Mixing tip

Abstract

The invention relates to a mixing tip (100) comprising a mixer housing (50) and a mixing element (3), wherein at least one of the mixing element and the mixer housing has one or more retaining members (10) formed thereat, with the one or more retaining members being configured to hold the mixing element in the mixer housing.

Description

[0001] medmix Switzerland AG M29273PWO - To / Fk

[0002] Mixing tip

[0003] The invention relates to a mixing tip comprising a mixer housing and a mixing element.

[0004] Static mixers respectively mixing tips, as they are also known as, are used to mix multi-component material dispensed from a multi-component cartridge. Such static mixers are used in a plethora of fields of application ranging from industrial applications, such as the use of adhesives to bond structural components one to another, or as protective coatings for buildings or vehicles, to medical and dental applications, for example, to make dental molds.

[0005] The multi-component material is, for example, a two-component adhesive comprising a filler material and a hardener. In order to obtain the best possible mixing result, e.g. an adhesive having the desired bond strength, the multicomponent material has to be thoroughly mixed.

[0006] For this purpose, the static mixers comprise several mixing segments arranged one after the other as a mixing element in a mixer housing, with the mixing segments repeatedly dividing and re-combining part flows of the multi-component material to thoroughly mix the multi-component material.

[0007] The mixing elements are designed in order to achieve mixing results suited to the respective application.

[0008] On occasion it has been found that the assembly of mixing elements and mixer housing to form the static mixer is cumbersome. It is therefore an object of the invention to provide a static mixer with which the above mentioned drawbacks can be overcome.

[0009] Exemplary embodiments and functions of the present invention are described herein in conjunction with the following drawings, wherein:

[0010] Such a mixing tip comprises a mixer housing and a mixing element, wherein at least one of the mixing element and the mixer housing has one or more retaining members formed thereat, with the one or more retaining members being configured to hold the mixing element in the mixer housing.

[0011] Such a retaining member can improve the handling of the mixing tips during manufacture thereof as they enable the mixing element to be retained, i.e. held in the mixer housing reducing the amount of mixing tips discarded due to a missing mixing element.

[0012] In this connection it should be noted that a retaining member is a member that can be formed to interact between the mixing element and the mixer housing in order to hold, i.e. retain the mixing element in the mixer housing.

[0013] Said one or more retaining members may be formed by a snap hook. A snap hook is a simple to form retaining member that can be used to securely retain the mixing element in the mixer housing.

[0014] Said one or more retaining members may be formed on an outer surface of the mixing element. In this way the mixing element can be reliably formed to be captively held in the mixer housing by having members that engage the mixer housing.

[0015] Said one or more retaining members may be formed on an inner surface of the mixer housing. In this way the mixer housing can be reliably formed to captively hold the mixing element in the mixer housing by having members that engage the mixer housing.

[0016] Said one or more retaining members may be formed by projections projecting from one of the mixer housing and the mixing element. Such a projection is a simple to form retaining member that can be used to securely retain the mixing element in the mixer housing.

[0017] In this connection it should be noted that a particularly beneficial design of a projection is a snap hook that can engage a structure and thereby lock it to one of the mixer housing and the mixing element.

[0018] Said one or more retaining members may be symmetrically arranged at a surface of one of said mixer housing and the mixing element. In this way the force of holding the mixing element in the mixer housing can be evenly distributed about the mixing tip.

[0019] Said one or more retaining members may be alternatively or additionally asymmetrically arranged at a surface of one of said mixer housing and the mixing element. In this way a force of retaining the mixing element in the mixer housing can be tailored to certain types of application.

[0020] Said one or more retaining members may have a triangular shaped cross-section, a trapezoidal shaped cross-section, a semi-circular shaped cross-section, a circular shaped cross-section, an oval shaped cross-section and a polygonal shaped cross-section. Such shapes can beneficially used to form the retaining member in order to enable an easily installation of the mixing element in the mixer housing while ensuring a reliable retention of the mixing element in the mixer housing. In this connection it should be noted that If more than one kind of retaining member is provided, i.e. two differently shaped retaining members then the one or more retaining members of the first kind can be e.g. shaped as a projection that can engage one of the mixing element and the mixer housing, e.g. in the form of an annular ring engaging an annular shaped recess, i.e. with the projection having one of the above shapes and one or more of the second kinds of retaining members are differently shaped, e.g. as elongate projections that are, for example, press fit into corresponding slots in the mixer housing.

