US2279553A - Method and apparatus for applying coatings to webs - Google Patents

Description

R. H. BRADT April 14, 1942.

METHOD AND APPARATUS FOR APPLYING COATI'NGS TO WEBS Filed July l, 1939 ..5 Sheets-Sheet l April 14, 1942. R, H BRADT 2,279,553

METHOD AND APPARATUS FOR APPLYING coATINGs To wES Filed July l, 1939 3 Sheets-Sheet 2 April M, 1942- RQH. BRADT 2,279,553

METHOD AN D APPARATUS FOR APPLYING COATINGS TO WEBS Filed July 1, 1939 3 Sheets-Sheet 3 TW/vena?.

i 'ritenga Aps .14, i 942 METHOD AND APPARATUS Fon APPLYING coaTiNGs To WEBS 'nexfora n. Braat,- Appieion, wie., Fox River Paper Corporation, Appleton,

a corporation of Wisconsin or to Wis., n

animation my i, 1939, serial No. '482,329

' 1.o (ci. sic-ss) My invention relates to an improved process and apparatus for the production of coated web material.

One purpose is the provision bf means ,fory

deaerating the web material prior to its coating and for thereby preparing it to receive and absorb the coating. y

Another purpose is the provision of means for coating the web.

Another purpose is the provision of means for controlling the thickness of the coating and for removing the excess coating material, preferably without scraping contact.

Another purpose is the, provision of means for preventing air at higher pressures from reaching the back of the deaerated Vcoated web until after such air has iirst acted topress the surface coating into the evacuated voids of the web, thus giving a 'lrmer coating bond or impregnation.

Another purpose is the provision of meansfor deaerating the web' or paper and for thereby rendering it susceptible to: a uniform stain.

Another purpose is the provision of an improved method and mechanism for continuously carrying out some or all of the above mentioned steps, in various orders, and for thereby producing, by continuous operation, a uniformly coated web having a ilrm coating bond or lmpregnation.

Another purpose is the provision of an improved means and method for doctoring a coated web, and, in particular, for doctoring it by the employment of a tangential or lateral ow of air through an oriilce formed by the web itself and by a lip member or members spaced from the coated face or faces of the web.

Other purposes will appear from time to time in the course of the specification and claims.

I illustrate my invention more or less diagrammatically in the accompanying drawings wherein: 'V

Fig. 1 is a longitudinal section through my dev1ce;

Fig. 2 is a longitudinal section through 4alvariant form; i

Fig. 3 is a longitudinal view of a further yariant form of the device showing the housingl m section; and

Fig. 4 is a vertical transverse section 'of avariant form of my invention.

Like parts are indicated." by like symbolsv throughout the specincaticn and drawings..

Referring to the drawings, and fo'r'example to ing wall members 2, 3, l, 5 and 8. It will be realized that the 'speciiic details and form of the housing and walls may be varied without departing from the spirit of my invention.

Mounted in any suitable fashion, for example upon any suitable shaft or support l. I illustrate a supporting roll 8. 8 indicates a ily roll mounted, for example, on a shaft I0, over which the web H passes toward the supporting roll 8. i2 is a tensioning or controlroll mounted, for example, on a shaft i3, which may. be adjusted-in any suitable manner along the slot M in the side walls of the housing or base l. It will be understood that it mayI be adjusted to vary the bearing or arc of contact of the web i'l upon the supporting roll u.

it is any suitable vacuum seal roll mounted, for example, on a shaft IB and yieldingly thrust against the supporting roll 8 and the web passing thereovr. It serves as a seal. for preventing any substantial penetration of air into the space vbelow it and between the'wall member 2 and the opposed face or arc of the supporting roll 8.

Fig. l, I is any suitable'exterlor housing or base,

which includes or Supports tr ansversely extend'- As indicating means for maintaining a sealing contact, I illustrate a hingedV member il, pivcted as at It to the upper edge of the wall portion 2 and urged as by the coilspring I9. The above described specific means is given as illustrated,

and it will be realized that a variety of means` for maintaining a sealing contact between the wall 2 and the web H maybe employed.

