US 3635192 A
An apparatus for coating foils, tapes with viscous solutions, comprising a guide member for the support to be coated, a wedge-type casting device as preliminary coating means and a striplike partition in the direction of movement of the support, forming a gap with a support extending over the width of the web. That partition now is serving as final coating means and is arranged between two chambers at different pressure, wherein the preliminary coating means is arranged just before partition. The housing of the preliminary coating means has a construction in the region of the flow slots extending over the width of the web. The flow slot is open in the vicinity of the overflow of the wedge-type casting device.
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Description (OCR text may contain errors)
1451 Jan. 18 1972 United States 1' Herzhoff et a1.
54 MEANS FOR COATING FOILS, TAPES 2,679,231 5/1954 Pomperetal........,....................
3,070,066 12/1962 Faeber.......
AND THE LIKE ll8/410X m h v S m m w mmm m C mmm M huB oea P KNN n h .m 370 667 999 a 111 .H 207 m. m 464 E 0026 W 388 a 1 1 m ,3 n 333 P  Inventors: Peter llerzhoff; Stephan Platz, both of Lsv rk enz Fritz e sr l9 s t Wolfgang Schweicher; Willi Wasser, both of Leverkusen; Kurt Browatzki, Opladen;
h 11 f ggi fiy Cologne Stamm a 0 Attorney-Connolly and Hutz Agfa-Gevaert Aktiengesellschaft, Leverkusen, Germany Sept. 19, 1969  Assignee:
An apparatus for coating foils, tapes with viscous solutions,
comprising a guide member for the support to be coated, a
wedge-type casting device as preliminary coating means and a striplike partition in the direction of movement of the support,
[211 Appl. No.:
forming a gap with a support extending over the width of the web. That partition now is serving as final coating means and is arranged between two chambers at different pressure, wherein the preliminary coating means is arranged just before Field ofSearch......................
I C t n I .1 1 5 1 18/413 407 partition. The housing of the preliminary coating means has a construction in the region of the flow slots extending over the  References cued width of the web. The flow slot is open in the vicinity of the UNITED STATES PATENTS overflow of the wedge-type casting device.
1,741,382 12/1929 Stokes.. ...............................118/62X 7Claims,1DrawingFigure PATENTED JAM 8 m2 INVENTOILS:
PETER HERZHOFF, STEPHAN PLATZ, FRITZ MAUD', WOLFGAHG SCHWEICHER, WILLI IVASSER,
KURT BROWATZKI, HANS GREF MEANS FOR COATING FOllLS, TAPES AND THE LTKE This invention relates to an apparatus for coating foils, tapes and the like with viscous solutions, which comprises a guide member for the support to be coated, a wedge-type casting device as preliminary coating means and a striplike partition which, seen in the direction of movement of the support, is arranged behind the wedge-type casting device and forms with the support a longitudinal gap. The partition serves as a final coating means and is arranged between two chambers operating at different pressures. in this way, the coating is blown in by a tangentially guided airstream produced by the pressure difference between the top and bottom sides of the partition.
With means of this type, the preliminary coating is effected from an upwardly open tray having an overflow and formed between the cylinder and the wedge-type casting device. The emulsion is transported from this open tray when using the wedge-casting method, through the wedgelike gap between the foil and casting device. After leaving the wedge-type casting device, the initially coated web is twisted in an angular path of about 130 to 140 up to the position of the formation of the final coating by the tangential airstream in the region of the airgap on the shaped strip or partition. It has now been found that with the travel through this comparatively long angular path of the web which has been uniformly coated initially by the wedge-type casting device (with a coating thickness substantially larger than the final coating), the casting operation is disturbed by the action of the air flowing past or by surface forces. More especially, longitudinal strips in irregular form occur.
With two-coating casting operations, for example, when applying a protective coating to a solidified black-and-white emulsion layer, wetting difficulties arise at relatively high-casting speeds, and these difficulties can no longer be overcome with the conventional wetting agents.
When the tangential airstream in the region of the shaped strip has only an insignificant component transversely of the direction of travel of the web, so-called diagonal strips are formed in the casting pattern. These strips are periodic fluc tuations in casting thicknesses, which extend at an angle of 30 to 60 to the direction of travel transversely across the web. These diagonal strips already occur with quite insignificant deviations in the dimensions of the airgap formed between the shaped strip and web.
Experience has also shown that, despite the utmost care in the manufacture of the casting cylinder, the unavoidable small defects in manufacture can sensibly disturb the casting operation. Already a cylinder deflection of the order of magnitude of only one-hundredth mm. produces periodic fluctuations in layer thicknesses with the revolving of the cylinder and these fluctuations can no longer be accepted with sensitive color castings.
It has now been found that the said difficulties are eliminated if the preliminary casting device is arranged according to the invention just before the partition. The housing of the preliminary or initial casting device has a constriction in the region of the flow slots, which are for example perpendicular to one another and extend over the width of the web. The flow slot which communicates with the wedge-shaped chamber formed between the wedge-type casting device and support opens in the vicinity of the overflow of the said chamber.
The casting arrangement is more fully described by reference to the FlGURE.
The foil 2 which is to be coated is guided over the cylinders 14, and 16 arranged on the supporting means 13 and also over the fixed saddle element 17 formed as a part of the supporting means 13. The layer or coating is formed in the region of the initial proportioning wedge 3 and the shaped partitioning strip 7, these elements being disposed closely adjacent one another in the construction which is provided here. In this region, the web is therefore not exposed to any cylinder oscillation and thus the difficulties referred to above are avoided.
