US2513394A

US2513394A - Apparatus for coating paper

Info

Publication number: US2513394A
Application number: US595618A
Authority: US
Inventors: William H Barrett; Bernard K Asdell
Original assignee: Minnesota and Ontario Paper Co
Current assignee: Minnesota and Ontario Paper Co
Priority date: 1945-05-24
Filing date: 1945-05-24
Publication date: 1950-07-04
Anticipated expiration: 1967-07-04

Description

9 w. H. BARRETT ErAL 2,

APPARATUS FOR comma PAPER Filed lay 24. 1945 5 Shoots-Sheet 1 Inventors: William H.Barre'tt.

Bernard K. Asdell.

B3 9/. 3; MM

Attorney J 4, 1950 w. H. BARRETT EI'AL 2,513,394

APPARATUS FOR COATING PAPER Filed llay 24. 1945 5 Sheets-Sheet 2 h Bernard. K.Asdell.

Inven'bors I W lliam H.Barr'e'tt.

July 4, 1950 Filed lay 24. 1945 W. H. BARRETT ET AL APPARATUS FOR COATING PAPER 5 Sheets-Sheet 3 Wuham H Barrett Bernard. K Asdell July 4, 1950 w. H. BARRETT ETAL 2,513,394

' mum-ms FOR comma PAPER Filed lay 24, 1945 5 Sheets-Sheet 4 lnveni'ors' William H.Barrett. Bernard. K. Asdell.

"fitter-neg.

July 4,. 1950 Filed lay 24. 1945 5 Sheets-Sheet 5 26 FRc -S 23 s 2 I 9'L j i I02 l l I04- I \05 39 1 2 a i l-L I I :4; 63 163T." L W J- I h r 6 I l 98 i G I a I 1 l '3 me O l l I Q59 I 1" I'l I I O] i 27 FigfG Mez 6| 0 I00 63' Inventor-s: I William HBarreHi Bernard K.Asdel\.

999 I lo 1 I 8 04 rr-M Attorney Patented July '4, 1950 APPARATUS FOR COATING PAPER William H. Barrett and Bernard K. Asdell, International Falls, Minn., assignors to Minnesota and Ontario Paper Company, Minneapolis,

Minn.

Application May 24, 1945, Serial No. 595,618

7 Claims.

This invention relates to new and useful improvements in coating and particularly seeks to provide a novel apparatus for applying a smooth and uniform coating to a continuously moving web of paper or the like.

The present invention is particularly concerned with a paper coating apparatus and process to produce coating superior in respect to smoothness, freedom from imperfections, etc.

The base stock in web form may be of any suitable kind and the ingredients contained in the coating applied thereto may be chosen from a number of different materials. The coating mixture may include clay, calcium carbonate, satin white, etc., and an adhesive or binder such as starch, glue, casein or other suitable material all contained in an active dispersion.

It is an object of the invention to apply a coating upon a fast traveling web of paper, and the term "paper as used herein is intended to include any and all materials in web form whereon a coating may be applied and treated in accordance with the present invention, and no distinction is intended by the various classes of paper such as, for example, printing, photography, or papers and paperboard.

One procedure which may be and has been employed in coating 9. web of paper is broadly to apply coating composition to the web in greater quantity than is required to produce the desired weight of coating, and then to remove the excess part by the use of wiping or smoothing device such as blades or doctor rolls.

Heretofore in following the normal procedure in applying'coating to a moving web of paper considerable difliculty has been encountered as a result of a formation or multiplicity of imperfections in the applied coating. These imperfections are generally caused as a result of a passage of a moving web of paper to which an excess of coating composition has been applied over some form of smoothing or wiping device.

According to this invention a uniform film of coating composition may be applied to one side of the paper web while the web is firmly supported on the reverse side by a suitable supporting means. It will be observed that the apparatus in this instance comprises one or more units for treating each side of the paper. The apparatus may be employed to affect the coating of paper from which a greater portion of moisture has been removed and generally superior results are obtained where the paper being coated contains about 3% to about 10% of moisture. So far as the coating apparatus is concerned, it may be made to operate satisfactorily on paper having wide variations in moisture content and may be applied to various types of webs.

With the foregoing and other objects in view, the nature of which will become more apparent,

2 the invention will be more fully understood by reference to the drawing, the accompanying detailed description, and the appended claims.

