US3195500A - Abrasive work back-up to recondition doctor blade - Google Patents

Description

ABRASIVE WORK BACK-UP T0 RECONDITION DOCTOR BLADE Filed Aug. 29, 1962 P. T. KUHNEL July 20, 1965 3 Sheets-Sheet 1 July 20, 1965 P. T. KUHNEL 3,195,500

ABRASIVE WORK BACK-UP TO RECONDITION DOCTOR BLADE Filed Aug 29, 1962 3 Sheets-Sheet 2 July 20 65 P. T. KUHNEL 3,195,500

ABRASIVE ,WORK BACK-UP TO RECONDITION DOCTOR BLADE Filed Aug. 29, 1962 3 Sheets-Sheet 3 United States Patent 3,195,500 ABRASIVE WORK BACK-UP T0 RECONDITIQN DOCTOR BLADE Paul T. Kuhnel, Neenah, Wis., assignor to Kimberly- Clarlr Corporation, Neenail, Wis, a corporation of Delaware Filed Aug. 29, 1962, Ser. No. 220,247

2 Claims. (Cl. 118-70) This invention relates to improvements in coating equipment and procedures and is particularly concerned with the coating of paper webs and the like.

In many coating processes a resiliently covered backing roll supports a traveling Web of paper as the web is directed between the backing roll and a flexible blade pressured against the backing roll and web. The web before reaching the blade is provided with an excess of coating composition, usually an aqueous mineral coating composition. This coating composition is troweled by the flexible blade to smooth some of the coating composition on th web while the excess of coating composition is removed; the contact of the blade with the coating and web results in significant wearing of the blade.

A principal object of this present invention is to provide a novel resiliently covered backing roll which is itself capable of honing and wearing a troweling blade at longitudinal zonal ends of the blade, where there is no web contact, to provide substantially uniform blade wear over the blade length; further, the novel resilient backing roll has been found to support the traveling paper web in such manner that wrinkles in the web as the Web moves under the blade are substantially avoided.

A particular object of the invention is to provide a novel combination of backing roll and blade in which characteristics of the backing roll improve the operating life of the blade and permit the coating of various web widths without blade change.

An important object of the present invention is the provision of a novel process for carrying out blade coating operations.

The invention will be more fully understood by reference to the following detailed description and accompanying drawings wherein:

FIG. 1 is a schematic view of one form of coating device useful in the practice of the invention;

FIG. 2 is a perspective view of the backing roll-blade combination of FIG. 1 with the metering mechanism removed and particularly illustrating the relationship of backing roll, web, and blade;

FIG. 3 is a view of the blade and holder of FIG. 1 particularly illustrating the cooperative relationship of the blade, web, and backing roll;

FIG. 4 is a fragmentary plan view of the blade of FIG. 3 illustrating blade wear;

FIG. 5 is a view similar to that of FIG. 2 but with the roll carrying a much wider web;

FIG. 6 is a view similar to that of FIG. 2 but with the roll carrying a much narrower web; and

FIG. 7 is a View of a portion of the structure of FIG. 2 particularly illustrating support mechanism for pivotal and oscillating movement of the blade holder.

While reference is made in the following detailed description to a single coating application to one side of a paper web in an operation on a papermaking machine, the principles of the invention are equally applicable to coating the second side of the web on the machine, to multiple superposed coating applications, and to similar coating applications on an oif-the-machine coater.

