US790026A - Reflector for artificial light. - Google Patents

Description

UNITED STATES Patented May 16, 1905.

PATENT OFFICE.

KRAFT BOOTH, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO GILLINDER & SONS, ING., OF PHILADELPHIA, PENNSYLVANIA.

FIEFLECTOR FOR ARTIFICIAL LIGHT.

SPECIFICATION forming part of Letters Patent No. 790,026, dated May 16, 1905.

i Application filed February 3, 1905. Serial No. 243,919.

enable others skilled in the art to which it appertains to make and use the same.

My invention relates to light-reflectors of transparent material, as glass, particularly designed for use upon incandescent electric lights, the invention being applicable' to that class of such refiectors known as prismatic.

The chief object of my invention is to improve this class of refieetors by making them more luminous without materially affecting their reflecting power.

The invention consists in forming upon the `exterior surface of reflectors alternate high and low prisms extending radially from at or near the neck of the reflector to or near the mouth thereof, as will appear from the following description and claim and the accompanying drawings.

In said drawings, Figure l is a view in side elevation of an ordinary form of reflector having my im roved prisms. Fig. 2 is a plan or top view t ereof. Fig. 3 is a sectional view of a portion of the reflector on an enlarged scale.

Prismatic electric reflectors are now made in a large variety of shapes and designs, ranging from a conic frustum to bell form, each with an annular neck at its inner end and increasing in diameter toward its outer end or mouth. It has been found that a large percentage of the light-rays emanating from the lamp to which the reflector is applied is reflected from the mouth of the reflector by forming it with external radial prisms. By pro erly constructing the prisms all but a sma l proportion of the light is thus reflected, the remainder passing through the sides of the refiector. This is caused by the light-rays striking one side of each prism and being reflected therefrom at a right angle to the opposite side of the prism and thence reflected through the mouth of the reflector. While this is desirable for reflecting purposes, it leaves the exterior of the 'reflector dull and the space surrounding the reflector comparatively dark. In other words, the light diffused from the side of the reflector is not sufficient for illuminating to an appreciable extent or for overcoming the dullness or lackluster of the refiector. This has been overcome partly by providing a portion ofthe reflector with diffusing instead of reflecting prisms. This is effective so far as it goes, but does not relieve the reflecting-prisms of dullness, and as these prisms cover the major portion of the refiector its general external appearance is dull.

Therefiector l indicated in the accompanying drawingsv is in the form of a conic frustum; but obviously the sides instead of being straight may be curved, flared, scalloped, or formed into any desirable shape. Exteriorly the reflector is surfaced with what I will term high prisms 2 and relatively low, and hence smaller, prisms 3, the prisms in this particular instance extending in a straight line from justfbelow the neck 4 of the reflector to the edge or mouth thereof. The high and low' prisms are arranged alternately-that is, a low prism beingplaced between every two high prisms. In some forms of reectors it is desirable that the low prisms do not extend toward the neck as far as the high prisms extend.

The high prisms serve to reflect the light through the mouth of the reflector the same as in the well-known prismatic electric refiectors above described. The low prisms also refiect the light in the same manner, but

to a less extent. They also perform an additional function, the light-rays which pass entirely through them being refracted upon the near exterior surface of the adjacent high prism, from which it is reflected laterally or outwardly, Thus the major portion of. the light is reflected through the mouth of the refiector, as with well-known forms of prismatic electric reflectors; but that portion of the light which passes through the sides of the reflector is made use of to render the eX- ternal surface of the reflector more brilliant and luminous than is the case with other reflectors. This increased brilliancy or luminosity is attained Without sacrificing to any material extent the reflecting quality of the reflector. Moreover, this is accomplished Without devoting a portion of the reflector to diffusing-prisms, practically the entire surface of the reflector deflecting and diffusing light at the same time. In this Way no portion of the reflector is dull, its entire external surface being brilliant and luminous.

My invention, it is to be understood, is not confined to the exact arrangement and proportion of prisms shown, although I have found that the object sought is Well attained bymaking the low prisms approximately onehalf the height of the high prisms; nor is my invention restricted to radial prisms extending in a straight line, as they may be curved or arranged spirally.

I claim as my invention- A prismatic light-reflector of transparent material formed on its exterior surface with 1 alternate high and low prisms extending radially from at or near the neck of the reflector to or near the mouth thereof, substantially as set forth.

In testimony whereof I allix my signature in presence of two witnesses.

KRAFT BOOTH.

Iitnesses GEO. A. STERN, J No. WALLACE.

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