US3184588A

US3184588A - Ceiling mounted fluorescent lighting system

Info

Publication number: US3184588A
Application number: US223023A
Authority: US
Inventors: Eugene F Gaines
Original assignee: Celotex Corp
Current assignee: Celotex Corp
Priority date: 1962-09-12
Filing date: 1962-09-12
Publication date: 1965-05-18
Anticipated expiration: 1982-05-18

Description

- May 18; 1965 E. F. GAINES CEILING MOUNTED FLUORESCENT LIGHTING SYSTEM 7 Sheets-Sheet 3 u Na o May 18, 1965 E. F. GAINES CEILING MOUNTED FLUORESCENT LIGHTING SYSTEM 7 Sheets-Sheet 4 Filed Sept. 12, 1962 E'WK I I I I 1 I II May 18, 1965 E. F. GAINES 3,184,588

CEILING MOUNTED FLUORESCENT LIGHTING SYSTEM Filed Sept. 12, 1962 7 Sheets-Sheet 5 May 18, 1965 E. F. GAINES 3,184,583

CEILING MOUNTED FLUORESCENT LIGHTING SYSTEM Filed Sept. 12, 1962 '7 Sheets-Sheet 6 May 18, 1965 E. F. GAINES CEILING MOUNTED FLUORESCENT LIGHTING SYSTEM 7 Sheets-Sheet '7 Filed Sept. 12, 1962 United States Patent ()fi ice dlddfili Federated May l8, i955 3,134,588 CEILENG lvlllllNillll) FL'U" RESCENT LEGHEHNG SYSllllid Eugene F. Gaines, .loplin, Mo, assigncr to The Eelutcx Qorpcration, Chicago, 21., a corporation of Delaware Filed Sept. 12, 962, $er. No. 223,023 7 Claims. ll. 2 ill-) This invention relates generally to illumination, and particularly to the illumination of buildings or rooms having a great ex nose of ceiling area, such as those encountered in shopping centers, supermarkets and the like, which are customarily provided with suspended or drop ceilings.

Commonly, the ceiling structures in buildings of the character referred to are constructed upon a relatively light framework which is suspended from a more sturdy superstructure, such as a roof structure. Customarily there is applied to the light framework a multiplicity of modular panels of ceiling material. The panels are usually of uniform size, such, for example, as two feet square or two feet by four feet, preformed or precut to that size at a factory, and shipped to the site of the building in which they are to be applied. Save for the necessity of providing for illuminating fixtures, all that need be done at the building site is to connect the panels or tiles with the light framework. Such connection may be accomplished either by the provision of a grid-work of stringers and cross-runners, frequently in the form of inverted T- bars, upon which the modular panels are laid from above so that the heads of the stringers and T-bars are exposed on the lower side of the finished ceiling; or by the provision of edge kerfs in the ceiling panels for the reception therein, at joints between the panels, of splines in one direction and the heads of Z-bars in the other direction, in which event the suspended framework is concealed from view from below the completed ceiling.

Regardless of how they are attached to the suspended framework, the ceiling materials are available on the market in standard sizes, and made from a variety of materials. Prominent among the materials from which such ceiling panels are made are so-called acoustical materials. The Acoustical Materials Association recogniZes as acoustical materials those products having a noise reduction ccefiicient of .15 or more, and that is the sense in which the expression acoustical materials is used in this specification.

Many of the acoustical materials available on the market as ceiling panels, and which are not incombustible,

are classed by the Underwriters Laboratories in certain Y combinations as fire rated. To obtain a two-hour fire rating, the Underwriters Laboratories suspends the ceiling panel below a specified type of roof construction and exposes the room below the ceiling to a temperature (with flame) of at least 1850 F. Not only the ceiling panels, but everything else, including the illumination fixtures which go into a ceiling and the metal members which constitute the framework upon which the ceiling panels are carried, are thus tested simultaneously for their capacity to contain fire. The structure must be such that the roof (above the ceiling) does not reach a temperature where failure would occur within the two-hour period.

For the illumination of ceilings of the character referred to, it has heretofore been customary to provide fluorescent lamps arranged in parallel rows. The rows are not uncommonly several hundred feet long, and are composed of a series of fluorescent tubes usually four to eight feet in length, and arranged end to end, frequently two or more in closely spaced parallel relationship. Depending upon the number of parallel tubes in a single row and the intensity of illumination desired, the rows of parallel tubes are usually spaced apart a distance of six to twelve feet.

