US3847731A

US3847731A - Twin wire paper making method in which controlled dewatering in tapering gap causes suspension to move at speed of wires

Info

Publication number: US3847731A
Application number: US00198304A
Authority: US
Inventors: H Arledter
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-11-16
Filing date: 1971-11-12
Publication date: 1974-11-12
Anticipated expiration: 1991-11-12
Also published as: FR2117102A5; GB1373249A; DE2155974A1; CA947553A; AT328283B; ATA1027370A

Abstract

Paper making method in which turbulent suspension under pressure is introduced to a tapering gap between a pair of traveling wires at the speed of the wires, and is dewatered therein by suction applied in a series of zones along the wires in such controlled manner that the quantity of liquid in the suspension decreases from zone-to-zone proportionally to gap width, and the suspension is caused to move through the gap at essentially the speed of the wires and without being subjected to substantial mechanical pressing by the wires.

Description

United States Patent 1191 Arledter.

[ TWIN WIRE PAPER MAKING METHOD IN WHICH CONTROLLED DEWATERING IN TAPERING GAP CAUSES SUSPENSION TO MOVE AT SPEED OF WIRES [76] Inventor: Hanns F. Arledter, Andritzer Reichsstrasse 122, 8046 Graz St. Viet, Austria [22] Filed:

Nov. 12, 1971 21 Appl. NO.I 198,304

[30] Foreign Application Priority Data Nov. 16, 1970 Austria 10273/70 52 us. c1 162/203, 162/209, 162/211, 162/301, 162/303, 162/337, 162/341, 162/342 51 11 1. c1. ..1)211 1/00 58 Field Of Search 162/203, 301, 303, 374, 162/352, 337, 186, 209, 341, 357, 363, 323,

[56] References Cited UNITED STATES PATENTS 1,645,068 10/1927 OBrien 162/301 2,046,271 6/1936 Lane et a1 162/323 X 3,103,463 9/1963 Justus 162/341 3,149,028 9/1964 Robinson.. 162/303 3,403,073 9/1968 Moran 162/203 3,438,854 4/1969 Means 162/374 X 1 Nov. 12, 1974 3,578,561 5/1971 McCarrick et a1 162/352 1,241,905 10/1917 Behr 100/153 X 1,875,075 8/1932 162/203 X 3,215,593 11/1965 Green 162/301 1 3,578,558 5/1971 McCarrick et al.. 162/303 3,034,577 5/1962 Cirrito 162/337 3,560,334 2/1971 Arledter [62/186 X 3,027,940 4/1962 Dunlap 162/363 X FOREIGN PATENTS OR APPLICATIONS 1,582,914 10/1969 France 162/203 1,005,530 4/1952 France 1. 162/209 560,577 4/1944 Great Britain 162/341 Primary Examiner-S. Leon Bashore Assistant Examiner-Richard 1-1. Tushin Attorney, Agent, or Firm-Robert A. Ostmann [57] ABSTRACT Paper making method in which turbulent suspension under pressure is introduced to a tapering gap between a pair of traveling wires at the speed of the wires, and is dewatered therein by suction applied in a series of zones along the wires in such controlled manner that the quantity of liquid in the suspension decreases from zone-to-zone proportionally to gap width, and the suspension is caused to move through the gap at essentially the speed of the wires and without being subjected to substantial mechanical pressing by the wires.

8 Claims, 4 Drawing Figures PATENTEUHGV 1 21974 3.847. 731

SHEEI I 0F 4 INVENTOR ATTORNEY PATENTEL W 1 3.847. 731

SNEEI 20$ 4 INVENTOR ATTORNEY PAH-INTEL HUV 1 21974 smt u gr 4 INVEN TOR ATTORNEY TWIN WIRE PAPER MAKING METHOD IN'WHICH CONTROLLED DEW'ATERING IN TAPERING GAP CAUSES SUSPENSION TO MOVE AT SPEED OF WIRES BACKGROUND OF THE INVENTION The invention relates to a paper making method employing a machine with two wires joining into a double wire area and confining in front of said area a narrow converging gap for sheet forming.

