the trigger.
It is a further object to provide a two round burst of ammunition in a weapon without interfering with its original capability of semiautomatic or automatic fire.
A still further object is to provide an automatic burst of two rounds per trigger pull in a weapon thereby providing controlled firepower which results in economy in the use of ammunition together with greater hit probability.
These and other objects and advantages of the present invention will be fully apparent from the following description when taken in connection with the annexed drawings, in which:
FIG. 1 is a partial side elevation of the receiver of a semiautomatic weapon, with parts being broken away and in section and showing the firing mechanism in position whereby the two burst lever is in position to momentarily interrupt the function of the disconnector relative to the hammer during a two burst fire cycle;
FIG. 2 is an exploded, perspective view of the elements of the two round burst mechanism;
FIG. 3 is a View, similar to FIG. 1, but showing the hammer being momentarily disengaged by the disconnector, during a two burst fire of the weapon;
FIG. 4 is a sectional view, taken along the line 4-4 of FIG. 5 and looking at the opposite side of FIGS. 1 and 3 and showing the two round burst lever, and with portions of the actuating cam, disconnector and trigger and their positions relative thereto;
FIG. 5 is a cross section taken through the receiver along line 5-5 of FIG. l; and,
FIG. 6 is a detail section view showing the selector shaft in its position to permit the two round burst lever from interfering with the disconnector.
Referring to the drawings in detail, there is illustrated in FIG. 1 the receiver portion of a conventional semiautomatic weapon indicated generally by reference character 1.
The receiver portion of the weapon is indicated generally by 2, and there is shown a stock 3, a back plate 4, a bolt carrier 5, a trigger 6, a hammer 7, a disconnector 8, a selector shaft 9 and a selector arm 10. Trigger 6, hammer 7 and disconnector 8 are all spring biased in a clockwise direction.
In the present invention, trigger 6 has been somewhat modified, but is provided with the usual trigger sear nose 11, and the hammer 7 is provided with the usual hammer lug 12 and a hammer sear notch 13.
The disconnector 8 is provided with the usual notch 14 to engage lug 12, but is rotatable independently of the trigger 6.
Both trigger 6 and disconnector 8 have rearwardly extending arms 15 and 16 respectively, as shown.
With the exception of the slightly modified trigger 6, which is independent of the disconnector 8, all of the aforesaid elements form no part of this invention, but the firing operation of these elements will be described herein for better understanding of the operation of the mechanism of the invention and its cooperation therewith, the two original modes of fire being: automatic fire and semi automatic fire.
Automatic In this mode the selector arm 10 is set for automatic fire and the disconnector 8 will be held clear of hammer lug 12. Therefore, once the trigger 6 is pulled, releasing the trigger sear nose 11 from the hammer sear notch 13, the hammer 7 will continue to follow the bolt carrier 5 towards a chambered round (not shown) and fire the round or rounds in the automatic mode until the magazine (not shown) is empty.
Semiautomatic (repetitive) In this mode the selector arm 10 is moved to semiautomatic position (repetitive), the disconnector 8 being spring loaded so as to catch and hold the hammer 7 after one round has been fired. To fire a subsequent round, the trigger 6 must be released, moving the disconnector 8 from contact with the hammer lug 12, allowing the hamer 7 to move slightly forward, to a point where it is held by the trigger sear nose 11. A subsequent round is fired J3 if the trigger 6 is pulled again, releasing the trigger sear nose 11 from the hammer sear notch 13.
Two round burst The two round burst mechanism of this invention is indicated generally by 17 and is located rearwardly of the trigger and hammer mechanism, as shown. This mechanism provides means to hold the disconnector 8 out of contact with hammer lug 12 on alternate rearward excursions of hammer 7. This results in the effect of firing the first round as if in the automatic mode, while the second round will cause the hamer 7 to remain in its rearward position as if having been held there in the semiautomatic mode by disconnector 8.
By the releasing and subsequent pulling of trigger 6, the above cycle is repeated, thereby causing two rounds to be fired per trigger pull.
The two round burst mechanism 17 comprises, essentially, an actuating cam assembly, indicated generally by 18, and a two round burst lever assembly, indicated generally by 19.
Actuating cam assembly As best seen in FIG. 2, the actuating carn assembly 18 includes a selector shaft, indicated generally by 20, a selector arm- 21, an actuating cam, indicated generally by 22, a pawl indicated generally by 23 and a ratchet spring, indicated generally by 24.
The selector shaft 29 is journaled in the sides of the receiver 2 as seen in FIG. 5 and is provided with an enlarged spool portion 25 having a pair of indentations 26 in the floor thereof. The spool portion is undercut as at 27 thereby providing a somewhat semicircular shape to the spool portion 25. Shaft 20 extends beyond one side of the receiver, as seen in FIG. 5, and the selector arm 21 is fixed thereon by a pin 28, see FIG. 2.
