AU683228B2 - Screen - Google Patents

Abstract

The invention relates to a screen, provided with a plurality of rotatable screening members, which are spaced transversally with respect to the proceeding direction of the material to be screened, designed for the fine screening of material. According to the invention the screening members (3, 21, 31, 32) are in cross section essentially deviant from circular form, in order to achieve essentially vertical and horizontal motional components for the material to be treated on the screen (2, 20); and that the screening members (3, 21, 31, 32) are mutually installed so that the screen aperture (11, 27) formed by two adjacent screening members (3, 21, 31, 32) can be kept essentially in the same size throughout the screening process.

Description

OPI DATE 24/05/94 APPLN. ID 51788/93 AOJP DATE 28/07/94 PCT NUMBER PCT/FI93/00435 1 lllflfll1111111111 1111 illlllifll 111Ill8 AU9351788 INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (51) International Patent Classification 5 (11) International Publication Number: WO 94/09917 B07B 1/14 Al (43) International Publication Date: 11 May 1994 (11.05.94) (21) International Application Number: PCT/FI93/00435 (81) Designated States: AU, US, European patent (AT, BE, CH, DE, DK, ES, FR, GB, GR, IE, IT, LU, MC, NL, (22) International Filing Date: 25 October 1993 (25.10.93) PT, SE).

Priority data: Published 924854 26 October 1992 (26.10.92) FI With international search report.

(71) Applicant (for all designated States except US): ROXON OY [FI/FI]; Keskikankaantie 19, FIN-15860 Hollola (FI).

(72) Inventor; and Inventor/Applicant (for US only) MEHTO, Petri [FI/FI]; Vanhatalontie 39 B 1, FIN-15870 Hollola (FI).

(74) Agent: OUTOKUMPU OY; Patent Services, P.O. Box 27, FIN-02201 ESPOO (FI).

(54)Title: SCREEN 2 i (57) Abstract The invention relates to a screen, provided with a plurality of rotatable screening members, which are spaced transversally with respect to the proceeding direction of the material to be screened, designed for the fine screening of material. According to the invention the screening members 21, 31, 32) are in cross section essentially deviant from circular form, in order to achieve essentially vertical and horizontal motional components for the material to be treated on the screen 20); and that the screening members 21, 31, 32) are mutually installed so that the screen aperture (11, 27) formed by two adjacent screening members (3, 21, 31, 32) can be kept essentially in the same size throughout the screening process.

-n I ~p~s, WO 94/09917 PP(r/F93/00438 1

SCREEN

The present invention relates to a screen used in the fine screening of solid material, such as rock material and coal, provided with a plurality of successive, rotatable screening members suitably spaced in the proceeding direction of the material.

Many material treatment processes require that for instance the coarsest and finest particles are removed of the material under treatment, in which case the said material is essentially a fraction between two limit measures. Thus an essentially desired size grade is obtained for the material.

Consequently, several different screens have been developed for sieving material into an advantageus particle size for the next, treatment stage. Usually the screens are arranged in an inclined position, so that the material to be screened passes over the screen by force of gravitation, or the screens are provided with vibrators, which set the material into motion on the screen. There are also developed roller screens, as in the Fl patent 56,131, comprising several rotatable transversal rollers. By means of these rollers, material is made to pass over the screen. Moreover, the roller screen of the FI patent 56,131 is adjustable, i.e.

the distance between the rollers is increased in the proceeding direction of the material in order to adjust the overflow, so that essentially all pellets forming the overflow are larger than those separated therefrom and returned to pelleting. The rotatable rollers of the Fl patent 56,131 set the material to be screened only and essentially into horizontal motion, in which case the material either rolls or slides on top of the rollers. Thus vertical motion, which is advantageous for screening and normally obtained by means of a vibrator, is not created in the process.

SUBSTITUTE

SHET

II~IY- -g~IIUI~B 1 2 An object of the present invention is to address one or more of the drawbacks of the prior art. Embodiments of the invention provide an improved screen which is more secure in operation.

The present invention provides a screen provided with a plurality of rotatable screening members which are spaced transversally with respect to the proceeding direction of the material to be screened, which screening members are in cross-section essentially deviant from circular form, in order to achieve essentially vertical and horizontal motional components for the material to be treated on the screen and that the screening members are mutually installed so that the screen aperture formed by two adjacent screening members can be kept essentially in the same size throughout the screening process and which screen is designed for the fine screening of material, wherein the screening members are shaped in cross-section essentially deviant from circular form so that the crosssection of the screening members is composed of at least two curved parts and at least two parts connecting these curved parts whereby at least 50% of the cross-sectional circumference of the screening member has a curved form, and that the screening member is essentially symmetrical 'in cross-section with respect to its rotating axis.

