Wedge Wire Filter Tubes with Narrowed Slots

Abstract

The invention provides novel slot tube screen material for filtering applications, in particular for separating solid particles from liquids. The slot tube filter screens manufactured according to the invention feature very small slot openings, which are narrowed with respect to a slot opening dimension of conventionally fabricated slot filter tubes. The slot tube construction of the invention comprises a torsion-rotation deformed structure of normally axially orientated parallel support members of the slot tube mantle, which further comprises spiral windings of profile wire around said support members, whereby at each contact crossing a solid weld connection fixes a crossing profile wire to a support member. The plastically twisted slot tube structure displays a helical distortion of the axial support ribs inside the slot tube. As a consequence the filter slot openings between adjoining windings of profile wire are markedly narrowed (versus undeformed slot tube), which offers the possibility of reliably achieving very small filter slot openings of less than 0.020 mm in slot tube filters or screens.

Claims

1. Method of fabricating a slot tube, in particular a slot tube (screen) filter, which enables controlled attuning of a desired fine filter slot opening, whereby use is made of a conventionally known slot tube assembly of interconnected basic elements, which consist of axially extending support profiles wrapped around with radially crossing wire windings of profile wire, which are solidly fixed together at each mutual crossing and whereby adjoining profile wire windings delimit and define an interstitial, continuous (filter-) slot opening, characterized in that said known slot tube is subjected to torsion deformation by rotary twist, whereby the slot tube mantle is twisted relative to the slot tube axis by an adjustable amount of rotations within the plastic torsion area causing a permanent twist of the axial support ribs, and this until a desired final slot opening width or a required narrowing of initial (filter) slot opening is reached.

2. Slot tube or slot tube filter directly obtained by the method of claim 1, wherein an original disposition of parallel, axially directed support or mantle profiles of said known slot tube displays a torsion deformation pattern of support profiles following helical lines, and this in combination with a narrowed slot opening between adjacent wrappings of profile wire, as depicted in FIGS. 1A to 1D.

3. Slot tube as defined in claim 2, characterized in that the narrowed slot opening is smaller than 0.040 mm, in particular smaller than 0.020 mm.

4. Slot tube according to claim 2 or 3, wherein profile wire is helically wound with given pace and pitch parameter around axially directed support profile ribs, and wherein at each crossing a solid connection between support ribs and profile wire is selected from a weld connection, a mechanical fixation or an adhesive bonding, and preferably comprises a metallurgical weld connection obtained by electrical resistance welding such as spot-welding or obtained by laser welding.

5. Slot tube as defined in one of claims 2 to 4, wherein the profile wire comprises a cross-section selected from a round, a flat or a polygonal cross-section, and preferably comprises a wedge-shaped, trapezoid- or triangular-shaped section.

6. Slot tube according to one of claims 2 to 5, wherein the slot tube body has a cross-section selected from a circular section, a round section of oval shape or nearby circular form, a regular polygon or rounded polygon approaching a circle and the like, and preferably comprises the circumference of a perfect circle.

7. Slot tube according to one of claims 2 to 6, characterized in that the profile wire comprises a wedge-shaped or triangular cross-section with rounded top angle, and whereby either the flat side or the rounded top of the wedge or triangular wire forms a solid weld connection with the supporting profile members, such that the interstitial slot opening between adjoining profile wires can be disposed as a widening gap or a narrowing (wedge) opening in a selected flow direction.

8. Flat grid/screen filter elements having a narrowed filter slot opening obtained by applying the method according to claim 1 or by using a slot tube as defined in claim 2, characterized in that the torsion-twisted slot tube is cut open in a longitudinal direction, developed into a plane and flattened to flat grid/screen filter panels.

Description

[0020] According to a preferred embodiment of carrying out the invention the supporting profiles are disposed in an axial-symmetric way and parallel to one another as peripheral mantle lines of a cylindrical tube with a circular cross-section of desired diameter, and the continuous profile wire is helically coiled around the support profiles, whereby the non-stop running wire is permanently fixed thereto at each crossing by means of a spot-welding connection. In this helical winding and assembling process by spot-welding a predetermined initial slot opening width is established between mutually adjoining profile wires, whereby the characterizing feature of the invention consists in the fact that the required final slot opening is realized by subjecting the slotted tubular screen or filter body to plastic torsion in the axial direction of the slotted screen tube.

[0021] A suitable method for carrying out the key feature of the invention may comprise immobilizing one outer end portion of the cylindrical slot tube body, and consequently connecting the opposed tubular end portion with an adapted claw or clutch of a torque motor and thereby driving the latter end portion into rotational twisting until the cylinder body undergoes a permanent plastic torsion deformation. As a result the original axial-parallel orientation of the supporting profiles of the peripheral cylinder mantle of the slot tube is tuned into a twisted path following a helical line; depending on the number of imposed torsional rotations said helical path will adopt a varying angle towards the axial direction of the slot filter tube.

