AU2401599A - Wear resistant screen, screen panel or the like - Google Patents

Description

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AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT 0R: ORIGINAL Name of Applicant/s: Neville Pigott Nixon Actual Inventor/s: Neville Pigott Nixon Address for Service: BALDWIN SHELSTON WATERS MARGARET STREET SYDNEY NSW 2000 Invention Title: "WEAR RESISTANT SCREEN, SCREEN PANEL OR THE LIKE" The following statement is a full description of this invention, including the best method of performing it known to me/us:- File: 22073.00 -2- WEAR RESISTANT SCREEN. SCREEN PANEL OR THE LIKE FIELD OF THE INVENTION This invention relates to a wear resistant screen, screen panel, or the like, which, for use, are usually attached to a supporting steel framework or other structure, such as a vibrating frame, and which are replaceable as and when the need arises in consequence of wear having taken place with resultant deleterious effect on apertures through the screen.

In this specification, for convenience, the term "screen panel" will be used •hereinafter, but it is to be understood that this term extends to a screen panel which constitutes the entire screen area of a screen; one which forms a part of the screen area, usually together with others in a tiled configuration on a support 10 frame; and also includes a screen element which may only define one aperture through the screen, with such screen elements also being arranged in a tiled configuration in plan view.

BACKGROUND TO THE INVENTION Screen panels are widely used for the purpose of grading and sorting mined ores, minerals or other natural products which have been sub-divided in order to 15 separate such materials into two fractions.

Screens used for this purpose often comprise one or more screen panels supported, interchangeably, on a rigid support structure such as a frame. The 1 -3entire panel, which may optionally be reinforced, is commonly cast or moulded from polyurethane material which has desirable wear resistant and somewhat elastomeric properties which are particularly well suited to a screening application.

s However, the polyurethane materials which are suitable for this application are costly and, as such screen panels are regarded as disposable items due to the usually highly abrasive nature of the materials being screened, such costs represent a significant overall cost in running a screening installation. Also, it is to be noted that the polyurethane material cannot practically be recycled and that only a relatively small amount of the material forming a panel is usefully sacrificed.

OBJECT OF THE INVENTION It is the object of this invention to provide a screen panel which can be produced appreciably less expensively than existing polyurethane screen panels and which will provide a decrease in cost of screen panels when related to the quantity of ore processed thereby.

SUMMARY OF THE INVENTION 15 In accordance with this invention there is provided a screen panel comprising a moulded or fabricated base made of structural plastics material and defining at least a basic frame for a screen panel having apertures therethrough and wherein the base supports, permanently secured thereto, a body of wear resistant elastomeric material defining, at least in the unworn condition, the entire t20 operative surface of the screen panel.

Further features of the invention provide for the wear resistant elastomeric material to be secured to the base either by bonding, or by means of mechanical formations, or both; for the base to be an injection moulded unit moulded of a suitably strong polymeric material such as polypropylene; for the body of wear resistant material to be moulded onto the prefabricated base, such body preferably being a thermoplastic elastomer; for the screen panel to be of the type in which a rectangular, or more commonly, a square screen panel has a series of rectangular, either elongate or square, apertures passing therethrough; and for the base to assume either a lattice form of construction defining, at least in outline, the screen apertures and wherein the lattice members are of -4- Tee-shape in cross-section and, at the periphery, of angle or rectangular shape in cross-section to thereby provide an enlarged upper surface to which said body of wear resistant elastomeric material is secured or for the base to define only a surrounding frame and optionally one or more transverse subsidiary frame members.

It will be understood that, by employing the invention defined above, a relatively inexpensive, but strong structural plastics material can be used for the base of the screen panel and this can carry the body of wear resistant elastomeric material which is substantially more expensive than the structural plastics material. The latter provides the required characteristics of the apertures at the position where the material being screened enters same. A substantial saving can thus be achieved whilst not forfeiting any advantages, whatsoever, as regards performance of the screen panel.

ooooo The plastics materials chosen must either be suitable for mutual bonding 15 together whether with the use of a bonding agent or simply in consequence of their coming into contact during manufacture, or the base will have to have formations, preferably a multitude thereof, for mechanically locking the wear resistant elastomer to the base. In the former case, for example, certain structural grades of polypropylene have been found to become adequately bonded to a thermoplastic elastomer material moulded thereon. One such :i thermoplastic elastomer material is sold under the trade name "Monoprene" by QST Inc. of the State of Vermont in the United States of America. Another, which applicant believes is presently under development, is a thermoplastic polyurethane.

In the latter case, the formations would be a multitude of laterally extending fingers or spike moulded integral with the base.

The invention also provides a screen panel assembly in which the outer surfaces of two opposed side edges of a screen panel have longitudinally extending recesses therein which co-operate, in clipping relationship, with a lateral head region of co-operant retaining members in turn releasably attached to a screen supporting frame.

Further features of this aspect of the invention provide for the retaining members to extend along substantially the entire length of the recessed region of the side edges of each screen panel and for each of the retaining members to have integral headed formations passing downwardly through co-operating apertures in the screen supporting frame.

