U.S. patent number 3,662,175 [Application Number 04/886,987] was granted by the patent office on 1972-05-09 for apparatus for generating ultra violet light.
This patent grant is currently assigned to Tuttle, Incorporated. Invention is credited to Renaldo M. Beltramo, George L. Davidson.
United States Patent |
3,662,175 |
Davidson , et al. |
May 9, 1972 |
APPARATUS FOR GENERATING ULTRA VIOLET LIGHT
Abstract
Apparatus for generating ultra-violet light which can be
controlled to provide a controlled erythemal effect.
Inventors: |
Davidson; George L.
(Cincinnati, OH), Beltramo; Renaldo M. (Cincinnati, OH) |
Assignee: |
Tuttle, Incorporated
(Cincinnati, OH)
|
Family
ID: |
25390215 |
Appl.
No.: |
04/886,987 |
Filed: |
December 22, 1969 |
Current U.S.
Class: |
250/504R;
250/372; 250/505.1; 313/642; 359/361 |
Current CPC
Class: |
G01J
3/10 (20130101); A61N 5/06 (20130101); A61N
2005/0644 (20130101) |
Current International
Class: |
A61N
5/06 (20060101); G01J 3/10 (20060101); G01J
3/00 (20060101); H01j 005/16 () |
Field of
Search: |
;250/84,86,88
;313/225,228 ;350/1,290 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
"Aluminum Reflecting Surfaces For Projection Work" By J. D. Edwards
from International Projectionist, Feb., 1935, pages 15, 16 &
23-25..
|
Primary Examiner: Lindquist; William F.
Claims
We claim
1. Apparatus for providing a controlled light output in the
ultra-violet range to provide an erythemal effect, comprising: lamp
means for generating a generally continuous output for
substantially the ultra-violet range, said lamp means comprising a
housing having an opening at one end, at least one lamp mounted in
said housing for transmitting light towards said opening, filter
means connected to said housing over said opening for providing a
filtered output from said lamp over a selected wave length range
whereby the filtered output can be used to provide an erythemal
effect, and calibration means separate from said lamp means for
determining the intensity of the filtered output over said selected
range, variable power supply means selectively actuable for varying
the power to said lamp and hence for selectively controlling the
intensity of the filtered output whereby the erythemal effect can
be controlled, said lamp comprising a mercury vapor gas lamp with
the gas doped with a small quantity of xenon being no greater than
around four percent of the gas by volume, said lamp having closely
spaced electrodes being spaced no greater than around 0.75 inch.
Description
SUMMARY BACKGROUND OF THE INVENTION
The present invention relates to apparatus for generating
ultra-violet light and more particularly to apparatus for providing
a controlled output of ultra-violet light.
It would be desireable to be able to provide a source of
ultra-violet which could be controlled in such a manner as to
provide a known output. In this way various effects of light in the
ultra-violet range could be utilized and/or analyzed. For example
it would be desireable to determine the erythemal effect on human
skin of various pigmentations as caused by sunlight. In this regard
it is known that certain wave lengths of ultra-violet are more
effective than others as to erythemal effect. To facilitate the
occurrence of erythemal effect it would be desireable to have a
source of ultra-violet which is rich in the desired wave lengths
and could be controlled such as to provide a known output at those
wave lengths. Prior devices and apparatus were unreliable in that
they either were deficient in the desired spectral region or such
extreme variations in output between similar devices occurred as to
make their use literally impractical.
Therefore it is an object of the present invention to provide
apparatus for providing ultra-violet light which can be controlled
to provide a known output over various spectral regions.
It is another object to provide apparatus for providing a
controlled erythemal effect.
It is another object to provide novel apparatus generating and
utilizing ultra-violet light.
