US3023304A - Shadow box - Google Patents

Description

Feb. 27, 1962 A. PETERSON SHADOW BOX Filed Aug. 7, 1958 INVENTOR. Lorenz A.Pe1erson ATTORNEYS United States Patent 3,023,304 SHADOW BOX Lorenz A. Peterson, Golden, Col0., assignor to Sinclair Oil & Gas Company Filed Aug. 7, 1958, Ser. No. 753,720 1 Claim. (Cl. 240-1) My invention relates to reproduction of drawings and the like and in particular provides a shadow box suitable for preparing tracings, retouching photographs and the like.

Shadow boxes, otherwise known as light tables, light boxes and retouching frames, conventionally include an enclosed box, the top of which is a sheet of frosted glass. The box contains a light source, thus lighting the frosted glass from beneath, to permit it to be used as a table for supporting drawings, photographic negatives, or the like, while at the same time transmitting light from beneath the drawing or negative to facilitate tracing or retouching. These prior devices are conventionally quite large and cumbersome because of the need to provide adequate space for the light source beneath the frosted glass. As a consequence, they cannot be readily transported and usually are separately mounted by themselves as an individual table used solely for the purpose.

It is an important object of my invention to provide an improved shadow box construction which can be made in any convenient size, which is light in Weight such that it could be carried from desk to desk, and which occupies a relatively small space such that it can be stored away when not required.

These and other objects of my invention are essentially obtained by utilizing the edge-lighting characteristics of certain plastic materials, such as methyl methacrylate resins. As is well known, resinous methyl methacrylate polymer, when extruded in tubing or cast in sheets, has the property of conducting light from one end of the tube to the other or from one edge to the other of a sheet with minimum light loss along the sides of the tube or through the faces of the sheet. I propose to utilize this edgelighting characteristic in the construction of a shadow box, thus making it unnecessary to provide an enclosed box beneath the tracing plate for confining the illuminationsource and thus rendering it practicable when so desired, to light the shadow box simply by employing a desk lamp. In order to make use of the edge-lighting properties of materials, such as methyl methacrylate resin, in the construction of a shadow box, I engrave, sandpaper or otherwise treat a substantial area of the surface of one face of a sheet of the edge-lighting material to define the flat working area on which tracing or other work is to be accomplished. Simply by positioning the illumination source along the edge of the sheet, I am thus able to pipe light through the sheet which then diffuses through the roughened portion providing a lighting effect similar to the effect of frosted glass illuminated from the obverse side in a conventional shadow box. In a more refined version, I light two opposite edges of a rectangular sheet of edge-lighting material having a roughened working area on one face while covering the other pair of opposite edges of the sheet of edge-lighting material with a reflecting material such as aluminum foil. In another modification, I have found it convenient to light a sheet of edge-lightingmaterial by providing a second roughened surface area against which the illumination source can be placed as an alternative to placing the illumination source against the edge of a sheet in order to introduce light into the sheet and achieve edge-lighting of the sheet.

' For a more complete understanding of the practical application of the principles ofmy invention, reference is made to the appended drawings, in which:

FIGURE 1 is an isometric view of a shadow box constructed in accordance with invention;

FIGURE 2 is a cross-section taken at line 2-2 in FIGURE 1;

FIGURE 3 is a cross-section taken at line 3-3 in FIGURE 1;

FIGURE 4 is an exploded view of another shadow box constructed in accordance with my invention; and

FIGURE 5 is an enlarged fragmentary vertical section taken at one end of the device shown in FIGURE 4.

