RACKET OR CLUB CONSISTING OF MAGNESIUM

Abstract

The present invention relates to a frame for a ball-game racket comprising a head portion and a handle portion, wherein the frame is configured as a hollow profile and comprises magnesium and wherein the wall thickness of the hollow profile varies along a cross-section through the hollow frame profile, as well as to a process for producing such a racket.

Claims

1. A frame for a ball-game racket comprising a head portion and a handle portion, wherein at least a part of the frame is configured as a hollow profile and comprises magnesium and wherein the wall thickness of the hollow profile varies along a cross-section through the hollow frame profile.

2. The frame according to claim 1, wherein further the wall thickness of the hollow profile varies in the longitudinal direction of the frame.

3. The frame according to claim 1, wherein the variation in the wall thickness along at least one cross-section and/or longitudinal section relative to the minimum wall thickness is at least 25%, preferably at least 50%, more preferably at least 75%, particularly preferably at least 100%.

4. The frame according to claim 1, wherein the wall thickness of the frame in sections is thinner than 1 mm, preferably thinner than 0.8 mm, more preferably thinner than 0.7 mm, particularly preferably thinner than 0.6 mm.

5. The frame according to claim 1, wherein the frame profile of the frame comprises an outer portion, an inner portion and two side portions in the head portion, and wherein the wall thickness of the inner and/or outer portion at least in sections is thicker than the wall thickness of the side portions.

6. The frame according to claim 1, wherein the frame profile of the frame comprises an outer portion, an inner portion and two side portions in the head portion, and wherein the wall thickness of the inner and/or outer portion at least in sections is thinner than the wall thickness of the side portions.

7. The frame according to claim 1, wherein the frame profile of the frame comprises an outer portion, an inner portion and two side portions in the head portion, and wherein the wall thickness of the inner portion at least in sections is thinner than the wall thickness of the outer portion.

8. The frame according to claim 1, wherein the frame comprises at least 50% (by weight), preferably at least 80% (by weight), more preferably at least 90% (by weight), particularly preferably at least 95% (by weight) of magnesium.

9. The frame according to claim 1, wherein the frame comprises a magnesium alloy, preferably a fiber-reinforced or particle-reinforced alloy, particularly preferably SAE SiC/AZ91.

10. The frame according to claim 1, wherein the frame is locally reinforced with carbon fiber material and/or glass fiber material.

11. The frame according to claim 10, wherein the frame is reinforced with carbon fiber material and/or glass fiber material in the area of the transition between the head portion and the handle portion.

12. The frame according to claim 1, wherein the frame comprises two frame halves which are welded to each other, pressed together and/or bonded to each other.

13. The frame according to claim 12, wherein the two frame halves are identical and wherein each of the two frame halves is asymmetrical with respect to the longitudinal axis of the frame.

14. The frame according to claim 1, wherein the frame comprises a frame portion comprising magnesium, and wherein the wall thickness of the hollow profile varies along a cross-section through this frame portion.

15. The frame according to claim 14, wherein the frame in said frame portion comprises at least 50% (by weight), more preferably at least 80% (by weight), more preferably at least 90% (by weight) and particularly preferably at least 95% (by weight) of magnesium.

16. The frame according to claim 14, wherein said frame portion comprises two frame portion halves which are welded to each other, pressed together and/or bonded to each other.

17. A process for producing a frame for a ball-game racket, in particular a frame according to claim 1, wherein the process comprises the following steps: providing an injection mold and a core, wherein the core consists of a material having a melting temperature below 400 C.; casting the frame by inserting a material comprising magnesium between the injection mold and the core, preferably by means of the thixo process; and melting the core by heating the racket including the core to above the melting temperature of the core, wherein the heat resistance temperature of the frame is not exceeded.

18. The process according to claim 17, wherein the frame material comprises at least 50% (by weight), preferably at least 80% (by weight), more preferably at least 90% (by weight), particularly preferably at least 95% (by weight) of magnesium.

19. The process according to claim 17 or 18, wherein the frame material comprises a magnesium alloy, preferably a fiber-reinforced or particle-reinforced alloy, particularly preferably SAE SiC/AZ91.

20. The process according to claim 17, wherein the core material comprises or consists of one of or a combination of the following materials: an alloy on the basis of tin, an alloy on the basis of bismuth, an alloy on the basis of lead, an alloy on the basis of zinc, an alloy on the basis of indium, glass, plastics with or without glass-fiber reinforcement, polyamide.

