US2465248A

US2465248A - Electric light fixture

Info

Publication number: US2465248A
Application number: US675845A
Authority: US
Inventors: Mccandless Stanley
Original assignee: Century Lighting Inc
Current assignee: Century Lighting Inc
Priority date: 1946-06-11
Filing date: 1946-06-11
Publication date: 1949-03-22
Anticipated expiration: 1966-03-22

Description

March 22, 1949. s. M CANDLESS 2,465,248

ELECTRIC LIGHT FIXTURE Filed June 11, 1946 Patented Mar. 22, 1949 UNITED STATES PATENT OFFICE ELECTRIC LIGHT FIXTURE Application June 11, 1946, Serial No. 675,845

9 Claims.

This invention relates to electric light fixtures. More particularly, the invention pertains to that type of electric light fixture known as a down light, this being a fixture which is set into a ceiling to illuminate the floor or an object directly beneath the light.

Down lights originally were developed to give a greater illumination to the working plane than is normally obtained from a hanging fixture. As a result, their distribution was chiefly downward and within a limited angle. At present many varieties of constructions are employed to obtain such a distribution. For example, in some down lights an ordinary electric light bulb merely is set in a housing in the ceiling. Other down lights use flash frosted panels or louvered projectors. Still others utilize optical equipment which directs a strong beam of light downward through an almost invisible small hole in the ceiling. The simple housing-bulb type of fixture is neither efiicient nor pleasant to look at. The others, likewise, are relatively inefficient despite their greater cost. Yet, with all their drawbacks of cost, inefficiency, glare and unpleasant lighting effects, the demand for down lights is constantly.

It is an object of the present invention to provide a down light which, although comparatively inexpensive to manufacture, is relatively efiicient and unobtrusive.

It is a further object of the invention to provide a down light which fitsin a small housing and is comparatively shallow.

It is another object of the invention to provide a down light whose visible surfaces within the, normal range of sight are illuminated to approximately the same brightness as the ceiling, that is to say, whose visible surfaces within the normal range of sight are neither very brightly illuminated so as to cause an unpleasant glare, nor very under-illuminated so as to create a black spot.

It is an additional object of the invention to provide a clown light which permits easy access .to the lamp bulb and which is so designed that it will direct the greatest possible number of rays downwardly within an angle not within' the normal angle of vision.

It is yet another object of the invention to provide a down light which achieves the foregoing objects with the use of a few simple parts.

Other objects of this invention will in part be obvious and in part hereinafter pointed out.

The invention accordingly consists in the features of construction, combinations of elements, and arrangement of parts which will be exempliincreasing fled in the constructions hereinafter described, and of which the scope of application will be indicated in the claims.

In the accompanying drawings, in which are shown various possible embodiments of this invention,

Fig. 1 is a side view of a down light made in accordance with the invention, a portion thereof being cut away through the axis of symmetry to illustrate the construction of the fixture;

Fig. 2 is a bottom view of the down light.

Fig. 3 is a detail perspective view of the interior of the down light; and Fig. 4 is a detail view illustrating a modified form of ceiling plate used in connection with I the down light.

Referring now to the drawings, ID denotes a down light embodying the invention and. comprising a tubular sheet metal can or housing l2 having a closed upper end 14 on which is mounted a conventional electric outlet box IE. A socket is provided at the upper end of the housing to hold an incandescent bulb [B which preferably is of the reflector type, i. e., with rearwardly converging surfaces covered with reflecting material, so that the bulb has an integral reflector. This type of bulb, which is well known as a reflector bulb, projects per cent of its total out-put within an angle of less than 30 to the axis of symmetry of the bulb and is optically a highly, efficient unit.

The lower end of the housing is supported by a plaster ring 20 comprising a stub tubular sleeve 22 having an integral out-turned flange 24 at its and secured against the upper concealed surface of the ceiling. If desired, wire loops 30 are threaded through the metal ceiling lathe 32 and the ends of the loops brought out through the openings 28 to' secure the ring in place more v firmly.

