Abstract
The invention relates to a frame for a ball game racket comprising a handle region and a head region with a bridge, wherein a part of the head region and/or the handle region comprise(s) a carbon fiber composite material and wherein the bridge comprises magnesium and is formed as one part.
Claims
1. A frame for a ball game racket having a handle region and a head region comprising a bridge, wherein a part of the head region and/or the handle region comprises a carbon fiber composite material and wherein the bridge comprises magnesium and is formed as one part.
2. The frame for a ball game racket according to claim 1, wherein the bridge is made from a uniform material.
3. The frame for a ball game racket according to claim 1, wherein the bridge material comprises at least 50 wt.-% magnesium.
4. The frame for a ball game racket according to claim 1, wherein the bridge material comprises at least 95 wt.-% magnesium.
5. The frame for a ball game racket according to claim 1, wherein the bridge material is a magnesium alloy.
6. The frame for a ball game racket according to claim 1, wherein the bridge material is a fiber or particle reinforced alloy.
7. The frame for a ball game racket according to claim 1, wherein the bridge material is AM60.
8. The frame for a ball game racket according to claim 1, wherein the bridge is made in a die casting process or an injection molding process.
9. The frame for a ball game racket according to claim 1, wherein the bridge is made by thixomolding.
10. The frame for a ball game racket according to claim 1, wherein the bridge is formed at least in portions as a solid profile.
11. The frame for a ball game racket according to claim 1, wherein the bridge is formed completely as a solid profile.
12. The frame for a ball game racket according to claim 1, wherein the bridge comprises at least four webs.
13. The frame for a ball game racket according to claim 1, wherein the bridge comprises at least six webs.
14. The frame for a ball game racket according to claim 12, wherein the webs extend, at least in portions, in a manner separated from each other.
15. The frame for a ball game racket according to claim 14, wherein the webs extend, at least in portions, in a manner separated from each other along a length of at least 5 mm along the frame profile.
16. The frame for a ball game racket according to claim 14, wherein the webs extend, at least in portions, in a manner separated from each other along a length of at least 15 mm along the frame profile.
17. The frame for a ball game racket according to claim 12, wherein two neighboring webs have, at least in portions, a distance of 1 mm to 30 mm measured parallel with respect to the string bed plane.
18. The frame for a ball game racket according to claim 12, wherein two neighboring webs have, at least in portions, a distance of 5 mm to 10 mm measured parallel with respect to the string bed plane.
19. The frame for a ball game racket according to claim 12, wherein two neighboring webs have, at least in portions, a distance of 1 mm to 20 mm measured perpendicularly with respect to the string bed plane.
20. The frame for a ball game racket according to claim 12, wherein two neighboring webs have, at least in portions, a distance of 5 mm to 10 mm measured perpendicularly with respect to the string bed plane.
21. The frame for a ball game racket according to claim 12, wherein the webs have a cross-section with a solid profile.
22. The frame for a ball game racket according to claim 12, wherein at least two webs have string openings.
23. The frame for a ball game racket according to claim 12, wherein the webs each have, at least in portions, a cross-sectional area of 1 mm.sup.2 to 100 mm.sup.2.
24. The frame for a ball game racket according to claim 12, wherein the webs each have, at least in portions, a cross-sectional area of 2 mm.sup.2 to 25 mm.sup.2.
25. The frame for a ball game racket according to claim 12, wherein the webs each have a length LS of 1 mm to 120 mm along the directrix of the respective web.
26. The frame for a ball game racket according to claim 12, wherein the webs each have a length LS of 20 mm to 50 mm along the directrix of the respective web.
27. The frame for a ball game racket according to claim 1, wherein the bridge comprises at least two brackets, wherein the brackets serve for connecting the bridge to at least one second frame region.
28. The frame for a ball game racket according to claim 1, wherein a cross-section through the bridge has a continuous cross-sectional profile along a continuous bridge length of between 10 mm and 100 mm along the frame contour and has a discontinuous cross-sectional profile along a continuous bridge length of between 5 mm and 100 mm along the frame contour.
29. The frame for a ball game racket according to claim 1, wherein a cross-section through the bridge has a continuous cross-sectional profile along a continuous bridge length of between 30 mm and 80 mm along the frame contour and has a discontinuous cross-sectional profile along a continuous bridge length of between 10 mm and 60 mm along the frame contour.
