WO2020027760A1

WO2020027760A1 - Trigger mechanism of bullpup-type automatic small arms

Info

Publication number: WO2020027760A1
Application number: PCT/UA2018/000096
Authority: WO
Inventors: Sergii VARIBRUSOV
Original assignee: Varibrusov Sergii
Priority date: 2018-08-03
Filing date: 2018-08-31
Publication date: 2020-02-06

Abstract

TRIGGER MECHANISM OF BULLPUP-TYPE AUTOMATIC SMALL ARMS comprises a mounted on a gun rod bullpup twist-type trigger (2), a means for release of a cock (13) mounted on an axle (6) within a breech box (1) together with spring-load sear (10), a Z-like pull bar (12) arranged along a left inner sidewall of the breech box (1) and pivotally connected with said twist-type trigger (2 and said means for release of the cock (13). The means for release of the cock (13) shaped as a double-arm lever (5), which is set onto a standard axle (6) retained after demounting of a standard twist-type trigger, and is equipped on the left by a ledge (7) having an eye (8) and below by a balance weight (9). This excludes spontaneous releases of the cock (13) and accidental shots.

Description

TRIGGER MECHANISM

OF BULLPUP-TYPE AUTOMATIC SMALL ARMS

Field of the Invention

This invention relates to the structure of a trigger mechanism of bullpup-type automatic small arms on the basis of any serial Kalashnikov’s gun.

Such arms meant for shooting preferably with cartridges 5.45 x 39 mm, 5.56 x 45 mm and 7.62 x 39 mm.

Background Art

All bullpup-type small arms characterizes in that a breech, a magazine and a percussion trigger are found behind a bullpup twist-type trigger (and a fire control handle, if it is provided). Typical samples of such arms are given on Fig.1 of the US 1340127 (1920) that shows a bullpup automatic pistol, on photos of the US D693.420 S (2013) that shows a bullpup firearm, and on many bullpup pictures that can easily find in Internet.

In comparison with any traditional analog, bullpup-type arms have lesser length (usually up to 20-25 cm) and are more easy-to-use. These advantages are especially important for arms, which can be using in time of warfares in cities and sallies of raiding and reconnaissance parties or which are meant for self-defense of tank or aircraft crews.

Unfortunately bullpup-type arms have not countrywide appreciation to this day, and only several originals had reached a state of real use, for example:

an antitank rifle PzB M.SS.41 /PzB-41 (t), which was projected for German armorpiercing cartridge 7.92 x 94 mm and was produced serially for German army in occupied Czech city Brno at the beginning of Second World War;

a French automatic rifle FAMAS F1 , which was produced in number about 400,000 copies, but was taken out of production in nineties of XX century and must be replaced by traditional arms,

an universal automatic rifle Steyr AUG of Austrian corporation Steyr-Daimler-Puch, which has commercial success from 1977 up to day; and

an automatic rifle TAR21 Tavor, which Israeli uses in its army from 2004 and promotes actively for export.

Absence of mass demand for the bullpup-type arms conditions dearness of their small-scale production in toto. Therefore we observe relatively young tendency to produce such arms by means of minimal addition or alteration of advantageous traditional serial rifles, which have accumulated in armories.

Particularly, RU 2485429 C2 discloses an attempt to transform of Kalashnikov AK74M having hollow folding buttstock into a hybrid weapon that can be used either traditionally (when the buttstock is straightened) or configured as bullpup-type gun (when the buttstock is folded during 6 - 10 s). For this purpose such additional trigger mechanism must be built- in into the buttstock cavity, which has a retractable bullpup twist-type trigger that is found in operative position before a magazine under a front part of a breech box at a distance about 2 cm and is kinematically linked with a standard trigger mechanism. Moreover a retractable dioptric sight and foresight fixed onto rotary uprights; a modified magazine catch and a support for shooting from left shoulder are provided additionally.

This exotic hybrid weapon, which has known as Kalashnikov AK74MB (where capital Cyrillic letter‘5’ is first letter in the Russian inventor and patent holder surname), exists only in trial embodiments.

