AU2012201297B2 - Screening apparatus and methods - Google Patents

Abstract

A screening apparatus 10 including a plurality of spaced apart beams 11 and a plurality of screen panels 15 mounted to form a broad screening surface. The panels 5 15 are mounted to the beam 11 by fixing members 20, that extend in the longitudinal direction of the beams 11 and that are fixed to the beam 11 to engage opposite side edges of the panels 15. The fixing members 20 include a pair of projections 34 and 35 that extend through openings 48, 49 in the beams 11 and each projection 34, 35 being engaged on the underside of the beams 11 by a releasable connector 55. The 10 openings 48, 49 through which the projections 34, 35 extend are of greater diameter than the outside diameter of the projections 34, 35, so that the projections 34, 35 are a loose fit within the openings 48, 49. 4Ulenams, tn' s lli'4 It& sll % A nl N, K\v clq V 0 ON & on % 14M n& % %% S1,4% IV% w% tA v v v ,%i ,%v sl %S&11% '%1 X kl % It It % § 0 n % tNv),Vlv % 1%, 1 1%, 'V& CN W Wv 10 M 'mox% v n4v y v y N % % S k% N LO llv 04 LO 0) C\1 co

Description

P/00/011 Regulation 3.2 AUSTRALIA Patents Act 1990 ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT Invention Title: SCREENING APPARATUS AND METHODS 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 BYC 2 SCREENING APPARATUS AND METHODS FIELD OF THE INVENTION The present invention relates generally to apparatus for screening, separating or 5 grading materials, principally for use in the mining industry. The present invention is particularly directed to a system for fixing screen panels to the support frame of a vibratory screening machine. The apparatus is applicable for screening, separating and grading mining ores and other materials, and it will be convenient to hereinafter describe the invention in relation to that use. It is to be appreciated, however, that the 10 invention is not limited to such apparatus and use. BACKGROUND OF THE INVENTION A reference herein to a patent document or other matter which is given as prior art is not to be taken as an admission that that document or matter was known or that the 15 information it contains 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 mining ores and 20 comprises an 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 an example of such a screen panel, 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 ores or materials typically being screened, and thus the screens require periodical replacement. This presents a difficulty with the attachment Clioname> 3 of the panels to the deck frame, as the attachment must be secure and robust, but preferably should also be releasable in a manner that is quick and easy. Systems have been developed in the past for fixing screen panels to a support frame 5 of a screening deck, whereby individual panels can be removed and replaced when worn. One system used for fixing screen panels to a support frame is disclosed in Australian patent 654091. The system of that patent provides an elongate U-shaped 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 10 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 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 15 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 maintain engagement between the connection elements when required. !0 The above fixing system performs generally satisfactorily. However, one disadvantage is the relatively complex configuration of the outer side surfaces of the connection portions and the side edge faces of the screen panels provided by the connection elements. That complexity can add to the cost of production of the screen panels. In addition, the connection elements can sometimes be susceptible to dirt 25 accumulation during use and/or storage. That accumulation must be removed before complete and proper interconnection of the connection elements can be achieved during screen panel installation, in turn leading to delays or difficulties with that installation. 30 Where the removal of a panel from a deck is not straight forward and quick, the maintenance personnel can often look for alternative methods of removal that quickly release the panel from the deck even though those methods might have other drawbacks. For example, it is known for maintenance personnel to cut out a portion of the moulded plastic material between the steel frame of a screen panel and to lift <filename> 4 the panel forcibly from the deck by crane or other lifting equipment. This meets the objective of quick removal but because it destroys the components fixing the panel to the frame of the deck, some of those components can be discharged into the screened material below the deck, thereby polluting that material with foreign matter. 5 That foreign matter can be plastic pins for example. End users of the screened material dislike the material they purchase polluted in this manner. In addition, the installation of a complete set of panels to a screening deck requires precise alignment of the panels adjacent to each other, so that the deck does not 10 include gaps between adjacent panels. In fine screening applications, gaps between panels can provide a pathway for material to flow through the deck that would otherwise be too large to pass through the screening openings in the panels. Thus, where the panels are not aligned precisely, the screened material will potentially include material that is of a different and larger grade to that intended. 