US2081945A - Means and method of drying coated flexible webs - Google Patents

Description

June 1, 1937. P. J. MAssEY ET Al. 2,081,945

MEANS AND METHOD oF DRYING COATED FLEXIBLE wEBs Filed Nov. 27, 1935 2 Sheets-Sheet 1 June 1, 1937. P, JjMAssEY ET Al.

MEANS AND METHOD OF DRYING COATED FLEXIBLE WEBS Filed Nov. 27, 1935 2 Sheets-Sheet 2 Patented June 1, 1937 UNITED STATES PATENT OFFICE MEANS AND METHOD F DBYING COATED FLEXIBLE WEBS y Peter J. Massey, River Forest, Ill., and William F. Thiele and Bert F. Baprsger, Wisconsin said Peter J. Massey Application November 27, 1935, Serial No. 51,740

3 Claims.

This invention relates to improvements in a method and means for drying wet webs, and refers specifically to a method and means vfor drying a freshly coated flexible web by passing the 5 same over a series of heated drying drums, the freshly coated surface being subjected to blasts of heated air or other fluid so directed as to provide an insulating air fllm or cushion between the coated surface and the surfaces of the drums so that the coated surface will not be disrupted or marred.

I n the coating of flexible paper and fabric webs, difficulty has heretofore been encountered in economically drying the same without disnguring or marrmg the coating. This dimculty is most pronounced in handling or conveying the web immediately after its exit from the coating device, since the coating, at this period, is most moist and susceptible to disflgurement.

Various expedients have heretofore been proposed, the most widely used being to festoon the coated web after its exit from the coating machine. This method of drying has serious drawbacks among which may be mentioned; that the festooning apparatus requires extensive plant space; the drying is inefficient and slow; and the drying section of the machine cannot be run in step with the coating device.

Drum driers have heretofore been deemed impractical or at best unsatisfactory since the contact between the drum surface and freshly coated web surface resulted in disflgurement and marring of the coated surface. Consequently, for the drying of coated webs where the smoothness and flneness of the coating is of importance,

such as the coating on paper webs used for printing purposes, drum driers with their other many advantageous features have been out of the question.

40 Our present invention contemplates a method and means whereby a freshly coated web may be passed over drum driers immediately after the coating operation without injuring the freshly applied coating.` This phenomenon is accom- 5 plshed by first subjecting the coated web to blasts of heated air under pressure to preliminarily set the coating and then passing the web over the initial rolls or drums of the drier while simultaneously directing air blasts between the web and the drum surface, entrapping the air therebetween so as to form an insulating air lm or cushion between the coated surface and the drum surface. In this manner actual physi- 55 cal contact between the drum surface and the coating is substantially prevented or at least harmful contact is eliminated.

Another difficulty inherent in the use of drum driers is the tendency of the freshly coated web, particularly thin webs, to rope in passing from the coater to the rst drying drum, or from drum to drum. Roping is the longitudinal wrinkling of the web due to its tension in being drawn over the drums and also due to the tendency for the web to creep transversely upon the drum surfaces. Both of these tendencies are intensied when the wet coating on the web meistens the body of the web thereby diminishing its normal rigidity or stiffness.

As a feature of our invention the air blasts, above referred to, are so directed with respect to the web that a transverse component of force is exerted upon the web in opposite directions thereby tending to place the web under slight transverse tension suflicient to eliminate the undesirable roping effect.

Other objects and advantages of our invention will be apparent from the accompanying drawings and following detailed description.

In the drawings, Fig. l is a diagrammatic side elevational view of suitable means for carrying out our invention.

Fig. 2 is an enlarged fragmentary side elevation illustrating the bellying of the web during its passage over the drier drums.

Fig. 3 is a fragmentary transverse sectional view illustrating the bulging of the web, during its passage over the drum due to the entrapped air.

Fig. 4 is a transverse sectional view taken on line 4 4 of Fig. 1.

Fig. 5 is a top plan View of one end of the ai discharging chests,

Referring in detail to the drawings, l and 2 indicate oppositely disposed co-acting coating rolls which are adapted to transfer amobile coating material from their respective surfaces to the opposite faces of a continuously passing flexible web 3. l

For purposes of example, our invention will be described in conjunction with a coating device utilized for coating both surfaces of a web of paper, the paper to be used for printing purposes. It is to be understood, of course, that our invention is not to be limited to this precise application-since it is equally applicable tc the drying of substantially any type of flexible web carrying a surface coating, on one or both surfaces, which coating is susceptible of being dried or set by heat.

