US3639751A

US3639751A - Thermally dissipative enclosure for portable high-intensity illuminating device

Info

Publication number: US3639751A
Application number: US27213A
Authority: US
Inventors: Marlowe A Pichel
Original assignee: PICHEL IND Inc
Current assignee: PICHEL IND Inc
Priority date: 1970-04-10
Filing date: 1970-04-10
Publication date: 1972-02-01
Anticipated expiration: 1989-02-01

Abstract

A sealed, thermally dissipative enclosure for a portable highintensity illuminating device is disclosed. The enclosure includes a housing shell having an exterior surface equipped with a plurality of outwardly extending fins and which is configured to form a cavity. A reflector having a specular mirrorlike surface is situated in the cavity of the housing shell. An aperture, extending through the housing shell and the reflector and generally aligned along the longitudinal axis of the enclosure, is provided to accommodate a light source. A cupshaped receptacle is included to provide a lamp socket, or other power connection, and to seal the aperture by having a portion thereof secured to the shell housing. The cavity is sealed by a faceplate which is securely retained in the mouth of the cavity. The dissipation of thermal energy is facilitated by positioning the reflector, in the cavity of the housing shell, to obtain optimal transfer of thermal energy from within the enclosure through the housing shell to the surrounding atmosphere.

Description

United States Patent Pichel [54] THERMALLY DISSIPATIVE ENCLOSURE FOR PORTABLE HIGH INTENSITY ILLUMINATING DEVICE [72] Inventor: Marlowe A. Pichel, Altadena, Calif.

[73] Assignee: Pichel Industries, Inc., Pasadena, Calif.

[22] Filed: Apr. 10, 1970 [21] Appl. No.: 27,213

[52] U.S.Cl. ..240/47,240/11.2 A

[51] Int. Cl. ..F21v 29/00 [58] Field of Search ..240/47,41.35,41,11.4,3, 240/13, 46.13

| 501 References Cited 1,37 1.2.112 'l/lloll Moore et ill. ..24()/4l .15

JJWLXOK 4/1968 'laillon ..24()/1 1.4

2,703,374 3/1955 Fruengal ..'.....3l3/149 3,018,365 1/1962 Wenman et al ..240/90 2,817,069 12/1957 Pennow ..340/25 3,361,903 1/1968 Brown ..240/47 1,494,134 5/1924 Ritterrath ..240/47 2,884,513 4/1959 Giller ..240/41.15

Feb. 1, i972 "FOREIGN PATENTS OR APPLICATIONS Primary Examiner-Richard C. Queisser Assistant Examiner-John Whalen Attorney-Jackson & Jones [57] ABSTRACT A sealed, thermally dissipative enclosure for a portable highintensity illuminating device is disclosed. The enclosure includes a housing shell having an exterior surface equipped with a plurality of outwardly extending fins and which is configured to form a cavity. A reflector having a specular mirrorlike surface is situated in the cavity of the housing shell, An aperture, extending through the housing shell and the reflector and generally aligned along the longitudinal axis of the enclosure, is provided to accommodate a light source. A eupshaped receptacle is included to provide a lamp socket, or other power connection, and to seal the aperture by having a portion thereof secured to the shell housing. The cavity is sealed by a faceplate which is securely retained in the mouth of the cavity. The dissipation of thermal energy is facilitated by positioning the reflector, in the cavity of the housing shell, to obtain optimal transfer of thermal energy from within the enclosure through the housing shell to the surrounding atmosphere.

9 Claims, 4 Drawing Figures THERMALLY DISSIPATIVE ENCLOSURE FOR PORTABLE HIGH-INTENSITY ILLUMINATING DEVICE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention generally relates to portable high intensity illuminating devices. More specifically, the present invention concerns a sealed thermally dissipative enclosure for high intensity illuminating devices, which enclosure is characterized by the ability to efficiently dissipate thermal energy generated by high intensity lamps or light sources employed in such devices.

