Efficient infrared absorption system for edge sealing medium density fiberboard (MDF) and other engineered wood laminates using powder and liquid coatings

Abstract

The present invention has to do with an efficient system for coating and caring engineered wood products (EWP) in general, and the edges of EWPs in particular. An efficient system for coating and curing coatings is provided.

Claims

1. A hybrid cure oven for curing of a material on a product having a plurality of edges and faces, the hybrid cure oven comprising: at least one infrared edge sealing oven, wherein the at least one infrared edge sealing oven comprises: at least one focused infrared (IR) emitter assembly for radiating IR energy onto at least one of the plurality of edges, wherein the at least one focused infrared (IR) emitter assembly is selected from the group consisting of emitters adaptable to emitting a first radiation emission within a first infrared range of a spectra absorbed by a first molecule and emitters adaptable to emitting a second radiation emission within the first infrared range of the spectra absorbed by the first molecule, wherein the at least one focused IR emitter assembly further comprises a reflector, wherein the reflector comprises an IR radiation multiplying reflector for effectively multiplying the emitted IR energy radiated onto the at least one of the plurality of edges; at least one focused infrared (IR) emitter assembly consisting of emitters adaptable to emitting a radiation emission within the first infrared range of the spectra absorbed by the first molecule selected from the group of water, polyethylene and polyvinyl chloride; at least one quartz glass infrared emitter; at least one infrared catalytic heater oven; and a continuous conveyor track connecting the at least one infrared edge sealing oven and the at least one infrared catalytic heater oven.

2. The hybrid cure oven as in claim 1 wherein the at least one edge sealing oven comprises a plurality of air knives.

3. The hybrid cure oven as in claim 1 wherein the at least one focused infrared (IR) emitter assembly further comprises a first transmission medium and wherein the transmission medium comprises a focusing lens.

4. The hybrid cure oven as in claim 3 wherein the focusing lens comprises a Fresnel lens.

5. The hybrid cure oven as in claim 1 wherein the at least one focused infrared (IR) emitter assembly further comprises a second transmission medium and wherein the second transmission medium comprises quartz glass.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

(2) FIG. 1 is a pictorial view of an edge sealing oven incorporating features of the present invention:

(3) FIG. 2 is a pictorial view of the edge sealing oven shown in FIG. 1 showing placement of one bank of infrared sources;

(4) FIG. 3 is top down view of the edge sealing oven shown in FIG. 1 showing relative placement and radiation angles of the infrared sources;

(5) FIG. 4 is top down view of an infrared source shown in FIG. 2 or FIG. 3;

(6) FIG. 5A is a perspective view of an infrared source shown in FIG. 2 or FIG. 3;

(7) FIG. 5B is a side view of an infrared source shown in FIG. 2 or FIG. 3;

(8) FIG. 5C is a frontal view of an infrared source shown in FIG. 2 or FIG. 3;

(9) FIG. 6 illustrates examples of infrared emission spectra of some infrared sources that may be used in accordance with the edge sealing oven shown in FIG. 1;

(10) FIG. 7 illustrates a temperature profile of an MDF board as it transits the edge sealing oven shown in FIG. 1;

(11) FIG. 8 is a diagram layout of a MDF board powder coating production line in accordance with one embodiment of the present invention; and

(12) FIG. 9 is a pictorial view of a hybrid multi-section oven incorporating the edge sealing oven shown in FIG. 1.

DETAILED DESCRIPTION

(13) The following brief definition of terms shall apply throughout the application:

(14) The term outer or outside refers to a direction away from a user, while the term inner or inside refers to a direction towards a user;

(15) The term comprising means including but not limited to, and should be interpreted in the manner it is typically used in the patent context;

(16) The phrases in one embodiment, according to one embodiment, and the like generally mean that the particular feature, structure, or characteristic following the phrase may be included in at least one embodiment of the present invention, and may be included in more than one embodiment of the present invention (importantly, such phrases do not necessarily refer to the same embodiment);

(17) If the specification describes something as exemplary or an example, it should be understood that refers to a non-exclusive example; and

(18) If the specification states a component or feature may, can, could, should, preferably, possibly, typically, optionally, for example, or might (or other such language) be included or have a characteristic, that particular component or feature is not required to be included or to have the characteristic.

(19) The term cure, cured or curing shall be understood to mean the hardening of a suitable edge covering material. Further, curing may be brought about by chemical additives, ultraviolet radiation (UV), or applied heat.

