M312, M315, M318 and M320 Excavators Hydraulic System Caterpillar


Service Brake (Disc)

Usage:

M318 6ES



Illustration 1g00551496

Rear axle

(1) Rigid axle




Illustration 2g00551499

Front axle

(2) Steering axle




Illustration 3g00549134

Wheel Brakes (Rear Disc)

Typical Example

(3) Planetary carrier

(4) Planetary gear

(5) Internal gear

(6) Final disc

(7) Outer disc

(8) Piston

(9) Oil passage

(10) Springs

(11) Spring plate

(12) Bolt

(13) Wheel hub

(14) Bleeder screw

(15) Housing

(16) Inner disc

(17) Port

(18) Oil passage

(19) Plate carrier

(20) Sun gear shaft

(21) Shaft

The wheel brake system on the steering axle and the rigid axle is activated by pushing down on the wheel brake pedal or by operating the oscillating axle brake valve on the left console.

The wheel brakes are locked when the oscillating axle brake valve is in position III.

The wheel brakes on the axles are released when the brake pressure is released.

The wheel brakes are located in planetary carrier (3) on the ends of steering axle (2) and rigid axle (1) .

The planetary carrier is driven by shaft (21). Shaft (21) is joined to gear (20). The shaft is inserted into plate carrier (19). Inner discs (16) rotate in the same direction.

Sun gear shaft (20) rotates planetary gears (4), internal gear (5) and discs (7) in the opposite direction.

The inner discs are provided with linings on each side. When brake pressure is applied, the inner discs are pressed together with the outer discs in order to obtain the braking action.

The planetary carriers on the wheel hub are filled with oil so that the discs and planetary gears run in an oil bath. When no pressure goes to port (17) on the wheel brakes, the brakes are released for machine movement. As no pressure is applied to piston (8), springs (10) hold the piston in position. The discs are free to rotate in the oil bath in the planetary carrier (3) .

When the machine is moving, centrifugal force will throw the oil outward from the space between the brake linings on the inner discs and the outer discs. Only some of the remaining oil must be squeezed from the discs when the brake is applied.

The light corrugation of the outer discs contacts the brake linings on the inner discs before the entire disc makes contact. In this way, smooth braking is achieved.

When brake pressure is applied through port (17), the oil goes through passage (18) and passage (9) in internal gear (5) and to the surface area of piston (8). The piston is guided by the internal gear and sealed by two backup rings and by two ring seals on each end. These ring seals prevent pressure oil from entering the planetary carrier.

Brake pressure must overcome the force of twelve springs (10) when the piston is pressed against discs (7) and (16). The pressure compresses the disc pack against the stop of final disc (6). The corrugation of the outer disc is countered and the oil between the outer discs and linings on the inner discs is displaced. The extent of compression depends on the amount of the applied braking pressure.

The compression of the inner discs against the outer discs gives the desired braking action.

When brake pressure is reduced, the twelve springs in the internal gear will push the piston back to the original position. The springs are supported by spring plate (11) and bolt (12). The brake lines can be purged via bleeder screw (14).

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