Abstract:
A curing apparatus comprises a curing chamber for accommodating a controlled atmosphere for a product being treated and an irradiator for providing radiation directed at the product. The curing chamber has spaced inlet and outlet openings for the product establishing a path of travel underneath the irradiator. First and second nozzle assemblies are disposed adjacent respective inlet and outlet openings for supplying inert gas into the chamber and maintaining an inert atmosphere within the chamber. The nozzle assemblies are removably secured to the chamber. A pre-chamber is provided in the nozzle assemblies to moderate the pressure distribution of the gas within the nozzle assemblies.

Description:
RELATED APPLICATIONS 
     This application is a division of application Ser. No. 09/158,603, filed on Sep. 23, 1998, which is a nonprovisional application of Ser. No. 60/099,666, filed Sep. 9, 1998. 
    
    
     FIELD OF THE INVENTION 
     The present is directed to an ultraviolet curing apparatus using an inert atmosphere chamber to exclude the presence or oxygen during the curing process. 
     The present invention is also directed to a removable nozzle cartridge with adjustable nozzles for delivery of inert gas, such as nitrogen, into a curing chamber. 
     BACKGROUND OF THE INVENTION 
     It is well known to apply ultraviolet curable coating to various types of object and to expose the same to ultraviolet radiation to produce a cured coating with desirable properties. For some curing chemistries, the presence of oxygen tends to inhibit the curing process, and so for such chemistries the amount of oxygen must be controlled. A common way of accomplishing this is to provide a curing chamber in which a flow of nitrogen is used to display the oxygen so that an inert atmosphere is provided. 
     A curing chamber is a relatively large and expensive structure, costing in the order of $150,000. The inert gas is introduced into the chamber by a variety of nozzles which are typically permanently secured to the chamber framework. When an improvement occurs in the nozzle technology, a brand new curing chamber would have to be built to incorporate the improvement, making the existing one obsolete. There is, therefore, a need for a curing chamber where the nozzles are removably secured to the chamber structure so that when improvement occurs in the nozzle technology, the existing chamber can be retrofitted with the new nozzles. 
     Prior art curing chambers are typically built for specific applications, such as using a specific ultraviolet processor for curing a product traversing through the chamber at a specific speed. If the user desires to increase the curing speed to cure more products per given time, the existing curing chamber may not be adequate, since the nozzles built into the machine may not be adequate to maintain the required inert atmosphere at the higher speed. In this case, the user would either deliver increased amount of nitrogen into the chamber to compensate for the increased speed or invest in a new curing chamber, requiring additional investments and space. Increasing the amount of nitrogen delivered to the curing chamber to accommodate the new application is relatively expensive, since nitrogen is an expensive commodity. There is, therefore, a need for a curing chamber where the nozzles can be changed or adjusted without replacing the entire curing chamber to accommodate the user&#39;s new application, without increasing nitrogen consumption or purchasing a new curing chamber. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is an object of the present invention provide a an inert gas curing chamber where the gas delivery system is removable so that the curing chamber can be used for different product runs. 
     It is another object of the present invention to provide a gas delivery system to a curing chamber that is in cartridge form so that it can be easily removed or replaced as desired or different applications. 
     It is still another object of the present invention to provide a gas delivery system for a curing chamber that provides a relatively uniform flow distribution across the path of the product being cured. 
     It is yet another object of the present invention to provide a gas delivery system for a curing chamber wherein the direction of gas flow coming from the system can be adjusted to accommodate increased product travel speed within the chamber without increasing gas consumption. 
     It is still further another object of the present invention to provide a gas delivery system for a curing chamber that is removable from the chamber so that adjustments to the system can be made outside of the chamber. 
     In summary, the present invention provides a curing apparatus comprising a curing chamber for accommodating a controlled atmosphere for a product being treated and an irradiator for providing radiation directed at the product. The curing chamber has spaced inlet and outlet openings for the product establishing a path of travel underneath the irradiator. First and second nozzle assemblies are disposed adjacent respective inlet and outlet openings for supplying inert gas into the chamber and maintaining an inert atmosphere within the chamber. The nozzle assemblies are removably secured to the chamber. A pre-chamber is provided in the nozzle assemblies to moderate the pressure distribution of the gas within the nozzle assemblies. 
