Abstract: A disclosed screen assembly includes a frame and a tensioned molded polyurethane screen attached to the frame. The frame has a perimeter that is a circle, square, rectangle, triangle, pentagon, hexagon, or other multi-sided polygon, and the screen may have similarly shaped apertures. The frame includes a support grid structure bounded by the perimeter and the screen may either be attached only to the perimeter of the frame, or may be attached to the perimeter of the frame and to one or more locations of the support grid structure. The screen may include uniaxial or biaxial reinforcement members that are integrally molded with the screen, and the tensioned screen may include tension along a direction that is parallel to, or perpendicular to, a direction of the reinforcement members. A disclosed method includes applying tension to a molded polyurethane screen and attaching the tensioned molded polyurethane screen to the frame.

Abstract: An apparatus for separating solids from solids laden drilling fluid is provided. The apparatus includes a shale shaker and a screen assembly. The shale shaker includes a base and a basket isolated from the base, a flow tray arranged in the basket for directing screened drilling fluid. The screen assembly includes at least one layer of screening material, a screen support having a perimeter with at least one support point within the perimeter, wherein the flow tray includes at least one raised portion to support the screen assembly. In some versions the shale shaker has a basket having side supports and at least one intermediate support arranged between the side supports. The screen assembly includes a screen support supporting at least one layer of screening material.

Abstract: A removable screen panel assembly for a vibratory screening machine for separating liquids and solids. The screen panel assembly includes a plate, a corrugated screen assembly supported by the plate, hook assemblies connected to opposite ends of the plate, and gaskets connected to the hook assemblies. A first hook assembly has a first end connected to a first end of the plate, a middle portion spaced above first apertures at the first end of the plate, and a second end parallel to the plate. The second end of the first hook assembly and the first end of the plate sandwich a first end of the corrugated screen assembly.

Abstract: Apparatus, systems, and methods for providing a screening surface in a vibratory machine are provided. In one example embodiment, a screening system includes a plurality of bucker bar covers. Each bucker bar cover is adapted to fit over one of a plurality of bucker bars. Each bucker bar cover can have one or more recesses. The system further includes a plurality of panel fastening members (e.g., panel fastening straps, panel fastening shrouds, etc.). Each panel fastening member is adapted to extend across the plurality of bucker bar covers in one of the one or more recesses of the bucker bar covers. Each panel fastening member can have a fastening feature. The system can further include a plurality of screen panels. Each screen panel can have a fastening recess having a shape adapted to engage with the fastening feature of one of the panel fastening members.

Abstract: Disclosed embodiments include a removable support structure for a vibratory screening machine. The removable support structure is a single structure including one or more of plastic, metal, and composite materials and may be configured to provide mechanical support to one or more screening assemblies of the vibratory screening machine. The removable support structure may further be configured to be removably fastened to the vibratory screening machine. The removable support structure may be a single thermoplastic injection molded piece or may be a single injection molded piece that includes nylon, carbon, and graphite. The removable support structure may have a concave shape that is configured to mechanically support a screening assembly held under compression or may have a convex shape that is configured to mechanically support a screening assembly held under tension. A disclosed wear protective covering, made of a flexible material, provides wear protection to the removable support structure.

Abstract: A downhole assembly can include screens along a length of a tubular member. Screens covering differing portions of a cross-sectional area of the tubular and less than an entirety of the cross-sectional area can be offset from one another along a length of the tubular. Fluid flowing through an area not covered by a first screen can encounter an area covered by an offset screen. If the offset screen is blocked with accumulated debris, fluid may pass the offset screen by passing through an area not covered by the offset screen.

Abstract: Apparatus, systems, and methods for providing a screening surface in a vibratory machine are provided. In one example embodiment, a screening system includes a plurality of bucker bar covers. Each bucker bar cover is adapted to fit over one of a plurality of bucker bars. Each bucker bar cover can have one or more recesses. The system further includes a plurality of panel fastening members (e.g., panel fastening straps, panel fastening shrouds, etc.). Each panel fastening member is adapted to extend across the plurality of bucker bar covers in one of the one or more recesses of the bucker bar covers. Each panel fastening member can have a fastening feature. The system can further include a plurality of screen panels. Each screen panel can have a fastening recess having a shape adapted to engage with the fastening feature of one of the panel fastening members.

