US2257113A - Coating apparatus - Google Patents

Description

Sept. 30, 1941. w. GEORGE 2,257,113

COATING APPARATUS Filed Feb. 2, 1959 2 Shee ts-Sheet 1 O r (J Sept. 30, 1941. w. GEORGE COATING APPARATUS Filed Feb. 2, 1939 2 Sheets-Sheet 2 i z A 9 i. m w

Patented Sept. 30, 1941 COATING APPARATUS Warren George, Neenah, Wis., assignor to K-C-M Company, Dayton, Ohio, a corporation of Delaware Application February 2, 1939, Serial No. 254,204

6 Claims.

This invention relates to the art of coating sheet materials and has particular reference to the art of coating flexible webs made of paper or similar material.

In general, the invention may be considered to be in the nature of a modification of the prior invention of John R. Fanselow as disclosed in his application for United States Patent filed February 2, 1938, Serial No. 188,369, Method and apparatus for coating sheet material, which application has been assigned to the assignee of this application. The said Fanselow application discloses the use of a vacuum chamber through which the web is propelled and to which web, either before or after it enters the vacuum chamber, there is applied a liquid coating which is doctored or leveled oi as or before the web passes out of the vacuum chamber. In

the Fanselow application, such doctoring or leveling off of the coating is effected by the use of a stationary doctor-ing blade or bar which is so spaced from the coated surface of the web as to provide a relatively narrow slit or suction gap through which atmospheric air is sucked by the vacuum effect within the chamber. Such atmospheric air entering the vacuum chamber has the effect of leveling off the coating and also of removing any excess coating which may have been applied to the web.

The principal objects of the present invention are to provide, in a system of the general character herein described, an improved doctoring or air gap arrangement which will permit of the more emcient use of vacuum, which will reduce the volume of air which is required to be pumped in order to maintain the required degree of vacuum within the vacuum chamber; to provide an arrangement which will enable the mechanical manipulations to be more readily and more quickly effected; to provide a system and apparatus which may be more easily controlled and by which a more uniform coating may be produced with greater certainty and facility; to provide an apparatus of the character described which will be virtually self-cleaning, wherein breakage of the web may be reduced to a minimum, and wherein such breaks as do occur cause a minimum amount of inconvenience and-lost production; to provide an apparatus which will be simple and inexpensive to design, construct and install, and which can be operated efliciently and economically; and in general to provide an improved apparatus of the character referred to.

In the drawings, which illustrate a preferred embodiment of the invention:

Fig. 1 is a diagrammatic elevation of the invention as applied to a Fourdrinier paper machine in order to apply a suitable surface'coating to both sides of the paper web before the latter leaves the paper machine;

Fig. 2 is an enlarged side elevation of one of the coating units shown in Fig. 1;

Fig. 3 is an enlarged sectional elevation of certain of the parts shown in Fig. 2 together with other associated instrumentalities;

Fig. 4 is a perspective view of the vacuum chamber through which the web is propelled; and

Fig. 5 is a fragmentary sectional side elevation similar to Fig. 3, but showing the apparatus arranged for the application of coating material to the web within instead of outside of the vacuum chamber.-

Referring to the drawings, the numeral H0 represents the web of paper which moves from left to right of Fig. 1. Said web as shown in Fig. 1 comes from the drying cylinders IH, passes through the first coating mechanism designated as a whole H2 where the top or felt side of the web is coated, and thence the web passes over a large drying cylinder H3 which dries the applied coating sufiiciently to enable the coating to be touched or handled without injury. From the dryer H3, the web is conducted through a second coating apparatus H4 which serves to apply the coating to the under or wire side of the web. From the coating mechanism 4, the web passes around a second large drying cylinder H5 and thence to a set of ordinary drying cylinders lll if it is found necessary to effect any further drying of the web.

It will be observed that the apparatus, which in this instance comprises two units for treating both sides of the paper web, is in effect introduced into the series of drying cylinders which constitute the drying section of a Fourdrinier paper machine. In some instances, it will be found ad vantageous, as shown in Fig. 1, to apply the coating before the paper has reached its final stage of dryness. However, the apparatus may be employed to effect thecoating of paper from which only a relatively small portion of moisture has been removed, or it may be used for coating paper which has passed the final drying stage. So far as the coating operation is concerned, the apparatus can be made to operate satisfactorily upon papers havin a very wide variance in moisture content, and, when properly adjusted, will apply various types and weights of coatings to diiferent types of webs.

In view of the fact that the coating units designated as a whole H2, 4 are of precisely similar construction but reversed in order to coat -opposite sides of the .web 0, only one of said coating units, namely the unit II2, need be specifically describem Said unit as shown best in Figs. 3 and 4 comprises a vacuum chamber H6, H1, H8 and H9. The roll IIB around which the web III! is' trained and by which the web is propelled through the vacuum chamber may be called a platen roll. The roll II'I immediately below the platen roll Ill may be termed the applicator roll for the reason that it cooperates with the paper and liquid' coating supply instrumentalities to apply the liquid coating to the adjacent side of the web IIO. Said function may be performed by the roll II'I whether the liquid coating is appliedto the web within the \vacuum' .which is formed by a set of four enclosure rolls rolls.

