US2025375A - Method of coating webs - Google Patents

Description

J. A. CAMERON ET! AL 2,025,375

METHOD OF COATING WEBS Filed July 13, 1955 Dec. 24, 1935.

5 Sheets-Sheet l INVENTORS ATTORNEY.

'J. A. CAMERON El AL METHop 0F COATING WEBS 5 Sheets-Sheet 2 Filed July 13. 1933 UL UUUUUULIUU INVENTORS A TTORNE Y.

Dec. 24,1935. J. 'A. CAMERON ET AL METHOD OF COATING WEBS 5 Sheets-Sheet 5 INVENTORS ATTORNEY.

Filed July 13, 1935 I Dec. 24, 1935. CAMERQN r 2,025,375

METHOD OF COATING WEBS 5 Sheets-Sheet 4 Filed July 15, 1933 INVENTORS ATTORNEY.-

1935- J. A. CAMERON El AL ,0

METHOD OF COATING WEBS Filed July 15, 1935 s Sheets-Sheet 5 INVENTORS Z Ww.

A TTORNEYL Patented Dec. 24, 1935 UNITED STATES PATENT OFFICE METHOD OF COATING WEBS Application July 13, 1933, Serial No. 680,242 2 Claims. (01. 91-68) Fig. 2 is a view in top elevation of the elements shown in Fig. 1, with parts broken away;

Fig. 3 is a view, on an enlarged scale of parts of the rolls constituting the coating couple;

Fig. 4 is a diagrammatic view of the nip of the rolls constituting the couple, and of the puddle of coating material:

Fig. 5 is a view in side elevation of a coating, drying and winding machine in which the coating couple of Fig. 1 is utilized;

Fig. 6 is a view in side elevation of a two-ply combining machine embodying the invention;

Fig. 7 is a, view in side elevation of a threeply combining machine embodying the invention; and

Fig. 8 is a view in side elevation of a machine showing a modified form of the invention, which machine can be used either for coating a web or for combining two Webs.

A indicates a coating couple composed of two rolls I and H arranged one above the other. Coating material is supplied to lower roll it in any suitable manner as by immersing the lower portion of said roll in a fountain, the rotation of said roll carrying the coating material to the nip of the two'rolls. The extent to which the lower roll is immersed in the fountain (not shown), the speed of rotation of the roll and the consistency of the coating material will determine the thickness of the film of coating material carried to the nip of the rolls, and these factors should be so coordinated that a puddle I4 of coating material is maintained at the ingoing side of the couple. To facilitate the maintaining of said puddle, rolls l0 and II preferably have their vertical center lines out of alinement, or, to put it differently, one roll is preferably set back with respect to the other so as to afford an exposed portion IS on the upper surface of the lower roll at said ingoing side of the couple. Care should be taken, however, especially when dealing with a volatile coating material, that an ex cessively large puddle is not created because in such case it will be diflicult, if not impossible to maintain the desired characteristics and/or consistency of the coating material as the amount of evaporation would be excessive and the coating material would become non-uniform in character. Therefore to properly control the character of the coating material, the fountain, if used, should be covered except at the point where the lower roll dips into it. Inasmuch as, under certain conditions, the volume of coating material to becarried up by the roll would require 10 a considerable opening in the fountain to permit said roll to be immersed the required distance, the factor of evaporation and the volume of coating material to be supplied to the nip might conflict, and it has therefore been found simpler to arrange a sort of a trough, indicated diagrammatically at it in Fig. 3 and to arrange a supply pipe or a series of nozzles l'l leading from an otherwise closed container to thereby supply the proper amount of coating material to the surface of the lower roll. By this means, the distance which the coating material has to travel is decreased, and the volume supplied and char-' acter of said coating material can be more easily controlled. In addition to the factors above mentioned, the size of the opening at the nip of the rolls also has an influence upon the puddle, because the closer these rolls are together the greater the backward pressure, other factors being equal, with respect to the material of said puddle. It is preferred not to use scrapers or doctor blades on the coated web, because to do so is apt to produce streaks and this is disadvantageous for the reason that a non-uniform coating will result, and not only is this a dis- 85 advantage in itself but, if the coated web is to be united to another web, imperfect adhesion of the two webs will occur, and if one of the webs is of transparent material such as cellophane, the streaks will be perceptible tothe eye and thereby render the combined product less desirable, sometimes so muchso that the customer will not use it. It is therefore preferred that rolls l0 and H be calendering rolls that will act not only to coat but also to calender the web. In Fig. 4 we have attempted to indicate what we believe takes place in the puddle at the nip of the rolls. From that figure it will be seen that film l8 of coating material, carried up by the lower roll, tends to move toward the nip but that the pressure exerted by the rolls at the nip causes a backflow which tends to create the puddle, part of said puddle being again turned toward the nip by the upper as well as by the lower roll. Inasmuch as the upper roll is set gages an internal gear 28 at said near side.