These rows of fluorescent lamp tubes are mounted in suitable fixtures which are sometimes suspended below the ceiling, sometimes recessed in the ceiling, and sometimes flush mounted on the ceiling. Regardless of the manner of mounting such fixtures, they have included metallic parts on the exposed (lower) side of the ceiling.

Where ceilings of the character referred to are subjected to fire of a normal temperature of 620 F., the exposed metal parts not only conduct the heat to the area above the ceiling, but expand to an extent such that in a one hundred foot run of lighting fixtures arranged end to end, there is a total increase in length of approximately five inches. Such expansion of the lighting fixtures (and other metal members which are not provided with expansion absorption features) causes them to buckle and fail, and, at the same time, either dislodge or leave openings between ceiling panels, so that the fire below the ceiling thereby gains access to the roof above. In either event, such expansion frequently deprives a structure, which might otherwise be fire rated, of the benefits of such rating.

One of the objects of the present invention is to illuminate ceilings of the character referred to by means of rows of fluorescent lamps arranged end to end, without incurring the hazards heretofore inherent in them.

Regardless of t re stye of fixture employed, and regardless of the manner in which they are mounted in accordance with the previous practice, they create a cluttered appearance and show a large amount of metal below the ceiling, thereby detracting from the aesthetic effect of the repetitive pattern of modular panels which compose the visible ceiling structure.

Another object of the invention is to provide a form of illumination with fluorescent tubes which does not so detract from the beauty of the ceiling.

Heretofore, the spacing of the parallel rows of lighting fixtures in ceilings of the character referred to has either been limited to multiples of the dimensions of the factorymade ceiling panels, or required special sizes. It is readily apparent that the use of oil-standard size panels results in unsightly non-uniformity of the finished ceiling, except when the non-uniformity is in the outermost rows and tiers Where lighting fixtures are seldom provided.

Accordingly, it is a further object of the present invention to provide a mode of illumination for ceilings of the character mentioned, in which the spacing of the rows of fluorescent tubes is neither limited to multiples of the modular size of ceiling panels nor requires special sizes of such panels in order to accommodate the desired location of the fluorescent tubes.

A still further object of the invention is to provide for the illumination of ceilings at higher efliciency and less cost than has heretofore been prevalent.

Qther objects and advantages of the invention will appear from the following disclosure.

Generally stated, the present invention contemplates ceilings constructed of modular panels of acoustical material, in which the only parts of the illumination system which are visible from the lower or exposed side of the ceiling are fluorescent lighting tubes and part of the receptacles into which the ends of the tubes are fitted and energized. All other necessary components of the lighting system are located above the ceiling with the panels of acoustical material between the fluorescent lamps and such other components. To accomplish this, the lamp receptacles, which are normally made of insulating material, are mounted above the ceiling and have the electrical connections made to them above the ceiling, but project through closely fitting holes in the panels of acoustical material for a distance sufficient to permit convenient manip ulation of fluorescent tubes into and out of connection. Such an arrangement makes possible substantial economics, as well as improving the appearance, and reducing the hazards inherent in the failure of ceilings because of the expansion of long runs of metallic members when exposed to fire, and in failure due to conduction of heat to the areas above the ceiling. The invention accomplishes a substantial economy in original cost, in that the exposed metallic fixtures heretofore deemed necessary are dispensed with, and in lieu thereof there is provided, above the ceiling, a simple and inexpensive above-ceiling harness including mounting and connection boxes for two or more receptacles, and an appropriate conduit for confining the wires to and from the receptacles, the ballast, and the power source. The above-ceiling harness arrangement makes possible a reduction in operating temperatures of ballast and wires; and the above-mentioned Underwriters Laboratories has approved smaller wire with cheaper insulation than is customary for such installations. For example, the arrangement of the present invention has been approved by the Underwriters Laboratories with the use of 60 C. type F, thermoplastic wiring with & inch of insulation, whereas with the conventional fixtures, the Underwriters Laboratories requires the use of type TI-IW thermoplastic heat resistant, 75 C., with inch of insulation, or type PHI-I rubber heat resistant, 90 0., Wiring.

