Sector having progressive thickness

Abstract

Some embodiments relate to a filtering sector for a filtering disc of a rotary filter, which includes: a structural element made up of a ribbed inner draining medium and a frame that surrounds the draining medium, which is provided with a connecting tube; and a filtering fabric that covers the structural element, wherein the structural element has a thickness which increases progressively towards the connecting tube and in that the draining medium is made up of a single sheet. The draining medium is made up of a single ribbed sheet provided with an alternation of channels, the depth of which increases as it gets closer to the mouth of the tube of the medium.

Claims

1. A filtering sector for a filtering disk of a rotary filter, comprising: a structural element including a ribbed inner draining support and a frame surrounding the draining support, which is provided with a connection tube; and a filtering fabric which covers the structural element, wherein the structural element has a thickness that increases progressively in a direction of the connection tube, and the draining support includes a single ribbed metal sheet, defining parallel channels with side walls, and wherein the draining support is perforated by aligned perforated holes, the aligned perforated holes placed in the side walls of the parallel channels, wherein the frame is constituted by two identical shells having a plurality of wings and the two identical shells are fixed together by the plurality of wings at a central axis of the sector, while confining the ribbed metal sheet.

2. The filtering sector as claimed in claim 1, wherein the frame only includes two shells produced by stamping.

3. The filtering sector as claimed in claim 2, wherein the two shells of the frame have a profile in the form of a “U” with sides with a progressive length.

4. The filtering sector as claimed in claim 3, wherein the draining support has channels in the form of a “U”.

5. The filtering sector as claimed in claim 3, wherein the draining support has channels in the form of a “V”.

6. The filtering sector as claimed in claim 2, wherein the draining support has channels in the form of a “U”.

7. The filtering sector as claimed in claim 2, wherein the draining support has channels in the form of a “V”.

8. The filtering sector as claimed in claim 1, wherein the draining support has channels in the form of a “U”.

9. The filtering sector as claimed in claim 1, wherein the draining support has channels in the form of a “V”.

10. A rotary filter, comprising: the filtering sector as claimed in claim 1.

11. The filtering sector as claimed in claim 1, wherein the two identical shells of the frame are connected to one another by at least two transverse reinforcements arranged on both sides of the ribbed metal sheet.

12. The filtering sector as claimed in claim 1, wherein the two identical shells are symmetrical shells and the wings constitute reinforcements, and are welded to one another.

13. The filtering sector as claimed in claim 12, wherein an end of the shells is bent after stamping in order to form an end of the frame, and wherein the two shells of the frame are connected by the wings and by the bent end of the frame constituting transverse reinforcements in order to prevent risks of deformation of the sector.

14. The filtering sector as claimed in claim 1, wherein the draining support is perforated by aligned holes, transverse to a radius of the sector, a diameter of which increases in phase with the thickness of the structural element.

15. The filtering sector as claimed in claim 1, wherein the channels form a series of parallel corrugations, and wherein a pitch of the corrugations, i.e. the distance which separates two consecutive corrugation tops, remains invariable along the length of the draining support.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Other advantages may also become apparent to persons of ordinary skill in the art from reading the following examples, illustrated by the appended figures, provided by way of example:

(2) FIG. 1 represents a front view of a sector according to the invention;

(3) FIG. 2 is a view in transverse cross-section according to II-II in FIG. 1;

(4) FIG. 3 is a view in transverse cross-section according to III-Ill in FIG. 1;

(5) FIG. 4 represents a view in perspective of the frame of a sector according to the invention;

(6) FIG. 5 is a view in perspective of a draining support of a sector according to the invention.

(7) FIG. 6 is a view of one of the shells of the frame in FIG. 4 before the stamping;

(8) FIG. 7 is a view of the metal sheet of the draining support before its transformation.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

(9) Hereinafter in the description, “inside” indicates the side of the sector which is arranged close to the axis of the filter, i.e. the connection tube side, and “outside” indicates the side opposite the axis.

(10) The sector represented in FIG. 1 is designed to be associated with other identical sectors which are all connected to a rotary support and drive shaft of a filter (not represented), which ensures the discharge of the liquid filtrate.

(11) Each sector includes a structural element 1 constituted by a ribbed rigid draining support 2 and a frame 4 which surrounds the draining support 2 and is provided with a connection tube 10. The structural element 1 acts as a support and a bearing device for a filtering fabric 3 (represented in cross-section only in FIG. 2). The filtering fabric 3, supported on the draining support 2, delimits the inner volume of the filtering sector 30 for the flow of the liquid filtrate during implementation of the liquid-solid separation cycle.

(12) The periphery of the draining support 2 constituted by a ribbed metal sheet is covered with a peripheral frame 4 with a transverse cross-section 40a in the form of a “U” which ensures the retention and rigidification of the draining support 2.

(13) The frame 4 is constituted by two symmetrical shells 40 and 41 with wings 42 which constitute reinforcements, and are welded to one another. Each shell 40 or 41 is made from a cut flat metal sheet according to FIG. 6, it is then stamped in order to provide a profile in the form of a “U”, and is then welded. The shell 40 illustrated in FIG. 6 includes a core 43 and four wings 42. The shells 40 and 41 can include more or less than four wings. The end 44 of the shells 40 and 41 with a length l is bent after stamping in order to form the end of the frame 4.

(14) The two shells 40 and 41 of the frame 4 are connected by the wings 42 and by the bent end 44 of the frame 4 constituting transverse reinforcements in order to prevent risks of deformation of the sector.