In the drawing, which illustrates an embodiment of the invention:

Figure 1 diagrammatically represents in elevation one form of the apparatus adapted to apply two coatings of the material to opposite sides of the web.

Figure 2 is a side view of a single coating unit with the fountain and coating receiving vessel in section, and is the preferred form,

Figure 3 is a side view of a modified form of a coating unit showing means for applying pressure between the various rolls and the means for separating these rolls.

Figure 4 is a front view and elevation of the coating fountain with the rolls removed.

Figure 5 is a side view of the fountain shown in Figure 4;

Figure 6 is a, view taken along line 6-6 of Figure 5.

Referring to the drawing, a paper web H is withdrawn from the suitable roll 10 and passes over roll l2. The roll i2 is supported by arm i3 and so arranged that tension is maintained upon the moving web of paper. The paper passes over the roll l4 and between tensioning rolls I5 and I6 and the web of paper passes over rolls l1 and 2| before reaching the coating unit.

It often occurs that paper having a moisture content of about 3% to about 10% is resistant to the absorption of moisture and thus the coating material does not uniformly wet the paper. This results in a non-uniform coating being applied to the web. This difllculty may be overcome by lightly brushing the surface of the paper just prior to the application of the coating material. A suitable way of accomplishing the foregoing is to softly brush the paper surface by rotating bush l8. These brushes preferably should rotate in the opposite direction to the travel of the web, and while the web is under tension. If the web is not under suflicient tension when it passes between the brushes l8, additional tension may be applied by roll l9 which is supported by arms 20.

The paper web is supported by rotatable rolls 22 when the coating is applied by applicator roll 23. The coating material is supplied to the container 28 from a suitable source of supply (not shown). The coating material withdrawn from the coating container passes into pipe 29, and then passing to pump 30 and then is forced through by the pump 30 through the pipe 3| to the fountain 21. A head of the coating material is maintained above the lower nip formed by the metering roll 26 and the applicator roll 23 so that a surplus of coating material is supplied at the nip of the said rolls. This may be fountain 2'l through pipe 3|.

6 of material.

accomplished by connecting coating head maintaining member 32 in the supply pipe 3|. The coating material is fed to the fountain 21 which has the open top closed by applicator roll 23 and metering 'roll 26. Positioned above the applicator roll 23 is smoothing roll 24 and there may be positioned above the smoothing roll a roll 25. One of the purposes of the roll 25 is to aid in cleaning the surface'of the smoothing roll. It is essential that the smoothing roll surface be clean at the time it is carrying out its function of smoothing the coating upon the applicator roll.

The paper after receiving the coating, passes over suitable drier or,driers such as 33, 34, and 35,

l and then over roll 40. It has been discovered that a smoother and more uniform coating is obtained when the coating on one side is made by two or more applications and at least partially dried between each application.

The four coating units shown in' Figure 1 are similar in construction and are indicated generally at 36, 31, 38, and 39. The paper after leaving the driers 4!, 43 and 42 passes over roll 44 and then the opposite side receives the coating mate- I there should be a differential hardness between rolls Hand, 23, between

rolls

23 and 26 and between rolls 23 and 65. In other words the hardness of

rolls

22 and 23 should be of different hardness. There should be a difference of hardness between

rolls

23 and 26 and likewise there should be a difference of hardness between rolls 23 and 65. This may be accomplished by using a rubber covered roll as the applicator roll 23 and using metal-surfaced rolls backing roll 22, metering roll 26 and smoothing roll 65. The coating material is supplied to container 28, which container has an agitator or screw conveyor 54 which keeps the material in motion, thus preventing dead spots in the coating material. The coating material is withdrawn from thecontainer 28 by pump 30 through means 29 and forced into the coating Positioned in the pipe 3| is a suitable means 55 for removing any heavy or foreign particles that may be contained in the coating material.

It is important that the temperature of the I coating material does not substantially vary. For

example, a variation of temperature greater than ten degrees will cause the viscosity of the coat- 1 ing material to change and thus result in a variation in the coating material applied to the web To hold the temperature of the coating material constant, a temperature control means 56 such as a cooling device is so'positioned that the pipe 3| passes therethrough. The temperature of the coating material should'be maintained below the point where skinning starts.

