Methods to package and transmit energy of high intensity LED devices

The curing assembly of this invention has one or more fiber optic cables, each transmitting light to a head, which distributes the light onto a substrate in a desired geometric pattern and intensity. Little or none of the heat generated by a light source is transmitted to the vicinity of the substrate. It is emphasized that this abstract is provided to comply with the rules requiring an abstract that will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. 37 C.F.R. §1.72(b).

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to curing assemblies and, in particular, this invention relates to assemblies curing UV-curable ink or coating on a substrate.

High intensity LED devices present great challenges in designing thermal and optical energy and optical energy management. One particular problem when designing LED light-emitting systems is that one must focus high levels of narrow or spot-focused energy in limited or small spaces, at heat-sensitive locations, or in otherwise hazardous locations. These applications may require a physically compact, low heat-emitting, focused (non-scattered) and electrically or intrinsically safe light source device at the working location. One typical application where these problems exist is, but is not limited to, curing UV (Ultraviolet) curing ink in an ink jet printing device, more specifically, the “pinning” or pre-curing (gelling) of dispensed UV ink jet printing ink. Following the dispensing of ink jet ink onto a substrate a “pinning” function is often employed. Ink jet heads must be grouped closely together when multiple colors are used to produce sharp clear images, whereas if not, the ink has a tendency to “sag” or blend together, thereby obscuring the crispness or sharpness of the image being printed. Because ink jet printing “heads” or nozzles must be grouped tightly together when multiple ink colors are dispensed, this gives rise to the need to employ the device disclosed herein. Further, the non-focused or randomly scattered light energy typically present in UV LED devices utilized for this purpose causes the UV ink to cure or gel on the heads or nozzles, thus impairing function, the impaired function resulting in reduced quality of printed media and an increase in maintenance time to clean the heads.

Additionally when pinning ink printed on substrates, the present known curing devices require the ink jets to be separated so as to allow these curing devices to deliver sufficient radiation to the ink on the printed substrate. This separation often results in a printed substrate having less than optimal clarity.

There is then a need for a curing device which cures ink with a radiation pattern which is flexible in shape and intensity, but which transmits little or no heat to the substrate being radiated and which minimizes the distance between ink jets.

SUMMARY OF THE INVENTION

This invention substantially meets the aforementioned needs of the industry by providing:

A device that utilizes, but is not limited to utilizing individually or in combination, fiber optic transmission bundles of glass or polymer, optical lenses or lens assemblies of glass or polymer, solid fiber (large scale) or similar light transmission methods.

A device, in one embodiment, that transmits the light from a square or rectangular LED light source to a narrow and compact emitting head or lamp.

A device that requires no cooling of thermal energy at the emitting head or lamp unit.

A device that can be fabricated in many shapes allowing it to be positioned between the ink jet print heads in a typical multi-color ink jet printing system.

A device that be rendered intrinsically safe, thus allowing it to operate in hazardous locations.

A device that can be custom tailored physically to integrate in, but not be limited to, many commercially produced printing, coating, dispensing and dosing machines.

A device that can be fabricated to operate in many optical energy emitting configurations.

A device that can be positioned within, but not be limited to a distance of 10 mm or less from the media or curing surface.

A device that emits zero or near zero excess thermal energy at the emitter or lamp unit.

Accordingly, there is provided a curing assembly having a singular lens or a plurality of lenses (optionally including a lens assembly), a fiber optic cable and a pinning head. The fiber optic cable has a plurality of optic fibers receiving light which has passed through the lens. The head positions the optic fibers so that light emitted from the optic fibers impinges a substrate in a geometric pattern. The geometric pattern may be remote from any light generator, which may also generate heat. The head may be fixed in a position relative to the substrate. The optic fibers may be fixed within the head as the head is manufactured. In some embodiments, a plurality of either or both of light generators or pinning heads (for example, bifurcated or trifurcated) will be present, in which case differing wave spectra with differing peak wave lengths can be generated and blended.

In some embodiments, light leaves a light source, passes through a lens or lens assembly for collimation, passes through another lens or lens assembly for focusing on the fiber bundle cable, which then transmits the light to the substrate. While light emitted directly from optic fiber ends may directly impinge the substrate, light emitted from optic fiber ends may pass through an optic, such as a rod optic or another optic with a hemispherical or aspherical profile to further focus the light before the light impinges the substrate.

These and other objects, features, and advantages of this invention will become apparent from the description which follows, when considered in view of the accompanying drawings.

