BRADEN CH SERIES Installation Maintenance And Service Manual page 7

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 assures that dynam-
ic braking takes place in the brake valve and that little, if
any, heat is absorbed by the friction brake.
The friction brake is a load holding brake only and has noth-
ing to do with dynamic braking or rate of descent of a load.
The brake clutch is splined to the primary sun gear shaft
between the motor and the primary sun gear. It will allow
this shaft to turn freely in the direction to raise a load and
lock up to force the brake discs to turn with the shaft in the
direction to lower a load. Figures 5 and 6.
The hydraulic cylinder, when pressurized, will release the
spring pressure on the brake discs, allowing the brake discs
to turn freely.
D B S – O
UAL RAKE YSTEM
When hoisting a load, the brake clutch which connects the
motor shaft to the primary sun gear, allows free rotation.
The sprag cams lay over and permit the inner race to turn
free of the outer race. Figure 5. The friction brake remains
fully engaged. The winch, in raising a load, is not affected
by any braking action. Figure 2.
When the lifting operation is stopped, the load attempts to
turn the primary sun gear in the opposite direction. This
reversed input causes the sprag cams to instantly roll
upward and firmly lock the shaft to the fully engaged friction
brake. Figure 6.
When the winch is powered in reverse, to lower the load,
the motor cannot rotate until sufficient pilot pressure is pres-
ent to open the brake valve. Figures 3 & 4. The friction
brake within the winch will completely release at a pressure
lower than that required to open the brake valve. The extent
to which the brake valve opens will determine the amount of
oil that can flow through it and the speed at which the load
will be lowered. Increasing the flow of oil to the winch motor
will cause the pressure to rise and the opening in the brake
valve to enlarge, speeding up the descent of the load.
Decreasing this flow causes the pressure to lower and the
opening in the brake valve to decrease thus slowing the
descent of the load.
When the control valve is shifted to neutral, the pressure will
drop and the brake valve will close, stopping the load. The
friction brake will engage and hold the load after the brake
valve has closed.
PERATION
When lowering a load very slowly for precise positioning, no
oil flow actually occurs through the winch motor. The pres-
sure will build up to a point where the brake will release suf-
ficiently to allow the load to rotate the motor through its own
internal leakage. This feature results in a very slow speed
and extremely accurate positioning.
The friction brake receives very little wear in the lowering
operation. All of the heat generated by the lowering and
stopping of a load is absorbed by the hydraulic oil where it
can be readily dissipated.
Static Friction Brake Applied
Figure 5
Sprag
Cams
Permits free
shaft rotation
while hoisting
Figure 6
Static Friction Brake Applied
Sprag
Cams
Load attempts to rotate shaft in opposite direction.
Brake clutch locks sun gear shaft to friction brake.
5
Hoisting
Stopped,
Holding
Load