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| Illustration 1 | g00513292 |
Sectional View of Pilot Manifold Valve (1) Line (pilot resolver shuttle valve) (2) Pilot manifold (3) Passage (pilot oil) (4) Passage (tank drain) (5) Line (travel parking brake and load sensing signal relief valve) (6) Spool (7) Control valve (travel parking brake dual pressure) | |
Travel parking brake dual pressure control valve (7) directs pilot oil to two circuits. One circuit supplies pilot oil to the load sensing signal relief valve in order to increase system pressure for travel. The second circuit sends pilot oil in order to release the travel parking brakes. Actuation of either travel pilot valve spool supplies pilot oil to line (1) and the pilot oil shifts the position of spool (6).
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| Illustration 2 | g00513293 |
Travel Parking Brake Dual Pressure Control Valve Shown with Brakes that are Engaged (1) Line (pilot resolver shuttle valve) (3) Passage (pilot oil) (4) Passage (tank drain) (5) Line (travel parking brake and load sensing signal relief valve) (6) Spool (8) Spring | |
When travel pilot valves are not actuated no travel pilot signals are sent to the pilot manifold. The force from pilot pressure in line (1) is less then the force of spring (8). Spring (8) moves spool (6) upward. Spool (6) in the upper position opens passage (4). Pilot oil in passage (5) vents through passage (4) to the tank drain. Spool (6) in the upper position closes passage (3). The force of the brake spring is greater than the force from pilot pressure and the brake spring applies the travel parking brakes.
When line (5) is vented to the tank drain, the load sensing signal relief valve regulates the main system pressure to a pressure of 31000 kPa (4500 psi) maximum.
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| Illustration 3 | g00513296 |
Travel Parking Brake Dual Pressure Control Valve Shown with Brakes that are Disengaged (1) Line (pilot resolver shuttle valve) (3) Passage (pilot oil) (4) Passage (tank drain) (5) Line (travel parking brake and load sensing signal relief valve) (6) Spool (8) Spring | |
When the travel pilot valves are activated, travel pilot pressure is sent through line (1) to the pilot manifold valve. The force from pilot pressure in line (1) is greater than the force of spring (8). The force from pilot pressure moves spool (6) downward. Spool (6) in the lower position opens passage (3). Pilot pressure is supplied from passage (3) through passage (5) to the ladder position solenoid valve. When the travel pilot valve is actuated, an electrical signal is sent to the machine control module. If the ladders are in the stowed position, an electrical signal is sent from the machine control module which energizes the ladder position solenoid valve. When the ladder position solenoid valve is energized, pilot oil is allowed to flow to the travel parking brakes and the load sensing signal relief valve. The force from pilot pressure releases the travel parking brakes. Spool (6) in the lower position closes tank drain passage (4).
The pilot oil in line (5) signals the load sensing signal relief valve in order to regulate the main system pressure to a maximum pressure of 35000 kPa (5075 psi).