1. Atmospheric suspended type.
2. Vacuum suspended type
3. Vacuum assist type 1. An atmospheric suspended brake booster has normal air pressure on both sides-of the diaphragm or piston when the brake pedal is released. As the brakes are applied a vacuum is formed in one side of the booster. Atmospheric pressure then pushes on and moves the piston or diaphragm. 2. A vacuum suspended brake booster has vacuum on both sides of the piston or diaphragm when the brake pedal is released. Pushing down on the brake pedal releases vacuum on one side of the booster. The difference in pressure pushes the piston or diaphragm for braking action. 3. Vacuum Assisted Power brakes can be classified in another way as:
1. The Integral type
2. Multiplier type
3. Assist type 1. The Integral Type It has the brake master cylinder as an integral part of the power brake assembly when the brake pedal is operated it activates a valve in the power brake assembly that applies atmospheric pressure to one side of the piston on diaphragm and vacuum to the other. This causes the piston on diaphragm to move and the movement forces a piston to move in to the master cylinder and there applies the brakes. 2. Multiplier Type This system multiplies the pressure produced by the muster cylinder. The pressure from he master cylinder is directed to the multiplier unit through a brake tube. In multiplier unit the pressure of the baker fluid activates a vale. The valve causes atmospheric pressure to be directed to one side of a piston or diaphragm and vacuum to the other side. The piston or diaphragm is thus breed to move and the movement causes a piston to move in a hydraulic cylinder that is part of the multiplier unit. This produce a higher hydraulic pressure, which is carried by brake lines to the wheel cylinders. To sum up the relatively to pressure from the master cylinder produced by brake pedal movement is multiplied to a high pressure by the multiplier unit. This relatively high brake pedal pressure produces heavy braking action. 3. Assist Type This type of power brake system has a power cylinder assembly that assists in applying the brakes through a mechanical linkage when the brake pedal is moved linkage to the power cylinder is actuated causing valve action and thus movement of a diaphragm or bellows with in the cylinder. This movement is carried through linkage to the master cylinder thereby increasing the total force being applied, which in turn increases the braking action.