US3161563A

US3161563A - Method and apparatus for the lateral stretching of webs, and resultant product

Info

Publication number: US3161563A
Application number: US222992A
Authority: US
Priority date: 1962-09-04
Filing date: 1962-09-04
Publication date: 1964-12-15
Anticipated expiration: 1981-12-15

Description

Dec. 15, 1964 w. c. WALKER ETAL METHOD AND APPARATUS FOR THE LATERAL STRETCHI OF WEBS, AND RESULTANT PRODUCT 4 Sheets-Sheet 1 Filed Sept. 4, 1962 wk wk INVENTORS W/'///'0m 6. Walker /V rman l/l eberg Dec. 15, 1964 w. c. WALKER ETAL 3,161,563

METHOD AND APPARATUS FOR THE LATERAL STRETCHING AND RESULTANT PRODUCT OF WEBS 4 Sheets-Sheet 2 Filed Sept. 4, 1962 INVENTORS W/'///'am 6. Wa/ker Norman Weberg Dec. 15, 1964 w. c. WALKER ETAL 3,161,563

METHOD AND APPARATUS FOR THE LATERAL STRETCHING OF WEBS, AND RESULTANT PRODUCT Filed Sept. 4, 1962 4 Sheets-Sheet 3 INVENTORS Wi/l/am 0. Walker Norman Weberg Dec. 15, 1964 w. c. WALKER ETAL 3,161,563 METHOD AND APPARATUS FOR THE. LATERAL STRETCHING OF WEBS, AND RESULTANT PRODUCT 4 Sheets-Sheet 4 Filed Sept. 4, 1962 r 6 Z W 8 W mm My WN wk mm 7 6% mm vb United States Patent METHOD AND APPARATUS FQR THE LATERAL STRETQHEQG 0F WEBS, AND RE$ULTANT PRQDUQT William C. Walker, Wiiliamsburg, and Norman Weherg, Altoona, Pa, assignors to West Virginia Pulp and Paper Qompany, New York, N.Y., a corporation of Delaware Filed Sept. 4, 1962, Ser. No. 222,992 15 (ll-aims. (Cl. 162-497) This invention relates to a method and apparatus for treating papers, especially so-called printing papers, to increase their dimensional stability with respect to Variation in moisture content, and the provide improvements in stiffness.

The present application is a continuation-in-part of our vcopending application, Serial No. 114,813, filed June 5, 1961, and now abandoned, for Method and Apparatus for Reducing Hygroexpansivity of Paper, and the Resultant Produc It is well konwn that when a sheet of paper is wetted, or even subjected to a substantial increase in relative humidity in the surrounding atmosphere, it will expand an appreciable amount. The expansion in paper made on a paper machine is not uniform in all directions, as the expansion in the cross-machine direction is greater than in the machine direction. Conversely, paper that is caused to lose moisture will shrink more in the crossmachine direction than in the machine direction. One important factor in the tendency of printing papers to non-uniformly change dimensions with changes in relative humidity is, that during manufacture on a paper machine, the paper is restrained in the machine direction so that little longitudinal shrinkage can occur, while in the cross-machine direction considerable shrinkage occurs because the paper is not restrained in that direction.

Printing papers that change dimensions with changes in relative humidity have been a source of much diificulty in printing pressrooms. These difiiculties arise from either a high sensitivity to humidity or from a difference in sensitivity from one side of the sheet to the other.

When paper is stacked on a skid, high sensitivity to humidity over all of a sheet results in a tendency toward wavy edges at high relative humidities, and tight edges at low relative humidities. Such paper can cause improper feeding to a printing press, or can cause wrinkling on the press. High sensitivity to relative humidity changes may also result in misregister between colors in multicolor work.

Because of the difference in the tendency of paper to change dimensions between the cross-machine and machine directions with changes in relative humidity, printing papers with low sensitivity to humidity in the machine direction may still cause difiiculties on a printing press due to the higher sensitivity of the paper in "the crossmachine direction. It is thus desirable to reduce the amount of sensitivity in the cross-machine direction during manufacture so that the final web becomes more uniform in sensitivity to humidity changes between the machine direction and cross-machine direction.

The sensitivity of a paper to change dimensions with changes in relative humidity has been called the hygroexpansivity of the paper. The coefiicient of hygroexpansivity is a measurement of the sensitivity of paper to change dimensions with changes in relative humidity and is defined as:

Coefficient of hygroexpansivity 10 It is not uncommon in various commercial grades of paper to find the coefticient of hygroexpansivity in the cross-machine direction to be as much as 3 or 4 times larger than the coefficient of hygroexpansivity in the machine direction. Such paper when subjected to changes in relative humidity gives rise to operational problems during the printing of such items as punch cards, map paper, recorder charts, and label paper, where dimensional stability is a requisite for satisfactory printing.

