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.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from Australian Patent Application No. 2011903208 filed on Aug. 10, 2011 which is incorporated herein by this reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to apparatus for screening, separating or grading materials, 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 relation to that use. It is to be appreciated, however, that the invention is not limited to such apparatus and use. 
         [0004]    2. Description of the Prior Art 
         [0005]    The following discussion of the background to the invention is intended to facilitate an understanding of the invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was published, known or part of the common general knowledge as at the priority date of the application. 
         [0006]    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 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. 
         [0007]    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) (also published as U.S. Pat. No. 4,674,251). The plastic moulding forms the major part of the panel and it is in the plastic moulding that the openings for screening are provided. 
         [0008]    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 replacement. This presents a difficulty with the attachment of the panels to the deck frame, as the attachment must be secure and robust, but should also be releasable in a manner that is quick and easy. 
         [0009]    The frame to which screen panels in a screen deck are secured usually comprises a framework of elongate beams. The beams can be of various section, but the present invention has been developed for the connection of the support panels to a top or upstanding edge of a beam. 
       SUMMARY OF THE INVENTION 
       [0010]    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 surface, each of the panels being generally square or rectangular to define four side edges and the panels being mounted adjacent to each other 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 two adjacent beams,   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 an edge of the beams and that engage opposite side edges of the panels, the fixing members including a pair of projections that extend into openings provided in the edge of the beams, each projection being engaged by a locking clip to lock the fixing members against release from the beams,   the openings into 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 to allow movement of the fixing rails and the screen panels before the projections are engaged by a locking clip to lock the projection against release from the opening.   
 
         [0015]    The present invention advantageously provides a system for connecting fixing members to an upper edge of supporting beams that form part of a screening deck. This system can be used with beams of any cross section that present an upper edge for connection of the fixing rails. In most cases, the beams will be planar beams, which extend in a single plane only and these are known in the industry sometimes as “stringers”. 
         [0016]    The present invention is also advantageous in providing a relatively simple method of connection between the fixing members and the elongate beams, while it also allows for ease in removal of the fixing rails when required, by disengagement of the locking clips with the projections of the fixing members. Thus, when necessary, the fixing members can be removed and replaced relatively easily, and this might occur for example, if the fixing members are damaged or worn. Damage can occur in some circumstances by the screening media, or they can be damaged when panels are being removed or inserted. In general, damage or wear of a fixing member occurs infrequently, and therefore the need for removing a member is not regular, but when it occurs, it is desirable that removal be made quickly and easily. 
         [0017]    The invention also provides benefits for the installation of fixing members, by enabling the fixing member a relatively small amount of movement on the beam to which it is fixed so that screen panels can be accurately aligned to form a continuous screening surface. In particular, by the employment of openings into which the projections extend that are of greater diameter than the outside diameter of the projections, so that the projections are a loose fit within the openings, the panels that are fixed to the fixing members on the beams can be shifted a small amount on the supporting deck. Thus, any misalignment between adjacent screening panels can be corrected. The amount of shifting movement need only be minor, as the initial accuracy of positioning of the panels on the screening deck is usually quite good. The shifting movement is generally required to correct small misalignment to ensure that where faces of adjacent screening panels that are intended to engage, the faces engage properly. 
         [0018]    The shifting movement of the present invention is not available in some prior art decks, in which the panels are fixed in place once they are fixed to the beams. In those prior art decks, any inaccuracy in the fixing arrangements employed with the panels can leave gaps between the panels. This can result in inefficient performance of a screening deck by allowing screening material to pass through gaps within the deck surface with that material being larger than the screened material is intended to be. There can also be an effect on the structural integrity of the screen deck through the misalignment of the screening panels. 
         [0019]    The amount of movement of the panels on the beams can be within the range of between 0-8 mm. Advantageously, by providing round openings in the edge of the beams, the movement can be in any direction. Alternatively, the openings could be formed other than round, such as in the form of elongate slots, if alternative or greater movement in a particular direction is required. 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 and directions of movement of the fixing members relative to the beams as considered suitable for the particular screening deck being manufactured. 
