US3791920A

US3791920A - Suction box arrangement for papermaking machine having partition wall between the top and bottom

Info

Publication number: US3791920A
Application number: US00147401A
Authority: US
Inventors: H Nisser; E Schoffmann; J Wolf; W Schoen
Original assignee: JM Voith GmbH
Current assignee: JM Voith GmbH
Priority date: 1970-06-13
Filing date: 1971-05-27
Publication date: 1974-02-12
Anticipated expiration: 1991-02-12
Also published as: SE385030B; FI51385C; GB1340213A; DE2029212A1; FI51385B; FR2109616A5

Abstract

A partition wall located between the top and bottom walls of a suction box has one or more apertures therein which can be controlled as to size by mask elements which are disposed on the top of the partition wall. The mask elements can be slidably moved by rods which extend through the side walls of the suction box to adjust the positioning of the mask elements in a direction parallel to the plane of the partition wall. The mask elements may be, for example, rectangular or trapezoidal in shape, and may be mounted in flexible or swivelable fashion.

Description

United States Patent Nisser et al.

[451 Feb. 12, 1974 [75] Inventors: Henrik Nisser, Korsnas, Sweden;

Jakob Wolf, Heidenheim/Brenz, Germany; Werner A. Schoen, Ridley Park, Pa.; Ernst Albert Schoffmann, Heidenheim/Brenz, Germany [73] Assignee: J. M. Voith GmbI-ll,

Heidenheim/Brenz, Germany [22] Filed: May 27, 1971 211 App]. No.: 147,401

[30] Foreign Application Priority Data June 13, 1970 Germany 2029212 [52] [1.8. CI 162/363, 162/351, 162/364, 162/366 [51] Int. Cl. ..1D2lfl/52 [58] Field oi Searc h 162 /351, 374,348, 363, 3 69, 162/370, 367, 211, 364, 365, 353, 366, 364

[56] References Cited UNITED STATES PATENTS 3,539,448 11/1970 Lopas 162/364 VII 1,375,517 4/1921 Johnson 162/374 X 1,664,801 4/1928 Vedder 162/363 1,790,852 2/1931 Berry 162/366 FOREIGN PATENTS OR APPLICATIONS Primary Examiner-S. Leon Bashore Assistant qrei" r:13har til-@ 31! Attorney, Agent, or Firm Melvin A. Crosby [57] ABSTRACT A partition wall located between the top and bottom walls of a suction box has one or more apertures therein which can be controlled as to size by mask elements which are disposed on the top of the partition wall. The mask elements can be slidably moved by rods which extend through the side walls of the suction box to adjust the positioning of the mask elements in a direction parallel to the plane of the partition wall. The mask elements may be, for example, rectangular or trapezoidal in shape, and may be mounted in flexible or swivelable fashion.

9 Claims, 18 Drawing Figures PATENTEIJFEB 12 19M 3.791; 920

' SHEEI 1 (IF a INVENTOR5 HENRIK NISSER JRKOB WOLF WERNER A. scape ERNST ALBERT scuosmauu maw PATENTEDFEB 12 mm SHEET 2 BF 4 L L42 747 a INVENTORS HENRM NISSER JAKOB WOLFE .WERNER a SCHOEN.

ERNST RLBLRT SEHOFfMANN PATENTEDFEBIZ mm alizsmzo saw u or 4 Fig. /8 P X211 J m INVENTORE HLNRM NISSER JAKOB WOLFE WERNER A. SCHOEN ERNST ALBERT SCHOFFMANN SUCTION BOX ARRANGEMENT FOR PAPERMAKING MACHINE HAVING PARTITION WALL BETWEEN THE TOP AND BOTTOM The present invention relates to papermaking machines and is particularly concerned with arrangements for controlling the draining of water from the fibrous suspension from which the web is formed as the suspension is supplied to a foraminous member such as a Fourdrinier wire or a cylinder.

