Abstract:
A system, apparatus and method is provided for curing ultraviolet (UV) curable coatings on articles using UV lamps while the article is immersed in an atmosphere if inert gas heavier than air. An example of an apparatus provided by the invention includes a flat table including a flat bar conveyor, a curing chamber dynamically sealed by gas knives and pivotally removable ultraviolet lamp assemblies for curing coatings in the absence of ambient air.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
       [0001]     This application is a continuation-in-part of U.S. application Ser. No. 11/077,073 filed Mar. 10, 2005. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates generally to the application of curable coatings to articles and more particularly to a curing apparatus utilizing ultraviolet radiation for curing coatings applied to multifaceted articles, such as cabinet doors, in an atmosphere of inert gas that has the property of being heavier than air.  
       BACKGROUND OF THE INVENTION  
       [0003]     Processes utilizing light radiation to cure coatings on articles have become established and important commercial processes. They have benefited from a trend away from environmentally unfriendly processes such as solvent based curing. Since many radiation curably coatings can cure quickly, they are useful in continuous and high speed applications where high output is essential to success in the market place. Examples of products which are now made routinely with such processes are graphic arts, wood panels, furniture parts, optical fibers and electrical components.  
         [0004]     Ultraviolet light (UV) is the radiation source most frequently used to cure coatings and accounts for a majority of the volume of products produced. UV curing is a photochemical process by which monomers having photoinitiators undergo polymerization or cross-linking upon exposure to the ultraviolet radiation. The rate of curing depends on the chemical composition of the coating, the thickness of the coating, the radiation intensity and the chemical composition of the atmosphere surrounding the part to be cured.  
         [0005]     The chemical composition of the coating is generally an organic resin combined with a light curing acrylate. Organic resins useful in the present invention include those with a radiation hardendable components used as bonding agents. Bonding agents contain radical or cation polymerizable chemical groups. In the preferred embodiment, examples of the organic resins include vinylether, vinylamide with maleic acid or fumaric acid and styrene as reactive solvents. In the preferred embodiment, examples of UV curing acrylates are polyester (meth)-acrylates, polyether (meth) acrylate, urethane (meth) acrylate, epoxi (meth) acrylate, silicon (meth) acrylate. Concentrations preferred are 40 mol percent to 60 mol percent radiation hardenable organic resin per (meth) acrylate group. Other reactive groups include melamin, isocyanate, epoxy, anhydride, alcohol, groups of carbonic acids for additional thermal hardening. Chemical reaction hardening can also be used in part by substitution of alcohol, carbonic acid, amine, epoxy, anhydride, isocyanates and other methyl groups contained in a binary cure process.  
         [0006]     The presence of oxygen can have a detrimental effect on the curing process known as oxygen inhibition. Oxygen reacts with free radicals and forms peroxy radicals by reaction with the photoinitiator, monomer or propagating chain radical. The reactivity of the peroxy radical becomes insufficient to continue the polymerization process, leading to chain termination and incomplete curing.  
         [0007]     One method of overcoming oxygen inhibition is curing in an inert gas atmosphere. Industrial processes generally require that the inert gas be heavier than air. The molar weight of the gas should be larger than 28.8 grams per mol and preferably larger than 32 grams per mol (oxygen and 80% nitrogen correspond in the molecular weight of a gas mixture of 20%, for instance). An inert gas atmosphere comprised of noble gases such as argon, hydrocarbon and halogen gases is also acceptable. Carbon dioxide (CO 2 ) is particularly suitable for use in providing an inert gas atmosphere to overcome oxygen inhibition. CO 2  can be conveniently stored in liquid form and transported in metal cylinders at normal room temperature.  
         [0008]     Methods and apparatus relating to the use of CO 2  gas in curing certain coatings with UV radiation has been described in German patent DE19957900A1 to Beck et al., U.S. Pat. No. 3,956,540 to Laliberte et al., U.S. Pat. No. 4,436,764 to Nakazima et al., U.S. Pat. No. 4,862,827 to Getson, and U.S. Pat. No. 6,620,251 to Kitano.  