The plaster ring also includes an annular plate I 34 having an outer diameter greater than that v of, the flange 24 and an inner diameter greater than the inner diameter of the sleeve 22. This in effect provides a step 36 on the exposed under surface of the flange 24, the purpose whereof will shortly be apparent. Said plate is rigidly attached to the plaster ring, for example, by spot welding 38, or, if desired, said plate can be formed in one piece with the ring.

The exposed surface of the ceiling surrounding the hole in which the ring is received is recessed to accommodate the flange 24 and plate 34 so that the under surface of the plate 34 will be substantially flush with the exposed surface of the ceiling.

A ceiling plate All is seated on the ledge formed by the flange 26 and step 36, the outer diameter of said plate being almost equal to the inner diameter of the annular plate 3 Said ceiling plate has a thickness equal to the height of the step 35 in order that it, like the annular plate 34, may be flush with the exposed surface of the ceiling.

The ceiling plate is held in position by a group of fiathead screws 42, Whose heads are set flush into countersunk recesses in said plate and whose shanks engage the flange 24.

The central circular opening 64 in the ceiling plate is arranged concentrically of the lamp socket and its diameter is so selected that the plate will cut off all light rays emanating from the bulb l8 at an angle within the normal range of sight (herein assumed to be about 45 to the horizontal) Such limiting cut off is indicated by the light ray 46.

Pursuant to my invention, the edge of said opening may be so shaped as to prevent glare, this result desirably being secured by forming said edge in such manner that no portion of its surface within the normal range of sight (and preferably no part of its surface visible to a passerby) is directly illuminated by the bulb I8.

More specifically, I accomplish prevention of glare by having said edge inclined to the horizontal at an angle not exceeding that of the normal range of vision. In general, this type of structure may be obtained in either of two ways.

Thus, the edge of the opening may be machined, stamped, forged or otherwise processed to-impart thereto a downwardly tapering frustoconical surface 48 (see Fig. 4) which meets the undersurface of the ceiling plate at a knife edge" 50 Said surface is inclined at an angle to the horizontal not exceeding 45 so that it will not be noticed by a casual pedestrian even though itis directly illuminated.

Alternatively, the edge of the openingmay be turned up to provide an upwardly tapering frustoconical surface 52 (see Fig. 1) which meets the upper surface of the ceiling plate at a knife edge 54. The surface 52 likewise is inclined at an angle to the horizontal not exceeding 45.

The housing i2 is secured to the plaster ring in any suitable fashion, e. g., by a set of machine screws 56 which are threaded into tapped apertures located around sleeve 22.

Inside of said housing and adjacent the open bottom end thereof are a series of parallel baflles comprising fiat centrally circularly apertured discs 58-, 60, 62, 64; each of which, except the top disc 64, has an upstanding peripheral flange 66 which serves as a spacing means. Said apertures all are concentric with the axis of symmetry of the bulb and are disposed in planes perpendicular to said axis. The diameters of the apertures range progressively from the maximum-diameter of the bulb to the diameter of the opening in the ceiling plate, with the optional exception of the aperture in the lowermost disc 58 which, since it is close to and therefore concealed by said plate, may be larger than the other apertures. In the illustrated down light the apertures in the discs 6!), 62, 64 are the same as that in the ceiling plate.

The lowermost disc 58 is held in place by sheet metal screws 68 which fasten the flange of said disc to the housing I2. The disc 61') immediately above the disc 58 rests upon the peripheral flange of the disc 58 or any other suitable spacing means, and, in general, successive discs are stacked or supported in the same manner. If desired, the discs may be prevented from rattling by employing a few angle brackets 70 having vertical legs welded to the housing and horizontal legs disposed in a common horizontal plane immediately'above and in abutment with the upper- .most disc 64, it being noted that this disc does not have any peripheral flange. The degree of support afforded the stacked discs may be increased by crimping in the upper edges of the several flanges 66 at a plurality of spaced points denoted by the numerals l2.