Referring to FIGURES 1-3, the reference numeral 10 generally indicates a shadow box constructed in accordance with my invention which basically includes a flat cast sheet of methyl methacrylate resin. The sheet is rectangular in shape, ten inches wide, fifteen inches long and three-eighths of an inch thick, has a specific gravity of 1.18, an index of refraction, 11 of 1.49 and about 91% light transmission at 4,500 Angstrom units. Sheet 11, on its top face is thoroughly sanded with No. 00 sandpaper to provide a roughened central rectangular surface 12. In preparing rectangular working surface 12, margins 13, 13 of one inch width along each side of sheet 11 and margins 14, 14 of two inches width along each end of sheet 11 are left smooth for reasons which will be described later. The bottom face 15 of sheet 11 is also left smooth. In a simplified version of the shadow box of my invention, sheet 11 is then suitable for employment directly as a shadow box simply by taking a desk fluorescent light fixture and placing its illuminating tube adjacent an end edge or a side edge of sheet 11. The light thus introduced into sheet 11 through its edge, is transmitted through sheet 11 and illuminates the roughened rectangular working area 12 sufliciently to permit use of sheet 11 as a tracing board or the like. The smooth margins 13, 13 and 14, 14, function to concentrate light emission through working area 12 and to prevent loss of light through areas normally required for fastening drawings and the like. It will be further noted, however, that the entire top surface of sheet 11, including working area 12 and margins 13, 13 and 14, 14 effectively is a unitary flat surface which facilitates the employment of drafting instruments, such as T-squares, which may be required in connection with the operations to be performed with shadow box 10.

In a preferred construction, however, as more fully shown in FIGURES 1, 2 and 3, it is desirable to provide shadow box 10 with a self-contained illumination source and a base and to provide durable, accurately squared edges facilitating the employment of drafting instruments. Thus, still referring to FIGURES 1-3, sheet 11 at its ends, is provided with illumination sources 16, 16, one such source 16 being associated with each end of sheet 11. Each illumination source 16 includes an elongated, tubular electric lamp 17, which can be a fluorescent lamp or an incandescent lamp, the former being preferred. Each lamp 17 is housed in a curved aluminum reflector channel 18, the long edge portions 19, 19 of which are spaced apart about /1" and extend beyond lamp 17 about the same distance.

Sheet 11 is also provided with a frame constructed of four wooden slats, 20, 2t 20, 2.0 and two wooden side frame members 22, 22. Side frame members 22, 22 in particular have a rectangular cross-section and are accurately squared, having dimensions of approximately 15" x x Mr", and are each provided with a central groove 24 in one 15 x face. Each groove 24 has a cross-section of approximately Ma" x A and is fitted with a single wire insulated conductor 25. The grooved face of each frame member 22 is furthermore covered with a strip 23 of aluminum foil, which is cemented to the entire grooved face covering groove 24.

Frame members 22, 22 are placed parallel to each other spaced 10" apart with sheet 11 received between them and with their aluminum foil 23 covered grooved faces abutting the long edges of sheet 11. Each slat is .0 /2" X 4" x 7 and two slats 2d, 2d are positioned transversely across frame members 22, with a slat 2t positioned at each end such that the ends of the two slats 2'9, 21) are positioned flush above the ends of frame members 22, 22. Slats 21?, 2d and frame members 22, 2a are then glued and screwed together, and the assembly is inverted, carefully holding sheet 11 in position, after which the remaining slats 2%, 23 are similarly positioned on the other side of the assembly and glued and screwed to frame members 22, 22. A sheet of A" plywood, 13 /2" x is then placed snugly between the two slats 2t 2% on the underside of box 10 covering under face 15 of plastic sheet 11 and is glued to frame members 22 along their under faces.

Edges 19, 19 of reflectors 18, 13 are placed over the shorter ends of sheet 11, bringing lamps 1'7, 17 to a position closely adjacent the end edges of sheet 11. Edges 19, 19 thus overlie smooth margins 1d, 14 and slats 2 20 on the top side of sheet 11 and lie under the ends of bottom surface 15 and slats 2%, 26 on the under side of sheet 11. Suitable rivets 21 are passed through the end portions 19, 19 of reflectors 18, 18, slats 2t), 2% and sheet 11 at each end of sheet 11 to secure illumination devices 16, 16, one at each end of sheet 11.

