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GENERAL DESCRIPTION:
The PULLMASTER Model M50 free fall is a planetary hydraulic winch having equal speed in both directions and the
ability to lower a load FAST. The free fall option comes in three variations: emergency free fall, controlled free fall,
or with both combined. The main components of this unit are:
jj ✛ Hydraulic gear motor
✛ Multi disc brake with static and dynamic function
✛ Over-running clutch
✛ Hydraulic gear motor
✛ Primary planet reduction
✛ Final planet reduction
✛ Brake housing
✛ Cable drum
✛ Free fall housing
✛ Free fall clutch assembly
✛ Metering pump assembly (for controlled free fall)
FUNCTION IN FORWARD ROTATION (HOISTING):
In forward rotation, the output torque and rpm of the hydraulic motor are transmitted to the sungear of the primary planet
reduction. The output of the primary reduction is transferred to the final sungear, which is splined to the primary planet
hub. The final planet assembly is locked in place by the free fall clutch and does not rotate, so the rotation is transmitted
to the cable drum by the final drive planet gears. In forward rotation, or when a load is lifted, 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. The pressure required to rotate the drum without load at full speed may vary up to 350 psi (24 bar).
When the winch rotation is stopped, the load on the cable drum causes the over-running clutch to lock and the maximum
load is held safely by the disc brake.
FUNCTION IN REVERSE ROTATION (LOWERING):
In reverse rotation, or when the winch is pressurized for lowering of a load, 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 against
a number of brake springs. The pressure required to rotate the drum at full speed may vary from 250 to 550 psi (17
to 38 bar) depending upon the load and without load from 500 to 1000 psi (34 to 69 bar). The over-running clutch,
connecting the motor drive shaft to the brake assembly, locks, causing the brake discs to rotate between divider plates,
which are engaged into the brake housing. If the load on the cable drum tends to effect the lowering speed, the resulting
pressure drop in the brake piston causes friction between the brake discs and the divider plates. In this way, a
completely smooth pay out speed can be achieved in a stepless operation by modulation of the winch control handle.
When the control handle is returned to neutral position, rotation stops and the disc brake applies automatically. A
hydraulic counter-balance valve or holding valve is not required for smooth and positive operation of the automatic
brake.
jlk
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 through the brake housing, supplied internally from the motor, or externally,
depending on the brake code of the winch. For efficient cooling of the automatic brake, models with external circulation
should be adjusted to supply 5 (US) gpm - 19 l/min. This flow must be returned directly to the reservoir with a permissible
back pressure of 30 psi (2 bar).
jlIMPORTANT: Under no circumstances must the pressure in the brake housing be permitted to exceed 30 psi
(2 bar). 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.
DESCRIPTION OF THE MODEL M50 FREE FALL
WARNING
PRIOR TO OPERATION OF THIS UNIT, VERIFY COMPLIANCE WITH
ALL NATIONAL AND LOCAL SAFETY CODES AND REGULATIONS
REGARDING THE USE OF FREE FALL WINCHES.
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