National Crane Published 5-27-2018 Control # 039-06 11-3
800D HOIST
INTRODUCTION AND THEORY OF OPERATION
The planetary hoist is designed to utilize a geroler, gear, or
piston motor, driving through a multiple-disc oil brake,
through a pair of planetary gearsets to the cable drum.
The multiple-disc oil brake is spring applied and hydraulically
released through a port in the brake housing. During inhaul,
the brake is not released, since the load is driven through a
one-way cam clutch, bypassing the brake. When the load
comes to a stop, the cam clutch locks up and the brake
prevents the load from moving.
During payout, a brake valve is used to prevent the load from
moving faster than desired. This brake valve partially blocks
the main line from the motor back to the directional control
valve, allowing only a limited amount of hydraulic fluid
through the motor. The brake valve is then modulated by
sensing pressure on the other main line, the line from the
directional control valve to the motor. Additionally, any time
there is sufficient pressure (225 PSI ±10%) to modulate the
brake valve; this same pressure releases the brake.
Fo
r
Reference
Only
To Next Page
Loading...
