Abstract: An extended drainage strip (3) is placed next to the primary sieve (5) of a double-sieve mold. It has a liquid-intake space (2), which is disposed between the part of the surface (4) facing the sieve and the sieve (5). Disposed next to the other sieve (6) is at least one adjustable strip (7) arranged so that it can be placed opposite the intake space (2). Intake space (2) has a cross-sectional size that increases, if necessary, in the direction in which the liquid flows. By pressing the adjustable strip (7) against the intake space (2) of the extended strip (3), the shape of the intake space (2) can be controlled, and the suction or intake of the liquid in the intake space (2) is regulated. One object is to achieve steadily increasing suction in the flow direction. This result assists in preventing undesired pressure surges. The drainage device is simplified and thus easy to monitor. Drainage proceeds carefully, with higher retention of fine particles in the sheet of material between the sieves.

Abstract: A process and apparatus for improving stock formation on an open surface paper making machine is described. By the use of both a path for the forming fabric which introduces a controlled level of agitation into the stock, and a low level of vacuum in a suction box extending continuously for at least the major proportion of the forming section, improvements both in paper quality, such as improved wire mark, and in machine operation, such as an improved first pass retention, are obtained.

Abstract: A mechanism and method for initially dewatering a paper stock slurry between looped traveling forming wires wherein the wires pass over turning bars, controlling the cross machine curvature of the turning bars to compensate for variations in curvature due to temperature effects on the turning bar and to control the cross machine curvature of the turning bar to a predetermined fixed shape for wide machines to control the travel of the wire over the bars by applying bending moments to a support beam for the turning bar such as by providing separate liquid chambers in the beam and directing heated or cooled water into the chambers to bend the bar to either a positive crown, to be straight or to a negative crown.

Abstract: A paper making machine forming board is described wherein the rate of drainage of the stock through the forming fabric is curtailed and controlled by applying a low positive air pressure (above ambient atmospheric) to the machine side of the forming fabric. Additionally, a controlled level of agitation is induced in the stock on the forming board, providing better initial paper formation.

Abstract: A ledge for resiliently supporting a paper making machine wire has a head ledge which extends across the direction of travel of the wire and over which the wire can slide. The head ledge is rigidly connected to a movable support ledge which also extends across the direction of travel of the wire and is guided on a stationary support structure. Between the movable support ledge and the stationary structure there is a resilient push device which can displace the movable support ledge together with the head ledge between a position of rest away from the wire and an operating position in which the head ledge is pressed with a predetermined force against the wire. The stationary structure has several guide arms distributed over the length of the support ledge which are the exclusive means for guiding the movable support ledge. Several guide arms arranged in pairs are provided which grip around the support ledge, in the manner of a clamp.

Abstract: Dewatering apparatus for papermaking machines, such as suction boxes, are provided with spaced cover elements of a composite structure. The cover elements include ceramic cover strips which engage the porous conveyor belt that conveys the paper web and are separated by drainage slots. The ceramic cover strips are bonded to support members of fiber-reinforced plastic. The cover elements are mounted on metal cross braces by mounting projections on the support members which slide into mounting slots of the same shape on the cross braces for attachment thereto without threaded fasteners or welding. The mounting slots and mounting projections may be of an interlocking shape, such as a dovetail shape or a T-shape, which prevents vertical movement of the cover elements toward or away from the conveyor belt while allowing horizontal sliding movement for insertion and removal of the cover elements into the mounting slots of the cross braces.

Abstract: The present invention relates to an apparatus for forming fibrous paper or board web on a double wire section of a paper machine. The double wire section includes a first wire loop and a second wire loop. In a first dewatering zone of the double wire section where the paths of both wire loops are substantially linear, the web direction is adjustably deviated towards the second wire loop. In a second dewatering zone located after the first dewatering zone, the web is curved towards the first wire loop to form a curved dewatering zone. In the linear dewatering zone, the second wire loop is loaded towards the first wire loop with wire support members. In the curved dewatering zone, the compression between the wires is effected by adjustably tightening the wires.

Abstract: The ledge is arranged transverse to the machine direction in a substantially flexure resistant manner and is adjustable for guiding the wires between which a web of material is formed. The ledge contains a guide surface which faces the wires and has a special contour. For improved control of the pressure changes occurring in the region of the ledge, the ledge contains a supporting member and a pressing member which contains the guide surface. A pressing device is supported at the supporting member and the pressing member can be adjusted in a direction relative to the wires as well as relative to the supporting member by using the pressing device for simultaneously elevating the pressing member and inclining the pressing member with respect to the machine direction. Advantageously the pressing device constitutes a hose which is subjected to a pressurizing medium and thereby deformable.