Heretofore, placement of baffles in a down light has been according to the theory that enough baffles should be put inside the housing to prevent the walls of the housing from being brightly illuminated, inasmuch as these walls are within the normal angle of vision of a casual passerby. In other words, enough baffles heretofore have been placed in a housing to prevent a passerby from being distracted by the presence of a highly illuminated area lying within his normal angle of vision. To make certain that such a highly illuminated area was eliminated, a large number of baflles commonly have been employed. I have found this a serious drawback because it increases manufacturing expense and produces an area lying within the normal angle of vision which is very much under illuminated. This area looks like a dead black spot and is almost as disturbing as 'a'very bright spot.

Pursuant to the present invention, both these extremesare avoided. This is accomplished by a'proper' relative spacing of the bafiles with regard to the bulb and size of the housing and by providing the surfaces of the baffles and the neighboringinternal surfaces of the side walls of the housing (actually the internal surface of the flanges 66) with different degrees of light reflec'tion, these two features (baffle spacing and differential reflectivity of the components of the baffle system) being so correlated that the interior portions of the down light lying within the normal angle of vision are illuminated to approximately the same degree as the surface illumination of the ceiling.

The baffle spacing (the ceiling plate is considered as part of the baffle system) is governed by two main factors. These are (1) that a reflector bulb directs most of its light downwardly within a relatively narrow cone, the degree of side illumination decreasing rapidly as the angle ofthe light rays to the horizontal decreases and 2) that in a bulb of this type the periphery of the light emitting end of the bulb is a relatively pcer source of illumination. The baffles are so "spaced that those portions of the internal surface of the fixture between adjacent baflies and lying within the normal angle of vision are substantially uniformly illuminated by a secondary illumination of strong light rays emitted from the bulband direct illumination of weak light rays emitted either at a small angle (30 or less) to the horizontal or from the periphery of the bulb.

This'rel'ativespacin'g may be more readily understood by'reference to'Fig. 1 and considera- .of the fixture.

tion of the illumination of the flange 66 between the

uppermost discs

62, 64 at the right hand side The area 14 of said flan e is blocked from the normal angle of vision by the edges of the circular openings in the ceiling plate 40 and disc 52 as indicated by the line 16. The area 18 of the flange is within the normal angle of vision and is directly but poorly illuminated by the reflector bulb, the limit of direct illumination being due to the presence of the disc 64 and being indicated by the line 89. The area 82 of the flange likewise is within the normal angle of vision but is not directly illuminated.

Due to the poor direct illumination of the area 18, to secondary illumination of the normal

visible areas

18, 82 and to the feathering (diffusing) of the line of light 80 caused by interception of a light beam at a slight angle, the

areas

18 and 82 will be illuminated to approximately the same degree and no sharp line of demarcation will be noticeable between the same. The secondary illumination of the area 82 is indicated by the

lines

84, 86. It will be observed that the secondary illumination of the area 18 is from a flatter emitted beam (flatter than the beam 89) thereby further evening the illumination of the

areas

18, 82.

The upper surfaces of the discs are fairly good reflective surfaces in order to secure the desired secondary illumination, although it will, of course, be understood that the surfaces need not be even approximately specular. For example, if the discs are made of sheet metal, e. g. aluminum, and the upper surfaces merely left unpainted or even painted a light gray (five parts of white to one part of black), satisfactory results will be obtained.

The foregoing factors control the spacing between the

discs

62, 64. The same considerations control the spacing between the

discs

60, 62 and between the ceiling plate 49 and disc 69, it being pointed out that the line of demarcation of

areas

18, 82 between the ceiling plate and disc 60 can be more distinct than similar higher lines, because, due to the flat angle of the limiting line 15 ,at this point, the passerby must be very far from the fixture. In the illustrated fixture no one area 18 exceeds about 35 per cent or is less than about 20 per cent of the distance between baffles. However, the baflle system will function in accordance with my invention if no area exceeds about 50 per cent, nor is smaller than about per cent of ,said distance.