30. A method for manufacturing a frame for a ball game racket, in particular a frame according to claim 1, wherein the method comprises the following steps: casting a bridge from a material comprising magnesium, preferably by thixomolding, providing a frame region which comprises a handle region and a head region, wherein a part of the head region and/or the handle region comprise(s) a carbon fiber composite material, connecting the bridge to the frame region to form a frame.
31. The method according to claim 30, wherein the provision of the frame region includes the provision of a prepreg tube.
32. The method according to claim 31, wherein the connection of the bridge to the frame region takes place in one method step with the curing of the prepreg tube.
Description
[0095] In the following, preferred embodiments of the frame according to the invention are described in more detail on the basis of the Figures in which
[0096] FIG. 1 shows a schematic front view of a frame according to the invention;
[0097] FIG. 2A shows a schematic perspective view of a bridge according to the invention;
[0098] FIG. 2B shows a schematic view of a cross-section of the bridge of FIG. 2A through the line A-B according to FIG. 1;
[0099] FIG. 2C shows a schematic view of a cross-section of the bridge of FIG. 2A through the line C-D according to FIG. 1;
[0100] FIG. 3A shows a schematic perspective view of a further bridge according to the invention;
[0101] FIG. 3B shows a schematic view of a cross-section of the bridge of FIG. 3A through the line A-B according to FIG. 1;
[0102] FIG. 3C shows a schematic view of a cross-section of the bridge of FIG. 3A through the line C-D according to FIG. 1;
[0103] FIG. 4 shows a schematic perspective view of a frame according to the invention in a front view seen in an inclined manner from the top;
[0104] FIGS. 5A-5D each show a schematic front view of a bridge according to the invention;
[0105] FIG. 6A shows a schematic perspective partial view of a bridge according to the invention;
[0106] FIG. 6B shows a schematic view of a cross-section of the bridge of FIG. 6A through the line A-B according to FIG. 1;
[0107] FIG. 6C shows a schematic view of a cross-section of the bridge of FIG. 6A through the line C-D according to FIG. 1;
[0108] FIG. 6D shows a schematic front view of a portion of a frame according to the invention with the bridge of FIG. 6A;
[0109] FIG. 6E shows an enlarged detail of FIG. 6D;
[0110] FIG. 7A shows the yz-sections of a bridge of a conventional frame of a ball game racket;
[0111] FIG. 7B shows a diagram of calculated geometrical moments of inertia of the yz-sections of FIG. 7A;
[0112] FIG. 7C shows the yz-sections of a bridge of a frame of a ball game racket according to the invention;
[0113] FIG. 7D shows a diagram of calculated geometrical moments of inertia of the yz-sections of FIG. 7C.
[0114] FIG. 1 shows a schematic front view of a frame 2 for a ball game racket according to the present invention. The frame 2 comprises a head region 4 with a bridge region or bridge 6. The head region 4 with the bridge 6 defines a string bed 8 for receiving a stringing (not shown). Moreover, the frame 2 comprises a handle region 10, the central axis of which coincides with the longitudinal axis 14 of the frame 2.
[0115] In the preferred embodiment of the frame 2 of FIG. 1, the bridge comprises a magnesium alloy and the frame comprises a carbon-fiber composite material. Furthermore, the bridge is formed as one part. In the shown preferred embodiment, the bridge is formed substantially completely from a uniform material.
[0116] A preferred embodiment of a bridge region or a bridge 6 according to the invention is shown in a perspective view in FIG. 2A. In its preferred embodiment of FIG. 2A, the bridge 6 comprises two brackets or mounting links 16a, 16b which serve for connecting the bridge to at least one further frame region. The brackets 16a, 16b limit the shown bridge 6 at both ends of its directrix. In the center between the two brackets 16, the bridge 6 comprises a central region 18 which, on two sides to which the indices a and b are assigned, is respectively connected via two upper webs or ligaments or beams 22a and 22b and one lower web 24a or 24b to the two brackets 16a and 16b.
[0117] In the shown preferred embodiment of FIG. 2A, the bridge 6 is configured as a one-part cast part having a solid profile and comprises a uniform magnesium alloy. FIG. 2B shows a cross-section of the bridge of FIG. 2A through the line A-B according to FIG. 1. FIG. 2B thus shows a cross-section through the central region 18 of the bridge of FIG. 2A. As shown in FIG. 2B, the bridge comprises a central region 18 with an exclusively convex cross-section which is herein exemplarily substantially rectangular. FIG. 2C shows a cross-section of the bridge of FIG. 2A through the line C-D according to FIG. 1. FIG. 2C thus shows a cross-section through the web region of the bridge of FIG. 2A. As shown in FIG. 2C, the webs 22 and 24 of the bridge also each have a convex cross-sectional profile, also exemplarily shown to be substantially rectangular.