Abstract: A double screen former for the manufacture of a paper web has two continuous screens forming together a double screen zone. The one screen runs in the double screen zone across rigid laths that are arranged on the dewatering box at a mutual spacing. Additionally, the other screen runs in the double screen zone across several laths which are supported by means of flexible elements and can be forced on the screen at a selective force. The space between the flexibly supported laths is at least approximately twice as large as the space between the rigid laths.

Abstract: Apparatus for extracting liquid from a slurry containing fine solids and liquid comprising an endless screen formed of woven monofilaments of thermoplastic material so as to define a multiplicity of small openings extending between opposite sides thereof and a supporting structure for supporting the endless screen for movement through initial and intermediate operative run portions along an underside thereof in such a way as to present an upper operative side thereof for the accumulation of solids thereon by the passage of liquid through the openings thereof. The screen supporting structure comprises a multiplicity of fixed closely spaced parallel bars formed of material having favorable wear and coefficient of friction characteristics with respect to the thermoplastic material of the endless screen.

Abstract: A twin-wire former for the production of a web of paper from a fiber suspension. An upper endless loop of wire belt having a lower horizontal run and a lower endless loop wire belt having an upper horizontal run. Guide rolls support the wire belts to define a twin-wire zone. The upstream inlet wedge of the twin-wire zone is disposed at the outlet from a head box. The initial part of the path of the twin-wire zone has a gradual curvature convexly with respect to the lower wire belt, and in that initial portion are positioned guide tables, suction boxes and dewatering elements. This curved initial part is followed by a forming roll within the loop of the upper wire belt. The twin-wires wrap an arcuate sector of the lower region of the forming roll. A support roll follows the forming roll. The support roll is upraised sufficiently to wrap the twin-wires around the bottom of the forming roll and over an arcuate sector at the top of the support roll.

Abstract: A method and apparatus are disclosed whereby the rate of drainage of the stock on a Fourdrinier paper making machine can be controlled for the full length of an open surface forming section. A continuous sealed drainage box is used from adjacent the head box slice to the end of the forming section, within which the air pressure can be controlled. In the area adjacent the head box slice drainage is hindered by the use of a positive (above ambient atmospheric) pressure, while further along the forming section the pressure is decreased to a negative value (below ambient atmospheric). Improved paper formation and first pass retention are obtained.

Abstract: A paper web forming apparatus essentially comprising two wires which move together with stock which is held therebetween and a plurality of wire supporting members for supporting the wires, each of the wire supporting members forming a wedge-shaped space as defined between the wire surface and the wire supporting member, wherein the wedge-shaped space is so designed that the width as measured therebetween decreases as seen in the direction of movement of the wires.

Abstract: The present invention relates to an apparatus for guiding the wires of a paper machine former. The former includes a double wire section including two wires (1,2) in parallel direction (R) in which on the other side of the wires (1,2) a dewatering unit (10) is arranged to drain water from the stock (3) flowing between the wires and in which at least the farthest wire (2) from the dewatering unit is compressed with foil lists (20) or equivalent support members against the wire (1) nearest to the dewatering unit (10) in cross-machine direction with respect to wire direction (R) and across the web width. The load of these foil lists (20) is achieved by separate pressurized load hose construction (21) arranged between each foil list (20) and support table or equivalent in order to achieve the desired press to the stock (3) between the wires (1,2).

Abstract: A component to be used in a papermaking machine for extracting moistu re from a paper web. The component includes a supporting structure and a water permeable member is mounted on the supporting structure and is adapted to support a paper web. The water permeable member comprises a rigid mass of ceramic foam having a plurality of interconnected cells. The ceramic foam has an air permeability in the range of 10 to 1,000 cubic feet per square foot of surface area per minute and has a density of 5 to 100 lbs/cubic foot. When a pressure differential is applied to the permeable member to the paper web, moisture will be extracted from the web and passes through the permeable member.