(20) Referring now to FIG. 1 there is shown a pictorial view of an edge sealing oven vestibule 10 incorporating features of the present invention. Included are vestibule hood 116, left vestibule 114, left air knife 214, right vestibule 112, right air knife 215, convection oven 1115, and wheels 118.

(21) Air knife 214 and air knife 215 provide gas flows 214A and 215A, respectively. Gas flows 214A, 214B may be any suitable gas flow, such as, for example, high pressure air.

(22) Referring also to FIG. 2 there is shown a pictorial view of the edge sealing oven shown in FIG. 1 showing placement of one bank of infrared sources 116A, 116B.

(23) Referring also to FIG. 3 there is shown a top down view of the edge sealing oven 10 shown in FIG. 1 showing relative placement and radiation angles of the infrared sources. The infrared sources 114A, 114B, 116A, and 116B are situated in housings 115A, 115B, 117A and 117B, respectively. It will be appreciated that said infrared sources are rotatable within their respective housing, thus the housing is adapted to allow the outward and unobstructed expression of the full radiation pattern emitted by the infrared source.

(24) As shown in FIG. 3, the infrared sources, e.g., 114A and 116A, are located on opposite sides of the product 33 and set at a predetermined angle to radiate infrared energy onto the trailing edge 33B of product 33 and wherein the radiated infrared energy is a focused infrared energy pattern or field comprising substantially a 60 degree arc. It will be understood that any suitable focused infrared energy pattern may be used. Also, as shown in FIG. 3, the infrared sources, e.g., 114A and 116A are staggered, or offset from a common axis, on either side of travel of product 33 by a predetermined amount 131. It will be appreciated that offsetting infrared sources by predetermined amount 131 controls the amount of combined or overlapped infrared energy imposed on trailing edge 33B.

(25) Also shown in FIG. 3 is an example of a coated product 33. Coated product 33 may include faces 33A and 33C. In general coated product 33 will include trailing edge 33B and leading edge 33D. It will be understood trailing and leading edges are defined according to the direction of travel through the edge sealing oven 10 as depicted by arrow 37.

(26) Referring also to FIG. 4 there is shown a top down view of an infrared source 40 shown in FIG. 2 or FIG. 3. The infrared source 40 may be any suitable focused infrared source, such as, for example, a short wave, medium wave, or long wave infrared emitter. It will also be appreciated that edge sealing ovens incorporating features of the present invention may utilize multiple groups or pluralities of infrared sources that optimally perform a desired function. For example, a first plurality of focused infrared sources may have a short wave emission wavelength that preferentially interacts with a predetermined absorption characteristic of a surface or edge of an MDF board, while a second plurality of infrared sources may have medium wave emission wavelength that preferentially interacts with a second predetermined absorption characteristic of an edge or face of the MDF board. Accordingly operations on an MDF board may be efficiently performed without expending energy emitting large amounts of radiation at unnecessary wave lengths.

(27) Still referring to FIG. 4, infrared source 40 includes fixture 41 and infrared assembly 42.

(28) Fixture 41 may be any suitable fixture for holding infrared assembly 42 and adaptable to rotating within respective housing (see FIG. 3).

(29) Focused infrared assembly 42 includes infrared emitter 5A1, transmission medium 5A2, and reflector 5A3. Infrared assembly 42 is adapted to emit a focused infrared energy pattern comprising a 60 degree arc.

(30) Infrared emitter 5A1 may be any suitable IR emitter for heating MDF boards 33. For example, infrared emitter 5A1 may be any suitable short wave, medium wave, or long wave IR emitter. For example, the IR emitter 5A1 may be a resistive element, a chromium alloy filament, or a tungsten filament. In alternate embodiments, IR emitter may include single or a pair of heating filaments.

(31) Still referring to FIG. 4, transmission medium 5A2 may be any suitable medium which substantially allows the IR energy emitted by IR emitter 5A1 to transition from its source to the MDF board to be heated. For example, the transmission medium may be any suitable transparent or semi-transparent quartz glass. It will also be appreciated that the transmission medium may be suitably shaped or formed to direct or focus the IR energy. For example, the transmission medium 5A2 may contain characteristics of a focusing lens, such as, for example, a Fresnel lens.

(32) Still referring to FIG. 4, reflector 5A3 may be any suitable reflector for reflecting IR energy generated by IR emitter 5A1 through transmission medium 5A2. For example, reflector 5A3 may comprise a gold coated reflector and/or an aluminum reflector. It will be appreciated that a gold coated reflector can almost double the effective radiation arriving at the edge 33B of the MDF board 33.

