US2163163A - Self-adjusting felt roll for paper machines - Google Patents

Description

M. T. WESTON,

Jung 20,. 1939.

SELF-ADJUSTING FELT ROLL FOR PAPER MACHINES Filed April 22, 1958 2 Sheets-Sheet l INVENTOR June 20, 1939. M. T. WESTON SELF-ADJUSTING FELT ROLL FOR PAPER MACHINES Filed April 22, 1938 2 Sheets-Sheet 2 INVENTO/f Patented June 20, 1939 UNITED STATES PATENT OFFICE SELF-ADJUSTING FELT ROLL FOR PAPER MACHINES 6 Claims.

My invention relates to improvements in selfadjusting felt rolls for paper machines and has particular reference to the felt rolls in the dryer section of the paper machine.

In present practice the dryer felt rolls are revolvable in bearings having fixed locations on the side frames of the machines and are not movable in operation from these predetermined positions. There is therefore at present no adjustment of the felt rolls with respect to their corresponding dryer cylinders to allow for the normal shrinkage or expansion of the dryer felts as they pass from cylinder to cylinder in their progress thru the dryer section. However, takeups are provided on the return runs of the felts to adjust the initial tension in them but on account of the snubbing action of so many dryer cylinders and felt rolls, these takeups can not regulate the progressively changing tension in the relatively large portion of the felts in contact with the dryer cylinders and felt rolls. In order to partially overcome the objectionable results of this common practice, the felts on the dryer section may be divided into two or more parts in order to reduce the amount of this uncontrolled shrinkage or expansion in each felt.

There are two kinds of felts used at the dryer section and the shrinkage and expansion characteristics of the one is directly opposite to those of the other. The two kinds are cotton and wool. The cotton felt, which is most widely used on modern high speed paper machines, will shrink when wet and expand when dried whereas the wool felt, also widely used, will expand when wet and shrink when dried.

From the foregoing description of the present practice of using non-adjustable felt rolls, it is obvious that both kinds of felts are now used in exactly the same manner regardless of their directly opposite shrinkage and expansion characteristics. In practice it is necessary to have a certain amount of tension in the felts in order to hold the paper web firmly in contact with the drying surface of the cylinders. This normal tension in the felts is safely below the allowable tension for which the felts are designed. However, in the case of the cotton felt as at present used, the normal tension at the first cylinder, when it is relatively dry, will be progres sively increased as more moisture is driven out of the paper web and into the felts by the successive cylinders. The result is that the felts become tensed far beyond their elastic limit and take a permanent stretch and this excessive stretching continues until the felts become hard and no longer useful on the machine. The life of the felt is thus greatlyshortened. In the case of wool felts, the normal tension may not be sufficient for proper operation and, as we have seen, there is no way at present to increase or decrease the tension either progressively or at any given point in the dryer section.

The principal objects of my invention are, therefore, to provide felt rolls which are individually or collectively self-adjusting with respect to their corresponding dryer cylinders and which will automatically compensate for the shrinkage or expansion of the dryer felts and will maintain at all times a predetermined normal operating tension in the dryer felts regardless of the shrinkage or expansion characteristics of the material from which the felts are made.

Another object is to provide individually selfadjusting felt rolls which permit changing the operating tension in the'dryer felts either progressively or at any point in the dryer section regardless of the felt characteristics.

It is also present practice to run all of the dryer cylinders at the same peripheral speed Which has the objectionable result of making the paper very much stronger in one direction than in the other. My pending applications on Micro-variable paper machine drives, Ser. No. 96,805, and on Paper machine drives, Ser. No. 183,745, contemplate the progressive slowing down of the successive dry-er cylinders to allow for the normal shrinkage of the paper web and thus substantially equalize its strength in both directions. However, the maximum shrinkage of some grades of paper is as much as 10% which, no doubt, is considerably more than the normal shrinkage of the felts. If the present non-adjustable felt rolls were used there would be a complete loss of the necessary operating tension and a considerable accumulation of slack in the felts due to the difference in shrinkage between the felts and the paper, making it im practicable to obtain the full benefit contemplated by my two pending applications above referred to. On the other hand, the self-adjusting felt rolls contemplated in this application will automatically take up all of the excess slack progressively and will also maintain the correct predetermined operating tension in the felts at all times regardless of their shrinkage characteristics. This, therefore, becomes a very important object of this invention.

Other objects and advantages will appear in the following specifications and are shown in the accompanying drawings in which similar reference numerals refer to like parts in all of the views.

Fig. 1 is a diagrammatic side view showing a typical arrangement of the dryer cylinders and felt rolls in a modern paper machine in accordance with present practice.

