FI129278B - Grooved and perforated reverse roll for a fibre web machine - Google Patents

Abstract

The invention relates to a grooved and perforated turning roll for a fibrous web machine. The turntable (12) includes grooves (22) formed in the shell (20) and the surface (21) of the shell (20). The grooves have suction holes (23) extending through the jacket (20). The open area (AR) of the suction hole (23) is twice the cross-sectional area (AU) of the groove (22).

Description

The invention relates to a grooved and perforated fiber web rotating roll comprising a casing and grooves formed in the surface of the casing with suction holes extending through the casing.

The turning roller is also called a turning suction roller, a vacuum roller or under the applicant's trademark VacRoll.

The turning roller is used for the single-wire export of the drying section of the fibrous web machine, where there is a turning roller between the two drying cylinders.

The drying wire guided through the drying cylinders and swivel rollers presses the fibrous web to be manufactured against the drying cylinders.

The fiber web on the turntable is then outermost without support on the drying wire.

However, the suction effect generated by the turning roller makes it possible for the fibrous web and, if necessary, the headband cut from it to remain attached to the drying wire even at high speeds.

FI patent number 83680 discloses a cylinder used in the export of a fibrous web, in practice the swivel roll described above.

Here, too, the surface of the turntable casing has grooves in the side roller with suction holes.

A certain type of dimensioning of the grooves and suction holes has been sought to ensure a uniform holding force on the fibrous web. > 25 ro However, there are problems with the known swivel rollers.

In particular, the use of recycled paper as a raw material has increased the fouling of the drying = part.

Especially at the beginning of the drying section, the finely divided bulk material together with the sticky substances has caused clogging of the grooves and suction holes.

Small vacuum cleaners in particular are easily soiled and even clogged.

Square grooves also collect dirt and can become clogged.

Due to the large number of suction holes, a large amount of air is transferred, which increases energy consumption.

In addition, the manufacture of the turntable is

list and slow down.

Despite the special dimensioning of the edge area, the suction effect in the head export area could be better.

The object of the invention is to provide a new type of grooved and perforated reversing roller for a fibrous web machine, which remains even cleaner and which achieves a more efficient suction effect with even less air.

The features of the turntable according to the present invention are set out in the appended claim 1. In the turntable according to the invention, the dimensioning of the grooves and suction holes is arranged in a new and surprising manner.

First, clogging of suction holes and grooves is avoided.

Secondly, the suction effect is made efficient and evenly distributed with an even smaller amount of sucked air.

Cleaning the turntable is also easier.

In addition, if necessary, the thickness of the turntable casing can be thinned and thus the turntable can be lightened.

The invention will now be described in more detail with reference to the accompanying drawings, which illustrate an embodiment of the invention, in which Figure 1a shows in principle a drying group of a drying section of a fibrous web machine Fig. 2b shows a part of the surface of the pivot roll casing according to the invention, Fig. 3a shows a cross-section of a casing of the pivot roll according to the invention, Fig. 3b shows a part of the pivot roll casing according to the invention seen from above.

Figure 1a shows separately one drying group 10, which are several in succession on the drying section of the fibrous web machine. The drying group consists of drying cylinders 11 and turning rollers 12, through which the drying wire 13 is passed as an endless loop. Today, a single wire export as shown is used, with only one drying wire per drying group. In practice, the fibrous web passes between the drying wire and the heated drying cylinder. Correspondingly, on the turntable, the fibrous web passes over the drying wire. In addition to the turntable, a runnability component 14 is used to control the fibrous web, which is placed in a pocket space 15 formed by successive drying cylinders and a turntable (Figure 1b). The turntable has a suction connection at at least one end and the turntable is absorbent from the entire circular sector.

