According to the different agencies, drum brakes are divided into the following three categories.
Wheeled brake, the use of rotation piston to promote the brake shoe open.
Cam open brake, the use of cam rotation to brake shoes open. According to the situation of cam force is divided into two kinds of non-balanced and balanced. The former cam and shaft fixed connection or made of one; the latter cam can be floating on the shaft, this structure is rarely used due to serious shortcomings.
Wedge brakes, the use of wedge wedge to brake shoes open.
Wheel cylinder piston, balance cam and wedge acting on the two feet of the opening force is equal, and the stroke range; unbalanced cam acting on the opening of the two hooves ranging from the same stroke. Wheel cylinder brakes, the wheel cylinder is arranged inside the brake, compact structure, but by the installation space constraints, wheel cylinder size can not be too large (diameter generally rarely more than 50mm).
In a cam-open brake, the brakes are mounted on a bracket that protrudes outside the brake floor or is mounted on a bracket fixed to the axle housing and is rotated by a brake arm. The structure is more cumbersome, transmission efficiency is low.