Overhead projector

Optics: image projectors – Temperature control – Blower

Patent

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Details

353 66, 353119, 353DIG4, 353 94, G03B 2116

Patent

active

045654301

ABSTRACT:
An overhead projector comprises a base, a hollow post extending up from the base and a projection head on an upper portion of the post. The projection head comprises a light source, an objective lens and a deflection mirror. A power supply unit housed in the post supplies power to the light source and to a ventilating fan inside the post between the power supply unit and the projection head. Openings in the post provide for circulation of cooling air by the fan over both the light source and the power supply unit. The power supply unit includes interchangeable input stages which can be plugged into a socket in the post to adapt the power supply unit to different voltages and currents. A slide or microfilm projector mounted adjacent the projection head projects on the base an image which is then re-projected onto a wall or screen by the projection head. For use at conferences, a conference table top is provided with a plurality of sockets into which the posts of overhead projectors can be plugged. Electrical contacts in the sockets engage contacts at the lower end of the post to provide current to the power supply unit. A reflecting Fresnel lens is preferably set in the base or the table top to reflect light rays from the light source to the objective lens.

REFERENCES:
patent: 2767611 (1956-10-01), Fitzgerald
patent: 3459475 (1969-08-01), Lucas
patent: 3525566 (1970-08-01), Altman
patent: 3632197 (1972-01-01), Shelton
patent: 3733121 (1973-05-01), Smitzer
patent: 3922079 (1975-11-01), Astero
patent: 4156561 (1979-05-01), Lucas
patent: 4206984 (1980-06-01), Mueller

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