US2828408A

US2828408A - Lighting fixture

Info

Publication number: US2828408A
Application number: US545385A
Authority: US
Inventors: Donald C Mccormack
Original assignee: J A Wilson Lighting & Display
Current assignee: J A Wilson Lighting & Display; J A Wilson Lighting & Display Inc
Priority date: 1955-11-07
Filing date: 1955-11-07
Publication date: 1958-03-25
Anticipated expiration: 1975-03-25

Description

March 1958 D. c. MCCORMACK 2,828,408

LIGHTING FIXTURE Filed Nov. 7, 1955 5 Sheets-Sheet 1 March 25, 1958 D. c. MCCORMACK LIGHTING FIXTURE 5 Sheets-Sheet 2 Filed Nov. 7, 1955 an 17a FIG.4

Inventor DONALD C. MCORMACK I ihf 7 Att ys March 25, 1958 Filed Nov. 7, 1955 D. c. MCCORMACK 2,828,408

LIGHTING FIXTURE 5 Sheets-Sheet 3 Inventor DONALD c. u ea/m4 cx BY? W W Attys March 25, 1958 D. c. M CORMACK 2,828,403

LIGHTING FIXTURE Filed NOV. '7, 1955 Y 5 Sheets-Sheet 4 Inventor DONALD .C. M CORMACK WMW Att 'ys March 1953 D. c. MCCQRMACK Q 2,828,408

LIGHTING FIXTURE Filed Nov. 7, 1955 5 Sheets-Sheet 5 FIG. IO

inventor I DONALD C. M CO RMACK Att'ys Unite signor to J. A. Wiison Lighting & Display Inc., Toronto,

Ontario, Canada Application November 7, E55, Serial No. 545,385

Claims. (Cl. 243-9) This invention relates to a lighting fixture and more particularly to a detachable difiuser construction,-for example, a louver construction, for use with a continuous row fluorescent lighting fixture.

Flourescent lighting fixtures at present in use comprise an elongated body member carrying illuminating tubes and underhung by a louver which provides reasonably eificient diffusion of light. Various modes of attachment have been used to engage the louver with the body memher and allow its removal when necessary for cleaning or dismantling or for the replacement of burned out tubes. However, the necessity of securely attaching the louver to the body member precludes its easy removability and requires time-consuming labor both for attachment and for removal. Also, the means of attachment of the louver to the body member usually consists of a metal band or clasp encompassing the louver which results in a decrease in the efficiency of illumination. Finally, in a continuous row lighting fixture consisting of a series of louvers gaps between each adjoining louver decrease the efiiciency of illumination and if overlapping joints are provided between adjoining louvers to cover the gaps then the louvers are not individually removable.

The present invention overcomes these disadvantages by providing, in a lighting fixture, a series of louvers in overlapping relationship. Portions of each louver overlapping or underlying adjoining louvers are constructed to allow for partial or complete disengagement of the individual louver. Each louver when in normal position engages supporting means and may be disengaged partially or completely by longitudinal movement of the louver. Partial disengagement allows the individual louver to be hinged down to obtain access to the fixture, for example, to replace tubes or carry out other repairs.

In the drawings, which illustrate one preferred embodiment of the invention and in which each reference character represents the same part in the various views:

Figure 1 is a perspective view, partly broken away, of a lighting fixture showing louvers suspended from a body member;

Figure 2 is a fragmentary broken away perspective view of the lighting fixture showing a louver engaged by one end of a support bracket;

Figure 3 is a fragmentary broken away perspective view of the lighting fixture showing the other end of the support bracket;

Figure 4 is a fragmentary perspective view of the louver showing a pocket adapted to receive said one end of the support bracket;

Figure 5 is a view similar to Figure 4 but taken from a difierent angle;

Figure 6 is a fragmentary plan view taken at the ends of adjacent louvers showing longitudinal ribs of the louvers in overlapped relationship;

Figure 7 is a section taken along the line 7--7 of Figure 6;

Figure 8 is a diagrammatic view showing the end to States Patent 0 ECQ end relationship between adjoining louvers and showing one of the support brackets, the proportions and shape of some of the parts being somewhat altered from those used in the other figures in order to facilitate an under standing of the manner in which the adjoining louvers cooperate at their ends;

Figure 9 is a perspective view of the lighting fixture showing one louver hinged down on one side from its support brackets; and

Figure 10 is a diagrammatic view similar to Figure 8 but showing three louvers arranged end to end.