The aforesaid and other objects and advantages are achieved by the illustrative embodiments shown in the accompanying drawings, in which:

FIGURE 1 is a perspective view of a corner of a room provided with an acoustical tile ceiling illuminated in accordance with the present invention, part being broken away to reveal the super-structure;

FIGURE 2 is a perspective view taken from above the ceiling shown in FIGURE 1, and illustrating the arrangement of supporting and lighting accessories above the ceiling;

FIGURE 3 is a sectional view taken along line 33 of FIGURES 1, 2 and 4, and showing one embodiment of the mechanical and electrical arrangement for supporting fluorescent lamp receptacles in accordance with the present invention;

FIGURE 4 is a sectional view (with some wires omitted for clarity) taken along line 44 of FIGURE 3;

FIGURE 5 is a sectional View taken along line 55 of FIGURE 4; 7

FIGURE 6 is a plan view of a terminal box and lamp receptacle support shown in FIGURES 2 through 5;

FIGURE 7 is a view in side elevation of the terminal box and lamp receptacle support;

FIGURE 8 is a sectional view taken along line 88 of FIGURE 6 in one form of terminal box and lamp receptacle support;

FIGURE 9 is a partial sectional view at the location of line 3-3 in FIGURE 4, but showing another mode of mounting the lamp receptacles upon the terminal box;

FIGURE 10 is a partial sectional view showing still another mode of mounting the lamp receptacles upon a modified form of terminal box;

FIGURE 11 is a perspective view of a pre-wired applicator harness for use in accordance with the present invention;

FIGURE 12 is an exploded perspective view of the abutting ends of two applicator harnesses of the character shown in FIGURE 11; and

FIGURE 13 is a perspective view of an acoustical ceiling tile readied for the accommodation of fluorescent lamp receptacles in accordance with the present invention.

The embodiment of the invention shown in the drawings illustrates the application of the invention to a conventional form of ceiling structure composed of square acoustical tile which, in their assembly, constitute a false or dropped ceiling suspended from structural members above. In the particular embodiment shown in FIG-

URES

1 and 2 of the drawings, the ceiling tile are hung in a manner such that no part of the tile-supporting members is visible from below the ceiling. This type of ceiling is chosen for illustration solely because it is the type of structure which is regarded as being the most difficult encountered with respect to the support and placement of long rows of fluorescent lighting fixtures, but it is to be understood that the invention is not limited to ceilings of the concealed support type, but is in fact applicable, in most instances with even greater facility, to the various forms of ceiling construction in which the supporting members for the acoustical tile are visible from below the ceiling.

In the form shown in FIGURES 1 and 2, the ceiling is composed of one foot square tile arranged in rows and tiers, so as to provide a repetitive pattern or equi-sized tile, with the exception that, in accordance with the usual practice, where the dimensions of the room are such that a fractional tile must be used to fill out the space, the row and/ or tier of fractional tile is located at the corner where the ceiling intersects with a side or end wall of the room. Such a row of fractional tile 1 is illustrated adjacent wall 2 of the room shown in FIGURE 1; and such a tier of fractional tile 3 is illustrated adjacent the wall 4 of the room shown in FIGURE 1. Otherwise, throughout the ceiling, the tile 5 are equi-sized. In the particular embodiment chosen for illustration, the several tile 5 are provided with edge kerfs into which there are received the lower flanges of long Z-bars 6 in one direction, and short flat splines '7 in the other direction. The Z-bars 6 extend between each longitudinal (parallel to wall 2) row of tile, while the flat splines 7 extend between each latitudinal tier (parallel to wall 4) of the tile.

In the usual construction of this type, the Z-bars 6 are supported from the super-structure of the building, as represented by bar joist 8. While the Z-bars 6 may be connected directly to the bar joists 8 by means of a series of wires 9, it is customary to provide a series of intermediate runners 10, such as a length of plasterers channel, extending cross-wise of the Z-bars and immediately above the same; and to connect the Z-bars to the cross-runner by means of U-shaped clips, such as 11, which extend astride the cross-runner and have their ends hooked under the top flange of the Z-bar. Of course, any other appropriate meanscmay be employed for connecting the ceiling structure with the superstructure. The ceiling supporting components as thus far described are, per se, known in the art.

