Elastic polyurethane collar for force fit ball joint coupling - shaped to ensure that withdrawal forces are much higher than insertion forces

摘要

Force-fitted ball coupling is accepted by a rigid hollow casing lined with a combination of a hemispherical seat in the base of the casing and an annular collar between the seat and the mouth of the casing. The collar/casing interface is partly relieved and partly stepped so that, during insertion of the ball end, the collar is compressed into the casing and deformed radially to allow the ball to enter. After insertion, the collar recovers a position overlapping the bore of the entry of the casing, so that much more force is needed to remove the ball than was necessary to insert it. Esp. suitable for couplings on mechanisms such as motor vehicle controls, where a combination of speed of assembly plus reliability in service is required. Typically ball and casing are of metal, the internal seal is of 'Nylon' (polyamide) filled with glass fibres, and the elastic collar is of polyurethane of 90 degree Shore hardness. For a collar with an inlet orifice, undilated, of 11 mm diam., the rod extraction force was 30 daN, compared with an insertion force of 5 daN.