In order that the invention may be more fully understood, various embodiments thereof will now be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:- Figure 1 is a schematic plan view of one form of a screen panel to which the invention may be applied; S. Figure 2 is a schematic cross-section thereof taken along line II to II in Figure 10 1; and Figure 3 is an exploded isometric view of part of a screen assembly illustrating the mounting of a screen panel to a screen supporting frame; Figure 4 is a cross-section through one retaining rail illustrating its attachment to the screen supporting frame; Figure 5 is a similar view to Figure 4, but illustrating an alternative form of attachment of a retaining rail to the screen supporting frame; Figures S-6a and 6b are sectional elevations taken through one form of screen panel at right-angles to each other along lines to and to in Figure 3; Figure 7 is an exploded view illustrating component frame members of the base of the screen panel illustrated in Figures 6a and 6b; and Figures 8a and 8b are similar to Figures 6a and 6b but of a different embodiment of the invention.

-6- DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE DRAWINGS In the implementation of the invention illustrated in Figures 1 and 2 of the drawings, the invention is applied to a square screen panel dimensioned to be compatible with screen support frames of substantially conventional and currently used type. The screen panel'has a series of square apertures (2) s therethrough when viewed from the top face As provided by this invention the panel has a base in this case made of injection moulded polypropylene material. The outer frame members of the base are each of inverted angle shape in cross-section to provide a flat face (6) directed upwardly, and each of the intermediate frame members defining the square apertures is of Tee-shape in cross-section so as to provide a structurally strong base with an upper surface defining the square apertures.

Moulded onto the top surface and of the base is a body of wear resistant thermoplastic elastomeric material and, in this case, the material is that sold S"under the trade name "Monoprene" as identified above. It has been found that "Monoprene" automatically bonds itself onto polypropylene when it is "•thermoplastically moulded onto the latter.

The moulding of the body of the wear resistant elastomeric material is carried out such that the apertures each have a divergent configuration as indicated by numeral at the operatively upper region of the aperture so as to conform with the normal tapered shape of apertures through currently available polyurethane panels. However, at the depth in theaperture determined by the depth of the body of elastomeric material, there is, unlike the prior art, a step increase in size of aperture as defined by the stem of the Tee and shown most clearly in Figure 2. This, it is envisaged, could be particularly advantageous in that the walls of the aperture below the operative size determining region thereof are protected from damage, at least to some extent.

The embodiment of the invention described above may well only be appropriate where the aperture size of the screen is fairly large. In instances where the aperture size is smaller or, at least narrower in one direction, it may be that the base moulded of polypropylene, only defines basically the surrounding frame and, optionally, one or two transverse subsidiary frame members. In this case -7the actual apertures are defined exclusively by the elastomeric material bonded to the moulded polypropylene face. Such an arrangement is illustrated in Figures 8a and 8b in which the elastomeric material (10) is simply bonded onto the top of an injection moulded surrounding frame (11) to form the entire upper surface of S the screen panel with the apertures (12) being formed only in the elastomeric material itself. Figures 8a and 8b also illustrate one subsidiary Tee-sectioned frame member (13) extending across the frame in one direction and forming part of the base.

It is also within the scope of this invention that the elastomeric material defining the apertures themselves need not be bonded to the supporting base but could be mechanically held relative thereto. Such is the case in respect of the panel illustrated in Figures 6a and 6b as well as Figure 7 of the drawings.

In this case the base is composed of a pair of opposite and parallel extruded frame members (14) each having longitudinally extending dove-tail shaped 15 recesses (15) into which the elastomeric material flows when it is moulded onto the frame. This is shown clearly in Figure 6a. In addition each frame member (14) has a Tee-shaped extension (16) on top whereat the cross-bar of the Tee also becomes embedded in the moulded material (17).

The ends of these two frame members (14) are interconnected by a pair of o 20 injection moulded frame members (18) which can be made of substantially the same material as the extruded frame members The injection moulded frame members (18) have dove-tail formations (19) for engaging in the ends of Sthe dove-tail formations (15) in the extruded frame members so that a square or rectangular frame can be fabricated extremely easily as will be apparent from the illustration of Figure 7. The injection moulded frame members (18) also have an extension (20) of Tee-shape in cross-section extending along their top edges.

Subsidiary frame members (21) which can also be injection moulded, can be employed to interconnect the central regions of the extruded frame members (14) and each of these subsidiary frame members (21) has dove-tail formations (22) at their ends such that they can be slid along the dove-tail shaped grooves in the extruded frame members (14) to the required position. One such subsidiary frame member (21) is illustrated in Figure 6b.

In addition, the injection moulded frame members each have a recess (22) extending along the length on the outside thereof (see Figure 6b and Figure 3).

These recesses extend along the entire length of the frame member but terminate short of the ends thereof so that an end stop is defined at each end of the recess (22) as indicated by numeral (23).

The elastomeric material (17) can, in this case, be any suitable thermoplastic elastomer and in particular, a thermoplastic polyurethane exhibiting the desired properties and is simply moulded onto and over the frame members of the base.

