EXTRUDED WING TUBE PORTION, WING TUBE COMPRISING AN EXTRUDED WING-TUBE PORTION, AND HEAT EXCHANGER COMPRISING A WING TUBE, AND METHOD FOR PRODUCING A WING-TUBE PORTION
An extruded wing tube section (10) according to the invention consists of a formed tube portion (12) comprising at least one first wing section (20) integrally formed thereon in a first radial plane of the tube portion (12). The first wing section (20) has a plurality of first radial cut-outs such that a plurality of first wings (22) is provided in the first wing portion (20). Each of the first wings (20) is rotated about a radial axis of rotation such that each of the first wings (22) is rotated out of the first radial plane by a first angle 0°<α1<π° A first continuous transition portion is provided between the tube region (12) and each of the first wings (22), which transition portion has a twisted portion in the portion of the axis of rotation, and at least one expansion portion adjacent thereto.
This application is a national phase application pursuant to 35 U.S.C. § 371 of International Application No. PCT/EP2020/070806, filed Jul. 23, 2020, which claims priority upon German Patent Application No. 20 2019 104 073.4, filed Jul. 23, 2019, the entire contents of each application herein being incorporated by reference.
FIELD OF THE INVENTIONThe present invention is related to an extruded wing tube section consisting of a shaped or formed tube portion with at least one wing section that is integrally formed thereon, a wing tube with at least two extruded wing tube sections and a heat exchanger with wing tube. Furthermore, the present invention relates to a production method an extruded wing tube section.
BACKGROUND OF THE INVENTIONWing tubes which are used in a heat exchanger are known in the state of the art. Thus, WO 2009/068979 A1 describes, for example, a heat exchanger tube for vaporizers or condensers of heating and cooling aggregates. The heat exchanger tube comprises at least one axially extending and wing-like configured enlarged heat transfer surface on the outside, which is formed from the material of the tube or is mechanically connected with the heat transfer tube.
A further heat exchanger is described in WO 2012/142070 A1. The heat exchanger includes a plurality of tubes which are arranged transverse to a direction of air flow through the heat exchanger and arranged in a plurality of rows of tubes extending along the air flow direction. The heat exchanger includes a plurality of rows formed integrally with two or more tubes of the plurality of tubes, each rows extending between adjacent tubes of the plurality of tubes and being connected with them. At least one tube of the plurality of tubes has a cross section with an aspect ratio of more than 1:1 relative to a horizontal row.
Finally, WO 2013/139507 A1 describes a heat exchanger for dissipating heat from a medium by means of at least one wing tube having a serpentine shape and being arranged in a housing. The straight wing sections of the wing tube are arranged in such a way that the wings of the wing sections enclose an angle in the range from 10°≤α≤30° with a flow direction.
Based on these known devices, it is the object of the present invention to provide a heat exchanger with wing tube, an associated wing tube as well as a corresponding wing tube section which are improved compared with the state of the art in terms of the heat dissipation as well as the removal of the condensate which develops in use.
SUMMARY OF THE INVENTIONThe above object is solved by an extruded wing tube section consisting of a shaped or formed tube portion with at least one wing section integrally formed to it, a wing tube with at least two extruded wind tube sections, a heat exchanger with wing tube as well as a production method for an extruded wing tube section according to the appended claims. Advantageous embodiments and further developments arise from the following description, the drawings as well as the appending claims.
An inventive, extruded wing tube section consists of a formed tube portion with at least one first wing section integrally formed thereon in a first radial plane of the tube portion, wherein the first wing section has a plurality of first radial cut-outs so that a plurality of first wings is present in the first wing section, and each of the first wings is rotated about a radial rotation axis so that each of the first wings is rotated out of the first radial plane about a first angle 0°<α1<90°, wherein a first continuous transition portion is present between tube portion and each of the first wings, which has a twisted portion in the portion of the rotation axis and at least one expansion portion adjacent to it.
For the better understanding of the present invention, the extruded wing tube section is subsequently explained in general based on a possible production method. Firstly, a wing tube section is extruded in the common manner, as is for example also described in WO 2009/068979 A1 with reference to FIG. 14. Due to the design of the present invention, it is preferred when the first wing section does not comprise a gap with connection to the tube portion. Preferably, the first wing section is therefore configured with a solid structure, i.e. it is not hollow. Thus, the extruded wing tube section consists of the formed tube portion with at least one first wing section integrally formed thereon in a first radial plane.