The lighting fixture illustrated consists of an elongated body member 1 carrying fluorescent lamp tubes 2 and having ditfusers, in the form of louvers 3, suspended therefrom. Mounting brackets 1a are fixed in the top surface 1!) of body member 1 for attachment to a ceiling or other supporting structure.

Each louver 3 is formed of two substantially vertical

parallel shields

4a and 4b interconnected transversely by a series of vertical vanes 5. The vanes 5, parallel to one another and normal to

shields

4a, 4b, are interconnected by a central rib 6 which lies parallel to

shields

4a, 4b midway between the shields. Rib 6 divides louver 3 longitudinally into two sides, a first side 3a and a second side 3b. In the drawings rib 6 is illustrated as V- shaped in cross-section with upright side members 6a and 6b. As shown in Figures 1 and 9, the vanes 5 have upwardly swept wings 5a and 5b adjacent their junction with

shields

4a and 4b. In addition, the upper portion of. each

shield

4a, 4b curves inwardly near its upper edge 7 to provide an overhanging portion 8. The resulting structure of louver 3 presents a longitudinal cavity 9 in the upper portion or" the louver in which body member 1 and tubes 2 are accommodated.

The louvers 3 are suspended from body member 1 by means of a series of support brackets 10 fast with (i. e. integral with or secured to) the body member, being in the embodiment illustrated secured to the top surface 1b of body member 1 and extending laterally to overhang each side of the body member. Each support bracket 10 consists of an elongated bar 11. One end of bar 11 terminates in a lug 12a (Figure 2) which projects at right angles from the bar. The opposite end of bar 11 also terminates in a lug 12b (Figure 3) which projects at right angles from the bar but in a direction opposite to lug 12a. Bracket 10 is fixed at right angles to the longitudinal axis of body member 1, causing

lugs

12a, 12b to be positioned parallel to the body member. Each of

lugs

12a, 12b has a, small ridge 13 extending upwardly from its free extremity. Bar 11 may be angled downwardly adjacent each end, as shown at 11a and 11b.

Lugs

12a, 12b of support brackets 10 pass through pockets 17a, 17b respectively in the overhanging portions 8 of the

shields

4a, 4b. Each pocket 17a, 17b is formed in a rectangular recess 18 in edge 7 of

shields

4a, 4b, recess 18 being defined by edges 18a, 18b and 180. Recess 18 has a back wall 19 depending from'edge 18a, an end wall 20 depending from adjacent edge 18b, and a bottom shelf 21. A wing 5a or 5b gives support to each pocket 17a or 17b, the wing extending between the wall 19 and the

adjoining shield

4a or 4b and also blending with the shelf 21.

A lip 22 extends downwardlyfrom the overhanging portion 8 at the end of each pocket 17a, 17b opposite the wall 20. Adjacent lip 22 a housing 23 is formed beneath the overhanging portion 8 by an elongated flange 24 and an end wall 25. Flange 24 extends downwardly from edge 7 a distance substantially equal to the depth of pocket 17a, 17b. Between the pocket 17a or 17b and the housing 23 is a slot 26 defined by the flange 24, the lip 22 and the back wall 19.

Each pocket 17b on shield 4b is positioned substantially opposite a companion pocket 17a on shield 4a in order that each pair of pockets may receive

lugs

12a and 12b of a support bracket 10. Also, pockets 17!: must be reversed end for end relative to pocket 17b since

lugs

12a and 12b project in opposite directions from bar 11. Louver 3 rests on support brackets as shown in Figure 1 by means of lips 22 resting upon

lugs

12a, 12b. Ridges 13 on

lugs

12a, 12b prevent lips 22 from sliding off the free ends of

lugs

12a, 12b and detaching louver 3.

The dimensions of each pocket 17a, 17b relative to

lugs

12a, 12b are important. The length of each pocket 17a, 17b from wall to lip 22 must be greater than the length of

lug

12a or 12b plus the width of the end of bar 11 in order that the lug may be received in the pocket and lie against shelf 21. The length of housing 23 from lip 22 to wall must be greater than the length of

lug

12a, 12b in order that the lug may slide longitudinally beneath lip 22 into the housing until bar 11 bears against the edge of flange 24. To allow

lugs

12a, 12b to slide beneath lips 22, the length of slot 26 between lip 22 and the plane of shelf 21 must be greater than the combined depth of lug 120 (or lug 12b) and ridge 13.

The relationship of each pocket 17a to its companion pocket 17b must be such that lug 12a may be inserted into pocket 170 while lug 12b is within housing 23 of pocket 17b and bar 11 is bearing against flange 24 of pocket 17b. Similarly the relationship of each pocket 17a to pocket 17b must be such that lug 12b may be inserted into pocket 17b while lug 12a is within housing 23 of pocket 17a and bar 11 is bearing against flange 24 of pocket 17b.

