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Patents: 395 of 511

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John M. Ewen
18 of 21
SPECIFICATION forming part of Letter Patent No. 595,264, dated December 7, 1897.
Application filed September 27, 1897. Serial No. 653,236. (No model.)
To all whom it may concern:
    Be it known that I, JOHN MEIGGS EWEN, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Prism Lights and Plates, of which the following is a specification.
    My invention relates to prism-lights, and has for its object to produce new and useful improvements in prism lights and plates designed to produce an increased illuminating effect when applied to the windows of apartments. The prism-lights as commonly used are molded, though of course they may be made in other ways. They consist usually of a comparatively thin substantially flat body of glass a few inches square, (though of course they may be larger,) and they have commonly on one side a series of prisms systematically arranged to produce an increased illuminating effect and on the other side a relatively smooth surface. In molding or forming these prism-lights it is found that this comparatively smooth surface will be somewhat irregular owing in part to the peculiarities of the glass and in part to the impossibility of always having an equal amount of glass in the mold and in part to the contraction and expansion and to the cooling and reheating of the glass in the process of molding, and perhaps to other causes. When the prism-lights are assembled together to form a prism-plate, the exterior surface of such prism-plate will be found to consist of a series of surfaces which are slightly wavy and irregular and which have occasionally serious blemishes and are almost throughout their entire extent glazed, as it were. When, therefore, you look at such a plate from without, the effect is to a very great degree inartistic and unsatisfactory. Moreover, in the formation of such prism-lights very great difficulties will be encountered owing to the irregularity of the contraction and expansion of the glass, and thus there is always a considerable percentage of breakages. This difficulty is particularly observed with reference to the smooth surface as the prism-lights are commonly formed. The bottom of the mold usually contains the prism-forming grooves, and the plunger which descends upon the glass
in the mold tends of course to cool its upper surface, and when this plunger is withdrawn the upper or smooth surface of the prism-light again becomes hot, and it is perhaps to this action that the glaze on the surface is due. The objects of my invention, among other things, are to avoid this wavy effect, to prevent or at least obscure and render imperceptible the irregularities and imperfections otherwise noticeable upon the receiving-surface of the prism-light, to prevent the contraction and expansion in the prism-light, and thus to prevent breakages. These results, among others, I accomplish by the means illustrated in the accompanying drawings.
    Broadly speaking, I propose to form on the receiving side of the prism-light a design as distinguished from mere corrugations, striations, light-directing prisms, or mere markings, which shall preferably be characterized by the absence of extended surface areas and the absence of broad or wide lines in the design, such design to be either raised or sunken and its various elements, if desired, of varying depths or altitudes, as the case may be, and of varying widths, if desired. Such a design formed on the receiving-surface of the prism-light will lead to various results. In the first place the design raised or depressed when seen from the prism side is varied or altered slightly as you move from position to position while observing such design. It is in a sense a variable design as seen through the prisms, and, moreover, its lines are softened, so as to produce a very pleasing effect and relieve the prism-light of its more or less otherwise harsh appearance when seen from within. In the second place such a design when seen from without, as well as when seen from within, has the appearance of a sort of texture formation, especially when seen from a considerable distance, as is necessarily the case in ordinary practice. The elements out of which the design are formed become thread-like, and if the design is properly made produce an effect like lace. In the third place the design having broken up the receiving-surface into several small divisions, areas, or sections necessarily destroys the wavy effect above referred to, for though these several areas or surfaces still individually have the