US2821120A

US2821120A - Dewatering pulp or stock on a paper or boardmaking machine

Info

Publication number: US2821120A
Application number: US373382A
Authority: US
Inventors: Thomas Reginald James; Smith Stanley Fred
Original assignee: St Annes Board Mill Co Ltd
Current assignee: St Annes Board Mill Co Ltd
Priority date: 1952-08-22
Filing date: 1953-08-10
Publication date: 1958-01-28
Anticipated expiration: 1975-01-28

Description

Jam. 28, 1958 R. J. THOMAS ETAL 2,321,120

DEWATERING PULP OR STOCK ON A PAPER OR BOARDMAKING MACHINE Filed Aug. 10, 1953 6 Sheets-Sheet 1 ATTUPNEYJ Jan. 28, 1958 R. J. THOMAS ETAL DEWATERING PULP OR STOCK ON A PAPER OR BOARDMAKING MACHINE 6 Sheets-Sheet 2 Filed Aug. 10. 1953 w w m m: m: 5 mm H mm? V. E 5% a n. n m N v m I. m m n m i w In N m N RM 3 H m; w:

AND

Jan. 28, 1958 R. .J. THOMAS Ef'rAL 2,821,120

DEWATERING PULP OR STOCK ON A PAPERVOR BOARDMAKING MACHINE IN VEN TOP 7'? E6 in 91.; Uknss Tia 119s A N.

umw vr/ M HITOQNEXQ Jan. 28, 1958 R. J. THOMAS ET'AL 2,821,120

DEWATERING PULP OR s'rocx ON A PAPER OR BOARDMAKING MACHINE Filed Aug. 10. 1953 6 Sheets-Sheet 4 INVENTOE PEG/WALD Jknss Tflvms' fi/ D STnm sy FRtD Sni H QTTOPNEYJ Jan. 1958 7R. J. THOMAS ETAL 2,821,120

DEWATERING PULP OR STOCK ON A PAPER OR BOARDMAKING MACHINE 6 Sheets-Sheet 5 Filed Aug. 10. 1953 INVENTOP -PE Gififllo J'n/aes Tflanns pm:

STawg y FRED 8mm HTTOPNEYS mN ww mi Jan. 28, 1958 R. J. THOMAS ETAL 2,821,120

DEWATERING PULP OR STOCK ON A PAPER OR BOARDMAKING MACHINE 6 Sheets-Sheet 6 Filed Aug. 10, 1953 INYENTOP Resin/5A0 Jnnss THC-"19.;

my Stan FRED $17177 United States Patent DEWATERING PULP R STOCK ON A PAPER 0R BOARDMAKIN G MACHINE Reginald James Thomas, Weston-Super-Mare, England, and Stanley Fred Smith, Pitfodels, Aberdeen, Scotland, assignors to St. Annes Board Mill Company Limited, Brislington, Bristol, England, a British company Application August 10, 1953, Serial No. 373,382

Claims priority, application Great Britain August 22, 1952 22 Claims. (Cl. 92-39) This invention relates to an improved method and apparatus for dewatering pulp or stock fed to the travelling band of a Fourdrinier type paper or board making machine.

This invention is applicable to either the single or multiply kind of Fourdrinier machine, i. e. either to the well known single-ply machine, or the lesser known multi-ply machine comprising a plurality of pulp boxes arranged above the forming band and spaced lengthwise thereof whereby separate layers of pulp may be delivered to the band in turn to form a multi-ply sheet.

The expression dewatering as used in this specification means the initial dewatering (usually carried out by natural drainage and by suction boxes arranged beneath the travelling forming band of a Fourdrinier type machine) that reduces the Water content of the pulp to, say, 96% so as to form the stock, and so provides a substantially continuous web or sheet.

In the known machines, unformed pulp or stock as delivered to the travelling forming band usually consists of /2 to 1 /2 of largely cellulosic vegetable fibre, with or without other materials, and 99 /2 to 98% of water and in this condition is fluid so that it flows freely on to and across the band. In the process of manufacture into paper or board, the pulp is initially dewatered to a content of, say, 4% solids. This is eifected chiefly by natural drainage, but in addition the band may be passed across a suction box or boxes to draw water through the band. At about this concentration the fibres interlock and assume a structural relationship to one another that thereafter remains susbtantially unaltered and the pulp is then said to be formed.

Further water can then, as the web is relatively strong, be removed from the formed pulp by various known methods, e. g. by additional suction boxes, a couch roll and wet presses, and it is finally dried by passing it as a continuous coherent sheet or web around drying cylinders.

The chief object of the present invention is to provide an improved method and apparatus for dewatering a layer of pulp fed to the travelling forming band of a Fourdrinier type paper or board making machine.

A further object of the present invention is to provide a Fourdrinier type paper or board making machine that may be run at higher speeds than was heretofore found practicable.

Another object is to provide a Fourdrinier type paper or board making machine in which a layer of pulp may be dewatered on a comparatively short travelling forming wire, whereby the total length of the machine may be cut down considerably or, with a normal length machine, several layers of pulp may be dewatered to provide a mu1tiply board or sheet.

A still further object is to provide improved method and apparatus for dewatering a layer of pulp fed to the travelling forming band of a Fourdrinier type paper or board making machine whereby clots and lumps that sometimes occur in the layer of pulp are substantially evened out so as to provide a well formed sheet.

2,821,120 Patented Jan. 28, 1958 ice The present invention consists in a method of dewatering a layer of pulp fed to the travelling forming band of a Fourdrinier type paper or board making machine of the single-ply kind, comprising the steps of supporting the upper stretch of the travelling forming band or part thereof, squeezing the layer between an upper pressing mechanism and the supported band, or part thereof, so as to express water therefrom, and removing the water so expressed, whereby the layer of pulp is formed and so provides a substantially continuous web or sheet.

Preferably the squeezing pressure exerted by the upper pressing mechanism is progressively increased as the band travels beneath it whereby, as the layer starts to form and the fibres commence to interlock, greater pressure is exerted on said layer to increase the dewatering operation.