2t illustrates anyv suitable suction outlet t0 any suitable pump or evacuating means not herein shown and the details oi which do not of themselves form part of the present invention. I1; will be understood, however, thatA I may employ any suitable means for maintaining a partial vacuum within the space indicated as A. The more or less porous web, as it passes about the supporting roller 8 and beyond the sealing roller I5, is thereby subjected to a vacuum, and the entrapped air is substantially exhausted from the voids and spaces within the web.

The wall portion e is shown as forming a species of pocket in which a volume of any suitable coating material is maintained. The coating roll 2,2, mounted in any suitable shaft 23, extends at its upper arc to close proximity to the web Il as it passes about the supporting roller t. The lower part of the roller 22 is immersed in the coating iluid 2l. As it'rotates in the direction of the arrow of Fig. 1, it carries an excess of the coating material 2| and applies it to the outer surface of the web Il. As the i y l 2,279,553 A receive and absorb thecoating. This excess coating adhering to the web is indicated as at 24.

.-As the web passes with the supporting roller trated as including a relatively flat blade 28 anda member 29 generally vertical thereto and genv 2,279,553 through which it passes', lit is in condition to shown. 44 indicates a return member for r'eturning excess coating to the container 38 below the coating roll 31.

Fig. 3 illustrates a variantrform of my device,

' in which a closed housing 50 is divided by bailes or walls l and 52 into three separately exerally tangential to the surface of the supporting roll 8, but slightly spaced therefrom. This spacl ing may be controlled-by' any suitable adjusting means, which may include, for example, the bolt and the nut 3l, thebolt passing through a slot 32 in the member 28. Outside air enters between the member 29 and the opposed surface of the web ll, and passes laterally or tangentially across the coating. The parts are preferably so spaced that there is no direct wiping or scraping contact, but the: current of air flowing across the coated surface of the web Il and downwardly into the chamber orspace indicated at B in Fig. 1 is effective to doctor or level ythe excess coating material on the web Il. A baille 42 may be used to -receive the excess coating.

The web, with'this excess material removed,

hausted chambers, indicated as`C, D and E. The

web Il enters the compartment C through'an aperture 53, its path being controlled by idlers or rollers 54 and 55, one being outside of and the other inside of the housing 50. Any suitable adjusting sealing means 56 may be employed to cut the entry of air down to a necessary minimum. The web then passes beneath a carrier roll 51, over a coating roll '58, and beneath another carrier roll 59 located in any suitable aperture in the baille 5l. 60 indicates any suitable adjustable-doctor, which may be raised or lowered to vary the distance b etween it' and the opposed arc of the roller 59. I'illustrate for exv ample adjusting bolt 6|.

and with the coating in place on its exterior sury face, is still,pressed against the outer surface of thesupporting roll 8, and the outside air cannot reach the rear of the web until after the web has travelled through a predetermined and adjustable arc of movement. The exterior air pressure has a compacting effect. Finally the web passes baille 52.

vadjustable 4doctor 66. Thereafter the web passes 62 indicates any suitable container for the coating, which partially surroundshthe roller 58. From the carrier roll 59, the web Il passes over the second coating roll 63, having its` associated coating container 64, and thence beneath the carrier roll 65 located in an aperture in the This aperture is provided with an over the final coating roll 61 and thereby receives a coating of the material from the container 68. It then passes beneath a carrier roll 69 and thence to the supporting or stripping roll 10, which is located in an aperture in the top of the housing 50. Y Y

1I is anysuitable adjustable seal with its adjusting securing means 12.' 13 is an adjustable doctor, with its adjusting securing means 14. 15,

over the adjustable roller l2 and, in the direction n of the top arrow of Fig. l, outwardly away from the mechanism or zone of treatment.

It will be understood that any suitable means may be employed for movingthe web and for rotating the various rollers. I may, for example, employ means for driving the rollers 8 and 22 in unison. The rollers 9 and I2 may, if desired, be idlers.

Referring to the form of Fig..2, I illustrate a Y modification-f my device in which the web Il,

instead of being coated as it passes over or about the supporting roller 8, receives a coating applied from a plurality of separate coating rollers. After the web passes the sealing roller I5, it

1B and 11 indicate vacuum lines or exhaust passages whereby air may be exhausted individually from the compartments C, D, and E of the housing 50.

