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DESCRIPTION OF THE MODEL M6
GENERAL DESCRIPTION:
The PULLMASTER Model M6 is a planetary, hydraulic winch having equal speed in both directions and an automatic
disc brake. The main components of this unit are:
✛ high torque, low speed hydraulic motor
✛ multi-disc brake with over-running clutch
✛ planetary reduction
✛ brake housing
✛ cable drum
✛ final drive housing
FUNCTION IN FORWARD ROTATION (HOISTING):
In forward rotation, the output torque and rpm of the hydraulic motor are transmitted through the brake shaft to the
final sungear. The planet gears are driven by the final sungear and cause the planet hub to drive the cable drum
at a reduction of 9.25:1. When a load is raised, an over-running clutch which connects the motor drive shaft to the
automatic brake assembly, permits free rotation of the sungear, without effecting the brake. When the winch rotation
is stopped, the load on the cable drum causes the over-running clutch to lock and the load is held safely by the disc
brake.
FUNCTION IN REVERSE ROTATION (LOWERING):
In reverse rotation, hydraulic pressure from the reverse side of the hydraulic motor is channelled to the brake piston,
causing the brake piston to release the multi-disc brake. The over-running clutch, connecting the motor drive shaft
to the brake assembly, locks, causing the brake discs to rotate between stationary divider plates. If the load on
the cable drum increases the pay out speed, the resulting pressure drop in the brake piston increases friction
between the friction plates and slows the drum. In this way, a completely smooth pay out speed can be achieved
in a stepless operation by modulation of the winch control valve. When the control valve is returned to neutral
position, rotation stops and the disc brake applies automatically.
During lowering operations of the winch, the friction created by the brake discs results in heat. This heat is dissipated
by the circulation of hydraulic fluid from the brake housing, supplied internally through the hydraulic motor. This
circulation flow is internally vented to the return line through a check valve arrangement inside the specially modified
motor. The circulation flow is supplied only when lowering a load. A separate vent line connecting the PULLMASTER
Model M6 with the hydraulic reservoir is not required (see TYPICAL HYDRAULIC CIRCUIT).
IMPORTANT: SAFETY VALVE
The PULLMASTER Model M6 winch does not require a drain line up to 100 psi permissible back
pressure in the brake housing. To indicate excessive pressure and potential damage to the
hydraulic motor or to the oil seal in the brake housing, a safety valve is installed on the motor
adaptor.
BREATHER RELIEF VALVE
Excessive pressure in the brake housing will damage the oil seal separating the brake housing from
the drum interior. Damage to this seal will cause the drum to fill up with hydraulic fluid. To prevent
damage to the drum seal and end cover of the final drive if the cable drum fills up with hydraulic
fluid, a breather relief (PARTS REFERENCE item 130) is installed on the end cover. The breather
relief does not prevent oil seal failure but serves as an indicator or warning that the seals between
brake housing and the cable drum interior have failed and must be replaced immediately.
184 REV.961001
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