BACKGROUND ART [0002] Various manufacturing processes include treating an object having an elongated three-dimensional surface, such as a curved surface, by irradiating the surface with, for example, ultraviolet (UV) light or other radiation. The radiation treatment may be related to curing, surface modification, disinfection, advanced oxidation or some other procedure. By way of example, in some printing processes a printed pattern is cured by irradiating the pattern. Obtaining a high quality, uniform product requires irradiating a two-dimensionally uniform high level of radiation over the entire object area of interest. Otherwise irregularities in the finished product may result.

[0003] Existing devices often expose the central area of an irradiated surface to more radiation than the edge areas of the surface. The areas of high radiation may receive more than the desired level, possibly causing damage, while the areas of low radiation may be undertreated.

[0004] Various techniques have been used in the past to control the uniformity of irradiation of planar target surfaces. By way of example, United States Patent No. 4,010, 374 discloses an UV light processor including a primary light source which exposes a target surface on a work piece to UV light, with the UV flux incident per unit area of the target surface greater in the central region of the surface than at edges of the surface, and a secondary light source, which is located in a different plane than the primary light source and which exposes the target surface to UV light, with the UV flux incident per unit area of the surface greater at the edge areas of the target surface than at the central region. Not only is such an UV light processor complex and expensive to manufacture and to operate, but also it is difficult to control in a manner that maintains the UV radiation received at the edge areas of the target surface from the secondary source at substantially the same level as the UV radiation received at the central area of the target surface from the primary source.

[0005] United States Patent No. 4,276, 479 discloses a tunnel type irradiation chamber through which an object to be treated is conveyed. A plurality of cylindrical UV-lenses are within the tunnel type chamber. Two sets of radiation sources, providing light of two different wavelengths, are within the chamber, providing irradiation in two stages. This apparatus is also complex to control, but yet it may not provide uniform radiation distribution on the object surface.

[0006] United States Patent No. 4,348, 015 shows a radiation projection system including complex lenses in order to provide uniform irradiance.

Numerous other systems have been attempted. These generally are complex and expensive, both to construct and to operate. Even so, they generally have difficulty in achieving uniform irradiance, especially two-dimensionally uniform irradiance of elongated curved objects.

DISCLOSURE OF INVENTION [0007] The present invention is an apparatus and a method providing substantially two-dimensionally uniform irradiation of elongated three- dimensional objects with a high level of radiation. While the present invention is described hereinbelow with reference to irradiation of curved objects, it is to be understood that it is equally applicable to other three-dimensional objects. In accordance with the present invention at least one source is provided for producing radiation to irradiate an elongated curved object surface. Each source may include an elongated discharge bulb. Each radiation source is arranged within a corresponding elongated elliptical reflecting trough, with the radiation source spaced from the focal axis within the trough. Preferably, planar reflectors extend from the troughs to the target surface. Preferably, also, these reflectors are pivotally attached to the troughs so as to accommodate various sizes of target surfaces and to aid in optimization of the uniformity of the radiation distribution. Additionally, preferably each radiation source is on the major axis of the ellipse defining its trough and is spaced from the focal axis within the trough.

Further, preferably, the position of each reflecting trough is adjustable in the direction of the minor axis of the ellipse defining the trough. Each source of radiation can be a light source, preferably a source of ultraviolet light such as a microwave electrodeless discharge bulb, an arc discharge bulb, or a fluorescent discharge bulb. The objects are moved past the radiation source and are rotated at a linear speed and an angular velocity determined by the desired dose of radiation.