[0021] One or more recesses may be formed at the other one of said mixing element and the mixer housing, with at least one of said retaining members being received in a respective one of said recesses.

[0022] In this connection it should further be noted that the recesses are formed complementary in shape to the respective retaining member received in the recess.

[0023] One retaining member may be provided at the mixing element, with said retaining member being formed by an annular ring. Such an annular ring can beneficially be used to create a particularly good connection between the mixing element and the mixer housing in order to facilitate a good retention between the mixer housing and the mixing element.

[0024] The mixer housing may comprise a recess formed to receive said annular ring, by way of example such a recess is formed by a ring catch configured to receive at least a part of said annular ring by press fit or snap fit. In this way the mixing element can be held in a particularly beneficial manner at the mixer housing.

[0025] Said at least one retaining member may be press-fit and / or friction fit into a respective receiving structure formed at the other one of the mixer housing and the mixing element. Such a form of connection ensures a particularly good connection between the mixing element and the mixer housing.

[0026] The retaining member may have an elongate extent, with the elongate extent extending in parallel to a longitudinal axis of the mixing element. Such projections can be fir particularly well into elongate slots by way of press fit and / or friction fit.

[0027] Said one or more retaining members may be held at the mixer housing by deforming a part of the mixer housing by hot welding after installation of the mixing element in the mixer housing. In this way a part of the mixer housing can be deformed to form e.g. a base against which the mixing element may abut during assembly with the mixing element not being able to pass past the base.

[0028] The mixing element may have one of a square or rectangular cross-section along at least a part of the length of the mixing element. Such cross-sections of mixing elements can be retained particularly well in a correspondingly shaped mixer housing by means of one or more of the retaining members shown herein.

[0029] Exemplary embodiments and functions of the present invention are described herein in conjunction with the following drawings, wherein:

[0030] FIG. 1 shows a perspective cross-sectional view of the basic configuration of a static mixer according to an exemplary embodiment of the present invention;

[0031] FIG. 2A shows a perspective view of a static mixer insert according to a first embodiment of the present invention;

[0032] FIG. 2B shows a top view of the static mixer insert of FIG. 2A;

[0033] FIG. 2C shows an enlarged view of a left end of FIG. 2B;

[0034] FIG. 2D shows a longitudinal view of the static mixer insert of FIG. 2A from a first end of the static mixer insert;

[0035] FIG. 2E shows a side view of the static mixer insert of FIG. 2A; FIG. 2F shows a longitudinal view of the static mixer insert of FIG. 2A from the second end of the static mixer insert;

[0036] FIG. 3A to C show part sectional views of a first kind of static mixer;

[0037] FIG. 4A&B show part sectional views of a second kind of static mixer;

[0038] FIG. 5A to C show part sectional views of a first kind of static mixer;

[0039] FIG. 6A&B show part sectional views of a second kind of static mixer; and FIG. 7A&B show part sectional views of a second kind of static mixer.

[0040] Throughout the drawings, identical reference numerals denote corresponding or at least similar elements. The static mixer inserts 1 described in the following are provided for a flow of the components to be mixed along the longitudinal axis LA of the corresponding mixing structure 3 as indicated by the arrow at the end of said longitudinal axis LA.

[0041] As can be seen in FIG. 1 , an exemplary static mixer 100 or mixing tip 100 as they are also known comprises a static mixer insert 1 and a mixing tube 51 . Said static mixer insert 1 comprises a mixing structure 3 extending longitudinally along a longitudinal axis LA of the mixing structure 3. In this connection it should be noted that the mixing structure 3 may also be referred to as a mixing element. The mixing structure 3 respectively the mixing element 3is received by a longitudinal central passageway 53 formed by the mixing tube 51 .

[0042] For reasons of support the static mixer insert 1 may comprise two longitudinally extending support bars 5 (see in particular Fig. 2), each then received by a longitudinal recess 55 along the central passageway 53 of the mixing tube 51 if provided.

[0043] The present static mixer insert 1 is provided with a head 21 comprising a flat disc portion 23 and two inlets 25 oriented in parallel with the longitudinal axis LA of the mixing structure 3. Each inlet 25 comprises a respective inlet passage 24 for conducting material to be mixed from a cartridge (not shown) to the mixing structure 3 for mixing and subsequent dispensing via a outlet 52 of the static mixer 100.