Preferably, the screen of claim 1, wherein the screen aperture formed by two adjacent screening members is between 4 to se* S S Moreover, the screening members may be coupled to each other so that the distance between two successive screening members may remain essentially the same at the different stages of screening.

By means of the cross-sectional surface of the screening

R

A members of the invention, which shape may deviate from a circle, two different motional components are achieved G:\USERS\MELB\SPEC\P1 9311 .SP 0 -3for the material which is fed and proceeded on the screen, i.e. both an essentially horizontal and an essentially vertical motional component. By means of these two motional components, the material located on the screen can be made to change its direction at different stages. Thus for instance an elongate particle that could not be screened with an essentially horizontal motion only, can now be screened owing to the alternating motion created by the screening members, which essentially increases screening efficiency with the screen of the present invention.

The screening members of the screen of the present invention may, for example, be essentially elliptical in cross-section, so that the whole cross-sectional circumference of the screening member is curved.

Alternatively, the cross-section of a screening member may also be a circle, which is removed of essentially equal-sized segments located symmetrically with respect to the rotating axis of the screening member, the number of these segments being advantageously two or three.

Thus at least 50% of the cross-sectional circumference may be curved and is composed of circular curves.

e According to some embodiments of the invention the o0o screening members are arranged in an advantageous fashion 25 with respect to each other so that two successive screening members are turned at an angle of essentially 900 in relation to each other. Thus, for instance when the screening members are elliptical in cross-section, *ee@0 every second member is essentially in horizontal 30 position, and every second member essentially in ve"t Ical position. While the material proceeds on the surface of the screening members of the screen, the particles are set to an essentially rising or lowering motion due to the effect of the screening members, so that both th horizontal and vertical motional components affect the Smaterial to be screened, and the single particles S ERS\MELB\SPECLU\P19311.SP 0)A O ERSELMSPEMP1931 1.SP LIIP~L"I 3Acontained therein.

It is preferred that the screening members of the screen of the invention are further installed so that the screen aperture in between two successive screening members is equal-sized in all intervals throughout the screen.

Moreover, two successive screening members may be synchronized by means of a gearing member so that the screen aperture remains essentially the same throughout the screening process owing to the advantageous crosssectional symmetry of the screening members.

0 a 6* 000 :\USERS\MELB\SPEC\P1 9311 .SP e *T O *\SRSM L\PC\131 I -c- WO 94/09917 PC/F193/00435 4 When the material is desired to be screened into several fractions, two or more screens with different screen apertures can be connected, so that they form a screen track of several screens. These screens are advantageously operated either with one and the same or with several different actuator devices.

The invention is explained in more detail below, with reference to the appended drawings, where figure 1 illustrates a preferred embodiment of the invention, seen in a partial side-view cross-section, figure 2 figure 3 figure 4 figure 5 figure 6 illustrates the coupling of the screening members of the preferred embodiment of figure 1, seen from the top, illustrates another preferred embodiment of the invention, seen in a partial side-view cross-section, illustrates the coupling of the screening members of the preferred embodiment of figure 3, seen from the top, further illustrates an advantageous cross-section of the screening member of thu invention, and further illustrates an advantageous cross-section of the screening member of the invention.

According to figures 1 and 2, the material conveyed on the conveyor belt 1 is fed onto the screen 2. The screen 2 is provided with screening members 3 arranged transversally to the proceeding direction of the material, spaced at a distance determined by the screen aperture 11. The SUBSTITUTE

SHEET

WO 94/09917 P(7rF193/0435 screening members 3 are essentially elliptical in cross-section, and the screening members 3 are mutually installed so that every second member 3 is essentially in vertical position, and every second member 3 is essentially in horizontal position, i.e. in alternate members, the long axis of the ellipse is in turns in vertical or in horizontal position. The screening members 3 are interconnected, so that at the end of the screening member 3 (figure 2) there is installed a sprocket 5 by intermediation of a gearing 4.

The sprockets 5 are further connected to each other by intermediation of roller chains 6. The rotation of the roller chains 6 is achieved by means of the actuator arrangement 7. For the underflow of the screen 2, there is provided a hopper 8 underneath the screen 2, through w ich hopper 8 the fine material that has penetrated the screen proceeds to an underflow conveyor belt 9 located below the hopper 8. For the screen overflow, there is provided a conveyor belt 10 at the end of the screen with respect to the proceeding direction of the material.