2. Description of the Prior Art The advent of much improved, miniature high intensity light sources has made possible a new generation of portable high intensity illuminating devices. Generally, such high intensity illuminating devices date back to at least World War II during which they were used in great numbers, for example, as aerial searchlights to enable the visual detection and observation of flying aircraft and other targets. These vintage illuminating devices were, for the most part, relatively large and presented then, as do contemporary devices now, the serious problem of controlling and dissipating the relatively large amount of heat or thermal energy generated by the light source, which problem if left unsolved would ultimately render the illuminating device inoperative.

The simplest method of dissipating the excessive heat or thermal energy is to leave the lamp housing unsealed and/or provide apertures in the housing to facilitate heat transfer to the atmosphere by, for example, forced convection and/or radiation. This method is obviously inapplicable to illuminating devices, such as the present invention, which are sealed for the purpose of providing a weatherproof and immersible unit which is maintained internally free of grit, grime, dirt and the like.

As such, other techniques have been employed with sealed lighting devices, which techniques generally involve the use of additional equipment or structure. One such technique is to employ a direct fan, or the like, for forcing air across and/or through the lighting device or, for sealed systems, some form of internal to external heat exchanger. This technique, while generally sufficiently efficient to accomplish the desired cooling, or dissipation of thermal energy, is cumbersome and contributes to added expense and size when used in connection with portable lighting devices intended to be hand-held, as with the present invention.

Another prior art technique of dissipating undesirable and excessive thermal energy is to employ a refrigerant type of fluid circulating system. Typically, such techniques can be employed to dissipate great amounts of thermal energy due to the extreme efficiency of such heat transfer methods. However, the capabilities of such fluid circulating systems generally far exceed the cooling requirements of portable hand-held lighting devices. Additionally, such fluid cooling systems have the disadvantages of being costly and requiring the use of potentially substantial amounts of auxiliary equipment. Consequently, such fluid cooling systems are considered to be generally unsuitable for use with portable, hand-held lighting devices.

It is therefore the intention of the present invention to provide an enclosure for a sealed, lightweight, hand-held, high intensity lighting device, which enclosure will efficiently and effectively enable excessive heat generated by the light source to be dissipated without having to resort to the cumbersome, costly and complex cooling techniques available in the prior art.

SUMMARY OF THE INVENTION Briefly described, the present invention involves a sealed thermally dissipative enclosure for a hand-held high intensity lighting device.

More particularly, the subject enclosure includes a housing shell having a multiplicity of outwardly extending fins and which is configured to provide a cavity. A reflector, having a specular mirrorlike surface is situated in the cavity in a manner allowing optimal transfer of thermal energy to the housing shell. A faceplate is employed to seal the mouth of the cavity, while a light source accommodating aperture, extending through the housing shell and the reflector, is sealed by a cuplike receptacle which is provided with an appropriate socket, or other electrical connection, for providing power to the light source. Where an elongate light source having elec trodes at opposing ends is employed, a spidensupport member is included for the purpose of providing an additional power connector, additional support for the light source, and an additional thermally conductive path to the housing shell.

The many attendant advantages of this invention will be more readily appreciated as the same becomes better understood by reference to the following detailed description which is to be considered in connection with the accompanying drawings wherein like reference symbols designate like parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram illustrating a cross-sectional side view of one embodiment of the present invention taken along the longitudinal axis thereof.

FIG. 2 is a schematic diagram illustrating an exterior side of DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 2 of the drawings, a sealed thermally dissipative enclosure, in accordance with the present invention, generally includes a housing shell 10, a faceplate l2 and a base receptacle 14.

The housing shell 10, which may be fabricated from a material such as aluminum, brass, or the like, that is strong and is characterized by good thermal conductivity, includes a closed wall 16 which forms an open-ended cavity 18 having a mouth portion 20 and a base portion 22. The wall 16 is generally thin to enable thermal energy contained in the cavity 18 to be readily dissipated by being transferred through the wall 16 to the surrounding atmosphere. An aperture 24 is provided at a base end 26 of the housing shell 10 for the purpose of receiving a light source 28.