In the first wing section a plurality of first radial cut-outs is now provided. The first radial cut-outs are thus made in the first radial plane, transverse or perpendicular with respect to the longitudinal direction of the tube portion. The first cut-outs preferably do not extend up to the tube portion. It is rather preferred that the cut-outs are made in not more than 99% of the extension of the first wing section in the radial plane, preferably not more than 97.5% and further preferred not more than 95%. If the extension of the first wing section in the first radial plane is for example 20 mm, then this means that the first cut-outs extend over not more than 19.8 mm, preferably not more than 19.5 mm and particularly preferred not more than 19 mm. That means that in the portion of the respective cut-out, a first wing section with an extension in the first radial plane remains, which is 0.2 mm, preferably 0.5 mm and further preferred 1 mm. After making the plurality of first cut-outs, the first wing section comprises a plurality of first wings.
Each of the first wings is rotated by the first angle α1 about a radial rotation axis so that it is rotated out of the radial plane. Therefore, the radial rotation axis of the respective first wing extends perpendicular to the longitudinal axis of the tube portion and lies in the first radial plane. In this context, 0°<α1<90° applies for the first wing α1. The value 0° is excluded as otherwise, no twisting out of the first radial plane would be present. Values over 90° are excluded due to the danger of the separation of the respective first wing due to the twisting.
The forces arising as a result of the twisting are received in the first continuous transition portion between each of the plurality of first wings and the tube portion. The first continuous transition portion is thus deformed and takes up the forces which arise during the twisting of the respective first wing while maintaining a connection to the tube portion. The deforming of the respective first continuous transition portion takes place in at least two portions, namely in a first portion which is twisted and in at least one further portion that is expanded. This is explained in the following by means of two examples.
Concerning this, it should firstly be pointed out that the radial rotation axis about which the respective first wing is rotated, can be arranged at different positions with respect to the width of the first wing. Here, width refers to the extension of the respective first wing in the first radial plane along the longitudinal axis of the tube portion. In the portion of the radial rotation axis, the respective first wing includes the first portion after the twisting, i.e. the twisted portion. Provided the rotation axis in the respective first wing is present directly adjacent to the cut-out, exactly one expansion portion develops adjacent to the twisted portion. If in an alternative example, the rotation axis does not extend directly adjacent to the cut-out but for example centrally through the respective first wing, two expansion portions develop, each being present adjacent to the twisted portion. The positioning of the radial rotation axis with respect to the respective first wing is therefore selected particularly depending on the desired first angle α1 and thus on the application which is desired later.
A technical effect and thus an advantage of this extruded wing tube portion is that due to the first cut-outs, the surface which is available for the heat exchange is enlarged compared with a wing portion without cut-outs. Furthermore, aerodynamic elements are provided due to the specific arrangement of the first wings, which increase the turbulences in the air stream, which in turn leads to an improved heat transmission coefficient. Compared with a wing tube section with a continuous flat wing section, i.e. one single wing that is exclusively arranged in the radial plane, increases in performance in the range from approximately 15 to 30% can be realized. Furthermore, no additional material for fastening individual wings at the tube portion is necessary, as the wing section is already available during the production of the wing tube by means of extrusion.
According to a preferred embodiment of the extruded wing tube section, the first angle α1 lies between 30° and 60°, preferably at 45°. In the course of examinations, it has been found out that precisely this angle portion, beside the above technical effects, also contributes to a particularly efficient removal of condensate which develops in the wing section or the respective wing. Furthermore, the condensate which arises during operation can be removed more reliably with this arrangement compared with the providing of cut-outs in a continuous wing section directly adjacent to the tube portion.
In a further advantageous embodiment, the extruded wing tube section consists of aluminum. It is particularly aluminum as the material for the extruded wing tube section which leads to a good deformability of the first continuous transition portion so that preferably, the first continuous transition portion ideally has the same width as the respective first wing, i.e. it preferably does not include any cracks. Preferably, the first continuous transition portion is completely connected with the tube portion on the one hand and with the respective wing on the other hand. Heat dissipation can be further improved by that.
