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| Illustration 1 | g00659653 |
(21) Compensating cylinder (27) Compensating valve (29) Tilt cylinder for quick coupler (30) Blocked oil | |
The compensating system for the quick coupler automatically maintains the selected angle of the quick coupler in relation to the ground when the boom is raised or lowered. To keep the angle of the quick coupler constant, the tilt cylinder for the quick coupler works in conjunction with the compensating cylinders. The compensating valve ensures that the pressure in the compensating system is controlled.
The system consists of tilt cylinder (29) for the quick coupler, compensating valve (27) and compensating cylinders (21) .
Oil is blocked in the hydraulic lines between the tilt cylinder and the compensating cylinders by check valves in the compensating valve that creates a closed hydraulic circuit. Illustration 1 illustrates blocked oil.
The piston rods of the compensating cylinder are attached to the boom, and the cylinders are attached to the machine frame. The piston rods are therefore extended when the boom is being raised. The piston rods are retracted when the boom is being lowered.
The head end for tilt cylinder is matched to the total volume of the head ends of the compensating cylinder. The rod ends are similarly matched. When the boom is raised or lowered the tilt cylinder extends or the tilt cylinder retracts in proportion to the movement of the compensating cylinders. The volume of oil in the closed circuit between the tilt cylinder and the compensating cylinder remains constant.
When the boom is lowered, the compensating cylinders retract and oil is displaced from the head ends. The oil flows into the head end of the tilt cylinder through the load control valve for the cylinder. As the tilt cylinder extends, the quick coupler is tilted back. At this point, the selected angle is maintained between the quick coupler and the ground. Oil that is displaced from the rod end of the tilt cylinder flows to the rod ends of the compensating cylinders.
When the boom is raised, the compensating cylinders are extended and oil is displaced from the rod ends and flows into the rod end of the tilt cylinder. The oil to the rod end of the tilt cylinder also provides a pilot signal that opens the load control valve. The tilt cylinder begins to retract. This tilts the quick coupler forward. Oil from the head end of the tilt cylinder now flows into the head ends of the compensating cylinders.
The tilt cylinder for the quick coupler could reach the end of stroke when the boom is being raised or lowered. The compensating cylinders would continue to move with the boom, and the pressure in the hydraulic lines between the compensating cylinders and the tilt cylinder would rise sharply. When this occurs, the relief valves open and the valves connect the oil flow from the compensating cylinders to the hydraulic tank. This prevents cylinder damage.