The apertures (24) are, once more, defined exclusively in the elastomeric material and are not directly connected to any supporting part of the base as in the case of the embodiment illustrated in Figures 1 and 2.

As provided by the second aspect of this invention, the panels illustrated in Figures 6a, 6b and 8a and 8b are adapted to be supported on a screen support frame (25) (see Figure 3) through the medium of short lengths of retaining member in the form of a rail (26).

As shown clearly in Figures 4 and 5, the retaining rails have a cross-section providing a foot (26) for engaging the upper surface of the frame and a head (27) "o extending laterally outwardly from a waisted central region (28).

Each of the retaining rails (26) has at least two headed retaining formations (29) :i~20 extending out of their under surface with the retaining formations either being simply resiliently deformable to pass through a smaller diameter hole (30) in the screen support frame (25) (as illustrated in Figure 5) or, alternatively, a bore (31) may pass through the rail and associated retaining formation (29) such that the latter can be introduced through the hole (30) by allowing the central region of the retaining formation to collapse and thereafter installing a locking pin (32) in the hole (31) as shown in Figure 4.

The head (27) is, in each case, adapted to allow a panel, generally indicated by numeral to be snapped into position between two adjacent rails (26) with the laterally projecting head extending into the recess (22) described above in the injection moulded frame members. Conveniently the retaining rails are made of polyurethane to allow sufficient resilient deformation to take place for this to happen.

-9- It will be understood that the foot portion (26) of each rail will protect the metal frame (25) against abrasion in use and the recesses (22) are dimensioned such that the edges of adjacent panels (33) touch each other to prevent material from passing adjacent edges of adjacent panels.

It will be understood that numerous variations may be made to the embodiment of the invention described above without departing from the scope hereof which is limited only to the screen panel having a base made of relatively inexpensive structural plastics and carrying at its operatively upper region a body of wear resistant elastomeric material.

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Claims (18)

1. A screen panel comprising a moulded or fabricated base made of structural plastics material and defining at least a basic frame for a screen panel having apertures therethrough and wherein the base supports, permanently secured thereto, a body of wear resistant elastomeric material defining, at least in the unworn condition, the entire operative surface of the screen panel.

2. A screen panel as claimed in claim 1 in which the wear resistant elastomeric material is secured to the base by bonding; by means of mechanical formations; or both. 10

3. A screen panel as claimed in either of claims 1 or 2 in which the base is injection moulded as a unit. oleo

4. A screen panel as claimed in either of claims 1 or 2 in which the base is fabricated from injection moulded and/or extruded plastics components.

5. A screen panel as claimed in any one of the preceding claims in which the 1 structural plastics material is a polypropylene material.

6. A screen panel as claimed in any one of the preceding claims in which the wear resistant elastomeric material is moulded onto the base.

7. A screen panel as claimed in any one of the preceding claims in which the base defines only a peripheral frame supporting the wear resistant -20 elastomeric material, optionally with one or more subsidiary frame members extending across the peripheral frame with the screen apertures being defined in an otherwise unsupported region of the screen panel.

8. A screen panel as claimed in any one of claims 1 to 6 in which the base is configured to provide support to the wear resistant elastomeric material between all screen apertures.

9. A screen panel as claimed in any one of the preceding claims in which the outer surface of the opposite sides of the panel are provided with recesses extending along the length thereof for co-operation with a head formation on a retaining rail carried by a screen supporting frame. A screen panel as claimed in claim 9 in which the recesses terminate short of the ends of the respective sides of the panel.

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11. A screen panel substantially as herein described and exemplified with reference to Figures 1 and 2; or Figures 6a, 6b and 7; or Figures 8a and 8b of the accompanying drawings.

12. A screen panel assembly comprising a plurality of screen panels as claimed in any one of claims 1 to 11 and including the recesses defined in claim 9, and a plurality of retaining rails carried by a screen supporting frame, the retaining rails having a laterally extending head portion engaging in an •associated recess of a screen panel.

S•13. A screen panel assembly as claimed in claim 12 in which each retaining rail is attached to the screen supporting frame by at least two spaced, headed, 15 retaining formations integral with the rail and extending through holes in the screen supporting frame.

"14. A screen panel assembly as claimed in either of claims 12 or 13 in which the S"-retaining rails are made of elastomeric material.

15. A screen panel assembly as claimed in any one of claims 12 to 14 in which the retaining rails have a laterally enlarged foot forming a protecting shield for the screen supporting frame.

16. A screen panel assembly as claimed in any one of claims 12 to 15 in which the retaining rails each have a length substantially equal of the recess in the screen panel frame.

17. A screen panel assembly substantially as herein described and as exemplified in Figure 3 of the accompanying drawings.

18. A retaining rail particularly adapted for use in a screen panel assembly as claimed in any one of claims 12 to 17. DATED this 27th day of April 1999. NEVILLE PIGOTT NIXON Attorney: STUART M SMITH Fellow Institute of Patent Attorneys of Australia of BALDWIN SHELSTON WATERS