US2918848A - Regulating means for a gas piston operated gun - Google Patents

Description

Dec. 29, 1959 B. MAILLARD 2,918,848

REGULATING MEANS FOR A GAS PISTON OPERATED GUN Filed July 9, 1956 n ninww Z 12 J2 J3 QUINE w\ I 5 "WI-TI IIIIII United States Fatent C barrel and the outside, generally at right angles. tothe barrel axis, for feeding some amount of powder gases,

immediately after the projectile has moved beyond the;

gas tap, to a device operated by the pressure of said gases and which cooperates in the automatic operation of the gun.

It is well known that with such guns; when a long burst is fired, the gun being initially cold, the rate of fire varies during the burst due to the modifications in the firing conditions caused by the heating of some parts of the gun (which heating causes said parts to expand, modifies the lubricating conditions and so on). This variation of the rate of fire which, in fact, is an increase of said rate, may cause serious damages when a very long burst is fired. As a matter of fact, the parts of the gun are adjusted to give initially, that is to say when the gun is cold and even at low temperatures, the normal rate of fire, and an increase of said rate beyond a given value may have serious consequences on the operation of the gun and in particular of the cartridge feed device thereof.

The object of my invention is to obviate this drawback.

For this purpose, I provide, between the gas tap and the device to be operated by the powder gases under pressure, heat responsive valve means arranged to control the passage through which said gases can flow so as to vary the cross section of said passage in response to variations in the temperature of operation of at least one part of the gun.

A preferred embodiment of the present invention will be hereinafter described with reference to the accompanying drawing given merely by way of example and in which:

Fig. 1 is a vertical sectional view of "aportion of an automatic gun made according to my invention.

Fig. 2 is a similar view on an enlarged scale of part of the structure of Fig. 1. I I

Fig. 3 is a view similar to Fig.2 showing a modification.

Fig. 4 is an explanatory diagram to' be referred to hereinafter.

The automatic gun shown on the drawing includes a barrel 2 provided with a gas tap 1 through which the powder gases are fed to a cylindrical cavity formed in a support 9 and one end of which constitutes a cylindrical chamber 3 in which is slidable a piston 4 which constitutes a power element for controlling for instance the release of the gun breech block (not shown on the drawing). 3

In order to prevent an undesirable rise of the rate of fire of this gun when a long burst is fired, I provide, in the construction of Figs. 1 and 2, acore 5 housed in a cylindrical portion of said cavity adjoining chamber 3, said core being mounted with a suitable annular clearance i ev . Z, hetweeni its periphery and. the: wall of said cylindricali cavity portion, asvisible at 6'. The gases from tap=1 conveyed through a conduit 7 to the above mentioned. bore upstream of said annular passage 6 so that they must flow through said passage in: order to reach chant! bet- '3.

Said-core is carried by a plug 8 screwed in the support I 9 in which the cavity is formed, conduit 7 being alscr formed: in said support 9; The left hand portion of plug. 8 may be provided with a blind hole 10 intended to facilitate cooling thereof.

With such an arrangement, core 5 may be considered. as a kind of throttlevalve member expansible in response toits being heated so as to modify the cross section. of passage 6. Thisresult is due to the fact that, plug, 8 and; support; 9 being for instance both: made of steel, whena relatively long burst (for instance shots) is fired, core 5 expands more rapidly than the cylindrical. wall ofi the bore in which it is housed in support 9 so that the. cross section of annular passage 6 decreases, which tends to reduce the rate of. fire; The materials of which sup-= port 9 and the core 5 are made may be chosen so that the core expands: more rapidly than the support 9.

In actual practice, it may often happen that this: cross section: reduction is: toov great and that, despite the tendency of the gun to have its rate of fire increased as a consequence of itsbeing heated up, the rate of. fire actually decreases due to too great a reduction of the cross section of passage 6. In order to overcome this drawback, it suflices to provide through core 5 passages 11 through which a portion of the gases flows directly from conduit 7 into chamber 3.

On Fig. 4, I have plotted in abscissas the temperatures and in ordinates the cross sections through which the gases can flow. The lower rectangle corresponds to passages 11 whereas the trapezium above this rectangle corresponds to the variable cross section of annular passage 6. It is thus possible, by suitably choosing the initial cross sections, to obtain the desired relative variation of the total cross section when the arm is heating by firing.

In the modification of Fig. 3, passage 7 opens directly into a cylindrical bore 12 provided in support 9, the end 13 of this bore being of frusto-conical shape and communicating witha passage 14 leading to chamber 3, the whole of bore 12, passage 14 and chamber 3 forming the above mentioned cavity.

A hollow plug 15 having a nut-shaped head 16 is screwed in cylindrical bore 12 and the end 17 of said plug is conical, shaped so that when plug 15 has been screwed in position, this point 17 is located opposite the frusto-conical end 13 of bore 12 and leaves, between 13 and 17, an annular passage 18 of suitable cross section.

When a long burst is fired, rod 17 is heated and expands quicker than member 9 so that the cross section of annular passage 18 decreases. The lefthand portion of the rod 17 may be provided with a blind hole ,20 in communication with the atmosphere.

The result is the same as with the arrangement of Fig. 2. In this case also, passages 19 of suitable constant cross section may be provided either in the end of rod 17 or in the portion 13 of the support, so as to ensure the desired variation of the rate of fire.

In a general manner, while I have, in the above description, disclosed what I deem to be practical and eflicient embodiments of my invention, it should be well understood that I do not wish to be limited thereto as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of the present invention as comprehended within the scope of the accompanying claims.

What I claim is:

1. An automatic gun comprising, in combination, a barrel provided with a gas tap,'means carried by said barrel forming a chamber communicating with saidsgas tap wherebygases flow from said gas tap into said chamber every time a shot is fired, a pistonvmovable in said chamber in response to pressure rises therein, and valve means interposed between said gas tap and said chamber for varying the flow of gases from said gas tap to said chamber, said valve means comprising awplug mounted in said chamber and having a free end of lessened diameter extending toward said piston beyond said gas tap so as to always leave an annulartpassage between the free end of said plug and the walls of said chamber for the passage of gases from said gas tap to said chamber, said free end being expansible under the efiect of heating by the gases flowing from said gas tap to said chamber during a burst of firing of the gun, whereby the cross-section of said annular passage is reduced as the burst becomes longer and longer, said plug being further provided with at least one other passage between said gas tap and said chamber and formed in said free end so that its cross-section is but little varied by thermal expansion of the free end of said plug.

2. An automatic gun according to claim 1 wherein said plug is provided with a blind hole in communication withthe atmosphere. 7

3. An automatic gun which comprises in combination a barrel provided with a gas tap, means carried by said barrel forming a cavity in communication with said gas tap whereby powder gases flow from said barrel to said cavity every time a shot is fired, one end of said means means at the end of said cavity opposed to that formed by said chamber, said rod extending toward said'partition beyond said gas tap to always leave an annular passage between the free end of said rodand the wall of said partition, said. free end being expansible under the efl ect of heating by the gases flowing from said cavity to said chamber during a burst of firing of the gun, whereby the crosssection of said annular passage is reduced as the burst becomes longer and longer.

4. An automatic gun according to claim 3 wherein said rod is provided with a blind hole in communication with the-atmosphere.

5. An automatic gun according to claim 3 and further including at least one passage in parallel with said ann'ular passage and formed so that its cross-section is but little varied by thermal expansion.

References Citedin the file of this patent UNITED STATES PATENTS 795,627 Larsson July 25, 1905 804,986 Stamm Nov. 21, 1905 960,825 Colleoni June 7, 1910 l l l

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