FI66933C - SUGOEVERFOERINGSVALS - Google Patents

Description

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National Board of Patents and Welfare ______ ________...____________ (W rmnemmpmon ft κμι · ιιπκ> ιμιι ρπΑ ·· _

Patent- och raghtarstyralsan '7 AmMo * ud ^ d od> utunmt— pnbBcnrad 31.08.8A

(32) (33) (31) tyj * er * «eaw» -Nw> * »·« «(71) Valmet Oy, Punanotkonkatu 2, 00130 Helsinki 13, Finland-Finland (FI) (72) Matti Kankaanpää, Espoo , Finland-Finiand (FI) (7A) Forssan δ Salomaa Oy (5A) Suction transfer roller - Sugöverföringsvals

(62) Separated from application 3720 / 7A - Avdelad frän trap 3720 / 7A

The invention relates to a suction transfer roll, which is in particular intended for detaching and further guiding a paper web from a press roll, the suction transfer roll forming a nip point with the press roll, and having a suction transfer roll jacket at least partially sandwich-structured. a specific sector of which is connected to the suction system by means of at least one fixed end piece associated with the roll in question.

The suction transfer roll according to the invention is especially intended for use in connection with the press part (Sym-Press, trademark) disclosed in the applicant's Finnish patent application No. 3235/72, although the invention is not intended to limit this in any way.

The previously well-known method in a paper machine for removing the web from the surface of a rotating press roll 2,66933 and moving it continuously to the next processing step is based on the fact that the speed of the web in that step will be higher than on the surface of the press roll. The web is thus detached by the effect of the speed difference, i.e. the traction. The tension causes stress and stretching on the web, which the web does not always withstand, but may break, which means the continuous production of the machine is interrupted and production pins are stopped.

Modern paper machines are characterized by high working speeds. The higher the speed of the machine, the shorter the time the web is under compression at the nips between the rollers. This reduces the water-carrying capacity of the press, so in order to increase the efficiency of the press, a high pressing pressure must be used when the speed of the machine is high. Increasing the compression pressure, in turn, causes the web to adhere more tightly to the surface of the smooth press roll and make it more difficult to remove. The susceptibility of the web to breakage increases and, as a result, and otherwise the speed of the machine increases, the production losses due to breakage increase correspondingly. Interference leading to web breakage Occurs especially at the edges of the web. Therefore, the present invention pays special attention to the treatment of web edges.

The pick-up blanket and the air roll cooperating therewith are previously known devices for transferring wet web from the grain portion of the paper machine to the pulver section. However, a conventional suction roll having a structure and function similar to a wire suction roll or a press suction roll and used to detach a web from a wire is not suitable for use with a press section. This is due to the structure and operating principle of the roll in question. Inside the perforated jacket, the suction roll has a jacket-length suction box connected to the suction system.

The suction box is equipped with sealing strips which are pressed against the inner surface of the roller blade. To reduce the wear of the seals and generally their friction, water is sprayed on the inner surface of the suction roll. The amount of sealing water can be up to 50 1 / min per meter. Some of this water is ejected by centrifugal force through the holes in the roller blade and enters the pick-up felt and further into the paper web. In addition, it can happen that due to the defective nozzle of the closure tube, the water el is evenly distributed over the width of the machine, i.e. the length of the roll, which adversely affects the moisture profile of the web.

When detached from the wire, the water content of the web is so high that the entry of sealing water into the pick-up felt and partially into the web is generally of little significance. Instead, if a release roller is used in the press section and is of conventional construction, the amount of sealing water is so large compared to the amount of water separated from the paper web in the last press nip that it substantially degrades the dusting efficiency of the press. If the dry content of the web in the last press nip increases from e.g. 37% to 40% at a machine speed of 800 m * min and a web weight of 50 g »m, this means that the press separates about 8 l = min of water per meter of machine width. . However, as much and more water can return to the web from the sealing water of the release suction roll placed after the last press nip. The diameter of the release roller cannot be very large when placed on the press section. Due to the small diameter of the roll, a large centrifugal force is due to which a particularly large amount of water is ejected.

In order to avoid the above-mentioned disadvantages, the suction roll according to the invention is mainly characterized in that the through-holes in the outer shell of the roll are substantially only in the region of both ends of the roll.

As briefly noted above, a significant portion of the breaks that occur when the web is removed from the press originate at the edges of the web. This is due in part to the fact that the edges of the web may be, to some extent, inhomogeneous and weak due to the unsatisfactory operation of the headbox and wire section. The susceptibility of the edges of the web to shear is partly due to the air flow caused by the rotating rollers, etc., which causes the web to flutter.

