US2409225A

US2409225A - Gas system for firearms

Info

Publication number: US2409225A
Application number: US552784A
Authority: US
Inventors: Wilbur A Schaich
Original assignee: Individual
Current assignee: Individual
Priority date: 1944-09-05
Filing date: 1944-09-05
Publication date: 1946-10-15
Anticipated expiration: 1963-10-15

Description

Oct. 15, 1946; w. A. SCHAICH GAS SYSTEM FOR FIREARMS Filed Sept. 5. 1944 Wilbur A- fichnl' Ch 33., a. AMMMD ZMAU Patented Oct. 15, 1946 omrso STATES PATENT OFFICE- (Granted under the act of March 3, 1883, as amended April 30, 1928; 3'70 0. G. 757) 1 Claim.

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 gas system for a firearm and particularly to a mechanism for deriving motive power from the gases developed within the barrel of an automatic firearm to secure automatic operation of the breech mechamsm.

While not limited thereto, this invention is particularly applicable to firearms wherein the gas port in the barrel is located close to the chamber end of the barrel, resulting in the application of gases of extremely high pressures to the gas system. Specifically a gas system in accordance with this invention may be applied to an automatic firearm similar to the U. S. carbine caliber .30 M1.

The location of the gas port as near as possible to the chamber end of the barrel is obviously desirable from the standpoint of reduction in length, and hence weight, of the operating rod member which transmits force received from the gas system to the breech mechanism to accomplish the conventional functions of an automatic breech mechanism, namely, unlocking of the breech, extraction and ejection of the fired case, and the loading of a fresh cartridge. With conventional gas systems however, utilizing merely a piston and cylinder, and with the piston arranged to receive the direct impact of the gases, such location of the gas port produces at least three well recognized undesirable features, First, the action of the gas on the piston is extremely violent and of very short duration thereby producing an undesirably high acceleration of the piston and the breech mechanism with accompanying breakage of parts after a few hundred rounds. Secondly, it is well recognized that the pressures developed by successive rounds of ammunition normally depart from the average pressure by a substantial margin. Accordingly, a round developing slightly higher pressure would accelerate the piston and breech mechanism at an even higher rate than would a normal round and in many instances would cause the breech mechanism to open while the pressure in the barrel was above the value generally recognized to be safe for opening of the breech. Thirdly, the short duration of the force exerted by the gases on a conventional piston required the acceleration of the breech mechanism to a velocity sufliciently high to insure that the kinetic energy imparted-to the breech mechanism in such short duration is sufficient to carry the breech mechanism to its full recoil position. For example, in the U. S. carbine caliber .30 M1, the operating slide is accelerated by the piston to a maximum velocity of from thirty to forty feet per second, which velocity is gradually reduced during the recoil travel of the slide by the energy required to open the bolt, extract the case, and compress the driving spring, to a value of from six to ten feet per second at full recoil position. This represents a substantial range of velocity change during the operating cycle and naturally requires higher shock and fatigue resistance properties in the moving parts.

Accordingly, it is an object of this invention to provide an improved gas system for an automatic firearm particularly adaptable for operation by high pressure gases.

A further object of this invention is to provide a gas system for an automatic firearm which is self compensating with respect to variations in pressure of the operating gases supplied, to the system.

Another object of this invention is to provide a gas system for an automatic firearm wherein the gases are permitted to operate on a moving piston by expansion rather than by an impact blow and wherein the duration of action of the gases is substantially increased. I

A particular object of this invention is to provide an improved gas system which may be applied to an automatic firearm similar to the U. S. carbine caliber .30 Ml which will substantially reduce the maximum velocity of the moving parts of the breech mechanism and which will substantially increase the time elapsing between firing of the cartridge and opening of the breech mechanism.

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 drawing in which:

Fig. 1 is an elevational view, partly in section, of the elements of the improved gas system assembled to a firearm.

Fig. 2 is a sectional view taken along the plane 2-2 of Fig. 1.

Fig. 3 is a sectional View taken along the plane 3@ of Fig. 1.

Fig. 4 is a sectional View of the cylinder member.

