TUBULAR FILTER MEMBRANE ELEMENT AND METHOD FOR THE PRODUCTION THEREOF

Abstract

In order to produce a tubular filter membrane element for microfiltration purposes, a plastic section of a small membrane tube is sealed at one axial end thereof and is fitted with a plastic adapter piece at the opposite end. The adapter piece is injection-molded onto the section of the small membrane tube and is preferably welded thereto. The section of the small membrane tube is sealed at the one axial end thereof by bringing this end into contact with a hot stamp.

Claims

1. A method for producing a tubular filter membrane element for microfiltration, the method comprising the steps of: sealing a membrane tube section consisting of plastic at one axial end of the membrane tube section to provide a sealed axial end; and providing an adapter piece consisting of plastic at another axial end of the membrane tube section, which is opposite to the sealed axial end, wherein the step of sealing comprises sealing the one axial end by contacting the one axial end with a hot punch forming the one axial end into a desired shape.

2. A method in accordance with claim 1, wherein the membrane tube section is positioned on a mandrel during the sealing of the one axial end.

3. A method in accordance with claim 1, wherein the one axial end of the membrane tube section is inserted into a recess of the hot punch.

4. A method in accordance with claim 1 wherein a shape tapering conically in the axial direction is formed at the sealed axial end of the membrane tube section.

5. A method in accordance with claim 1, wherein the membrane tube section is rotated or pivoted about a longitudinal axis thereof during the step of sealing the one axial end.

6. A method in accordance with claim 1, wherein the hot punch is rotated or pivoted during the step of sealing the one axial end of the membrane tube section.

7. A method in accordance with claim 1, wherein the adapter piece is injection-molded onto the membrane tube section.

8. A method in accordance with claim 7, wherein the membrane tube section is arranged on a positioning mandrel in a cavity of an injection molding device and is held by the positioning mandrel during the injection molding.

9. A method in accordance with claim 8, wherein the membrane tube section is seated with a close fit on the positioning mandrel.

10. A method in accordance with claim 8, wherein the positioning mandrel has a receiving section, onto which the membrane tube section is pushed, and an enlarged mandrel section, which is arranged axially offset in relation thereto.

11. A method in accordance with claim 8, wherein a plastic melt is introduced into the cavity through a feed channel, wherein the opening of the feed channel is oriented such that the plastic melt reaches the positioning mandrel at a spaced location from the membrane tube section.

12. A method in accordance with claim 11, wherein the plastic melt reaches the enlarged mandrel section.

13. A method in accordance with claim 11, wherein the feed channel is divided into at least two branch channels upstream of the opening in the cavity.

14. A method in accordance with claim 1, wherein the adapter piece is welded to the membrane tube section.

15. A filter membrane element comprising: a membrane tube section consisting of plastic, which is sealed at one axial end by contacting the one axial end with a hot punch to form a desired shape sealed axial end; and an adapter piece consisting of plastic at another axial end of the membrane tube section, which is opposite to the desired shape sealed axial end, wherein the desired shape is such that the membrane tube section has a shape tapering conically in an axial direction at the desired shape sealed axial end.

16. A filter membrane element in accordance with claim 15, wherein the adapter piece is injection-molded to the membrane tube section and is welded to same.

17. A filter membrane element in accordance with claim 1, wherein the adapter piece is a connection sleeve for a fluid line.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In the drawings:

[0034] FIG. 1 is a longitudinal view through a filter membrane element;

[0035] FIG. 2 is a first phase of the preparation of a membrane tube section;

[0036] FIG. 3 is a second phase of the preparation of the membrane tube section;

[0037] FIG. 4 is a third phase of the preparation of the membrane tube section;

[0038] FIG. 5 is a fourth phase of the preparation of the membrane tube section;

[0039] FIG. 6 is a vertical section through an injection molding device after introduction of the plastic melt; and

[0040] FIG. 7 is section VII-VII in FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] Referring to the drawings, FIG. 1 shows a tubular filter membrane element 10 for microfiltration. The filter membrane element 10 has a membrane tube section 11 consisting of plastic, which is sealed at one of its ends, at the left-hand axial end according to FIG. 1, forming a shape tapering conically in the axial direction, and which is connected at its opposite end, at the right-hand end according to FIG. 1, to an adapter piece 20 consisting of plastic which forms a connection sleeve for a fluid line. The membrane tube section 11 consists of a permeable plastic material, wherein the permeability may be formed by a basic porosity of the material and/or by a subsequently prepared perforation.

