GB2222237A

GB2222237A - Cooling of firearms

Info

Publication number: GB2222237A
Application number: GB8817747A
Authority: GB
Inventors: Adrian Price
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-07-26
Filing date: 1988-07-26
Publication date: 1990-02-28
Also published as: GB8817747D0

Abstract

A firearm comprises a piston 7, with piston rod 8 and seal 24, reciprocally mounted within a chamber 26 and driven by expansion gases created by the firing of a cartridge 2. The firearm includes a bolt lock 16 which is driven rearwardly within the firearm by means of the piston 7 on firing of the cartridge 2. Cooling means, in the form of first and second one-way valves 28, 30 communicate between the chamber 26 and the exterior of the firearm. The one-way valves 28, 30 are positioned in relation to the piston 7, piston rod 8 and chamber 26 so that operation of the firearm gives rise to a pump action which draws cool air from outside the firearm via a port 36 into a cooling jacket 34 surrounding the barrel 4 and through valve 30 into chamber 26, subsequently being expelled through valve 28 on the return (i.e. rearward) movement of the piston 7. <IMAGE>

Description

FIREARMS This invention relates to firearms, and in particular, to gas action firearms.

A previously proposed firearm of a gas action type is the "Browning0 automatic rifle. A spring loaded mechanism is used to feed cartridges from a magazine into a firing position.

When the trigger of the rifle is squeezed, a slide is released and moves forward under the action of a piston spring. The movement of the slide eventually brings a hammer into contact with a firing pin which strikes the cartridge. Firing of the cartrige produces expansion gases which drive the bullet past a port in the barrel of the rifle. The port is connected to a gas piston and cylinder, the expansion gases causing the gas piston to be driven rearwardly within the cylinder. The gas piston is coupled to the slide, the rearward movement of the gas piston causing the slide also to move rearwardly. The rearward movement of the slide causes unlocking of a bolt lock. As the bolt and slide move backwards, an extractor mechanism extracts the expended cartridge from the chamber.A fresh cartridge is collected from the magazine as the slide and bolt return forward under pressure from the piston spring.

An example of this firearm is described on pages 24 and 25 of a book entitled "How Weapons Work" (2nd edition 1980) published by Marshall Cavendish Limited.

Gas action automatic rifles of this type have the advantage that they enable many rounds of cartridges to be fired per minute. For example, modern automatic weapons of this type can fire up to 1,200 rounds per minute. Firing cartridges at this rate leads to a problem in that overheating of the barrel of the rifle, and in particular, the cartridge loading area, occurs.

Overheating of the gun barrel can cause cartridges within the rifle, or conceivably within the magazine, to explode.

A previously proposed machine gun, namely the "Lewis" machine gun, employed a cooling system for the barrel.

The cooling system of this machine gun consisted of an open ended cylindrical metal jacket which surrounded the barrel, substantially co-axially therewith. The cooling of the gun during operation of the firearm was effected by conduction and convection of heat from the rifle. In order to be effective, the metal jacket needed to be relatively heavy and bulky.

It is an aim of the present invention to overcome the aforementioned problem of overheating in automatic firearmS.

According to the present invention, there is provided a firearm comprising: a cartridge loading means for loading cartridges into a firing position from a magazine, which loading means is driven by expansion gases produced from firing a cartridge in the firing position; and cooling means for cooperating with the cartridge loading means so as to create a pump action during operation of the firearm, whereby a relatively low pressure region is created within the firearm into which relatively cool air is drawn from outside the firearm, thereby cooling the firearm.

The loading means may comprise a piston and piston rod reciprocally mounted within a chamber and driven by the expansion gases.

The cooling means may be in the form of first and second one-way valves. The first and second valves each communicate between the chamber of the loading means and the exterior of the firearm.

The piston and piston rod are preferably sealingly mounted within the chamber.

In a preferred embodiment, the first one-way valve permits the escape of air from the chamber when the piston is driven, by the expansion gases, from a rest position.

Bias means may be provided for biasing the piston against the action of the expansion gases and for returning the piston to the rest position thereby producing the relatively low pressure region within the chamber.

The second one-way valve is provided for permitting the entry of the relatively cool air into the chamber as the piston moves towards the rest position.

