U.S. Philips Corporation

John Fitzgerald

Jan Antoon Kesseler

Willem L Van Hoorn

Bowl mirrored lamps according to the invention have a filament which is arranged asymmetrically with respect to the axis of the lamp envelope and surrounds the axis over an angle greater than 180.degree. in such a manner that it does not coincide at any point with the image of the filament formed by the mirrored bowl portion of the lamp envelope. As a result of this filament positioning the lamp can in combination with a reflector provide a light beam having a very high central intensity.

Bowl mirrored lamp

In electric incandescent lamps the efficiency can be increased by surrounding the filament with a light-pervious, infra-red radiation-reflecting filter. It has hitherto always been assumed that the geometry of the filter and that of the filament should be well matched to each other. This, however, results in a complex filament construction. According to the invention, near the center of a spherical filter, a flat filament consisting of several parts is accommodated, being situated within a square the sides of which are from 0.25 to 0.04 times the diameter of the filter. Such a filament has a relatively simple construction and provides a highly efficient lamp despite the fact that its geometry is very different from that of the filter.

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Eindhoven, Netherlands

John Fitzgerald