In practice it is more preferable to remodel traditional small arms into bullpup-type weaponry. It can see in many publications, for example:

RU 8790 U1 discloses alteration of SAIGA-type hunting carabines, which were created on the basis of Kalashnikov’s gun for single shooting with cartridges 7.62 x 39 mm, into bullpup-type rifles by change of a rod and insertion of polyarticular kinematic link between an additional bullpup twist-type trigger and a standard sear;

US 9,109,856 discloses alteration of serial Soviet semiautomatic SKS-carabines into bullpup-type weaponry by transfer of twist-type trigger nearer to a muzzle and insertion of kinematic link between said trigger and a standard sear;

US 20140075812 A1 discloses alteration of serial American automatic rifles AR-15 into bullpup-type weaponry by transfer of a fire control handle nearer to a muzzle, installation of an additional twist-type trigger in said handle and insertion of kinematic link between additional and standard twist-type triggers.

Such approach allows to preserve a barrel, a breech box, a slide with a gas plunger; a breechblock with its slide and return spring; a gas-outlet tube with a patch piece, a magazine, accessories such as a bayonet-knife, a cleaning rod etc. and the most part of an original percussion trigger (i.e. a firing pin, a cock, a sear, a mainspring and an autorelease), and to introduce inexpensive amendments only in a trigger mechanism.

However stores of unsold SAIGA-type hunting carabines, SKS-carabines and AR-15 rifles are relatively small.

Therefore it is reasonably to use of above-demonstrated approach to remodeling of widely spread small arms such as Kalashnikov’s guns, which have single-type percussion triggers irrespective of caliber and point of origin (see <http://fb.ru/article/382541 /usm-ak-- naznachenie-i-ustrovstvo-udarno-spuskovogo-mehanizma-avtomata-kalashnikova>).

First specimen for armament is known under name «Benp» (‘Vepr’). It is a bullpup- type gun developed in 2001 -2003 by Ukrainian Science-Technical Center of precision engineering on the basis of Soviet Kalashnikov’s gun AK74 having caliber 5.45 mm (https://ru.wikipedia.org/wiki/Benp).

Unfortunately, supply price of this piece has sharply grown since development up to this day so that serial production of it has not started.

Moreover, trials of said gun “Vepr” and its embodiments had revealed a serious defect such as tendency to spontaneous shots in consequence of sharp impacts.

Ground of this disadvantage can easily disclose by analysis of a trigger mechanism of bullpup-configured Kalashnikov, which is known from RU 2525464 C2, and subject matter of which is the nearest to the proposed below mechanism. It comprises - an additional bullpup twist-type trigger mounted on a rod (particularly in a fire control handle that had been taken from original gun),

a standard twist-type trigger that is placed within a breech box on a standard axle together with a not showed especially spring-loaded sear and serves as a means for release of a standard cock,

a protective housing of said standard twist-type trigger (that must be provided because said standard fire control handle had been used for placement of said additional bullpup twist-type trigger), and

a Z-like pull bar, which can be whole (unbroken) or composed of two rigidly connected in operative position parts, arranged along left inner sidewall of breech box under a force cross bar and above axles of a standard autorelease and said standard cock, and pivotally connected with both twist-type triggers.

It is clear for each person skilled in the art that above-mentioned standard cock is placed on the own axle so that can be stopping by above-mentioned sear.

However use of two practically identical twist-type triggers and Z-like pull bar for kinematic connection of theirs leads to occurrence of an unbalanced force loop, which cannot secure retention of the cocked cock in the event of accidental sharp impacts (especially in a barrel butt or in a buttstock of said bullpup-type gun). Accordingly, spontaneous shots and injuries of servicemen are possible.

Summary of the Invention

The invention is based on the problem to create - by change of structure - such trigger mechanism that excludes spontaneous releases of the cock owing to accidental sharp impacts and ipso facto allows increasing appreciably safety of bullpup-type weapon on the basis of Kalashnikov’s gun.

This problem has solved in that in a trigger mechanism of bullpup-type automatic small arms on the basis of Kalashnikov’s gun comprising - a mounted on a rod bullpup twist-type trigger,

a means for release of a cock mounted on an axle together with spring-load sear within a breech box, and

a Z-like pull bar arranged along a left inner sidewall of the breech box and pivotally connected with said twist-type trigger and said means for release of the cock,

according to the invention

said means for release of the cock shaped as a double-arm lever, which is set onto a standard axle retained after demounting of a standard twist-type trigger, and is equipped on the left by a ledge having an eye and below by a balance weight.