The first one-way valve is preferably positioned at an end of the chamber which is remote from the rest position. The second valve is preferably positioned in the chamber in the vicinity of the rest position.

The second one-way valve permits entry of the relatively cool air into the chamber after the piston has returned to the rest position.

The second one-way valve is preferably coupled to the exterior surface of the barrel of the firearm so that the relatively cool air is drawn therealong prior to entry into the chamber. Drawing the relatively cool air along the barrel in this way further assists cooling of the firearm.

Embodiments of the invention have the advantage that they permit efficient cooling of the firearm during operation thereof. The configuration of embodiments according to the present invention can be such that an effectively continuous stream of cool air is pumped along the barrel and past the components of the firearm in the vicinity of the firing position.

Embodiments of the present invention are also advantageous because use is made of the reciprocal action of the loading means so that the pump action is effected in order to draw cool air into the firearm, and for subsequently pumping heated air out of the firearm.

The barrel may be surrounded by a light alloy cooling jacket which defines a cavity around the outer surface of the barrel. The relatively cool air can be drawn along the barrel within the cavity by means of the pump action of the loading means and cooling means to effect cooling of the firearm.

In a preferred embodiment of the present invention, the piston is driven past the first one-way valve for allowing the expansion gases to be bled from the interior of the firearm.

Since embodiments of the invention may be effected by making relatively minor modifications to existing loading mechanisms. the significant advantages of the invention may be achieved without adding excessive weight and bulk, if any, to the firearm. In addition, the modifications may be effected for a relatively low cost.

Since embodiments of the invention permit a more efficient cooling of the firearm, they eliminate or at last reduce the frequency of the need to replace the barrel of the firearm due to overheating. In conventional firearms of the gas action type. it is necessary to change the barrel approximately every 500 rounds due to overheating.

The present invention will now be further described. by way of example with reference to the accompanying drawings, in which: Figure 1 is a schematic view of a loading mechanism in a conventional gas action automatic rifle; and Figure 2 is a schematic view of an embodiment of the present invention.

In Figure 1. a cartridge 2 is shown loaded in a firing position at one end of a barrel 4. When the cartridge 2 has fired. gases are produced from the explosion of gunpowder, and gases within the cavity 6 of the barrel 4 expand so as to drive a loading mechanism of the firearm.

The loading mechanism comprises a piston 7 and a piston rod 8 which is driven rearwardly by the action of the expansion gases against the action of a spring 10. The rearward end 12 of the piston 8 pushes against a peg 14 of a bolt lock 16. The rearward movement of the peg 14 causes unlocking of the bolt thereby providing for ejection of the spent cartridge 2 from the firearm, and replacement thereof by a new cartridge from the magazine (not shown). The details of the cartridge replacement and loading mechanism correspond to those of the "Browning" automatic rifle referred to hereinabove.

Before the piston 7 reaches its full rearward travel, the piston 7 passes a valve 20 positioned in a wall 22 of the firearm (this position not illustrated in Figure 1. the piston 7 being to the right hand side of the valve 20 when in the rearwardmost position). The valve 20 permits the escape of the expansion gases from within the cavity 6 and serves to permit pressure equalization of the gas within the locking mechanism with that outside the firearm during movement of the piston 7.

In an alternative arrangement, the piston 7 may not pass the valve 20. In this case the valve 20 serves only to permit pressure equalization.

As explained hereinabove, this type of firearm has the disadvantage that overheating of the barrel 4 and loading mechanism can occur owing to the absence of any effective mechanism for removing the heat passed by the expansion gases.

Figure 2 illustrates an embodiment of the present invention in which like reference numerals designate like elements shown in Figure 1.

In this embodiment, a cooling means is provided which cooperates with the piston rod 7 and piston 8 of the loading mechanism in order to cool the barrel 4 and loading mechanism of the rifle.

In this embodiment, a seal 24 is provided around the piston rod 8 at one end of a chamber 26. The piston 7 is sealingly and reciprocally slidable within the chamber 26. First and second one-way valves 28 and 30 respectively are provided in the wall 22 of the chamber 26. The first one-way valve 28 permits gases to pass only from within the chamber 26 to outside of the firearm. The second one-way valve 30 permits gases to enter the chamber 26 from outside the firearm. A duct 32 is provided for linking the second valve 30 to a jacket 34 surrounding the barrel 4 of the rifle. The jacket is provided with an inlet port 36 for permitting relatively cool air from outside the firearm to pass therethrough into a cavity 38 defined by the jacket 34 and the barrel 4.

