US2911040A - Press section - Google Patents

Description

Nov. 3, 1959 L. HORNBOSTEL PRESS SECTJIION Filed Jan. 29, 1958 Fa l Lloyd Horn bosfel @QTZHE United States Patent PRESS SECTION Lloyd Hombo stel, Beloit, Wis., assignor to Beloit Iron Works, Beloit, Wis.,ja corporation of Wisconsin I Application January 29, 1958, Serial No. 711,826

1 Claims. (Cl. 162-305) through one or more suction presses, whereby moisture 'is removed from the web by mechanical nip pressure of a pair of cooperating press rolls, together with suction exerted at the press nip. Generally, Fourdrinier type paper making machines are designed'to dry a web sufficiently'by suction while still on the forming wire so that suction alone in a later press section is not effective to further dewater the web. Accordingly, the use of mechanical pressure either alone or in conjunction with suction is-necessary for'further dewatering. Press feltsiare generally used to convey the web from the forming wire to the paper machine press section, and the felts also serve to absorb moisture from the web in surface contact therewith.

I As will be appreciated, both the web and the felt are squeezed when passing through the press nip. Such squeezing serves to dewater both and the water squeezed therefrom flows in part into the perforations in the suction press roll at the nip. Heretofore, it has been assumed that the suction area must be covered by felts 'alone'or by the felt and the web. The suction area in a;suction press roll extends from a'sealing strip at'the oncoming side to a sealing strip at the otfrunning side 'of the nip. The oncoming and offrunning sides being determined by the direction of travel of the felt and web. ,An' improvement in high speed press operation is described in Lloyd Hornbostel U.S. Patent No. 2,694,347

wherein the web is separated from the felt at both the oncoming and otfrunning sides of the suction area (which straddles'the press nip), so that improved drying action opening'of the pores of the felt may be accomplished both before and after the press nip.

The instantinvention is based upon diiferent concepts, which apply particularly to certain types of press section arrangements. It has been found that the arrangement of Lloyd Hornbostel US. Patent No. 2,694,347 may 'not be practical in certain press sections, because of the particular type of web being handled,.or the moisture content of the web, or the actual positioning of the press rolls. It has also been found that during extensive surface contact between a web and a felt, the

vfelt picks up moisture from the web and, if it is travelling on the underside, effects an accumulation of moisturealong the bottom side of the felt. The instant invention is based upon this discovery and the discovery of a suction press arrangement which is particularly useful in certain press section designs and which is particularly efiective in the removal of excess water from the felt, 7

In the'instant invention, the felt and web are separated imrnediately upon leaving the nip, with the felt Patented Nov. 3, 1959 "ice however, on the oncoming side the felt urges the web up against the surface of a bare press roll, so as to leave uncovered substantially the entire suction area in the suction roll at the oncoming side of the nip. This results in a sweeping effect of the air following the bottom of the web and passing in through the perforations in the suction roll at the oncoming side. This sweeping of air results in the removal of water tending toaccumulate along the bottom side of the felt, so that a substantial amount of water is' drawn from the felt as it enters into the press nip. It has been found that this results in unique advantages in the operation of certain press sections, and particularly press sections wherein it is of advantage to pick up the web from'a prior nip almost immediately after that nip with the instant felt in question. In such an arrangement the relatively wetweb passes from the first nip and is received immediately by the felt. This felt then carries the Web into the suction press of the instant invention.

It is, therefore, an important object of the instant invention to provide an improved suction press.

It is a further object of the instant invention to provide an improved paper machine suction press comprising a pair ofpress rolls defining a press nip therebetween, at least one of said rolls being a suction 'roll having a suction area straddling said nip, and a looped felt lapping said suction roll, said felt being separated from the suction roll surface to permit air to sweep between the felt and the suction roll immediately before the nip and after the oncoming limit of the suction area.

Other and further objects, features and advantages of the present invention will become apparent to those skilled in the art from the following detailed disclosure thereof and the drawings attached hereto and made a part hereof.

. and

Figure 2 is a fragmentary detail elevational view with parts broken away and parts shown in section of a press nip and its immediate environment for the suction press of the instant invention. A

As shown on the drawings:

In Figure 1, the reference numeral 10 indicates generally a paper machine comprising a looped forming wire 11 whereon a web W is formed and the forming wire 11 travels over a suction roll 12, which is a couch roll with suction area 12a; and the wire 11 passes around a turning roll 13 to reverse the direction thereof.

