DESCRIPTION OF HOIST
The hoist is made up of the following sub-assemblies:
1. Hydraulic motor and brake valve
2. Cable drum, drum closure, ball bearings and oil
seals
3. Base, bearing support and motor adapter
4. Brake clutch assembly
5. Brake cylinder assembly and multi-disc brake parts
6. Planetary gear assemblies and ring gear
7. Auxiliary brake system
THEORY OF OPERATION
The hydraulic motor shaft is directly coupled to the pri-
mary sun gear through the inner race of the brake clutch
assembly. As the motor turns in the hoisting direction,
the planetary gear assemblies reduce the speed provid-
ed by the motor and rotate the hoist cable drum.
In the hoisting direction, the static brake assembly
remains fully applied and the input shaft rotates freely
within the brake clutch assembly. With the motor
stopped, or the winch in neutral, the load tries to rotate
the hoist gear train in the opposite direction. The brake
clutch on the input shaft immediately locks up, allowing
the fully applied static brake to hold the load from drop-
ping.
D
UAL
B
RAKE
S
YSTEM WITH
A
UXILIARY
B
RAKE
- D
ESCRIPTION
The dual brake system consists of a dynamic brake sys-
tem and a static brake system, both located on the
motor end of the hoist. The auxiliary brake system is
installed on the end of the hoist opposite the motor end.
The dynamic brake system consists of two operating
components:
1. Brake valve assembly
2. Hydraulic motor
The brake valve is basically a counterbalance valve. It
contains a check valve to allow free flow of oil to the
motor in the hoisting direction and a pilot operated,
spring loaded spool valve that blocks oil flow out of the
motor when the control lever is returned to neutral.
When the control lever is moved into the lowering posi-
tion, the spool valve remains closed until sufficient 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 flow dependent and modulates the spool
valve opening, which controls the lowering speed of the
hoist. (See figures 2, 3 & 4).
The static brake is released by the brake valve pilot
pressure at a pressure lower than that required to open
the pilot operated spool valve. This sequence assures
that dynamic braking takes place within the brake valve,
and that little, if any, heat is absorbed by the static fric-
tion brake.
The static friction brake is a load holding brake only, and
has nothing to do with dynamic braking or rate of
descent of a load. The static brake system consists of
the following components:
1. Multi-disc, spring-applied brake cylinder assembly
2. Brake clutch assembly
3. Hydraulic piston and brake cylinder
5
BASIC OPERATION
Pump
Brake
Valve
Static
Brake
Motor
Control
Valve
Low Pressure Medium Pressure High Pressure
Pump
Brake
Valve
Static
Brake
Motor
Control
Valve
Low Pressure Medium Pressure High Pressure
To
Tank
To
Tank
Figure 2
Figure 3