AU2012208984B2 - Screen panel fixing system - Google Patents

Abstract

A screen panel 10 having a generally square or rectangular shape and generally planar top and bottom faces. The panel 10 including a plurality of screening openings 5 extending through the panel between the top and bottom faces. A first pair of edges 35, 36 each being arranged to engage a respective fixing member 20 that is employed to secure a panel 10 in place on a screen deck frame of an ore screening apparatus. At least one of the first pair of edges 35, 36 including a pair of spaced apart generally parallel flanges 37, 38, which extend from the edge 35, 36 and which 10 define a groove 41 therebetween. The groove 41 is provided to accept a projection 44 of a fixing member 20 of an ore screening apparatus. A first of the flanges 37being located at or towards the top face 39 and a second of the flanges 38 being located between the first flange 37 and the bottom face 40. The second flange 38 having a first face 43 that defines a surface of the groove 41 and a second face 45 on 15 the other side of the flange 38 that that is inclined in a direction from the edge of the panel 10 from which the flange 38 extends towards the groove 41 so that the second flange 38 can be pushed into engagement with the fixing member projection 44 and the projection 44 will ride along the inclined face 45 prior to the projection 44 entering the groove 41.

Description

P/00/011 Regulation 3.2 AUSTRALIA Patents Act 1990 ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT Invention Title: SCREEN PANEL FIXING SYSTEM Applicant: Lettela Pty Limited The following statement is a full description of this invention, including the best method of performing it known to me: 1 6067 SYC 2 SCREEN PANEL FIXING SYSTEM AND SCREEN PANELS FIELD OF THE INVENTION The present invention relates generally to apparatus for screening, separating or 5 grading materials, and is principally for use in the mining industry. The present invention is particularly directed to arrangements for fixing screen panels to the support frame of a vibratory screening machine and to the screen panels themselves. The system and panels are applicable for screening, separating and grading ores and other materials, and it will be convenient to hereinafter describe the invention in 10 relation to that use. It is to be appreciated, however, that the invention is not limited to such apparatus and use. BACKGROUND OF THE INVENTION A reference herein to prior art is not to be taken as an admission that the prior art was 15 known or that it was part of the common general knowledge as at the priority date of any of the claims. Screening apparatus of the type with which the invention is concerned is generally used for screening, grading, or separating materials such as ores and comprises an 20 array of screen panels which are removably fixed to a frame to provide a continuous screen deck. The material to be screened is fed onto the deck at one end and the apparatus is vibrated so that the material moves over and through its screening surface. 25 One form of screen panel includes a steel frame moulded within a resilient plastic material, such as polyurethane. See for example Australian Patent No. 577767 (66006/86). The plastic moulding forms the major part of the panel and it is in the plastic moulding that the openings for screening are provided. 30 The screen panels in a screen deck are usually subject to wear, due to the abrasiveness of the mining materials typically being screened, and thus the screens require periodical r. This presents a difficulty with the attachment of the panels to the deck frame, as the attachment must be secure and robust and easily made, but it should also be releasable in a manner that is quick and easy.