Figure 1b also shows the opening groove 16 defined by the drying cylinder 11 and the drying wire 13 and the closing groove 17 formed by the drying wire 13 and the turning roller 12, respectively. the air creates an overpressure which tends to release both the headband and the fibrous web from the surface of the drying wire 13 at the turntable roll. Without coming into the closing groove 17, a straight arrow is shown here. The grooved and perforated turntable roller forms a suction effect, which, however, is substantially reduced due to the blockage of the suction holes and grooves. The invention therefore relates to a pivot roller 12 for a grooved and perforated fibrous web 30. The pivot roll 12 comprises grooves 22 formed in the jacket 20 and = a surface 22 in the jacket 20. Figure 2a shows a part of the jacket 20 in the machine direction. The jacket 20 has suction holes 23 extending through the jacket 20 (Figure 3a). The vacuum created through the suction holes inside the turntable extends

through the web to the fibrous web. At the very least, the negative pressure eliminates the overpressure caused by the closing gill. In the invention, the open area Ar of the suction hole 23 is greater than twice the cross-sectional area Ay of the groove 22. The open area Ar of the suction hole 23 is shown in particular in Figure 3b. That is, the surface area of the suction hole is larger than the sum of the cross-sectional areas of the airflows coming from the two directions of the suction hole along the groove, i.e. the cross-sectional area of the groove continuous over the suction hole on both sides of the suction hole. That is, the second multiple of the cross-sectional area Au of the groove 22 is greater than. This ensures efficient flow in the grooves and at the same time avoids the formation of a bottleneck in the suction hole. The area of the suction hole is determined at its narrowest point, in which case any strain is ignored.

More specifically, the open area Ar of the suction hole 23 is 2.01 to 4.0, more preferably 2.8 to 3.6 times the cross-sectional area Ay of the groove 22. In this case, the air that can fit in the grooves can be removed, and the suction effect spreads as efficiently as possible. In practice, this has been achieved by changing the drilling pattern, which has even larger holes with fewer and fewer holes. In addition, the sizing and career spacing have been changed. In Figure 2b, the cross-sectional area Au of the groove 22 is illustrated by two dashed areas. Figures 2a-3b do not show the fabric which closes the fiber web by the part of the fiber web rotating from the top of the groove. A smaller hole ratio than described above is also likely to work better than at present. Thus, with a suction hole 1.8 to 1.99 times the groove, a 2. benefits. co S The drilling pattern has further been changed so that there are N suction holes 23 in only every other groove 22 (Fig. 2a). It has surprisingly been found in the tests that the air also moves laterally inside the drying wire. In this case, the absorbent effect of the perforated grooves

also for non-perforated grooves.

Thus, by the closing friction, excess air travels from the non-perforated grooves to the perforated grooves and through them into the turntable.

In this case, the number of holes can be reduced, which can compensate for the known increased need for air required by the larger holes.

In practice, however, the new drilling pattern achieves an even smoother and higher vacuum with less air than before.

The drilling pattern also has a phase shift of the suction holes, which further equalizes the distribution of the suction effect in the area of the turntable.

In Fig. 2a, the end of the pivot roll also has a head input region 26, in which each groove has suction holes 23. In the invention, the width L of the groove 22 is 1.0 to 1.3 times the diameter D of the suction hole 23.

In this case, the width of the groove can be used to the maximum.

In addition, the suction effect is effectively spread over the entire groove area.

The cross-sectional area has been reduced by reducing the depth of the groove.

Generally, the depth S of the groove 22 is 0.2 to 0.4 times the width L of the groove 22.

In other words, the groove is clearly wider in depth.

The dimensioning of the groove is chosen so that twice the cross-sectional area of the groove does not exceed the area of the suction hole.

Figure 3a shows in more detail the dimensioning and shaping of the groove 22.

Preferably, the bottom 24 of the groove 22 has at least one radius of curvature.

In this case, the groove is formed smooth without corners, thus avoiding contamination of the groove.

Correspondingly, cleaning a smooth groove is easy.

In addition, there is a rounding 25 between the edge of the groove 22 and the surface 21 of the jacket 20. The rounding equalizes the air flow and reduces the wear of the drying wire.

