U.S. patent number 3,684,883 [Application Number 05/075,073] was granted by the patent office on 1972-08-15 for lamphead for tungsten-halogen lamps.
Invention is credited to Olive Entwistle.
United States Patent |
3,684,883 |
Entwistle |
August 15, 1972 |
**Please see images for:
( Certificate of Correction ) ** |
LAMPHEAD FOR TUNGSTEN-HALOGEN LAMPS
Abstract
A lamphead for a tungsten-halogen bulb, the lamphead being
constituted by a convex reflector joined to a cylindrical chimney
having a socket concentrically mounted therein for supporting a
cylindrical bulb, thereby defining an annular air space within
which a draft is created to cool the bulb. Extending between the
periphery of a flange at the upper end of the chimney and the
outwardly extending rim at the lower end of the reflector is an
array of tensile wires that are spaced from the body of the
reflector and of the chimney to form a protective cage making it
possible to safely handle the hot lamphead.
Inventors: |
Entwistle; Olive (New York,
NY) |
Family
ID: |
22123370 |
Appl.
No.: |
05/075,073 |
Filed: |
September 24, 1970 |
Current U.S.
Class: |
362/269;
362/294 |
Current CPC
Class: |
F21V
25/00 (20130101); F21V 15/02 (20130101); F21V
7/06 (20130101) |
Current International
Class: |
F21V
29/00 (20060101); F21V 25/00 (20060101); F21V
15/02 (20060101); F21V 15/00 (20060101); F21v
013/00 () |
Field of
Search: |
;240/92,12B,54R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Myracle; Jerry W.
Claims
I claim:
1. A lamphead for a tungsten-halogen lamp having a cylindrical
bulb, said lamphead comprising:
A. a reflector having an outwardly extending rim,
B. a cylindrical chimney joined at its lower end to said reflector
and communicating therewith, said chimney having an outwardly
extending flange at its upper end, said chimney having a circular
apron at an intermediate position thereon,
C. a socket concentrically mounted within said chimney to support
said lamp, thereby defining an annular air space within which a
draft is created to cool said bulb, and
D. an array of wires threaded through said apron and extending
between the periphery of said flange and the periphery of said rim,
said wires being spaced from the body of said chimney and said
reflector to define a protective cage permitting safe handling of
the lamphead.
2. A lamphead as set forth in claim 1, wherein said reflector and
chimney are fabricated of aluminum of high purity.
3. A lamphead as set forth in claim 1, wherein the periphery of
said flange and said rim are protectively ensheathed in a plastic
bead.
4. A lamphead as set forth in claim 1, further including a dimmer
connected between said lamp and a power source to vary both the
intensity and color of the light produced thereby.
5. A lamphead as set forth in claim 1, wherein said reflector has a
concave form.
6. A lamphead as set forth in claim 1, further including a pair of
pulleys mounted on said chimney at diametrically opposed positions,
and a pair of resilient wires for supporting said lamphead, said
wires having crook-shaped ends engaging said pulleys whereby said
lamphead may be angularly adjusted.
Description
BACKGROUND OF THE INVENTION
This invention relates generally to lampheads, and more
particularly to a lamphead for a tungsten-halogen lamp.
In table, floor and wall lamps for residential and office
illumination, it is the usual practice to use incandescent bulbs
having tungsten filaments. The bulb is mounted in a socket
contained within a lamphead which includes a reflector to
concentrate and direct the light.
With standard incandescent bulbs, one must use larger bulbs in
order to produce higher levels of illumination. For example, in a
40-watt incandescent bulb, the filament is mounted within a
relatively small glass envelope, whereas a 150-watt bulb employs a
much larger envelope. Consequently, lampheads intended for
incandescent bulbs must take the bulb dimensions into account. It
is not possible, when employing a standard bulb of large size, to
make use of a highly compact lamphead. Thus the dimensions and form
of a conventional lamphead are dictated by the maximum size of the
incandescent bulb for which it is designed, and one is not free to
use a small lamphead, however well designed and attractive, with a
large bulb.
To some extent, this drawback has been overcome by the recently
introduced tungsten-halogen lamp, for such lamps, which have
relatively small quartz envelopes, are available at exceptionally
high wattages and are capable of generating high levels of
illumination far more efficiently than conventional tungsten
bulbs.