The present invention also consists in a method of dewatering each layer of pulp fed to the travelling forming band of a Fourdrinier type paper or board making machine of the multi-ply type, comprising the steps of supporting the upper stretch of the travelling forming band, or part thereof, squeezing each layer between an upper pressing mechanism and a supported part of the band so as to express Water therefrom and so form the layer, and removing the water so expressed, whereby the formed layers of pulp consolidate to provide a substantially unitary web or sheet.

Preferably the squeezing pressure exerted by each upper pressing mechanism increases as the band travels beneath it so that, as each layer starts to form and the fibres commence to interlock, greater pressure is exerted on each said layer to increase the dewatering operation.

The present invention further consists in apparatus for dewatering a layer of pulp fed to the travelling forming band of a Fourdrinier type paper or board making machine, of whicha part, at least, of its band is supported, said dewatering apparatus comprising pressing mechanism arranged above the supported part of the band for squeezing the layer of pulp against the supported part after it is fed to the band and so express water therefrom, and means for removing some of the water so expressed, whereby said layer of pulp is formed into a substantially continuous web or sheet.

The present invention also consists in a Fourdrinier type paper or board making machine having a part, at least, of its travelling forming band supported, in combination with apparatus for dewatcring a layer of pulp fed to said band, said apparatus comprising pressing mechanism arranged above the supported part of the band for squeezing the layer of pulp against the supported part after it is fed to the band and so express water therefrom, and means for removing some of the water so expressed, whereby said layer of pulp is formed into a substantially continuous web or sheet.

The present invention further consists in a Fourdrinier type paper or board making machine adapted to make a multi-ply board or sheet and having a part, at least, of its travelling forming band supported, in combination with apparatus for dewatering each layer of pulp fed to said band, each said apparatus comprising pressing mechanism arranged above the supported part of the band for squeezing the layer of pulp concerned against the supported part after it is fed to the band and so express water therefrom, and means for removing some of the water so expressed, whereby each layer is formed and the formed layers of pulp consolidate to make a substantially unitary multi-ply web or sheet.

The present invention also consists in the features hereinafter described and claimed.

Single and multi-ply Fourdrinier type paper or board making machines that include devices for facilitating the removal of water from the upper surface of the travelling bands are diagrammatically indicated in the accompanying drawings, in which:

Fig. 1 is a side elevation of a single-ply machine.

Fig.2 is a 'plan'corresponding to Fig. 1 but taken on the'lin'e2+-2 of thatfigure.

Fig. 3 is a plan of Fig. 1 but omitting the short wire cloth band.

Fig. 4 is'a side elevation of the first and last dewate'ring apparatusof a multi-ply machine.

Fig.5 is a perspective view ofa sloping chute for removing water from the upper surface of a layer of pulp. This figure also illustrates the operative position of the sloping chute as regards the short endless wire cloth band.

Fig. 6 is a section through a-suction slice for removing water from the uppersurface of a'layer of pulp.

Fig. 7 is a perspective view of a'suction'slice.

Fig. 8 'is an enlarged side' elevational view of the-roller 96 and fixed member 63 and associated parts.

Referring p'articularly to Figs. 1 to 3, the machine bed comprises a pair of longitudinal'girders 14, 15. Each girder is boltedto two supports 11, 12 and these in turn are bolted to the ground.

Stretching the Whole length 'of'the machine is a brick walled pit 113, the

Walls

114, 115 of which are arranged outside the supports 11, 12, whereby the sump collects any water draining from the 'main perforated endless travelling formingband '1 and other parts of the machine.

At 116, 117 concrete plinths are set into the line of the

walls

114, 115 and these plinths are thicker than the walls, so that the excess thicker parts of said plinths 116, 117,liein the lines of the

girders

14, 15 respectively.

To each 'of the plinths 116, 117 is secured a casting 16, 17 and these castingsprovide rotatable bearings for a suction press roll 9.

To the top of the castings 16, 17 are secured pairs of

legs

18, 19 and 20, 21, while towards the rear end of the girders '14, 15 are secured two more pairs of legs 22, 23 and "24, 25 and thesefour pairs of legs provide supports for two

longitudinal girders

26, 126.

Pliiminer blocks are bolted to the

girders

14, 15 in such positions that they provide rotatable bearings for a breast roll 2 and supporting

rolls

4, 5, 100, 6, 7 and 8.

Pi'votedtothe castings 16, 17 at 94, 95 are arms 90, 91 and these arms provide rotatable bearings for a rear end plain roller 40, the arrangement being such that weights may be suspended at 92, 93 so as to provide an adjustable pressure between said roller and the suction press roll 9.

In Fig. 1 the parts of the frame of themachine on one'side have been omitted so that a clear view of the rolls and rollers may be obtained. Thus the girder 15, wall 115 supports 11, 12' (at that side), casting 17,

legs

20, 21 and 24, 25 girder 126 have all been omitted, and other parts on the same side of the machine subsequently referred to have also been omitted.

To the

girders

26, 126 is secured a tray 27 that is connected by 'piping168 to the pulp supply. The

girders

26, 126 also carry channel shaped

brackets

29, 32 that constitute mountings for a pair of plummer blocks that provide'rotatable bearings for a tension roller 36. Each plurn'r'n'er block carries an angle piece to which is secured a doctor blade44 and a gutter 43, whereby any fibres that adhere to 'the surface of the tension roller 36 may be fetur'ned to'the'pulp supply. g

V Stays45,'46, 47 and 49, 51, 53 depend from the'girders 26'and 126 respectively and to these stays arepivotally connected arms 48, 50, 52. To the lower "end of each stay and to each of the arms is secured a slide (eQg. 162, 163, 164, 165, 166 'and 167 which are shown only in Fig. 1) and these slides "provide rotatable mountings for wheels 55, 57, 59 and 54, 56, 58. 'Ihe abovedescribed arrangement of stays and arms carrying slides and wheels constitutes frames for controlling the rotatable mounting of permeable rollers, e. g. dandy ronersso, 6 i s 1.

extractor roller 62 and for locating them above their respective rolls 6, 7 and 8.

The said dandy rollers include, at their ends, rims of smaller diameter than the roller proper, and said rims are engaged by the wheels above referred to so that, when a short endless wire cloth band 69 (to be subsequently described) is in motion, said rollers rotate idly in the controllingframes and the'y'are biassed downwardly by the weight of the arms.

