COMPONENT OPERATION ／ Orbitrol

・When relief valve activated

When the steering cylinder reaches the stroke ends or the setting pressure predetermined by the relief valve (9) but it is tried to be turned further, the relief valve (9) initiates its operation. The oil discharged from the main pump flows to the tank through the orifice in the sleeve (8) and the relief valve.

COMPONENT OPERATION ／ Control Valve

・Control Valve

The control valve consists of the inlet section (7), lift plunger section (2), tilt plunger section (3) and outlet section (1). It is a 2-plunger valve which controls the direction of the flow and the pressure of the oil discharged from the main pump to operate the bucket and lift arm.

・ Relief valve

This control valve equips main relief valve (4), which is installed in inlet section. The main relief valve (4) controls the pressure in the shovel circuit to 20.6 MPa maximum.

The overload relief valves are installed to the cylinder port which connects with the rod and the bottom side of the tilt cylinder. When a great external force is applied to the bucket and an excessively high pressure is created in the tilt cylinder through the link, the overload relief valves (5) operate at a pressure of 22.6 MPa to prevent each device from being damaged. Each overload relief valve also acts as a check valve.

・ Detent mechanism

As a detent mechanism for this valve, an electromagnetic detent (auto-leveler) is equipped to the tilt plunger section.

1-Outlet section

2-Lift plunger section

3-Tilt plunger section

4-Main relief valve

5-Overload relief valve

6-Anti-void valve

7-Inlet section

8-Electromagnetic Detent

A1-To rod side of tilt cylinder (Bucket dump)

A2-To rod side of lift cylinder (Lift arm lowering)

B1-To bottom side of tilt cylinder (Bucket tilt back)

B2-To bottom side of lift cylinder (Lift arm raising)

P-From pump

T-To oil tank (to return filter)