WO2020016731A1

WO2020016731A1 - Variable port pressure device for use on a multiple grenade launcher

Info

Publication number: WO2020016731A1
Application number: PCT/IB2019/056002
Authority: WO
Inventors: Christo Botes
Original assignee: Rippel Effect Systems (Pty) Limited
Priority date: 2018-07-17
Filing date: 2019-07-15
Publication date: 2020-01-23
Also published as: ZA202100366B

Abstract

The invention relates to a variable port pressure device (10) or gas plug, adapted for use on a multiple grenade launcher, and configured to improve indexing of such a weapon, particularly when used with lower velocity ammunition. The device comprises a piston (14) which is co-axially displaceable within a piston housing (12), the piston (14) comprising a groove (16) extending about an exterior wall surface (14.1) of the piston (14) so as to create a tortuous gas flow path between the piston (14) and the piston housing (12), and a hollow cylindrical body (14.2) which terminates at one end thereof in a concave base wall (20).

Description

VARIABLE PORT PRESSURE DEVICE FOR USE ON A MULTIPLE GRENADE

LAUNCHER

INTRODUCTION

The invention relates to a variable port pressure device, also referred to as a gas plug or pressure piston, adapted for use on a multiple grenade launcher, and configured to improve indexing of such a weapon, particularly when used with lower velocity ammunition.

BACKGROUND TO THE INVENTION

A grenade launcher is a weapon that fires a specially-designed large-calibre projectile, often with an explosive, smoke or gas, anti-riot baton, irritant or pyrotechnic warhead. The term typically refers to a class of dedicated firearms firing unitary grenade cartridges, of which the most common type are man-portable, shoulder-fired weapons used by individuals. Although intended primarily for offensive and defensive use with high-explosive rounds, with appropriate ammunition a grenade launcher is suitable for anti-riot and other non-lethal security operations, allowing it to fire less lethal rounds at much lower pressures and velocities.

A Multiple Grenade Launcher (abbreviated as“MGL”) is generally a lightweight, low- velocity, shoulder-fired 40mm weapon, although variations also fire 37mm or 38mm cartridges. The MGL includes a lightweight, progressively rifled steel barrel, sight assembly, frame with firing mechanism and a folding stock. It also includes a spring- actuated, usually six-round, revolver-style cylinder which rotates automatically while firing, as well as a pressure piston which is located adjacent and operatively associated with the cylinder for locking the cylinder in place each time a new round is fired. The MGL is loaded by releasing a cylinder axis pin and swinging the frame away from the cylinder. The rear of the cylinder (including a pistol grip) is unlatched and pivoted counter-clockwise against its driving spring to expose the cylinder chambers during reloading. Grenades are then inserted into the cylinder chambers, the frame closed, and the axis pin re-engaged to lock the cylinder into position. When a trigger is pressed, a double-action takes place and a firing pin is cocked and released to fire a grenade. Gas pressure on the pressure piston displaces the piston such that it becomes disengaged from the cylinder, thereby unlocking the cylinder and allowing the spring to rotate the cylinder until the next chamber is aligned with the firing pin, whereupon the piston re-engages the cylinder and the next round can be fired. A 40mm grenade typically includes a projectile and fuse contained within a 40mm cartridge casing. The cartridge casing includes a heavy cup-shaped high-pressure chamber. Upon firing, a propellant builds up pressure within the high-pressure chamber until it releases the projectile down the barrel. The resultant gas pressure also displaces the pressure piston so as to unlock the cylinder and allow it to rotate to the next round. In the event that the MGL is used with lethal cartridges, firing of the cartridge releases sufficient gas pressure effectively to displace the pressure piston, allowing for effortless rotation of the cylinder.

However, non-lethal / less-lethal cartridges, such as baton rounds (rubber or plastic bullets), beanbag, rubber buckshot (stinger) or pepper ball rounds, are larger than lethal lead-carrying cartridges and they are fired at lower pressures and velocities. A shortcoming that occurs when firing such non-lethal / less-lethal cartridges with an MGL, is that the resultant gas pressure that is released upon firing, is often insufficient to displace the pressure piston into full disengagement away from the cylinder. Accordingly, the weapon cannot index properly, which means the cylinder fails to rotate automatically to the next position and needs to be rotated manually after each successive shot is fired. It will be appreciated that in riot control or other combat situations, such a shortcoming can have extremely adverse consequences for a user. Accordingly, the applicant has identified a need to decrease gas leakage so as to increase gas pressure being exerted on the pressure piston during the firing of particularly non-lethal / less-lethal cartridges, so as to ensure continuous indexing of the cylinder after each successive shot fired. SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided a variable port pressure device, suitable for, although not limited to, use in a Multiple Grenade Launcher which includes a rotating cylinder, the device including - a piston housing arranged approximate the cylinder;