[0118] It is stressed that the arrangement of the webs relative to one another as well as the areas of the individual web cross-sections are understood to be only schematic and exemplary. Thus, in particular the surface distances between two neighboring webs are not restricted to the shown web surface distances h, w1 and w2, wherein h is a surface distance between two neighboring webs perpendicular with respect to the string bed plane and w1 and w2 each show a surface distance between two neighboring webs parallel with respect to the string bed plane. Alternative embodiments with other web arrangements, web profile shapes, cross-sectional areas of the webs and/or surface distances of the webs are possible. In particular, oval, round, convexly or concavely polygonal and/or irregular web cross-sections are possible. Cross-sectional areas and shapes of webs of the same embodiment can generally differ from each other. The values of web arrangements, web lengths, web profile shapes, cross-sectional areas of webs and/or web surface distances and also the values of bridge lengths, bridge profile shapes and/or cross-sectional areas of bridges preferably is in the ranges described above.
[0119] As shown in FIGS. 2A and 2C, the use of a one-part solid profile made from a magnesium alloy allows the formation of particularly filigree structures such as, e.g., the upper webs 22a, 22b, whose minimum extension along a cross-sectional area can, e.g., be smaller than 3 mm. For example, cross-sectional areas in the range of 5 mm.sup.2 to 10 mm.sup.2 can be achieved without increasing the risk of fracture of the bridge substantially.
[0120] FIG. 3A shows a further embodiment of a bridge 6 of a frame 2 according to the invention, in which also the central region 18 is more filigree than in the case of FIG. 2A. The bridge 6 of FIG. 3A comprises uniformly a magnesium alloy and is configured as one-part cast part having a solid profile. In the center between the two brackets 16, the bridge 6 comprises a central region 18 which, on two sides to which the indices a and b are again assigned, is respectively connected via two upper webs 22a and 22b and one lower web 24a or 24b to the two brackets 16a and 16b. FIG. 3B shows a cross-section of the bridge of FIG. 3A through the line A-B according to FIG. 1. FIG. 3B thus shows a cross-section through the central region 18 of the bridge of FIG. 3A. As shown in FIG. 3B, the bridge of FIG. 3A has a groove-shaped recess 26 in the central region 18. The groove-shaped recess 26 has a side which is open towards the string bed but is closed on both sides a and b, and, therefore, can be called pot-shaped. Furthermore, FIG. 3C shows a cross-section of the bridge of FIG. 3A through the line C-D according to FIG. 1. FIG. 3C thus shows a cross-section through the web region of the bridge of FIG. 3A. The bridge 6 of FIG. 3A comprises webs 22 and 24 with convex cross-sectional profiles, exemplarily shown as being substantially rectangular. Also this pot-shaped central region 18 of the bridge of FIG. 3A is formed as solid profile or is solid, i.e. the pot-shaped central region does not have any hollow spaces and, in particular, is not formed of opposing wall regions which would enclose a hollow space.
[0121] It is stressed that the arrangement of the webs relative to one another as well as the areas of the individual web cross-sections are understood to be only schematic and exemplary. Thus, in particular the surface distances between two neighboring webs are not restricted to the shown web surface distances h, w1 and w2, wherein h is a surface distance between two neighboring webs perpendicular with respect to the string bed plane and w1 and w2 each show a surface distance between two neighboring webs parallel with respect to the string bed plane. Alternative embodiments with other web arrangements, web profile shapes, cross-sectional shapes of the webs and/or web surface distances are possible. In particular, oval, round, convexly or concavely polygonal and/or irregular web cross-sections are possible. Cross-sectional areas and shapes of webs of the same embodiment can generally differ from each other. The values of web arrangements, web lengths, web profile shapes, cross-sectional areas of webs and/or web surface distances and also the values of bridge lengths, bridge profile shapes and/or cross-sectional areas of bridges preferably is in the ranges described above.
