Brake

In a self-adjusting brake having a brake drum, two brake shoes having curved ends, said brake shoes being mounted interiorly of the brake drum and coacting therewith, brake cylinder means and stationary brake shoe support means for floatingly mounting said brake shoes, and return spring means for pressing one curved end of each respective brake shoe against said brake cylinder means and the other curved end of each respective brake shoe against said brake shoe support means and for lifting said brake shoes off the brake drum when the brake is in non-actuated condition, one of said brake shoes being, with respect to the normal direction of rotation of the brake drum, the primary brake shoe and the other being the secondary brake shoe, the primary brake shoe being the one the leading edge of which, during such normal rotation of the brake drum, contacts the brake cylinder, each of the brake shoes having a T-shaped cross section constituted by a flange forming the top of the T and a web forming the stem of the T, the flange of each brake shoe carrying a brake lining, there being associated with the web of each brake shoe means forming an inclined surface coacting with respective stationary pin means, the inclination of said surfaces being such that the amount of the play between the brake lining carried, said brake shoes and the brake drum, when the brake is in non-actuated condition, remains substantially constant during displacement of the brake shoes resulting from wear of the brake lining, the improvement that

• a. said return spring means are configured and arranged such that the line of action of the resultant spring force acting on said primary brake shoe passes through the instantaneous axis M.sub.p of said primary brake shoe and the line of action of the resultant spring force acting on said second brake shoe passes through the instantaneous axis M.sub.s of said secondary brake shoe;
• and
• b. said means forming said inclined surfaces are arranged in that half of each respective brake shoe which abuts said brake cylinder means, with each inclined surface being tangential to the instantaneous axis of the respective brake shoe.