A sleeve is rotatably mounted on the main body and the two define a reservoir cavity therebetween. Projections integral with the body extend radially through the reservoir cavity to contact the inner wall of the sleeve. Spaced axially along the cylinder are a plurality of openings which extend through the projections from the cylinder cavity to the outer end of the projections. On the inner wall of the sleeve in juxtaposition to the outer end of the openings are a plurality of generally annular grooves. The oil path or duct for release of oil from the cylinder cavity to the reservoir cavity when the piston moves inwardly is through the openings and those parts of the grooves at the distal ends of the projections. In one embodiment these grooves vary in cross-sectional size throughout their length. In another embodiment they are helical, at a slight angle to the axis of rotation. Thus as the sleeve is rotated the cross-sectional size of the oil path from the cylinder cavity to the reservoir cavity is varied thereby varying the resistance to flow of the hydraulic fluid.

A mechanical lock normally preventing axial motion of a rod with respect to a housing sleeve that surrounds the rod includes a coil spring whose diameter is slightly less than the diameter of the rod so that the coil spring normally encircles and grips the rod tightly. The coil spring is mounted on the rod between a bushing fixed to the housing sleeve at one end of the spring and a second bushing that is rotatable with respect to the housing at the other end of the spring. The rotary bushing is rotated by an actuating lever to unwind the spring so as to increase its diameter and thereby to release its grip on the rod. Both the fixed bushing and the rotatable bushing include beveled faces which permit the last few turns at both ends of the spring to become cocked on the rod to provide a true locking engagement with the rod. The last few turns of the spring adjacent the rotatable bushing are immediately released by a minimum of rotation of the bushing since it is not necessary for the unwinding of the spring to be transmitted through the entire length of the spring. Because the spring is shorter than in prior locks, the entire device is shorter and accordingly more resistant to bending and lighter in weight. The structure of the device simplifies its assembly and this, along with its reduced length appreciably reduces the cost of producing the device.

A mechanical lock normally preventing axial motion of a rod with respect to a housing includes a coil spring which normally encircles and grips the rod tightly. The coil spring is mounted on the rod between a fixed bushing and a rotatable bushing. The two bushings are identical and interchangeable to reduce the cost and complexity of the device. The rotatable bushing is rotated by an actuating lever to unwind the spring so as to increase its diameter and thereby to release its grip on the rod. Both the fixed bushing and the rotatable bushing include beveled faces which permit the last few turns at both ends of the spring to become cocked on the rod to provide a true locking engagement with the rod. The last few turns of the spring adjacent the rotatable bushing are immediately released by a minimum of rotation of the bushing since it is not necessary for the unwinding of the spring to be transmitted through the entire length of the spring.

The invention relates to an industrial shock absorber requiring very few component parts, which can be cost-effectively produced while expensive milling operations are avoided, wherein different damping curves can be realized relatively simply. The shock absorber has good temperature stability in the cold and warm states, wherein the largest possible piston diameter can be achieved because of the special construction in accordance with the invention, which further contributes to stability and safety.

A heavy duty hydraulic shock absorber having an inner tube in which is slidably mounted an impact receiving piston assembly. Upon application of an impact force on the piston assembly, the piston assembly is moved inwardly of the inner tube and fluid from the inner tube is metered through a plurality of exponentially disposed metering orifices into an accumulator chamber formed between the inner tube and an outer tube which encloses the inner tube. An adjustable, slidable metering spool is operatively mounted in the accumulator chamber, over the metering orifices, for regulating the flow of fluid through the metering orifices into the accumulator chamber.