The present invention is particularly concerned with a papermaking machine having a closed head box wherein the upper wall inclines downwardly toward the machine wire at an acute angle and defines with the wire a formation zone while beneath the wire along the formation zone there are provided suction boxes to withdraw water from the suspension through the wire and thereby to cause a paper web to form on the wire. The channel along the formation zone, which is formed by the walls of the head box, is maintained filled throughout the full length thereof.

It is desirable in a papermaking machine constructed in the manner described above to produce a web in which the fibers making up the web are deposited uniformly across the width of the wire and, ordinarily, have completely random orientation. To accomplish this desirable end result, it is necessary to regulate the rate at which liquid is drawn from the suspension through the wire and at various lateral and longitudinal regions of the formation zone.

One way of regulating the rate at which water is withdrawn from various regions of the formation zone is to provide several suction units or suction boxes beneath the wire along the formation zone which are equipped individually, or in groups, with means for regulating the water removed thereby from the suspension. It is well known with suction units of this nature to control the value of the negative pressure developed in each suction unit, or in each group thereof, but this is not satisfactory for achieving the regulation of fiber deposition desired.

It is also known to regulate the water being withdrawn by each suction unit, or each group thereof, by regulating the water flow volumetrically as by means of a pump or regulating valve arrangement.

This last mentioned method more closely regulates the rate of water withdrawal, but still permits an irregular deposition of fibers on the machine wire and especially within the region of the individual suction units or boxes. This comes about because the suction boxes are relatively wide in a direction lateral to the direction of movement of the machine wire, and irregular distribution of the water velocity across the width of such a suction box can occur, leading to the aforementioned irregular distribution of fibers on the machine web.

The problem to be solved by the present invention is, thus, that of how to obtain a uniform velocity of the liquid withdrawn from the fibrous suspension across the entire area of each individual suction box.

With the foregoing in mind, a primary object of the present invention is the provision of an arrangement for making the velocity of the liquid drawn into each suction box of a papermaking machine of the nature referred to substantially constant over the entire area of the suction box.

Another object of the present invention is the provision of an arrangement for adjusting the velocity with which the liquid streams into a suction box in different portions of the suction box.

A still further object of the present invention is the .provision of a suction box arrangement for a papermaking machine of the nature referred to in which several boxes are distributed in the direction of movement of the machine wire in which the individual suction boxes complement each other and result in uniform deposition of fibers on the machine wire across the full width thereof.

Still another object of the invention is the provision of a suction box arrangement of the nature referred to in which the velocity at which liquid is drawn into the box can be finely adjusted in various lateral regions of the box thereby to provide for desired liquid withdrawing conditions across the entire width of the wire passing over the box.

The foregoing objects, as well as still other objects and advantages of the present invention, will become more apparent upon reference to the following detailed specification, taken in connection with the accompanying drawings, in which:

FIG. 1 is a section through a suction box constructed according to the present invention with the plane of the section parallel to the direction of a movement of the machine wire;

FIG. 2 is a sectional view like FIG. 1 showing a somewhat different arrangement;

FIG. 3 is a graph showing the manner in which the velocity of the liquid drawn into the box of FIG. 1 varies across the width of the box considered in the direction of wire movement;

FIG. 4 is a view like FIG. 3 but shows the distribution of liquid velocity across the section box of FIG. 2 considered in the direction of movement of the machine wire;

FIG. 5 is a section indicated by line V-V on FIG. 6 and shows a suction box arrangement with the machine wire running perpendicularly to the plane of the drawing;

FIG. 6 is a sectional view indicated by line VI-VI on FIG. 5 showing the subdivisions of the suction box;

FIG. 7 is a plan sectional view indicated by line VII- --VII on FIG. 5 showing control members in the suction box for regulating the rate of liquid flow into the box;

FIG. 8 is a sectional view indicated by line VIIIVIII on FIG. 9 showing a different arrangement for controlling the distribution of liquid flow into a box;

FIG. 9 is a sectional view indicated by line IXIX on FIG. 8;