If desired weights may 'be hungfromthe arms, e. g. 48, to increase the pressure of the rollers-on the 'wire69.

A main endless travelling forming band 1 is mounted so that its upper stretch 3 extends from the breast roll 2 to the suction press roll 9 and is supported by the rolls 4 to 8 and 100, while its lower stretch-returns tothe breast roll 2 via tension rolls 10, 89 that are rotatably mounted in brackets securedto the walls114, 115. It will be seen that the

rolls

4, 5, 100, 6 and 7 constitute a-support-for at least a part of the upper stretch 3 of the forming band 1, i. e. from the position to the position 107,'and'this part corresponds to the operative position of the pressing mechanism, generally indicated by 111, as will hereinafter be more fully described.

The longitudinal girders 26, 126' carry plummer blocks 28, 30 and 31, 33, that provide rotary bearings for-

guide rollers

34 and 35

Blocks

37, 38 are mountedon the

legs

22, 23 and 24, respectively and these provide bearings for a forward end plain guide roller 39. The

rollers

34, 35, 40,39 constitute guides that act to carry a permeable member that comprises the short endless wire cloth band 69, whose action will hereinafter be'more fully described. I

A further guide for the short endless wire cloth band comprises apermeable roller, i. e dandy roller 96.

This dandy roller 96 (seeFig. 8) is mounted so as to rotate idly on a pair of

wheels

97, 98 at each end. These wheels are rotatably mounted ona pair of-arms 118,119 that are pivotally secured'to brackets 120, thelatter being mounted on legs 121 extending upwardly from the girders14, 15 (in the drawingsFig. 1--only the-bracket 1 20'securedto thegirder 14 is shown, i. e. they are not shown in Figs. 2 m3). By this arrangement the

arms

118, 119 may be adjustedto vary the portion of the weight of the roller 96 that is applied to the band 70, as is hereinafter more fully described with reference to Fig. 8. If desired, a biasing arm and roller 182 may be arranged above the roller 96.

The side frames 14,-15 also have secured thereto suit able brackets (not shown) for carrying a fixed member in the form of-a sloping chute 63 that constitutes a rigid guide for the band 69. This guide is arranged in front of'the-roller 96. Similar brackets are also provided to carry

suction members

64, 65,66, 67 arranged after the

rollers

96, 60, '61 and 62 that act to remove water expressedfrom the-upper surface-ofa layer ofpulp through the upper'wir'e'69 as it is fed alongby-the main travelling band. As the rollers 60, 61'and 62coact respectively with rollers 6, '7 and8 they function as squeeze rollers'to squeeze the paper web formed between the traveling co acting wires 1 and 69. The chute 63 actsto guide the band 69 "downon to the main band 1 as willhereinafter-be more fully described, and'also to remove water expressed from the pulp layer. Due to the action of the-chute 63 on the upper wire -6 9,'the wires 1' and '69 define therebetween an up-wireof the chute a converging gap of wedgeshape or diminishing height which receives the stock. The operation of the slopingc'htite and suction me'mbers will be more fully described later but their construction is illustratedin Figs. 5, 6, 7and 8.

Referring to Figs. 5 and 8-the sloping-chute 63-00mprises a channel trough or. gutter 68 extending acrossthe uppersurface of the lower'run 7 0 of the short endless wire clothiband' 69'for draining" the white water. To the rear'side 73 of the gutter 68 is"secured'acurved shield 74, and'this carries 'a pair of anglefbrackets 75, 7610 which is secured a cross plate 77. The plate 77 in 'turn carries a slice 78, also known as a doctor or scraper. To the underneath of the plate 77 is secured an angle strip 171 and this provides a bearing for the tips of thumb screws 172, 173 as will hereinafter be described.

To the

long arms

174, 175 of the

angle brackets

75, 76 are brazed curved hinge strips 176, 177 and these strips provide a hinged mounting for the whole of the fixed member (sloping chute 63) in the following manner.

To the

girders

14, 15 are bolted

bent supports

169, 170 respectively, said supports being of angle cross-section, and the supports are drilled and threaded to receive the thumb screws 172, 173 hereinbefore referred to.

The supports are also drilled and threaded to receive

hinge pins

178, 179 adapted to provide, in conjunction with the strips 176, 177, the hinged mounting for the fixed member 63. Loosening of the screws acts to bring the slice clear of the bands due to the resiliency of the latter.

Fig. 8 also shows the adjustment for the

arms

118, 119 to vary the portion of the weight of the roller 96 to be applied to the band 70. Thus a flange 180 on each arm is threaded to receive a thumb screw 181 whose tip bears against the upper end of the legs 121, so that by screwing down the thumb screws 181 the

arms

118, 119 will be lifted and vice versa.

It will be noticed that hinging mechanism for the fixed member 63 is omitted from Fig. 8.

Referring to Figs. 6 and 7, each suction member comprises a block ended tube 80 carried in brackets (not shown) supported on the side frames 14, 15, the open end of the tube communicating through a passage 81 with a source of suction and a drain. To the outside of the tube 80 is secured a shield 83 that at its upper end covers a slot 84 provided in the tube. The lower end of the shield 83 is curved at 85.

To the lower edge of the slot 84 is secured a bracket 86 that provides a mounting for a slice 87 adapted to rest on the band 70, the arrangement being such that when the slice rests on the band the curved end 85 just clears said band so as to provide a mouth 88 for the entry of water.

As hereinbefore described, the rear end bare roller 40 is biassed so as to press firmly on the suction press roll 9, and it will be appreciated that .the

dandy rollers

60, 61 and extractor roller 62 rotate idly on the lower run and cannot yield upwardly appreciably, being located in position above their respective supporting rolls 6, 7 and 8 by the small wheels running in the controlling frames hereinbefore referred to.

Referring again to the separate endless wire cloth band 69, this is arranged around the

guide rollers

34, 35, 40, 96, the rigid guide 63 and guide roller 39 so that, as will be seen in Fig. 1, it runs in an approximately rectangular path with its lower run 70 substantially parallel to the upper stretch 3 of the main forming band 1.