The coating devicc shown diagrammatically in Fig. 1 is intended to illustrate a coating machine similar to that described in our co-pending application, Serial No. 40,150 flied Sept.`11, 1935. In this type of coating device a mobile coating material 4 is carried between two juxtaposed gate rolls 5 and E. By controlling the relative speeds of rotation of rolls 5 and 6 a controlled quantity of the coating material 4 may be carried upon the exterior surface of the rolls 6 and may be transferred to a series of osculatin'g distributing rolls l. The last roll of the series in both the upper and lower tiers is adapted to contact the coating rolls I and 2' and transfer to the surface thereof a smooth, uniformly distributed iilm of coating material. s has been hereinbefore described, this nlm is subsequently transferred from the surfaces of the'rolls I and 2 to the opposite faces of a continuously passing Apaper web 3. In many coating operations, particularly when coating paper which ls to be used for printing or similar purposes, it is imperative that the finished coating be smooth and uniformly distributed over the surface of the paper. As described in our hereinbefore mentioned co-pending application such a surface may be deposited upon the web 3. Therefore, it is essential that after the web 3 passes from between the rolls I and 2, extreme care be taken that the coating be undisturbed particularly While said coating is yet wet and unset. Of course, after leaving rolls I` and 2 the coating on web 3 still contains a considerable quantity of moisture and although immobile in the sense that it will not flow, the coating is still suiiiciently pliable or mobile as to be susceptible to scratches and disgurement by contact with solid bodies.

In order, therefore, to dry and set the coating upon the opposite faces of the web 3 after its exit from between rolls I and 2, we contemplate passing the coated web between chests 8 and 9, respectively, disposed above and below the passing web. The chests 8 and 9 preferably extend transversely across the entire width ofthe web 3 and the respective opposed surfaces of said chests are spaced from the-web. Said opposed surfaces of the chests may be provided with a series of apertures I whichopen into the interior of the chests. 'I'he chests 8 and 9 may form portions of a larger supply or equalizing chest II which may be connected to a source of heated air or fluid under pressure. It is obvious that, afterv web 3 passes between chests 8 and 9 the heated fluid within said chests will be discharged through the apertures I 0 and said heated air will contact the coated surface of the web 3 thereby tending to preliminarily setthe coating material. YIn view of the fact that the coating material at this stage is in a more or less pliable state, it is es-v sential that the velocity of the Ilui'd striking the coating material be so controlledas not to displace or disturb the coating.

In view of the fact that the web 3 is adapted to travel in a continuous manner, said web must be maintained under longitudinal tension. Moreover, in order to thoroughly dry the coating mate-- rial said web is to be passed over a-series of drum driers. When the coating material is applied to the web a quantity of the moisture carried by the coating material permeates the-web thereby rendering said web less rigid or stiff. Due to the fact that the web is under tension and is passing over a roll surface, the web when traveling between the chests 8 and 9 would tend to rope", that is, wrinkle longitudinally. 'I'his roping is due primarily to the longitudinal tension of the web and also the fact that in passing over` the fectively prevents longitudinal wrinkling of the web. As clearly illustrated in Fig. 4 of the drawings the apertures III adjacent the longitudinal edges of the web are so inclined as to discharge the air at an angle to the web surface. The apertures I0 adjacent the opposite longitudinal edge of the web discharge the air at angles to the web which are oppositely inclined to those upon the other end. The apertures I0 at the center of the chests 8 and 9 discharge air blasts at right angles to the surfaces of the web and therefore exert no component in either direction.

The apertures III in addition to being inclined in a transverse direction with respect to the web are all, including the central apertures, inclined in a longitudinal direction so as to exert a component of force which acts in the direction of motion of the web. Therefore, the web 3 after leaving rolls I and 2 and while the same is between the chests 8 and 9, is in both transverse and longitudinal tension thereby maintaining the web surface flat and preventing distortion of the coating films due to wrinkling.

A conduit I3 may also be connected to the chest II, said conduit being arcuate in shape and following the contour of roll I2. That face of conduit ls which-1s adjacent rou Iz 1s also provided with apertures I0 which are inclined in the same manner as those provided in the chests 8 and 9. When the web 3 passes from between the chests 8 and 9, said web is trained around roll I2 and is thereafter passed over the surface of drying drum I4 which may comprise the rst drum of a series of driers, the remaining drums not being shown.