[0022] Owing to the fact that the solid weld connections are undeformable and hence will stay co-determinating for an axial interdistance between adjoining profile wires, it is consequently obvious that the oblique stretch deformation of the filter tube mantle's support profiles under the effect of torsional rotation, whereby the number of rotational twists determines the final oblique position of the helical path of the support profiles, will give rise to a proportional decrease or narrowing of the resulting slot width between adjacent profile wires.

[0023] This implies that the invention enables to adjust in a controlled way a slot width of a filter slot tube, incl. controlled narrowing the same.

[0024] As a consequence the invention allows to decrease the filter slot opening of filter slot screen tubes, which are known per se, to such an extent that the resulting slot tubes become suitable for filtering separations of much finer particles than formerly possible with state of the art devices.

[0025] Other preferred embodiments of carrying out the method according to the invention, and furthermore slot tube grid/screen components and slot tube filter elements as preferential products embodied by the present invention are defined in one or more subordinate claims depending from main claims 1 and 2.

[0026] A deeper understanding of the essence of the invention and further peculiar details and advantages of the invention will become more apparent from the following description of a preferred exemplary embodiment of the invention, which is illustrated and elucidated by the figures of drawing sheet 1/1.

[0027] The lower drawings A and C shown in the figure columns 1A and 1C on sheet 1/1 give a perspective view resp. overall picture of a slot tube filter screen of circular cross-section. Tubular filter screen C as well as A is assembled from supporting profile rods with axial-symmetric disposition, located at circumference of above-mentioned circular cross-section, which is clearly shown in sectional views A-A en C-C in the center part of figure columns 1 A and 1C of sheet 1/1.

[0028] De external mantle of filter tube A and filter tube C consists of profile wire with wedge-shaped cross-section, which is helically wound up and around the axially arranged support profiles and at each crossing is firmly secured by a welding connection.

[0029] FIG. 1A illustrates a slot tube A wherein a flat side of the wedge profile wire is directed to the tube outside (with rounded top angle of wedge section spot-weld attached upon the supporting profile rods), such that interstitial filter slot openings between adjoining profile wire windings are widening in a flow direction from outside to inside the slot filter tube.

[0030] The slot filter tube C example of FIG. 1C shows the opposite situation: here a flat lower side of the wedge profile wire is weld-connected to the support profile rods, and adjacent wedge profile wire windings delimit interstitial filter slots that are widening in a flow direction from inside to outside the slotted filter tube.

[0031] The picture A-A with detail A1 and picture C-C with detail C1 in the upper part of FIGS. (columns) 1A and 1B on sheet 1/1 show an axial longitudinal section van filter tube A resp. filter tube C, whereby detailed close-up sections A1 en C1 clarify an initial filter slot opening of width “a” before subjecting slot filter tube A as well as slot filter tube C to permanent torsion deformation by rotary torsioning.

[0032] Figures B1 and D1 showing longitudinal section views B-B, D-D, with details B1, D1 and further depicting overall perspective views of slot tubes B en D illustrated in the lower drawing row on sheet 1/1, elucidate more clearly which technical effect the invention is exerting, as a consequence of imposed torsional rotations, on a resulting slot opening width “b” of a slot filter tube and on the external aspect view of the tubular filter body exhibiting a helical twist of its internally arranged supporting profiles.

[0033] It is self evident that the present invention is not limited to the exemplary embodiments of slot tubes described herein above and illustrated on drawing sheet 1/1.

[0034] Flat filter screen elements having narrowed slot openings can be manufactured in a similar but deduced way, e.g. starting from tubular slit screens provided with narrowed slot openings obtained by torsional rotation, and axial cutting/opening the tubular body and flattening out the developed slot tube jacket mantle.

[0035] Curved and flat screen or grating elements having narrowed slot openings obtained by applying the key principle of the invention, including their working up and use in filter devices and systems also fall within the scope of protection of the present invention, which is primarily defined by the technical features recited in the appended claims.

[0036] The material used for fabricating slot tube filters for the purpose of solid/liquid filtering separations is mostly selected from stainless steels of a type suitable for withstanding the corrosivity of the liquid medium, and/or requires a particular stainless steel grade satisfying specific use conditions (hygienic, toxicity, etc.) imposed by the related industrial sector, such as for instance the food industries.

[0037] It is however obvious that the inventive concept of the present invention is not restricted to the normally used stainless steel alloys, but is equally applicable to other metals and metal alloys such as copper, nickel, aluminium and alloys thereof, as for instance monel (CuNi) and also titanium, special metal alloys as superalloys etc., provided said corrosion resistant metals and alloys can be worked up to profile wire and the like profile members, and are moreover mutually connectable by welding.