Shoe operating cam for drum brake - has symmetrical S=shape to produce rotary motion proportional to resulting brake force

摘要

A drum brake assembly has two brake shoes which have pivot locations on one end. Between the opposite ends of the brake shoe pair, there is a rotating spreader cam with which the brake shoes are forced radially apart against the brake drum. The cam faces (I1, I2) are involutes which are constructed from axially offset basis circles (B1, B2). The symmetrical, S-shaped cam operates the pressure rollers on the brake shoes in such a way that the resulting brake force produced by the cam is proportional to the angular movement of the cam shaft (34).