To hinge down one side of a louver 3 from its support brackets 10 and obtain access to body member 1 and fluorescent tubes 2, as shown in Figure 9, the following procedure is carried out. Side 3b of the louver is moved upwardly until lugs 12b bear against shelves 21 of pockets 17b. Louver 3 is then moved longitudinally to the left as viewed in Figures 1-3 until ridges 13 clear housings 23 and lips 22 and are located in the pockets 17b. At the end of this longitudinal movement of louver 3 flanges 24 adjacent pockets 17a bear against bars 11 of support brackets 10, and the louver continues to be supported at shield 4a by lips 22 which rest on lugs 12a. Side 3b is then hinged downwardly about lugs 12a, louver 3 remaining suspended therefrom.

To completely detach a louver 3 from its support brackets 10, the procedure described above in hinging down the louver is followed to disengage lugs 12b from pockets 17b. After side 3b has been moved downwardly to clear lugs 12b from pockets 17b, side 3a is raised and louver 3 is moved longitudinally to the right until ridges 13 on lugs 12a clear housings 23 and lips 22 and are located in the pockets 17a whereupon the louver 3 is lowered to clear lugs 12a from pockets 17a and the louver 3 is completely detached.

To attach a louver 3 to its support brackets 10, a procedure is followed opposite to that described above in detaching the louver. Lugs 12a of support brackets 10 are brought into registration with. pockets 17a of shield 4a and side 3a of louver 3 is moved upwardly until lugs 12a bear against shelves 21 in each pocket. Louver 3 is then moved longitudinally to the left allowing lugs 12a to enter housings 23 through slots 26 until flanges 24 bear against bars 11. Side 3a of louver 3 is then lowered until lips 22 bear against lugs 12a. Using lugs 12a as hinges, the opposite side 3b of louver 3 is moved upwardly until lugs 12b register with pockets 17b and bear against shelves 21 therein. Louver 3 is then moved longitudinally to the right until ridges 13 on lugs 12b pass beneathlips 22 and enter-housings '23 whereupon side 3b of the louver is lowered until 4 lips 22 bear against lugs 12b. The louver is then in attached position on the body member 1 of the lighting fixture.

It should be noted that louver 3 may be hinged down from either side (i. 6. either

shield

4a or 4b may be moved downwardly) and likewise may be detached and attached from either side.

In order that louvers 3 may be attached in series to their support brackets 10, some clearance must be provided between adjoining louvers for longitudinal movement on hinging down, detachment and attachment. On the other hand, the series of louvers should have no intermediate gaps to cause an uneven distribution of illumination. Both these problems are overcome by the use of lap joints 28 between the shields of adjoining

louvers

3 and 3, as shown in Figures 1, 8 and 9 of the drawings. are formed by a flange 28a integral with one end of shield 4a and a flange 28b integral with the diagonally opposite end of shield 4b on each louver. The remaining two diagonally opposite ends 29 of

shields

4a and 4b do not carry flanges. Flange 28a and flange 28b each cover a gap g" between adjoining louvers 3 and 3' when the louvers are attached to support brackets 10; therefore the minimum width of flanges 28a, 28b is governed by the width of gap g. Referring to Figure 8 of the drawings, two adjoining

louvers

3 and 3 are shown, diagrammatically, together with one of the support brackets 10. Lips 22 rest upon

lugs

12a, 12b a length d from the free end of each lug. Now (1 cannot be greater than one-half the length of the

lug

12a, 12b because the louver must be shifted longitudinally a distance at least equal to d to disengage a lip 22 from, say, lug 12a, and the opposite lip 22 bearing against lug 12b must be free to move the same distance towards bar 11; i. e. the distance e between each lip 22 and the bar 11 must be at least as great as the distance d. Also, for the lips 22 to be disengaged from their

respective lugs

12a, 12b on longitw dinal shifts of the louver, d cannot be less than the thickness of ridge 13. To detach louver 3 (disengaging shield 4a first) side 3a is moved upwardly and louver 3 is moved longitudinally from its position of rest to the right as viewed in Figure 8 a distance 11 until ridges 13 of lugs 12a clear lips 22. Therefore the minimum width of gap g and consequently the minimum width of flange 28a, 28b is length d.