FIG. 10 is a sectional view indicated by line X-X on FIG. 11 which shows an arrangement somewhat similar to that of FIG. 8 but including an additional flow control member;

FIG. 11 is a sectional view indicated by line XI-XI on FIG. 10;

FIG. 12 is a fragmentary view similar to FIGS. 8 and 10 but drawn at enlarged scale showing a still further modification;

FIG. 13 is a sectional view indicated by line XIIIX- III on FIG. 14 and showing a modified arrangement in which the flow controlling member is in the form of a belt;

FIG. 14 is a vertical sectional view indicated by line XIV-XIV on FIG. 13;

FIG. is a plan sectional view indicated by line XVXV on FIG. 16 and showing still another modification;

FIG. 16 is a sectional view indicated by line XVI- -XVI on FIG. 15;

FIG. 17 is a plan sectional view similar to FIG. 15 and is indicated by line XVlI-XVII on FIG. 18; and

FIG. 18 is a sectional view indicated by line XVIII- XVIII on FIG. 17.

BRIEF SUMMARY OF THE INVENTION According to the present invention, the suction boxes positioned beneath the wire and the web formation zone are provided with foraminous upper walls over which the machine wire moves and through which liquid is drawn into the respective box. Each box has a suction connection near the bottom for withdrawing liquid therefrom and each box, furthermore, has an intermediate partition, or false bottom, dividing the respective box into upper and lower chambers.

The intermediate partition has aperture means therein and by selecting the location of the aperture means, and/or the distribution thereof when more than one aperture is provided, or by providing adjustable members for controlling the effective size of the aperture means, the velocity at which liquid is drawn into each suction box and the distribution thereof across the area of the suction box can be closely regulated.

The invention is adaptable to machines in which a wire runs in a plane over a plurality of suction boxes or to a cylinder type machine in which suction boxes are arranged inside a cylinder.

In each case, the formation zone for the web being formed, and which is located over the suction boxes, is supplied with fibrous suspension by way of a head box having confining side walls and a confining top wall converging with the machine wire or the machine cylinder in the direction of movement thereof so as to form a completely closed head box that is continuously filled with suspension.

GENERAL DISCUSSION The problem of maintaining the fiber deposition on the machine wire substantially uniform across the width of the wire is solved according to the present invention by providing a flat suction box, the top of which is open to the bottom of the wire, while the bottom of which is provided with at least one discharge opening, and disposing in the box between the top and bottom is a partition member extending substantially parallel to the wire and having at least one opening therein communicating with the chamber above the partition wall and which opens to the bottom of the wire with the chamber below the partition wall and which is communicated to the discharge conduit.

With such a construction, the velocity of the liquid entering the suction box can be adjusted with respect to either the width of the suction box laterally of the direction of movement of the wire or longitudinally in the direction of movement of the wire. It is possible to influence the pressure distribution inside such a box so that the pressure difference between the upper side of the machine wire and the portion of the suction box beneath the wire is substantially the same across the entire area of the suction box.

Suction boxes, in general, are wide in the direction of the width of the wire and somewhat more narrow in the direction of movement of the wire. The suction box, in any case, presents a substantially greater area to the wire than is presented to the suction box by the discharge conduit connected thereto, whereby the liquid entering the wire side of the suction box at different regions will have different distances to flow to the discharge conduit.

It will be apparent that the particular location of the discharge conduit to the suction box will influence the flow pattern of liquid through the suction box and that, furthermore, even with an intermediate apertured partition between the top and bottom of the suction box, the location of the aperture, or apertures, in the partition wall, together with the location of the discharge opening, or openings, in the bottom of the suction box, will influence the liquid flow into the wire side, or top, of the suction box.

In general, the strongest stream of liquid into a suction box will be disposed directly over an aperture in a partition wall and decrease in directions away from the aperture toward the vertical confining walls of the suction box.