Abstract: The invention relates to a screen frame adapted for use in a shaker and to which woven wire mesh is to be attached, comprising an outer perimeter and a plurality of plastics ribs extending between opposing regions of the perimeter, the frame being arranged such that, when fitted in a shaker to which it is adapted for, a portion of the opposing regions is clamped in place and a portion of the opposing regions is not clamped with the number of plastics ribs per unit length for the clamped portion greater than the number of plastics ribs per unit length for the unclamped portion, and to a shaker comprising at least one such screen frame.

Abstract: A scalping insert includes a scalping surface having a plurality of scalping slots therethrough, and a vertical base portion. A shaker screen assembly includes a screen frame having at least one slot. A scalping insert is positioned in the at least one slot of the screen frame. Processing fluid using a shaker screen assembly includes providing a flow of fluid to the shaker screen assembly and flowing the fluid through both a scalping surface and a screen surface of a single shaker screen deck.

Abstract: A system includes a first screen having a first latch on a first end of the first screen, a second screen having a first catch on a first end of the second screen, and a screen adapter that connects the first screen and the second screen. The screen adapter includes an elongate body, a first catch formed on a first side of the elongate body that engages the first latch on the first end of the first screen, and a first latch formed on a second side of the elongate body that engages the first catch on the first end of the second screen. A method includes inserting a first screen into a vibratory separator, inserting a screen adapter into the vibratory separator, coupling the screen adapter to the first screen, inserting a second screen into the vibratory separator, and coupling the second screen to the screen adapter.

Abstract: A screening apparatus includes elongate beams and screen panels mounted to the beams to form a broad screening surface. Each of the panels are mounted so that side edges of adjacent panels are in facing relationship. Each panel is mounted to a pair of beams to bridge between two adjacent beams. The panels are mounted to the beams by fixing members. The fixing members have a pair of upstanding rails that are spaced apart to define a longitudinal gap between them. The panels are mounted to the beams by cooperation between the side edges with a rail of a fixing member. Cover strips extend along the beams and include a cover portion and a locking portion. The cover portion bears against an upper surface of a pair of adjacent panels and the locking portion bears against facing surfaces of the rails to resist movement of the rails towards each other.

Abstract: This disclosure is generally drawn to systems, devices, apparatus, and/or methods related to sealing mechanisms for vibratory separators. Specifically, the disclosed systems, devices, apparatus, and/or methods relate to seals having support(s) for improved installation in and/or removal from a vibratory separator. In some examples, an apparatus may include a seal and a support member. The seal may have two opposing side members and an end member coupled to and extending between the two opposing side members. The support member, which is at least partially rigid, may be coupled to the end member of the seal. In some examples, the support member may be integrated with or removably coupled to the seal.

Abstract: System, method and/or apparatus repairs an area of damaged mesh in a sifter screen (80). Such sifter screens (80) have woven wire mesh (81) stretched, tensioned and/or secured over a supporting frame (85) having cells (82). Damage occurs to the mesh (81) over certain cells (82). A plug (10) having a mesh layer (14) inserts and/or locks into place in the damaged cell (89). The mesh layer (14) of the plug (10) is flush with the mesh (81) on the sifting screen (80). Ridges (62) and/or ledges (66) secure the plug (10) in place by engaging a lip (96) in the damaged cell (89) to snap-fit the plug (10) in place.

Abstract: A scalping insert includes a scalping surface having a plurality of scalping slots therethrough, and a vertical base portion. A shaker screen assembly includes a screen frame having at least one slot, and at least one scalping insert disposed in the at least one slot of the screen frame. A method of processing fluid includes providing a flow of fluid to a shaker screen assembly; and flowing the fluid through a scalping surface and a screen surface of a single shaker screen deck.

Abstract: A vibratory separator includes a screen frame having an upper screen surface and a plurality of openings and a first screen insert disposed in a first opening of the plurality of openings of the screen frame, the screen insert having a screen surface positioned at a first height above the supper screen surface. The vibratory separator also includes a second screen insert disposed in a second opening of the plurality of openings of the second screen frame, wherein a screen surface of the second screen insert is positioned at a second height. The second height may be different from the first height. A method of processing fluid includes providing a flow of fluid to a vibratory separator, and flowing the fluid over a screen having a first screen insert positioned at a first height.