The plain roller 39, however, is secured so that it rotates a short distance above said stretch 3, and the rigid guide 63 is adjusted by screwing the thumb screws 172, 173 so that its free edge 79 presses firmly and evenly on the lower stretch 70 and guides said stretch 70 firmly down on to the upper stretch 3 of the main band 1 where said stretch 3 is supported by the

rolls

4 and 5. Thus the band 69 passes across the free edge 79 of the guide 63 and this acts to deflect the lower stretch 70 so as in eifect to divide the lower run 70 of the wire band 69 into two sections, one, the section 101, being at a slight angle, say, 4 to the upper stretch 3, and the other section 102 being substantially parallel to said stretch 3, and it is under this section 102 as far as the position 107 that the pressing mechanism squeezes the supported part (from position 110 to 107) of the main forming band. The section 101, as shown, coacts with the stretch 3 to define a converging gap between the wires with an entrance mouth at the divergent end thereof under the 6 guide roll 39 and a nip at the convergent end thereof under the slice or doctor 78.

A pulp box 103 is secured to a fixed part of the machine and this is connected to the pulp supply by the pipe 104.

-In operation the main forming band 1 is set in motion in the direction of the arrow B (Fig. 1), e. g. through the drive pulley 99. The rollers on which the short wire :cloth band 69 runs are freely rotatable and said band 69 is driven frictionally by the wire 1. Thus it is also set in motion so that its lower run 70 travels in the same direction and at the same speed as the upper stretch 3 of the main forming wire. The pulp supply is then put into operation and a stream of pulp issues from the box so that it flows as an open top layer across the upper stretch 3 of the forming band 1, where it is dewatered to form a web or sheet in the following manner.

The open top layer of pulp is first carried on the upper stretch 3 of the bottom wire 69 and beneath the section 101 of the lower run 70 of the top wire. The open top of the layer to fit beneath the section 101, of course, has a level lower than the entrance mouth of the converging gap between the section 101 and the stretch 3 of the bottom wire. The layer thus is thinner than the mouth of the gap. The wires converge to the nip provided by the slice or doctor 78 of the rigid guide 63. The layer is partly dewatered with some water falling by gravity to the pit 113 through the stretch 3 of the bottom wire and with some water passing through the permeable wire 69 and, due to its momentum, flowing up the slice or doctor 78 into the gutter 68. The shield 74 prevents spillage and the water in the gutter 68 is returned through the

pipes

71, 72 to the pulp supply. The partly dewatered material then passes into the section 102 and is squeezed by the pressing mechanism 111 and the supported part of the band 1 to remove more water from the fibers.

It will be noted from the drawings that the nip at the pressure point created by the slice or doctor 78 extends across both the top and bottom wires along a line that is between the supporting

rolls

4 and 5 for the stretch 3 of the bottom wire. The ni-p is thus at an unsupported span of the bottom wire and is therefore soft or yielding.

In other words, dilute stock or pulp from the box 103 is deposited onto the upper horizontal run of the traveling perforated band or wire 1 to define an open top layer or pond of stock or pulp which is subjected to the movement of the wire. This Wire movement imparts momentum to the open top layer of stock and advances it to the inlet or entrance mouth of the converging or wedgeshaped gap defined by the converging upper and lower wires. The upper surface of the stock layer or pond is then contacted by the upper wire. As the stock is advanced through this gap, hydrostatic pressure is generated in the stock which peaks at a pressure point effected by the slice ahead of or upwire from the slide. This bydrostatic pressure is dissipated by flinging water through the upper wire 69 with sufiicient force to throw it up the slice 78 to the collecting gutter 68. From the rigid guide 63 to the end of the section 102 the layer is constantly subjected to the squeezing action between the two bands 1 and 69. Thus when the layer reaches the intermediate dandy roller 96, as considerable pressure is exerted by said roller, a considerable quantity of water is expressed from the layer both upwardly through'the permeable wire 69 and downwardly through the perforated travelling forming band 1, and the former is then removed by being drawn into the suction slice 64 and returned to the pulp supply, while the latter is removed via sump 113 and suitable drain pipes and is also returned to the pulp supply.

At this stage fibres in the stock are interlocked and hence the layer is stronger and will withstand greater pressure.

Thus the pulp layer passes between-the second dandy ro'llerdl) and 'its supportingroll 6 and these-being more heavily weighted, exert .greaterjpressiire thanthe dandy roller96 and 's'o' fu'rtherwater is squeezed out of the layer, some being "expressed upwardly to be drawn away by the suction slice 65 and some passing to the sump to be returnedto the pulp supply.

This action is repeated by the third dandy roller 61 which'is still more heavily weighted and its support roll 7 in c'ohjun'cti'on'with suction slice 66. It will be "appre'cia'ted that by further biassing'the controllingframes to'i'ncrease'the pressure on the rollers, the pressure on the layer of pulp "may be progressively increased as it passes beneath said -'run so that quite a short length of band is necessary'on' which to form the pulp.

At "this stage, i. e. the position 107, the solid content ofthe'stock'is'say, 4%,i. e. the layer of pulp is formed and so provides a substantially continuous web or sheet. v lt'will 'be appreciated that the short wire cloth band 69 and its (to-operating parts including particularly the rigid guide 63, intermediate dandy roller 96 and

second and'third'dandy rollers

60, 61, comprises pressing mechanism, arrangedahove'the'main forming band 1, for squeezing 'a layer of pulp against a part of the upper stretch 3"o'f said band 1 that is supported by the

rolls

4,5, 100, 6"and 7,'and that the waterso expressed is removed downwardlyto the'pit'and upwardly bythe sloping chute 63 andsuction'slices64, 65, 66"so as to form the pulp and provide 'a substantially continuous web or sheet. If desired, a sloping chute similar to 63 may replace one or more of the suction members.

The web then. passes between wire cloth covered rollers 62, 8 with suction slice 67, a'nd'the rear plain roller 40 with suctionpress roll 9. The last stages, i. e. from the position 197, do not, however, form'part of the present invention as it is usual practice to pass a formed web or sheet in between such rollers to remove water. It has been found convenient, however, to combine these known rollers in the same short wire band that constitutes the pressing-mechanism of the-present invention.

