Note: Descriptions are shown in the official language in which they were submitted.
714
FIELD OF THE INVENTION
The field of the invention relates to a generator for
"cool" ultraviolet light.
The generation of ultraviolet light by means of an
ultraviolet lamp is accompanied by the production of large amounts
; of infrared or heat radiation. For example, a piece of 2" x 4"
wood spaced at a distance of one foot from a 1000 watt UV lamp
will ignite within 15 seconds. Hitherto, no satisfactory method
has been available for removing this unwanted heat energy so as to
~10 produce cool ultraviolet radiation.
Accordingly the present invention provides the method
of obtaining cool ultraviolet rays from a source of UV radiation
which produces both infrared and ultraviolet radiations, which
comprises the step of filtering the radiations from said source
through steam.
The invention will now be described in more detail, by
way of example only, with reference to the accompanying drawings.
DESCRIPTION OF THE DRAWINGS
Fig. 1 is a perspective view illustrating an applica-
tion of the subject invention as applied to means for curing, by
ultraviolet radiat1on and steam, the radiation-curable decorative
;~ and/or protective coating on a heat-sensitive substrate of paper,
textile material or the like.
Fig. 2 iS a vertical section of Fig. 1.
Fig. 3 is a view taken on line 3-3 of Fig. 2.
Fig. 4 is an enlarged sectional view of a device which
embodies the present invention wherein the relationship between
the steam filter and the source of UV radiation is illustrated.
Fig. 5 is a plan view of an electrode plate which con-
~30 stltutes a detail of the apparatus of Figs. 1-4.
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714
DESCRIPTION OF THE INVENTION
A source of radiant energy such as, by way of example
a UV lamp 10 is suitably housed or encapsulated within an elon-
gate, substantially cylindrical tube 12. The opposite ends of
lamp 10 terminate at, and are supported by, a pair of axially
aligned electrodes 14 and 16, each of which are secured to,
carried by, and project through the centrally disposed opening
18 of a pair of stainless steel electrode plates 20 and 22.
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As best illustrated in Fig. 5, electrode plates
20 and 22 comprise a solid intermediate portion 26 which
extends outwardly from the central opening 18 to a peripheral
edge 26, from which a plurality of fins 28 project, as
illustrated, wherein each fin includes an outer terminal
end 30.
Tube 12 and the electrode plates 20 and 22 define
a moisture-impervious first chamber A in which lamp 10
is housed, and when suitably energized, the tube will
operate at its rated operating temperature, such as, by
way of example, at 500 C for a commercial 24 inch lamp.
A second elongate, substantially cylindrical tube
40 is disposed in spaced~ circumscribing, axial relation-
ship with tube 12 for defining an elongate passageway Q
along the entire length of tube 12, wherein the spaced
electrode fins 28 are disposed at opposite ends of said
passageway. Preferrably tube 40, like tube 12, is of
actinic quartz, being transparent to ultraviolet rays
in the 2000 A - 4000 A range.
In the preferred embodiment of the invention, the
outer terminal ends 30 of fins 28 of the electrode plates
20 and 22 abuttingly engage the inner surface 42 of tube
40 for thereby disposing and maintaining outer tube 40 in
spaced axial alignment with inner tube 12.
The opposite ends 44 and 46 of outer tube 40
abuttingly engage the inner surfaces S of end plates 50
and 52 respectively which are provided with a circular
recess R dimensioned to snugly receive the outer diameter
of outer tube 40 to provide a vapor-proof seal.
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End plate 50 is provided with an inlet port I whereas
end plate 52 is provided with an outlet port O.
As best illustrated in Figs. 3 and 4, the outer
surfaces of electrode plates 20 and 22 are spaced laterally
from the respective end walls S0 and 52 for providing end
areas T and T' therebetween, wherein said end areas T and
T' are in open communication with one another by reason
of the elongate passageway Q as defined by the inner and
outer tubes 12 and 40.
Electrodes 14 and 16 are adapted to be energized
from a suitable source, not illustrated, by means of
electrical conductors 70 and 72, respectivbly, suitably
housed within moisture and heat impervious sheaths such
as, by way of example, of a silicone polymer, a glass
cloth sheathed silicone polymer, or the like, 74 and 76,
Conductors 70 and 72 are disposed in conducting relationship
with their respective electrode plates 20 and 22 as at 78.
The end areas T-T' and passageway Q define a
second chamber B, which is moisture-impervious and
completely encloses or houses the first chamber A.