Fig. 2 is a diagrammatic side view of a portion of the dryer section showing the collective arrangement of my self-adjusting felt rolls. The dryer cylinders in this view are the ones where the greatest evaporation takes place, represented at B in Fig. 1.

Fig. 3 is a diagrammatic side view simil-arto Fig. 2 and shows the application of my indivdual self-adjusting felt rolls to the same group of dryer cylinders.

Fig. 4 is a partial sectional elevation of one of my self-adjusting felt rolls. The sections are taken on a line 4-4 of Fig. 9.

Fig. 5 is a partial sectional elevation of the operating end of one of my individual self-adjusting felt rolls. The section is taken on lines 5-5 in Figs. 7 and 8.

Fig. 6 is a partial horizontal sectional View of the operating end of -one of my individual selfadjusting felt-rolls. The section is taken on a line 6-6 in Fig. 8.

Fig. '7 is an exterior elevation of either end of one of my self-adjusting felt rolls as illustrated in Fig. 4, showing a bracket and guide.

Fig. 8 is a sectional elevation of the operating end of one of my individual self-adjusting felt rolls. The view is taken-on lines 88 in Figs. 5 and 6.

Fig. 9 is an enlarged partial side elevation of the collective arrangement of my self-adjusting felt rolls. The view is similar 'to Fig. 2.

Fig. 10 is a diagrammatic View showinga different application of the tension cable from that shown in Fig. 8.

In Fig. 1 the paper web I is shown entering the dryer section between the first lower dryer cylinder 2 and the bottom felt 3 and continuing alternately under lower cylinders 2 and over upper cylinders 4 and emerging fromthedryer section at Ia. Obviously the bottomfelt .3 can not follow the paper web I continuously as it would pass between the upper cylinders '4 and the paper web I. The felt is therefore divided into bottom felts 3 and top felts 5 and eachis shown in two parts and indicated by dotted lines .in'Fig. 1. However, the felts 3 and 5 are shown continuous in Figs. 2 and 3. The bottom felt 3 passes over the first bottom feltrollB and alternately under lower cylinders 2 and over bottom felt rolls 6 and returns aroundfelt idler "I, a takeup -8 and felt idler 9. Similarly the top felt '5 passes: under first top felt roll I0 and alternately over upper cylinders 4 and under top felt rolls I0 and returns around felt idler II, takeup I2 and feltidler I 3. This is substantially present practice employing non-adjustable felt rolls, whether the felts are in one, two or more parts.

In Fig. 1 the dryer cylinders are divided'into three groups A, B and C. Group' A brings the temperature of the paperweb- I up to the .point where evaporation begins. In group B evaporation is accelerated and. reaches itsmaximum toward the end ofthe group. In group'C therelatively small amount of moisture remaining is reduced to the commercial requirement of from 8% to 10%.

It will be understood that, because of the relatively small amount of moisture being driven'off in groups A and C, there will be very little -25 feet.

'terior rack 22.

.any endwise movement. opposite ends of the shaft I'I adjacent to the guide blocks '23 are the pinions '24 which mesh change in the length of the felts due to shrinkage in cotton felts or expansion in wool felts and consequently the non-adjusting felt rolls 6 and Ill may be retained in these groups. It is in group B that the self-adjusting felt rolls, in this application, are most advantageously used. Figs. 2 and 3 show their application to this group.

My invention, clearly shown in Fig. 4, comprises a tubular roll I4 which corresponds in length to the width of the paper web I and which, in a modern machine, may be as long as The tubular felt roll I4 is provided at each end with a spider or head I5 securely fixed therein. The heads I5 are provided with antifriction bearings I6 and the whole is mounted torevolve on a shaft I! which passes thru the center of the tubular roll. The shaft I! being very long relative to its required diameter would, no .doubt, deflect excessively. I overcome this excessive deflection by providing two anti-friction bearings I6 in each head I5 spaced apart axially which holds the outer ends of the shaft I'I concentrically'true with tubular roll I 4. Any deflection in the shaft I'I between the two inner bearings IB-is taken care of by an interior spider I8 toward .the middle of the tubular roll I4 thru which the shaft I1 passes and by which it is concentrically-supported. Shaft II, which partially revolves only when the complete felt roll functions by moving up or down to take up any slack in the felt or to maintain the predetermined working tension, is mounted in the following manner. End brackets I9 are mounted on the side frames 20 of the paper machine, in place of the fixed bearings now used, and are provided with double interior guides 2| and a single in- On the outer ends of the shaft I! are mounted'the guide blocks 23, in which the shaft is free to turn, engaging the guides 2I.

These guide blocks 23 serve to keep the tubular .40

feltroll I4 in vertical alignment and to prevent Also mounted on the with the racks 22 in the brackets I9. The guide blocks "'23 also function to positively keep the pinions 24 in mesh with the racks 22. The brackets I9 are open atone end for ease in assembling the parts.