BRIEF DESCRIPTION OF THE DRAWINGS [0008] These and other aspects and advantages of the present invention are more apparent from the following detailed description and claims, particularly when considered in conjunction with the accompanying drawings. In the drawings: [0009] Figure 1 is an isometric view of a first embodiment of an apparatus providing substantially two-dimensionally uniform irradiation of the surfaces of elongated curved objects in accordance with the present invention; [0010] Figure 2 is an isometric view of an elliptical reflecting trough, with a bulb installed in the trough, suitable for use in an apparatus for providing substantially two-dimensionally uniform irradiation of an elongated curved object surface in accordance with the present invention; [0011] Figure 3 is a top view of the embodiment of Figure 1, illustrating relative locations of the apparatus, the direction of the major axis of the ellipse defining the trough, and the irradiated objects, and exemplary directions of linear movement and rotation of the objects; [0012] Figure 4 is a top view of the embodiment of Figure 1, illustrating the angle of rotation and direction of linear movement of an object undergoing radiation; [0013] Figure 5 is a fragmentary view of a bulb suitable for use in an apparatus for providing irradiation of an elongated curved object surface in accordance with the present invention, illustrating relative locations of the bulb and the focal axis of its trough; [0014] Figure 6 is a side view of the embodiment of Figure. 1, illustrating relative locations of the trough, the first and second focal axes of the trough, and the object being irradiated; [0015] Figure 7 is a front view of the embodiment of Figure 1; [0016] Figure 8 is a view of the embodiment of Figure 1 from the left side as seen in Figure 7; [0017] Figure 9 is a view of the embodiment of Figure 1 from the right side as seen in Figure 7; [0018] Figure 10 is an isometric view of a variation of the embodiment of Figure 1, having increased length of the trough, bulb and flat reflectors for irradiation of longer objects; [0019] Figure 11 is an isometric view of a second embodiment of an apparatus for providing substantially two-dimensionally uniform irradiation of an elongated curved object surface in accordance with the present invention; [0020] Figure 12 is a front view of the embodiment of Figure 11; [0021] Figures 13A and 13B are, respectively, top and bottom views of the embodiment of Figure 11; [0022] Figures 14A and 14B are, respectively, left and right side views of the embodiment of Figure 11; [0023] Figure 15 is an isometric view of a third embodiment of an apparatus for providing substantially two-dimensionally uniform irradiation of an elongated curved object surface in accordance with the present invention; [0024] Figures 16 and 17 are graphs illustrating the operation of the embodiment of Figure1 ; [0025] Figures 18 and 19 are graphs illustrating the operation of the embodiment of Figure 11.

BEST MODE FOR CARRYING OUT THE INVENTION [0026] In the following description of the present invention, reference is made to the accompanying drawings which form a part hereof and in which are shown by way of illustration various embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and that structural and functional modifications may be made without departing the scope of the present invention.

[0027] Figures 1-9 illustrate a first embodiment of an irradiation apparatus and method in accordance with the present invention. Apparatus 13 includes a radiation source 7, which is depicted as an elongated discharge bulb having a longitudinal axis. By way of example, in this embodiment radiation source 7 might be a six-inch long, 2400-watt ultraviolet lamp. Radiation source 7 is positioned within a trough 1. Trough 1 preferably is substantially one-half of an elliptical cylinder defined by an ellipse having a major axis, the direction of which is shown by arrow 27, although the trough cross section could be less or more than one- half of an ellipse if desired. Trough 1 has a first focal axes 10 within the trough and a second focal axis 11 outside the trough. Focal axes 10 and 11 are parallel to the longitudinal axis of radiation source 7.

[0028] Radiation source 7 irradiates one or more elongated curved objects 17 as the objects move in the direction across the irradiator while rotating. In a production process, a plurality of objects 17 might be moved in a line across the irradiator, as depicted in the Figure 1, or objects may be processed one at a time, with the figures depicting successive positions of the object during its movement.

Figures 3 and 4 illustrate irradiated objects 17 moving linearly across irradiation apparatus 13 while rotating through an angle 0. In some processes it might be desired to irradiate the entire surface of the object, providing full azimuthal <BR> <BR> illumination--i. e. , ¢ = 2zz. In certain processes several rotations of the object might be desired--i. e., ¢ > 2n. In other processes, it may be desired to irradiate only a selected sector of the surface of the object--i. e., < 2Z7--as depicted in Figure 4.

[0029] The angular velocity w of the object 17 as it rotates during movement along the path of travel is determined by the desired dose of radiation and is defined by w = ¢ V/L, where L is the illuminated length of the path of travel and V is the linear speed of the object 17 through that illuminated length. In a typical process providing full azimuthal illumination (o = 2ru) with the illuminated length of the path L = 20cm, the objects might move at a linear speed of from about 1 cm/sec. to about 500 cm/sec., while rotating at a rate of from about 0.05 revolutions per second to about 25 revolutions per second.

[0030] The ellipse of trough 1 has a first focal point within the trough and a second focal point outside the trough. The locus of the first focal point along the length of trough 1 defines a first focal axis 10 of the trough, while the locus of the second focal point defines a second focal axis 11. Radiation source 7 is spaced from the first focal axis 10 and object 17 is spaced from the second focal axis 11 at positions on the major axis of the ellipse which defines trough 1 that results in optimum two-dimensional uniformity of the radiation distribution on elongated curved object 17. For source 7 this might be a position toward elongated curved object 17 by, for example, about ten percent of the focal length of the ellipse. For object 17 this might be a position spaced from radiation source 7 by, for example, about 150 percent of the focal length of the ellipse.

[0031] Elliptical reflecting trough 1 terminates in a right side edge 9a and a left side edge 9b. Edges 9a and 9b of trough 1 define a plane which is substantially perpendicular to the major axis of the ellipse of trough 1 and substantially parallel to the longitudinal axis of radiation source 7. The upper end of trough 1 is closed by a substantially flat upper elliptical reflector 2a which terminates in an upper forward edge 8a. Similarly, the lower end of trough 1 is closed by a substantially flat lower elliptical reflector 2b which terminates in a lower forward edge 8b.