In order that louver 3 may be swung down when grasped at side 3b, flange 28b must be able to clear edge 29 of adjoining louver 3' when louver 3 is detached from lugs 12b. To detach louver 3 from lugs 12b, side 3b is moved upwardly and louver 3 is moved longitudinally to the left as viewed in Figure 8 a distance d from its position of rest toclear ridges 13 on lugs 12b from lips 22, side 3b being then moved downwardly to clear lugs 12b from pockets 17b. Therefore the width f of the portion of flange 28a, 28b overlapping the adjoining louver must be not greater than length d.

When louver 3 is hinged downwardly about lugs 12!) (or lugs 12a) the upper end of flange 28b (or flange 28a) moves inwardly and slightly downwardly. There fore at each end 29 of

shields

4a and 4b the upper edges 7 have recesses 37 to provide clearance for flanges 28a, 28b of the adjoining louver. Where upper edge 7 terminates at a vane 5, wings 5a, 5b of the vane are chamfered at their uppermost portions 38 adjacent recesses 37.

Flange 28b of louver 3 must be positioned at that end of shield 4b nearest to walls 20 and remote from lips 22 of pockets 17b, as shown in Figure 8. Such a positioning of flange 28b is necessary to allow the flange to clear end 29 of the adjoining louver 3' when louver 3 is shifted to the left as viewed in Figure 8 in order to disengage lugs 12b from lips 22 and swing side 3b of louver 3 down about lugslza.

Lap joints 28 between

louvers

3 and 3" To ensure: that the louvers. present. an apparently unbroken length when mounted end to end on thei'r'support brackets, and to ensure an even distribution of illumination from the series of louvers, ribs 6 of adjoining louvers are provided with a lap joint 31' as. shown par.- ticularly in Figures 6, 7 and 8 of the drawings. Lap joint 31 comprises two pairs. of flanges 31a,

31'b'and

31c, 31d,

one pair at each end of rib 6 of each louver. 3. Although each pair of

flanges

31a, 31b and 31c; 31d' follows generally the V-shaped configuration of rib 6, the flanges are moderately convex in vertical cross-section. In addition, flange 31a positioned at side 3a of louver 3, is-oflset from the plane of side member 6a of rib 6 by a distance at least equal to the thickness of flange 31d. Similarly flange 31c, positioned at side 3b of louver 3, is offset from the plane of side member 6b of rib 6by a distance at least equal to the thickness of flange 31b.

Flanges

31b and 31d terminate at their lower ends 32 so that they do not intersect with

flanges

31a and 310 respectively, leaving a space 33 between

flanges

31a, 31b and between

flanges

31c, 31d.

Flanges

31b and 31d are also angled inwardly near their upper ends 34 towards

flanges

31a and 31c respectively. A brace 35 across rib 6 provides a support for

flanges

31c and 31d in the absence of a vane 5 at the end of louver 3 having flange 285, one vane 5- being omitted from louver 3'to prevent the existence of a double vane between adjoining louvers when the louvers are attached in series to body member 1.

Flange 31c of each louver 3 overlaps the outer side of flange 31b of an adjoining louver while flange 31d is overlapped at its outer side by flange 3100f the adjoining louver,

flanges

31a, 31b being reversed from

flanges

31c, 31d at each end of rib 6 of each louver as= shown'in Figures 6 and 8. As with lap joints 28 between adjoining shields 4 of louvers 3, lap joints 31 must provide clear ance for longitudinal movement of an individual louver.

The gap It between the free edges of

flanges

31c, 31d

and the adjoining vane 5, and between

flanges

31a, 31b and the adjoining brace 35, must again be not less than the distance d between lip 22 and the free edge of lug 12a or12b. When thelouvers 3 are in their normal positions, the width of overlap k between adjoining

pairsof flanges

31a, 31b and 31c, 31d must not be greater. thanthe length d for the same reason that the. overlapping portion of flanges 28a, 28b must not be greater than thelength d.

In hinging down side 3a of louver 3 about lugs 12b, side So is moved upwardly and louver 3 is moved longitudinally to the right as viewed in-Figure 8- until lugs 12a clear lips 22. Gaps g and h between

louvers

3 and 3 are thus substantially closed. Side 3a is then moved downwardly in an arc. about lugs 12b, causing flange 31d on louver 3 to move laterally across the inner side of adjacent flange 310 on louver 3' and through space 33 while flange 310 on louver 3 moves laterally away from the outer side of flange 31b onlouver 3. At the end of louver 3 opposite from flange 28b,

flanges

31a, 31b will be clear of

flanges

31c, 31d on the adjoining louver.

