| 摘要 |
An S-cam assembly (33) is disclosed for expanding internal shoe brakes of the type comprising a pair of pivotally mounted brake shoes (17) located within a brake drum (11), each brake shoe carrying a cam follower (31). The assembly comprises an S-cam member (35) comprising a pair of substantially identical working portions (37), each working portion defining a working surface (39) and defining a nominal lift circle having a diameter D1. Each working portion includes a ramp member (43) pivotable about a pin (47) from a retracted position (FIG. 2) in which a ramp surface (51) is disposed within the nominal lift circle. Each ramp member has an extended position (FIG. 5) in which the ramp surface is disposed outward of the nominal lift circle and in engagement with the adjacent cam follower (31) and defining a larger lift circle having a diameter D2. The substantially increased reserve lift is accomplished without increasing the minimum installation diameter of the S-cam assembly.
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