CA1225266A

CA1225266A - Press arrangement

Info

Publication number: CA1225266A
Application number: CA000434267A
Authority: CA
Inventors: Jan I. Bergstrom
Original assignee: Beloit Corp
Current assignee: Beloit Corp
Priority date: 1982-09-29
Filing date: 1983-08-10
Publication date: 1987-08-11
Also published as: GB8325581D0; IT8323014A0; GB2127449A; KR840005847A; ES8406604A1; MX158734A; IN160964B; JPS6035476B2; GB2127449B; JPS5966593A; IT1194407B; ES525950A0; IT8323014A1; KR860001607B1

Abstract

ABSTRACT OF THE DISCLOSURE
A press mechanism and method for removing liquid from a traveling fibrous web such as in a papermaking machine including a pick-up carrier felt receiving the web from a forming wire, a second felt sandwiching the web therebetween, the first carrier felt passing successively through a first downwardly extending elongate press nip and thereafter immediately through an upwardly extending elongate press nip, each of said press nips being formed between centrally located shoes URGED apart toward the nips and outer press rolls with a single belt passing successively through the nips, and the second press roll for the second nip being a smooth surface roll for the transfer of the web with the web taken off on the downrunning side of the second smooth surface roll.

Description

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BAY RUG ROW IN OF' THE I NVF NT I ON
he inventiorl relates to an improved method anal mechanism or pressing water from a traveling puffier web, an-l more particularly to a press arrangement known as an extended press wherein the web is subjected to pressing pressures for a longer period of time than the usual arrangement wherein it passes between two opposed press rolls.
Further, the invention to a method and structure wherein the web is carried from the forming section of the paper making machine and taken down through a vertical nip through first extended press and carried on the same carrier felt up through a vertical nip in a second extended nip press and thereafter transferred Jo a press roll which forms part of the second nip. The nits are constructed so that the residence time of the web in the nip is increased over that wherein the wok is merely passed through a roll couple Other structures have been provided heretofore which have had an objective to increase the time over which the wok is subjected to a pressure and yet permit the web to continue movement at a speed necessary in a high speed papermakin~ machine. such structures have met with degrees of success and are exemplified by the disclosures in Us Patent Nos. 3,748~225 7 Buster et at 3,783,097, Justice;
3,797,384, Hoff, 3,798,121, Buster et at; 3,804,707, Moor;
3,808,032, Buster; 3,808,096, Buster et at; 3,840,42~, Buster et at; and 3,853,698, Moor. The devices and methods discussed by these previous patents have utilized the knowledge that the attic application mechanical pressure to wet paper mat can reduce the moisture content in the mat to below 40%. Under the dynamic shorter mechanical. pressing which occurs in the usual paper machine where the web is run between a series ox nips formed between tress roll couples, it is difficult to maintain moisture levels below fix%. Attempts to obtain increased dryness ~L225~6~

in the conventional roll couples are usllally made by increase in press nip pressures, buy a plateau is soon reached where major increases in roll loading result in relatively smell decreases in moisture.
As is known, it is far more efficient to remove water in the press section of a paper machine than in the thermal dryer section and significant reduction in energy costs and significant reduction in space needed for the dryer drum section of the machine are achieved for every fraction of a percent ox moisture that can be additionally removed in the press section. the difficulty of removing moisture in the press section is increased with increase in machine speed because limiting factors are reached in press nip Pressures in that compacting and crushing of the web results with higher nip pressures and resultant higher hydraulic pressures within the paper mat. The most feasible way that has been discovered to increase water removal at high speeds has been to increase the residence time of the web in the press or the pressure time to allow more time for the water to flow within and out of the paper mat and For the hydraulic pressure to dissipate.
Constructions have been made which utilize mechanical principles to improve the compactness of the pressing arrangement and to reduce the mechanical framework needed for the elongated press structure. One such structure is shown in US. Patent 4,201,624, Moor et at where the web is first passed through an upwardly extending elongate nip and then carried downwardly through a succeeding nip. However, disadvantages have occurred in this and other structures in that it has been difficult to transfer the web at high speeds and with breakage, it is difficult to get rid of the broke.
It is accordingly an object of the present invention to provide an improved high speed extended nip press wherein an