In line with the above construction, the baffles may be arranged by placing the uppermost bafile 62 in any desired position relative to the bulb (actually very close in order to reduce the height of the housing). When the bulb is lit, a line of demarcation between the directly illuminated area and the area 82 (now wholly in shadow) will be clearly visible. The disc 62 then is inserted and moved toward the disc 64 until the line of demarcation is not distinct or noticeable without,

,however, entirely eliminating the directly illuminated area 18. Placement of succeeding discs and the ceiling plate can be determined in the same manner.

Obviously, once the spacing of the components of the baffle system has been determined, such spacing is duplicated in production. To simplify manufacture, it is desirable to have all the flanges 66 made of the same height, which may be taken as an average of the optimum spacing between the discs determined for most satisfactory results. In practice this modification of the best spacing does not greatly affect the result inasmuch as with optimum spacing the discs are disposed almost equally apart.

The baflle spacing just described obtains an ap proximately uniform illumination of the sides of the housing within the normal angle of vision, but the intensity of this illumination is below the intensity of illumination of the undersurfaces of the discs 69, B2, 64 and it is in order to secure an apparent evenness of illumination of these two types of surfaces that I treat said surfaces to impart thereto different degrees of reflectivity. Pursuant to this phase of my invention, I provide the undersurfaces of the discs 69, B2, 64 with a finish which is more light absorbing (reflects less light) than the finish of the flanges 66. Moreover, the finish of the flanges must be more light absorbing (reflect less light) than the comparatively good reflecting top surfaces of the ceiling plate and discs in order that said flanges may not seem too brightly illuminated. It will be recalled that the surfaces which are to be the best reflectors (the upper surfaces of the ceiling plate and

discs

40, 60, 62) may be left unpainted or painted with a five to one (five white to one black) light flat gray paint. By way of example, the surfaces which are to be the next best reflectors (the internal surfaces of the flanges) will function satisfactorily if painted with a one-to-one flat gray paint; and the surfaces which are to be the least reflecting will function satisfactorily if painted flat black. The undersurface of the ceil ing plate can be painted the color of the ceiling. If desired, the interior surfaces of the housing and the several baffles also may be tinted to match the color of the ceiling.

The edges 88 of the discs preferably are shaped in the same manner as the edge of the ceiling plate to eliminate glare, said edges, as best seen in Fig. 1, being turned up at an angle of 45 to the vertical. All of the edges of the openings are directly and strongly illuminated and, therefore, are painted flat black.

In the event it is desired to color the beam cast by the downlight, a filter 90 is employed, the same consisting of a pressed circular roundel of colored glass or a circular pane 92 composed of several strips 94 of colored glass held together by a metal strip 96. Spring fingers 98 welded to the strip 96 detachably hold the filter to the uppermost disc.

It will thus be seen that I have provided an electric light fixture which achieves the several objects of my invention and is well adapted to meet the conditions of practical use.

As various possible embodiments might be made of the above invention, and as various changes might be made of the embodiments above set forth, it is to be understood that all material herein described or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim as new and desire to secure by Letters Patent:

' 1. An electric light fixture comprising a housing having an open bottom and a closed top end, a socket at said top end, a reflector bulb in said socket for directing a beam of light through the bottom end of said housing and a set of parallel baflles arranged one above another and disposed around the interior of the side walls of said housing, each baffle having a circular aperture concentric with and perpendicular to the axis of symmetry of the bulb, the upper surfaces of all the baffles below the uppermost baflle being reflective, and the undersurfaces of all the baffles above the lowermost 'baflle being black, said baffles being so relatively spaced with respect to each other and the bulb that the internal surfaces of the housing between adjacent baffles and lying within the normal angle of vision'are substantially uniformly illuminated by a secondary -illumination of strong light rays emitted from the bulb and reflected to said surfaces from the upper surfaces of the baflies and by direct illumination of weak light rays emitted from the bulb.