         [0020]    The openings provided in the edge of the beams can be provided in any suitable form. In some forms of the invention, annular rings are provided to form the openings and those rings are fitted to the edge of the beams. The annular rings can be circular but this is not essential. In some forms of the invention, the rings are fitted into slots which are formed in the edge of the beams. The annular rings can include an annular wall and in that form of the invention, the wall can include an opening through which the locking clip extends for engagement with a projection. 
         [0021]    In other forms of the invention, the projections can extend through the annular rings so that a portion of the projections project from the opposite end of the ring to which they entered. In these forms of the invention, the locking clip can be arranged to engage that portion of the projection that extends through or projects from the annular ring. In these forms of the invention, an opening which extends through the wall of the annular ring is not required. 
         [0022]    The annular rings can be formed of two or more parts. In these forms of the invention, the first part can be fixed into a slot in the edge of the beam and the second part can be connected to the first part such as by threaded engagement, bayonet fitting or snap fit. Advantageously, in some prior art arrangements, threaded annular rings are already employed and form a first part according to this form of the invention, so that the present invention can be easily retro-fitted by the application of a threaded second part. 
         [0023]    The first part can be fitted to the edge of the beam in any suitable manner, and in some forms of the invention, a weld is employed to fit the first part into a slot in the edge of the beam. 
         [0024]    In forms of the invention in which the annular ring is formed of two parts, the second part of the annular ring can include an opening through which the locking clip extends. In some forms of the invention including a two part annular ring, at least two openings can be provided for acceptance of the locking clip. This is advantageous, as the connection of a second part to a first part does not necessarily mean that the opening through the second part will always be positioned for good access by the locking clip. For example, if the first part is an internally threaded annular ring and the second part is threaded into engagement with the first part, the final position of the opening in the second part will not be established until the threaded engagement is complete. Thus, a single opening in the second part might be positioned other than optimally for acceptance of the locking clip and the provision of a second or more than two openings in the second part can allow an installer of the locking clip to select the most conveniently positioned opening through which to insert the locking clip. 
         [0025]    While some forms of the invention include two openings in the second part, it is equally applicable to include three or four openings, or more as required. The openings can be spaced apart in any suitable spacing, but most likely they will be spaced equidistantly apart. 
         [0026]    The annular rings can be positioned within a slot formed in the edge of the beams either to project to a position below the beam edge, flush with the beam edge or above the beam edge. Where the annular rings project to a position above the beam edge, the fixing members can include recesses into which the projecting portion of the annular rings is received. 
         [0027]    The locking clips can engage the projections in any suitable manner. In some forms, the locking clips include a space within which the projection is engaged. That space can, in some forms of the invention, be formed by a pair of spaced apart arms which define a space therebetween, which includes an entrance portion and an engagement portion. The arms can be flexible, so that they can shift outwardly from a locking position in order to accept a projection through the entrance portion and can return to the locking position on receipt of the projection into the engagement portion. The invention contemplates an arrangement in which the locking clip is positioned in the opening prior to the projection being inserted into the opening. In that arrangement, the projection is forced into the opening past the locking clip. Alternatively, the invention also contemplates an arrangement in which the projection is first inserted in to the opening of the beam and the locking clip is then itself inserted in the opening to engage the projection. In the latter arrangement, the form of the locking clip which has a pair of spaced apart arms as described above is particularly appropriate for use. 
         [0028]    In alternative forms of the invention, the locking clip can include an opening which is closed, i.e. which includes a continuous periphery and which does not include an open or entrance end. Thus, the locking clip can be formed as a plate with a bore or aperture through the plate. In this form of the locking clip, the projection can be pushed through the bore or aperture with the edges of the bore or aperture flexing or distorting resiliently to allow the projection to pass through and recovering so as to lock the projection from release from the beam. The locking clip can achieve this such as by engaging or being engageable with an abutment of the projection. 
