FI79731C - Press section of a paper machine - Google Patents

Description

1 79731

PRESS OF A PAPER MACHINE

The present invention is directed to a press section of a paper machine according to the preamble of claim 1, wherein a similar press and dewatering is applied to both surfaces of the freshly felted paper web. In particular, it is an object of the invention to provide an sheet of paper web with equal ink receiving or absorbing capacity on both sides of the sheet.

Although the dewatering presses of the paper machine are already quite advanced, they can still be developed.

The previously known press parts have several drawbacks, such as structural complexity, excessive length, uneven compression and felting of opposite sides of the web, "open" stretches of the web (the web runs 15 without the support of the blankets) and high energy consumption.

The following U.S. patents are disclosed in the prior art: 2,672,078 - the web "open draw" and does not provide a symmetrical sheet size on either side of the web 20 3 023 805 - the number of nips (contact surface between press rolls) not available for high speed dewatering of some grades of paper not large enough 3 286 360 - a small number of nips limits the increase in operating speed and a multi-nip press requires too much space in the direction of the paper machine 4 075 056 - does not provide uniform compression and felting of the paper web 4 086 131 - does not provide uniform compression and felt-30 bulging on each side of the paper web because the other side is pressed in several nips with the felt.

The main object of the invention is to eliminate the disadvantages, shortcomings and problems in the previously known press parts and their operation, and to provide a new and better press part in which the paper made of freshly felt paper web has equal ink, adhesive or coating absorption or absorption on both sides. . consistency. The above object can be achieved according to the invention in a simple manner in a small space without "open" stretches of the paper web and in an energy-saving manner. In addition, in the press section according to the invention, a uniform compression and uniform felting are provided on both sides of the web.

The above-mentioned object is achieved by a press part 1a according to the invention, which is characterized by what is set forth in the characterizing part of claim 1.

Through the first nip of this press, the web 15 runs underneath supported by a dewatering felt, while the top of the web is in direct contact with the press roll, in the second nip both sides of the web are in direct contact with the rolls and in the third nip the top of the web is in contact with the second dewatering felt 20, while the underside is in direct contact with the press roll so that the paper web left by the press section is equally treated on both sides and has similar ink, adhesive or coating receiving or absorbing capabilities.

The invention also relates to a method according to claim 3 for providing substantially equal compression and dewatering on both sides of a freshly felted paper web in a dewatering press section of a paper machine. Other objects, features and advantages of the invention will become apparent from the embodiment shown in the accompanying description and the accompanying drawing, in which Figure 1 is a schematic side view of a press section of a paper machine according to the invention, Figure 2 is an enlarged and partial section taken along line II-II in Figure 1. , and 3,79731 in Figures 3 and * + are similarly enlarged and partial sections taken along lines III-III and IV-IV in Figure 1.

According to Figure 1, the dewatering press part 5 of a paper machine comprises, according to the invention, a pickoff device located in the immediate vicinity of the web-forming devices, operating in their direction of travel, the function of which is to lift the newly formed, i. felted, paper web W from dewatering strip, wire or fabric 10 for further processing in the press section. For this purpose, the trapping device 7 comprises a trapping roller 9 provided with a suction cell 10, which is surrounded by a dewatering felt 11 made of endless strip, which is pressed against the web VI on the dewatering fabric 8 in a nip between the roll 9 and the cup 8 The suction in the cell 10 causes the web W to detach from the upper surface of the fabric 8 and to adhere to it; the lower surface of the dewatering felt 11, where it passes with the felt to the first press 12.

The felt 11 passes into the press 12 with a second endless, porous dewatering felt 13 on the upper surface 20, whereby the web W is fixed between the felts as it passes through the pressing and dewatering nip N-1 between the suction roll 1M and the groove roll 15. In the press, the suction roll l1 * is below the nip N1 and the groove roll is above it, whereby the nip itself provides equal dewatering from both surfaces of the web W, suction of the roll 1 * + suction device 17: causes the web W to detach from the upper felt 11, whereby the web W can travel in the machine direction forward supported by the upper surface of the lower felt 13. The upper roll 15 may, if desired, be essentially of the type disclosed in U.S. Patent No. 3,198,697, the circumference of the roll having a plurality of axially spaced annular grooves 18.

After the nip N-1, the web VI is further pressed to remove water in a second press 19, which comprises four superimposed rolls, between which the web passes through the nips N-2, N-3 and N-1 *. The nip N-2 is between the upper, porous-coated press roll 20 and the lower groove roll 21. In the nip N-2, the felt 13 is in contact with the groove roll 21 and the lower surface of the web W, and the roll 20 with the porous coating is in contact with the upper surface of the web. The groove roll 21 is most similar to the groove roll 15 and has a plurality of axially spaced annular grooves 22 on its circumference (Figure 2). In addition to facilitating drainage through the felt 13, the grooves 22 do not have any suction effect 10 which allows the web V / to remain attached to the felt 13, resulting in the web easily detaching from the felt 13 on the N-2 outlet side of the nip 20 -3.

