Double piston propulsion unit

Details Double piston propulsion unit Double piston propulsion unit

1993-04-23

1994-05-24

Brown, David H.

Ordnance

Recoilless gun

Having a reaction mass

F41A 110

Patent

active

053138708

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention;
The invention relates to a double piston propulsion unit for a recoilless mass/countermass projectile launcher and in particular for a hand-held shoulder-launched system suitable for launching a projectile from a confined space.


DISCUSSION OF PRIOR ART

Recoilless mass/countermass launchers operate by simultaneously firing a projectile forwardly and a countermass rearwardly with equal and opposite momentum. This prevents any recoil from being transmitted to the launcher, so that the launcher requires no recoil support and can be hand-held provided that the weight of the launcher can be supported by a human operator.
Propulsion units for recoilless mass/countermass projectile launchers are known in which an open ended launch tube has two cylindrical pistons of equal mass located in a back-to-back relationship within it which are releasably restrained either side of a propellant charge (see FIG. 1). One piston is for propelling the projectile out of the open forward end of the tube and the other is for propelling the countermass out of the open rearward end of the tube. The two pistons are releasably restrained by an axially-located connecting rod secured therebetween in which an area of weakness is provided. The propellant charge is located in the space surrounding the rod between the two pistons.
These known propulsion units are oprated by the activation of triggering means which initiates the propellant charge, the combustion of which causes a build up of hot gases in the space between the pistons. When the pressure of the gas reaches a predetermined level the weakness provided in the connecting rod causes the rod to fail in tension and the pistons are projected along the launch tube in opposite directions, thus projecting the projectile forwards and the countermass rearwards. The launch tube has piston intercepts at both its ends which halt the pistons but allow the projectile and countermass to leave the tube.
Such units with the pistons connected by an axially-located connecting rod carry a substantial mass penalty. This is because the pistons need to be axially thickened to withstand the tensile and compressive forces transmitted to them by the rod during the launching of a projectile. A high mass propulsion unit is clearly a disadvantage especially for a launcher designed to be hand-held and shoulder launched.


SUMMARY OF THE INVENTION

The present invention provides a propulsion unit for a recoilless mass/countermass projectile launcher which enables a significant mass reduction to be made. Furthermore the present invention enables a significant length reduction to be made in the unit which increases the effective stroke of the pistons for any given launch system length and provides a potentially safer and more cheaply and easily manufactured propulsion unit.
According to a first aspect of the present invention there is provided a double piston propulsion unit for a recoilless mass/countermass projectile launch system comprising two pistons of substantially equal mass arranged in a back-to-back relationship and a propellant charge disposed between the two pistons, wherein the pistons comprise hollow cylinders with closed outer ends and open inner ends, said open inner ends being joined together by a circumferentially rupturable connecting means so that the hollow cylinders together form a vessel enclosing said propellant charge.
The two hollow cylindrical pistons are joined together at their open ends so removing the need for an axially-located connecting rod and bolts between the pistons. Therefore the pistons no longer have to withstand the large tensile and compressive forces associated with attachment to the connecting rod, so enabling the thickness and thus the mass of the pistons to be reduced substantially. The reduced mass of the pistons also enables the mass of propellant used to launch the projectile at a required velocity to be reduced. The combined effect of the reduced mass of the pistons and propellant charge means that the pro

REFERENCES:
patent: 3128670 (1964-04-01), Blacker
patent: 3800656 (1974-04-01), Schnabele
patent: 4643071 (1987-02-01), Baechler et al.
patent: 4676136 (1987-06-01), Kalin

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