Abstract: A pressure tube piston unit (10) with a pressure tube (11) which is subdivided into a first working space (14) and a second working space (15) by a piston (12) adapted to be extended and retracted on a piston rod (13). The two working spaces are adapted to be in a lockable flow connection with each other via an externally actuable valve arrangement (18). The piston (12) is radially externally provided with an encircling groove (19) and a packing ring (20) is inserted into the groove. The groove (19) is provided with a radially inwardly directed widened portion, the widening being of a predeterminable height. The packing ring (20) inserted into the bottom of the groove (19) is capable of being displaced axially into the widened portion.

Abstract: According to an illustrative example of the present invention, a gas spring comprises a pressure tube, a piston rod and a piston connected with the piston rod within the pressure tube. The piston divides the pressure tube into two working spaces, the two working spaces are connected by a control flow passage. A control valve body is allocated to the control valve passage and is controlled through a bore of the piston rod. The control valve body contains an excess pressure flow passage. An excess pressure valve member is provided within the excess pressure flow passage and biased toward an excess pressure valve seat of said control valve body.

Abstract: According to an illustrative example of the invention, a gas spring comprises adjacent one end of the cylinder two axially spaced sealing rings, namely an axially inner and an axially outer sealing ring. A lubricant chamber is defined axially between the axially inner and the axially outer sealing rings. The axially inner sealing ring is pressure-resistant against the elevated gas pressure within the working chamber such as to maintain the pressure of gas within the working chamber at a level exceeding the pressure within the lubricant chamber.

Abstract: A hydropneumatic spring usable as steplessly blockable setting device comprises a by-pass connection in its piston. In this by-pass connection there is arranged a shut-off valve actuatable from the exterior. Furthermore the by-pass connection can be opened by excess pressure in each of the two working chambers. In this way the setting of length of the hydropneumatic spring can be altered by predetermined inward and/or outward thrust forces even when the shut-off valve is closed.

Abstract: A gas spring particularly for jumping stilts comprises a working cylinder and a plunger. In the working cylinder there is a working chamber containing a mass of gas. A gas exchange chamber is fixed with respect to the working cylinder. An exchange passage connects the working chamber and the gas exchange chamber. A gas exchange valve is provided in the exchange passage. An exchange operating handle is provided separate from the plunger.

Abstract: In the illustrative embodiments disclosed, a pressurized cylinder-and-piston rod device, such as a gas spring, includes structure for releasably retaining the piston rod at a terminal position within the cylinder against the fluid pressure tending to expel it. Provision is also made for the fluid pressure to aid in further withdrawing the piston rod into the cylinder after the retaining structure has been engaged.

Abstract: A pneumatic spring of the piston-and-cylinder type constitutes a support column whose length may be adjusted when a valve connects the two cylinder compartments on opposite sides of the piston. The valve is normally closed by gas pressure and may be opened by a releasing rod coaxially movable in the bore of a tubular column member. An operating lever for the releasing rod passes radially through an opening in the tubular member and is coupled to the releasing rod during assembly of the apparatus by a cam face on the radially moving lever displacing the rod against the gas pressure in the cylinder, whereupon the rod drops into an axially open recess of the lever from which it can no longer be released because of the limited clearance in the column opening.

Abstract: A column which includes an elongated guide tube receiving a pneumatic spring of the piston-and-cylinder type in its bore. A bar is fixedly fastened to the piston rod member or the cylinder member of the spring in longitudinal alignment and extends in the guide tube bore from the associated spring member toward one of the two longitudinally terminal parts of the guide tube. A spring assembly extending about the bar is interposed between spring seats on the pneumatic spring member fixedly fastened to the bar and the one terminal part of the guide tube. Cooperating abutments on the bar and on the one terminal part of the guide tube limit movement of the bar toward the other longitudinally terminal part of the guide tube.

Abstract: A gas spring includes a cylinder, filled with compressed gas, a piston rod movable axially inward and outward of the cylinder cavity, and a piston axially movable on the end of the piston rod in the cavity and resiliently biased into engagement with an abutment on the free end of the piston rod. One of two passages bounded by the piston and connecting the two compartments into which the cylinder cavity is divided by the piston is blocked when the piston engages the abutment and opened when the piston is moved away from the abutment against the resilient bias. The other passage is opened during outward movement of the piston rod from the cylinder cavity.

Abstract: A column in which an inner elongated member of circular cross section is partly received in the polygonal bore of an outer, tubular member and secured against angular displacement about the common axis by guide elements secured against longitudinal movement in respective recesses of the inner member open toward the outer member and engaging the outer member in respective corners of its polygonal cross section. A manually controlled arresting mechanism permits the two column members to be arrested against relative longitudinal movement in a multiplicity of relative positions.

Abstract: A column including a cylinder, a piston axially slidable in the cylinder cavity, a piston rod axially projecting from the cylinder, and a valve permitting selective communication between the two compartments of the cylinder cavity separated by the piston for flow of fluid between the compartments is additionally provided with a helical compression spring coiled about the piston rod and impeding axial movement of the piston on the piston rod in one direction, movement in the other direction being limited by a radial abutment flange on the piston rod. The spring favorably affects the comfort of a chair whose seat is mounted on the column.

Abstract: The height of a chair and the inclination of its back support may be varied by changing the respective, effective lengths of two pneumatic springs whose assembly forms the chair leg. The cylinder of one spring is coaxially received in the cylinder or the hollow piston rod of the other spring, and relative axial movement of the received spring and the receiving element of the other spring is limited or entirely prevented. A valve connects the two compartments separated in the cylinder of each spring and may be operated by a mechanism separate from the valve operating mechanism of the other spring.