DESCRIPTION

This invention relates to screening. More particularly it relates to a screening apparatus and to a method of modifying a screening apparatus.

It is known to use, in the mining and bulk material producing plant, screening apparatus which makes use of one or more screening decks. The or each screening deck includes a support structure on which one or more flat relatively rigid screening panels are supported. The screen panels are made of steel or moulded elastomer (rubber, polyurethane) and are rigid or semi-rigid. A problem with these panels is that they suffer from blinding, i.e. the holes in the panels tend to become blocked thereby reducing the efficacy of these panels.

In an attempt to overcome the blinding problems associated with the rigid panels, It is known to use screening apparatus which makes use of elastically deformable screening panels formed of an elastomeric material. These panels are attached to a so-called floating frame which shakes the panels at a high frequency, thereby reducing the blinding effect associated with rigid panels. Examples of panels of this type are the panels sold under the trade mark "Liwell" by Hein-Lehmann AG or "Trisomat" by IFE Aufbereitungstechnik GmbH or "BIVITEC" by Binder+Co. This type of screening apparatus is sometimes referred to as a "flip-flop" screen.

A problem associated with the "Flip-flop" technology is that it is relatively expensive. In addition, in screening installations, e.g. in an ore treatment plant, use is often made of several machines located one next to the other. As a consequence replacing a conventional rigid screening unit with a "flip-flop" type screening unit is both difficult and expensive.

Furthermore the down time required to replace an installed screening machine with another technology like a flip-flop screen is substantial and it is well understood that any interruption in the operation of a mining or bulk material producing plant will have an adverse impact on profitability.

Besides, the decision to replace an existing screening machine with a flip-flop screen is not guaranteed to solve the blinding or screening efficiency problem. This results in a reticence to pay for a new technology and interrupting plant production which has an adverse impact on productivity where no or only a minor benefit may be obtained.

It is an object of this invention to provide screening means which are able to at least alleviate at least some of the problems mentioned above.

According to one aspect of the invention there is provided a method of modifying a screening apparatus comprising at least one screen deck having a support structure on which at least one steel or moulded elastomer (rubber, polyurethane) screening panel is mounted, which method includes the steps of mounting a plurality of spaced apart clamp bars to the support structure, each clamp bar being formed, at least in part, of a resiliently deformable elastomeric material; and securing a plurality of resiliently deformable screening panels to the clamp bars.

By modifying a conventional rigid deck screening apparatus with the method of the invention, the obtained screening apparatus has the advantages of the "flip-flop" system thereby reducing the risk of blinding.

According to another aspect of the invention, there is provided screening apparatus which includes:

at least one screen deck having a support structure;

a plurality of spaced apart clamp bars attached to the support structure, each clamp bar being formed, at least in part, of a resiliently deformable elastomeric material; and a plurality of resiliently deformable screening panels secured to the clamp bars.

The method may include, prior to mounting the clamp bars to the support structure, positioning a plurality of deck protection bars on the support structure such that the deck protection bars are positioned between the clamp bars and the support structure. Typically the deck protection bars and the clamp bars are perpendicular to one another. The deck protection bars are typically formed of an elastomeric material such as polyurethane. Each deck protection bar may include a planar support structure engaging surface and a convex clamp bar support surface.

The clamp bars and screening panels may be provided with complementary engaging formations. More particularly the complementary engaging formations may be complementary male and female formations which are snap-lockingly engageable.

Each clamp bar may include an elongate body having an operatively lower surface and at least one female engaging formation which opens upwardly out of the body, i.e. in a direction opposite to the lower surface. The engaging formation may extend for the entire length of the body.

In one embodiment of the invention, the clamp bar may include two parallel spaced apart female engaging formations which open out of the body. A wedge receiving slot may be provided between the engaging formations. Each female engaging formation may include an inner portion which is generally circular in transverse cross-section and an outer portion which tapers inwardly towards the inner portion such that a neck which has a width which is less than the width of the inner portion is defined at the intersection of the inner and outer portions. The body may be formed of an elastomeric material such as polyurethane. A reinforcing core may be embedded in the body. The reinforcing core may be in the form of metal reinforcing. The reinforcing may be in the form of a channel having a web and a pair of flanges which protrude from the web towards the lower surface. An inwardly directed lip may protrude from the free edge of each flange. A hole or slot may extend from the lower surface of the body into the channel between the lips.

