EP3016721A1

EP3016721A1 - Racket or club consisting of magnesium

Info

Publication number: EP3016721A1
Application number: EP14745093.6A
Authority: EP
Inventors: Daniel Lau; Harald Rosenkranz; Ralf Schwenger
Original assignee: Head Technology GmbH
Current assignee: Head Technology GmbH
Priority date: 2013-07-04
Filing date: 2014-07-04
Publication date: 2016-05-11
Anticipated expiration: 2034-07-04
Also published as: US20170050090A1; EP3016721B1; CN105407987A; WO2015001077A1; DE102013011174B4; DE102013011174A1; CN105407987B; ES2758727T3

Abstract

The present invention relates to a frame for a ball-game racket or club having a head portion and a handle portion, the frame being a hollow profile and comprising magnesium, and the wall thickness of the hollow profile varying over a cross-section through the hollow profile of the frame, and method for producing said racket or club.

Description

magnesium bat

The present invention relates to a frame for a ball game racket having magnesium, and a method of manufacturing such a frame.

As a material for the frame of a ball game racket, especially a tennis racket, the most diverse materials have already been proposed. However, technically enforced after initial wooden clubs only aluminum rackets whose frame is bent from an aluminum profile, and glass fiber reinforced rackets and in particular carbon fiber reinforced rackets whose frame is formed from one or more so-called prepreg hoses.

Further, for example, from US 3,874,667 known to use magnesium as a material for the frame of ball game rackets. The racket disclosed in US 3,874,667 consists of a solid metal frame. Such a solid metal frame can meet the usual weight and playability requirements of today

Ball game racket do not do justice.

If, however, as is customary today, the frame for a ball game racket in the blown from prepregs made, so it is extremely challenging to vary the wall thickness of the frame specifically to influence the local stiffness of the frame and the weight distribution of the same. On the other hand, if the frame is bent from an aluminum hollow profile, the wall thickness of the frame profile is usually constant, since aluminum profiles with a constant cross-section are used.

The present invention has as its object to provide a frame for a ball game racket or a manufacturing method of such a frame, which allows to selectively optimize the rigidity of the frame locally on the variation of the wall thickness and to achieve an optimal weight distribution the total weight of the racket should be kept as low as possible. This object is achieved by a frame for a ball game racket according to claim 1 and by a method for producing a frame for a ball game racket according to claim 17. The frame according to the invention for a ball game racket, in particular for a tennis racket, has a head section and a handle section. The frame is designed as a hollow profile and has magnesium, wherein the wall thickness of the hollow profile varies along a cross section through the frame hollow profile.

The term "hollow profile" is understood in the context of the present invention, a real hollow profile, which is formed only by a frame wall, a

Cavity encloses, this cavity is free of additional walls, struts and the like. In other words, according to the invention, mechanical properties such as flexural stiffness and natural frequencies are determined essentially exclusively by the variable wall thickness of the hollow profile, without it being additional, for example

Stabilization striving would need.

It has been found in the context of the invention that magnesium or

Use magnesium alloys for a frame hollow profile for a ball game racket. The manufacturing techniques used in this case advantageously allow a targeted variation of the wall thickness of the hollow profile, in particular also along one

Cross section through the frame hollow profile. Under the cross section through the frame hollow profile is in the context of the present invention, a section perpendicular to the contour of the

Frame profile understood. By means of the commonly used tubular blowing method, a targeted variation of the wall thickness along such a cross section through the

Frame hollow profile practically impossible, since the prepreg layers are usually wound so that they extend along such a cross section through the frame hollow profile.

Usually only different cross-sectional shapes and / or dimensions can be realized in the blow-molding process.

The frame according to the invention can, for example, by means of

Magnesium injection molding techniques such as the so-called Thixoverfahren be made. Using this technique, wall thickness can be easily achieved appropriate training of the injection mold specifically vary. Particular preference is given to the so-called melt-core technique, in which an injection-molded core is melted after the frame has been formed.

