Shutter for use with a light source

Details Shutter for use with a light source Shutter for use with a light source

2002-08-20

2004-04-13

Berman, Jack (Department: 2881)

Radiant energy

Radiant energy generation and sources

With radiation modifying member

C250S505100, C362S321000, C362S346000, C362S347000

Reexamination Certificate

active

06720566

ABSTRACT:

BACKGROUND
Light energy irradiators find many applications in manufacturing, universities, research facilities, and in the medical field. Irradiator systems are commonly powered by medium pressure mercury vapor lamps which are sometimes referred to in the art as arc lamps, ultraviolet (UV) lamps, cal rods, or UV curing systems. These systems have a wide range of uses and can be used, for example, in the curing of polymers such as photo polymer paints, the curing of inks and coatings, photo activation of adhesives, production of compact discs, and in photo resistant activation. A UV lamp produces high intensity radiation energy in the UV, visible, and infrared spectrums. This high intensity radiation energy may be used to cure inks, coatings, and adhesives that are applied to a variety of substrates, such as paper, plastic film, wood, and metal. The UV lamp or other light source that is used in these processes is typically supported next to a reflecting surface. The reflecting surface is configured in order to provide either a focused or a non-focused reflection of the light. Typically, when the apparatus is used for the curing of materials, the reflector surface will have an elliptical profile to provide a focused optical configuration. Here, the light energy is concentrated into a narrow beam on the curing surface. Typically, elliptical reflectors are used in curing photo reactive fast moving films and webs and printing inks on paper and plastic film that are carried on a conveyor.
The reflecting surface may also be configured to have a semi-circular or parabolic profile. Such a profile provides for a non-focused optical configuration of the reflected light from the light source. Such an optical configuration may be used in applications seeking to cure thicker or slower moving films such as adhesives.
A mechanical shutter is one common feature found in most high-powered light energy irradiators. The purpose of a mechanical shutter is to serve as a light-blocking device to prevent light from the UV lamp from reaching the substance that is being cured. When the shutter is in a closed position, it contains the radiation energy within the lamp housing to prevent energy exposure to the substrate and the material to be cured. In a common production process, the mechanical shutter will typically close when the production machine stops, in order to prevent thermal damage to the substrate. The mechanical shutter will open when the machine starts production, which therefore allows for complete exposure of the UV light to the UV curable material applied to the substrate that is moving under the UV light source.
Generally, two types of mechanical shutters are used in light energy irradiators. The first type is a rotating shutter. A rotating shutter is typically made of one piece of metal, usually aluminum due to its excellent conductivity. In order to close the shutter, the shutter simply rotates in front of the UV lamp to block the light from the substrate and the material to be cured. A rotating shutter is typically water-cooled to prevent thermal damage to the UV lamp system and the material being cured. However, some of the shutters may be air-cooled.
A second type of shutter is commonly referred to as a “clam shell” type shutter. This is so because the shutter is configured to open and close much like a clam shell. The shutter is constructed of two halves that are mirror images of one another and are mounted around the UV lamp. Each half of the shutter pivots around a strategically located pivot pin. When the shutter pivots to its closed position, it completely isolates the UV light within its closed cavity. This of course blocks the light from the substrate and the material to be cured. The shutter may also pivot to its open position to allow for UV light to be imparted onto the substrate and the material to be cured. These types of shutters are typically air-cooled.
Reflector sheets which are typically polished aluminum are mounted inside of the mechanical shutter in order to provide for the proper reflection of light energy from the UV lamp. A significant problem with reflector sheets are that the surface deteriorates over time, decreasing the performance of the light energy irradiator system. Additionally, these reflector sheets are difficult to replace. Current shutters make use of one or more rails along either the whole, or partial length of the shutter to retain the reflector sheets thereon. One way of replacing reflector sheets is to slide the entire reflector sheet out from one piece of the mechanical shutter. Such a procedure is problematic in that, aside from being a slow and difficult process, the new elongated reflector sheet when being slid back into the mechanical shutter may become slightly bent or may allow for air to be trapped between the reflector sheet and the mechanical shutter. In operation after having been replaced, heat from the light source will cause a warping of the reflector sheet due to the air being present between the reflector sheet and the mechanical shutter. Such warping will negatively impact the reflective condition of the reflector sheet resulting in decreased performance of the light energy irradiator system.
FIG. 7
shows a prior art shutter
110
. Here, the shutter
110
is housed within a lamp housing
106
. The reflector liner
20
is attached to a shutter section
102
. This attachment is facilitated by way of a retaining clip
100
which attaches the shutter section
102
and the reflector liner
20
.
The current state of the art employs UV lamp systems that have replaceable reflector liners
20
that are removed by disassembling a side of the lamp housing
106
and sliding the reflector liner
20
into a top and bottom retaining groove in a shutter
110
which is normally a very snug fit. This snug fit makes it difficult to slide the reflector liner
20
into position. In some instances, sliding friction can be so high as to cause the reflector liner
20
to bend as it is being forced into position. Such bending will negatively impact the reflector liner's
20
ability to reflect light energy. Additionally, it will also cause air gaps between the reflector liner
20
and the shutter
110
which consequently reduces heat transmission from the reflector liner
20
into the shutter
110
. These air gaps can cause the reflector liner
20
to over heat and warp during lamp operation which will subsequently negatively impact the reflective ability of the reflector liner
20
, reduce the light output of the UV lamp system, reduce the life of the reflector liner
20
, and could possibly cause the UV lamp system to overheat and impact the life of the lamp. On the other hand, if the reflector liner
20
is cut too small and fits too loosely within the grooves in the shutter, the liner
20
will not properly fit against the shutter
110
which may also cause air gaps between the reflector liner
20
and the shutter
110
and hence produce the same negative results as previously stated.
As shown in
FIG. 8
, the retaining clip
100
may be attached by the use of a screw
104
. One or more retaining clips
100
may be employed along the length of the prior art shutter
110
as shown in FIG.
9
. Here, three retaining clips
100
are employed on one section of the prior art shutter
110
and four retaining clips
100
are employed along the length of another section of the prior art shutter
110
. The retaining clips
100
are mounted every few inches along the length of the prior art shutter
110
, and are not continuous along the length of the prior art shutter
110
. As shown in
FIG. 7
, such a configuration does not prevent the occurrence of air gaps between the reflector liner
20
and the shutter section
102
hence resulting in a warped area
98
of the reflector liner
20
. Further, the retaining clips
100
do not help conform the reflector liner
20
to the shape of the shutter section
102
, but only help to retain the reflector liner
20
onto the shutter section
102
. Since the retaining clip
100
does not force the reflector l

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