GB1263229A - Brake-actuating cylinder assemblies - Google Patents

Abstract

1,263,229. Spot-type disc brakes; hydraulic brake actuators; cylinders; seals. ALFRED TEVES G.m.b.H. 9 April, 1970, No. 16914/70. Headings F2B, F2E, F2F and F2T. An actuating cylinder assembly 2 for an hydraulic brake system, particularly a motor vehicle disc brake system, wherein the piston 1, Fig. 2, which transmits the brake force to the brake surface, bears a protective cap 6 in the form of an annular-disc-like element of resilient material attached by its outer edge to the actuating cylinder and clamped by its inner edge in a groove on the piston periphery, the piston and cylinder being made of different materials, is characterized in that a ring made of a material more electronegative than that of which the piston is made is disposed on the cylinder in the region where the outer edge of the protective cap is attached: the ring is not shown in Fig. 2. As shown in Fig. 3, the ring, 13a, is located between the protective cap 6a and a radial shoulder of the cylinder 2a. Preferably the ring is made of pure zinc or steel with a zinc deposit more than 200 microns thick. Preferably a ring of the same material, 9a, is located in a similar position on the piston 1a. Alternative materials for the rings, (depending on the piston and cylinder materials), are aluminium and chromium. Preferably the piston is grey cast iron with its surface electro-galvanized, while the cylinder is grey cast iron with its surface electrically cadmium-plated. Subject to the electronegative requirement specified above, the piston may be extruded aluminium or porcelain. In Fig. 3, 14a is the conventional sealing ring between piston and cylinder, while 15a represents the products of corrosion which would form in the absence of ring 13a.