Patent Publication Number: US-2007101885-A1

Title: System for monitoring contamination of a substrate surface using a contact cleaning roller

Description:
RELATIONSHIP TO OTHER APPLICATIONS AND PATENTS  
      The present application draws priority from a pending U.S. Provisional patent application, Ser. No. 60/735,540, filed Nov. 10, 2005. 
    
    
     TECHNICAL FIELD  
      The present invention relates to method and apparatus for assessing contamination type and severity on a substrate; more particularly, to method and apparatus for permitting video analysis of substrate particulate contamination removed from a substrate surface by a contact cleaning roller.  
     BACKGROUND OF THE INVENTION  
      In many sheet-based and web-based processes today, the sheet or web must be cleaned of particulate contaminants before a coating can be applied. It is known to clean sheets and rollers by rolling impingment of a high-tack roller surface; see, for example, U.S. Pat. Nos. 5,611,281 and 6,196,128. A polymer-covered roller having a particle-attractive surface is known generally in the art as a “contact cleaning” roller (CCR). A CCR functions by having an attraction for particles greater than the attraction of the surface to be cleaned by the roller.  
      In some sheet-based and web-based processes, it is of especial interest to know the size, shape, type, and/or frequency of particles contaminating a substrate surface. Conducting such analysis in real time on the substrate itself can be difficult or impossible, as the substrate is typically moving at high speed and the contaminants may be widely separated in both length and width of the substrate.  
      What is needed in the art is an improved method and apparatus for monitoring substrate contamination.  
      It is a principal object of the present invention to monitor substrate contamination by collecting, concentrating, and video analyzing particles from a substrate surface.  
     SUMMARY OF THE INVENTION  
      Briefly described, a CCR system for removing and analyzing particulate contaminants from a substrate surface comprises at least one CCR selectively contactable with the substrate surface. The CCR rolls along the surface which typically is drawn past the CCR as a continuous moving web, the CCR being rotatably mounted on an axle of the system. The CCR may remain in operation for real-time analysis of removed contamination, or the CCR may be removed for off-line analysis of the partculate contamination. A video camera scans the CCR surface and transmits images or data for visual and/or computer analysis of the contamination, which analysis may include, but is not limited to, computerized shape analysis of particles, areal distribution of particles, and composition of particles. The computer may be programmed in known fashion for conducting such analyses. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:  
       FIG. 1  is a plan view of a first embodiment of a substrate contamination monitoring system employing a contact cleaning roller, in accordance with the invention;  
       FIG. 2  is an end view of the first embodiment shown in  FIG. 1 ; and  
       FIG. 3  is an end view of a second embodiment of a substrate contamination monitoring system employing a contact cleaning roller, in accordance with the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Referring to  FIGS. 1 and 2 , in a first embodiment  100  of a substrate contamination monitoring system in accordance with the invention, a planar flexible substrate  102  having particulate contamination on a first surface  104  thereof is conveyed on a second surface thereof  106  around a roller  108  in a first conveyance direction  110  in known fashion. A prior art traversing CCR assembly  112  comprising a contact cleaning roller  113 , which assembly preferably includes a speed-matching motor  114  for bringing the rotational speed of CCR  113  to substrate conveyance speed prior to engagement therewith in known fashion, is mounted on a first stationary rail  116  for traversing assembly  112  transversely to any of a plurality of first positions adjacent surface  104  for removing particles therefrom in known fashion. A prior art CCR wash unit  118  is mounted on a second stationary rail  120  adjacent an edge of substrate  102  for cleaning and regenerating CCR  113  off-line in known fashion. A camera means  122  is also mounted on second stationary rail  120  adjacent an edge of substrate  102  in position to photograph the surface of CCR  113  after CCR  113  has been retracted from substrate-cleaning mode along first stationary rail  116  to one or more second positions. Means may be provided for rotating and axially displacing CCR  113  before camera means  122  to permit photographing of any portion of the CCR surface as may be desired. Camera means  122  (not visible in  FIG. 2 ) may employ any desired data acquisition technology, such as but not limited to, visible light photography, infrared and ultraviolet photography, silver halide film, CCD video, and nuclear radiation detection. Images and data acquired by camera means  122  may be analyzed in any fashion desired, which analysis may be facilitated by computer means  124  which may be disposed, for example, in a housing with camera means  122 . Many such analytical techniques are well known in the prior art and need not be elaborated upon here.  
      A presently-preferred method for using first embodiment  100  to monitor particulates on a substrate surface includes any or all of the following steps:  
      a) moving CCR assembly  112  along first rail  116  to a predetermined axial location adjacent substrate surface  104 ;  
      b) engaging CCR  113  in rolling contact with substrate surface  104  to collect particulates therefrom;  
      c) disengaging CCR  113  from substrate surface  104 ;  
      d) moving CCR assembly  112  along first rail  116  to a predetermined axial location adjacent camera means  122 ;  
      e) acquiring data from CCR  113  by camera means  122   
      f) sending acquired data to computer means  124 ; and  
      g) engaging CCR  113  with CCR wash unit  118  to regenerate the surface of CCR  113  for reuse.  
      In a presently preferred embodiment, CCR  113  is relatively short with respect to the width of substrate  102 . A short CCR can collect a concentrated contaminant sample by being moved to various axial locations across the substrate. Such a sample can thus represent a widthwise averaging of substrate particulate contamination. A potential drawback of embodiment  100  in some applications is that the particulate information is not obtained in real time, as data acquisition, obtained off-line by camera means  122 , inherently occurs at some time period after the relevant portion of the substrate has passed the CCR.  
      Referring now to  FIG. 3 , a second embodiment  200  of a substrate contamination monitoring system in accordance with the invention is similar in most respects to first embodiment  100 . The CCR assembly and CCR cleaning components may be identical. The important difference in second embodiment  200  is that camera means  222  is mounted on the CCR carrier  230  rather than on second rails  120  and thus travels with CCR  113  and is able to acquire data in real time about particulates removed from the the surface of CCR  113 , while the CCR is actively cleaning substrate surface  104 .  
      In use of either embodiment  100  or embodiment  200 , it is good practice to bring the rotational speed of CCR  113  up to the linear speed of substrate  102  through use of speed match motor  114  prior to engagement of the substrate by the CCR to prevent scuffing of the substrate surface.  
      While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.