A plurality of outwardly extending fins 30 are spacedly situated on the exterior surface 32 of the wall 16 and extend along the longitudinal dimension of the housing shell 10. These fins 30 serve to effectively increase the exterior surface area of the housing shell 10 and thereby enhance the amount of cooling or heat dissipation that can be obtained by convection and/or radiation from the exterior surface 32 to the surrounding atmosphere. The fins 30 should be relatively thin but yet thick enough to allow thermal energy to be effectively and readily conducted outwardly from the cavity 18 through the wall 16 and out through the fins 30 for the width thereof.

The faceplate 12 is retained at the mouth portion 20 of the cavity 18, for the purpose of sealing the cavity 18. A peripheral ledge portion 34, formed about the interior surface of the wall 16, near the mouth portion 20, may be provided to receive the faceplate 12. An annular retaining ring 36, which may be seated in a groove 38, can be used to secure the faceplate against the ledge portion 34. Preferably the outer diameter of the faceplate 12 is appropriately sized, relative to the inner diameter of the cavity 18, at the mouth portion 20, to allow the faceplate 12 to be seated against the ledge portion 34. An annular sealing ring 40 is situated in a groove 42 which is essentially centered on the edge of the faceplate 12, when such faceplate 12 is seated against the ledge portion 34. This annular sealing ring 40 is provided to enhance the sealing accomplished by the faceplate 12.

The faceplate 12 should be transparent and be made of a strong heat resistant material such as Pyrex," or the like. Where, for example, the enclosure is intended to house an infrared source, then the faceplate 12 should be constructed ofa material that optimally allows only electromagnetic energy having infrared wavelengths to be projected therethrough. It is to be understood that the faceplate 12 may also serve as a transmissive filter for electromagnetic energy having any other desired wavelengths.

The base receptacle 14 may be generally configured to have a cuplike shape. A closed end 44 is equipped with an appropriate power connection such as a terminal 46. An open end 48 of the receptacle 14 is physically mounted on the base end 26 of the housing shell in any fashion and is preferably aligned along the longitudinal axis 50 of the housing shell 10. In addition to providing a power connection for the light source 28, the receptacle 14 serves to seal the cavity 18 which communicates with the interior of the receptacle 14 through the aperture 24. This sealing provided by the receptacle 14, not only accomplishes the earlier-mentioned objectives of keeping the enclosure internally clean, but additionally, isolates the components ofa power source (not shown) from corrosive gases, such as ozone, that may be formed by the intensive radiant energy generated in the cavity 18 A material characterized by good thermal conductivity and capable of serving as an electrical and radio frequency insulator should be used in fabricating the receptacle 14.

Any high intensity lamp that is readily available in the prior art may be used for the light source 28. For example, an incandescent bulb, as shown in FIG. 3, or an arc lamp, as shown in F101, may be used.

An exemplary high intensity are lamp would be a Xenon short are lamp which is structurally illustrative of arc lamps in general. Such a Xenon short are lamp generally includes a pair of closely spaced electrodes which are illustrated as being an anode 52 and a cathode 54. The application ofa high voltage pulse, usually of radio frequency, via the terminal 56 will produce ionization of the Xenon gas contained within a quartz envelope 58. This ionization permits current flow through the ionized gas between the anode 52 and the cathode 54, which current flow causes an are between the tips of the anode 52 and the cathode 54. High intensity light is thereby produced. Otherwise stated, the current flow effectively creates a plasma ball of relatively small size and high radiant energy intensity between the tips of the anode 52 and the cathode 54, high intensity light being thereby produced. An electrical path to ground is provided by a spider-support member 60 having a plurality of outspread legs 61 which are appropriately secured at one end to the housing shell 10 and which are mutually secured at the other end.

The radiant energy is directed out of the cavity 18 by a reflector 62 which is provided with a specular, mirrorlike surface. The reflector 62 may be generally constructed of a metal, such as nickel, copper or aluminum, which lends itself to a variety of conventional fabrication techniques. The reflector 62 should also be appropriately coated with a high reflectivity material such that a relatively small percentage of the thermal energy generated by the light source 28 is absorbed. The reflector 62 may of course be fabricated to have any desired shape such as a deep concave configuration which is intended to maximize the reflection of radiant energy out of the cavity 18. In that the fabrication techniques concerning reflectors having a desired degree of geometric accuracy is not intended as a part of the present invention, further discussion relating to the construction of reflectors is not hereinafter pursued.

