US3044392A - Papermaking machine - Google Patents

Description

July 17, 1962 R. G. MINARIK PAPERMAKING MACHINE 4 Sheets-Sheet 1 Filed July 10, 1959 y 1962 R. G. MINARIK 3,044,392

PAPERMAKING MACHINE Filed July 10, 1959 4 Sheets-Sheet 3 g .4. i ABA (0-98) J9 Ace (0.69)

,/J ADC (058) v 3 1/7 1/6 AFE (0.50 x

J5 AGF (0.49)

AHG (0.75)

July 17, 1962 R. G. MINARIK PAPFRMAKING MACHINE 4 Sheets-Sheet 4 Filed July 10, 1959 United States Patent Ofifice 3,044,392 PAPERMAKENG MACH-EYE Rudoif G. Minarik, Menasha, Wis, assignor to Kimberly- Clark Corporation, Neenah, Wis, a corporation of Deiaware Filed July 10, 1959, Ser. No. 826,301 6 Claims. (Cl. 100162) This invention relates to papermaking machines and more particularly to calenders or calender stacks.

A calender for paper or like material comprises in general, a plurality of uprightly aligned calender rolls in a stack. The bottom roll or king roll of the stack is driven by a suitable mechanical or electrical mechanism, and each of the rolls above the lowest roll is driven by the roll immediately below it by friction. Paper sheet is passed through the nips of these rolls downwardly through the stack, and the paper is acted on so as to be smoothed, ironed, compacted and given a fine smooth finish.

Such a calender is employed as a part of the drier section of a papermaking machine, and the rolls are made of a fine grained cast iron that takes a high polish in order to give a fine finish to the paper. A calender stack may also be employed beyond the drier end of the machine for imparting higher degrees of finish to paper than is possible with machine calenders. These are so-called supercalenders and have alternate intermediate filled rolls of materials possessing resilient properties in lieu of inert metal rolls.

It has been found in the operation of such calender stacks, particularly those in the drier end of a papermaking machine, that the stacks produce a barring or alternate depressions and high areas in the paper across its width. I have determined that apparently these crosswise depressions and ridges in the paper are due to vibrations of the calender rolls horizontally, and thus this barring is in reality chatter marks caused by roll vibration.

Each of the intermediate rolls in such a stack at each of its nips is subjected to at least two horizontal forces. One of these forces is from the tension on the paper sheet as it passes around the roll, and the other force is due to the transmission of the power that is utilized for driving the stack from the lowermost or king roll.

These forces are horizontal and additive and tend to deflect each roll horizontally, similarly to a uniformly loaded beam, to pull the centers of the rolls out from the roll nips. The roll centers on leaving the nips, which contain the forces causing the horizontal deflecting movements, tend to return into the nips, since the weight of the upper rolls is thus relieved from the particular roll being considered. These horizontal movements of the rolls occur quite rapidly, and the actions of the rolls in leaving and then returning to the nips apparently result in the horizontal bars or changes in thickness of the paper.

As might be expected, among the factors that may increase barring are increased calender roll width, more slender rolls, higher speeds, higher sheet moisture, and

varying friction characteristics of the sheet being calendered. The speed of operation and width of calenders has been increased from time to time, and under these conditions the barring effect of the calender stack becomes intolerable.

It is an object of the present invention to provide an improved calender construction so improved that barring of the paper or other sheet material passing through the calender is substantially prevented.

I have found that if the horizontal forces on the calender rolls at the nips are neutralized, the rolls will not be drawn out of the nips as previously described, and the horizontal vibration of the rolls causing barring of the paper stock does not occur. It is therefore an object of the invention to provide an improved calender construction in which the lateral forces on the rolls at the nips are essentially neutralized.

Concisely, the invention contemplates the offsetting of each of the rolls of a calender stack with respect to the rolls above and beneath it in order to balance out the lateral forces and prevent lateral deflections and vibrations of the rolls. Since the paper sheet passes around opposite sides of alternate rolls of the calender stack, the rolls are each offset in an opposite direction with respect to rolls above and beneath it in order to so balance the lateral forces on the roll.

