Metal halide accent fixture with adjustable reflector/beam spread

[0001] This invention relates to lighting fixtures, and more importantly to fixtures usable for indoor or outdoor lighting and which are adjustable to provide various beam spreads.

[0002] A particular lighting fixture type may need to be adjustable to provide various beam spreads to accomplish a given task; e.g., in one location a fixture may require a wide spread to illuminate a specified area and in another location may require more intense illumination over a smaller area. While fixtures are available with some adjustment in beam spreads, a limited number of beam spreads are available.

[0003] There is a need for a low cost, compact, metal halide lighting fixture which is suitably sealed to permit outdoor installation and which is adjustable to provide an infinite range of beam spreads from a spotlight to floodlight, while maintaining a relatively uniform intensity across the beam, particularly without low intensity or dark spots at different beam spreads. Such a lamp should also require lower maintenance than other metal halide lamps presently available.

[0004] The invention described herein comprises a lighting fixture formed of three generally cylindrical threadedly engaged parts, which include a lamp housing, an intermediate sleeve and a focusing sleeve. The lamp housing is connected through a swivel connection to a lamp base or mounting member. Ports are provided in the mounting member and the lamp housing for conducting wires from the lamp base past the swivel connection and the mounting member to an exterior connector.

[0005] The lamp housing includes an exterior groove containing an O-ring seal which seals against an internal surface of the intermediate sleeve. At the opposite end of the intermediate sleeve is a groove containing an O-ring seal which seals against a cylindrical internal surface of the focusing sleeve. An elongated lamp, such as a T-6 halide lamp having an axially extending arc tube, is secured in the lamp housing.

[0006] The focusing sleeve includes internal threads which engage external threads on the intermediate sleeve. Carried within the focusing sleeve is a reflector member having a generally concave interior surface. A lens is secured to the inside of the focusing sleeve and a light-absorbing layer is secured between the reflector member and the lens. The focusing sleeve includes a groove and two internal ridges, one of which serves as a stop for locating the reflector member and the other which cooperates with a locking ring carried in the groove to secure the lens in place. Turning the focusing sleeve also carries the intermediate sleeve causing the focusing sleeve and the reflector member to move axially with respect to the lamp light source, i.e., arc tube. This causes the light output of the light fixture to change from floodlight to spotlight and vice versa.

[0007] This invention utilizes a particular characteristic of standard metal halide lamps to cooperate with the reflector and adjustment mechanism to provide a continuously variable beam spread with relatively uniform light level across the beam from full flood to narrow beam.

[0008] The adjustment range of the beam from flood to spot is determined by varying the position of the reflector relative to the elongated arc tube of the lamp. This produces a relatively uniform light level without dark spots across the beam at any position as well as a markedly wide beam spread depending upon the longitudinal adjustment of the apertured reflector.

[0009] The elongated metal halide lamp is mounted on the central axis of the fixture and extends through a central aperture of the reflector and the elongated arc tube or light source is positioned on the axis of the lamp. The generally cylindrical light source envelope has a relatively large diameter compared with the size of the reflector. In the usual prior art fixture, the goal is to provide the smallest point source of light captured by the largest practical collector. A typical incandescent auto headlamp, for example, has a very small filament positioned as closely as possible to the focal point of a large, parabolic reflector. In the fixture described herein, the reflector may be conical or somewhat curved, as in a parabola, and its maximum diameter is only about two and one-half times the diameter of the lamp and just slightly over seven times the diameter of the arc tube.

[0010] When the fixture is adjusted to the maximum “spotlight” position, the inner edge of the arc tube (that edge closest to the lamp housing) is substantially aligned with the inner edge of the reflector. As the adjusting sleeve is moved toward the “floodlight” position, the reflector is moved rearwardly away from the arc tube until at full floodlight position the arc tube is positioned closer to the outer edge of the reflector (closer to the lens).

[0011] One feature of this invention is that the focusing function is performed without opening the housing, rather by merely twisting the focusing sleeve which changes the longitudinal position of the reflector.

[0012] Another feature of this invention is that the reflector may be a spun metal or a casting.

[0013] Still another feature is the simplicity of the design, which allows lamps of various wattage, e.g. 35 watt or 75 watt, to be produced merely by scaling up or down some of the parts of the fixture.

[0022] Referring now to FIG. 1, which is a perspective view of a metal halide lighting fixture 10 according to the invention, fixture 10 includes a lamp housing 12, an intermediate sleeve 14 and a focusing sleeve 16. The lamp housing is secured to a mounting assembly 17 which includes certain parts discussed below, including a flange 20 and a sleeve 18 which is threadedly engaged with flange 20.

[0023] FIG. 2 is an exploded longitudinal sectional view of the lighting fixture 10 of FIG. 1; and FIG. 3 is a longitudinal sectional view of the fixture as assembled. In FIGS. 2 and 3 are shown the lamp housing 12, the intermediate sleeve 14, and the focusing sleeve 16. Shown separated from lamp housing 12 in FIG. 2 is a mounting assembly 17, which incorporates a body 15, a sleeve 18 and a flange 20 to provide a swivelable mounting structure for lighting fixture 10. Note that mounting assembly 17 is secured to the cut-out portion at the right end of lamp housing 12 by means of a screw 22 passing through body 15 and secured in threaded port 24. This permits lamp housing 12 to pivot around screw 22. Once the angle between lamp housing 12 and mounting assembly 17 is established, this angle is secured by means of a set screw 26, which is accessible through an opening 28 to engage body 15 to retain the desired angle.