In the machine 10, there is provided a looped pickup felt 14, a suction pickup r011 15 (With suction area 15a and save-all pan 1512) within the loop of the pickup felt 14 urging the pickup felt 14 against the web W on the forming wire 11 to transfer the web W to the underside of pickup felt 14, and a guide roll 16 within the loop of the pickup felt 14 and cooperating with the suction pickup roll 15 to define a downwardly inclined reach 14a of the pickup felt 14. The guide roll 16 is provided with a suction area 16a for retaining the web W upon the felt 14 as it is reversed around the guide roll 16.

Above the guide roll 16 there is positioned a reverse press, indicated generally by the reference numeral P, comprising a first suction press roll 17 presenting a suction area 1711 within the loop of the pickup felt 14, a plane surfaced or bare roll 18 defining a first press nip N-.-1 with the first suction press roll 17, a press felt 19,

a second suction press roll 20 with a suction area 20a within the loop of the press felt 19 defining a second press nip N-2 with the plane surfaced roll 18. The press nip N-1 extends generally upwardly and is aligned angularly with respect to the first 'fel't reach 14a of the felt 14. The suction area 17a extends from the oncoming side to just about the main nip or pressure area for the nip 'N1. The web W is transferred at the nip N,1 onto .he bare roll surface and on this surface the web 'W remains as it passes through the second nip vN-2. At the second nip N-2, the suction area is arranged (in accordance with the principle of Hornbostel US. Patent No. 2,694,347) in that the suction area 20a straddles the press nip N-2 and the press felt 19 covers the entire suction area 20a, but is itself uncovered by the web for the greater portion of its travel at both the oncoming and oifrunning sides of the nip N-2.

Nextin Figure 1, there is shown an upper plane roll 21 and a lower suction roll 22, with suction area 22a, defining a press nip N3. If an attempt is made to feed the web W directly from the second nip N-2 to the third nip N-3, without the support of a felt, there is a tendency for the web to waver in its course of travel, and this may lead to breaks in the web at this area. Accordingly, it is particularly advantageous to pass the web W beneath a small guide roll 23 which urges the web W against the top side of a press felt 24 at or near a felt roll 25. The press felt 24 is urged gently against the web W at the roll 23. The rolls 23 and 25 are mounted immediately after the nip N-2, so that the .web W may pass therethrough without the slightest waver in its "travel. It may be mentioned also that a doctor D is mounted on the bare roll 18 for the usual purposes inkeeping the roll 18 clean and also for handling of broke during startup. The web W is thus taken from the surface of the bare roll 18 prior to the doctor D and passed between the rolls 23 and 25. Thereafter, the web W is carried by the felt 24 into the nip N-3.

As will be noted from Figure l, the felt 24 turns around a guide roll 26 at the oifrunning side of the nip N-3 so that the felt covers the entire offrunningside of the suction area 22a, but is uncovered by the Web W during most of its run on the ofirunning side of the suction area 220, because the web W is guided away by a roll 27 (and by its natural tendency to adhere to the bare roll surface 21). Thisfeature of the arrangementfor the press rolls 21 and 22 is similar to that described in Hornbostel US. Patent No. 2,694,347, and will also be brought out in Figure 2 of the instant description. 1

Referring now to Figure-2, it will be seen that thebare roll 21 carries the web W away from the nip N3,immediately after pressure is relieved at the nip N-3, so that the felt 24 covering the offrunning suction area is uncovered by the web during the majority of its travel at the offrunning side of the nip N-3.

As is indicated the nip pressure is applied during an area expressed by the angle A shown in Figure 2, and the felt 24 is uncovered by the web W at the ofirunning side through an angle'B. The angle B is greater than the angle A. The suction area 22a for the suction roll 22 extends, as shown in Figure 2, from an oncoming limit defined by the oncoming sealing strip 22b to an offrunning limit-defined by the offrunning sealing strip 22c. -In actual practice, the olfrunning area B is two to ten times greater than the nip area A and the oncoming area C is of substantially smaller size than A or B.