the near side.

back of the vertical center line of the lower roll it will be seen that gravity also plays a part in causing the coating material to flow toward the nip. Thegp u ddle therefore extends from the nip to a point substantially in advance of the nip. l9 indicates the web of flexible material which is guided into close contact with the dry surface of the upper roll at a point well in advance of the puddle and which, after it has passed through the nip, is retained in close contact with the surface of the upper roll, at the outgoing side of the couple, for a distance beyond the point where the film of coating material, common to the two rolls at the point of nip, breaks. In this way it is unnecessary to provide dams to confine the coating material as is usually done to prevent said coating material from working over the dry side of the web and over the surface of the upper roll that contacts with the dry side of the web. In connection with this it should be explained that there is, of course, a film of coating material between the upper and lower rolls at the point of nip and that this film is carried outward a certain distance, at the outgoing side of the couple, before it breaks, and that when it snaps it causes a series of miniature explosions which sends particles of coating material in all directions, and some of which would work behind the web if the latter leaves the rolls say at a tangent to the nip. So likewise by bringing the web into close contact with the upper roll, at the ingoing side of the couple, at a point well in advance of the puddle, the bubbling and boiling of the material of said puddle will not throw particles of coating material on the dry surface of the drum or on the uncoated side of the web. The absence of dams renders it very easy to change from one web-width to another, as no adjustment is necessary.

Rolls l and II are preferably driven at the same surface speed as the web. Roll H is here shown mounted in stationary bearings 20, and roll in is mounted in slidable boxes 2|, one at each end. Said boxes carry upwardly extending non-rotatable screws 22 that engage rotatable but non-slidable nuts 29, each of which nuts is provided with a gear 24. Extending transversely of the machine is a shaft 25 carrying a pinion. 25, at the far side of the machine, which engages gear 24 at that side, and carrying also a slidably mounted gear 21, at the near side, which en- Internal gear 28 is carried by a sleeve 29 loosely surrounding shaft 25, and said sleeve further carries a pinion 38 that meshes with gear 24 at Mounted on shaft 25, at the near side, is a handwheel 3|. It will now be understood that, when gears 21 and 28 arein mesh, shaft 25 and sleeve 29 are connected, and therefore rotation of handwheel 3| will actuate both pinions 26 and 30, which will cause both gears 24 to be rotated in unison and that rotation of gears 24 will raise or lower both ends of roll l9 equally. If for any reason it is desired to raise or lower one end of said roll independently of the other, then slidable gear 21 can be moved out of mesh with gear 28 thereby disconnecting shaft 25 and, sleeve 29. If this is done, then rotation of handwheel 3| will raise or lower the far end of roll l0 independently of the near end of said roll, and if it is desired to raise or lower the near end of roll it) independently oi its far end, then gear 28 can be rotated independently by hand thereby-actuating sleeve 29 but not shaft 25.

In Fig. the invention is shown embodied in a coating machine. As there shown, the web to be coated comes from source of supply 32 and 5' after passing over suitableguides as 33 is led between feed rollers 94 either or both of which may be driven. The web then passes between the rollers of coating unit A, in the manner previously described, and over guides 35 to drier 86'. It will be seen that in so doing, the coated side of the web is out. The web is now reversed over guide 31 and passes over guides 88, 39 and 40 to winder'4l, here of the two-drum type, where it is wound with the coated and dried side in and with the uncoated side out.

