AU700529B2 - Screen construction - Google Patents

Description

AUSTRALIA

Patents Act 1990 HUNTER WIRE PRODUCTS LIMITED

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT hI ceij(l (jiol Title.

SCREEN CONSTRUCTION The following statement is a full description of this invention including the best method of performing it known to us:- SCREEN CONSTRUCTION Field of the Invention The present invention relates generally to industrial screening systems and in particular the invention provides a new screen construction with improved properties.

Background of the Invention Vibrating screens are used in a variety of industrial and mining applicalions to separate and size material being processed. Traditionally such screens were of woven wire construction, although more recently welded wedge wire screens have also become popular particularly for smaller sizing applications.

A drawback of metal screens has always been their rate of wear with screen elements having to be replaced frequently.

Even more recently, polyurethane screens have been designed which S because of their resilient nature have exhibited better wear characteristics than traditional metal screens, however polyurethane screens typically have the drawback that they have a lower open area ratio than metal screens, which reduces throughput, and they can be prone to blinding with some process materials or alternatively they are too flexible and pass unacceptable levels of oversize material, Each of these drawbacks are partially or wholly because of the location of cross members flush with the upper surface of the S' screen to accurately maintain the aperture and provide structural strength.

Summary of the Invention The present invention consists in a screen panel for use in vibrating i screening equipment, the panel comprising a plurality of screen surface members running in a first direction to define a surface of the panel and a :i I'plurality of underlying supporting members running substantially transversely of and connected to each of the surface members to locate the surface members relative to one another and to provide structural strength, 3i each surface member separated from its adjacent surface members by gaps having a dimension defining the discriminating size of the screen panel, and the surface members protruding above the transverse members to provide a plurality of open slots at the surface of the panel over a substantial part of its length, extending the length of the panel, the screen panel being formed of a resilient plastics material and said surface members being constructed so as to be able to twist relative to the support members about a substantially longitudinal axis of the surface members.

Preferably the screen panel is formed in a resilient plastics material such as polyurethane and the transverse members run generally perpendi, ular to the average direction of the surface members and are s p aced below the surface of the panel by a distance which is not less than the distance separating the surface members.

Preferably, the surface members, in regions between the supporting members, are flexible to provide horizontal flexibility in a direction 11transverse to a direction of material movement and a vertical flexibility normal to a plane of the surface members.

In a particularly preferred embodiment of the invention the surface members are not straight, but are formed with a regular repJeating deviation in the horizontal plane, Preferably the surface members are formed with a 1 r wave pattern having an amplitude which is a small multiple of the gap between the surface members and a wavelength which is approximately an order of magnitude greater than the amplitude. The wave pattern may be a sinusoidal, triangular or circular wave shape or any similar shape.

Preferably, also the slots are open over the length of the panel, and are open through the end of the module where they align with respective slots of an adjacent panel.

The surface members in the preferred embodiment will have a substantially rectangular profile with a slight taper, in the range of 00 to 130 in the bottom third of the member. In another embodiment, a slight taper in 5 the range of 0" to 130 in the top two-thirds of the member. The taper angle is selected to suit aperture size and the application of the screen, In at least one advantageous form of the invention the taper is approximately 6°.

.".Brief Description of the Drawings Embodiments of the invention will now be described, by way of i11 example with reference to the accompanying drawings in which: Figure 1 is a top view of a portion of a screening panel made in accordance with a first embodiment of the invention; Figure 2 is an end view of a portion of the panel of Figure 1; Figure 3 is a detail of the end view of Figure 2; 3) Figure 4 is a detail of a sectional side view of the panel of Figure 1; Figure 5 is a top view of a portion of a screening panel made in accordance with a second embodiment of the invention; Figure 6 is a top view of a portion of a screening panel made in accordance with a third embodiment of the invention; Figure 7 is a top view of a portion of a screening panel made in accordance with a fourth embodiment of the invention; Figure 8 illustrates examples of four possible alternative wave patterns which may be employed in surface member designs; Figure 9 illustrates a rectangular surface member profile; i Figure 10 illustrates a surface member profile tapered over its top two thirds: Figure 11 illustrates four different transverse member arrangements; and Figure 12 is a perspective view of the panel of Figure 1 Detailed Description of the Preferred Embodiments Referring to Figure 1, a top view of a section of screening panel is illustrated. The panel is intended to be mounted in such a way that material to be screened will flow over the panel generally in the direction of arrow The panel comprises a plurality of surface members 11 running 1 generally in the direction'A' and supported on transverse members 12. The surface members 11 define a substantially raised surface having a plurality of slots or gaps 13 of substantially constant dimension through which mateiial to be screened will pass if it is below the screen size defined by the Sgaps 13.

