US2926600A - Method and means of supercalendering - Google Patents

Description

March 1, 1960 w. G. ENGELGAU 2,926,600

METHOD AND MEANS OF SUPERCALENDERING Filed Jan. 23, 1958 2 Sheets-Sheet 1 2171222 Mil/7K0 4'. [44a 4040 March 1, 1960 w. a. ENGELGAU 2,926,600

METHOD AND MEANS OF SUPERCALENDERING Filed Jan. 23, 1958 2 Sheets-Sheet 2 METHOD AND MEANS OF SUPERCALENDERING Willard G. Engeihau, Rhinelander, Wis., assignor to st.

Regis Paper Company, a corporation of Wisconsin Application January 23, 1958, Serial No. 710,695

' 9 Claims. (Cl. 100-41) Ufl id ates Patent T i p c I 2,926,600

Fatented Man], 1960;

on the rollers which corresponds to the position of the A brief review of the art of supercalendfiring will be helpful in the understanding of this invention. Supercalendering per se is well known to the paperindustry and is used with suitable variations in'the processing of many kinds of paper to giveieach kind of paper the desired smoothness, gloss, density, or transparency and combinations of these characteristics. The device used for this purpose is asupercalendertwhich usually comprises a vertical stack of rolls orrollers in which some of the rolls are hard, such as being made of steel, and some of the rolls are relatively soft, such as being made of compressed paper or other fibera The number and arrangement of rolls is varied to suit the-requirements'of the specific grade and the hard'and soft rolls are generaledges of the paper. Similarly, if successive paper rolls increase in width, the edges of the first part of at least the first roll of each increased width will be calendered harder than the balance of the width at these edgesare running between portions of the roller which are less worn than the portions of the roller in the central portion of the paper web.

If several narrow rolls of paper are supercalendered and then it is desired to supercalender several wider rolls of paper on the same stack, the soft supercalender rolls must be dressed or refinished prior to running the wider paper rolls, because if this not be done, the position of the edges of the narrower roll of paper will show in a number of successive rolls of paper of a wider width.

I have found that the ridging of the supercalender tion of theuseful surface of the soft rolls or rollers.

. Accordingly, it is a principaldbject of this invention g to provide for more uniform wear of the soft rolls of ly alternated, though several hard or soft rolls may be Usuallyonlythe bottom roll of the stack is driven, although other rolls maybe driven. The paper to be, treated is unwound and is threaded through the stack from the top to the bottom passing through some or all of the nips between rolls, and if desired may be led away from the rolls between nips over fly rolls principally to provide for and to control the drying of the paperwhich may be at an entering moisture, content ranging from about four to about thirty percent. a a

As, the paper passe's downwardly through the stack, it is subjected to pressing at increasing pressure at each nip due to the weight of the rolls, Extra loading may be applied through the journals of the top roll. Thus pressures at the bottom nip. may range from less than one,- thousand pounds to more than four-thousand pounds, perlinear inch The stack may be operated at speeds ranging from about four hundred to more than two thousand feet per minute. Shear forces-are exerted on;

the. paper by the deformation of the soft-rolls which occurs at thenip, and the'nature of this deformation is determined largely by pressure, speed, and thematerial from'which the soft rolls are made. The manner in whi h the method of operating a supercalender stack may be changed to accomplish the different'results with, specific grades of paper is well known in the industry. One principal difiieulty in operating a supercalender is the One of avoiding uneven wear and damage to the soft rolls of the stack. The paper web usually does not extend across the complete width of the soft rolls and maxi: mum wear occurs on the area engaged by thepaper web'. If a constant width of paper is runin the same position, it becomes necessary at intervals to sand or otherwise dressthe exposed ends of the sqf t rolls outside of-the area engaged by the paper. I

- If successive rolls of paper being calendered are of ences being produced by the supercalendering, and which Y would 'be objectionable and which results from uneven wear of the supercalender rolls.

Yet another object of the present invention is to minimize roll-defects commonly known as ridges or corrugations which result from damaged or worn areas in the soft or hard rolls, as the effect of these usually minute imperfections is multiplied in the finished roll of paper a as the diameter thereof increases.

Many other advantages, features, and additional objects of the present invention will become manifest to those versed in the art upon making reference to the detailed description and the accompanying sheets of draw- U ings in which a preferred structural embodiment incorpo- Inatic, of an unwinding mechanism for a; paper roll;

Figure-4 is a front'view of a rewinding mechanism, and isfalso partly diagrammatic; and I Figure 5 is a fragmentary schematic view of a pair of adjacent supercalender rolls, the view being-greatly enlarged in the vertical direction.