In hinging down side 3b of louver 3 about lugs 12a the same inter-relationship between

flanges

31a, 31b of louver 3 and

flanges

31c, 31d of the adjoining louver will allow the two pairs of flanges to be disengaged. from one another. In this instance there willbe no overlapping between louver 3 and louver 3' because of movement of tion' of each louver is. such. that it can be formed as a single piece by the injection moulding process about a parting line along the edges 7.

It is also to be noted that each louver 3 is identical.

with the next louver 3', 3" so that all louversmay be formed in the same mould.

It will be understood that the form of. the invention herewith shown and described isa preferred example and various modifications can be carried out without depart ing from the spirit of the invention or the scope of. the appended claims;

What we claim is:

1. A lighting fi'xt'ure'comprising a firstand second elon,

gated light diffuser, the diffusers being normally aligned with each other with one end of the first diffuser adjacent but spaced from one end of the second difluser, the first diffuser having at said one end a flange overlapping part of the second diffuser, the first diffuser having a first side and a second side, support means engaging between the adjacent ends ofthe first and second difa fusers being suflicient to permit such longitudinal shifting, thefirst diffuser then being pivotable on the support means at its second side to swing the first side downwardly, and the flange being so arranged relative to the second diffuser that it does not interfere with such longitudinal shifting nor with such pivoting of the first diffuser.

2. A lighting fixture as claimed in claim 1 wherein,

the flange'is at the second side of the first diffuser and overlaps the adjacent side of the second diffuser.

3; A lighting fixture as claimed'in claim 2 including a flange on the second diffuser at said one end adjacent and overlapping the'first' side of the first diffuser.

4. A lighting fixture as claimed in claim 1 wherein the first diflfuser is disengageable from the support means at its second side by. shifting the first diffuser longitudinally away from the second diffuser, the first diffuser then being pivotable on the' support means at its first side to swing the second side downwardly.

5. A lighting fixture-as claimed in claim 1 wherein sup-- port means engage the second diffuser at opposite sides of the diffuser to support: the second diffuser in its normallyaligned relationship with the first difluser, the second diffuser having a first side adjacent the first side of the first diffuser and a second side adjacent the second side of thefirst diffuser, the second diffuser being disengageablerfrom the support means at its second side by shifting the second diffuser longitudinally'toward the first difluser, the second diffuser then being pivotable on its;

support means at its first side to swing its second side downwardly.

6. A lighting fixture as claimed in claim 5 wherein the second diffuser is disengageable from the support means at its first side by shifting the second diffuser longitudinally awayfrom the first diffuser, the second-diffuser then being pivotable on its support means at its second side to swing its first side downwardly.

7. A lighting fixture comprising a first and S6COl'ld'.

said one endofits respective diffuser, a rib flange on the first diffuser being adjacent and overlapping the outer side of one rib flange on the second diffuser, the companion rib flangeon the first diffuser being adjacent and being overlapped at its outer side by the other rib flangeon the second diffuser, the first diffuser'having; at

first and second side, the second side of the first diffuser being adjacent said overlapping rib flange, support means engaging the sides of the first diffuser to support the first diffuser in its normally aligned relationship with the second diffuser, the first diffuser being disengagable from the support means at its first side by shifting the first diffuser longitudinally towards the second diffuser, the spacing between said ends being sufficient to permit such longitudinal shifting, the first diffuser then being pivotable on the support means at its second side to swing the first side downwardly, the rib flanges of the first diffuser moving downwardly therewith away from the rib flanges of the second diffuser.

8. A lighting fixture as claimed in claim 7 wherein the first diffuser is disen-gagable from the support means at its second side by shifting the first diffuser longitudinally away from the second diffuser, the first diffuser then being pivotable on the support means at its first side to swing the second side downwardly.

9. A lighting fixture as claimed in claim 8 in which the first diffuser has at its said one end a side flange overlapping the second diffuser, said side flange being located at the second side of the first diffuser.

10. A lighting fixture as claimed in claim 7 wherein support means engage the second diffuser at opposite sides of the diffuser to support the second diffuser in its normally aligned relationship with the first diffuser, the second diffuser having a first side adjacent the first side of the first diffuser and a second side adjacent the second side of the first diffuser, the second diffuser being disengagable from the support means at its second side by shifting the second diffuser longitudinally towards the first diffuser, the second diffuser then being pivotable on its support means at its first side to swing its second side downwardly.

11. A lighting fixture as claimed in claim 10 wherein the second diffuser is disengagable from the support means at its first side by shifting the second diffuser longitudinally away from the first diffuser, the second diffuser then being pivotable on its support means at its second side to swing its first side downwardly.