Depending on the respective application field, different dimensions of both the tube portion as well as of the wings are advantageous. In a first alternative, it is therefore preferred that an outer diameter of the tube portion extending in a straight manner lies between 3 and 10 mm and/or a wall thickness in the tube portion is 0.3 to 0.9 mm. In addition or alternatively, it is of advantage that the first wing section has an extension in the radial direction between 10 and 20 mm and/or each of the first cut-outs has a width of 3 to 8 mm. By that, a large application field for the extruded wing tube section is given on the one hand. On the other hand, the maintenance of the above-mentioned technical effects in different application fields is enabled at the same time. Preferably, the radial extension of the first wing section is defined as a distance between the rotation-symmetrical longitudinal axis of the tube section and of the radial outside of the first wing.
In a particularly preferred embodiment, the first continuous transition portion includes two expansion portions on opposite sides with respect to the twisted portion. This embodiment has already been briefly discussed above. Here, the rotation axis does not extend directly adjacent to the cut-out but for example centrally through the respective first wing with respect to the width of the first wing. Alternatively, the rotation axis extends through the first wing at any other position, with the exception of the locations directly adjacent to the respective first cut-out. In this manner, two expansion portions develop, each being present adjacent to the twisted portion. The design in which the rotation axis extends centrally through the respective first wing is particularly preferred in this context.
In a further advantageous design, the extruded wing tube section furthermore includes a second wing tube section which is formed integrally at the tube portion in a second radial plane of the tube portion, with the second wing section comprising a plurality of second radial cut-outs so that a plurality of second wings is present in the second wing section, and each of the second wings is rotated about a radial rotation axis so that each of the second wings is rotated out of the second radial plane by a second angle 0°<α2<90°, with a second continuous transition portion being present between tube portion and each second wing, the second continuous transition portion comprising a twisted portion in the portion of the rotation axis and at least one expansion portion adjacent to it. A second wing section is introduced by means of this design. The effects caused by the wings which are designed according to the invention are further increased, so that reference is made to the above explanations as to the first wing section with the plurality of first wings in terms of the arising technical effects and advantages. In this context, the explanations with respect to the first wing section and the associated first wings analogously apply to the second wing section and each further possible wing section.
In a preferred embodiment of the extruded wing tube section with two wing sections, the second wing section is arranged opposite to the first wing section at the tube section extending in a straight manner, so that the first radial plane and the second radial plane form a joint plane in which the longitudinal axis of the tube portion lies. With regard to a later use of an extruded wing tube section which has been designed in this manner, special advantages can be reached particularly due to the opposite arrangement of the wing sections and the heat dissipation can be further improved.
In a further preferred embodiment of the extruded wing tube section with two wing sections, the first α1 and the second angle α2 are the same. This design further increases the technical effects which are achieved with the extruded wing tube section, particularly due to synergy effects of the first and the second wing section.
In an advantageous embodiment of the extruded wing tube section with two wing sections, the second wing section has an extension in the radial direction between 10 and 20 mm and/or each of the second cut-outs has a width of 3 to 8 mm. Similarly, it is preferred with the embodiment of the extruded wing tube section with two wing sections that the second continuous transition portion comprises two expansion portions on opposite sides with respect to the twisted portion. With respect to the arising technical effects, reference is made to the above explanations in connection with the correspondingly designed first wing section. Preferably, the radial extension of the first wing section is defined as a distance between the rotation symmetrical longitudinal axis of the tube section and the radial outside of the first wing. Accordingly, it is also preferred when a distance AF between the wing tips of two wings that are arranged opposite to one another lies in a range of 20 mm≤AF≤40 mm.
In a further preferred embodiment, a twisting of the respective wings in the same direction or in opposite directions is carried out in case of two wing sections out of the radial plane. In other words, the wings of a wing section are rotated in a first rotation direction. The wings of the second wing section are rotated either in the same direction or in the opposite direction. In this manner, the wing tube section can be adjusted further to the desired application. Additionally or alternatively, the wings of a wing section are for example rotated in alternation in opposite rotation directions or all wings of a wing section have the same rotation direction.
An inventive wing tube for a heat exchanger, in particular an evaporator or a condenser, includes at least two inventively extruded wing tube sections, the longitudinal axes of which extend parallel to one another and which are connected by means of a wingless bent section. As the wing tube comprises the inventively extruded wing tube section, reference is made to the above descriptions in terms of the arising technical effects and advantages, in order to avoid repetitions.
An inventive heat exchanger comprises an inventive wing tube. The heat exchanger is preferably an evaporator or condenser with an inventive wing tube. Reference is made to the descriptions regarding the inventively extruded wing tube section in this respect, too.