Referring to the drawings and initially in particular to FIG. 1, the numeral 1 designates a freshly formed paper web of a conventional printing paper furnish traveling as on a papermaking machine at papermaking speed over a guide roll 2 to a backing roll 3 and through a pressure nip 4 formed between the backing roll and an applicator roll 5. Coating composition from a pond 6 is applied to the applicator roll 5 by metering rolls 7, 8 rotating in the direction indicated by the arrows. Coating composition is directed to the pond 6 through an inlet 9 positioned above the pond and supplied by any suitable source (not shown). Backing roll 3 and coating applicator roll 5 are longitudinally coextensive and independently driven at substantially the same speed in opposite rotational directions as indicated by the arrows. Web 1 travels at substantially the speed of the backing roll. Backing roll 3 is resiliently covered, of about 30" diameter, and rotates at a speed of 600 f.p.m., for example, while applicator roll 5 is of a similar diameter and resiliently covered as indicated; applicator roll 5 may be of chrome plated steel, if desired. The backing roll and applicator roll in usual practice may have an axial length in the range of 30 to 250"-aa conventional length being about 144.

The coating composition is carried in film form on the applicator roll to the nip 4 where an excess of coating is applied to the traveling web in the nip. The pressure between the applicator roll and the backing roll controls the quantity of coating applied to the web, and the pressure is usually a light positive pressure of between about 2-20 pounds per lineal inch.

The traveling Web 1 is carried from the nip 4 on the resiliently covered backing roll 3 to a second nip 10 formed between the backing roll and a flexible blade 11. Blade 11 serves to trowel some of the coating composition on to the web and to remove excess designated at 12; this excess drains off over a coating composition deflector 15 to a receiver 13 positioned below the applicator roll 5 and may be recirculated. The web passes from the blade over a guide rol 14 in the direction indicated by the arrow to conventional dryers.

Flexible blade 11 is of spring steel of about Rockwell C hardness of 47-51 and quite thin, usually between about 0.012" and'0.024". This blade extends longitudinally of the backing roll (FIG. 2) and projects beyond the backing roll at each backing roll end for a distance of about 1. However, if desired, the blade may be from /2 to 1 narrower than the backing roll face and arranged to preclude development of lip overhang. The blade 11 is supported by a holder 16 from which it extends about to 1" in usual practice. This blade is pressured to the backing roll by any conventional mechanism, one form of which is illustrated in FIG. 2 and discussed hereinafter. Under pressure the blade flexes transversely, as indicated in FIG. 1, and also flexes longitudinally to conform to the web and backing roll configuration. The blade, prior to installation, is suitably honed to assist initial conformation of the blade with the roll; further, the resiliently covered roll is itself deformed slightly (FIG. 3) under blade pressure and the blade tip is quickly worn in by the traveling web-coating combination so that intimate contact is attained at nip 10. The web itself, tensioned around the backing roll and wetted by the coating composition, is elongated locally and stretched by the blade action.

Blade wear causes a decrease in the projection of the blade from the holder; such wear may conventionally be A on an original projection without blade change. This tends to lead to non-uniform coating since the wear occurs substantially only where the blade contacts the web.

The bipartite blade holder 16 (FIG. 2) is suitably retained as a unit by bolts 17 and is suitably retained as a unit by bolts 17 and is supported on a lower carrier member 18 by alternate threaded bolts 19. The carrier member (FIG. 2) carries on opposite sides pivot shafts 20 (one shown) which arereceived bearings 21 to" provide for pivotal movernen'tof the'holder toward and away from the backing roll while shaft enlargements 20a (one shown) restrain the carrier against longitudinal movement relative to thelbearing. Fluid pressure means designated generally at 22 and comprising air cylinders.

are secured on pivot joints 23 between platforms 24 and lever. arms 25 on opposite rearward sides of the carrier 4; out the coverbody. Thus the paper web is'carried on a grit-filled or'abradant surface in which a myriad of abrasive grit grains are surrounded and embedded in the rubmember 18 for urging the holder pivotally to the back-' ing roll 3 and the web 1- carried thereon. Platforms 24 are supported for rectilineal movement with end mounts 26 which are integral with a cross-member 27;" end. mounts 26 each have a sliding engagement with apair of short parallel rods 28 through the medium-of bushings 31. Each pair of rods 28 is fixedly retained by an upstanding support 29 of a base 30, and theparallel rods prevent rotation of the end'mounts 26 and bearings 21 which latter are retained positioned on the end mounts.