It will be understood that any suitable pumps or exhaust means may be associated with these various passages,. the details of which do not form part of the present invention. It will be passes about idlers 30, 3| and 32, within a laterl ally extended closed housing 33. I provide there- .in plurality of coating rolls 34, 35, 36 and 31,

each penetrating an associated container 38, having therein a body 39 of coating material. Intermediate idlers or rollers 40 are employed to maintain the web Il in contact with the upper surfaces of the rolls 34 to 31. Any suitable means are employed to drive said four rolls in a counter-.clockwise direction, whereby the coating Ais supplied to the lower surface of the web.

After the four coating increment has been received by the web, it passes under the final idler 4I, and thence about a supporting roller 8. Any suitable means, for example the baille 42, may be employed for receiving excess coating blown oiI by the air passing about the member 29. The entire interior ofY the housing 33 may be exhausted through the outlet 43 by means of any Vsuitable pump or exhausting means not herein understood that the degrees of vacuum in the,

chambers C, D and E may be regulated in different amounts, \or, if desired, the adjustable doctors and 56 may be dropped, and the pressurefmay be made uniform throughout. Under some circumstances it may be desirable to heat the coating rolls 58, 63 and 61 and the supporting or stripping roll 10.

The air which passes inwardly past the adjustable doctor 13 is effective to strip the excess coating from the web, as described in connection with the form of Fig. l. If additional stripping action is desired for the individual coating 'rolls or individual coatings deliveredby the coating rolls, I may adjust the doctors 60 and 66 to close proximity to the opposed surface of the web,

and then provide a vacuum drop from chamber matter depends upon whether or not Va multiplicity of coats or coatings is desired.

Referring to the form of Fig. 4, I illustrate a further application of my invention, in which a, large roll is employed, for which preferably any suitable heating means, not herein shown in detail, may be provided. The web indicated at passes over a guiding roll |0| and thence about the periphery of the roll |00 to an adjustable roll |02, which' may be moved along any suitable adjusting slot |03 in order to control the degree of arc through-which the web contacts the surface of the roll |00; This is effective to vary or control the arc of contact of the web with the roll |00, after it passes through the doctoring orifice below described.

|04 generally indicates a` housing structure, which may be mounted for ready movement toward and away from the surface of the roll |00. I may, for example, mount the entire structure on slides |05, which are diagrammatically indicated in Fig. 4. The general housing struc-- follows:

I illustrate a method and anapparatus for the production of coated web material by continuous operation, in which the web -is passed into a vacuum chamber, deaerated, suitably coated with an excess of coated material, and thereafter conducted from the vacuumvchamber throughk an adjustable orifice or vacuum lip or passage, which is effective to suck or draw the excess coating material uniformly from the surface of the web andback into the chamber. At the same time the coating is leveled without being scraped. l

Jing a 'firmer coating bond or impregnation.

within the housing |04. The housing. |04 has an may be adjusted toward and away from the opposed face of the web thus dening or controlling the width of the aperture. The edgell I5 may, if desired, be provided with a terminal member H6, generally tangential to the roll.A

Within the housing 2 are any suitable baiiles which are effective to trap and return any liquid which may be drawn inwardly by the air flowing through the gap between the web` and the opposed member ||6.

The ready applicability and removability of the housing structure above described is advantageous as permitting very easy threading of the paper through the roll and easy cleaning of the apparatus as a whole. It will be understood that the details of the supporting, guiding means may be widely varied.

It will be realized that whereas I have described and` illustrated a practical and operative device, nevertheless many changes may be made in the size, shape, number and disposition of parts without departing from the spirit of my invention. I therefore wish my description and drawings to be taken as in a broad sense illustrative or diagrammatic, rather than as limiting me to my precise showing.

It will be realized particularly that, although I have illustrated various forms of my device, including means for deaerating the web and for subsequently doctoring it by a iiow of air, the deaerating step may be omitted and the doctoring may be done without the preliminary deaeration.

'It will also be understood that where in my description or claims I use the term vacuum." I wish it to be understood that a partial vacuum is employed, and I wish the term "vacuum to be interpreted to indicate a partial vacuum.

Deaeration may also `be employed-in connection with my process and apparatus for preparing the web or paper to take a uniform stain.

