WASHER-TAB 1100861 - Caterpillar

Illustration 1 g03390014
Parking brake (parking brake engaged)
(1) Port (supply oil or return oil)
(2) Port (supply oil or return oil)
(3) Housing
(4) Barrel
(5) Friction disks
(6) Separator plates
(7) Brake piston
(8) Brake spring
(9) Piston chamber
(10) Passage
(11) Passage
(12) Orifice
(13) Passage
(14) Orifice
(15) Counterbalance valve
(16) Valve
(17) Spring
(18) Passage In the parking brake section of the travel motor, separator plates (6) are splined to housing (3). Friction disks (5) are splined to barrel (4). Brake springs (8) force brake piston (7) to the left. Brake piston (7) presses separator plates (6) and friction disks (5) together. Pressing the plates and discs together locks barrel (4) to housing (3). The motor shaft is splined to barrel (4). Because the plates and disks lock the barrel to the housing, the motor shaft is locked to the housing. The parking brake prevents rotation of the motor shaft.When no pump oil is supplied to the travel motor, brake piston (7) is pushed to the left by the force of brake springs (8). The oil in piston chamber (9) flows through passage (10), passage (11) to orifice (12). The oil flows through orifice (12) and passage (13) into valve (16). The oil then flows through valve (16) and orifice (14) to the drain line. Brake piston (7) moves to the left. Friction disks (5) and separator plates (6) are held together by brake springs (8). The rotation of the travel motor stops.Orifice (12) and orifice (14) restrict return oil flow from piston chamber (9) to the return line. The restriction of the oil flow delays the application of the parking brake. The parking brake is delayed in order to give the machine time to stop. Severe wear and/or damage to the machine could result if the machine stayed in motion when the parking brake is engaged.Prior to the operation of the travel motor, oil flows through port (2) and into counterbalance valve (15). The oil then flows through passage (18) to valve (16). Valve (16) shifts against the force of spring (17). Oil flows to passage (13) and to orifice (12). The oil then flows through passage (11) and passage (10) to piston chamber (9). Brake piston (7) moves to the right against the force of brake springs (8). The spring load which compresses friction disks (5) and separator plates (6) together is released.Oil flows from port (2) into counterbalance valve (15) to barrel (4). Since the parking brake is disengaged, barrel (4) and the motor shaft now rotate. Return oil from barrel (4) flows through counterbalance valve (15) to port (1) and to the return system.