The ends of the vacuum chamber are closed by means of end seals I which are provided with inwardly facing rubber parts which overlap the ends of the rolls [and thereby prevent leakage of air into the chamber. Air is withdrawn from the chamber .by means of a relatively large pipe I2I which extends through the chamber from off the applied coating so as to smooth or level of! the same and to remove any excess coating material which may have been applied to the web.

Preferably the doctor roll I I9 is rotated in such direction that that portion ofi-ts periphery which forms the orifice or suction gap will move upwardly; i. e. in the same direction as the movement of the web in the gap, and usually, in the case where four rolls are employed-to form the enclosure for the vacuum chamber, it will be found advantageous to drive said doctor roll at a speed which will cause its periphery to move at the same speed as the rate of travel of the web. In most cases, I have found it advisable to equip doctor roll II! with a positive drive so that it is not necessary to depend upon the frictional drag between the periphery of said roll 9 and the periphery of the sealing roll II8 with which roll II! is in contact.

In practice, it is found that the surface of the doctor roll 9, as it emerges from the suction gap or orifice, carries a thin, quite uniform coating of the coating liquid, which coating is squeezed oil! in the nip between rolls I I9 and H8.

and may be collected and re-used in the equipment. Ifdesired, a stationary doctor 9 01' the knife type may be applied to the periphery of the doctor roll I I9 in order to clean of! and collect the said liquid coating on its periphery and also in order to remove any grit or other foreign mat- 'ter which may be carried up out of the orifice by the doctor roll II9.

A relatively narrow gap is obviously desirable in order to save pumping capacity. As indicating the type of gap which can be used with the end to end and along its length is provided with "a series of apertures I22 properly spaced and of the proper size to produce a uniform withdrawal of air across the entire width of the web. Said suction pipe I2I is connected at its ends to a pipe I23 which leads into a settling drum I24 connected by means of the pipe I25 to a vacuum pump (not shown) of the required capacity.

In the case of the arrangement shown in Fig. 3 which shows the apparatus adapted for application of liquid coating to the web on the outside of the vacuum chamber, such application is ef-. fected as follows:

A pump I26 forces a supply of liquid coating through the pipe I 21 into a distributing trough I28 which discharges through suitably spaced I apertures into an application trough I29, the

described equipment, it may be said that with a web speed of from 200 feet to 700 feet a minute a-paper web can be supplied with a satisfactory coating when the gap between the paper and the doctor roll measures between 10 and 20 onethousandths of an inch, in connection with a vacuum equal to between 2 and 4 inches of mer-- cury. The thickness of coating will naturally depend upon the character and consistency of the coating liquid, the spacing or width of the orifice, the speed of travel of the web, and the degree of vacuum.

The roll H8 is merely a sealing roll which inner side of which is open to the upper surface of the roll I".

The pipe I 30 is connected to a reservoir (not shown) of coating material and delivers to the pump I26 a suflicient amount of coating mate rial to provide a coating of the required weight upon the web which is being treated, with sufiicient additional coating material to supply any loss due to leakage or wastage. Any excess coating material which is removed through the suction pipe I.2I is collected in the settling drum I24 and is returned to the pump through the pipe I3I.

The rolls H6, H1, H8 and II! are all mounted in suitable bearings provided with more or less conventional arrangements whereby the pressures between pairs of rolls or cooperating rolls can be conveniently, regulated or adjusted according to the requirements of the apparatus and also whereby, if desired, any roll may be swung away from the roll or rolls with which it cooperates so that the web may be manipulated by the operators as desired. For example, as shown in Fig. 2, the roll H3 is mounted on bearings which are arranged to slide in a frame I32 under the influence of a tension spring I33 which draws the bearings towards the axis of the roll I". Said arm I32 is mounted to swing concentric with the axis of the roll II'I so that the roll II3 will always be in proper engagement with the roll I", regardless of the angular position ofthe arms I32. Said arms I32 are adapted to be swung resiliently upward so as to bring the roll Ill in proper engagement with the doctor roll II9 by means of bell-crank arms I34 integral with the arms I32, the lower ends of the arms being drawn in the proper direction by cables I35 to which tension is applied by a spring or weight (not shown). a

