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| Illustration 1 | g00813582 |
Control Valve
The medium pressure attachment control valve is mounted on the end of the pilot manifold. Oil flow that is not used by the pilot system is directed to the medium pressure attachment control valve. 15 L/min (4 US gpm) of oil is required in the pilot system. A pilot control valve diverts oil at the rate of 15 L/min (4 US gpm) to the pilot system. The remaining oil is sent to the medium pressure circuit.
The medium pressure control valve is a three-position solenoid valve. Modulation of flow from the control valve is not possible.
This control valve is used to operate the following attachments that require low flow and medium pressure.
- Clamshell rotor
- Rotator for a grapple
- Hydraulic low flow consumers
Line Relief Valves
The two medium pressure line relief valves are located in the section between the pilot manifold and the medium pressure attachment control valves. The line relief valves limit the line pressure at ports "A" and "B" by supplying oil to the attachment circuit.
The attachment block for medium pressure that contains the medium pressure line relief valves also contains two makeup check valves. When the tank pressure is higher than the pressure at port "A" or "B", the makeup valves provide oil to the medium pressure circuit from return port "T" in order to avoid cavitation.
Solenoid Valve
The attachment control valve is a valve with three positions that is actuated by the switches on the joysticks. The oil flow to the attachment solenoid valve for medium pressure is supplied through the pilot control valve from the pilot manifold.
When the attachment control valve is de-energized, oil flow is returned to the hydraulic tank.
When the solenoid is energized, the spool in the solenoid valve is shifted. When the left joystick is used, the spool will shift downward.
When the right switch on the joystick is activated, the lower solenoid in the medium pressure control valve is energized. By energizing the lower solenoid, the spool is shifted upward. Pilot oil is directed through the medium pressure control valve through "B" of the control valve to the left auxiliary lines. By directing pressure oil to the left auxiliary lines, the attachment is operated in the right direction (clockwise direction).
When the left switch on the joystick is activated, the upper solenoid in the medium pressure control valve is energized. By energizing the upper solenoid, the spool is shifted downward. Pilot oil is directed through the medium pressure control valve through port "A" of the control valve to the right side auxiliary lines. By directing pressure oil to the right side auxiliary lines, the attachment is operated in the left direction (counterclockwise direction).