Both the smooth shape and the rounding can be done in a single operation, such as shape turning.

In this case, the curvature of the groove and the rounding of the edges are obtained in one machining step.

A suction hole with a diameter of eight millimeters was used for testing.

In addition, there were fewer and fewer suction holes.

Preferably, the diameter of the suction hole is 6.5 to 10 mm.

Now the 1500 mm diameter swivel roller had ten suction holes evenly distributed around the circumference of the jacket.

Unusual, the suction holes were made only in every other groove.

In addition, the shape of the groove was low and gentle.

The groove depth was 2.5 mm with a width of 9 mm.

At the same time, the groove spacing and the groove width increased, increasing the opacity of the turntable by 0.23%. However, the number of grooves decreased by 20%. With the new dimensioning, the cross-sectional area of the grooves was 20% smaller than at present and the total cross-sectional area of the grooves is about half of the current one.

At the same time, the diameter of the suction hole was almost double.

Surprisingly, therefore, a smaller amount of suction air than before makes the fibrous web remain well on the outer surface of the drying wire, while an even larger suction hole reduces losses.

In practice, there were up to 70% fewer suction holes and up to 30% fewer grooves than in the known turntable.

In this case, drilling the suction holes and machining the grooves takes clearly less time than before.

The machining time can even be halved by machining several grooves simultaneously.

Based on the tests, the runnability of the turntable was good and the head export worked properly.

In addition, air leakage through the grooves on the rising side of the co turntable was negligible.

This was due to at least> 25 lower known grooves.

Based on the test results, the new swivel roller consumes even less energy, even though the suction effect is higher than before and the vacuum level = even higher. The pivot roller according to the invention improves the problem of fouling of the grooves and suction holes.

In other words, the swivel roller remains N clean and clogging of the suction holes is avoided.

At the same time, energy consumption is reduced.

Turntable manufacturing is also accelerating and raw material costs are falling.

In practice, fiber

The runnability and head output of the machine are improved, which means that head export takes less time and track breaks are reduced. Due to the reduced groove depth and notching effect of the even lower and gentler groove, the casing can also be thinned. Cleaning a smooth and low groove is easy. The clearly larger suction hole can also be cleaned quickly. An even thinner casing speeds up drilling, reduces the weight of the casing and reduces the amount of material. At the same time, the depth of the suction holes is reduced, resulting in slower fouling. As the weight of the turntable decreases, the drive motor can be dimensioned even smaller. 00

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Claims (8)

PATENT CLAIMS A grooved and perforated roll of a fibrous web machine comprising grooves (22) formed in the surface (21) of the jacket (20) and suction holes (23) extending through the jacket (20) inside the jacket (20), characterized in that that the open area (Ar) of the suction hole (23) is greater than twice the cross-sectional area (Av) of the groove (22), and the bottom (24) of the groove (22) has at least one radius of curvature when the groove (22) is fluid without corners. Turning roller according to Claim 1, characterized in that the open area (Ar) of the suction hole (23) is 2.01 to 4.0, more preferably 2.8 to 3.6 times the cross-sectional area (Ay) of the groove (22). . Swivel roller according to Claim 1 or 2, characterized in that the suction holes (23) are in every other groove (22). Turning roller according to one of Claims 1 to 3, characterized in that the width (L) of the groove (22) is 1.0 to 1.3 times the diameter (D) of the suction hole (23). o Swivel according to one of Claims 1 to 4, characterized in that there is a rounding (25) between the edge of the groove (22) and the surface (21) of the jacket (20). x z Swivel according to one of Claims 1 to 5, characterized in that the depth (S) of the groove (22) is 0.2 to 0.4 s 30 times the width (L) of the groove (22). © OF Turning roller according to one of Claims 1 to 6, characterized in that the groove (22) is form-turned. Turning roller according to one of Claims 1 to 7, characterized in that the diameter (D) of the suction hole (23) is 6.5 to 10 mm. oO OF O N + OF I Jami a o N + O 00 O OF