Abstract:
A system and method for monitoring ultraviolet radiation levels within the cure chamber of an ultraviolet curing station. An ultraviolet sensor is located within a cure chamber for sensing the strength of ultraviolet radiation reaching the sensor. The sensor is repositionable within the cure chamber for taking readings at a plurality of locations. Sensor readings at a plurality of predetermined positions within the cure chamber are communicated to a controller and stored in electronic memory, along with an identification of the sensor position when the reading was obtained. A report is generated setting forth correlated sensor readings and reading locations, and providing any appropriate warnings of existing or impending equipment failure impacting the level of ultraviolet radiation in the cure chamber (e.g., a bulb failure).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Elongate flexible workpieces, such as guidewires and catheters, are often coated to provide a desired property or characteristic, such as enhanced lubricity, improved biological compatibility, anti-coagulation or rust resistance. The coating is commonly applied by dipping the workpiece into a coating solution, removing the workpiece from the coating solution, and curing the coating using heat or ultraviolet (UV) radiation. 
         [0002]    Typical UV curing stations include a bank or array of UV bulbs along one wall of the curing station for emitting UV radiation into a cure chamber. 
         [0003]    As UV bulbs approach the end of their useful life they tend to emit an increased or decreased intensity of UV radiation into the cure chamber, resulting in excessive or insufficient UV radiation at certain location within the cure chamber to achieve the desired cure. Early detection of failing bulbs is critical as excessively or insufficiently cured workpieces are prone to failure, and unless caught early can result in the need to dispose of a large number of suspect workpieces and even a recall. 
         [0004]    The operational status of UV bulbs are currently checked on an ad hoc basis using a hand-held UV sensor. While significantly better than simply waiting for a bulb to fail completely, this procedure is inefficient and unreliable. 
         [0005]    Accordingly, a continuing need exists for a system and method of consistently and reliably monitoring ultraviolet radiation levels throughout an ultraviolet curing chamber. 
       SUMMARY OF THE INVENTION 
       [0006]    A first aspect of the invention is a system for monitoring ultraviolet radiation levels within the cure chamber of an ultraviolet curing station. The system includes an ultraviolet sensor, a sensor repositioning means, a controller, electronic memory and an interface device. The ultraviolet sensor is located within the cure chamber for sensing the strength of any ultraviolet radiation reaching the sensor. The sensor repositioning means is capable of repositioning the sensor within the cure chamber. The controller is in electrical communication with the ultraviolet sensor and the sensor repositioning means for obtaining sensor readings at a plurality of predetermined positions within the cure chamber. The electronic memory records data comprising at least the sensor readings correlated with the sensor position when the reading was obtained. The interface device performs at least one of (i) reporting the recorded data in a human perceptible format, (ii) generating a perceptible warning signal when a sensor reading falls above a threshold value indicative of excessive ultraviolet radiation for achieving the desired cure, (iii) generating a perceptible warning signal when a sensor reading falls below a threshold value indicative of insufficient ultraviolet radiation for achieving the desired cure, and (iv) reporting a change in consecutive sensor readings at a single sensor position exceeding a threshold value indicative of an impending cure failure. 
         [0007]    A second aspect of the invention is a method of monitoring ultraviolet curing within a cure chamber. The method includes the steps of (i) positioning an ultraviolet sensor at a defined location within an ultraviolet cure chamber, (ii) sensing the strength of any ultraviolet radiation reaching the positioned sensor, (iii) recording data comprising at least the sensor reading correlated with the sensor position when the reading was obtained, (iv) repositioning the ultraviolet sensor to a different defined location within the ultraviolet cure chamber, (v) repeating steps (ii) through (iv) at a plurality of defined locations to produce a data set comprising at least a plurality of sensor reading correlated with the sensor position when the reading was obtained, and generating a human perceptible report, comprising at least one of (i) a report of the data set, (ii) a report that a sensor reading fell above a threshold value indicative of excessive ultraviolet radiation for achieving the desired cure, and/or (iii) a report that a sensor reading fell below a threshold value indicative of insufficient ultraviolet radiation for achieving the desired cure. 
         [0008]    The system and method is particularly suited for monitoring ultraviolet curing within a cure chamber when the source of UV radiation is a plurality of ultraviolet bulbs. For such applications, the defined locations at which the sensor senses the strength of ultraviolet radiation are selected so that a single ultraviolet bulb dominates the reading taken at each defined location. The report generated by the monitoring system includes an identification of the bulb emitting the ultraviolet radiation dominating the reading taken by the sensor, thereby allowing replacement of a bulb as soon as a sensor reading correlated to that bulb indicates excessive or insufficient ultraviolet radiation for achieving the desired cure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a perspective view of one embodiment of the invention with the cure chamber door closed. 