15 Also, gaps that exist between panels can allow ingress of fine material ("fines") into the mechanisms that are used to fix the panels to the screening deck. This can have two disadvantageous consequences. Firstly, with the vibratory machine vibrating, the fines act as an abrasive against the fixing mechanism, often causing it to wear and M thus loosen, and eventually to fail. Secondly, the fines can become highly compressed between components, such as in gaps created by wear, due to the constant vibration and impact of ore in that condition, which can hinder the removal of panels and their fixing mechanisms. The compressed fines can also form layers that have to be removed before new parts are installed and removal can be time 25 consuming and difficult. Applicant has recognised the desirability to provide a screen panel fixing system which is simplified compared to some of the prior art arrangements and which provides for quick or quicker release of screen panels from a screen deck. Applicant 30 has also recognised the desirability of a system that allows for some flexibility in the positioning of the panels in a deck, so that the panels can be aligned to eliminate gaps between adjacent panels. <rdename> 5 SUMMARY OF THE INVENTION In one form of the invention, there is provided a screening apparatus, including: a plurality of spaced apart, substantially parallel elongate beams, a plurality of screen panels mounted to the beams to form a broad screening 5 surface, each of the panels being generally square or rectangular to define four side edges and the panels being mounted so that facing side edges of adjacent panels are in close facing relationship, each panel being mounted to a pair of beams along opposite side edges to bridge between a two adjacent beams, the panels being mounted to the beams by elongate fixing members that 10 extend in the longitudinal direction of the beams and that are fixed to the beams and engage opposite side edges of the panels, the fixing members including a pair of projections that extend through openings in the beams from an upper side of the beams, each projection being engaged on the underside of the beams by a releasable connector to releasably connect the fixing members against release from 15 the beams, the openings through which the projections extend being of a greater diameter than the outside diameter of the projections, so that the projections are a loose fit within the openings. 20 A screening apparatus according to the above form of the invention has various advantages, in particular that it allows shifting movement of the panels fixed to the fixing members on the beams, by the openings of the beams being of a greater diameter than the outside diameter of the projections of the fixing members. This allows the panels to be shifted relative to one another and relative to the beams on 25 which they are mounted, to ensure close fitting and aligned connection or engagement between side edges of adjacent panels. This form of the invention minimises or even eliminates the prospect of misalignment between panels of a screening deck. In some prior art decks, the panels are fixed in 30 place once they are fixed to the beams. Accordingly, any inaccuracy in the fixing arrangements employed with those panels could leave gaps between the panels or misaligned panels. For reasons given earlier herein, misalignment of panels can result in inefficient performance of the screening deck. In the present invention, once the panels are fitted to the beams through the fixing members, the panels can still be crde.mt> 6 shifted relative to the beams, albeit only through a small amount of movement. That amount of movement however can be enough to ensure that the panels engage properly along side edges thereof and in proper alignment, as required for better performance. 5 The amount of movement of panels on the beams can be within the range of above 0 to 8mm. The movement can be in any direction by providing round openings through the beams. Alternatively, the openings could be slots which are other than round if movement in a particular direction should be greater than movement in another 10 direction. In this latter form of the invention, a slot which allows movement perpendicular to the lengthwise extent of the beams could be provided within one range, and movement longitudinally of the beams could be provided in a different range. Thus, the invention provides flexibility to provide different levels of movement of the fixing members relative to the beams as considered suitable for the particular 15 screening deck being manufactured. In some forms of the invention, the projections have an engagement portion for engagement by the releasable connector which forms a shoulder facing the underside of the beam. A portion of the releasable connector can be inserted between and in !0 engagement with the underside of the beam and the shoulder to fix the fixing members to the beams. The arrangement can be a wedge arrangement so that the releasable connector applies a load to the fixing member through the shoulder tending to pull the projection through the opening. By appropriate selection of the materials of the projections and the connector, the load can be permanent, so that the 25 releasable connector continues to apply the load for the time it remains in place. This advantageously enhances secure positioning of the fixing member to the beam. The shoulder can take any. suitable form and for example, it can be an annular shoulder formed between first and second cylindrical sections, in which the second 30 cylindrical section is of a greater diameter than the first cylindrical section. In this form, the projections are circular, and while that is preferred, the shape of the projections can be other than circular. For example, the projections could be oval shaped, or they could include cylindrical and non-cylindrical sections. For example, to renamee> 7 create a shoulder, a cylindrical section could be connected to a non-cylindrical section to create a step between the sections with the shoulder being formed by the step. It is also possible to create a shoulder by forming a groove in the wall of the 5 projection, and then have the releasable connector include a portion which extends into the groove. The groove could be an annular groove, or a short section of groove formed in a portion of the projection wall. A pair of grooves on opposite sides of the projection could be provided. 