Hydraulic system

5.4Boom summation — raise

Both P1 and P2 pumps are used to raise the boom at higher speed.

Raising the boom

• Moving the joystick also controls a second segment (boom 2).

• Pump P2 supplies the boom 2 segment with oil.

• The summation time (the time the boom 2 segment is switched) is specified by the piston spring in the boom 2 segment.

Lowering the boom

See Lowering the boom on page5-17.

5.5Check valve (load retaining valve)

• Boom cylinder base side

A pilot-operated load retaining valve is used to prevent spool leakage, which allows the cylinder to retain its home position.

Raising the boom

The oil opens the check valve and flows to the base side of the boom cylinder.

Lowering the boom

The load on the check valve is reduced by means of the pilot control line and a piston (return to tank). This allows the base side oil to flow back via the check valve.

5.6Dipper arm cylinder summation

Both P1 and P2 pumps are used to fold the dipper arm at higher speed.

Retracting the dipper arm cylinder

• Moving the joystick also controls a second segment (dipper arm 2).

• Pump P1 supplies the dipper arm 2 segment with oil.