The ends of reflectors 18, 13 extend beyond each side edge of sheet 11 to the outer faces of side frame memers 22, 22, and electrical conductors 25, 25 are connected at such reflector ends to lamps 17 and an external two wire insulated conductor cable 26 to connect lamps 17, 17 in series across cable 26.

It will be evident that shadow box 111 is utilized simply by connecting conductor cable 26 to a suitable source of electric power to energize lamps 17, 17, thereby introducing light edgewise into the ends of sheet 11. The smooth underside 15 and marginal portions 14, 14 and 13, 13, and aluminum strips 23, 23 prevent the escape of light from sheet 11 except through roughened central surface area 12 which becomes illuminated. Frame members 22, 22, as indicated above, are accurately squared, and thus not only can shadow box 10 be employed as a conventional tracing table but at the same time T-squares and other drawing instruments can be employed in a conventional manner.

Although I have described shadow box 115 provided with edge-lighting devices, I have found that if a face of a sheet of cast acrylic resin which has edge-lighting properties is roughened, not only will such roughening facilitate escape of the light but it will also permit introduction of the light with exactly the same results as if light had been introduced along the edge of the sheet. Thus in FiGURES 4 and 5 I have illustrated a second arrangement of a shadow box 31? which includes basically a rectangular sheet of methyl methacrylate resin having dimensions and properties similar to those of sheet 11, although dimensions are in no way critical. Sheet 31, on its upper face, is similarly roughened by sandpapering over its entire surface area, except for a transverse smooth strip 32 which is left to separate the roughened area into a narrow roughened portion 33 adjacent one end of sheet 31 and a larger roughened portion 34 covering most of the top side of sheet 11. Strips of aluminum foil 35 are cemented to all four edges of sheet 31. A curved reflector channel 36, provided at its base with an angled portion 37, is received over ground portion 33 of sheet as shown more clearly in FIGURE 5, with its angled portion 37 extending grasping the underside of sheet 11 to hold reflector channel 36 firmly in position over narrow roughened area 33. Reflector 36 in its thusly clamped position defines an aperture extending transversely across roughened portion 33 of sheet 11 in which an elongated, tubular-type incandescent lamp 333 is mounted.

It will be evident that shadow box 311 is employed simply by connecting lamp 38 to a suitable power supply. The light thus generated enters sheet 31 through ground portion 33 and can exit only through ground portion 34 which serves as the copying table portion of shadow box 36.

From the preceding description, it will be apparent that many variations within the principles of my invention are permissible. It is, however, always desirable to keep the roughened surface, through which light is to be exited from the acrylic resin sheet to a minimum size required by the particular copying, retouching or like operation for which the box is designed in order to concentrate the light in the working surface and thereby minimize the size of lamp required to illuminate the surface.

I claim:

A shadow box which includes a fiat sheet of edgelighting material, means on one face of said sheet defining a flat substantially roughened working area on said one face of said sheet, means defining a second substantially roughened, area on said one face of said sheet, means defining a substantially smooth area on said one face of said sheet separating said second named roughened area from said first named roughened area, and illuminating means positioned adjacent said one face of said sheet overlying said second roughened area whereby said working area of said sheet is lighted by said illuminating means.

References Cited in the file of this patent UNiTED STATES PATENTS 1,139,723 Rich May 18, 1915 1,466,038 Brubaker Aug. 28, 1923 1,760,253 Parrish May 27, 1930 2,120,813 Riotte June 14, 1938 2,214,209 Triplett Sept. 10, 1940 2,347,665 Christensen May 2, 1944 2,594,081 Chlenker -2 Apr. 22, 1952 2,671,163 Minter Mar. 2, 1954 FORElGN PATENTS 664,193 Great Britain Ian. 2, 1952 167,111 Australia Feb. 28, 1956

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