Since the web is only guided in the region of the elements forming the coating over the fixed saddle element 17, the corresponding wrapping angle and thus also the increase in web tension due to friction are small. The saddle element 17 is formed with holes 26, and this arrangement permits a lubricating air cushion to be developed beneath the frequently scratch-sensitive foil 2 from the interior of the support member 13. The support member 13 is constructed as a hollow body and is connected to an air pipe, whereby the friction is further reduced or completely eliminated.
The support member 13 is mounted to swivel about the axis 25, so that the saddle element can easily be cleaned.
The emulsion is supplied under pressure to the casting position through the supply pipe 4 and the slotlike ducts 18 and 19. Due to the cross section being reduced at 11 between the ducts 18/19 which extend over the entire width of the casting device, a dynamic pressure is obtained in the duct 18 and thus there is an improved distribution of the emulsion over the width of the web. The stream of emulsion is divided at the upper end of the duct 19. One part thereof is conveyed with the web 2 over the initial proportioning wedge 3, while the other part is fed opposite the web and over the overflow edge 20 and through the overflow pipe 5 to the emulsion storage ar' rangement. Due to this flow over the overflow edge 20 opposite to the direction of the web, a more reliable wetting is obtained. Consequently, the wetting difficulties which were referred to above are obviated.
With the constructional arrangement as now provided, the tip of the wedge 3 is brought so close to the shaped partitioning strip 7 that the spacing is in no case larger than l0 mm.. The emulsion, immediately after emerging from the wedgelike gap 10, is strongly exposed to the action of the blowing air which flows in an opposite direction between the strip 7 and foil 2 and forms the final layer. in this way, the disadvantage referred to above of the long time of action and undesirable forces on the precoated web which interfere with the uniformity of the casting pattern is avoided. The formation of the finished coating in the region of the strip 7 by the tangential airstream is effected in known manner. That portion of casting solution which is blown off flows away over the front side of the initial proportioning wedge 3 and is carried away through the tank and the return pipe 12.
The air flowing in at the tip of the shaped strip 7 tangentially into the tank 8 which is under vacuum, is discharged through the gap 9.
Arranged beneath the shaped partitioning strip 7 is a second shaped strip, which is the so-called nozzle plate straight edge 21. The latter forms, with the strip 7, a cavity 22 which extends over the entire width of the web and is closed at the ends. Fine passages 23 are formed at very close uniform intervals at the pointed end of the member 21. The cavity 22 communicates with the outside atmosphere or possibly with a compressed air pipe. By means of this piping system 24-222 3, many fine air jets arranged in the form of a rake are produced over the entire width of the foil. The intensity of the fine jets directed at the location of the finished layer formation can be so adjusted with appropriate regulation of the superatmospheric pressure in the pipe 24 that firstly the separate jets do not appear in the casting pattern, but secondly the flow in the region of the tip of the straight edge is so stabilized that the diagonal strips referred to above no longer occur. The stabiliz' ing action of the nozzle straight edge is also maintained to a certain extent if said straight edge is arranged above the shaped strip 7.
1. An apparatus for depositing a coating of viscous solution on a longitudinally moving foil comprising a guide member over and against which said foil is longitudinally traversed, a wedge-type casting device disposed closely adjacent the side of said foil opposite said guide member for feeding said viscous fluid and applying it to said opposite side of said foil, an air chamber partitioning strip having an edge disposed after said casting device in the direction of movement of said foil and spaced closely adjacent said opposite side of said foil, a gap between said edge of said partitioning strip and the adjacent edge of said casting device, airflow means disposed in said gap for directing a tangential flow of air against said deposited coating of viscous solution in a direction opposite to the direction of movement of said foil for smoothly spreading said deposited coating in contact over the width of said opposite side of said foil, and said gap being not greater that l mm. whereby the thickness and smoothness of said deposited coating are precisely controlled and maintained.
2. An apparatus as set forth in claim 1 wherein conduit means is connected to said casting device for supplying viscous fluid to it, and said conduit means including a restricted outlet to said casting device whereby back pressure is maintained in said conduit for facilitating the smooth feeding of said solution to said casting device and the distribution of said viscous solution to said opposite side of said foil.
3. An apparatus as set forth in claim 1 wherein an overflowcollecting device is disposed on the side of said wedge-type casting device remote from said partitioning strip and said overflow-collecting device including an overflow lip disposed adjacent said casting device over which excess viscous solution flows away from said casting device.
4. An apparatus as set forth in claim 3 wherein the outlet portion of said conduit means between said restricted portion and said casting device has divided outlet means, one of said outlet means being connected to said casting device and the other of said outlet means being connected to said overflow means.
5. An apparatus as set forth in claim 1 wherein said airflow means includes a nozzle plate disposed next to the side of said partitioning strip adjacent said casting device, and a plurality of air ducts being disposed within and parallel to each other through the edge of said nozzle plate adjacent said partitioning strip and substantially perpendicular to direction of travel of said foil.
6. An apparatus as set forth in claim 1 wherein said guide member comprises a curved saddle-shaped element and said saddle-shaped element being mounted on a movable support whereby it may be moved toward and away from said foil.
7. An apparatus as set forth in claim 6 whereby said saddlesllaped element is perforated to provide air supply passages through it for forming an air cushion between it and said foil.