10 In the above form of screening apparatus, the diameter of the openings in the beams can be greater than the first cylindrical section, but smaller than the second cylindrical section, or the diameter of the openings can be greater than each of the first and second cylindrical sections. Where the diameter of the openings is greater than the first cylindrical section, but smaller than the second cylindrical section, the second 15 cylindrical section can have a substantially conical leading end to assist forcing of the second cylindrical section through the opening. In some forms of the invention, the releasable connector is termed a "locking clip" and while different forms of locking clip are disclosed below, is not intended that these !0 particular forms of a releasable connector excludes other forms of releasable connectors. The locking clip can thus take any suitable form, but in one form includes a pair of arms which are spaced apart to define an opening having an open end and a blind end, for receipt of a projection of the fixing members. The spacing between the arms can define a particular shape of opening to engage the side surfaces of the 25 projection, such as to snugly receive the outer surface of the projection, and for a cylindrical projection, the opening can be part circular. The open end of the opening can be narrower than the outside diameter of the projection to cause the arms to splay apart and then to recover as the narrow section of the opening passes the projection and the projection is received in the wider portion of the opening. This 30 provides a form of snap-fit arrangement between the locking clip and the projection so that the locking clip resists withdrawal from about the projection laterally to the axis of the projection. <rdename> 8 The locking clip can be otherwise formed and can, for example, include a closed opening which includes a continuous periphery, i.e. which does not have an open end of the kind described above. Thus, the locking clip can be formed as a plate with a bore or an aperture through the plate. The plate can engage a shoulder of the kind 5 described above and can be a push fit onto the projection, so that the edges of the opening resiliently distort to pass over the shoulder and recover to engage the shoulder surface. Alternatively, a circlip arrangement can be employed. Forms of releasable connectors which are different from the locking clips discussed 10 above include pins or plates that extend through an opening in the projections of the fixing members, or screws that also extend through the same form of openings and to which can be fixed threaded nuts at one end. These arrangements can also operate to apply a load to the fixing member tending to pull the projection through the opening in a similar manner to the locking clip discussed above and the load can be 15 permanent so that the releasable connector continues to apply the load for the time it remains in place. The releasable connector or the locking clip can also include facility for assisting release of the connector from connection with the projection of the fixing member. In !0 some forms of the invention, a projection is provided that can be engaged by a suitable tool. Alternative arrangements can include. openings in the releasable connector that can be engaged by a tool. Where the releasable connector is a locking clip of a form that includes arms and a 25 projection for assisting release of the clip from connection with the projection of the fixing member, the arms can extend from one end of the locking clip in generally the same plane and the projection can extend from that end laterally to the plane of the arms. The projection can be engaged by any suitable tool such as a mallet or a hammer, or a screwdriver or the like. No specific form of tool is required, while 30 removing the locking clip requires no particular skill. Thus, the locking clip can be inserted and removed relatively easily. This can also apply to other forms of releasable connector. <flename> 9 The fixing members can alternatively be referred to as "fixing rails" and are elongate and can extend for any suitable length relative to the side edges of the panels. It is preferred however, that the length of the fixing members is substantially the full length of the side edges of the panels, so that the side edges are fully or at least 5 substantially fully supported. It is preferred that the projections of the fixing members are positioned towards each longitudinal end of the fixing members. In another form of the invention there is provided a method of assembling a screening apparatus, the apparatus including: 10 a plurality of spaced apart, substantially parallel elongate beams which include a plurality of openings, a plurality of screen panels for mounting to the beams to form a broad screening surface, each of the panels being generally square or rectangular to define four side edges, 15 elongate fixing members for fixing the screen panels to the beams, the fixing members including projections for extending through the openings of the beams, the openings of the beams being of a greater diameter than the outside diameter of the projections, so that the projections are a loose fit within the openings the method including the steps of mounting a pair of fixing members to a pair of 20 beams by inserting the projections of the fixing members through the openings of the beams, mounting a screen panel to the pair of fixing members, shifting the panel and the fixing members relative to the beams so that each side edge of the panel that faces a side edge of an adjacent panel is in abutting contact with the facing side edge of the adjacent panel, and inserting a releasable connector to engage each projection 25 on the underside of the beam to lock the fixing members against release from the beams. The materials that are used to form the components of the invention can be selected from any suitable materials. Polyurethane is a material that is suitable for panel 30 construction and for construction of the fixing members. Other polymer materials can also be used as can metal, plastics and rubbers or any other suitable material. The present invention further extends to a fixing member, a screen panel and a releasable connector for the screening apparatus discussed above.