'It is evident from this construction that the shaft I! can move up or down only by turning since the pinions 24 are positivelykeyed or otherwise secured on the shaft II. It is also evident, for the same reason, that both ends of the shaft I1 must move equally in either direction regardless of any inequality of stresses at the ends.

"It follows therefore that the roll I4 must also move up or down in perfect alignment whether 'the tension in the felt is the same at both ends It will therefore be observed of the-roll or not. from the foregoing that a force may be applied at one end of the shaft H to move the felt roll I4 up or down in perfect alignment regardless of the variable stresses which may occur at opposite ends of the roll. This is very important because it obviates the necessity of having obstructing mechanism at the front of the paper machine which would hinder the clearing of the dryer section in case of a break in the paper web.

In my invention I therefore apply this force at the rear of the paper machine which is now more or less inaccessible on account of the continuous train of dryer gears.

This force or tension is applied to the shaft I! in the following manner. I mount a sheave 25 on shaft I! at the rear of the machine next to the pinion 24. In the collective type shown in Figs. 2, 4 and 9, the sheave 25 is provided with a bushing 26 which permits the shaft I! to turn therein. A continuous tension cable 21, clearly shown in Figs. 2 and 9, is passed over sheaves 25 on stationary felt rolls 28 at each end of the adjustable group and then alternately under the sheave 25 on the adjustable bottom felt rolls I4 and over the sheave 25 on the adjustable top felt rolls I4. The free ends of the cable 21 are provided with weights 29 which produce the required operating tension in all of the adjustable felt rolls I4 in the group between the stationary felt rolls 28. The tendency of the cable 21 is to pull all of the adjustable top felt rolls I4 downward and all of the adjustable bottom felt rolls I4 upward which movements are resisted by the top and bottom felts themselves thus taking up slack automatically and at the same time maintaining the required operating tension provided 'by the weights 29.

In the individual type of tension adjustment shown in Figs. 3, 5, 6, 7 and 8, the sheave 25 is keyed to the shaft I1 and is otherwise the same as in Figs. 4 and 9. However in this type, the individual tension cable 30 is preferably fastened to the rim of the sheave 25 at 3| and passes over the sheave and a weight 32 is attached to the free end. This is clearly shown in Fig. 8. By reference to this figure, which shows it applied to a bottom felt roll, the operation of this type will be clear. Because of the difference in the radii of the pinion 24 and sheave 25, the mechanical advantage is greatly in favor of the weight 32 acting at the periphery of the sheave 25 and therefore can be made relatively small. Acting on the periphery of the sheave 25 the weight 32 tends to revolve the pinion 24 clockwise causing it to travel upward on the rack 22. As we have seen, the pinion 24 on the other end of the shaft I'I must also move upward exactly the same distance which moves the felt roll I4 upward to adjust the tension in the felt. On the other hand, if the felt shrinks it pulls. the roll I4 downward, which revolves the pinion contraclockwise and lifts the weight. In either case the tension in the felt remains the same. This view serves to illustrate clearly how my self-adjusting felt rolls function to automatically take up slack in the felts and to maintain the correct operating tension therein whether they expand or shrink in operation. When applied to a top felt roll, which must move downward, the bracket I9 may be inverted as in Fig. 9 which obviously brings the rack 22 on the opposite side and reverses the movement of the pinions 24, or the cable 30 may pass over the sheave 25 contraclockwise instead of clockwise as shown.

There are, no doubt, other arrangements which might be made by any one skilled in the art as for example in Fig. 10 where the tension cable 33 is secured to a fixed anchor 34 and passes over the loose sheave 35. However, the sheave 35 may be reduced in diameter to a mere anti-friction hub 35a shown in dotted lines in this figure since there is no advantage in the larger sheave, as is the case in Fig. 8. However, a heavier weight must be used.

The operation of my automatic self-adjusting felt rolls has been made clear in the foregoing. However, I would like to point out the difference in operation between the collective type shown in Fig. 2 and the individual type shown in Fig. 3.

In Fig. 2 the self-adjusting felt rolls I4 are shown in the relative positions they would assume in cases where the felt expands more than the normal amount due to the progressive slowing down of the dryer cylinders to allow for the shrinkage of the paper web as previously explained. The self-adjusting bottom and top felt rolls I4, at the beginning of the group where the bottom felt 3 and the top felt enter, are shown in the lowest and highest positions with respect to their corresponding dryer cylinders and as the two felts progress and at the same time increase in length for the reason given, the rolls I4 move farther away from their corresponding dryer cylinders in order to take up the increased length or slack progressively and to maintain the correct operating tension in the felts. The extreme positions of the bottom and top felt rolls I4 at each end of the self-adjusting group are clearly shown in Fig. 9 with respect to the end brackets I9. There is no individual adjustment of the felt rolls I4 in this arrangement.

