Abstract: A spring system for relatively displacing elements attached to end mounts of the rod assembly comprises a housing having a rod member movable between extended and retracted positions relative thereto, and a first compression spring in the housing surrounded by a second compression spring for biasing the rod member to one of an extended or retracted position relative to the housing. The two springs are oppositely wound whereby, from a compressed condition, the spring rod exerts an expansion force which increases at a linear rate. The spring system includes a valve arrangement to control the rate at which the spring rod moves from a retracted position to an extended position.

Abstract: A compression spring rod for relatively displacing elements attached to end mounts of the rod assembly comprises a housing having a rod member moveable between extended and retracted positions relative thereto, and a first compression spring in the housing surrounded by a second compression spring for biasing the rod member to one of an extended or retracted position relative to the housing. The two springs are oppositely wound, of different length, of different outside diameter, and of different wire diameter whereby, from a compressed condition, the spring rod exerts an expansion force which increases at a linear rate. Two sets of the springs can be arranged for biasing the rod member to a central position relative to the housing.

Abstract: A compression spring rod for relatively displacing elements attached to end mounts of the rod assembly comprises a housing having a rod member moveable between extended and retracted positions relative thereto, and a first compression spring in the housing surrounded by a second compression spring for biasing the rod member to one of an extended or retracted position relative to the housing. The two springs are oppositely wound, of different length, of different outside diameter, and of different wire diameter whereby, from a compressed condition, the spring rod exerts an expansion force which increases at a linear rate. Two sets of the springs can be arranged for biasing the rod member to a central position relative to the housing.

Abstract: A shock absorber for use between the reciprocating member of an oil well pumping mechanism and a polish rod connected to the rod spring and movable along a vertical pumping axis. The shock absorber comprises an upper and lower end plate having a peripheral surface around the plumping axis and defining a polish rod clearance opening. A coil spring is located between the plates and is concentric with and surrounding the pumping axis. A friction reducing centering head secured to at least one of the plates (preferably the lower plates) centers polish rod in the clearance opening and holds the polish rod away from the peripheral wall of the plate.

Abstract: A compression spring rod for relatively displacing elements attached to end mounts of the rod assembly comprises a housing having a rod member moveable between extended and retracted positions relative thereto, and a first compression spring in the housing surrounded by a second compression spring for biasing the rod member to one of an extended or retracted position relative to the housing. The two springs are oppositely wound, of different length, of different outside diameter, and of different wire diameter whereby, from a compressed condition, the spring rod exerts an expansion force which increases at a linear rate. Two sets of the springs can be arranged for biasing the rod member to a central position relative to the housing.