Automatic braking-gap adjuster system for mechanical drum brakes

An automatic brake-gap adjuster system for mechanical drum brakes comprising a pair of brake shoes, each brake shoe having one end pivotally supported on a back plate and the other end adapted to move outwardly into engagement with the inner periphery of a brake drum;

• a cam member rotatably disposed through said back plate between said other ends of said pair of brake shoes and adapted to be rotated by a brake arm, said cam member comprising a cam portion having a pair of opposed flat sides and a tapered axial guide groove in each said side tapering from a shallower depth at the end proximate said back plate to a greater depth at the distal end thereof;
• cam collars slidably disposed in said guide grooves to abut onto said other ends of said brake shoes, whereby said cam collars are rotatable with said cam member, slidable toward a cam shaft and movable in the expanding direction of said brake shoes;
• an actuating member threaded into said cam member to abut onto the end faces of said collars;
• and an adjusting member adapted to rotate said actuating member in response to the abrasion of said brake shoes, thereby threadedly moving said actuating member toward said cam shaft;
• whereby said cam collars are slidingly moved toward said cam shaft along said tapered groove to thereby expand said brake shoes and adjust the brake-gap between the inner periphery of said brake drum and said brake shoes.