When the screen 2 of the invention is in operation, material to be screened is fed onto the screen 2 from the conveyor belt 1. The screening members 3 are rotated by means of the actuator arrangement 7, so that the screen aperture 11 in between two screening members 3 remains essentially equal during the whole screening process. The essentially vertical and horizontal screening members 3 shift the material to be screened forwa:rd on the screen, and essentially give the material both vertical and horizontal motional components. Thus the efficiency of the screening can be essentially increased. The fine material located on the screen 2 falls in between the screening members 3 to the hopper 8 and further to the conveyor belt 9 of the screen underflow. That part of the material that does not fall in the underflow proceeds into the overflow of the screen 2 and further to the conveyor belt SUBSTOTUTE SHEET WO 94/09917 PCF/F[93/00435 6 In figures 3 and 4, the screening members 21 are spaced according to an interval determined by the screen aperture 27. In order to operate the screening members 21, at the end of each member 21 there is installed a sprocket 23 by intermediation of a gearing 22. The sprockets 23 are interconnected by a roller chain 24. The roller chain 24 is further arranged to pass around a special return roller The actuator arrangement 26 of the screen 20 is connected to the return roller 25 according to the drawing. As for the material treatment, the screen of figures 3 and 4 essentially corresponds to the preferred embodiment illustrated in figures 1 and 2.

In figure 5, the screening member 31 is in cross-section composed of two opposite circular curves and two connecting, parallel linear parts. According to the invention, two adjacent screening members 31 are advantageously installed, with respect to each other, so that the parallel linear parts of the cross-sectional surface of the screening member 31 are alternatingly either essentially in vertical position or essentially in horizontal position, The cross-sectional shape of the screening member 32 of figure 6 is advantageously achieved so, that from a circular cross-sectional surface, there are removed, symmetrically with respect to the rotating axis of the screening member 32, three seg-,r in which case the cross-sectional surface its formn:. ,Zt± clurved and linear parts, and the proportion of the cuved parts is at least 50% of the whole cross-sectional circumference.

Although several preferred embodiments of the invention are described in the above specification, it is obvious that the invention can be modified even to a large extent within the scope of the appended patent claims. Similarly, for instance the location of the actuator arrangement of the screen can vary in the different .pplications. The actuator SUBSTITUTE

SMEMET

WO 94/09917 PC~/F93/0435 7 arrangement can be operated either through specific gearing, or the actuator arrangement can be connected to some known sprocket, or each screening member may obtain its rotatory force from a power transmission axis running along the side of the screening members, which axis is connected to the screening member by means of sprocket gearing. Moreover, the cross-section of the screening members may vary within the scope of the appended patent claims.

SUBSTITUTE SKEET

Claims (5)

1. A screen provided with a plurality of rotatable screening members which are spaced transversally with respect to the proceeding direction of the material to be screened, which screening members are in cross-section essentially deviant from circular form, in order to achieve essentially vertical and horizontal motional components for the material to be treated on the screen and that the screening members are mutually installed so that the screen aperture formed by two adjacent screening members can be kept essentially in the same size throughout the scree:iing process and which screen is designed for the fine screening of material, wherein the screening members are shaped in cross-section essentially deviant from circular form so that the cross-section of the screening members is composed of at least two curved parts and at least two parts connecting these curved parts whereby at least 50% of the cross-sectional circumference of the screening member has a curved form, and that the screening member is essentially symmetrical in cross-section with respect to its rotating axis. oe

2. The screen of claim 1, wherein the screen aperture formed by two adjacent screening members is between 4 to *9* *5

3. The screen of any one of the preceding claims, wherein two adjacent screening members are installed as c turned at an angle of essentially 900 with respect to *each other. S

4. The screen of any one of the preceding claims, wherein in order to rotate the screening member, the screening members are inter-connected by means of at least one chain. i:\USERS\MELB\SPEC\P1 0G1 1.SP I -9 The screen of any one of the preceding claims, wherein in order to rotate the screening member, two adjacent screening members are interconnectea by a chain,

6. A screen as hereinbefore described with reference to one or more of the accompanying drawings. DATED this 5th day of August 1997 ROXON OY By its Patent Attorneys GRIFFITH HACK Fellows Institute of Patent Attorneys of Australia a o e o ;ERS\MELB\SPEC\P19311.SP I-p