US 3354867 A
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Nov. 28, 1967 A PQMPER ET AL 334,85?
MEANS TO VARY EFFECTIVE WIDTH OF PROJECTED COATING MATERIAL Filed July 12, 1965 2 Sheets-Sheet l IMHIHIHM MW vm !!L INVENTORS- a ANTHONY w. POMPER a Y ORLAND w. GR
ATTORNEY NOV. 28, 1967 w, PQMPER ET AL 3,354,867
MEANS TO VARY EFFECTIVE WIDTH OF PROJECTED COATING MATERIAL Filed July 12, 1965 2 Sheets-Sheet 2 ATTORNEY United States Patent 3,354,867 MEANS TO VARY EFFECTIVE WIDTH OF PROJECTED COATHJG MATERIAL Anthony W. Pomper, Metuchen, and Orland W. Grant,
East Brunswick, N.J., assignors to Midland-Ross Corporation, Cleveland, Ohio, a corporation of Ohio Filed July 12, 1965, Ser. No. 470,997 Claims. (Cl. 118-603) ABSTRACT OF THE DISCLOSURE A web passes against a backup roll which is spaced a coating thickness plus web thickness away from a counterrotating roll. A supply nozzle is mounted to supply coating material to the nip of the rolls. Coating flow directing means are mounted on the nozzle and divert predetermined portions of coating material issuing from the nozzle away from the nip. The directing means are laterally adjustably mounted so that the width of the coating supplied to the web in the nip is adjustable.
This invention relates to improvements in apparatus for the coating of paper webs and the like material and, more specifically, to an improved means for applying and distributing a coating to a moving web to provide for a more uniform and, simultaneously, an economic application of the coating mixture.
The generally known method of knife coating has been improved upon by one now known as flexible blade coating method where a flexible doctor blade is positioned in contact with a web at an angle with the edge in the direction of web travel. In such method a coating material is introduced onto the web prior to the blade which spreads it over the web surface. Broadly, the blade with margin determining sides and the web being coated form a reservoir as well as meter the coating material that is being applied.
This invention is an improvement to coating apparatus as referred to and known as a flexible blade coater. It concerns an improved coating applicator metering and applying a measured coating readily and evenly marginally to the web and whatever excess it in turn carries it to a flexible blade removal blade for salvage. This immediate premetering gives a uniformly finished product. By means of the present apparatus rather than impressing the coating material by a blade, a reversely rotating roll forces the coating into intimate contact with the web. Application of coating by a reverse rotating roll has been found to be increasingly advantageous and flexible and coats of various weights or thicknesses substantially al- 3,354,867 Patented Nov. 28, 1967 lowing specification taken with the accompanying drawings, wherein:
FIGURE 1 is a partial schematic representation, in section, of the coating apparatus, the coating introducing nozzle means as positioned relative the nip formed by the web backing roll and reverse rotating and metering applicator roll, as well as of blade removal of the coating and of the coating recirculating means;
FIGURE 2 is a schematic perspective showing the relative positions of the parts of the coating apparatus particularly the extrusion nozzle at the nip of the backing and metering applicator roll;
FIGURE 3 is an enlarged view in cross section of the coating applicator nozzle and of parts of adjacent apways free of foreign material such as loose fibers, sand, I
grit, etc. are applied. Doctor blades are used on the reverse roll applicator to keep the roll surface clean and to prevent the coating from being carried around and redeposited on the Web. The doctored coating is salvaged and continually refiltered and added to new coating material. Application of the coating material advantageously is under constant and uniform pressure over the full width of the paper web.
More specifically, the coating apparatus of this invention comprises a web backup roll and a reverse rotating coating metering roll with an extrusion nozzle having a width determining means introducing a uniform amount of a coating material on the web as it enters the nip formed by the rolls. The web carries the coating into the nip where it is firmly impressed onto its surface by the counter-rotating metering roll, and any surplus is carried away to be doctored into a drain from whence, refiltered, it is recirculated. These and other advantages of the present invention will now be described in detail in the folparatus; and
FIGURE 4 is a further partial sectional detail of FIG- URE 3 taken along line 4-4 showing the inner construction of the coating nozzle.