2. An electric'light fixture as set forth in claim 1 wherein the edge of the circular aperture in at least the lowermost baflle has no portion of its surface within the normal angle of vision directly illuminated by the bulb.

3. An electric light fixture as set forth in claim 1 wherein the edge of the circular aperture in at least the lowermost bafile comprises a downwardly tapering frusto-conical surface inclined at an angle to the horizontal not exceeding angle of cut off.

4. An electric light fixture comprising a housing having an open bottom and a closed top end, a socket at said top end, a reflector bulb in said socket for directing a beam of light through the bottom end of said housing and a set of parallel bafiles aranged one above another and disposed around the interior of the side walls of said housing, each baflle having a circular aperture concentric with and perpendicular to the axis of symmetry of the bulb, said baflles being so relatively spaced that the internal surfaces of the housing between adjacent baffles and lying within the normal angle of vision are substantially uniformly illuminated by a secondary illumination of strong light rays emitted from the bulb and reflected to said surface from the upper surfaces of the bafiles and by direct illumination of weak light rays emitted from the bulb, the undersurfaces of all but the lowermost of said baflles having a greater light absorptivity than the upper surfaces of at least all but the uppermost of said baffles and the edge of the circular aperture in at least thelowermost bafile comprising an upwardly tapering frusto-conical surface inclined at an angle to the horizontal not exceeding the normal angle of vision.

5. An electric light fixture as set forth in claim 1 wherein the height of each of the areas of the internal surfaces of the housing between adjacent bailles which are directly illuminated and lie within the normal angle of vision does not extend over more than 50 per cent of the distance between adjacent baffles.

6. An electric light fixture comprising a hous- I aperture in at least the lowermost baflle com-'- prising a downwardly tapering frusto-conical surface inclined at an angle to the horizontal not exceeding the angle of cut oil".

7. An electric light fixture comprising a housing having an open bottom and a closed top end, a socket at said top end, a reflector bulb in said socket for directing a beam of light through the bottom end of said housing and a set of parallel bafiles arranged one above another and disposed around the interior of the side walls of said housing, each baffle having a circular aperture concentric with and perpendicular to the axis of symmetry of the bulb, the edge of the circular aperture in at least the lowermost baflle comprising an upwardly tapering frusto-conical surface inclined at an angle to the horizontal not exceeding the normal angle of vision.

8. An electric light fixture comprisin a housing having an open bottom and a closed top end, a socket at said top end, a reflector bulb in said socket for directing a beam of light through the bottom end of said housing and a set of parallel baifies arranged one above another and disposed around the interior of the side walls of said housing, each bafiie having a circular aperture concentric with and perpendicular to the axis of symmetry of the bulb, the undersurfaces of all the baffles above the lowermost baffle being black said baffles being so relatively spaced with respect to each other and the bulb that the internal surfaces of the housing between adjacent baffles and lying within the normal angle of vision are illuminated by direct illumination of weak light rays emitted from the bulb.

9. An electric light fixture as set forth in claim 8 each of the areas of the internal surfaces of the housing between adjacent baffles which are directly illuminated and lie within the normal angle of vision does not extend over more than 50 per cent of the distance between adjacent baflles.

STANLEY McCANDLESS.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,799,304 Logan Apr. 7, 1931 1,869,823 Reader Aug. 2, 1932 1,905,082 Wuebling Apr. 25, 1933 2,094,670 Rambusch Oct. 5, 1937 2,142,395 Herron Jan. 3, 1939 2,179,161 Rambusch Nov. 7, 1939 2,297,124 Anderson Sept. 29, 1942 2,381,451 Hrabak Aug. 7, 1945 2,426,093 Hardman Aug. 19, 1947 2,437,522 Handler Mar. 9, 1948 FOREIGN PATENTS Number Country Date Great Britain July 7-, 1938