The screening apparatus may include a clamping wedge which is receivable in the wedge receiving slot, the wedge receiving slot and the complementary clamping wedge being configured such that when the wedge is positioned in the slot it serves to inhibit disengagement of the complementary male and female engaging formations, thereby securing the screening panels to the clamp bars.

The screening apparatus may include lateral protection elements which protrude upwardly from opposed edges of a deck formed by the screening panels. In one embodiment of the invention, the lateral protection elements may be attached to clamp bars.

The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings.

In the drawings:

Figure 1 shows a three-dimensional partially exploded view of part of a screening apparatus in accordance with the invention;

Figure 2 shows a three-dimensional view of the screening apparatus of Figure 2;

Figure 3 shows an end view of the screening apparatus of Figure 1 ;

Figure 4 shows a sectional view taken at IV- IV in Figure 3;

Figure 5 shows a side view of a clamp bar forming part of the screening apparatus;

Figure 6 shows a sectional view taken at VI- VI in Figure 5;

Figure 7 shows a section view of a screening panel forming part of the screening apparatus;

Figure 8 shows a three-dimensional view of a clamping wedge forming part of the screening apparatus;

Figure 9 shows a three-dimensional view of a lateral protection element forming part of the screening apparatus;

Figure 10 shows a sectional view of the lateral protection element of Figure 9;

Figure 11 shows a side view of a locking member whereby the lateral protection element is secured in position;

Figure 12 shows a three-dimensional view of a deck protection bar forming part of the screening apparatus;

Figure 13 shows a three-dimensional partially exploded view of part of another screening apparatus in accordance with the invention;

Figure 14 shows an end view of the screening apparatus of Figure 13;

Figure 15 shows on an enlarged scale part of the screening apparatus of Figure 14;

Figure 16 shows a three-dimensional view of a screening panel forming part of the screening apparatus of Figure 13;

Figure 17 shows a transverse sectional view of the screening panel of Figure 16;

Figure 18 shows a three-dimensional view of a lateral protection element forming part of the screening apparatus of Figure 13;

Figure 19 shows a sectional view of the lateral protection element of Figure 18;

Figure 20 shows a three-dimensional view of another screening panel forming part of the screening apparatus of Figure 13;

Figure 21 shows a sectional view of the screening panel of Figure 20;

Figure 22 shows a clamp bar forming part of the screening apparatus of Figure 13; and

Figure 23 shows a sectional view of the clamp bar of Figure 22.

With reference to Figures 1 to 12 of the drawings, reference numeral 10 refers generally to part of a screening apparatus in accordance with the invention.

The screening apparatus 10 includes a plurality of spaced- apart clamp bars 12 which are attached to a support structure (not shown) and a plurality of resiliently deformable screening panels, generally indicated by reference numeral 14 secured to the clamp bars 12.

The screening apparatus 10 includes a plurality of deck protection bars 16 on which the clamp bars 12 are supported as discussed in more detail here below.

As can best be seen in Figure 12 of the drawings, each deck protection bar 16 includes an elongate body 18 and a flange 20 at each end of the body 18. The body 18 has a planar lower or support structure engaging surface 22 and a convex clamp bar support surface 24. The deck protection bar 16 is typically formed as a unitary moulding of an elastomeric material such as polyurethane.

With reference to Figures 1 to 6 of the drawings, each clamp bar 12 includes an elongate body, generally indicated by reference numeral 26. The body has an operatively lower surface 28 which is generally planar and a pair of parallel sides 30 extending upwardly from the lower surface 28. Two parallel transversely spaced female engaging formations 32 are provided in the body 26 and open upwardly out of an upper surface 34 of the body 26. Each female engaging formation 32 includes an inner portion 36 which is generally circular in transverse cross-section, and an outer portion 38 which tapers inwardly towards the inner portion such that a neck 40 defined at the intersection of the inner portion 36 and outer portion 38. The female engaging formation 32 has the general appearance of an inverted keyhole with the neck 40 having a width which is less than the width of the inner portion 36. In the embodiment shown, the female engaging formation 32 extends for the length of the body. A wedge receiving slot 42 is positioned between and extends parallel with the female engaging formations 32, and opens out of the upper surface 34. A complementary clamping wedge 44 (see Figure 8) is snugly receivable in the wedge receiving slot 42 as described in more detail here below.

