SWITCH AS 1773842 - Caterpillar

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Above differential on the tractor (1) Quick release and holding valve
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Scraper (2) Quick release and holding valve (3) Air tank (scraper)
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Quick release and holding valve in the RELEASE positionThe parking and secondary brakes are applied in this position. (4) Outlet port to brake chamber (5) Sealing washer (6) Exhaust port to atmosphere (7) Outlet port to brake chamber (8) Rubber sealing band (9) Inlet port (10) Shuttle assemblyWhen the parking and secondary brake control valve is pushed to release the brakes, air enters the quick release and holding valve through inlet port (9). Shuttle assembly (10) moves against sealing washer (5) to close exhaust port (6). Air pressure enters a drilled passage inside shuttle (10), which expands rubber sealing band (8). As sealing band (8) expands, sealing band (8) unseats from the opening in the air passage. This allows air to flow to the parking and secondary brake chambers in order to release the brakes. When the valve assumes the HOLDING position, the pressures at inlet port (9) and outlet ports (4) and (7) are equal. Sealing band (8) closes the air passage through shuttle (10) by contracting. This blocks the air from returning from the secondary brake chambers.A pressure reduction at inlet port (9) will actuate the quick release and holding valves. This could be caused by either an application of the parking and secondary brake control valve or a failure. Shuttle (10) unseats from exhaust port (6), which allows the air in the parking and secondary brake chambers to exit in order to apply the brakes.