It is well konwn that when paper is dried, moisture Within the fibers is driven out, causing the fibers to shrink. On a paper machine, shrinkage is greater in the crossmachine direction than in the machine direction for'two main reasons. First, the fibers are oriented preferentially in the machine direction, and when moisture is driven out from within the fibers, the greatest shrinkage occurs in the cross-machine direction since the fibers shrink more in a lateral direction than along their length. This shrinkage is partially transmitted to the dimensions of the web and is considered to be one reason for the dimensional instability of paper. Secondly, the web is subjected to restraint from shrinking in the machine direction during drying due to the tension put on the web as it is drawn through the dryer sections of a paper machine, while no such restraint is applied to the web in the cross-machine direction. The web, consequently, may lose as much as 5% in width or deckle during the drying operation.

According to the present invention, it has been found that a lateral stretching of the paper beyond its elastic limit during the drying operation will cause a reduction in the hygroexpansivity of the paper in the cross-machine direction. It was at first though that restraint on the web in the cross-machine direction during the whole drying process would be necessary to effect a significant reduction in the cross-machine hygroexpansivity. But such an operation would involve a large portion of the paper machine and would be difficult to arrange. By restraint, we mean not allowing the web to shrink in the cross-machine direction during drying. Surprisingly, however, we have found that the web may be allowed to shrink a certain amount due to a partial drying, and then by subjecting the web to a momentary lateral stretching beyond its elastic limit, at the proper moisture con ditions, a very significant reduction in the cross-machine hygroexpansivity can be obtained.

While it is dimcult to overcome the fiber orientation problem that exists, and its effect upon hygroexpansivity, it has been found that a more dimensionally stabilized paper can be produced in the manner according to our invention. Various known devices may be employed for the purpose of lateral stretching, namely, so-called toroid or bowed rolls. Other devices used for edge tentering,

3 could also be employed. An example of this type of device is shown in the Wiley et al. Patent 2,412,187.

Because the bowed roll is a simple and compact device readily mounted upon the machine, and will stretch the web only in the cross-machine direction, it is the one preferred by us, and accordingly we have shown this type of device in connection with our invention. We have found that through the use of such devices, under the proper conditions, a substantial fraction of the loss in deckle that has been sustained due to shrinkage of the web in the cross-machine direction can be permanently restored, and that such restoration is effective in reducing the coefficient of hygroexpansivity in the cross-machine direction. As much as 75% of the deckle loss has been permanently restored to paper treated in the manner of our invention, and there is no reason why even greater amounts can not be restored through the use of multiple bowed rolls.

A bowed roll is sometimes provided as part of, or immediately following the dryer section of a paper machine and serves to remove any wrinkles that the web may have acquired, but such a roll is not arranged or designed to effect any appreciable permanent stretching of the web in a lateral direction. A bowed roll is also sometimes used near or at the wet end of a paper machine for the purpose of increasing deckle. The effect on hygroexpansivity by the use of a roll in this manner is very little for two main reasons: (1) the moisture content of the web is too high to result in any marked reduction in hygroexpansivity, as is explained later: (2) the web is not stretched enough because the bow of rolls known in the art is usually less than 1%, and the amount of deckle recovery produced is also only about 1%. Furthermore, we have found that the use of two bowed rolls in tandem is preferred over the use of a single bowed roll. Substantial improvements in the reduction of the coeh'icient of hygroexpansivity are obtained through the combination of a high degree of bow in the rolls and a high degree of web wrap around the rolls. The geometry of the paper web run is such that the machine direction path length varies across the machine as the web passes over a highly bowed roll with a high degree of web wrap, and some sections of the web are slack when only one bowed roll is used. This results in problems in runability, as for example, there is more web wrinkling due to the uneven web path length, more machine direction distortion in the length of the web, and greater frequency of web breaks because the machine direction tension is applied to less than the full width of the web. By using two bowed rolls in tandem, it is possible to position the rolls so as to reduce to a negligible amount the variation in web path length across the paper machine, and, hence, avoid endangering the runability of the web on the paper machine.