Therefore, the present invention seeks to ensure the removal of the edges of the web by arranging the suction to act substantially at each end of the roll.

In order not to place an unnecessary load on the suction system, the suction can be completely omitted from the central area of the web in cases where the paper to be produced allows for its runnability and quality. However, this may result in a so-called the phenomenon of air penetrating between the felt and the release roller. To avoid blowing, the surface of the release roller can be provided with a groove in the middle or blind holes that do not penetrate the outer sheath. Blind perforation, which in density and diameter of the holes corresponds to the through routing of the roll ends, is therefore advantageous in that the effect of the routing on the quality of the paper as a more or less visible marking is similar over the entire width of the web. A number of different possibilities in the drilling pattern are shown below 4 66933.

Some honeycomb suction rollers are known per se, for example from Finnish patent no. 18,972. Such suction rolls have been used as suction rolls for the front part of a paper machine, but their dewatering capacity has been limited and they have caused an additional load on the heat system due to their structure. By contrast, with the structure of the suction transfer roll according to the invention, low air consumption is achieved.

The load on the suction pump connected to the suction roll is affected not only by the amount of air flowing through the sump at the suction zone, but also by the amount of air that the holes or cells of the suction roll bring into the suction zone. The thicker the perforated jacket of the suction roll or the larger the cells of the suction roll, the more air enters the suction system, which must be removed in addition to the air coming through the paper web or felt in order to create a vacuum holding the web. A small amount of extra enters the suction system even from the leaks at the seals.

In the heat roller according to the invention, the excess air volume can be minimized by limiting the common volume of the holes in the outer casing of the suction roll and the cells of the suction roll with structures which will become apparent from the description of the embodiments of the invention.

The invention will now be described in detail with reference to the figures of the accompanying drawing, which show some application examples of the invention, to which, however, the invention is not intended to be limited in any way.

Figure 1 shows a roll according to the invention applied to a press section (Sym-Press) with a closed outlet.

Figure 2 shows an axial cross-section of a honeycomb transfer node roll according to the invention. Figure 2 is at the same time a partial section along the line I-I in Figure 4.

Fig. 3 shows a part of the end of the suction roll according to Fig. 2 in an axonometric view.

66933

Fig. A shows the slir roll of Fig. 2 seen from the end side.

Figure 5 shows an alternative implementation of the slir roll roller lift and outer jacket according to the invention.

The press part (Sym-Press) according to Fig. 1, in which the roll of the invention is particularly advantageously comprised of a relatively large diameter, smooth-surfaced center 10. The first nip point of the press part is formed by rollers 11 and 12, of which roll 11 is a suction roll and roll 12 is a grooved roll. Both of the rollers 11 and 12 have their own felt loops IA resp. 13 so that the web W passes at the first nip point between the two felts 13, IA. The suction roll 11 together with the chat 10 forms the second nip point Nj of the pressing part. A third nip point is formed between the center 10 and the press roll 15, which press roll 15 is provided with its own tooth loop 16, the guide roll of which is marked with the reference number 18. The press part may have a fourth and even a fifth press nip.

Figure 1 shows a preferred arrangement of the suction transfer roll 20 according to the invention. This transfer roll 20 is provided with its own felt loop 19 (pick-up felt), the guide roll of which is also indicated by reference numeral 18. Said suction roll 20 is pressed against the press center 10 at the web removal point W so that the web W moves to the pick-up felt 19 and adheres to its surface by the vacuum in the suction zone a of the suction roll 20 (Fig. A). The supporting web W of the felt 19 is further passed to the drying section of the paper machine. The guide roller 17 of the felt 19 is placed as close as possible to the suction roller 20.

The suction roll 20 according to Figures 2, 3, 5 and 5 has two nested coaxial sheaths 21 and 22, and between them cells 32 delimited by substantially radial partitions 3A. The outer sheath 21 is perforated 33 and may be made of e.g. bronze. The thickness of the outer sheath 21 is the same throughout. The inner jacket 22 is preferably a steel tube which can be machined conically so that the distance between the outer jacket 21 and the inner jacket 22 and at the same time the cross-sectional area of the cells 32 is smaller at the center of the roll than at the ends of the roll. The partitions 3A are, for example, steel or other suitable metal. According to the figures, the partitions 3A are straight and parallel to the axis of the roll 20. The partitions 3A may also be arranged in a helical shape in the space between the sheaths 21 and 22. The cells 32 delimited by the partitions 3A are long and narrow and extend continuously from the center of the roll 20 to the ends of the roll into which they open.