         [0029]    The projections of the fixing members extend from the base of an elongate rail of the fixing member that extends along the edge of the beam. In addition, the projections can include a shoulder which faces the base or the rail. The locking clip can then engage the projection between the shoulder and the rail so that movement of the projection in a direction out of the opening is prevented by engagement of the locking clip and the shoulder. 
         [0030]    The projections of the fixing members can be formed as cylinders and can include an annular recess which is coaxial with the cylinder and the shoulder described above can be a face of the recess which faces the rail. The annular recess can be of any suitable cross section, such as square or U-shaped, and the shoulder described above is the side of the recess that faces upwardly when installed. In these forms of the invention, the locking clip can engage within the recess and while that engagement can be a loose fit, it can also be a friction or even an interference fit, to securely fix the fixing members to the beam. 
         [0031]    While the shoulder can be formed as part of an annular recess as discussed above, it can alternatively be formed as a groove in a section of the wall of a projection, or even a lateral projection which extends laterally outwardly from the surface of the projection. 
         [0032]    If an annular recess is provided, then the projection will comprise a section of reduced diameter (the annular recess) which is formed between sections of greater diameter. The diameter of the opening in the beam edge can then be of a greater diameter than the diameter of the sections of the projections on either side of the annular recess so that the projections are a loose fit in the openings as required. 
         [0033]    It is a feature of the present invention that the locking clip can be arranged so that it is releasable from engagement with a projection so that the fixing member can be released from a beam. Thus, the locking clip can be insertable into the opening formed in the edge of the beam to engage a projection and can be withdrawable from the opening to disengage the projection. 
         [0034]    The fixing members can extend for substantially the full length of each of the opposite side edges of the panels so that they can engage the side edges along substantially their full length. In this arrangement, the projections can be positioned towards each longitudinal end of the fixing members. 
         [0035]    The present invention also extends to a method of assembling a screening apparatus, the apparatus including:
   a plurality of spaced apart, substantially parallel elongate beams which include a plurality of openings formed in an upwardly facing edge of the beams,   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,   elongate fixing members for fixing the screen panels to the beams, the fixing members including projections for extending into 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 beams by inserting the projections of the fixing members into 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 alignment with and in abutting contact with the facing side edge of the adjacent panel, and inserting a locking clip to engage each projection so as to fix the fixing members in place on the beam.   
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0041]    In order that the invention may be more fully understood, some embodiments will now be described with reference to the figures in which: 
           [0042]      FIG. 1  illustrates a portion of a screening deck according to one embodiment of the invention. 
           [0043]      FIG. 2  illustrates a portion of a beam of a screening deck to which the present invention applies. 
           [0044]      FIG. 3  illustrates the beam portion of  FIG. 2  with an additional component fixed thereto. 
           [0045]      FIG. 4  is a view of a portion of the beam shown in  FIGS. 2 and 3 , with a locking clip applied. 
           [0046]      FIG. 4   a  is a perspective view of a locking clip according to the invention. 
           [0047]      FIGS. 5 and 6  are perspective and side views respectively of a fixing member according to the invention. 
           [0048]      FIG. 7  is a view of an end portion of the fixing member of  FIGS. 5 and 6 . 
           [0049]      FIG. 8  is a cross sectional view showing a pair of screen panels fixed to a fixing member and beam. 
           [0050]      FIG. 9  is a perspective view of the beam portion of  FIG. 3 , with a fixing member attached. 
           [0051]      FIG. 10  is a side view of the beam portion of  FIG. 9 . 
           [0052]      FIG. 11  is a perspective view of the beam portion of  FIG. 9  with locking clips installed. 
