Patent Publication Number: US-6708617-B2

Title: Traversing contact cleaning roller system

Description:
This application is a Continuation-in-Part of our pending application Ser. No. 09/579,645, filed May 26, 2000 now U.S. Pat. No. 6,568,326, which is a Continuation-in-Part of our application, Ser. No. 09/294,952, filed Apr. 20, 1999, now matured as U.S. Pat. No. 6,196,128, issued Mar. 6, 2001. 
    
    
     The present invention relates to methods and apparatus for cleaning particulate contamination from a moving substrate surface; more particularly, to methods and apparatus for traversing a contact cleaning roller axially while rolling along a moving substrate to transfer contaminant particles from the moving substrate to the contact cleaning roller; and most particularly, to methods and apparatus for progressively and continuously cleaning a contact cleaning roller while the roller itself is continuously cleaning a moving substrate. 
     In many manufacturing processes involving substrates, for example, in continuous-web printing and in the coating of photographic films and papers, particulate contamination of the substrate surface can lead to reduced to quality of the coated product and to increased waste. It is known to use a polymer-covered roller in rolling contact with a planar substrate to remove particles from the surface of the planar substrate ahead of the printing or coating point. It is also known to use a polymer-covered roller in rolling contact with another roller, for example, a process roller such as another contact cleaning roller, calendar roller, offset printing roller, and the like. The surface of such a polymer-covered roller (known in the art as a contact cleaning roller and also referred to herein as a CCR), may comprise a polymer having a high surface energy, for example, polyurethane or silicone rubber, or alternatively, a polymer exhibiting adhesive tack, such as any of the well-known tape adhesives. The CCR surface exhibits a greater attraction for particles than does the substrate surface, so that particles are transferred from the substrate to the CCR at the point of rolling contact. 
     A CCR may itself function as a conveyance roller, for example, in a string of web conveyance rollers, in which use the CCR may enjoy a substantial angle of wrap of the web, for example, a wrap angle of 90° or even greater. A conveyance roller as used herein is a roller whose position defines a portion of a web conveyance path. Such engagement by a CCR may be on either side of the web being conveyed. See, for example, U.S. Pat. No. 5,251,348 issued Oct. 12, 1993 to Corrado et al. A CCR may also function as a non-conveyance roller, that is, the web conveyance path is not a function of the presence or absence of the CCR. In such use, a CCR typically is positioned as a nip roller urged against a non-CCR conveyance roller (backing roller), the web passing therebetween, whereby the web is conveyed on a first or back side against the conveyance roller and is cleaned on a second or front side by the CCR. See, for example, U.S. Pat. No. 5,611,281 (&#39;281) issued Mar. 18, 1997 to Corrado et al. which is hereby incorporated by reference. 
     Many substrates, for example, web substrates, have particulate contamination concentrated along the outer edges of the substrate surface which can lead to premature clogging and failure of a full-width CCR while more central portions of the CCR surface are still non-clogged and serviceable. The U.S. Pat. No. 5,611,281 patent discloses to prolong the useful life of a CCR between renewals (removal of accumulated particles) by oscillating the CCR axially a short distance by transverse translating means while it is rolling along the substrate surface; thereby causing accumulating particles to be distributed as a broad band over a substantial portion of the axial length of the roller along each substrate edge. 
     Through use, the surface of a CCR becomes progressively clogged with removed particles and progressively loses cleaning effectiveness. Cleaning, also known as renewal, of a CCR surface may be accomplished through washing, for example, as disclosed in U.S. Pat. Nos. 5,275,104 and 5,611,281, the latter of which being incorporated herein by reference, wherein a plurality of CCR&#39;s are alterably provided such that continuous cleaning of the substrate surface can be maintained by a fresh CCR while each CCR in turn is rotated out of service for offline renewal, including drying. This is necessary in the prior art because washing of a CCR while in service against a substrate risks undesirable transfer of cleaning fluid onto the substrate. Such a multiple-CCR installation is complex and costly to build and to maintain. 
     Alternatively, as disclosed in the &#39;281 patent, a higher-tack, or secondary, CCR may be engaged to clean particles from a lower-tack, or primary, CCR (which procedure is defined hereby as secondary cleaning) which itself has cleaned, or is actively cleaning, particles from some other substrate surface such as a web or another process roller (which procedure is defined hereby as primary cleaning) For continuous primary cleaning, this arrangement requires continuous contact of the primary CCR with the substrate. Thus, a problem arises as to how to clean or renew the secondary CCR without reverse-contaminating the primary CCR and, indirectly, the substrate being cleaned 
     Typically, a secondary CCR, like a primary CCR, comprises a solid polymer covered roller or a length of adhesive tape wound on a core with the adhesive surface facing outwards In the prior art, renewal of the secondary CCR requires first that the roller be retracted from contact with the primary CCR to avoid contamination thereof and replaced in its cleaning function by another secondary CCR A secondary CCR may then be washed automatically offline, as referenced above, or manually by an operator, either in place or after being removed to a washing station. A tape-type secondary CCR is renewed either by unwinding and discarding the exposed tape to present a fresh convolution or by replacing the roll of tape when spent, as disclosed in U.S. Pat. No. 4,009,047. In such a prior art application, at least two alternable secondary CCR&#39;s are required, at an increase in expense and complexity 
     Thus there is a need for a method and apparatus for providing online renewal cleaning of a CCR, either primary or secondary, which permits regular renewal of the CCR without requiring any additional or replacement CCR&#39;s and without endangering the substrate being cleaned. 
     It is a principal object of the invention to provide an improved method and apparatus for safe, inexpensive, simple, and frequent renewal of a primary and/or secondary CCR while performing its online cleaning function. 
     It is a further object of the invention to provide an improved method and apparatus for continuous cleaning of a substrate by a single CCR. 
     Briefly described, a system for cleaning a moving substrate includes a contact cleaning roller mounted on translating means for axially oscillating the CCR, an example of such translating means being a carriage on a rail mounted adjacent to the substrate surface and substantially transverse to the direction of movement thereof, the roller being in rolling contact with the substrate surface, substantially as disclosed in Patent &#39;281. First and second renewal stations for cleaning the CCR are fixedly mounted adjacent the rail, one being so disposed outboard of each longitudinal edge of the substrate. The CCR is at least twice as long as the width of the substrate and therefore is in renewal contact with at least one of the renewal stations at all times. The CCR is axially oscillable for a distance sufficient that all portions of the CCR surface are cleaned by the first and second renewal stations in combination during one oscillation cycle of the CCR while the CCR maintains continuous contact across the full width of the substrate. Viewed in plan view, the left renewal station cleans the entire left half of the CCR during that portion of the oscillation cycle wherein the CCR extends beyond the left edge of the substrate, and the right renewal station cleans the entire right half of the CCR during that portion of the oscillation cycle wherein the CCR extends beyond the right edge of the substrate. In a preferred method, the cleaning station is engaged with the CCR for renewal during the outward stoke of the CCR past the station and is retracted during the inward stroke, although the station may also be left in contact with the CCR during the inward stroke if so desired. Generally, this is not necessary. 
     Thus, a single CCR may be continuously cleaned without being pivoted out of contact with the substrate and without risk of contamination to the substrate as in the prior art. 
     In a first preferred embodiment, a contact cleaning roller mounted on the carriage is a primary CCR and the substrate is an object such as a continuous flexible web or rigid sheet to be cleaned by the apparatus and method of the system. 
     In a second preferred embodiment, a contact cleaning roller mounted on the carriage is a secondary CCR and the substrate is a primary CCR for cleaning an object such as a web. The primary CCR is positionable to be in contact with a surface of a substrate to be cleaned and may also be positionable to be out of contact with the substrate surface as desired. The primary CCR preferably is axially fixed and in length is of the order of the width of the substrate. The secondary CCR may be moved axially along the surface of the primary CCR either in contact or out of contact therewith. 
     Two substantially identical CCR cleaning systems in accordance with the invention may be disposed on opposite sides of a substrate to clean both sides in a single pass of the substrate through the apparatus. 
    