Referring to Figures 2 and 3 which are both end views of the surface members 11, it will be noted that the surface members 11 project a significant distance above the transverse members 12 in order to provide a surface having substantially uninterrupted slots 13. It has not previously been known to manufacture panels out of plastics material, and more 39 specifically polyurethane, in such a configuration. Polyurethane panels in the past have typically been manufactured with both the longitudinal and transverse members extending to the top surface of the panel to provide rigidity and strength. Such a structure was considered necessary in polyurethane panels in order to maintain accurate sizing, because excessive flexibility would lead to oversized material passing through the screen.

These prior art screens suffer from problems with blinding where material builds up against transverse members at the downstrcamn ends of each slot, and eventually closes the entire slot. This problem is particularly severe in some operating environments and can lead to screens requiring cleaning several times a clay, with significant loss of throughput resulting.

The screen of Figures 1-3 has several characteristics which enable it to overcome the blinding problems of prior art screens, First, because the transverse members 12 are located below the surface of the screen, the slots 13 are open along their entire length, thereby reducing the opportunity for buildup to occur. This feature can be enhanced if panels are manufactured in such a way that the slots 13 are open through the ends of the )anel and slots from one panel line up with slots in the next panel.

The second feature of the panel of Figures 1-3 which enhances its performance is that the increased flexibility of the panel assists in keeping the panel clear without any significant degradation of the sizing capability I of the screen. The panel of Figures 1-3 has three flexing modes which assist in clearing the panel, these being horizontal bending of the surface members S".11 in the direction (ref Figure vertical bending of the members 11 in the direction (refer Figure and twisting of the members 11 about the longitudinal axis as indicated by in Figure 3, It will be recognised that o u the bending motions and will be greatest between the transverse imembers 12 with little or no motion at the transverse members, but the twisting motion while reduced at the transverse members, can occur along the entire length of the surface members and significantly enhances e•their clearing efficiency.

theircThe surface members in the preferred embodiment will have a substantially rectangular profile with a slight taper, in the range of O0 to 130 in the bottom third of the member, In another embodiment, a slight taper in the range of 0 to 13" may be provided in the top two thirds of the member.

The taper angle is selected to suit aperture size and the application of the screen. In at least one advantageous form of the invention the taper is approximately Referring to Figure 4, a detail is illustrated of a cut away side view of a transverse member "12 of the panel of Figure 1. It will be seen that the profile of the transverse member 12 is champhered or rounded on its upper leading edge to deflect material over the transverse member, Alternative embodiments may have the leading edge running backwards away from the direction of flow to deflect buildup through the screen.

Turning now to Figure 5, an alternative embodiment is illustrated in which the surface members 21 (corresponding to members 11 of Figure 1) are shaped in the longitudinal direction with a repeating wave pattern, A perspective view of a similar embodiment is shown in Figure 12. As illustrated the wave pattern has an amplitude in the range of 10%-20% of the wavelength, however it will be recognised that advantageous effects may be obtained with wave pattern amplitude of from 0-50% of the I U wave length, depending upon the application. In the illustrated embodiment the wavelength of the pattern is approximately 10 times the gap width 23 but might range from a fraction of the gap width to an essentially infinite multiple of the gap width (in the case of a substantially straight pattern) again depending on the application.

The relationship between the spacing of the transverse menibers 12 and the wavelength of the surface members 21 will also vary depending upon the application, but the transverse menber spacing may vary from approximately 1-3 wavelengths.

The additional advantage provided by the embodiment of Figure 5 is that additional flexibility is provided by virtue of the wave pattern thereby improving the clearing characteristics of the panel. At the same time, sizing is improved because elongated particles which might otherwise have aligned with surface members 11 of Figure 1 and wedged their way through the screen will be blocked by the screen of Figure 5 due to the bends in the slots 25 23. Longer particles will therefore lay across the curved members 21 and will be less likely to enter the gap.

The screen of Figure 5 is shown with the wave pattern of adjacent surface miembers 21 in phase, however in an alternative embodiment the wave patterns of adjacent members 21 may be out of phase by 1800 (1/2 3 U wavelength) in which case the wide portions of each slot will form apertures which are approximately square, providing improved sizing in some circumstances.

In the embodiment of Figure 5 and the alternative, out of phase, embodiment, the motion of the machine and the material being screened creates an oscillation in the members 21 in the longitudinal direction 'A' which enhances the clearing of the screen. A similar effect could be expected in the embodiment of Figure 6 and other wave pattern emnbod iments, The panels illustratedt in Figures 6 and 7 show alternative shalpes to that of Figure 5 which will also provide the advantages of improved sizing and clearing characteristics over the embodiment of Figure -1 in some circumstances. It will be appreciated that many other surface member shapes will also p~rovide this advantage such as triangular wave shape~s, square wave shapes and circular shapes (semii-circular half waves).