It is understood that the above-described figures are only illustrative of the present invention and are not contemplated to limit the scope thereof.

DETAILED DESCRIPTION

Each of the additional features and methods disclosed herein may be utilized separately or in conjunction with other features and methods to provide improved devices of this invention and methods for making and using the same. Representative examples of the teachings of the present invention, which examples utilize many of these additional features and methods in conjunction, will now be described in detail with reference to the drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Therefore, combinations of features and methods disclosed in the following detailed description may not be necessary to practice the invention in the broadest sense and are instead taught merely to particularly describe representative embodiments of the invention.

A person of ordinary skill in the art will readily appreciate that individual components shown on various embodiments of the present invention are interchangeable to some extent and may be added or interchanged on other embodiments without departing from the spirit and scope of this invention.

FIGS. 1a-1f, 2a-2eshow one embodiment of a head assembly100of this invention, the head assembly100having a pinning head104with a pinning head body105and a fiber optic cable106. Present in each fiber optic cable106is a plurality of optic fibers108to convey radiation such as ultraviolet (UV) light from a light source to a substrate such as a page being printed and on which has been deposited a UV-curing ink during printing. The heads104may be formed by injection molding or by first inserting material into a mold into which the optic cables106and fibers108are positioned previously. The material is then allowed to solidify or to cure to thereby secure the optic cables106and fibers108in position. As can be seen, the light is transmitted to the head assembly by the fiber optic cable106which is round or elliptical in cross section. However, once in the head assembly100, the light is transmitted to be emitted from ends110of the optic fibers into a focused beam having a desired geometrical shape, such as the linear shape shown inFIGS. 1a-1f, 2a-e. Light emitted from the embodiments inFIGS. 1a-1f, 2a-2ewould impinge a substrate in a linear pattern with a substantially equal or uniform level of illumination throughout the pattern, for example from a distance between about 1 mm and 10 mm. Optionally, a rod optic112, such as shown inFIGS. 12d-12f, may be present between the optic fiber ends110and the substrate on which is a deposited substance to be cured.

While not shown, a ball lens or a collimating lens may be present over the terminal fiber optic configuration to further provide the desired pattern, intensity, and uniformity of illumination. Additionally, a ball lens, e.g., 20 mm (+/−1%, 5%, 10%), or collimating lens may be present proximate (such as downstream from) the light source to focus or collimate the light entering the fiber optic cable106. A person of ordinary skill in the art will realize that the desired geometric shape for the emitted focused light may include rectangular and square shapes, as well as round and oval, the configuration of these shapes being determined by factors such as the amount of light needed, the type of ink being cured, and the amount of time or speed necessary to cure the ink being deposited on the substrate.

Referring toFIGS. 3a-3d, one embodiment of a curing assembly120is shown to include a light source122, a plurality of fiber optic cables106and a plurality of pinning heads104. The heads are mounted to, and held in position by, one or more plates124. Each optic cable106contains a plurality of optic fibers108(not shown), which transmit radiation from the light source, through one of the heads104, where the radiation is emitted from the optic fiber ends110(such as shown inFIG. 2c) to impinge on a substrate. For example, UV light is generated by a light source, e.g., including UV-emitting LEDs. Within the light source may also be a cooling apparatus (not shown) to remove heat generated by the LEDs when operating to emit UV light. As stated above, a lens may be positioned to focus or collimate UV light emitted from the LEDs before the light enters the fiber optic cables. The focused or collimated UV light is then transmitted from the light source to the heads, where the generally linearly configured fibers at the terminal end of each head direct UV light emitted into a generally linear pattern providing generally equal illumination throughout the pattern, optionally by further means of a lens positioned at the terminal end of each head (not shown). The multiple heads are held in a desired configuration (e.g., offset) by being attached to a plate. The plate, in turn, can be attached to a printing press at a desired location, position, and distance from the ink jet head(s) and substrate. The fiber optic cable may be about 1 m in length; however, lengths considerable longer or shorter are contemplated and would be determined by the materials used in the fiber optic cable, types of lens present, desired relative positions of the printing press apparatus, types of ink to be cured, and substrate to be printed upon.

FIG. 4shows an exemplary curing assembly120being used between ink jet heads130,132. The ink jet heads130,132are in close proximity and are depositing UV-curable ink on a substrate134. The deposited ink is then cured by UV light emitted from head104after the light has been generated by a light source (not shown), focused or collimated, then transmitted to the head104through optic fibers within optic cable106. A plate or other device fixing the head104in a desired position is not shown, but may be present.