To achieve optimal results, the press roll 20 is provided with a porous elastomeric coating 23, which in a typical press application may be 2.5 cm thick, made of elastomer with a hardness ranging from 5 to 30 on a P&J scale, which allows the roll 20 to be slightly a pressure lower than the compressive strength of the web, thereby minimizing breakage of the fibers of the paper web. The degree of hardness of the coating 23 can be controlled at least to some extent according to the degree of porosity of the coating, i. by changing the size and number of pores 2 * + in the coating-25 theme material. As shown in Fig. 2, some pores 2b open outward from the circumference of the roll 20 at the nip, which enhances the operation of the roll 20 by retaining water compressed from the web W, which facilitates the release of the web W from the roll 20 as the web passes through the nip N-3. The accumulation of excess water on the periphery of the roll 20 is prevented by a scraper 25 which removes water from the roll 23 with respect to the free portion of its nip N-3. If desired, a felt strip 27 may be used in contact with the periphery of the roll 20. brings to the roll a lubricant promoting the release of the web from the container 28, from which the substance is absorbed into the felt strip.A suitable spray device can be used instead of felt strip 27. Of course, it should be noted that the porosity of the coating 23 in the compressed state is such that the n-2 and N-3 rolls the V / surface 5 of the web in contact with it was not damaged.

In the nip N-3, the web W which has passed from the nip N-2 on the surface of the roll 20 is pressed between the roll 20 and the hard-surfaced roll 29. Although roll 29 may have a plastic coating, it should be bone hard and the hardness of paper machine standards should be 0 on the P&J scale. Because the surface of the roll 29 is smooth, the web W detaches easily from the softer, porous surface of the roll 20 onto the roll 29, which it follows away from the nip N-3. Detachment can, of course, be promoted by treating the surface of the roll 20 with a lubricant derived from the strip 27. In the most preferred drive system of the press 19, only the roller 29 is rotated by drive devices: 30) whereby the roller 29 forces the other rollers of the press 19 to rotate.

In the nip, the lower surface of the N-M web VJ is in direct contact with the roll 29 and its upper surface is in contact with the dewatering felt 31 with which the web passes through the nip N-if. The felt 31, in turn, is in contact on one side with a groove roll 32 of the same type as the rollers 15 and 21 and having circumferentially spaced annular grooves 33 (Fig. 1 and Fig. * +).

After the nip N - * +, the web condensed due to dewatering: W / S, which has already become paper-like, separates: from the roll 29 and the felt 31, and passes, for example, around the guide roll. The W / S of the web has 30 equal absorption or absorption capabilities of the ink, adhesive or coating. Since the front end of the web W, which is pulled: through the press 19, can stick to the roll · after the nip N-1 *; 29 is brought into contact with it to remove the front end of the scraper 35 so that it can be guided around the guide roll 3 * + and onwards to a calender, reel, etc. Normally, the scraper 35 is of course used to keep the surface of the roll 29 clean.

6 79731

As can be seen from the above description, the paper web W / S coming from the press section 5 is provided with uniform surface properties by removing equal amounts of water on both sides as the web passes through the press section 5. In the nip N-1, dewatering takes place on both sides of the web, i. water is forced to exit through each surface, with the fine fibrous material in the center of the web moving in equal amounts towards each surface of the web.

10, in the nip N-2 dewatering is done through the lower surface of the web 2 in the direction shown by the arrow, while the upper surface of the sealing roller 20.

As it passes through the nip N-3 to the web V, each surface is sealed equally between the rollers 20 and 29, as shown by the double arrow in Figure 3.

In the nip N-1 * of the web W from the upper surface, finally removing water from an image * in the + direction of the arrow, while the web of the lower surface of the end seal of a roller 29. Thus, the web W is not only throughout the compact, which can provide 20 to have a strong paper sheet WS, but each face is an equal concentration of fines that allows uniform absorption properties.

The invention may be modified within the scope of the appended claims.