Other objects, features, and advantages of the present invention
will become apparent from the subsequent description and the
appended claims, taken in conjunction with the accompanying
drawings, in which:
FIG. 1 is a pictorial view depicting a system utilizing features of
the present invention;
FIG. 2 is a side elevational view with some parts broken away of
the generating device of FIG. 1 taken generally in the direction of
the arrows 2--2;
FIG. 3 is a sectional view, to increased scale of the apparatus of
FIG. 2, taken generally along the line 3--3; and
FIGS. 4 A--C are curves of relative intensity versus wave length
for different ultra-violet light generating tubes.
Looking now to the drawings, FIG. 1 shows a lamp assembly 10
electrically connected to a variable power supply 12 via conductors
14. The supply 12 is provided with a suitable dial actuated element
16 whereby the voltage to the lamp assembly 10 can be selectively
varied. A voltmeter 18 and ammeter 20 are connected to the power
supply 12 to provide an indication of the magnitude of voltage and
current to the lamp assembly 10. The output from power supply 12
can be controlled by a timer 22 whereby the time interval for
energization of the assembly 10 can be selectively varied. The
timer 22 could also provide an audible signal for operator control
or could be connected to actuate a shutter structure (such as
defined below by straps 36, etc.)
The lamp assembly 10 is readily portable and includes a housing 24
which has a handle 25 mounted at its rearward side. The housing 24
has an open forward face which is generally closed by a cover
assembly 26. A pair of gas lamps 28 (the details of which are to be
described) are supported in the housing 24 with an arcurately
shaped reflector 30 supported behind. A suitable filter system 32
(the details of which are to be described) is located between the
lamps 28 and the cover assembly 26. The cover assembly 26 has a
pair of side by side slots 34 which when open will, of course,
transmit the light energy from the lamps 28 as enhanced by the
reflector 30. A pair of strap members 36 are slidably supported in
guides 38 and 40 and can be selectively moved relative to the slots
34 whereby the area of light transmission through the slots 34 can
be selectively varied.
It has been indicated in some prior literature that a wave length
of 296.7 nanometers provides maximum erythemal effect on human
skin. However, it is believed that substantial erythemal effect can
be obtained at other wave lengths. Therefore it would be desireable
to have a device capable of generating a significant output over
the entire UV range such that any desired wave length could be (by
proper filtering) selected and effectively utilized. Such a device
could have substantial clinicial and domestic use. With prior UV
apparatus mercury vapor tubes have been used to generate
ultra-violet (UV) light. The output from a mercury vapor tube,
however, in the UV range is erratic and generally composed of a
series of peaks and valleys (see FIG. 4A). In fact the mercury
vapor tube output could have a minimum output point at the desired
wave length; for example 296.7 nanometers. A xenon gas tube in the
UV range (see FIG. 4B) has a relatively uniform output. It has been
found that by adding a relatively small percent of xenon to a
mercury vapor tube that the relative intensity of the resultant
tube over the UV range will be quite smooth when compared to the
tube with mercury without xenon (FIG. 4A); of especial significance
is the fact that the valleys or minimal output points are
substantially eliminated. The result is a tube or lamp which can be
effectively used at generally any desired wave length in the UV
range. It should be noted that mercury - xenon lamps have
previously been used for street lighting. Xenon alone will provide
a high relative intensity in the visible light range and also a
high relative intensity in the infra-red range. For lighting, a
large quantity of xenon is used to enhance the visible light
output. At the same time, of course, a considerable amount of heat
is generated as a result of the high infra-red (IR) output of
xenon. For devices utilizing the UV range it is desireable to
minimize the generation of IR. It was found by limiting the percent
of volume of xenon in the tube, e.g. to a maximum of between around
4 to 6 percent, the desired results can be obtained without undue
heat generation. In a preferred form good results were obtained
with a mercury vapor tube doped with 4 percent by volume of xenon
with the tube at a pressure of around 3.5 atmospheres; of course,
the tube could also include some argon which aids the firing of the
tube.
The desired wave length can be obtained by proper selection and
design of the filter 32. While the filter 32 is shown as a single
glass element it should be understood that in actual practice a
plurality of such elements may be utilized. The apparatus as shown
in FIG. 1 is for clinical use to test erythemal effect on human
skin. In such a case the filter 32 is designed to be relatively
sharp cut at the desired UV wave length such as 296.7 nanometers.
