DOWEL-REACTION 4M1677 - Caterpillar

Illustration 1 g02741643
Service brakes
(1) Sun gear
(2) Piston
(3) Friction discs
(4) Reaction plate
(5) Ring gear
(6) Carrier
(7) Axle
(8) Dowel
(9) Springs (three)
(10) Planetary gear
Illustration 2 g02703142
View B-B
(9) Spring
(11) Dowel All four service brakes are located in the axle assemblies. The service brakes are actuated by the left pedal. The service brakes are in both the front axle and in the rear axle.Each service brake consists of the following components: piston (2), friction disc (3), reaction plate (4), dowel (8) and (11), three springs (9) and two dowels (11).Reaction plate (4) and piston (2) are held stationary by dowels (8) and (11). The dowels are fastened in the differential housing and in the housing for the axle shaft. Piston (2) and reaction plate (4) are able to slide on three dowels (8,11), but do not rotate. Springs (9) keep piston (2) in the RETRACTED position so long as the oil behind piston (2) is not pressurized.The friction disc (3) have splines on the inside diameter that fit on the splines of sun gear (1). The spline causes the friction disc (3) to rotate at the speed of the sun gear. Grooves are cut into the face of the friction disc (3). The grooves allow the passage of cooling oil between reaction plates (4) and friction disc (3), and between piston (2) and friction disc (3).This cooling will occur even when the service brakes are applied. If the groove depths in the friction disc (3) are within specifications, cooling oil will constantly flow as the friction disc (3) rotates.Carrier (6) is fastened with splines to axle shaft (7). The axle shaft turns with the carrier. The planetary gears (10) in carrier (6) rotate between sun gear (1) and stationary ring gear (5).When you depress a brake pedal, pressurized oil from the service brake control valve flows through an oil passage in the differential housing. The force of the oil behind piston (2) moves the piston against the force of springs (9).The force of the oil also pushes the friction disc (3) against the reaction plate (4). This causes friction between friction disc (3) and piston (2), and between the friction disc (3) and reaction plate (4). The friction causes sun gear (1), axle shaft (7), carrier (6), and the wheels to stop.The heat that is created from the friction of the service brakes is removed by the oil that is in the axle housings.When the brake pedal is released, the oil behind piston (2) flows through an oil passage in the differential housing. This oil flows to the service brake control valve. The oil then returns to the hydraulic oil tank. With no oil pressure behind piston (2), springs (11) move the piston to the DISENGAGED position and the service brakes are released.If the machine loses power, or if the hydraulic pump fails, the service brakes can still be applied. The pressure in the nitrogen charged accumulators for the service brakes allows several applications of the brake pedals. The service brakes are for stopping the machine