Support tube, filter element and filter system having a support tube and method and device for producing the support tube

Abstract

A support tube for a filter element, in which the support tube is an elongated tubular member having a central longitudinal axis extending through a hollow interior of the support tube. The support tube has a plurality of through openings extending through a circumferential wall of the support tube and is formed in one piece and a unitary component. The plurality of through openings are bounded by at least five longitudinal webs which are polygonal in cross section in at least some sections in the longitudinal direction of the support tube. The at least five longitudinal webs are in each case formed symmetrically.

Claims

1. A device for producing by injection molding a one-piece support tube made of plastic, wherein the one-piece support tube is an elongated tubular member having a central longitudinal axis extending through a hollow interior of the one-piece support tube, the one-piece support tube elongated in a longitudinal direction defined by the central axis, the one-piece support tube having a plurality of through openings extending through a circumferential wall of the one-piece support tube; wherein the one-piece support tube is formed in one piece and a unitary component; wherein the plurality of through openings are bounded by at least five longitudinal webs which are polygonal in cross section in at least some sections in the longitudinal direction of the one-piece support tube; wherein the at least five longitudinal webs are in each case formed symmetrically with respect to a central plane thereof, the central plane running in the longitudinal direction of the one-piece support tube and intersecting the central longitudinal axis of the one-piece support tube; wherein the device has a mandrel which is substantially cylindrical in shape and the outside of which bounds the inside of the support tube during the production thereof; wherein the device has at least three outer elements which can be arranged around the mandrel; wherein plastic is introduced between the mandrel and the outer elements into empty spaces of the device which are provided to form the longitudinal webs of the one-piece support tube; wherein the empty spaces are formed symmetrically with respect to the central plane thereof which runs in a longitudinal direction of the mandrel and intersects the central longitudinal axis of the mandrel.

2. The device according to claim 1, wherein empty space for a longitudinal web is provided in at least one region between two outer elements and the mandrel.

3. The device according to claim 2, wherein the empty spaces is at least five empty spaces; wherein for s longitudinal webs, a=s/2 outer elements are provided on the device and a is a rounded-up whole number.

4. The device according to claim 1, wherein the one-piece support tube is formed radially symmetrically with respect to its central longitudinal axis.

5. The device according to claim 1, wherein the longitudinal webs are formed rotationally symmetrically with respect to the central longitudinal axis of the support tube.

6. The device according to claim 1, wherein all longitudinal webs have a same quadrangular cross section.

7. A method for producing by injection molding a one-piece support tube, wherein the one-piece support tube is an elongated tubular member having a central longitudinal axis extending through a hollow interior of the one-piece support tube, the one-piece support tube elongated in a longitudinal direction defined by the central axis, the one-piece support tube having a plurality of through openings extending through a circumferential wall of the one-piece support tube; wherein the one-piece support tube is formed in one piece and a unitary component; wherein the plurality of through openings are bounded by at least five longitudinal webs which are polygonal in cross section in at least some sections in the longitudinal direction of the one-piece support tube; wherein the at least five longitudinal webs are in each case formed symmetrically with respect to a central plane thereof, the central plane running in the longitudinal direction of the one-piece support tube and intersecting the central longitudinal axis of the one-piece support tube; wherein the method for producing by injection molding the one-piece support tube comprises the following steps: providing a mandrel; pressing of at least three outer elements against an outside of the mandrel; wherein empty spaces running at least in sections in a longitudinal direction of the mandrel are produced between the outer elements and the mandrel which in each case are formed symmetrically with respect to the central plane thereof which runs in the longitudinal direction of the mandrel and intersects a central longitudinal axis of the mandrel; introducing plastic material into the empty spaces; allowing the plastic to cool and set; and spacing of the outer elements from the mandrel along the central planes of the empty spaces which intersect the central longitudinal axis of the mandrel.

8. The method for producing by injection molding a one-piece support tube according to claim 7, wherein the one-piece support tube is formed radially symmetrically with respect to its central longitudinal axis.

9. The method for producing by injection molding a one-piece support tube according to claim 7, wherein the longitudinal webs are formed rotationally symmetrically with respect to the central longitudinal axis of the support tube.

10. The method for producing by injection molding a one-piece support tube according to claim 7, wherein all longitudinal webs have a same quadrangular cross section.

11. The method for producing by injection molding a one-piece support tube according to claim 7, wherein, after the spacing step, the method further comprises arranging a ring-shaped filter medium onto a radially outer side of the one-piece support tube, so as to rest directly against the longitudinal webs on the radially outer side of the one-piece support tube.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further characteristics and advantages of the invention can be seen from the following detailed description of a plurality of exemplary embodiments of the invention based on the figures, the drawing, which shows the details essential to the invention, and from the patent claims.