           [0053]      FIG. 12  is an underneath view of the screening deck of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0054]    With reference to  FIG. 1 , a portion of a screening deck  10  is illustrated comprising a plurality of elongate, longitudinal beams  11  each of which is formed from a planar beam section, sometimes known as a “stringer”. Each of the beams  11  extends in the longitudinal direction of the screening deck  10 , although they can equally extend in a direction perpendicular to the beams  11 . 
         [0055]    The deck  10  illustrated in  FIG. 1  is a portion of a deck only and does not include side edge beams that define the edge of the deck and other components of the deck. These are not necessary to understand the operation of the invention. 
         [0056]    The beams  11  extend parallel to one another and present an edge  12  ( FIG. 2 ) to which a plurality of fixing members  13  ( FIG. 1 ) are fixed to support the screen panels  14 . 
         [0057]    As indicated above, the screening deck  10  is one part of an overall screening apparatus. In practice, the deck  10  is supported on a frame and the entire apparatus is vibrated so that the screen deck  10  vibrates. Openings or apertures in the screen panels  14  allow certain sizes of screening material to fall through and others to remain on top of the deck. Ultimately, the aim of the screening exercise might be to collect the screened material which passes through the panels  14 , or the material which remains on top of the panels  14 , or both. The process is normally adopted in the mining industry either to separate or sift mined ore, or to size or grade such ore. 
         [0058]      FIG. 1  shows several portions of the deck  10  that do not have panels installed. Those portions without panels are intended to illustrate the fixing members  13  that are applied to the edges  12  of the beams  11  shown in  FIG. 2 . In addition, those portions show how the screen panels  14  are connected along opposite edges to the fixing members  13 . 
         [0059]    The screen panels  14  form a screening deck in which facing side edges of adjacent panels are in close facing relationship, or most preferably, are in abutting engagement. By this latter arrangement, the screen panel can be assembled so that it does not include gaps between adjacent panels, which can otherwise allow ingress of screening material between panels rather than just through the openings of the screen panels. If that ingress occurs, the screening material can come into contact with components of the screen deck during vibration and can damage or wear those components prematurely. In addition, material that enters any gaps between adjacent panels might pass through the screening deck even though it is oversized relative to the openings in the screen panels and this can compromise the screened material. 
         [0060]    It will be evident from the discussion which follows, that the accuracy of fitting between adjacent panels is enhanced by the present invention. It will be evident that the fixing member  13  permits slight movement of the screen panels  14  relative to one another so that accurate alignment between adjacent panels can be achieved. 
         [0061]    With reference now to  FIGS. 2 and 3 , a short section of a beam  11  is illustrated to illustrate one embodiment of the present invention. The beam  11  includes an upward facing edge  12  and a pair of annular rings  18  and  19  which define a central opening for receipt of a projection of a fixing member as will be described later herein. In  FIG. 2 , the annular ring  18  is shown as having a two part construction, comprising a first part  20  and a second part  21 . In  FIG. 2 , only a first part  22  of the annular ring  19  is shown to facilitate better understanding of the construction of the annular rings. In  FIG. 3 , the annular ring  19  is shown including both of its first and second parts  22  and  23 . 
         [0062]    The first parts  20  and  22  of the annular rings  18  and  19  are formed as annular rings which are inserted into slots  24  ( FIG. 2 ) formed in the edge  12  of the beam  11 . As illustrated in  FIG. 2 , the upper end of the first part  22  of the ring  19  is below the edge  12 , while the addition of the second part  23  of the ring  19  as shown in  FIG. 3  brings the annular ring  19  to a position above the edge  12 . This arrangement could be altered so that the upper end of the second part  23  is below the edge  12  or is flush with the edge. The arrangement of the ring  18  is the same as the ring  19  in terms of the position of the first and second parts  20  and  21  relative to the edge  12 . 
         [0063]    The first parts  20  and  22  are metal and are welded into the slots  24 . While not shown, the inner surface  25  of the first parts  20  and  22  is threaded and the second parts  21  and  23  include a complementary threaded outer surface (also not shown) for threaded engagement between the first and second parts of each annular ring  18  and  19 . 
