Electricity: electrical systems and devices – Control circuits for electromagnetic devices – Systems for magnetizing – demagnetizing – or controlling the...
Patent
1994-04-04
1996-09-10
Fleming, Fritz M.
Electricity: electrical systems and devices
Control circuits for electromagnetic devices
Systems for magnetizing, demagnetizing, or controlling the...
361206, H01F 718
Patent
active
055554849
ABSTRACT:
An electromagnetic doorholder for retaining a door in an open position by magnetic interaction with an armature secured to the door. The doorholder includes a core having a face confronting the armature and a coil of wire surrounding the core. A cup having an inside diameter somewhat greater than the coil outside diameter receives the coil, the core extending from the face to the cup bottom. A power control circuit including a resistor circuit controls electrical power supplied to the coil, the power control circuit being mounted on a circuit board situated between the coil rear surface and the cup bottom. The resistor circuit being situated in sufficiently close proximity to the cup bottom for transfer of heat from the resistor circuit to the cup. The power control circuit also includes a low resistance circuit coupled to the resistor circuit, the low resistance circuit including a fusible link, the fusible link being selected to carry current when the power input terminals are coupled to a lower voltage power source and to stop carrying current when the power input terminals are coupled to a higher voltage power source.
REFERENCES:
patent: 1406039 (1922-02-01), Lee
patent: 2472397 (1949-06-01), Bennett
patent: 3533652 (1970-10-01), Crane et al.
patent: 3913958 (1975-10-01), Larime
patent: 4696500 (1987-09-01), Zunkel
patent: 5139293 (1992-08-01), Zimmerman et al.
Dye William P.
Hoggard Paul J.
Fleming Fritz M.
Palermo Robert F.
Richardson A. James
Von Duprin, Inc.
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