108 indicates the completed web passing to the usual main presserfollowedby the heated drying cylinders, but as these are known and form no part of the present invention they are not indicated in the drawings.

In the machine as described above, the mounting of the intermediate dandy roller 96 so that it rests on the lower run 70 running on the small wheels. 97, 98 at each end acts to press the said run yieldably against the pulp to be squeezed, and'the squeezing pressure exerted by the second and third

dandy rollers

60, 61 can be progressivelyincreased, e. g. by adding weights to the arms 48, 50.

In the modification, however, the rollers-6t), 61 may be mounted so that they rotate on small pairs of wheels at each end, in known manner.

It will also be observed that in the machine as described, the-main band lbeneath the rigid guide 63 and the intermediate dandy roller '96, being supported by the spaced rolls '4, and 100, may yield at the spaces underthe pressure caused by the adjustment of the guide; 63 and the weightof said dandy roller 96.

If desired a dandy roller may be usedin place ofthe rigidIg'uide 63 to guide the band 69'down on to the band L'i. c. to divide the lower streach 3 into two

sections

101, 102.

Instead-of arranging a'ri'gidguide, as shown in "Fig. 5, thismay be resiliently mounted. Thus the angle brackets 75, -76may be hingedly connected to the shield 74 and-be biasedby a'spring'in the counterclockwise direction as seen in that'figure.

A rigid or resiliently mounted guide (e. g. as shown in Fig.5 or as described in the last paragraph) may replace other of theguide rollers in a similarmanner.

Fig. 4 shows a multi-ply Fourdrinierpaper or board making machine. The drawing depicts thefirst and last sections of a multi-ply machine, each section including 'a pulpbo'x, 'dewateriirgappara'tusto form the layer of pulp,

and additional rollers and rolls for further 'd'rying'of the layer of pulp concerned. A common m'ain "travelling forming'ban'd runs throughout the'length of the r'nachi'ne,

The drawing'is shown broken at 161 to indicatethat further sections may be incorporated to provide e. g. a three, four or more-ply machine, such sections, of course, being duplicates of the'first and last sections.

A description of the apparatus, shown in Fig. 4, is unnecessary asthe details of pulp supply and dewatering are almost the same as shown in Figs. 1 to 3 and 5 to 7.

The same numerals have been utilised in Fig. 4 as are used-in the other figures except the pulp boxes have been numbered 103, 203 and the pressing mechanisms 'have been numbered 111, 211, this being to avoidconfusion when describing 'how the apparatus works.

The only difierence in-the drawing is the provision of table rolls 109 to support the upper stretch 3 of the main travelling forming band 1 between the sections.

The apparatus shown in Fig. 4 works in thefollowing manner. Ea'chof the pulp boxes 103,203 etc. is'supplied witha-head of pulp, the main travelling forming band 1 is'set in motion and'this, through friction, drives each of the

pressing mechanisms

111, 211 Main such a direction that their lower runs travel in the-same direction as the main band 1.

A layer of pulp then starts to flow onto and across the upper stretch '3 of the main band 1 from each box 1 03, 203.

Considering the operation from the box-103 onwards, the layer from this box passes below the lower run 70 of the pressing mechanism 111 beneath the rigidguide 63 into the section 102. There the Iayer-iss'queeZed between thepa'rt'o'f the band-3 that'issupported by the

rolls

4, 5, 100, 6 and 7 and the upper pressing mechanism. Water iS-SClllfiCZCd' out bothupwardly-and downwardly. The latter passes to the pit 113 while the former passes up the guide 63 and is also "drawn up in the suction slices 64 to 66. At the position 107 the pulp is formed.

Thereafter further water is removed by the extractor roller 62 and the rear end plain roller 40.

At this stage the layer ofp'ulp'is dewatered and further dried to a water content of'less than, say, 96%. Such dewatered and further dried'layer is hereinafter referred to as a partly dried layer, but it must 'notbe confused with a layer that has been dried in the known'man'ner by heated drying cylinders and other processes.

In this partly dried condition it will readily combine with another layer of pulp although thefibres'of a partly.

dried layer haveinterlocked' and their structural relation ship will remain substantially unaltered.

Thus said partly dried layer then continues on the band 3 acrossthe table'rolls 109 until it passes beneath the delivery orifice of the pulp box 203 where'afurther layer of pulp fiows on to and across said partly dried layer.

The double layer then passes beneath the pressing mechanism 211'Where the upper layer is dewater'ed inthe same w'ayas above described with regard to, what is now, the lower layer,b'ut-instead of 'bei'ngsqueezed directly between the pressing-mechanism"and the main-wire, a partly dried layer-lies beneath it. As a consequence, "of course, a larger proportion of the Water-in the'upper layer will be expressed upwardly, though some will s'tilljpass downwardlyto the'pit 113. It :will readily be appreciated that'this squeezing action helps to combine the twolayers together, as well as dewatering the upper-layer.

The upper layer thus becomes a partly dried layer in a similar manner to the lower layer.

It will'thus be seen that each layer of pulp is formed, and the'formed layers of pulp consolidate'to make a substantially multiply web or sheet.

Atutther layer "or layers maybe added in a similar manner.

A "machine has been constructed whicla works quite satisfactorily with four layers of pulp and it is thought that any reasonable number of plies may be combined because, due to expressing the water and removing almost all of it upwardly to form the layer, the difiiculty of drawing water through an already formed layer or layers is avoided.

It will be appreciated that, due to including the extractor roller 62 and plain rear roller 40 in the same short wire band 69 as the pressing rollers of the present invention, an unformed layer is combined with a formed layer that has also been partly dried. This is only so, because it has been found advantageous to apply the further layer of pulp to a partly dried layer.

In a modified machine for making a multi-ply board or sheet, the first layer or first two layers may be dewatered in the usual manner.

