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| Illustration 1 | g00681926 |
Hydraulic schematic for towing hitch system (3) Control valve (33) Cylinder for hydraulic hitch (34) Lock valve (35) Suction oil (36) Pump delivery flow (37) Frame leveling system flow (38) Return oil | |
Hydraulic Towing Hitch (If Equipped)
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| Illustration 2 | g00663811 |
(33) Hydraulic cylinder (34) Lock valve | |
As an option, the TH62 machines can be equipped with a hydraulic towing hitch. The hydraulic towing hitch is raised and lowered by hydraulic cylinder (33). Lock valve (34) isolates the cylinder when the control valve is in the HOLD position.
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| Illustration 3 | g00663815 |
Switch (39) for the towing hitch is located at the back of the joystick control. | |
Push the left side of switch (39) and hold the switch in order to lower the towing hitch. Release the switch in order to stop the towing hitch from lowering. Push the right side of the switch and hold the switch in order to raise the towing hitch. Release the switch in order to stop the towing hitch from rising. The control for the towing hitch is a three-position switch.
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| Illustration 4 | g00663835 |
Control valve (3) for the towing hitch is located inside the engine compartment. | |
Note: Control valve (3) is used to control the towing hitch on the TH62. Control valve (3) is used to control the frame leveling system on the TH63, TH82, and TH83. Refer to the System Operation, "Frame Leveling System".
Towed Attachment Control Valve (If Equipped)
To operate a powered trailer hitch on the rear of the machine, the towed attachment control valve supplies oil flow and the towed attachment control valve also regulates oil flow. This control valve operates the service brakes, and the body hoist on a towed machine.
The control valve block contains four valves. The body hoist is controlled by two, two-position solenoid valves. The brake is controlled by service brake system pressure.
Each of the valves is connected through a check valve to a load sense port which is connected to the load sensing system of the bank valve.
Service ports on the towed attachment are connected to the hitch cylinder. Service ports are also connected to the quick release fittings that are located on the rear of the machine. The fittings supply the body hoist and the service brakes.
Body Hoist System (Trailer)
The control valve for the hoist is intended for operation of a single acting cylinder. When the control switch in the machine cab is moved to the raise position, the cylinder is extended. When the switch is moved to the lower position the cylinder is retracted by the weight of the raised body.
Body Hoist Switch in the Hold Position
Solenoid valve (2) for the body raise is de-energized and control valve (23) for lowering the body is also de-energized. This blocks oil from pump inlet (1) and from port (19) for the body hoist.
Body Hoist in the Raise Position
Solenoid valve (2) for the body raise is energized to the open position. Pump oil flows through the valve, and through check valve (20) to the piston end of the hoist cylinder. The flow is regulated by restrictor (21). Load pressure is transmitted through check valve (22) in order to control the pump output.
When the switch is moved to the hold position, solenoid valve (2) is de-energized and the valve is repositioned by spring force. To hold hoist cylinder in the selected position, check valve (20) closes and this blocks oil into the hoist cylinder.
Body Hoist in the Lower Position
Body lower solenoid (23) is energized. Oil from the cylinder flows through the solenoid valve and flows through the line to the tank. Flow is regulated by restrictor (3) .
Towing Hitch
To raise the hitch, the system operates a double acting cylinder. To lower the hitch, this cylinder is also used. The cylinder is mounted on the rear of the machine.
Control Switch for the Towing Hitch in the Hold Position
Solenoid operated control valves (4) are de-energized. The valve spool is spring centered. The valve spool connects cylinder ports (13), and (16) together. The valve spool also connects the cylinder ports to the tank.
Control Switch for the Towing Hitch in the Hitch Lower Position
To lower the hitch, solenoid control valve (4) is energized. This connects pump flow to the piston end of the hitch cylinder through port (16). This flow is regulated by restrictor (17). Load pressure is transmitted through check valve (18 ) to the pump output. Oil from the rod end of the cylinder passes through port (13), and valve (4) to the tank.
Control Switch for the Towing Hitch in the Hitch Raise Position
To raise the hitch, solenoid control valve (4) is energized. This connects pump flow to the rod end of the hitch cylinder through port (13). This flow is regulated by restrictor (14). Load pressure is transmitted through check valve (15) to the load sensing system of the bank valve to the pump output. Oil from the piston end of the cylinder passes through port (16) and solenoid valve (4) to the tank.
Brake Valve
The brake valve consists of a cartridge which contains a pressure reducing valve (5) and an actuator piston (6). When the service brake for the machine is released, the pressure for the machine system is blocked at the reducing valve. When the service brake is applied, brake line pressure at port (8) moves actuator piston (6). The actuator piston opens the reducing valve by compressing a spring. Pressure which is proportional to the pressure in the service brake system of the machine is transmitted from the machine system through the reducing valve to port (11). The pressure for the brake on the trailer increases as pedal pressure is increased. The pressure for the brake on the trailer decreases as pedal pressure is decreased.
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| Illustration 5 | g00684657 |
Schematic of solenoid control valves (1) Inlet port (2) Solenoid valve (body raise) (3) Restrictor (body lower) (4) Solenoid valve (hitch raise and hitch lower) (5) Pressure reducing valve (brake) (6) Actuator piston (brake) (7) Air purge valve (8) Inlet from service brake (9) Outlet to the load sensing system in the bank valve (10) Load sense port that is not used (11) Outlet to the brake lines for the trailer (12) Check valve for the load sensing system (13) Port for hitch raise (14) Restrictor for hitch raise (15) Check valve for load sensing system (hitch raise) (16) Port for hitch lower (17) Restrictor for hitch lower (18) Check valve for load sensing system for hitch lower (19) Port for body hoist (20) Check valve for body hoist (21) Restrictor for body hoist (22) Check valve for load sensing system for body hoist (23) Control valve for body lower (24) Tank port | |