Control ofcylinder pressure'effects the control of'the.

pressure of the blade on the backingroll and web. Since the blade is flexible longitudinally and transversely,jthe

blade bears against the backing roll at the ends despite the paper thickness which usually isabout 0.003". To minimize wear of. the resilient 'coverby the bladeoni the roll end zones 32, 33, water sprays 35, 36 are provided adjacent eachend ofthe roll. Such sprays also serve to insure against coating composition buildup n the roll end zones and may be adjustable to provide for varying lengths of the end zones." Additionally, to extend the.

longitudinal wear zones of the blade in the vicinity of the junctures 37, 33 of the web and end zones 32, 33, the blade is oscillated longitudinally of" the roll; for this purpose the right hand end mount 26 (FIG. 2) receives coating operations.

bery or elastomeric compound, Preferably, the grit grains 'cover to of the surface of the backing roll. The grains are, however, discrete particles, resiliently'embed.

' simply from surface friction'etfects or fromother physical characteristics of the grit surface is not readily deter minable. In any event, the draws through thecoating device are improved. Y

The grit which provides the abradant surface may'vary in size, in proportions present,: andin specific'nature, that is, it may be aluminum oxide, silicon dioxide, silicon carbide, or the like. Since the specific nature of the blade, blade pressure, the nature of the web, machine speed, and the coating'composition affect the blade Wear rate, the grit size and proportions shouldbe selected ;to wear the blade in the extremities .46, 47 at the same rate as in the medial portion 48. The optimum conditions are readily determinable by simple test for any specific set ofconditio'ns.

oscillator rod 39 which, through pin 40,- is connectedto cam 41 and motor-gear box combination 4 2, 43. By

such blade oscillating means the blade is worn moregradually longitudinally by the Web'at the junctures 37, 38.

However, oifsets, such as designated at45 in FIG. '4 by V v the dashed line, develop and limit the utility of the blade for use with other web widths; also, blade wear from the original blade tip 44 at the blade extremities 46, 47 is much less thanvin the blademedial portion 43 '(FIG. 2). Accordingly, blade pressures tend to vary. along the blade length during operation. and. this'requires blade changeat frequency intervals. Further, when blade high spots develop in the end zones relative to the blade,

medial portion, the amount of composition applied tends to increase, resulting, as'already noted, in nonuniform coating application over the length of the web. 7

The specific blade pivotal and oscillating mechanism shown is illustrative only and forms no part of thepresent invention; other blade oscillating apparatus and blade pressure devices, of which-many are commonly employed, are useful in the practice of the invention. 7

In the practice of this invention, at least the roll end zones 32, 33, that is, the peripheral area of the rolls which are'not covered by the paper web, are roughened and are composed of a resilient rubbery compound which 'in-. This grit in the' cludes a portion of abrasive grit. roll surface serves to Wear the blade extremities 46, 47 to substantially the same extent as the combination of web and coating composition etfectwear in the blade medial portion 48. Such arrangement inhibitsagainst the development of the offsets in the blade designated at 45 (FIG; 4) and results in uniform blade wear indicated by the straight dashed line 4-9 in FIG. 4.

The use of blade oscillation with mechanism .such as 5 previously described tends to aid uniformity of blade wear;

the blade longitudinal movement'is very slow compared} Grits of aluminum oxide having a mesh of between about 100 to 400are generally useful and may be present ,to'the extent of from about 15% by weight; of the cover '50 to about 50%. The grit specific gravity is usually greater than and about twice the density of the rubber in which it is embedded. The larger size. grit, mesh (about 150 microns), provides-a coarse surface;.a smaller size grit, 325 mesh (about 43 microns), provides a'somewhat more uniform surface-overall forthe same weight or grit. A 325 mesh grit to the extent of about 15% by weight ofthe rubber cover 50 (Pusey and Jonesplastometer density of 67) has been found to be very satisfactory for minimizing Web wrinkles on the roll in advance of the blade in the specific apparatus arrangement de-- scribed. Under the conditions specifically described herein, about 25 to 30% by weight of aluminum oxide grit of amesh of about 220 appears to provide, optimum blade wear (about 0.003" per hour) and weblcontrol also 1 when cover 50 has a P and J .of about 67.

