US3389249A - Shield support for a luminaire - Google Patents

Description

June 18, 1968 c. E. RACKLEY SHIELD SUPPORT FOR A LUMINAIRE Filed June 10, 1966 INVENTOR Corle E. Ruclkley BY 8m 0m 0[ f a W 6 im 2 m in ATTORNEY United States Patent 3,389,249 SHIELD SUPPORT FOR A LUMINAIRE Carle E. Raclrley, Westlake, Ohio, assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed June 10, 1966, Ser. No. 556,619 9 Claims. (Cl. 240147) ABSTRACT OF THE DISCLOSURE A luminaire having a housing defining a bottom opening and a light transmissive shield mounted within and closing off the bottom opening which is releasable from the housing under certain temperature conditions. Resilient thermoplastic clip means are provided along the parallel longitudinal edges of the housing opening which releasably grip the shield and which soften under elevated temperature to release the flammable shield from the ceiling. The luminaire may further include a baffled air entrance path when air handling is required.

This invention relates generally to luminaires having releasable shield or refractor supports and, more particularly, to such luminaires wherein the shield is released when the support means is raised to a predetermined temperature.

The shields of refractors for luminaires are often made of plastic materials which are generally flammable. Such flammable shields are required to be supported in such a way that in the event of a fire, the shield is released from the housing. Thus, burning in place is avoided.

Another difficulty with plastic shields is the tendency to sag between the supports therefor, unless supported along closely spaced positions. Further, the shields in airhandling luminaires acoumulate dust from the return air that passes therethrough, and they must be cleaned periodically.

It is therefore an object of this invention to provide a luminaire having improved support for the shield thereof.

It is a further object of this invention to provide a luminaire having a support for the shield thereof which releases the shield when the temperature of the support reaches a predetermined value.

It is an additional object of this invention to provide a luminaire having a support and a safety fastener for the shield thereof both of which release the shield when the temperature thereof reaches a predetermined value.

It is another object of this invention to provide a luminaire having a releasable support for the shield thereof which prevents the shield from sagging.

It is a further object of this invention to provide a luminaire having a support for the shield thereof which prevents shadows around the periphery of the shield.

It is an additional object of this invention to provide a luminaire having an improved air return passage.

It is still a further object of this invention to provide a luminaire having an air return passage which aids in removing dust from the return air.

Briefly, these and other objects are achieved by providing a clip means connected to the luminaire for supporting the shield. The clip is formed of a thermoplastic material which has a low softening point. In the event of a fire, the clip softens and releases the shield from the housing. The clip means extend substantially the entire longitudinal dimension of the shield to support the shield in a non-sag manner. The clip means are light transmitting and eliminates shadows around the edges of the shield. If the luminaire is of the air-handling type, the return air passage for the luminaire is equipped with baflle means which direct the air returning therethrough through a tortuous 3,389,249 Patented June 18, 1968 path. As the return air turns along the path, dust and particles of foreign matter settle out of the air before the air passes into the luminaire enclosure. Less dust is deposited on the shield.

For a better understanding of the invention, reference should be made to the accompanying detailed description and drawing in which:

FIGURE 1 is a sectional view, taken on the line I-I in FIG. 2, of a luminaire with the center portions broken away and showing the present shield support;

FIG. 2 is a fragmentary sectional view taken along line II--II of FIG. 1, showing the return air passage into the luminaire;

FIG. 3 is a bottom plan view of a modified luminaire showing the open space about the periphery of the shield therefor; and

FIG. 4 is a fragmentary sectional elevational view of a modified shield support.

Referring to FIGURE 1, there is shown a luminaire 10 having a housing 12 with a bottom opening 14. A shield 16, which is at least partially light transmitting, is disposed over the bottom opening 14 forming a luminaire enclosure 18 with the housing 12. Lampholders 20 are affixed to the housing 12 and support light sources 22 within the luminaire enclosure 18 for illuminating the region below the luminaire 10. Upwardly projecting support members 24 and 26 are connected to the shield 16 and extend along a substantial portion of the longitudinal dimension thereof proximate the longitudinal edges 28 and 30 of the shield 16. The support members 24 and 26 are provided with grooves 24a and 26a, respectively. Downwardly projecting support members 32 and 34 are connected to the housing 12 and extend along a substantial portion of the longitudinal dimension thereof proximate the upwardly projecting support members 24 and 26, respectively. Clips 32a and 34a are positioned along each of the downwardly projecting support members 32 and 34 for engaging the grooves 24a and 26a. The engagement between the grooves 24a and 26a and the clips 32a and 34a include inclined surfaces 24b, 26b, 32b, and 34b respectively, which tend to spread the clips when the shield 16 is subjected to a downward force. Thus, the shield supporting engagement is readily disengaged by a predetermined downward force on the shield 16. It is to be understood that the positions of the clips and grooves may be reversed without interfering with the operation thereof. That is, the clips 32:: and 34a may be connected to the edges of upwardly projecting support members 24 and 26, respectively, and grooves 24a and 26a may be provided in downwardly projecting support members 32 and 34, respectively. Also, only one inclined surface may be included in each engagement between the clips and grooves.

