Patent ID: 7278632

Claim:
A gas spring for a pressing tool comprising a tube which forms a wall of a cylindrical chamber, a piston designed to at least partially rest against said tube and is capable of reciprocating axially in said chamber, a piston rod connected to said piston, and a piston rod guide; said chamber having a first end wall and a second end wall, said first end wall forming a first base surface of said chamber and said second end wall forming a second base surface of said chamber, said piston dividing said chamber into a first space between said piston and said first end wall and a second space between said piston and said second end wall, said piston rod guide positioned at said first end wall and designed to support said piston rod as said piston rod axially moves in said cylinder chamber, said piston divided into at least first and second portions, said piston including at least one passageway between ends of said first and second portions that permit a flow of gas between said first and second spaces in said chamber during axial movement of said piston rod, said first and second portions including gas passage structures that also permit a flow of gas between said first and second spaces in said chamber during axial movement of said piston rod, at least one of said first and second spaces including a gas pressure which acts on said piston so as to create an opposing force counteracting axial movement of said piston rod, said at least one passageway between ends of said first and second portions of said piston and said gas passage structures in said first and second portions of said piston occupying an area which is greater than about 5% of an area of said piston, said area of said piston being the difference between the cross-sectional areas of the chamber and the piston rod.