It is clear for each person skilled in the art that the balance weight can calculate by well-known method so that center of mass (and center of gravity) of the trigger mechanism will be permanently found practically on geometrical axis of above-mentioned standard material axle. This excludes appearance of detrimental moments of force and spontaneous angular displacements of the double-arm lever in the event of accidental sharp impacts. Accordingly, spontaneous releases of the cock and accidental shots must be excluded too. Testing of sample quantity of bullpup-type guns made according to the invention had confirmed said technical outcome and, correspondingly, heightened safety of weapon.

First additional feature consists in that the Z-like pull bar arranged in the breech box above a force cross bar. This facilitates disassembly and assembly of the trigger mechanism in the time of maintenance and repair.

Second additional feature consists in that the Z-like pull bar is composed of two parts, one of which has a threaded bush, and second of which is equipped with a threaded protrusion that has screwed into said bush in operative position. This facilitates adjustment of effective length of said pull bar taking into account actual distance between the bullpup twist-type trigger and the means for release of standard cock.

Third additional feature consists in that the trigger mechanism has equipped with a limiter of motion of the cock. This depresses cyclic load onto all percussion mechanism.

It is clear for each person skilled in the art that said additional features can use in various combinations with basic conception of the invention and that this conception can be realized in many embodiments within scope of rights that are confined only by added claims.

Brief Description of Drawings

The invention will now be explained by detailed description of structure and operation of the trigger mechanism of bullpup-type small arms on the basis of Kalashnikov's gun with references to the accompanying drawings, in which -

Fig.1 shows a general view of the trigger mechanism mounted in connection with a sidewall of a breech box (axonometric view);

Fig.2 shows a set of the trigger mechanism components with a glance of their spatial relationship (axonometric view);

Fig.3 shows a means for release of standard cock (axonometric view);

Fig.4 shows a limiter of motion of a cock (axonometric view);

Fig.5 shows location of center of mass of the trigger mechanism relative to combination «the means for release of the cock - the Z-like pull bar» (side view);

Fig.6 shows location of the cock relative to the limiter of its motion after shot.

Best Embodiments of the Invention

The trigger mechanism is found in breech box 1 of reworked Kalashnikov’s gun. In any possible embodiments this mechanism has (see Figsl and 2):

a bullpup twist-type trigger 2 mounted on an axle 3 onto a not shown here rod and having a ledge 4;

a means for release of a cock shaped as a double-arm lever 5, which has no designated especially a front arm and a lower arm, is set onto a standard axle 6 retained after demounting of a standard twist-type trigger, and is equipped on the left by a ledge 7 having an eye 8 and below by a balance weight 9 (see also Fig.3);

a sear 10, which also placed onto said axle 6 within the breech box 1 and set against a return spring 11 ;

a Z-like pull bar 12, which arranged along left sidewall within the breech box 1 and pivotally connected with ledge 4 of said twist-type trigger 2 and with said eye 8 of the ledge 7 of the double-arm lever 5,

a standard cock 13 placed on an own axle 14, and

a limiter 15 of motion of the cock 13 after shot (this limiter 15 is separately showed with a zoom on the Fig.4).

Moreover Figs 1 and 2 show also such components as a force cross bar 16 (between visible on drawings left sidewall of the breech box 1 and not showed right sidewall of said box) and an axle 17 of not showed autorelease. These components are presented in all variants of Kalashnikov's guns and their arrangement must be taken into consideration in the trigger mechanism structure. Particularly, it is desirable if the Z-like pull bar 12 is arranged in the breech box 1 above said force cross bar 16 (and, respectively, above the axle 17 of said autorelease).

It is also desirable, if the Z-like pull bar 12 is composed of two parts 12a and 12 b, which are rigidly connected in operative position by two threaded components. For example, Fig.2 shows variant, in which a part 12a of said pull bar 12 is Z-shaped and equipped with a threaded protrusion 18, and a part 12b is rod-shaped and equipped with a threaded bush 19.