Referring to Fig. l a gas cylinder bracket I0 is shown secured to a barrel l in the vicinity of a gas port 2. The bracket [0 may comprise either a separate member slipped over the barrel or may be integrally formed with the barrel. In the depending portion of bracket it) a longitudinal hole ll is drilled parallel to the axis of the barrel. A tubular gas cylinder element is inserted into the hole H and retained therein by any suitable means, preferably by a press fit engagement. A radial collar on the rear end of gas cylinder 29 bottoms against the rear wall of bracket m, The top surface of the collar 2! is provided with a fiat portion 22 which snugly engages a correspondingly flat surface 3 provided on the bottom of barrel l and thereby serves to prevent rotational shifting of the gas cylinder 20 with respect to the bracket H3. As previously mentioned the gas cylinder 28 is hollow and defines a gas chamber 23 which opens from the rear of gas cylinder 2%. A gas port 24 is provided thru bracket ii! and gas cylinder 20 at a position to align with the end of barrel port 2. The port 24 is preferably made substantially larger than port 2 in order to compensate for any. slight misalignment of parts in assembly. A cylindrical piston 36 snugly engages the interior cylindrical surface of gas chamber 23. The periphery of piston 36 is provided with a plurality of annular gas recesses 3i which in effect produce a gas seal between the exterior of the piston 38 and the interior of the gas cylinder 26. Piston is also partially. hollow, being provided with an axial hole 3.: opening from the forward end of the piston. The rear end oi piston SS is solid and is arranged to lie in abutment to breech operating member 49. Operating member it is suitably connected to the breech mechanism (not shown) of the firearm and arranged to reciprocate and thereby impart the necessary movement to such breech mechanism to produce automatic operation of the weapon. In the specific application of this invention to the U. S. carbine caliber .30 M1, breech operating member lB comprises the standard operating rod of such weapon.

It should be understood that the full recoil stroke of operating member to is preferably less than the length of piston 38 which is inserted within gas cylinder 2!), thus insuring that piston 30 is engaged in gas cylinder 28 during normal operation of the firearm in all positions of the operating member 46. Hence no stops are needed to retain piston within gas cylinder 20. An operating spring 53 is provided to return operating member Gil to its battery position, and piston 3i) is in turn returned to a position Within gas cylinder it where the forward end of piston 33 bottoms against the base of gas chamber 23. An annular recess 33 is provided about the periphery of piston 30 in such position as to lie adjacent to cylinder port 24 when piston 38 is in its battery position. A plurality of radial ports 3 are provided, passing thru the wall of piston 38 and located in the center of annular recess 33. Ports 35 thus assure passage of the gases into the hollow portion 32 of piston 33 independent of the relative angular position of piston 39 with respect to gas cylinder 20. 1

In operation, a cartridge is fired and the bullet is driven thru the bore by the gases thus formed. After the bullet passes the barrel port 2, a portion of the gases are diverted thru the barrel port 2, the cylinder port 24, and the piston ports 36 into the hollow interior 32 of piston 30. The

hollow interior 32 is of appreciable volume but preferably less than 25% of the barrel bore volume and hence the gases must fill such volume before being effective to move the piston 33 rearwardly. Thus one element of delay is introduced in the initiation of movement of piston 30. When piston 3H begins to move rearwardly, the eifect is to misalign piston port 34 with cylinder port 24 and in effect cut off the entry of further gases into the gas system and trap the gases which have already entered the system. Further action of the gases upon the piston is then dependent upon the expansion of the gases and accordingly a very uniform accelerating force is applied to the piston 39, Expansion of the gases will continue until the ports 35 pass rearwardly out of the end of cylinder 23 whereupon the gases will be exhausted to atmosphere. A power stroke of any desired length may obviously be obtained by increasing the spacing between the rear end of cylinder 25 and the location of cylinder port 24. It is generally desirable to have the power stroke substantially less than the recoil movement of the breech operating member in order that exhaust of the gases will occur at a substantial pressure, thereby insuring that carbon and other combustion products will be blown out of the piston and cylinder chambers.

When a gas system constructed in accordance with this invention was applied to a gun similar to the U. S. carbine, caliber .30 M1, the maximum velocity attained by the moving parts in their recoil stroke was not over twenty feet per second. Furthermore the time elapsing between the firing of a cartridge and the opening of the breech mechanism was more than doubled. Thus a gas system construction in accordance with this invention not only insures longer life of moving parts of the firearm by decreasing shock and fatigue effects but in addition provides a substantial increase in delay of breech opening, thereby insuring opening of the breech mechanism when the pressure remaining in the barrel doesnot exceed that known in the art to be most desirable for opening of the breech and extraction of the fired case. It is obvious that a gas system constructed in accordance with this invention is very adaptable to large production manufacture inasmuch as all the principal parts are tubular.

I claim:

In an automatic firearm having a barrel with a gas port therein and a reciprocating breech operating member. the improvement comprising a gas cylinder secured to the barrel in the vicinity of the barrel gas port, said gas cylinder defining a rearwardly opening, cylindrical chamber disposed parallel to the path of movement of said breech operating member, a cylindrical piston slidably and rotatably mounted within said cylinder chamber, said piston having a forwardly opening hollow portion, the rear end of said piston arranged to abut the breech operating member to impart rearward movement thereto, said cylinder having a gas passage therein communicating between the barrel gas port and the interior of said cylinder chamber, said piston having a reduced diameter annular groove on its periphery located in substantial alignment with said gas passage when said piston is in its forward position, said piston having at least one generally radial hole in said reduced diameter annular groove, communicating with the said hollow portion of said piston.

WILBUR A. SCI-IAICH.