US3499786A

US3499786A - Method and apparatus for coating films

Info

Publication number: US3499786A
Application number: US616927A
Authority: US
Inventors: Horace P Fry Jr
Original assignee: FMC Corp
Current assignee: FMC Corp
Priority date: 1967-02-17
Filing date: 1967-02-17
Publication date: 1970-03-10
Anticipated expiration: 1987-03-10

Description

March 10, 1970 H. P. FRY, JR

METHOD AND APPARATUS FOR COATING FILMS Filed Feb. 17, 1967 United States Patent US. Cl. 117-111 8 Claims ABSTRACT OF THE DISCLOSURE A method and apparatus is disclosed in which a layer of coating material of controlled thickness is applied to a film having longitudinal elements of different length by a transfer roller which is contoured to cause the film to contact therewith generally evenly across its entire width.

The present invention relates to an improved method and apparatus for coating continuous films.

During the manufacture of regenerated cellulose films, as well as films formed of other materials, forces within and/or applied to the film often cause the longitudinal edge portions of the film to be longer than other portions and particularly the mid-portions thereof. The longer edge portions of such film, referred to in the art as floppy edges, present a wavy edge outline which makes subsequent film processing, and particularly coating, diflicult to control.

Generally, coating of such film is performed by a kiss coating process in which a thin layer of coating material is deposited onto the surface of a roating cylinder and then transferred to a surface of the film as it is advanced relative to and temporarily in contact with the transfer cylinder. Since the film being coated has longitudinal edge elements which differ in length from the remainder of the film, uniform contact of the film with the rotating cylinder, across the entire film width, cannot be achieved and results in poor coating transfer. Accordingly, a primary object of this invention is to provide a generally new or improved and more satisfactory method and apparatus for coating continuous films.

Another object of this invention is to provide an improved method and apparatus for applying a layer of coating material of controlled thickness onto a traveling continuous film having longitudinal elements which differ in length.

Still another object of the invention is an improved transfer coating apparatus in which a continuous traveling film, having longitudinal elements which differ in length, is caused to contact generally evenly across its entire width with a coating transfer member.

A further object is the provision of a method and apparatus for applying a layer of coating material onto a continuous traveling film, such method and apparatus being simple, economical, flexible in use, and capable of accurate control.

In the drawing, FIGURE 1 is a diagrammatic front view of the coating apparatus of the present invention; and FIGURE 2 is a side view illustrating the relationship of coating transfer and metering rollers employed in the apparatus shown in FIGURE 1.

The above and other objects of the invention are achieved by a method and apparatus in which a continuous advancing film, having longitudinal edge elements which are longer than other portions of the film is caused to make generally even or uniform contact along its entire width with a transfer or applicator roller from which a layer of coating material of predetermined and controlled thickness is transferred to the film itself. The coating transfer roller has a peripheral surface which is con- Car 3,4%,786 Patented Mar. 10, 1970 ice toured to compensate for the differences in length between the edge and other elements of the film which is being coated so that such longer film edge elements travel greater distances than the shorter of such elements. More particularly, in coating a film having floppy edges; that is, a film in which the longitudinal edge portions are longer than the mid-portion thereof, the transfer roller would have a double-tapered configuration as provided, for example, by a pair of truncated cones which are abutted and connected together at their ends of smaller diameter. With a transfer roller of this configuration, the longer edge portions of such film would engage with sections of the transfer roller which are of larger diameter than the roller section which is contacted. by the mid-portion of the film. Thus, the longer edge portions of the film would travel greater distances than the mid-portion of the film, with the net result being a flattening of the film edges against the transfer roller surface.

In conventional kiss coating apparatus, as well as in the apparatus of the present invention, the film being coated contacts with the surface of the transfer roller along an arc of from 5 to 15, during which contact the layer of coating material is transferred to the film. The transfer roller is positioned horizontally and the layer of coating material is deposited onto its surface by maintaining a pool of such material between the transfer roller surface and a co-operating stationary dam or metering roller. Such dam or metering roller would be shaped to conform with the contoured shape of the transfer roller and would be spaced therefrom a distance substantially equal to the thickness of the coating material which is desired.

A further and preferred arrangement for depositing a layer of coating material of controlled thickness onto the transfer roller involves the use of a cylindrical metering roller which is adapted to be canted about a point located in an axial plane of the metering roller which is substantially perpendicular to an axial plane of the transfer roller. Such cylindrical metering roller is simple and less costly to fabricate than a tapered dam or tapered metering roller, and is especially suited for use in coating of conventional films having longitudinal edge portions which are longer than the remainder of the film.

