US3078822A - Coating apparatus - Google Patents

Description

Feb. 26, 1963 T. N. CARTER COATING APPARATUS Filed March 25, 1959 [JV/[M739 United States Patent Ofiiice 3,078,822 Fatented Feb. 26, 1963 3,678,822 COATING APPARATUS Thomas N. Carter, Hamilton, Ohio, assignor to Champion Papers Inc, a corporation of Osiris Filed Mar. 25, 1959, $591. No. 891,774 3 Claims. (Ci. 11S33) This invention is concerned with an apparatus for the production of coated substrates, primarily paper substrates. More particularly, the invention is concerned with an apparatus for producing cast coated substrates wherein an aqueous suspension including a mineral pigment such as clay or calcium carbonate and an adhesive, such as casein, is applied to the substrate and, prior to drying and while still in a moldable state, the coated surface is pressed against a polished metal surface, such as a rotating drum or endless belt, and subsequently dried to reproduce on the coating surface a mirror image of the surface against which it is dried. The resultant coated substrate, primarily coated paper, is characterized in that it is provided with an exceptionally fine printing surface of high absorbency and smoothness, enabling the use of printing techniques and the excellent reproduction of printed material of a quality not fully realized with other types of coated papers. This method is described in Patent 1,719,166, dated July 2, 1929, issued to Donald B. Bradner.

By paper, is meant a substrate which is formed on a Fourdrinier or cylinder machine regardless of its basis weight or such distinction as might be made between paper and, for example, board, as is customary in the industry.

The present invention therefore has broad application in the paper industry and represents an improvement over the apparatus and method of coating paper as shown, for

example, in Patent 2,316,202 dated April 13, 1943, issued to Edgar Warner.

One of the problems encountered in the manufacture of cast coated papers is that of manufacturing speeds. Another problem is cost of manufacture which is a function of not only speed of manufacture but also the cost of raw materials. Still a further problem is that of securing a proper raw stock upon which the cast coated product may be formed.

Various proposals have been made in attempts to solve one or more of these problems. Such proposals have included machine coating of the base raw stock prior to cast coating, and even more recently, combining a pre coating operation with the cast coating operation to obtain the advantages of a wet precoat, among others, as described in the copending application of Edgar Warner, S.N. 797,123 filed March 4, 1959. All of these proposals have merit and as such have some effect on the results, but prior to the development of the present apparatus the advantages to be gained from the most promising of the proposals, namely that disclosed in the aforesaid Warner application, have not met with the success believed to be desirable.

It has been found that the apparatus disclosed herein may be used toperform the aforesaid method and that the costs of cast coated paper may be reduced somewhat due to the increased speeds with which the coating and casting operation may be carried out.

An object of the invention is to produce an apparatus for the manufacture of cast coated paper.

Additionally, an object of the invention is to produce apparatus for manufacturing a cast coated paper of superior quality and at less cost than was heretofore possible.

A further object of'the invention lies in the development of apparatus for manufacturing coated paper of superior quality and at greater manufacturing efficiency than heretofore possible.

These and other objects of the invention not specifically set forth but nonetheless inherent therein, may be accomplished by providing a combination of a web tensioning means for flattening the substrate as it is fed into the coating equipment, said means acting to relieve the tension as the substrate is fed into a precoating unit and means disposed behind the precoating unit for doctoring or trowelling in the precoat, followed by means for applying a final coating to the precoated substrate immediately prior to the means for molding the coating and drying same. Preferably the distance between the doctoring or trowelling means and the final coating means is maintained at a minimum, in accordance with method in aforesaid copending application of Edgar Warner.

Having referred in general terms to the nature and objects of the invention, a detailed description thereof will now be set forth. In describing the invention, reference Will be made to the drawing appended hereto and forming a part of the specification which comprises a side elevational view of the novel apparatus which may be used in effecting the method referred to hcreinabove.

It will be seen from an inspection of the drawing that the substrate S is mounted in roll form on an unwind stand 1. This stand is adapted to receive a roll of raw stock 3 which has been wound on a suitable mandrel 5. The mandrel 5 has its ends removably fixed in a pair of journals 7 (only one shown). Preferably, a braking mechanism 9 is associated with the journals 7 such that the rate of rotation of the mandrel 5 may be varied. As shown in the drawing, the brake mechanism is in schematic form since there are available on the market several types of braking devices which may be used to produce the desired result.