     These and other objects of the present invention will become apparent from the following detailed description. 
    
    
     BRIEF DESCRIPTIONS OF THE DRAWINGS 
     FIG. 1 is a side elevational view of a curing chamber made in accordance with the present invention. 
     FIG. 2 is a fragmentary view of the curing chamber of FIG. 1, showing a nozzle cartridge being replaced or taken out from the curing chamber. 
     FIG. 3 is a perspective view of the nozzle cartridge shown in FIG.  2 . 
     FIG. 4 is a perspective assembly view of the nozzle cartridge of FIG.  3 . 
     FIG. 5A is a cross-sectional view taken along line  5 A— 5 A in FIG.  4 . 
     FIG. 5B is a cross-sectional view taken along line  5 B— 5 B of FIG.  5 A. 
     FIG. 6 is a cross-sectional view taken along line  6 — 6  in FIG.  3 . 
     FIG. 7 is similar to FIG. 6, showing the nozzle bodies adjusted to different angular positions from the vertical axis. 
     FIG. 8 is a fragmentary view, partly in cross-section, of the nozzle cartridge of FIG. 4, showing details of the endcaps of the pipe nozzle assembly. 
     FIG. 9 is a schematic illustration of pressure distribution in the pre-chamber and final chamber along the length of the distribution slot of the nozzle cartridge of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An ultraviolet curing apparatus R made in accordance with the present invention is disclosed in FIG.  1 . The apparatus R includes a chamber  2  in which ultraviolet curing of a product is done. The chamber  2  has an inlet opening  4  and an outlet opening  6  through which the product is conveyed into the chamber by means of a web  7 . A pair of rollers  8  pull the web  7  through the chamber  2 . An irradiator  10 , such as a standard ultraviolet lamp, is used to provide the curing process for the product. The irradiator  10  includes a bulb  12  disposed within a reflector cavity  14 . 
     Nozzle cartridges  16  and  18  are disposed within the chamber across the width of the web  7  and adjacent the inlet and outlet openings  4  and  6 , respectively, to provide a curtain barrier of an inert gas at the respective openings and to flood the interior of the curing chamber  2  with the same inert gas, preferably nitrogen, to exclude oxygen during the curing process of the product when it is subjected to the ultraviolet radiation of the bulb  12 . The nozzle cartridges  16  and  18  are identical to each other, except each is shown turned 180° with respect to the other. Although each of the nozzle cartridges  16  and  18  is disclosed as having a slot nozzle assembly  20  and a pipe nozzle assembly  22 , each cartridge may also carry only one nozzle assembly, depending on the specific application. 
     The slot nozzle assembly  20 , which is disposed closer to the respective inlet or outlet opening is used to provide a curtain barrier of inert gas to isolate the interior of the curing chamber  2  from the outside. The pipe nozzle assembly  22  is used to flood the chamber  2  with the inert gas. 
     The nozzle cartridges  16  and  18  are removably secured to the curing chamber  2  by means of screws  24 , as best shown in FIG.  2 . An opening  26  on top at each end of the curing chamber  2  is adapted to accommodate the nozzle cartridges  16  and  18  into the curing chamber  2 . Each of the nozzle cartridges  16  and  18  includes a top plate or support  28  to which the slot nozzle assembly  20  and the pipe nozzle assembly  22  are secured. A plurality of holes  30  around the outer edge of the plate  28  accommodate respective screws  24 , which are used to secure the nozzle cartridge in the opening  26  of the curing chamber  2 , as best shown in FIG.  3 . 
     The removability of the nozzle cartridges  16  and  18  from the curing chamber  2  advantageously provide the user with flexibility when a change in application of the curing chamber occurs, such as when the web speed is desired to be increased to accommodate a different product, without purchasing another curing chamber. Further, the removability of the cartridges from the curing chamber means that the cartridges can be adjusted on the workbench, which is a much easier operation than if the nozzle assembly is adjusted inside the curing chamber. Also, several previously adjusted cartridges can be stored aside that are then easily installed whenever the need arises for their use on a different application, thereby minimizing downtime in the job. 