(15) The width of the core 43 of each shell 40 or 41 of the frame 4 increases, on the lateral edges of the frame 4, in order to follow the variation of the depth h of the channels 22 along the draining support 2. Once the core 43 is bent, it has the form of a “U” with two sides 43a.

(16) The height H of the sides 43a of the section in the form of a “U” of the frame 4 also increases on the lateral edges of the frame as it gets closer radially to the mouth of the tube 10 of the sector. This height H can vary for example between 15 and 45 mm.

(17) Preferably, the frame 4 is constituted by two identical shells obtained by stamping a flat metal sheet, which are fixed according to the central axis of the sector, for example by welding, thus confining the draining support 2.

(18) In order to reduce the weight of the sector and enhance or improve the flow of the liquid filtrate, the draining support 2 is constituted by a single ribbed metal sheet 20 provided with an alternation of channels or grooves 22, the depth h of which increases as they get closer to the mouth of the tube 10, as represented in the figures. The depth h0 at the mouth of the tube 10 is greater than the depth h1 at the end 11.

(19) The juxtaposition of these channels 22 which extend from the mouth of the tube 10 to the end 11 on the sector forms globally the draining support 2 for the flow of the liquid filtrate.

(20) The depth of the channels 22 increases as they get closer to the mouth of the tube. The tops 23 of the corrugations which form the channels 22 ensure the support of the filtering fabric 3 locally.

(21) For a sector with a length of between 1.5 and 2.5 m, the depth h of the channels 22 of the draining support 2 can vary for example from 5 mm to 35 mm.

(22) In the embodiment illustrated by the figures, the channels 22 form a series of parallel corrugations with a cross-section substantially in the form of a “V”, each top 23 of which has a rounded profile with a radius of curvature of between 2 and 3 mm.

(23) The pitch d of the corrugations, i.e. the distance which separates two consecutive tops 23, is between 10 and 20 mm, and in this case remains invariable along the length of the draining support 2.

(24) However in a variant not represented, it would be possible for the draining support 2 corrugations to have a variable pitch between the outer edge of the sector and its mouth, such that they are thus not necessarily parallel, and could for example be radiating.

(25) The channels 22 are produced by deformation and/or stamping of a flat steel sheet, the thickness of which is between 0.5 and 1.5 mm.

(26) The embodiment of the draining support 2 consists of perforation and bending of a flat metal sheet 20, such as to obtain an corrugated metal sheet forming channels 22 with a progressive height, which are or are not parallel, the walls 24 of which are provided with holes 21. It will be noted that the diameter of the holes 21 increases from one edge to the other of the metal sheet 20 along its length. Finally, the holes 21 are arranged in the walls 24 of the channels 22 such as to facilitate the flow of the filtrate.

(27) Step 1 includes tracing lines of holes 21 and bending generatrices 201. This tracing must firstly guarantee the positioning of the holes 21 in the middle of the walls 24 of the channels 22, and secondly ensure the regularity of the corrugations.

(28) Taking into account the progressive depth of the channels 22, the theoretical evolute is corrected by a non-constant creep factor from one edge to the other along the length of the metal sheet 20.

(29) The creep factor, which varies according to the material, the thickness, and/or a heat treatment, will be adjusted by a series of forming tests.

(30) Step 2 includes cutting and perforating the metal sheet 20, for example by means of a laser or a punch. In this step, guide tongues 200 will also be cut at the ends of the bending generatrices 201.

(31) Step 3 includes forming corrugations, for example by means of a stamping tool provided with a punch and a die.

(32) The height of the punch and the depth of the die increase progressively from one end to the other along the length of the tool, in order to form channels with an increasing thickness.

(33) Consequently, the contact of the punch with the metal sheet 20 takes place progressively from one end of the tool to the other. It is therefore helpful or necessary to guide the metal sheet perfectly from the start to the end of the forming of the channels 22. The guide tongues 200 which are provided at the end of each bending generatrix 201 slide vertically in grooves cut in the die of the tool, thus preventing any lateral displacement of the metal sheet 20. The channels 22 are thus formed one after another, whilst guaranteeing the regularity of the corrugations.

(34) The cycle of liquid-solid separation will now be described as follows:

(35) The inner volume of the filtering sector delimited by the fabric 30 which surrounds it is kept under low pressure during the filtration phase, when the sector is immersed in the solution to be filtered.

(36) During this phase, the filtering fabric 3 is placed against the draining support 2, and the liquid is aspirated through the filtering fabric 3 to the inner volume of the sector 30, towards the connection tube 10, and is then discharged by the collector shaft situated on the axis of the filter, whereas the solid materials continue to be applied against the outer face of the filtering fabric 3 in the form of “caking”.

(37) By rotation of the disk, the filtration-aspiration phase is followed by a phase of cleaning-blowing of the filtering fabric 3, during which the inner volume of the filtering sector 30 is subjected to pressure by compressed air, which detaches the caking from the sector by passing through the filtering fabric 3.

(38) The filtration flow rate and yield are enhanced or optimized by the global decrease in the inner volume of the sector 30, by reducing its thickness at the outer edge 11 of the sector, whilst maintaining a sufficient cross-section at the mouth of its tube 10 for connection to the collector shaft.

(39) The thickness of the inner volume of the filtering sector 30 thus vanes continuously along the entire radial length of the sector, and increases from the outer edge 11 to the mouth of the tube 10.

(40) The profile of the draining support and thus of the sector is therefore tapered in the manner of a blade or a wing.