10 For a better understanding of the invention and to show how it may be performed, embodiments thereof will now be described, by way of non-limiting example only, with reference to the accompanying drawings. 5 BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates a portion of a screening deck according to one embodiment of the invention. 10 Figure 2 illustrates a fixing member according to the present invention. Figure 3 is a cross-sectional view of a screen panel and fixing members connected together. 15 Figure 4 is a view of a section of a longitudinal beam with a fixing member fitted thereto. Figure 5 is a perspective view of a releasable connector in the form of a locking clip for use in the screening deck of Figure 1. 20 Figure 6 is an underneath view of the screening deck of Figure 1. 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 each of which is formed from an angle of steel having a long portion 12 and a short portion 13 disposed substantially at right angles. While the beams extend in the longitudinal direction of the screening deck 30 10, the beams can equally extend perpendicular to the beams 11 and the invention applies to that form of screening deck as well. The beams 11 in a screening deck can be of any length, such as increasing from 4' to 28' in 2' increments. The width dimensions likewise can be of any length, such as increasing from 2' to 14' in 2' increments. Metric sizes in screening decks are less common than imperial sizes.

11 The deck 10 illustrated in Figure 1 is a portion of a deck only and does not show the side edge beams that define the edge of the deck. The portion of the deck that is shown in Figure 1 is sufficient however to describe the invention. Six beams 11 are 5 illustrated in Figure 1. In current machinery, the beams 11 are often spaced an imperial foot apart thus requiring nine beams for an 8' width. The beams 11 extend parallel to one another and support screen panels 15 on the upper face of the short portion 13 of each beam 11. The panels illustrated in Figure 1 10 can be of any suitable size, but a common size is an imperial square foot (305mm x 305mm). However, alternative sizes of panels can be employed, such as 1' x 2' (305mm x 610mm). As indicated above, the screening deck is one part of the overall screening apparatus. 15 The deck is supported on a frame and is connected to a vibration generator. 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 required to be secure, the preference is also that the panels be easily releasable to facilitate replacement. 20 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 large to very small depending on the size of the screened material which is to be produced. 25 Typically, an ore is fed onto one end of the deck 10 and a vibrating arrangement vibrates the deck 10 tending to shift the ore from one end to the other, with some of the ore passing through the openings of the panels 15 as it travels over the deck. Ore which does not pass through openings in the panels 15 is collected at the trailing end 30 of the deck 10 opposite to the feeding end and can be retreated, such as re-crushed, or it can be used for other purposes or discarded. Figure 1 shows several portions on the deck 10 that do not have panels installed. These vacant portions illustrate that the panels 15 can be removed when they have 12 become worn or otherwise damaged. The portion of the deck 10 marked R 1 shows four missing panels, but otherwise illustrates fixing rails 20 to which panels 15 are attached. The fixing rails 20 are fixed to the upper surface of the short portion 13 of the beams 11 and more detail on the construction of the fixing rails 20 and their 5 connection to the beams 11 will be made later herein. The portion of the deck 10 marked R 2 shows three missing panels, and also shows the upper surface 21 of the short portion 13 of the beams 11 with the fixing rails 20 absent. 10 The screening deck 10 includes panels 15 shown in close proximity to each other. The preference is that the panels 15 actually make contact along their edges so that there are no gaps between the panels when they are fitted. Any gaps between adjacent panels 15 can provide a pathway for the flow of material being screened. In 15 some prior art arrangements, a cover strip has been applied between adjacent panels to overlie the junction at the upper surface of adjacent panels to cover any gaps between them. However, the cover strip added another component to the fixing system of those kinds and therefore was not a satisfactory solution. In the present invention, in order to ensure a close fit between the side edges of the panels 15, a 20 unique form of fixing rail and fixing rail system has been invented. Figure 2 is a perspective view of a fixing rail 20 according to one form of the invention and comprises a top surface 25 which is formed of two inclined surfaces 26 and 27 which meet at an apex 28. The top surface 25 forms part of a head 29 which extends 25 from a web 30 while the web 30 extends from a base 31. The head 29 has a greater lateral extent than the web 30 and so the head overlies the web 30 on each side of the web and as shown in Figure 2, forms a recess 32 with the base 31 on each side of the web 30. 