Patent ID: 9046146
Filing Date: 2015-06-02
Classification: F16F

Abstract:
1. A gas spring for forming equipment, comprising: a casing; a piston rod housing received at least in part in the casing; a piston rod received at least in part in the casing and extending through the piston rod housing for reciprocation between extended and retracted positions over a cycle of the gas spring including a retraction stroke and an extension stroke, and including a body having a cylindrical outer surface extending out of the casing through the piston rod housing and having an outer axial end of the piston rod disposed outside of the casing, and a head adjacent an inner axial end of the piston rod; a shock collar carried by the piston rod at an axial location along the piston rod between the piston rod head and the piston rod housing, wherein the shock collar surrounds a portion of the piston rod, is axially spaced from the piston rod housing in the retracted position of the piston rod, and engages the piston rod housing in the extended position of the piston rod, and wherein the shock collar includes a collapsible portion that is flexible and axially displaceable, and a mounting portion extending axially from the collapsible portion and mounted to the piston rod; a piston rod seal carried by the piston rod housing and normally in sealing engagement with the cylindrical outer surface of the piston rod; an annular relief in the cylindrical outer surface of the piston rod and adjacent the collar; a vent passage in the piston rod and communicating with the annular relief; and when the piston rod exceeds a predetermined velocity during the extension stroke, the collapsible portion of the shock collar axially collapses between the piston rod head and the piston rod housing to such an extent that the annular relief in the cylindrical outer surface of the piston rod interrupts the sealing engagement of the piston rod seal with the piston rod and thereby allows discharge of compressed gas past the piston rod housing.