It is possible, according to the present invention, so to adjust and locate apertures in the partition wall in the suction box that substantially uniform liquid flow conditions will exist across the entire area of the suction box. However, it is also convenient to provide the partition wall with one or more apertures with which there is associated adjustable control members, in the form of mask elements, for example, for varying the effective flow through area of the respective apertures. Such mask elements might be slidable or pivotal. In one modification, the control member consists of a moveable belt or a band apertured in a certain manner and disposed on the partition wall.

Where a plurality of suction boxes are arranged one following another in the direction of wire movement, each suction box is provided with a partition wall between the top and bottom thereof which has apertures therein, and the apertures from one box to the next may be staggered relative to each other in the direction transverse to the direction of wire movement.

One convenient manner of obtaining staggered openings, for example, is to provide alternate ones of the suction boxes with an even number of apertures in the partition walls thereof and the others with an odd number of apertures in the respective partition walls.

It is possible, still further, to adjust the effective areas of such apertures by moveable mask, or shutter, elements.

The mask elements, which are adjustable to vary the effective flow through areas of the respective apertures in the partition walls, may be slidably supported on the partition wall so as to be adjustable for more or less covering a respective aperture, or the mask elements can be tiltably supported on a partition wall as by being mounted on a rock shaft and swing about the axis of the supporting rock shaft for covering a respective aperture an adjustable amount.

For fine control of the manner in which the effective area of an aperture is varied, particularly when a swingable mask element is employed, it is proposed to provide a secondary mask element pivotally supported on a main mask element and independently adjustable thereon.

In still another modification, the mask element employed is flexible in a direction parallel to the plane of the respective partition wall and can thus be adjusted as to contour so as to vary the area of the pertaining aperture predetermined amounts in selected regions thereof. Such a mask element might be made flexible by slits extending therein, for example.

DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings somewhat more in detail, in FIG. 1, there is shown a flat suction box having a horizontal perforated top or cover member 22 across which moves a machine wire 21 in the direction of the arrow P. The suction box has vertical

lateral walls

23 and 24 and a bottom wall 26 extending substantially horizontal and being provided in about the middle with a discharge conduit 25.

According to the present invention, there is disposed in the suction box and in a plane substantially parallel to the plane of top wall 22, an intermediate partition wall, or false bottom, 27 which divides the suction box into an upper chamber 28 communicating with the bottom of wire 21 and a lower chamber 29 communicating with discharge conduit 25.

In intermediate partition wall 27, there is provided an aperture 30 providing communication between

chambers

28 and 29. In FIG. 1, aperture 30 is arranged fairly close to wall 24 and the flow pattern of liquid drawn through wire 21 and flowing through chamber 28 to aperture 30 is indicated by the lines R.

FIG. 2 shows a suction box substantially the same as that illustrated in FIG. 1 and bearing the same reference numerals, and differing from FIG. 1 only in that aperture 30 in FIG. 2 is located in about the middle of partition wall 27, substantially midway between

lateral walls

23 and 24.

The graphs of FIGS. 3 and 4 will show how the placement of the aperture 30 in the partition wall influences the flow velocity through wire 21 over the region thereof between

walls

23 and 24. Thus, in FIGS. 3 and 4, the velocity, or quantity, of fluid is represented by the ordinate O which will be seen, in FIG. 3, to be greatest in the region over aperture 30 of FIG. 1, which is to say, the flow rate charted increases from lateral wall 24 to about the center of aperture 30 and then steadily diminishes toward lateral wall 23.

FIG. 4 shows that the flow velocity in FIG. 2 is greatest immediately over the centrally located apertures 30 and diminishes in both directions therefrom toward

lateral walls

23 and 24.

The suction boxes in FIGS. 1 and 2, as is the case with all of the other suction boxes illustrated herein, are disposed beneath the wire 21 along a formation zone thereof with suspension being supplied to the top of the wire along the suspension zone by a closed head box, which has, for example, vertical side walls extending in the direction of wire movement near the ends of the suction boxes and a confining top wall which inclines downwardly at an acute angle toward the wire in the direction of movement of the wire, so as to leave a slit-like opening at the exit end through which the web developed in the formation zone will pass. Such a head box, which is known and which is not, therefore, illustrated in detail herein, is maintained filled with suspension at all times during the operation of the machine.

