Avm, Incorporated

Daniel P Dodson

George C Ludwig

A pneumatic spring counterbalance extensible link including a closed end cylinder with an end connector, a piston and rod assembly within the cylinder and maintained therein by the crimped over end portion of the cylinder retaining a rod bushing and rod to cylinder seal assembly. The cylinder is pressurized preferably prior to assembly of the bushing and seal assembly into the cylinder. The piston assembly includes an effective check valve and orifice by-pass structure for metered gas flow past the piston in one direction and free flow past the piston in the other direction of piston movement. A small predetermined amount of oil is contained in the cylinder and provides lubrication for the seals and piston and provides a damping effect at the end of the extension stroke. A standpipe sleeve is secured on the piston extending toward the seal assembly around the piston rod and controls disposition of the oil to assure damping at the end of the extension stroke. A piston and piston ring structure enhance reliability of control of the oil flow, by providing a peripheral piston to cylinder seal and assures that fluid only passes across the piston via the check valve and orifice by-pass structure in the piston.

Pneumatic spring counterbalance having improved damping structure

A pneumatic, piston/cylinder counterbalance in which the counterbalance force is obtained by differential pressure across the piston and in which the force changes due to temperature are compensated by use of a variable volume cylinder having one or more auxiliary chambers separated by walls, each including a temperature responsive bi-metal disc valve normally acting as a check valve permitting flow into the auxiliary chambers but preventing flow out of the chambers except when the temperature drops to a predetermined value. In the multiple auxiliary chamber embodiment, flow into and out from each chamber is controlled by an associated bi-metal disc valve responsive to successively lower temperatures to enable a more linear stabilization of force output regardless of temperature.

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Florence, SC, United States of America

Daniel P Dodson