Radiant energy – Radiant energy generation and sources – With radiation modifying member
Reexamination Certificate
1998-06-30
2001-02-20
Anderson, Bruce C. (Department: 2881)
Radiant energy
Radiant energy generation and sources
With radiation modifying member
C250S503100, C250S493100, C250S498100, C378S160000
Reexamination Certificate
active
06191428
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to apparatus and method for exposing curable material to high intensity ultraviolet light.
Of particular relevance to the present invention, are systems and methods by which curable material forms part of a protective or decorative surface on objects that, typically are of a size which can be held in a human hand, and which are to be processed at a relatively high rate. This processing can be of a high speed batch type, whereby each object having curable material thereon, is fixtured in spaced relation from a series of other such objects, and conveyed to a particular location where each object is subjected to high intensity ultraviolet (UV) curing light. The light passes through a shutter which opens and closes to control the duration of the curing exposure. Such conveying can be implemented by an indexing conveyor, such as a rotary indexing table of the type described in pending U.S. patent application Ser. No. 08/668,445 filed Jun. 20, 1996 for “Rotary Indexing Table”, now U.S. Pat. No. 5,784,932 the disclosure of which is hereby incorporated by reference.
Indexing conveyors have been used in the decorating field for screen printing, hot stamping, pad printing, ink-jet printing, impact marking, laser marking, spray painting and other decorative purposes. As one particular example, rotary indexing tables are employed for multi-color screen printing onto work pieces such as compact discs, credit cards, key fobs etc. Typically, the dial of a rotary indexing table supports multiple, equidistantly positioned fixtures. The fixtures support the work pieces during the printing and curing operations. At a first work station (or section of a work station), a work piece is automatically positioned onto the fixture. The dial then rotates through a precise angle or distance to position the work piece under a first screen printing apparatus. The dial is thereafter indexed one more increment such that the work piece is positioned beneath a source of UV light. A shutter is opened, the work piece is exposed for a preset time interval during the dwell time of the indexing conveyor, and the shutter is then closed. The dial is then indexed for the screen printing of a subsequent pattern or image, and indexed again for another UV curing step, whereby the process continues until all the printing and curing has been completed for a particular work piece.
In the particular example of the work piece being a compact disc, the work piece is generally flat, with a length and width that are measured in inches, e.g., a compact disc is typically about 5 inches in diameter.
In conventional equipment of the type employed for such UV curing, the shutter system may have single or dual slide gates, single or dual pivoting reflectors, or so-called “bombay doors”. For example, if two bombay doors open and close across a six by six area, each door is rotated 90° downward to a substantially vertical orientation, for opening the shutter. Of course, the doors would then each rotate 90° back to the horizontal, for closing the shutters. Therefore, the exposure of the work piece below the shutter would have a duration determined in part by the time required for the doors to cycle 180°, i.e., actuate 90° to full open, then actuate 90° to full closure.
One can readily appreciate that with an indexing conveyor system, whereby a series of work pieces are conveyed beneath the shutter, so that an individual work piece periodically is located in a stationary condition for a pre-determined time interval, the center of the work piece (which lies directly under the juncture of the bombay or other conventional doors), will receive significantly more UV exposure than the outer surfaces of the work piece. This can present a problem because curing of UV inks or adhesives, requires a precise and even dosage of light energy for optimum results. Moreover, not only do the bombay doors and other conventional types of shutters produce uneven exposure, but the speed at which the shutters can operate through a full cycle, is limited by the need to mechanically accelerate and decelerate one or two relatively larger shutter elements through 180° of angular motion (i.e., 90° clockwise to open and then 90° counter-clockwise to close), or through a complete reversal of linear sliding.
SUMMARY OF THE INVENTION
It is, accordingly, an object of the present invention to provide a system and method for reducing the cycle time and improving the exposure control of a UV shutter assembly of the type used in curing work pieces.
It is a particular object to provide a system and method for reducing the cycle time and improving the exposure control of a UV shutter assembly of the type used in curing work pieces on an indexing conveyor or the like, where the work piece is stationary during UV exposure.
It is a more particular object of the invention, to provide a system and method for periodically positioning curable material at a location subject to high intensity UV curing light passing through a shutter assembly which opens and closes at a faster than conventional speed to better control the duration of curing exposure.
It is still a further object of the invention to provide a system and method for exposing curable material to high intensity UV light through a shutter assembly for a target exposure interval, wherein the actuation time for the shutters to open plus the actuation time for the shutters to close (i.e., the cycle time) totals less than ten percent of the target exposure interval, whereby work pieces carrying UV curable material are subjected to exposure that is more uniform over the surface of the work piece, than is available conventionally.
According to a broad aspect of the invention, the UV shutter assembly comprises at least three shutter segments, which can be simultaneously actuated through an included angle of no greater than about 90°.
Preferably, at least four shutter segments are provided, with each segment in the closed configuration, forming an acute angle relative to, and overlapping with, an adjacent segment.
It is a further preferred feature that the simultaneously actuated shutter segments be driven through an included angle of about 45° for each segment to open, and about 45° for each segment to close, for a total of about 90° rotation during a full cycle of operation.
The invention is preferably implemented in an arrangement of at least four shutter segments each having longitudinally opposed ends, front and back edges, and top and bottom solid surfaces, wherein each segment is adjacent at least one other segment. The segments are arranged with the front and back edges of each segment in parallel along a first direction, and with one of the front or back edge of each segment substantially abutting and preferably overlapping one of the top or bottom surfaces of an adjacent segment. A drive hub is rigidly connected to each segment, respectively. A drive train engages all of the drive hubs, for simultaneously reciprocating the hubs and connected shutter segments rotatively through an actuation angle of no more than approximately 90° around respective axes of rotation which are parallel and coplanar along the first direction.
In one embodiment, a pinion gear is operatively connected respectively to each drive hub. Each pinion gear engages an adjacent pinion gear. One of the gears is driven, whereby all gears rotate to open and close the shutter assembly.
In a second embodiment, the drive train includes a plurality of pinion gears operatively connected respectively to each drive hub, but not directly to each other. A first drive rack operatively engages a first set of pinion gears consisting of every other one of the pinion gears. A second drive rack operatively engages a second set of pinion gears consisting of all the pinion gears that are not engaged by the first drive rack. The first and second drive racks are reciprocated synchronously and in opposite directions, whereby the first set of pinion gears all reciprocate clockwise then counterclockwise in unison, while t
Alix Yale & Ristas, LLP
Anderson Bruce C.
Gilberti Joseph J.
Wells Nikita
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