Abstract: The suction box cover able to support a stock wire (31) over it, the stock wire running as in the prior art of paper mill machinery, the suction box cover 10 having a frame structure constructed by external side member 11,111 and a plurality of blades 13, 14, 15, intermediate, front and back, including a carrier 18 and running blades 19 connected together, the blades 13, 14, 15 being the running table of the wire and being supported by a plurality of profiled or shaped staffs oriented orthogonally to the blades and connected to the external side members 11, 111. The suction box cover is closed at the sides by removable seals 29, and the suction box cover is connectable by means of the side members to a lower suction box 26.

Abstract: An improved suction box for paper making machine includes a cover for contacting a press fabric with an elongated slot. The slot is covered with a mesh to eliminate noise and reduce wear on the fabric.

Abstract: Apparatus for stabilizing the trailing end of a web that is to be spliced to the leading end of a new web includes a knife for severing the old web and for creating a tail that must be stabilized, a suction box over which the trailing end passes, which provides stability to the trailing end, a pressure roll movable to move the cut trailing end of the old web against the leading end of the new web and a leaf-spring-like extension extending downstream of the suction box to the connection point or splice point between the webs. The extension is deflectable with the pressure roll and the extension carries the vacuum of the suction box further downstream and also supports the trailing end of the cut old web. The extension is cantilevered to the downstream side of the suction box.

Abstract: A twin-wire former for a paper machine having a lower wire and an upper wire. The former has a twin-wire forming zone which has forming members and forming zones situated in a specific sequence as follows. A downwardly curved forming zone is confined to a sector of a large-diameter forming roll mounted on a frame of a lower wire unit, the magnitude of this sector being within the range of <90.degree.. A second forming roll then follows which is preferably provided with a hollow face and onto which the wires arrive from the first forming roll. The twin-wire forming zone is curved within a certain sector of less than 90.degree. on the second forming roll so as to become horizontal. A forming shoe is provided with a ribbed deck and fitted after the second forming roll inside the lower wire loop, this forming shoe having a relatively large curve radius after which the twin-wire forming zone ends and the web is arranged to follow along with the lower wire.

Abstract: A joint dewatering zone of wires for dewatering a web to be formed in a two-wire papermachine having a first wire loop and a second wire loop, includes a first forming roll which is situated inside the second wire loop and other dewatering means which are situated after the first forming roll inside the first wire loop. The other dewatering means comprises as a combination a first suction box, a second suction box with a curved guiding surface, and a roll interposed between the suction boxes.

Abstract: Hybrid former for a paper machine which has a lower-wire loop forming a single-wire dewatering zone in which water is removed from a web being formed by a dewatering member situated inside the wire loop through the lower wire. The former also has an upper-wire unit which includes an upper-wire loop forming a second twin-wire dewatering zone after the first single-wire dewatering zone, together with a run of the lower wire. The former additionally includes a hollow-faced first forming roll fitted inside the upper-wire loop, at which the second, twin-wire dewatering zone starts, this zone being curved upwardly over a certain sector of this forming roll. A forming shoe is fitted inside the lower-wire loop after the forming roll and guides the second dewatering zone. This forming shoe is provided with a curved deck for guiding the lower-wire loop.

Abstract: The invention relates to a roll (8) for the forming section of a paper machine or the like, comprising a perforated shell (17) for removing water from a fibre suspension through holes (18) in the shell (17) into the roll (8) and being arranged to be mounted rotatably in the machine. A wire (3; 10) or the like within the forming section is arranged to be in contact with the shell (17) of the roll (8) over a part of its periphery. For improving the dewatering and the formation, the roll (8) comprises, at least substantially over the peripheral portion in contact with the wire (3; 10), bladelike means (21; 33) extending in the longitudinal direction of the roll (8). The blades are positioned within the shell (17) close to the inner surface thereof and mounted in such a manner that the shell (17) moves relative to the blades when the roll (8) rotates.

Abstract: The cover piece for a suction box of a dewatering unit for a fleece made of a pulp material conveyed over the suction box on an endless conveyor belt is provided with at least one zigzag or wavelike passage extending substantially transversely to the conveyor belt travel direction composed of a plurality of passage portions inclined to the travel direction of the conveyor belt and distributed on both sides of the medium plane of the cover piece. Advantageously the distance across the passage in the travel direction of the conveyor belt is maintained constant so that the open surface area per unit length across the passage is substantially constant, although the width across the passage may differ for portions of the passage which widen in the conveyor belt travel direction and portions which constrict in the conveyor belt travel direction.