The particular suction boxes illustrated in FIGS. 1 and 2 are adapted for use in a Fourdrinier machine in which a wire runs in a generally horizontally extending plane, but the invention is also useful in respect of cylinder type machines in which the head box supplies suspension to the outer surface of a rotating cylinder and suction boxes are disposed inside the cylinder opposite the head box. All of the illustrations herein are of a Fourdrinier type machine.

In FIGS. 5, 6 and 7, a suction box unit illustrated is divided into three

adjacent sections

40, 40" and 40" in the direction of movement P of wire 41. In this particular case, the top wall of the suction box unit may incline upwardly rather steeply in the direction of wire movement.

The suction box unit comprises the vertical

frontal walls

43 and 44 and at the fore and aft sides, with respect to the direction of wire movement, is confined by the vertical walls 43A and 438. The individual sections of the suction box unit are formed by two vertical intermediate walls 44A and 44B parallel to and spaced from walls 43A and 43B.

The suction box unit has a bottom wall 46 common to all of the sections thereof and

intermediate partition walls

47, 47" and 47", which may be substantially coplanar, and which are disposed between the upper and bottom walls of the individual suction box units.

In wall 44, there are provided connections 45 45" and 45" for the respective suction box sections for connection to individual discharge conduits.

Each of the aforementioned partition walls divides the respective suction box into an

upper chamber

48, 48" and 48" and a respective

lower chamber

49, 49 and 49". The respective upper and lower chambers of each suction box communicate with each other via apertures 50', 50" and 50", respectively, with the apertures in each partition wall being distributed laterally to the direction of movement of the machine wire and preferably staggered from one suction box to the next in the direction of movement of the machine wire.

Each of the aforementioned apertures has associated therewith a flow control member in the form of a slidable mask element as indicated 51', 51" and 51", and to each of which is connected a respective push rod 52. Each push rod extends sealingly through one of the

walls

43 or 44 of the suction box unit and is advantageously provided with an adjusting handle 53 so that the respective mask elements can be adjusted with respect to the pertaining apertures to vary the effective area thereof.

The selection of the sizes of the apertures in the respective partition walls and the location thereof and the adjustment of the respective mask elements provides for the establishment of conditions of liquid flow in the suction boxes which is quite uniform across the entire width of the boxes and which will bring about a uniform deposition of fibers upon the machine wire.

In FIGS. 8 and 9, a flat suction box 60 is illustrated which has

frontal walls

63 and 64 and a partition wall 67 dividing the suction box into an upper chamber 68 and a lower chamber 69 which are in communication by way of an elongated aperture 70 formed in partition wall 67.

Aperture 70 extends substantially the entire width of machine wire 61 and is substantially rectangular while being spaced from the

aforementioned walls

63 and 64 and also from the walls 63A and 6313 which are fore and aft of suction box 60 in the direction of wire movement.

As a mask element in the FIGS. 8 and 9 modification, a generally trapezoidal, or trapezium, shaped mask member 71 is employed, having a smaller end fixed to a rock shaft 72 that extends downwardly and through bottom wall 66 of the suction box where it is connected to a lever 73 to which a pull rod 75 is connected and which has a handle 74.

It will be evident that adjustment of rod 75 will bring about swinging movement of member 71 relative to aperture 70 and thereby vary the effective flow through area of the aperture. The discharge connection to the suction box is indicated at 65, which is at the side of the suction box opposite shaft 72, so that mask element 71 is operable for varying the effective area of the aperture to a greater degree near the discharge conduit than toward the other end of the suction box.

The edge of member 71 extending over aperture 70 may be rectilineal, as shown at 76 in full lines, or it may be configured in some other manner, such as curvilineal as indicated by the dot-dash line 77 in FIG. 8.