Thus the first layer is first applied to the main band 3 and is dewatered by natural drainage and suction boxes, in the known manner, then the second layer is applied on to the formed first layer and this second layer is dewatered by natural drainage and by suction boxes acting to draw water through the first layer. The twoply web then passes to the apparatus shown in Figs. 1 to 3 and 5 to 8 or Figs. 4 to 8 according to whether only one, or more than one, additional layer is to be added.

In any of the machines hereinbefore described, with reference to Figs. 1 to 8, a suction box or boxes may be provided in addition to the pressing mechanism to assist in forming a sheet, but these are not essential and are not shown in the drawings.

In the forms of the invention described with reference to the drawings it is stated that at the position 107 the layer of pulp is formed, that is its constitution approximates to 4% solids and 96% water. It is to be understood, however, that this position 107 is chosen as an example of a machine that has been constructed and is working satisfactorily. That is to say, with the pulp utilised, it was found that the pressure exerted by a rigid guide and three dandy rollers in series resulted in a formed layer. It must be borne in mind, however, that many factors enter into the problem, e. g. the pressure of the rigid guide, the weight of the dandy rollers, the rigidity of the supports, and thus it is to be understood that the essence of the invention resides in applying a squeezing pressure to unformed pump to dewater it to a solid content in the neighbourhood of 4% solids, and that the construction shown is merely an experimental example that has been found satisfactory.

In practice, after the machine has been started up, adjustment is made to the pressure exerted by the rigid guide and the various rollers, the former by adjusting the thumb screws 172, 173 and the latter by adding weights where convenient, or, in the case of the roller 96, by adjusting the

arm

118, 119 by means of thumb screws 181. For example the thumb screws 172, 173 are screwed down tightly, the thumb screw 181 is turned to allow the arm 118 to be lowered to allow the whole weight of roller 6 to run on the band, weights of x pounds are added to arms 48, x+y pounds to arms 50, and x+2y pounds to arms 52. By this means a progressive increasing pressure is exerted on the pulp layer as it passes beneath the pressing mechanism and the fibres in the stock commence to interlock to form the pulp.

It will be appreciated that by effecting the initial dewatering of the layer of pulp upwardly and downwardly simultaneously (which in the case of a single layer in effect forms the layer partly by the underside of the short wire band and partly by the upper surface of the main travelling band, while in the case of a multilayer it is formed partly through the layer or layers below, so in efifect forms on the layer immediately below) and carrying out such dewatering under a squeezing action, considerably less time is required than when it is done by the heretofore known methods.

This time factor can be utilised in difierent ways. Assuming it is applied to a normal single-ply Fourdrinier machine on easily dewaterable pulp, then that machine may, in accordance with this invention, be run satisfactorily at a greatly increased speed with the same length forming wire, that is to say, it may be run at a higher speed than was heretofore found practicable.

Alternatively, as the pulp needs to be subjected to the dewatering operation for a considerably reduced length of time, the machine may be run at the same speed, but a shorter forming wire may be employed, i. e. the total length of a single-ply machine may be cut down considerably, or a multi-ply machine may be constructed that is not inconveniently long.

The invention is particularly advantageous when dewatering wet beaten stock, i. e. stock that does not readily part with its water, for such papers as greaseproof, imitation parchment, or draughtsmans tracing paper.

The invention has also been found advantageous when dewatering long stock which, on the known single-ply types of Fourdrinier machine, tends to form in clots or lumps. The squeezing action of the upper short wire, in accordance with the present invention, evens out the clots or lumps so as to provide a well formed sheet. I

We claim:

1. The method of making a web which comprises introducing an open top layer of dilute aqueous stock between a top forming wire and a web on a bottom forming wire, advancing the forming wires, the web and the stock therebetween, discharging water from said stock through the top forming wire to form a web on the underface of said top forming wire, and pressing the two wires toward each other to squeeze the web on said underface into interlocked unitary relation with the web on the bottom forming wire.

2. The method of making a fibrous web which comprises depositing an open top layer of dilute web forming stock on the upper run of a' looped forming wire, contacting the open top layer of stock on said upper run with the bottom run of a top forming wire, advancing said upper run and said bottom run in the same direction at the same speed, thereby imparting momentum to the stock and generating a hydraulic head of stock between the wires from the point of initial contact of the top wire with the stock to a point downstream therefrom, applying mechanical pressure to the stock between the wires at said downstream point, discharging water from the stock through both wires to form the stock thereon, and separating water discharged through the top Wire from contact with said wire under the influence of momentum developed in the water by the advancing stock.

3. The method of making a fibrous web which comprises advancing opposed forming surfaces in the same direction along converging paths to form therebetwecn a gap of diminishing height, introducing a layer of stock into said gap, maintaining the thickness of said layer less than the width of the entrance mouth of said gap, moving the stock with the surfaces through the gap, applying mechanical pressure to the stock between the surfaces at the convergent end of said gap, removing water from the stock through one of said surfaces under the influence of momentum built up in the water by the traveling stock in the gap, and forming the stock on said opposed forming surfaces into a unitary web.

4. The method of dewatering stock to form a sheet which comprises depositing an open top layer of fibrous stock on a traveling forming wire, contacting the open top of the stock layer on the wire with a traveling top wire before the stock forms into a sheet, draining water from the stock through the forming wire, doctoring the top wire toward tbe'forming wire to squeeze the-stock between the wires, flinging water from thetop of the top wire over the doctor under the influence ofkinetic energy'imp'arted to the waterby the advancing wires, and forming the stock on the opposed wires into a unitary sheet.

5. The method of making a multilayer sheet which comprises depositing'open top layers of dilute aqueous stock on the top run of a traveling bottom wire at a plurality of longitudinally spaced zones along the length thereof, contacting each open top'layer of stock with a traveling top wire defining gaps having entrance mouths wider than the thickness of the stock layers, progressively diminishing'the gap between the top and bottom wires to squeeze the stock between the wires, separating 'water from thestock through'the top wires to form webs on the underfaces of said wires, effecting said water separation with the momentum of the traveling wires and stock, and pressing all of the webs together in interlocked rela# tion.

