Lock for telescopic crane mast - has springs to hold notched levers against pins projecting inside outer tube

摘要

The telescopic mast of a large crane is assembled from two square tubes (1) (2) which fit one inside the other. Two levers (6) are mounted on opposite ends of a common shaft (3) which passes through the inner tube (1). The end of each lever (6) is notched to engage short pins (7) projecting inwards from the walls of the outer tube (2). A spring (10) holds the lever (6) against the pin in the assembled position. If the inner tube (1) is partially withdrawn, the lever (6) is pulled clear of the pin (7) so that the inner tube (1) can be pushed fully into the outer tube (2).