7
THEORY OF OPERATION
DESCRIPTION OF WINCH
The winch consists of three basic assemblies:
1. Hydraulic motor, brake valve block and counter- balance
cartridges
2. Static brake assembly
3. Cable drum assembly
The hydraulic motor is bolted to the motor adapter which, in
turn, is bolted to the brake cylinder end plate of the winch.
The cable drum assembly is supported on each end by an
antifriction ball bearings. The ball bearings are located in
the end plates and the end plates are connected by two tie
plates. The dual stage planetary reduction multiples motor
torque and delivers it to the drum. The cable drum features
an anchor hole with two setscrews for winding cable onto the
drum in either direction.
DESCRIPTION OF DUAL BRAKE SYSTEM
Dynamic Brake
The dynamic brake system consists of two basic compo-
nents:
1. Brake valve block and counterbalance cartridges
2. Hydraulic motor
The counterbalance cartridges are installed into a brake
valve block which also contains an internal shuttle valve.
The shuttle valve directs hydraulic pressure to the brake re-
lease port of the winch when the winch is operated in either
direction.
Static Brake
The static brake consists of three basic components:
1. Spring-applied, multiple friction disk brake pack
2. Solid brake coupling
3. Hydraulic brake cylinder and spring plate
The brake pack consists of alternately stacked friction
and steel brake disks. The steel brake disks are externally
splined to the motor adapter and cannot rotate. The friction
disks are internally splined to the brake coupling. When the
winch is not being operated, spring force compresses the
brake pack and locks the brake coupling to the motor adapt-
er, preventing the gear train or cable drum from rotating in
either direction. The solid brake coupling makes the static
brake effective both directions. This means the static brake
must be released before the winch can operate in either the
hoist or lower direction.
The static brake is released by pilot pressure applied to the
brake cylinder. It releases at a pressure lower than that re-
quired to open the pilot-operated counterbalance cartridge.
This sequence assures that dynamic braking is accom-
plished by the counterbalance cartridge and that little heat, if
any, is absorbed by the friction brake.
The static or friction brake is primarily a load-holding brake
and will provide dynamic braking only during extremely slow
operation when there is insufficient flow and pressure to
open the counterbalance cartridge.