From the unwind stand 1 the substrate, as a continuous web, S, is threaded over a pair of guide rolls 11 and 13 which are mounted on a frame 10 by means of a pair of identical depending arms 17. The rolls 11 and 13 serve to flex the substrate to condition it, i.e., aid in removing wrinkles and the entrapped stresses which are formed therein during its manufacture, prior to the time the web enters the coating operations.

From the rolls 11 and 13 the substrate is passed over a rubber covered tension regulating roll 19. This roll 19 is mounted in suitable journals on the frame 10 and is characterized in that it is a driven roll, being driven by belt 21 through a variable speed transmission 20 which derives its power from shaft 22 which in turn is driven from the same prime mover 25 that drives the mechanism imparting movement to the traveling surface against which the coated substrate is to be pressed and dried. The surface of the rubber covered roll is such that the friction generated between web and roll surface is sufficient to prevent slippage between the substrate and the roll surface.

In carrying out the operation of the apparatus thus far described, the rubber covered roll 19 is driven at a speed slightly in excess of the speed of the substrate S as measured at a point between roll 13 and the lead in side of the roll 19. The effect of this arrangement is to maintain a tension between rollstand 1 and regulating roll 19 and to reduce and maintain a substantially constant tension in the web between roll 19 and the first coating operation. This reduction in tension on the feed-off side of the roll 19 is possible because of the fact that the substrate possesses inherent stretchability, up to .6% per unit length. Thus the substrate is stretched into the lead in side of roll 19 because the friction is SllffiClCIliI between roll 19 and the substrate to cause it to be put under tension and stretched. However, as

the substrate passes to the feed-off side of the roll it contracts to a substantially zero stretch, i.e., the stretch induced by roll 19 is dissipated, with the net result being that the tension is reduced from one-half to two-thirds or more of its value on the unwind side of the roll 19, but is constant.

From the tension regulating roll 19 the substrate is threaded beneath a further guide roll also mounted on the frame 10. Guide roll 15 is not driven. From guide roll 15 the substrate is passed into the precoating operation. The precoater, so called to distinguish it from the final coater, is comprised of a driven color roll 24 partly immersed in the coating suspension provided by suitable feeding means to a trough-like pan 26. This color roll 24 may be rotated in either direction and serves to pick up coating from the pan 26 and carry it onto the substrate S.

From the color roll 24 the substrate is fed into a trowelling and doctoring apparatus 30. This apparatus consists of a pair of spaced rolls 32 and 34 and a doctor blade 48. The rolls 32 and 34 are mounted for vertical adjustment in a pair of vertically slotted depending arms 36. Each of the adjustment means may comprise a. journal block 38 slidable in slot 40 and fixed in the desired position by means of a vertically disposed threaded hanger bolt 42 attached to the journal blocks 38 and passing upward through a horizontal ear or lug 44 and locked thereto by a nut 46.

The rolls 32 and 34 are as indicated, spaced in the direction of travel of the substrate S through the apparatus. Disposed in this intervening space and fixed to the frame 10 is the doctor blade 48. Preferably, the doctor blade is a rotating doctor, such as shown in Patent 2,598,733 issued June 3, 1952 to Edgar Warner. It will be noted that the relationship between the doctor blade 48 and the rolls 32 and 34, one each of which immediately precedes and immediately follows the doctor blade 48, is such that the substrate is caused to break over the doctor 48 in a generally serpentine path. This arrangement, coupled with the constant tension in the web as controlled by roll 19, causes the coated substrate to draw against the doctor blade 48 and results in a trowelling of the coating into the interstices of the paper.

Since there are various factors which affect the degree of trowelling and doctoring action that the doctor blade 48, among the more important of which are, the angle at which the substrate passes over the doctor blade and the amount of break effected thereover, it may be seen that because the rolls 32 and 34 are vertically adjustable relative to the doctor, they may be adjusted to vary both the approach angle of the substrate S and the degree of break over the doctor blade 48.

The substrate is thus precoated, the precoat consisting of an aqueous dispersion of an adhesive and a mineral pigment having been applied thereto and thoroughly trowelled onto the surface of the paper. From the precoating operation the substrate S travels in a horizontal path from roll 34 to a roll 52 which rotates in the direction of movement of the substrate.

From roll 52 the coated substrate is passed into a final coating apparatus 50 including a color roll 51 where it receives a further coating of the aqueous suspension of adhesive and mineral pigment before it is pressed into contact with the polished non-adherent surface 100 shown in the form of a rotating drum. Preferably, the second coating is comprised of the same mineral pigment and adhesive, but the slurry may be less viscous than that applied at the precoater.