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improved structural arrangement is achieved which permits the web to he carried directly from the forming machine through first and second extended nips and transferred immediately from the second nip in a manner so that it the web breaks, it can travel downwardly or easy handling of the broke. As is known to paper makers, when the web is traveling at the high speed found in odyssey paper making machine, any wok breakage can result in disastrous effects in that the excessive paper will immediately pile up in huge accumulations and can damage or destroy successive mechanical parts in the paper machine as well as presenting a risk to life and limb of the attendant who is operating the paper making machine.
A further object of the invention is to provide an improved arrangement for an extended nip paper making machine wherein the web is first pressed in a double feted nip, and wherein the second nip is so arranged so that the web is carried and handled in an improved fashion.
A further object of the invention is to provide an improved extended nip press utilizing first and second extended nips wherein the structure is so arranged so as to cancel out oppose forces and reduce the amount of framework and support structure that is needed.
A feature of the invention is that the web it carried from a forming section and passed in a downward direction Thor a double felled nip and carried by the first carrier felt up through a second nip and removed from the second nip on the smooth surface roll which provides the pressure for the second nip and taken off of that roll on the down running side.

Other objects, advantages and features as well as equivalent structures and methods which are intended to be covered herein will become more apparent with the teaching of the principles ox the invention in connection with the I 2~5;,Z6~

disclosure of the preferred embodiments thereof in the specification, claims and drawings, in which:
DRAWINGS

-The single Figure of the drawing labeled FIGURE 1 is a somewhat schematic side elevation Al view showing the elements of a paper machine press constructed and operating in accordance with the principles of the present invention.
DESCRIPTION
As illustrated in Figure 1, a web W is formed in a forming section of a paper making machine such as between a win wire on a fourdrinier wire and is shown being carried from the forming machine on a wire 10 to be transferred to the press section. The forming wire passes down over a couch roll 11 and over a turning roll 12.
On the down running side of the wire 10 the web is picked off of the wire by a pick-up or carrier felt 13. The felt is brought into web transfer relationship with the wire by a pick-up roll 14 having a suction pick-up gland 15 therein which aids in the transfer of the web W to the undersurface of the felt 13.
After the web is transferred to the felt, it is sandwiched against the felt by a second felt 17 which is guided up beneath the first carrier felt 13 so that the web is then carried through the first nip in double felled water removal relationship.
The press section has a first vertical down running extended nip N-l, and a successive up running vertical second extended nip N-2.
The first nip N-l is formed between a first outer press surface which is provided by a cylindrical roll 18 having a relieved surface preferably in the form of annular grooves pa to help in the transfer of water into the second felt 17 and into the grooves at the first press. Because the web normally is Sue it quite wet at the first press, the double-3 felled support and the grooved roll will accommoflate the relcltively large flow of water.
he first nip is completed by a shoe 23 at the other side of the nip. A traveling belt which is of a strong material such as reinforced rubber used in extended nip presses passes through both of the nips and is suitably guided by rolls and in particular is carried on a turning roll 28 following the first nip prior to its entering the second nip.
For the pressing detouring force within the nip, the first shoe 23 is pressed toward the nip with a predetermined controllable pressure, and the shoe is provided with a relieved leading edge at 21. Hydraulic fluid is delivered by a nozzle foe along the full length of the shoe so that the hydraulic fluid is carried into the nip over the shoe surface, and the belt is supported by a dynamic hydraulic layer of liquid this liquid builds up in pressure from the relieved loading edge along the shoe and the hydraulic pressure continues along the length of the shoe so as to provide a continuous pressing force over a relatively long extended time and length of travel of the web.
the hydraulic pressure, of course, is applied against the impervious rubber belt which presses the web between the two felts 13 and 17 in the extended nip N-l as the Deb is traveling downwardly.
Following the first nip the web continues traveling downwardly and is transferred to the first felt by a felt turning roll I which is a perforate suction roll and has a gland 30 therein extending to where the first felt 30 is turned away from the second felt 17 so as to insure web transfer. The web is carried along around the turning roll 29 on the first felt and carried up into the second nip N-2.