[0032] A substantially flat right side middle reflector 4a extends from right side edge 9a of trough 1 to a substantially flat right side outer reflector 5a. In like manner, a substantially flat left side middle reflector 4b extends from left side edge 9b of trough 1 to a substantially flat left side outer reflector 5b. A substantially flat upper middle reflector 3a extends from upper forward edge 8a of upper elliptical reflector 2a to the inner edge of substantially flat upper outer reflector 6a. In like manner, a substantially flat lower middle reflector 3b extends from lower forward edge 8b of lower elliptical reflector 2b to the inner edge of a substantially flat lower outer reflector (not shown). The right side outer reflector 5a extends from the outer edge 14 of the right side middle reflector 4a toward the objects 17. In like manner, the left side outer reflector 5b extends from the outer edge 15 of the left side middle reflector 4b toward the objects 17. The upper outer reflector 6a extends from the edge 16 of the upper middle reflector 3a toward the objects 17. In like manner, the lower outer reflector extends from the edge 12 of the lower middle reflector 3b toward the objects 17.

[0033] Preferably, the several reflectors are mounted by pivotal mounts 28 and telescope so as to accommodate objects 17 of various sizes and to optimize the uniformity of the radiation intensity. Preferably, also, radiation source 7 is mounted on adjustable mounts 30 to permit adjustment of the distance along major axis that source 7 is positioned from first focal axis 10. Likewise, preferably, the position of reflecting trough 1 is adjustable in the direction of the minor axis of the ellipse of the trough. These position adjustments aid in optimization of the two-dimensional uniformity of the radiation.

[0034] Although in Figures 1-9 and the related description trough 1 and elongated discharge bulb 7 are depicted and described as having their longitudinal axes extending vertically, the axes could extend horizontally or at an angle, if desired.

[0035] Figure 8 is an isometric view of a variation of the embodiment of Figure 1, having a longer trough, bulb, and side reflectors for irradiation of longer objects.

[0036] Figures 11-14 illustrate a second embodiment of an irradiation apparatus 13a and method in accordance with the present invention. Apparatus 13a includes at least two devices, such as described in the first embodiment, which may have the major axes of the respective ellipses turned slightly so as to intersect at an angle 0 for irradiation of shorter objects when a higher level of irradiance is needed. Thus, apparatus 13a includes at least two radiation sources 7a and 7b, each of which is depicted as an elongated discharge bulb having a longitudinal axis. By way of example, in this embodiment radiation sources 7a and 7b might each be a six-inch long, 2400-watt ultraviolet lamp.

Radiation sources 7a and 7b are positioned within troughs 1 a and 1 b, respectively. Each of troughs 1a and 1b preferably is substantially one half of an ellipse, although each trough could be less or more than one half of an ellipse if desired. Each ellipse has a respective major axis 27a and 27b. As depicted in Figure 11, the major axes 27a and 27b of the ellipses of troughs 1a and 1b of apparatus 13a intersect at an angle 0 in front of the troughs. The angle 9 might be in the range of from 0° to 90°, preferably from about 5° to about 35°. Figure 11 depicts a preferred angle 0 of 20°.

[0037] Radiation source 7a irradiates elongated curved objects 17. The ellipse of trough 1a has a first focal point within the trough. The locus of the first focal point along the length of trough 1a defines a first focal axis of trough 1a.

Radiation source 7a is spaced from the first focal axis of trough 1a at a position on the major axis 27a of the ellipse of trough 1a that results in optimum two- dimensional uniformity of the radiation distribution on elongated curved objects 17. This might be a position toward elongated curved objects 17 by, for example, about ten percent of the focal length of the ellipse. In like manner, radiation source 7b irradiates elongated curved objects 17. The ellipse of trough 1 b has a first focal point within the trough. The locus of the first focal point along the length of trough 1 b defines a first focal axis of trough 1 b. Radiation source 7b is spaced from the first focal axis of trough 1 b at a position on the major axis 27b of the ellipse of trough 1b that results in optimum two-dimensional uniformity of the radiation distribution on elongated curved objects 17. This might be a position toward elongated curved objects 17 by, for example, about ten percent of the focal length of the ellipse.

[0038] Each trough 1a and 1b is similar to trough 1 of the embodiment of Figures 1-9. Thus, elliptical reflecting trough 1a terminates in a right side edge and a left side edge. These edges of trough 1 a define a plane which is substantially perpendicular to the major axis 27a of the ellipse of trough 1a and substantially parallel to the longitudinal axis of radiation source 7a. Substantially, flat upper elliptical reflector 20a of trough 1a terminates in an upper angled edge.

