AU772638B2 - Ore screening panel - Google Patents

Description

AUSTRALIA

Patents Act

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Application Number: 101 Lodgement Date: 2 4 t h July 2001 Nominated Patentee: Screenex Australia Pty Ltd Invention Title: Ore Screening Panel The following statement is a full description of this invention, including the best method of performing it known to the applicant.

Ore Screening Panel This invention relates to improvements in ore screening panels used in the separation and grading of materials in the mining and quarrying industries.

Background to the invention Australian patent 482212 proposed a modular screening panel system for ore screening decks which is now widely used by the mining industry and replaced the earlier screening cloths, and large wire screening frames. The screening panels were all of the same size [eg. 300mm] and made of reinforced polyurethane. The panels are adapted to be secured to an underlying support frame using dependent spigots which are a force fit into corresponding apertures in the support frame. Patent 517319 provided an alternative method of securing the panels to the frame using a pin expanded fastening concept.

difficulty encountered in using these panels is that the screening apertures can become clogged with material failing to pass through the apertures.

20 When a portion of a screen deck is affected in this way it is said to be blinded and a blinded screen is less efficient because of the reduction in open area.

"Blinding of screening panels is most prevalent in dry screening where there is no water to wash out the apertures and where the aperture size is below 10mm. Problems are encountered also in dry screening where the water 25 content of the ore is high enough to encourage agglomeration of ore fines.

Patent 538559 attempted to address this problem by making the ribs which define individual screen apertures of different flexural strengths by varying the cross sectional dimensions or internal reinforcements.

Patent 608392 also sought to overcome this problem by providing greater flexibility to the periphery of each aperture. This was achieved by providing zig-zag ribs extending across the panel to define screening apertures between the ribs. The self cleaning action is thus dependent on the shape and arrangement of the apertures in the screening surface.

Patent 731011 sought to prevent blinding by providing a flexible ore screening panel adapted for mounting on a screening deck, which includes a screening surface integrally formed on a reinforcing frame part of which lies below said screening surface, wherein the screening surface is only attached to the frame at its periphery. This arrangement has been successful but the provision of a support frame across the screening surface and the arrangement of apertures does inhibit the efficiency of screening.

It is an object of this invention to improve the throughput and screening efficiency.

Brief description of the invention io To this end the present invention provides an ore screening panel adapted for mounting on a screening deck, composed of polymeric material having a shore hardness greater than 20 which includes a) a peripheral frame in which reinforcing is incorporated in the peripheral frame members.

b) a screening surface extending between the peripheral frame members, c) said screening surface having hexagonal apertures below in size arranged in the surface in staggered formation so that the ribs which define the apertures are regular in width.

20 d) the aperture width to rib width ratio is 0.8:1 to 2.8: 1 the rib width to rib thickness ratio is 1:0.8 to 1:2.

00 The panel is cast, injection moulded or vulcanised elastomeric material, preferably polyurethane or rubber, which has embedded within it reinforcing •ill bars which define the outer edges of the panel to provide support to the screening surface. The reinforcing can be of plastic or metal. Steel has 0conventionally been used, but fibre reinforced plastics are preferred because "0 of their lighter weight and resistance to corrosion.

The apertures are preferably equal sided hexagons. The apertures extend 0 0 00 30 across the surface to the edges of the panel. The apertures are tapered inwardly so that they are wider at the screening surface. The depth of the *0"apertures which corresponds to the thickness of the screening surface determines the rigidity of the screening surface.

The surface is able to flex and vibrate in a manner akin to a screening cloth.

The panels function effectively and are self cleaning. The parameters that enable the flexibility of the screen to be varied to suit a particular application are the thickness of the screening surface, the hardness of the elastomeric material and the distance between adjacent hexagonal apertures which is the same as the width of the ribs which form the apertures.

Preferably the ratio of aperture width to rib thickness is from 0.8: 1 to 2.5: 1.

This invention is applicable to any modular screening panel including those of the type described in patent specifications 482212, 517319, 644293 and to 69852/98. The disclosures of these patents are incorporated herein by reference.

The method of manufacturing the panels according to this invention is the same as for conventional panels as outlined in the above mentioned patents.

Detailed description of the invention A preferred form of the invention will now be described with reference to the drawings in which: Fig. 1 is a plan view of one screening panel in accordance with the invention; Fig. 2 is side view of the panel shown in fig. 1; The screening panel 10 is apart from the modification proposed by this O000invention a conventional modular screening panel. It will be made from polyurethane or some other hard wearing plastic or rubber material and have a shore hardness of 20-95 selected to correspond to the type of particulate ore to be screened and the method of moulding. If the panels are made by injection moulding the hardness cannot be lower than 40, but with air casting the hardness can be as low as 20. In screening iron ore, hardness values above 40 are preferred but for screening coal hardness values as low as may be used 30 The screening surface 12 is shown with ribs 14 forming equilateral hexagonal apertures 16. The hexagonal apertures taper inwardly in cross-section. The depth of the apertures corresponds to the thickness of the screening surface which is the main determinant of the flexibility of the screen surface. The

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apertures are tapered so that the apertures are wider at the screening surface than at the underside of the screening surface.

The panel 10 is stiffened by the frame 18 The whole panel is an integral unit.

Reinforcing bars may be embedded in the frame 18 and may be of steel or rigid plastic such as fibre reinforced plastic.

The screening surface 12 can be stiffened to counteract its increased flexibility by providing dependent ribs beneath the surface or by increasing the thickness of the surface 12 of the panel 10. By varying these parameters an optimum panel can be designed for a particular ore and screen deck loading.

io Some examples of rib width and rib thickness are given in table 1.

Table 1 Aperture size mm Rib width mm Rib thickness mm 4 2.5 3.0 3.5 6 4.0-7.0 4.0-6.0 6.0-8.0 5.0-8.0 14 7.0 9.0 8.0 12.0 0:0. 15s From the above it can be seen that the present invention provides an improved self cleaning panel with a high open area.

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