Such machines are known. As other known paper making machines, suchmachines have the disadvantage that the formed sheet is composed of layers with fibres orientated in the plane of said layers. With increasing wire speed and decreasing consistency of the suspension the layers get more distinct. The single layers are badly connected to each other. Besides, most of the fibres in the layers'are orientated in the direction of wire travel, resulting in different strengths of the sheet in longitudinal and lateral direction.

Paper making method in which turbulent suspension under pressure is introduced to a tapering gap between a pair of traveling wires at the speedof the wires, and is dewatered therein by suction applied in a series of zones along the wires in such controlled manner that the quantity of liquid in the suspension decreases from zone-to-zone proportionally to gap width, and the suspension is caused to move through the gap at essentially the speed of the wires and without being subjected to substantial mechanical pressing by the wires.

SUMMARY OF THE INVENTION The purpose of the invention is to provide a paper making method in which the machine delivers in a wet process a sheet having a fibre orientation distributed on all dimensional directions equally, and which can utilize high wire speeds.

According to the invention, atleast and preferably more than 50%, of web formation takes place in the converging gap, and the suspension is fed to the gap in a turbulent condition and under a pressure which causes it to enter at the speed of the wires. The suspension is dewatered by suction applied in a series of zones positioned along the path of travel of each wire, and the degree of suction dewatering in each zone is set so that the quantity of liquid in the suspension decreases from zone-to-zone in the direction of wire travel proportionally to the width of the gap. This technique causes the suspension to move through the gap at essentially the speed of the wires and without being subjected to appreciable mechanical pressing by the wires.

The fibres coming in a turbulent suspension into the gap maintain their orientation in all dimensional directions even during depositing on the wires. Good sheet quality is especially achieved if thequantities of liquid to be sucked away in the zones, and/or the width of the gap is so adjusted that the suspension has reached the frozen condition at the outlet of the gap. Under frozen condition is understood the condition wherein the fibres cannot change their orientation because of the.

The gap definedby. thewires has a length of .300 to 2,000 mm, an inlet width of 6 to mm, and anoutlet width of up to 5 mmrEach dewatering zone preferably has a length, measured in thedirection of wire travel, of 60 to mm, and is provided with a wire supporting surface having a radius of curvature of l,000mm to infinite. These zones are equipped with separate devices foradjusting the quantities of liquid to besucked. away. It is of great advantage-if the dewatering ele ments are stationary suction boxes having perforated wire supporting wallswhich are convex domed against the wires. Manufacturing costs are reduced if the surface of the convex domed wall has the form of a cylin-. der section, the generatrix of which-is an arc of a circle. with a sector angle of less than 15. The domed walls guarantee, under thetension of the-wires, a smooth joining of each wire to the surfacesof the boxes, resulting in a definite distance between the wires and the boxes and minimal by-passing of air. Therefore, in each zone a definite vacuum can be established, and a definite quantity of liquid can be sucked away.

For adjusting the machine in respect of the kind of suspension, the kind of sheet to be formed, or different wire speeds, advantageously the width of the inlet and- /or outlet of the gap is adjustable. Equally, the radius of curvature of the dewatering elements can be adjustable. For this purpose, the dewatering elements can be made of links turnable against each other, or can be.

substitutable by elements with another radius of curvation) of the element is adjustable too.

Deposition of the fibres on the wires can be advantageously influenced, while maintaining equal speeds for suspension and wires, by hav-ing the quantity of liquid to be sucked away at one side of the gap bigger than, .at the other side of the gap, and then the quantity of liquid at the other side of the gap bigger than at the one side of the gap, alternating in directionof wire travel. The result is a suspension flowing in the form of a serpentine through the gap.

Orientation of the fibres in the suspension can also be influenced by adjusting the quantities of liquid to be sucked away so as to have for one orsome zones a certain speed difference between suspension and wires. Neglecting this, that is taken essentially, the suspension is kept at the same speed as the wires.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the inventionv are described herein in detail with reference to the accompanying drawings in which:

FIG. 1 shows a vertical section, in the direction of wire travel, through a paper making machine FIG. 2 a corresponding vertical section through part of another embodiment, and

FIGS. 3 and 4 show each one form of a gap and dimensioning data for further gaps.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The paper making machine shown in FIG. 1 has two

wires

1 and 2 which join into a double wire area 3. In front of the double wire area 3, .immediatly before the. wires 1, 2join into area 3 the

wires

1, 2 form a converging gap 4 between themselves. The length of the gap 4 is 300 to 2,000 mm. The width of the gap 4 is at the inlet 4 of the gap 6 to 100 mm, and the width of the gap is at its outlet 4 some tenth of millimeter to 5 mm. The

wires

1 and 2 travel over dewatering

elements

5 and 6, respectively, arranged on both sides of the gap 4. The dewatering elements are subdivided into a plurality of zones, i.e. into

zones

7, 9, l1, l3, l5 and 8, 10, 12, l4, 16, respectively. Each of the zones has an adjusting device-not shownfor adjusting the quantity of the liquid to be sucked away in the respective zone.