         [0009]     The use of CO 2  gas when curing certain coatings using UV radiation has also been described in PCT application PCT/EP00/11589 to Beck, et al., titled “Light Curing of Radiation Curable Materials under a Protective Gas”. The process described by Beck, et al., however, is not easily adapted to a high volume, production environment.  
         [0010]     The UV lamps, reflective surfaces and other optical components making up the curing system directly affect the amount of UV energy that encounters the curing surface. During production, various deposits can accumulate on the optical components that can greatly lessen the efficiency of the system. Currently, most systems, such as Beck, et al., do not provide for easy replacement, cleaning or maintenance of the optical components of the system.  
         [0011]     What is needed, therefore, is a curing system and method used for hardening UV curable coatings in an inert gas while also having the capability of maintaining high production volumes.  
         [0012]     It is further desirable for a curing system and method to permit the operator to easily access the required optical components to allow efficient replacement, cleaning, and/or general maintenance.  
         [0013]     It is further desirable that a curing system and method be adapted to provide for rapid delivery of a large volume of inert gas to the apparatus evenly by a gas distribution means.  
         [0014]     It is further desirable to provide a curing system adapted to allow a linear curing path without doors or changes in elevation in the curing path to increase the number of articles cured by the device per time.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The feature characteristics of the present are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects, and advantages thereof, are best understood by reference to the following detailed description when read in conjunction with the accompanying drawings, wherein:  
         [0016]      FIG. 1  is an isometric view of the curing apparatus.  
         [0017]      FIG. 2  is a partial side view of the curing apparatus.  
         [0018]      FIG. 3  is a partial side view of the curing apparatus.  
         [0019]      FIGS. 4   a - 4   c  show various views of an air knife of the invention in one preferred embodiment.  
         [0020]      FIG. 5  shows the one preferred embodiment of the gas distribution system of the invention.  
         [0021]      FIG. 6   a  shows a partial pictorial view of a UV lamp assembly in one preferred embodiment of the invention.  
         [0022]      FIG. 6   b  shows a cutaway side view of a preferred embodiment of a UV lamp assembly of the invention.  
         [0023]      FIG. 7  shows the electrical architecture of a preferred embodiment of the invention.  
         [0024]      FIG. 8  shows the steps initiated by the electronic microcontroller in one preferred embodiment of the invention.  
         [0025]      FIG. 9  is a partial bottom view of the curing apparatus.  
     
    
     DETAILED DESCRIPTION  
       [0026]     The present invention is described in this specification in terms of a device and a method for using the device. The invention may be made and the method carried out in different configurations or alternate embodiments without deviating from the spirit and scope of the invention which is defined only by the appended claims.  
         [0027]      FIG. 1  shows an isometric view of the curing apparatus  100 . Channels  110  and  111  are welded to a set of four table legs  105   a - 105   d . The channels are attached to a flat table panel  115  across their full length to form a solid platform. In the preferred embodiment, the channels have a square cross section. But in other embodiments, differently shaped cross sections will also function equally as well. Support cross members  112  and  113  are mounted between the table legs. In the preferred embodiment, the channels, table panel, table legs and crossmembers are constructed of mild strength steel. Of course, other heat resistant rigid materials will suffice.  
         [0028]     Steel roller bars  120  are mounted perpendicularly along the length of the channels. Suitable bearing blocks  121  and  122  are fitted in both channels to support the roller bars. In the preferred embodiment the roller bars  120  are approximately 2″ in diameter and spaced approximately 4″ apart. Of course, other dimensions and spacings will serve as well in other embodiments. In yet other embodiments, fixed roller and bar conveyors can be used in commercially available dimensions.  
         [0029]     During operation of the device, the roller bars function to move a set of planar objects  190  from entrance  101  under baffle plates  185   a  and  185   b  and UV light assemblies  150   a  and  150   b  and to exit  102 . In the preferred embodiment the objects are planner but objects of other shapes are also accommodated by the invention.  
