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| Illustration 1 | g00997584 |
Components for air system and brakes (A) Tractor (B) Scraper (AA) Standard air lines (BB) Attachment (CC) Division between the wheel tractor and the scraper (1) Check valve (2) Main air relief valve (3) Reserve air tank (4) Dry air tank (5) Wet air tank (6) Air horn (7) Air dryer (8) Differential lock control valve (9) Air compressor (10) Air block (11) Seat suspension (12) Air horn solenoid valve (13) Parking brake control valve (14) Air compressor governor (15) Lockup clutch solenoid valve (16) Secondary pilot valve (17) Pressure protection valve (18) Secondary brake control valve (19) Brake control valve (20) Lockup clutch selector valve (21) Air pressure gauge (22) Differential lock (23) Parking brake chamber (24) Brake housing assemblies (25) Double check valve (26) Relay valve (27) Differential (28) Scraper relay valve (29) Air tank | |
All of the brakes in the brake system are shoe type brakes. There is a brake at each wheel of the tractor and the scraper. The wheel tractor is equipped with a parking brake. The parking brake is located on the output shaft of the output transfer gear group. The service brakes are activated by air pressure in the brake housing assemblies (24). The parking brake is activated by a spring in chamber (23). The brake housing assemblies (24) and parking brake chamber (23) provide the machine with the following three types of brakes:
- Service
- Secondary
- Parking
The air compressor (9) supplies the air to the air tanks of the wheel tractor: (3), (4) and (5). The flow of air is divided into the following four separate circuits:
- Service brake
- Parking
- Secondary brake
- Accessory air circuits
Refer to Systems Operation, "Brake System" for more information on the brake system.
Accessory Circuits
Pressurized air for the accessory air circuits goes from brake control valve (19) to pressure protection valve (17) and to air block (10). Valve (17) opens at approximately 520 kPa (75 psi). Pressurized air is directed from air block (10) to four locations:
- Differential lock control valve (8)
- Air horn solenoid valve (12)
- Seat suspension (11)
- Lockup clutch solenoid valve (15)
When differential lock control valve (8) is depressed, pressurized air is sent to the differential lock (22). The differential lock is located inside the differential (27). Solenoid valve (12) is activated by the horn button inside the cab. Valve (12) directs air flow to air horns (6). Solenoid valve (15) directs air flow to selector valve (20). Selector valve (20) engages the lockup clutch in the torque converter.
Pressure Protection Valve
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| Illustration 2 | g01044628 |
(30) Supply port (31) Valve spool (32) Delivery port | |
All air flow to the accessory air circuits must pass through the pressure protection valve. No air will flow through the pressure protection valve until spool (31) raises. As spool (31) raises, air is allowed to pass through the pressure protection valve and out delivery port (32) .