US 3112075 A
Description (OCR text may contain errors)
A. 1.. SPARKS 3,112,075
LAMP HOUSINGS FOR USE IN CONNECTION WITH PHOTOGRAPHIC APPARATUS Nov. 26, 1963 Filed July 16, 1962 ///l E/YTOR ARTHUR .L. sP/mKs BY M iw fi United States Patent 3,112,075 LAMP HOUSINGS FOR USE IN CONNECTION WITH PHOTOGRAPHIC APPARATUS Arthur Leonard Sparks, Thalia Works, Thayers Farm Road, Beckeuham, Kent, England Filed July 16, 1962, Ser. No. 210,174 Claims priority, application Great Britain July 27, 1961 2 Claims. (Cl. 240-20) This invention relates to improvements in lamp housings for use in connection with photographic apparatus, and has for its object to provide a light source the illumination from which is evenly difiused over an area which may contain a photographic negative, and not concentrated on any one portion thereof. Such a concentration often causes over exposure or uneven exposure of a photographic print.
According to the said invention photographic printing apparatus comprises an open bottom outer casing, light filtering and diffusing means extending across the said open bottom, a plurality of electric lamp holders each mounted in an individual reflector unit arranged to direct rays towards the said light filtering and diffusing means, the said reflector units with their respective lamp holders being spaced around and supported by a central block rotatably mounted on the ceiling of the outer casing, an electric lead above the top of each reflector unit and serving the lamp holder therein, said leads extending from a contact plate fast with the central block, said contact plate having a brush connection with feed contacts fixed in the ceiling of the casing, and means for rotating the reflector units and central block assembly within the casing and for cooling the apparatus consisting of an air jet tube mounted on the casing at an angle to direct its air jet upon the lamps and reflectors. There is preferably a light baffle carried within each reflector and positioned to cut off a substantial portion of direct rays from a lamp held in the holder which would otherwise pass towards light filtering and difiusing means at the open bottom of the casing.
In order that the said invention may be readily understood, an embodiment thereof will be described by way of example with the assistance of the accompanying drawings wherein:
FIGURE 1 is an elevation of the embodiment mainly in vertical section; and
FIGURE 2 is a perspective view of a four-lamp reflector employed in said embodiment.
Referring to the drawings there is a cylindrical outer casing I intended to be used on a vertical axis. The casing has an inturned annular lip 2 around its bottom edge so that the light passing out of the casing is projected through a central opening 3 of less diameter than that of the main body of the casing whereby direct light rays passing substantially vertically downwardly from a lamp or lamps disposed away from the central axis of the casing do not pass through the central opening 3.
In the embodiment four lamp-and-reflector units are employed mounted in the cylindrical outer casing disposed and arranged so as to rotate on the vertical axis of the casing. These four reflector units are equiangularly spaced within the casing and are built together as a single rotatable body. For this purpose the reflectors are made from a pair of inverted troughs 4 and 5 of substantially parabolic section which intersect each other at rightangles providing four separate reflectors one at each end of each trough extending radially from a common centre and so disposed as to direct the rays of light emerging from the lamps housed therein downwards towards the opening 3. Their respective outer extremities are open as shown at 4a in FIGURE 1 and spaced away from the casing wall a short distance, and an electric lamp holder 6 3,1 12,075 Patented Nov. 26, 1963 ice is mounted centrally in each reflector trough by means of holes 6a (FIGURE 2) approximately on the focal axis, and directed downwardly. The holders are situated as near as possible to the respective ends of the reflectors so that filament or other lamps 7 secured therein just clear the casing wall.
Below the casing is a circular diffusing chamber 8 with means for supporting a light filter slide 9 and a diffusing plate 10.
The rotatable body formed by the four combined lampand-reflector units made by the intersecting troughs 4 and 5 is mounted on a central rotatable block 11 having an upwardly extending spindle 12 (FIGURE 1) mounted in suitable bearings in a bearing housing 13 carried by the ceiling 14 of the casing 1, and above this is any suitable form of cowling 15 having air openings.
Extending radially from the central block 11 are four horizontal tubes 16, one above each reflector, containing the electric leads for the lamp holders, and the feed lead is led out of the tube at an appropriate place along its length to a circular contact plate 17 fast with the rotatable block 11 and which is engaged by contact brushes '1-8 electrically connected to respective terminals fixed to the ceiling 14 under the cowling 15.
Within each reflector is fixed a thin rod 19 extending down from the top parallel to the axis of the lamp holder 6, and on the end of the rod is a light baflle 20 so bent and arranged to assist in cutting off :a substantial portion of direct rays from the lamp 7 which might pass to and through the central opening 3 in the bottom of the casing.
Motive power for rotating the body of the combined lamp-and-reflector units (comprising the reflectors, lamp holders, lamps, central block and its tubes, and contact plate) is derived from an air jet tube 21, the orifice of which projects into the interior of the casing 1 at such an angle that an air current from said air jet impinges upon the sides of the lamps and reflectors causing rotatory movement thereof. In the embodiment, a speed of about 60 rpm. has been found to provide optimum conditions for most work required of the light source, but the speed can, of course, be varied as necessary. The air issuing 'from the jet 21 is provided by any suitable means, which can be sited independently of the lamp housing; the air current within the housing serves also as a means of cooling the entire apparatus.
It is to be understood that any plurality of lamp-andreflector unit-s, other than four, may be used.
A lamp housing constructed substantially in accordance with the present invention provides a bright and well diffused light over a given area upon which photographic negatives may be placed without any fear of uneven illumination caused by peak bright spots.
1. Photographic printing apparatus comprising an open bottom outer casing, light filtering and diffusing means extending across the said open bottom, a plurality of electric lamp holders each mounted in an individual reflector unit arranged to direct rays towards the said light filtering and diffusing means, the said reflector units with their respective lamp holders being spaced around and supported by a central block rotatably mounted on the ceiling of the outer casing, an electric lead above the top of each reflector unit and serving the lamp holder therein, said leads extending from a contact plate fast with the central block, said contact plate having a brush connection with feed contacts fixed in the ceiling of the casing, and means for rotating the reflector units and central block assembly within the casing and for cooling the apparatus consisting of an air jet tube mounted on the casing at an angle to direct its air jet upon the lamps and reflectors.
2. Photographic printing apparatus according to claim 1 in which the reflector units are made as diametrically opposite pairs from inverted troughs of substantially parabolic section, said troughs intersecting one another dividing them each into two individual reflectors each of which individual reflectors extends radially from the central block with an open end spaced away from the casing wall, the said lamp holders being situated near the said open ends to locate lamps carried thereby just clear of the said wall, in conjunction with a light baflle within each reflector to assist in cutting otf some of the direct light rays which might pass on to the light filtering and 10 diffusing means.
References Cited in the file of this patent UNITED STATES PATENTS Longley June 3, 1941 Harling Feb. 24, 1959 Belau May 16, 1961 FOREIGN PATENTS Great Britain Apr. 15, 1940