An important feature here, however, is that the oncoming area C of the suction roll 22 is not covered by either the felt 24 or the combination of the felt and the web W. Instead, the suction area C is substantially un- .covered by both the felt 24 and the web W. Theweb W is urged by the. felt 24 against the bare roll 21 at the oncoming side. During the travel of the felt 24 from the initial guide rolls 23, 25 of Figure 1 to the nipN- 3, a--substantial amount of water is picked up by the felt 24 from the web W. Since the felt 24 is beneath the web W, there is a tendency for loose water to accumulate at the underside of the felt 24. This water would otherwise be forced back into the web W and the felt 24 at a press nip, if it were not for the present arrangement, which permits air to sweep beneath the felt 24 and into the oncoming area C of the suction area 22a. The sweeping of air tends to move loose water from the bottom of the felt 24 and also to open up the bottom portion of the felt 24 and even draw water therefrom. In this way, the felt 24 has had an additional drying effect imparted thereto prior to the nip N-3, so that it will not tend to force water back into the web W at the nip N-3. Instead, the water will tend to flow primarily from the web W through the felt 24 and into the shell perforations 22d at the nip area A.

It will be understood that modifications and variations may be effected without departing from the spirit and scope of the novel concepts of the present invention.

I claim as my invention:

1. A paper machine suction press comprising a .pair of press rolls defining a press nip therebetween, at least one of said rolls being a suction roll having a suction area straddling said nip, and a looped felt lapping said suction roll, said felt being separated from the suction roll surface to permit air to sweep between the felt and the suction roll immediately before the nip and after the oncoming limit of the suction area, said felt further covering the offrunning side of said suction area.

2. In a paper machine, a bare press roll, a suction press roll defining a press nip therewith, said suction roll having a suction area straddling said nip, a looped press felt lapping said suction roll and carrying a paper web through said nip, and guide means for the felt separating the felt from the suction roll immediately before thenip and after the oncoming limit of the suction area, said felt further covering the oifrunning side of said suction area.

3. A paper machine suction press comprising a pair of press rolls defining a press nip therebetween lying in a plane generally tangential to booth said rolls, at least one of said rolls being a suction roll having a suction area straddling said nip, a looped felt lapping said suction roll, saidfelt being separated fromthe suction roll surface to permit air to sweep between the felt and the suction roll immediately before the nip and after the oncoming limit of the suction area, said felt covering the offrunning side of the suction area completely, and web guide means mountedon the side of said plane opposite said suction roll to maintain the felt uncovered for most of its run over the suction area at the offrunning side.

4. A paper machine comprising a first pair of'press rolls defining a first press nip.therebet ween, meansfeeding a web through said first nip, a second pair of press rolls defining a second press nip ftherebetween, at least one of said second pair of press rolls being a suction roll having a suction area straddling said second nip, and a looped felt receiving the web at the ofirunning side of said first nip and lapping the suction roll to feed the web through the, second nip, said felt being separated from the suction roll surfaceto permit air to sweep between the felt and the suction roll'immediately before the nip and after the oncoming limit of the suction area.

5. A paper machine comprising a first bare roll, a first suction roll defining a first nip therewith, a second bare roll, a second suction roll defining a second trip therewith, each suction roll having a suction area straddling its nip, a first felt feeding a web through the first nip and covering the entire suction area of the first suction roll, means maintaining the first felt uncovered by the web for most of its run on both the oncoming and olfrunning sides of the first suction area, and second :felt receiving the web fro'mthe first nip and feeding the web into the second nip, said second felt being separated from the surface of the second suction roll to permit air to sweep between the felt and the suction roll immediately before the nip and after the oncoming limit of the suction area.

6. A paper machine suction press, comprising a bare roll and a suction roll defining therebetween a nip, and a looped press felt lying against the bare roll in advance of the nip and against the suction roll after the nip.

7. A paper machine suction press, comprising a bare roll and a suction roll defining therebetween a nip, and a looped press felt lying against the bare roll in advance of the nip and against the suction roll after References Cited in the file of this patent UNITED STATES PATENTS 1,905,911 Kellett Apr. 25, 1933 2,083,818 Berry (1) June 15, 1937 2,204,426 Millspaugh June 11, 1940 2,209,578 Berry (2) July 30, 1940 2,764,917 Niks Oct. 2, 1956

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