The reason a tungsten-halogen lamp is more efficient than a
standard tungsten bulb is because of the halogen cycle. Ordinary
incandescent lamps darken in the course of their life due to the
evaporation of tungsten particles from the filament onto the
relatively cool wall of the glass envelope. The introduction of a
halogen (i.e., iodine or bromine) into the atmosphere of the
envelope brings about an interception of the tungsten particles by
the halogen gas. The tungsten particles are then redeposited back
on the filament, and the halogen gas is released to repeat the
cycle.
The halogen cycle results in clean bulb walls and more efficient
transmission of light over the life of the bulb. Tungsten-halogen
lamps of the type commercially available have an average rated life
of 2,000 to 4,000 hours, which is a much longer period than is
obtainable with ordinary incandescent bulbs. Moreover, at its rated
voltage, a tungsten-halogen lamp furnishes a much whiter light than
that produced by an ordinary bulb.
Nevertheless, while tungsten-halogen lamps of high wattage are
available in small bulb sizes, their use has heretofore been
limited to commercial and industrial installations, such as for
floodlighting of signs, service stations and loading platforms. The
practical reason for this is that despite the excellent color
rendition and shock resistance of tungsten-halogen lamps, since
they are generally of high wattage and run at elevated
temperatures, it has been considered hazardous to make use of them
in lampheads for table, wall and floor lamps intended for
residential and office use, or in other exposed situations in which
one may run the risk of touching the lamphead.
The heat produced by a tungsten-halogen lamp is usually so great,
particularly after prolonged use, that if the lamp were placed in a
lamphead of conventional design, a person making physical contact
with the lamphead might be severely burned. Since in many lamps,
the lamphead is adjustably mounted in order to enable the user to
direct the light as desired, one must anticipate that the user
would at some time touch the lamphead. Thus the use of
tungsten-halogen lamps in conventional lampheads has heretofore
been precluded because of the danger involved.
SUMMARY OF THE INVENTION
In view of the foregoing, it is the main object of this invention
to provide a lamphead for a tungsten-halogen bulb, which lamphead,
while the bulb is burning, may be handled comfortably and directed
at will, without in any way endangering personnel.
It is to be noted that the term "tungsten-halogen bulb" is
interchangeable with the term "quartz-halogen bulb," the latter
term bringing in the fact that the envelope is of quartz. The term
"tungsten-halogen" has supplanted the designation "iodine-quartz"
in describing this type of light source, for modern halogen bulbs
are not limited to iodine for the atmosphere.
More specifically, it is an object of the invention to provide a
lamphead for a tungsten-halogen lamp, which head includes a
protective tensile wire cage or cradle to permit the user to touch
and move the lamphead without burning his fingers.
Also an object of the invention is to provide a lamphead of the
above-noted type which incorporates a chimney to effect rapid
dissipation of heat from the lamp.
Yet another object of the invention is to provide a lamphead for a
tungsten-halogen bulb operating in conjunction with a solid-state
dimmer whereby the light from the head may be progressively changed
in color as well as in intensity.
Briefly stated, these objects are accomplished in a lamphead
constituted by a convex reflector joined to a cylindrical chimney
within which is concentrically mounted a socket for supporting a
tungsten-halogen lamp whose bulb is cylindrical, whereby an annular
air space is defined in the chimney between the inner wall thereof
and the surface of the socket and bulb. The up-draft created in
this space when the lamp is burning serves to cool the bulb.
Extending between the periphery of a flange secured to the upper
end of the chimney and the outwardly extending rim at the lower end
of the reflector is an array of tensile wires, spaced from the body
of the reflector and of the chimney to form a protective cage,
making it possible to safely handle the hot lamphead.
OUTLINE OF THE DRAWING
For a better understanding of the invention, as well as other
objects and further features thereof, reference is made to the
following detailed description to be read in conjunction with the
accompanying drawings, in which:
FIG. 1 is a side elevational view of a lamphead in accordance with
the invention;
FIG. 2 is a plan view of the lamphead;
FIG. 3 is a longitudinal section taken through the lamphead in the
plane indicated by line 3--3 in FIG. 2; and
FIG. 4 is a transverse section taken through the lamphead in the
plane indicated by line 4--4 in FIG. 3.
