Patent Publication Number: US-8113357-B2

Title: Screening module

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority from Australian Provisional Patent Application No 2006900170 filed on 13 Jan. 2006, the contents of which are incorporated herein by reference. 
     FIELD 
     This invention relates generally to the screening of particulate materials and, more particularly, to a screening module and to a screening assembly including such a module. 
     BACKGROUND 
     In the screening of particulate materials, such as ores, using screening modules there is a trade off between flexibility of a screening panel of the screening module, screening accuracy and open area of the screening module. There is a desire to have the screening panel reasonably flexible to inhibit blinding or pegging of screening apertures of the screening panel. However, if the screening panel is too flexible, there is a risk that oversized ore particles may pass through the apertures. This can have adverse consequences downstream of a screen deck comprising a plurality of the screening modules and may also give rise to penalties. 
     There is always the desire to have as great an open area as possible to allow the maximum throughput through the screen deck. The open area is generally understood to be the percentage of a surface of the screening panel of the module that is constituted by apertures. Once again, if there is too high a percentage of open area, i.e. a large percentage of the panel is constituted by apertures, there is a risk that the panel will be too flexible and oversized ore particles may pass through the apertures. 
     Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. 
     SUMMARY 
     According to the invention there is provided a screening module which comprises 
     a frame component to be secured to an underlying screen deck, in use; and 
     a screening panel carried by the frame component, the screening panel comprising an operatively upper screening surface and a support structure underlying the screening surface, with a plurality of spaced protrusions being supported by and standing proud of the support structure, operatively upper ends of the protrusions lying substantially in a plane of the screening surface and the protrusions defining a plurality of screening apertures in the screening surface. 
     The support structure may comprise a plurality of cross members. In one embodiment, the cross members may be arranged in a grid or lattice of intersecting cross members. The protrusions may be arranged on the cross members where the cross members intersect. In another embodiment, the cross members may be arranged in spaced parallel relationship. The cross members may extend in an in-flow direction of the module. In this embodiment, the protrusions may be arranged at spaced intervals on the cross members. The protrusions of adjacent cross members may be aligned with each other or, instead, the protrusions of adjacent cross members may be staggered with respect to each other. 
     If desired, each of at least certain of the cross members may be convex, or bowed, when viewed from a side of the cross member, to provide increasing stiffness towards a central region of the cross member. 
     Each protrusion may be in the form of a flat topped projection extending from the grid structure. Sides of each projection may taper inwardly from the top of the projection to a mounting position of the projection on the support structure. It will be appreciated that such tapering assists in inhibiting blinding of the screening apertures. It will further be appreciated that the support structure defines a plurality of openings, the openings underlying the screening apertures. However due to the tapered nature of the projections and the cross-sectional dimensions of the cross members, the openings are larger than the apertures. Thus, material passing through the apertures should pass with ease through the openings of the support structure. 
     The projections may have any suitable outline in plan. Thus, the projections may be rectangular (including square) in plan view. The projections may be arranged diagonally on their associated cross members. Instead, to increase the open area of the screening module further, the projections may be cruciform in plan view. The projections may be arranged on their associated cross members with arms of the cross-shaped projections extending diagonally relative to the cross members when viewed in plan. 
     The frame component and the screening panel may be integrally formed as a one-piece unit. The unit may be moulded from a suitable synthetic plastics material. The material may be polyurethane. At least the frame component may carry reinforcing to impart rigidity to the unit. 
     Instead, the frame component and the screening panel may be formed as two separate elements, the screening panel being removably attached to the frame component. 
     The module may be rectangular. At least the shorter sides of the module may carry mounting formations for securing the module to an underlying screen deck. The mounting formations may be clips carried on the shorter sides of the module, the clips engaging retention rails on the screen deck. Instead of the clips, the mounting formations of the screening module may be receiving formations in each of which a part of a retaining member, as described in International Patent Application No. PCT/AU2005/001376 entitled “A screening module retaining member” dated 9 Sep. 2005, or any modification thereof, is received. 
