R&M Materials Handling ELECTRIC CHAIN HOISTS LoadMate Chain Hoist LM 5 Stepless - Manual (Page 25)

LoadMate
®
LM05 STEPLESS I&M/EN/11.30.2010
25/71
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Copyright © (2010) R&M Materials Handling, Inc. All rights reserved.
7.2 Motor / Body
The hoist motors are designed to provide dependable hoisting service. The standard motors are enclosed
for IP55 rated protection against normal hazards of dust and moisture. The motor bearings are sealed and
do not require further greasing.
The hoist body is constructed of aluminum and requires no maintenance. Remove from service and replace
the hoist body if damaged.
7.3 Hoist Motor Brake and Load-Limiting Device
The load-limiting device is a slip clutch and it is integrated into the design of the hoist motor brake. Even if
the clutch slips, once power is removed, the brake will engage to stop and hold the load.
7.3.1 Slip Clutch Operation
Static situation with a load suspended
The torque load is transmitted to brake through the pinion (12). The brake linings are compressing the
anchor discs (3 and 6) due to the force of the springs (4).
Hoisting movement
The load is creating a counter torque on the gear shaft (12) compared to the motor torque on the shaft (13).
Due to that torque, the cam system (9, 10, and 11) is opening by compressing the springs (4). When
the cam system opens, it releases the brake discs (1 and 5) which can rotate freely from the anchor
discs (3 and 6) which are connected to the frame by the pins (2). The flywheel (8) is transmitting the motor
torque to the brake disc (1) thru the clutch lining (17). The gearbox is then driven by that brake disc (1) thru
the pinion (12). If an overload occurs while hoisting, the clutch lining (17) slides and the load is not lifted.
Lowering movement
The load torque and the motor torque on the brake are in the same direction. Still, when the motor is
powered, the cam system is slightly opened due to the inertia in the flywheel (8) until there is a balance
between the load torque and the motor torque. The load is then lowered at the motor speed been kept
under the control of the friction of the brake linings (16) and the anchor disc (3 and 6). The heat generated
is dissipated in the oil bath.