| 摘要 |
An apparatus for shifting a gate from a closed position to an opened position and from the open position to the closed position with respect to an access opening. The apparatus comprises a housing with a motor in the housing, as for example, an electric motor. A drive shaft extends outwardly from the housing and is operable by the motor by means of a drive mechanism. A drive arm is connected to the outer end of the drive shaft, outwardly of the housing, and is rotatable thereby. The drive arm is designed to permit a lever arm or a lever arm assembly to be coupled thereto and which is also capable of being coupled to a gate for moving the same between the opened and closed positions. Further, the apparatus comprises a shaft coupling mechanism operatively associated with the drive arm for coupling the drive arm to the drive shaft so that the drive arm is rotatable with the drive shaft when the motor is operated. In addition, a disconnect mechanism, preferably a manually operable disconnect mechanism, is associated with the drive arm, and is operatively connected to the coupling mechanism for disengaging the drive shaft from the drive arm. This permits the drive arm to rotate independently of the drive shaft in emergency situations, as for example, in cases of power failure where the motor cannot be operated. The drive mechanism is designed with a worm and worm gear construction so that one cannot unauthorizedly attempt to rotate the drive arm without completing disengaging the drive arm from the drive shaft.
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