3 Systems have been developed in the past for fixing screen panels to a support frame of a screening deck, whereby individual panels can be removed and replaced when worn. For example, one system known to applicant provides an elongate U-shaped 5 fixing member for securing to the support frame so as to extend longitudinally between side edge regions of adjacent screen panels. The fixing member has a pair of connection portions, with connection elements being provided along the outer side surfaces of the connection portions and the side edge faces of the screen panels. The connection elements of each connection portion and an associated screen panel 10 interconnect to hold the screen panels in position on the support frame. The connection portions are inwardly deflectable away from the side edge faces of the screen panels in order to disengage the connection elements and disconnect the screen panels from the fixing member. A retaining member is provided for insertion between the connection portions to resist their inadvertent deflection, and thus 15 maintain engagement between the connection elements when required. The system described above has met with widespread acceptance in major sections of the Australian market. However, over time, some disadvantages in the system have become apparent. For example, while removing screen panels from the support 20 frame has been found to be relatively easy, refitting a panel can sometimes be more difficult than desirable. Moreover, the removal of screen panels from the support frame can sometimes damage the panel. Applicant has therefore developed a new form of screen panel which is intended to 25 provide advantages over the current forms of screen panel and which is intended in one form to assist in fitting or installing a panel into the support frame and in another form to resist damage to the panel when removing the panel for repair or replacement. 30 SUMMARY OF THE INVENTION According to one embodiment of the present invention there is provided a screen panel having a generally square or rectangular shape defining a first pair of substantially parallel edges and a second pair of substantially parallel edges, and generally planar top and bottom faces, the panel including a plurality of screening 4 openings extending through the panel between the top and bottom faces, the first pair of edges each being arranged to engage a respective fixing member that is employed to secure a panel in place on a screen deck frame of an ore screening apparatus, at least one of the first pair of edges including a pair of spaced apart generally parallel 5 flanges which extend from the edge and which define a groove therebetween, the groove being provided to accept a projection of a fixing member of an ore screening apparatus, a first of the flanges being located at or towards the top face and a second of the flanges being located between the first flange and the bottom face, the second flange having a first face that defines a surface of the groove and a second face on 10 the other side of the flange that that is inclined in a direction from the edge of the panel from which the flange extends towards the groove, so that the second flange can be pushed into engagement with the fixing member projection and the projection will ride along the inclined face prior to the projection entering the groove. 15 The screen panel according to the present invention advantageously facilitates installation into the frame of an ore screening apparatus. Typically, in such an apparatus, the panel is inserted into the apparatus at an angle so that one of the first pair of edges of the screen panel is engaged with the projection of the fixing member first without the need for the fixing member to ride along the inclined face of the 20 second flange at that edge. The panel is then rotated about that edge to bring the opposite edge into engagement with the projection of a second fixing member. Thus, the provision of an inclined face as one of the faces of the second flange allows the projection of the second fixing member, to ride up the surface of the second flange and into the groove. This differs from prior art arrangements, in which the face of the 25 second flange is not inclined, so that the resistance to movement of the fixing member past the second flange is greater than in the present invention. Advantageously, by the present invention, installation of a screen panel into the ore screening apparatus is thus less difficult than in the prior art, and that has an effect in relation to the amount of effort required to install screen panels in an ore screening apparatus, as 30 well as the amount of time taken to complete that installation. It will be appreciated that the screening panels of the kind described herein typically are formed of a flexible polymer material, typically a polyurethane, with most of the panels employing a steel or metal frame about which the polymer material is 5 moulded. Thus, the first and second flanges of the side edges are flexible, so that they can deform during installation of a screen panel into an ore screening apparatus. In particular, the flanges can deform to allow the projection of the fixing member to enter the groove between the flanges and to allow the projection to be removed from 5 the groove. However, the flanges will have limited flexibility, as they are also required to be robust and to securely hold the screen panels in place, so that even though they are flexible, their flexibility is limited. Thus, assistance to movement of the projection into the groove can help to ensure that the flanges are sufficiently stiff to properly retain a screen panel. 10 In some forms of the invention, the inclined face of the second flange is a planar face. In other forms of the invention, the inclined face can be a curved face, such as of constant curve and constant radius. Alternatively, the inclined face can include a combination of both curved and planar sections. 15 The inclined face can form a discrete portion of the face of the second flange, and that portion can be a minor or major portion. Thus, the inclined face can extend from adjacent the surface of the edge of the panel from which the second flange extends, or it can extend directly from the surface of the edge of the panel. Alternatively, the 20 inclined face can extend from a position spaced from the surface of the edge of the panel. Thus, the inclined face can form a major portion of the height of the second flange, or only a minor portion of that height (where the height is the dimension measured between the top and bottom surfaces of the panel). If the portion is minor portion only, then that portion preferably is positioned remote or spaced from the 25 surface or the edge of the panel from which the second flange extends, i.e. close to the distal or leading end of the flange. The groove defined by the first and second flanges can include a base and a pair of spaced apart, substantially parallel facing walls and the second flange can have a top 30 surface which extends from the groove wall and the inclined face can then extend from that top surface. In this arrangement, the second flange thus includes both an inclined face, a top surface and a groove wall. The inclined face thus allows the fixing member of the ore screening apparatus to ride up that face, and then over the top surface. A second flange constructed in this manner has sufficient bulk at the distal 6 end to provide strong and robust support to the projection of a fixing member. The top surface can be substantially perpendicular to the top and bottom faces of the panel. 5 In other forms of the invention, the groove can be defined by a base and a pair of spaced apart substantially parallel facing walls of the first and second flanges and the inclined face can extend from the groove wall of the second flange directly. In these arrangements, the top surface described above is not provided. 10 In other forms of the invention, the profile of the groove can be other than as described above, and can for example, be U-shaped. Other shaped grooves can include an interlocking section that interlocks with the fixing member of the ore screening apparatus. However, in most cases, the fixing member is expected to be of generally square or rectangular cross section, and the groove formed between the 15 first and second flanges is therefore of a similar shape to closely receive the fixing member. The first and second flanges can extend generally parallel to the top and bottom surfaces of the panel. 20 In another form of the invention there is provided a screen panel having a generally square or rectangular shape defining a first pair of substantially parallel edges and a second pair of substantially parallel edges, and generally planar top and bottom faces, the panel including a plurality of screening openings extending through the 25 panel between the top and bottom faces, the first pair of edges each being arranged to engage a respective fixing member that is employed to secure a panel in place on a screen deck frame of an ore screening apparatus, at least one of the first pair of edges including a pair of spaced apart generally parallel flanges which extend from the edge and which define a groove therebetween, the groove being provided to 30 accept a projection of a fixing member of an ore screening apparatus, a first of the flanges being located at or towards the top face and a second of the flanges being located between the first flange and the bottom face, the first flange of the pair of flanges including a gap for the insertion of a panel removal tool into the groove, the 7 gap of the first flange including side walls spaced apart lengthwise of the first flange and the side walls being curved. In the above form of the invention, the tool can be a customised tool, or it can be 5 common tool, such as a flat head screw driver. Effectively any tool which can be used to lever a screen panel out of the ore screening apparatus can be employed, subject to having an end portion that can be inserted through the gap in the first flange. 10 The side walls which are curved in the gap advantageously limit tearing of the gap during removal of a screen panel from the ore screening apparatus. If the side walls are not curved, but rather are straight and lead to a base of the gap, there is a potential for tearing of the panel at the junction between the side walls and the base. Thus, the provision of a curve in the side walls can help to eliminate the stress 15 concentration that is otherwise present and thus tearing damage to the screen panel can also be minimised. In some forms of the invention, each of the pair of flanges includes a gap for the insertion of a tool and the respective gaps are generally aligned, so that the tool can !0 be inserted through the gap of the first flange and into the gap of the second flange. In some forms of the invention, the gap of the second flange extends completely through the second flange from one side to the other. This enables a panel to be more easily removed from ore screening apparatus by a tool. 25 It is preferred that the curved side walls of the gap of the first flange are also employed in the gap of the second flange, if provided. The present invention also goes to a combination of the above embodiments, so that a screen panel according to the invention can include a pair of flanges, in which the 30 second flange includes an inclined face of the kind discussed above, and can also include a gap in one or each of the flanges, preferably with curved side walls of the above discussed kind.