Steam, from a suitable source, not illustrated,
is introduced into chamber B via inlet port I into end
area T, thence in~o passageway Q to end area T' and thence
into outlet port O, for thereby providing a steam barrier
or filter which completely encompasses the entire light
emitting length of the lamp, and through which filter
the rays from lamp 10 must pass. The steam within chamber
B also completely encompasses the outer surfaces of the
electrode plates 20 and 22 of the first chamber A.
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I have determined that steam has the unique
property of absorbing or otherwise effectively blocking
the passage of infrared rays while permitting the sub-
stantially unimpaired passage of ultraviolet rays from
a source of radiant energy, such as, by way of example,
a mercury vapor arc lamp 10.
The following example will demonstTate the degree
to which steam will prevent the passage of infrared rays
while passing ultraviolet rays from a source of radiant
energy.
Steam was injected into a metal hood containing
sixteen (16) one thousand (1000) watt mercury vapor lamps
each having an aluminum reflector. ~ web of paper .002
thick~ coated with a resin containing an ul~raviolet
sensitive curing agent of the type that was oxygen
inhibited was passed beneath the hood with all of the
16 lamps on, generating ultravîolet radiation and about -~
eight thousand (8000) watts of infrared radiation. The
paper emerged from beneath the hood with the resin fully
cured within 1 1/2 seconds with the paper uneffected by
the heat generated by the lamps. Thereafter movement of
the paper web beneath the hood was stopped with all 16
of the lamps on, as aforesaid, and after exposure or
ten ~10) minutes at a distance of 3/~ inch from the
lamps the paper as removed from beneath the hood was
entirely free of discoloration or charring.
The steam supply to the hood was then turned off,
and within three seconds as the steam within the hood was
being dissipated, the paper web being subjected to the
radiant energy from the lamps within the hood, burst into
flame.
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1~317~4
To more fully appreciate the tremendous amount of
infrared radiation generated by a 1000 watt mercury vapor
lamp, it may be noted that a piece of ~" X 4" wood spaced
at a distance of one foot from a 1000 watt UV lamp will
ignite within 15 seconds.
Since steam is an infrared emitter as well as an
absorber, the degree of absorption of infrared energy in
passageway Q of chamber B is proportional to the rate of
steam flow, that is, the higher the rate of steam flow,
the greater the absorption of infrared energy by the
steam filter. ~ - -
I have determined that the rate of steam flow
through chamber B may be easily and accurately controlled
by means of a valve, not illustrated, in the steam supply
line, to inlet I whereby to provide and maintain a steam
temperature at outlet 0 from 215 F to 220 F, in those
instances in which the temp~rature of the steam entering
inlet I is 212 F, at atmospheric pressure. The ultra- -
violet radiation thus produced may be characterized as
"cool" since it is free or substantially free of infrared
rays. Such "cool" ultraviolet radiation is ideally
adapted for exposure to thermally sensitive substrates
such as paper, textiles, thermoplastics, food, and the like.
Higher steam temperatures at outlet 0 may be
permitted when thermally insensitive material such as
glass, metal, and the like, is being subjected to the
resultant "cool" ultraviolet radiation from the steam
filter.
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It will be understood that the source of steam
must have sufficient pressure to overcome the friction
losses and back pressure due to flow obstruction, to insure
an adequate rate of steam flow through chamber B. The
steam, under pressure from 5 to 20 p.s.i. enters inlet I
at 212 F or at the boiling point of water, as saturated
steam at atmospheric pressure.
The passage of steam through passageway Q not only
effectively absorbs infrared energy from the light-
emitting length of lamp 10, it also effectively coolsthe electrode plates 20-22 in the end areas T and T'
to such an extent or degree that the outer surfaces of
said plates and their heat dissipating fins 28 is in the
neighborhood of 250 F - 275 F well below 300 F. By
thus cooling the electrode plates the life of lamp 10 is
increased many fold.
Since infrared radiation is thus absorbed by the
steam, the resultant "cool" ultraviolet rays may be
utilized in those applications where high intensity
"cool" ultraviolet radiation is desired, but wherein
such ultravlolet rays could not heretofore be success-
fully utilized by reason of the ever-present infrared
radiation which accompanied and was inseparable from
the ultraviolet radiation.
With particular reference now to Figs. 1 and 2,
the numeral 80 designates a length of material at least
one surface of which is provided with a radiation-curable
material in the presence of ultraviolet rays and in an
inert environment. Heretofore nitrogen, helium, argon,
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neon, carbon dioxide, or other inert gas, has been
flooded onto those portions of a web of material containing
radiation-curable material undergoing exposure to ultra-
violet rays, for displacing the thin film of air on the
surface of the radiation-curable material.