As indicated hereinbef-ore, the present invention contemplates that fiuorescent lamps be arranged close to the acoustical material of the ceiling with a minimum of, and preferably with no, metallic plates or luminaire-supporting structures visible from below. To accomplish this, the fluorescent lamp receptacles have their metallic mountings arranged above the ceiling tile, but have their lamp-receiving parts below the ceiling tile. The conventional fluorescent lamp receptacle comprises a base portion and a pillar portion made of insulating material. The base portion of the receptacles, usually employed with so-called Slimline lamps, is about an inch and three-eights, by an inch and five-sights, by five-eights inch, has provision for accommodating mounting bolts or screws, and also houses the terminal contacts. Extending from the base portion is a pillar about an inch and three-quarters in length parallel to the five-eights dimension of the base. The pillar is provided with a hole near the end thereof remote from the base, and on the interior of the pillar, aligned with the hole, there is arranged a pair of contacts which are connected to the terminals in the base portion. The present invention thus contem plates that the acoustical tile which are to be located at the position of the lamp receptacles be provided with holes to permit at least the pillar portion of the lamp receptacles to pass therethrough. Because of the idiosyncrasies of each individual installation, it is usually impractical to cut the holes in the acoustical tile at the factory where the tile are cut to dimensions and kerfed, but since relatively few of the acoustical tile used in any given job will require holes for the accommodation of the fluorescent lamp receptacles, it is not only more convenient but economically feasible to cut the holes in the tile at the site of installation. For example, a typical lrerfed tile is shown in FIGURE 13, and provided with spaced

apertures

12 and 13. Each of the

holes

12 and 13 is of a size such as to accommodate at least the pillar portion (and in some embodiments, of a size suflicient to accommodate the base portion) of two fluorescent lamp receptacles arranged back-to-back (or a unitary receptacle with provision on opposite sides for accommodating the terminals of different alinged lamps), so that their lampreceiving openings are faced in opposite directions. The holes 12- and 13 may be cut at any desired location on a tile, or part in one tile and part in another tile, or one in one tile and one in another tile, with the limitation only that if one of the holes is cut at a joint between two tile, which joint is bridged by a Z-bar, such as 6, or other supporting member, there must be a connection between the Z-bar (or other supporting member) and the super-struc ture relatively close to it. In the form shown in FIG- URE 13, a strip 14 of the acoustical material remains integral with the balance of the tile between the two

holes

12 and 13, but this is optional, and the strip 14 may, for convenience, be cut out to consolidate holes 12- and 13 into one. In the latter event, a filler strip of any appropriate material, including the acoustical material from which the tile are made, may be positioned between the bases of the lamp receptacles after they are in place; or, if desired, the space occupied by such a removed strip 14 may be left unfilled because (at least when the lights are on) such a gap in the ceiling material is not discerned by a casual observer.

Referring now to FIGURE 2, the arrangement for supporting Z-bars 6 by means of runners 1%, clips 11 and suspending wires 9, is more clearly illustrated, but as previously indicated, such arrangement is conventional.

Over each pair of

tile apertures

12 and 13, there is arranged a terminal box and lamp receptacle support 15, upon which is mounted the customary ballast 16, and between the terminal boxes in the same row of lamps, there extends a conduit 17 for the accommodation and protection of the electrical wires. The conduit may be either flexible or rigid, as it is not required to support mechanical load. The conduit 17 and its associated terminal boxes may be, and preferably are, pre-assemoled and pre-wired, as shown in FIGURE 1 l, as a ready-made, and preferably pre-wired, harness for quick and easy application above the ceiling after the tile are in place, or in the course of applying them.

The construction and arrangement of the terminal box and lamp receptacle support 15 is shown in greater detail in FIGURES 3 through 8. In the embodiment shown, the terminal box and lamp receptacle support 15 is divided in twain and separable in the middle. Each terrninal box 15 consists of two part-

boxes

18 and 19, shown in FIGURES 6, 7 and 8. The part-boxes are arranged in reverse orientation, but are identical, save in one respect to be pointed out later. FIGURES 6, 7 and 8 show partbox 19 which is formed of a piece of sheet metal, cut, punched and folded so as to provide a bottom Wall 2% side wall 21,

end walls

22 and 23, and part-

side walls

24 and 25. A space 26 is left between the part-

side walls

24 and 25. The side wall 21 is provided with an aperture 27 to accommodate the conduit 17. The bottom wall is provided with two identical apertures 2S and 29 for the accommodation of lamp receptacles with the base portion thereof either above or below bottom 26. The bottom 2t) is also provided with three

screw holes

39, 31 and 3-2.