8 The present invention also covers a screening deck in which a plurality of screen panels of the above described kind are employed. BRIEF DESCRIPTION OF THE DRAWINGS 5 Figure 1 is a portion of a screening deck according to one embodiment of the invention. Figure 2 illustrates in cross sectional view the connection of a pair of screening panels in a deck according to an embodiment of the invention. 10 Figure 3 illustrates in perspective view the connection of a pair of screening panels in a deck according to an embodiment of the invention. Figure 4 is a perspective view of a panel according to an embodiment of the 15 invention. Figure 5 is a cross sectional view of an edge portion of the panel of Figure 4. Figure 6 is a perspective view of an edge portion of the panel of Figure 4. ?0 Figure 7 is a further cross sectional view of an edge portion of the panel of Figure 4. Figures 8 to 13 illustrate the process of removing a panel from a screening deck according to one embodiment of the invention. 25 DETAILED DESCRIPTION OF THE DRAWINGS With reference to Figure 1, a portion of a screening deck 10 is illustrated, comprising a plurality of elongate, longitudinal beams 11 each of which is formed from an angle of steel having a long portion 12 and a short portion 13 disposed substantially at right 30 angles. While the beams extend in the longitudinal direction of the screening deck 10, the beams can equally extend perpendicular to the beams 11. The deck 10 illustrated in Figure 1 is a portion of a deck only and illustrates only one of the side edge beams 14 that define the edge of the deck 10. Accordingly, the deck 9 10 can extend further in the direction away from the illustrated edge beam 14 to broaden the width of the deck, while the length of the beams 11 can be greater to increase the length of the deck. 5 The beams 11 extend parallel to one another and support panels 15 on the upper face of the short portion 13 of each beam 11. The panels illustrated in Figure 1 can be of any suitable size, but a common size 305mm x 305mm. However, alternative sizes of panels can be employed, such as 305mm x 610mm. 10 As indicated above, the screening deck is one part of the overall screening apparatus. The screen deck is supported on a subframe which includes the beams 11 and which is part of a vibratory screen machine. The vibration that is generated is significant and requires the panels 15 to be securely fixed to the beams 11. The panels are also subject to wear over time and even though the fixing of the panels to the beams is 15 required to be secure, the preference is also that the panels be easily releasable to facilitate replacement, with replacement of panels also being relatively easy. The panels 15 include a plurality of openings through the top surface thereof for screening product such as mining ore. The openings in the panel 15 can vary from ?0 large to very small depending on the screened media required from the screening process. Typically, an ore is fed onto one end of the deck 10 and the deck is vibrated so that the ore tends to shift from one end to the other, with some of the ore passing through 25 the openings of the panels 15 as it travels over the deck. Depending on the operation, the valuable ore could be the ore which passes through the openings or the ore which remains on the deck. The panels 15 are attached to the screen deck 10 via connecting rails 20 (see Figure 30 2) which are fixed to the short portion 13 of the beams 11 by any suitable manner such as by bolts which extend through the short portion. The connecting rails 20 can extend for the length of a single panel 15, or for more than one panel 15.