Actuating cam 22 comprises a double ratchet Wheel having cam 29 integral with one saide thereof. Cam 29 is so shaped as to provide three flat surfaces 30 along its perimeter and three lobes 31 A ratchet wheel portion 32 is integral also with cam 29 and, as shown, is provided with six ratchet teeth 32a along its circumference.
Actuating cam 22 is provided with an integral hub portion 33 having crown teeth 34 along its inner face, and the entire cam member 22 is centrally bored as at 35 to permit it to be rotatably mounted on selector shaft 20 adjacent spool portion 25.
Pawl 23 comprises a hub 36 having a bore 37 which is larger in diameter than selector shaft 29 and a wall 38 which is centrally bored as at 39 to receive selector shaft 20 therein so that pawl 23 may also also be rotatably mounted thereon.
A bushing 40 (see FIGS. 2 and 5) is provided and encircles selector shaft 20 and provides a bearing for pawl 23 as shown. Hub 36 is provided with inwardly facing crown teeth 36a as shown.
Pawl 23 further is provided with an arm 41 integral with the outer end of hub 36 and has a bore 42 to receive one end of a spring 43' which normally biases arm 41 clockwise towards bolt receiver 5.
A tang 44 is integral with the lower portion of arm 41 as shown.
Ratchet spring 24 is bifurcated as at 45 to provide a pair of fingers 46 and 47. Spring 24 is mounted on the floor of receiver 2 by a nut and bolt 48 as seen in FIGS. 1 and 3.
In assembly, finger 46 engages tang 44 of arm 41 and acts as a stop, whereas finger 47 engages the teeth of ratchet 32 to prevent reverse movement thereof.
Pawl 23 is biased inwardly by a coil spring 4 9 so that the teeth 36a normally will mesh with teeth 34 of cam 22.
Both pawl and cam 22 are freely rotatably on shaft 20 and are also capable of slidable movement thereon.
Arm 41 will be limited in rearward movement by a stop 50 as shown in FIGS. 1 and 3.
Two round burst lever The two round burst lever 19 defines essentially a fork having a body 51 and a pair of forwardly extending tines 52 and 53.
Body 51 is provided with an integral hub 54 which is tubular and is also provided with a cut-out 55 for accommodation of arms 15 and 16.
The rearward portion of body 51 is provided on one side with an undercut 56 which forms a shoulder and a downwardly depending lug 57 at its rearmost end, as seen in FIG. 4.
Lever 19 may be mounted for rotation in receiver 2, for example, by stub shafts 54a fixed to the side walls of receiver 2 (one only being shown) which are received in each end of hub 54.
Tine 52 is offset from body 51 as shown, and is beveled as at 58 and its forward end rounded as at 59 so as to not interfere with the travel of bolt carrier 5.
The outer side of body 51 is recessed, as at 60.
Tine 53 is provided with an upper flat surface 61 and an upstanding lug 62 having an upper flat surface 63.
A position selector 64 is rotatably mounted on stub shaft 54a and is disposed within the recess 60 in body 51.
Position selector 64 is provided with a rearwardly extending arm 65 having a downwardly depending point 66 which is received in either indentation 26.
Arm 65 has an integral, inwardly turned lug 67 which is bored as at 68 and a coil spring 69 which has one of its ends received in bore 68 and its other end received in lever 19, as shown, normally urges lever 19 in a clockwise manner and position selector 64 in a counterclockwise manner.
As best seen in FIGS. 4 and 5, surface 61 bears against the actuator cam 29 and surface 63 will bear against the circumference of spool portion 25 of the selector shaft 20 due to spring 69.
Operation As seen in FIGS. 1 and 3, the function of the two round burst lever 19 is to alternately release and interrupt the function of the disconnector in its capability to engage or disengage the hammer.
Due to the number of teeth 36a and 34 on the pawl 23 and hub portion 33 (six in number), and the six teeth on ratchet wheel 32; each time the bolt carrier 5 moves rearward towards the back plate 4, the pawl arm 41 will be rotated counterclockwise by tang Be on the underside of bolt carrier 5 through an arc of 60 to move the actuating cam 29 in a position whereby one of the flats 30 will cause clockwise movement of lever 19 due to bias of coil spring 69, which, in turn, causes lug 57 to rotate disconnector 8 counterclockwise and free hammer 7 to follow the bolt carrier 5.
Upon two rearward excursions of bolt carrier 5, the hammer 7 will fire two rounds whereupon the bolt carrier 5 Will cause actuating cam 29 to be rotated to a point, as in FIG. 1, whereby one of the lobes 31 will contact surface 61 of lever 19 to prevent clockwise rotation of lever 19 and permit disconnector 8 to again engage and hold hammer 7 to interrupt the cycle.
The two round burst may be repeated again by releasing the trigger 6, then pulling it again. Each flat 30 on cam 29 will produce two rounds to be fired.
During the two round burst action, the selector arm 21 will be up as shown in FIGS. 1 and 3 and the original selector arm 10 will be in its semiautomatic position.