(2) The characteristics shown in the drawing are presented in such a way that the special features according to the invention can be made clearly visible. The different characteristics can be realized individually in their own right or jointly in any combination in variants of the invention.

(3) The prior art and exemplary embodiments of the invention are shown in the schematic drawing and are explained in more detail in the following description.

(4) In the drawings:

(5) FIG. 1 shows a sectional side view of a filter system according to the invention having a support tube according to the invention;

(6) FIG. 2 shows a sectional plan view on a filter system according to FIG. 1 having a support tube according to the prior art;

(7) FIG. 3 shows a sectional plan view on the filter system according to FIG. 1 having a support tube according to the invention;

(8) FIG. 4 shows a sectional plan view on a device for the production of the support tube from FIG. 2 according to the prior art; and

(9) FIG. 5 shows a sectional plan view on a device according to the invention for the production of the support tube according to the invention according to FIG. 1 and FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

(10) FIG. 1 shows a filter system 1 according to the invention, here an air filter system, having a filter element 6. The filter element 6 has a first end plate 8 and a second end plate 10 and is arranged in a housing 12 which has a fluid inlet 14 and a fluid outlet 16. The fluid to be cleaned (not shown), here air to be cleaned, flows in the direction of a first arrow 18 onto a filter medium 20 of the filter element 6, which is folded several times and surrounds a central or support tube 22 of the filter element 6. In doing so, the filter medium 20 rests directly on the outside of the support tube 22.

(11) The support tube 22 is formed in one piece from plastic and has a multiplicity of transverse webs and longitudinal webs which bound a multiplicity of through openings. For reasons of clarity, only a first transverse strut 24, a second transverse strut 26, a first longitudinal web 28 and a second longitudinal web 30 are assigned a reference. Together with the longitudinal webs 28, 30, the transverse webs 24, 26 define a first through opening 32.

(12) The fluid cleaned by the filter medium 20 flows from the outside through the through openings, for example the first through opening 32, into the support tube 22, from where the fluid flows axially out of the support tube 22 in the direction of a second arrow 34 and further in the direction of a third arrow 36 out of the housing 12.

(13) A fluid sensor 38 in the form of a fluid mass sensor, here an air mass sensor, is arranged between the support tube 22 and the fluid outlet 16. The fluid sensor 38 measures part of the fluid flow. From this, the total quantity of fluid per unit time leaving the filter system 1 or the filter element 6 can be determined. However, the measurement of the fluid sensor 38 is only sufficiently precise when there is no or only a small amount of turbulence in the fluid flow. Such turbulence or other irregularities in the fluid flow occur particularly when the filter element 6 is arranged in a differently rotationally oriented position in the housing 12.

(14) The inventors have now discovered that the extent of turbulence or the homogeneity of the fluid flow depends significantly on the shape of the longitudinal webs, for examples of the longitudinal webs 28, 30.

(15) FIG. 2 shows a sectional plan view on a filter system 1a according to the prior art which is constructed substantially as the filter system 1 according to FIG. 1 but has a disadvantageous support tube 22a. The support tube 22a has a plurality of longitudinal webs, of which only a first longitudinal web 28a and a second longitudinal web 30a are assigned a reference for reasons of clarity. The longitudinal webs 28a and 30a have a different cross section. In particular, the longitudinal webs 28a, 30a differ with regard to their shape and therefore their flow resistance. This can result in an incoming radial flow of fluid (not shown) of different strength in the center of the support tube 22a.

(16) In contrast, FIG. 3 shows a sectional plan view on the filter system 1 according to FIG. 1. From FIG. 3, it can be seen that all longitudinal webs, for example the longitudinal webs 28, 30, have the same quadrangular cross section. Furthermore, all longitudinal webs are aligned towards the center 40 of the support tube 22. At the same time, the longitudinal webs are arranged rotationally symmetrically with respect to the center 40.

(17) The central longitudinal axis of the support tube 22 runs through the center 40. All longitudinal webs, for example the longitudinal webs 28, 30, are formed symmetrically with respect to the central plane thereof which runs in the longitudinal direction of the support tube 22 and intersects the central longitudinal axis of the support tube 22. In FIG. 3, only a first central plane 42 of the first longitudinal web 28 and a second central plane 44 of the second longitudinal web 30 are assigned a reference for reasons of clarity. The arrangement according to the invention of the longitudinal webs produces an equally high resistance when the fluid (not shown) flows radially into the support tube 22.

