Electricity: motive power systems – Plural diverse motor controls – Motor-reversing
Patent
1975-09-02
1977-02-01
Dobeck, B.
Electricity: motive power systems
Plural diverse motor controls
Motor-reversing
318283, 318467, G05D 308
Patent
active
040063925
ABSTRACT:
An electronic door control system is disclosed having a d.c. motor rotatable in one direction for opening a door and in the opposite direction for closing the door. One or more semiconductor devices (preferably SCR's) supply d.c. power to the motor from an a.c. power source when rendered conductive. A polarity selecting circuit controls the polarity of d.c. power supplied to the motor and thus its rotational direction. A sensor (e.g. floor mat) senses body pressure near the door to enable conduction of the semiconductor device and provide a first d.c. power polarity for a predetermined period to open the door. A circuit reverses the polarity after the door is opened, thereby closing the door. A speed control circuit responsive to counterelectromotive force developed by the motor effectively controllably varies the conductivity of the semiconductor device in a sense tending normally to cause motor rotation, and thereby door movement, at a predetermined speed. Preferably, this speed control circuit also operated in response to change in said counterelectromotive force caused by door blockage to effectively reduce the conductivity of the semiconductor device whereby motor rotation, and thus door movement, is stopped as long as the door blockage is present.
REFERENCES:
patent: 3728605 (1973-04-01), Purtilo
patent: 3813590 (1974-05-01), Ellmore
patent: 3891909 (1975-06-01), Newson
Blake James A.
Catlett John C.
Dobeck B.
Kalish Ralph W.
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