6. A paper'making machine which comprises an elongated looped main forming wire having a top active run, a looped top forming wire having an active bottom run overlying the top run of the main wire, a guide roller in the loop of the top wire spaced above the active top run of the bottom wire to direct the top wire in spaced relation over the bottom Wire, a scraper in the loop of the top wire acting thereon downstream from said guide roller'to provide an inclined bottom run on the top wire converging toward the top run of thebottom wire, a stock inlet for introducing stock into the gap between the top run of the bottom wire and the converging run of the top wire to create a hydraulic head of stock in said gap, said scraper applying mechanical pressure to the stock between the wires at the converging end of said gap, means for driving said wires to advance the top run of the bottom wire and the bottom run of the top wire in the same direction at a'speed sufficient to impart momentum to the white water in the stock for carrying said white water over the scraper and above the bottom run-of the top wire, a drain trough in the loop of said top wire coacting with said scraper to receive white Water therefrom, squeeze roll assemblies having rolls in the loops of the respective wires downstream from said scraper to squeeze the paper stock between the wires, and suction slices coacting with said squeeze roll assemblies in the loop of the top wire to remove the white water squeezed from the web by said assemblies.

7.-A dewatering apparatus for forming fibrous webs which comprises a main forming wire having an active upper run, a plurality of stock inlets at longitudinally spaced intervals along the length of said upper run to supply stock thereto, a top wire for each inlet having an active bottom run starting adjacent each inlet and converging with the main forming wire downstream from theinlet to provide stock forming gaps of progressively decreasing height, means for driving all of said wires so that their active runs travel in the same direction, doctors within the loops of each top wire pressing the active runs thereof against the stock between the'wires to squeeze the stock, said doctors having inclined top surfaces disposed at an angle relative to the bottom runs of the top wires adapted for receiving a flow of white water thereover under the influence of momentum built up in the stock by the advancing wires, and a white water drain means associated with each doctor to receive said water and prevent re-wetting of the stock.

3. A multi-layer Web forming machine which comprises ,a main forming wire having an active upper run, a main stock inlet at one end of said wire, a secondary stock inlet downstream from said main inlet, said inlets feeding aqueous stock over the upper run of the main forming wire,-a separate top wire adjacent 'ea'ch inlet'having an active bottom run, doctor m'ea'ns in the loop of each top wire pressing the wire against stock between 12 the wires, a'directing roll cooperating with said doctor means to :provide an inclined run of the active bottom face of each top wire for cooperating with the main forming wire to form a gap of decreasing height receiving stock from the adjacent inlet, means for driving each of the wires so that their active runs travel in the same direction at speeds sufiiciently to impart appreciable momentum to the water in the stock in advance of the doctor means, said doctor means having inclined top surfaces adapted to receive water thereover for directing the water away from the stock, and drain means in the loop of each top wire associated with the doctor means to receive the water from the doctor means.

9. A web making machine which comprises a looped bottom forming wire having an active upper run whereon to form a web, a looped top'forming wire having an active under run overlying said upper run and coacting'therewith to define a stock receiving gap, means for feeding a layer of aqueous stock into the leading end of said gap having less thickness than the width of said leading end, means for driving said wires to advance the stock along said gap while dewatering the stock upwardly through the under run of the top wire to deposit alayer of fibers on the underface of said under run, water removingmeans in the loop of the top wire receiving the water from the under run of the topwire, and means for pressing said layer of fibers on the underface of the under run against the web on the upper run of the bottom forming wire to interlock the layer and web.

10. A paper making machine comprising a bottom looped forming wire having an active upper run whereon to form a layer of stock, atop looped forming wire having an active under run overlying said upper run, means for fiowing'an open top layer of aqueous stock between said runs, means for driving said wires to advance said runs in the same direction, means locally depressing said under run downstream from the point of introduction of paper stock to press the stock and cooperate with the drive means for discharging water upwardly through the under run for forming a'layer of'stock on the underface of said under run, means for removing water from the top-face of 'the under run, and means for pressing theformed layer on the underside of said under run against the formedlayer'on the upper run to unite the layers in interlocked relation.

11. In a paper making apparatus having a top wire, the improvement ofa trough in the loop of said top wire spanning the bottom run thereof, a flat scraper tiltably mounted adjacent said trough having an active bottom edge engaging the upper face of said bottom run of the wire and an upper edge discharging into said trough, and means for adjusting said scraper to vary the degree of inclination thereof;

12. The method of making a web from a stock composed generally of water and fibers which comprises delivering stock to an upper horizontal run of a main forming'wire to form 'an open top layer of stock, advancing thewire to impart momentum to the stock, advancing the stock layer beneath a lower run of an upper forming wire, advancing 'the upper wire gradually into coaction with the top of the stock layer and the main wire to develop a'hydrostatic pressure in the stock, separating water from the stock through the main wire with the aid of gravity to form a fibrous layer of stock thereon, forming a fibrous layer on the stock engaging face of said upper wire, and urging the wires together to press the fibrous layers into interlocked relation and form a unitary web. I

13. The method of making a web from a stock composed generally of water and fibers which comprises delivering stock to an'upper horizontal run of a main forming wire to form an open top layer of stock, advancing'the wireto momentum to the stock, advancing the stock layer beneath a lower run of an upper forming wire, advancing the'upperwir'e gradually into coaction with the top of'the'stock layer and the main Wire to develop a 13 hydrostatic head, simultaneously separating water from the stock through the main and upper forming wires, simultaneously forming a fibrous layer on each of the stock-engaging faces of the wires, and urging the wires together to unite the fibrous layers into interlocked relation and form a unitary web.

14. The method of making a web from a stock composed generally of water and fibers which comprises delivering stock to an upper horizontal run of a main forming wire to form an open top layer of stock, advancing the wire to impart momentum to the stock, advancing the stock layer beneath a lower run of an upper forming wire, advancing the upper wire gradually into coaction with the top of the stock layer and the main wire to develop a hydrostatic head, simultaneously separating water from the stock through the main wire with the aid of gravity and through the upper wire with the aid of the momentum of the advancing stock, simultaneously forming a fibrous layer on each of the opposed stock-engaging faces of the wires, and gradually urging the wires together to unite the fibrous layers into interlocked relation and form a unitary web.