[0122] FIG. 4 shows a schematic perspective view of a frame according to the invention with the bridge according to FIG. 3. The frame comprises a handle region 10 and a head region 4 with bridge 6 in a front view seen in an inclined manner from the top. The central region 18 is in the center of the bridge 6. Two upper webs 22a and two upper webs 22b extend from the central region 18 and extend towards the closest bracket, respectively, with the brackets not shown here because in the finished racket frame the brackets are preferably incorporated in the carbon fiber composite material of the racket head. The central region 18 has a groove-shaped recess 26 which is open towards the string bed 8. The end sides facing in the direction of sides a and b, as well as the side (bottom) of the groove facing in the direction of the handle region 10, however, are closed, so that the central region 18 can be called pot-shaped. The bottom of the pot-shaped groove 26 has a string opening 28, as specified above, through which a string of the stringing is passed. At least one string opening 28 is provided in the bottom of the pot-shaped groove 26. In the preferred embodiment of FIG. 4, the bottom of the groove 26 has four string openings 28.
[0123] FIGS. 5A to 5D exemplarily show four further embodiments of the bridge in a schematic front view. The embodiments correspond to the embodiments of FIG. 2 or FIGS. 3 and/or 4, but in addition to the features already described in connection with FIGS. 2, 3 and/or 4, they have a lattice or truss structure 30 in the central region 18. The lattice structure depends on the mutually dependent shapes of the struts 32 and the gaps 34 and on the number thereof.
[0124] The number of gaps or through openings 34 in FIGS. 5A and 5B is five. In alternative embodiments, the number of gaps 34 can have other values. For example, the embodiment of FIG. 5C shows three gaps 34, while the embodiment of FIG. 5D shows nine gaps 34. However, the number of gaps 34 is preferably at least 2.
[0125] In general, the gaps can have many shapes. For example, the gaps 34 can be oval, triangular, quadrangular, convexly or concavely polygonal and/or have an irregular shape, wherein corners can be pointed or rounded.
[0126] In a front view, the embodiment of a bridge 6 according to the invention as shown in FIG. 5A has five round gaps 34. The alternative embodiment of a bridge 6 according to the invention as shown in FIG. 5B has, in a front view, five mostly triangular gaps 34, the apexes of which point alternatingly towards the racket head 4 and towards the handle region 10 (wherein the orientation of the triangular gaps 34 might also be inverted). The gap-triangles can have rounded corners and be oblique, equal-sided and/or equilateral. In the shown embodiment, the apexes of the middle and the two outer gap-triangles point towards the head region 4 and the apexes of the remaining two triangles towards the handle region 10. In alternative embodiments, the directions into which the apexes of the triangles point are the other way round. Alternatively, the triangles can also point in other directions.
[0127] A lattice structure according to the invention can have similarly shaped gaps 34 and/or similarly shaped struts 32 and additionally or alternatively non-similarly shaped gaps 34 and/or non-similarly shaped struts. The areas of the gap shapes can remain the same within one embodiment, as shown in FIGS. 5A and 5B, or vary between the gap shapes, as shown in FIG. 5D.
[0128] The different lattice or truss structures shown in FIGS. 5A to 5D are only meant to be exemplary and should clarify that very complex and delicate structures can be manufactured by means of a one-part bridge made from a magnesium alloy. The use of magnesium provides for the required stability and light-weight construction, whereas the one-part form i.a. guarantees that the shown structures can be made with the required precision without fractures possibly occurring at joints. Preferably, the shown structures can be made in a casting, particularly preferably injection molding process, so that the finished bridge is made as one single cast or injection molded part.