It has been found that one critical factor in our method of laterally stretching the web is the moisture content of the web at the time of stretching. If the stretching is done at the web end of the machine or where the moisture content of the web is relatively high, the inter-fiber bonds have not yet been fully formed, and the result is that fibers tend to slide over one another, and bonds are formed elsewhere when the proper moisture conditions are met. Hence, such stretching has been found to have little effect on the hygroexpansivity of the sheet. If the stretching is done after the web is too dry, improvements in the hygroexpansivity properties are hard to effect through lateral stretching by bowed rolls because of the strength of the paper and its resistance to such stretching. The stretch that is sought in the present case is had after the web has been dried sufficiently to cause some interfiber bonding and after some lateral shrinkage has occurred, which we pull back out. The theory behind our process, though not conclusively proved, is that we change the internal strain situation in the cross-machine direction of the fibers in the Web so that less of the lateral expansion of the fibers caused by high humidity conditions is transmitted as lateral expansion to the whole web. After many trials, we have determined that the desired interbonding of the fibers will occur when the moisture content is in the range of from 8 to 50%, with a preferred range of from 10 to 30%. When the moisture content is greater than 30%, the action of the stretching devices, especially bowed rolls, is somewhat less effective on the hygroexpansivity improvement, although improvements have been noted when the moisture content is as high as 50%. Surprisingly, we have also found that within our preferred moisture range, the amount of hygroexpansivity improvement is greater when the paper is drier during the treating operation, i.e., a one percent increase in total web width due to laterally stretching the web at a moisture content of 10% reduces the coeflicient of hygroexpansivity more than a one percent increase in web width due to laterally stretching the web at a moisture content of 30%.

One type of bowed roll employed by us is an article of commerce, and while it has been generally illustrated in the drawings, satisfactory types are well known in the art, an example being that shown in Patent 2,393,191, I. D. Robertson, as well as in other patents standing in the name of this patentee.

The effectiveness of the bowed rolls depends not only upon the moisture content of the web, but also on the amount of the bow in the roll, the friction between the web and the bowed roll, and the degree of wrap of the web around the bowed roll. It has also been found that as the machine direction tension is increased, the effectiveness of the bowed rolls is also increased, since with increased tension, the web is held more strongly against the bowed rolls. Web tensions up to about 6 /2 pounds per linear inch in the machine direction have been employed. Web wraps around the bowed rolls have been in the range of from 50 to 180, with the preferred wrap in the range of from to Rolls with bows up to 4% have been employed successfully. Throughout the specification and claims, the word bow is defined as the maximum change in length that the resilient face of the roll undergoes as it rotates about the axis of the roll.

In one type of bowed roll as presently manufactured, it is possible to vary the bow Without removing the roll from the machine, and this type of roll has been found to be of advantage, not only because the amount of stretch imparted to the paper may thereby be varied, but having the rolls temporarily in straight form has been found to be an advantage in the threading of a reduced width of the paper through the machine at the start of a run.

In the normal manufacture of paper on a paper machine, the profile of the cross-machine direction hygroexpansivity is not uniform as the eoeflicient of hygroexpansivity is higher at the edges of the web than in the center. When the web is stretched in the manner of our invention by uniformly bowed rolls, more stretching takes place in the center of the web than at the web margins due to slippage between the web and the bowed rolls at the web margins. The cross-machine direction hygroexpansivity of the web is lowered, but the cross-machine direction profile is not improved. However, for some purposes, this may be suitable to the manufacturer. We have found that it is possible to compensate for the uneven profile inherent in the web and also for that produced by the bowed rolls by employing means for grip ping the web at its margins during the stretching operation. Therefore it is desirable to provide auxiliary holding or edge grippings means at the web margins, such as retaining bands that press the marginal portions of the web against the corresponding portions of the bowed rolls to prevent lateral slippage between the roll and the web at the margins, and to effect a more uniform stretching action across the web, resulting in a more uniform crossmachine direction hygroexpansivity profile. The apparatus for accomplishing this is described in detail later.

In addition to employing rolls in which the amount of bow may be varied, the bowed rolls may be modified so as to make the bow nonuniform, thereby obtaining greater stretching action at the edges of the web. This is accomplished by decreasing the radius of curvature of the rolls at their end portions to provide a higher bow at the ends of the roll than in the center of the roll. Accordingly, in the preferred embodiment of our invention, rolls are employed in which the amount of how at the central portion is in the order of 1% and the amount of how at the end portions is as high as 3%, with the amount of bow progressively increasing from the central portion of the roll toward each end thereof. It is further desirable to provide auxiliary retaining means at the web margins to press the marginal portions of the web against the corresponding portions of increased curvature of the rolls.

Non-uniformly bowed rolls are known in the art, an example being that shown in Patent 2,689,392 to I. D. Robertson.

From the foregoing description, it is evident that the point in the paper machine at which the bowed rolls or other devices are located is determined by the amount of moisture in the web at a given point. In the manufacture of paper, it is common practice to locate a so-called size press between dryer sections. We had supposed that it would be necessary to locate the bowed rolls after the size press for the reason that the moisture introduced into the web at the size press would be expected to reduce the improvement in hygroexpansivity. Surprisingly enough, however, we have found that the bowed rolls may, if desired, be disposed before the size press, since the moisture picked up at the size press has been found not to disturb the relationship of the hygroexpansivity of treated and untreated webs.