    
     The foregoing and other objects, features, and advantages of the invention, as well as presently preferred embodiments thereof, will become more apparent from a reading of the following description in connection with the accompanying drawings in which: 
     FIG. 1 is a front elevational view of a first embodiment of an axially oscillable CCR system for cleaning a substrate in accordance with the invention; 
     FIG. 2 is a side elevational view of the system shown in FIG. 1; 
     FIG. 3 is a schematic cross-sectional view of the CCR system shown in FIG. 1 taken along line  3 — 3 , showing the primary CCR in nipped relationship with a backing roller for cleaning a surface of a substrate passing therebetween; 
     FIG. 4 is a plan schematic view of the system shown in FIG. 1, showing the CCR at the midpoint of an oscillation cycle; 
     FIG. 5 is a view like FIG. 4, showing the CCR at a first travel extreme in an oscillation cycle; 
     FIG. 6 is a schematic view like FIG. 4, showing the CCR at a second travel extreme opposite to that shown in FIG. 5; 
     FIG. 7 is a side elevational view of a second embodiment in accordance with the invention, showing a CCR positioned for cleaning a process roller, which roller may be a primary CCR; 
     FIG. 8 is a schematic cross-sectional view of the CCR system shown in FIG. 7, showing the primary CCR in nipped relationship with a backing roller for cleaning a surface of a substrate passing therebetween, and an oscillable secondary CCR cleaning the primary CCR; 
     FIG. 9 is a schematic cross-sectional view of a multiple system of CCR&#39;s like that shown in FIG. 8, disposed for cleaning opposite surfaces of a substrate simultaneously; and 
     FIG. 10 is a view similar to the view shown in FIG. 8 but wherein the primary CCR is a conveyance roller engaged on a free span of the substrate. 
    