In Fig. 3, I illustrate the indvdual type used alternately wth the present non-adjustable felt rolls 5 and I0 where the change in length of the felts is within a moderate range. The arrangement of the adjustable felt rolls I4 in this figure illustrates their relative positions when the felts shrink, which are just opposite to their respective positions as shown in Figs 2 and 9. Furthermore the individually adjustable type has the advantage of being individually weighted to meet any contingency, as for example, the top felt rolls add their weight to the tension in the top felts while the bottom felt rolls subtract their weights from the tension in the bottom felts. The tension in both felts may be equalized by simply adding sufiicient weight to the bottom rolls to make up the difference, as illustrated in Fig. 3. Then it may be desirable to increase the tension in both felts at the point of greatest evaporation in order to hold the paper web more firmly in contact with the cylinders at this point. This is easily accomplished by adding weight in equal amounts to both top and bottom felt rolls at this point to get the desired results.

Having thus described my invention I claim as new and desire to secure by Letters Patent:

1. A self-adjusting felt roll for the dryer section of a paper machine, said felt roll comprising in combination a revolvable tubular roll around which the dryer felt passes, a torsion torsion shaft and said tubular roll with respect to the dryer felt to take up slack and to maintain a predetermined tension therein.

2. In a self-adjusting felt roll for the dryer section of a paper machine the combination with a continuously moving felt looped between adjacent dryer cylinders, of a plurality of adjustable tubular rolls nested in the loops of said felt, a plurality of partially revolvable shafts on which said tubular rolls are mounted to revolve independent of any rotative movement of said shafts, gear elements secured on the ends of said shafts, gear racks fixed on the side frames of the paper machine and co-operating with the gear elements on said shafts to effect a turning movement thereof to cause a resulting parallel movement of said shafts and said tubular rolls with respect to said felt, and torsion means mounted on one end of each of said shafts to maintain a positive turning effort therein.

3. In a self-adjusting felt roll for the dryer section of a paper machine the combination with a continuously moving felt looped between adjacent dryer cylinders, of a revolvable tubular roll nested in a loop in said felt, a partially revolvable shaft on which said tubular roll is mounted to revolve independent of said shaft, gear elements secured on the ends of said shaft, gear racks mounted on the side frames of the paper machine and adapted to co-operate with the gear elements on said shaft to effect a rotative movement thereof, and Weighted means mounted on one end of said shaft to effect a parallel movement of said shaft and tubular roll with respect to said felt to take up slack and to maintain a constant tension therein.

4. In a self-adjusting felt roll for the dryer section of a paper machine the combination with continuously moving top and bottom felts looped between adjacent dryer cylinders, of a plurality oftop and bottom adjustable tubular felt rolls nested respectively in the loops of said top and bottom felts, a plurality of partially revolvable shafts on which said tubular felt rolls are mounted to revolve independent of said shafts, gear elements mounted on each end of said shafts, gear racks mounted on the side frames of the paper machine and cooperating with the gear elements on said shafts whereby any vertical movement of one end of said shafts will positively cause an equal vertical movement of the opposite ends thereof by effecting a turning movement therein, a sheave mounted on one end of each of said shafts in which the said shafts are free to turn, and a tension cable passing continuously and alternately over and under the top and bottom sheaves respectively to move the said shafts and tubular rolls in parallel relation to said felts to take up slack and to maintain a predetermined tension therein.

5, A self-adjusting felt roll for the felts on the dryer section of a paper machine, comprising in combination a revolvable tubular roll, a partially revolvable torsion shaft by which said roll is revolvably supported, gear elements on said shaft for supporting and turning same, cooperating gear racks oppositely disposed on the side frames of the paper machine in positive engagement with the gear elements on said shaft, co-operating guides on said shaft and on said oppositely disposed gear racks on the side frames of the machine to maintain positive engagement between respective co-operating gear members, a pulley member secured on one end of said shaft, and a weighted tension cable anchored to the periphry of said pulley member and adapted to maintain a constant torsion in said shaft.

6. A self-adjusting felt roll for the felts on the dryer section of a paper machine, comprising in combination a revolvable tubular roll, a torsion shaft on which said tubular roll freely revolves, said torsion shaft having gear elements mounted on the ends thereof by which it may be turned and by which it is movably supported, gear racks oppositely disposed on the side frames of the paper machine and engaging the said gear elements on said shaft, and torsion means mounted on one end of said shaft to maintain a constant turning effort therein to effect a resulting parallel movement of said shaft and said roll with respect to said felt.

MILTON T. WESTON.

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