As may be readily appreciated, a high intensity light source such as a Xenon short arc lamp will generate a significant amount of nonradiated thermal energy along with the desired radiated energy. This thermal energy will of course be substantially derivative from the earlier mentioned plasma ball but will also be contributed to by reason of the anode 52 and cathode 54 becoming extremely hot due to resistance to the relatively high currents required to operate the light source Although a relatively small percentage of the heat generated by the source is usually absorbed by the reflector 62, temperatures in the neighborhood of 400 F. have been measured at the reflector 62 in the vicinity of the aperture 24. These high temperatures, unless compensated for by the efficient dissipation of thermal energy, will ultimately produce the destruction of the light source 28.

To this end, the reflector 62 may be mounted on the interior surface of the wall 16 of the housing shell 10 to provide an efficient thermally conductive path to the housing shell 10 such that the thermal energy absorbed by the reflector 62 may be readily and efficiently conducted to the cooler exterior surface of the wall 16, including the fins 30, and thereby be dissipated by convection and/or radiation.

In some instances, the reflector 62 may be integrally secured to or formed on the interior surface of the wall 16 to provide the best thermally conductive path. Any of the available techniques presently known in the prior art may be used for this purpose. in other instances, where practical considerations dictate that specific mirror materials or fabrication techniques, such as electroforming, be used, the reflector 62 may be separately fabricated and subsequently mounted on the interior surface of the wall 16. In such instances, it may be difficult to obtain a perfect match between the configuration of the outer surface of the reflector 62 and the interior surface of the wall 16. Should this be the case, vacant pockets, provid ing a poor thermally conductive path, would be present if the reflector 62 were to be merely mounted against the housing shell 10. As such, a filler material 64, may be sandwiched between the reflector 62 and the wall 16. The thermal conductivity of such a filler material 64 may be enhanced by the inclusion of metal particles therein. It is to be noted that, the filler material 64 may also serve as an adhesive for the purpose of bonding the reflector 62 to the wall 16 if the reflector is not otherwise secured to the wall 16. Additionally, to compensate for differences in the coefficient of thermal expansion between mirror and housing materials, or different amounts of thermal expansion due to temperature differentials between the reflector 62 and the housing shell 10, the filler material 64 should be somewhat flexible, It has been found that silicon rubber or certain epoxy adhesives, having suspended metal particles therein, are suitable filler materials.

Additional thermally conductive paths are provided to the housing shell 10 by the legs 61 of the spider-support member 60, by the receptacle 14, and by the faceplate 12. For example, the legs 61 of the spider-support member 60 serve to provide a direct thermally conductive path to the housing shell 10 for thermal energy conducted to the spider-support member from the cathode 54 and for absorbed thermal energy radiated thereon from the light source 28.

The receptacle 14 similarly serves to provide a thermally conductive path to the housing shell 10 for the thermal energy conducted to the receptacle from the anode 52 through the electrical connector 46, and for the absorbed thermal energy radiated thereon, from the light source 28 and the included heated anode 52.

The faceplate 12 will ordinarily absorb some thermal energy as the radiant energy provided by the light source 28 is projected therethrough. This absorbed thermal energy is conducted to the ordinarily cooler peripheral portions of the faceplate 12 and then conductivity transferred to the yet cooler housing shell 10 where the thermal energy is dissipated.

As earlier mentioned, heat or thermal energy transferred to the housing shell 10 will be dissipated by being conducted outwardly to the cooler exterior surface 32 including the fins 30 which serve to greatly increase the area of the exterior surface contacting the surrounding atmosphere. Dissipation of the thermal energy conducted to the exterior surface of the housing shell is then accomplished by the convention and/or by radiation to the atmosphere.

While the illustrated arrangement of the fins 30 in FIGS. 1 and 2 is generally longitudinal with respect to the housing shell 10, any other arrangement of the fins 30 may be readily employed. For example, FIG. 3 illustrates the fins 30 as being formed on the exterior surface of the housing shell 10 as a series of outwardly extending, generally concentric rings that are spacedly distributed along the length of the housing shell 10.

