| 摘要 |
An upward acting door, such as a flexible curtain rollup door, is moveable between open and closed positions by an electric motor drive unit wherein the motor has a drive shaft with an external drive tang for engagement with a hand crank member. The crank member is adapted for mounting on a wall bracket and in engagement with a switch connected to a motor control unit. When the crank member is removed from its bracket, the switch causes the motor control unit to prevent transmission of electrical power to the motor. A manually disengageable brake is associated with the motor drive unit and is connected via an actuating member to a foot pedal which may be operated by a person using the crank member to disengage the brake and to allow free rotation of the motor drive shaft.
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