         [0064]    The second parts  21  and  23  each includes openings  55  to accept a locking clip, which is shown in more detail in  FIGS. 4 and 4   a . With reference to  FIGS. 4 and 4   a , the locking clip  27  includes a first locking part  28  and a second insertion part  29 . The insertion part  29  extends substantially perpendicular to the locking part  28 . The insertion part  29  can be used to push the locking clip  27  into place and to pull on the locking clip  27  to remove it. However, the shape of the locking clip  27  could be different to that illustrated. 
         [0065]    The locking clip  27  includes an opening or space  30  which defines an engagement portion into which a projection of a fixing member can extend. The space  30  is defined by a pair of arms  31  that are resiliently flexible and which define an entrance portion in the form of a narrow entrance  32  which leads to the circular and larger space  30 . The locking clip  27  can be formed of any suitable material such as stainless steel, aluminium, plastic and urethane. The locking clip  27  is inserted in the direction A into the annular ring  18  by pressure applied to the insertion part  29  after the projection of a fixing member has been inserted into the annular ring  18 . If the locking clip  27  has been formed of a resilient material, the arms  31  can splay or shift outwardly to accept the projection and return resiliently about the projection when the projection has entered the space  30 . If the locking clip  27  has been formed of a rigid material, then the projections can distort to allow the arms  31  to engage them in the space  30 . Typically, the projections are of a plastic material such as a urethane, which will allow that distortion if required. 
         [0066]    The above explanation will be better understood with reference to  FIGS. 5 to 7 . In those figures, a fixing member  13  is illustrated which includes a top or upper surface which is formed of two inclined surfaces  36  and  37  and which meet at an apex  38 . The inclined surfaces  36  and  37  form part of a head  33  which extends from a web  40  that extends from a rail or a base  41 . The head  33  has a greater lateral extent than the web  40  so that the head  33  overlies the web  40  on each side of the web  40 . That arrangement defines a recess  42  ( FIG. 6 ) on each side of the web  40 . 
         [0067]      FIG. 8  shows a fixing member  13  of the kind Illustrated in  FIGS. 5 to 7  and described above with a pair of screen panels  14  in connection on either side of the member  13 . It can be seen from  FIG. 8 , that the side edges of the screen panels  14  are shaped complementary to the profiles of the fixing members  13 , so as to create an interlock between the side edges of the screen panels  14  and the fixing member  13 . It can further be seen that the side edges of the screen panels  14  are in abutting engagement at the position above the apex  38  of the fixing member  13 . 
         [0068]    Returning to  FIGS. 5 to 7 , the fixing members  13  include a pair of projections  45  that extend from a base  41  of the members  13 . The projections are cylindrical and are best shown in  FIG. 7  and include first and second annular portions  47  and  48 . The first annular portion  47  is of greater outer diameter than the second annular portion  48 . The second annular portion  48  terminates in a frustoconical end  51 . 
         [0069]    The first and second annular portions  47  and  48  define a shoulder  52  that faces towards the base  41 . 
         [0070]    The profile of the fixing members  13  as it applies to interconnection with the side edges of screen panels  14  is described in co-pending Australian patent application no. 2012201297 filed by applicant with a claim to priority of 3 Mar. 2011. The disclosure of that application is herein incorporated by cross reference in its entirety. 
         [0071]      FIGS. 9 to 11  illustrate the fixing members  13  attached to the beam  11 .  FIGS. 9 and 10  show that attachment without the locking clips  27  inserted, while  FIG. 11  shows the locking clips  27  in place. 
         [0072]    With respect to  FIGS. 9 and 10 , the fixing members  13  have been positioned relative to the beam  11  with the projections  45  ( FIGS. 5 and 6 ) inserted through the openings of the annular rings  18  and  19 .  FIGS. 9 and 10  further show the openings  55  into which the locking clips  27  can be inserted. Those openings are also illustrated in  FIGS. 2 and 3 , while they are also clearly evident in  FIG. 4 . 