Examples of some other possible wave shapes are illustrated in Figure 8 in u which Figures and show various wavelength sine waves and Figure 8(b) shows a triangular wave shape. Figures 9 and 10 show examples of possible different surface member profiles which may be effective ini some circumstances, including a plain rectangular profile (Figure 9) and a profile tapered for approximately the two top thirds and then squared at the bottom 1 5 (Figure Four examples of cross member profiles are illustrated in Figure 11 including: Figure 11(a) a plain rectangular profile; Figure 11(b) a profile flaired out at its upper end; adFigure 11(c) a profile with chamnphered or rounded upper corners; 4*a d Figure 11(d) a profile having fillets between the underside of the s urface members and the upper sides of the transverse member, It will be appreciated by persons skilled in the art that numerous a variations and/or modifications may be made to the invention as shownl in the specific embodiments without departing from the spirit or scope of the iniventioni as broadly described. The present embodiments are, therefore, to be considlered in all respects as illustrative and not restrictive.

Claims (17)

1. A screen panel for use in screening equipnmnt, the panel comprising a plurality of screen surface members running in a first direction to define a surface of the panel and a plurality of underlying supporting members running substantially transversely of and connected to each of the surface miembers to locate the surface members relative to one another and to provide structural strength, each surface member separated from its adjacent surface members by gaps having a dimension defining the discriminating size of the screen panel, and the surface members protruding above the transverse members to provide a plurality of open slots at the surface of the panel extending the length of the panel, the screen panel being formed of a resilient plastics material and said surface members being constructed so as to be able to twist relative to the support members about a substantially longitudinal axis of the surface members.

2. The screen panel of claim 1, wherein the surface members are flexible to provide a horizontal flexibility that is transverse to a direction of ii:material movement on the flexible screen panel, and a vertical flexibility normal to a plane of the surface members.

3. The screen panel of claim 2, wherein the plastics material is polyurelihane.

4. The screen panel of claim 1, 2 or 3 wherein the transverse members run generally perpendicular to the average direction of the surface members.

The screen panel of any one of the preceding claims wherein the transverse members are spaced below the surface of the panel by a distance o which is not less than the distance separating the surface members.

6. The screen panel as claimed in any one of claims 1 to 5 wherein the slots are open through the ends of the panel.

7. The screen panel as claimed in claim 6 wherein the ends of the panel are configured such that slots at one end of one panel will align with slots at 3 U an adjacent end of an abutting panel in use.

8. The screen panel of any one of the preceding claims wherein the surface members are ,.ot straight.

9. The screen paml of claim 8 wherein the surface members are formed with a regular repeating deviation in the horizontal plane.

10. The screen panel of claim 9 wherein the surface members are formed with a wave pattern having an amplitude which is a small multiple of the gap between the surface members and a wavelength which is approximately an order of magnitude greater than the amplitude.

11. The screen panel of claim 10 wherein the wave pattern is a sinusoidal, triangular or circular wave shape.

12. The screen panel of any one of the preceding claims wherein the surface members have a substantially rectangular profile.

13. The screen panel of claim 12 wherein the surface members have a slight taper in the range of 0" to 13°' in the bottom third of the member.

14. The screen panel of claim 12 wherein the surface members have a slight taper in the range of 00 to 13" in the top two thirds of the member.

The screen panel of claim 13 or 14 wherein the taper is al)proximately 6".

16. The screen panel as claimed in any one of the preceding claims wherein the support members are spaced below the surface by a distance xwhich is not less than the distance separating the surface members.

17. A screen panel substantially as hereinbefore described with reference to the accompanying drawings. a Dated this sixth day of November 1998, HUNTER WIRE PRODUCTS LIMITED Patent Attorney for the Applicant: FBRICE &CO I ABSTRACT A screening panel moulded in one piece in plastics material has a plurality of surface members 11 running generally in the direction and supported on transverse members 12. The surface iiembers 11 define a substantially raised surface having a plurality of slots or gaps 13 of substantially constant dimension through which material to be screened will pass if it is below the screen size defined by the gaps 13. The surface members 11 project a significant distance above the transverse members 12 in order to provide a surface having substantially uninterrupted slots 13. The structure and material are designed to increase flexibility of the panel which assists in keeping the panel clear without any significant degradation of the sizing capability of the screen. The panel has three flexing modes which assist in clearing the panel, these being horizontal bending of the surface members 11 in the direction vertical bending of the members 11 in the direction and twisting of the members 11 abou.t the longitudinal axis. *o ft