The invention consists of the novel constructions, ar-

rangements, and devices to be hereinafter described and claimed for carrying out the above stated objects and such der stack of the type embodying the principles of theinvention;

FIGURE 2 is a schematic side view of the calender stack illustrating the forces acting on the rolls when the rolls are positioned on a single vertical axis, with the rolls shown separated for better illustration of these forces;

FEGURE 3 is a schematic side view of the two top rolls of the calender stack showing the offsetting of the lower roll (the offsetting being shown exaggerated for purposes of illustration) with respect to the top roll according to the present invention;

FlGURE 4 is a diagram showing the directions in which the centers of the rolls in the calender stack are offset with respect to vertical center lines of higher rolls, according ot the invention; and

FIGURE -5 is a schematic side view of a paper calender stack constituting a modification of the invention,

Like characters of reference designate like parts in the several views.

Referring now to the drawings, the calender illustrated in FIGURE 1 comprises a pair of upright frame members 10 and 11 fixed on a floor 12 and calender rolls 13, 14, 15, 16, 17, 18, 19, and 20 disposed in an upright stack.

Each of the rolls 4 to .20 is illustrated as being of the same size, and the lowermost roll 13, which may be termed a king roll, is larger in size than the others. The king roll 13 is provided with opposite journals fitting in bearings 21 that are disposed in a frame 22 by means of which the king roll is rotatably mounted. The king roll 13 is driven from a suitable prime mover such as a motor 23, and any suitable power transmitting connections may be provided between the motor 23 and one of the journals of the king roll 13 for this purpose.

Each of the rolls 14 to 20 is provided with opposite journals fitting within bearings 24. The bearings are carried by arms 25 which are mounted by means of pivots 26 on the frame member 11. Each of the rolls 14 to 20 bears with its weight and the weight of the rolls above it on the roll below it. The rolls may be separated from each other by use of a link 27 acting on the uppermost arm 25 and the links 28 connecting the consecutive arms 25 together for the purpose of cleaning the rolls or for other maintenance work.

A guide roll 29 is supported by the frame member 11, and the paper sheet 30 acted on by the calender stack extends over the guide roll 29, into the nip between the rolls 19 and 2% around the right side of the roll 19, through the nip between the rolls 18 and 19 and around the left side of the rolls 18. The paper 30 extends through the nip between the rolls 17 and 18 and from thence extends in the same manner around opposite sides Patented July 17; 1962- of the r olls 17, 1 6, 15 ,and 14 and. through the nips hetussnl s e ll T paper t nd a n e t side of the roll 14 as seen in FIGURE 1 and through the nip between the king roll 13 and the roll.14 as shown.

The sheet 30 may be drawn from the drier end of a paper machine (not shown) to the guide roll 29 and may be drawn from the calender stack to a winder (not shown).

Each of the rolls 13 to 20 has at each of its nips horizontal forces acting on the roll, which would tend produces a corresponding force (t) on the roll 18 but in the opposite. direction. The forces due to the sheet on the. rolls 19, 17, and 15 are toward the left as seen in the figures, and the forces on the other intermediate rolls 18, 1 6, and 14 are to the right as seen in the figures. As far as is known, the forces due to the tension on the sheeti30 are substantially the same throughout the calender stack.

A formula for determining the force (1') at each nip due to tension in the paper Web is as follows:

i- (lbs. per lineal inch) horsepower stack to drierX 33,000

sheet Width in inchesX speed of sheet in feet per minute Ina particular example, the power transmitted through thesheet 30 from the calender roll stack back into the drier section, of the associated paper machine was 32 horsepower. The power transmitted through the paper sheet 39' between the stack and a winder in back of the stack was about the same, namely, 32 horsepower. The speed of the paper was 1850 feet per minute and the sheet width was 320 inches. The formula givenabove with these values sub stituted is as follows:

t= g=1.8 p.l.i. (pounds per lineal inch) Thus, for theexample just given, the horizontal forces tangential to therolls due to the tension in the sheet is ]l.8 pounds per lineal inch, and this is apparently approximately thev same ateach nip as is illustrated in FIGURE 2.

Although the forces dueto the paper sheet at each 7 nipare appreciable, nevertheless, the major parts of the total. horizontal forces at thenips between the rolls are ratherdue to the driving forces on the rolls. As has been mentioned, the calender roll stack is driven from thernotor 2 3, and thepower fromthe motor provides additional forces .at the nips between the rolls.

the upper roll, may .be determined by the following formula. (assuming thatthe upper rolls 14 'tol20 are identical: and thereforethatthe horsepower is equally distributed betwecn the, nips of the stack) 1.15 p.l.i.