a complimentarily configured pressure-actuated piston which is displaceable within the piston housing between a first position, in which it is operatively engaged with the cylinder, and a second position in which it is operatively disengaged from the cylinder; the device being characterised therein that it includes at least one groove extending about an exterior wall surface of the piston and/or an interior wall surface of the piston housing so as to create a tortuous gas flow path between the exterior wall surface of the piston and the interior wall surface of the piston housing for decreasing gas leakage during a firing process.

The pressure-actuated piston may longitudinally axially be displaceable within the piston housing between the first and second positions and the piston may include at least one groove which at least partially circumferentially extends about the exterior wall surface of the piston. Particularly, the piston may include at least one continuous groove extending circumferentially about a lower portion of the piston, the groove being bordered by two groove threads, with a small clearance existing between tips of the groove threads and the interior wall surface of the piston housing. More particularly, the piston may include two or more circumferentially extending grooves arranged in longitudinal axial displacement about the exterior wall surface of the piston so as to create a labyrinth type of seal between the piston and the piston housing, the arrangement being such that gas released by the firing process becomes entrapped within a labyrinth groove, thereby decreasing gas leakage, increasing effective displacement of the piston between the first and second positions, and increasing indexing of the weapon after each successive shot.

In an alternative embodiment, the device may include at least one groove which at least partially circumferentially extends about the interior wall surface of the piston housing. Particularly, the piston housing may include at least one continuous groove extending circumferentially about a lower portion of the piston housing, the groove being bordered by two groove threads, with a small clearance existing between tips of the groove threads and the exterior wall surface of the piston. More particularly, the piston housing may include two or more circumferentially extending grooves arranged in longitudinal axial displacement about the interior wall surface of the piston housing so as to create a labyrinth type of seal between the piston housing and the piston.

The device further may be characterised therein that the piston comprises a substantially hollow cylindrical body. The hollow cylindrical body may terminate at opposing ends thereof in a base wall and top wall respectively for sealing the hollow interior of the piston body to prevent ingress of dirt or other elements into the piston body.

The device further may be characterised therein that the piston terminates at one end thereof in a substantially concave base wall, so as to increase pressure surface area at a pressure actuated end of the piston.

According to a second aspect of the invention there is provided a variable port pressure device, suitable for, although not limited to, use in a Multiple Grenade Launcher which includes a rotating cylinder, the device including - a piston housing arranged approximate the cylinder;

a complimentarily configured pressure-actuated piston which is displaceable within the piston housing between a first position, in which it is operatively engaged with the cylinder, and a second position in which it is operatively disengaged from the cylinder; the device being characterised therein that the piston comprises a substantially hollow cylindrical body terminating at opposing ends thereof in a base wall and top wall respectively for sealing a hollow interior of the piston body. The device further may be characterised therein that the piston terminates at one end thereof in a substantially concave base wall, so as to increase pressure surface area at a pressure actuated end of the piston.

The device also may include at least one groove extending about an exterior wall surface of the piston and/or an interior wall surface of the piston housing so as to create a tortuous gas flow path between the exterior wall surface of the piston and the interior wall surface of the piston housing for decreasing gas leakage during a firing process. According to a third aspect of the invention there is provided a variable port pressure device, suitable for, although not limited to, use in a Multiple Grenade Launcher which includes a rotating cylinder, the device including - a piston housing arranged approximate the cylinder;

a complimentarily configured pressure-actuated piston which is displaceable within the piston housing between a first position, in which it is operatively engaged with the cylinder, and a second position in which it is operatively disengaged from the cylinder;

the device being characterised therein that the piston terminates at one thereof in a substantially concave base wall, so as to increase pressure surface area at a pressure actuated end of the piston. The device further may be characterised therein that the piston comprises a substantially hollow cylindrical body. The hollow cylindrical body may terminate at opposing ends thereof in a base wall and top wall respectively for sealing the hollow interior of the piston body to prevent ingress of dirt or other elements into the piston body.