         [0030]     In order to move planar objects  190  from the entrance to the device to the exit, a drive system is provided to impart rotation to the roller bars. Turning to  FIG. 2 , the table roller drive  200  is shown. Each roller bar  120  has a reduced diameter gear shaft  123  which extends through a corresponding hole in channel  111 . A single drive sprocket  223  is attached to each gear shaft. A drive chain  220  connects the drive sprockets together so that the roller bars can be made to rotate in unison. A primary drive sprocket  233   c  is attached to the gear shaft of roller bar  120   c . The primary drive sprocket is connected by drive chain  230  to gear  214  which is attached to the axle  212  of a reduction gearbox  210 . Reduction gearbox  210  is driven by drive motor  205  through motor axle  207 . The combination of reduction gearbox  210  and drive motor  205 , which are connected by mount brackets  218 , are attached to drive mount bracket  219  which is in turn bolted to table leg  105   d  and channel  111 . Drive motor  205  is electrically connected via power connection  204  to motor control unit  201  which includes a start/stop switch  202 . Motor control unit  201  powers the motor  205  via connection to outside AC power  203 . In another preferred embodiment the drive chain and drive sprockets are replaced with a notched reinforced rubber belt and associated toothed sprockets.  
         [0031]     As shown best in  FIGS. 1 and 6   a , the UV curing function of the curing apparatus  100  is accomplished by a set of components that are fastened to channels  110  and  111  and table panel  115 , as can best be seen in  FIGS. 1 and 3 . Lamp support housing  140   a  and lamp support housing  140   b  are positioned on channels  110  and  111 . Each abuts a center tray  634  at the center of curing apparatus  100 . The lamp support housings each form a frame which supports pivoting UV lamp assemblies  150   a  and  150   b  and an open tray into which fit crystal glass panes that allow illumination to pass from the UV lamp assemblies to the products on the roller bars below. In the preferred embodiment, the support housings are positioned directly against the channels. In an alternate embodiment (not shown), the support housings can be mounted at an angle with respect to the channels in order to facilitate different types of UV lamp assemblies or to provide different angles of incidence. The crystal glass panes and open tray associated with lamp support housing  140   a  are shown as  635  and  636 , respectively. In an alternate embodiment, the crystal glass pane can be replaced by shutters placed lengthwise in the trays. The switches can be closed to allow presentation of the inert gas during periods of non-use or can be opened to allow light to pass. The sides of each housing form part of the curing chamber that contains the inert gas. UV lamp assembly  150   a  is fastened to lamp support housing  140   a  by lamp hinges  151   a  and  151   b  so that it can be rotated to an open position away from the center of curing apparatus  100 . UV lamp assembly  150   b  is fastened to lamp support housing  140   b  by lamp hinges  151   c  and a second lamp hinge not shown in the drawings, so that it can be rotated to an open position away from the center of curing apparatus  100 . The open position allows for easy maintenance and cleaning of the lamp assemblies and other optical components such as the glass panels and reflectors. Each UV lamp assembly can also be rotated into a closed position. When in a closed position, the UV lamp assemblies are positioned directly above the trays in the lamp support housings. The transparent glass substrate  635  positioned in the trays allows the transmission of UV light from the lamp assemblies while also forming the top of the curing chamber.  
         [0032]     Curing processes require UV light radiation of significant intensity. These lamps generate excess heat which must be removed from the curing apparatus  100 . Two rows of lamp cooling fans  152   a  and  152   b  are fitted to the top of UV lamp assemblies  150   a  and  150   b  to circulate air through said lamp assemblies to cool the UV lamps. Impellers or other sources of high pressure ambient air may be used in other embodiments. Refrigerated air may also be used to reduce the flow rate or volume of air needed to cool the lamps. Heat shields  180   a ,  180   b  and  180   c  are removably fitted to the top of lamp supports  140   a  and  140   b  to act as heat sinks and to protect operators from the hot surface of the lamp supports  140   a  and  140   b . Handles  188  are mounted on the heat shields  180   a - c  to allow for ease of removal. In the preferred embodiment, there are eight cooling fans for each UV lamp assembly. Each fan operated at a flow rate of about 2 CFS in order to maintain an acceptable operating temperature of about 100 degrees Fahrenheit. Of course, other fan arrangements can function as well so long as they maintain the UV lamp assemblies at a stable operating temperature.  
         [0033]     The UV curing process is inhibited by the presence of oxygen. Lamp support housings  140   a  and  140   b , glass substrate  635 , table panel  115 , gas knives  170   a  and  170   b , inner baffles  354   a  and  354   b  and baffle plates  185   a  and  185   b  form a curing chamber through which products may pass unhindered on the roller bars and be irradiated with UV light out of the presence of oxygen.  