Abstract: A seamed papermaking fabric having a multilayer base fabric includes an endless woven fabric forming a tubular belt that is flattened to form a base fabric with at least one helical coil seaming member inserted between opposing sidewall portions at each respective lengthwise extremity of the base fabric. The helical axes of the seaming members extend transverse to the lengthwise direction of the fabric and the coils of the seaming member extend through spaces between adjacent machine direction yarns and supportably engage the machine direction yarns. The opposed lengthwise extremities of the base fabric are joined together by interengagement of the coils of the respective seaming members and insertion of the pintle member axially through the interengaged coils to form a seamed endless fabric of substantially twice the predetermined thickness.

Abstract: The invention is directed to a method for extracting water from a paper web in a paper making machine using a ceramic foam component. The component includes a supporting structure and a water permeable member is mounted on the supporting structure and is adapted to support a paper web. The water permeable member comprises a rigid mass of ceramic foam having a plurality of interconnected cells. The ceramic foam has an air permeability in the range of 10 to 1,000 cubic feet per square foot of surface area per minute and has a density of 5 to 100 lbs/cubic foot. When a pressure differential is applied to the permeable member to the paper web, moisture will be extracted from the web and passes through the permeable member.

Abstract: A papermaking machine is modified by replacing a conventional rotatable couch roll by a stationary couch device that still serves the essential functions of the roll, namely dewatering of the furnish carried by the web and modification of the direction of travel of the web to turn it down towards the main drive roll. This stationary device is made of an abrasion resistant ceramic material and has a member with a convexly curved upper surface on which the web slides. Water is sucked from the furnish by a vacuum applied through perforations in the member. The majority of these perforations preferably take the form of slots that extend obliquely to both the transverse extent of the machine and the direction of web travel. The arrangement permits easier and more effective maintenance of the vacuum than with a couch roll and more efficient dewatering, with no rewetting of the web or furnish when leaving the couch device.

Abstract: All of the essential operating parts for adding a top former assembly to a new Fourdrinier paper machine or for converting an existing Fourdrinier paper machine into a top former are carried by a supplemental frame assembly which can be mounted on the main Fourdrinier frame with minimal modification of the latter except the addition of simple parts for securing the supplemental frame assembly on top of the main frame. The primary operating parts of the top wire assembly are a hollow foraminous roll and a top wire deflector which cooperate to collect and deliver liquid expressed through the top wire into a receptacle that is carried by the supplemental frame assembly, and special provision is made for utilizing the top wire deflector to correct for irregularities in the cross machine profile of the paper sheet as it is being formed. Provision is also made for operating the resulting top former in roll former mode, blade former mode, or a combination roll and blade former modes.

Abstract: Expanding body which is essentially designed as a hollow beam and, viewed in the cross-section, composed of several flexible walls. At least one of these walls has a higher expandability than the other walls. The internal chamber of the expanding body can be pressurized by a variable fluid pressure. On the use of such an expanding body in a paper machine headbox a wall with a relatively low expandability forms the downstream end piece of a flow guide wall. Its position, which determines the clear width of the discharge opening, is alterable by varying the internal pressure.

Abstract: The invention relates to a stationary supporting member for the drainage wire belt of a paper machine. The supporting member has a transverse head board with a doctor-like leading edge which contacts the underside of the wire belt. The head board is formed from hard material, which has a drainage area forming a small, variable angle of inclination with the direction of travel of the wire belt. Two C-beams support the head board, one secured rigidly in the machine and the other, which carries the head board, being hinged to the rigid beam. An adjusting board on the rigid beam and having several adjustable stop surfaces distributed over its length, engages stops on which the movable beam is supported. The two beams are clamped together by means of an inflatable hose between the arms of the beam.

Abstract: A dual compartment vacufoil unit for making linerboard grade or other multi-layer paper comprising a dual compartment vacufoil and a forming blade and a method of using same. The dual compartment vacufoil unit is positioned beneath the forming blade, with an upstream compartment located on the upstream portion of the forming blade evacuating air through a primary paper sheet prior to application of the secondary discharge, and a downstream compartment located on the downstream portion of the forming blade. The forming blade is positioned directly beneath the secondary pulp discharge.

Abstract: A hydrofoil blade for use in a paper making machine wherein a plurality of variously angulated surfaces is provided for producing turbulence having controllable scale and intensity while independently controlling the rate of dewatering.