30 The underneath surface 33 of the base 31 is generally planar or flat. It is the surface 33 which rests on the upper surface 21 of the longitudinal beams 11. The base 31 extends laterally beyond the opposite sides of the web 30 and the head 29. The distal edge of the base 31 on each side of the web 30 is formed with an upwardly extending lip 39. The lip 39 is shown as extending fully along the length of the fixing 13 rail 20, although this is not required in all forms of the invention. For example, the lip 39 could be provided only at each end of the base 31 and centrally between each end. Other discontinuous or intermittent arrangements of this kind could be employed. 5 The fixing rail 20 includes a pair of projections in the form of locating posts 34 and 35 that extend from the base 31 away from the head 29. The post 34 comprises a first cylindrical section 36 and a second cylindrical section 37. The first cylindrical section 36 is of greater length but reduced diameter compared to the second cylindrical 10 section 37. Accordingly, a step or shoulder 38 is formed at the junction between the first and second cylindrical sections 36 and 37. The construction of the post 35 is identical to the post 34 as discussed above. The configuration of the fixing rail 20 is such as to capture a side edge of a panel 15 15 as shown in cross-section in Figure 3. In that figure, a panel 15 is shown connected between a pair of fixing rails 20 which are each of the same identical form. The side edges 40 of the panel 15 include an inclined face 41 which is inclined at approximately the same angle as the inclined surfaces 26 and 27 of the fixing rails 20. The side edges 40 further include recesses 42 to accept a portion of the head 29 and 20 they include a projection 43 to fit within the recesses R of the fixing rails 20. By this arrangement, an interconnection is created between the side edges 40 of the panels 15 and one side of a pair of facing fixing rails 20. It can be seen that the inclined face 41 extends to a side surface 44 and this surface 25 44 extends slightly beyond the apex 28 of the fixing rails 20. This slight extension beyond the apex 28 is to ensure abutting and preferably compressive contact between adjacent panels 15. Thus, it will be appreciated that in the arrangement of Figure 3, further panels 15 will be fitted to the sides of the fixing rails 20 not already connected to the illustrated panel 15. Those further panels 15 will have the same 30 construction as the illustrated panel 15 so that they will each include equivalent surfaces 44. Because those surfaces would, without any interference, extend just past the apex 28, the surfaces 44 of adjacent panels 15 will firmly abut each other. Moreover, because the side edges 40 of the panels 15 are of a flexible material, the 14 edges 40 will compress in abutment. This ensures that in side to side contact between adjacent panels 15, gaps are either minimised or eliminated. The construction of the fixing rails 20 and the panels 15 shown in Figure 3 also permit 5 easy installation of a panel 15 into connection with the fixing rails 20. The fixing is made by inserting the projection 43 of one side edge 40 of the panel 15 into the corresponding recess R of the fixing rail 20 with the panel at an angle, for example at 300. The panel 15 is then pivoted about the projection 43 in recess R to bring the other side edge 40 down toward the other fixing rail 20. Because the panels 15 and 10 the fixing rails 20 are made of a flexible material, polyurethane for example, the other projection 43 can be forced into the recess R. The force load is one which any worker would be expected to be able to apply manually. The fitting is thus simple and easy and requires no particular skill. 