         [0034]     As shown best in  FIGS. 3 and 9 , a gas distribution system is placed within the curing chamber to provide a well distributed and constant supply of inert gas to the curing chamber to displace oxygen in the ambient atmosphere. The gas distribution system comprises a set of gas distribution assemblies for supplying gas to the curing chamber and to “gas knives” which form a positive pressure gas curtain at the entry and exit of the curing chamber.  
         [0035]      FIG. 5  shows the gas distribution assemblies  160   a  and  160   b . Gas distribution assemblies  160   a  and  160   b  pass through and are supported by lamp supports  140   a  and  140   b . The gas distribution assembly  160   a  is comprised of gas manifolds  390   a  and  390   b  connected by a series of pipe fittings. In particular, gas manifold  390   a  is connected to elbow  391   a  which connects to one end of connector pipe  392   a . Gas manifold  390   b  is connected to tee fitting  393   a  which, in turn, connects to the other end of connector pipe  392   a . Tee fitting  393   a  also connects to a solenoid valve  395   a  which is in turn connected to connector  365 . Connector  365  connects to gas line  364  which is in turn connected to gas regulator  362 . The gas distribution assembly  160   b  is comprised of gas manifolds  390   c  and  390   d  connected by a series of pipe fittings. In particular, gas manifold  390   d  is connected to elbow  391   b  which connects to one end of connector pipe  392   b . Gas manifold  390   c  is connected to tee fitting  393   b  a which, in turn, connects to the other end of connector pipe  392   b . Tee fitting  393   b  also connects to a solenoid valve  395   b  which is in turn connected to connector  365 . Connector  365  connects to gas line  364  which is in turn connected to gas regulator  362 . Gas regulator  362  connects to a gas control switch  361  which in turn is connected to a pressurized gas reservoir  360  through gas line  365 . Gas reservoir  360  provides the source of gas for the gas distribution assemblies  160   a  and  160   b . In the other embodiments, the gas distribution assemblies may utilize separate gas control switches and gas reservoirs.  
         [0036]     Gas manifolds  390   a  and  390   b  span the width of table panel  115 . They are capped by end caps  398  and have gas exit holes  397  to feed gas downward into the curing chamber. Each of the exit holes of the preferred embodiment is sized to provide a #20 natural gas orifice. In other embodiments, the holes can be graduated in diameter to provide a uniform flow rate which accounts for the pressure drop across the length of each manifold. Gas regulator  362  is typically set at a gas flow rate out of the distribution assembly in the range 300 CFH (cubic feet/hr). Solenoid valves  395   a  and  395   b  switches the flow of gas into the curing chamber and is electrically connected to a control unit (not shown).  
         [0037]     The piping used for the gas distribution assemblies in the preferred embodiment is ¾″ AGA rated stainless steel gas pipe. Of course, other sizes and types of materials will suffice for differing flow rates and orifice sizes as is known in the art.  
         [0038]     In the preferred embodiment, the gas supplied to the curing chamber is CO 2  because of its widespread availability and low cost. In other alternate embodiments, other gases such as nitrogen, argon, hydrocarbons, or halogenated hydrocarbons can be used.  
         [0039]     Moving to  FIGS. 9 and 4   a - 4   c , the gas knives and gas distribution assemblies for distribution of inert gas to the gas knives is shown. Gas knives  170   a  and  170   b  are attached to the entrance and exit sides of lamp supports  140   a  and  140   b , respectively. Gas knives  170   a  and  170   b  are made of 2″ square steel tube  381  with endcaps  382   a  and  382   b  welded in place. In each endcap  382   a  and  382   b  are threaded holes  384   a  and  384   b  for attachment to gas lines  371   a  and  372   a . The square steel tube  381  includes slot  389  lengthwise along its bottom side. Angles  386  and  388  are mounted back to back along slot  389  forming a linear orifice  390  sealed to and spanning the length of the gas knife. In the preferred embodiment, the linear orifice is approximately 0.04″ wide. As gas flows into gas knife  170   a  through threaded holes  384   a  and  384   b , it flows out of the linear orifice to form a positive pressure curtain of gas along the length of the gas knife. In the preferred embodiment, a constant CO 2  gas flow of about 200 to 300 CFH is used for the gas knife distribution system. Gas knife  170   b  is constructed identically to gas knife  170   a.    