Finally, an embodiment of an inventive production method the extruded wing tube section is briefly explained. In a first step, the wing tube section consisting of the tube portion as well as at least one first wing section integrally formed to it is extruded. If the wing tube section is intended to include both a plurality of first wings as well as a plurality of second wings, the wing tube section is additionally extruded with a second wing section integrally formed to it. The same applies analogously to further possible wing sections.
After the extrusion of the wing tube section, the same thus includes a first radial plane and a longitudinal axis defined by the tube portion, which lies in the radial plane. The first wing section as well as possible further wing sections are thus configured planar and extend radially from the tube portion to the outside.
Now, the plurality of radial cut-outs transverse to the longitudinal axis of the tube portion is made into the respective wing section, so that with regard to the first wing section, a plurality of first wings develops. Due to the plurality of cut-outs, the surface of the respective wing section is already enlarged. At the same time of or following the making of the cut-outs, a twisting of at least one wing of the plurality of first wings out of the radial plane takes place. In this connection, a continuous transition portion which is present between the respective wing and the tube portion is deformed and takes up the forces arising during the twisting of the wing by maintaining a connection to the tube portion. After finishing the twisting, the continuous transition portion therefore comprises a twisted portion in the portion of the rotation axis as well as at least one expansion portion, depending on the positioning of the rotation axis with respect to the width of the respective wing.
In the following, the present invention will be described in detail based on the drawings. In the drawings, the same reference signs relate to the same components and/or elements. It shows:
In the following, a preferred embodiment of an inventively extruded wing tube section is described. This extruded wing tube section can be a component of a wing tube and is used in heat exchangers, as for example an evaporator or condenser.
Firstly and with reference to
Now, with reference to
Based on the extruded wing tube section 1 which is shown in
For example, a first cut-out in the first wing section 20 can be made at the same time as a second cut-out in the second wing section 30. Alternatively, firstly, a desired number of first cut-outs is made in the first wing section 20 and subsequently a desired number of second cut-outs is made in the second wing section 30.
Each cut-out has a width of 3 to 8 mm and provides for an enlargement of the surface which is streamed against and is thus available for the heat exchange compared with a wing section without cut-outs. Cut-outs with a width of 3 to 8 mm, in particular, have been identified as particularly advantageous.
Both wing sections 20, 30 have a preferred extension each in radial direction between 10 and 20 mm. A radial extension in this direction is also referred to as radial length of the wing sections 20, 30 which is measured between the rotation symmetrical center point of the tube section and the radial outside or tip of the wing. Thus, the radial cut-outs are made in the radial plane transverse or perpendicular to the longitudinal direction of the tube portion 12. Here, the respective cut-outs preferably do not extend up to the tube portion 12 but over not more than 99% of the respective wing section 20, 30 in the radial plane.
If the extension of the respective wing section 20, 30 in the radial plane is for example 20 mm, then the cut-outs extend over at most 19.8 mm. Thus, a wing section 20, 30 with an extension in the radial plane remains in the portion of the respective cut-out, which is 0.2 mm. After making the plurality of cut-outs, each wing section 20, 30 has a plurality of wings 22, 32.
As becomes clear from this description, no additional material for the fastening of individual wings at the tube portion is necessary as the wing sections 20, 30 are already present when producing the tube section 10 by means of extrusion.
Each wing 22, 32 is rotated by an angle α1, α2 about a radial rotation axis, so that it is rotated out of the radial plane. Therefore, the radial rotation axis of the respective wing 22, 32 extends perpendicular to the longitudinal axis of the tube portion 12 and is arranged in the radial plane.
0°<α1, α2<90° applies for the angles α1, α2 in this context. The value of 0° is excluded as otherwise, no rotating out of the radial plane would be present, and values over 90° are excluded due to the danger of separation of the respective wing caused by the rotating or twisting. In the shown embodiment, the angles α1, α2 are 45°.
In this regard, angles between 30° and 60° are generally preferred as it is particularly this angle range which contributes to a particularly efficient removal of condensate arising in the wing section 20, 30 or the respective wing 22, 32, respectively. In particular, the condensate which develops during operation can be removed more reliably compared with the providing of cut-outs in a continuous wing section directly adjacent to the tube portion. Furthermore, aerodynamic elements are provided due to the specific arrangement of the wings, which increase turbulences in the air stream, which in turn leads to an improved heat transmission coefficient.
