| 摘要 |
A motor-driven cylinder for lifting apparatus has screw means including intermeshed internally and externally threaded screw means by which a load can be moved upwardly and downwardly by the torque of a motor, the motor-driven cylinder including torque transmission means movable in a first direction and a second direction opposite thereto for transmitting the torque of the motor to the screw means. During operation, the torque transmission means is moved in the first direction by the applied torque of the motor causing compression of a spring. When no torque is produced from the motor due to its malfunctioning or due to a lack of electrical power applied to the motor the torque transmission means is moved in the second direction under the restoring force of the compressed spring into a mechanically braked condition. Thus, a compact, integral, low-cost safety device is provided for preventing the lifting apparatus from falling, accidentally, under the force of gravity. |
