Traversing contact cleaning roller system

Abstract

A system for cleaning a moving substrate includes a rail mounted adjacent to the substrate surface and substantially transverse to the direction of movement thereof. A carriage for supporting a contact cleaning roller (CCR) is deployed on the rail for allowing axial translation of the CCR transversely of the substrate while in rolling contact therewith. Two renewal stations for cleaning the CCR are mounted adjacent the rail, one outboard of each substrate edge. The CCR is at least twice as long as the width of the substrate and is axially oscillable for a distance sufficient that all portions of the CCR surface may be cleaned by the renewal stations during one oscillation cycle of the CCR while the CCR maintains continuous contact with the substrate across the full width thereof. The CCR mounted on the carriage may be a primary CCR and the substrate may be a continuous web or sheet, or the CCR mounted on the carriage may be a secondary CCR and the substrate may be a primary CCR or other process roller.

Description

DESCRIPTION

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 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 ('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 discloses to prolong the useful life of a CCR between renewals (removal of accumulated particles) by oscillating the CCR axially a short distance 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, wherein a plurality of CCR's are alternably 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 off-line 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 '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'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'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 and translating means for axially oscillating the CCR, such as a carriage on a rail mounted adjacent to the substrate surface and substantially transverse to the direction of movement thereof, while in rolling contact with the substrate surface, substantially as disclosed in Patent '281. Two renewal stations for cleaning the CCR are mounted adjacent the rail, one station being mounted outboard of each longitudinal edge of the substrate. The CCR is at least twice as long as the width of the substrate and 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 renewal stations in combination during one oscillation cycle of the CCR while the CCR maintains continuous contact across the full width of the substrate. In a preferred method, the cleaning station is engaged with the CCR for renewal during the outward stroke 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'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 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 '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.

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 are adapted to be driven reciprocably along rail 34 at such axial translational rates as are disclosed in Patent '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 T) 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.

Claims

1. A method for continuously cleaning a moving substrate surface by rolling contact with a surface of a contact cleaning roller and simultaneously and continuously renewing the surface of the contact cleaning roller, comprising the steps of:a) providing a contact cleaning roller at least twice as long as the width of said substrate; b) engaging said contact cleaning roller surface in rolling contact with said moving substrate surface to clean said substrate surface; c) providing first and second renewal stations adjacent opposite edges, respectively, of the substrate; d) engaging at least one of said renewal stations in renewal contact with said contact cleaning roller; e) axially oscillating said contact cleaning roller transversely of said substrate surface during said rolling contact therewith by an oscillatory distance sufficient that at least one half of said contact cleaning roller surface is renewed by each one of said renewal stations during one complete cycle of said oscillation; and f) engaging both of said first and second renewal stations with said contact cleaning roller.

2. A method in accordance with claim 1 wherein at least one of said renewal stations is renewingly engaged with said contact cleaning roller while said contact cleaning roller surface is moving axially away from said substrate surface and is retracted from renewing contact when said contact cleaning roller surface is moving axially toward said substrate surface.