It has also been found that the above described method of laterally stretching a traveling web of paper produces a product with improved stiffness characteristics due to improvements realized in the modulus of elasticity of the product. As is well known, the stiffness of paper varies directly with the modulus of elasticity. Improvements in stiffness up to about 21 percent in the cross-machine direction have been derived on papers of basis weight between 40 and 48 pounds per 3000 square feet of paper, with the average increase being in the order of percent.

Our invention will be further understood by reference to the following detailed description taken with the annexed drawings, in which:

FIGURE 1 is a View in front vertical elevation showing a pair of bowed rolls equipped with the web edge gripping device forming part of the present invention;

FIGURE 2 is an enlarged vertical sectional View taken on line 2-2 of FIGURE 1;

FIGURE 3 is an enlarged vertical sectional View taken on line 33 of FIGURE 1 and showing the tension arm of an edge gripping device;

FIGURE 4 is a View in vertical sectional elevation taken on line 4i--4 of FIGURE 1 and showing a pair of bowed rolls disposed between successive dryer drums in a paper machine;

FIGURE 5 is an elevational View, partly sectioned, showing the mounting arrangement of an edge gripping device;

FIGURE 6 is an exploded view of an edge gripping device and associated mounting clamp;

FIGURE 7 is a sectional view of one of the pulleys employed in an edge gripping device.

Referring to FIGURES 1 and 4, the paper web P passes around dryer drum It), paper carrying roll 12 mounted on shaft I3 held at its opposite ends by bearings 14 and 16 on frame members It; and 2d, and then passes around bowed

rolls

22 and 24 before continuing around dryer drum 26 and through the rest of the dryer units in the machine. Bowed roll 22, of the type herein employed, has a surface 28 of rubber or other flexible material engaged over a series of roll sections, not shown, which are rotatably mounted upon a curved shaft 30 held at its opposite ends in clamps, not shown, mounted on the frame members 32 and 34 of the paper machine dryer section. It is understood that for the purpose of illustration, bowed

rolls

22 and 24 are identical in size and construction, and the description of one roll serves as a description for the other.

The bowed rolls 22 and 24 are disposed with their longitudinal axes substantially at right angles to the longitudinal axis of the paper machine, and are positioned in relation to each other such that the machine direction Web path length from dryer drum 1% to dryer drum 26 is substantially the same all across the web P. In operation, the traveling paper web P reaches each of the bowed rolls 22 and 2d at the inner or concave side and leaves at the outer or convex side thereof, and, hence, is subjected to a lateral stretching action by each of the bowed rolls 2?. and 24-. In the preferred arrangement, each bowed

roll

22 and 24 is positioned with its direction of bow oriented such that the angle bisector of the angle of web wrap around the roll is perpendicular to the direction of bow in order to utilize the maximum stretching action of the roll.

For the purpose of confining the paper web P to the bowed rolls 22 and 24 at the margins thereof, an edge gripping

device comprising pulleys

35, 36, and 37 rotatably mounted on pulley bracket 38 and tension arm 3?, as described later, and carrying an endless belt 40 of rubber or other resilient material, is provided. It will be understood that such gripping devices are provided at the opposite ends of each of the bowed rolls 22 and 24 to press the web margins against the bowed rolls 22 and 24 and thus grip the web at the margins between the bowed rolls and the endless belt 46 to prevent the web P from slipping laterally relative to the bowed rolls.

With particular reference to FIGURES 3, 5, and 6, it is seen that pulleys 35 and 36 are rotatably mounted on

shafts

42 and 44, respectively, which are held at one end by pulley bracket 33. Pulley 37 is rotatably mounted on shaft 46 which is held at one end by tension arm 39, the latter being adjustably mounted about shaft 44 between pulley 36 and pulley bracket .38. A lateral extension 4-8 on tension arm 39 has an open portion 50 to receive the shank 52 of bolt 54 which passes into the tapped hole 56 in pulley bracket 38. The tension on the endless belt it? is adjustable by loosening bolt 54 and moving the tension arm 39 toward or away from pulley 35, thus moving pulley 37 likewise and causing the tension on the endless belt 4b to be increased or decreased.

Pulley bracket 38 has a slotted member 6t) mounted thereon, on the side opposite the

pulleys

35, 36, and 37. Slotted member 6i has an opening 62 which corresponds with opening 64 of pulley bracket 38 (FIGURE 3). A bolt 66 is received by opening 64, and its shank 63, passes through opening 62 of slotted member 66 for the purpose of mounting the gripping device on a bowed roll.