[0129] FIG. 6A schematically shows a perspective detail of a further preferred embodiment of a bridge 6 according to the invention. In the shown preferred embodiment of FIG. 6A, the bridge 6 is realized as a one-part cast part having a solid profile and comprises a uniform magnesium alloy. A part of the frame region, with which the bridge is connected by way of the bracket, is indicated in dashed lines. The shown bridge portion of the bridge 6 of FIG. 6A comprises a bracket 16 and a part of the central region 18. The central region 18 is cut off in the drawing after the longitudinal axis 14. In this embodiment, the bridge 6 has four struts per side a or b, two upper struts 22 and two lower struts 24. FIG. 6B shows a cross-section of the bridge of FIG. 6A through the line A-B according to FIG. 1. FIG. 6B thus shows a cross-section through the central region 18 of the bridge of FIG. 6A. As shown in FIG. 6B, the bridge 6 has a central region 18 with solely convex cross-section, which is here exemplarily shown to be substantially rectangular. FIG. 6C shows a cross-section of the bridge 6 of FIG. 6A through the line C-D according to FIG. 1. FIG. 6C thus shows a cross-section through the web region of the bridge 6 of FIG. 6A. As shown in FIG. 6C, the webs or ligaments or beams 22 and 24 of the bridge 6 each also have a convex cross-sectional profile, which is also exemplarily shown to be substantially rectangular. It is stressed that the arrangement of the webs relative to one another as well as the areas of the individual web cross-sections are understood to be only schematic and exemplary. Thus, in particular the surface distances between two neighboring webs are not restricted to the shown web surface distances h1, h2, w1 and w2, wherein h1 and h2 each are a surface distance between two neighboring webs perpendicular with respect to the string bed plane and w1 and w2 each show a surface distance between two neighboring webs parallel with respect to the string bed plane. Alternative embodiments with other web arrangements, web profile shapes, cross-sectional areas of the webs and/or surface distances of the webs are possible. In particular, oval, round, convexly or concavely polygonal and/or irregular web cross-sections are possible. Cross-sectional areas and shapes of webs of the same embodiment can generally differ from each other. The values of web arrangements, web lengths, web profile shapes, cross-sectional areas of webs and/or web surface distances and also the values of bridge lengths, bridge profile shapes and/or cross-sectional areas of bridges preferably is in the ranges described above.
[0130] The embodiment of FIG. 6A is shown in a front view in FIG. 6D, so that the extension of the strings of the stringing is easily visible. In the embodiment of FIGS. 6A to 6E, none of the webs has a string opening 28. Instead, the longitudinal strings 36 and 37 each extend in a contactless manner between the two upper webs 22 of the corresponding side a or b and between the two lower webs 24 of the corresponding side a or b. The longitudinal strings 36 and 37 each engage with a string opening 28 in the bracket 16 of the corresponding side a or b. This is particularly clearly visible in FIG. 6E which shows an enlarged view of the frame area around side a of the bridge 6 of FIG. 6D. In FIGS. 6D and 6E, the boundaries between the brackets 16 and the adjoining, carbon-containing frame region are schematically marked by dashed lines. Alternatively or additionally, a string 36 and/or 37 can engage with the frame also outside the brackets and outside the bridge.
[0131] FIGS. 7A to 7D relate to calculated geometrical moments of inertia at different places of a bridge of a preferred embodiment of a frame of a ball game racket according to the invention as compared to a conventional bridge of a conventional frame of a ball game racket.
[0132] FIG. 7A shows yz-sections of a bridge of a conventional frame of a ball game racket at different places of the x-axis, wherein the x-axis is in accordance with the already described definition. The conventional frame of a ball game racket used as a basis for the calculation is a frame of a ball game racket which has a bridge that is configured substantially as a tube and is symmetrical with respect to a central plane. The yz-sections are, as already defined, sections perpendicular with respect to the x-axis. The places on the x-axis at which the shown yz-sections are located are spaced apart from each other by 2.5 mm on the x-axis, starting from the central plane of the bridge (x=0) up to a maximum value of x=35 mm. In terms of mathematics, thus yz-sections are shown for all x that are characterized in that x is taken from the set of {0 mm, 2.5 mm, 5.0 mm, . . . , 35.0 mm}. The yz-section at x=0 is referred to as A-A, the yz-section at x=2.5 mm as B-B, etc., up to O-O for the yz-section at x=35 mm. FIG. 7A also shows for the sake of clarity the y- and z-directions. Because of the symmetry of the bridges shown in FIGS. 7A and 7B, the yz-sections for the corresponding places in the negative x-axis area are identical to the respective yz-section at the positive x-value having the same absolute value |x|.
[0133] FIG. 7B shows the calculated geometrical moments of inertia for the yz-sections of a conventional frame of a ball game racket as shown in FIG. 7A. The graph shows the position on the racket's x-axis as abscissa and the geometrical moment of inertia as ordinate. The calculated Iz-values are shown as squares, the calculated Iy-values as rhombs. Both geometrical moments of inertia moderately increase as the absolute value of x increases. The Iz- and Iy-values run substantially parallel, i.e. the respective absolute increase from a first x-value x.sub.m to a second x-value x.sub.n is substantially the same for Iz and Iy. For all calculated values x.sub.i it holds true that Iz(x=x.sub.i) is smaller than Iy(x=x.sub.i). Iz of the conventional frame of a ball game racket ranges from about 500 mm.sup.4 to about 1600 mm.sup.4. Iy of the conventional frame of a ball game racket ranges from about 1900 mm.sup.4 to about 2800 mm.sup.4. A maximum and/or minimum do/does not occur.
