Axially adjustable pneumatic spring

Claim 1

A pneumatic spring, including a housing having first and second ends and consisting of an inner tube coaxially residing within an outer tube, said tubes together defining a cylindrical channel, and further including a piston having an end face and sealingly guided in said inner tube and attached to a piston rod which sealingly emerges from said first end of said housing through a sealing plug, and further including valve means disposed at and sealing the second end of said housing, said valve means including an axially displaceable plunger for controlling communication between the interior volume of said inner tube and said cylindrical channel, and wherein there are provided auxiliary pneumatic means for inhiting inward movement of said piston rod as said piston approaches said valve means, said auxiliary pneumatic means comprising: an auxiliary valve chamber having a central bore and a coaxial chamber separated from said central bore, said auxiliary valve chamber being located in said inner tube between said valve means and said piston; a valve-closing element disposed on the end face of said piston remote from said piston rod, for entering said auxiliary valve chamber and sealing it to define a volume downstream thereof in said auxiliary valve chamber and a volume upstream thereof; said coaxial chamber being in communication with the interior volume of said inner tube, and the relative dimensions of said auxiliary valve chamber and of said valve-closing element are such that when said auxiliary valve chamber is closed by said valve-closing element, the ratio of the effective annular area of the end face of said piston carrying said valve-closing element to the effective crossectional area of said valve-closing element is greater than the ratio of said remaining volume to the volume of said auxiliary valve chamber.