The use of the fin arrangement shown in FIG. 2 has been found to enable a greater amount of cooling by convection due to air being readily permitted to flow upwardly across the exterior surface of the housing shell 10. This upward airflow of course occurs with the fin arrangement of FIGS. 1 and 2, but is not as readily accomplished as with the fin arrangement of FIG. 3.

Referring to FIG. 3 in greater detail, along with FIG. 4, a modified mounting arrangement for the reflector 62 and the receptacle 14 is illustrated. As shown, both the reflector 62 and the receptacle 14 are spacedly mounted, in an essentially concentric arrangement, within the housing shell 10, such that a surrounding channel 66 is provided between the wall 16 of the housing shell 10 and the receptacle I4 and reflector 62.

In this arrangement, the reflector 62 may be formed to have a flange 67 to enable the reflector 62 to be appropriately mechanically secured to the housing shell 10.

The housing shell 10 may then be formed to have intermittent protrusions 68 which provide points of attachment that allow open passage of gas between the housing shell 10 and the reflector 62. In the alternative, or in addition, intermittent protrusions 69 (FIG. 4) may be situated in the neighborhood of the ledge 34 to secure the reflector 62 at the mouth thereof.

The receptacle 14 may have the closed end 44 thereof secured to the base end 26 of the housing shell 10. Any mechanical or other method may be employed. It is to be noted that the base end 26 of the housing shell 10 has been lengthened, or extended, to encompass the receptacle 14 in the arrangement of FIGS. 3 and 4.

A plurality of apertures 70 may be provided in the walls of the receptacle 14. These apertures 70 serve to connect the surrounding channel 66 with the interior ofthe receptacle 14.

In the mounting arrangement of FIGS. 3 and 4, the thermal energy generated by the light source 28, and confined in the housing shell 10, is transferred to the housing shell 10 by convection via the surrounding channel 66, as well as by conduction through the thermally conductive paths provided by the receptacle 14, the faceplate l2, and the legs 61 of the spidersupport member 60, when used.

More specifically, let it be assumed that the housing shell 10 of the enclosure is maintained in a horizontal position, i.e., the longitudinal axis 50 is horizontal. Heat generated by the light source 28 will naturally tend to flow upwards in the general direction of the arrows 74 and 76. In that the housing shell 10 is sealed, the coolest gas situated at the lowest part of the housing shell 10 will consequently be continually forced or drawn upward into the cavity 18 by convective currents, as generally indicated by the arrow 78. These convective currents will thus tend to carry the heat away from the hottest region ofthe cavity 18, near the base portion 22 of the cavity 18, and then out of the cavity 18 primarily towards the upper portions of the surrounding channel 66 where the thermal energy is absorbed by the wall 16 ofthe housing shell 10. The convection currents will also tend to distribute the heat or thermal energy throughout the surrounding channel 66 and thereby expose large portions of the wall 16 to the heat.

As earlier discussed, the thermal energy absorbed by the receptacle I4 and the faceplate 12 will be conducted to the housing shell 10. The heat absorbed by the walls of the receptacle 14 will also be transferred to the housing shell 10 by convection, and by radiation.

Similarly, the thermal energy absorbed by the reflector 62 will be transferred to the housing shell 10 by convection and by radiation. Additionally, the points of attachment through the protrusions 68 and/or 69 will serve to conduct a portion of the thennal energy absorbed by the reflector 62 to the housing shell 10.

It is to be noted that although the convective cooling provided by the arrangement of FIG. 3 has been explained in connection with an enclosure that is maintained in a horizontal position, it has been found that the convective cooling is as, if not more, effective when the illuminating device is being waved and turned about in the ordinary course of usage.

It is to be further noted that although an incandescent lamp has been illustrated in the modified arrangement of FIG. 3, that an elongate arc lamp having a pair of electrodes extending to the opposed ends thereof may be accommodated by the mere employment of a spider-support member 60. FIG. 4 illustrates a frontal view of such a combination.