Another example of a curing assembly of this invention is shown inFIGS. 5a, 5bat140. In this example, light generated from a light source (not shown) impinges the surface142of a collimating lens144, then is focused in a lens assembly146. An aspherical lens maybe present in addition to the foregoing lens(es),144,146. Accordingly, the lens144may be an aspherical lens rather than a collimating lens. The focused light then enters a proximal end148of a fiber bundle150(or106) and exits at a distal end152to be distributed in a desired geometric pattern by the pinning head154(or104). A plate or other device fixing the head154or104in a desired position is not shown, but may be present.

FIGS. 6a-6dshow still another embodiment of the curing assembly of this invention at160, the curing assembly160including light sources162,163, lens assemblies164,165, and fiber optic cables166,167which transmit light to fiber optic cable168. Light is then transmitted through fiber optic cable168to a pinning heat104. In this embodiment, optic fibers from the fiber optic cables166,167extend continuously through fiber optic cable168and terminate in pinning head104as shown and described above. Differing peak wavelengths of UV light could be emitted from the light sources162,163.

FIGS. 7a-7ddepict yet another embodiment of the curing assembly of this invention at170. The curing assembly170has a light source172, a lens assembly174, fiber optic cables176,178,179, and two pinning heads104.

Separate optic fibers from fiber optic cable176extend into one of fiber optic cables178,179and terminate in one of heads104as described above.

FIGS. 8a-8dshow still yet another embodiment of the curing assembly of this invention at180and include light sources182,183,184, lens assemblies186,187,188, fiber optic cables190,191,192,193, and a pinning head104. Individual optic fibers from each of the fiber optic cables190,191,192extend through fiber optic cable193and terminate in pinning head104as described above.

FIGS. 9a-9ddepict still another embodiment of the curing assembly of this invention at200, which has a light source202, lens assembly204, fiber optic cables206,207,208,209, and three pinning heads104. In this embodiment, individual optic fibers from fiber optic cable206extend through one of fiber optic cables207,208,209, and terminate in one of the three heads104.

Referring toFIGS. 10a-10c, the pinning head104has a block base220. The fiber optic cable221encases a plurality of optic fibers108in a bundle indicated at236, the fiber optic cable enclosed by a sheathing228. The proximal end232of the fiber optic cable221is indicated by end tip230, a collar222present distal from the end top230. The pinning head104has a cover226and terminates in a distal end234. The pinning head104positions and secures optic fibers108in a linear bundle configuration237is the embodiment shown. InFIGS. 10a-10call dimensions are shown in inches and all dimensions will vary by about 1%, about 5%, or about 10% from values depicted. The width dimension238may be about 0.54 inch or less than about 15 mm, such width dimension varying by about 1%, about 5%, or about 10%.

The embodiments with a plurality of light sources can provide a plurality of light spectra with differing peak wave lengths for curing a blend of inks with differing wave length requirements. Multiple light sources can also be combined to provide a greater intensity of light or the same intensity of light on a longer print head. A single light source (e.g., LED) can be used to illuminate two or more heads with corresponding reduced intensity, but effecting a longer cure length or enabling multiple curing positions. Accordingly, the curing assembly of this invention includes one or a plurality of both light sources and pinning heads. While not depicted, curing assemblies with pluralities of both light sources and pinning heads are contemplated to be included in this invention.

In certain embodiments, the pinning heads of this invention have no electronics. There is accordingly, no necessity to cool these pinning heads. Thus, these pinning heads have no cooling apparatus. Cooling apparatus may be present within or proximate the light source. However, the light source is remote from the instant pinning head(s). Because there are no electronics to cool in the pinning head and because the light source is remote, there is no air turbulence generated by the pinning heads of this invention. Therefore, ink patterns being deposited by ink jet heads130,132(seeFIG. 4) are not affected by air turbulence from the pinning head104because the pinning head104generates no air turbulence at all.

A curing assembly240shown inFIGS. 11a-11chas one or more light sources242producing light (e.g., UV), which is being transmitted by optic fibers within optic cables244to pinning heads246. Because of the economies achieved by the lack of cooling structure, the dimensions of the pinning heads can be greatly reduced to enable a continuously linear pattern of optic fibers248. This continuous linear pattern of optic fibers248provides a more uniform illumination of the substrate being printed. Indeed, the continuous linear pattern of optic fibers248is uninterrupted and remains continuous over the entire length of the plurality of pinning heads246present in the embodiment shown.

