Table of Contents
Advertisement
27. NEVER allow anyone to stand or position any part of
his or her body under a suspended load.
28. Avoid sudden "shock" loads, or attempting to "jerk"
a load free. This type of operation may cause heavy
loads, in excess of rated capacity, which may result in
a failure of the wire rope and/or the winch.
29. Whenever possible, install the winch in a location that
is not immediately adjacent to a "normal" operator's
station.
BASIC DESCRIPTION
The winch consists of the following sub-assemblies:
1. Hydraulic motor and brake valve
2. Planetary gear reducer assembly
3. Static brake system
4. Cable drum, drum shaft and clutch
5. Base
The primary sun gear is directly coupled to the hydraulic
motor by the inner race of the brake clutch assembly. As
the motor shaft turns in the haul-in direction, the planetary
assemblies reduce the speed input by the motor to rotate
the cable drum. In the haul-in direction, the static brake
remains fully applied and the input shaft rotates freely
through the sprag clutch. When the motor is stopped, the
load attempts to rotate the winch gear train in the opposite
direction locking the brake clutch to the input shaft, allow-
ing the fully applied static brake to hold the load fi rm.
DUAL BRAKE SYSTEM
The dual brake system consists of a dynamic brake sys-
tem and a static brake system.
The dynamic brake system has two operating compo-
nents:
1. Brake Valve Assembly
2. Hydraulic Motor
The brake valve is basically a counterbalance valve with
better metering characteristics for load control. It contains
a check valve to allow free oil fl ow to the motor in the haul-
in direction, and a pilot operated, spring-loaded spool
valve that blocks the fl ow of oil out of the motor when the
control valve is placed in neutral. With the control valve
lever moved toward the pay-out direction, the spool valve
THEORY OF OPERATION
6
30. ALL winch controls should be located within easy
reach of the operator. The controls shall be installed
in such a location that the operator is removed from
the electrical path to ground if the load, rigging or wire
rope comes into contact with or within proximity to an
electrically energized conductor.
remains closed until suffi cient pilot pressure is applied to
the end of the spool to shift it against the spring pressure
and open a passage. After the spool valve cracks open,
the pilot pressure becomes fl ow dependent and modulates
the spool valve opening, controlling the pay-out speed of
the winch. See Figures 1, 2, and 3.
The static brake system has three main components for
all winches:
1. Spring-Applied, Multiple Friction Disc Static Brake
2. Hydraulic Piston and Cylinder
3. Brake Clutch Assembly
The static brake is released by the brake valve pilot pres-
sure at a pressure lower than that required to open the
pilot operated spool valve. This sequence ensures that dy-
namic braking takes place within the brake valve, and that
little, if any, heat is absorbed by the static, friction brake.
The static friction brake is load holding brake only, and has
nothing to do with dynamic braking or the rate of descent
of a load.
The brake clutch assembly is splined to the primary sun
gear shaft between the hydraulic motor and primary sun
gear. It will allow this shaft to turn freely in the direction
to haul-in a load, and locks up to force the brake discs to
turn with the shaft in the pay-out direction. See Figures 4
and 5.
The hydraulic brake cylinder, when pressurized, will re-
lease the spring pressure on the brake discs, allowing the
discs to turn freely.
Advertisement
Table of Contents