End walls

22 and 23 are cut and folded so as to pro vide an integral flange 33 extending outwardly and downwardly therefrom, for a purpose to be later described. At their top edges, end

walls

22 and 23 are deformed so as to provide beads 34, for a purpose to be later described. The

end walls

22 and 23 are recessed at their top edges as shown at 35 in FIGURE 8, and it is in this respect only that part-box 13 diiiers from part-box 19, the latter being provided-with such a recess 35, the former not.

The pro-wired harness shown in FIGURE 11 has a par-t- =box 13 at the near end of conduit 17, and a part-box 19 at the other end of conduit 17, but when two harnesses are connected end-to-end, as they Will be for the arrange ment of long continuous rows of fluorescent lamps such as shown in FIGURE 1, a par-t box 18 abuts against a part-box 19 (as shown in FIGURE 12), with the spaces 26 (between part-walls 24 and 25) thereof in alignment, and the part-boxes are connected together by a splicing plate 36, shown clearly in FIGURE 5, which is secured in position by screws 37 received in holes 32 of the respective part-boxes. When thus assembled, the two partboxes together constitute a composite terminal box and lamp receptacle support for one end of four fluorescent lamps As shown in FIGURE 4,

fluorescent lamp receptacles

38 and 39 are arranged back-to-back to receive the terminals of fluorescent lamps 4t) and 41, respectively, which are aligned lengthwise and located on the lower side of ceiling tile 5. The base portion 42 of lamp receptacle 39 is connected by means of bolt 4-3 and nut 44 to the bottom Zil of a part-box 18. Likewise, the base portion 45 of lamp receptacle 38 is connected by means of bolt 46 and nut 47 to the bot-tom 2t) of a part-box 19. In this instance, the

bases

42 and 45 of the respective lamp receptacles extend through hole 13 in a tile 5.

Alongside

lamp receptacles

38 and 39, with a small space intervening, is another pair of

lamp receptacles

48 and 49 extending through hole 12 in tile 5, and connected to the bottoms of part-

boxes

18 and 19 in like manner to that described above. Ballast 16 is mounted on a unitary lid 56 for the composite terminal box and lamp receptacle support 15. The lid 50 is provided with beaded edges 51 for snap engagement with beads 34 on the ends of

partboxes

18 and 19. The beaded edges 51 on lid 50 are cut away at those areas which will be in alignment with the recesses 35 in the ends of part-box 19, in order to accommodate wire troughs 52 connected to the bottom of the ballast 16 and extending laterally (as seen in FIGURE 3) from the part-box 19, The wire troughs 52 may be socured to the ballast by expanding fasteners 53, at opposite ends thereof, and are each provided, at the inner ends thereof, with an overhanging flange 54 which overhangs the interior of

end walls

22 and 23, as shown clearly in FIGURE 3, so that when lid 50 is snapped in place the wire troughs 52 are secured against dislodgement from part-box 19. The wire trough 52 at one end of part-box 19 accommodates primary conductors 55, While the wire trough 52, at the other end of part-box 19 accommodates lamp conductors 5'6 and 57, the former supplying lamp receptacle 39, the latter lamp receptacle 49, it being understood that one ballast serves two side-by-side fluorescent larnps. Part-box 18, on the other hand, accommodates the service connections, as well as the connections for

lamp receptacles

38 and 48 whose ballast is at the opposite end of the conduit 17 connected to a part-box 18 there. If, as is frequently the case, it is desired to run through a composite terminal box 15 a conductor which does not serve any lamp receptacle located therein, the conduits extending from the respecive part-boxes may be prewired with a conductor, such as 58, the free ends of which are accessible within the respective part-boxes and may be connected together, as by a wire nut 59.