As can be best be seen in Figure 6 of the drawings, a reinforcing core 46 is embedded in the body 26. The reinforcing core 46 includes a lower portion generally indicated by reference numeral 48 and an upper portion, general indicated by reference numeral 50. The lower portion 48 is generally in the form of a channel having a web 52 and a pair of parallel flanges 54 which protrude from the web 52 towards the lower surface 28. An inwardly directed lip 56 protrudes inwardly and upwardly from the free edge of each flange 54. A hole or slot 58 extends through the body from the lower surface 28 into the interior of the channel. The upper portion 50 includes a pair of L-shaped members 60 which are attached to the web 52. The body 26 is typically moulded of an elastomeric material such as polyurethane. Typically, the reinforcing core 46 will be positioned in a mould prior to the introduction of the elastomeric material such that the reinforcing core is embodied in the body 26. The reinforcing core is typically formed of metal such as steel.

As can best be seen in Figure 5 of the drawings, a plurality of longitudinally spaced-apart transversely extending curved recesses 62 is provided in the lower surface 28 of the body 26. The curvature of the recesses 62 is complementary to that of the clamp bar support surfaces 24 of the deck protection bars 16.

Each clamp bar 12 includes an attachment formation, generally indicated by reference numeral 64 which protrudes from an end of the body 26. The attachment formation includes, on an under surface thereof, a steel plate 66 whereby the clamp bar can be secured to a support structure as described in more detail here below.

Referring to Figures 1, 2, 3, 4 and 7 of the drawings, each screening panel 14 includes a rectangular frame 68 having a pair of ends 70 and a pair of sides 72. A foraminous web 74 extends between the ends 70 and sides 72. The web is upwardly concave.

The screening panel 14 includes a male engaging formation 76 protruding downwardly from each of the sides 72, the male engaging formations 76 being complementary to the female engaging formations 32.

The screening apparatus 10 includes lateral protection elements 78 which are attached to and protrude upwardly from the ends 70 of the screening panels 14 as described in more detail here below.

As can best be seen in Figures 9 and 10 of the drawings, each lateral protection element 78 includes a base 80 and a side wall 82 protruding operatively upwardly from the base 80. The base 80 includes a plurality of longitudinally spaced-apart holes 84 extending therethrough whereby the lateral protection elements 78 are secured to the screening panels 14. The lateral protection elements 78 are typically formed as unitary mouldings of a synthetic plastics material such as polyurethane.

In use, when it is desired to modify a conventional steel or moulded elastomer screening panel, a plurality of the clamp bars 12 are positioned on the deck protection bars 16 with the clamp bar support surface 24 of the deck protection bars 16 being positioned in the recesses 62. The clamp bars 12 are secured in position by inserting a T-bolt in steel core 48 and securing to the existing support structure. Consequently a plurality of the deck protection bars 16 are laid on and clamped with the clamp bars 12. The deck protection bars are positioned such that they extend parallel to the direction of flow of the material to be screened.

The screening panels 14 are then positioned such that the male engaging formations 76 are positioned in engagement with the complementary female engaging formations 32 of adjacent clamp bars 12 as illustrated in Figure 4 of the drawings. The male engaging formations 76 are complementary in shape to the female engaging formations and are snap-lockingly receivable therein.

The clamping wedges 44 are then introduced into the wedge receiving slots 42 of the clamp bars 12 which effectively serves to lock the male engaging formations more firmly within the female engaging formations 32.

The ends 70 of every screen panel 14 are secured in position to the lateral protection elements 78 by means of fasteners 86, one of which is shown in Figure 11 of the drawings which are inserted through the holes 84 and into engagement with complementary holes 87 provided in the ends 70 of the screening panels 14. Each base 80 is provided with a notch 88 which engages with a complementary protrusion 90 provided at the end of the body 26 from which the attachment formation 64 protrudes and which serves more firmly to locate the lateral protection elements 78 in position.