     The screening apertures may be arranged in a plurality of aperture arrays. Each aperture array may be delineated by a skirt portion underlying the screening surface. Each skirt portion may bound the support structure associated with that aperture array. 
     The invention extends also to a screening assembly including a screening module as described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a three dimensional view, from above, of a screening module, in accordance with a first embodiment of the invention; 
         FIG. 2  shows a three dimensional view, from below, of the screening module of  FIG. 1 ; 
         FIG. 3  shows a plan view of the screening module of  FIG. 1 ; 
         FIG. 4  shows a bottom view of the screening module of  FIG. 1 ; 
         FIG. 5  shows, on an enlarged scale, a plan view of the detail “A” in  FIG. 3  of the drawings; 
         FIG. 6  shows, on an enlarged scale, a bottom view of the detail “B” in  FIG. 4  of the drawings; 
         FIG. 7  shows, on an enlarged scale, a three dimensional front view of the detail “A” in  FIG. 3  of the drawings; 
         FIG. 8  shows, on an enlarged scale, a three dimensional rear view of the detail “B” in  FIG. 4  of the drawings; 
         FIG. 9  shows, on a substantially enlarged scale, a plan view of a part of the screening module of  FIG. 1 ; 
         FIG. 10  shows a plan view of a screening panel of a screening module, in accordance with a second embodiment of the invention; 
         FIG. 11  shows a sectional side view of a part of the screening panel of  FIG. 10  taken along line XI-XI in  FIG. 10 ; 
         FIG. 12  shows a bottom view of the screening panel of  FIG. 10 ; 
         FIG. 13  shows a plan view of a screening panel of a screening module, in accordance with a third embodiment of the invention; 
         FIG. 14  shows a bottom view of the screening panel of  FIG. 13 ; 
         FIG. 15  shows a plan view of a part of a screening module in accordance with a fourth embodiment of the invention; 
         FIG. 16  shows, on an enlarged scale a plan view of a part of an aperture array of the screening module of  FIG. 15 ; 
         FIG. 17  shows a sectional side view taken along line XVII-XVII in  FIG. 16 ; and 
         FIG. 18  shows a plan view of a part of a variation of an aperture array of the module of  FIG. 15 . 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     In  FIG. 1 to 9  of the drawings, reference numeral  10  generally designates a screening module, in accordance with a first embodiment of the invention. The module  10  comprises a frame component  12  and a screening panel  14  carried by the frame component  12 . In this embodiment, the frame component  12  and the screening panel  14  are formed integrally as a one-piece unit. 
     The module  10  is a one-piece moulding of a suitable synthetic plastics material, more particularly, a polyurethane material. Typically, the polyurethane material has a Shore Hardness in the range from about 85 to 93 depending on the application of the module  10 . 
     It will, however, be appreciated that, instead, the screening panel  14  could either be moulded separately from the frame component  12  and adhered to the frame component  12 . Instead, the screening panel  14  could be releasably secured to the frame component  12  to be replaceable separately from the frame component  12 . Thus, in the embodiment shown in  FIGS. 10-14  of the drawings, the screening panel  14  defines slots  15  in the underside of the screening panel  14 . The slots  15  receive clips (not shown) of the underlying frame component  12  so that the screening panel  14  is able to be removed from the frame component  12  while the frame component  12  is secured to an underlying screen deck. 
     The screening panel  14  defines a screening surface  16 . A support structure  18  ( FIG. 2 ) is arranged operatively below the screening surface  16 . The support structure  18  supports a plurality of protrusions  20 . The protrusions  20  project upwardly from the support structure  18  terminating in a plane defined by the screening surface  16  of the screening panel  14 . 
     The protrusions  20  define, between them, a plurality of screening apertures  22 . As shown most clearly in  FIG. 9  of the drawings, each screening aperture  22  has an effective screening size governed by the dimension ‘d’. 
