Illumination – Light modifier – Reflector
Reexamination Certificate
2002-10-31
2004-12-28
Ward, John Anthony (Department: 2875)
Illumination
Light modifier
Reflector
C362S293000, C362S304000, C362S305000, C362S343000, C250S503100
Reexamination Certificate
active
06834984
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to lamps and the heat absorption and transfer properties associated therewith. More particularly, the invention relates in one embodiment to improving the content of light usable in ultraviolet (“UV”) light curing applications along with improving the capture of unusable light and dissipating the heat associated therewith.
2. Description of the Related Art
The purpose of reflective surfaces in a UV curing system is to gather and direct the light emitted from a lamp (also referred to as a “light source”) directly to a two dimensional or three dimensional plane(s) or object(s) where UV curing will take place. In general, the mechanical structure that holds these reflective surfaces and the light source is called a housing. Some reflective surfaces discussed in detail herein are, in actuality, band-pass filters. These band-pass filters transmit certain wavelengths of light and reflect other wavelengths of light. Other reflective surfaces, referred to as “reflectors” reflect substantially all light incident thereon.
The light emitted from the light source is composed of three main regions of the electromagnetic spectrum: (a) wavelengths from about 200 nm to about 400 nm are generally considered to fall within the UV portion of the spectrum; (b) wavelengths from about 400 nm to about 760 nm are generally consider to fall within the visible part of the spectrum; and (c) wavelengths from about 760 nm to about 3,000 nm are generally considered to fall within the near infrared (“IR”) portion of the spectrum.
In conventional housings, the light is reflected by a planar reflector or mirror
16
, as shown in FIG.
1
. Inherent in this reflector design is the gathering and redirecting of a part of the IR portion of the spectrum back across the surface of the lamp. This reflected IR light has been shown to cause unwanted radiant heat transfer back into the exterior and interior of the lamp. This additional heat can: (a) impair the efficient functioning of the lamp; (b) increase the operating temperature of the lamp; and (c) reduce the UV light output of the lamp.
One way to reduce the possibility of directing IR light back into the lamp is to remove the mirror
16
behind the lamp and to remove other reflective surfaces therearound that would otherwise redirect the IR light back into the lamp. However, as the mirror
16
and reflective surfaces redirect not only IR light but also UV and visible light, removing them to reduce the redirection of IR light would reduce the amount of UV light available in a UV curing application and decrease the overall efficiency of the system.
After the light is redirected in a second direction, it joins other light which originated on that second direction from the lamp; this combination of light must be separated into useable and unusable wavelengths. One way to separate the light is by using an optical filter such as a band-pass filter which may, for example, separate UV light from other types of light (e.g., IR and visible light) so that the UV light can be used in applications which depend on UV light (and which may be hampered by other types of light), such as UV curing applications.
Thus, the purpose of a band-pass filter in an optical system is to reflect light in a specific range of wavelengths and to transmit light of a different set of wavelengths. A particular type of band-pass filter, often referred to as a “cold mirror,” is used to provide good reflection of light having wavelengths in a particular range and to transmit light outside of that range. For example, one type of cold mirror reflects light having wavelengths between about 200 nm and about 450 nm (i.e., UV light and the lower end of the visible light spectrum) and transmits light having wavelengths above about 450 nm, i.e., light which includes most visible light and IR light.
Band-pass filters may be used to separate light into usable and unusable light. For example, a cold mirror may be used to separate light into UV light and visible/IR light. The UV light may be reflected toward a material, such as a web, that is to be cured via a curing application. By way of contrast, the visible/IR light may be transmitted through the cold mirror (i.e., it is not directed toward the curing application at hand), to prevent unnecessary and unwanted heating of the materials that are to be cured. A prior art embodiment incorporating a band-pass filter will be described with respect to FIG.
1
.
FIG. 1
is a schematic view of a prior art lamp housing
100
. The lamp housing
100
contains a lamp
26
(also called a “light source
26
”) which projects diverging light having a variety of wavelengths from the interior
24
of the lamp
26
. Some of the light is directed toward a reflective mirror
16
which reflects the light toward a band-pass filter
20
, which may be a cold mirror. In some prior art embodiments, the mirror
16
is planar (as shown) whereas in other prior art embodiments the mirror
16
is curved. However, in all prior art embodiments, at least some of the light reflected by the mirror
16
is redirected back toward the light source
26
.
Some of the light from the light source
26
is also reflected off shutters
12
toward the band-pass filter
20
. The shutters
12
, which rotate on axes
14
, have inside surfaces (i.e., on the side facing the light source) which are highly polished. As a result, when an object
8
(which may be in the form of a tape or label) to be cured is moved across a window
22
in the housing
100
, the shutters
12
may be opened and the polished surface of the shutters
12
used to gather and direct the light toward the band-pass filter
20
.
The shutters
12
may be opened due to their being adapted to rotate on the axes
14
. In a first position (not shown), the distal ends
13
of the shutters
12
approach each other, thereby substantially containing the light emitted by light source
26
. In a second position, shown in
FIG. 1
, the distal ends
13
of the shutters
12
are separated so that the light emitted by the light source
26
can be reflected toward the band-pass filter
20
.
The shutters
12
also serve a heat containment function. The temperature of the light source
26
may reach from about 650° C. to about 850° C. In some embodiments, as the light source
26
is reasonably close to the moving object
8
, if the object
8
is stopped while the lamp housing
100
is emitting light, it may be preferable to protect the object
8
from the heat associated with the light emitted by light source
26
by closing the shutters
12
.
The band-pass filter
20
is adapted to reflect light having a wavelength which falls within a specified range and to transmit light having wavelengths outside of that range. For example, in UV curing applications, if a cold mirror is used for the band-pass filter
20
, it may reflect light having wavelengths between about 200 nm and about 450 nm (i.e., UV light coupled with the lower end of the visible light spectrum) and transmit light outside of this range including the remainder of the visible light and IR light. The light which is reflected by the cold mirror passes through a protective window
22
and may be used in applications calling for a particular type of light, e.g., UV light.
As the remaining light (e.g. visible/IR) is transmitted through the band-pass filter
20
, it may be necessary to protect people and/or items which may be harmed by exposure to this light. To address this concern, the light which is transmitted through the band-pass filter
20
may pass through an air corridor
52
and into a solid heat sink
30
where it may be absorbed and converted into heat energy via radiant heat transfer.
Air, which is fed into the air corridor
52
via inlets
50
, may be used to cool the heat sink
30
. Similarly, air may be fed into the housing
100
via inlets
40
. The air passing through the inlets
40
may be used to cool the light source
26
, the mirror
16
, and the shutters
12
. Further, the heat sink
30
may be design
Alexander Charles
Tausch Mark
Choi Jacob Y.
Delaware Captial Formation, Inc.
Foley & Lardner LLP
Ward John Anthony
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