The gripping device described above is mounted on each end of the shaft of a bowed roll, as for example shaft 31 of bowed roll 24 (FIGURES 5 and 6) by means of a mounting bracket comprising

clamp members

76 and 72, bracket member 74 which is mounted on clamp member 72 and rigidly held by supports 76 and '78. The clamp members iii and 72 are positioned about shaft 31 of bowed roll 24 and are held fast onto shaft 331 by means of bolts 79 passing through holes 8 Bracket member 74 contains a semi-split sleeve 82 for receiving positioning rod 84 which is held fast in sleeve d2 by means of bolts 85 passing through holes 36 and secured at their threaded ends by nuts 87. Positioning rod 8 has a squared end 83 which is received by slotted member 69 of pulley bracket 38. The shank 68 of bolt 66 passes through the opening 62 of slotted member 69, through hole of I positioning rod 84 and is locked at its threaded end by nut 92. Pulley bracket 38 can thus be adjusted toward and away from the bowed roll 24 by loosening nut 92 and sliding the pulley bracket 38, by means of slotted member 60, relative to the squared end 88 of positioned rod 84.

Edge gripping devices are provided near each of the ends of bowed rolls 22 and 24, and are mounted on the

shafts

30 and 31 of the bowed rolls 22 and 24 as described above. Each of the edge gripping devices are so mounted in relation to the bowed rolls that the endless belt 40 of each device contacts the bowed roll for a substantial portion of the belt run. The belts 40 are driven by contacting the bowed rolls, and the direction of travel of each belt is perpendicular to the longitudinal roll axis at the point of contact between the belt and the bowed roll. In operation, the web P is pressed at its margins against each bowed

roll

22 and 24 by endless belt 40 of each gripping device and is thus gripped therebetween, whereby lateral slippage between each bowed roll and the web is reduced to a minimum, and the stretching effect of each bowed roll on the traveling web is accordingly increased.

The pulley of FIGURE 7 is illustrative of the type of pulleys that have been employed in the edge gripping devices. The peripheral edge of the pulley casing 100 is flanged to receive an endless belt. The casing 100 rides on ball bearings 101 housed within the inner and

outer races

102 and 103 which are retained in bearing

blocks

104 and 105 by means of snap ring 106. Spacer ring 107 is provided between the outer race-s 102. The ball bearings are retained on the extended shaft portion 108 of shaft 109 by means of snap ring 110. A grease fitting 111 and passageway 112 are provided for lubrication purposes.

The following data are illustrative for a publication paper of about 50 pounds basis weight which has been treated in a manner according to the present invention, employing two bowed rolls in tandem. The moisture trol sample web, which was not subjected to the stretchaction at the first bowed roll was 17%. The amount of bow of each roll was 4%. The web wrap on each roll was 140, and the web tension in the machine direction was about 4 /2 pounds per linear inch.

All of the following coefiicients of hydroexpansivity were measured in the center of the web. For purposes of determining the coefficient of hygroexpansivity, the relative humidity was varied from to 80%. The control sample web, which was not subjected to the stretching action of the bowed rolls, had a coefiicient of hygroexpansivity in the cross-machine direction of 13.9. The paper that was stretched by the bowed rolls exhibited a coefficient of hygroexpansivity in the cross-machine direction of 7.3, which amounted to an improvement of about 47.5%. The coefficient of hygroexpansivity in the machine direction of the control sample was about 4, and the stretched paper had a value of about 3 in that direction. It can be seen that the effect of stretching the paper laterally had no harmful effect on the hygroexpansivity of the paper in the machine direction, and, in fact, the machine direction hygroexpansivity was reduced.

The deckle loss of the web in the above example was 5% for the control sample. After final drying, the deckle loss of the treated sample was only 2.0%, indicating that a permanent restoration of 60% of deckle loss was effected by the lateral stretching of the web.

As previously mentioned, it has been found that greater improvements in hygroexpansivity per degree of deckle recovery are effected in the preferred moisture range when the paper is drier. The following data are illustrative of this point. In one instance, paper was treated in the manner according to this invention while the web had a moisture content of about For a 1% increase in total reel width, the percent reduction in the co- 0 efficient of hygroexpansivity in the cross-machine direction as compared to that of the untreated web, was about 11%. Paper of similar quality which was treated in the identical manner according to this invention while the web had a moisture content of about 10%, exhibited a reduction in the coefiicient of hygroexpansivity in the crossmachine direction of about 19% for a 1% increase in total reel width, indicating that almost twice as much improvement in hygroexpansivity was effected at the lower moisture content.

Improvements in the stiffness of the paper have also been obtained by treating webs in the manner of this invention, and the following data are illustrative of a paper of about 48 pounds basis weight which has been laterally stretched by the use of bowed rolls in tandem to effect an improvement in the coefficient of hygroexpansivity of about 20%. The stiffness of this same paper was increased ll% in the cross-machine direction over the stiffness of the untreated paper. Over a series of commercial runs, improvements in stiffness as high as 21% in the cross-machine direction have been noted, with an average of about 10% improvement in stiffness in the cross-machine direction and about 7% improvement in the machine direction.