From the foregoing discussion, it is now evident that the present invention provides a thermally dissipative enclosure that is usable to form a sealed, hand-held high intensity illuminating device.

While preferred embodiments of the present invention have been described hereinabove, it is intended that all matter contained in the above description and shown in the accompanying drawings be interpreted as illustrative, and not in a limiting sense, and that all modifications, constructions and arrangements which fall within the scope and spirit of the present invention, may be made.

What is claimed is:

l. A thermally dissipative, sealed enclosure for a hand-held illuminating device accommodating an arc lamp having an elongate shape and a pair of longitudinally aligned electrical terminals said enclosure comprising:

a housing shell including a closed wall configured to form a cavity having an open-mouthed portion and a base aperture, and a plurality of outwardly extending fins spacedly formed on said closed wall for effectively increasing the exterior surface area of said housing shell;

a thermally conductive receptacle having a cuplike configuration forming a closed portion and an open portion, said receptacle being secured to said housing shell for sealing said base aperture, said receptacle serving as a radio frequency insulator;

a thermally conductive faceplate secured to said housing shell for sealing said open-mouthed portion;

a thermally conductive reflector having a configuration conforming to said cavity and positioned in said cavity to facilitate the transfer of thermal energy, generated in said cavity by said source of radiant energy, to said housing shell; and

a thermally conductive spider support member including one or more elongate legs having one end thereof secured at the open-mouthed portion of said housing shell and another end thereof mutually secured to support an electrical terminal of said are lamp.

2. The apparatus defined by claim I wherein said wall of said housing shell includes an interior surface, said apparatus further including a filler material sandwiched between said interior surface and said reflector, said filler material being adapted to provide thermal conduction between said reflector and said housing shell.

3. The apparatus defined by claim 2 wherein said filler material includes particles of thermally conductive material.

4. The apparatus defined by claim 3 wherein said outwardly extending fins are elongate and longitudinally extend across the exterior surface of said closed wall of said housing shell.

5. The apparatus defined by claim 3 wherein said outwardly extending fins are a series of protruding rings longitudinally distributed across the length of the exterior surface of said closed wall of said housing shell.

6. The apparatus defined by claim 1 wherein said wall of said housing shell includes an interior surface, and wherein said reflector is mounted a predetermined distance from said interior surface for providing a channel between said interior surface and said reflector.

the exterior surface of said closed wall of said housing shell.

9. The apparatus defined by claim 7 wherein said outwardly extending fins are a series of protruding rings longitudinally distributed across the length of the exterior surface of said closed wall of said housing shell.

Claims

1. A thermally dissipative, sealed enclosure for a hand-held illuminating device accommodating an arc lamp having an elongate shape and a pair of longitudinally aligned electrical terminals said enclosure comprising: a housing shell including a closed wall configured to form a cavity having an open-mouthed portion and a base aperture, and a plurality of outwardly extending fins spacedly formed on said closed wall for effectively increasing the exterior surface area of said housing shell; a thermally conductive receptacle having a cuplike configuration forming a closed portion and an open portion, said receptacle being secured to said housing shell for sealing said base aperture, said receptacle serving as a radio frequency insulator; a thermally conductive faceplate secured to said housing shell for sealing said open-mouthed portion; a thermally conductive reflector having a configuration conforming to said cavity and positioned in said cavity to facilitate the transfer of thermal energy, generated in said cavity by said source of radiant energy, to said housing shell; and a thermally conductive spider support member including one or more elongate legs having one end thereof secured at the openmouthed portion of said housing shell and another end thereof mutually secured to support an electrical terminal of said arc lamp.

2. The apparatus defined by claim 1 wherein said wall of said housing shell includes an interior surface, said apparatus further including a filler material sandwiched between said interior surface and said reflector, said filler material being adapted to provide thermal conduction between said reflector and said housing shell.

7. The apparatus defined by claim 6 wherein said receptacle includes a portion thereof that is partially enclosed by said housing shell, said partially enclosed portion of said receptacle including a plurality of apertures.

8. The apparatus defined by claim 7 wherein said outwardly extending fins are elongate and longitudinally extend across the exterior surface of said closed wall of said housing shell.