Description

[0026] In the following, preferred embodiments of the frame according to the invention are described in more detail by means of the Figures, in which:

[0027] FIG. 1 shows a perspective view of the frame according to the invention;

[0028] FIG. 2 shows a perspective view of a frame half of the frame according to FIG. 1;

[0029] FIG. 3 shows an enlarged perspective view of the throat portion of the frame according to FIG. 2;

[0030] FIG. 4 shows a perspective view of the transition from the handle portion into the throat portion of the frame according to FIG. 2;

[0031] FIG. 5 shows a perspective view of a portion of the head portion of the frame according to FIG. 2;

[0032] FIG. 6 shows a perspective cross-section through the head portion of the frame according to FIG. 1;

[0033] FIG. 7 shows a perspective cross-section through the bridge of the frame according to FIG. 1;

[0034] FIG. 8 shows a perspective longitudinal section through the handle portion of the frame according to FIG. 1;

[0035] FIG. 9 shows a top view on a separate component for a frame according to a preferred embodiment of the present invention;

[0036] FIG. 10 shows a side view as viewed from the stringbed plane onto the component of FIG. 9;

[0037] FIG. 11 shows a side view from a side opposite FIG. 10 onto the component according to FIG. 9;

[0038] FIG. 12 shows a perspective view of the component according to FIG. 9; and

[0039] FIG. 13 shows a further perspective view of the component according to FIG. 9.

[0040] FIG. 1 shows a perspective view of a frame for a ball-game racket according to a preferred embodiment of the present invention. The frame is configured as a hollow profile and comprises a head portion 1 for accommodating strings that are not shown, a handle portion 2 and a throat portion 3 comprising two branches 4a and 4b as well as a bridge 5. The frame of this preferred embodiment is composed of two identical frame halves which are asymmetrical with respect to the longitudinal axis of the frame. A perspective view of one of these two identical frame halves is shown in FIG. 2.

[0041] As apparent from FIG. 2, the asymmetry of the frame halves is such that the two frame halves can engage with each other when being joined. This can be seen particularly clearly in the enlarged detail according to FIG. 3 illustrating the throat portion 3 of the frame half of FIG. 2: The projecting ridges 5a of the bridge 5, for example, can engage with the stepped portions 5b of the bridge 5 of the other frame half. This enables a flush connection of the two frame halves to form a frame. The head portion (cf. FIG. 5) similarly comprises areas with projecting ridges 1a and stepped portions 1b.

[0042] In the illustrated preferred embodiment, the step forms a kind of limit stop for the second frame half, and the ridge and step can be welded or bonded to each other, for example. Alternatively or additionally, the frame halves can also comprise, for example, projections and grooves or similar areas permitting that the two frame halves interlock.

[0043] FIG. 6 illustrates a cross-section through the hollow frame profile of the frame of FIG. 1 in the area of the head portion 1. As can be clearly seen in FIG. 6, the wall thickness of the hollow frame profile can quite considerably vary according to the invention along a cross-section through the hollow frame profile. In the depicted preferred embodiment, the frame profile comprises an outer portion 7, an inner portion 6 and two side portions 8a and 8b in the area of the head portion, wherein in the depicted cross-section the wall thickness of the inner portion 6 and the outer portion 7 is considerably greater than the wall thickness of the two side portions 8a and 8b. There is a continuous and/or gradual transition of the wall thickness from the inner and/or outer portion to the two side portions. Such a finely adjusted cross-sectional profile could not be achieved by means of the conventional tube blowing process. However, when magnesium and/or magnesium alloys are injection molded, such a cross-sectional profile can be configured in a simple way by means of the respective configuration of the injection mold, wherein the cross-sectional profile can additionally vary along the frame contour in the longitudinal direction.

[0044] FIG. 7 illustrates a cross-section through the hollow profile in the area of the bridge 5. The wall thickness of the hollow profile varies in this area, too, even though the variation is not as distinct as in the example of FIG. 6.

[0045] An additional variation in the wall thickness in the longitudinal direction of the frame, i.e., along the frame contour, is illustrated in FIG. 8, which shows a longitudinal section through the handle portion 2 of the frame of FIG. 1. As can be clearly seen here, the wall thickness of the hollow frame profile significantly increases in the area of the transition to the branch 4b.

[0046] According to the invention, it is not the entire frame that has to comprise magnesium. It is rather possible according to the invention that the frame comprises a portion or a separate component that is made of magnesium or a magnesium alloy. A preferred embodiment of such a separate component from a magnesium alloy is depicted in FIGS. 9 to 13. This separate component is a section from the throat area, namely the bridge 5 as well as portions of the branches 4a and 4b and in the transition from the throat portion into the head portion. During the game, the stress of this frame part is particularly complex so that the greatest effect by means of a variation in the wall thickness of the hollow profile can be achieved in this area. According to the invention, it is, however, also possible to produce other insert components from magnesium or a magnesium alloy, such as, for example the handle portion or areas of the head portion, and incorporate them into the frame according to the invention. To this end, the separate magnesium component preferably is pressed together with the prepreg layers of the remaining frame by mans of the tube blowing process. As can be seen, for example, in the side view of FIG. 10, the injection molding operation can be controlled by means of the process according to the invention so well that even the string holes 10, through which the strings forming the stringbed are passed, can be accordingly produced without any additional drilling step being required.