While our invention has disclosed the use of two bowed rolls for laterally stretching a web of paper, more than two such rolls have been employed successfully, and such use is therefore contemplated to be within the scope of our invention. Also, while we have mentioned webs of paper, it is to be noted that webs of paperboard and other material in web form may be treated in the manner of this invention.

While a preferred embodiment of the invention has been illustrated and described in detail, it is to be understood that changes may be made therein and the invention practiced in other forms. It is not, therefore, our intenton to limit the patent to the specific details illustratively described, but to cover the invention broadly in whatever form its principles may be utilized.

We claim:

1. A device for increasing the lateral stretching effect of a bowed roll on a traveling web of paper passing around the surface of the bowed roll which comprises a bracket member and an endless resilient belt rotatably mounted on said bracket member, said device mounted and disposed in relation to the bowed roll whereby a portion of the endless resilient belt presses the traveling web at the web margin against the surface of the bowed roll to grip the web between the endless resilient belt and the bowed roll surface.

2. A device for increasing the lateral stretching effect of a bowed roll on a traveling web of paper passing around the surface of the bowed roll which comprises a bracket member, rotatable means mounted on said bracket member, and an endless resilient belt passing around said rotatable means, said device mounted and disposed in relation to the bowed roll whereby a portion of the endless resilient belt presses the traveling web at the web margin against the surface of the bowed roll to grip the web between the endless resilient belt and the bowed roll surface.

3. A device for increasing the lateral stretching effect of a bowed roll on a traveling web of paper passing around the surface of the bowed roll which comprises a bracket member, rotatable means mounted on said bracket member, an endless resilient belt passing around said rotatable means, and means for mounting said bracket member on the shaft of a bowed roll, said device disposed in relation to the bowed roll whereby a portion of the endless resilient belt presses the traveling web at the web margin against the surface of the bowed roll to grip the web between the endless resilient belt and the bowed roll surface.

4. A device for increasing the lateral stretching effect of a bowed roll on a traveling web of paper passing around the surface of the bowed roll which comprises a bracket member, rotatable means mounted on said bracket member, tensioning means adjustably mounted on said bracket member, rotatable means mounted on said tensioning means, an endless resilient belt passing around the rotatable means mounted on the bracket member and on the tensioning means, and means for mounting said bracket member on the shaft of a bowed roll, said device disposed in relation to the bowed roll whereby a portion of the endless resilient belt presses the traveling web at the web margin against the surface of the bowed roll to grip the web between the endless resilient belt and the bowed roll surface.

5. A device for increasing the lateral stretching effect of a bowed roll on a traveling web of paper passing around the surface of the bowed roll which comprises a bracket member, rotatable means mounted on said bracket member, a tension arm rotatably mounted at one end on said bracket member, rotatable means mounted on the tension arm, an endless resilient belt passing around the rotatable means mounted on the bracket member and on the tension arm, means for adjusting the position of the tension arm to increase and decrease the tension on the endless resilient belt, and means for mounting said bracket member on the s'-aft of a bowed roll, said device disposed in relation to the bowed roll whereby a portion of the endless resilient belt presses the traveling web. at the web margin against the surface of the bowed roll to grip the web between the endless resilient belt and the bowed roll surface.

6. A device for increasing the lateral stretching eifect of a bowed roll on a traveling web of paper passing around the surface of the bowed roll which comprises a pulley bracket, pulleys rotatably mounted on said pulley bracket, a tension arm rotatably mounted at one end on said pulley bracket, a pulley rotatably mounted on said tension arm, an endless resilient belt passing around and received by the said pulleys, means for adjusting the position of the tension arm to increase and decrease the tension on the endless resilient belt, means for mounting the pulley bracket on the shaft of a bowed roll, and pulley bracket positioning means connecting said pulley bracket to said pulley bracket mounting means, whereby said pulley bracket may be adjusted toward and away from the bowed roll, said device disposed in relation to the bowed roll whereby a portion of the endless resilient belt presses the traveling web at the web margin against the surface of the bowed roll to grip the web between the endless resilient belt and the bowed roll surface.

7. In combination, a bowed roll for laterally stretching a traveling Web of paper and the like passing thereover, and a web edge gripping device for increasing the lateral stretching effect of the bowed roll on the traveling web, comprising a bracket member and an endless resilient belt rotatably mounted on said bracket member, said web edge gripping device disposed and mounted in relation to the bowed roll whereby a portion of the endless resilient belt presses the traveling web at the web margin against the surface of the bowed roll to grip the web between the endless resilient belt and the bowed roll surface.

8. In combination, a bowed roll for laterally stretching a traveling web of paper and the like passing thereover, and a web edge gripping device for increasing the lateral stretching effect of said bowed roll on the traveling web, said web edge gripping device comprising a bracket member, rotatable means mounted on said bracket member, an endless resilient belt passing around said rotatable means, and means for mounting said bracket member on the shaft of said bowed roll, said web edge gripping device disposed in relation to said bowed roll whereby a portion of the endless resilient belt presses the traveling web at the web margin against the surface of the bowed roll to grip the web between the endless resilient belt and the bowed roll surface.