The skinning point varies with the different kinds of coating compositions. The coating material after passing the temperature control means passes to a member 32 which maintains a head I above the lower nip formed by the metering and applicator roll. Any overflow from the means for maintaining the head passes back to the coating container 28 by means of pipe 58.v The coatmember 59 positioned in the fountain and follows the course indicated by the arrows in Figure 2. This keeps the coating material in constant motionin the fountain.

Secured to the upper wall of the fountain is sealing blade 62 carfied by suitable support 61. Also as illustrated in Figures 2 and 5 of the drawings, there is secured to the open side of the fountain a member 63 which supports sealing doctor member 64. The purpose of the doctor member 64 is to seal the fountain and at the same time clean the surface of the metering roll 26 as it leaves the position of the fountain where the coating material contacts this roll. When it is desired to change the coating color or shut down the coating apparatus, any coating material left in the fountain 21 is removed by opening suitable drain 60 positioned in the bottom of the coating fountain. The drain is normally closed by a suitable cut-off valve. The coating fountain as shown in Figure 2 has a partly rounded bottom and with the coating being forced into the fountain and following the path shown by the arrows prevents any dead spots in the coating in the fountain.

The coating material is picked up by the applicator roll 23 and the amount carried by this roll is determined by metering roll 26. The coating material then passes under the surface of the smoothing roll 65 which eliminates any blemishes which might be contained in the film of coating material on applicator roll 23. Any coating material that may be picked up by the smoothing roll 65 is removed from the surface of this roll bysuitable doctor 66. The material removed by the doctor 66 is returned to the coating supply by any suitable means, for example, trough 61.

To control the pressure applied to the smoothing roll surface, suitable air diaphragm loading device 68 (Figure 2) is provided and this is connected to the smoothing roll shaft through means 69. For separating the smoothing roll from the applicator roll there is provided lift arm or means 10 which may be connected to any suitable lift means such as a motor, and this arm '70 is connected to the shaft of the smoothing roll 65 at 1|. Any coating material that may have accumulated on the backing roll is removed by a suitable doctor blade I09 and returned by trough I III or other means to coating supply container.

In Figure 3 is shown a modified form of coating unit in which means of separating the metering roll from the applicator roll and the backing roll from the applicator roll and the smoothing roll from the applicator roll. The same means may be utilized for varying and controlling the amount of pressure between these rolls. It is to be understood that the means for separating the rolls may be used with the coating units shown in Figures 1 and 2. This .is essential as it tends to control the amount of coating applied to the paper and facilitates cleaning of the coating unit after any particular run or when the coating color is to be changed. The smoothing roll 65 is lifted by arm I0 which is connected to a shaft and a motor (not shown).

The backing roll 22 is supported by a member 82 which is hingedly mounted at 83. From member 82 extends a substantially horizontal arm 84 and to this member near its outer end is con-' nected piston 86 which is part of pressure cylin der 85. The pressure cylinder 85 is hingedly connected at 81. This cylinder permits the control of pressure as applied by the backing roll and applicator roll and provides means for separating the applicator roll and the backing roll. Should any coating be transferred to the surface of the backing roll 22 the coating is removed by suitable doctor I08 and the removed coating material is carried away by trough I81.

The applicator roll is supported by suitable members BI and this roll 23 has a covering that has resilient properties. The covering may be of rubber, synthetic or natural, in fact any material that has resilient properties. By providing the applicator roll with a covering that has resilient properties a superior coating is produced.

The metering roll 26 is movablysupported by members which are hingedly connected at 16 to a suitable base member. Formed as a part of the member 15 and extending outwardly therefrom are arms I1. To the arms 11 are attached pistons which are operatively mounted in cylinder 18. These pressure cylinders are hingedly connected to the base at 88. The pressure cylinder 18 is used for the purpose of controlling the pressure applied between the metering roll and the applicator roll as well as for quick separation of the metering roll and the applicator roll. There is provided a suitable adjustable means between the

rolls

23 and 28 and this means is composed of members 12 and I3 and internally threaded member 14. This suitable means can be adjusted so as to control the space distance between the metering roll and the applicator roll so that the amount of coating remaining on surface of the applicator roll is controlled. Positioned above the applicator roll is smoothing roll 24 and any coating picked up by the smoothing roll is removed from the roll surface by the doctor blade 66a and the removed coating material is returned to the coating container through suitable catch pan or trough 81a.