15 The inclined surfaces 26 and 27 form a ramp for the side edge to slide down as the panel 15 is rotated to bring the projection 43 into the recess R. When the projection 43 is captured in the recess R, the head 29 secures the panel 15 against lifting. The dimensions of the side edge 40 of the panel 15 and of the fixing rail 20 ensure the panels 15 are securely held in place. 20 The fixing rails 20 are fixed to the beams 11 by passing the projections (hereinafter "posts") 34 and 35 through openings 48 and 49 (see Figure 1) in the beam 11. The openings 48 and 49 can be of a greater diameter than each of the first and second cylindrical sections 36 and 37, or the openings can be of a greater diameter than just 25 the first cylindrical section 36. Where the openings 48 and 49 have a greater diameter than the second cylindrical section 37, each of the posts 34 and 35 can pass through the openings 48 and 49 easily. Alternatively, where the opening is of a greater diameter than the first cylindrical section 36 but not the second cylindrical section 37, the posts 34 and 35 are forced through the openings 48 and 49. 30 Figure 4 shows an underneath view of a section 50 of a longitudinal beam 11, with a fixing rail 20 applied to the upper surface 21 of the short portion 13. The post 35 is shown extending through the opening 49. It can be seen that the second cylindrical section 37 has cleared the opening 49 and is spaced below the lower surface 51 of 15 the short portion 13. In the arrangement of Figure 4, the opening 49 is slightly of reduced diameter compared to the second cylindrical section 37. Thus the section 37 must be forced through the opening 49 and in order to facilitate this, the section 37 includes a conical leading end 52. 5 It will be appreciated that the clearance between the first cylindrical section 36 and the opening 49 occurs for each of the locating posts 34 and 35. Thus, when the posts have been inserted through the openings 49, the fixing rails 20 have a degree of movement available to them relative to the beams 11, such as up to 8mm or more. 10 That small amount of movement permits the rails to be moved so that the panels 15 can be shifted as necessary to bring adjacent side edges into abutting contact. That differs from the prior art in which no flexibility of this kind is available. That is, the fixing systems of the prior art often requires precise manufacture of the components, because any inaccuracy could mean that the panels could be inaccurately positioned 15 in the deck, leaving gaps between panels. Because of this, some prior art arrangements employed the cover strips discussed above. In contrast, the present invention permits limited movement of the panels prior to final fixing, so that any inaccuracy in the component manufacture can be accommodated. Advantageously, this movement is in any direction lengthwise or widthwise of the screening deck. 20 In order to fix the fixing rail 20 to the beam section 50, a releasable connector in the form of a locking clip 55 is employed. The locking clip 55 is shown in perspective view on its own in Figure 5 and comprises arms 56 and 57 which extend on either side of a part cylindrical opening 58. The diameter of the opening 58 is sized to 25 snugly receive and engage against the first cylindrical section 36 of each of the posts 34 and 35. The locking clip 55 is formed of a flexible material which allows the arms 56 and 57 to splay outwardly so that the opening can accept the first cylindrical section 36 and to move back in to a position snugly about that section. The material can be polyurethane. 30 Installation of the locking clip 55 is simple. The clip 55 is simply pushed into place about the first cylindrical section 36 between the lower surface 51 of the beam 11 and the shoulder 38 of the locating posts 34 and 35. This can be by finger pressure, or 16 more likely by a suitable tool, e.g. a hammer or mallet. To facilitate ease of installation, the leading edge of the arms 56 and 57 is chamfered on each side. The thickness W of the locking clip 55 can be varied to suit different dimensions of 5 beam and locating post length. What is preferred is that the wall thickness of the locking clip 55 forms a tight fit or a friction fit between the lower surface 51 of the beam 11 and the shoulder 38 of the locating posts 34 and 35. The locking clip is intended to apply a load to the shoulder 38 to fix the fixing rail 20 in place against movement relative to the beam 11. Thus, once the locking clips 55 have been 10 inserted, the fixing rails 20 should no longer have freedom for release of the locating posts 34 and 35 from the openings 48 and 49 of the beams 11. The locking clip 55 includes a release projection 59 which is provided to facilitate release of the locking