     The nozzle cartridge  18 , which is identical to the cartridge  16  except that they are shown 180° apart, is shown in an assembly view in FIG.  4 . The slot nozzle assembly  20  includes a nozzle body  32 , endcaps  34 , shims  36  and connectors  38 . The connectors  38  are threadedly secured to the respective endcaps  34  through respective openings  37  in the plate  28  to thereby secure the endcaps  34  to the plate  28 . Screws  39  secure the endcaps  34  to the respective ends of the nozzle body  32  to form an integral pre-chamber  41  within the nozzle body  32 . The connectors  38  are used to connect the nozzle assembly to an inert gas supply. 
     The pipe nozzle assembly  22  includes a nozzle body  40 , a pipe diffuser  42 , endcaps  44  and connectors  46 . Screws  50  secure the endcaps  44  to the sides of the nozzle body  40  to form an enclosed pre-chamber  52 . The connectors  46  are threadedly secured to the respective endcaps  44  through respective openings  43  in the plate  28 . The connectors  46  are used to connect the nozzle assembly to an inert gas supply. 
     Studs  54  extending from the top surface of the plate  28  are configured to store unused shims  36 . Screws  55  secure the top part of the endcaps  34  to the top plate  28 . 
     The pipe diffuser  42  has a linear array of holes  56  disposed along the length and side of the pipe diffuser  42  facing the nozzle body  40 . Another linear array of smaller holes  58  are disposed on the diametrically opposite side of pipe diffuser  42 , as best shown in FIGS. 5A and 5B. 
     A pair of handles  60  disposed at respective end portions of the plate  28  allow the user to conveniently handle the cartridge when removing or replacing it in the curing chamber  2 . 
     Each of the endcaps  34  has an L-shaped passageway  62  to allow the flow of the inert gas from the connector  38  to the pre-chamber  41 . Similarly, each of the endcaps  44  also includes an L-shaped passageway  64  to allow the flow of the inert gas from the connectors  46  to the pre-chamber  52 . 
     The slot nozzle body  32  is made from two identical castings  66 , which are joined together by a plurality of bolts  68 . An interior longitudinal distribution slot  70  is formed between the pair of casting  66  along the length of the pre-chamber  41  in communication therewith. An exit slot  72  is also formed between the two castings  66  at the lower portions thereof to allow the inert gas to flow out into the curing chamber and form a curtain barrier. A final chamber  74  is provided by the castings  66  and is disposed between the slots  70  and  72  and runs along the length thereof. The distribution slot  70  allows the inert gas from the pre-chamber  41  to flow to the final chamber  74 . 
     A plurality of bolts  76  and springs  78  provide a means for adjusting the gap of the exit slot  72  as desired for a specific application. Turning the bolts  76  in either direction will either decrease or increase the gap of the exit slot  72 . The springs  78  urge the castings  66  away from each other so that when the bolts  76  are turned counter-clockwise in a conventional unscrewing direction, the castings  66  will move a corresponding distance under the spreading force of the springs  78 . 
     The slot nozzle body  32  is secured to the underside of the plate  28  by means of a bracket  80  and a resilient member  82  that advantageously allows the nozzle body  32  to be angularly adjusted. 
     The shims  36  are used to adjust the height of the exit slot  72  above the rollers  8 , as best shown in FIG.  1 . 
     The nozzle body  40  includes an arcuate wall  84  conformed to the diameter of the pipe diffuser  42 , as best shown in FIG.  6 . The arcuate wall  84  is used to support the pipe diffuser  42 . A longitudinal opening  86  is disposed in a top portion of the arcuate wall  84  and extends along the length of the pipe diffuser  42  to thereby expose the holes  56  to the pre-chamber  52 , as best shown in FIG.  6 . The end portions of the pipe diffuser  42  are received in respective bore holes  88  and endcaps  44  where set screws  90  permit the pipe diffuser  42  to be angularly adjusted and locked in place (see FIG. 8) 
     A gasket  92  is disposed around the underside periphery of the plate  28  to provide a seal around the opening  26  when the nozzle assembly is secured in place to the frame of the curing of the curing chamber  2 . 
     The nozzle body  32  includes a plurality of screw-receiving slots  98  and  100 , as best shown in FIGS. 6 and 7, that are aligned with respective holes  102  and  104  and are used to provide angular positioning of the nozzle body  32  to change the direction of flow of the inert gas exiting from the exit slot  72 . When the holes  102  are used in conjunction with the screw-receiving slots  98  when attaching the nozzle body  32  to the endcaps  34 , the exit slots  72  would be directed downwardly at zero degree to the vertical. If the holes  104  are used with the screw-receiving slots  100 , the nozzle body  32  and the exit slots  72  would be positioned at an angle from the vertical toward the inlet opening  4  in the case for the cartridge  16 . 
