Pistons 3 and 4 (Fig. 194) actuate different circuits. Both pistons take their initial position under the action of springs 7. The movement of the pistons under the action of the springs is limited by screws 6. The tightness of the pistons in the cylinder is ensured by four sealing rings 5. The cylinder body 2 is closed at the front by plug 1. In the initial position of the pistons, the spacer rings 9 rest against screws 6. In this case, the sealing rings 5 move away from the end surface of the piston grooves and through the resulting gaps B the working cavities of the cylinder are filled with liquid from the tank. The spacer ring 9 stops pressing on the sealing ring 5, and it, pressed under the action of spring 8 to the end of the piston groove, separates the cavity of the tank from the cavity of the cylinder. This ends the free travel of the piston, which on the brake pedal is 3-5 mm. With further movement of piston 4, the pressure in the cavity of the drive of the front wheel brake mechanisms increases and under its action, piston 3 of the drive of another circuit moves. With serviceable circuits, the pressure in both working cavities of the cylinder will increase equally.
The text is copied from the online portal (VazBook)