[0044] Said head 21 is provided for a fluidical coupling of the mixing structure 3 with outlets of a dispensing device (not illustrated) comprising two chambers, each filled with one of the two viscous components, which are to be mixed with each other prior to application thereof at a desired area. The term component as used herein includes both of pure materials and composite material.

[0045] In the illustrated embodiment, the disc portion 23 of the head 21 is ultrasonic- welded to a coupling ring 61 provided at a cover portion 59 of the mixing tube 51 to provide a further fixation of the static mixer insert 1 to the mixing housing 51 in addition to a press-fit fixation formed between the longitudinal support bars 5 of the static mixer insert 1 and the recesses 55 of the mixing tube 51 . Furthermore, the mixing tube 51 is provided with a coupling portion 57 for connecting a dispensing tip (not illustrated) thereto. However, such a dispensing tip could also be integrated directly into the mixing tube 51 .

[0046] The cover 59 can comprise coupling means 62 (see e.g. Fig. 7a that are provided in Fig. 7a in the form of an inner thread 64) in order to couple the static mixer 100 to a cartridge (also not shown).

[0047] In the illustrated embodiment, the mixing structure 3 is connected to said head 21 in an orientation resulting in that a first separation wall (described further below; 7) of the mixing structure 3 is oriented perpendicular with respect to a common extension plane of the two inlets 25 (substantially corresponding to the sectional plane of FIG. 1 ). Thus, the two inlets 25 are separated from each other, vie said first separation wall, preventing any leakage of the component from one inlet 25 through the other into the chamber for the other component within the dispensing device. Alternatively, said first separation wall 7 can lie within said common extension plane resulting in a direct mixing of the components from the two inlets 25.

[0048] In the following, further details are described with respect to exemplary embodiments for static mixer inserts 1 according to the present invention. Although not illustrated here, each of said static mixer inserts 1 can be supplemented by the head 21 described above or similar configurations.

[0049] The static mixer 100 indicated in Fig. 1 comprises a snap fit element 56 adjacent the outlet 52, i.e. at its end comprising the outlet 52. The snap fit element 56 is presently formed as an annular projection surrounding a mixer housing 50. In this connection it should be noted that the mixer housing 50 could comprise an annular recess at the position of the snap fit element 56 or be formed with a continuous outer surface at this part of the housing 50.

[0050] The snap fit element 56 is configured to cooperate with a correspondingly shaped snap fit element (not shown) of an accessory (also not shown) that can be connected to the static mixer 100 at the connection portion 57.

[0051] The accessory can be a dispensing outlet, such as a intra oral reflector that more freely enables a variation of the position of a point of application of a material to be dispensed.

[0052] As can be seen in Figures 2A to 2F, a static mixer insert 1 according to a first embodiment of the present invention comprises a mixing structure 3 formed of various flat elements 7, 9 and 13, and therewith integrally formed, for example via an injection-moulding process, two support bars 5 with semi-circular crosssections. In this embodiment, the mixing structure 3 comprises a first set of separation walls 7 connecting the two support bars 5 to each other, a second set of separation walls 9 connecting successive separation walls 7 of the first set of separation wall 7 to each other, and deflection plates 13 coupled to the separation walls 7 and 8. The separation walls 7 of the first set of separation walls 7 lie within a first plane along the longitudinal axis LA of the mixing structure 3 (parallel to the image plane of FIGS. 2B and 2C). The separation walls 9 of the second set of separation walls 9 lie within a second plane along the longitudinal axis LA of the mixing structure 3 but in perpendicular with respect to the first plane of the separation walls 7 of the first set of separation walls 7 (parallel to the image plane of FIG. 2E). The deflection plates 13 are oriented substantially perpendicular with respect to both of the first plane of the separation walls 7 of the first set of separation walls 7 and the second plane of the separation walls 9 of the second set of separation walls 9 (i.e. parallel to the image plane one FIGS. 2D and 2F).