The device also may include at least one groove extending about an exterior wall surface of the piston and/or an interior wall surface of the piston housing so as to create a tortuous gas flow path between the exterior wall surface of the piston and the interior wall surface of the piston housing for decreasing gas leakage during a firing process.

According to a fourth aspect of the invention there is provided a variable port pressure device, suitable for, although not limited to, use in a Multiple Grenade Launcher which includes a rotating cylinder, the device including - a piston housing arranged approximate the cylinder;

the device being characterised therein that it includes at least one groove extending about an exterior wall surface of the piston and/or an interior wall surface of the piston housing so as to create a tortuous gas flow path between the exterior wall surface of the piston and the interior wall surface of the piston housing for decreasing gas leakage during a firing process;

the device further being characterised therein that the piston comprises a substantially hollow cylindrical body terminating at opposing ends thereof in a base wall and top wall respectively for sealing a hollow interior of the piston body; and

that the piston terminates at one thereof in a substantially concave base wall, so as to increase pressure surface area of the piston at a pressure actuated end of the piston. SPECIFIC EMBODIMENT OF THE INVENTION

Without wishing to be bound thereto, the invention will now further be described and illustrated with reference to the following non-limiting examples in which - FIGURE 1 is a perspective view of a PRIOR ART pressure piston with the piston in a first position in which it would be engaging a cylinder (not shown);

FIGURE 2 is a longitudinal sectional side elevation of the pressure piston of Figure

1 ;

FIGURE 3 is a perspective view of the PRIOR ART pressure piston of Figure 1 with the piston in a second position in which it would be disengaged from the cylinder;

FIGURE 4 is a longitudinal sectional side elevation of the pressure piston of Figure

3;

FIGURE 5 is an exploded perspective view of a variable port pressure device according to the INVENTION; FIGURE 6 is an assembled perspective view of a variable port pressure device according to the INVENTION with the piston in a first position in which it would be engaged with a cylinder (not shown);

FIGURE 7 is a longitudinal sectional side elevation of the pressure piston of Figure

6;

FIGURE 8 is an assembled perspective view of a variable port pressure device according to the INVENTION with the piston in a second position in which it would be disengaged from the cylinder (not shown); and

FIGURE 9 is a longitudinal sectional side elevation of the pressure piston of Figure

8.

Referring first to prior art Figures 1 to 4, a pressure piston device [1 ] typically includes a piston housing [2] and a pressure-actuated piston [3] which is longitudinally axially displaceable within the piston housing [2] The piston [3] includes a cylinder-engaging arm [4] which protrudes through an elongate slot [5] within a wall of the piston housing [2] The piston [3] is displaceable within the piston housing [2] between a first position, in which the cylinder-engaging arm [4] engages a cylinder (not shown), and a second position in which the cylinder-engaging arm [4] is disengaged from the cylinder. The piston [3] has an even, pressure actuated end, base wall [6] and a piston diameter [X] of approximately 8mm. As a result, approximately 3 BAR of pressure is required to displace the cylinder-engaging arm [4] of the piston [3] into full disengagement from the cylinder.

