AU712862B2 - Fine ore screening panel - Google Patents

Description

AUSTRALIA

Patents Act

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT a.

a..

a *aa Application Number: Lodgement Date: Invention Title: FINE ORE SCREENING PANEL The following statement is a full description of this invention, including the best method of performing it known to the applicant.

Fine Ore Screening Panel Field of the invention This invention relates to improvements in ore screening panels used in the separation and grading of materials in the mining and quarrying industries and in particular is concerned with fine aperture screens.

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 °15 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.

These modular panel systems have been useful over the general range of aperture sizes but have not been able to be adapted for aperture sizes below 2mm. The difficulty encountered in using these panels is that the screening apertures can become clogged with material failing to pass through the apertures. 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.

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. It has not been applicable for aperture sizes below 3mm.

Patent 608392 also sought to overcome this problem by providing greater flexibility to the periphery of each aperture. This was achieved by providing zigzag 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. Again this panel has not been used on apertures below 2mm.

It is an object of this invention to provide a screening panel suitable for use with fine screening where apertures are below 2mm in size.

Brief description of the invention *.To this end the present invention provides a flexible ore screening panel adapted for mounting on a screening deck, which includes a screening surface integrally formed on a frame, wherein the screening surface has apertures formed between ribs having projections on their opposed edges to define apertures between said projections which are capable of screening material below 2mm in ~size. The apertures are preferably 0.5 to 2mm. The ribs formed in the screening surface preferably have a width and thickness of 1 to

C

2 times the aperture size and a length of up to 20 times the aperture size. The width and thickness of the aperture ribs determine the flexibility and self cleaning action of the screening surface. The ribs defining the screening apertures extend between strengthening ribs which extend below the screening surface. To strengthen the aperture ribs support shoulders extend from the strengthening ribs about 2 aperture lengths beneath each end of the aperture ribs.

These shoulders may be triangular with a thickness the same as the average width of the aperture rib. The projections from opposing rib edges define the apertures and may be any suitable shape. The rib edges can be corrugated or serrated in plan view. The amplitude of such projections will be less than 0.5 of the aperture size.

The panel is cast, injection moulded or vulcanised elastomeric material, preferably polyurethane, having embedded within it metal, preferably steel, reinforcing bars which define the outer edges of the panel and extend across the inner area of the panel to provide support to the screening surface. The minimum reinforcing used is a set of edge bars and a cross bar extending from one edge to the opposite edge parallel to the remaining two edges. In this arrangement there is no connection or attachment between the screening surface and the cross bar in accordance with the o• *improvement disclosed in co-pending application

PO

Unexpectedly the aperture rib shape and dimensions for apertures below 2mm has a dramatic effect on the ability of the screening surface to be self cleaning. The surface is able to flex and vibrate in ooot a manner not expected or previously obtained with small aperture screening panels. The cleaning action is such that dry screening of some coals is now possible, where in the past wet screening was necessary, even with apertures above 2mm. The panel of this 20 invention can be used in wet screening down to 0.5mm and also for :dry screening down to 0.5mm where the moisture content is insufficient to cause blinding of the screen.

This invention is applicable to any modular screening panel including those of the type described in patent specifications 482212, 517319, 538559, 608392 and 644293. 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; Fig. 3 is a partial enlarged view of a screening surface illustrating a staggered aperture pattern; Fig. 4 is a partial enlarged view of a screening surface illustrating an aligned aperture pattern; Fig. 5 is a fragmentary plan view of a screen deck with a panel as o• shown in fig. 1 in place; Fig. 6 is a view along the line 4-4 of figure 1.

IIII

The screening panel 10 is apart from the modifications proposed by this invention a conventional modular screening panel. It will be made from polyurethane or some other hard wearing plastic or ooo° rubber material and have a shore hardness of 70-90 selected to 20 correspond to the type of particulate ore to be screened.

The screening surface 12 is shown with the edges of ribs 14 forming apertures 32 defined by opposing pairs of rib projections 15. The panel 10 is stiffened by the reinforced peripheral frame 16 and the central cross ribl 8 which extends between two opposed sides of the frame 16. The whole panel is an integral unit moulded about the reinforcing steel bars which are embedded in the frame 16 and the cross rib 18. Alternatively a moulded plastic frame can be used in place of the steel reinforcing.

In order to secure the panel in place on the screen deck 25, the panel 10 has a series of protrusions 22 dependent from the frame 16 and composed of the same material as the panel. The protrusions shown are of the kind proposed in patent 482212 and are headed spigots with shoulders 24 which abut the underside of the support frame 26. The support frame 26 is of L or U section steel and has a series of holes 28 to accept opposing pairs of protrusions 22 from abutting panels 10. In the case of headed spigots 22 as shown the protrusions are forced through the holes 28 so that the shoulders 24 lie on the underside of frame 26. Alternatively the shouldered protrusions can be replaced by grooved protrusions used in combination with protrusion expanding pins as taught in patent 517319.

The improvement provided by this invention can best be seen in figures 1 and 4. The apertures 32 formed between opposing pairs of ~rib projections 15 can be staggered as shown in figure 3] in which case the apertures are in parallel rows at an angle to the panel side frame. Alternatively as shown in fig 4, they can be aligned so that C o ~the rows of apertures are parallel to the panel side frame. The width of each rib taken as the average width as seen in plan view [fig 1] is ~from 1 to 2 times the aperture dimension. The thickness of the screening surface which is the thickness of the ribs 14 away from 20 their edges is also from 1 to 2 aperture dimensions. The aperture ribs 14 extend between the strengthening ribs 19 which extend below the screen surface at least 5 aperture dimensions. The aperture ribs 14 may be of any suitable length limited by loss of strength with increasing length and loss of flexibility with decreasing length. An optimal length lies between 10 and 20 aperture dimensions. The rib projections 15 can be of any desired profile with a semi oval or partial ellipse being the preferred plan view. At each end of the aperture ribs 14, where they join the strengthening ribs 19, there are provided support shoulders 21 which are triangular or arched webs of the same thickness as the smallest width of the ribs 14 and extend up to 2 aperture dimensions along the ribs 14 and down the ribs 19.

Field tests show that the panels of this invention are so effective in screening fine material down to a 400 micron cut that it is possible to do away with wet screening in some applications and to use these panels in dry screening materials such as diamonds, iron ore or coal having a moisture content of 4% or less. Screen panels in accordance with this invention have been used to dry screen diamonds having a cut size of 1.4mm. For screening fine ore material below 2mm, in which the moisture content causes the material to agglomerate and blind the screen, wet screening is 4*° recommended as this prevents blinding when using the small Q• 4apertures of this invention.

From the above it can be seen that the present invention provides an improved self cleaning panel that is functional for aperture sizes .4*4 c below 2mm.

se

Claims (1)

1. 9.9. 6) An ore screening panel as claimed in claim 1 in which the aperture 25 size is from 0.5mm to 2mm. 25 size is from 0.5mm to 2mm. Richard Pacific Limited