FR2677268A1 - Metal fabric filter cloth, process for its manufacture and its application in a filter element - Google Patents

Abstract

The filter cloth consists of a stiff deformable fabric (1) made of metal warp and weft filaments the meshes of which determine the filtration orifices, the said fabric being shaped to so as to form parallel waves, called "first waves", characterised in that each first wave (5') itself consists of a series of secondary waves which lies in the length of the wave, and the process is characterised in that the fabric is moved in a direction that forms an angle of 45 DEG in relation to the direction of the warp or weft filaments. Application to the filtration of solid particles in a fluid (for example a fuel, an oil or a gas).

Description

 The invention relates to a metallic cloth filter sheet, a method for manufacturing it and its application in a filter element, in particular for filtering solid particles in a fluid (for example a fuel, an oil, a gas).

 It is known to use as filter cloth a fabric having stiffness but deformable formed by interlacing of warp and weft metal threads stretched and perpendicular to each other, the interlacing determining mesh openings which, according to the weave, c that is to say the mode of interlacing and the texture (diameters, spacing and materials of the wires) are square, rectangular or triangular.

 To increase the filtration surface, it is known to form parallel folds in the fabric, the edges of which are straight.

 To do this, the fabric is waved so as to create a series of parallel waves and the waves are compressed laterally, which transforms them into more or less tight folds with rectilinear edges.

 The filtration surface increases with the number of plies but it is in fact limited by the fact that the pressure drop and the risk of fouling also increase when the plies are tighter.

 The present invention aims to increase the filtration area of a filter sheet without suffering these drawbacks.

According to the invention, this is achieved by forming in the tissue parallel waves or "first waves" such that each first wave itself constitutes a series of secondary waves which extends in the length of the first wave.
An exemplary embodiment of a filter element using a filter sheet according to the invention will be described below, with reference to the figures in the accompanying drawing in which
- Figure I is an elevation of a conventional filter element
- Figure 2 is a section along the transverse plane BB of Figure 1
- Figure 3 is an elevation of a filter element according to the invention;
FIG. 4 is a section along the transverse plane AA of FIG. 3, and
- Figures 5 to 9 are schematic views illustrating different stages of the manufacturing process of a filter sheet according to the invention.

 The description and the figures will show various advantageous features of the element of the invention and its manufacturing process.

 The known filter element shown in FIGS. 1 and 2 consists of a metallic fabric filter sheet 1 wound on a tubular core 2 and held by two cheeks 4. The meshes are such that the filtration orifices have an equivalent diameter ( diameter of the circle inscribed in the mesh) in the range 5-150 micrometers.

 This fabric was waved in a manner known per se by passing under a suitable tool, for example a roller having an adequate surface, and the waves thus obtained were tightened in a manner known per se to form folds 5 parallel to the axis of the tube 2 and whose edges are rectilinear.

 According to the invention, to increase the filtration surface, the waves are waved so that each 5 ′ wave, instead of becoming a fold, turns into a series of waves which extends in a zig-zag lengthwise of the wave (Figures 3 and 4).

To produce such a sheet, it is possible to implement a method which comprises the operations consisting in
- supply a woven tablecloth 6 with metallic warp and weft threads, and cut it into rectangular sections having two parallel sides 7,7 '(or 8,8') oblique to the direction of the warp threads, preferably 450 warp (or weft) threads (Figure 5) ;;
- move the flat section parallel to the sides 7.7 '(or 8.8'), that is to say in the case shown in a direction 9 to 450 of the warp (or weft) threads by making it pass in contact with a roller 10 capable of creating in the section of the sheet parallel waves 11 oriented perpendicular to the direction of movement (Figures 6 and 7)
- Keep the section of sheet flat, for example between two plates, and compress the edge of the sheet in a direction 12 parallel to the orientation of the waves, which has the consequence that each wave 11 is transformed into a series of waves 12 in zigzag (figure 9).

 This sheet twice corrugated in perpendicular directions can be used in a filter element, flat or wound on a tubular core whose wall allows the medium to be filtered or the filtrate to pass, depending on the direction of filtration.

 The invention is not limited to the embodiments which have been described. In particular, the fabric can receive various coatings or undergo other treatments.

Claims (9)

1. Filter cloth made up of a stiff but deformable fabric (1) made of metallic warp and weft threads, the meshes of which determine the filtration orifices, said fabric being shaped to form parallel waves, called "first waves", characterized in that each first wave (5 ') is itself constituted by a series of secondary waves which extends in the length of the wave. 2. Filter cloth according to claim 1, characterized in that the first waves are oriented obliquely with respect to the direction of the warp (or weft) threads of the fabric. 3. Filter mat according to claim 2, characterized in that the first waves are oriented at 450 with respect to the direction of the warp (or weft) threads. 4. Filter cloth according to claim 2 or 3, characterized in that it consists of a rectangular section of fabric having two parallel sides (7,7 ′ or 8,8 ′) perpendicular to the direction of the first waves. 5. Method for manufacturing a filter sheet according to one of claims 2 to 4, which comprises the operations consisting in:  - supply a fabric (6) with metallic warp and weft threads,  - move the fabric flat in a direction (9) oblique to the direction of the warp (or weft) son, passing it in contact with a roller (10) capable of creating in the fabric of the first waves oriented perpendicular to the direction of travel  - keep the tissue flat and compress the edge of the tissue in a direction (12) parallel to the orientation of the first waves so that each first wave forms a series of secondary waves which extends in the length of the wave first. 6. Method according to claim 5, characterized in that the fabric is moved in a direction which makes an angle of 450 with respect to the direction of the warp (or weft) threads.  7. Method according to claim 5 or 6, characterized in that the fabric (6) is cut into rectangular sections of which two parallel sides (7,7 ′ or 8,8 ′) are oblique with respect to the warp threads and in that that the fabric is moved parallel to one of said sides to pass it in contact with said roller (10). 8. Filter element, characterized in that it comprises a sheet according to one of claims 1 to 4 and / or obtained by a method according to one of claims 5 to 7. 9. Filter element according to claim 8, characterized in that the filter sheet is wound on a tubular core (2) whose wall allows the medium to be filtered or the filtrate to pass, depending on the direction of filtration.