It will be understood that means are included for locking rod 75 in any position of adjustment thereof.

FIGS. and 11 show an arrangement somewhat similar to that of FIGS. 8 and 9, except that the flat suction box 80 in FIGS. 10 and 11, elongated in the direction of the width of the machine and having a bottom wall 86 and

vertical walls

83 and 84 at the narrow ends the suction box, is provided with two discharge outlets 85 and 85' disposed near the narrow ends of the suction box. The machine wire 81 runs on top of the suction box in the direction indicated by arrow P, and the suction box comprises an intermediate partition wall 87 having an elongated aperture 90 therein.

In the FIGS. 10 and 11 modification, two mask elements 91 and 91' are provided, and these are advantageously supported on

respective rock shafts

92 and 92 which extend vertically downwardly through the partition wall 87 and bottom wall 86 and have respective actuating levers 93 and 93' thereon to which are connected respective adjusting rods 95 and 95' having handles 94 and 94'. The mask element 91' is slotted to permit rock shaft 92 to pass therethrough because the mask elements are arranged in overlapping relation near the lateral center of the suction box.

By the described arrangement, the aperture 90 can be variably restricted in the regions nearest each of the discharge connections thereby to provide for uniform flow velocity conditions across the entire area of the suction box.

As in the case of the FIGS. 8 and 9 modification, the mask elements can have straight leading edges, as indicated at 96 and 96', or these edges can be configured in a different manner as, for example, in a curved manner as shown by the dot-dash lines 97 and 97'.

In FIG. 12, which is drawn at somewhat enlarged scale, and which shows an arrangement somewhat similar to that of FIG. 10, the suction box 100 is provided with a vertical wall 103 at the narrow end, from which leads a discharge opening 105. The intermediate partition wall 107 has an elongated aperture 110 therein. This aperture is adapted for being variably restricted at one end by mask element 111 and at the other end by mask element 121 and at which other end is preferably a further discharge connection, not shown.

Mask element 111 is mounted on a rock shaft 1 12 for pivotal movement laterally of aperture 110. Similarly, mask element 121 is mounted on a rock shaft 122. The

rock shafts 112 and 122 have attached thereto, beneath the suction box, respective actuating levers 113, 123 to which are connected rods 115, 125 for tilting of the mask elements.

Mask element 111, at a point thereon remote from rock shaft 112, supports an additional mask element or blade 119 on a rock shaft 120 having connected thereto a lever 126 and to which is connected a rod 127 which leads to a lever 128 mounted on rock shaft 112. Lever 128 may, for example, be fixed to a hollow shaft concentric with rock shaft 112 and have an actuating lever thereon for adjusting mask element 119 independently of mask element 111.

The rock shafts extend downwardly through the bottom wall of the suction box and mask element 121, which is beneath mask element 111, as viewed in FIG. 12, is slotted to permit rock shaft 122, and the hollow shaft on which lever 128 is mounted, to pass therethrough.

FIGS. 13 and 14 show a modified arrangement in which a suction box is provided with a discharge chamber 149 beneath the partition wall 147 therein. The partition wall is provided with an enlarged aperture 150 and mounted in chamber 149 is a pair of

pulleys

142 and 152 about which is entrained a band 141 which is fluid impervious as, for example, being formed of a rubber-like material or metal.

Band 141 is provided with the opening 158 and the openings 148. Opening 158 is disposed in operative relation with aperture 150 and can be adjusted therealong by rotation of a crank 156 mounted on a shaft 159 extending through a bearing and having a gear 154 inside the suction box meshing with a gear 153 fixed to pulley 152.

A locking device at 157 is provided for locking the belt in any selected adjusted position in the suction box. The flow through aperture at 158 can be of any selected shape or size in order to obtain the flow conditions desired. The apertured region at 148 of the belt permits the aspirated water to pass freely to the bottom of the suction box and to flow out the discharge conduit 145.