Abstract: A screen lining having an adapter strip for fastening a screen mat or two screen mats arranged adjacent to each other to a supporting substructure in such a way that the screen mat or screen mats can be replaced. The adapter strip has projections on the side of the adapter strip facing away from the screen mats, which projections are integrally formed on the adapter strip in order to be inserted into openings on the substructure and have a bearing region on the side of the projections facing the screen mats, in which bearing region at least one hollow for the form-fitting fastening of the screen mats is arranged. The adapter strip has integrated deflecting blades, the top sides of which are angled downward with respect to a plane defined by the screen mats.

Abstract: A screen panel 15 for mounting to a vibratory screening apparatus that includes a plurality of beams 11 to which screen panels 15 can be mounted. The screen panel 15 comprises a square or rectangular frame 21 including a pair of spaced apart and parallel side frame members 25 and a pair of spaced apart and parallel end frame members 38 connected to the side frame members 25. The frame 21 defines an upper edge and the side and end frame members define a square or rectangular outwardly facing surface. The frame 21 is connectable to a pair of adjacent beams 11 by connectors 20 that connect with the outwardly facing surface of the side frame members 25. The screen panel 15 also comprises a square or rectangular screen 22 connected to the frame 21 which extends over the upper edge of the frame 21 and forms a square or rectangular skirt 33, 36.

Abstract: A laminate screen for a vibratory separator, the screen including a product screen mesh layer having a plurality of wires. The screen further including a structural screen mesh layer having a plurality of wires secured to the product screen mesh layer with a thermoplastic polymer, wherein the structural screen mesh layer is configured to provide structural integrity to the laminate screen, and wherein a diameter of the product screen mesh layer wires is less than a diameter of the structural screen mesh layer wires.

Abstract: A screen system having a plurality of screen elements that can be readily removed and replaced to vary one or more characteristics of the screen surface formed by the screen system. The screen system includes a support system for supporting at least one screen element to prevent deformation of the screen element that typically would occur due to the insufficient structural stability of the at least one screen element relative to the weight of the product being screened. Preferably, the support system includes one or more support elements that can be readily and easily installed and removed from the screen system. The support system is preferably configured to permit the one or more support elements to be positioned at different locations in the screen system. Preferably, the support system is configured to permit a variety of different support elements to be used to allow a greater variety of screen elements to be used.

Abstract: Flip-flow screens having crossbars which extend transversely to the screening direction, carry a screen liner and are mounted alternately fixedly and movably with respect to a screen frame, where the screen liner is mounted on liner carriers which are curved upward in their lateral edge regions. In order to improve lateral sealing, provision is made for all the liner carriers to be fastened, preferably screwed, by their end regions to the screen frame. The lateral edge regions are preferably curved by 80-90°, and the liner carriers of the movable crossmembers may have in their curved portion a cross section which is tapered in relation to the rectilinear portion and/or which may consist of a softer material.

Abstract: A fixing arrangement (10) for a screen panel comprising at least a screen panel(11) having side edges/side faces(4,7) on either side. The panel is adapted to be fixed to an adapter bar(1) and said bar(1) is adapted to be mounted on a screen deck frame. This bar(1) extends horizontally over said screen deck frame and between side edge regions of a pair of said screen panels(11), said adapter bar has at least a female portion in the form of a fixing groove (5) on its top surface(21) such that said groove(5) has an internal profile that exactly matches the outer profile of the bottom part(3) of said screen panel(11) for receiving said bottom part(3) securedly and snap fitting therewith and said adapter bar(1) is fixed on a portion(2) of said screen deck frame by suitable fixing means.

Abstract: A screening machine includes wall members, screen assembly guide members, a screen assembly and a compression assembly. The screen assembly includes a frame with a plurality of side members and a screen supported by the frame. The compression assembly is attached to at least one wall member and forms the screen assembly into a concave shape.

Abstract: A molded polyurethane vibratory screen including a body having opposite side edge portions, upper and lower edge portions, an upper surface and a lower surface, first members extending between the side edge portions and the second members extending between the lower edge portion and the upper edge portion, third members substantially parallel and extending transversely between the side edge portions and having multiple first members therebetween, the fourth members substantially parallel and extending transversely between the lower edge portion and the upper edge portion and having multiple second members therebetween, reinforcement members molded integrally with the third and fourth members.