It is further preferred that the wall thickness of the hollow profile not only along a

Cross-section through the frame hollow profile varies, but also in the longitudinal direction of the frame, i. varies along the frame contour. Thus, the wall thickness in the heart region or in the transition between the bridge and head portion of the frame is preferably greater than in the remaining head portion.

According to a preferred embodiment, the variation of the wall thickness along at least one transverse and / or longitudinal section based on the minimum wall thickness is at least 25%, preferably at least 50%, more preferably at least 75% and particularly preferably at least 100%.

Using magnesium and / or magnesium alloys, particularly thin wall thicknesses can be achieved with the help of magnesium injection molding in particular. Thus, according to a preferred embodiment, the wall thickness of the frame according to the invention is thinner in sections than 1 mm, preferably thinner than 0.8 mm, more preferably thinner than 0.7 mm and particularly preferably thinner than 0.6 mm.

The frame profile of the frame according to the invention preferably has in the head portion an outer portion facing outward, an inner portion facing inwardly to the fabric, and two side portions, wherein at least partially the wall thickness of the inner and / or outer portion is thicker than the wall thickness of side sections. In this case, the frame profile does not have to be rectangular. Rather, further sections can form a flowing transition from the inner or outer section to the two side sections, so that a polygon, a rectangle with rounded corners or the like is formed. According to an alternative preferred embodiment, the wall thickness of the inner or outer portion is at least partially thinner than the wall thickness of the side portions. Additionally or alternatively, at least in sections, the wall thickness of

Inner portion may be thinner or thicker than the wall thickness of the outer portion. The frame preferably has at least 50% by weight, more preferably at least 80% by weight, even more preferably at least 90% by weight and most preferably at least 95% by weight of magnesium. According to a preferred embodiment, the frame has a magnesium alloy, preferably a fiber-reinforced or particle-reinforced alloy, particularly preferably SAE SiC / AZ91. Particularly preferably, substantially the entire frame is made of such an alloy. In addition, the frame may be locally reinforced with carbon and / or fiberglass material. Such a reinforcement is preferably provided in the region of the transition between the head section and the grip section.

According to the invention, the magnesium or magnesium alloy content does not have to be evenly distributed over the ball game racket frame. Rather, it is also preferred that the frame has a frame portion having magnesium, wherein the wall thickness of the hollow profile varies along a cross section through this frame portion. In this case, preferably, the frame in this frame portion has at least 50% by weight, more preferably at least 80% by weight, even more preferably at least 90% by weight and most preferably at least 95% by weight of magnesium. In this preferred

Embodiment one or more components can be made separately from magnesium or a magnesium alloy, in particular injection-molded, be. These components can then be placed in a tubular shape together with the prepreg layers in a mold and pressed together with the prepreg layers. These separate components may be individual sections of the head section or handle section. Particularly preferred according to the invention, however, a separate heart area is provided, the

Magnesium or magnesium or magnesium alloys, since can be achieved in this area with a corresponding variation of the wall thickness particularly advantageous effects.

The magnesium-containing frame portion is preferably made of two

Frame section halves that are welded together, pressed and / or glued. If the entire frame has magnesium, then preferably the entire frame consists of two frame halves which are welded together, pressed and / or glued together. The

Frame halves or frame portion halves are preferably identical, with each of the two Frame halves or frame portion halves is formed asymmetrically with respect to the frame longitudinal axis or frame portion longitudinal axis. In this way, using the injection molding process, two identical halves can be produced in a particularly simple manner, which then interlock when connecting.

The present invention further relates to a method of manufacturing a frame for a ball game racket. The frame produced by the method according to the invention is preferably a frame with the properties described above. According to a preferred embodiment of the method according to the invention for producing a frame or frame section, an injection mold and a core are provided, wherein the core preferably consists of a material with a melting temperature below the melting temperature or heat resistance temperature of the frame material. Preferably, the melting temperature of the core material is less than 400 ° C, more preferably less than 370 ° C. It is further preferred that the melting temperature of the

Core material above 190 ° C, more preferably above 200 ° C. The frame (or frame member) is then molded between the injection mold and the core, preferably by the thixotropic method, by introducing a material comprising magnesium. The

Nuclear material is chosen so that during the molding of the frame not enough heat energy is introduced into the core to melt this, with a slight softening may be tolerated. After the frame has been molded, removed from the mold, and cooled to keep its shape stable, the core is melted, preferably by heating the entire racket above the melting temperature of the core, such that the core material is formed from the cavity formed by the frame can escape. At this time, the heat-resistant temperature of the frame is preferably not exceeded.