In the modification shown in FIGS. 15 and 16, the suction box means 160 is provided with

frontal walls

163 and 164 and a bottom wall and an intermediate partition wall 167 forming an upper chamber 162 immediately beneath the wire moving over the suction box. Partition wall 167 has an elongated aperture 170 therein near a vertical confining wall 168 which is on the upstream side of the suction box with respect to the direction of wire movement.

Adjacent one side edge of aperture 170, namely, the edge 176 nearest wall 168, is a mask element 171 having associated therewith near one end a push rod 172 that extends swivelly and reciprocably through wall 163. At a point along mask element 171 spaced from wall 163 is a control lever 178 pivoted to the mask element and to the partition wall.

The mask element adjacent rod 172 carries a pivoted bearing 179 through which the rod extends and also has an inclined slot 180 through which a trunnion member or pin on rod 172 extends. The arrangement is such that mask element 171 can be adjusted in parallelism with itself relative to edge 176 of aperture 170.

Aperture 170 has another edge 177 spaced from edge 176 and associated therewith is a second mask element 181 which is flexible in its own plane, namely,

in a plane parallel to the plane of partition wall 167. Mask element 181 can consist of a relatively thin flexible material, such as a rubberlike material, or metal and the flexibility thereof may be enhanced by slits 193 extending therein from the side opposite aperture 170. These slits may extend rather deeply into the mask element up to a point close to the edge 177 but preferably not far enough to expose aperture 170.

At each end of mask element 181, there is provided an inclined slit or slot 182 which may be reinforced along the lateral edges and into each of which extends a trunnion element 185 connected to a respective push rod 173. The push rods are sealed to the adjacent

frontal walls

163, 164 of the box and are guided for straight line movement therein, for example, by guide means attached to the partition wall.

Three further inclined

slots

183, 184 are provided in spaced relation along mask element 181, as by being arranged in

extension pieces

188 and 189 of the mask element. Each of these last mentioned inclined slots, and which also may be laterally reinforced, receive respective trunnions 185 connected to respective push rods 174i, 175 which extends sealingly through the frontal walls of the suction box and which are guided for straight line movement as by the guide eyes 179 mounted on the partition wall.

The

extension parts

188, 189 may advantageously be provided with

guide rods

191, 192 and guide rods 190 may be provided connected to mask element 171 near the ends. These guide rods extend guidingly through wall 169 of the suction box and prevent the mask element from moving therein in the direction of the length thereof.

Due to the flexibility of the mask element 171, manipulation of the various push rods connected thereto can flex it in the lateral direction of aperture 170 and thereby effect fine adjustment in the effective flow through area in selected regions along the aperture.

The edge of mask element 171 facing aperture 170 may be straight or curved or it may be somewhat wavelike as shown in FIG. 15.

In the modification of FIGS. 17 and 18, an arrangement is shown which is somewhat similar to that of FIGS. and 16. In FIGS. 17 and 18, flat suction box 190' has an intermediate partition wall 197 dividing the suction box into an upper chamber 192' and a lower chamber 205. Leading from lower chamber 205 is a discharge connection 209. The suction box has

walls

198 and 204 spaced in the direction of movement of the wire and the partition wall 197 has an elongated aperture 200 closer to wall 198 than to wall 204.

Pertaining to aperture 200 is a mask element 191' which is adjacent the downstream edge 207 of aperture 200 and spaced from upstream edge 206 thereof.

The mask element is provided with slits 193' extending therein to impart flexibility thereto while spaced extension members 195, thereon, and free of slits, are provided for connection of the mask element to the

push rods

201, 202 and 203, which extend sealingly through wall 204. By individual adjustment of the push rods, either manually or by power devices, the mask element can be adjusted relative to the aperture and can be flexed or bent in its own plane thereby to vary the change in the flow through area of specific regions along aperture 200.

The edge of the mask element facing aperture 200 may be straight or curved or inclined or it may be, as shown, somewhat wave-like in configuration.