clip 55 from about the first cylindrical section 36 of the posts 34 15 and 35. Release of the locking clip 55 is required when the fixing rail 20 is to be removed from the beams 11 upon wear or failure. The release is likewise simple as the projection 59 can be gripped by fingers or a suitable tool to physically withdraw the locking clip from the position shown in Figure 4. Once the locking clip 55 is removed, and this is the case in respect of the post 35 shown in Figure 4, the post 35 20 can be withdrawn from the opening 49. Figure 6 illustrates an underneath view of the screening deck 10 of Figure 1 showing the locking clips 55 in position about the posts 34 and 35 of various fixing rails 20. 25 A screening deck 10 is assembled by firstly arranging the beams 11 in position and thereafter fixing the rails 20 to those beams 11. The fixing rails 20 can be positioned and the locking clips 55 applied and the panels 15 then fitted. The preference is to fit the clips 55 to the fixing rails from above the deck 10, rather than from below the deck 10. In fact, for safety reasons, access to the deck 10 from underneath may be 30 restricted so that fitting of the fixing rails 20 must take place from above the deck. With the fixing rails 20 in place, the panels 15 of a first row can be connected to the fixing rails 20. Advantageously, the use of oversize openings 48 and 49 allows movement of the panels and fixing rails relative to the beams 11 so that a snug 17 abutting fit between side edges of adjacent panels can be created. The locking clips 55 can be arranged so as to allow movement of the fixing rails 20 and thus the panels 15 even though the locking clips are in place. The locking clips can resist movement of the fixing rails 20 and the panels 15 but not exclude it. 5 Thus, by the use of the oversize openings 48 and 49, the screening deck 10 can be formed without gaps between adjacent panels 15 and without the need for covers of the kind described above between adjacent panels. This differs from some prior art arrangements, in which the fixing rails 20 are fixed relative to the beams 11 without 10 allowing for movement to ensure abutting engagement between adjacent panels. Because of this, gaps between panels can arise and this can allow screenings which are produced to travel through the deck 10 and into the mechanism below it, or the screenings below it. 15 Moreover, the construction of the fixing rails 20 comprising a central post and a head which can be used to capture the side edge of a panel provides for quick and easy installation of panels to the fixing rails 20. The same arrangement also allows for quick and easy removal of panels, whereby simple insertion of a screw driver or other suitable removal tool at one end of a fixing rail can dislodge the panel from the fixing 20 rail and the panel can thereafter be lifted or rotated out of engagement with the fixing rail. Once disengagement of one side edge of the panel from a fixing rail has been made, the panel can easily be removed out of connection with the other fixing rail. Still further, once a worn or damaged panel has been removed, replacement with a 25 another panel is a simple operation which involves inserting one side edge of the panel into one of the fixing rails and thereafter rotating the panel to fit the other side edge into the opposite fixing rail. The apparatus described in relation to the figures is also very simple, comprising a 30 limited number of parts. In fact, the fixing system simply comprises the fixing rails 20 and the pair of locking clips 55, each of which is identical. Thus, each fixing rail which can fix a pair of side edges of two panels, comprises three parts for installation, being the fixing rail itself and two locking clips. This differs from previous arrangements where a greater number of parts was required and this is disadvantageous from both 18 a manufacturing and storage point of view, and an assembly point of view. In relation to assembly, it needs to be kept in mind that once a screening apparatus is in place in a mining environment, down time of the screening machine for repair or replacement of panels can be costly and therefore a simple system to facilitate quick and easy 5 panel replacement is desirable. Moreover, systems which do not foul the screened material are also desirable. The present invention can provide advantages in each of these areas. The invention described herein is susceptible to variations, modifications and/or 10 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 the spirit and scope of the present disclosure.