Abstract: There is provided a plug (1) for repairing a sifting or filtering screen, the plug having at least one line of weakening (5) which can be ruptured whereby the plug has a plurality of possible plug sizes so that the plug is capable of plugging at least two different sizes of cell of the screen. Each possible plug size has a seal (2) extending around the complete periphery of the chosen plug size, in use the seal serving to engage and seal against the screen in order to plug a cell aligned with a damaged area of the screen.

Abstract: A support structure for supporting screening media in a vibrating screen. The support structure is received on longitudinal beams of the vibrating screen. The support structure is formed of fixation strips having fixation parts, on which fixation parts carriers are received. The fixation strips and carriers are placed perpendicular to each other.

Abstract: A screen panel for mining and quarrying industries adapted to be mounted on a screen deck, including a screening surface made up of materials such as herein described formed on a reinforcing frame, said screening surface having suitably designed apertures of desired shape for allowing materials of desired size to pass through, said apertures having walls (2) made of abrasion resistant material such as herein described, whereby retention of said desired shape of said apertures is ensured for a substantially long period of time.

Abstract: A screen has a plurality of flattened wires. The wires are arranged longitudinally in a first direction, and of those wires there are first and second flattened wires are spaced a predetermined distance from each other or contact or appear to contact each other at spaced intervals to form a polygonic spacing to form a desired screen spacing. The deviation from the desired screen spacing is equal to or less than the standard industry tolerance as established by ASTM E2016-11, table 8. A first and second polymeric support member homogenously encase, respectively, a first and second limited selected portions of the plurality of flattened wires spaced apart. There is no additional metal material in, within, or on the first or second polymeric support members, and the desired screen spacing is maintained even when the first and second polymeric support members are applied and cured.

Abstract: A screen deck assembly has an elongated connecting member for securing screen panels to a vibratory machine. The connecting member has a first end and a second end, a body, a transverse arm contiguous with and generally perpendicular to the body, and a radial dome top extending above the transverse arm such that a locking channel is formed between the transverse arm and the radial dome top. A screen, which has a locking profile that corresponds to the locking channel in the connecting member, is detachably secured to the connecting member by sliding or pressing the locking profile into the locking channel.

Abstract: A screen panel with wear protective apertures for mining and quarrying industries adapted to be mounted on a screen deck, including a screening surface made up of materials such as herein described formed on a reinforcing frame, said screening surface having suitably designed apertures of desired shape for allowing materials of desired size to pass through, said apertures having walls made of abrasion resistant material such as herein described said walls having plurality of slits(1) cut along the vertical as well as horizontal line in the top and bottom portion of the apertural walls, whereby utmost flexibility of the apertures is ensured simultaneously ensuring wear protection.

Abstract: An apparatus includes a vibratory separator, a screen support coupled to an inner surface of the vibratory separator, a screen having a first side with a sloped edge and a second side, the second side having a sloped edge, a screen retainer coupled to the vibratory separator, a wedge retainer coupled to a sidewall of the vibratory separator opposite the screen retainer, and a wedge having a first surface configured to engage the wedge retainer and a second surface configured to engage the a sloped edge of the second side of the screen. A method includes disposing a screen on a screen support in a vibratory separator, engaging a first side of the screen with a screen retainer coupled to the vibratory separator, and applying at least one of a downward vertical force and a lateral force to a second side of the screen with a clamping apparatus.

Abstract: Mechanical separators and screening machines, and methods for flexible sieve mat screening are disclosed. In an example configuration, a flip-flow type flexible mat screening apparatus is provided with optimized relative elevation positions for adjacent pairs of first and second mat supports. In one configuration, a portion of the first mat supports is arranged at a lowered or offset position relative to adjacent second mat supports.

Abstract: A screening apparatus includes beams and screen panels forming a broad screening surface. Each panel is mounted to a pair of beams along opposite side edges to bridge between two adjacent beams. The panels are mounted to an upwardly facing edge of the beams by elongate fixing members extending in the longitudinal direction of the beams. The fixing members engage opposite side edges of the panels and include a pair of projections that extend into openings provided in the edge of the beams. Each projection is engaged by a locking clip to prevent release from the openings. The openings into which the projections extend are of greater diameter than the outside diameter of the projections providing a loose fit within the openings, to allow movement of the fixing rails and the screen panels before the projections are engaged by a locking clip.