Figures 5 to 9 illustrate a variable port pressure device [10] according to the invention. The device [10] is particularly suitable for, although not limited to, use in a Multiple Grenade Launcher which includes a rotating cylinder (not shown). The device [10] includes a piston housing [12] arranged approximate the cylinder and a complimentarily configured pressure-actuated piston [14] which is displaceable within the piston housing [12] between a first position (Figures 6 and 7), in which it is operatively engaged with the cylinder, and a second position (Figures 8 and 9) in which it is operatively disengaged from the cylinder. The pressure-actuated piston [14] is longitudinally axially displaceable within the piston housing [12] between the first and second positions. The piston housing [12] includes a slot [13] within a wall of the piston housing [12]. The piston [14] includes a cylinder-engaging arm [15] which is connected to the piston [14] and which protrudes through the slot [13] of the piston housing [12]. When the piston [14] is displaced to the first position, the cylinder- engaging arm [15] engages the cylinder, and when the piston [14] is displaced to the second position, the cylinder-engaging arm [15] is disengaged from the cylinder. The device [10] includes, as a first feature, at least one groove [16] extending about an exterior wall surface [14.1 ] of the piston [14] and/or an interior wall surface [12.1] of the piston housing [12]. The groove [16] creates a tortuous gas flow path between the exterior wall surface [14.1 ] of the piston [14] and the interior wall surface [12.1 ] of the piston housing [12] for decreasing gas leakage during a firing process. Particularly, in the illustrated embodiment, the device [10] includes two continuous grooves [16] which circumferentially extend about the exterior wall surface [14.1 ] of the piston [14] about a lower region of the piston [14]. Each groove [16] is bordered by two groove threads [18], with a small clearance existing between tips of the groove threads [18] and the interior wall surface [12.1 ] of the piston housing [12]. The two grooves [16], which are longitudinally axially displaced relative to each other, create a labyrinth type of seal between the piston [14] and the piston housing [12], the arrangement being such that gas released by the firing process becomes entrapped within the labyrinth-type grooves [16], thereby decreasing gas leakage, increasing effective displacement of the piston [14] between the first and second positions, and increasing indexing of the weapon after each successive shot. In the illustrated embodiment, the grooves [16] are aligned with the slot [13] within the wall of the piston housing [12] when the piston is displaced to the second position (refer Figures 8 and 9). As a second feature, the device [10] is characterised therein that the piston [14] comprises a substantially hollow cylindrical body [14.2] The hollow cylindrical body [14.2] terminates at opposing ends thereof in a base wall [20] and top wall [22] respectively for sealing the hollow interior [14.3] of the piston body [14.2] to prevent ingress of dirt or other elements into the piston body [14.2]

The device [10] is further characterised therein that the piston [14] terminates at one thereof in a substantially concave base wall [20], so as to increase pressure surface area at a pressure actuated end of the piston [14] The piston diameter [Y] is approximately 12mm. As a result of the features introduced by the invention, only approximately 1 BAR of pressure is required to displace the piston [14] into full disengagement from the cylinder.

It will be appreciated that other embodiments of the invention as possible without departing from the spirit or scope of the invention as defined in the claims.

Claims

1. A variable port pressure device [10], suitable for, although not limited to, use in a Multiple Grenade Launcher which includes a rotating cylinder, the device [10] including - a piston housing [12] arranged approximate the cylinder; a complimentarily configured pressure-actuated piston [14] which is displaceable within the piston housing [12] between a first position, in which it is operatively engaged with the cylinder, and a second position in which it is operatively disengaged from the cylinder;

the device [10] being characterised therein that it includes at least one groove [16] extending about an exterior wall surface [14.1 ] of the piston [14] and/or an interior wall surface [12.1 ] of the piston housing [12] so as to create a tortuous gas flow path between the exterior wall surface [14.1] of the piston [14] and the interior wall surface [12.1 ] of the piston housing [12] for decreasing gas leakage during a firing process.

2. The variable port pressure device [10] according to claim 1 wherein the pressure- actuated piston [14] includes at least one groove [16] which at least partially circumferentially extends about the exterior wall surface [14.1] of the piston.

3. The variable port pressure device [10] according to claim 2 wherein the piston

[14] includes at least one continuous groove [16] extending circumferentially about a lower portion of the piston, the groove [16] being bordered by two groove threads [18], with a small clearance existing between tips of the groove threads [18] and the interior wall surface [12.1 ] of the piston housing [12]

4. The variable port pressure device [10] according to claim 3 wherein the piston

[14] includes two or more circumferentially extending grooves [16] arranged in longitudinal axial displacement relative to each other about the exterior wall surface [14.1 ] of the piston [14] so as to create a labyrinth type of seal between the piston [14] and the piston housing [12], the arrangement being such that gas released by the firing process becomes entrapped within a labyrinth groove [16].

5. The variable port pressure device [10] according to claim 1 wherein the piston housing [12] includes at least one groove [16] which at least partially circumferentially extends about the interior wall surface [12.1 ] of the piston housing [12]

6. The variable port pressure device [10] according to claim 5 wherein the piston housing [12] includes at least one continuous groove [16] extending circumferentially about a lower portion of the piston housing [12], the groove [16] being bordered by two groove threads [18], with a small clearance existing between tips of the groove threads [18] and the exterior wall surface [14.1 ] of the piston [14]

7. The variable port pressure device [10] according to claim 6 wherein the piston housing [12] includes two or more circumferentially extending grooves [16] arranged in longitudinal axial displacement relative to each other about the interior wall surface [12.1 ] of the piston housing [12] so as to create a labyrinth type of seal between the piston housing [12] and the piston [14].

