US3141621A - Luminaire with lamp temperature control - Google Patents

Abstract

957,921. Electric discharge lamps. GENERAL ELECTRIC CO. Nov. 24, 1961 [Dec. 27, 1960], No. 42095/61. Heading H1D. [Also in Division F4] An illuminating device comprises an enclosure having a transparent wall and means for holding in the enclosure a lamp containing a vaporizable substance, the temperature of the lamp being controlled by a heat-conducting device which extends from the interior of the lamp to the exterior, and is so arranged that its inner end contacts for heat conduction a restricted area of the lamp and its projection extending outside of the enclosure serves for heat dissipation. In one form, a part 5 of a lamp 3 is contacted by a tubular container 4 which extends upwardly to the outside of the enclosure 1 and which contains a vaporizable liquid and a non-condensable gas, and in operation, the liquid is co-operated, the vapour condensed in a copper condenser 9 and the liquid returned to the lower part of the device. Alternatively, two hollow tubes may be used, one inside the other, and the vapour forced up the inside of the smaller tube to be condensed on a heat-dissipating surface preferably cooled with cooling fins, and the condensed liquid returned between the two tubes. In either case, the outside tube may be lagged with material 20, and a heat-conducting grease used between the lamp and the heat-conducting device. Specifications 472,307 and 821,321 are referred to.

Description

July 21, 1964 J. A. TOLBERT LUMINAIRE WITH LAMP TEMPERATURE CONTROL Filed Dec. 27. 1960 lnven tor: Joseph A.TOLbeT"G' b9 a-flfi fi His A t bo neg United States Patent "ice 3,141,621 LUMINAIRE WITH LAMP TEMPERATURE CONTROL Joseph A. Tolhert, Hendersonville, N.C., assignor to General Electric Company, a corporation of New York Filed Dec. 27, 1960, Ser. No. 78,521 14 Claims. (Cl. Mil-51.11)

This invention relates generally to lighting equipment utilizing electric discharge lamps containing a vaporizable and readily condensable ionizing medium, and more particularly to means for stabilizing the operation of such lamps by the use of temperature control means for regulating the vapor pressure.

The power consumption of a vapor lamp and its illuminating output are variables dependent in part upon the operating temperature of the lamp. Generally, one temperature exists at which it may be preferable to operate the lamp. As is well known in the art, and more fully described in US. Patent No. 2,122,285, the performance of a vapor lamp is dependent upon the coldest spot of the lamp wall. The task of keeping a vapor lamp, such asthe well-known fluorescent lamp, operating at peak efliciency can therefore be reduced to one of maintaining this cold spot at a desired temperature.

One solution which has been proposed to give this result is to incorporate, as part of the lamp structure, a temperature controlling device such as that disclosed in the aforementioned patent. This device, while operable in an open housing such as that illustrated in that patent, if put in an enclosure such as a luminaire will quickly lose its cooling potential since heat dissipation by the device is limited. As a result, many contemporary luminaire designs incorporate fans and the like to insure adequate cooling of the lamps.

It is therefore an object of this invention to provide a temperature control system for an enclosed lamp.

It is also an object of this invention to provide a temperature control system for enclosed lamps wherein the lamp may be changed without changing the control system.

It is a further object of this invention to provide a temperature control system for an enclosed lamp which will be operable over a wide range of ambient temperatures.

It is a further object of this invention to provide a temperature control system for an enclosed lamp which requires no power to operate.

It is a further object of this invention to provide a temperature control system for an enclosed lamp which has high reliability in that no mechanical moving parts are employed.

Briefly stated, in carrying out the invention in one form which may be preferred, a fluorescent lamp is removably secured in an enclosure having a transparent wall. A temperature controlling device is provided which includes a container having a liquid refrigerant and a non-condensable gas therein. A portion of the temperature controlling device is positioned to removably contact some point on the lamp wall and transfer heat to the refrigerant from this point. The container includes a portion positioned outside the enclosure so as to be cooled by the atmosphere and cause condensation of any refrigerant which has been vaporized.

The invention will be better understood from the following description taken in connection with the accompanying drawings, in which:

FIGURE 1 is a schematic cross-section of a fluorescent street-lighting luminaire incorporating a temperature control system according to the invention;

FIGURE 2 is a schematic cross-section of a fluorescent luminaire incorporating an alternative embodiment of a 3,141,621 Patented July 21, 1964 temperature control system according to the invention; and

FIGURE 3 is a schematic enlarged detail of a portion of the temperature control system shown in FIGURE 2.

