Technical Field

The present invention concerns a screening mat, to be used in a vibrating screen.

Prior Art

Vibrating screens are used to fractionize for example crushed stones and gravel into fractions of stones with different sizes. For the fractionizing screening media is used having screening holes, whereby stones smaller than the screening holes will pass through the screening holes. Stones bigger than the screening holes will be transported on top of the screening media and feed out at the end of the vibrating screen.

The screening media has traditionally been made in a press or formed in a mould.

Summary of the Invention

According to the present invention the screening media is made by extrusion and are then cut into screening mats of appropriate widths or lengths. The screening media is made of a rubber or polymeric material. In extrusion the screening mats are produced either longitudinally or transversally. The extruded screening media has side parts, adapted to be fixed in a carrier of the vibrating screen. See for example the application entitled "A Vibrating Screen Having Modular Screening Media" filed by the same applicant.

By making the screening media through extrusion the manufacturing process may be faster, endless screening mats may be produced, the manufacturing costs are lowered and the manufacturing is more flexible.

To reinforce the screening media, fibres are integrated in the rubber or polymeric material used for the extrusion. By the integrated fibres the strength of the screening media will increase. The fibres may be made of a polymer, such as polyester or polyamide, or any other suitable material giving a reinforcement of the screening media. In one embodiment carbon fibres are used. The screening media is normally made of rubber or polyurethane. The material of the screening media is reusable.

By means of the reinforcement the screening media will be able to take a bigger load without yielding. Thereby it is possible to decrease the thickness of the screening media. It is also possible to decrease the amount of material between the openings of the screening media, increasing the total open area of the screening media. These measures will increase the screening efficiency of the screening media.

The screening holes are punched in the extruded screening media. By means of the reinforcing fibres of the screening media the dimensional stability is increased. The increased dimensional stability of the screening media makes it possible to have a closer fit in the punching step.

The extrusion of the rubber or poymeric material, including reinforcing fibres, gives the same properties throughout the entire screening media. By controlling the ratio of the reinforcing fibres in the screening media, it is possible to control the properties of the extruded screening media without amending the rubber material. Thus, the same rubber or polymeric material may be used independently of the desired characteristics of the screening media.

For storage and transportation the extruded screening media may be rolled into coils. In time of use screening media is rolled off from the coil and is then cut into suitable lengths. The extruded screening media may also be delivered in relatively long lengths and then cut into appropriate lengths at installation. The cut off screening mats, either from coils or long lengths, are then installed in the vibrating screen. Today normally the screening mats are stored and transported in form of modules, including a support structure for the screening mat. However, the only part that is worn at normal use is the screening mat. By only replacing the screening mats and not using modules including a support structure less parts are transported and discarded, which is beneficial both financially and for the environment. Furthermore, the parts replaced are of the one and same material making recycling easier.

Further objects and advantages of the present invention will be obvious to a person skilled in the art when reading the detailed description below of different embodiments of the invention. Brief Description of the Drawings

The invention will be described further below by way of example and with reference to the enclosed drawings. In the drawings:

Fig. 1 is a perspective view of a vibrating screen in which screening media according to the present invention may be used, and

Fig. 2 is a cross sectional view of one example of screening media, with different dimension, manufactured in accordance with the present invention.

Detailed Description of Embodiments

A person skilled in the art realizes that the cross sectional form of the screening media may vary within the scope of protection of the present invention.

In Fig. 1 one example of a vibrating screen 1 is shown schematically. Normally, the vibrating screen 1 has some kind of support structure 2, on which screening mats 3 are placed. Normally a number of screening mats 3 are placed side by side. In Fig. 2 one general example of a screening media 4 is shown in different dimensions. The shown screening media 4 has end parts 5, 6, which are formed to be received in some kind of carrier or the like of the support structure 2, to fix the screening mats 3, cut from the screening media 4, to the support structure 2. The exact form of the end parts 5, 6 of the screening media 4 is of no importance for the present invention and may vary depending on the design of the vibrating screen 1 and the parts receiving the end parts 5, 6 of respective screening mat 3. The end parts 5, 6 are integrated parts of the screening media 4, and are thus formed in the extrusion of the screening media 4. By using extrusion it is relatively easy to vary forms and dimensions of the extruded screening media. After the extrusion, screening holes are formed in the screening media 4 by punching. The extruded screen media 4 is normally rolled into a coil of appropriate size, or cut into relatively long lengths. If rolled into a coil the screening media 4 is rolled off from the formed coil in time of use and screening mats 3 are cut in lengths or widths appropriate for the vibrating screen 1 , in which the screening mats 3 are to be installed. If the screening media is delivered in long lengths it is also cut to appropriate lengths in time of use.

According to the present invention the screening media 4 is

manufactured by extrusion. Fibres are blended into or integrated in the polymeric or rubber material used for the extrusion. As indicated above, the fibres may be made of a polymer, such as polyester or polyamide, or may be carbon fibres. By means of the fibres the extruded screening media 4 is reinforced. Thereby the screening media 4 may take a bigger load without yielding. As indicated above it is possible to control the properties of the screening media 4 by controlling the amount of reinforcing fibres in the screening media.

The disclosures in the Swedish patent application No. 1050199-7, from which this application claims priority, are incorporated herein by reference.