Abstract: A papermaking machine having a forming wire, a headbox and a forming board is disclosed. The headbox includes a lower slice having an apron positioned substantially in alignment with and closely adjacent the forming board such that as the forming wire travels over the the forming board the jet of paper stock leaving the headbox is laid onto the wire at the board at substantially zero angle of impingement. The forming board further includes a lead-in blade over which the wire travels. The blade acts to deflect fluid, normally pumped by the wire along its path of travel, away from the underside to the jet of paper stock prior to this jet reaching the forming board.

Abstract: A two-wire paper forming apparatus wherein the co-running forming wires converge over a forming roll and diverge over a couch roll downstream of the forming roll. A curved forming zone begins where the forming wires converge over the forming roll to receive a stock stream, and extends to before the couch roll whereby the forming roll in conjuction with a pair of convexly curved dewatering shoes disposed against the forming wires between the forming roll and the couch roll form the web while providing improved retention and formation.

Abstract: Skimming blades in papermaking machines have a dewatering surface 4 adjoining the supporting surface 3 supporting the wire 1. To sustain the desired microturbulence of the fiber suspension 2 on the wire 1, the dewatering surface 4 is provided with troughs 7. The troughs 7 have a wavy shape, in which the wave crests 5 have a smaller radius r than the wave valleys 6.

Abstract: A dual compartment vacufoil unit for making linerboard grade or other multi-layer paper comprising a dual compartment vacufoil and a forming blade and a method of using same. The dual compartment vacufoil unit is positioned beneath the forming blade, with an upstream compartment located on the upstream portion of the forming blade evacuating air through primary paper sheet prior to application of the secondary discharge, and a downstream compartment located on the downsteam portion of the forming blade. The forming blade is positioned directly beneath the secondary pulp discharge.

Abstract: The present invention relates to a support apparatus of a dewatering unit (30) below a bottom wire of the twin wire forming section of a paper or board machine.The problem in known, corresponding arrangements has been insufficient crosswise stiffness of the dewatering unit and lack of adjustability.The above-mentioned disadvantages have been eliminated or minimized by a support arrangement, characterized in that the dewatering unit (30) is supported on beams (36) transversely in view of the machine direction by means of a hose-like pressure-medium filled elements (37), which also allow a longitudinal adjustment of the dewatering unit by means of an adjusting element (38).

Abstract: A system for forming a web from a dilute, aqueous slurry of fibers wherein a thin, horizontally-extending aqueous stream of fibers is projected onto a travelling foraminous forming wire. The forming wire is disposed to travel over a forming board which has a leading lip which is deflected downwardly with respect to the oncoming jet stream. The lower surface of the jet stream is disposed substantially parallel with the surface of the travelling foraminous wire wire at the point where the stream contacts the wire to minimize turbulence at the point of initial contact of the jet stream on the wire and subsequent spouting of the fibrous stock downstream in the forming zone.

Abstract: All of the essential operating parts for converting an existing Fourdrinier paper machine into a top former are carried by a supplemental frame assembly which can be mounted on the main Fourdrinier frame with no modification of the latter except the addition of a pair of pivotal mountings and a pair of adjusting jacks for the supplemental frame assembly. The primary operating parts of the top wire assembly are a hollow foraminous roll and a top deflector which cooperate to collect and deliver liquid extruded through the top wire into a receptacle which is carried by the supplemental frame assembly. Provision is also made for operating the resulting top former in roll formation mode, blade formation mode, or a combination roll and blade formation mode.

Abstract: An improved papermaking apparatus of the type in which a headbox directs a jet of papermaking slurry onto the upper surface of the wire which moves longitudinally over and is supported by a forming board. The improvement is means for adjusting the length of the leading forming board strip and means for adjusting the position of that strip to properly relate the strip to the intercept of the jet with the wire.

Abstract: A hydrofoil blade and support for use in a paper making machine, and a method using a hydrofoil blade for dewatering and forming a paper web on a paper machine forming medium wherein a single phase fluid is formed in a gap between the hydrofoil blade and forming medium, and the gap is extended a sufficient distance in the machine direction to prevent expansion and corresponding cavitation of the single phase fluid in the gap.

Abstract: A method for operably adjusting a leading strip of a forming board of papermaking wire wherein the position and length of an impinging papermaking slurry is detected and the length of the leading strip adjusted.