           [0010]      FIG. 2  is a front view of the invention shown in  FIG. 1  with the cure chamber door fully open to facilitate viewing of internal components. 
           [0011]      FIG. 3  is an electrical schematic of the invention shown in  FIGS. 1 and 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Nomenclature 
       [0000]    
       
           10  Ultraviolet Curing Station 
           11  Base Section of Station 
           12  Hinged Door on Station 
           19  Cure Chamber 
           20  Workpiece Support Assembly 
           30  Bank of Ultraviolet Bulbs 
           31  First Row of UV Bulbs 
           32  Second Row of UV Bulbs 
           100  Monitoring System 
           140  Ultraviolet Sensors 
           141  First UV Sensor 
           142  Second UV Sensor 
           150  Repositioning System 
           151  Styles 
           151   a  First Style 
           151   b  Second Style 
           152  Rail 
           153  Motor 
           154  Belt 
           160  Controller 
           161  Memory 
           162  Display Panel 
           163  Interface Port 
           164  Warning Light 
         W Workpiece 
         x Horizontal Direction 
         y Transverse Direction 
         z Vertical Direction 
         z 1  Upward Direction 
         z 2  Downward Direction 
       
     
       Construction 
       [0042]    Referring to  FIGS. 1 and 2 , a “typical” ultraviolet curing station  10  is shown. The station  10  includes a base section  11  and a hinged door  12  defining a cure chamber  19 . A workpiece support assembly  20  for releasably supporting coated workpieces W within the cure chamber  19  is provided on inside of the back wall (unnumbered) of the base section  11 . A wide variety of different workpieces W can be cured using the station  10 .  FIG. 2  generically depicts elongate workpieces W such as guidewires and catheters, but the invention is not restricted to the curing of coatings on such workpieces W. 
         [0043]    A source of ultraviolet radiation, typically a bank of ultraviolet bulbs  30 , is provided on the inside of the door  12  for bathing the cure chamber  19  in ultraviolet radiation. The number and arrangement of the UV bulbs  30  can vary from station to station depending upon various design factors such as the size, shape and configuration of the cure chamber  19 , the size, shape and configuration of the coated workpiece W, and the nature of the coating to be cured. For illustration purposes only,  FIG. 2  depicts two columns of bulbs  31  and  32 , each containing five bulbs. 
         [0044]    Referring to  FIG. 2 , the monitoring system  100  includes at least one ultraviolet sensor  140  within the cure chamber  19 , a sensor repositioning system  150 , a controller  160 , electronic memory  161  and a means for interfacing with an operator (not shown) and/or peripheral electronics (not shown). 
         [0045]    The monitoring system  100  shown in  FIG. 2  includes first  141  and second  142  ultraviolet sensors (collectively  140 ) transversely y spaced from the bank of ultraviolet bulbs  30 , with each sensor  141  and  142  vertically aligned with one of the columns of bulbs  31  and  32  respectively. The desired sensing could also be performed with a single sensor  140  provided the sensor repositioning system  150  can repositioning the sensor  140  both vertically z and horizontally x. Ultraviolet sensors  140  suitable for use in this invention are widely available from a number of suppliers. 
         [0046]    The sensor repositioning system  150  needs to be able to reposition the sensor(s)  140  within the cure chamber  19  so that readings can be taken at various locations throughout the chamber  19 . While three-dimensional repositioning of the sensor(s)  140  within the cure chamber  19  can be achieved, I have discovered that sufficient information can be obtained by sensing ultraviolet levels within a single vertical plane z. 
         [0047]    Referring to  FIG. 2 , the depicted sensor repositioning system  150  is attached to the base  11  for moving the sensors upward z 1  and downward z 2  within a vertical z plane. The sensors  140  are mounted onto a horizontal rail  152 . The horizontal rail  152  slidably engages horizontally x spaced vertical z styles  151   a  and  151   b  (collectively  151 ). The rail  152  can be vertically z repositioned along the styles  151  by a drive system such as a motor  153  and a belt  154 . Other repositioning systems and drive systems known to those of routine skill in the art can also be employed, including pneumatic, hydraulic and/or electrically powered systems. 
