US2054214A - Process and apparatus for making paper - Google Patents

Description

Sept. 15, 1936. J. BUSS 2,054,214

' PROCESS AND APPARATUS FOR MAKING PAPER Filed April 26, 1954 on the machine.

Patented Sept. 15, 1936 UNITED STATES PATENT OFFICE John Buss, Toronto, Ontario, Canada, assignor to Provincial Paper Limited, Toronto, Ontario,

Canada Application April 26, 1934, Serial No. 722,548

11 Claims.

It is a well recognized fact that in all machine made paper there is a grain and the direction of the grain is understood to run parallel with the direction of movement of the paper as it is made The existence of this grain is evidenced in several ways, among which may be mentioned, first the paper is stiffer inthe grain direction, second, the paper is stronger in tensile strength in the grain direction, and third, the paper has less resistance to tearing in the grain direction than transversely thereto. ing, this grain effect possesses a number of disadvantages. One of these disadvantages is that the paper does not fold as readily or evenly across the grain as along the grain, with A the result that the folds transversely of the grain 55 ditioned press rooms, in maintaining proper reg-.

are more or less uneven and there is a greater tendency to crack the paper on such fold lines.

Paper is also very susceptible to atmospheric changes, particularly as regards humidity, and one of the main disadvantages of paper having a grain is that the paper is not affected evenly in all directions, and it is found that the larger and consequently more serious change is always in the cross grain direction of the paper, which manifests itself in producing wavy edges, bagging of the centre of a sheet, or curling of the sheet. For example, paper, when sheeted and stacked in unprotected piles, is susceptible to atmospheric changes along the edges of the sheet or sides of the pile. When the relationship of the moisture content of the paper and the humidity of the surrounding air is such that the pile absorbs moisture, the paper stretches at the edges and forms a series of waves, which waves are almost wholly along the cross-grain edge of the paper. Conversely, though less frequently, moisture evaporation from the paper causes the sheets in a pile to become tight at the edges and baggy in the centre. For some printing processes paper in either of these conditions. is diflicult to use.

Paper in roll form will also stretch, and rolls from certain types of winders, particularly those 'making hard, tightly wound rolls, frequently acquire ridges running around the roll surface, and are caused by moisture absorption and consequent stretching.

Such waving, bagging or ridging of the paper results in .a paper having an objectionable appearance and is very difficult to flatten out, and for certain work a considerable portion of thepaper has to be wasted.

In multi-colored printing operations, difiiculty is frequently experienced, particularly in uncon- Paper .hav-- solved in or mixed with water, there is a distinct tendency for the paper to curl, and it is f0und' O that the curling occurs so that the valley formed is parallel with'the grain.

The behaviour of the paper as above set forth is generally understood to be due to the theory that more fibres run parallel with the grain than 15 at right angles thereto, and that this arrangement of the fibres has been due to t fibres having a tendency to arrange themselves lengthwise of the stream flow as the thin suspension of fibres in water flow on to the screen of the Fourdrinier machine. It has been found, however, that the influence of the fiow of stock on the wire is by no means as great as is commonly supposed, and that the wet sheet as it leaves the screen of the Fourdrinier machine shrinks on dry-'- ing and expands on remoistening almost as much in the grain direction as at right angles thereto. This indicates that the conditions which contribute to the greater differences, due to grain, which actually are present in the finished paper, occur after the sheet is formed on the wire. In this respect it will be noted that in the regular Fourdrinier machine the sheet is allowed to shrink more or less unrestrictedly across the grain during its progress through the machine, whereas in the grain direction the sheet is not only prevented from shrinking, but is actually stretched, which stretching is produced by the drawing or pulling of the sheet through and between the machine sections, and particularly as there is a tendency to drive any one section at a slightly greater speed than the section immediately behind it. This longitudinal stretching tends to narrow the sheet, and further tends to pull the fibres into the directionof longitudinal travel of the sheet and causes the grain effect.

My object therefore is to devise a method and apparatus for making paper which in its finished state will have more nearly the same characteristics in .a direction transversely of the sheet as in the direction longitudinally of the sheet, having reference to its direction of travel through the apparatus, and which will therefore be substantially free of the disadvantages above referred to.

,I attain my object by providing means for at least maintaining the width of the paper web as it is drawn through the drying apparatus and preferably for subjecting the paper to stretching in a direction transversely of the web.