10 Figure 2 illustrates in cross sectional view, a connecting rail 20 in place in the deck 10 and in connection with facing sides of a pair of panels 15. Figure 3 is a perspective view of the Figure 2 arrangement. 5 The connecting rail 20 includes a threaded shank 21 of metal and a rail section 22 of polyurethane or other suitable material, within which one end of the threaded shank 21 is embedded and secured. The shank 21 is fitted through an opening in the short portion 13 of the beams 11 and a nut (not shown) can be threaded onto the free end to secure the connecting rail 20 in place on a beam 11. Alternatively, a different form 10 of fixing can be employed, such as a bolt that extends through the base 23 of the rail 22 and then through the short portion 13, for engagement by a nut. In a further alternative, in place of the shank 21, a pair of polyurethane legs can be provided that are pushed through the opening that the shank 21 extends through and which can be splayed apart by insertion through the opening 26 of an expanding pin with a enlarged 15 head. The enlarged head splays the legs apart and the rail 20 is thus captured on the beam 11. The rail section 22 of the rail 20 includes a base 23 and a pair of upstanding members 24 and 25. A central opening 26 is defined between the upstanding members 24 and 20 25. The opening 26 is configured to accept a locking leg 27 of a retaining strip 28 (Figure 3). The opening 26 includes a neck region 29 and a recess 30 (Figure 2). The recess 30 is wider than the neck region 29 and is intended to receive a shoulder of the locking leg 27. The locking leg 27 is configured for nesting engagement in the opening 26. Once the locking leg 27 is received in the recess 30, the upstanding 25 members 24 and 25 are prevented against inward flexing movement towards each other. With reference to Figures 2 and 3, the mechanism by which the panels 15 of Figure 1 are fixed to the connecting rails 20, involves nesting engagement of the side edges of 30 the panels 15 with the outer facing surfaces of the upstanding members 24 and 25. In order to nest the side edges of the panels 15 with the connecting rails 20, one side edge of a panel 15 is brought into engagement with one of the upstanding members 24 and 25 of a first rail 20 at an angle. With that engagement made, the panel is pivoted downwardly so that the opposite side edge of the same panel approaches the 11 upstanding members 24 and 25 of a second connecting rail 20. The panel 15 is forced into engagement with the second rail 20 and that causes the relevant upstanding member 24 and 25 of the second rail 20 to flex inwardly to allow the panel 15 to nestingly engage the relevant upstanding member. The panel 15 thus becomes 5 properly nested at either side edge with respective upstanding members of a pair of connecting rails 20, as shown in Figure 2. Thus, in the Figure 2 embodiment, the upstanding member 25 flexes inwardly as the right hand panel 15 is pivoted anticlockwise in the direction of arrow A to bring that panel into nesting engagement with the rail 20. Once panels have been inserted on each side of the rail 20, the 10 locking leg 27 of the retaining strip 28 is forced into the opening 26 of the rail 20 and inward deflection of the upstanding members 24 and 25 is thereafter prevented. The panels 15 are therefore connected securely to the connecting rails 20. As is evident from Figure 3, for connection to the connecting rails 20, the edges of the 15 panels 15 have a particular profile, which is better illustrated in Figures 4 to 7. In Figure 4, a perspective view of a panel 15 is illustrated, while Figures 5 to 7 show in more detail, a portion of one edge of the panel 15. The panel 15 includes opposite edges 35 and 36. Each of the edges is arranged to ?0 engage an outer facing surface of a respective upstanding member 24 or 25. Each of the edges 35 and 36 includes a pair of spaced apart and parallel flanges 37 and 38, with the flange 37 being adjacent the top surface 39 of the panel 15 and the flange 38 being between the flange 37 and the bottom surface 40. 25 Wi reference to Figure 5, the flanges 37 and 38 define a square groove 41 which has a base 42 and a pair of side walls 43. The groove 41 is provided to receive projections 44 (see Figure 2), of the upstanding members 24 and 25. The groove 41 is shaped to closely receive the projections 44. 30 To facilitate receipt of the projections 44 within the grooves 41 in the manner described above whereby the panel 15 is rotated into engagement with the connecting rails 20, a surface of the flange 38 is curved as shown in Figures 5 and 6. It will be appreciated that by curving the surface 45, the projection 44 will ride over the flange 38 more easily than if the surface 45 was square as in the prior art.