The device would be used by contacting the test patient's body with
the front cover 26. This will automatically locate the skin a
preselected distance from the tubes 28. Next the tubes 28 can be
energized for a fixed time by the timer 22. By moving the straps 36
the exposed skin area can be selectively varied. In this manner
erythemal effect at different wave lengths (by changing filter 32)
and for different time intervals can be selected. The apparatus
would be useful for determining the effectiveness of various sun
tan lotions, etc., which purport to be effective against crythemal
effect (sunburn) from the sun. Note that in minimizing the
magnitude of IR generation heat problems are minimized and
discomfort to the patient is avoided. Some air cooling, via a small
fan (not shown) could be provided to cool the filter 32.
The UV output from the assembly 10 can be calibrated by calibration
apparatus 44. The apparatus 44 can include a photosensitive element
50 and may or may not utilize an additional filter 48 to attenuate
the output from the assembly 10. The intensity of the transmitted
UV light can be read upon a meter 52 and can then be adjusted to
the desired magnitude by manipulation of the voltage output from
the power supply 12. In this way tests can be repeated at the
desired wave length for a selected time at a selected
intensity.
To improve the efficiency of the assembly 10 the reflector 30 was
designed to have a parabolic curvature. In addition it was found
that the type of surface finish was significant. It was found that
a dull, matte like finish resulted in a substantially higher
percentage reflectance than a polished finish. Thus an aluminum
reflector polished, e.g. to have a micro finish of from around 5 to
20 micro inches, and subsequently sand blasted with fine grain sand
to dull the finish will have a higher percentage of reflectance in
the UV range than a polished, shiny reflector. A magnesium oxide
coat, applied by electro-deposition to a polished surface, also
provides a dull finish having higher reflectance than the polished
reflector; the same is true of a polished surface which has been
dulled by chemical etching. Thus the reflector 30 constructed to
have a dull, matte like finish improved the efficiency of the
assembly 10 in the UV region.
While some discussion has been made with regard to mercury street
lights which use a substantial amount of xenon, it is significant
to note that conventional mercury sun lamps do not use xenon. Such
lamps, in order to increase the UV output, locate the electrodes a
substantial distance apart, i.e. in some lamps around 1.75 inches,
requiring higher operating voltages. These lamps also, at the
higher voltages, have a substantial IR output or heat generation.
In the mercury - xenon tube of the present invention the UV output
is enhanced (by the xenon) and as a result the operating voltage
need not be as high. This permits the electrodes 54 to be spaced
relatively close to each other. The result is an efficient UV
generator with less heat (IR) generation for a given output in the
UV range. In one form, the electrodes were located 0.75 inch
apart.
The more proximate location of the electrodes 54 provides an added
advantage. With conventional sun lamps in order to maintain the arc
pressure (and hence the arc), supplemental heat to the tube is
required; it has been the practice to locate the ballast near the
tube and to use its heat generation as the source of supplemental
heat. This, of course, results in a cumbersome design. In the
present invention, with the electrodes 54 located so close the
internal local temperatures are more readily maintained at the
necessary level to maintain arc pressure (and hence the arc) and as
a result no supplemental heat source is required. Thus the ballast
can be located remotely from the lamp assembly 10 permitting the
design of a readily, portable device.
Note that the tubes 28 have an output characteristic (see FIG. 4C)
which encompasses not only those wave lengths causing erythemal
effect but also in the germicidal range. Hence the tubes 28 could
be used effectively for sterilization of clinical instruments,
control of bacteria, molds, and other micro-organisms.
While it will be apparent that the preferred embodiments of the
invention disclosed are well calculated to fulfill the objects
above stated, it will be appreciated that the invention is
susceptible to modification, variation and change without departing
from the proper scope or fair meaning of the invention.
* * * * *