[0042] The preparation of the tubular filter membrane element 10 will be explained below in individual steps on the basis of FIGS. 2 through 7.

[0043] The material of which the membrane tube section 11 consists is a flexible membrane tube strand 12, i.e., a so-called endless material. The membrane tube strand 12 is gripped and fixed at its free end by means of a gripper 14, suggested only schematically, after which a membrane tube section 11 having a predefined length is cut off from the membrane tube strand 12 by means of a knife 13.

[0044] The membrane tube section 11 is gripped, further, by means of the gripper 14 and is pushed by this onto a pin-like mandrel 15 until the end of the membrane tube section 11 facing away from the gripper contact with a stop 16 of the mandrel 15. The membrane tube section 11 is held on the mandrel 15 by friction and optionally while undergoing elastic deformation. This state is shown in FIG. 3.

[0045] The free axial end of the membrane tube section 11 facing away from the stop 16 is then brought into contact with a hot punch 17, which has a conical or semi-ellipsoidal recess 18, as it is suggested by the arrow in FIG. 4. The hot punch 17 is heated to a temperature that softens the material of the membrane tube section 11 and melts it at least partially. Due to the free end of the membrane tube section being pressed into the recess 18 of the hot punch 17, this end of the membrane tube section 11 is sealed, on the one hand, and shapes it at the same time to a desired contour, for example, a contour ending in a point, as it is shown in FIG. 5.

[0046] While the axial end of the membrane tube section 11, which end is to be sealed, is in contact with the recess 18 of the hot punch, the mandrel 15 together with the membrane tube section 11 and/or the hot punch 17 are rotated or pivoted about the longitudinal axis of the membrane tube section 11 in order to prevent the membrane tube section 11 from adhering to the hot punch 17.

[0047] The prefabricated membrane tube section 11, sealed at one axial end, is then inserted into an injection molding device 19, as it is schematically shown in FIG. 6. The injection molding device 19 has a pin-like positioning mandrel 21, which has an end-side receiving section 22a, onto which the membrane tube section 11 is pushed while the latter undergoes elastic widening. The receiving section 22a of the positioning mandrel 21 is adjoined by an enlarged mandrel section 22b, which has an enlarged external diameter, and a step, which forms a stop 25, which is struck by the open end of the membrane tube section 11, is formed in the transition area between the receiving section 22a and the enlarged mandrel section 22b.

[0048] After closing the injection molding device 19, the end area of the membrane tube section 11, which end area is located opposite the sealed axial end, and the area adjoining same around the enlarged mandrel section 22b of the positioning mandrel 21 are surrounded by a mold cavity or a cavity 23. A feed channel 24 for a plastic melt opens into the cavity 23. As is shown in FIG. 7, the feed channel 24 is divided directly in front of the opening into the cavity 23 into two branch channels 26, which open each into the cavity 23.

[0049] It is suggested in FIG. 6 that the opening of the feed channel 24 or of the branch channels 26 is oriented such that the plastic melt entering the cavity 23 through the opening does not reach directly the membrane tube section 11, but the outer side of the enlarged mandrel section 22b of the positioning mandrel 21, as is suggested by the arrow S1. The plastic melt rebounds from there and is distributed in the cavity 23, as it is suggested by the arrows S2.

[0050] The plastic melt is welded to the plastic material of the membrane tube section 11 and is firmly connected to same via a molecular bond.

[0051] After opening the injection molding device 19, the filter membrane element 10 shown in FIG. 1, in which the interior of the membrane tube section 11 is accessible through the sleeve-like adapter piece 20, is formed.

[0052] While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.