Preferably, the clips have sufficient resilience or spring to allow removal and replacement of the shield 16 for shield cleaning and luminaire maintenance. When so removed, the shield is preferably suspended by a safety support or flexible suspending means such as cords 35 provided at each longitudinal end of the shield 16. The cord 35 is long enough to suspend the shield 16 below the luminaire 10 and out of the way of the maintenance man. The cord 35 eliminates the need of the maintenance man to hand the removed shield 16 down to a second maintenance man, or otherwise dispose of the shield 16. Further, the cord provides a safety support in case the shield should inadvertently become released from the supports therefor. As can be seen in FIGS. 1 and 2, the cord 35 is in a slack position when the shield 16 is installed in the luminaire 10. The dotted line portion of FIGURE 1 shows the shield 16 as suspended from the cord 35 during maintenance.

The clips 32a and 34a and the cords 35 are formed of an organic thermoplastic material which distorts and/ or softens at a predetermined low temperature. The clips are exposed to the region below the luminaire through the peripheral spaces 28a and 30a along the longitudinal edges 28 and 30 of the shield 16. A fire in this region will heat the clips to a temperature above the low softening temperature. The clips are then spread apart by the coaction of the above-mentioned inclined surfaces and the weight of the shield 16, and the shield 16 is released. The cords 35, which are also softened by the fire, cannot suspend the shield 16, and the shield 16 falls. Preferably, the combustion temperature of the shield 16 is greater than the softening temperature of the clips and cords to prevent the shield 16 from initially catching fire while in place within, or suspended from, the luminaire 10. It is desirable that the clips are thin enough to allow relatively easy weakening. For example, the clips 32 and 34 may be formed of polyvinylchloride, approximately ,4 of an inch, which starts to soften at a temperature of about 140 F. The cords 35 are preferably formed of nylon about of an inch in diameter which softens at a temperature of from about 150 to about 186 F. The shield 16 is preferably formed of polystyrene or acrylic. Other materials may be employed for the cord 35 and the shield 16. Generally, the clips may be formed of any of the materials listed in the table presented below. The softening temperature range for each material is also given. Other thermoplastic materials may be employed.

Table Softening temperature Material: Range in F. Ethyl cellulose 115-185 Polyvinyl chloride 120-160 Acrylic polymers 140-190 and copolymers thereof 140-200 Acrylonitrile-butadiene-styrene 140-200 Styrene-acrylonitrile 140-205 Cellulose acetate 140-220 Cellulose acetate butyrate 140-220 Polyvinylchloride acetate 150-175 Cellulose propionate 155-220 Referring to FIG. 2, there is shown a return air passage at one end of lurninaire 10 opening from the illuminated region into the luminaire enclosure 18. The shield 16 has an end wall 42, which forms one side of the return passage 40. The end wall 42 has an upper bafile 44 and a lower bafiie 46 extending longitudinally and generally horizontally therefrom. The housing 12 has an intermediate baffle 48 extending generally horizontally towards the end wall 42, transversely into the passage 40, at a height intermediate the baffles 44 and 46.

The bafiies force the air returning from the illuminated region to follow a tortuous path through the passage 40 which contains five ninety degree turns. These multiple turns cause the return air to change directions many times and release the dust and particles of foreign matter carried therein. The dust may deposit on the upper surface of the batfies. To facilitate cleaning of the baflies, the intermediate bafiie 48 may be removable. As mentioned hereinbefore, the shield 16 is removable.

The upper baffle 44 has the additional function of preventing line-of-sight vision into the luminaire enclosure 18 from the room 23. The passage 40 is wide to minimize the air pressure drop thereacross. Without bathe 44 the wide passage 40 would permit a clear view into the luminaire 10.

In order to prevent the return air from entering the enclosure 18 at points other than the passage 40, the support members 24, 26, 32 and 34 desirably extend continuously along the longitudinal dimension of the shield 16. The clip and groove engagement forms a generally air tight continous seal. Also, such a continuous support will prevent the shield 16 from sagging.

It is to be understood that a return air passage similar to passage 40 may be used at each end of the luminaire 10. Further, the passage 40 may not be employed at all, if desired. In the latter case, the lurninaire 10 would not be of the air-handling type, and both ends thereof would appear as the end 43 shown in FIG. 2 without the passage.

Referring to FIG. 3, there is shown the peripheral opening around the shield 16. This peripheral opening includes the longitudinal peripheral spaces 28a and 30a, and the return air passages 40 at each longitudinal end of the shield 16. The upwardly projecting support members are light transmitting, allowing this peripheral opening to be illuminated by the light sources 22 and objectionable shadows are eliminated therefrom.