More particularly, in the coating of a film having floppy edges, the cylindrical metering roller is positioned adjacent to but spaced from the transfer roller, which would be of double-tapered configuration, as described above, so as to flatten, and more particularly, smooth the film in its transverse direction into a generally arcuate contour as it contacts therewith. With the cylindrical metering roller disposed substantially parallel to the axis of the transfer roller, the layer of coating material deposited onto the transfer roller and subsequently applied to the film would, of course, have a greater thickness at its center than at its edges. However, canting or inclining the metering roller about its center and in a plane parallel to a similar plane passing through and including the axis of the transfer roller, the opening formed. by the opposing surfaces of the metering and transfer rollers, while remaining the same at its center, is gradually increased in width progressively from its center toward its ends. Actually, the opening which is formed by the transfer and metering rollers has one side which extends generally helically along the transfer roller and one straight side as defined by the surface of the metering roller. As a result, the layer of coating material which issues from such opening is, in general, of uniform thickness even though the transfer roller which assists in shaping such layer is contoured.

The degree to which the metering roller is canted will depend upon the particular variations, if any, which may be desired in the coating transversely of the film length. More particularly, canting of the metering roller to a degree substantially equal to the slope of the transfer roller tapered surface will dispose the surface of the metering roller in parallel relationship to the opposite tapered portions of the transfer roller so that a layer of coating material of generally uniform thickness across its entire width will be deposited upon the transfer roller surface. On the other hand, canting the metering roller to a greater or lesser degree than the slope of the transfer roller surface will result in coating layers which are, respectively, thicker or thinner at their edges than at their mid-sections. Once the metering roller has been canted to the desired degree it may, if necessary, be moved horizontally toward or away from the transfer roller to vary the width of the opening between the rollers surfaces uniformly along its entire length.

The slope of the transfer roller tapered surface will depend upon the differences in length of the logitudinal edge elements and the remainder of the particular film which is being processed. With conventional regenerated cellulose films, a transfer roller in which the sections which are to engage with the film edges are from about 5% to 70% greater in diameter than at the mid-section of the roller will generally achieve satisfactory flattening of the film against the transfer roller surface.

In coating of regenerated cellulose film having floppy edges, the contour of the transfer roller employed in the apparatus of the present invention will be symmetrical, as described above. This configuration, however, may be varied so as to accommodate the particular longitudinal edge variations in the film which is to be coated. For example, if the film is such as to have longitudinal edge portions which are longer than the remainder of the film and in themselves differ in length, the transfer roller would, in effect, be formed of two sections of truncated cones having surfaces which differ in taper or slope, with the smallest diameter of the transfer roller being at such location as to receive the longitudinal element of the film which is the shortest in length. The cylindrical metering roller would be canted as heretofore described, with the exception that its inclination would occur about a point on its axis which is opposite the section of the transfer roller of smallest diameter.

Referring now to the drawing, the apparatus of the present invention has a suitable supporting framework, including spaced side plates 11 which rotatably support the opposite ends of shafts 13 of coating transfer rollers 15. Pairs of brackets 17 are fixed at 19 to the side plates 11 and are each provided with a arcuate slot 21 which receives a pair of pins 23 projecting from an adjacent metering roll support 25. The outermost ends of the pins 23 are threaded for receiving nuts 27 which, when tightened against the respective brackets 17, lock the supports 25 in positions to which they have been adjusted.

The metering roll supports 25 are identical in construction, each including bearing member 29 having a slot 31, for guiding a slide block 33 as it is moved by an adjusting screw 35. The screws 35 are threaded through the hearing members 29 and are rotatably connected to the respective slide blocks 33 so as to move the latter linearly along their guide slots.

A cylindrical metering roller 37 is mounted by a shaft 39 between a pair of slide blocks 33 and co-operates with an adjacent transfer roller in depositing a layer of coating material onto the transfer roller surface from a pool 41 of such material, as supplied by a pipe 43. As in conventional apparatus, dams are provided to prevent the coating material from spilling over the ends of the rollers. The transfer and metering rollers are all driven at the same speed by any suitable means, not shown, as for example by an endless belt driven by a single motor and laced over pulleys which are fixed to the ends of the respective roller shafts.

The film to be coated, indicated at 45, is drawn from its source of supply, not shown, guided by

idler rollers

47 and 49 and then passed in between and in contact with 4 the coating transfer rollers 15. The transfer rollers 15 and the guide roller 49 are supported by the side plates 11 in such positions as to cause the film 45 to contact each of the transfer rollers 15 along an arc of from 5 to 15 of its peripheral surface. If necessary, additional guide rollers 49 may be provided to achieve this result.

In coating a conventional regenerated cellulosic film, such as film 45, having longitudinal edges which are longer than the middle portion thereof, the transfer rollers 15 would be of double-tapered configuration and, as heretofore described and shown in FIGURE 2, would correspond to a roller as formed by two turncated cones connected together at their smaller ends. Normally a transfer roller which is from 5 to 10% larger in diameter at its ends than at its center will achieve a desired flattening or smoothing of a conventionally formed regenerated cellulose film as it travels thereover. As heretofore described, and as also shown in FIGURE 2, the metering rollers 37 are of cylindrical configuration.