I s p At the. nip betweenthe upper two rolls 19 and 20, for exan'rple, the force f)' on 'the'upper. roll, which is the force driving.

As is indicated in FIGURE 2, the tangential force on the roll 19 at its upper nip is the sum of the forces (1.) and (1) which, for the particular example given, is l.8+1.l5 or 2.95 pounds per lineal inch.

The horizontal forces at the other nips are likewise the sums of the forces due to the sheet tension and the roll driving forces. For successively lower nips below the highest, the tangential driving forces increase in arithmetic progression. In the particular example given, the tangential driving forces at the second nip from the top is 2.30 p.l.i. or 2 l.15 p.l.i., which is the tangential driving force (f) at the highest nip. Likewise, for the 3rd, 4th, 5th, 6th, and 7th nips from the top, the tangential driving forces are respectively 3, 4, 5, 6, and 7 times the unit tangential driving force (1) or 1.15 p.l.i. for the particular example mentioned. For each of the rolls at its nips, the forces due to the sheet tension and the driving forces are additive, and for the particular example previously mentioned, the magnitudes of these combined forces are indicated in FIGURE'Z. V

The invention contemplates that all of these lateral forces, which are the sums of the forces due to driving the rolls and due to the tension on the sheet, shall be reduced substantially, preferably to substantially zero, thus materially decreasing or eliminating the roll bowing forces and roll vibration and sheet barring due to the roll bowing forces. This is done according to the invention by offsetting each of the rolls with respect to the rolls above and below by varying amounts. The amount of offsetting is determined by the tangential forces at the nips on. each of the rolls and the nip pressures, that is, the pressures of successive'rolls at each nip on each other.

.The' pressure at the nip between the upper two rolls 19 and 20 is determined by the weight of the roll 20. The rolls 14 to 20 in the illustrated calender stack have equal diameters and weights, and in the particular example mentioned, the upper roll 20 provides a nip pressure of 60 pounds per lineal inch. In the next lowest nip, namely between rolls 18 and 19, the nip pressure in pounds per lineal inch is doubled since both of the rolls 19 and 20 are supported by the roll 18. Likewise the nip pressures in the successively lower nips are respectively, 3, 4, 5, 6, and 7 times the unit nip pressure in pounds per lineal inch between the rolls 19 and 20.

In order that the aggregate horizontal force (t)+(f) on the roll 19 existing at its upper nip shall he reduced substantially to zero, the roll 19, according to the invention, is oifset slightly to the right as seen in the figures with respect to the roll 26. This is in the direction of the paper carrying side of-the roll 19, which is the right side of the roll 19. Referring to the diagram shown in FIGURE 3, the distance that the center of the roll 19 is offset with respect to a vertical center line 31 passing through the center of the upper roll 20 is indicated by the quantity (A Referring to FIGURE 3, the tangentof; an angle (a) is determined by the forces acting on the upper nip of the roll 19, (t-l-f), and (N which is the nip pressure in pounds per lineal inc-h that exists betweentherolls 19 and 20. The tangent is The tangent rnust also be 51 This relationship assumes that the nip forces act vertically and horizontally and disregards the small angularity errors. Transposing, the relationship becomes:

I ABA: A'i' B)( In the particular example mentioned above in which the roll radii are 10 inches, this equation becomes:

Thus, the roll 19 is displaced to the right as seen in the figures about 1 inch in order to balance, and reduce substantially to zero, the lateral force on the roll 19 at its upper nip, which is the sum of the force (1) due to sheet tension and the force (f) due to the driving of the roll 20 from the roll 19.

The oflsetting of the roll 18 with respect to the roll 19, which is to the left as seen in the figures (see FIG- URE 4 in particular), is determined in the same manner. The corresponding formula is:

013 B-P C) where (R and (R are the diameters of the rolls 19 and 18 respectively, and (N is the nip pressure between these rolls.

Referring to the particular example mentioned, substituting numerical values, this formula becomes:

Thus the roll 18 is offset 0.69 inch with respect to the vert cal center lines through the center of the roll 19.

Likewise, the formulae for the amount of displacement of the other lower rolls, with respect to center lines passing through the rolls immediately above, and also the substituted values for the specific example mentioned, are as follows:

Where DC), nn), nn) GF), nd) are respectively the displacements of the rolls 17, 16, 15, 14, and e), e), E), F); e), (RH) are p tively the radii of the rolls 18, 17, 16, 15, 14, 13; and on), on) nr), FG) an) are respectivgly the nip pressures that exist in the lower 5 nips of the calender stack starting with the nip between the rolls 17 and 18.