The belt travels following its turning roll 28 up into 5_ ED
~L~tb!b the second nip which is formed between a second outer press surface provided by a Sue Dracula solid surface smooth roll 19. the second nip No is completed by a shoe 22 which has a relieved leading edge 24. Each of the shoes 23 and 22 axe concavely shaped so as to conform essentially to the curvature of the rolls 18 and 19, and are supported on roll pins 35 and 36 so that the shoes are pivotal supported. A force is developed or pressing the shoes against the nip by pistons 37 and 38 which are situated in a cylinder with a pressure chamber 39 there between to which hydraulic pressure 40 is delivered so that the shoes are pressed apart with equal and opposite forces.
Since these ores oppose each other, the supporting structure for the shoes need only be sufficient to carry their weight and their opposed forces for creating a nip pressure are canceled. A nozzle 27 is provided ahead of the second shoe to direct hydraulic fluid along its length at its relieved leading edge 24 so that a dynamic hydraulic layer of liquid forms between the nip and the shoe.
On the off running side of the second nip, the web will follow the smooth surface roll 19 and the carrier felt 13 travels upwardly separating from the roll 19.
The web travels over the top of the roll lug and is led off the roll by a separating guide roll 31. This roll 31 is located on the down running side of the roll 19 so that if web breakage occurs at this location, the web will travel downwardly as indicated by the dotted line web indication 330 A doctor blade 32 is mounted in close adjacency to the roll 19 on the down running side to separate the web from the roll in the event breakage should occur Since this is the first open draw for the web, while it is fairly dry at that location, this is the location where breakage can occur. The web is otherwise completely supported through its entire travel through the ~22~Z6~

press, and as will be noted, the press being arranged vertically is relatively compact and takes a relatively small amount ox machine room In operation, a wet web W is carried on the forming worry and transferred to the first felt lo and thereafter sandwiched by a second felt 17 to be carried downwardly in doubled felled relationship through a first vertical downwardly extending nip N-l. The web follows the first carrier felt around a perforated felt turning and web transfer roll 29l and is carried on the surface of the photo 13 up into the vertical second nip N-l If the web should be lost or breakage occur at the point of the turning of the felt, the web will be traveling downwardly and can be easily transferred to the broke pit. the web then passes upwardly through the second nip and is transferred to the smooth outer surface of the roll I where the web is removed from the smooth surface roll by a transfer roll Al. In the event of breakage at this first open draw, the web would travel downwardly to a broke pit as indicated by the dotted line indication 33.
Thus, it will. be seen that I have provided an improved web pressing arrangement which meets the objectives and advantages above set forth and utilizes the concepts of an extended press nip in an improved manner so as to provide advantages of a compact space, a rapid pressing of a web and improved handling in the event of web breakage.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A web former having a traveling wire delivering a wet web to said former for dewatering therein comprising:
a first felt;
means for guiding said first felt in pick-up relation with said wire for receiving said web;
an endless belt;
means for guiding said belt in a loop having a downrunning side and an uprunning side;
a first press roll, said first roll being an open roll and disposed for pressing against said downrunning side of said belt loop;
a second felt;
means for guiding said second felt and said first felt around said first press roll with said web therebetween;
a second press roll having a surface with a greater affinity for said web than does said belt and disposed for pressing against said uprunning side of said belt loop;
opposed first and second backing shoes disposed between said first and second press rolls and means loading said first and second backing shoes for respectively forming a first extended nip in combination with said first press roll and the downrunning side of said belt and a second extended nip in combination with said second press roll and the uprunning side of said belt;
said second press roll having an unobstructed down-running side opposite said second backing shoe;
and means for removing broke from said second roll surface permitting said broke to fall for disposal in the same direction as the web is traveling on said unobstructed downrunning side.

2. A web former as claimed in claim 1 wherein said means loading said first and second backing shoe comprises:
opposed pistons disposed between said first and second backing shoes and being respectively pivotally connected in each of said shoes; and fluid pressure means for applying equal and opposite forces to said pistons urging said pistons respectively toward said first and second press roll.

3. A web former as claimed in claim 2 further comprising:
relieved leading noses disposed on each of said first and second backing shoes; and means for delivering lubricating fluid to said relieved noses of each of said backing shoes for forming a dynamic layer of hydraulic fluid between the shoes and the belt in each of said extended nips.