The forces arising as a result of the twisting are received in the first continuous transition portion between each of the plurality of the wings 22, 32 and the tube portion. The continuous transition portion is thus deformed and receives the forces arising during the twisting of the respective wings 22, 32 by maintaining a connection to the tube portion 12. The deforming of the respective continuous transition portion takes place in at least two portions, namely in a first portion that is twisted or subject to torsion and in at least one further portion that is extended or stretched.
In the embodiment shown in
In an alternative, not shown embodiment, the rotation axis is arranged directly adjacent to the cut-out. In this case, exactly one expansion portion develops adjacent to the twisted portion. The positioning of the rotation axis with respect to the respective wing 22, 32 is therefore selected particularly depending on the desired angle α1, α2 and thus on the application desired later.
For the sake of completeness, it is pointed out that in case of two wing sections 20, 30, a twisting of the respective wings 22, 32 in the same direction or in opposite directions out of the radial plane can take place. The respective rotation direction is particularly determined by the application which is desired later. With respect to
Aluminum is used as material for the extruded wing tube section 10. Aluminum in particular leads to a good deformability of the continuous transition portion so that preferably, the continuous transition portion preferably has the same width as the respective wing 22, 32, i.e. preferably, it does not have any cracks. Preferably, the continuous transition portion is completely connected with the tube portion 12 on the one hand and with the respective wing 22, 32 on the other hand so that the heat dissipation can be improved further, particularly compared with a connection between wings 22, 32 and tube portion 12 at only one point.
Compared with the extruded wing tube section shown in
A not-shown embodiment of the inventive wing tube for a heat exchanger, in particular for an evaporator or a condenser, includes at least two wing tube sections 10 according to
An embodiment of an inventive heat exchanger which is also not illustrated includes the above-described embodiment of the wing tube. Preferably, the heat exchanger is an evaporator or condenser.
With respect to
Therefore, after the extrusion of the wing tube section 10, it includes a first and a second radial plane, which form a joint plane, as well as a longitudinal axis defined by the tube portion 12, with the longitudinal axis lying in the joint plane. Each wing section 20, 30 is thus configured planar and extends on opposite sides from the tube portion 12 radially to the outside.
In a subsequent step B, the plurality of cut-outs is now made into the respective wing section 20, 30 transverse to the longitudinal axis of the tube portion 12 so that a plurality of wings 22, 32 arises. Due to the plurality of cut-outs, the surface of the respective wing section 20, 30 is already increased.
At the same time of or subsequently to the making of the cut-outs, a twisting of a wing 22, 32 from the plurality of wings 22, 32 takes place in step C. The continuous transition portion which is present between the respective wing 22, 32 and the tube portion 12 is deformed and takes up the forces arising when twisting the wing 22, 32 by maintaining the connection to the tube portion 12. After concluding the twisting, the continuous transition portion therefore includes a twisted portion in the portion of the rotation axis as well as at least one expansion portion, depending on the positioning of the rotation axis with respect to the width of the respective wing 22, 32.
LIST OF REFERENCE SIGNS1 extruded wing tube section
3 tube portion
5 first wing section
7 second wing section
10 extruded wing tube section
12 tube portion
20 first wing section
22 first wing
30 second wing section
32 second wing
Er radial extension of the wing
AF distance between wing tips opposing each other
It will be apparent that there are other variations and modifications that can be made based on the inventive aspects discussed herein, and in accordance with the following claims.
Claims
1-20. (canceled)
21. An extruded wing tube section having a formed tube portion with at least one first integrally formed wing section in a first radial plane of the formed tube portion, wherein
- a. the at least one first wing section has a plurality of first radial cut-outs so that a plurality of first wings is present in the at least one first wing section, and
- b. each of the first wings of the plurality of first wings is rotated about a radial rotation axis so that each of the first wings of the plurality of first wings is rotated out of the first radial plane about a first angle 0°<α1<90°, wherein
- c. a first continuous transition portion is present between the formed tube portion and each of the first wings of the plurality of first wings, the first continuous transition portion having a twisted portion in the portion of the rotation axis and at least one adjacent expansion portion.