Abstract: A papermaking machine including a non-dewatering forming board comprising a plurality of contiguous blades and a plurality of shower nozzles for showering stock carried by a forming medium over the forming board with a plurality of needle jets of water, each needle jet of water extending in a downstream direction, forming a small acute angle with the stock, and being in close proximity with the stock so that the needle jets of water impinge upon the stock as continuous streams.

Abstract: A twin wire paper former incorporating a forming shoe having a curved solid forming surface across which the forming wires pass with one of the wires in direct contact therewith and the other sandwiching the stock from which the paper is to be formed therebetween. The tension in the other wire drives water from the stock contained between the two wires, out through the other wire, and the shoe is vibrated thereby to reduce the friction between the wire contacting the shoe, to reduce wear of the contacting wire and to improve drainage.

Abstract: A lower wire loop of a paper machine has an initial single-wire portion of a dewatering zone defined by an initial portion of the wire of the lower wire loop, succeeded by an upper wire unit defining a twin-wire dewatering zone with a coinciding upper run of the wire of the lower wire loop. Dewatering occurs in the twin-water dewatering zone through the wire of the lower wire loop and the wire of the upper wire loop. The twin-wire dewatering zone is located above the level of the initial portion of the wire of the lower wire loop. A first dewatering element is a first forming shoe in the direction of the web run in the upper wire loop. The twin-wire zone curves in a first direction in a first sector on the first forming shoe so that dewatering occurs primarily through the wire of the lower wire loop. A second dewatering element is a second forming shoe following the first forming shoe and spaced therefrom in the lower wire loop.

Abstract: A web-forming section and method in a paper machine. The web-forming section includes a lower wire loop having an initial lower wire run constituting an initial single-wire dewatering zone of the web-forming section in which the web is dewatered through the lower wire, and an upper wire loop having a joint run with a subsequent run of the lower wire to form a two-wire dewatering zone of the web-forming section within which dewatering takes place substantially through the upper wire. A first open faced forming roll is situated within the upper wire loop so that the two-wire dewatering zone begins and curves upwardly in the region of the first forming roll. A forming shoe within the lower wire loop has a curved deck whose center of curvature is situated on the side of the lower wire loop and further guides the joint run of the upper and lower wires in the two-wire dewatering zone.

Abstract: A process in the forming of a paper web, the dewatering of the pulp web, and of the paper web being formed comprises feeding the pulp suspension jet from the slice of the headbox into a gap formed by two wires, the gap becoming narrower in the feeding direction of the pump suspension jet. Water is removed from the pulp web when the web is in compression between the carrying wire and the covering wire within the twin-wire forming zone, which begins immediately after the feeding gap. The twin-wire forming zone is curved towards the loop of the carrying wire with a curve radius which is selected large enough so that the wire tensioning pressure resulting from it and acting upon the pulp web becomes low and the water removed from the pulp web is not splashed from the inside surface of the wire loop by the effect of centrifugal force dependent upon the curve radius.

Abstract: A forming roll positioned in the forming section of a Fourdrinier papermaking machine and supported above the forming medium in contact with one surface of a constituent material to sandwich the material between a substantial arc segment of the forming roll surface and the forming medium.

Abstract: In a forming section of a papermaking machine, a foil blade for being positioned in close running relation with a wire for dewatering a web on the wire, a mount for the foil positioned to support the foil in its operative position and an inflatable member between the mount and foil securing the foil tightly in operative position preventing rocking when inflated and releasing the foil when deflated so that the foil can be slid out in a cross-machine direction.

Abstract: Mechanism for automatically controlling and maintaining a selectively differentiated vacuum pressure in a vacuum head accommodating to the transverse width of a moving web passing relative thereto involving means for supplying air to the vacuum head at spaced points along the width and control means for detecting the need for an increase or decrease in the vacuum at the spaced points along the length and selectively charging more or less air to the vacuum head at the corresponding points along the length.

Abstract: Apparatus for de-watering fibrous suspensions, which apparatus comprises a suction housing and a cover. The cover comprises two or more plank members releasably secured to the suction housing and each having secured thereto a number of foil strips. Each foil strip is secured to the plank member by way of a plurality of spaced apart pins which are carried by and project from the plank member. A channel is defined between the foil strips and the plank member which serves for the removal of water extracted from the suspension. A weir may be disposed in this channel to control the flow of water over the foils and air may be introduced into the channel by way of drillings to assist in control of the water and prevent plugging.