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| Illustration 1 | g01718734 |
Section View of Air Control Valve for the Service Brakes (1) Spring (2) Delivery port (3) Exhaust seat (4) Delivery port (5) Seat (6) Relay piston (7) Seat (8) Rubber spring (9) Inlet and exhaust valve (10) Plunger (11) Exhaust port (12) Screw (13) Spring seat (14) Supply port (15) Piston (16) Seat (17) Supply port (18) Exhaust passage (19) Spring (20) Inlet and exhaust valve (21) Exhaust passage | |
Application of the Right Brakes
When the service brake control (pedal) is depressed, plunger (10) applies force on spring seat (13), on rubber spring (8), and on piston (15). Inlet and exhaust valve (20) contacts seat (5). This closes exhaust passage (21). Air pressure from supply port (14) flows out of delivery port (4) and to the service brakes for the right side of the machine.
Note: Only a small amount of pedal movement and a small amount of air are needed in order to move relay piston (6). Therefore, the service brakes for the left side of the machine are applied almost at the same time as the service brakes for the right side of the machine.
Application of the Left Brakes
When inlet and exhaust valve (20) is moved off seat (7), inlet and exhaust valve (9) contacts exhaust seat (3). This closes exhaust passage (18). Inlet and exhaust valve (9) is moved off seat (16) so that air pressure from supply port (17) flows out of delivery port (2) and to the service brakes for the left side of the machine.
Releasing the Brakes
When the pedal is released, mechanical force is removed from spring seat (13), from rubber spring (8), and from piston (15). Air pressure and spring force move piston (15), which moves relay piston (6) by way of screw (12). Seat (5) is moved away from inlet and exhaust valve (20). Inlet and exhaust valve (20) contacts seat (7). Air pressure from the service brakes on the right side of the machine flows through the center of inlet and exhaust valve (20) and out of exhaust port (11). The service brakes for the right side of the machine are released. At the same time, exhaust seat (3) moves away from inlet and exhaust valve (9). Inlet and exhaust valve (9) contacts seat (16). Exhaust passage (18) is closed in order to stop the flow of air from supply port (17) to delivery port (2). Air pressure from the service brakes on the left side of the machine flows through the center of inlet and exhaust valve (9) and out of exhaust port (11). The service brakes for the left side of the machine are released.
Loss of Brakes for the Left Side
If air pressure in the brake circuit for the left side is lost, the brake circuit for the right side will still provide air pressure to the brakes on the right side.
Loss of Brakes for the Right Side
If air pressure in the brake circuit for the right side is lost, the service brakes on the left side of the machine can still be applied.
Balancing the Right Side Brakes
When the air pressure at delivery port (4) is identical to the mechanical force of the pedal, piston (15) will move and inlet and exhaust valve (20) will close. This stops the flow of air from supply port (14). Inlet and exhaust valve (9) will stay closed and air pressure will not be allowed to flow out of exhaust port (11) .
Balancing the Left Side Brakes
When the air pressure under relay piston (6) is near the air pressure on the top of relay piston (6), relay piston (6) moves in order to close exhaust passage (18). This stops the flow of air from supply port (17) to delivery port (2). Exhaust port (11) will stay closed as the air pressure for the service brakes on the left side becomes identical to the air pressure for the service brakes on the right side.
During gradual brake applications, a balance position is reached in the valve section for the service brakes on the right side when the air pressure at delivery port (4) is identical to the pressure of the operator's foot on the pedal. A balance position is reached in the valve section for the brakes on the left side when the air pressure under relay piston (6) approaches the air pressure on the top of relay piston (6) .
When the pedal is depressed all the way, inlet and exhaust valves (9) and (20) are open and full air pressure from the air tank flows to the service brakes on both sides of the machine.