     The apertures  22  are arranged in a plurality of discrete aperture arrays  24 . In this embodiment, these aperture arrays  24  are formed by a central member  26  of the module  10  and a plurality of lateral members  28  extending at right angles from the central member  26 . These members  26 , together with sides  30  and  32  of the module  10 , effectively define the aperture arrays  24 . More particularly, each aperture array  24  comprises a skirt portion  34  ( FIG. 2 ) bounding the relevant aperture array  24 . Each skirt portion  34  supports its associated support structure  18 . 
     In this embodiment, each support structure  18  is in the form of a lattice structure or grid  36 . The grid  36  comprises a plurality of orthogonally arranged, intersecting cross-members  40  intersecting at points  38 . A protrusion  20  is arranged on each intersecting point  38  of the grid  36 . 
     Each protrusion  20  is in the form of a flat topped projection  42  terminating in the plane of the screening surface  16  of the screening panel  14  of the module  10 . 
     Further, each projection  42  has inwardly tapering sides  44  tapering from its top towards it mounting point  38  on the grid  36 . These tapering sides  44  inhibit blinding of the apertures  22  (in the case of wet screening of materials) or pegging (in the case of dry screening of materials). 
     The cross-members  40  of the grid  36  are of narrow cross-section. As a result, openings  46  (shown most clearly in  FIG. 2  of the drawings), bounded by the intersecting cross-members  40  and underlying the apertures  22 , are substantially larger than the apertures  22 . Thus, material passing through the apertures  22  will pass readily through the openings  46  and is unlikely to block the openings  46 . 
     It is also to be noted that some projections  42  are formed integrally with the lateral members  28  or the side members  32 , as the case may be. 
     As illustrated, the screening module  10  is substantially rectangular and the shorter sides  32  carry mounting formations in the form of clips  48  for clipping to retention rails (not shown) of an underlying screen deck (also not shown). Because the aperture arrays  24  are square and, therefore, symmetrical, the screening modules  10  can be arranged either with their shorter sides parallel to the direction of flow of material over the screen deck or at right angles to the direction of flow of material over the screen deck. 
     Referring now to  FIGS. 10 to 12  of the drawings, a screening panel  14  of a second embodiment of a screening module  10  is illustrated. With reference to the previous drawings, like reference numerals refer to like parts, unless otherwise specified. 
     In this embodiment, the grid  36  of the support structure  18  has a coarser pitch than the grid  36  of the previous embodiment. By “coarser pitch” is meant that the openings  46  defined by the cross members  40  are of larger cross sectional area. Also, there are fewer mounting points for the projections  42 . Thus, there are fewer projections  42  than in the previous embodiment. This therefore increases the size of the apertures  22  defined by the projections  42  and results in a screening panel  14  having an even higher open area than the preceding embodiment. 
     The cross members have a convex, or bowed, lower edge as shown most clearly in  FIG. 11  of the drawings in order to increase the stiffness of the cross members  40  and to reduce the flexibility of the cross members  40  and the projections  42 . 
     It is also to be noted that, unlike the embodiment shown in  FIGS. 1 to 9  of the drawings, the screening panel  14  illustrated in  FIGS. 10 to 12  has three aperture arrays as opposed to the eight aperture array configuration of the preceding embodiment. 
     Referring to  FIGS. 13 and 14  of the drawings, a screening panel  14  of a third embodiment of a screening module  10  is shown. Once again, with reference to the previous drawings, like reference numerals refer to like parts, unless otherwise specified. 
     In this embodiment, two different configurations of aperture arrays  50  and  52  are provided for illustrative purposes. A central part of the illustrated panel shows a conventional aperture array  54  not using the present invention. The aperture array  54  is illustrated for comparative purposes only and forms no part of the present invention. 
