Light Fixture

In the art of commercial and industrial lighting fixtures such as disclosed, for example, in U.S. Pat. Nos. 3,246,135, 3,254,205, 3,609,337 and 3,610,915, it is desirable to provide for tightly sealing the fixture housing which receives the lamp element and the reflectors in order to avoid the seepage of dust, dirt and moisture into the housing and onto the lamp element and reflectors. As shown in above U.S. Pat. Nos. 3,246,135 and 3,609,337, one form of seal is provided by positioning a resilient gasket between the frame-like surface on the cast metal housing and the covering glass lens element which is retained by a surrounding cast metal frame. Due to the cast construction of the metal housings and frames and the difficulty of obtaining precisely parallel surfaces between each housing and frame, it is frequently difficult to obtain a positive, fluid-tight and dependable seal which prevents the seepage of dust and moisture into the lamp and reflector chamber.

It has also been found desirable to provide a high intensity commercial and industrial light fixture with means for conveniently changing the projected angle of the light from the fixture in order to change the area of illumination or to concentrate the projected light in a specified area. Furthermore, it has been found desirable to provide for conveniently constructing the light fixture in different sizes for different intensities of illumination and thus be able to accommodate electric lamp elements of different sizes or lengths.

It is apparent after carefully reviewing the disclosures of the above patents and of other prior art lighting fixtures such as disclosed in U.S. Pat. Nos. 1,873,392, 2,849,598 and 3,679,886, that none of the light fixtures which have been either constructed or proposed, provide all of the desirable features mentioned above.

The present invention is directed to an improved electrical light fixture which is ideally suited for use in an environment where the fixture is exposed to high moisture and/or a high concentration of dust particles, and which is simple and inexpensive in construction in addition to having high rigidity and durability. The light fixture of the invention also provides for conveniently changing the angle through which light is projected and thereby provides for conveniently changing the area of illumination. The light fixture further provides for thermal expansion and contraction of the assembled components in response to energizing and deenergizing the electric lamp element, and is adapted to be easily constructed in different sizes for accommodating lamp elements of different wattage such as, for example, a lamp element of 400 watts and one of 1,000 watts.

In accordance with the illustrated embodiment, the above desirable features and advantages are generally provided by a lamp fixture which includes an elongated cylindrical tube of high strength glass. A flat rectangular reflector sheet of relatively stiff metal is curved into the general shape of a parabola and is inserted into the tube so that opposite edge portions and an intermediate center portion are urged outwardly against the inner surface of the tube. A set of end caps or closure members are provided with annular grooves and gaskets for receiving the opposite end portions of the glass tube, and the closure members are clamped against the ends of the tube by a pair of tie rods which extend axially between the inner surface of the tube and the reflector sheet.

The closure members have corresponding eccentrically located and outwardly projecting hollow hub portions. One of the hub portions receives a socket for supporting the threaded end of an electric lamp element, and the hub portion of the other end closure member supports a spring biased member which engages the opposite end of the lamp element for conducting heat from the lamp element and for aiding in its support. The closure members also support corresponding end reflector panels which project into the glass tube, and spaced heat radiating ribs are formed as integral parts of the end closure members.

Other features and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.

FIG. 1 is a perspective view of an electric light fixture constructed in accordance with the invention;

FIG. 2 is an axial section of the light fixture shown in FIG. 1 and with an end closure member shown in an exploded position;

FIG. 3 is a radial section taken generally on the line 3--3 of FIG. 2; and

FIG. 4 is a perspective view of the exploded end closure member shown in FIG. 2.

The light fixture illustrated in FIG. 1 includes an elongated cylindrical tube 15 of high strength or tempered transparent glass and which has a smooth cylindrical inner surface 16 and a smooth cylindrical outer surface 18. A reflector member or sheet 20 consists of a rectangular panel or sheet of aluminum having a highly polished reflective surface 21. Prior to being inserted into the tube 15, the relatively stiff reflector panel or sheet 20 is stored as a flat sheet. When a light fixture is assembled, the sheet is trimmed to a predetermined length according to the angle of light projection and the desired area of illumination. The reflector sheet is then manually bent or curved into a generally parabolic configuration (FIG. 3) and is inserted into the tube 15 so that the opposite edge or end portions 22 and an intermediate center portion 23 of the sheet are urged outwardly against the inner surface 16 of the tube 15 due to the inherent spring characteristic of the relatively stiff aluminum reflector sheet 20. This spring characteristic assures that the reflector sheet 20 remains in position, as illustrated in FIG. 3, but permits the edge portions 22 of the sheet to shift slightly relative to the inner surface 16 of the tube 15 in response to thermal expansion and contraction of the reflector sheet as its temperature changes.

As shown in FIG. 2, the axial length of the reflector sheet 20 is slightly less than the axial length of the tube 15, and the opposite end portions of the tube 15 receive a corresponding set of end closure members 26 and 28 which are preferably cast from aluminum. Each of the end closure members 26 and 28 includes an annular groove 29 which receives the corresponding end portion of the tube 15 and which confines an annular resilient rubber-like gasket 31 for engaging the corresponding end surface of the tube 15.

A pair of parallel spaced tie bolts 32 extend axially within the tube 15 between the reflector sheet 20 and the inner surface 16 of the tube and are disposed in diametrically opposite positions within the tube 15. The opposite end portions of each tie rod 32 are threaded and extend through corresponding holes within the end closure members 26 and 28, and each end portion receives a washer 33 and a cap-nut 34. When the nuts 34 are tightened, the end closure members 26 and 28 are drawn towards the ends of the tube 15 in order to compress and deform the gaskets 31 and to form a fluid-tight seal between the tube 15 and each end closure member.