Referring now to FIGURE 1, an enclosure is shown consisting of a sheet metal hood element 1 and a globe or transparent wall 2 which may be made of an acrylic resin. Removably secured in the enclosure is a tubular fluorescent lamp 3 (shown in cross-section) which is supported by suitable supporting means not shown. The lamp may be of the type described and claimed in Patent 2,915,664, wherein its elongated envelope is indented or grooved along its length giving it a kidney-shaped crosssection thereat.

In accordance with the invention, a heat conducting rod 4 is provided, which may be of copper or any other good heat conducting material, and which is positioned so as to have one end preferably notched at 4' and removably contacting the lamp 3 at the area 5 which may be midway of the length of the lamp. The conducting rod 4 extends into and is joined to a tubular metal evaporator 6, preferably of stainless steel. The inner end 5' of the rod 4- is serrated to promote boiling of a refrigerant in evaporator 6. Extending upwardly from the evaporator 6 is a conduit 7, of stairdess steel for example, which passes through an aperture 8 in the hood wall to connect with a condenser 9, here illustrated as a hemispherical chamber of copper and which may be secured to the exterior of the hood 1 by suitable brackets with interposed thermal insulation indicated at 9'. In order to limit the heat transferred to the control system from the interior of the luminaire to that transferred from the lamp 3 to the evaporator 6, particularly from the area 5 of the lamp at which the conducting rod 4 makes contact, a suitable heat insulating substance, which may be a polyester or urethane foam insulation generally indicated at 20, is provided to enclose the remaining portions of the rod 4, the boiler 6, and the conduit 7, which are contained in the enclosure formed by the hood 1 and the transparent Wall 2.

As is Well known to those skilled in the art, a reflector 21 may be provided to direct light from the lamp 3 in a desired manner. The conducting rod 4 and the insulation 26, which surrounds this rod, extend through an aperture 22 in the reflector 21. All joints between parts of the cooling device are preferably silver soldered to form a hermetically sealed system.

In order to prevent deterioration of the parts within the enclosure by the effects of the atmosphere, it is usually preferable to provide a gasket 23 at the junction of the hood 1 and the transparent wall 2. For the same reason, a sealing washer 24- may be provided around the conduit 7 to seal the aperture 8 in the wall of the hood 1.

To facilitate the transfer of heat between the lamp 3 and the conducting rod 4, a suitable biasing means such as the spring 25 may be provided. The spring 25 may be attached to the lamp 3 by means of a clip 19 which may be removed when the lamp is to be changed. The heat transfer is also improved, in the operation of a lamp cooled in accordance with the invention, by applying a grease with high heat conductivity at the area 5 between the rod 4 and the lamp 3. A suitable grease for this purpose has been found to be the product manufactured by Iohns-Manville under the trademark Nodrseal-type HK.

As will be evident from FIGURE 1 of the drawings, a second lamp, not shown, may be provided within the enclosure formed by the hood 1 and the transparent wall 2 on the left side of this enclosure as viewed in this figure. When this is done, a temperature control device similar to that already described is provided and it exv 3 tends upwardly to the righ. Of course, the luminaire may be designed to accommodate more than two lamps.

The lamp 3 may contain a quantity of a vaporizable substance such as mercury, and as is well known to those skilled in the art, a small amount of a gas such as argon which facilitates starting of the lamp. The vapor pressure of this vaporizable substance is dependent upon the temperature of the coldest spot or area of the lamp wall. In the illuminating device of FIGURE 1, this spot becomes the area 5 through the effects of the temperature control system of the invention.

A quantity of a liquid refrigerant is placed in the container formed by the evaporator 6, the conduit 7 and the condenser 9, together with a non-condensable gas, that is, a gas which has a boiling point far below normal ambient conditions, which will not become dissolved in the refrigerant. By selection of a suitable refrigerant and by filling the container with a gas at the proper pressure, the boiling temperature of the refrigerant can be controlled. For example, a temperature of 100 F. can be obtained as the boiling temperature. As the lamp 3 tends to rise to a temperature higher than 100 F., the refrigerant in the boiler 6 will become heated to its boiling point and begin to vaporize. The vaporizing of the refrigerant absorbs heat transferred from the lamp 3 along the rod 4 thereby cooling the area 5 on the lamp 3 to a temperature near the desired temperature. The refrigerant vapors rise from the boiler along through the conduit 7 to the condenser 9 which may be provided with fins (not shown) to facilitate the transfer of heat to the ambient air. By this transfer of heat to the ambient air, the walls of the condenser 9 become relatively cool and the refrigerant will therefore condense. The condensed refrigerant will flow back down the conduit 7 to the evaporator 6 where it once again may be boiled.

The liquid refrigerant in evaporator 6 may suitably consist of, for example, methylene chloride or one of a group of fiuorochloromethanes and ethanes available under the trademark Freon, preferably that designated Freon 11 and consisting of Trichloromonofluoromethane (CCl F). The noncondensable filling gas in the container may suitably consist of a gas such as nitrogen, helium, etc.