It will be noted that the portion of the chest 9 adjacent roll I2 terminates in a more or less pointed edge. 'I'he extreme edge of the chest substantially at said point is provided with a transverse row of apertures I which direct blasts of air into the nip between the lower surface of the web and the surface of roll I2. 'I'hat end of the chest 9 hereinabove described is illustrated in detail in Fig. 5 which clearly shows the apertures I5. It Iwill be noted that in general the angular inclination of the apertures I5 follow adjacentthe sides are inclined transversely outwardly and the apertures adjacent the center are inclined, with respect to their transverse inclination, at right angles to the web surface and that all of the apertures are inclinedlongitudinally, in the direction of motion of the web.

In passing over the roll I2 it is our intention that a lm or cushion or air or other fluid be interposed between the surface of the web and the surface of the roll I2 so that injurious'contact between the coated surface of the web and said roll will be prevented. In discharging the air or other fluid from the apertures I5, said fluid is directed between these opposed surfaces. 'I'he web is therefore slightly raised from the surface of the roll I2 during its passage therearound, being carried upon the air discharged from the apertures I5. In order to prevent the rapid escape of this cushioning air, the apertures I8 are so arranged as to size that a greater quantity of air is delivered at the central portion of the web than is discharged by said apertures adjacent the longitudinal edges of the web. 'I'his construction is clearly shown in Fig. 5 and results in the bulging or bellying" of the web as shown at I6 in Fig. 3. It can readily be seen that inasmuch as a greater quantity of air is discharged from the central apertures I5, the longitudinal central portion of the web will be blown as in a convex manner and the edges of the web will be disposed closer to the roll surface.

In this manner a quantity of fluid will be entrapped in the space Il, the only exits for the escape of said fluid being the relatively small clearance spaces I3 adjacent the edges of the web. By so entrapping the fluid the web 3 may be caused to travel around roll I2 without injuriously contacting the surface of said roll.

The end of the conduit I3 is so constructed as to direct air or fluid from the endmost row of apertures I9 between the web and the surface of the rst drier I4. 'I'he apertures I9 extend transversely across the conduit I3 and are con- 'structed with respect to size and angular inclination similar to apertures I5. The air or uid discharged from apertures I9 tends to belly web 3 in the manner shown in Fig. 3 thereby providing a trapped body of iluid between the web and drum I4 which serve as a cushion or insulating medium for said web during its passage around drum I4.

It is to be understood, of course, that the air or other iiuid discharged through apertures I0, I5 and I9 may be heated or said air may be at normal temperature. Moreover, if desired, the air may be impregnated with adesired agent which may produce a chemical or physical effect upon the coating. In the drying of some coating materials it may be desirable to provide the insulating cushions of fluid described in conjunction with the passage of the web over rolls I 2 and I 4 throughout the entire drier. With coating materials which set more quickly it may be necessary only to provide said fluid cushions during the passage of the web over the initial roll or rolls of the drier. Our invention, of course, contemplates either operation.

I claim as my invention:

1. A method of drying a coated flexible web which comprises, continuously passing a freshly.

coated web forwardly over a drum and discharging uid under pressure between the web and drum surface so as to provide a fluid cushion between the web and drum surface, a greater quantity of fluid being discharged adjacent the longitudinal center of the web than that discharged adjacent its edges so as to belly the web away from the drum and entrap the fluid between the web and the drum surface.

2. A method of drying a coated exible web which comprises, continuously passing a freshly coated web forwardly over a. heated drum and discharging fluid under pressure between the web and drum surface so as to provide a fluid cushion between the web and drum surface, a greater.

quantity of fluid being discharged adjacent the longitudinal center of the web than that discharged adjacent its edges so as to belly the web away from the drum and entrap the fluid between the web and the drum surface.

3. A method of drying the coated area of a flexible web comprising, continuously passing a web forwardly having a wet mobile substance upon its surface, discharging heated fluid under pressure into contact with the wet areas of said surface to dry said substance, said fluid contacting the web in such a manner as to place the web under transverse tension, passing said web over a drum and discharging heated fluid under pressure between the web and drum surface so as to provide a uid cushion between the web and drum surface, a greater quantity of fluidbeing discharged adjacent the longitudinal center of the web than that discharged adjacent its edges so as to belly the web away from the drum and entrap the uid

Images