Ventilator controller for a greenhouse

Claim 1

In a controller for opening and closing a ventilator for a greenhouse wherein a capacitor start motor is connected so as to position the ventilator, said motor having a running winding and a starting winding which is connected in series with a centrifugal switch and wherein a reversing relay is coupled to the windings of the motor to cause the drive motor to drive in a direction to open the ventilator when an open-relay coil in the relay is energized and to cause the drive motor to drive in a direction to close the ventilator when a close-relay coil in the relay is energized, a delay system to prevent alternating current from being supplied to the motor windings to reverse the same for a time period sufficient to allow the centrifugal switch to close, comprising a power supply, a delay motor geared down to provide a low rotational velocity on its output shaft, said delay motor having one side thereof coupled to one side of said power supply, each of said relay coils having one side connected to said one side of said power supply, a thermostat having a pair of contacts, a first of aid contacts being closed and a second of said contacts being opened by temperature rise and said first contact being opened and said second contact being closed by a temperature drop, one side of said first and one side of said second contact being coupled to the other side of said power supply, a first switch means having a normally open third contact and a normally closed fourth contact, one side of said third contact and one side of said fourth contact being coupled to the other side of said first contact, the other side of said third contact being coupled to the other side of said delay motor, the other side of said fourth contact being coupled to the other side of said open relay coil, a second switch means having a normally open fifth contact and a normally closed sixth contact, one side of said fifth contact and one side of said sixth contact being coupled to the other side of said second contact, the other side of said fifth contact being coupled to the other side of said delay motor, the other side of said sixth contact being coupled to the other side of said relay coil, and cam means connected to the output shaft of the delay motor for maintaining said first and second switch means in operated positions and sequentially switching said first and second switch means to their normal positions at least once for each revolution of said cam means.