A pressure ride roll 25 is mounted above the smoothing roll and in contact with the smoothing roll surface. The pressure and riding roll is adapted to rotate in the same direction to that of the smoothing roll and the riding roll speed is so controlled that any tendency of the smoothing roll 24 to whip or to assume a position different from that selected can be controlled.

Connected to the smoothingroll shaft is arm 88 which has connected to its outer end at 89 two pressure indicating scales 98. If the smoothing roll tends to move in either direction from its normal position this movement i indicated on the scales 98. The scales used may be of any suitable type which will indicate the pressure being applied to them by the outer end 89 of arm 88. By changing the speed of rotation of the riding roll the tendencyfor the smoothing roll to move from its normal position is overcome. Means are provided for loading pressure on the riding roll and this is accomplished by air diaphragm member 9| which is connected through means 92 to the shaft of the riding roll. For separating the smoothing roll from the applicator roll and the riding roll from the smoothing roll there is provided motor rod 94 which is connected to member 95 which is mounted on the shaft of the riding roll 25. A member 95A is attached to member 95 and is operatively connected to the arm 88 at 96.

As shown in Figure 5, the fountain 21 is suitably supported in relationship to the applicator roll 23 and the doctor roll 26 so that the area adjacent the nip formed by these two rolls normally contains coating material. The open top of the fountain has a seal doctor blade 62 positioned along one of the open sides and on the opposite open side is positioned doctor seal 64. On the opposite side end of the top of the fountain is positioned dike member I02 which c0- operates with applicator roll 23 and metering roll 28. Sealed doctor 62, the doctor seal 64 and dikes I82 form part of the fountain and cooperate with the surface of the metering roll and a notch formed along the outer ends of the applicator roll as shown in Figure 5.

Dike supports I84 are suitably secured to the fountain sides and the dike adjusting screws are operatively connected to the (like supports. Secured to the outer end of the dike adjusting screw is handle wheel I05 for adjusting the position of the dike. Mounted on the inner side of the dike are members 1211 which cooperate with the sealing blade 62 and seal in the fountain in any adjusted position of the dike.

To permit adjustment of and positive contact between seal member 64 and the surface of the metering r011 26 there is provided an adjustable doctor pull rod 98 having handle wheel 99v mounted near the outer end thereof. Spring I08 is mounted on the pull rod 98 for maintaining the member 69 in positive contact with the surface of the metering roll. The pull rods are connected to seal member 64 at IIII. The fountain 21 is suitably supported in position by members 91.

The apparatus may-be used with coating composition having a solid contents varying over considerable range but applicants process requires that the coating composition have a solid contents in excess of about 60 to about 75%.

By way of example the process may be carried out as follows: 7

The surface of the moving web to be coated is brushed while the paper is under tension and the paper then passes between the applicator roll 23 and the backing roll 22. A coating material is picked up by the applicator roll surface from the fountain 21 and the metering roll controls the amount of coating material that the applicator roll will carry off to the smoothing roll. The

- smoothing roll then removes any surface defect that may be in the coating film and thereafter the film is transferred to the paper while supported on the backing roll. The film of coating material is then dried and the second application of coating material is applied to the same side. Thereafter in like manner the coating material is applied to the opposite side of the sheet.

Selected amounts of coating material is applied to the sheet, and this is accomplished by controlling the shearing speed between the metering roll and the applicator roll. For example, at a shearing speed of 1,300 feet per minute a coating weight per ream of about nine pounds is obtained by each coating application while at a shearing speed of about 1,500 feet per minute about three pounds of coating per ream is obtained by each coating application. It has been discovered that the coating weight can be more sharply controlled if the shearing speed between the metering roll and the applicator roll and between the smoothing roll and the applicator roll is controlled. As

. the shearing speed is increased the coating weight wise the sum of the speed of the applicator roll and the smoothing roll. The preferred form of the invention includes a backing roll, an applicator roll and a doctor roll mounted in substan= tially the same horizontal plane, a coating foun-' tain positioned under a portion of the doctor roll and under a portion of the applicator roll so that the area adjacent the nip formed by the

rolls

23 and 26 is in the coating material container; means for supplying a continuous stream of coating material at a substantially constant temperature and under super-atmospheric pressure to the coating container.

