Mechanical guns and projectors – Fluid pressure – Applied to intermediate projectile-engaging member
Reexamination Certificate
1999-02-25
2001-01-09
Carone, Michael J. (Department: 3643)
Mechanical guns and projectors
Fluid pressure
Applied to intermediate projectile-engaging member
C124S069000, C124S070000, C124S074000, C124S080000, C042S001140, C089S001810
Reexamination Certificate
active
06170477
ABSTRACT:
BACKGROUND OF THE INVENTION
Spear guns are devices for propelling spears and are typically used under water as a weapon or for hunting purposes. Known spear guns use various mechanisms for propelling a spear, one of which is a pneumatic system in which air is compressed to provide the propulsive force. Spear guns which employ a pneumatic system for propelling a spear are commonly referred to as pneumatic spear guns.
A pneumatic spear gun includes a barrel into which the shaft of a spear to be propelled by the spear gun can be received. A piston is slidingly and sealingly received within the barrel. One side of the piston communicates with a supply of air which undergoes compression upon retraction of the piston when the shaft of a spear is introduced into the barrel. The compressed air provides a propulsive force for propelling the piston along the barrel so as to discharge the spear. The air is contained in a reservoir within the body of the spear gun and an inlet is provided for replenishing the air as necessary.
While pneumatic spear guns are satisfactory in operation, they do have a deficiency in that it is not possible to selectively vary the propulsive force which can be applied to the piston.
DISCLOSURE OF THE INVENTION
It would be advantageous to provide a pneumatic spear gun in which the propulsive force applied to a spear discharged by the spear gun can be selectively varied.
The present invention provides a spear gun comprising a barrel having an open end through which a shaft of a spear can be received, a first piston slidingly and sealingly received in the barrel for movement towards and away from a retracted position, a retaining means for releasably retaining the piston in the retracted position, a source of compressible fluid arranged to undergo compression upon movement of the piston into the retracted position and to propel the piston along the barrel from the retracted position upon release of the piston thereby to propel the spear, and control means for selectively increasing the pressure of the compressible fluid for varying the propulsive force applied to the piston.
The control means may comprise means for effecting a volume reduction of the compressible fluid.
The compressible fluid may be contained in a reservoir and the means for effecting a volume reduction of the compressible fluid may comprise a wall of the reservoir movable to reduce the volume of the reservoir.
The reservoir may comprise a cylinder having a second piston slidingly and sealingly mounted therein to define the movable wall, one side of the second piston being exposed to the compressible fluid whereby movement of the second piston along the cylinder effects a variation of the volume of the reservoir, and wherein a second control means is provided for controlling movement of the second piston along the cylinder.
The second control means may comprise means for applying fluid pressure to the other side of the second piston. In this regard, the second control means may comprise a pump means for delivering the fluid pressure by way of an incompressible fluid.
Conveniently, the incompressible fluid comprises water received from an underwater environment in which the spear gun is being used.
Conveniently, the pump means comprises a hand operable pump.
The cylinder may be of annular configuration in cross-section and positioned around at least part of the barrel, with porting means providing for communication of the compressible fluid between the cylinder and the barrel.
The pump means may comprise a piston pump having a suction stroke and a delivery stroke.
The piston pump may comprise a pump piston slidingly and sealingly mounted in a pump cylinder, the pump piston and pump cylinder co-operating to define a pumping chamber, the pump piston including a sealing element movable axially between first and second positions upon a reciprocatory movement of the pump piston in the pump cylinder whereby upon a suction stroke of the piston the sealing element assumes the first position in which fluid can flow past the piston into the pumping chamber and upon a delivery stroke of the piston the sealing element assumes the second position in which the sealing element seals against fluid flow past the piston.
An intake path may be provided in the piston along which fluid can flow when the sealing element is in the first position.
Conveniently, the sealing element comprises an O-ring mounted on the piston body.
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Carone Michael J.
French III Fredrick T.
Hogan & Hartson LLP
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