The core material preferably comprises one or a combination of the following materials or consists of one or a combination of the following materials: tin-based alloys (preferably at least 50% tin and optionally zinc, bismuth, antimony, copper, silver, lead, indium), Bismuth based alloys (preferably at least 50% bismuth and optionally tin, silver, germanium), lead based alloys (preferably at least 50% lead and optionally tin, antimony, bismuth, silver, indium), zinc based alloys (preferred at least 50% zinc), zinc die cast alloys such as ZnA14, ZnA14Cul, ZnA14Cu3, alloys based on indium, glass, plastic with or without glass fiber reinforcement such as polyamide. Particularly preferred are metallic integral foam cores based on these low-melting alloys. These can be produced, for example, by die casting. The addition of a propellant results in an integral foam with closed outer skin. For example, the relative density may be 50% to 100% of the absolute

Material density amount. Thus, by using a foam, for example, only half the amount of material is needed compared to a solid core.

According to a further preferred embodiment of the method according to the invention for producing a frame, an injection mold and a core are provided, wherein the core consists of a salt. The frame (or frame member) is then molded between the injection mold and the core, preferably by the thixotropic method, by introducing a material comprising magnesium. After the frame has been molded, removed from the mold, and cooled enough to stably retain its shape, the core is washed out by introducing water into the cavity formed by the frame.

According to a further preferred embodiment of the method according to the invention for producing a frame, the core can also be made of an acid-soluble material, e.g. glass base, so that the core can be removed from the frame after forming the frame with the help of an acid.

According to a further preferred embodiment of the method according to the invention for producing a frame, first two frame halves are cast from a material which comprises magnesium. This is preferably done by means of the so-called

Thixoverfahrens. Subsequently, the two frame halves are connected to form a frame.

In the method according to the invention of this second embodiment for producing a frame section, first two frame section halves of a material comprising magnesium are cast, and then the two frame section halves are firstly cast Frame section connected. In order to produce a frame for a ball game racket from this first frame section, a second frame section is provided and the first and second frame sections are connected to form a frame. According to the invention, the second frame section may be an unfinished section, for example a prepreg tube, so that the completion of the second frame section and the connection of the second frame section to the first frame section in one

Process step done.

The injection molding of the magnesium-containing material is preferably carried out at temperatures between 500 ° C and 800 ° C, more preferably at temperatures between 550 ° C and 700 ° C. The injection of the material into the mold is preferably carried out in less than 80 ms, more preferably in less than 60 ms and particularly preferably in less than 50 ms.

The step of connecting the two frame halves or frame section halves preferably comprises welding and / or pressing and / or gluing. Furthermore, the two frame halves or frame section halves are preferably identical, wherein each of the two frame halves or frame section halves is formed asymmetrically with respect to the longitudinal axis.

The frame according to the invention for a ball game racket has a number of technical advantages over the prior art. Although magnesium has higher density, lower specific stiffness, and lower specific strength than conventional prepreg materials, a frame for a magnesium or magnesium magnesium racket can be better optimized for stiffness and strength with the same weight, as the wall thickness can be reduced to simple Way can be optimally designed. The use of magnesium injection molding allows automated production with short cycle times of approx. 35 seconds. A pre- and post-processing, which is often done manually by conventional Perpregverfahren, eliminates virtually completely. Injection molding also allows excellent production stability and allows to produce exactly the desired structure using a defined injection mold. Hereinafter, preferred embodiments of the inventive frame will be described with reference to the figures. Show it:

Fig. 1 is a perspective view of the frame according to the invention;

FIG. 2 is a perspective view of a frame half of the frame according to FIG. 1; FIG.