After the connections are made to the lamp receptacle binding posts within terminal box 15, it is desirable to cover the binding posts with an appropriate closure of insulating material 60, which is cut to fit the rectilinear edges of

openings

28 and 29 in the bottoms 20 of

partboxes

18 and 19.

In the embodiment thus far described, the

lamp receptacles

38, 39, 4S and 49 have their bases of greater thickness than is conventional. Whereas the fluorescent lamp receptacles now on the market universally have bases of a thickness ranging between one-half inch and five-eighths of an inch, the acoustical tile presently on the market conventionally has a thickness of three-quarters of an inch. Consequently, in order to arrange the fluorescent lamps with the necessary clearance below the exposed surface of the ceiling, and yet accommodate ceiling tile of the thickness presently available upon the market, it is preferred to increase the thickness of the base portions of the fluorescent lamp sockets in order to approximate the thickness of the tile, and in FIGURES 3 and 4, the base portions of the lamp receptacles have been so indicated, Alternatively, it will be understood that an appropriate filler member, preferably of insulating material, may be interposed between the base of the lamp receptacles and the bottoms of the several terminal boxes. Another alternative is illustrated in FIGURE 9, where the lamp receptacle 138 is of greater length beyond its base portion 142 than is conventional, but the base portion 142 is of convention-a1 thickness. In this form, the length of the pillar portion of the receptacle has been increased by substantially the thicness of the tile 5, so as to project for the requisite distance below the tile. A still further alternative making use of lamp receptacles 139, whose size is conventional in all respects, is shown in FIGURE 10. In this case, the metal in the bottom 20 of the part-boxes 18 and 19 (where

openings

28 and 29 are formed) is not completely severed, but is left intact near side wall 21 and bent downwardly as shown at 120, and then laterally as shown at 121, in order to accommodate bolt 146 which is, in this instance, inserted from the exposed side of the ceiling to secure the lamp receptacle 1'39, and hence is visible, albeit with difficulty (at least when the lights are on), from below. Of course, if desired, and in situations where it is not objectionable to have the additional metal visible from below, the lateral lip 121 may be bifurcated so as toprovide a pair of fingers 122 astride the pillar part and extending along the ledges at the junction between the pillar part and the base part of the fluorescent lamp receptacle.

In situations where the ceiling is formed of acoustical material whose physical strength is insutficient to sustain the load of the harness (conduit, wires, terminal boxes, and lamp receptacles with or without ballast), metallic members may be provided to bridge metallic ceiling supporting members, and thus transfer the load of the harness away from the acoustical material. To accomplish this result, a pair of angle bars 61 may be arranged one at each end of each of the

terminal boxes

18 and 19, and of length sufficient to over-reach the distance between metal lic ceiling supporting members, such as channels 1t? 01 their counterpart (such as inverted Ts) suspended from the super-structure in other forms of ceiling. The bars 61 v are connected to the channels 10 at opposite ends thereof as by hooks 6 2. The upper edge of one of the angle bars 61 is received into the gap between end wall 22 of the terminal boxes and its overhanging flange 33, as clearly shown in FIGURE 3; and similarly the other angle bar 61 is received into the gap between end wall 23 and its overhanging flange 33. In the form shown in the drawing, the upper edge of the vertical flange of angle bar 61 is preferably flush with the lower side of the channels 16, but if this results in so elevating the bottoms 2%) of the terminal boxes above the top surface of the acoustical tile that a gap results, the hooks 62 may be made long enough to leave a gap between the top edges of bars 61 and the bottom edges of channels 10, thereby to eliminate the gap between the bottoms 21) and the tile 5. Since the height of the bottoms 20 determines the extent to which the pillar parts of the lamp receptacles will project below the bottom surface of the ceiling, it is necessary, in any event, to coordinate the elevation of the vertical flange of angle bars 61 with other variables so as to achieve the desired projection of the pillar parts of the lamp receptacles below the lower surface of the ceiling.

It will be understood, of course, that in any situation where the customer desires, an escutcheon plate of metal, plastic, or any desired material, may be placed about the lamp receptacles to conceal any raggedness or other unsightliness which may have resulted from the cutting of

holes

12 and 13 through the ceiling tile.

