Friction lock mechanisms

Abstract

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.