Fig.5 shows that center A of mass (and center of gravity) of the trigger mechanism must be found onto geometrical axis of said standard physical axle 6. Thereto mass of balance weight 9 can be calculated using suitable MCAD (e.g. Creo Parametric 2.0) on the basis of kinematic diagram and values of mass of each segment.

Thus, such masses were specified for experimental bullpup guns based on AKM having caliber 7.62 mm:

46 g for the double-arm lever 5,

12 g for the sear 10,

5 g for the limiter 15 of motion of the cock 13,

0.5 g for the ledge 7;

12 g for the Z-like part 12a of the pull bar 12 having treaded protrusion,

14 g for rod-shaped part 12b of the pull bar 12 having treaded bush;

2.5 g for ledge 4 of the bullpup twist-type trigger 2, and

6 g for the standard axle 6.

As a result of calculation was stated that the balance weight 9 must be equal 25 g.

The described trigger mechanism operates as follows.

A shooter fixes an equipped magazine by a catch, twitches a breechblock that cocks the cock 13, which engages with the double-arm lever 5 front arm, and releases the breechblock that seats a cartridge into a cartridge-chamber. In this state the balance weight

9 secures keeping of the trigger mechanism from spontaneous releases of the cock 13 in the event of sharp impacts. If the gun was adjusted to individual fire by a not shown here change lever, pressure of the shooter onto the bullpup twist-type trigger 2 moves the Z-like pull bar 12. It turns the double-arm lever 5 that has set on the standard axle 6. As a result this lever 5 uncouples from the cock 13, this cock 13 interengages not for long with the sear

10 and owing to further turn of said lever 5 and said sear 10 on said axle 6 becomes finally free and strikes in a standard firing pin that has placed within the breechblock. When a shot had happened, the breechblock moves back and pushes cock 13 that leans against the limiter 15 of its motion (see Fig.6) and engages temporarily with the sear 10. When the shooter releases the twist-type trigger 2, the cock 13 uncouples from the sear 10 and couples anew with the double-arm lever 5 front arm.

Thereupon the shooter can reiterate this process as it described above.

If the gun was adjusted to automatic fire, this shooting mode allows such well-known (but not showed here ) gun component as autorelease.

Industrial Applicability

The trigger mechanism of bullpup-type automatic small arms can serially produce from available materials using traditional metal-working equipment for the purpose of inexpensive remodeling of Kalashnikovs guns into bullpup-type arms.

LIST OF ITEMS ON DRAWINGS

1 breech box

2 twist-type trigger bullpup-type

3 axle of the twist-type trigger 2

4 ledge of the twist-type trigger 2 means for release of a cock 13, including

5 double-arm lever

6 axle of the double-arm lever

7 ledge of the double-arm lever

8 eye of the ledge 7

9 balance weight

10 sear

11 return spring of the sear 10

12 Z-like pull bar as a whole

13 cock

14 axle of the cock 13

15 limiter of motion of the cock 13

16 force cross bar of the breech box 1

17 autorelease axle

12a Z-like part of pull bar 12 having a threaded protrusion 18 12 b rod-shaped part of pull bar 12 having a threaded bush 19.

Claims

1. A trigger mechanism of bullpup-type automatic small arms on the basis of Kalashnikov’s gun comprising - a mounted on a rod bullpup twist-type trigger (2),

a means for release of a cock (13) mounted on an axle (6) within a breech box (1 ) together with spring-load sear (10),

Z-like pull bar arranged along a left inner sidewall of the breech box and pivotally connected with said twist-type trigger and said means for release of the cock,

characterized in that

the means for release of the cock (13) shaped as a double-arm lever (5), which is set onto a standard axle (6) retained after demounting of a standard twist-type trigger, and is equipped on the left by a ledge (7) having an eye (8) and below by a balance weight (9)

2. The trigger mechanism according to the claim 1 characterized in that said Z-like pull bar (12) arranged in the breech box (1 ) above a force cross bar (16);

3. The trigger mechanism according to the claim 2 characterized in that said Z-like pull bar (12) is composed of two parts, one of which (12a) has a threaded bush (19), and second of which (126) is equipped with a threaded protrusion (18) that has screwed into said bush (19) in operative position.

4. The trigger mechanism according to the claim 1 characterized in that it has equipped with a limiter (15) of motion of the cock (13).