As shown on the drawings:

The principles of this invention are particularly useful. when embodied in a supercalender stack such as illustrated in Figures 1 and 2, generally indicated byv the. numeral 10. The stack includes a series of soft or paper filled rolls 11 and a series of hard rolls 12 such as of steel. The steel roll or rollers 12 may be steam-heated if desired, and, the uppermost steel roll may beprovided with means 13 for, applying additional loading through the bearings to the journals of the roll. A series of fly rolls also be provided as desired.

A roll of uncalendered paper 20 is supported by an unwinding mechanism 21, and a roll of calendered paper 22 is shown as supported by a rewind mechanism 23.

Referring to Figure 2, it will be noted that the soft rolls 11 have been shown as being somewhat shorter in length than the steel rolls 12, and that the paper web 24 is at one limit of the useful width of the stack, the Width of the paper rolls and paper web being somewhat less than the width of the soft stack rolls 11.

Figures 1 and 2 are obviously schematic, and the various rolls are maintained in alignment in a suitable frame having ways for the bearings of each journal, while the unwind and rewind mechanisms include shafts supported on suitable brackets or frames. These details have been omitted since they are well known in the art, since they do not form a part of the instant invention, and since a clearer result is obtained by their omission.

Referring now to Figure 3, there is shown a front view of the 1 unwind mechanism generally indicated by the numeral 21. The mechanism 21 includes a horizontal shaft 30 which corotatably supports a core 31 for the roll of paper to be unwound. The shaft 30 is rotatably supported by a pair of split bearings 32 and 33. The hearing 32 also slidably supports the shaft 30 with respect to a portion of the frame 45 of the supercalender. The bearing 33 is supported by a slide assembly 34 which includes a stub shaft 35 bearingly mounted thereon. The stub shaft 35 has a helper drive pulley and friction drum assembly 36 at one end thereof, and a slide coupling 37 is provided at the other end thereof for rotatably joining the shafts 30 and 35 together, for corotation. The slide assembly 34 is laterally movable on a slide or ways 40 by means of the action of a hydraulic actuator 41 which is operatively connectei intermediate the slide assembly 34 and the slide 40. A portion 42 of the slide assembly 34 is arranged to alternatively engage means such as valves or limit switches 43 which are operatively connected to valves (not shown) which control a fluid pressure me dium directed to the hydraulic actuator 41. The fluid system employed to reciprocate the slide assembly 34 may be any of thewell-known systems and does not form a part of the instant invention, and therefore it need not be shown herein in greater detail.

' The core 31 is secured to the shaft 30 by any convenient means which prevents relative axial or angular movement therebetween. The shaft30 may be held in position in relation to the slide assembly 34 by a collar 46 afiixed to the end of the shaft 30, which bears against the bearing 33,'and the adjacent end of the stub shaft 35. If desired, a second collar 46a may also be employed. The bearing 33 is of split construction for opening for easy removal of the shaft 30 therefrom, and the bearing 32 is of similar construction.

Referring now to Figure 4, there is shown a front view of the rewind mechanism generally indicated by the numeral 23. The rewind mechanism 23 includes a shaft 50 which axially slidably and corotatably supports a core 51 for supporting the rewind roll 22, their mutual surfaces, by way of example being non-circular or splined. 1 The rewind mechanism includes a right and lefthand threaded screw 52 which threadably engages with a pair of arms 53 and 54. The core 51 is disposed intermediate the distal ends of'the arms 53 and 54 at which ends a plurality of rollers 55 may be provided.

50 is provided with at leasttwo oppositely directed collars 50a or shoulders whichpreclude axial shaft movement, one of which is removable. The shaft 50 may be rotated by means of a helper drive pulley and friction drum assembly 57 carried on a stub shaft 35a which corotatably is removably joined to the shaft 50 by a slide coupling 37a. The shaft 50 and core 51 may thus be removed from the mechanism, the connection with the arms 53, 54 being releasable. The shaft 35a is bearingly supported by stationary means equivalent to that shown for the stub shaft 35 in Figure 3.

The arms 53 and 54 are supported by rollers 60 which engage a track or ways 61, and which are movable therealong. A hydraulic actuator 62 is operatively connected to the shaft 52 or to the arm 54 for reciprocating the core 51 in a direction parallel to its axis.