Claims (16)

1. A screening apparatus, including: a plurality of spaced apart, substantially parallel elongate beams, 5 a plurality of screen panels mounted to the beams to form a broad screening surface, each of the panels being generally square or rectangular to define four side edges and the panels being mounted so that facing side edges of adjacent panels are in close facing relationship, each panel being mounted to a pair of beams along opposite side edges to bridge between a two adjacent beams, 10 the panels being mounted to the beams by elongate fixing members that extend in the longitudinal direction of the beams and that are fixed to the beams and engage opposite side edges of the panels, the fixing members including a pair of projections that extend through openings in the beams from an upper side of the beams, each projection being engaged on the underside of the beams by a 15 releasable connector to releasably connect the fixing members against release from the beams, the openings through which the projections extend being of a greater diameter than the outside diameter of the projections, so that the projections are a loose fit within the openings. 20

2. A screening apparatus according to claim 1, the projections having an engagement portion for engagement by the releasable connector, the engagement portion forming a shoulder which faces the underside of the beam and a portion of the releasable connector being inserted between and in engagement with the underside 25 of the beam and the shoulder.

3. A screening apparatus according to claim 2, the shoulder being an annular shoulder formed between first and second cylindrical sections, the second cylindrical section being of a greater diameter than the first cylindrical section. 30

4. A screening apparatus according to claim 3, the diameter of the openings being greater than the first cylindrical section, but smaller than the second cylindrical section. 20

5. A screening apparatus according to claim 4, the second cylindrical section having substantially conical leading end that extends away from the underside of the beam. 5

6. A screening apparatus according to claim 3, the diameter of the openings being greater than each of the first and second cylindrical sections.

7. A screening apparatus according to any one of claims 1 to 6, the releasable connector including a pair of arms which are spaced apart to define an opening for 10 receipt of a projection of the fixing members.

8. A screening apparatus according to claim 7, the releasable connector including a projection for assisting release of the releasable connector from connection with the projection. 15

9. A screening apparatus according to claim 8, the arms extending from one end of the releasable connector in generally the same plane and the projection extending from the end laterally to the plane of the arms. 20

10. A screening apparatus according to any one of claims 7 to 9, the opening defined by the pair of arms being open at one end and the open end being narrower than the opening inboard of the open end and the open end being narrower than the outside diameter of the portion of the projection to which the releasable connector is applied. 25

11. A screening apparatus according to claim 10, the opening inboard of the open end being part circular.

12. A screening apparatus according to any one of claims 1 to 11, the fixing 30 members extending for substantially the full length of each of the opposite side edges of the panels and engaging the side edges along substantially their full length, the projections being positioned toward each longitudinal end of the fixing members.

13. A method of assembling a screening apparatus, the apparatus including: 21 a plurality of spaced apart, substantially parallel elongate beams which include a plurality of openings, a plurality of screen panels for mounting to the beams to form a broad screening surface, each of the panels being generally square or rectangular to define 5 four side edges, elongate fixing members for fixing the screen panels to the beams, the fixing members including projections for extending through the openings of the beams, the openings of the beams being of a greater diameter than the outside diameter of the projections, so that the projections are a loose fit within the openings 10 the method including the steps of mounting a pair of fixing members to a pair of beams by inserting the projections of the fixing members through the openings of the beams, mounting a screen panel to the pair of fixing members, shifting the panel and the fixing members relative to the beams so that each side edge of the panel that faces a side edge of an adjacent panel is in abutting contact with the facing side edge 15 of the adjacent panel, and inserting a releasable connector to engage each projection on the underside of the beam, to lock the fixing members against release from the beams..

14. A fixing member for a screening apparatus of any one of claims 1 to 12. 20

15. A screen panel for a screening apparatus of any one of claims 1 to 12.

16. A releasable connector for a screening apparatus of any one of claims 1 to 12, the releasable connector including a pair of arms which are spaced apart to define an 25 opening for receipt of a projection of the fixing members of the screening apparatus of any one of claims 1 to 12.