A modified form of the invention requires the use of the riding rol125 as shown in Figure 3. For most coating operations, the use of the riding roll is not required.

To those skilled in the art many modifications and widely different embodiments and applications of the invention in the general field of coattor roll, a sealing means attached to the opposite side of the open top of the fountain and contacting the applicator, dike-like members attached -.to the ends of the fountain and contacting the applicator roll and the, metering roll, and means niaterialv in the fountain for maintaining coating under super-atmospheric pressure. 3

5. In a coating apparatus comprising a back 7 ing roll, an applicator roll and a metering roll,

ing will be readily apparent. It should be understood that the details of our preferred process as described may be subject to some change without departing from either thespirit or scope of from the applicator roll, a fountain directed tothe invention. It is intended that the invention said three rolls mounted at substantially the same horizontal plane, a fountain having an open side directed toward the metering roll and the.

applicator roll, a doctor blade mounted along-one side of the open top of the fountain and contact- -ing the doctor roll, a sealing means mounted'on the opposite side, of the" open top or fountain and contacting the. applicator-roll, dike-like members mounted on'the other two sides of the open top of the fountain and contacting the doctor roll'and the applicator roll,and means-for supplying coating to the fountain under e.- super-' atmospheric pressure.

6. In a coating. apparatus comprising a ba'cking roll, an applicator roll and a metering roll said three rolls mounted in substantially the same horizontal plane, a fountain having an open ward the applicator and metering roll so that the K fountain and the said applicator and metering rolls form a coating container, a coating mate- 1 rial inlet in said fountain, and means in the fountain positioned in alinement with the inlet to cause the incoming coating materia1 to follow a path along the walls of the fountain.

2. In a coating apparatus, comprising 'an applicator roll, a metering roll at a selected distance from the applicator roll, a smoothing roll at I a selected distance from the applicator roll,

means for controlling the pressure between metering roll and applicator'roll, means for controlling the pressure between the smoothing roll and the applicator roll, a fountain having an open side directed toward the applicator roll and the metering r011 so that the fountain and the metering roll and the applicator roll form a coating container, means for supplying a continuous stream of coating to the fountain and means for controlling the temperature of the coating material supplied to the fountain.

3. A coating apparatus for coating a moving web of paper comprising, a backing roll, anapplicator roll and a metering roll mounted in substantially a horizontal plane, a fountain in juxtaposition to the metering roll and the applicator roll, a smoothing roll in juxtaposition to the applicator roll for smoothing the coating on the roll, an applicator roll and a metering roll, said three rolls mounted in substantially the same horizontal plane, a fountain having an open top top and positioned below a portion of the metering roll and a portion of the applicator roll so that the fountain encloses the area adjacent the nip formed by the saidmetering roll and the said applicator roll, means for maintaining a substantially constant supply of coating material in the said fountain and means for controlling the temperature of the coating material flowing through the fountainl I 7. In a coating apparatus said three rolls mounted in substantiallythesame horizontal plane, a smoothing roll mounted above the applicator roll and spaced at a pre-determined distance therefrom, a fountain positioned beneath a portion of the metering roll and a portion of the applicator roll, whereby the fountain,

the metering roll and the applicator rollform a closed coating container, and means for supplying coating material to the fountainrat a pressure greater than atmospheric pressure. 7

WILLIAM H. BARRE'I'I. BERNARD'K. ASDELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,202,165 Conner Oct. 24, 1916 1,212,854 Vuono Jan. 16, 1917 1,556,087 Dittmar Dot. 6, 1925 2,064,776 Wilkinson et al. Dec. 15, 1936 2,105,488 Massey et al. Jan. 18, 1938 2,263,131 I-Ioza Nov. 18, 1941 2,277,287 Beckman Mar. 24, 1942 2,287,905, Richmond et al. June 30, 1942 2,312,927 Murray Mar. 2, 1943 2,316,176 Lavett Apr. 13, 1943 2,355,919 Lipsius Aug. 15, 1944 2,369,378 Thiele et al. Feb. 13, 1945 2,398,844 Muggleton et a1. Apr. 23, 1946 2,406,056 Barrett Aug. 20, 1946 2,406,057 Barrett et al Aug. 20, 1946 2,416,789 Barrett et al. 'Mar. 4, 1947 'comprising'a back ing roll, an applicator roll and a metering roll,