Fig. 3 is an enlarged perspective view of the heart region of the frame according to

Figure 2;

Fig. 4 is a perspective view of the transition from the handle portion in the

Heart area of the frame according to FIG. 2;

FIG. 5 is a perspective view of a portion of the head portion of the frame of FIG. 2; FIG.

Fig. 6 is a perspective cross-section through the head portion of the frame according to

FIG. 1;

Fig. 7 is a perspective cross-section through the bridge of the frame according to FIG

l;

Fig. 8 is a perspective longitudinal section through the handle portion of the frame

according to Figure 1;

9 is a plan view of a separate component for a frame according to a

preferred embodiment of the present invention;

Fig. 10 is a side view viewed from the clothing plane on the component

Figure 9;

11 is a side view of a figure 10 opposite side on the component according to Figure 9;

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

13 is a further perspective view of the component according to FIG. 9.

Figure 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 as

Hollow profile formed and has a head portion 1 for receiving a fabric, not shown, a handle portion 2 and a heart portion 3, which has two arms 4a and 4b and a bridge 5. The scope of this preferred embodiment is composed of two identical frame halves, with respect to the frame longitudinal axis are formed asymmetrically. One of these two identical frame halves is shown in a perspective view in FIG.

As can be seen in Figure 2, the asymmetry of the frame half is provided such that the two frame halves can engage with each other during assembly. In the enlarged section of FIG. 3, which shows the heart region 3 of the frame half from FIG. 2, this can be seen particularly clearly: for example, the protruding webs 5a of the bridge 5 can engage with the step-shaped sections 5b of the bridge 5 of the respective other frame half , This allows a flush connection of the two

Frame halves to a frame. Similarly, the head portion (see Fig. 5) has portions with protruding lands 1a and step-shaped portions 1b.

In the illustrated preferred embodiment, the step forms a kind stop for the second frame half and web and stage can be welded or glued together, for example. Alternatively or additionally, the frame halves may also, for example, projections and grooves or similar areas have, which allow the two

Frame halves to lock together.

FIG. 6 shows a cross section through the frame hollow profile of the frame of FIG. 1 in the region of the head section 1. As can be seen clearly in FIG. 6, the wall thickness of the hollow frame profile according to the invention can vary considerably considerably along a cross section through the frame hollow profile. In the illustrated preferred embodiment, the

Frame profile in the region of the head portion on an outer portion 7, an inner portion 6 and two side portions 8a and 8b, wherein in the illustrated cross section, the wall thickness of the inner portion 6 and the outer portion 7 is considerably larger than the wall thickness of the two side portions 8a and 8b. There is a continuous or gradual transition from the wall thickness of the inner or outer portion towards the two

Page sections held. Such a finely tuned cross-sectional profile could not be achieved using the conventional bubble-blowing process. However, if magnesium or a magnesium alloy injection-molded, such a cross-sectional profile can be designed in a simple manner by appropriate design of the injection mold, wherein the

Cross-sectional profile can additionally vary along the frame contour in the longitudinal direction. FIG. 7 shows a cross section through the hollow profile in the region of the bridge 5. Again, the wall thickness of the hollow profile varies, although the variation is not as pronounced as in the example of Figure 6.

An additional variation of wall thickness in the longitudinal direction of the frame, i. along the frame contour, can be seen in Figure 8, which shows a longitudinal section through the handle portion 2 of the frame of Figure 1. As can be clearly seen here, the wall thickness of the frame hollow profile increases significantly in the region of the transition to the arm 4b.

According to the invention does not have the entire frame magnesium. Rather, according to the invention, the frame can also have a section or a separate component made of magnesium or a magnesium alloy. A preferred

Embodiment of such a separate component of magnesium alloy is shown in Figures 9 to 13. This is a section of the heart area, namely the bridge 5 and sections of the arms 4a and 4b and in the transition of the heart area in the head section. The use of this frame part during the game is particularly complex, so that in this area by means of a variation of the wall thickness of the

Hollow profiles can achieve the greatest effect. According to the invention, however, other insert components such as, for example, the grip section or regions of the head section can likewise be made of magnesium or a magnesium alloy and inserted into the frame according to the invention. This is preferably done by the separate magnesium component is pressed with the prepreg layers of the rest of the frame in the tube blowing process. As can be seen, for example, in the side view of FIG. 10, injection molding can be controlled so well with the aid of the method according to the invention that even the string openings 10 for the passages of the string forming the string can be manufactured without requiring an additional step of drilling is.