The lamp receptacles, which constitute the end of a row of fluorescent lamps, are supported in the same manner as lamp receptacles intermediate the ends of the row, but at the ends only one part-

box

18 or 19 is required. The endmost receptacle at one end of the row will require a part-box 19 because, at that end, a ballast will normally be provided, whereas at the other end, no ballast being required, a part-box 18 will be utilized. Such endmost part-boxes may be provided with a cover plate to close the gap 26 between its part-

Walls

24 and 25, and such cover plate preferably is provided with a laterally extending part through which a screw may be passed into hole 32 to connect the cover plate in place, instead of connecting a splice plate 36 in the same position.

In the installation of ceilings illuminated in accordance with the present invention, and utilizing, for illustration, one foot square acoustical tile as previously described, the location of the rows of fluorescent lamps and their spacing having been previously decided upon, as, for example, at a spacing of eight feet between rows of lamps, the appropriate row and tier for the beginning of each row is selected at, say, four feet from wall 4; The tile at the intersection of the selected row and tier is provided with holes (corresponding to 12 and 13) at the appropriate place, but such holes are only one half the length of those illustrated in FIGURE 13 because the respective holes accommodate only one rather than two) fluorescent lamp receptacles. If, as is usual, lamps of the so-called eight-foot length are to be utilized, every eighth tile in the selected row will be provided with

holes

12 and 13 in exactly the same position proceeding down that row. For eight-foot spacing of the rows of lamps, each tile in the same tier as, but eight rows away from, those apertured for the first row of lamps are apertured in exactly the same position and in the same manner to accommodate the lamp receptacles for the second row of lamps. Likewise, for each additional row of lamps. Preferably, the several tile which are to be apertured are apertured before being hung, but when desired, they may be apertured after they are hung. With all tile required to be thus apertured, a succession of the harnesses, such as shown in FIGURE 11, may be successively applied from above, so that the pillar parts of the several fluorescent lamp receptacles project through the apertures and are exposed below the ceiling for a distance suflicient to accommodate the lamps. When the harnesses are in proper position, they may be mechanically connected end to end by the application of splice plates 36, and when the wires extending through the several conduits 17 are appropriately connected in a given row, that row is ready for the reception of fluorescent lamps (below the ceiling) and connection with the source of electrical power at the chosen location, The process is repeated for each row.

For most universal application, the conduits 17 are preferably rigid, although, in many instances, flexible conduits, such as that known as BX or that known as Romex, are adequate. Where rigid conduit is used, it is unnecessary to connect the terminal boxes to the supporting structures in any manner other than to sustain their dead weight because the rigid conduit functions as a tension member between the terminal boxes at each end thereof, and consequently, when a fluorescent lamp is inserted and removed, the forces incident thereto are not sustained by the acoustical material of the ceiling tile. In the application of fluorescent lamps to their receptacles, a force is frequently exerted lengthwise of the fluorescent lamp tube, and an opposite force is exerted in the removal of such tube. This imposes a strain on the receptacle tending to move it in the direction of the force, but the provision of rigid conduits 17 between the termi- 9 nal boxes sustains this force either in tension or compression, depending upon the direction in which the force is applied, and consequently, prevents its transmission to the acoustical material.

From the foregoing description, those skflled in the art will readily recognize that the invention produces an illuminated ceiling wherein the exposed surface of the celling can be completely devoid of metallic parts, and even where the ceiling tile suspension system employed is one in which the tile supporting members are in part exposed below the ceiling, the present invention leaves the exposed surface of the ceiling completely devoid of metallic parts which are necessitated by the lighting system. The absence, on the exposed surface of the ceiling, of metallic parts associated with the lighting system accomplishes several desiderata other than that of appearance. In the first place, the conduction of heat from the heated or cooled area below the ceiling to the area above the ceiling (which is normally neither cooled nor heated) is reduced; in the second place, the transmission of ballast noise to the area below the ceiling is completely eliminated save in rare instances; and in the third place, in case of fire, there are no metallic parts which are not provided with accommodation for expansion, subject to expansion, and resultant distortion or rupturing of the acoustical material, so that fire might gain access from the area below to the area above the ceiling.

