Hydraulic brakes

Claim 1

An hydraulic brake actuator comprising a cylinder, two unitary pistons spaced apart axially of the cylinder and each being sealingly and slidingly received in the cylinder, each piston including an integral annular skirt member extending axially toward the other piston, a sleeve member separate from the cylinder and having its opposite ends sealing and slidably received within the skirt members of the two pistons respectively, said sleeve member dividing the space enclosed within the cylinder between the two pistons into separate inner and outer co-axial fluid pressure chambers, a pair of sealing means one each between each of said piston skirt members and said common sleeve and constructed and arranged to normally isolate the two pressure chambers from each other, means for visually indicating a leaking condition of either of said sealing means wherein each of said sealing means comprises a pair of annular sealing elements between each skirt member and said common sleeve member, said elements being axially spaced apart so as to define a space between them, and passage means in the skirt of each of said piston members leading from said space to atmosphere outwardly of said cylinder so that fluid passing any of said elements from either of said chambers flows freely to a region outside of the cylinder to indicate that a seal element is leaking.