(33) Still referring to FIG. 4, reflector 5A3 may be an opaque quartz glass located directly on the emitter 5A1 and therefore needs not be brought into the correct position first as is the case with external reflectors.

(34) It will also be appreciated that the transmission medium 5A2 and/or the reflector 5A3 may be suitably shaped or formed to direct, focus, or concentrate the IR energy onto a particular area of an MDF board. For example, the transmission medium 5A2 may contain characteristics of a Fresnel lens.

(35) Referring also to FIG. 5A there is shown a perspective view of infrared assembly 42 shown in FIG. 4. Infrared assembly may be any suitable focused infrared assembly such as, for example, a tubular assembly.

(36) Referring also to FIG. 5B there is shown a side view of infrared assembly 42 shown in FIG. 4. Reflector 5A3 may be any suitable reflector material such as, for example, gold, ceramic, or any suitable manmade or natural material.

(37) Referring also to FIG. 5C there is shown a frontal view of infrared assembly 42 shown in FIG. 4. It will be appreciated that infrared assembly may include any suitable number of IR emitters 5A1.

(38) Referring also to FIG. 6 there is shown an illustration of examples of infrared emission spectra of some infrared sources that may be used in accordance with the edge sealing oven shown in FIG. 1. Absorption patterns of various powders or liquids that may be exposed to radiation from infrared sources within a hybrid oven 90 (see FIG. 9) in accordance with the present invention are illustrated. These materials, as well as others, may comprise components of an item to be cured and/or dried. As polyethylene is a material that may frequently be encountered in the MDF powdering process the absorption spectrum for polyethylene 560 is illustrated, showing the wavelengths at which polyethylene preferentially absorbs infrared radiation. Infrared sources may be selected to preferentially interact with polyethylene (if the intention is to heat the polyethylene) or to avoid absorption by polyethylene (if the intention is to avoid heating the polyethylene). Infrared sources may be selected for use in an oven in accordance with the present invention based upon the rate at which radiation from those sources will, or will not, interact with typical powders or liquids.

(39) Still referring to FIG. 6, an absorption spectrum for water 580 is also illustrated. As briefly described above, ovens in accordance with the present invention may frequently be employed to evaporate water from an MDF board for curing and/or drying purposes. Accordingly, infrared sources used in an oven in accordance with the present invention may be preferentially selected from sources having a relatively high amount of emissions within the mid infrared range of the spectra highly absorbed by water molecules. Conversely, if the evaporation of water is not desired, sources that emit lesser amounts of radiation in a range of the spectrum preferentially absorbed by water molecules may be selected.

(40) Still referring to FIG. 6, there is illustrated a few other examples of the emission spectra of infrared sources that may be used in an oven in accordance with the invention. The present invention may utilize various types of sources with similar or different emission spectra than depicted in the example of FIG. 6. For example, a halogen based near infrared source may provide an emission spectrum similar to that depicted as 510. A short wave infrared source may provide an emission spectrum such as that depicted as 520, while a fast response medium wave infrared source may provide a spectrum such as depicted as 530. An exemplary carbon infrared source may provide an emission spectrum such as depicted as 540, while a medium wave source may provide a spectrum such as depicted as 550. As illustrated in FIG. 6, each of these exemplary infrared sources produce an emission spectrum with a range of wavelengths, depicted along the x-axis, and a relative radiation power for a given source depicted along the y-axis. The radiative power depicted on the y-axis relates to the wavelength (or frequency) of the radiation in a known fashion.

(41) As can be seen in FIG. 6, each of these example sources has a peak emitted wavelength outside of the visible region of electromagnetic radiation while emitting at a range of other wavelengths. However, infrared sources with narrower or broader emission spectra may be used in accordance with the present invention. Further, the effective relative power of different types of sources used in accordance with the present invention may varied by using different wattages, different numbers of sources of a given type, different densities of sources, and different distances of sources from an item to be cured

(42) Referring also to FIG. 7 there is shown an illustration of a temperature profile of an MDF board as it transits the edge sealing oven shown in FIG. 1;

(43) Referring also to FIG. 8, there is shown a diagram layout of an EWP powder coating production line 10 for coating and curing EWPs or MDF boards 11A. MDF boards 11A are mounted on continuously moving conveyor track 13 at point A1. It will be appreciated that any suitable EWP may be used and that MDF and EWP are often used interchangeably. The MDF board 11A is moved by conveyor track 13 to preheat oven 12. Preheat oven 12 heats the MDF board 11A to approximately 200 degrees Fahrenheit in approximately 1.5 minutes. It will be appreciated that the conveyor track 13 can operate at any suitable line speed. For example, the conveyor track can continuously operate at a speed of 6 feet per minute.