[0053] As can be seen best in FIG. 2A in view of FIG. 2B, the separation walls 7 and 9 of the two sets of separation walls 7 and 9 from passage windows 11 along said first plane. Said passage windows 11 are formed with an aspect ratio (i.e. with a ratio of the height B to the width F of each of said passage windows 11 ) of 0.5 to 1 .0. In the illustrated embodiment, the deflection plates 13 are provided on an upstream side of each of said passage windows 11 and oriented perpendicular to the longitudinal axis LA of the mixing structure 3. However, said deflection plates 13 can be position also on a downstream side and / or can be tilted with respect to the longitudinal axis LA by an angle a (see FIG. 2C) in the range of 60° to 120°.

[0054] The parts 7, 9 and 13 of the mixing structure are dimensioned such that the mixing structure 3 has a substantially rectangular cross-section with an aspect ratio, i.e. with a ratio of its width S to its depth T of 0.7 to 1 .3, in particular of 1 .0 (see FIG. 2D). The provided support bars 5 allow mixing structures 3 with a width S of 1 .0mm to 4.0mm and in particular of 1 .8mm. With respect to the support bars 5, it is pointed to the fact these can also be formed with other cross-sectional shapes, like with partially or fully polygonal cross-sections, for example with a preferably equilateral triangular, quadrangular, pentagonal, hexagonal or octagonal cross-sections, at least partially or fullly oval cross-sections and / or other partially or even fully circular cross-sections. Additionally or alternatively, each support bar 5 can be provided with a tapered portion 5a for facilitating an insertion operation into a corresponding mixing tube 51 for forming a static mixer 100 in accordance with the present invention (see for example FIG. 2B).

[0055] Preferably, the ratio of the thickness D to the width C of each of the support bars 5 is in the range of 0.4 to 0.7 while the ratio of the width C of each of the support bars 5 to the width S of the mixing structure is in the range of 0.2 to 0.5, to ensure a preferable structural stability.

[0056] As not illustrated, and in contrast to the above configuration, in which a separation wall 7 of the first set of separation walls 7 forms the first separation wall of the mixing structure 3, also a separation wall 9 from the second set of separation walls 9 can form the first separation wall of the mixing structure 3.

[0057] With respect to the above described two sets of separation walls 7 and 9, and the deflection plates 13 it is pointed to the fact that sets of two connected separation walls 7 and 9 with a thereto connected deflection plate 13 can be considered as one mixing element, wherein several, like for example twelve as in the illustrated embodiment or even more like for example twenty-four, of these mixing elements can form the mixing structure 3. These mixing elements can be supplemented by one or multiple of special elements (not shown) for optimizing flow-guiding and mixing characteristics of the mixing structure 3.

[0058] It should further be noted that the mixing structure 3 can be formed without the support bars 5.

[0059] Fig. 3a to c show a further type of static mixer 100. The static mixer 100 comprises integrally formed coupling means 62 by means of which the static mixer 100 can be coupled to a cartridge (not shown).

[0060] In the present example the coupling means are formed by an inner thread 64 that would mate and couple to a complementary shaped outer thread present at the cartridge.

[0061] Alternatively plug and rotate type of coupling means such as a bayonet connection means could be provided as a coupling means 62 (not shown). Further types of coupling means could also be used such as a plug and shift type of coupling means 62 as indicated in Fig. 1 .

[0062] A retaining member 10 is formed both at the mixer housing 50 and at the mixing element 3 in order to lock the mixing element 3, to the mixer housing 50, i.e. in order to retain the mixing element 3 in the housing 50 after forming the static mixer 100.

[0063] According to Fig. 3a, the mixing element 3 is inserted into the mixer housing 50. The mixing element 3 comprises projections 18 as a retaining member 10 at a distal end 34 of the mixing element 3. The retaining members 10 are press-fit and friction fit into a respective receiving structure 36 formed at the mixer housing 50 in the form of recesses 28.

[0064] The retaining member 10, i.e. the projection 18 has an elongate extent, with the elongate extent extending in parallel to a longitudinal axis LA of the mixing element 3.

[0065] In the present embodiment four projections 18 received in four recesses 28 are provided. It should be noted in this connection that between one and 8 such pairs of projections 18 and recesses 28 can be provided.

[0066] Fig. 3B shows a further view of the static mixer 100 with a welding apparatus 38 present, this welding apparatus is used in order to seal off the recesses 28 at the distal end 34 of the mixing element 3 and to thereby prevent an axial movement of the mixing element 3 out of the mixer housing 50.