The arrangement of the illumination accessories in accordance with the present invention is applicable to all known varieties of drop ceiling suspension systems, and may be manufactured and installed at lower cost than the illumination devices heretofore provided for such ceilings. The present invention permits almost unlimited choice of location and direction for the rows of fluorescent tubes on the lower side of the ceiling, whereas with the recessed and surface-mounted fixtures heretofore employed, stringent limitations on location were imposed, and it was wholly impractical to run them in directions other than parallel with the joints in the tile. Moreover, the conventional systems of supporting recessed and surface-mounted fixtures upon drop ceilings have involved the provision of runs of plasterers channel, or other hangers, in addition to those required to support the ceiling alone.

The present invention further lends itself to the production of fire rated ceilings without necessitating that the ballast and other electrical parts be enclosed in fire rated material.

Other advantages of the present invention will be apparent to those skilled in the art.

While one complete embodiment has been disclosed heretofore and illustrated in the accompanying drawings, and some modifications and variations thereof have been herein suggested, it is not to be understood that the invention is limited to the detail of the foregoing disclosure, but, on the contrary, the concepts thereof are applicable in various ways to various basic ceiling arrangements without departing from the spirit of the invention or the scope of the appended claims.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. In a ceiling structure composed of modular nonmetallic acoustical panels, at least one of said panels having a hole in it, said hole being substantially smaller in each direction than either the length or the width of said panels, means for supporting said panels, paired fluorescent lamp receptacles, said receptacles each having a pillar portion and a base portion, said pillar portion providing a terminal for a fluorescent lamp tube, said base portion providing a terminal for connection with a power source, the base portion of said receptacles being disposed in part at least above the lower surface of said panels, means above the panels for supporting said base portion, and at least the pillar portions of said receptacles extending through said hole to fully expose its fluorescent tube terminal in spaced relation with and on the lower side of said panel.

2. The ceiling of claim 1 wherein the fluorescent lamp receptacles of different pairs are arranged in back-toback relation with their fluorescent lamp terminals addressed away from each other, and the pillar portions of said receptacles from different pairs extend through the same hole in a panel.

3. The ceiling of claim 1 wherein a tension member extends between opposite ones of the paired receptacles, and said tension member is located on the upper side of said panels.

4. In a ceiling composed of modular panels of nonmetallic acoustical material and having fluorescent lamp tubes and the terminal parts of receptacles arranged be neath and in closely spaced relation to the ceiling but at a distance therebelow sufiicient to permit the reception of a fluorescent tube in said terminal parts, the improvement which comprises, at least some of said panels having a hole therethrough, said holes being substantially smaller in each direction than either the length or the width of said panels, at least part of said receptacles extending through said holes and mounted upon a support above the panels.

5. The improvement of claim 4 wherein said receptacles are mounted upon terminal boxes located above said acoustical panels.

6. The improvement of claim 5 wherein a ballast is mounted on some of said terminal boxes, each ballast being electrically connected with a receptacle.

7. In combination with a ceiling structure formed of non-metallic acoustical material, a plurality of fluorescent lighting tubes and receptacles mounted end to end in a row and in close proximity to the exposed surface of said ceiling, said receptacles extending below said ceiling for a distance sufiicient to permit reception therein of a fluorescent tube below said ceiling, the receptacles extending through closely fitting holes in the acoustical material and connected to a support member above the ceiling, and a ballast mounted above said ceiling and electrically connected with a receptacle, the exposed surface of said ceiling being free of metal parts which are in noise-transmitting connection with said ballast.

References titted by the Exaner UNITED STATES PATENTS 2,153,366 4/39 Darley 339-52 2,175,155 10/39 Miller et a1 399-55 2,441,456 5/48 Thayer 399-52 2,521,228 9/50 Ketelsen 240-51.11 2,888,113 5/59 Schwartz et al 240-9 X 2,926,237 2/60 Sorenson 240-9 2,988,633 6/61 Rosenfield 240-9 3,001,001 9/61 Bibb 240-9 X 3,097,903 7/63 Moore 339-55 FOREIGN PATENTS 166,518 1/56 Australia.

NORTON ANSHER, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3,184,588 May 18, 1965 Eugene F. Gaines It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 23, for "factory" read manufacturetory column 5, line 11, for "alinged" read aligned column 6, line 62, for "respecive" read respective column 7, line 21, for "thicness" read thickness column 8, line 33 for "one rather than two)" read one (rather than two) Signed and sealed this 21st day of December 1965.

( L) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents