Basic Operation - BRADEN CH280 Installation Maintenance And Service Manual

DESCRIPTION OF HOIST
The hoist is made up of the following subassemblies:
1. Hydraulic motor and brake valve
2. Drum, drum closure, ball bearings and oil seals
3. Support end plate and bearing support
4. Motor end plate and motor adapter
5. Tie plates
6. Brake clutch assembly
7. Brake cylinder assembly and multiple-disc brake parts
8. Primary, second stage and output planetary reducer
assemblies
9. Ring gear
THEORY OF OPERATION
The primary sun gear is directly coupled to the hydraulic
motor by the inner race of the brake clutch assembly. As
the motor turns in the hoisting direction, the two planetary
assemblies reduce the input speed of the motor and rotate
the planetary gearing and the cable drum. The ring gear is
held stationary by the brake cylinder and the output planet
carrier is coupled directly to the cable drum causing the
drum to rotate in the same direction as the motor shaft.
In the hoisting direction, the static brake remains applied
and the input shaft rotates freely through the brake clutch.
When the motor is stopped, the load tries to rotate the
hoist gear train in the opposite direction. The brake clutch
immediately locks up, allowing the fully applied static
brake to hold the load firm. See "Dual Brake System –
Operation" for a detailed description of the sequence of
operation in the lowering direction.
Dual Brake System – Description
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. It
contains a check valve to allow free flow of oil to the motor
in the hoisting direction and a pilot operated, spring-load-
ed spool valve that blocks the flow of oil out of the motor
when the control valve is placed in neutral. When the con-
trol valve is placed in the lowering position, the spool valve
remains closed until sufficient pilot pressure is applied to
the end of the spool to shift it against spring pressure and
open a passage. After the spool valve cracks open, the pi-
lot pressure becomes flow-dependent and modulates the
spool valve opening which controls the lowering speed.
See Figures 2, 3, and 4.

BASIC OPERATION

The static brake system has three operating compo-
nents:
1. Spring-applied, multiple friction-disc static brake
2. Brake clutch assembly
3. Hydraulic piston and cylinder
6
Motor
Static
Brake
Brake
Valve
Pump
Low Pressure
Medium Pressure
Motor
Static
Brake
Brake
Valve
Pump
Low Pressure
Medium Pressure
Motor
Static
Brake
Brake
Valve
Pump
Low Pressure
Medium Pressure
Figure 2
To
Tank
Control
Valve
High Pressure
Figure 3
To
Tank
Control
Valve
High Pressure
Figure 4
To
Tank
Control
Valve
High Pressure