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| Illustration 1 | g00739329 |
Tilt System (1) Bank valve (2) End section of bank valve (3) Joystick (4) Implement section of bank valve (quick coupler) (5) Implement section of bank valve (frame leveling or towing hitch) (6) Implement section of bank valve (auxiliary services) (7) Frame leveling cylinder ( TH63, TH82, TH83) or towing hitch cylinder ( TH62) (8) Load control valve for frame leveling cylinder or towing hitch cylinder (9) Brake reservoir (10) Implement section of bank valve (coupler tilt) (11) Dual relief valve (12) Relief valve (coupler tilt) (13) Pilot control valve (14) Solenoid valve (15) Solenoid valve (16) Solenoid valve (17) Solenoid valve (differential lock valve) (18) Line (service brake system) (19) Line (differential lock cylinder) (20) Lines to steering system (21) Metering pump (22) Filter (23) Hydraulic tank (24) Line (load sensing) (25) Piston pump (26) Compensating cylinders (27) Inlet section of bank valve (28) Implement section of bank valve (boom raise/lower) (29) Implement section of bank valve (boom extend/retract) (30) Load control valve (boom extend/retract) (31) Telescoping cylinder (boom extend/retract) (32) Load control valve (boom raise/lower) (33) Boom cylinder (boom raise/lower) (34) Relief valve (coupler tilt) (35) Relief valve (36) Implement relief valve (37) Control valve (compensating cylinders) (38) Load control valve (coupler tilt) (39) Tilt cylinder (coupler tilt) (40) Diverter valve (41) Coupler cylinder (42) Load control valve (coupler cylinder) (PP) Pump delivery (CP1) Tilt cylinder pressure (R) Return oil (S) Suction oil (P) Pilot oil (LS) Load sensing oil | |
The implement section (10) of bank valve (1) that is used for tilting the quick coupler is operated by pilot oil pressure from joystick (3).
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| Illustration 2 | g00739330 |
Location of push button (coupler tilt) | |
Joystick (3) is moved left in order to tilt the quick coupler backward and the joystick is moved right in order to tilt the quick coupler forward. These movements are performed with the push button on the front of the joystick, pressed. The push button on the front of the joystick energizes solenoid valves (14), (15) and (16) .
When a backward tilt of the quick coupler is selected, pilot pressure is transmitted from the joystick through solenoid valve (15) to implement section (10) of bank valve (1) .
Oil from piston pump (25) flows from implement section (10) to the piston side of tilt cylinder (39) through load control valve (38) in order to tilt the quick coupler. As the tilt cylinder extends, the quick coupler is tilted backward and oil from the rod side of the cylinder flows through the bank valve and returns to hydraulic tank (23) .
System pressure that is used for tilting the quick coupler is transmitted through the load sensing resolver network of bank valve (1). If the system pressure at that particular time is higher than the load pressure in any other system, the pressure is transmitted to the pressure and flow compensator valve of piston pump (25) in order to adjust the pump to the required output.
The following description refers to a machine that is equipped with a type B control arrangement.
When the joystick is moved to the HOLD position, load control valve (38) is closed by spring force, locking oil into the piston side of tilt cylinder (39) in order to hold the quick coupler at the selected angle. Oil is locked into the compensating cylinders and lines by the spool in implement section (10) .
When a forward tilt of the quick coupler is selected, pump oil flows to the rod side of tilt cylinder (39). The load control valve (38) is piloted open by oil pressure that develops in the rod side of the cylinder. Oil then flows from the piston side of the cylinder through load control valve (38), control valve (37), bank valve (1) and returns to hydraulic tank (23) .
The load control valve meters oil from the piston side of the tilt cylinder in proportion to the pressure in the rod side of the tilt cylinder in order to regulate the selected speed of the cylinder. This function also prevents a sudden forward tilt of the quick coupler. If the quick coupler is being tilted forward or backward and the flow of oil to the tilt cylinder fails, the load control valve will be closed by spring force. This would lock oil into the piston side of the tilt cylinder which will prevent further movement.
When the quick coupler is tilting backward the tilt cylinder is extending and pressure is transmitted to the piston sides of the compensating cylinders and control valve (37). If the quick coupler is heavily loaded, or the tilt cylinder is fully extended, the pressure can rise sharply. When a sharp rise in pressure occurs, control valve (37) closes. This controls the pressure which is acting on the piston sides of the compensating cylinders.
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| Illustration 3 | g00760889 |
Location of Relief Valves (coupler tilt) in the Bank Valve (1) Bank valve (10) Implement section of bank valve (coupler tilt) (12) Relief valve (coupler tilt) (34) Relief valve (coupler tilt) | |
In order to control the rise of pressure in the system, relief valves (34) and (12) are installed in implement section (10) of bank valve (1). Relief valve (34) will operate when the boom is being raised. Relief valve (12) will operate when the boom is being lowered.
Relief valve (34) and relief valve (12) have anticavitation features which allow makeup oil to flow into the compensating system from the return gallery of bank valve (1), if the pressure in the compensating system falls below the return oil pressure.
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| Illustration 4 | g00742107 |
Relief Valve (coupler tilt) (43) Service port (44) Anticavitation piston (45) Tank return port (46) Orifice (pilot stage) (47) Piston (pressure relief) (48) Pilot valve (49) Spring (50) Spring (51) Valve seat (52) Spring (53) Anticavitation chamber (54) Hole | |
Pressure Relief
Pressure in service port (43) for tilting the quick coupler acts on the face of anticavitation piston (44). Pressure also acts on pilot valve (48) and at the rear of piston (47) through orifice (46) .
At the set pressure, pilot valve (48) is unseated. The pilot valve moves away from valve seat (51) against the force of spring (49). Pressure in anticavitation chamber (53) is now relieved past the pilot valve and around the outside of anticavitation piston (44) into the tank return port (45) .
Pressure that acts upon the face of piston (47) unseats the piston and the piston moves away from the seat in anticavitation piston (44) against the force of spring (52). This allows pressure in service port (43) to be relieved through holes (54) in the anticavitation piston.
Makeup Flow
If pressure in service port (43) falls below the pressure in tank return port (45), anticavitation piston (44) is offset by pressure in the tank return port and spring (50) is compressed. Oil enters the service port from the tank return port. When the pressure in the service port is equal to the pressure in the tank return port, anticavitation piston (44) is reseated by spring (50).