In web coating there are three fundamental y operations, as follows:

(1) Application of the coating;

(3) The leveling of the coating.

tained in each such vstep are superior to those obtained by any previous mechanism or method intimacy of the union of the finished coating V and web. It is-advantageous, in web coating, to apply an excess of coating material and subsequently to remove the excess. By my process and apparatusI obtain the evacuation and deaeration of the web prior to the application of the excess of coating material. This deaeration or evacuation results in a more uniform wetting of the web by the coating composition. The evacuation of the web prior to the applicationof the coating material also results' in a superior anchorage' of the coating material to the web. Deaeration of the web prior to coating also permits a higher speed of wetting or coating, and thus a higher speed of operation of the machine and a greater output per unit of time.

My method and apparatus, broadly stated, cover means for causing a doctoring action by providing a ow of air across the treated surface through an aperture one side of whichis defined by the paper or fabric treated and the other side of which is defined by a lip, wall or the like. It will ibe understood, of course, that any suitable means may be employed for coating the web with a coating mixture `of. any desired composition, for example, clay' compounds, enamels, lacquers or photosensitive mixtures. I prefer to provide an enclosure or housing the purpose of which is to maintain a pressure of air which is different from the atmospheric pressure. I prefer a partial vacuum, but it will be understood, of course, that any pressure differential may be employed. In any event, air is caused to flow through an orifice or slot, or a plurality of orifices or slots, preferably adjustable in any suitable enclosure or housing or container, throughv which the sheet passes. The air may be caused to ow through one or more ori- The use and operation of my invention' areas I By my process and apparatus the results obkiices or slots simultaneously with the sheet and level the remaining coating. This is, of course, Y

is deaerated, and no air is left init to form hubbles and consequent pin holes.

tacting doctoring action, with the consequent formation of bubbles or foam. SincevI obtain my doctoring by a direct ow of air through the web lip, there is no formation of bubbles and a differentiation from any possible method or apparatus in which a ow of air is directed through a slot which is deiined on both 'sides by walls, solid members, or the like.

My method and apparatus will permit the unlform doctoring of plastic coatings having a high solids content. The controlled ilow of air between the adjustable lip 29 or 13 and the web strikes the web substantially tangentially. The air has the greatest stripping action on the coating material when it passes tangentially across the coating. Consequently a higher solids content coating may be handled with my vacuum lip technique than with any directed jet or air blast. 'I'he inherent tangential iiow of air along or across the web, combined with'thehigh velocity speeds and lower drying costs.

In my mechanism the moving parts are -re-` duced to a minimum. The only moving parts are rolls which. carry the-webs or excess amounts of l coating material. I avoid the employment of any contacting bars or blades, or any other elements which actually contact the coating material and which could be fouled by deposits of coating material. The inilowing air, not a contacting mechanical member, effects the doctoring, and I provide means, such as the baille 42 of Fig. 2 and the members 80 and 8| of Fig. 3, for returning the excess coating to the coating containers.

foam, and this further cause of pin holes is thereby eliminated.

With my apparatus and method the operator is able to control the penetration 'of the coating in the web to a considerable extent. Controlled absorption and penetration is obtained by causing the deaerated coated web to cling to the roll 8 or 10, after the web Il emerges from the vacuum chamber. The exterior air pressure is higher than in the vacuum chamber but is able merely to press against the coated or outer side of the web H and is thus effective Ato force the coating material into the pores of the web I I.

An important feature of my invention and of my mechanism, which may be employed independently of the deaerating step .or means, isthe employment of the characteristic doctoring lip This also reduces'the necessity of cleaning the apparatus, is* obtained simultaneously with the removal of the excess coating by' the action of the vacuum lip. This leveling action is particularlyeilcient because the web iteslf, as it passes over the supporting or stripping roll 8 or 10, forms one side of the aperture through which the inilowing air passes. y The high velocity and turbulence free flow of air gives my coatings freedom from the wavy or windbiow eirect which would be obtained were a thick film applied or controlled by a directed jet of compressed air.

With my process the forming oi' pin holes is reduced to a Such pin holes may be formed from air displaced from the voids in the web, which air forms bubbles which may not vthe roll structure.

structure and the use of a rapid lateral or `tangential iiow of air to obtain the doctoring elect. d

or provides one side of the orice, in contrast to less ellicient structures in which a separate and independently defined oriiice having no connection with the `web might be employed, and the fact that the air follows a tangential path across the face of the coating gives it a particularly ef-V flcient doctoring eiect.