(44) Preheated MDF board 11B exiting preheat oven 12 at point A is at approximately 200 degrees Fahrenheit and thus conductive which allows powder to electrostatically adhere to the board. Conveyor track 13 moves preheated board 11B from point A to point B in about 2 minutes where the preheated MDF board 11B enters primer booth 14 at approximately 100 degrees Fahrenheit.

(45) Primer booth or vestibule 14 electrostatically epoxy powder coats the face and edges of MDF board 11B in approximately 1.5 minutes. Exiting primer booth 14 the primed MDF board 11C is conveyed by conveyor track 13 from point C to point D in approximately 2 minutes where the primed MDF board 11C enters a hybrid multi-section infrared gel oven 16. The infrared catalytic heater portion of the hybrid multi-section infrared gel oven is described in U.S. Pat. No. 7,159,535 and incorporated herein. In general, heat is produced when a gaseous fuel is brought into contact with a catalyst in the presence of air containing a normal level of oxygen. Typically, the fuels are natural gas, propane and butane, for example.

(46) Generally, the gaseous fuel is fed through a bottom of the catalytic heater and is dispersed at atmospheric pressure into contact with a porous active layer. This active layer contains a catalyst which may be platinum, for example. Oxygen from the atmosphere enters the porous catalytic layer and reacts with the gaseous fuel, promoted by the catalyst.

(47) This reaction releases the BTU content in the fuel in the form of infrared heat. The chemical reaction that occurs during the oxidation reduction process produces temperatures within the catalyst of from about 500 to 1000 degrees Fahrenheit (F.). The by-products of the reaction include carbon dioxide and water vapor.

(48) In approximately 3 minutes the 3-section infrared gel oven 16 heats the primed MDF board 11C to approximately 300 degrees Fahrenheit causing the epoxy powder on the MDF board 11C to gel or partially liquefy.

(49) Exiting the gel oven 16, the gelled MDF board 11D is conveyed from point E to point F by conveyor track 13 in approximately 8 minutes where the gelled MDF board 11D enters the top coat booth 18 at approximately 130 degrees Fahrenheit. The top coat booth 18 top coats the gelled MDF board 11D with another powder layer on all faces and edges of the gelled MDF board 11D in approximately 1.5 minutes.

(50) Exiting the topcoat booth 18 at point G the top coated MDF board 11E is conveyed to point H where the board 11E enters the multi-section hybrid cure oven 19 (see also FIG. 9item 90). The multi-section hybrid cure oven 19 heats the top coated MDF board 11E to approximately 300 degrees Fahrenheit in approximately 5.5 minutes which cures and hardens the previously applied primer coat and the previously applied top coat.

(51) Exiting the multi-section hybrid cure oven 19 at point I the cured MDF board 11F is conveyed to point J approximately 20 minutes allowing for the cured MDF board 11F exiting the cure oven 19 at approximately 300 degrees Fahrenheit to air cool. At point J the cooled and cured MDF board 11F is removed from conveyor track 13.

(52) Referring also to FIG. 9 there is shown a pictorial view of a hybrid multi-section oven 90 incorporating the edge sealing oven 10 shown in FIG. 1. It will be appreciated that the hybrid multi-section oven 90 may comprise any suitable number of edge sealing ovens 10 as described herein and any suitable number of curing ovens 92. It will be further appreciated that the infrared sources within the hybrid multi-section oven 90 may operate with different heating parameters. Heating parameters may comprise, but are not limited to, a peak spectral wavelength, an output power, a distance between one or more infrared sources and an item to be heated, a density of infrared sources within an area of an oven, a shape of infrared sources, an arrangement of infrared sources relative to an item to be heated, and air flow rate around an item to be heated, a relative humidity of air around an item to be heated, etc.

(53) Different heating zones and/or different pluralities of infrared sources may share all, some or no heating parameters. For example, different pluralities of infrared sources may operate at different peak spectrums, and may have different spectral spreads (see FIG. 6). By way of further example, different pluralities of infrared sources may be spaced at different distances from an MDF board with greater numbers of sources per linear distance through the oven.