In accordance with this invention, a supply of paper Web material It), to be coated, is led between the backing roll 11 mounted for rotation about its shaft 12 and the oppositely rotating coating metering and applying roll 13 rotating about its shaft 14. The spacing or pressure between the two rolls 11, 13 is adjusted to provide for a firm and even application of the desired amount of a coating material to the surface of the traveling web 10. The coating material 15 can be pump supplied from any source, such as a trough or a well supply 30 positioned below the rolls, through an interconnecting conduit 31 to the applying nozzle means 18. The liquid type coating 15 is pump fed into the extrusion nozzle 18, through a hollow supporting shaft 54 (FIGURE 4). The coating is fed into an interior channel 20 of the nozzle 18 and therethrough through an internal liquid pressure equalizing area (to be hereinafter described) outwardly through the nozzle outlet 23 as a transverse sheet of equal transverse thickness onto the web 10 and, advantageously, at an excess quantity to form a slight pool in the nip created by rolls 11, 13.
The coating is doctored from and impressed on the web by the metallic surface of pressure roll 13 which rotates in a reverse direction to that of the web 10 and backing roll 11 carrying the paper web. Excess coating material 15 that is doctored or wiped off the web 10, and whatever surplus that adheres to the surface of the oppositely rotating applying roll 13, is continually and cleanly removed by a further doctor blade 41 that is positioned in contact with its surface. The applying roll 13 is thus kept free and clean of coating, always presenting a fresh surface for doctoring of the web. The removed coating 15 due to downward rotation is further assisted by gravity and is directed into a drain by the doctor 41 then to a collecting trough 30. After being passed through filter 32 and bucked up, it is recirculated by means of the pump 33 back into the extrusion nozzle 18.
In some cases it is desirable to allow and to apply an excess coating material 15 and to let it travel beyond the nip of the rolls 11, 13. In such event, the thickness desired can be doctored by a further flexible blade 40 placed in contact with the web 10 and roll 11. The blade 40 is desirably positioned and preset for finally determining the thickness that is to remain on the traveling web 10. The doctored excess coating material from blade 40 as that scraped off the metering roll 13 is also, advantageously by gravity, drained off and directed into the same collecting trough 30. As herein stated, all coating material 15 that is in the trough 30, before it is again used, is cleaned of foreign matter by being passed through a filter 32 that is positioned in the circulating line 31 with freshly added material, then is recirculated. The pump 33 feeds the circulatory system and the extrusion nozzle 18.
The application of coating material 15 to the traveling web 1% is shown in greater detail in FIGURE 2. As web passes about and in between the backing roll 11 and coating applying roll 13, a coating is applied. It 18 shown being pumped out from the applicator 18 nozzle 23 as an even transverse stream initially onto the web 10 as it about enters the nip formed by the two rolls 11, 13. A continuous desirable excess of coating is fed to the nlp by the nozzle and this excess forms a transverse pool the length of the nip. The reverse rotating applicator roll 13 continually and immediately carries off the excess coating material 15 to a doctor blade 41 for removal wh1le simultaneously wiping off or doctoring the roll 11 and Web 10 itself. Such excess coating that is carried away by the metering roll is completely removed by the flexible doctor blade 41 advantageously firmly positioned against the roll surface on the entry side of the nip, the removed coating flow being directed into the drain 31 that is positioned directly below.
A further coating weight determining flexible blade 40 can be placed on the opposite side of the nip of the rolls 11, 13 in pressing relation against the coated Web 10 while on the backup roll 11. The coating matter in this instance is not permitted to reach roll 13 but is drained off directly to the sump or well 30.
As shown, the width of the nozzle 18 application opening 23 is determined by laterally adjustable side elements 24, 25 secured to the nozzle body. The trough width determining elements 24, 25 are laterally adjustably secured to the top section 19 of the applicator 18 by means of bolts 26, 27. The coating width determining means 24, 25 are shown as being curved downwardly. This curving advantageously deflects and directs excess end issuing coating immediately onto the metering reverse roll 13 rather than into the trough-formed at the nip wherein only a desired coating width is fed. Thus controlled, a Constant flow of a desired coating width is maintained assuring a constant cross section of feed without hang-up or stagnation which could form streaks or decomposition where nozzles with deckle rods are used. Or, where with dam type coating feeds, edge leakage may and does occur to spread beyond a desired width. In the present system excess deflected coating is directed onto the reverse roll which immediately carries it away and from which it is immediately cleaned and carried off, thus preventing any reapplication of the coating and from spreading out beyond the width desired.