9. In combination, a bowed roll for laterally stretching a traveling web of paper and the like passing thereover,

lil

and a web edge gripping device for increasing the lateral stretching effect of said bowed roll on the traveling web, said web edge gripping device comprising a pulley bracket, pulleys rotatably mounted on said pulley bracket, a tension arm rotatably mounted at one end of said pulley bracket, a pulley rotatably mounted on said tension arm, an endless resilient belt passing around and received by said pulleys, means for adjusting the position of the tension arm to increase and decrease the tension on the endless resilient belt, means for mounting the pulley bracket on the shaft of said bowed roll, and pulley bracket positioning means connecting said pulley bracket to said pulley bracket mounting means, whereby said pulley bracket may be adjusted toward and away from said bowed roll, said web edge gripping device disposed in relation to said bowed roll whereby a portion of the endless resilient belt presses the traveling web at the web margin against the surface of the bowed roll to grip the web between the endless resilient belt and the bowed roll surface.

10. In the method of treating a traveling web of paper which involves passing the web before final drying around successive bowed rolls in tandem disposed with their longitudinal axes substantially at right angles to the longitudinal axis of the paper machine, stretching the web laterally as said web passes around each bowed roll to recover a substantial fraction of the loss of deckle that has been sustained due to shrinkage of the web in the cross-machine direction, and completing the drying operation, the improvement for reducing the coefficient of hygroexpansivity of the paper in the cross-machine direction and increasing the stifiness of the paper which comprises gripping the web at its margins as said web passes around each bowed roll to decrease the lateral slippage between the web and the bowed rolls.

11. In the method of treating a traveling web of paper which involves steps of (a) passing the web before final drying around successive bowed rolls in tandem disposed with their longitudinal axes substantially at right angles to the longitudinal axis of the paper machine, (b) stretching the web laterally as said web passes around each bowed roll to recover a substantial fraction of the loss of deckle that has been sustained due to shrinkage of the web in the cross-machine direction, and (c) completing the drying operation, the improvement for reducing the coetiicient of hygroexpansivity of the paper in the cross-machine direction and increasing the stiffness of the paper which comprises (a') gripping the web at the margins as said web passes around each bowed roll to decrease the lateral slippage between the web and the bowed rolls, and (e) laterally stretching the web in step (b) above while the web has a moisture content in the range of from 8 to 50%.

12. In the method of treating a traveling web of paper which involves steps of (a) passing the web before final rying around successive bowed rolls in tandem disposed with their longitudinal axes substantially at right angles to the longitudinal axis of the paper machine, (b) stretching the web laterally as said web passes around each bowed roll to recover a substantial fraction of the loss of deckle that has been sustained due to shrinkage of the web in the cross-machine direction, and (c) completing the drying operation, the improvement for reducing the coefiicient of hygroexpansivity of the paper in the cross-machine direction and increasing the stiffness of the paper in the cross-machine direction which comprises (d) passing the web in step (a) above around bowed rolls which have a bowed surface in the range of from 1 to 4%, (e) gripping the web at its margins, as. the web wraps each bowed roll in the range of from 50 to of the circumference of each bowed roll, to decrease the lateral slippage between the web and the bowed rolls, and (f) laterally stretching the web in step (b) above while the web has a moisture content in the range of from 8 to 50%.

13. In the method of treating a traveling web of paper which involves passing the web before final drying around successive, non-uniformly bowed rolls in tandem disposed with their longitudinal axes substantially at right angles to the longitudinal axis of the paper machine, each of said rolls having a greater degree of bow at the end portions than in the central portion thereof, stretching the web laterally, more so at the web margins than at the center of the web, as said web passes around each nonuniformly bowed roll to recover a substantial fraction of the loss of deckle that has been sustained due to shrinkage of the web in the cross-machine direction, and completing the drying operation, the improvement for reducing the coefficient of hygroexpansivity of the paper in the cross-machine direction and increasing the stiffness of the paper which comprises gripping the web at its margins as said web passes around each non-uniformly bowed roll to decrease the lateral slippage between the web and the non-uniformly bowed rolls.