Claims (7)

7 79731 A press section of a paper machine, wherein both surfaces of the freshly felted paper web (W) are subjected to similar pressing and dewatering without an open web-pull of the paper web having a first press roll means (12) forming two first nip (N-1) operatively dewatering. the web passes between the two co-advancing porous dewatering felts (11, 13) in contact with them, so that both surfaces of the web (W) are compressed and dewatered substantially equally in said first nip (N-1), characterized in that that it further comprises: a second press roll means (19) having four overlapping rolls including a first dewatering roll (21) and a first non-dewatering roll (20) forming a second nip (N-2), a second a non-dewatering roll (29) forming a third nip (N-3) with said first non-dewatering roll (20), said second the surface hardness of the non-dewatering roll (29) is greater than the surface hardness of said first non-dewatering roll (20), and a second dewatering roll (32) forming a fourth nip with said second non-dewatering roll (29) (N-4) through which said web (W) passes in succession, a dewatering felt (13) extending in contact with the first side of said web (W) and said first dewatering roll (21) through said second nip (N-2), and the opposite surface of said web (W) being in direct non-dewatering pressing contact with said first non-dewatering roll (20) - in said second nip (N-2), 8 79731 the two surfaces of said web (W) being in the respective direct non-dewatering in press contact with said first and second non-dewatering rollers (20, 29) in said third nip (N-3) 5 and a dewatering felt (31) advancing with said opposite surface of said web (W) and said second dewatering roll (32) in said fourth nip (N-4), and said first surface 10 of said web (W) in direct non-dewatering contact with said second non-dewatering roll ( 29) in said fourth nip (N-4), so that said web (W) exits said press section as a paper web, both surfaces of which are compressed and dewatered in substantially the same manner. Press part according to claim 1, characterized in that said first dewatering roll (21) is a grooved press roll in contact with said dewatering felt (13) in said second nip (N-2) and said first non-dewatering roll (20) is a press roll sealing the surface of a paper web (W) having a hard circumference except for a relatively thin substantially impermeable closed ring elastomeric 25 coating in the hardness range of 5 to 30 P&J in direct contact with the web at said second nip (N-2) . 3. A method of achieving substantially equal compression and dewatering on both sides of a freshly felted paper web 30 in a dewatering press section of a paper machine, wherein the web is pressed in contact with advancing porous dewatering felts in a dip (N-1) similar pressing and dewatering in said first nip (N -1) and web (W) is carried out after this 5 to 5 in succession of the second, third and fourth nips (N-2, N-3) of the second press (19) formed by four overlapping rolls; N-4), characterized in that it comprises: (a) guiding a dewatering felt (13) in said second nip (N-2) in contact with a first surface of said web (W) and a first dewatering roll (21) and said web (W) conducting the opposite surface in a straight non-dewatering manner in a web-sealing contact with the first non-dewatering roll (20), 15 (b) providing direct non-dewatering web-sealing contact of both surfaces of the web (W) at said third nip (N-3) by passing said web (W) to said first non-dewatering roll. between a dewatering roll (20) and a second non-dewatering roll (29), the second roll having a higher surface hardness than said first non-dewatering roll (20), and (c) passing a second dewatering felt (31) in said fourth in a nip (N-4) in contact with said opposite surface of the web (W) and a second dewatering roll (32), said first surface of the web being passed in direct non-dewatering web-sealing contact to said second non-dewatering roll (29), then that said web (W) exits said part of the press-30 as a paper web on both sides of which a substantial similar compression and dewatering, and thus have substantially similar ink, adhesive and coating uptake and absorption properties. 10 79731 A method according to claim 3, characterized in that step (a) further comprises contacting the dewatering felt (13) with the grooved press roll (21) and bringing the web (W) directly into contact with the elastomeric dewatering press roll (13). 20) with a hard shell except for a relatively thin closed flamethrone elastomeric coating (23) having a hardness range of 5 to 30 P&J. A method according to claim 3, characterized in that step (b) further comprises guiding said web (W) in direct contact between a smooth hard surface press roll (29) and a non-dewatering web sealing press roll (20) having: hard shell except for a relatively thin coating (23) in the hardness range of 5 to 30 P&J. A method according to claim 3, characterized in that step (c) further comprises guiding the web (W) in direct surface sealing contact with a smooth hard surface roll (29) and guiding said second dewatering felt (31) in contact with the groove roll (32). A method according to claim 3, characterized in that it comprises a two-step dewatering in said first nip (N-1) between the suction roll (14) and the groove roll (15) and guiding the web (W) in said second nip (N-2) between the groove roll (21) and the non-dewatering web surface sealing roll (20) having a hard shell except for a relatively thin coating (23) in the 5 to 30 P&J hardness range-30a, conducting the web (W) to a smooth hard surface roll (29) ) and a roll (20) sealing the surface of said non-dewatering web in said third nip (N-3) and a grooved press roll (32) for guiding the web (W) and a hard surface press roll (29) cooperating therewith in said fourth nip. in the nip (N-4). 5 PATENTKRAV