US3423582A

US3423582A - Lighting unit

Info

Publication number: US3423582A
Application number: US606738A
Authority: US
Inventors: William B Elmer
Original assignee: Sylvania Electric Products Inc
Current assignee: GTE Sylvania Inc
Priority date: 1967-01-03
Filing date: 1967-01-03
Publication date: 1969-01-21
Anticipated expiration: 1986-01-21

Description

Jan. 21, 1969 w. a. ELMER 3,423,582

LIGHTING UNIT Filed Jan. 5, 1967 FIG.2

B b o A FIGA FIG.3

WILLIAM B. ELMER INVENTOR BYM 6 ATTORNEY United States Patent O Claims ABSTRACT OF THE DISCLOSURE A reflector for producing a generally rectangular beam for illuminating an area for taking photographs. The reflector is composed of four parabolic quadrants, each with a somewhat different axis, so that each produces a beam in a quadrant of a rectangle that it is desired to illuminate, the reflector surface being dimpled and the filament large enough to be only vaguely focussed, in order to smooth out the light into a single rectangle. The quadrants are as it cut from a paraboloid of revolution, the vertical cuts being made in a plane passing through the focal point at a 4 /2 angle, the horizontal at a 3%, angle. The commercial reflector is stamped from a single piece of sheet metal.

BACKGROUND OF THE INVENTION Field of invention The invention relates to equipment for producing a beam of light. Such equipment generally includes a lamp and reflector. The present application is directed particularly to equipment having a lamp of the tungsten filament type in a quartz envelope containing a halogen vapor, usually iodine or bromine. Such lamps are now generally called tungsten halogen lamps. The invention is especially directed to the combination of such lamps with a reflector giving a generally rectangular beam, useful in illuminating an area for photography.

Description of the prior art The prior devices in the field generally used beams of circular cross-section, which can be produced simply. US. patent application Ser. No. 414,073 filed Nov. 27, 1964 and now U.S. Patent No. 3,331,960, dated July 18, 1967 by the applicant taught the production of a rectangular beam by overlapping the beams from four separate parts of a reflector, the curvature of the parts diverging from the parabola.

SUMMARY OF THE INVENTION The applicant has discovered that a generally rectangular beam can be produced by using four approximate quadrants of the same parabola, each being tipped toward the axis of the resultant piece, so that the light from each quadrant crosses the reflector axis and illuminates a quadrant of a rectangle at a distance from the reflector, the filament being large enough so that the image of the filament on the rectangular field to be illuminated will not produce appreciable non-uniformity in the beam. The reflector surface can be etched or peened to diffuse the image further.

In practice, a paraboloid of revolution can be formed from sheet metal, and if set with its main axis horizontal, one quadrant can be cut from it by cutting in two planes transverse to each other, for example, one nearly horizontal and one nearly vertical. The horizontal cut is made in a plane passing through the focal point of the paraboloid at small angle, say about 3 /2 to the horizontal and directed downwardl toward the rear of the reflector. The other cut is made in a plane at a small angle, say about 4 /2 to the vertical, directed toward the quad- 3,423,582 Patented Jan. 21, 1969 ICC rant to be cut, and passing through the focal point. Quadrants cut in this manner are placed opposite each other on opposite sides of the axis of the assembled reflector, and another type of quadrant, in which the 4V2 cut is made on the other side of the vertical and the 3 /2 cut made on the other side of the horizontal, are used as the intermediate quadrants. The final reflector will generally be made in one piece, with each quadrant being the same in size, shape and position as if made up of four separate quadrants joined together.

BRIEF DESCRIPTION OF DRAWINGS In the drawings, FIG. 1 is a general view of the finished device; FIGURE 2 is a schematic diagram of how the cuts are taken; FIGURE 3 is a view of the open end of the reflector; and FIGURE 4 is a view of the rectanglar field illuminated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGURE 1, the reflector 1 has a hole 2 at its apex through which the lamp 3 extends into the concave front of said reflector 1. The lamp 3 has the envelope 4 with the coiled-coil filament 5 transverse to the axis of the reflector, and supported in the envelope 4 by lead-in Wires, in the usual manner, not shown. The envelope 4 has a base of the usual type (not shown) inside socket 6, into which it fits and is held.