(18) FIG. 4 shows a sectional view of a device 46a according to the prior art for producing the support tube 22a from FIG. 2 by injection molding.

(19) The device 46a comprises a one-piece mandrel 48a with a circular cross section, against the radial outer side of which a first outer element 50a and a second outer element 52a are pressed. The outer elements 50a, 52a have recesses, of which only a first recess 58a and a second recess 60a are assigned a reference for reasons of clarity. As a result, empty spaces, of which a first empty space 62a and a second empty space 64a are assigned a reference, are formed between the mandrel 48a and the outer elements 50a, 52a. Plastic (not shown) is injected into and sets in the empty spaces, for example the empty spaces 62a, 64a. The first outer element 50a is then separated from the mandrel 48a in the direction of a fourth arrow 66a, and the second outer element 52a in the direction of a fifth arrow 68a. At the same time, the empty spaces, for example the empty spaces 62a, 64a, are designed so that the recesses, for example the recesses 58a, 60a, have no undercut, thus enabling the outer elements 50a, 52a to be moved away from the mandrel 48a in the direction of the arrow 66a, 68a without damaging the newly produced support tube 22a (see FIG. 2).

(20) In contrast, FIG. 5 shows a device 46 according to the invention for the production of the support tube 22 according to the invention according to FIG. 3. The device 46 has a one-piece, cylindrical, that is to say circular in cross section, mandrel 48, against the radial outer side of which a first outer element 50, a second outer element 52, a third outer element 54 and a fourth outer element 56 are pressed. The outer elements 50, 52, 54, 56 have recesses, of which only a first recess 58 and a second recess 60 are assigned a reference for reasons of clarity. As a result of the recesses, for example the recesses 58, 60, empty spaces, of which a first empty space 62 and a second empty space 64 are assigned a reference, are formed between the mandrel 48 and the outer elements 50, 52, 54, 56. Plastic (not shown) is injected into and sets in the empty spaces, for example the empty spaces 62, 64, in order to produce the support tube 22 (see FIG. 3) with its longitudinal webs, for example the longitudinal webs 28, 30 (see FIG. 3). As an alternative or in addition to their formation on the outer elements 50, 52, 54, 56, the recesses, for example the recesses 58, 60, can be formed on the mandrel 48.

(21) After the plastic has set, the first outer element 50 is moved radially away from the center 74 of the mandrel 48 in the direction of a sixth arrow 66, the second outer element 52 in the direction of a seventh arrow 68, the third outer element 54 in the direction of an eighth arrow 70 and the fourth outer element 56 in the direction of a ninth arrow 72. The empty spaces, for example the empty spaces 62, 64, are formed symmetrically with respect to the central plane thereof which runs in the longitudinal direction of the mandrel 48 and intersects the central longitudinal axis of the mandrel 48. By way of example, a first central plane 76 of the first empty space 62 and a second central plane 78 of the second empty space 64 are shown in FIG. 5.

(22) The empty spaces, for example the empty spaces 62, 64, are arranged rotationally symmetrically with respect to the center 74 of the mandrel 48 and all have the same quadrangular cross section.

(23) An empty space is in each case provided in all regions between two outer elements 50, 52, 54, 56 and the mandrel 48. For example, the second empty space 64 is provided in the region between the first outer element 50 and the third outer element 54. This enables the device 46 to be formed with a minimum number of outer elements without damaging the support tube 22 (see FIG. 3) when removing from the mold.

(24) In summary, the invention therefore relates to a device for producing a support tube made of plastic for a filter element of a filter system. The longitudinal webs of the support tube are formed symmetrically with respect to the center of the support tube and preferably have the same, in particular quadrangular, cross section. At the same time, the support tube is preferably substantially cylindrical in shape overall. The support tube can be produced by injection molding by carrying out a method according to the invention in a device according to the invention, which has a mandrel, which, in particular, is cylindrical in shape, against which outer elements with recesses can be pressed. Empty spaces for the longitudinal webs are provided between the mandrel and the outer elements. The empty spaces are aligned symmetrically with respect to the center of the mandrel. In doing so, the outer elements are arranged around the mandrel so that they can be removed from the mandrel without forming undercuts in the empty spaces, so that the support tube produced with the device is not damaged when removing from the mold. By means of the invention, a support tube, into which a fluid can be sucked or pressed, can be created in a structurally simple and cost-effective manner. This is an advantage for a measurement, which is necessary in many applications, of the fluid flow fed out of the filter system or the filter element.