         [0040]     A gas knife distribution system  370  is provided to distribute gas to gas knives  170   a  and  170   b . A pressurized gas reservoir  360  is connected by a gas line to gas control valve  361 . Gas control valve  361  is further connected by a gas line to a gas regulator  377  which regulates the flow of gas into distribution system  370  and ultimately regulates the speed of gas flow out of the gas knives  170   a  and  170   b . Gas knife distribution system  370  includes pipelines flow out of the gas knives  170   a  and  170   b . Gas knife distribution system  370  includes pipelines connected by tee fittings  379   a ,  379   b  and  379   c  to the regulator by gas line  378 . Gas knife distribution system  370  is connected to the gas knives by gas lines  371   a  and  371   b  and by flexible gas lines  372   a  and  372   b.    
         [0041]      FIGS. 1 and 3  best illustrate the location of the entry baffles, exit baffles, gas knives and reflective tray. Baffle plates  185   a  and  185   b  are attached between channels  110  and  111  and adjacent the entry and exit of the device. Baffle plates  185   a  and  185   b  limit stray UV light which escapes the unit to acceptable safety levels and further serve to insulate operators from hot components of the device. Gas knives  170   a  and  170   b  are positioned between baffle plates  185   a  and  185   b  and lamp supports  140   a  and  140   b , respectively.  
         [0042]     Reflective tray  350  is a generally flat rectangular polished pan having short sidewalls. Reflective tray  350  is mounted to table panel  115  centrally under both UV light assemblies and below roller bars  120 . The reflective tray extends from the leading edge of UV light assembly  150   a  to the trailing edge of UV light assembly  150   b  and across the curing apparatus from channel  110  to channel  111 . Reflective tray  350  has short sidewalls  351   a  and  351   b  which are situated so as to contain gas within the curing chamber. Reflective tray  350  serves a dual function. It provides a settling basin for the inert gas and a reflector for the UV radiation of the UV lamps during operation. The reflective tray is made of polished stainless steel. In other embodiments, polished aluminum is also used as are other, rigid, reflective and heat resistant materials.  
         [0043]     Entry baffles  354   a  and  355   a  are steel angle mounted on table panel  115 , beneath the roller bars and extend the width of the table from channel  110  to channel  111 . Gas knife  170   a  is located above and adjacent entry baffle  354   a . Exit baffles  354   b  and  355   b  are steel angle brackets mounted on panel  115  parallel to and beneath the roller bars and extend the width of the table from channel  110  to channel  111 . Gas knife  170   b  is located above and adjacent exit baffle  354   b . The entry baffles and exit baffles extend upward from table panel  115  toward the rollers. The entry and exit baffles are seated against the roller directly above each by a linear rubber gasket (not shown). The gas escaping from the gas knives flows downward toward and past the baffles and in conjunction with them prevents entry of oxygen into the curing chamber and the escape of inert gas from the curing chamber in the preferred embodiment.  
         [0044]     As shown best in  FIGS. 3 and 9 , an oxygen sensor assembly is shown which comprises sensor input heads and an oxygen sensor connected by appropriate tubing. The role of oxygen sensor assembly  310  is to monitor the oxygen levels in the curing chamber. Oxygen sensor input heads  311   a  are attached by appropriate hollow standoffs  311   b  to elbow fittings  313   a  and  313   b . Standoffs  311   b  protrude through reflective tray  350  near the midpoint between the channels to a height just below the bottom surface of objects  190  as they travel on the roller bars. Elbow fittings  313   a  and  313   b  attach to tubing  314   a  and  314   b  which in turn are attached to oxygen sensor  315 . In the preferred embodiment, the oxygen sensor is a transducer that measures absence of oxygen in the atmosphere within the curing chamber. In the preferred embodiment, oxygen sensor head  315  is manufactured by Alpha Omega Instruments and is set to alarm when O 2  fraction by volume is less than 3%. In other embodiments, the percentage can be adjusted to assure that a properly inert atmosphere is in place, such as in high volume applications when many pieces are presented simultaneously. An electrical connection  318  from oxygen sensor head  315  to a sensor electronics unit  320  is also provided. The oxygen level result is displayed to the operator and sent to the control system. embodiment, the UV lamp is a single cylindrical tube being mechanically supported at each end by a socket. The UV lamp of the preferred embodiment of the present invention is a Mercury gas lamp which operates at a temperature of about 750 degrees Fahrenheit, has an arc length of approximately 52″ and draws about 7-8 kW of power. In the preferred embodiment, UV lamp is model number 530-300, supplied by Ultraviolet Systems, Ltd. of Houston, Tex., USA. In alternate embodiments, ultraviolet lamps having low, medium or high pressure gas can be used as well as doped lamps including amalgam, gallium or iron. In yet other embodiments ultraviolet arc lamps may be used. In other embodiments, other power ranges and gas mixtures can be utilized to cure different coatings.  