The cooling system may be charged, for example, with 2 cc. of Freon 11 at atmospheric pressure and 0 F. temperature, and with helium gas at atmospheric pressure and room temperature. The evaporator 6 is proportioned to hold the entire charge of refrigerant, and it is preferably enlarged in diameter, as shown, so that a minimum liquid height is available for heat conduction up the tube 7. On the other hand, the tube 7 is preferably minimized as to diameter and wall thickness so that heat conduction to the exterior under low ambient conditions does not result in excessive cooling of the wall of the lamp 3.

It was previously mentioned that there is a temperature at which a fluorescent lamp will operate most efiiciently, and it is well known that the illuminating efficiency of a fluorescent lamp will drop off sharply at temperatures below the desired temperature and less sharply at higher temperatures. It is relatively easy to keep a lamp hot enough despite a cold ambient temperature merely by placing the lamp in an enclosure, since the heat generated by the lamp tends to be retained in the enclosure. The problem of controlling the lamp temperature is reduced therefore to one of maintaining the cold spot of the lamp at the desired temperature.

By the temperature controlling system of this invention, the cold spot of the lamp can be maintained at the desired temperature as long as the ambient temperature remains somewhat less than this desired temperature. With the temperature controlling system of this invention, therefore, if the selected operating temperature of the lamp is made high enough, the lamp can be made to operate at this temperature regardless of variations in the ambient temperature.

Referring now to FIGURES 2 and 3 of the drawing, an alternative embodiment of the invention will be described. An enclosure is shown comprising a hood 1 and a transparent wall 2 in which is removably supported a lamp 3 in a manner similar to that described in connection with FIGURE 1. A heat-conducting rod 26 is positioned so as to have a portion near one end removably positioned in good heat-conducting relationship with a selected area of the lamp 3. The other end of the heat-conducting rod 26 extends into a con- 7 tainer 27 which may be formed from thin-walled metal tubing. Substantially concentric with the container 27 is a small tube 28 which is supported within the container 27 so as to provide inner and outer chambers. The container 27 extends upwardly from its connection with the heat-conducting rod 26, through an aperture 29 in the hood member 1, and is preferably provided with cooling fins 27' at its outer end. A sealing Washer 30 is provided around the container 27 so as to seal the aperture 29 in the wall of the hood 1. That portion of the container 27 which is located outside the enclosure formed by the hood 1 and the transparent wall 2 functions as a condenser 31. In a similar manner to the embodiment of FIGURE 1, a suitable heat insulating substance generally indicated at 20 is provided to enclose the remaining portions of the rod 26 and the container 27 which are contained Within the enclosure.

Referring to FIGURE 3, the bottom of the inner tube 28 is shown as being joined to the container 27 at the area 33 where the heat-conducting rod 26 enters the container 27. One or more apertures 34 are provided in the wall of the inner tube 28 near the bottom end of this tube. A quantity of a liquid refrigerant 35 is placed in the container 27 and by means of the aperture 34 fills the lower end of the inner tube 28 so as to cover the portion of the heat-conducting rod 26 extending into this tube. In order to cause boiling of the refrigerant at a point in the inner tube 23 above the aperture 34, a heatinsulating glass sleeve 36 may be placed about the portions of the heat-conducting rod 26 which are positioned adjacent to the aperture 34. That portion of the inner tube which encloses the uninsulated portions of the heatconducting rod 26 therefore functions as a boiler.

In operation, this embodiment of the invention functions in a similar manner to a coffee percolator. When the end 37 of the heat-conducting rod 26 reaches the boiling point of the liquid refrigerant 35, the liquid refrigerant boils, forcing drops of the refrigerant up the inner tube 28. These drops, and the vaporized refrigerant rise to the upper end of the inner tube 28 and emerge from the open top 38 of this inner tube to flow against and be cooled by the walls of the condenser portion 31 of the container 27. The cooled refrigerant then flows down the inside of the container 27 to the bottom where it may pass back into the inner tube 28 by means of the aperture 34.

While a particular embodiment of a temperature controlling device for a fluorescent lamp employing this invention has been shown and described, it will be obvious that changes and modifications can be made without departing from the spirit of the invention and the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

. 1. An illuminating device comprising an enclosure having a transparent wall, a lamp containing a vaporizable substance removably mounted in said enclosure, a temperature controlling device for said lamp, said device including a container having a first portion removably contacting in heat-conducting relation a selected area of said lamp within said enclosure, said container also having a second portion positioned outside said enclosure, and a vaporizable liquid and a non-condensable gas in said container.

2. The illuminating device defined in claim 1 wherein said container includes a conduit upwardly extending from said first portion to said second portion.