[0067] Thus, said one or more retaining members 10 are thereby held at the mixer housing 50 by deforming a part of the mixer housing 50 by hot welding after installation of the mixing element 3 in the mixer housing 50.

[0068] Fig. 3C shows the static mixer 100 of Fig. 3B following the deformation of the mixer housing 50 after hot welding. The resultant static mixer 100 has retaining bases 40 formed therein that act as a base and thereby an abutment for the projections 18 formed at the distal end 34 of the mixing element 3.

[0069] In this connection it should be noted that the term distal refers to the position of the mixing element 3 of the static mixer 100 relative to a point of application (not shown) with distal meaning it is more distant from the point of application in contrast to proximal which means it would be closest to the point of application. Fig. 4A & B show further views of a further kind of static mixer 100. In addition to the projections 18 shown in connection with Fig. 3, the mixing element 3 comprises a second kind of projection 18 in the form of snap hooks 14.

[0070] The snap hooks are configured to engage second kinds of recesses 28 formed in an inner surface 16 of the mixer housing.

[0071] The snap hooks 14 are formed on an outer surface 12 of the mixing element 3.

[0072] It should be noted in this connection that the projections 18, i.e. the retaining members 10 can also be formed on an inner surface 16 of the mixer housing 50 (see e.g. Fig. 6 in this connection).

[0073] In this connection it should be noted that between two to 20 such snap hooks 14 can be provided.

[0074] It should further be noted that between two and 20 correspondingly shaped recesses 28 cooperating with the snap hooks 14 can be provided.

[0075] Fig. 5A to C show a static mixer 100 only comprising the elongate projections 18 shown in connection with Fig. 3. The mixing element 3 is held in the static mixer merely by a friction fit between the projections 18 and the elongate recess 36.

[0076] Fig. 6A&B show projections 18 formed as retaining members 10 projecting from an inner surface 16 of the mixer housing 50 towards the mixing element 3.

[0077] The mixing element 3 comprises spaces therein where material can flow and the projections 18 are received in these spaces, i.e. a region with now wall or material of the mixing element 3. On attempting to move the mixing element parts of the projections 18 can abut material of the mixing element 3, preventing movement of this out of the mixer housing 3.

[0078] By way of example such spaces are formed between the first and second kinds of separation walls 7, 9 of the mixing element 3 as e.g. shown in Fig. 2A.

[0079] Fig. 7a & B show a further kind of static mixer 100. In the present example only one retaining member 10 is provided at the static mixer 100. The retaining member 10 is formed by an annular ring 30.

[0080] The annular ring 30 is arranged at the distal end 34 of the mixing element 3.

[0081] The mixer housing 50 of Fig. 7 comprises a ring catch 32 configured to receive a part of said annular ring 30. The ring catch 32 is an annular recess into which the annular ring 30 of the mixing element 3 is press fit.

[0082] An outer diameter of the annular ring is selected to be 5 to 30% larger than an imaginary outer ring enveloping and comprising the mixing element 3.

[0083] The retaining members 10 shown in the foregoing can have at least one of a triangular shaped cross-section, a trapezoidal shaped cross-section, a semicircular shaped cross-section, a circular shaped cross-section, an oval shaped cross-section and a polygonal shaped cross-section.

[0084] The different kinds of retaining members 10 shown in the foregoing can be installed in arbitrary combinations at respective static mixers 100 or also be formed on their own with only one kind of retaining member being formed at a static mixer 100. It should be noted that in all of the above mentioned embodiments the mixing element 3 of the respective static mixer 100 has one of a square or rectangular cross-section along at least a part of the length of the mixing element 3, i.e. between a proximal end 42 (see Fig. 1 ) and the distal end 34 thereof.

[0085] It should be noted in this connection that said at least part of the length of the mixing element 3, corresponds to a length selected in the range of 80 to 100% of the length of the mixing element 3.

[0086] The various retaining members 10 discussed herein can be symmetrically arranged at a surface 12; 16 of one of said mixer housing 50 and the mixing element 3. In this way the mixing element 3 can be effectively retained in the mixer housing 50

[0087] It should be noted in this connection that the retaining members 10 can also be asymmetrically arranged at a surface 12; 16 of one of said mixer housing 50 and the mixing element 3.

[0088] On forming the static mixer 100, the mixing element 3 is inserted into the mixer housing 50 and is captively held therein by one or more kinds of retaining members 10 as discussed herein.