The details of the method and apparatus are hereinafter more specifically described .and illustrated in the accompanying drawing in which Fig. 1 is a diagrammatic view of part of papermaking apparatus constructed in accordance with my invention;

Fig. 2 a front view partly broken away of one of the stretching rolls;

Fig. 3 a detail showing the method of mounting the stretching roll;

Fig. 4 a front view of a modified form of stretching roll; and

Fig. 5 a detail showing a modified arrangement of stretching rolls.

In the drawing like numerals of referen e indicate corresponding parts in the different figures.

In manufacturing paper with my process and apparatus, the standard method is employed, in which the thin suspension of fibres and water is fed on to the screen (not shown) of the Fourdrinier machine from which the wet web I thus formed is led on to an endless fabric band 2 and passed between one or more pairs of squeezing rollers 3, around a guide roll 4, thence over a heated cylinder 5, around another guide roll 6 to other squeezing or drying rolls 1, only one pair of which is shown, it will be apparent that there is aconsiderable pull on the web, with the result that the web is stretched longitudinally, which at the same time effects a narrowing of the web transversely, and it is this stretching of the web in the longitudinal direction and contraction in the transverse direction which results in the formation of the grain in the finished paper.

I therefore provide means for effecting a stretching or expansion of the paper transversely of the web as it travels through the drying apparatus. As a convenient method of effecting this transverse stretching, I utilize certain of the rolls, for example, the guide rolls 4 and 6, and these rolls, are preferably of the special construction as shown in Fig. 2. Each of the rolls 4 and 6 is formed with a non-rotatable supporting bar 8 which is slightly curved from end to end, and on this bar is sleeved a tubular roller 9 of rubber hose or other suitable flexible material. The tube 9 is free to rotate on the bar 8. To facilitate the rotation of the flexible tube 9 on the bar 8, a film of water is maintained between their adjacent surfaces, and as the most convenient way of supplying this water film, the bar 8 is preferably formed as a tube and has a plurality of small outlets I0 formed in its wall for the escape of water into the interior of the tube 9, water is fed under pressure to the interior of the tubular bar 8 from a pipe IQ connected with a main H. The water escaping from each end of the tubular roller 9 is collected in a receiver I2 into which the end of the roller 9 projects, and a pipe 13 carries off the water collected in the receiver.

It will be evident, however, that air or other fluid may be used in place of the water to reduce the friction between the bar 8 and roller 9.

The supporting bar 8 is preferably arranged so that its convex side is directed on a line substantially at right angles to a line bisecting the angle formed by the paper passing from the preceding roll to the following roll. As the paper passing over the stretching roll tends to travel at right angles to the axis of the roll, it Will be seen that there is a transverse stretching of the paper, as

will be evident from Fig. 2 of the drawing, from the point it engages the stretching roll to the point it disengages. Care must be taken to avoid uneven stretching which might produce slackness either at the centre or at the edge portions of the sheet, and the rolls 4 and 6 are therefore mounted so they may be adjusted to a position which ensures substantially even stretching throughout the width of the web. In Fig. 3, the bar 8 is shown as supported from a supporting bar M by a U-bo lt |5. By loosening the nuts on the U-bolt IS, the bar 8 may be rotated and then secured in adjusted position by tightening the nuts I6.

The operation of the apparatus is as follows. The web from the rolls 3 is passed around the roller 4, which, due to its convexing, effects a slight stretching of the paper transversely and the paper passes immediately in its stretched condition to the roll 5, from which it in turn passes around the roll 6, where it is again slightly stretched before passing to the rolls 1.

While, theoretically, the desired amount of transverse stretching could be accomplished by one or two stretching rolls, to avoid splitting the web and also to avoid any bagginess or slackness of the web at the centre, I prefer to use a number of these stretching rolls, each one contributing its share to the complete stretching, and to secure proper results, it is evident that the stretching roll is arranged so that the stretched web is fed over an ordinarystraight or substantially straight roll. It is also preferred that these stretching rolls be arranged in conjunction with rolls which provide a large lap for the web.

While best results are obtained if the stretching rolls are positioned in or near the wet end of the apparatus, it will be evident that these stretching rolls may be positioned at any point in the apparatus where the paper retains at least a small percentage of moisture and a certain measure of success obtained in this transverse stretching.

