Ogura clutch used for opening and closing heavy doors.
Ogura CT Electromagnetic clutches
Description of Operation
The 0.5 horsepower motor drives the 80:1 reducer which in turn drives the Ogura clutch that drives the rack and gear. The motor is bi-directional and is used to either open or close the door. In the case of an emergency and power is lost, the doors must be manually closed or opened by hand. Since it is impossible to back drive many high reduction gear boxes, a clutch must be used so that personnel are not trapped inside or outside of the doors.
Reason for Selection of the Ogura Electromagnetic Clutch
The clutch is a relatively simple device which is either on or off. In the off conditions the armature is pulled away from the rotor allowing complete disengagement. The clutch can also be driven in either direction and in this case it either opens or closes the doors. The doors may also be fitted with a sensor that could detect if someone was trapped in between when the door was closing. This sensor in turn could be relayed back to the clutch which would allow the clutch to disconnect immediately if the sensor was tripped, thereby preventing serious injury.
Besides heavy lead doors that can be used in test facilities or nuclear power plants, any large doors may have a device such as this. There are some companies that manufacture large refrigerators for restaurant use that have very heavy doors and occasionally use some type of safety device such as a clutch on the output side. Besides the rack and gear configuration, sometimes a chain drive or a ball screw set up can also be used to control the doors opening and closing.