As shown in the sectional drawing in FIGURE 3, one form of the nozzle 18 comprises an initial enlarged receiving chamber 20 taking the sectional form of a tear drop or a fiat sided cone. The peak of the cone or its narrow, transverse outlet section is transversely serrated (FIG- URE 4) to provide a number of restrictive flow passages for the coating material into a further smaller pressure equalizing chamber 21. The described construction emits an even stream of coating material into about th nip formed by the backup rolls 11, 13. The extrusion nozzle 18 is desirably spaced from the surface of the web 10 on the roll 11. A constant transverse pool at the nip is rolled forward, the excess being taken away by the roll 13, and the coating Width is deter-mined by the end 24, adjusters. Excess coating material 15 and that deflected by the nozzle adjusters is prevented from following the web by the reverse rotation of the metering roll 13. The retained coating by the web 10 is firmly and evenly applied, and distributed thereover.
Advantageously, desirably, the slight pool of coating material 15 is maintained in the nip to insure sufiiciency and all excess thereover, as described, is carried away at once by the counter-rotating applicator roll 13 to the supply reservoir for reapplication. Additional coating matter that is permitted to pass through the nip is applied as an additional coat controlled as to amount or depth by an oppositely positioned flexible blade 40. The blade 40 can be an air knife or also be a flexible metallic blade.
The coating extrusion nozzle 18 is formed of essentially two sections, the main body 26 containing the initial receiving chamber 20 and the removable top cover 19. The chambers 20, 21 have their ends closed off by end plates 27 and attached to the nozzle 18 by bolts 28. The cover 19 in conjunction with the main body of the device complete and form the chambers 20, 21. If assurance of outlet pressure is found necessary, an intervening serrated back pressure creating path or outlet 22 can be inserted leading into a pressure equalization chamber 21 and therefrom into the outlet nozzle 23. The outlet 23 is controllable in width by the end downwardly curved coating directing members 24, 25. The top section 19 is pivotally connected to the lower or second section 26 by means of depending hinge knuckle members 17 at each side and l cked against any movement by pressure by a number of threaded bolts 16 as shown.
Further, the coating extrusion nozzle 18 is also desirably adjustable in position relative to the nip of rolls 11, 13. Mounting means creating such adjustability can be, of course, varied. One general form is that shown in the drawing where the applicator is secured to a rigid mounting 50 which itself is made laterally movable, being secured by bolts 52 placed in elongated slots 51. The body or base 50 supporting the coating applicating means 18 is itself mounted above a pivot 49. It can be made adjustable in a horizontal direction as well as swung about for examination and cleaning. The means for rotation of the body can be any desirable kind such as gearing or pneumatic.
The coating extrusion nozzle 18 itself (FIGURE 4), independently of its base 50, can be rotated about sealed side trunions 54 also used to conduct coating materials into their interior. Gearing 55, 56 will effect rotation of the shaft 54 and of the applicator 18 to which it is secured.
Where, as in the case of roll coaters, the coating is picked up by partial immersion of the applying roll, it is herein preferred to keep the applying roll dry and to pump the coating onto a web at about the nip formed by the backing and applying rolls. Foaming and other physical but disturbing phenomena is thus avoided. The c ating material enters the applicator 18 through its supporting hollow shafts 54 into interior channel 20 under pressure which, in turn, feeds the coating through a pressure adjusting channel 21, if needed, and then through the die outlet 23 onto the traveling web 10 as a solid stream. The air-free, cleaned, coating stream is directed to the nip between the backing roll and the metering roll. The reverse rotating metering roll 13 carries away the excess coating and is doctored of it cleanly so that it continually presents a smooth clean surface to the web to meter the coating without ridges or thin areas commonly produced by the splitting of the coating film when the coating roll surface is traveling in the same direction as the web or when the coating is aerated.