12. A lighting fixture comprising a first, second and third elongated light diffuser, the diffuser being normally aligned with each other with the first diffuser located between the second and third diffusers and with the ends of the first'diifuser adjacent but spaced from one end of each of the second and third diffusers, the first diffuser having at one end a flange overlapping the second diffuser and at the other end a flange overlapping the third diffuser, the first diffuser having a first side and a second side, support means engaging the sides of the first diffuser to support the first diffuser in its normally aligned relationship with the second and third diffusers, the first diffuser being disengagable from the support means at its first side by shifting the first diffuser longitudinally towards the second diffuser and at its second side by shifting the first diffuser longitudinally towards the third diffuser, the spacing between the adjacent ends of the diffusers being sufficient to permit such longitudinal shifting, the first diffuser then being pivotable on the support means at the side opposite the disengagable side to swing the disengaged side downwardly, the spacing between the adjacent ends of the diffusers being sufficient to permit each flange on the first diffuser to clear the adjacent diffuser when the first diffuser is shifted away from said adjacent diffuser and swung downwardly, and each flange being so arranged relative to the diffuser that it overlaps that, when the first diffuser is shifted towards said overlapped diffuser, the flange does not interfere with such shifting nor with the subsequent swinging down of the first diffuser.

13. A lighting fixture as claimed in claim 12 wherein one flange is on the second side of the first diffuser and overlaps the adjacent side of the second diffuser, and

the other flange is on the first side of the first diffuser and overlaps theadjacent side of the third diffuser.

14. A lighting fixture as claimed in claim 13 including a flange on the. side of the second diffuser adjacent the first side of the first diffuser and overlapping the first side of the first diffuser, and a flange on the side of the third diffuser adjacent the second side of the first diffuser and overlapping the second side of the first diffuser.

15. A lighting fixture comprising a first, second and third elongated light diffuser, the diffusers being normally aligned with each other with the ends of the first diffusers adjacent but spaced from one end of each of the second and third diffusers, an elongated doublewalled central rib on each diffuser, each central rib having a pair of companion flanges at said adjacent ends, one rib flange on the first diffuser being adjacent and overlapping the outer side of one rib flange on the second diffuser, the companion rib flange on the first diffuser being adjacent and being overlapped at its outer side by the other rib flange on the second diffuser, the relationship of the pair of flanges of the first diffuser to the adjacent pair of flanges of the third diffuser being the same as the relationship of the pair of flanges of the second diffuser to the adjacent pair of flanges of the first diffuser, support means engaging the first diffuser at opposite sides to support the first diffuser in its normally aligned relationship with the second and third diffusers, the first diffuser being disengagable from the support means at one side by shifting the first diffuser longitudinally towards the second diffuser and at the other side by shifting the first diffuser longitudinally towards the third diffuser, the spacing between the adjacent ends of the diffusers being suflicient to permit such longitudinal shifting, the first diffuser then being pivotable on the support means at the side opposite the disengagable side to swing the disengaged side downwardly, the spacing between the adjacent ends of the diffusers being sufficient to permit each pair of rib flanges on the first diffuser to clear the adjacent pair of flanges on the adjacent diffuser when the first diffuser is shifted away from said adjacent diffuser and swung downwardly, and each pair of rib flanges on the first diffuser being so arranged relative to the adjacent pair of flanges on another diffuser that, when the first diffuser is shifted towards said other diffuser, the flanges do not interfere with such shifting nor with the subsequent swinging down of the first diffuser.

16. A lighting fixture comprising a first and a second elongated light diffuser, the diffusers being normally aligned with each other with one end of the first diffuser adjacent but spaced from one end of the second diffuser, an end flange of one of the diffusers overlapping part of the other diffuser, the first diffuser having a first side and a second side, support means engaging the sides of the first diffuser to support the first diffuser in its normally aligned relationship with the second diffuser, the first diffuser being disengageable from the support means at its first side by shifting the first diffuser longitudinally towards the second diffuser, the spacing between the adjacent ends of the first and second diffusers being sufficient to permit such longitudinal shifting, the first diffuser then being pivotable on the support means at its second side to swing the first side downwardly, and the flange on the one diffuser being so arranged relative to the other diffuser that it does not interfere with such longitudinal shifting nor with such pivoting of the first diffuser.