[0089] Reference numeral list

[0090] I static mixer insert

[0091] 3 mixing structure

[0092] 5 support bar

[0093] 5a tapered portion

[0094] 7 separation wall of first set of separation walls

[0095] 9 separation wall of second set of separation walls

[0096] 10 retaining member

[0097] I I passage window

[0098] 12 outer surface of 3

[0099] 13 deflection plate

[0100] 14 snap hook

[0101] 16 inner surface of 50

[0102] 18 projection 21 head

[0103] 23 disc portion

[0104] 24 inlet passage

[0105] 25 inlet

[0106] 28 recess

[0107] 30 annular ring

[0108] 32 ring

[0109] 34 distal end

[0110] 36 receiving structure

[0111] 38 welding apparatus

[0112] 40 retaining base

[0113] 42 proximal end

[0114] 50 mixer housing

[0115] 51 mixing tube

[0116] 52 outlet of static mixer

[0117] 53 central passageway

[0118] 54 channel

[0119] 55 recess

[0120] 56 snap fit / projection

[0121] 57 coupling portion

[0122] 59 cover portion

[0123] 62 coupling means

[0124] 64 thread

[0125] 100 static mixer

[0126] C width of the support bar(s) 5

[0127] D thickness of the support bar(s) 5

[0128] S width of the mixing structure 3

[0129] LA longitudinal axis of mixing structure 3

Claims

medmix Switzerland AG M29273PWO - To / FkClaims1 . A mixing tip (100) comprising a mixer housing (50) and a mixing element (3), wherein at least one of the mixing element (3) and the mixer housing (50) has one or more retaining members (10) formed thereat, with the one or more retaining members (10) being configured to hold the mixing element (3) in the mixer housing (50).

2. A mixing tip (100) according to claim 1 , wherein said one or more retaining members (10) are formed by a snap hook (14).

3. A mixing tip (100) according to claim 1 or claim 2, wherein said one or more retaining members (10) are formed on an outer surface (12) of the mixing element (3).

4. A mixing tip (100) according to claim 1 or claim 2, wherein said one or more retaining members (10) are formed on an inner surface (16) of the mixer housing (50).

5. A mixing tip (100) according to one of claims 1 to 4, wherein said one or more retaining members (10) are formed by projections (18) projecting from one of the mixer housing (50) and the mixing element (3).

6. A mixing tip (100) according to one of claims 1 to 5, wherein said one or more retaining members (10) are symmetrically arranged at a surface (12;7. A mixing tip (100) according to one of claims 1 to 5, wherein said one or more retaining members (10) are asymmetrically arranged at a surface (12; 16) of one of said mixer housing (50) and the mixing element (3).

8. A mixing tip (100) according to one of claims 1 to 7, wherein said one or more retaining members (10) have a triangular shaped cross-section, a trapezoidal shaped cross-section, a semi-circular shaped cross-section, a circular shaped cross-section, an oval shaped cross-section and a polygonal shaped cross-section.

9. A mixing tip (100) according to one of claims 1 to 8, wherein one or more recesses () are formed at the other one of said mixing element (3) and the mixer housing (50), with at least one of said retaining members (10) being received in a respective one of said recesses (28).

10. A mixing tip (100) according to at least one of claims 2 to 9, wherein one retaining member (10) is provided at the static mixer (100), with said retaining member (10) being formed by a annular ring (30).

11. A mixing tip (100) according to claim 9 and claim 10, wherein the mixer housing (50) comprises a ring catch (32) configured to receive a part of said annular ring (30).

12. A mixing tip (100) according to at least one of the preceding claims, wherein said at least one retaining member (10) is press-fit and / or friction fit into a respective receiving structure formed at the other one of the mixer housing (50) and the mixing element (3).

13. A mixing tip (100) according to claim 12, wherein the retaining member (10) has an elongate extent, with the elongate extent extending in parallel to a longitudinal axis (LA) of the mixing element (3).

14. A mixing tip (100) according to at least one of the preceding claims, wherein said one or more retaining members (10) are held at the mixer housing (50) by deforming a part of the mixer housing (50) by hot welding after installation of the mixing element (3) in the mixer housing (50).

15. A mixing tip (100) according to one of the preceding claims, wherein the mixing element (3) has one of a square or rectangular cross-section along at least a part of the length of the mixing element (3).

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