3. The illuminating device defined in claim 1 wherein a heat-insulating substance encloses the portions of said container within said enclosure.

4. An illuminating device comprising an enclosure having a transparent wall, a lamp containing a vaporizable substance removably mounted in said enclosure, a temperature controlling device for said lamp, said device including a heat-conducting rod having a first portion removably contacting in heat-conducting relation a selected area of said lamp within said enclosure, a container having a first portion in heat-conducting relation to said rod within said enclosure, said container also having a second portion positioned outside said enclosure, and a vaporizable liquid and a non-condensable gas in said container.

5. An illuminating device comprising an enclosure having a transparent wall, a lamp containing a vaporizable substance removably mounted in said enclosure, a temperature controlling device for said lamp, said device including a heat-conducting rod having a first portion removably contacting in heat-conducting relation a selected area of said lamp within said enclosure, a container comprising an evaporator section in heat-conducting relation to said rod, a condenser section positioned outside said enclosure, a conduit connecting said evaporator and condenser sections, said conduit extending upwardly from said evaporator section to said condenser section, and a vaporizable liquid and non-condensable gas in said container.

6. An illuminating device as defined in claim 5 wherein a heat-insulating substance encloses the portions of said container within said enclosure.

7. An illuminating device as defined in claim 6 further including releasable biasing means for biasing said first portion of said heat-conducting rod and said selected area of said lamp together.

8. An illuminating device as defined in claim 7 further including a heat-conducting grease between said first portion of said heat-conducting rod and said selected area of said lamp.

9. An illuminating device comprising an enclosure having a transparent wall, a lamp containing a vaporizable substance removably mounted in said enclosure, a temperature controlling device for said lamp, said device including a heat-conducting rod having a first portion removably biased against said lamp, a container comprising a boiler section in heat-conducting relation to said rod, a condenser section positioned outside said enclosure, a conduit connecting said boiler and condenser section, said conduit extending upwardly from said boiler section to said condenser section, and a quantity of liquid refrigerant and a non-condensable gas in said container.

10. An illuminating device comprising an enclosure having a transparent wall, a lamp containing a vaporizable substance removably mounted in said enclosure, a temperature controlling device for said lamp, said device including a heat-conducting rod having a first portion removably biased against said lamp, an elongated tube having positioned in the bottom end thereof a second portion of said heat-conducting rod, said tube further having at least one aperture adjacent to said second portion of said heat-conducting rod, an elongated container enclosing said tube and sealed to said tube at the bottom so as to provide a chamber outside said tube, said elongated container having a condenser portion extending outside said enclosure, and a vaporizable liquid and non-condensable gas in said container.

11. The illuminating device defined in claim 10 wherein said second portion of said heat-conducting rod is enclosed in an insulating sleeve extending from the bottom of said elongated tube past said aperture.

12. The illuminating device defined in claim 11 where in said vaporizable liquid is a liquid refrigerant.

13. The illuminating device defined in claim 12 wherein a heat-insulating substance encloses the portions of said elongated container within said enclosure.

14. A luminaire comprising a hood having a transparent globe sealed thereto defining an enclosure, a lamp containing a vaporizable substance removably mounted in said enclosure, a reflector for directing light from the lamp through the globe mounted within said enclosure, and means for controlling the temperature of a selected area of the lamp, said means including a heat conducting rod having a first portion removably biased against the selected area of said lamp and a second portion extending through said reflector, an elongated conduit mounted between said reflector and said hood having positioned in a container portion thereof said second portion of said heat conducting rod, said elongated conduit having a condenser portion extending outside said hood, and a vaporizable liquid and non-condensable gas in said container.

References Cited in the file of this patent UNITED STATES PATENTS 1,188,774 Hewitt June 27, 1916 1,917,703 Daumann July 11, 1933 2,300,892 Harada Nov. 3, 1942

Claims (1)

1. AN ILLUMINATING DEVICE COMPRISING AN ENCLOSURE HAVING A TRANSPARENT WALL, A LAMP CONTAINING A VAPORIZABLE SUBSTANCE REMOVABLY MOUNTED IN SAID ENCLOSURE, A TEMPERATURE CONTROLLING DEVICE FOR SAID LAMP, SAID DEVICE INCLUDING A CONTAINER HAVING A FIRST PORTION REMOVABLY CONTACTING IN HEAT-CONDUCTING RELATION A SELECTED AREA OF SAID LAMP WITHIN SAID ENCLOSURE, SAID CONTAINER ALSO HAVING A SECOND PORTION POSITIONED OUTSIDE SAID ENCLOSURE, AND A VAPORIZABLE LIQUID AND A NON-CONDENSABLE GAS IN SAID CONTAINER.

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