' in backing. rolls.

, be in the conventional rangeof, stock density forrubber covered rolls, that is, from about 30 to' upto 150 and usually lies in the range of 60 to The stock is compounded with the grit therein so that it is thoroughly dispersed andinterrnixedjthe stock is applied to the shell and tie plyand, after curing, is ground true to provide a peripheral surface of uniform'diameter with the grit randomly exposed. 7

Referring now to FIG. 5, since the blade is worn uniformly over its length in the course of a coating operation (FIGS. 1 and 2), the wider width web55 (FIG. 5) may be" substituted. and coated without blade change.

. Similarly, if desired, a narrower width web 56 may be employ'ed. More specifically, blade wear does not impose limitations on thesuccessioni of widths which'may be coated-without blade change. 7, V 7

It is to befnoted that even though the blade" extremities are worn by the action of the novel roll, it isistill desirable to utilizethewatersprays on the roll edges; such protects the roll against wear and cools the blade as well as pre-' 7 Most suitably, the backing roll 1 in the peripheral'resilient coverporti0u 50 includes gritj'SIL'distributed throughventing coating buildup on the roll end zones. 7 I

The coating compositions which may be employed are those customarily useful in the coating of paper webs and may include clays, fillers, binders, and the like. Typical of such a composition is the following:

Parts by weight Clay 70 Sodium hexametaphosphate 0.2 Calcium carbonate 30 Caustic 0.2 Starch 17 Calcium stearate 0.5 Water sufiicient to make 58% solids.

Viscosity, 3000 centipoises.

By way of specific example, the web to which such coating is applied may have a basis weight uncoated of about 55 pounds, basis weight being predicated upon 500 sheets 25"x38". The coat weight applied may be about 12 pounds per side depending somewhat upon the lineal pressure of the blade on the backing roll. Such pressure may be controlled to achieve particular results between about 1% to 9 pounds per inch.

It is to be noted that it is known in the coating field to extend the life of backing rolls by providing end sleeves which may replace worn roll ends. Such sleeves are rubber covered in the same manner as the main roll body. It is contemplated that such sleeves may incorporate grit in accordance with the practice of this invention.

The rate of wear of a conventional blade pressured against a web carrying coating compositions of the general type described is dependent upon a plurality of factors but has been found to be very generally about 0.003" per hour. thus develops in an hour of running an oifset or blade 10w spot equivalent to about paper web thickness. This wear, in the medial portion of the blade, is uniform over the medial portion and, if permitted to continue, results in poor roll life due to higher pressures exerted by the blade in the unworn blade extremities. By the practice of the present invention, roll life is itself extended due to uniform application of pressure throughout a coating operation and, in fact, throughout continued coating operations with the same blade.

The blade itself may also be honed over its length initially by running it against the roll prior to presentation of the web to the backing roll-thus eliminating time consuming honing operations preliminary to blade mounting.

Foreign particles do not tend to accumulate in the roll surface as the deforming action of the blade exerted on the resilient matrix in which the grit particles are embedded, followed by the restoring resilient action of the matrix, apparently tends to aid maintaining the roll surface clean.

With the grit distributed in uniform but substantially randomly oriented and haphazard arrangement through the resilient backing roll cover, any wear of the cover itself continuously exposes new abrasive granules to the blade since the pressure on the blade continuously urges the blade and roll into intimate engagement.

