| 摘要 |
1,008,824. Internal shoe drum brakes; fluid-pressure control of brakes. ROCKWELL STANDARD CORPORATION. March 2, 1964 [June 6, 1963], No. 8671/64. Headings F2E and F2F. An internal shoe drum brake comprises a pair of brake shoes 32, 34, a housing 28 having aligned bores 42, 44 communicating with a side opening 50 and plungers 46, 48 slidably mounted in the bores to urge the shoes against the drum. The plungers 46, 48 are spread apart by a wedge assembly 56 reciprocably extending through the side opening 50, the wedge assembly being actuated by a fluid pressure-operated diaphragm 94 mounted in a service chamber. The service chamber and the side opening are connected by an elongated tubular member 113 which has a diameter substantially smaller than that of the service chamber. A rod assembly 52, 102 extends through the tubular member 113 to connect the diaphragm 94 to the wedge assembly 56. A pair of plunger seal assemblies 78, 80, 82 carried by the housing 28 sealingly engage the outer ends of the plungers 46, 48 and an additional seal 128 cooperates with the rod assembly and the tubular member to isolate the wedge assembly and rod assembly from the interior of the service chamber. In the construction shown, the plunger 48 is provided with a wear adjuster as disclosed in Specification 965,262, and the brake actuator 54 which includes the diaphragm and an emergency section 92 is of the type disclosed in Specification 932,631. The rod assembly 52, 102 consists of a plunger 52 the rounded end of which is housed in a recess 104 in a push-rod 102, the push-rod being provided with a guide made of a suitable plastics material and having a cylindrical portion 124 pressfitted on to the push-rod and a conical portion 126 which keeps the push-rod, on assembly of the brake, centred with respect to the tubular member 113. The conical portion 126 also guides the rounded end of plunger 52 into the recess 104. The rod assembly is spring-loaded against the actuation of the brakes by a spring 116. The additional seal is formed with a breather hole 136 of approximately 0À06 inch in diameter and a plurality of larger breather holes 138 are formed in the service chamber member 96. The actuator 54 may be formed' without the emergency section (Fig. 4, not shown). Reference has been directed by the Comptroller to Specifications 862,439, 932,631 and 965,262. |
