motor. When hoisting up, oil enters the IN port of
the hoist control valve and unseats the free flow
poppet. Oil then flows from the OUT port of the
valve to the up port of the motor, which drives the
The Grove Model HO-15 hoist is a single speed hoist
hoist to wind cable onto the drum.
consisting of a hoist control valve, a vane type mo-
tor, the brake, the side and base plates, and the ca-
When hoisting down, oil flows to the down port of
ble drum assembly. The cable drum assembly in-
the hoist motor, the hoist brake, and the pilot line of
cludes the drum and a gear reduction unit.
the hoist control valve. The pilot operated poppet of
the hoist control valve and the hoist brake are con-
trolled by the pressure in the down line. Because the
poppet in the hoist control valve is closed and oil
cannot flow from the raise port of the motor, pres-
sure rises in the down line. As the pressure rises, the
cated in the drum ends. A shaft splined to the drive
hoist brake will release and as pressure continues to
motor transmits the drive motor rotation to the pri-
rise, the pilot pressure in the hoist control valve will
mary carrier assembly in the gear reduction unit. A
open the poppet allowing the hoist to run in a down
second shaft transmits this rotation from the secon-
direction and oil to flow to the reservoir. If the load-
dary carrier assembly in the gear reduction unit to
drop speed increases, the pressure in the down line
the overrunning clutch. The overrunning clutch will
will decrease. This decrease in pressure will cause the
restrict or stop drum rotation as determined by the
poppet in the hoist control valve to close and causes
action of the hydraulic operated brake.
the spring actuated brake to slow or stop the hoist.
The hoist control valve prevents the load from driv-
Oil from the hoist directional control valve flows to
ing the hoist motor during hoist down operation.
the hoist control valve mounted on the hoist drive