Claims

claims

1. frame for a ball game racket with a head portion (1) and a handle portion (2), wherein at least a part of the frame is formed as a hollow profile and magnesium and wherein the wall thickness of the hollow profile varies along a cross section through the frame hollow profile.

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

3. Frame according to one of the preceding claims, wherein the variation of the wall thickness along at least one transverse and / or longitudinal section based on the minimum wall thickness of at least 25%, preferably at least 50%, more preferably at least 75%, particularly preferably at least 100%.

4. Frame according to one of the preceding claims, wherein the wall thickness of the frame in sections thinner than 1 mm, preferably thinner than 0.8 mm, more preferably thinner than 0.7 mm, more preferably thinner than 0.6 mm.

5. Frame according to one of the preceding claims, wherein the frame profile of the frame in the head portion (1) has an outer portion (7), an inner portion (6) and two side portions (8a, 8b) and wherein at least partially the wall thickness of the interior and / or or outer portion is thicker than the wall thickness of the side portions.

6. Frame according to one of the preceding claims, wherein the frame profile of the frame in the head portion (1) has an outer portion (7), an inner portion (6) and two side portions (8a, 8b) and wherein at least partially the wall thickness of the indoor and / or or outer portion is thinner than the wall thickness of the side portions.

7. Frame according to one of the preceding claims, wherein the frame profile of the frame in the head portion (1) has an outer portion (7), an inner portion (6) and two side portions (8a, 8b) and wherein at least in sections the wall thickness of the inner portion is thinner than the wall thickness of the outer portion.

8. Frame according to one of the preceding claims, wherein the frame at least 50% (wt.), Preferably at least 80% (wt.), More preferably at least 90% (wt.), More preferably at least 95% (wt.) Magnesium ,

9. Frame according to one of the preceding claims, wherein the frame comprises a magnesium alloy, preferably a fiber or particle-reinforced alloy, particularly preferably SAE SiC / AZ91.

10. Frame according to one of the preceding claims, wherein the frame is locally reinforced with carbon and / or glass fiber material.

11. Frame according to claim 10, wherein the frame is reinforced in the region of the transition between the head portion (1) and the handle portion (2) with carbon and / or glass fiber material.

12. Frame according to one of the preceding claims, wherein the frame has two frame halves which are welded together, pressed and or glued together.

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

14. Frame according to one of the preceding claims, wherein the frame has a frame portion having magnesium, and wherein the wall thickness of the hollow profile varies along a cross section through this frame portion.

15. Frame according to claim 14, wherein the frame in this frame section at least 50% (wt.), Preferably at least 80% (wt.), More preferably at least 90% (wt.), More preferably at least 95% (wt.) Magnesium having.

16. Frame according to claim 14 or 15, wherein said frame portion comprises two frame portion halves which are welded together, pressed and / or glued.

17. A method for producing a frame for a ball game racket, in particular a frame according to one of the preceding claims, wherein the method comprises the following steps:

Providing a mold and a core, the core consisting of a material having a melting temperature below 400 ° C;

Casting the frame by introducing a material comprising magnesium between the mold and the core, preferably by the Thixo method; and

Melting of the core by heating the beater including core above the melting temperature of the core, wherein the heat resistance temperature of the frame is not exceeded.

18. The method of claim 17, wherein the frame material comprises at least 50% (wt), preferably at least 80% (wt), more preferably at least 90% (wt), more preferably at least 95% (wt) magnesium.

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

20. The method of claim 17, 18 or 19, wherein the core material comprises one or a combination of the following materials or consists of one or a combination of the following materials: tin-based alloy, bismuth-based alloy, lead-based alloy, zinc-based alloy, alloy indium-based, glass, plastic with or without glass fiber reinforcement, polyamide.