15. The method of making a web which comprises depositing an open top layer of aqueous stock on a previously formed fibrous web, covering the open top layer of stock with a top forming wire, advancing the web and wire to impart momentum to the stock, applying mechanical pressure to the top wire to squeeze the stock and web, generating hydrostatic pressure in the stock under said top wire which peaks adjacent the point of application of mechanical pressure, dissipating the hydrostatic pressure by flinging water from the stock upwardly through the top wire to form a layer of stock fibers on the under face of the top wire, and pressing said layer of stock fibers against said previously formed fibrous web to unite the layer with the web and form a unitary web.

16. The method of forming a fibrous web which comprises depositing an open top layer of dilute paper stock on the upper run of a substantially horizontal looped forming wire, advancing the stock on said wire while draining water from the stock through said upper run, covering the open top of the stock layer with the bottom run of a top wire which coacts with the upper run of the horizontal looped forming wire to provide a gap of pro gressively decreasing height having an entrance mouth wider than the thickness of the open top layer of stock on said upper run of the horizontal looped forming wire, advancing said top wire with the stock, applying mechanical pressure to the stock at the narrow end of said gap, generating hydraulic pressure in said stock between said wires in advance of said point of application of mechanical pressure, dissipating said hydraulic pressure by flinging water from the stock through said top wire, and removing said water from the top wire to thereby form a web on the top wire as well as on the bottom wire.

17. In the method of forming a paper web from aqueous stock between foraminous forming wires, the improvements which comprise feeding a layer of aqueous stock into the entrance mouth of a gap between two foraminous forming wires, maintaining said layer thinner than the width of said entrance mouth to provide a stock and air interface in said gap, removing water from the stock in said gap through both forming wires to form webs on each wire, and uniting said webs.

18. The method of making a paper web which comprises depositing an open top layer of dilute aqueous paper stock on a traveling lower forming wire, contacting the open top of the deposited stock layer with a top forming wire, advancing both forming wires in the same direction to impart momentum to the stock, draining Water from the stock through the lower forming wire, flinging water from the stock through the top forming wire, and directing said water away from said top wire under the influence of its own momentum thereby forming the stock on both forming wires.

19. The process of making a fibrous web from watery pulp on the traveling forming wire of a Fourdrinier type paper making machine which comprises advancing a layer of watery pulp on said forming wire, contacting the top of said layer with a top forming wire which cooperates with the Fourdrinier wire to provide a pulp receiving gap with an entrance mouth wider than the thickness of said layer of watery pulp, draining water from the pulp through the Fourdrinier wire, and removing a substantial portion of the water from said layer of watery pulp through said top forming wire thereby forming the pulp on both wires.

20. The method of making a web which comprises advancing a layer of dilute aqueous stock on the top run of a bottom forming wire, covering the layer of stock on said top run with the bottom run of an advancing top wire before said layer forms into a sheet, locally pressing said bottom run of the top wire against the top run of the bottom wire downstream from the point of covering the layer of paper stock on the top run of the bottom wire to provide a converging gap between the wires, maintaining the height of said layer on said top run less than the height of the entrance mouth of said gap, supporting the top run of the bottom wire in spaced relation from the locally pressed part of the bottom run of the top wire and forming a yielding nip between the wires, discharging water from said layer upwardly through the bottom run of the top wire and downwardly through the top run of the bottom wire ahead of said nip, and passing the dewatered layer through said nip.

21. In a paper making machine, a bottom looped wire having a top forming run, a top looped wire having a bottom forming run, a plurality of spaced supporting means in the loop of the bottom wire supporting the top run thereof, a scraper in the loop of the top wire locally depressing the bottom run of the top Wire against the top run of the bottom Wire along a line across the wires in a space between said supporting means to provide a nip between the wires accommodating passage of a layer of stock fibers on the wires through the nip without damaging the fibers, and means for driving said wires to build up suificient momentum in the stock between the wires in advance of the nip for flinging water from the stock through the top wire over said scraper and through the bottom wire for forming webs on both wires simultaneously.

22. A paper making machine which comprises a looped bottom forming wire having an active top run, a looped top forming Wire having an active bottom run, a roll in the loop of the top wire, a doctor in the loop of the top wire downstream from said roll and inclined upwardly and downstream from the bottom run of the top wire, said roll and doctor acting on the bottom run of the top Wire to direct the bottom run relative to the top run of the bottom wire for defining between the wires a gap having an entrance upstream from the doctor which is wider than at the doctor, a pulp box having an outlet for delivering a layer of stock into said gap which is thinner than the entrance width of said gap, means for driving said wires to advance the active runs thereof for carrying the stock through said gap while forming the stock on both wires, said doctor providing a waterway for water passed through the bottom run of the top wire, and a drain conduit in the loop of the top wire for receiving water from the doctor.

References Cited in the file of this patent UNITED STATES PATENTS 611,422 Savery Sept. 27, 1898 1,018,588 Scanlan Feb. 27, 1912 1,143,931 Babcock June 22, 1915 1,347,724 Wagner July 27, 1920 (Other references on following page) 15 1' mm ED'STATES'PATENTS Shaw Ju1y8,1924 "'Antoine Aug. 6, 1927 Bidwell Sept. 4, 1928 I-Iinde Jan. 15, 1929 Upson Apr. 2,1929 Barnes Apr. 7, 1931 Brooks etal. Mar. 1, 1932 Sheperd 'Dec. 20, 1932 Edge Sept. 19, 1933 Germanson Sept. 26, 1933 Becher Dec. 12, 1933 Frost 2 Mar. 19,1935 Richardson Feb. 11, 1936 Ellis' July 16, 1940 Nash Jam-20, 1942 Tuten 2." June 16, 1942 Wilson Dec. 21, 1943 Easterberg e681. Iune 17, 19:47 Worden Iljne 1 5, 1948 'Okawa N6v. 9, 1954 FOREIGN PATENTS Austria I111y10, 1923 Germany "(Oct- 9, 1916 Germahy "Apr. 24, 1920 Germany 'May' 1'2, 1939 Germany Mar. 18,1943 Gre'at'JBri'tain Feb. 27, 1930 GreatBfitain Aug. 10,1933 Sweden Jan. 9, "1936 OTHER REFERENCES and 36.