US 734020 A
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PATBNTED JULY 21,1903.
I. L. 0. WADSWORTH. ILLUMINATING STRUCTURE.
APPLIUATION FILED JULY 28, 1898.
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UNITED STATES Patented July 21, 1903.
FRANK L. O. l/VADSWORTH, OF \VILLIAMS BAY, WISCONSIN, ASSIGNOR, BY MESNE ASSIGNMENTS, TO PRESSED PRISM PLATE GLASS COMPANY, A CORPORATION OF WEST VIRGINIA.
SPECIFICATION forming part of Letters Patent No. 734,020, dated July 21, 1903.
Application filed July 28,1898. Serial No. 687,132. (No model.)
To (tZZ whom it may concern.-
Be it known that I, FRANK L. O. VVADS- WORTH, of Williams Bay, in the county of lValwoi-th and State of Wisconsin, have in-' venteda newand useful Improvement in Illu' minating Structures, of which the following is a full, clear, and exact description.
My invention relates to illuminating structures; and the object is to secure a form of to structure which will be more efiicient in collecting and directing into the room a larger proportion of the light from the outside than is ordinarily obtained. The means and method of securing this result are fully illustrated I5 in the accompanying drawings, in which Figure 1 representsin cross-section myimproved structure. Fig. 2 isadiagram. Figs. and 4 are modifications.
In many cases it is desirable that allthe light collected by a prism structure from outside be sent into the room in practically one direction. In order to.secure this result, as shown in Fig. 2, I take advantage of the fact that those rays, such as 2, coming from directions more nearly vertical than the principal direction 1 strike the deflecting-faces w of the prism elements at points 2' inside of that at which the principal rays strike, while rays coming from the more nearly horizontal 3o directions 3 and 4t strike these elements at points 3 4 outside of the point 1. It is therefore possible to shape the deflecting-faces w of the prism elements a in such a way that the different rays b b b 19 are each and all reflected at the face 20 in the same direction, as in Fig. 2. I have discovered that the form of surface necessary to secure this result is a parabola, of which the focal point lies at the point 6011 the receivingface' of the prism 0 elements and the vertex 1) of which lies ona line passing through the focal point I) and parallel to the lines 2 2", along which the rays falling on the face 10 are reflected. When the surfacew of the prism elementis so shaped, all of the rays passing through the point I) on the front surface of the'illuminating structure are reflected from w in the same direction, and consequently all emerge from the face u of the prism element in the same direction into the room, as at 1 2 3 4, Fig. 5d
- curved lower faces to, laid out as already described, and a second series of fiat faces Lt it, which in general are preferably made parallel to the direction 19 which the principal rays take after refractionat the front surface of the prismatic structure. These prismatic elementsgenerally extend transversely across the entire width of the illuminating structure, and the lower curved surfaces 10, each of which corresponds in cross-section to a portion of the parabolic curve, as just described, thus become as a whole portions of parabolic cylinders of which the vertices are lines parallel with and in front of the front surface of the structure.
It is of course evident that all of the rays of light which fall on the front surface of the structure do not pass through the points I) b which are opposite the center of each prism element. Consequently the whole bundle of rays from any one direction, such as the bundle 1 1 1 or 3 3 3, Fig. 1, does not fall on that part of the deflecting-faces 10 which is inclined at the right angle to-reflect them in the properdirection. If, however, the points Z) are so located that the central ray of each bundle strikes at the proper points of the faces to w, the other rays on each side of this central one will strike at such points that they will be converged along the direction 1*, as at 1" 1", so that the main direction of the whole bundle is that desired.
By making the deflecting-faces w of the prism elements portions of parabolic cylinders laid out as above described I am enabled to collect from the outside rays coming from many different directions and direct them all intothe room in substantially the same direction, securing thus a much greater illuminating effect at any desired point than is possible with prismatic structures Whose elements have plain surfaces.
My invention as illustrated iirFig. 4 is like Fig. 1, except that the receiving-surface of the glass instead of being plain is ribbed or corrugated.
I am aware that prism elements have been formed with curved surfaces heretefore; but the nature of'these surfaces has not been accurately determined and made such as to secure the result desired. 5
My invention, Which consists in the use of a prism having curved surfaces of defined and definite curvature, may be applied not only to cases in which such curvedsurfaceis an internally reflecting surface, as illustrated in the drawings of this specification,
but also to cases Where such curved surface is a refracting-surface. In an application filed by me this date, Serial No. 687,134, I illustrated the application of my invention to a refracting-surface as last mentioned.
I claim- 1. An illuminating prism-plate With a series of prism elements each having a one fiat face and one internally-reflecting face, the latter curved to correspond in cross-section to a parabolic curve of which the focal point lies in the front face of the prism element; substantially as described.
2.. An illuminating prism-plate having on one side a receiving-face and on the other side a series of curved internal-reflecting faces curved to correspond to parabolic cylinders Whose focal lines lie in the receiving-face and whose vertices lie in front; of said face; substantially as described.
3. Au illuminating prism-plate having on one side a receiving-surface and on the other side a series of plane refracting-faces u, and a series of reflecting-faces w, the latter being curved to correspond in transverse cross-section to a parabolic curve Whose 'focal point lies at Z) on the receiving side of the plate and Whose vertex lies at "a on a line passing through the point I) and parallel to the rays reflected from the parabolic face 10; substantially as described.
4. An illuminating prism-plate having a series of prism-faces curved to correspond to portions of parabolic cylinders with the focal lines of these cylinders on the receiving-surface of the plate, and so disposed and adapted as to direct in one direction all rays falling on the receiving side of the plate at the focal lines; substantially as described.
. In testimony whereof I have hereunto set my hand.
FRANK L. O. VVADSWORTH.
O. BYRNEs, G. I. HOLDSHIP.