The rewind mechanism 23 is provided with a means for aligning the edge of the calendered paper with respect to a reference point which is movable with the core of the rewind mechanism 23. Referring to Figure 1, there is shown a source of light 65 which is directed across the edge of the paper 24 and onto a photocell 66. The photocell 66 is connected to a suitable amplifier (not shown) which is operative to regulate valving which in turn controls the operation of the fluid actuator 62. If desired, additional ways may be provided for the support of the photocell 66. It is preferred that the bracket rod 70 of the actuator 62, it then being necessary to provide for 'geater lateral adjustment thereof.

By means of a hand wheel 56 corotatably carried on the -Where the rate of fluid flow to the actuator 41 is rather low, a rather slow rate of oscillation of the unwinding roll 20 is provided. There will always be some lag occurring through the stack so that the axial position along the lowermost stack roll will slightly lag the lateral position of the paper 24 at the unwinding mechanism. In certain instances, this lag will be so slight that it need not be compensated for. Under such circumstances, the arms 53 and 54 of the rewinding mechanism may be mechanically coupled to the unwinding mechanism for translation by the actuator 41.

It has been supposed that it would be impractical to oscillate the paper on the stack itself, both because of the difficulty in preventing wrinkles and so-called calender cuts resulting from wrinkles, and because oscillation would not effectively equalize wear. By way of illustration, it has been heretofore assumed that if a 40 inch width of paper was run on a supercalender stack having a useful width of 60 inches, and if the paper were oscillated for a distance of 20 inches, the wear in the central 20 inches of the useful face would continue to be more than that on the two outer 20inch portions of the useful face. I have found, however, that when this is done the wear is substantially even over the entire 60 inches. In over six months of use of this invention, there has been no increase in the difference between the edges and the'center of the calendered paper in gloss, finish, transparency, or density. Heretofore, there has been some diflference between the edges and the center due to the manner in which the load is applied to the supercalender, and if oscillation caused uneven wear, it would be expected to increase this difference and produce a higher gloss finish, transparency, and density on the edges.

It has been found that wrinkling in the stack can be avoided during oscillation by using slow oscillating speeds, a higher rotational speed in the stack permitting faster lateral'or sideways oscillating movement. By way of example, no difi'leulty with wrinkling has been ea: countered with oscillating rates of 5 inches per minute at ..pared to the same paper calendered without oscillation,

results from two principal factors. Thismaybe explained by reference to Figure 5 which shows a view, exaggerated I in the vertical direction, of what is believed to' happen In the figure,

at a single nip between a pair of rolls. the'distance ADis the useful width of the nip and is the total distance engaged by the paper. web 24 during'oscillation between the rolls 11 and 12 of the calender stack. The distance AB indicates the zone of travel of one edge of the web 24, while the distance CD indicates the zone of travel of the other edge of the web 24. The paper is shown in the position defined by the limits B and D.

Between the points B and C, there is always paper between the two rolls of the nip. From B to A and from C to D there is paper between the rolls for a decreasing length of time, the time at any point depending on the characteristics of the oscillating motion. The type of oscillation does not appear to be important, as both harmonic and linear oscillation has been successfully used. Since in the ideal case the paper is uniformly compressible across its width, the pressure between the paper and the rolls near D is probably greater than between the paper and the rolls in the area between the points B and C, becausein the oscillation cycle just completed, this portion of the rolls has not been exposed ,to the same amount of wear as has the portion between B and C. This higher pressure near- D appears to cause faster wear of the soft rolls than occurs in the areaBC.

Restated, it would appearthat the rate of wear increases from B to A and from C to D about the same as the time 'ofwear decreases, resulting in substantially equal wear from A to D. r

Further, apparently the distance between the rolls at A is somewhat less than the distance between the rolls at B, as a result of normally equal loading of both journals of the top roll of the stack and the resistance to this load of the paper in the position BD. Therefore, the position of each roll, except the bottom roll in the stack, is the result of balance between the loading forces, which can be thought of as being applied at points A and D, and the 'resistance to compression offered by the paper.

must'be marred or less together. I prefer to a means foroscillating the unwinding roll parallel to its axis witha substantially linear motion as this is a'most convenient method. I prefer also to move the winding roll parallel to its axis by means actuated by a photoelectric or other type of edge alignment device to which an identical motion is imparted so that the winding roll follows from side to side of the stack the position. of the paper web, as it is delivered from the stack.

i It is to be understood that in the case of either the winding mechanism or the unwinding mechanism, structure may be used which axially shifts the shaft and'the rll toge thier, or which axially shifts the roll and c; r=.' with respect to 'the shaft. The choice is a matterof' convenience and either type of shifting device may be used for either roll of paper. As explained above, it is also possible without departing from the spirit of this invention, to dispense with the edgealignment device and shift both rolls simultaneously or with a time delay or lag between the motion of the unwind and winding rolls.