     The range of adjustment for the pipe diffuser  42  is 0°-45° with respect to a vertical axis. The opening  86  in the arcuate wall  84  is configured for the maximum angular adjustment without interfering with the holes  56 . The angular positioning of the exit slot  72  and the pipe diffuser  42  will depend on the specific application. Preferably, the slot nozzle  72  for the nozzle cartridge  16  adjacent the inlet opening  4  is preferably directed at an angle toward the inlet opening, while the pipe diffuse  42  would be preferably angled toward the center of the curing chamber  2 . The exit nozzle  72  for the nozzle cartridge  18  would be preferably directed perpendicularly toward the web  7 , while the pipe diffuser  42  would be preferably directed toward the center of the curing chamber. 
     The pre-chamber  41  advantageously provides for an even flow of inert gas along the length of the exit slot  72 . In the prior art, in order to obtain an even distribution of flow, multiple feeds are provided along the length of the manifold. With the present invention, even distribution of flow is achieved with only two feeds, one at each end of the nozzle body  32  through the connectors  38 . The gas flow is substantially made more uniform as it flows from the pre-chamber  41  to the final chamber  74  through the distribution slot  70 . The pre-chamber  41  advantageously provides a moderating effect to the pressure distribution within the final chamber  74 . This is schematically illustrated in FIG. 9, where a variation of less than 10% along the length of exit slot  72  is achieved with the present invention. In the prior art, about 30% variation in flow rate along the slot length is typical. With the present invention, an inert atmosphere of approximately 50 ppm of oxygen is achieved. 
     The pre-chamber  52  in the pipe nozzle body  40  also provides for even flow of inert gas along the length of the pipe diffuser  42  as the gas exit through the linear array of exit holes  58 . The variation of pressure within the pre-chamber  52  alone the length of the pipe diffuser  42  is also illustrated schematically in FIG. 9, where about 30% variation in the pre-chamber  52  is reduced substantially to about 10% inside the pipe diffuser  42  prior to the gas exiting through the exit holes  58 . The pre-chamber  52  advantageously provides a moderating effect to the pressure distribution within the interior of the pipe diffuser  42 . 
     The angular adjustment to the pipe diffuser  42  advantageously permits the curing chamber  2  to accommodate higher web speed. In the prior art, the flow rate of the inerting gas is increased for higher web speed, resulting in higher gas consumption, which in the case of nitrogen could be fairly expensive. With the present invention, adjusting the angle of flow through the pipe diffuser  42  while maintaining the flow rate of the gas feeds through the connectors  46  would still maintain the inerted atmosphere at the higher web speed. At higher web speed, the pipe diffuser  42  would be angled toward the flow of the web at a larger angle from the vertical than at lower web speed. With 15 ppm oxygen of inert gas being introduced to the chamber, 50 ppm oxygen atmosphere can be maintained with the present invention. Maintaining a uniform distribution of inert gas within the chamber, for example at 50 ppm oxygen, is important to the proper curing of the product being cured. If the inert atmosphere varies across the product, then the material properties of the product would vary depending on the variation on the inert atmosphere across the product when it is subjected to the UV radiation. 
     With the cartridge design of the present invention, the nozzle assemblies  20  and  22  can be pre-adjusted outside the curing chamber for a specific application or job. When a different job is desired to be processed through the chamber, a nozzle assembly which has already been adjusted for that job would be used to replace the one that is in the machine. In this manner, a low level technician can perform the change-over, since no further adjustments to the nozzles would be needed. In the prior art, where adjustments has to be made in the machine, a high level technician or engineer would be required to make the adjustment. 
     Although the present invention has been described using an ultraviolet irradiator, other types of irradiators, such a thermal heater, would be equally applicable. 
     While this invention has been described as having preferred design, it is understood that it is capable of further modification, uses and/or adaptations following in general the principle of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains, and as may be applied to the essential features set forth, and fall within the scope of the invention or the limits of the appended claims.