     In this embodiment of the invention, the support structure  18  comprises a support arrangement of spaced, parallel cross members  40 . In other words, intersecting cross members are not included so that slot shaped openings  56  ( FIG. 13 ) are defined between adjacent cross members  40 . As in the case of the previous embodiment, the cross members  42  have a convex lower edge to enhance the stiffness of the cross members  40  and to inhibit flexibility of the aperture array  50 ,  52 , as the case may be. 
     It is to be noted that the cross members  40  are arranged in an in-flow direction in the module  10 , i.e. extending parallel to the direction of flow of material over the screening surface  16  of the screening module  10 . 
     The projections  42  are arranged at spaced intervals along each cross member  40 . In the case of the aperture array illustrated at  50  in  FIGS. 13 and 14  of the drawings, projections of adjacent cross members  40  are aligned with each other. In the case of the aperture array illustrated at  52 , the projections  42  on one cross member  40  are staggered with respect to the projections  42  on an adjacent cross member  40 , effectively further increasing the open area of a screening module  10  made up of the aperture arrays  52 . 
     In  FIGS. 15 to 18  of the drawings, yet a further embodiment of a screening module  10  is illustrated. As in the case of the previous embodiments, like reference numerals refer to like parts unless otherwise specified. 
     In this embodiment, instead of the projections  42  being square in plan view outline, the projections  42  are cruciform in shape having outwardly projecting arms  58 . When viewed in plan, the arms  58  are diagonally arranged relative to the cross members  40  on which the projections are mounted. Thus a pair of projections  42  on one of the cross members  40  and a corresponding pair of projections  42  on an adjacent cross member  40  form rhombus-shaped apertures  22 . 
     In the version shown in  FIGS. 15 and 16 , the projections  42  on one cross member  40  are staggered with respect to the projections  42  on the adjacent cross member  40  to form large apertures  22 . With this configuration, the open area of the module  10  is even greater than in the previous embodiments. In the version shown in  FIG. 18 , the projections  42  on one cross member  40  are aligned with the projections  42  of the adjacent cross member  40  to reduce the size of the apertures  22 . 
     End faces  60  of the arms  58  of the projections  42  are tapered to inhibit blinding or pegging. 
     The screening module  10  may, instead of being secured to the underlying rails using clips  48 , be attached to the underlying rails using the Applicant&#39;s pin system as described in International Patent Application No. PCT/AU200S/01376 entitled “A screening module retaining member” or using one of the systems described in International Patent Application Nos. PCT/AUO2/01463 or PCT/AUO2/01668, both entitled “Screening panel securing system”. 
     In use, as the screen deck vibrates and material passes over the screening modules  10 , materials having dimensions smaller than dimension ‘d’ pass through the apertures  22  and the openings  46  or  56  in the support structure  18 . The tapered nature of the projections  42  inhibits blinding or pegging of the apertures  22  and facilitates passage of material through the screening module  10 . A further advantage of this configuration of screening module  10  is that the projections  42 , themselves, vibrate. In so doing, this assists in dislodging material. 
     As described above, there is a trade off between flexibility of the screening module  10 , screening accuracy and open area of the screening module. Because the projections  42  protrude upwardly from the support structure  18 , there is a greater open area defined. It will be appreciated that, because the support structure  18  sits at a level below the screening surface  16  of the module  10 , it does not reduce the open area of the screening module  10 . This substantially increases the open area of the screening module  10 . The Applicant has calculated that, with a screening module in accordance with at least the first embodiment of the invention, due to the absence of cross and in-flow ligaments defining screening apertures, an aperture pattern having an open area exceeding 64% can be obtained. This compares extremely favourably with conventional aperture patterns (such as shown at  54  in  FIGS. 13 and 14  of the drawings) having open areas in the range of about 20% for conventional, square apertures and about 30% for slotted apertures. Thus, the screening capacity of the screening module  10  of the invention is substantially enhanced while still providing the necessary screening accuracy and improved flexibility. 
     It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.