Although various minor modifications might be suggested by those versed in the art, it should be understood that I wish to embody within the scope of the patent warranted hereon all such embodiments as reasonably and properly come within the scope of my contribution to the art.

I claim as my invention: I

1. In a supercalendering machine having a stack of rolls,.means for unwinding a'roll of paper to be'treated by the rolls, and means for rewinding the treated paper,

cillation of the paper on the supercalender rolls.

2. In a supercalendering machine having a'stack of rolls, means for unwinding a roll of paper to be treated by the rolls, and means for rewinding the treated paper,

theimprovement of means for continually laterally os-' cillating the paper unwinding means by a an amount needed to produce thereby a lateral oscillation of the paper on the supercalender rolls.

3. In a supercalendering machine having a stack of rolls, means for unwinding a roll of paper to be treated by the rolls, and means for rewinding the treated paper, the

improvement of means acting on the roll of paper as it is being unwound, to oscillate the portion of the paper Since the differences in roll diameters or position de-- scribed are fairly small and incapable of measurement, I have been unable to determine which effect is responsible for the uniformity I have observed or whether both factors are involved and may vary in relative importance as operating conditions change. v

While I have not observed thatvthe characteristics of the oscillating motion are critical, and have used both harmonic and linear oscillation with equally good results,

it is possible that with either particlarly soft or abrasive papers a particular form of motion would prove advan tageous.

For the purpose of minimizing roll defects by distribu ing the causes of ridges and corrugations over a wider area or width of the face of the roll, a total oscillation of from 1 to 3 inches is generally found satisfactory. For the purpose of equalizing wear and securing uniform results across the useful face of a supercalender stack, an oscillation of 20% or more'of the paper width is satisfactory. 'It appears that the lower limit of effectiveness probably falls within the range between'10 and 20% of the paper width. For maximum effectiveness, the oscillation distance should equal the difference between the paper width and the useful width of the supercalender stack.

To secure thedesired oscillation, obviously both the unwinding roll of'paper and the winding roll of paper being supercalendered laterally along the length of the supercalender rolls, and means synchronizing the lateral postion of the rewind means with the lateral position of the paper being discharged from the stack.

4. In a method of operating a supercalender having a stack of rolls, means for unwinding a roll of paper to be treated by the rolls, and means for rewinding the treated paper, the improvement of continually slowly oscillating the roll of paper in an axial direction, as it is being unwound, by an axial distance sufficient to produce thereby a lateral oscillation of the paper calender rolls. a v I 5. In a method of operating a supercalender having a stack of rolls, means for unwinding a roll of paper to be treated by the rolls, and means for rewinding the treated on the superpaper, the improvement of continually slowly oscillating the unwinding means in a direction parallel to the roll axes by an amount needed to produce thereby a lateral oscillation of the paper on the supercalender rolls.

6. In a method of operating a supercalenderhaving a stack of rolls, means for unwinding a roll of pa'perto be treated by the rolls, and means for rewinding the treated a paper, the improvement of continually slowly oscillating the roll-of paper a selected distance in a direction parallel to its axis, as it is being unwound, to thereby oscillate the portion of the web of paper being supercalendered a selected distance along the length of the supercalender rolls, and oscillating the rewind means in a similar direction in substantial synchronization with the position of the paper being discharged from the stack of rolls.

7. In a method of supercalenderiug a web OfPflPCI', the improvement of supercalendering a portion-of the web and continually laterally oscillating said portion of the web while it is being supercalendered.

8. In a supercalendering machine having a stack of supercalender rolls, the improvement in combination therewith of means for continually laterally oscillating the portion of the web being supercalendered, along the length of the supercalender rolls.

9. In a method of supercalendering paper including the step of feeding a web of paper intermediate a stack'of calender rolls, the improvement of applying a continually oscillatinglateral movement to the web prior to its en,-' gagement with the stack, said movement being of a magnitude sufficient to thereby gradually move the paper back and forth along the length of the calender rolls dur- 5 ing the supercalendering of the paper.

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

Images