Abstract: A securing device for securing a screening panel to a support frame of a vibrating screen assembly. The securing device has a body with a securing means at one end and a stub at the lower end. The securing means is shaped to mate with a complementary securing cavity in the screening panel and has a hole that receives a pin located in the securing cavity. The stub may be threaded to engage the support frame.

Abstract: An ore screening deck frame system which consists of a machine frame having a machine attachment portion and a panel attachment portion having holes spaced along the length there of and a cover which is adapted to extend parallel to the panel attachment support portion has dependent edge skirts that depend below the surface of the panel attachment support portion and also has dependent tubular bosses spaced to fit in the holes of said panel attachment support portion. The frame is made from an inverted L section steel frame member with the upper flange providing the panel attachment support portion. The cover is molded from polyurethane or rubber and encloses the upper flange. The tubular bosses extend from recesses in the surface of the cover and the recesses incorporate an annular shoulder that corresponds to the top of the tubular bosses. The tubular bosses are adapted to receive fastening pins that extend into the bosses and end below the lower surface of the upper flange.

Abstract: A frame over which woven wire mesh is to be stretched and secured to form a sieving screen and which can be used to screen solids from drilling mud recovered from down-hole when drilling for oil or gas. The frame is a rectilinear moulded plastics frame having edge regions by which it is secured in place in a shaker. Within the frame is a plurality of rectilinear windows formed by an orthogonal array of intersecting ribs also of moulded plastics material. Some of the ribs are internally reinforced by rigid metal members which extend orthogonally between hollow box-section members which define a sub-frame for reinforcing the four edge regions of the frame. The orthogonal members are secured at their ends to the sub-frame. The ends of the sub-frame members are joined at the four corners of the sub-frame. In this way not are only the edge regions of the frame reinforced internally but so also are some of the orthogonally intersecting ribs, so as thereby to produce a rigid frame for the screen.

Abstract: A molded polyurethane vibratory screen including a body having opposite side edge portions, upper and lower edge portions, an upper surface and a lower surface, first members extending between the side edge portions and the second members extending between the lower edge portion and the upper edge portion, third members substantially parallel and extending transversely between the side edge portions and having multiple first members therebetween, the fourth members substantially parallel and extending transversely between the lower edge portion and the upper edge portion and having multiple second members therebetween, reinforcement members molded integrally with the third and fourth members.

Abstract: A method of forming a shaker screen includes forming a frame, and attaching a first sealing element to at least one side of an outer perimeter of the frame, wherein the attaching comprises aligning a first mating surface of the frame to a second mating surface of the first sealing element, and wherein the first mating surface of the frame includes an extension, and the second mating surface of the first sealing element includes a groove configured to align with the extension. A system of sealing shaker screens includes a first screen and a second screen disposed adjacent the first screen, wherein a first sealing element of a first frame and a portion of the second screen interact to provide a seal between the first screen and the second screen.

Abstract: A screen element (2) of a screen (1) has longitudinal sides adapted to be arranged in a longitudinal direction of a screen frame (4) and transverse sides adapted to be arranged in a transverse direction of the screen frame (4). The transverse sides of the screen element (2) are provided with at least one projection (6) and/or at least one recess (7) for locking engagement, in a direction transversely to the plane of the screen element (2), with a corresponding projection (6) and/or recess (7) on neighboring screen elements arranged in the screen frame (4). A screen (1) with a screen element (2) arranged in a screen frame (4) is also disclosed.

Abstract: A shaker apparatus including a basket having an upstream side, a downstream side, and two side walls, at least one wedge guide and one support rail disposed on each side wall, and at least one screen assembly. The support rails and the wedge guides may be configured to engage the screen assembly. The screen assembly may have one or more layers of screen mesh mounted on a screen frame. The screen frame may include a first and a second side rail, each having an upstream end, a downstream end, a top surface, and a bottom surface. A slope of the top surfaces intermediate the upstream end and the downstream end may be different than a slope of the bottom surfaces intermediate the upstream end and the downstream end.

Abstract: A shaker screen including a composite frame, a removable grid attached to the composite frame, and at least one filtering element attached to the removable grid is disclosed. A method including forming a composite frame, forming a removable grid, attaching at least one filtering element to the removable grid, and attaching the removable grid to the composite frame is disclosed. Additionally, a method for rebuilding a shaker screen, the method including removing a first screen assembly from a composite frame, the screen assembly having a removable grid and at least one filtering element, and attaching a second screen assembly to the composite frame is disclosed.