DESCRIPTION OF THE INVENTION
Referring now to the drawings, the main components of a lamphead in
accordance with the invention are a reflector 10, a chimney 11
joined to the reflector, and a lamp socket 12 mounted within the
chimney. Supported by lamp socket 12 is a tungsten-halogen bulb
13.
Reflector 10, which is preferably fabricated of high-purity
aluminum, is dome-shaped to define a convex reflecting surface.
Reflector 10 is provided with an outwardly extending circular rim
14 whose periphery is protected by an annular bead 15 of
heat-stabilized Nylon 103 or other suitable plastic material.
Reflector 10 is provided with a central opening surrounded by a
collar 16 which telescopes within the lower end of chimney 11.
Chimney 11 is in the form of an elongated tube of the same material
as reflector 10. Secured at an intermediate position to the chimney
is an annular apron 17 which, as best seen in FIG. 4, is provided
with a circular series of slots 17A forming retaining hooks for
engaging wires passing therethrough. Mounted on top of the chimney
is a bowl-shaped flange 18 having a collar 19 which telescopes into
the upper end of the chimney. The periphery of the flange is
protected by a circular bead 20.
Socket 12 is preferably fabricated of solid carbon tetrafluoride or
other heat-resistant material of low thermal conductivity and is
supported concentrically within the chimney by four equi-spaced
radial pins 21 of similar material. Bulb 13, which is a
tungsten-halogen lamp, such as one rated at 250 watts of the type
currently manufactured by General Electric or Sylvania, is provided
with a screw base. The bulb has a generally cylindrical envelope,
so that when it is seated in the round socket, an annular air space
exists within the chimney in the region between the bulb and socket
and the interior wall of the chimney.
Extending outwardly from diametrically opposed positions on the
chimney are a pair of rods 23 and 24, each of which terminates in a
small pulley 25 and 26, respectively, the pulleys being also made
of a material of low thermal conductivity. Pulleys 25 and 26 are
frictionally engaged by a pair of crook-shaped resilient wires 27
and 28 whereby the lamphead is rotatable about the common axis of
rods 23 and 24 to assume any desired angular position with respect
to this axis.
Threaded between the periphery of flange 18 and the periphery of
rim 14 is a uniform array of tensile wires 29, the wires passing
through the slots 17A in apron 17. Thus the wires, which are spaced
both from the body of the chimney and the reflector, form a
protective cage or cradle therefor.
In practice, the wires, whose extremities are covered by the beads
15 and 20, are preferably constituted by a seven-wire stainless
steel strand, each wire being about 1 mil in diameter. The wire
cage enables one to safely handle the lamphead while it is burning.
It will be seen that the wires, being attached only to the
peripheral parts of the reflector and upper cone which are
relatively cool, and being of very small cross-section and of
material of low thermal conductivity, remain effectively at the
temperature of the ambient air.
It will also be evident that bulb 13 is partially within the
chimney and partially within the reflector. Because of its high
operating temperature, bulb 13 heats the air within the reflector
10 and the chimney. As is well known, a chimney produces a draft by
virtue of a simple principle of thermodynamics. When air is heated,
it expands in volume and decreases in density, in which condition
it may be displaced by a denser gas. The light, hot gas is confined
by the chimney and its tendency to move up the chimney is
proportional to the height of the stack.
Because of the up-draft created by chimney 11, the hot air in the
reflector and in the chimney is drawn upwardly in the annular air
space 22 and discharged through the opening in flange 18, thereby
preventing excessive heating of the lamphead, despite its close
proximity to the lamp.
In practice, the tungsten-halogen lamp is supplied with power
through a solid-state dimmer (not shown) which acts to
progressively lower the operating voltage and thereby reduce the
intensity of illumination. The dimmer may be of the standard type
using SCR devices. However, because of the fact that a
tungsten-halogen lamp, when operating at its rated voltage,
generates light of almost solar whiteness (3,000.degree. K), it
becomes possible, by means of the dimmer action, to change the
color of the light, for as the intensity is diminished, the
radiated color of the lamp goes from white down through shades of
gold and orange before it is extinguished.
While there has been shown and described a preferred embodiment of
lamphead for a tungsten-halogen lamp in accordance with the
invention, it will be appreciated that many changes and
modifications may be made therein without, however, departing from
the essential spirit thereof.
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