14. In the method of treating a traveling web of paper which involves steps of (a) passing the web before final drying around successive, non-uniformly bowed rolls in tandem disposed with their longitudinal axes substantially at right angles to the longitudinal axis of the paper rnachine, each of said rolls having a greater degree of bow at the end portions than in the central portion thereof, (b) stretching the web laterally, more so at the web margins than at the center of the web, as said web passes around each non-uniformly bowed roll to recover a substantial fraction of the loss of deckle that has been sustained due to shrinkage of the web in the cross-machine direction, and (c) completing the drying operation, the improvement for reducing the coefficient of hygroexpansivity of the paper in the cross-machine direction and increasing the stiffness of the paper which comprises (d) gripping the web at its margins, as said web wraps each non-uniformly bowed roll in the range of from 50 to 180 of the circumference of each non-uniformly bowed roll, to decrease the lateral slippage between the web and the non-uniformly bowed rolls, and (e) laterally 12 stretching the 'web in step (b) above while the web has a moisture content in the range of from 8 to 50%.

15. In the method of treating a traveling web of paper which involves steps of (a) passing the web before final drying around successive, non-uniformly bowed rolls in tandem disposed with their longitudinal axes substantially at right angles to the longitudinal axis of the paper machine, each of said rolls having a greater degree of bow at the end portions than in the central portion thereof, (b) stretching the web laterally, more so at the web margins than at the center of the web, as said web passes around each non-uniformly bowed roll to recover a substantial fraction of the loss of deckle that has been sustained due to shrinkage of the web in the cross-machine direction, and (c) completing the drying operation, the improvement for reducing the coelficient of hygroexpansivity of the paper in the cross-machine direction and increasing the stiffness of the paper in the cross-machine direction which comprises (d) gripping the Web at its margins, as said web wraps each non-uniformly bowed roll in the range of from 90 to 145 of the circumference of each non-uniformly bowed roll, to decrease the lateral slippage between the Web and the non-uniformly bowed rolls, and (e) laterally stretching the web in step (b) above while the web has a moisture content in the range of from 10 to 30%.

References Cited in the file of this patent UNITED STATES PATENTS 754,797 Ostrander Mar. 15, 1904 1,077,126 Doughty Oct. 28, 1913 2,054,214 Buss Sept. 15, 1936 2,547,975 Robertson Apr. 10, 1951 3,012,301 Rogers et a1. Dec. 12, 1961 FOREIGN PATENTS 1,073,292 Germany Jan. 14, 1960 5 UNITED STATES PATENT OFFICE v CERTIFICATE OF CORRECTION Patent No. 3 1 61 ,563 December 15 1964 William C Walker et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2 line 21 for "konwn'" read known line 4L4 for "though" read thought column 3, line 58, for "web" read wet column 7 line 5 for "positioned" read gl ositioning line 4% for '"trol sample web which was not subjected to the stretch-" read content of the web when it was subjected to the stretching Signed and sealed this 20th day of April 1965.

(SEAL).

Attes t:

ERNEST w. SWIDER' EDWARD J. BRENNER ,Attesting Officer Commissioner of Patents

Claims

1. A DEVICE FOR INCREASING THE LATERAL STRETCHING EFFECT OF A BOWED ROLL ON A TRAVELING WEB OF PAPER PASSING AROUND THE SURFACE OF THE BOWED ROLL WHICH COMPRISES A BRACKET MEMBER AND AN ENDLESS RESILIENT BELT ROTATABLY MOUNTED ON SAID BRACKET MEMBER, SID DEVICE MOUNTED AND DISPOSED IN RELATION TO THE BOWED ROLL WHEREBY A PORTION OF THE ENDLESS RESILIENT BELT PRESSES THE TRAVELING WEB AT THE WEB MARGIN AGAINST THE SURFACE OF THE BOWED ROLL TO GRIP THE WEB BETWEEN THE ENDLESS RESILIENT BELT AND THE BOWED ROLL SURFACE.

10. IN THE METHOD OF TREATING A TRAVELIN WEB OF PAPER WHICH INVOLVES PASSING THE WEB BEFORE FINAL DRYING AROUND SUCCESSIVE BOWED ROLLS IN TANDEM DISPOSED WITH THEIR LONGITUDINAL AXES SUBSTANTIALLY AT RIGHT ANGLES TO THE LONGITUDINAL AXIS OF THE PAPER MACHINE, STRETCHING THE WEB LATERALLY AS SAID WEB PASSES AROUND EACH BOWED ROLL TO RECOVER A SUBSTANTIAL FRACTION OF THE LOSS OF DECKLE THAT HAS BEEN SUSTAINED DUE TO SHRINKAGE OF THE WEB IN THE CROSS-MACHINE DIRECTION, AND COMPLETING THE DRYING OPERATION, THE IMPROVEMENT FOR REDUCING THE COEFFICIENT OF HYGOREXPANSIVITY OF THE PAPER IN THE CROSS-MACHINE DIRECTION AND INCREASING THE STIFFNESS OF THE PAPER WHICH COMPRISES GRIPPING THE WEB AT ITS MARGINS AS SAID WEB PASSES AROUND EACH BOWED ROLL TO DECREASE TH LATERAL SLIPPAGE BETWEEN THE WEB AND THE BOWED ROLLS.