Disc brake caliper with molded flex piston

摘要

A light weight metal caliper housing has cored holes in the cast bore. A nylon bore insert lines the bore side wall. A molded flex piston has hydraulic fittings incorporated as a part of it and the fittings extend through the cored holes. The center portion of the piston is shaped to permit piston flexibility for axial expansion and contraction. The forward end of the piston is closed by a thermal protector, the outer surface of which is engaged by the back of the brake shoe. A low rate extension spring within the piston returns the piston to the fully non-applied position. The spring has one end attached to a plate which resists movement within the free piston but is moved when sufficient brake lining wear occurs so that the extension force applied through the spring during brake apply overcomes the resistance of the movable plate to such movement, causing the movable plate to assume an adjusted position. The arrangement eliminates machining of the bore surfaces and the threading of ports in the casting for bleeder and pressure inlet fittings.