8. The variable port pressure device [10] according to claim 1 wherein the piston

[14] further comprises a substantially hollow cylindrical piston body [14.2] which terminates at opposing ends thereof in a base wall [20] and top wall [22] respectively for sealing the hollow interior of the piston body [14.2]

9. The variable port pressure device [10] according to claim 1 wherein the piston

[14] further terminates at one thereof in a substantially concave base wall [20].

10. A variable port pressure device [10], suitable for, although not limited to, use in a Multiple Grenade Launcher which includes a rotating cylinder, the device [10] including - a piston housing [12] arranged approximate the cylinder; a complimentarily configured pressure-actuated piston [14] which is displaceable within the piston housing [12] between a first position, in which it is operatively engaged with the cylinder, and a second position in which it is operatively disengaged from the cylinder;

the device [10] being characterised therein that the piston [14] comprises a substantially hollow cylindrical piston body [14.2] terminating at opposing ends thereof in a base wall [20] and top wall [22] respectively for sealing a hollow interior of the piston body [14.2]

1 1. The variable port pressure device [10] according to claim 10 wherein the piston [14] terminates at one thereof in a substantially concave base wall [20], so as to increase pressure surface area at a pressure actuated end of the piston [14]. 12. The variable port pressure device [10] according to claim 10 wherein the device

[10] also includes at least one groove [16] extending about an exterior wall surface [14.1] of the piston [14] and/or an interior wall surface [12.1] of the piston housing [12] so as to create a tortuous gas flow path between the exterior wall surface [14.1 ] of the piston [14] and the interior wall surface [12.1 ] of the piston housing [12] for decreasing gas leakage during a firing process.

13. A variable port pressure device [10], suitable for, although not limited to, use in a Multiple Grenade Launcher which includes a rotating cylinder, the device [10] including - a piston housing [12] arranged approximate the cylinder; a complimentarily configured pressure-actuated piston [14] which is displaceable within the piston housing [12] between a first position, in which it is operatively engaged with the cylinder, and a second position in which it is operatively disengaged from the cylinder;

the device [10] being characterised therein that the piston [14] terminates at one end thereof in a substantially concave base wall, so as to increase pressure surface area at a pressure actuated end of the piston.

14. The variable port pressure device [10] according to claim 13 wherein the piston

[14] comprises a substantially hollow cylindrical body [14.2] which terminates at opposing ends thereof in a base wall [20] and top wall [22] respectively for sealing the hollow interior of the piston body [14.2] to prevent ingress of dirt or other elements into the piston body [14.2] 15. The variable port pressure device [10] according to claim 13 wherein the device

[10] also includes at least one groove [16] extending about an exterior wall surface [14.1] of the piston [14] and/or an interior wall surface [12.1 ] of the piston housing [12] so as to create a tortuous gas flow path between the exterior wall surface [14.1 ] of the piston [14] and the interior wall surface [12.1 ] of the piston housing [12] for decreasing gas leakage during a firing process.

16. A variable port pressure device [10], suitable for, although not limited to, use in a Multiple Grenade Launcher which includes a rotating cylinder, the device [10] including - a piston housing [12] arranged approximate the cylinder; a complimentarily configured pressure-actuated piston [14] which is displaceable within the piston housing [12] between a first position, in which it is operatively engaged with the cylinder, and a second position in which it is operatively disengaged from the cylinder;

the device [10] being characterised therein that it includes at least one groove [16] extending about an exterior wall surface [14.1 ] of the piston [14] and/or an interior wall surface [12.1 ] of the piston housing [12] so as to create a tortuous gas flow path between the exterior wall surface [14.1 ] of the piston [14] and the interior wall surface [12.1 ] of the piston housing [12] for decreasing gas leakage during a firing process; the device [10] further being characterised therein that the piston [14] comprises a substantially hollow cylindrical piston body [14.2] terminating at opposing ends thereof in a base wall [20] and top wall [22] respectively for sealing a hollow interior of the piston body [14.2]; and

that the piston [14] terminates at one end thereof in a substantially concave base wall, so as to increase pressure surface area of the piston [14] at a pressure actuated end of the piston.

17. A variable port pressure device [10] according to anyone of claims 1 , 10, 13 or 16 substantially as herein illustrated with reference to Figures 5 to 9.