Filter cloth, filtering process, and filtering device for liquid filtration

• US 6,103,132 A
• Filed: 12/16/1998
• Issued: 08/15/2000
• Est. Priority Date: 06/19/1996
• Status: Expired due to Term

• Current Assignee: Carl Franz Seyfried, Ulrich Grabbe
• Original Assignee: Carl Franz Seyfried, Ulrich Grabbe
• Inventors: Seyfried, Carl Franz, Grabbe, Ulrich
• Primary Examiner(s): Popovics, Robert J.
• Application Number:
  US09/216,639
• Time in Patent Office: 608 Days
• Field of Search: 210/784, 210/791, 210/402, 210/391, 210/407, 210/408, 210/409, 210/410, 210/330, 210/331, 210/332, 210/333.01, 55/290
• US Class Current: 210/791
• CPC Class Codes: B01D 2239/0208 Single-component fibres
• CPC Class Codes: B01D 2239/0216 Bicomponent or multicomponent fibres
• CPC Class Codes: B01D 2239/0241 comprising electrically conductive fibres or particles
• CPC Class Codes: B01D 2239/04 Additives and treatments of the filtering material
• CPC Class Codes: B01D 2239/0478 on a layer of the filter
• CPC Class Codes: B01D 2239/065 More than one layer present in the filtering material apparatus incorporating such gas filtering material B01D2275/10
• CPC Class Codes: B01D 2239/0672 The layers being joined by welding
• CPC Class Codes: B01D 2239/0681 The layers being joined by gluing
• CPC Class Codes: B01D 33/073 arranged for inward flow filtration
• CPC Class Codes: B01D 33/21 with hollow filtering discs transversely mounted on a hollow rotary shaft
• CPC Class Codes: B01D 33/50 with backwash arms, shoes or nozzles
• CPC Class Codes: B01D 33/503 the backwash arms, shoes acting on the cake side
• CPC Class Codes: B01D 35/10 Brush filters ; Rotary brush filters
• CPC Class Codes: B01D 39/083 of organic material

Abstract

A filter cloth for liquid filtration is made as a long-pile fabric, the pile threads 21 of which lie on the flow side and are flattened against the supporting fabric during the filtration and form a deep filter. At the time of back washing they are straightened by the back washing and release the dirt particles. The back washing is performed preferably by means of a suction bar 13, which at the same time acts mechanically on the pile threads, in order to promote an abrupt straightening of the pile threads at the time of back washing and the flattening of the pile threads after the back washing.

Claims

1. A process for filtering liquid, comprising the steps of:

a. guiding a flow of liquid to be filtered through a filter cloth having a supporting fabric (20) and a pile made of pile threads (21) on the side against which the liquid flows;

said flow of liquid causing the pile threads (21) to be flattened toward the supporting fabric (20) and to form a spacial filter having angled and multiply curved flow channels;

b. back washing the filter cloth at time intervals by moving a suction bar (13) having a suction slit (17) over said filter cloth on the pile thread side thereof and causing the suction bar to exert a suction force to create a back washing flow by sucking the liquid through the filter cloth;

said back washing flow causing the pile threads (21) in the area of the suction slit (17) to be straightened up to a position directed away from the supporting fabric (20);

c. subjecting said pile threads (21), prior to entering the suction slit, to a mechanical retaining action which retains the pile threads (21) in their flattened position against the fabric and prevents them from straightening up; and

d. abruptly releasing the pile threads (21) from said mechanical retaining action upon partial entry thereof into the suction slit whereby the pile threads (21) are caused to straighten abruptly within the suction slit.

2. The process of claim 1, wherein the width of the suction slit is a multiple of the length of the pile threads (21).

3. The process of claim 1, comprising the further step of subjecting the pile threads (21) leaving a suction slit to a mechanical flattening action to return the pile threads (21) to their flattened position as they leave the suction slit.

4. A device for filtering liquid comprising a filter cloth located in the path of flow of the liquid to be filtered, the filter cloth having a support fabric and a pile made of pile threads (21) on its side exposed to the flow, the length, stiffness, and density of the pile threads being controlled so that they are flattened by the flow of the liquid being filtered and form a deep filter with angled and multiply curved flow channels,

a suction bar (13) on the pile side of the filter cloth, with a suction slit (17) for sucking a back washing flow through the filter cloth at a flow rate such that in the back washing the pile threads straighten out into a position directed away from the filter cloth,

and means for creating relative motion between the suction bar and the filter cloth (6) in a direction of motion parallel to the plane of the filter cloth, the suction bar (13) having a surface (18) turned toward the filter cloth (6) at least on the side of the suction slit (17) lying upstream with respect to the relative motion, which surface is spaced from the filter cloth (6) by such a short distance that it acts mechanically on the pile threads (21) prior to entering the suction slot to retain the pile threads in their flattened position against the fabric and abruptly release the pile threads upon entry into the suction slit.

5. The device of claim 4, wherein the surface (18) forms a sharp edge (19) on the edge of the suction slit (17).

6. The device of claim 4, wherein the width (3) of the suction slit (17) is greater than the length of the pile threads (21).

7. The device of claim 6, wherein the width (8) of the suction slit (17) amounts to a multiple of the length of the pile threads (21).

8. The device of claim 4, wherein the pile threads (21) consist of multifilaments with free ends separated into individual filaments.