(54) Yet further variation is possible by selecting or controlling the power output of individual infrared sources. For example, a first plurality of infrared sources may operate predominately in the mid infrared region, while a second plurality of infrared sources may operate in the near infrared portion of the spectrum. The plurality of mid infrared sources may be operated at a first wattage, while the plurality of near infrared sources may be operated at a second wattage. Similarly, the plurality of mid infrared sources may be positioned at a first distance from an MDF board to be cured with a first linear distance between individual sources of the plurality of infrared sources of the mid infrared plurality, while the plurality of near infrared sources may be positioned at a second distance from an MDF board to be cured with a second linear spacing.

(55) Still referring to FIG. 9 The peak wavelength of one or more infrared source used in hybrid oven 90 in accordance with the present invention may be selected based upon the stage of a curing and/or drying process to be performed using a given source. Different stages of curing and/or drying may involve different edges or faces of the MDF board to be cured and/or dried. For example, one or more mid infrared sources may be used at an early stage of an oven in order to quickly dry MDF board, as water molecules readily absorb mid infrared radiation, thereby evaporating, the water molecules.

(56) Other types of materials, such as polyethylene, may preferentially absorb mid infrared radiation, thereby enabling such materials to be rapidly heated using mid infrared sources. Other types of materials may preferentially absorb other wavelengths, and infrared sources strongly emitting, at those wavelengths may be selected to heat such materials. Based upon the heating to be performed, energy restrictions, time limitations, materials used, etc., different types of sources in different arrangements and numbers/densities may be used at various stages of an oven in accordance with the present invention.

(57) In alternate embodiments MDF board edges 33B may be pre-primed by a liquid primer. It will be understood that the liquid primer may be cured by any suitable method, such as heat curing (e.g., infrared absorption), for example; or, by chemical reaction from catalyst curing and accelerators. It will be also be understood that the liquid primer may be any suitable liquid primer such as PVA glue or other solvent based liquid such as, for example, a lacquer or enamel based primer. It will also be understood that the liquid primer may be a suitable water based primer.

(58) Property characteristics of a suitable primer, water based or solvent based, include, but are not limited to, the capacity to be cured prior to any liquid induced deformation of the MDF board; and, after curing, sufficient mechanical strength (which may be measured by hardness, toughness, stiffness and/or creep, or strength) to resist any deformation of the cured primer due to out-gassing or water vaporization discussed earlier.

(59) Suitable primers, water or solvent based, may also include particulate matter such as resins, polymerized synthetics or chemically modified natural resins including, thermoplastic and/or thermosetting polymers. Suitable primers may also include amorphous solid particulate matter, such as, for example, glass or nanostructured materials, which may or may not, exhibit glass-liquid transition.

(60) It should be understood that the foregoing description is only illustrative of the invention. Thus, various alternatives and modifications can be devised by those skilled in the art without departing from the invention. For example, the EWP boards are often flat, however the same application technique applies to molded. EWP components as in the case of molded plywood seats that are also stacked to expose the multiple layers of edges in a similar uniform fashion. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances that fall within the scope of the appended claims. For example, any engineered wood product (EWP) having non-uniform densities may be edge coated as described herein.

(61) Additionally, the section headings used herein are provided for consistency with the suggestions under 37 C.F.R. 1.77 or to otherwise provide, organizational cues. These headings shall not limit or characterize the invention(s) set out in any claims that may issue from this disclosure. Specifically and by way of example, although the headings might refer to a Field, the claims should not, be limited by the language chosen under this heading to describe the so-called field. Further, a description of a technology in the Background is not to be construed as an admission that certain technology is prior art to any invention(s) in this disclosure. Neither is the Summary to be considered as a limiting characterization of the invention(s) set forth in issued claims. Furthermore, any reference in this disclosure to invention in the singular should not be used to argue that there is only a single point of novelty in this disclosure. Multiple inventions may be set forth according to the limitations of the multiple claims issuing from this disclosure, and such claims accordingly define the invention(s), and their equivalents, that are protected thereby. In all instances, the scope of the claims shall be considered on their own merits in light of this disclosure, but should not be constrained by the headings set forth herein.

(62) Finally, it will be understood that use of broader terms such as comprises, includes, and having should be understood to provide support for narrower terms such as consisting of, consisting essentially of, and comprised substantially of Use of the term optionally, may, might, possibly, and the like with respect to any element of an embodiment means that the element is not required, or alternatively, the element is required, both alternatives being within the scope of the embodiment(s). Also, references to examples are merely provided for illustrative purposes, and are not intended to be exclusive.