Inreferring to the form of Fig. 4, the web Il may be very easilyvand quickly threaded through The web is not supported on or positioned by the housing structure |04, H2. This housing structure may be readily moved toward and away from the roll |00. It is selfcontained and supports the coating roll H0 and the coating' material. It also serves to dene the aperture, by means of. the member H6, through which the air flows into the spaces within the housing |04, H2, and doctors the coating on the web.

It will be understood, as to all forms of the device herein shown, that the rate of iiow of air across the doctored surface can be controlled,

not merely by varying the relative pressure conl ditions within and without the housing, but by burst until after the coating film has set sumciently tojpreven't it from flowing andcovering holes thus formed. With my process, the web varying the air gap between the members 29, for

First, the degree of suction within the hous-A ing; Second. the size of the doctoring gap, one of which carries the web and the other of which acts Y to control the slot through which the air passes;

Third, the amount of the coating applied to the sheet; and

Fourth, the speed of the web through the machine.

Another possible cause of pm holes is by actual brushing or con-V l claim:

which includes deaerating the Web, thereafter applying an excess of a coating material to said deaerated web, and thereafter removing the excess portion of the material by causing a ow of air across the coated surface of said web.

2. The method of coating a web of material which includes deaerating the web, thereafter applying an excess of a coating material to said deaerated web, thereafter removing the excess portion o the material by causing a ilow of air across the coated surface of said web, and consolidating the coating by subjecting the coated surface of the web to air pressure.

3. The method ofV coating a web of material which includes passing a web continuously through a partial vacuum and thereby deaerating it, applying an excess of coating material to said deaerated web, while maintaining it in said vacuum, thereafter removing the excess material by the passage of air across the coated surface of said web, and thereafter subjecting' the coated surface to air pressure-and thereby consolidat- Lag it.

d. The method or coating a web of material which includes deaerating the web, thereafter applying in succession a plurality of excess coats of coating material to said deaerated web, and removing the excess portion of each coat by causing a new ci air across the coated surface of the web,

the web through said housing, means for applying a succession of coatings to said web as it passes through said housing.. and means for thereafter directing a flow of air across a coated surface of the weband for thereby removing the excess coating.

'7. The method of coating a web of material which includes conveying such web through a partial vacuum, vcoating said web after it has entered and been subjected to such vacuum with an excess of liquid coating material, and causing air to iiow directly and tangentially across the coated surface of said web in the direction of the entered. and been subjected to such vacuum with 5. 'In a machine for coating webs of paper or stantial inow of air to said housing, means located within said housing for delivering an excess of a coating material in fluid form to a surface of said web, and means for causing a now oi air across the coated surface of said web as it passes from the housing, and for thereby removing the excess portion of the coating, said means including an aperture dening member spaced from the coated face of the web, the coated face of the web itself providing another side of the aperture through which the air passes, said sealing means being located above the level of said uid.

6. In a machine for coating webs of paper or the like, a housing, means for maintaining a partial vacuum in said housing, means for guiding an excess of liquid coating material, and causing air to flow directly and tangentially across the coated surface of said web in the direction of the vacuum as the web escapes from the vacuum through an aperture one side of which is defined by the coated surface of the web.'

9. In a machine for coating webs of paper or the like, a housing, a horizontally axised roller extending into said housing, means for maintaining a partial vacuum within the rspace defined by said housing and roller, means for guiding a web for lpassage about said roller, a liquid transporting means located within said housing' and entirely within said Vacuum, means for maintaining a body of liquid in said housing out of contact with said roller but in contact with said transporting means, and means for doctoring said coating as the web passes out of the housing.

10. In a machine for coating Webs of Paper or vthe like, a housing, a horizontally axised roller extending into said housing, means for maintaining a partial vacuum within the space dened by 4said housing and roller, means for guiding a web for passage about said roller, a liquid transporting means located within said housing and entirely within ,said vacuum, means for maintaining a body of liquid in said housing out of contact with said roller but in contact with said transporting means, and means for doctoring said coating as the web passes out of the housing, said means including a horizontally axised feed roller, the lower portion of which is immersed in said body of liquid, an upper portion of which is opposed to the web passing about said first mentioned roller.

REXFORD H. BRADT.

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