[0134] FIG. 7C shows yz-sections of a bridge of a frame of a ball game racket according to the invention. The yz-sections are positioned and oriented in the coordinate system of the racket in the same manner as the yz-sections of FIG. 7A. Also the bridge of the embodiment of FIG. 7C is symmetrical with respect to the central plane, so that the shown yz-sections do not only apply, as shown, to the respective positive x-values but also to the respective negative x-values having the same absolute values |x|.
[0135] FIG. 7D shows the calculated geometrical moments of inertia for the yz-sections of a frame of a ball game racket according to the invention as shown in FIG. 7C. The abscissa again shows the x-values, the ordinate the geometrical moment of inertia, and the calculated Iz-values are shown as squares and the calculated Iy-values as rhombs. The graph shows clear differences as compared to the conventional frame of a ball game racket. For example, the calculated geometrical moments of inertia Iz(x=x.sub.i) of the bridge of an embodiment according to the invention are larger than the corresponding values of Iy(x=x.sub.i). Furthermore, the course of the values differs as x increases. In the embodiment according to the invention, there is a first region or range A2-1, approximately from x=0 mm to x=15 mm, in which Iz and Iy run substantially parallel with respect to each other and moreover show only a slight decrease as x increases. In a second region A2-2, Iz and Iy also extend substantially parallel with respect to each other, but they clearly increase as x increases. A2-2 covers the range of approximately 20 mm to 25 mm on the x-axis. In a third range A1, approximately from x=25 mm to x=35 mm, Iz increases steeply as x increases, while Iy decreases moderately as x increases. As already mentioned, the consideration of the geometrical moments of inertia with respect to a division into the ranges A1 to A3 relates to the global behavior. The value Iz(x=27.5 mm) for the yz-section L-L is thus to be classified as outlier because this yz-section has a reduced surface because of a string opening. Iz has a clearly higher value for all calculated x.sub.i than the conventional frame of a ball game racket as shown in FIGS. 7A and 7B. Moreover, the geometrical moment of inertia Iz is particularly high in the edge regions of the bridge according to the invention as compared to the Iz-values of a conventional frame of a ball game racket.
[0136] As the bridge of a ball game racket according to the invention has an increased Iz (as compared to a conventional racket frame), it has a clearly higher stiffness when being bent about the z-axis (the z-axis is perpendicular with respect to the stringing plane or string bed), wherein the forces act along the longitudinal strings. This is advantageous under the aspect of the energy balance during a strike. During a normal strike, a ball hits the stringing, i.e. the strings of a stringed frame of a ball game racket. The energy of the ball, in particular the kinetic energy of the ball relative to the racket, is transmitted in the form of vibrations, potential energy and friction to the ball itself, to the strings and to the frame of the ball game racket. It is generally known that during this process the stringing absorbs the smallest amount of the transmitted energy and the ball the greatest amount. The amount of energy that is absorbed by the frame of the ball game racket lies therebetween. The increased stiffness of the frame of the ball game racket according to the invention helps that less energy is absorbed and dissipated by the frame and instead more energy is absorbed by the strings. Thus, more energy can be made available for the acceleration of the ball, and the playing behavior of the ball game racket is improved.
[0137] The embodiments described on the basis of FIGS. 1A to 7D are—by no means final—examples for one-part bridges with filigree regions and for frames of ball game rackets comprising such bridges according to claim 1. By means of the presently known prior art, the fine structures in the form of webs or arms and/or in the form of the lattice or truss structure as shown in the examples cannot be made or can only be made with extremely high technical efforts. For example, the bridges as shown in the Figures could not be made with the required stability by the blow tube molding. On the basis of the manufacturing method suggested in the present application and by using a bridge that is formed as a one-part cast part, however, it is possible to manufacture also such and other, not explicitly described filigree structures.
[0138] The embodiments shown in FIGS. 1A to 7D are exemplary and by no means final. All Figures are considered to be schematic illustrations by means of which specific preferred features are to be discussed. Therefore, it is possible that features have been omitted in illustrations of embodiments for reasons of clarity. For example, in FIGS. 2A to 2C, 3A to 3C, 4 and 6A to 6D, the string openings 28 have been omitted completely or partly. This means that features from different illustrations can be combined as far as this is not explicitly excluded.