Dewatering elements

17 and 18, arranged in front of the inlet 4 also each have an adjusting device-mot shown-for adjusting the liquid to be sucked away. The dewatering elements can be moved-by means not shownrelatively to each other so as to make the width of the gap 4 at the inlet 4 or at the outlet 4 bigger or smaller.

A chamber 19 for feeding suspension to the gap 4 opens against the inlet 4, i.e. the lower end of gap 4. This chamber 19 has two

feeding conduits

20, 21 arranged symmetrically to the gap 4, and a return conduit 22, for the suspension.

The inlet width (4) of the gap 4 and the pressure of the suspension to be lead to the gap 4 are so adjustable as to make the speed of the suspension at the inlet 4 equal to the speed of the

wires

1, 2. The quantities of liquid to be sucked away with the zones 7 to 16 are so adjustable as to make the speed of the suspension along the gap, i.e. from the inlet 4 to the outlet 4 essentially equal to the speed of the

wires

1, 2. Thereby, the quantities of liquid to be sucked away with the zones and/or the width of the gap 4 are so adjustable as to have reached at least at the outlet 4 of the gap 4 a consistency at which the suspension is in the frozen condition.

The

dewatering elements

17, 18 at the transition between chamber 19 and inlet 4 are formed as stationary suction boxes with a perforated wire-supporting convex domed wall. In the chamber 19 are inserted turbulence generators, i.e. rotatable perforated

rollers

23, 24, rotatable bodies 25, 26 and a rotatable cylinder 27.

An element of the chamber 19, that is the wall of said chamber can be set under oscillations with periodic frequencies of more than 5 per second, by a vibrator 28. Similarly,

vibrators

29 and 30 serve for oscillating the

dewatering elements

5 and 6, respectively with periodic frequencies of more than 50 per second. The direction of oscillating is at an angle of at least degress relatively to the plane of the wires, i.e. as for the vibrator 28 an angle of 30, and for the

vibrators

29 and 30 an angle of 90.

The suspension has in the chamber 19 practically constant consistency. 1n the gap 4, the consistency increases with short fibre lengths (1 to 6 mm) from 0.1 to 1.5% at the inlet 4 up to 3 to 6% at the outlet 4 With long fibre lengths (6 to 30 mm), the consistency increases from 0.001 to 0.1% at the inlet 4 up to 0.5 to 1% at the outlet 4 Thereby, with the invention, very high wire speeds can be achieved, even with the higher consistencies.

1n the double wire area 3 in which the two

wires

1, 2 support the formed sheet at both sides, the dewatering process can be brought up to 44% consistency, i.e. solids per solids plus liquid, with the help of boxes 31 having perforated wire-supporting convex domed walls, grooved cylinders 32, and a pair of cylinders 33.

The gap 4 is arranged vertical and converges in direction of wire travel from below to above. The suspension flows upward in the gap 4.

With the embodiment according to FIG. 2, the gap 4 is arranged vertically too, yet the gap converges downwards, and the suspension flows downwards. The chamber for feeding the suspension to the gap 4 is formed as a box 34 the bottom of which is formed by the

wires

1 and 2. 1n the box 34, a bath of suspension is maintained. Under the box 34, suction boxes 35 and 36 are arranged. Part of sheet forming takes place on the

wires

1, 2 before these wires enter the gap 4. The layer of the sheet lying between the layers formed in box 34 are then formed in gap 4 according to the invention.