Each of the end closure members 26 and 28 includes an outwardly projecting hollow hub portion 38 which is offset or positioned eccentrically relative to the axis of the tube 15. The tubular hub portion 38 of the end closure member 26 has an outer end which is closed by a circular plug-like end wall 42 secured by a set of screws 43.

A porcelain lamp socket 45 is supported within the tubular portion 38 of the end closure member 26 by a set of screws 46 which extend through corresponding spacer tubes 47. The lamp socket 45 receives the threaded base of an elongated lamp element 50 which may be of the sodium high vapor pressure type such as the lamp element marketed by the General Electric Company under the trademark Lucalox. The lamp element 50 may also be of other types such as quartz-iodine or xenon lamp.

As shown in FIG. 3, the axis of the lamp element 50 is substantially coincedent or common with the axis of the tubular hub portions 38 of the end closure members 26 and 28 and is also substantially coincedent or common with the focal axis 52 of the curved reflector sheet 20. Electrical power is supplied through the lamp socket 45 to the lamp element 50 by a power cord 54 which is connected to a suitable transformer or ballast (not shown). The cord 54 extends through a tubular fitting 56 threaded into a center opening within the end wall 42 of the tubular hub portion 38. The fitting 56 has a frusto-conical internal end surface which receives a mating surface on a resilient annular sealing member 58. The sealing member 58 is retained by an annular cap 62 which is threadably connected to the fitting 56. Thus when the cap 62 is tightened, the sealing member 58 is compressed firmly between the outer surface of the power supply cord 54 and the inner surface of the fitting 56 to form a positive fluid-tight seal.

The tubular or hollow hub portion 38 of the opposite enclosure cap or member 28 includes a removable outer end wall 68 which is also secured by a set of screws 43. The end wall 68 includes a centrally located blind cylindrical bore 69 which slidably receives one end portion of a cylindrical aluminum rod 72. An intermediate portion of the rod 72 is supported by a cup-shaped sheet metal housing 74 having a bottom flange portion secured to the end wall 68 by a set of screws 76. The housing 74 surrounds an outwardly projecting circumferential flange 78 formed on the rod 72 and encloses a compression coil spring 82 which extends between the flange 78 and the inner surface of the wall 68.

The outer end portion of the rod 72 supports an aluminum cup member 84 which is adapted to engage the outer corresponding end portion of the lamp element 50 when the end closure member 28 is mounted on the corresponding end of the tube 15. The spring loaded cup member 84 serves not only to position and support the outer end portion of the lamp element 50 but also cooperates to conduct heat from the lamp element 50 through the rod 72 and the housing 74 to the end wall 68 of the hub portion 38. The cup member 84 may be lined with a thin layer of asbestos material to provide a cushion support for the outer end of the lamp element 50.

As shown in FIGS. 1 and 2, both of the end closure members 26 and 28 are provided with a series of outwardly projecting arcuate fins or ribs 92 which extend concentrically with the corresponding hollow hub portion 38. The integral ribs 92 of the aluminum end closure members 26 and 28 cooperate to aid in dissipating heat which is generated when the lamp element 50 is energized.

The end closure members 26 and 28 also support a corresponding set or pair of end reflector sheets or members 95 which are formed from the same relatively stiff aluminum sheet material used to form the reflector sheet 20. Each of the end reflector members 95 includes an edge portion which is secured to the corresponding end closure member by a screw 96. The remaining or major portion of the reflector member projects in a cantilevered manner from the corresponding end closure member into the corresponding end portion of the tube 15 and curved reflector sheet 20. The inner end portion of each reflector sheet 95 has an arcuate recess 98 for receiving the corresponding end portion of the lamp element 50.

From the drawing and the above description, it is apparent that a light fixture constructed in accordance with the present invention, provides desirable features and advantages. For example, the light fixture is not only durable in construction but is also simple and economical to construct. As mentioned above, the reflector sheet 20 is adapted to be stored as a flat rectangular sheet and is simply trimmed along one edge according to the desired angle of light projection. Thus as illustrated in FIG. 3, the projected light rays are substantially parallel. However, by simply trimming off an edge portion of the flat sheet, when the sheet is curved and inserted into the glass tube 15, it is apparent that the end portions 22 of the sheet will move further outwardly within the tube to provide for a wider angle of reflection and diverging light rays. This flexibility permits one light fixture to be quickly and inexpensively modified to change the area of illumination.

The light fixture is also adapted to be conveniently constructed to accommodate lamp elements 50 of different wattage and corresponding length. Thus when it is desired to use a longer lamp element having a greater wattage, it is only necessary to increase the length of the tube 15 and the corresponding length of the tie rods 32. This flexibility is highly desirable in order to accommodate different types of lamp elements.

The generally cylindrical configuration of the glass tube 15 is also desirable in that it is self-cleaning when exposed to wind and rain. However, while a clear transparent glass tube 15 is illustrated in the drawing, it is apparent that the tube may be provided with a filter. The glass tube may also be provided with outwardly projecting integral ribs or the tube may be partially surrounded with a metal sleeve having outwardly projecting integral ribs for dissipating heat, for example, when lamp elements of high wattage are used within the tube. It is also apparent that either or both of the tubular hub portions 38 of the end closure members 26 and 28 may be provided with an outer end wall coupled by a quick release fastener, such as a bayonet type connection, to facilitate quick removal and interchangement of the lamp element 50.

While the form of light fixture herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of fixture, and that changes may be made therein without departing from the scope and spirit of the invention as defined in the appended claims.