The bearings for the doctor roll II! are similarly arranged to slide in arms I36 pivoted at I31 upon a stationary part of the machine. Said bearings are forced downwardly within the slide arms I36 by means of compression springs I34 sog'that there is the proper degree of contact between roll I I8 and roll H8. The doctor roll II! may-be readily adjusted with reference to the web and platen roll H6, or it may be swung away from the platen roll II 6 and the sealing roll II8 completely by means of cables I39 attached to the arms I36 and adjusted by a suitable traverse screw I40 operated by a hand-wheel I In Fig. 5, I have shown the coating unit ar-- ranged for internal application of coating fluid. This is effected by eliminating the outside troughs I28 and I29 and connecting the end of the coating supply pipe I21 directly to the ends of a distributing pipe I42 which extends through and between the end seals adjacent to the nip between rolls I I8 and III. Said distributing pipe I42 is provided with suitable apertures I43 through which the coating fluid is directed into the nip and against the surface of the traveling web IIO. If desired the internal distributing pipe I 42 may be used in combination with the external trou h H9. The presence or absence or extent of the internal pool depending upon conditions does not seem to be important.

In most cases, whether the liquid coating be applied inside or outside of the vacuum chamber, or both inside and outside, I have found it more convenient to supply and circulate a considerable excess of coating fluid, the thickness or weight of the ultimate coating being preferably regulated by adjustment of the doctor roll, or by regulation of the amount of vacuum within the chamber, or by both. However, in the application of certain types of coatings, it may be found desirable in certain instances to first regulate the doctor and the vacuum so as to provide a coating somewhat in excess of that which is desired and then to cut down the supply of coating material to an amount which will furnish a coating of the required weight. In the case of the outside application as shown in Fig. 3, the supply of coating to the web can be cut down by reducing the gap or increasing the pressure between rolls H6 and III, while in the case of the apparatus shown in Fig. 5 such reduction in liquid supply may be effected by suitably controlling the flow through pipe I21.

The scope of the invention should be determined by reference to the appended claims, said claims being construed as broadly as possible consistent with the state of the art.

I claim:

1. Apparatus for coating webs which comprises a platen roll around which the web may be propelled, a doctor roll having its periphery spaced slightly from the web at a point where the web is supported by the platen roll and rotatably supported so that said spacing may be maintained constant independent of different angular positions of said doctor roll, means cooperating with said rolls to form a chamber through which the web is propelled while it is supported on the platen roll, means for applying a coating liquid to the traveling web on that side thereof which is presented towards the doctor roll and before the web passes between said rolls and out of said chamber, and means for withdrawing air from said chamber to create an inward suction between said rolls so as to level off said coating.

2. Apparatus for coating webs which comprises a platen roll around which the web may be propelled, a doctor roll having its periphery spaced A sented towards the doctor roll and before the web passes between said rolls and out of said chamber, and means for withdrawing air from said chamber to create an inward suction between said platen and doctor rolls so as to level of! said coating.

3. Apparatus for coating webs which comprises a platen roll around which the web may be propelled, a doctor roll having its periphery spaced slightly from the web at a point where the web is supported by the platen roll and rotatably supported so that said spacing may be maintained constant independent of the angular position of the doctor roll, means cooperating with said rolls to form a chamber through which the web is propelled while it is supported on the platen roll, means for applying an excess of coating liquid to the traveling web on that side thereof which is presented towards the doctor roll and before the web passes between said rolls and out of said chamber, and means for withdrawing .air from said chamber to create an inward suction between said rolls so as to level oil said coating and to reduce the said coating to the desired thickness.

4. Apparatus for coating webs which comprises a platen roll around which the web may be propelled, a doctor roll having its periphery spaced slightly from the web at a point where the web is supported by the platen roll, means for rotating said doctor roll so that its periphery adjacent the platen roll will move in the same direction as the direction of web propulsion, means cooperating with said rolls to form a chamber through which the web is propelled while it is supported on the platen roll, means for applying a coating liquid to the traveling web on that side thereof which is presented towards the doctor roll and before the web passes betweensaid rolls and out of said chamber, and means for withdrawing air from said chamber to create an inward suction between said platen and doctor rolls so as to level oil said coating.

5. Apparatus for coating webs which comprises a platen roll around which the web may be proslightly from the web at a point where the web is supported by the platen roll and rotatably supported so that said spacing may be maintained constant independent of different angular positions of said doctor roll, means cooperating with said rolls to form a chamber through which the web is propelled while it is supported on the platen roll including a roller engaging and rolling upon said doctor roll, means for applying a coating liquid to the traveling web on that side thereof which is presented towards the doctor roll and before the web passes between said rolls and out of said chamber, and means for withdrawing air from said chamber to create an inward suction between said platen and doctor rolls so as to level cooperating with each other and respectively with the platen and doctor rolls to form an enclosure forming part of a chamber through which the for applying a coating liquid to the traveling web on that side thereof which is presented towards the doctor roll and before the web passes between said rolls and out of said chamber, and means for withdrawing air from said chamber to create an inward suction between said platen and doctor rolls so as to level ofl said coating.

- v WARREN GEORGE.

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