JPS6219614B

In the illustrative embodiments of the invention described, a gas spring useful as a height-adjustment and weight-compensation device, as, for example, in a height-adjustable table, includes structure that is responsive to the drop in gas pressure within the primary cylinder below a predetermined level to lock or brake the piston rod against abrupt movement with respect to the primary cylinder if a compressive load is thereafter applied to the gas spring. The pressure-responsive structure preferably includes a sealed auxiliary cylinder-piston unit carried by the piston rod internally of the gas spring. The auxiliary unit contains a separate pressurized body of gas, and either the auxiliary cylinder or piston is axially movable, in response to the greater internal pressure within the auxiliary unit when gas pressure within the primary cylinder drops too low, to engage the locking or braking device. So long as gas pressure within the primary cylinder remains above the predetermined minimum level, the braking device is biased away from the engaged position.