Fig. 6 shows a two-ply combining machine in which the web passes from source of supply 42 over suitable guide rollers 43 to coating couple A and thence to combining drum 44. Another web which may or may not be coated is led from source of supply 45 over suitable guide rolls 46 and thence to pressure roll 41 coacting with combining drum 44. The .two webs are thus united under pressure between 44 and 41, and the combined webs are then led still further over combining drum 44' and may, if desired, be subjected to additional pressure by a second pressure roll 48. After this, the combined webs are led over suitable guide rolls 49 to winder 50. The combining drum is driven preferably at 'web speed, and pressure rolls 41 and 48 may or may not be driven. The rolls of the coating couple and the combining drum may or may not be heated or may be chilled in a manner well understood, 'de- 86 pending upon the character of the coating material used. Some of the guide rolls may also be heated or chilled as may be desired.

In Fig. 7 is shown a three-ply combining machine. Here a web is led from source of supply 5| pover suitable guide rolls 52 to coating couple A and thence to combining drum 59. A second web is led from source 54 over suitable guide rolls 55 to pressure roll 58 and combining drum 59 where the two webs are combined. A third 4 web is led from source 51 over suitable guide rolls 59 to coating couple Al and thence to combining drum 59. The previously combined webs are led from combining drum Glover roller 89 and thence to pressure roll 5i and combining drum 59 where they meet the web from coating couple Al and are combined into a three-ply product which then continues over combining drum 59 and, if desired, passes under another pressure roll 62. The three-ply product now passes over guide rolls 53 to winder 94.

In Fig. 8 is shown the same machine as in Fig. '1, except that a diflerent winder, viz: a onedrum type winder is disclosed. The webs may here be led exactly as described in Fig. '1 and a no three-ply product be obtained. If it is desired, however, merely to coat a webinstead of combining it with other webs, then the web may be led as follows, as shown in dash-and-dot lines: from source of supply 5| the web passes over two guide rollers 52, but instead of passing thence to the third guide roller 52 and to coating couple A, the web is led over a different guide roller 66, around pressure roller 56 and thence between pressure roller 55 and combining drum 59 which now act merely as feed rolls. The web is then led to coating couple A-and thence to idler rollers 55 and 60 and so to a drier or other instrumentality for further manipulation. Thus it will be seen that none of the driven rolls'have to have their direction of rotation reversed.

Throughout the specification and claims, the expression coating material" has been used and it will be evident from the foregoing that this expression is used in a very broad sense and is intended to cover any material whether adhesive or not.

We claim:

l. The method of coating one surface of a web of flexible material which consists in: guiding the web into contact with the dry surface of one roll of a coating couple at a point. on the ingoing side of the rolls, well in advance of the point of nip of said rolls; supplying coating material to the entire width of the surface of the other roll of said couple at a point-relatively remote from said nip; maintaining at said nip on the ingoing side of the couple, by rotation of said rolls at substantially equal speed in the same direction as the movement of the web. an unconfined puddle of coating material of controlled volume to thereby keep the character of the coating material substantially uniform and to app said coating material to the exposed surface of the iirst-mene tioned roll as well as to the flexible web; passing said web through the nip of said couple; and retaining said web, in contact with the dry surface of the first-mentioned roll at the outgoing side of said couple for a distance beyond the point where the film of coating material, common to the two rolls at their point of nip, breaks.

2. The method of coating one surface of a web of flexible material which consists in: guiding the 6 web into contact with the dry surface of one roll of a coating couple at a point, on the ingoing side of the rolls, well in advance of the point of nip .of said rolls; supplying coating material to the entire width of the surface of the other roll of 10 said couple at a point relatively remote from said contact with the dry surface of the first-mentioned roll at the outgoing side of said couple for a distance beyond the point where the film ll of coating material common to the two rolls at l their point of nip, breaks.

JAMES A. CAMERON.

ROBERT M00. JOHNS'IONE.

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