For the particular examplegiven, the radius of the king roll is 22 inches, and for this particular example, and as indicated in FIGURE 4, the displacements for the rolls 18, 17, 16, 15, 14, and 13 with respect to vertical center lines through the rolls immediately above ese rolls, are 0.58 inch, 0.53 inch, 0.50 inch, 0.49 inch, and 0.75 inch.

It will be observed particularly from FIGURE 4 that the displacements of each lower roll is in a direction opposite to the sheet tension at the two nips of the roll. The rolls 19, 18, 17, 16, 15, 14, and 13 are alternately displaced in a zig-zag fashion, to the right and to the left with respect to the roll immediately above each roll. As will be seen from FIGURE 4, in which a vertical center line 32 for the king roll 13 has been drawn, the rolls above the king roll 13 are all displaced to the left, that is, in the direction from which the sheet 30 passes between the rolls 19 and 20, with respect to the center line 32. The uppermost roll 20 has the largest displacement from the center line 32, and the rolls 18, 16, and 14 progressively approach the center line 32. The roll 19 is closest to the center line 32, and the rolls 17 and 15 progressively are at greater displacements from the center line 32.

Preferably, in such a roll stack with olfset rolls, none of the rolls, with the exception of the king roll 13, is crowned. In view of the fact that the offsetting of the rolls with respect to each other is for relatively small dis tances, the offsetting has no discernible eifect on existing roll crowns used with vertical stacks.

In order that the rolls may be offset asabove described with respect to each other, the arms 25 may be made of different lengths, or else the arms 25 may be mounted on the frame member 11 using shims of different thicknesses,

.change the results materially. Since the roll bowing forces are substantially eliminated, any tendency for the,

rolls to vibrate horizontally with movement of the roll center portions into and out of the nips between the rolls and the barring effect on the paper passing between the rolls are substantially eliminated. The paper processed in the calender stack of the invention is thus of much higher quality and has a much more uniform thickness and finish than paper processed with conventional roll stacks in which the rolls are vertically aligned.

As will be observed from FIGURE 2, each of the intermediate rolls 14 to 19 maybe considered to have unresolved couples on them, that is, there is a greater lateral force at the lower nip on each roll than at the upper nip. For example, referring to FIGURE 2, the lateral force at the upper nip on the roll 19 is (t-H) while the.

lateral force at the lower nip on this roll is (t-i-Zf). I In the particular case mentioned, the force on the upper nip amounts to 2.95 p.l.i. and the force on the lower nip amounts to 4.10 p.l.i. In order to balance these unresolved couples, for the purpose of providing a calender stack that is even more stable than one in which the rolls are simply offset as previously described, each of the upper rolls 14 to 20 may be driven in addition to the normally driven king roll. Referring to FIGURE 5, motors 33 to 39 are respectively provided for driving the rolls 14 to 20, and the motors are so controlled as to provide a torque on the rolls driven by the motors just suficient to balance the unresolved couples. As will be apparent, the unresolved couple for any particular roll amounts to the difference between the lateral forces at the nips multiplied by the radius of the roll. If desired, only half of the upper rolls may be driven with the same results; for example, the motors 34, 36, and 38 may be used.

I Wish it to be understood that the invention is not to be limited to the specific constructions and arrangements shown and described, except only insofar as the claims may be so limited, as it will be understood to those skilled in the art that changes may be made without departing from the principles of the invention.

I claim:

1. In a calender for a paper web, a first calender roll, means for mounting said roll to hold it axially fixed and permit it to rotate, means for driving said roll in rotation, a plurality of other calender rolls, a fixed frame, and mounting means connected to said frame for each of said other rolls permitting vertical movement and roll rotation of each of said other rolls and holding saidi otherrolls disposed in a generally vertical stack with said first roll so that the paper web may pass through. the nips between said rolls and over and in contact with opposite sides of alternate ones of the intermediate rolls in the stack withsaid first roll supporting the weight of said other rolls andsaid first roll driving said other rolls due,

to the friction between the adjacent ones of the rolls and the web, said mounting means disposing said rolls so thatlalternate ones have their centers on one side of a verticalaxis and the others have their centers onthe other side of said axis with the sides of the rolls over which the web passes'being remote from said axis and with the center of each said lower other roll being closer to said axis than the center of said other roll immediately there,- above in said stack.