         [0045]     A parabolic reflector  625  is fastened by screws  626  to lamp housing  600  and is made of polished stainless steel in the preferred embodiment. In other embodiments, polished aluminum can be used as well as other rigid, reflective and heat resistant materials. Heat sinks  620  and  622  are mounted on the upper surface of reflector  625  inside lamp cavity  601 . Heat sinks  620  and  622  aid in the dispersal of heat from the reflector and from the lamp cavity  601  and are typically made of a copper alloy or aluminum. Of course, other alloys capable of efficient heat dissipation can be employed. The parabolic reflector acts to reflect light toward the curing chamber.  
         [0046]     Flanges  627   a  and  627   b  are attached to lamp housing  600 . The flanges provide support for heat shields  180   b  and  185   a . The space between flanges  627   a  and  627   b  and the lamp support housing allows airflow from lamp cooling fans into the lamp region and through lamp cavity  601  via slots  628  in the reflector  625 . Airflow is directed over heat sinks  620  and  622  and exhausted out of the UV lamp assembly  150   b . In other embodiments, the slots can take the shape of round holes or angled vents.  
         [0047]     Lamp hinge  151   b  includes a rotating joint  640  which is mounted to lamp housing  600  a similar lamp hinge  151   a  and rotating joint are connected on the opposite side of the lamp housing together the hinge and joints allow for the rotation of the entire UV lamp assembly  150   b . UV lamp assembly  150   b  can be rotated by an angle of approximately 100° to an open position when the curing apparatus is not in operation. Rotating the lamp assembly  150   b  automatically stops operation of the curing apparatus and shuts down the UV lamp by opening a switch  645  which is electrically connected to a control unit (not shown).  
         [0048]     UV lamp assembly  150   a  is constructed in the same way and operates in the same way as UV lamp assembly  150   b , with the exception that UV lamp assembly  150   a  rotates in a direction opposite to that of UV lamp  150   b . The two lamp assemblies both open outwards from the center of curing apparatus  100 . In another embodiment, the lamp assemblies can open along axes parallel to the table or another axis as is convenient to accommodate UV lamp choices and cooling designs. Each lamp assembly has separate electrical connections and switches which are connected to a control unit (not shown).  
         [0049]     The functions of the apparatus are controlled by a controller  700  which is physically located in separate standalone housing from the curing table in the preferred embodiment. The controller is connected to the gas control switch  361 , gas solenoids  395   a  and  395   b , drive motor  205 , UV lamp assemblies  150   a  and  150   b , cooling fans  152   a  and  152   b , a start and stop switch  202 , oxygen sensor  315  and switches  645 . The standalone controller includes front access panel indicators  720  to indicate various states of the curing apparatus  100 .  
         [0050]      FIG. 7  shows the logical arrangement of controller  700 . The functions of controller  700  are provided by a programmable logic controller  710 . In the preferred embodiment, programmable logic controller  710  is a “PICO” type programmable logic controller available from Allen-Bradley of Milwaukee, Wis., USA. Of course, other programmable controllers such as a personal computer can be used in other embodiments. Hardwired controllers as well as discrete analog controllers may be employed in other embodiments. In the preferred embodiment, ladder logic is used to program the controller. Programmable logic controller  710  is connected to relay block  722 . Relay block  722  includes circuitry to convert digital signals from programmable logic controller  710  into analog signals with sufficient current to drive the various peripheral devices required by the apparatus. Relay block  722  is connected to gas solenoids  395   a  and  395   b  through a gas control connection  724 . Relay block  722  is connected to drive motor  205  through a motor control connection  726 . Connection  726  includes a motor controller capable of starting and altering the speed of drive motor  205  and for applying sufficient current for that purpose.  