I have ascertained that the use of inert gaseous
materials such as) by way of example, nitrogen, etc. is
not required but that uniformly satisfactory, if not
superior results can be obtained in those instances in
which the surface of the radiation-curable material is
subjected to "cool" ultraviolet rays in the presence of
dry, that is, super-heated steam of a temperature sufficiently
high to minimize condensation of the steam on the surface
of the material being treated, cured, or the like.
In Fig. 2 the numeral 90 designates a source of
dry, super-heated steam which is continuously discharged
onto the upper coated surface of web 80 while said web is
being advanced to the left in the direction of the headed
arrow 82 whereby to be exposed to the "cool" ultraviolet
rays from the lamp 10 while being literally immersed in
an atmosphere of dry, super-heated steam, which if desired,
may be obtained from outlet O of housing 60 via a well-
insulated steam conduit 92.
In passing it will be noted that steam is not an
inert gas in the sense that nitrogen, helium, carbon
dioxide, and the like, are inert,
The su~ject device is ideally suited or use in
those instances and applications wherein "cool" ultra-
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violet radiation is utilized to dry, cure 5 or otherwisereact with various types of finishes 9 coatings, pigments,
and the like which are classified as radiation-curable.
It should, of course, be understood that the subject
device is ideally adapted to generate cool ultraviolet
radiation absent the customary infrared components thereof
whereby it is now feasible for the first time to employ
extremely high wattages without having to be concerned with
the tremendous heat radiated via the infrared rays.
A steam enveloped ultraviolet tube of high wattage
may be utilized in sterilizing food products such as, by way
of example, fresh and/or wrapped meat for effectively
killing the surface bacteria thereon, but without elevating
the temperature of the meat product being so treated.
Uniformly satisfactory results have been obtained
in those instances in which the effective lighted-length
of lamp 10 is twenty-five inches and wherein the wattage
input is 200 watts/inch of lighted length, for a total of
5000 watts. Lamp 10 operates at a temperature of 500 C
within the confines of tube 12 and the electrode plates
20 and 2~.
The steam passing through passageway Q literally
absorbs the infrared radiation generated by the lamp, while
per~itting the passage of ultraviolet radiation therefrom.
The temperature of the steam as it leaves port O
is ~lways greater than the temperature of the steam entering
port I by reason of the heat imparted thereto by the infrared
radiation absorbed by the steam.
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By controlling the rate of flow of steam through
the device such that the temperature at outlet 0 is in the
215 F - 220 F range the rate of steam flow will be
adequate to absorb any wattage of infrared radiation
from lamp 10, and the temperature of the steam leaving
outlet 0 will be sufficiently superheated and dry, by
way of example, to be utilized as illustrated in Fig. 2
for application, via conduit gO, directly onto the upper
surface of web 80; or if the steam is not so used it may
be exhausted or it may be returned to the source from
which the steam is supplied to inlet I. `'
Returning now to the drawings, the numeral 62
denotes a substantially U-shaped reflector which is anchored
in place by a mounting strap 64, the opposite ends of which
are suitably secured to end plates 50 and 52, whereas the
numeral 66 denotes a housing in which the device is
contained in such a manner as to prevent the uncontrolled
escape of ultraviolet radiation.
`^ Uniformly satisfactory results have been obtained
,~ 20 in those instances in which the spacing between the adjacen,t
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surfaces of tubes 12 and 40 is one-half inch when lamp 10
is 24 inches long. This space dimension may be increased
to one inch for a 36 inch lamp, and to one and one-half
inches for a forty-eight inch lamp. By thus increasing
the width of passageway Q of chamber B, the rate of flow '
of steam therethrough wi,ll be comparatively low for'all
lengths of lamps in order to maintain the temperature of
the steam being exhausted from outlet 0 in the 214~ F - -
220 F range.
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It should be understood that if desired an
elongate tubular passageway such as Q defined by a pair
of spaced inner and outer tubes 12 and 40 may be slipped
over at least the light-emitting length of a UV lamp 10
for filtering the rays eminating from the lamp but without
utilizing the end areas T and Tt. In other words, steam
would be supplied to one end of the space between the two
tubes and exhausted at the other end, in which event "cool"
ultraviolet radiations, absent infrared radiation, would
pass from tube 40, however, the cooling effect of the
steam on the electrode plates will have been sacrificed.
In summary, what I have provided is a live steam
filter for the infrared and ultraviolet components of
energy from a source of UV radiation wherein the steam
absorbs the infrared radiation while passing the ultra-
violet radiation.
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