The operation of the embodiment will be described as follows.

When firing of the cartridge 2 takes place, the explosion gives rise to gases and the expansion of existing gases within the cavity 6. These expansion gases are high in temperature and expand so as to push the piston 7 rearwardly from the position illustrated in Figure 2. This rearward movement operates the loading mechanism as described with reference to Figure 1.

Since the cavity 26 is sealed at both ends by the piston 7 and the seal 24 respectively, the gases therein are expelled from the firearm via the first valve 28. When the pressure exerted by the expansion gases subsides, the spring 10 urges the bolt 16 and the peg 14 (towards the left of Figure 2) thereby driving the piston forwardly towards and eventually past the second valve 30. Since the first valve is one-way, gas cannot enter the chamber 26 as the piston 7 moves towards the second valve 30. Consequently, the pressure within the cavity 26 decreases. As the piston 7 passes the second valve 30, the relatively high pressure and cool air from outside of the firearm is drawn into the port 36, along the barrel 4 in the cavity 38, along the duct 32, through the valve 30 and into the low pressure region of the chamber 26.This relatively cool air cools the barrel 4, the intermediary components of the rifle, and the loading mechanism. This cool air warms and is subsequently expelled when the piston 7 moves rearwardly owing to firing of the next cartridge.

It would be clear to the skilled man in the art that modifications may be made to the embodiment as described above without departing from the scope of the present invention. For example, the duct 32 may pass through the loading mechanism itself so as to enhance the cooling effect of the relatively cool air from outside the firearm. Also, vanes may be positioned on the outer surface of the barrel 4 for guiding the cool air through the cavity 38 to ensure that it passes over all parts of the barrel 4 so as to provide for efficient cooling thereof. The jacket 34 could be provided with a plurality of ports 36 for permitting the entry of the cool relatively high pressure air from outside the firearm.

Embodiments of the invention may be used in association with loading mechanisms which are different from the one used in the "Browning" automatic rifle.

Claims

1. A firearm comprising: a cartridge loading means for loading cartridges into a firing position from a magazine, which loading means is driven by expansion gases produced from firing a cartridge in the firing position; and cooling means for cooperating with the cartridge loading means so as to create a pump action during operation of the firearm, whereby a relatively low pressure region is created within the firearm into which relatively cool air is drawn from outside the firearm, thereby cooling the firearm.

2. A firearm according to claim 1, wherein the loading means comprises a piston and piston rod reciprocally mounted within a chamber and driven by the expansion gases.

3. A firearm according to claim 2, wherein the cooling means is in the form of first and second one-way valves1 the first and second valves each communicating between the chamber of the loading means and the exterior of the firearm.

4. A firearm according to claim 2 or claim 3, wherein the piston and piston rod are sealingly mounted within the chamber.

5. A firearm according to claim 2, claim 3 or claim 4, wherein the first one-way valve permits the escape of expansion gases from the chamber when the piston is driven past the first one-way valve, by the expansion gases, from a rest position.

6. A firearm according to claim 5, wherein bias means is provided for biasing the piston against the action of the expansion gases and for returning the piston to the rest position thereby producing the relatively low pressure region within the chamber.

7. A firearm according to claim 5 or claim 6, wherein the second one-way valve is positioned so that the relatively cool air enters into the chamber after the piston has returned to the rest position.

8. A firearm according to claim 5, claim 6 or claim 7, wherein the first one-way valve is positioned at an end of the chamber which is remote from the rest postion.

9. A firearm according to any one of claims 2 to 8, wherein the second one-way valve is coupled to the exterior surface of a barrel of the firearm so that the relatively cool air is drawn therealong prior to entry into the chamber.

10. A firearm according to claim 9, wherein means is provided for directing the relatively cool air along the barrel of the firearm prior to entry into the firearm, thereby assisting cooling of the barrel.

11. A firearm according to claim 10, wherein the means comprises a cooling jacket defining a cavity around the outer surface of the barrel, the relatively cool air being drawn along the barrel within the cavity by means of the pump action.

12. A firearm substantially as hereinbefore described with reference to figure 2 of the accompanying drawings.