The screening apparatus 10 is arranged such that the screening panels 14 extend transversely to the direction of flow, indicated by arrow 92 of matter to be screened. The screening deck formed by the screening panels 14 is inclined from an upper end 94 to a lower end 96. In use, matter to be screened is fed onto the screening panels towards the upper end 94 and the screening apparatus 10 is vibrated such that the matter moves in the direction of arrow 92. It will be appreciated that in the drawings only a portion of a screening apparatus in accordance with the invention is shown. In the embodiment shown, two screening panels 14 are provided. It will be appreciated, however, that the screening deck formed by the panels will typically comprise several of the panels 14 arranged side by side as illustrated in the drawings.

The number of panels is not fixed. Typically, however, the number will be between a minimum of 4 panels and a maximum of 30. However, it is conceivable that larger machines (requiring a higher number of panels) may be required.

Reference is now made to Figures 13 to 23 of the drawings in which reference numeral 100 refers generally to part of another screening apparatus in accordance with the invention and unless otherwise indicated, the same reference numerals above are used to designate similar parts.

The screening apparatus 100 makes use of two types of screening panels 102 and 104. As can best be seen in Figures 16 and 17 of the drawings, the screening panel 102 includes a rectangular planar foraminous body 106 with male engaging formations 76 protruding downwardly from the long edges of the body 16.

As can best be seen in Figures 20 and 21 of the drawings, each screening panel 104 includes a rectangular body 108 which is approximately twice as wide as the body 106. A male engaging formation 76 protrudes downwardly from each long edge of the body 108. A centrally disposed longitudinally extending male engaging formation 110 protrudes downwardly from the body close to but slightly offset from the centre of the body. In the embodiment shown, parallel transversely extending rows of substantially square apertures are provided in the body. However, the arrangement, shape and size of the apertures may vary depending upon the intended application.

In addition to the clamp bars 12, the screening apparatus 100 makes use of clamp bars 112 which, as can best be seen in Figures 22 and 23 of the drawings each comprise an elongate body 114 surrounding a reinforcing core 116 which is in the form of a channel similar to that embedded in the clamp bars 12. However, an upper surface of the body 114 defines a single upwardly opening female engaging formation 32 which is configured snap-lockingly to engage with the male engaging formations 110 as described in more detail here below.

In order to assemble the screening apparatus 100 a procedure similar to that described above with reference to the screening apparatus 10 is followed. In particular, a plurality of deck protection bars 16 is positioned on a support structure. The deck protection bars are arranged in longitudinally spaced-apart parallel transversely extending rows. Each row comprising a plurality of the deck protection bars.

A plurality of the clamp bars 12 and 112 are laid on the deck protection bars 16 such that they are transversely spaced and extend longitudinally.

The screening panels 102 and 104 are then positioned such that the male engaging formations of the screening panels engage snap-lockingly with the complementary female engaging formations of the clamp bars 12, 112. In this regard, the clamp bars 112 are positioned such that they are in alignment with and engaged with the central male engaging formations 110 of the securing panels 114.

As described above, once the male engaging formations are in engagement with the female engaging formations, a clamping wedge 44 which is typically formed of an elastomeric material such as rubber is inserted into the wedge receiving slot 42 in order to lock the panels in place.

It will be appreciated that, in this embodiment, the clamp bars 12 extend longitudinally. The screening apparatus 100 makes use of lateral protection bars 118 each of which has an integrally formed male engaging formation 20 which, as can best be seen in Figures 14 and 15 of the drawings, engages snap-lockingly with a complementary female engaging formation 32 of a clamp bar 12 positioned at the edge of the screening apparatus.

In this case, the screening deck formed by the screening panels 102 and 104 is horizontal or slightly inclined. The screening apparatus is vibrated and matter to be screened is fed onto the deck formed by the screening panels towards a feed end thereof.

As the apparatus vibrates, matter to be screened moves from the feed end to the discharge end, across the surface of the deck with a proportion of the matter passing through the holes in the screening panel.

It is clear from the above description that the screening apparatus and the method of modifying a screening apparatus in accordance with the invention permits a conventional screening apparatus which makes use of a steel or moulded rubber/polyurethane screen deck to be modified so as it can be operated in the manner of a "flip-flop" system with the advantages associated therewith, at a fraction of the cost of what would be involved to replace existing screening apparatus with screening apparatus of the "flip-flop" type.

Several variations can be made to the screening apparatus and to the method of modifying a screening apparatus thus conceived, all falling within the scope of the attached claims. In practice, the materials used and the contingent dimensions and shapes can be any, according to requirements and to the state of the art.