The quantities of liquid to be sucked away in the zones of the gap 4 are so adjusted as to make the speed of the suspension along the gap essentially equal to the speed of the wires. Maintaining this condition, alternating from zone to zone in the direction of wire travel, firstly, at one side of the gap 4 is sucked away a bigger quantity of liquid than at the other side of the gap 4, then at said other side of the gap is sucked away a bigger quantity of liquid than at the one side of the gap, then in the, in the direction of wire travel, third zone vice versa. That is, the quantity in zone 7 is bigger than in zone 8, in zone 10 bigger than in zone 9, in zone 11 bigger than in zone 12, in zone 14 bigger than in zone 13, in zone 15 bigger than in zone 16. The stream of suspension in gap 4 gets therefore the form of a serpentine.

For acting on the fibres in the direction of flow, the quantities of liquid to be sucked away in the zones are so adjusted that with a pair of zones, i.e. with the

zones

9 and 10, a difference of speeds between suspension and wires occurs. Such a local acceleration or retardation could be repeated in further pairs of zones. Especially if accelerated and retarded zone pairs alternate, the speed of the suspension can be in general kept equal to the speed of the wires all the same.

The ends of the

dewatering elements

5 and 6 are staggered relatively to each other at the outlet 4 of gap 4. This is advantageous with small widths of the outlet 4 With the box 34, more than two feeding and/or return conduits open into it, that is the feeding

conduits

37 and 38, and the

return conduits

39 and 40. The kind of sheet forming in the box 34 as well as the condition of the suspension delivered to the gap 4 can thereby be influenced.

The walls of the

dewatering elements

5 and 6 are lightly convex domed against the wires, and have the form of a cylinder section the generatrix of which is an arc of circle with a big radius. The surface of the convex domed wall is made of a material having a coefficient of friction of smaller than 0.1 relatively to a wire made of metal.

With the gaps given with FIG. 3 the sketch at the left side of the drawing shows an inlet width d an outlet width d and a length 1 of the gap. The gap is in the drawing confined by two arcs of circle, each of them reaching from the inlet to the outlet of the gap, and having a radius r and a sector angle a. The gap is subdivided-into twelve zones of equal length. At the right hand of the sketch, a table gives the portion of the liquid to be sucked away, which is left in the suspension at the end of each zone (in of the total quantity of liquid to be sucked away in the whole gap) for four different forms of gap. The length l of the gaps is equal with all forms, namely 1,200 mm, while the difference d between inlet width d and outlet width d as well as the radius 'r and the corresponding sector angle a are different. 5 by the invention.

FIG. 4 corresponds to FIG. 3. Yet, the length 1 of the Table 6 Shows Production capacities for p p made gaps i 500 mm d th gaps are bdi id d i fi of synthetic fibres, dependent on fibre lengths and corzones. There are seven different forms of gaps. responding consistencies of the Suspension With the shown forms of gaps, the table given quancomblhlhg Tables 2 to 5 Ph can See P- hh f tity of liquid decreases in the direction of wire travel 10 hohs of m of the Speed qhahthy Ofhqhld from zone to zone proportionally to the width of the to be Shcked hl lehgth of the-suction e and gap The diff between the total quantity (100%) productlon capacity are a function of the consistency and the quantity given in the table has to be sucked of the h h' away at the respective zone end. This way the speed of Suspensions with ng fibres for tion-woven webs can the Suspension in the gap is constant AS to make'this be dewatered according to the lnventlon with wire speed exactly constant, the perforations of the suction Speeds of 1,000 to 1,200 m P mlhute, fh at the boxes can differ with a zone in the direction of wire Inlet, of the gap of 40 to 70 h and quamltles of have] in respect of form and/Or Size pension of 48,000 to 70,000l1ter permlnute and lateral With the gap forms according to FIG. 3, the total h of the Sheet quantity f liquid to be Sucked away in the gap is With short fibre suspensions, wire speeds of 1,000 to 40,000, with the FIG. 4 forms 30,000,liter per minute 1,500 m Per Ihlhhtei h at the 1hlet of the g and meter lateral width f the Sheet of 20 mm, the production of paper with the machine In order tofeed the suspension into the gap 4 with acicordlhg to the Invention reaches 100 to 300 kg P wire speed the suspension has to be fed to the chamber mlhhte i m lateral Width of the Sheet 19 with a pressure that is higher than the pressure cor- The Wldth at the hlet 41 of the gap 4 has he f responding to wire speed. Table 1 shows the respective than the length of thehhres; As Shown thls Cohdl' pressures (meter water column) for some wire speeds hoh can he met whhthe lhvehhoh- (meter per minute). Under paper making machlne and paper is also The width (mm) of the inlet 1 of the gap 4 is a func understood, in the sense of th s specification, a mation of the quantity of suspension (liter per minute and Chlhe Produces a paper'hke Sheet for example meter lateral width of the sheet) flowing through the a machhe for pmdhc'hg hoh'woveh websgap and of the wire speed. For equal'speeds of suspension and wires, Table 2 shows some examples. TABLES:

In Table 3, the production of paper (Kilogramm per Table 1 minute and meter lateral width of the sheet, or metric tons per 24 hours and meter lateral width of the sheet) S d Inlet Pressure Inlet Pressure for is given as a function of consistency (per cent) and hf as? 4 (m WC) Chamber WC) quantity of suspension flowing through the gap.

The production of the machine according to the in- 40 88 vention furthermore-depends on the degree of freeness, 600 610 the dewateringor suction area, the weight of square 900 meter of paper, and thedewatering vacuum or suction 2M pressure. Dewatering on the double wire system, that is from two sides of the-sheet, and up to consistencies of l to 6% results in big quantities of liquid sucked away. In Table 4,'the quantities (liter/per minute and Table 2 square meter suction area) are given for some kinds of suspension, dependent on different suction pressures Quantity of Liquid (llmin/m) (meter water column). hi on widths d (mm) of Table 5 shows for a suction box with plane wiresupporting wall (radius of curvature being infinite) and 10 20 40 a length Of 1 meter, subdivided into 10 zones, the quan- 1500 15 000 30 ()00 0 000 9() 000 112 000 tity of liquid to be sucked away witheach zone. With 1000 lo 000 20 000 40 000 60 000 75 000 1 meter lateral width of the sheet, each zone has a suc- 55 tion area of 1,000 cm The quantity of liquid (liter per 500 5 000 10 000 20 000 30 000 37 500 minute) is given dependent on wire speed (meter per 250 2 500 5 000 I0 000 15 000 I8 750 minute) and width d (mm) of the gap. A

Table 3 Consist- Production (kg/min/m) above (to/24 hours/m) cncy on Quantities of Suspension (l/min/m) of By adjusting the width d of the-gap (10 bis mm) and the suction pressure (2 to 8 m water column), any quantities of liquid to be sucked away with the production of the different paper quanlities are easily coped Table 3 Continued Consist- Production (kg/min/m) ahovc (to/24 hours/m) ency (Cl 1 on Quantities of Suspension (l/min/m) of Table 4 20 a pair of traveling wires, the method comprising the steps of Material Quantity of Liquid (l/min/m) a. establishing and maintaining, in a region ad acent S r P WC f the gap inlet, a volume of fiber suspension which 15 on "assure m )0 under pressure, has uniform consistency, and is in 5 a turbulent state,

Nomwoven 60 000 I20 000 b. sa1d pressure bemg such as to cause suspens1on to flow 1nto the gap at the speed of the w1res;

40 c. causing the wires to pass in contact with suspen- Low Freeness sion in sa1d reg1on 1mmed1ately before they define P111, with 20 000 40 000 60000 Said Mcdium Freeness d w1thdraw1ng l1qu1d from the suspenslon 1n sa1d req n j 000 20 000 30 gion through each wire by suction to thereby cause deposition of fibers on the wires and effect partial Pulp with Very 2 000 4 000 0 000 formation of the sheet;

e. withdrawing liquid from the suspension in the gap through each of the wires by suction applied in each of a series of separate zones positioned along Table 5 the path of travel of the wire, whereby the consis- 40 tency of the suspension increases gradually as the Wire Ouamjrg p q l g R Zone suspension travels through the gap and a sheet is 2323, m lea formed therefrom between the two wires; and