17. A lighting fixture as claimed in claim 16 wherein the first diffuser is disengageable from the support means at its second side and the overlap of said flange is eliminated by shifting the first diffuser longitudinally away from the second diffuser, the first diffuser then being pivotable on the support means at its first side to swing the second side downwardly. I

' 18. A lighting fixture comprising a first and second elongated light diffuser; the diffusers being normally aligned-with each other with one end of the first diffuser adjacent but spaced from one end' of the second diffuser, an'end flange of one of the diffusers overlapping part of the other diffuser, diffuser supporting" means, suspension means on' the first diffuser adapted to rest upon the supporting'means in the normally aligned relationshipof the diffusers, the suspension means being so arranged that by shifting the first diffuser longitudinally towards the second diffuser the suspension means clear the supporting means to permit the first diffuser to move downwardly relative to the supporting means, the spacing between the adjacent ends of the first andsecond diffusers being sufficient to permit such longitudinal? shifting, and the flange on said'one diffuser being so arranged relative tothe other diffuser that it does not interfere with such longitudinal shifting nor with such downward movement of the first diffusen.

19. A lighting fixture comprising a first and a second elongated light diffuser, the' diffusers being normally aligned'with each other with one end of the first diffuser adjacent butspaced from one end of: the second diffuser, an end flange of one of the diffusers overlapping part ofthe other diffuser, the first diffuser having opposite longitudinal sides, diffuser supporting means comprising a rigid structure providing a pair of supports fast with said structure for one side of the first diffuser and means for engaging the opposite side of the first diffuser, said supports being spaced apart a predetermined fixed distance longitudinally of the first diffuser, the first diffuser having at said one side a pair of rigid integral parts of the diffuser immovable relative to the diffuser itself, each of said integral parts corresponding to a different one of s id supports and the integral parts being so located that they can simultaneously engage their respective suports to hold the first diffuser in its normally aligned relationship with the second diffuser, the first diffuser being disengageable from said supports by shifting the first diffuser longitudinally towards the second diffuser, the spacing between the adjacent ends of the first and second diffusers being sufiicient to permit such longitudinal shifting, the first diffuser then being pivotable on the engaging means at its said opposite side to swing said one side downwardly,v and the flange on said one diffuser being so arranged relative to the other difiuser that it does not interfere with such longitudinal shifting nor with such pivoting of the first diffuser.

20. A lighting fixture comprising a first and a second elongated light diffuser, the diffusers being normally aligned with each other with one end of the first diffuser adjacent but spaced from one end of the second diffuser, the first diffuser having at said one end a flange normally overlapping part of the second differ, the first diffuser having opposite longitudinal sides, diffuser supporting means comprising a rigid structure providing a pair of supports fast with said structure for each side of the first diffuser, the supports for each side being spaced apart a predetermined fixed distance longitudinally of the first diffuser, the first diffuser having at each side a pair of rigid intergral parts of the diffuser immovable relative to the diffuser itself, each of said integral parts corresponding to a different one of said supports and the integral parts being so located that they can all rest simultaneously upon their respective supports to hold the first diffuser in its normally aligned relationship with the second diffuser, the integral parts at one side being so arranged that by shifting the first diffuser longitudinally towards the second diffuser they clear their supports to permit said one side of the first diffuser to move downwardly relative to the supporting means, the integral parts and the supports at the opposite side of the first diffuser constituting pivots on which the first diffuser can swing when said one side moves downwardly, the spacing between the adjacent ends of the first and second diffusers being sufficient to permit such longitudinal shifting, the integral 10 parts at said opposite side" of the first diffuser being, so' arranged that by shifting the first diffuser" longitudinally away from the second diffuser they'clear'their' supports to permit'said opposite side of'the first diffuser to move downwardly relative to the supporting means, the integral parts'and the supportsat said one side of the first" diffuserconstituting pivots on' which the first diffuser can swing when said opposite side moves downwardly, and the flange being so arranged relative to the second diffuser that its overlap does not interfere with such longitudinal shifting of the first diffuser towards" the second diffuser nor with such pivotingof the first diffuser on.said opposite side, and its overlap is eliminated: by such longitudinal shiftingiof th'e'firstdiffuser away from. the second diffuser and the flange clears the seconddiffuser on such pivoting of the first diffuser on said one side.