It is also important to secure most efiicient results that the stretching rolls be .arranged at points in the machine where a change in direction of travel of the paper web takes place, thus ensuring a longer contact of the web with the paper roll, and therefore a more effective transverse stretching of the web.

In Fig. 4 a modified form of stretching roll is I shown. On a curved rod I! a plurality of closely set rolls [8 are mounted, preferably with ball or are closely arranged and preferably comparatively narrow to reduce the gaps between the rolls at the convex side of the supporting bar.

It will be understood, of course, that the arrangement of. rolls may be varied in many ways. In Fig. 5 a modified arrangement is shown in which the web is led from'a roll l9 over a series of stretching rolls 20 to anotherv roll 2|, each of the stretching rolls being positioned to effect a change in the direction of travel of the'web.

What I claim as my invention is:-

1. In apparatus for making paper, the com-- bination of a plurality of rolls over which the web is drawn' while in a moist condition; and means for stretching the web transversely as it passes to one of said rolls, said means comprising a longitudinally curved supporting bar and a flexible tube rotatable on said bar with which the is drawn while drying; and means for stretching the web transversely as it passes to one of roller bearings to reduce friction. These rolls said rolls said means comprising a longitudinally curved tubular supporting bar and a flexible tube rotatable on said bar with which the web engages, said bar having holes formed in its surface, and means for supplying fluid to the interior of said bar.

3. In apparatus for making paper, the combination of a plurality of rolls over which the web is drawn while drying; and means for stretchingfthe web transversely as it passes to one'of said rolls said means comprising a longitudinally curved tubular supporting bar and a flexible tube rotatable on said bar with which the web engages, said bar having holes formed in its surface, and means for supplying fluid to the interior of said bar and means for collecting fluid from the ends of the flexible tube.

4. In apparatus for making paper, the combination of a plurality of rolls over which the web is drawn while in a moist condition; and means for stretching the web transversely as it passes to one of said rolls, said means comprising a member with which the web engages, the surface of said member with which the web en,- gages being convexed transversely of said web and means for rotarily adjusting the position of said member relative to the preceding roll.

5. In apparatus for making paper, the combination of a plurality of rolls over which the web is drawn whilein a moist condition; and means for stretching the web transversely as it passes to one of said rolls, said means comprising a member with which the web engages, the surface of said member with which the web engages being convexed transversely (if said web, said member being positioned to effect a change in direction of travel of the web and means for rotarily adjusting the position of said member relative to the preceding roll.

6. In apparatus for making paper, the combination of a plurality of rolls over which the web travels while in a moist condition, said rolls being arranged to effect changes in the direction of travel of said web; one of said rolls being longitudinally curved with its convex surface engaging the web, and the following roll being substantially straight longitudinally, said curved roll comprising a longitudinally curved support having paper web engaging means rotatable thereon, said support being rotarily adjustable relative to the preceding roll.

'7. In a method of making paper, the step of drawing the unsupported web of paper under tension over a plurality of rolls while drying,

and simultaneously stretching the web in a direction at right angles to that in which it is travelling as it passes between two of said rolls.

8. In a method of making paper, the step of drawing the unsupported web of paper under tension over a plurality of rolls while drying, and simultaneously stretching the web at intervals in a direction at right angles to that in which it is travelling as it passes between pairs of said rolls.

9. In apparatus for making paper, the combination with a pair of rolls over which the paper travels while in a moist condition, of an intermediate roll positioned to effect a change in direction of travel of the paper as it passes from one roll to the other, said intermediate roll having its axis curved longitudinally, the convex side of said roll engaging the web and its concave side facing the approaching paper.

10. In apparatus for making paper, the combination with a pair of rolls over which the paper travels while drying-,mf an intermediate roll positioned to eiiect a change in direction of travel of the paper as it passes from one roll to the other, said intermediate roll having its axis curved longitudinally, the convex side of said roll being directed on a line substantially at right angles to a line bisecting the angle formed by the paper passing between the two first mentioned rolls.

11. In apparatus for making paper, the combination with a pair of rolls over which the paper travels while drying, of an intermediate roll positioned to effect a change in direction of travel of the paper as itpasses from one roll to the other, said intermediate roll being of substantially the same diameter throughout its webengaging surface and having its axis curved longitudinally, the convex side of said roll engaging the web and its concave side facing the JOHN BUSS.

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