FIGS. 12a-12fshow a pinning head104of this invention, in which the optic fibers108emit, e.g., UV light. The emitted light is then focused or refracted by a rod optic112before being directed at a substrate for curing.

FIGS. 13a-13ddepict a pinning head250, which has a pinning head body252and a plurality of optic fibers108positioned by the pinning head body252. The optic fibers, before being present in the pinning head body252are bundled in a fiber optic cable106. Due in part to the lack of cooling apparatus, the distal end254of the pinning head body252can be extremely small in cross sectional dimension. For example, the exemplary distal end254depicted has a depth of 0.197 (+/−1%, 5%, 10%) inch and the optical fibers may be 0.118 (+/−1%, 5%, 10%) inch in depth. The pinning head250is shown deployed between two printing heads256,258, which may be about 2.402 inches in height and 4.921 inches in length. However, any dimension for the printing heads may be utilized to achieve the desired pattern of ink of a substrate being printed.

In the context of this invention and as enabled herein, one typical ink-curing application occurs within an ink printing device. In the ink printing device, ink is dispensed by multiple ink-dispensing units, which are applying various colors or treatments to the substrate. The precision of application and quality of this process is greatly affected by the distance between the dispensing units. As the distance between dispensing units decreases, the better the quality of printing will be enhanced.

Thus, the device of this invention greatly reduces the distance between the printing units and improves the overall process and printing quality dramatically. The present device also allows flexibility of application by increasing or decreasing intensity as needed by the process without adversely impacting required space.

A suitable fiber optic cable will efficiently transmit UV light from the light source through the lens to the substrate. Acceptable materials for fiber optic cable of this invention include silica, fluorozirconate, fluoroaluminate, phosphate, and chalcogenide glasses, and low loss plastic optical fibers as well as crystalline materials such as sapphire. Regarding silica materials, a high OH concentration has been found to be suitable for UV transmission. Suitable materials for some fiber optic embodiments include Poly(methyl methacrylate) (PMMA), polystyrene and BK-7. Suitable lenses may include sapphire and BK-7. Specific materials suitable for certain embodiments include borosilicate and fused silica.

While the instant heads are contemplated to include aluminum, other materials such as polymers, wood, or metals could be used as well. Suitable synthetic resins may be used for the heads of this invention and a person of ordinary skill in the art will readily recognize that other synthetic resins may be suitable for a given embodiment of this invention. Other suitable synthetic resins may be found in the Handbook of Plastics, Elastomers, and Composites, Charles A. Harper, Editor in Chief, Third Edition, McGraw-Hill, New York, 1996, hereby incorporated by reference.

A suitable lens assembly for this invention is designed to collect and collimate the light leaving the light source to deliver maximum curing effect to the substrate. The first stage of the lens array or assembly may collect the light, which may leave the light source with a lambertian angular distribution. The second stage of the lens array or assembly then focuses the collected light onto the fiber bundle, with an incident angle less than the critical angle. The lens may be designed in such a way as to create a focused image of the light source on the fiber bundle, delivering uniformly distributed light onto the curing substrate. An alternative embodiment is to use a molded optic lens, which has a complex three-dimensional geometric shape. This lens would accomplish collection, collimation, and focusing with a single lens, instead of a lens assembly or plurality of lenses. Optics could also be used between the light-emitting head and the substrate to further improve printing performance.

Thus, the present invention provides UV light to cure ink deposited on a substrate remote to the LED or other device used to emit UV spectrum electromagnetic radiation. Being remotely configured allows for light to be delivered to desired locations without allocating space for the LEDs themselves. Additionally, heat can be removed remotely as well to reduce or eliminate undesirable effects of heat on ink jets, substrate, or ink being cured.

While UV-curable inks are commonly used in printing, some inks cure more efficiently when exposed to UV light having specific spectral compositions. Accordingly, differing spectra can be delivered onto substrate being printed. For example a spectrum having differing wavelength compositions could be emitted from each of the heads to enable more thorough curing for inks being used.

The larger LED chips contemplated for use in this invention generate desired light spectra over a larger area than previously possible. Accordingly, the optic fiber bundle is dimensioned and has a geometry sufficient for essentially all generated light to be transmitted by the optic fibers.

Because numerous modifications of this invention may be made without departing from the spirit thereof, the scope of the invention is not to be limited to the embodiments illustrated and described. Rather, the scope of the invention is to be determined by the appended claims and their equivalents.