         [0051]     Relay block  722  is also connected to UV lamps  150   a  and  150   b  through a connector  727  and to cooling fans  152   a  and  152   b  through a connector  728 . Programmable logic controller  710  is also connected to input connector block  730 . Input connector block  730  is capable of accepting analog or communication signals from the various peripheral devices required by the apparatus and converting them into digital signals accepted by programmable logic controller  710 .  
         [0052]     Input connector block  730  is connected by lamp switch connector  734  to oxygen level sensor  315  via RS232 connection  732 . Programmable logic controller  710  converts the reported voltage to a percent oxygen level.  
         [0053]     Input connector block  730  is also connected to switches  645 , one for each UV lamp assembly, to indicate the open or closed position of the lamp assemblies.  
         [0054]     Input connector block  730  is also connected to motor stop/start switch  202  via stop connection  736  and start connection  738 . Also attached to input connector block  730  is numerical keypad  742  for entry of digital data by an operator  750 , as required by the programmable logic controller to perform its functions.  
         [0055]     Programmable logic controller  710  is also connected to durable memory  708 . In the preferred embodiment, durable memory  708  is a battery backed up RAM. Of course, in other embodiments, durable memory  708  can be peripheral memory, magnetic or optical disk drives or network memory connected to the programmable logic controller through a network connection.  
         [0056]     In operation, programmable logic controller  710  initiates a program  800 , the steps of which are shown in  FIG. 8 , to operate the functions of the curing apparatus.  
         [0057]     Referring then to  FIG. 8 , the program  800  is initiated at start block  805 . As a first mode selection step  807 , the program requires input to determine if it should enter run mode  817  or program mode  809 . Upon entry into program mode  809 , several parameters are required to be set for the operation of the curing apparatus. Initially, a timer is set to delay startup until the lamps have reached operational temperature. Program mode  809  then requires an input step to supply the warm-up time  811  and input step  813  to supply a cool-down time  813  for the UV lamps. Other parameters such as the speed of the table rollers, rates of gas flow, curing time and automatic start and stop times can be programmed in other embodiments. Upon proper entry of the required data parameters, the program returns to mode selection step  807 .  
         [0058]     Upon entry into run mode at  817 , the program loads the parameters previously input in program mode. If the parameters are not present, the program returns to mode selection  807 . If program parameters are present, the program activates the apparatus by first activating gas control switch  361  and solenoids  395  to initiate gas flow at step  821 . When gas flow is activated, inert gas from gas reservoir  360  is admitted to gas distribution assemblies  160   a ,  160   b  and  170  through gas control switch  361 . Once the gas enters the gas manifolds, the gas is distributed through the gas manifolds and enters the curing chamber. The inert gas, being heavier than air, fills the curing chamber. Consequently, the inert gas displaces the oxygen and other gases present in the curing chamber before operation of the apparatus. After the step  821 , gas flow region  353  provides an oxygen free environment within curing apparatus  100 .  
         [0059]     At step  823 , the program activates UV lamp assemblies  150   a  and  150   b  including the UV lamps and lamp cooling fans. Depending on the type of lamp used, a warm-up period may be required. A delay is instituted as programmed in the parameters to allow the UV lamps  605  to rise to operating temperature. Upon activation of the UV lamps at step  823 , the program also activates the cooling fans. Once at operating temperature, UV lamps  605  produce an intense ultraviolet light which is reflected from each of the lamp reflectors  625  and from the surface of reflective pan  350  resulting in a high ultraviolet light intensity in the curing chamber. In the preferred embodiment a warm-up time for the UV lamps is set between 3 and 5 minutes.  