12 It will be appreciated, that the curved surface 45 could be a planar surface which is inclined rather than a curved surface, or it could be a combination of both. 5 Testing has shown that the adoption of a curved surface 45 as shown in Figures 5 and 6 can increase the ease of insertion of a panel 15 into a connecting rail 20. Thus, less effort is required to install a panel 15, but once installed, the panel 15 is held as securely as it is in prior art arrangements in which the curved surface 45 is not provided. Given that panels are often required to be replaced, an increase in the 10 ease in which this replacement occurs is advantageous. Panels of the kind shown in the figures discussed above are generally removed from connection to connecting rails through a sequence of removal steps illustrated in Figures 8 to 13. In Figure 8, a tool T, usually a screwdriver, is inserted between the 15 retaining strip 28 and the upper surface of the panel 15 to lever the locking leg 27 of the retaining strip 28 out of the opening 26 of the connecting rail 20. Figure 9 shows the retaining strip partly lifted by the tool T and with the locking leg 27 starting to be released from the opening 26. Continued leverage by the tool T allows complete release of the locking leg 27 from the opening 26. That release only needs to occur in ?0 a section of the retaining strip 28, such as at one end of the strip 28. Once a portion of the locking leg 27 has been released from the opening 26, the retaining strip 28, which is usually a long length of polyurethane strip extending along a large number of panels (see Figure 1), can usually be pulled by hand to remove it completely along its length. 25 With the retaining strip 28 removed, Figures 10 to 13 show the tool T being inserted between the upstanding member 25 of a connecting rail 20 and the facing edge of the panel 15. The tool T is inserted to enter the groove 41 of the panel 15 (see Figures 5 and 6) and to deflect the upstanding member 25 inwardly, so that the projection 44 of 30 the upstanding 25 is dislodged from the groove 41. As shown in Figure 12, the tool T is then inserted further to a point just past the flange 38 of the panel edge, and anticlockwise movement of the tool T can then lever up the panel 15 for removal as shown in Figure 13.

13 Returning to Figures 4, 6 and 7, the present invention employs a gap G in each of the flanges 37 and 38 to facilitate insertion of the distal end of the tool T. A plurality of gaps G is evident in Figure 10. 5 To ensure that damage to the panel by the levering movement is minimised or eliminated, the gap G in each of the flanges 37 and 38 includes curved side walls 48. The curved side walls minimise the stress concentration that can occur when the levering movement through the tool T takes place and thus limits tearing of the 10 flanges 37 or 37. The invention described herein is susceptible to variations, modifications and/or additions other than those specifically described and it is to be understood that the invention includes all such variations, modifications and/or additions which fall within 15 the spirit and scope of the present disclosure.

