Allied H6G, Service Manual

Page: 25 / 112

Section 1
1 - 17
Sequence of Operation, HI-SPEED LINE-IN
The operator pulls back the control lever which sends
pilot control pressure to the directional control valve and
the brake release valve. Oil fl ows from the pump supply
line into the directional control spool and through a check
valve in the counterbalance valve cartridge. Oil fl ow con-
tinues through to the inlet A port of the hydraulic motor
and builds pressure from the induced load on the winch.
This pressure is communicated to the tractor pump load
sense controller, and the pump displacement is increased
or decreased depending on the load induced pressure.
Oil fl ows through the motor back through the directional
control spool and to the tractor reservoir. Simultaneously,
pilot control pressure at the brake valve is connected to
the brake release port, and the brake is fully released.
Low pressure case drain oil fl ows from the hydraulic motor
back to the tractor reservoir.
When pressure on the inlet A port of the motor exceeds
3500 psi, the load sense relief valve opens. The load sense
pressure signal decreases and the tractor pump strokes
back reducing displacement so pressure at the hydraulic
motor decreases a corresponding amount.
When the operator depresses the HI-SPEED switch the
HI-SPEED solenoid valve in the logic manifold opens and
pilot control pressure is communicated to the HI-SPEED
spool in the hydraulic motor. The spool shifts to close half
of the vein ports in the motor. Full pump fl ow now fl ows
through the motor at half displacement thus increasing
the output rpm.
Inlet pressure to the hydraulic motor is sensed by a pres-
sure switch in the directional control manifold. When pres-
sure at the switch reaches 1750 psi, the switch opens and
the circuit to the
HI-SPEED solenoid valve is deactivated.
Pressure at the HI-SPEED spool in the hydraulic motor is
vented back to the reservoir, and the spool spring biases
back to the standard speed position. The winch remains
in standard speed until the operator depresses the
HI-
SPEED switch again and load induced pressure on the
motor remains below 1750 psi.