         [0060]     At step  825 , the program activates drive motor  205  and sends an activation indicator to the display at step  827 . Its speed is adjusted by motor controller  726  to correspond with the desired speed of the material to be cured. Drive motor  205  in turn activates reduction gearbox  210  and primary drive chain  230  to motivate the drive chain  220 . Simultaneously, the program sends a message through programmable logic controller  710  to display  720  to indicate a “run” condition indicating that the curing apparatus is functioning.  
         [0061]     In use, one or more polymer coated objects are placed on the table roller bars  120  at the entrance  101  automatically or by an operator. The objects are moved by the roller bars under baffle  185   a  and through the gas curtain provided by air knife  170   a  into the curing chamber. The objects then track under the UV lights and pass between lamp assemblies  150   a  and  150   b  and the reflective pan  350  and are illuminated by the UV light generated from UV lamps  605 .  
         [0062]     While in the curing chamber, the ultraviolet sensitive coating on the object cures. In the preferred embodiment, the product is immersed the inert gas in the curing chamber and underneath the UV lamps for approximately 20 to 30 seconds. Of course, this time period can be adjusted by adjusting the speed of drive motor  205 . In one embodiment, the cycle provided by the drive motor is continuous, but in others a delay may be instructed, momentarily halting progress of the objects while they are under the UV lamps.  
         [0063]     After being cured the objects move past gas knife  170   b , out of the curing chamber and past baffle plate  185   b . As the objects  190  exit they are removed by an operator or proceed to another production area from the curing apparatus  100 .  
         [0064]     During continuous operations of the apparatus, the program enters a loop after step  825 , starting at step  829  by checking oxygen sensor  315  to determine if the curing chamber is indeed completely filled with inert gas. In one preferred embodiment, the voltage output of oxygen sensor  325  is used as a threshold to begin operation of the process. In another preferred embodiment, the voltage output of oxygen sensor  325  is variable and is used by programmable logic controller  710  to proportionately open or close gas solenoids  395   a  and  395   b  via gas controller  724 . If the oxygen reported by oxygen sensor  315  is high, programmable logic controller  710  opens solenoids  395   a  and  395   b  proportionately to allow more inert gas to enter gas flow region  353 . As the level of oxygen drops, oxygen sensor  315  proportionately reduces voltage read by programmable logic controller  710 . At a certain voltage minimum, an alarm display is sent to indicator  720  by programmable logic controller  710  at step  831 . If the gas level is sufficient, then the program checks to assure that switches  645  are closed at step  833 . If not, an alarm is sent from programmable logic controller  710  to display  720  at step  835 . If both switches are indeed closed, the program proceeds to step  837 . At step  837 , programmable logic controller  710  polls the input connector block  730  to determine if stop switch  736  has been activated. If not, the loop returns, repeating step  829  and following steps, allowing continuous function of the curing apparatus.  
         [0065]     If the stop switch  736  has been activated, then a cool-down procedure is initiated at step  839 . Upon initiating cool-down, gas flow is terminated at step  840  by deactivating solenoids  395   a  and  395   b . At step  841 , drive motor  205  is deactivated through a gradual slowing of its speed to zero to avoid an instantaneous stop. Once the motor has been deactivated, the program deactivates the UV lamps  605  at step  847 . The cooling fans  152   a  and  152   b  are allowed to run for the time indicated by the parameters  819  as set by step  813  in program mode  809 . After cool-down time, at step  849 , the display is sent a “stop” message indicating a stop condition of the apparatus and the program terminates at step  851 . After step  851 , a loop is entered, checking for start condition  738  which will then return the program to step  805 .  
         [0066]     In an alternate embodiment, the steps carried out by programmable logic controller  710  in program  800  can be accomplished manually. In this process, the drive motor and gas valves (or solenoids) are manually activated. Gas level  207  is maintained in gas flow region  353  by a hand held sensor device suitable for monitoring O 2  levels or alternately, the inert gas levels.  
         [0067]     This invention is susceptible to considerable variation in its practice. Accordingly, this invention is not limited to the specific exemplifications set forth herein above. Rather, this invention is within the spirit and scope of the appended claims, including the equivalents thereof available as a matter of law.  
         [0068]     The patentees do not intend to dedicate any disclosed embodiments to the public, and to the extent any disclosed modifications or alterations may not literally fall within the scope of the claims, they are considered to be part of the invention under the doctrine of equivalents.