         [0073]    With reference to  FIG. 4 , a pair of openings  55   1  and  55   2  is shown at 90° to one another. While not apparent in the figures, it is to be appreciated that the annular rings  18  and  19  actually include four openings  55 , spaced at 90° to each other and provided in the second parts  21  and  23  of the annular rings  18  and  19 . This is to ensure that an opening  55  is always presented at a position which is convenient for insertion of a locking clip  27 . It will be appreciated that, by the threaded engagement between the first parts  20 ,  22  and the second parts  21 ,  23 , if only a single opening  55  is provided, it will not always be easy to ensure that the second parts  21 ,  23  will finish their threading at a position at which the single opening  55  will be positioned for convenient insertion of a locking clip  27 . For example, the opening  55   1  shown in  FIG. 4  will not conveniently receive a locking clip  27 , but by the provision of the second opening  55   2 , the locking clip  27  is easily installed. Thus, the provision of multiple openings  55  will ordinarily ensure that an opening  55  is always positioned for convenient acceptance of the locking clip  27 . 
         [0074]    With the fixing members  13  installed relative to the beam edges  11  as shown in  FIGS. 9 and 10 , i.e. with the projections  45  inserted into the annular rings  18  and  19 , the annular portion  48  of the projections  45  is positioned in alignment with the openings  55 . Locking clips  27  can therefore be inserted through the openings  55  to engage within the surfaces  56  of the annular portions  48 . The arms  31  of the locking clip  27  will splay outwardly as that engagement takes place and each projection  45  enters the entrance portion  32  of the locking clips  27 . As the arms  31  move relative to the projections  45  and the annular portions  48  are received within the spaces  30 , the arms  31  can resiliently return to the position shown in  FIG. 4  and the projections  45  are thus captured against movement out of the annular rings  18  and  19  by the locking clips  27 , in particular by engagement between the locking clips  27  and the shoulders  52 . 
         [0075]    As is apparent from  FIGS. 6 and 10 , the base  41  of the fixing member  13  includes recesses  60  for receipt of the upper projecting portion of the annular rings  18  and  19 . This allows the portion of the base  41  between the recesses  60  to rest on the facing surface of the edge  12  of the beam  11 . 
         [0076]    Advantageously, prior to securing the locking clips  27  in place, the fixing members  13  and any screen panels  14  connected to them can be shifted by virtue of the outer diameter of the first annular portion  47  ( FIG. 7 ) of the projections  45 , being of reduced diameter compared to the internal diameter of the openings of the annular rings  18  and  19  so that accurate alignment of the panels  14  can be made. As indicated earlier, the movement can typically be up to 8 mm in any direction. Once the fixing members  13  and the screen panels  14  have been accurately aligned, the locking clips  27  can be inserted to fix the position of the fixing members  13  on the beams  11  and thus to fix the screen panels  14  in place. It is to be appreciated that the fixing members  13  and the screen panels  14  can shift away from the edge  12 , ie lift away from the edge  12 , during vibration of the screen deck  10 , but that movement is not movement that results in subsequent misalignment of the screen panels from the installed position. 
         [0077]    Further advantageously, the locking clips  27  can be inserted from above the screening deck  10 , so that access to beneath the deck is not required for installation of screen panels. This is far more favourable than requiring access to below the deck. 
         [0078]      FIG. 12  is an underneath view of a portion of the deck  10  showing the beams  11 , the fixing members  13 , the panels  14 , the annular rings  18  and  19  and the locking clips  27 . As in  FIG. 1 , several of the panels  14  are absent from Figure to clearly illustrate the invention. 
         [0079]    Throughout the description and claims of this specification the word “comprise” and variations of that word, such as “comprises” and “comprising”, are not intended to exclude other additives, components, integers or steps. 
         [0080]    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 the spirit and scope of the present disclosure.