Now, if it is desired to use the weapon for its original semiautomatic or full automatic fire, selector arm 21 is rotated to its down position whereby the semicircular portion of spool portion 25 on selector shaft 20 will engage surface 63 of lever 19, as shown in FIG. 6. This prevents lever 19 and its lug 57 from interfering with disconnector 8.
The mechanism of this invention may be adapted for several types of weapons by changing the dimensions of the various parts and, by changing the design of the actuating cam 29, more than a two round burst could be achieved. For instance, if the cam 29 were rectangular shaped (not shown) a three round burst could be made, such cam having but two lobes instead of three.
While only a preferred form of the invention is shown and described, other forms thereof are contemplated and numerous changes and modifications may be made therein without departing from the spirit of the invention as set forth in the appended claims.
What is claimed is:
1. In combination with a rifle having conventional automatic and semiautomatic firing modes, said rifle including a receiver, a bolt carrier slidable on said receiver, a hammer actuated by said bolt carrier, a disconnector for releasable engagement with said hammer, a trigger for releasable engagement with said hammer and a first selector means for preventing engagement of said disconnector with said hammer during the automatic firing mode; a two round burst mechanism for providing a two round burst firing cycle in said rifle and housed in said receiver, said mechanism comprising a two burst lever assem'bly mounted in said receiver and normally having its forward end in contact with said disconnect-or, there being first and second contact surfaces at its rearward end, a second selector means transversely journ'aled in said receiver and adapted to engage said first contact surface and prevent said two burst lever from contacting said disconnector whereby said rifle may optionally retain its original firing modes, a spring loaded pawl rotatably mounted on said second selector means, an actuating cam rotatable on said second selector means, and normally in engagement with said pawl, said pawl being rotated in a counterclockwise manner by recoil of said bolt carrier to rotate said cam to engage a said second contact surface on said two burst lever whereby said lever will disengage said disconnector from said hammer and permit firing of two rounds of ammunition in said rifle per single pull of said trigger, and means in said receiver to limit clockwise rotation of said pawl and said actuating cam.
2. A two round burst mechanism as claimed in claim 1 wherein said lever assembly comprises a spring loaded lever having a hub portion for rotatable mounting in said receiver, a body portion integral with said hub portion and having an integral lug on its forward end normally engaging said disconnector and said trigger, its rearward portion defining a fork having upper and lower tines, said lower tine having upper and lower planar contact surfaces for engagement with said second selector means and said actuating cam respectively, and a spring loaded position selector rotatably mounted within said body portion and having a rea-rwardly extending arm and a downwardly depending point at its rearmost end for engagement with said second selector means whereby said lever may be positioned in operative and inoperative positions relative to said disconnector and said trigger.
3. A two round burst mechanism as claimed in claim 1 6 wherein said second selector means comprises a shaft journaled transversely in said receiver and having one of its ends extending beyond thereof, an operating arm fixed to the extending portion and a spool portion adjacent its extending portion, said spool portion having a pair of positioning indents in its floor for cooperation with said lever assembly for optionally positioning said assembly in and out of operative position relative to said disconnector and said lever, there being an undercut in said spool shaft to accommodate rotational movement of said lever when said shaft is turned to an operative position.
4. A two round burst mechanism as claimed in claim 1 wherein said pawl comprises a hub for rotatable mounting on said second selector means, an upstanding arm integral with the outer end of said hub and having a tang at its lower end for engagement with said means for limiting clockwise rotation thereof, and a series of crown teeth integral with the inner end of said hub and normally engaging said actuating cam.
5. A device as set forth in claim 4 wherein said crown teeth are six in number.
6. A two round burst mechanism as claimed in claim 1 wherein said actuating cam comprises a hub portion for rotatably mounting on said second selector means, a series of crown teeth integral with one end thereof, a ratchet wheel integral with the other end of said hub portion for engagement with said means limiting clockwise rotation of said pawl and said actuating cam, and a cam fixed on the outer face of said ratchet wheel for intermittent engagement with said lower contact surface on said spring loaded lever, said cam defining three flat edges and three lobes.
7. A device as set forth in claim 6 wherein said crown teeth on said hub are six in number and said ratchet wheel is provided with six teeth.
8. A two round burst mechanism as claimed in claim 1 wherein said means to limit clockwise rotation of said pawl and said actuating cam comprises an angular ratchet spring fixed at one of its ends to the floor of said receiver and being bifurcated at its other end to provide a pair of stops for engagement, one each, with said pawl and said actuating cam.
9. A two round burst mechanism as claimed in claim 1 wherein said pawl will rotate said actuating cam through an arc of sixty degrees on each rearward excursion of said bolt carrier whereby said lever assembly will be intermittently rocked to move said disconnector in and out of engagement with said hammer to provide two round firing cycles in said rifle.
References Cited UNITED STATES PATENTS 3,292,492 12/1966 Sturtevant 89128 BENJAMIN A. BORCHELT, Primary Examiner.
S. C. BENTLEY, Assistant Examiner.