The drum 100 or other means is driven from a prime mover which as has been indicated is that which also drives the tension regulating roll 19 through the variable speed transmission 20. With the peripheral speed aforementioned Warner Patent 2,316,202 and need not therefore be described in detail. It will be noted that the final unit 50 acts to flood the still wet substrate with an excess of coating prior to the time it passes into the nip defined between press roll 51 and polished surface of drum or other supporting medium 101.

The novel combination of apparatus described is highly effective in carrying out the referred to Warner method of cast coating paper. An essential operation performed by the apparatus is that proper tensioning of the web throughout the entire operation to assure proper operation of each phase of the coating application which results in a continuous cast coating operation at an increased speed over that which has been realized before.

Having described the invention, both novel method and novel apparatus for the production of cast coated papers, it will be apparent that changes and modification thereof will occur to one skilled in the art and which are within the spirit and scope of the inventive concept limited as it is only as defined hereinafter, where- What is claimed is:

1. An apparatus for manufacturing coated paper comprising a frame; a tension control means, a plurality of coating applicator means and a rotatable casting drum and press roll defining a nip mounted in sequence on said frame; an unwind stand associated with said frame, for playing off a web of paper under tension from a roll carried thereon through said tension control means, said plurality of coating applicator means and onto said casting drum; drive means mounted on said frame and connected to both said casting drum and said tension control means; said last mentioned means comprising a rubber covered roll in contact with said web over at least half its circumferential surface and said drive means including a variable speed transmission means whereby the relationship of speed between the nip defined between said press roll and said drum and said rubber covered roll may be varied to produce a constant tension in said web from said drum, irrespective of variations in tension which may occur between said unwind stand and said rubber covered roll.

2. An apparatus as defined in claim 1 wherein the first of said coating applicator means comprises a color roll and a doctor means including a blade disposed transversely to the path of movement of the web and in contact therewith and adjustable roll means immediately preceding and following said blade for adjustably controlling the angles at which the web passes over and leaves the line of contact with said blade.

3. An apparatus as defined in claim 1 including further roll means mounted on said frame interposed between said unwind stand and said tension regulator means, said roll means being arranged to cause said web to flex first in one direction then in the opposite direction before its entry into said tension regulator means.

References Cited in the file of this patent UNITED STATES PATENTS 956,602 Pulsifer May 3, 1910 2,631,561 Calton Mar. 17, 1953 2,678,284 Holt May 11, 1954 2,678,890 Leighten May 18, 1954 2,810,966 Bicknell Oct, 29, 1957

Claims (1)

1. AN APPARATUS FOR MANUFACTURING COATED PAPER COMPRISING A FRAME; A TENSION CONTROL MEANS, A PLURALITY OF COATING APPLICATOR MEANS AND A ROTATABLE CASTING DRUM AND PRESS ROLL DEFINING A NIP MOUNTED IN SEQUENCE ON SAID FRAME; AN UNWIND STAND ASSOCIATED WITH SAID FRAME, FOR PLAYING OFF A WEB OF PAPER UNDER TENSION FROM A ROLL CARRIED THEREON THROUGH SAID TENSION CONTROL MEANS, SAID PLURALITY OF COATING APPLICATOR MEANS AND ONTO SAID CASTING DRUM; DRIVE MEANS MOUNTED ON SAID FRAME AND CONNECTED TO BOTH SAID CASTING DRUM AND SAID TENSION CONTROL MEANS; SAID LAST MENTIONED MEANS COMPRISING A RUBBER COVERED ROLL IN CONTACT WITH SAID WEB OVER AT LEAST HALF ITS CIRCUMFERENTIAL SURFACE AND SAID DRIVE MEANS INCLUDING A VARIABLE SPEED TRANSMISSION MEANS WHEREBY THE RELATIONSHIP OF SPEED BETWEEN THE NIP DEFINED BETWEEN SAID PRESS ROLL AND SAID DRUM AND SAID RUBBER COVERED ROLL MAY BE VARIED TO PRODUCE A CONSTANT TENSION IN SAID WEB FROM SAID DRUM, IRRESPECTIVE OF VARIATIONS IN TENSION WHICH MAY OCCUR BETWEEN SAID UNWIND STAND AND SAID RUBBER COVERED ROLL.

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