22. The extruded wing tube section according to claim 21, where the first angle α1 lies between 30° and 60°.
23. The extruded wing tube section according to claim 21, which is made from aluminum.
24. The extruded wing tube section according to claim 21, where an outer diameter of the formed tube portion extending in a straight manner lies between 3 and 10 mm and/or a wall thickness in the formed tube portion is 0.3 to 0.9 mm.
25. The extruded wing tube section according to claim 21, where the at least one first wing section has an extension Er in the radial direction between 10 and 20 mm and/or each of the first radial cut-outs has a width of 3 to 8 mm.
26. The extruded wing tube section according to claim 21, where the first continuous transition portion includes two expansion portions on opposite sides with respect to the twisted portion.
27. The extruded wing tube section according to claim 21, which further includes a second wing section which is formed integrally at the formed tube portion in a second radial plane of the formed tube portion, wherein
- a. the second wing section comprises a plurality of second radial cut-outs so that a plurality of second wings is present in the second wing section, and
- b. each one of the second wings of the plurality of second wings is rotated about a radial rotation axis so that each one of the second wings of the plurality of second wings is rotated out of the second radial plane by a second angle 0°<α2<90°, wherein
- c. a second continuous transition portion is present between the formed tube portion and each second wing, the second continuous transition portion comprising a twisted portion in the portion of the rotation axis and at least one adjacent expansion portion.
28. The extruded wing tube section according to claim 27, where the second wing section is arranged opposite the first wing section at the tube portion which extends in a straight manner, so that the first radial plane and the second radial plane form a joint plane in which the longitudinal axis of the formed tube portion is arranged.
29. The extruded wing tube section according to claim 27, where the first α1 and the second angle α2 are the same.
30. The extruded wing tube section according to claim 27, where the second wing section has an extension Er in the radial direction between 10 and 20 mm and/or each one of the second cut-outs has a width of 3 to 8 mm.
31. The extruded wing tube section according to claim 27, where the second continuous transition portion comprises two expansion portions on opposite sides with respect to the twisted portion.
32. A wing tube for a heat exchanger, said wing tube including at least two extruded wing tube sections according to claim 21, the longitudinal axes of which extend parallel to one another and which are connected by means of a wingless bent section.
33. A heat exchanger comprising a wing tube according to claim 32.
34. A production method of an extruded wing tube section according to claim 21, comprising the following steps:
- a. extruding the wing tube section having a tube portion as well as at least one integrally configured wing section,
- b. making a plurality of radial cut-outs transverse to the longitudinal axis of the tube portion into the first wing section, so that with respect to the first wing section, a plurality of first wings develops, and
- c. twisting of at least one wing out of the plurality of first wings out of the radial plane at the same time of or following the making of the cut-outs, so that a first continuous transition portion develops having a twisted portion in the portion of the rotation axis as well as at least one adjacent expansion portion after concluding the twisting.
35. The production method according to claim 34 wherein the step of extruding includes the extruding of the wing tube section with at least one further integrally formed wing section.
36. The extruded wing tube section according to claim 22, which is made from aluminum.
37. The extruded wing tube section according to claim 22, where an outer diameter of the formed tube portion extending in a straight manner lies between 3 and 10 mm and/or a wall thickness in the formed tube portion is 0.3 to 0.9 mm.
38. The extruded wing tube section according to claim 22, where the at least one first wing section has an extension Er in the radial direction between 10 and 20 mm and/or each of the first cut-outs has a width of 3 to 8 mm.
39. The extruded wing tube section according to claim 22, where the first continuous transition portion includes two expansion portions on opposite sides with respect to the twisted portion.
40. The extruded wing tube section according to claim 22, which further includes a second wing section which is formed integrally at the formed tube portion in a second radial plane of the formed tube portion, wherein
- a. the second wing section comprises a plurality of second radial cut-outs so that a plurality of second wings is present in the second wing section, and
- b. each one of the second wings of the plurality of second wings is rotated about a radial rotation axis so that each one of the second wings of the plurality of second wings is rotated out of the second radial plane by a second angle 0°<α2<90°, wherein
- c. a second continuous transition portion is present between the formed tube portion and each second wing, the second continuous transition portion comprising a twisted portion in the portion of the rotation axis and at least one adjacent expansion portion.
Type: Application
Filed: Jul 23, 2020
Publication Date: Jan 19, 2023
Inventors: Jörg Kirchner (Lipprechterode), Sascha Wieland (Haynrode), Matteo Codecasa (Göttingen)
Application Number: 17/628,705