    
     The invention is defined by the claims. Apparatus and methods in accordance therewith are useful in processes for cleaning flexible substrates comprising, but not limited to, plastic, metal, and paper webs and sheets, and rigid planar substrates comprising, but not limited to, circuit boards and silicon wafers. Process rollers such as other contact cleaning rollers, printing rollers, conveyance rollers, coating backing rollers, and calendar rollers are also cleanable substrates within the scope of the invention. 
     Referring to FIGS. 1 through 6, there is shown a first embodiment of a CCR system  10  in accordance with the invention for continuous cleaning of a substrate  12  having a first surface  14  by means of continuous rolling contact with a contact cleaning roller  16 , and for continuous renewal of the contact cleaning roller  16  by continuous contact with at least one renewal station  18 ,  18 ′. 
     Substrate  12  is moving in the direction  13  shown, and CCR  16  is mounted for rotation about an axis  20  disposed substantially orthogonal to direction  13 . Substrate  12  is of indefinite length and has first and second longitudinal edges  22 ,  22 ′ and a surface width  24  therebetween. CCR  16  has a length  26  of roller surface  28  which is at least twice width  24 . 
     Renewal stations  18 ,  18 ′ are mounted to machine frame  19  adjacent and outboard of edges  22 ,  22 ′ such that CCR  16  is in cleaning contact with at least one of stations  18 ,  18 ′ at all times while CCR  16  is cleaning surface  14  Renewal stations  18 ,  18 ′ are preferably identical and may be fashioned conventionally, for example, as disclosed as “cleaner  52 ” (except for the traversing mechanism in Patent &#39;281. Stations  18 ,  18 ′ preferably may be mounted conventionally for retraction from contact with the CCR as desired, for example, during the inward stroke of the renewed CCR back onto the substrate, or for maintenance of the stations in known fashion Preferably, each renewal station is provided with an associated drying nozzle  21  supplied with air from a clean air supply (not shown) for evaporating cleaning fluid which may be residual on the surface of the CCR after renewal, to prevent tracking of such fluid onto the substrate surface being cleaned. 
     For translation across the web, CCR  16  is rotatably supported at the ends thereof in carriage  30  which in turn is translatably suspended by hangers  32  from rail  34  mounted on frame  19 . Carriage  30  and CCR  16  may be driven reciprocably along rail  34 , for example, by such known translating means as are fully discussed and illustrated in incorporated reference Patent &#39;281. 
     In first embodiment  10 , CCR  16  is disposed in nipped relationship with a backing roller  36  to urge substrate  12  against CCR  16  as the substrate is passed between the CCR and the backing roller. 
     In operation, CCR  16 , being in rolling, cleaning contact with surface  14  across the entire width of the surface and also in renewal contact with renewal stations  18 ,  18 ′, as shown in FIG. 4, is progressively translated in a first direction, which is to the left in FIG. 4 such that eventually the entire left half  38  of CCR  16  is renewed by station  18  (and the outer portion of right half  40  by station  18 ′) while surface  14  is still being cleaned. At the travel extreme shown in FIG. 5, left half  38  is fully renewed and the surface is being cleaned solely by right half  40 . The carriage direction is reversed and the cleanings are repeated in reverse, until the entire right half is cleaned by station  18 ′, the opposite travel extreme shown in FIG. 6 is reached, and the surface is being cleaned solely by left half  38 . The carriage direction is then reversed to return the CCR to the starting position shown in FIG. 4, completing one oscillation of the apparatus. In this way, a single CCR may be renewed regularly, reliably, automatically, and online while simultaneously cleaning continuously a moving substrate surface 
     Some substrates, such as very thin webs or fragile sheets, can be wrinkled, distorted, or otherwise damaged by oscillation of a CCR. As shown in a second embodiment  42  in FIGS. 7 and 8, a primary CCR  46  can be mounted in fixed bearings  44  in place of backing roller  36  in embodiment  10 , and CCR  16  becomes therefore a secondary CCR as defined above Backing roller  36  may be relocated to a new nipped relationship with CCR  46 . System  42  thus affords the regular CCR renewal benefits of system  10  without axial oscillation of the primary CCR against the substrate, at a cost of one additional CCR. Alternatively, as shown in a third embodiment  45  in FIG. 10, primary CCR  46  may be a substrate conveyance roller disposed on a free span  47  of the substrate  12  without a backing roller. 
     In some applications, as shown in a fourth embodiment  48  in FIG. 9, it may be desirable to have two substantially identical individual CCR systems  50 ,  50 ′ similar to system  42  and having analogous components mounted in opposition, substrate  12  passing in nipped relationship therebetween, such that first substrate surface  14  and second substrate surface  52  may be cleaned simultaneously. 
     From the foregoing description, it will be apparent that there has been provided an improved method and apparatus for cleaning particles from a moving substrate, wherein a contact cleaning roller at least twice as long as the width of the substrate is translated axially of itself and transversely of the substrate while in rolling contact with a surface of the substrate for cleaning particles therefrom, and wherein cleaning stations outside each edge of the substrate continuously renew portions of the CCR surface not in such rolling contact. Variations and modifications of the herein described improved method and apparatus, in accordance with the invention, will undoubtedly suggest themselves to those skilled in this art. Accordingly, the foregoing description should be taken as illustrative and not in a limiting sense.