In practicing the method of the present invention with the above described apparatus, the film 45 which is to be coated is first laced over

guide rollers

47 and 49, passed inbetween and in contact with the transfer rollers 15 and then advanced to a suitable collection means, not shown. The metering rollers 37 are then adjusted relative to the respective transfer rollers 15 by movement of the screws 35 and the slide blocks 33 to which such screws are attached. With the supports 25 free for movement, the respective metering rollers 37 are then canted about their centers in planes parallel to similar planes passing through and including the axes of the transfer rollers. More specifically, each metering roller is tilted so that its axial is substantially perpendicular to an axial plane of the adjacent transfer roller, with the point about which the metering roller is tilted lying along a line at which such planes intersect. Once adjusted, the nuts 27 are tightened to lock the supports in their adjusted positions.

With transfer rollers having a configuration as described above, the metering rollers are preferably canted to a degree equal to the slope of the transfer roller surface to provide the film with a coating of generally uniform thickness across its entire width. As heretofore mentioned, the metering rollers may be canted to a greater or lesser degree than that indicated above if a coating which differs in thickness across its width is desired. Once adjusted as described above, the metering rollers may be moved horizontally toward or away from the respective transfer rollers if it is necessary to vary the opening between the roller surfaces along its entire length.

Flowable coating material is then delivered by the pipes 43 to provide a pool 41 between each pair of metering and transfer rollers. Once set in operation, the transfer rollers each carry, from the respective pools 41, a layer of coating material which conforms in cross-section with the opening provided between the transfer roller and the adjacent metering roller and apply the same to the film 45 while it is in contact with and flattened by such contoured transfer roller. After moving past the transfer rollers, the film may be heated to dry the applied layers of coating material and is then collected.

I claim:

1. Apparatus for coating a continuous film having longitudinal edge elements which are longer than the remainder of the film including a frame, a horizontally disposed coating transfer roller rotatably carried by said frame, a metering roller, means supporting said metering roller adjacent to said transfer roller with its longitudinal axis lying in a plane parallel to a similar plane passing through the axis of said transfer roller, means for supplying a pool of coating material in between said transfer and metering rollers, means for adjusting said metering roller relative to said transfer roller to provide an elongated opening between the surfaces of said rollers, means for rotating said transfer and metering rollers at substantially the same speed and in opposite directions whereby a layer of coating material is carried on the surface of said trans fer roller from the pool of coating material and through said elongated opening, and means for advancing a film to be coated relative to and in contact with only a portion of the surface of said transfer roller for applying a layer of coating material from said transfer roller to the film, said transfer roller having a double-tapered configuration and being of largest diameter at its ends so as to cause the longer edge elements of the film to travel greater distances than the shorter elements thereof when the film is in contact with said transfer roller.

2. Apparatus as defined in claim 1 wherein said metering roller is of cylindrical construction and further including means for adjusting said metering roller into an inclined position in a plane substantially parallel to a plane passing through and including the axis of said transfer roller and about a point located along a line at which the plane of the metering roller intersects with a substantially perpendicular plane passing through and including the axis of said transfer roller.

3. Apparatus as defined in claim 2 wherein said transfer roller is of smallest diameter at its mid-section and wherein the point about which the metering roller is inclined is opposite the mid-section of the transfer roller.

4. Apparatus as defined in claim 3 wherein the surface of the transfer roller tapers substantially uniformly from the mid-section to the ends thereof and wherein the midsection of said transfer roller is from 5 to smaller in diameter than the ends thereof.

5. A method of coating a continuous film having longitudinal edge elements which are longer than the remainder of the film including the steps of advancing the film in a longitudinal direction, smoothing the film in its transverse direction into a generally arcuate contour, contacting the generally arcuately contoured, advancing film evenly across its entire width with a shaped layer of flowable coating material of uniform thickness, and solidifying the applied layer of coating material Z 6. A method as defined in claim 5 wherein the film is generally arcuately contoured in its tranverse direction by contacting from 5 to 15 of the peripheral surface of a rotatable transfer roller of double-tapered configuration which is of largest diameter at its ends, and wherein said layer of coating material is applied onto the surface of the transfer roller at one location and is transferred to the film at another location as the film engages therewith.

7. A method as defined in claim 6 wherein the thick ness of the layer of flowable coating material applied onto the transfer roller is controlled by a cylindrical metering roller which is disposed adjacent and canted relative to the transfer roller in a plane substantially parallel to an axial plane of the transfer roller and about a point located along a line at which the plane of the metering roller intersects with a substantially perpendicular plane passing through and including the axis of the transv fer roller.

References Cited UNITED STATES PATENTS l/1965 Parker 1l8252 6/1967 Thorp 1l8262 X ALFRED L. LEAVITT, Primary Examiner CHARLES R. WILSON, Assistant Examiner US. 01. XR. 118246, 26;

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 s 9a7 D d March 10, 197

Inventor(s) Horace P, Fry JP It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

r- Column 1. line 32, "roating" should read rotating 7 Column 3 line 17, "lo itudinal" should read longitudinal line 22, 7073" should read 10% Column 1; line 12 "tuI'nc-ated" should read truncated line 32, after "axial" insert plane SIGNED KN SEALED JUL281970 N Attest:

'1 mum: E. sum. .1. Attestmg Officer Comissionn of PM.