Similarly, substantially flat lower elliptical reflector 21 a of trough 1a terminates in a lower angled edge. In like manner, elliptical reflecting trough 1 b terminates in a right side edge and a left side edge. These edges of trough 1b define a plane which is substantially perpendicular to the major axis 27b of the ellipse of trough 1 b and substantially parallel to the longitudinal axis of radiation source 7b. Upper elliptical reflector 20b of trough 1 b terminates in an upper angled edge. Similarly, lower elliptical reflector 21 b of trough 1 b terminates in a lower angled edge.

[0039] A substantially flat upper middle reflector 18a extends from the upper angled edges of troughs 1a and 1 b to the inner edge of a substantially flat upper outer reflector 19a. Upper outer reflector 19a extends from upper middle reflector 18a toward objects 17. In like manner, a substantially flat lower middle reflector 18b extends from lower angled edges of troughs 1a and 1b to the inner edge of a substantially flat lower outer reflector 19b. Lower outer reflector 19b extends from lower middle reflector 18b toward objects 17. A substantially flat right outer reflector 22a extends from the right side edge of trough 1a toward objects 17, and a substantially flat left outer reflector 22b extends from the left or second side edge of trough 1b toward objects 17. Preferably, the left side edge of trough 1a contacts the right side edge of trough 1b over the length of these vertical edges. Alternatively, these edges are joined by a reflective vertical panel so as to prevent escape of radiation.

[0040] Although in Figures 11-14 and the related description troughs 1a and 1 b and elongated discharge bulbs 7a and 7b are depicted and described as having their longitudinal axes extending vertically, the axes could extend horizontally or at an angle, if desired.

[0041] Figure 15 depicts a third embodiment of an irradiation apparatus in accordance with the present invention. This embodiment includes at least two of the devices 13 described in the first embodiment of Figures 1-9, stacked one on the top of another to irradiate longer objects.

[0042] To show the advantages of the present invention, the following examples were obtained using computer simulations.

Example 1 [0043] An apparatus in accordance with Figures 1-9 includes an elongated irradiation source 7 in the form of a six-inch long, 2400-watt tubular microwave powered ultraviolet discharge bulb. The source 7 is in an associated trough 1.

The trough 1 is one half of an ellipse having a major axis of approximately six inches and a minor axis of approximately four inches. Radiation source 7 is positioned approximately 0.15 inch from the first focal axis 10 of the trough 1 toward a set of elongated objects 17, for example, cans or the cylindrical parts of bottles, each of which has a radius R=1.13 inches and a height of 6 inches.

Reflectors 4a, 4b, 5a, and 5b are pivoted on pivotable mounts 28 to further optimize the uniformity of the radiation distribution. Objects 17 are moved at approximately 36 centimeters per second and are rotated at approximately 2 revolutions per second. Figure 16 depicts the distribution of the radiation reaching the surfaces of objects 17 along the horizontal direction or direction across the irradiator, while Figure 17 depicts the distribution of the radiation reaching the surfaces of objects 17 along the vertical direction or direction along the irradiator. The directions are shown in Figure 1. As can be seen from Figures 16 and 17, the distribution of the radiation is substantially uniform.

Example 2 [0044] In an apparatus having two radiation sources in two associated troughs, as depicted in Figures 11-14, each of radiation sources 7a and 7b is a six-inch long, 2400-watt tubular microwave powered ultraviolet discharge bulb.

The sources 7a and 7b are in associated troughs 1a and 1b. Each trough is one half of an ellipse having a major axis of approximately six inches and a minor axis of approximately four inches. Radiation sources 7a and 7b are positioned approximately 0.15 inch from the respective first focal axes of the troughs toward a set of elongated objects 17, for example, cans or the cylindrical parts of bottles each of which has a radius R=1.13 inches and a height of 6 inches. Objects 17 are moved at approximately 36 centimeters per second and rotated at approximately 2 revolutions per second. Figure 18 depicts the distribution of the radiation reaching the surfaces of objects 17 along the horizontal direction or direction across the irradiator, while Figure 19 depicts the distribution of the radiation reaching the surfaces of the objects 17 along the vertical direction or direction along the irradiator. As can be seen from Figures 18 and 19, the distribution of the radiation is substantially uniform.

[0045] It can thus be seen that the present invention is an apparatus for and a method of providing substantially two-dimensionally uniform irradiation of elongated three-dimensional objects with a high level of irradiance. Although the present invention has been described with reference to preferred embodiments, various rearrangements, alterations, and substitutions might be made, and still the result would be within the scope of the invention.