The suction box is formed with a recess 208 between wall 204 and wall 199 of the next adjacent suction box into which the outer ends of the push rods extend for ready access thereto.

Modifications may be made within the purview of the appended claims.

What is claimed is:

1. In a suction box for a papermaking machine; said box extending laterally of said machine and having a top wall over which a machine wire slides and which top wall is fluid pervious, said box also having side wall means and a bottom wall, suction means connected to a lower region of said suction box, and a false bottom in said suction box between said top wall and said lower region, said false bottom having at least one opening therein for liquid flow downwardly through said false bottom, mask element means adjacent said opening, and control means connected to said mask element means and extending through said side wall means for adjustment of said mask element means in a direction parallel to the plane of the false bottom to control the effective area of said opening exposed for liquid flow, said mask element means engaging said false bottom and being disposed in spaced relation to the underside of said top wall whereby adjustment of said mask element means influences only the opening in said false bottom.

2. A suction box according to claim 1 in which a plurality of openings are arranged in said false bottom in spaced relation in the lateral direction of said suction box, and said mask element means comprising an independent mask element for each said opening.

3. A suction box according to claim 1 in which said opening comprises a single opening elongated in the lateral direction of said machine, and said mask element means comprising a single mask element slidably mounted on said false bottom.

4. A suction box according to claim 3 in which said mask element in plan is substantially the shape of a trapezium, a rock shaft near one side of the suction box pivotally connecting the narrow end of said mask element to said false bottom, said mask element being disposed on top of said false bottom.

5. A suction box according to claim 4 which includes a second and smaller mask element also substantially trapezium shaped when viewed in plan, the larger end of said second mask element being near the larger end of the first mentioned mask element and the smaller end of the second mask element being spaced along the first mentioned mask element from the larger end thereof, means pivotally connecting the smaller end of said second mask element to the first mentioned mask element, and said control means includes a respective control means for each mask element.

6. A suction box according to claim 1 in which said opening is in the form of a single elongated opening extending transversely of said suction box, said mask ele ment means comprising a mask element supported on said false bottom adjacent one lateral edge of said opening and flexible in a direction parallel to said false bottom, and said control means comprising independent adjusting elements connected to said mask ele ment at points spaced along the length thereof and each operable for adjusting the adjacent region of the mask element in the lateral direction of said opening.

9. A suction box according to claim 1 in which said opening comprises-a single opening elongated in the lateral direction of said machine, and said mask element means comprises a pair of mask elements on said false bottom disposed adjacent said opening at one side thereof with the adjacent ends in overlapping relation, pivot means perpendicular to the plane of said false bottom pivotally connecting said adjacent ends of said mask elements to said false bottom, said mask elements forming a scissor-like arrangement for controlling the said opening, said control means including a respective control element connected to each mask element.

Claims

6. A suction box according to claim 1 in which said opening is in the form of a single elongated opening extending transversely of said suction box, said mask element means comprising a mask element supported on said false bottom adjacent one lateral edge of said opening and flexible in a direction parallel to said false bottom, and said control means comprising independent adjusting elements connected to said mask element at points spaced along the length thereof and each operable for adjusting the adjacent region of the mask element in the lateral direction of said opening.

7. A suction box according to claim 6 in which said mask element comprises slits therein extending into said mask element from the edge of the mask element nearest said opening and imparting flexibility to said mask element in the plane thereof.

8. A suction box according to claim 6 which includes a further mask element extending along said opening on the side thereof opposite the first mentioned mask element, said further mask element being independently adjustable in the lateral direction of said opening.

9. A suction box according to claim 1 in which said opening comprises a single opening elongated in the lateral direction of said machine, and said mask element means comprises a pair of mask elements on said false bottom disposed adjacent said opening at one side thereof with the adjacent ends in overlapping relation, pivot means perpendicular to the plane of said false bottom pivotally connecting said adjacent ends of said mask elements to said false bottom, said mask elements forming a scissor-like arrangement for controlling the said opening, said control means including a respective control element connected to each mask element.