21. A lighting, fixture comprising a diffuser having opposite longitudinal sides, diffuser sup'portingmeans comprising a rigid structure providingza pair of supports fast with said structure for each side of the diffuser, the, supports for each side being spaced apart a predetermined fixed distance longitudinallyof the diffuser, the diffuser having at each side a pair of rigid integral parts of the diffuser'immovable relative to the diffuser itself, each of said integral'parts corresponding to a'different one of said supports and the integral'parts being so located that they can all rest simultaneously upon their respective supports to hold the diffuser in a normal position relative to the supporting means, the diffuser being movable from the normal position longitudinally relative to the supporting means in one direction and in the opposite direction, the integral parts at one side being so arranged that with the diffuser moved longitudinally in said one direction they clear their supports to permit said one side of the diffuser to move downwardly relative to the supporting means, the integral parts and the supports at the opposite side constituting pivots on which the diffuser can swing when the said one side moves downwardly, and conversely the integral parts at said opposite side being so arranged that with the diffuser moved longitudinally in said opposite direction they clear their supports to permit said opposite side of the diflfuser to move downwardly relative to the supporting means, the integral parts and the supports at said one side constituting pivots on which the diffuser can swing when said opposite side moves downwardly.

22. A lighting fixture as claimed in claim 21, wherein the diffuser and said integral parts are a unitary moulded plastic structure.

23. A lighting fixture as claimed in claim 22, wherein the rigid structure of the supporting means comprises an elongated body member parallel to the diffuser and wherein the supports are provided by the ends of brackets fixed to the body member and extending transversely thereof.

24. A lighting fixture as claimed in claim 23, wherein the supports are diffuser engaging lugs of the brackets parallel to the body member.

25. A lighting fixture as claimed in claim 24, wherein the rigid integral parts of the diffuser overhang the lugs to rest upon them, the diffuser having recesses in said overhanging parts and from which the lugs extend under the overhanging parts and in which the lugs upon longitudinal movement of the diffuser are cleared by the diffuser.

26. A lighting fixture as claimed in claim 25, wherein each lug has an upwardly extending ridge and each overhanging part has a depending lip, the lip and ridge re quiring the diffuser to be raised slightly before it can be moved longitudinally to clear the lug.

27. A lighting fixture as claimed in claim 26, wherein the diffuser has below each recess a shelf that engages the lug when the diffuser is raised to limit the amount by which the diffuser is raised.

28. A lighting fixture comprising a diffuser having opposite longitudinal sides, diffuser supporting means comprising a rigid structure providing a pair of supports fast with said structure for one side of the difiuser, and means for engaging the opposite side of the diffuser, said supports being spaced apart a predetermined fixed distance longitudinally of the diffuser, the diffuser having at said one side a pair of rigid integral parts of the diffuser immovable relative to the diffuser itself, each of said integral parts corresponding to a different one of said supports and the integral parts being so located that they can rest simultaneously upon their respective supports to hold the difiuser in a normal position relative to the supporting means, the difiuser being movable from the normal position longitudinally relative to the supporting means in at least one direction, said integral parts being so arranged that with the diffuser moved longitudinally in said one direction they clear their supports to permit said one side of the diffuser to move downwardly relative to the supporting means, the engaging means for the opposite side constituting pivot means on which the diffuser can swing when said one side moves downwardly.

29. A lighting fixture comprising a diffuser having opposite longitudinal sides, diffuser supporting means comprising a rigid structure providing a pair of supports fast with said structure for one side of the diffuser, and means for engaging the opposite side of the diffuser, said supports being spaced apart a predetermined fixed distance longitudinally of the difiuser, the dilfuser having at said one side a pair of rigid integral parts of the difiuser immovable relative to the diffuser itself, each of said integral parts corresponding to a different one of said supports and the integral parts being so located that they can rest simultaneously upon their respective supports to hold the difiuser in a normal position relative to the supporting means, the diffuser being movable from the normal position longitudinally relative to the supporting means in at least one direction, said integral parts being so arranged that with the diffuser moved longitudinally in said one direction they clear their supports to permit said one side of the diffuser to move downwardly relative to the supporting means.

30. A lighting fixture as claimed in claim 29, wherein the diffuser and said integral parts are a unitary moulded plastic structure.

References Cited in the file of this patent UNITED STATES PATENTS 1,334,944 Arenberg Mar. 30, 1920 2,259,151 Claspy Oct. 14, 1941 2,525,315 Schepmoes Oct. 10, 1950 2,567,779 Mitchell Sept. 11, 1951 2,701,840 Carlson Feb. 8, 1955 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Donald G o Mefiormack It is hereby certified that error appears in. the above numbered patent requiring correction and. that the seicl Letters Patent should read as corrected below,

In the grant, lines 2 an-cl l2, and in the heading to the printed specification, line 4, name of assignee, for "J, Ag Wilson Lighting & Display Inca" each occurrence, read Jr. Ao Wilson Lighting & Display Ltd.

Signed and sealed this 29th day of July 19580 (SEAL) Attest: KARL AXLINE ROBERT c. WATSON Attesting Officer Commissioner of Patents