Referring to FIG. 4, there is shown a releasable pivotal mechanism 50 which may be used in place of the groove and clip engagement along one edge of the shield 16. The mechanism 50 comprises a horizontal portion 52 extending from the upwardly projecting support member 53, and a horizontal member 54 extending from downwardly projecting support member 55. The horizontal portions 52 and 54 overlap to support the shield 16 along the edge 30 thereof. If the clip and groove engagement along the other longitudinal edge 18 is released, the releasable pivotal mechanism 50 becomes disengaged and the shield 16 falls away. Numerous modifications of the mechanism 50 are possible.

It will be apparent to those skilled in the art that the objects of this invention have been achieved by providing a shield support which softens in the event of a fire and releases the shield. The shield is supported along substantially all of the longitudinal dimension thereof to prevent sag. In the case of an air-handiing lurninaire, less dust accumulates on the shield because the return air passage is provided with plural bafiies for causing the return air to flow through a tortuous path.

Since numerous changes may be made in the above described apparatus and different embodiments of the invention may be made without departing from the spirit thereof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings, shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. In combination with a lurninaire comprising: a housing having a bottom opening, lampholder means mounted within said housing and adapted to support light source means for illuminating the region below said lurninaire, and a shield which is at least partially light transmitting disposed over the bottom opening in said housing; the improved support for said shield comprising:

upwardly projecting support means connected to said shield and extending along a substantial portion of the longitudinal dimension thereof proximate at least one longitudinal edge thereof;

support means connected to said housing and extending along a substantial portion of the longitudinal dimension thereof proximate said upwardly projecting sup port means;

resilient clip means positioned along one of said support means; and

groove means provided in the other of said support means and releasably gripped by said clip means to support said shield along a substantial portion of the longitudinal dimension thereof, at least one of said groove means and said clip means having at least one inclined surface which tends to spread said clip means,

the shield supporting engagement between said clip means and said groove means being readily disengaged by exerting a predetermined downward force on said shield, and said clip means comprising organic thermoplastic material which softens at a predetermined low temperature for allowing said groove means to be released from said clip means by the ii downward force exerted by the weight of said shield when said clip means is raised above said predetermined softening temperature.

2. The combination as specified in claim 1, wherein said shield is formed of an organic plastic which is combustible when raised above said predetermined temperature at which said clip means softens.

3. The combination as specified in claim 1, wherein a flexible safety fastening means is connected between said luminaire and said shield, said safety fastening means comprising an organic thermoplastic material which softens at a predetermined low softening temperature for aliowing said shield to fall from said luminaire when the temperature of said fastening means is raised above its softening temperature and said clip means and said groove are disengaged.

4. The combination as specified in claim 1, wherein said clip means is positioned on said support means which is connected to said housing, and said groove means is provided in said upwardly projecting support means for engaging said clip means.

5. The combination as specified in claim 1, wherein an elongated ilexible suspending means is connected between said shield and said luminaire for suspending said shield in a position below said luminaire when said clip means and said groove means are disengaged, said suspending means being in a slack position when said clip means and said groove means are engaged, said suspending means comprising organic thermoplastic material which softens and breaks at a predetermined low temperature for allowing said shield to fall when said suspending means is raised above its softening temperature and said clip means and said groove means are disengaged.

6. The combination as specified in claim 1, wherein end Walls are provided proximate each longitudinal end of said shield, at least one of said end walls having an air return passage adjacent thereto which opens from the region to be illuminated and into said luminaire, said upwardly pro- (ii jecting support means extending continuously along the entire longitudinal dimension of said shield, said support means which is connected to said housing extending continuously along the longitudinal dimension of said housing, and both said support means forming with each other a substantially airtight engagement.

7. The combination as specified in claim 6, wherein an end wall of said shield has upper bafile means and lower bafiie means projecting therefrom and extending into said air return passage, and said housing has intermediate battle means at an intermediate height between said upper baifie means and said lower bathe means, said bafile means causing the return air to flow through a tortuous path and release any dust therefrom before passing into said luminaire.

8. The combination as specified in claim 1, wherein said groove means and said clip means are positioned proximate one longitudinal edge of said shield, and releasable pivotal means are connected to said shield and said housing proximate the other longitudinal edge of said shield.

9. The combination as specified in claim 8, wherein said releasable pivotal means includes overlapping horizontal support portions which are respectively connected to said shield and said housing.

References Cited UNITED STATES PATENTS 2,659,807 11/1953 Wakefield 240-9 3,012,133 12/1961 Archer 240-9 3,140,833 7/1964 Woloski 24078 3,246,432 4/1966 Young 169-42 FOREIGN PATENTS 391,100 8/1965 Switzerland.

NORTON ANSI-1BR, Primary Examiner.

J. W. PRICE, Assistant Examiner.

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