Abstract: A filter screen to be used in conjunction with a shale shaker in removing solid matter from drilling fluids includes a filter plate having a plurality of perforations, a plurality of hold-down apertures, and a pair of end caps attached to the filter plate, wherein each end cap is configured to isolate the hold down apertures from the plurality of perforations.

Abstract: A screen panel center retainer system for a vibrating separatory machine utilizes a center retainer that is provided with a retainer base which is adapted to be secured to screen stringer rails of a vibrating separatory machine. A pair of retainer channel legs form an upper portion of the center retainer and have screen panel edge receiving slots. A locking strip, having a wedging tongue, is used in conjunction with the center retainer. The wedging tongue is insertable into the channel on the center retainer which is defined by the two retainer channel legs. Flow control dams and cross dam retainers are used in conjunction with, and in addition to the center retainers and locking strips. The cross dam retainers are provided with locking strip end receiving pockets, to compensate for changes in the length of the locking strips. The screen panel center retainer system is configured to provide a functional, universal installation of screen panels on vibrating separating machines.

Abstract: A screening module for a screening assembly includes a panel member defining a plurality of screening apertures; and a support arrangement with which the panel member is fast. The support arrangement includes a plurality of strengthening arrays arranged, in use, beneath the panel member, each strengthening array comprising a skirt portion bounding an area on a bottom surface of the panel member.

Abstract: A perforated plate for a vibratory sifter, the perforated plate including a base plate comprising a plurality of openings formed therethrough, and a flange integrally formed with the base plate. A method of forming a screen assembly for a vibratory sifter, the method including forming a base plate, forming a plurality of openings extending from a top surface to a bottom surface of the base plate, and forming an integral flange on the base plate.

Abstract: A screen assembly for separating solid materials of differing sizes in a material stream, having a support, and a screen arrangement placed upon the support, wherein the support has at least one seal placed on the support, the seal configured to interface with a mounting surface of a shaking apparatus.

Abstract: A supporting structure for different screening media on a vibrating screen is disclosed, as well as a support carrier of the supporting structure. The supporting structure is received on a vibrating screen and has a number of support carriers arranged parallel to each other and perpendicular to a number of transversal carriers. The support carriers and the transversal carriers form a grid. The support carriers have grooves at each end to be snapped on and locked on circular ribs on top of the transversal carriers. The support carriers are made of a polymeric material and are elongated elements.

Abstract: A rider bar (5) is essentially made of elastomeric material. The rider bar (5) is intended for a surface of a screen cloth (1) or a wear-resistant lining over which pieces or particles of material are intended to move. The rider bar (5) comprises a wear-resistant element (6).

Abstract: A magnetic clamping system for a shale shaker including at least one screen having at least two side ends extending between a first side and a second side and at least one attachment surface. The system further includes at least one mating surface of the shale shaker configured to receive the at least one screen, and at least one magnet disposed between the at least one screen and the shale shaker, wherein the at least one magnet is configured to magnetically couple the at least one screen directly to the shale shaker. Additionally, the system includes at least one decoupling apparatus, the decoupling apparatus having a handle disposed proximate a perimeter of a shale shaker, and at least one shaft that extends horizontally between the handle and one of the at least one magnet, wherein the handle is rotatable to reverse the polarity of the magnet.

Abstract: A screen for a gyratory sifter including a frame having a plurality of cross-members and a rigid external extension. Additionally, the screen including a filtering element securably attached to the frame. Also, a method for installing a pre-tensioned screen in a gyratory sifter including inserting the pre-tensioned screen into the gyratory sifter. The pre-tensioned screen including a frame having a plurality of cross-members and a rigid external extension and a filtering element securably attached to the frame. Additionally, the method including mating the pre-tensioned screen to a ball box, wherein the mating includes placing the pre-tensioned screen against a contoured section of the ball box, and securing the pre-tensioned screen with a screen plate.

Abstract: A screening arrangement in a vibrating screen for screening of material, such as crushed stone, gravel or the like. The screening arrangement is a cross-tensioned or longitudinally tensioned screening media including elements arranged on top of the screening media for stirring or mixing the screened material, the stirring elements being raised portions, which are arranged transversely to the travel direction of the screened material.