Claims (20)

1. A screen panel having a generally square or rectangular shape defining a first pair of substantially parallel edges and a second pair of substantially parallel edges, 5 and generally planar top and bottom faces, the panel including a plurality of screening openings extending through the panel between the top and bottom faces, the first pair of edges each being arranged to engage a respective fixing member that is employed to secure a panel in place on a screen deck frame of an ore screening apparatus, at least one of the first pair of edges including a pair of spaced apart generally parallel 10 flanges which extend from the edge and which define a groove therebetween, the groove being provided to accept a projection of a fixing member of an ore screening apparatus, a first of the flanges being located at or towards the top face and a second of the flanges being located between the first flange and the bottom face, the second flange having a first face that defines a surface of the groove and a second face on 15 the other side of the flange that that is inclined in a direction from the edge of the panel from which the flange extends towards the groove so that the second flange can be pushed into engagement with the fixing member projection and the projection will ride along the inclined face prior to the projection entering the groove. 20

2. A screen panel according to claim 1, the inclined face being a planar face.

3. A screen panel according to claim 1, the inclined face being a curved face.

4. A screen panel according to claim 3, the inclined face being of a constant 25 curve.

5. A screen panel according to claim 1, the inclined face being a combination of a curved and a planar face. 30

6. A screen panel according to any one of claims 1 to 5, the inclined face extending from adjacent the surface of the edge of the panel from which the second flange extends. 15

7. A screen panel according to any one of claims 1 to 5, the inclined face extending from a position spaced the surface of the edge of the panel from which the second flange extends. 5

8. A screen panel according to any one of claims 1 to 7, the groove being defined by a base and by a pair of spaced apart substantially parallel facing walls of the first and second flanges, the second flange having a top surface extending from the groove wall and the inclined face extending from the top surface. 10

9. A screen panel according to claim 8, the top surface being substantially perpendicular to the top and bottom faces of the panel.

10. A screen panel according to any one of claims 1 to 7, the groove being defined by a base and by a pair of spaced apart substantially parallel facing walls of the first 15 and second flanges, the inclined face extending from the groove wall of the second flange.

11. A screen panel according to any one of claims 1 to 10, the first flange of the pair of flanges including a gap for the insertion of a panel removal tool into the groove. 20

12. A screen panel according to claim 11, each of the flanges of the pair of flanges including a gap for the insertion of a tool, the respective gaps being generally aligned so that the tool can be inserted through the gap of the first flange and into the gap of the second flange. 25

13. A screen panel according to claim 12, the gap of the second flange extending completely through the second flange.

14. A screen panel according to any one of claims 11 to 13, the gap of the first 30 flange including side walls spaced apart lengthwise of the first flange and the side walls being curved. 16

15. A screen panel according to any one of claims 11 to 14, the gap of the second flange including side walls spaced apart lengthwise of the second flange and the side walls being curved. 5

16. A screen panel having a generally square or rectangular shape defining a first pair of substantially parallel edges and a second pair of substantially parallel edges, and generally planar top and bottom faces, the panel including a plurality of screening openings extending through the panel between the top and bottom faces, the first pair of edges each being arranged to engage a respective fixing member that is employed 10 to secure a panel in place on a screen deck frame of an ore screening apparatus, at least one of the first pair of edges including a pair of spaced apart generally parallel flanges which extend from the edge and which define a groove therebetween, the groove being provided to accept a projection of a fixing member of an ore screening apparatus, a first of the flanges being located at or towards the top face and a second 15 of the flanges being located between the first flange and the bottom face, the first flange of the pair of flanges including a gap for the insertion of a panel removal tool into the groove, the gap of the first flange including side walls spaced apart lengthwise of the first flange and the side walls being curved. 20

17. A screen panel according to claim 16, each of the flanges of the pair of flanges including a gap for the insertion of a tool, the respective gaps being generally aligned so that the tool can be inserted through the gap of the first flange and into the gap of the second flange. 25

18. A screen panel according to claim 17, the gap of the second flange extending completely through the second flange.

19. A screen panel according to any one of claims 16 to 18, the gap of the second flange including side walls spaced apart lengthwise of the second flange and the side 30 walls being curved.

20. A screen deck comprising plurality of screen panels according to any one of claims 1 to 19.