The roll 20 is provided with a fixed end piece 27 which is either at both ends or only at one end, the cells 32 being closed at one end of the roll 20. The end piece 27 has a channel 28, the width of which determines how many of the cells are connected to the air system at a time (arrow B), i.e. how wide the suction sector a is on the surface of the roll. In connection with the end piece 27, there is a bearing 26 for the shaft 23 of the roll 20. The end piece 27 has a seal 31 around its suction opening 28a (sector a). The rotating roll 20 has a annular seal 30, respectively, which seals 30,31 together form a sealing surface 29. Between the roll covers 21 and 22 there is a support ring 35 at the center AA of the roll 20 in applications where at each end of the roll 20 there are air ends 27. The shaft 23 and the inner flange 22 are connected to each other by a spacer 24.

With regard to the structure and perforation of the outer sheath 21, several different alternatives are possible in order to achieve the objects of the invention. For example, the following embodiments are possible: a) The jacket is evenly perforated throughout, but some of the relays in the central region of the jacket are so-called. blind holes that are not through. Honeycomb structure throughout the mantle area.

b) The sheath is evenly perforated throughout, but the holes in the middle area are all blind holes. In the edge areas, the holes are through. Honeycomb structure only in the area of the through rail.

c) Perforation is sparse and through in the middle of the sheath, denser in the areas of the sheath ends.

d) The valve is a through-hole only at the ends, the jacket in the middle part is provided with a groove 37 by making it from a profile strip 36 by wrapping, for example, in accordance with the applicant's Finnish patent No. 45583. In this case, the cells 32 do not extend into the central region of the roll 30.

(e) The sheath shall have a perforation only in the areas of the ends, the center being unreliable and smooth. The cell structure is only in the torn area.

7 66933 (f) The center of the sheath shall be either smooth and non-perforated or grooved. Each end of the sheath has through-perforation in two zones, the zone at the extreme end having a hole area of e.g. 20-25% or more and the next zone having a hole area of only 10-15% or less.

The size of the hole area required depends, for example, on the paper to be produced and the quality of the felt or drying wire used with the transfer roller.

Dense perforation in this context means tearing in which the common free cross-sectional area of the holes on the surface of the roll is about 20-25% or more of the corresponding surface of the casing. A certain free hole surface can be achieved either with a large number of small holes or with a smaller number of larger diameter holes. Few perforations refer to the following perforations of about 10-15% or less of the jacket surface.

With respect to the cell structure 32,34 between the outer and inner sheath 21,22, the following preferred embodiments come into question.

a) The partitions 34 of the cells 32 are radial and parallel to the axis of the roll, the height and width of the cells and thus their cross-sectional area are the same for the entire length of the roll 20.

b) The cells 32 are parallel to the axis of the roll 20 and the height of the cells 32 is smaller in the middle than at the ends.

c) The partitions 34 of the cells 32 form a gentle spiral starting from the center of the roll 20.

d) The cells 32 are only at the ends of the roll 20 in the part which is perforated in the outer hub 21 of the roll.

The honeycomb roller 20 described above has the following structural solutions to reduce excess air and reserve air: 8 66933 a) Small relay volume in the outer casing, which is achieved by 1) limiting the number of through holes 33 in the roll casing 21 as little as possible 2) using a thin outer casing 21 the required strength of the roll 20 is achieved by the inner sheath 22.

b) A small cell volume, which is possible because the cells 32 are low and are dimensioned solely for the purpose of air flow, so that the cross-section of the cells 32 is equal to the common cross-sectional area of the holes 33 in the corresponding air zone.

Claims (7)

9 66933 A suction transfer roll, in particular for detaching and further guiding a paper web from a nozzle roll, the suction nip roll forming an end point (10/20) with the nip roll (10), the transfer roll casing being at least partially sandwich-structured, comprising at least a partially perforated and partially perforated (21) and a non-perforated inner jacket (22) and a suction cell therebetween, a sector (oi) of which is connected to the suction system by means of at least one fixed end piece (27) associated with said roll, characterized in that the roll outer jacket (21) the through holes are essentially only in the area of the rubber end of the roll. Roll according to Claim 1, characterized in that the outer casing (21) is substantially evenly perforated over its entire surface and that the holes (33) in the central part of the outer casing (21) do not extend through the outer casing (21) when blindly drilled. Roll according to Claim 1, characterized in that the central part of the outer shell (21) of the roll is completely without through holes. Roll according to Claim 3, characterized in that the central part of the outer casing (21) is smooth. Roll according to Claim 3, characterized in that the central part of the outer casing (21) is grooved (37). Roll according to Claim 5, characterized in that the grooved part of the outer casing (21) is made by wrapping the profile strip (36) (Fig. 5). Roll according to Claims 1 to 6, characterized in that the cell structure is only in the region which is passed through the outer shell (21) of the roll.