Paccar Winch BRADEN BA3A, Installation Maintenance And Service Manual

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6
DESCRIPTION OF HOIST
The hoist is made up of the following sub-assemblies:
1. Air motor
2. Drum, drum closure, ball bearings and oil seals
3. Base, bearing support and motor adapter
4. Brake clutch assembly
5. Brake cylinder assembly and multiple-disc brake
parts
6. Planetary gear reducer assemblies
7. Ring gear machined into drum
8. Band brake
DESCRIPTION OF OPERATION
The primary sun gear is directly coupled to the air motor
by the inner race of the brake clutch assembly. As the
motor turns in the hoisting direction (normally clockwise),
the planetary assemblies reduce the input speed of the
motor and rotate the winch drum. The drum rotates in the
opposite direction of the motor input shaft. In the hoist-
ing direction, the static brake remains fully applied and
the input shaft rotates freely through the sprag clutch.
When the motor is stopped, the load tries to rotate the
winch gear train in the opposite direction. The sprag
clutch on the input shaft immediately locks up, allowing
the fully applied static brake to hold the 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 air cylinder, when pressurized during lowering, will
release the spring pressure on the brake discs, allowing
the brake discs to turn freely.
B
RAKE
S
YSTEM
– O
PERATION
When hoisting a load, the brake clutch which connects
the motor shaft to the primary sun gear, allows free rota-
tion. 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.
BASIC OPERATION
Figure 5
Figure 6
Static Friction Brake Applied
Static Friction Brake Applied
Sprag
Cams
Permits free
shaft rotation
while hoisting
Load attempts to rotate shaft in opposite direction.
Brake clutch locks sun gear shaft to friction brake.
Sprag
Cams
Hoisting
Stopped,
Holding
Load