The reflector 1, although in a single metal piece, is made up of four quadrants. The quadrants can be considered as being cut from a paraboloid of revolution 7 as in FIGURE 2. Quadrant A is cut by one plane passing through the focal point P of the paraboloid 7 at a dihedral angle C of about 3 /2 to a plane passing through the axis 8, and by another plane 9 making an angle D of about 4 /2" with a plane at right angles to the plane through the axis 8. That is if the angle of 3 /2" is to a horizontal plane, the angle of 4 /2 would be to a vertical plane.

This makes one quadrant A, and in FIGURE 3, showing a front view of the reflector 1, this quadrant A is used in the two opposite but contiguous positions shown, with a quadrant B intermediate each of the quadrants A and joined to them to form an integral unit.

The quadrant B would be similar to A, but the angles would be opposite or reversed. That is, if the angle 3 /2" in FIGURE 2 for quadrant A extends downwardly, the corresponding angle for quadrant B would extend upwardly; and if the 4 /2" angles of quadrant A is to the right at the reflector, then in quadrant B it would be to the left at the reflector. We refer to the direction at the reflector because the plane of the cut crosses the axis 8 at the focal point.

Two quadrants A are made and two quadrants B; only one quadrant A can be cut from a single paraboloid, because of the angles. Although we have spoken of cutting the segments out and then fitting them together to form my composite reflector, the commercial units are punched out of a single sheet of metal by a die formed to the same shape as it cut as described.

The resultant reflector 1 and lamp 3 are put together with the filament 5 of said lamp 3, or the center of said filament, being at the focal point with the filament transverse and the reflector axis. However, the lamp can be moved in or out of the reflector, somewhat away from the focal point, to spread or narrow the beam. FIGURE 4 shows a schematic diagram of the generally rectangular field to be illuminated by my device. The field is divided into four rectangular quandrants A, B, A, B. The beam from the top quadrant A in FIGURE 3 will illuminate the lower quadrant A in FIGURE 4 and vice versa, the beam from each quadrant crossing the axis 8 of the reflector 1 because of the tipping of the reflector quadrants toward said axis. The same relationship exists between the quadrant B on the reflector of FIGURE 3 and on the rectangularly illuminated field of FIGURE 4.

The center a, b of beams A, B are approximately along the diagonals 10, 11 and about two-thirds of the distance from the center of the illuminated rectangle to the corner. The beams from the four quadrants will overlap at the center portion of the rectangle, so that a centering of each beam at the distance given results in most uniform illumination.

In one embodiment of the invention, the original paraboloid was formed from a parabola =0.5714y and the open face was about 2.5 inches in diameter. The lamp used was the kind designated in the industry as a DVY.

What I claim is:

1. A lighting unit for producing a generally rectangular beam, said unit comprising: two quadrants of a paraboloid of revolution, each quadrant being bounded by two planes, one plane passing through the focal point of the paraboloid at a small dihedral angle and the other plane passing through said focal point at a small dihedral angle to a plane which is at a dihedral angle of about 90 with said plane through the axis, said quadrants being set opposite each other on opposite sides of said axis to form two contiguous portions of the surface of a reflector; and two intermediate quadrants, each set between the other two quadrants and joined therewith to form an integral complete reflector, each of said intermediate quadrants being quadrants of a paraboloid substantially identical with that of the first two quadrants, but in which the boundary planes are at dihedral angles with the axis plane 4 and the plane at about 90 to it, such that the dihedral angles are the same in magnitude but opposite in direction to those of the two first-mentioned quadrants.

2. The lighting unit of claim 1, in which the firstmentioned small dihedral angle is about 3 /2 and the second-mentioned small dihedral angle is about 4 /2.

3. The lighting unit of claim 1, in which each quadrant of the reflector is set to direct light to a different quadrant of the rectangular field to be illuminated.

4. The lighting unit of claim 3, in which each quadrant of the reflector reflects a beam across the axis of the reflector as a whole.

5. The lighting unit of claim 4, in which the beam from each quadrant is centered on a point on a diagonal of the rectangular field to be illuminated and about twothirds of the distance from the center of the rectangle to the corner along the diagonal.

References Cited UNITED STATES PATENTS 1,417,926 5/1922 Lester 24041.37 1,663,008 3/1928 Johnson 24041.37 3,132,812 5/1964 Strobel 240103 XR 3,331,960 7/1967 Elmer 240-403 NORTON ANSHER, Primary Examiner.

ROBERT P. GREINER, Assistant Examiner.

US. Cl. X.R. 24011.4, 103