Patent ID: 7178643
Filing Date: 2007-02-20
Classification: F16D

Abstract:
1. A drum brake apparatus comprising: a first and a second brake shoes disposed in a drum to oppose each other; and a cam mechanism for generating a braking force by opening the first and second brake shoes outward according to a shoe operating force generated by an operating force generator, and for controlling the braking force by utilizing a reaction force exerted from the brake shoes during a braking period, wherein the cam mechanism includes: a cam supporting plate, having a central circular aperture portion is continuous with two opposed circular aperture portions, loosely and rotatably fitted on an anchor pin projecting upright on a backing plate, and having an input power receiving portion for receiving the shoe operating force at a position radially inwardly of the drum with respect to the anchor pin; a first cam plate, rotatably connected to the cam supporting plate at an outer cam supporting position which is located radially outwardly of the drum with respect to the anchor pin, and having a first shoe receiving arcuate portion which comes into abutment with an end of one of the brake shoes; and a second cam plate, rotatably connected to the cam supporting plate at an inner cam supporting position along a point between the anchor pin and the input power receiving portion, and having a second shoe receiving arcuate portion which comes into abutment with the end of the other brake shoe.