[0024] A lamp socket 30 includes spring members 32, which retain a metal halide lamp 34 (in this case a compact T-6 lamp). Lamp socket 30 is secured in lamp housing 12 by means of a pair of screws 36. Wires extending from the lamp socket 30 are fed through a port 38 in lamp housing 12 and from there into and through a channel 40 in body 15 and a port 42 in flange 20. The portions of the wires installed in lamp housing 12 are coiled or bent, and the port 38 is potted to secure the wires in place and to protect them from moisture. The wires are also subjected to an anti-wicking process to further prevent moisture from wicking along the wires to the lamp socket.

[0025] Lamp housing 12 includes on its exterior surface a groove 44 which receives an O-ring 46. This O-ring 46 seals against an interior surface 48 of intermediate sleeve 14. Lamp housing 12 also includes external threads 50 which mate with internal threads 52 in intermediate sleeve 14. A plurality (e.g., 3) of openings 54 around the periphery of intermediate sleeve 14 provide “weep holes” permitting moisture to escape from the interior of fixture 10. A set screw 56 having left-hand threads is set in a cap screw 58 threaded into intermediate sleeve 14. Cap screw 58 is turned into intermediate sleeve 14 to force screw 56 against a surface of lamp housing 12 to secure the relative positions of lamp housing 12 and intermediate sleeve 14.

[0026] Intermediate sleeve 14 has an external groove 60 which receives an O-ring 62 which seals against a smooth internal surface 64 of focusing sleeve 16. Focusing sleeve 16 also includes internal threads 66, which mate with threads 68 on the external surface of intermediate sleeve 14. A generally concave reflector member 70, which includes external threads 71 mating with threads 66 is positioned within sleeve 16. Lamp 34 extends through an aperture 70a in reflector 70. A pair of screws 72, having upstanding heads, are located on one face of reflector member 70 to provide a means for turning reflector member 70 on threads 66. Other irregular surface features may be formed on the right-hand surface of reflector 70 as aids to turning it on threads 66. An internal ridge 74 provides a stop limiting travel of reflector member 70 toward the left. A second internal ridge 76 serves to locate a lens 78, which is secured against ridge 76 by means of a locking ring 80 which seats in a groove 82. A layer of anti-reflection material 84 is secured to an inside surface of focusing sleeve 16 between ridges 74 and 76 to prevent excessive internal reflections. Anti-reflecting paint is preferably applied to the inside surface of focusing sleeve 16 to the left of locking ring 80, as shown in FIG. 3.

[0027] FIG. 4 is a cross-sectional view of an alternate form of reflector member 70b different from member 70 of FIGS. 2 and 3. Member 70 is typically machined from a casting. For many applications, a reflector member 70b, which may be of spun aluminum, will be quite adequate and is less expensive to fabricate.

[0028] FIG. 5 is a view, partly in section, of the lighting fixture 10 showing details of lamp 34 in relation to reflector member 70. Reflector member 70, which may be of the type shown in FIG. 4, abuts against ridge 74 and is held against ridge 74 by means of a ring member 71, which is threadedly engaged with threads 66. Lamp 34 includes an elongated light source, an arc tube 90 in which, as shown in FIG. 5, its longitudinal center 92 identified in FIGS. 5 and 6 by a black dot in the center of arc tube 90 is behind aperture 70a. Lamp 34 has an elongated clear glass envelope 88 secured to lamp socket 30. Arc tube 90 is in the form of a cylinder of significant diameter and axial length. Focusing of light from lamp 10 from a spot to a floodlight position or vice versa is accomplished by rotating focusing member 16 and intermediate member 14 on threads 52 such that the reflector member 70 moves axially with respect to arc tube 90. Thus with respect to FIG. 5, illumination from arc tube 90 extends radially against reflector 70 and is mostly reflected from reflector 70 as a narrow beam through aperture 70a and through lens 78. Other illumination is directed straight through lens 78. In this position, fixture 10 operates as a spotlight.

[0029] FIG. 6 is a view similar to FIG. 5 but showing reflector member 70 or 70b in a significantly different position relative to arc tube 90. Focusing member 16 and intermediate sleeve 14 have been rotated such that sleeve 14 has moved rearwardly such that the longitudinal center of arc tube 90 is in front of the aperture 70a. The change of relative positions of the two O rings shown as black areas in FIGS. 5 and 6 also illustrates the difference in position of the arc tube 90 between FIGS. 5 and 6. In FIGS. 5 and 6, the longitudinal center 92 of the arc tube 90 is marked by a dot and a vertical lead line. Illumination from arc tube 90 is reflected in several angles or directions from reflector member 70b through lens 78, or directed straight through lens 78. When the parts are in the position shown in FIG. 6, fixture 10 operates as a floodlight.

[0030] As an example, a Philips 35/T6/830 lamp has an arc tube approximately 0.375 in. long and a diameter of approximately 0.25 in. The glass envelope 88 is approximately 0.75 in. in diameter. The maximum diameter of reflector 70b is 1.805 in., and the diameter of the aperture is 0.842 in.

[0031] FIGS. 7A and 7B are graphs showing typical lighting patterns of fixture 10 in floodlight and spotlight positions, respectively, as projected on a grid. Although both patterns show a reduction in light intensity toward the outside edges, both the floodlight pattern and the spotlight pattern are complete and clean without the usual dark spots which are commonly seen in the light patterns of adjustable beam illuminators using lamps with transverse filaments, such as flashlights. More details relative to illumination patterns of fixture 10 are described in the report of Luminaire Testing Laboratory, Inc. attached as an Appendix at the back of the present application.

[0032] The above-described embodiments of the present invention are merely descriptive of its principles and are not to be considered limiting. The scope of the present invention instead shall be determined from the scope of the following claims including their equivalents.