U.S. patent number 3,639,751 [Application Number 05/027,213] was granted by the patent office on 1972-02-01 for thermally dissipative enclosure for portable high-intensity illuminating device.
This patent grant is currently assigned to Pichel Industries, Inc.. Invention is credited to Marlowe A. Pichel.
United States Patent |
3,639,751 |
Pichel |
February 1, 1972 |
THERMALLY DISSIPATIVE ENCLOSURE FOR PORTABLE HIGH-INTENSITY
ILLUMINATING DEVICE
Abstract
A sealed, thermally dissipative enclosure for a portable
high-intensity 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 cup-shaped 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.
Inventors: |
Pichel; Marlowe A. (Altadena,
CA) |
Assignee: |
Pichel Industries, Inc.
(Pasadena, CA)
|
Family
ID: |
21836376 |
Appl.
No.: |
05/027,213 |
Filed: |
April 10, 1970 |
Current U.S.
Class: |
362/261;
362/294 |
Current CPC
Class: |
F21V
29/767 (20150115); F21S 8/003 (20130101); F21V
29/773 (20150115); F21V 29/75 (20150115); F21V
29/505 (20150115) |
Current International
Class: |
F21V
29/00 (20060101); F21S 8/00 (20060101); F21v
029/00 () |
Field of
Search: |
;240/47,41.35,41,11.4,3,1.3,46.13 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
386,538 |
|
Jan 1933 |
|
GB |
|
182,785 |
|
Jan 1955 |
|
OE |
|
884,136 |
|
Apr 1943 |
|
FR |
|
928,966 |
|
Jun 1963 |
|
GB |
|
Primary Examiner: Queisser; Richard C.
Assistant Examiner: Whalen; John
Claims
What is claimed is:
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 open-mouthed
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.
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.
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.
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.
Description
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 electrodes at opposing ends is
employed, a spider-support 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 a
housing shell incorporated in the present invention.
FIG. 3 is a schematic diagram illustrating a cross-sectional side
view of a modified embodiment of the present invention taken along
the longitudinal axis thereof.
FIG. 4 is a schematic diagram illustrating a front view of the
embodiment shown in FIG. 3 wherein a spider-support member is
included to accommodate an elongate light source having electrodes
at opposing ends.
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 12 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 of a 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 10 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 of a 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 FIG. 1, may
be used.
An exemplary high intensity arc lamp would be a Xenon short arc
lamp which is structurally illustrative of arc lamps in general.
Such a Xenon short arc lamp generally includes a pair of closely
spaced electrodes which are illustrated as being an anode 52 and a
cathode 54. The application of a 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 arc 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 28.
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.degree. 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, providing 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 10 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 14 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 of the 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 12, and the legs 61 of the spider-support 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 of the 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 of the 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
14 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 thermal 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.
* * * * *