Spring powered gas operated weapon

Abstract

A piston head ( 1 ) suitable for a spring powered gas operated weapon such as an air rifle or air pistol is disclosed. The piston head ( 1 ) is comprised of a piston end and a spring abutment means in which the piston end is comprised of a head ( 5 ) and a plunger ( 3 ), the spring abutment means is comprised of a body ( 2 ) and an extended boss ( 4 ). At least the body ( 2 ) of the spring abutment means defines a blind bore ( 20 ) which extends from the surface of the body ( 20 ) remote from the extended boss ( 4 ) and towards the extended boss ( 4 ) and preferably into the extended boss ( 4 ). The plunger ( 3 ) and blind bore ( 20 ) are dimensioned to allow the plunger ( 3 ) to fit within the blind bore ( 20 ), and the plunger ( 3 ) is provided with at least one means for mounting a seal means ( 6 ) around the plunger ( 3 ) to allow the creation of a seal between the plunger ( 3 ) and the or each wall defining the blind bore ( 20 ).

1 . A piston head suitable for a spring powered gas operated weapon characterized in that
 the piston head is comprised of a piston end and a spring abutment,   the piston end is comprised of a head and a plunger,   the spring abutment is comprised of a body and an extended boss, at least the body of the spring abutment defines a blind bore which extends through at least the body where the blind bore extends from the surface of the body remote from the extended boss and towards the extended boss,   the plunger and blind bore are dimensioned to allow the plunger to fit within the blind bore, and   the plunger is provided with at least one feature for mounting a seal around the plunger to allow the creation of a seal between the plunger and at least one wall defining the blind bore.   
     
     
         2 . A piston head according to  claim 1  in which the body and extended boss of the spring abutment both have substantially cylindrical curved surfaces and the cylindrical curved surfaces of the body and extended boss have a substantially common axis. 
     
     
         3 . A piston head according to  claim 2  in which the surface defining the longitudinal extent of the blind bore is substantially cylindrical and the axis of that cylinder is substantially common with the axis of the body and the blind boss. 
     
     
         4 . A piston head according to  claim 1 , characterized in that the head and the plunger of the piston end both have substantially cylindrical curved surfaces and the cylindrical curved surfaces of the head and the plunger have a substantially common axis. 
     
     
         5 . (canceled) 
     
     
         6 . (canceled) 
     
     
         7 . A piston head according to  claim 1 , in which the blind bore in the spring abutment is defined by the body and extended boss. 
     
     
         8 . A piston head according to  claim 1 , in which the depth of the blind bore defined by the spring abutment is equal to or greater than the length of the plunger of the piston end. 
     
     
         9 . A piston head according to  claim 1 , in which the feature for mounting a seal around the plunger is at least one groove. 
     
     
         10 . A piston head according to  claim 9  in which there is at most four grooves. 
     
     
         11 . A piston head according to  claim 9  in which at least one groove is closer to the end of the plunger remote from the head of the piston end than it is to the head of the piston end. 
     
     
         12 . A piston head according to  claim 9  in which the piston end further comprises an O-ring located in at least one of the grooves. 
     
     
         13 . A piston head according to  claim 9  in which at least one of the grooves has a cross-sectional profile such that the groove has first and second side walls and a base, in which both side walls intersect with the base and extend there from to the surface of the plunger, the first side wall is closer to the head of the piston end than the second side wall, and the first side wall is planar and substantially perpendicular to the longitudinal axis of the plunger. 
     
     
         14 . A piston head according to  claim 13  in which the second side wall is not parallel to the first side wall and the second side wall is closest to the first side wall at the second side wall's intersection with the base of the groove. 
     
     
         15 . A piston head according to  claim 13  in which the base of the groove or gland is concave. 
     
     
         16 . A piston head according to  claim 1  in which the intersection of the blind bore and the surface of the body of the spring abutment is at least one of chamfered, beveled, and rounded. 
     
     
         17 . A piston head according to  claim 1  in which the piston end further comprises an energy absorbent material surrounding the plunger adjacent the intersection of the plunger and the head of the piston end. 
     
     
         18 . A piston end according to  claim 17  in which the energy absorbent material surrounding the plunger is an O-ring. 
     
     
         19 . A spring powered gas operated weapon comprising a barrel, a cylinder, a helical compression spring, and a trigger mechanism, in which the compression spring is located within the cylinder, characterized in that a piston head according to  claim 1  is attached to a first end of the spring. 
     
     
         20 . (canceled) 
     
     
         21 . A piston head suitable for a spring powered gas operated weapon, in which:
 the piston head is comprised of a piston end and a spring abutment,   the piston end is comprised of a head and a plunger,   the spring abutment is comprised of a body and an extended boss, at least the body of the spring abutment defines a blind bore which extends through at least the body where the blind bore extends from the surface of the body remote from the extended boss and towards the extended boss,   the plunger and blind bore are dimensioned to allow the plunger to fit within the blind bore, and   the plunger is provided with at least one feature for mounting a seal around the plunger to allow the creation of a seal between the plunger and at least one wall defining the blind bore;   the body and extended boss of the spring abutment both have substantially cylindrical curved surfaces and the cylindrical curved surfaces of the body and extended boss have a substantially common axis;   the body, extended boss, piston end and plunger all have a substantially common axis when the plunger is within the blind bore; and   the radii of the substantially cylindrical surfaces of the boss of the spring abutment and the head of the piston end are substantially the same.   
     
     
         22 . A spring powered gas operated weapon comprising a barrel, a cylinder, a helical compression spring, and a trigger mechanism, in which the compression spring is located within the cylinder, characterized in that a piston head according to  claim 21  is attached to a first end of the spring, the radii of the substantially cylindrical surfaces of the boss and piston end are substantially the same, and the substantially cylindrical surfaces of the boss and piston end are in sliding contact with the cylindrical surface defining the compression cylinder of the spring powered gas operated weapon.