         [0048]    Repositioning of the sensor(s)  140  is controlled by a suitable controller  160 . The controller  160  is also preferably equipped with a display panel  162  for communicating directly with an operator, an interface port  163  form communicating with a peripheral device (not shown) such as a CPU, printer, keyboard etc., and/or a warning signal such as a warning light  164 , buzzer (not shown), etc. 
         [0049]    Sensor readings are taken at a plurality of predetermined locations within the cure chamber  19 . Sensor readings, correlated with the sensor  140  position when the reading was obtained, is communicated to and stored in electronic memory  161 . This data can then be reported to an operator (not shown) in any number of ways. The data may simply be printed or displayed in a human perceptible format. Alternatively, a perceptible warning signal may be generated when (i) a sensor reading falls above a threshold value indicative of excessive ultraviolet radiation for achieving the desired cure, (ii) a sensor reading falls below a threshold value indicative of insufficient ultraviolet radiation for achieving the desired cure, and/or (iii) reporting a change in consecutive sensor readings at a single sensor position exceeding a threshold value indicative of an impending cure failure. The nature of the perceptible warning signal can be selected from a wide range of signals such as activating a warning light  164 , activating a warning buzzer (not shown), displaying a warning message on the display panel  162 , displaying a warning message on an attached monitor (not shown), printing a warning message on a printout (not shown) generated upon the completion of each monitoring cycle, etc. 
         [0050]    The monitoring system  100  can greatly simply the identification and replacement of a failing bulb in a bank of bulbs  30  by (i) programming the controller  160  to take sensor readings at locations where the ultraviolet radiation sensed by the sensor is dominated by the ultraviolet radiation emitted by a single bulb, (ii) correlating these sensor readings with an identification of the bulb emitting the ultraviolet radiation dominating the reading taken by the sensor  140 , and (iii) reporting a bulb as “failing” when a sensor reading correlated to that bulb indicates excessive or insufficient ultraviolet radiation for achieving the desired cure. 
       Use 
       [0051]    The strength of ultraviolet radiation provided throughout a cure chamber  19  can be monitored for ensuring lot quality assurance, permitting preventative maintenance, and/or facilitating the identification of equipment in need of repair and/or replacement. Monitoring involves the steps of (i) sensing the strength of ultraviolet radiation reaching an ultraviolet sensor  140  positioned at a defined location within the cure chamber  19 , (ii) recording data comprising at least the sensor reading correlated with the sensor position when the reading was obtained, (iii) repositioning the ultraviolet sensor  140  to a different defined location within the cure chamber  19 , (iv) repeating steps (i) through (iii) at a plurality of defined locations to produce a data set comprising at least a plurality of sensor reading correlated with the sensor position when the reading was obtained, and (v) generating a human perceptible report, comprising at least one of (a) a report of the data set, (b) a report that a sensor reading fell above a threshold value indicative of excessive ultraviolet radiation for achieving the desired cure, and/or (c) a report that a sensor reading fell below a threshold value indicative of insufficient ultraviolet radiation for achieving the desired cure. 
         [0052]    A monitoring cycle can be performed on any desired schedule, but is preferably performed prior to each cure cycle (i.e., placing a workpiece W coated with an ultraviolet curable material within the cure chamber  19 , (ii) curing the coating, and (iii) removing the workpiece W with a cured coating from the curing chamber  19 ) to minimize the possibility that product was defectively cured in the cure chamber  19  between monitoring cycles. 
         [0053]    By repeating monitoring cycles over time and taking sensor readings at the same defined locations, a performance profile can be obtained for each location. An unusual or unexpected change in a performance profile can then be used as an indicator of an impending equipment failure (e.g., bulb failure) and a preemptive repair or replacement can be completed. 
         [0054]    The monitoring system  100  can facilitate replacement of failing bulbs, often prior to actual failure, by simply (i) taking sensor readings at locations where the ultraviolet radiation sensed by the sensor is dominated by the ultraviolet radiation emitted by a single bulb, (ii) correlating each sensor reading with an identification of the bulb emitting the ultraviolet radiation dominating the reading taken by the sensor  140 , and (iii) reporting a bulb as “failing” when a sensor reading correlated to that bulb indicates (a) excessive or insufficient ultraviolet radiation for achieving the desired cure, or (b) a change in consecutive sensor readings exceeding a threshold value indicative of an impending cure failure. Upon receiving such a report, an operator need merely located and replace the bulb identified in the report as “failing”.