on W1dths d of f. setting the degree of suction dewatering effected in 80 60 40 20 0 each zone so that the quantlty of l1qu1d 1n thesuspens1on decreases from zone-to-zone 1n the d1rec- 1200 600 tion of wire travel proportionally to the width of L000 4000 3000 2000 1000 500 the gap, and the suspension is caused to move 00 7400 I600 800 400 through the gap at essent1ally the speed of the w1res and without being subjected to appreciable me- 000 2400 I800 1200 600 300 chanical pressing by the wires. 400 600 1200 800 400 200 2. A method as defined ln cla m 1 1n wh1ch a. w1thdrawal of sa1d l1qu1d 1n the gap 15 effected through two sets of suction boxes having perfo- T rated wire-supporting walls which are convex able 6 domed agalnst the w1res, H, L h C t P d I, b. whereby contact between the w1res and the walls C C I) C I)" l t rp ""21 (kg/mink; (w/day/m) mmimiz es by-passmg of a r 1nto sa1d boxesand 1nsures w1thdrawal of defimte quantlties of l1qu1d 1n 3 10 0 0.100 48.0 68.0 Said Zones 0 m 10 0.050 24.0 34.0 3. A method as defined in claim 1 in which a. th uantities of li 'd wi h w h t 10 m 15 0.020 14.0 20.8 t dra n throug he two w1res 1n each zone are unequal; and 10 to 30 0.005 3.5 b. in adjacent zones the greater quantity is withdrawn through different wires, c. whereby the suspension in the gap has a tendency I claim: to form a serpentme.

l. A paper making method in which at at least 30% of the forming of a continuous sheet is effected by dewatering a fiber suspension in a tapered gap defined by 4. A method as defined in claim 1 including the step of continuously circulating suspension through said region between a plurality of feeding and return conduits.

5. A method as defined in claim 1 including the step of vibrating suspension in said region at a frequency greater than 5 cycles per second.

6. A method as defined in claim 1 including the step of vibrating suspension in the gap at a frequency greater than 50 cycles per second.

Claims

1. A PAPER MAKING METHOD IN WHICH AT LEAST 30% OF THE FORMING OF A CONTINUOUS SHEET IS EFFECTED BY DEWATERING A FIBER SUSPENSION IN A TAPERED GAP DEFINED BY A PAIR OF TRAVELING WIRES, THE METHOD COMPRISING THE STEPS OF A. ESTABLICHING AND MAINTAINING, IN A REGION ADJACENT THE GAP INLET, A VOLUME OF FIBER SUSPENSION WHICH IS UNDER PRESSURE, HAS UNIFORM CONSISTENCY, AND IS IN A TURBULENT STATE, B. SAID PRESSURE BEING SUCH AS TO CAUSE SUSPENSION TO FLOW INTO THE GAP AT THE SPEED OF THE WIRES; C. CAUSING THE WIRES TO PASS IN CONTACT WITH SUSPENSION IN SAID REGION IMMEDIATELY BEFORE THEY DEFINE SAID GAP; D. WITHDRAWING LIQUID FROM THE SUSPENSION IN SAID REGION THROUGH EACH WIRE BY SUCTION TO THEREBY CAUSE DEPOSITION OF FIBERS ON THE WIRES AND EFFECT PARTIAL FORMATION OF THE SHEET; E. WITHDRAWING LIQUID FROM THE SUSPENSION IN THE GAP THROUGH EACH OF THE WIRES BY SUCTION APPLIED IN EACH OF A SERIES OF SEPARATE ZONES POSITIONED ALONG THE PATH OF TRAVEL OF THE WIRE, WHEREBY THE CONSISTENCY OF THE SUSPENSION INCREASES GRADUALLY AS THE SUSPENSION TRAVELS THROUGH

2. A method as defined in claim 1 in which a. withdrawal of said liquid in the gap is effected through two sets of suction boxes having perforated wire-supporting walls which are convex domed against the wires, b. whereby contact between the wires and the walls minimizes by-passing of air into said boxes and insures withdrawal of definite quantities of liquid in said zones.

3. A method as defined in claim 1 in which a. the quantities of liquid withdrawn through the two wires in each zone are unequal; and b. in adjacent zones the greater quantity is withdrawn through different wires, c. whereby the suspension in the gap has a tendency to form a serpentine.

4. A method as defined in claim 1 including the step of continuously circulating suspension through said region between a plurality of feeding and return conduits.

7. A method as defined in claim 6 in which the suspension in the gap is vibrated in a plane forming an angle of at least 20* with the planes of the wires.

8. A method as defined in claim 1 in which turbulence in said region is produced mechanically by a rotating body.