2. In a calender for a paper web, a relatively large diameter calender king roll, means for mounting said roll to holdit-axially fixed and permit it to rotate, means for driving said roll' in rotation, a plurality of other. smaller diameter calender rolls, a fixed frame, an arm swingably mounting each of said smaller rolls with respect to said frame to permit vertical movement and roll rotation of each of said smaller rolls, and holding said smaller rolls disposed in a generally vertical stack with said king roll so that the paper web may pass, through the nips between said rolls and over and in contact with opposite sides of alternate ones ofthe intermediate rolls in the stack with said king roll supporting the weight of said smaller rolls and said king roll driving said smaller rolls due to the friction between the adjacent ones of the rolls and the web, said arms disposing said smaller rolls so that alternate ones have their centers. on one side of a vertical axis and the others have their centers on the other side of said axis with the sides of the smaller rolls over which the web passes being remote from said axis and with each of said smaller rolls below the uppermost in said stack having its center, closer to said vertical axis than the smaller roll immediately thereabove and withsaid king roll having its center farther from said: axis than the- 4. In acalender for a paper web, a firstcalender roll,

means for mounting said roll to hold it axiallyrfixed, and.

permit itto rotate, means for driving, said roll in rotation, a plurality of other calender rolls, and mounting means for each of said other rolls permitting roll rotation and vertical movement of each of said other rolls andholding said other rolls disposed in a generally vertical stack with said first roll so that the paper web may pass through the nips between said rolls and over and in contact withopposite sidesof alternate onesof' the, intermediate rolls in the stack with said first roll supporting the weight of said other rolls and said first roll driving said? other rolls; due to the friction between adjacent ones of the rolls and the web, said mounting meansdisposing said rolls'so that alternate ones have their centers on one side of avertical the relation where R and R are the diameters in inches of the particular pair of rolls being considered, T is the tension in center of said smaller roll immediately thereabove in the,

stack. a

3. In a calender for a paper-web, a first calender roll,

means for mounting said roll' to hold it axially fixed and permit it to rotate, means for driving said roll in rotation, a plurality of other calender rolls, and mounting means for each oflsaid other rolls permitting roll rotationfand, verticalmovement of each of, said other rolls andholding rolls and said firstroll-driving said other rolls due to the frictionbetween adjacent ones of therolls and the web,

saidmountingmeans disposingsaid rolls so that alternate; ones have their centers on one side of a vertical axis and;

the others havetheir centers on the other sideof said. axis withthe sides of the rolls over which the web passes being remote from said axis, the distancethat each of said rolls below the top roll is, set offwith respect to. the roll im mediately thereabove being determined by, the relation.

where C- is a constant, T is the tension of the-paper web throughouttheroll stack, Ejis the force driving the upper. roll of the pair oflrolls being considered and Ntisthe,

nip pressure between the particular pair of rolls being considered.

pounds per lineal inch of the paper web throughout the roll staclg F is the force in pounds per lineal inch driving the upper roll of the pair of rolls being considered and N is the nip pressure in pounds per lineal inch between the particular pair of rolls being considered.

5. In a calender for a paper web, a first lower calender roll, journals for mounting said roll to hold itaxially fixed and permitv it to rotate, means acting on one of said journals for driving said roll in rotation, a plurality of other calender rolls each of which is smaller than said first roll, and mounting means for each of said smaller rolls permitting roll rotation and vertical movement of each of said smaller rolls and holding said smaller rolls disposed in a generally vertical stack with said first roll and above the first roll so that the paper Web may pass through the nips between said rolls and over and in contact with opposite sides of alternate, ones of the intermediate rolls in the stack with said first roll supporting the weight of said smaller rolls and said first roll driving said smaller rolls due tothe friction between adjacent ones of the rolls and the web, said mounting means disposing said rolls so that each smaller roll has its center horizontally displaced withrespect to a vertical axis passing through the roll just below it toward the side of the roll over which the web passes, the lowermost one of said smaller rolls being displaced farther from the vertical axis through said first roll than from the vertical axis through the said smaller roll immediately above this lowermost smaller roll inzthe stack.

6. In a calender fora paper web, the combination as set forth in claim 5, and means for driving a pluralityofsaid rolls in the stack above said first calender roll.

References Cited, in the file of this patent UNITED STATES PATENTS

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