In the specific description set forth hereinbefore, the ap- Such a blade, usually of stainless or spring steel,

plicator roll 5 has been indicated to be in light positive pressured engagement with the backing roll; such is not necessary and the usual pan type applicator roll wherein a considerable excess of coating is provided to the applicator roll-backing roll nip may be employed. However, in such instances the nip may be zero pressure and may be open as much as 0.060". However, even where the positive pressure exists as in the instance of FIG. 1, the pulverulent nature of the grit particles does not adversely affect the applicator roll as long as the roll speeds are approximately the same.

It will be understood that this invention is susceptible to modification in order to adapt to different usages and conditions and, accordingly, it is desired to comprehend such modifications within the invention as may fall within the scope of the appended claims.

What is claimed is:

1. The combination in a coating device for a traveling paper Web or the like, of a longitudinally extending backing roll having a resilient deformable peripheral cover for supporting a traveling web Wrapped therearound, a longitudinally and transversely flexible doctor blade extending axially with said backing roll and defining with said backing roll a nip through which said web passes, means for urging said doctor blade against the backing roll and a web thereon to load the flexible doctor blade against the roll and web, means on the oncoming side of the nip for applying an excess of coating composition to the side of the web on which the doctor blade bears, said doctor blade extending substantially the full length of said backing roll and exerting a pressure against said backing roll and traveling web which locally deforms the web and the backing roll over the length of the backing roll, and said backing roll being characterized by a grit containing surface which wears said doctor blade in portions of the backing roll exposed to the doctor blade and which surface also provides traction for the traveling web.

2. The combination as claimed in claim 1 and in which water sprays are positioned to apply w-ater to the backing roll in the said portions of the backing roll which are exposed to the doctor blade.

References Cited by the Examiner UNITED STATES PATENTS 1,787,890 1/31 Woodward 29-132 2,062,317 12/36 Joseph 29-132 2,155,083 4/39 Drewsen. 2,280,208 4/42 Wilkie 29-132 2,297,128 9/42 Benson 226-193 2,534,320 12/50 Taylor 118-126 3,080,847 3/63 Justus 118-126 FOREIGN PATENTS 643,764 9/50 Great Britain.

RICHARD D. NEVIUS, Primary Examiner.

Claims (1)

1. THE COMBINATION IN A COATING DEVICE FOR A TRAVELING PAPER WEB OR THE LIKE, OF A LONGITUDINALLY EXTENDING BACKING ROLL HAVING A RESILIENT DEFORMABLE PERIPHERAL COVER FOR SUPPORTING A RESILIENT DEFORMABLE PERIPHERAL COVER LONGITUDINALLY AND TRANSVERSELY FLEXIBLE DOCTOR BLADE EXTENDING AXIALLY WITH SAID BACKING ROLL AND DEFINING WITH SAID BACKING ROLL A NIP THROUGH WHICH SAID WEB PASSES, MEANS FOR URGING SAID DOCTOR BLADE AGAINST THE BACKING ROLL AND A WEB THEREON TO LOAD THE FLEXIBLE DOCTOR BLADE AGAINST THE ROLL AND WEB, MEANS ON THE ONCOMING SIDE OF THE NIP FOR APPLYING AN EXCESS OF COATING COMPOSITION TO THE SIDE OF THE WEB ON WHICH THE DOCTOR BLADE BEARS, SAID DOCTOR BLADE EXTENDING SUBSTANTIALLY THE FULL LENGTH OF SAID BACKING ROLL AND EXERTING AS PRESSURE AGAINST SAID BACKING ROLL AND TRAVELING WEB WHICH LOCALLY DEFORMS THE WEB AND THE BACKING ROLL OVER THE LENGTH OF THE BACKING ROLL, AND SAID BACKING ROLL BEING CHARACTERIZED BY A GRIT CONTAINING SURFACE WHICH WEARS SAID DOCTOR BLADE IN PORTIONS OF THE BACKING ROLL EXPOSED TO THE DOCTOR BLADE AND WHICH SURFACE ALSO PROVIDES RACTION FOR THE TRAVELING WEB.

Images