The apparatus herein described meters the coating to the nip, returning whatever excess to a collecting pool for reuse through circulating equipment. The counter rotation of the application roll provides for a clean, smooth and uniform metering of the material to the web being coated. The further blade on the other side of the nip advantageously returns whatever excess to the drain where, cleaned of foreign matter, it is reused thus making for an economic operation. The extrusion nozzle 18 advantageously is adjustable in both the horizontal application width and in vertical as well as horizontal direction permitting the best position for the application of the coating material. This adjustability permits a rapid clean out of the nozzle. An additional advantage of this arrangement is that of applying the coating material with some force onto the web at the nip maintaining a predetermined pool, this improves the coating adherence and insures a sufiiciency for coating at all times.
Problems of foaming also are eliminated, especially when polyvinyl chloride and similar type dispersions are used. A deae'rated coating can be pumped to the nozzle and onto a web with the excess directed and carried away by the reverse metering roll before any foaming can occur or come into contact with the web. A coater roll r0tating in a coating pan necessarily causes foaming and thus irreg-ular pick-up with resulting uneven application.
What is claimed is:
1. In a web coating apparatus, the combination comprising a backup roll for a traveling web to be coated; a counter-rotating metering roll disposed beneath said backup roll and in contact relationship with a coated portion of said web entrained about said backup roll; a coating material supply nozzle having a slotted outlet of fixed width which is substantially coextensive with the nip formed by said rolls; said nozzle disposed with respect to said nip whereby to project a sheet of coating material into said nip, and onto the portion of the traveling web thereat; a coating material supply reservoir disposed beneath said metering roll; coating material feed means communicating said reservoir with the nozzle; troughshaped means mounted on each transverse end of said nozzle and having sections thereof spaced from the nozzle outlet and disposed in the path of the sheet of coating material projected from the fixed slot outlet whereby to intercept portions of such projected sheet; said troughshaped means further disposed so that the intercepted portions of coating material are returned to the reservoir; said trough-shaped means being laterally adjustably mounted on said nozzle ends whereby to effect variation of the width of said sheet of coating material projected and delivered into said nip and onto the traveling web portion thereat.
2. The apparatus of claim 1 in which a coating removing blade is positioned in contact with the metering roll for keeping it free of said coating material.
3. The apparatus of claim 1 in which a coating removing blade is positioned in contact with the Web on the backup roll on the opposite side of the nip, and another blade in contact with the metering roll on the same side of the nip.
4. The apparatus of claim 1 wherein the troughshaped means is further so positioned with respect to the metering roll whereby the intercepted portions of coating material are directed onto said metering roll.
5. The apparatus of claim 1 wherein first blade means is disposed in contact With the metering roll to remove coating material therefrom; second blade means is disposed in contact with a coated portion of the Web past said nip whereby to further meter the coated web; each of said blade means being positioned with respect to the reservoir whereby material removed by said blades is returned to the reservoir; and said means communicating the reservoir with the nozzle includes a filter and a pump.
References Cited UNITED STATES PATENTS Re. 25,535 3/1964 Magn-uson 222-318 X 418,058 12/1889 Porter 118-413 1,246,092 11/1917 Hardie 239-513 X 1,390,367 9/1921 Massey 118-301 1,566,800 12/1925 MacAuthur 118-119 X 1,741,169 12/1929 Thompson 2139-510 X 1,778,994 10/1930 Allen 239-512 X 1,841,431 1/1932 Chapin 118-301 1,901,080 3/1933 Bradner 118-405 X 2,009,631 7/ 1935 Montgomery 118-414 2,035,677 3/1936 Steinke 118-301 X 2,208,126 7/ 1940 Fitchett 118-407 X 2,382,065 8/ 1945 Kappeler 118-301 2,512,542 6/1950 Goda 118-301 X 2,874,674 2/ 1959 Hornbostel 118-104 2,963,002 12/ 1960 Glaus 118-324 3,143,438 8/1964 Campbell 118-119 X 3,179,536 4/1965 Martinek 118-119 X 3,194,210 7/1965 Harris 118-104 FOREIGN PATENTS 908,653 10/ 1962 Great Britain.
MORRIS KAPLAN, Primary Examiner.