Abstract
The present invention relates to a ball-striking device (1), in particular a tennis, squash, or badminton racket, having a head frame (2), which comprises a striking surface, is of a hollow design, and is produced from plastic, in particular from a fiber-reinforced plastic, and a shaft formed thereon with grip, wherein the striking surface (12) is defined by at least one string (8), which is tensioned in a crisscross manner and which forms string portions fastened substantially in parallel to one another on the head frame, wherein the anchoring of the string portions on the head frame (2) is performed via retainers (20) which are fastened on the inner side of the head frame so that they each extend substantially perpendicularly in relation to the striking surface, whereby the ends (10) of the string portions clamped in the retainers (20) can be laterally deflected upon impact of a ball. With the goal of specifying such a ball-striking device and a method for the production thereof, in which the anchoring of the string portions on the head frame is performed via retainers which may be arranged precisely and easily in the head frame and are also suitable for a mass production method, it is provided that the retainers (20) are open toward one of the two sides of the striking surface (12) and/or are freely accessible from one of the two sides of the striking surface (12) for clamping the string which defines the striking surface.
Claims
1. A ball-striking device (1), in particular a tennis, squash, or badminton racket, having a head frame (2), which comprises a striking surface, is of a hollow design, and is produced from plastic, in particular from a fiber-reinforced plastic, and a shaft formed thereon with grip, wherein the striking surface (12) is defined by at least one string (8), which is tensioned in a crisscross manner and which forms string portions fastened substantially in parallel to one another on the head frame, wherein the anchoring of the string portions on the head frame (2) is performed via retainers (20) which are fastened on the inner side of the head frame so that they each extend substantially perpendicularly in relation to the striking surface, whereby the ends (10) of the string portions clamped in the retainers (20; 23) can be laterally deflected upon impact of a ball, characterized in that the retainers (20; 23) are open toward one of the two sides of the striking surface (12) and/or are freely accessible from one of the two sides of the striking surface (12) for clamping the string which defines the striking surface.
2. The ball-striking device according to claim 1, characterized in that, for anchoring the string portions on the head frame, a set of retainers (20; 23) is provided, which comprises a first number of retainers having a first predetermined length (L1) in the circumferential direction of the head frame, at least one second number of retainers having a second predetermined length (L2) in the circumferential direction of the head frame, optionally at least one third, fourth, and fifth number of retainers having a third, fourth, and fifth predetermined length (L3, L4, L5) in the circumferential direction of the head frame.
3. The ball-striking device according to claim 1, characterized in that the retainers (20, 23), in the state fastened on the head frame (2), each comprise a retainer portion (24) protruding therefrom and a fastening portion (22) anchored inside the head frame (2).
4. The ball-striking device according to claim 3, characterized in that the fastening portion (22) of each retainer (20) has longitudinal (26) and transverse structures (27) for the formfitted and friction-locked anchoring inside the head frame (2).
5. The ball-striking device, in particular according to claim 1, wherein the retainer portion (24) is designed as either open toward one side and/or freely accessible toward one side, in particular as hooked, preferably oval-hooked, or closed toward both sides, in particular ring-shaped, characterized in that the fastening portion (22) of each retainer (20; 23) is embedded between two frame halves (4, 6), which define the head frame (2).
6. The ball-striking device according to claim 5, characterized in that the head frame (2) is formed by two frame halves, each made of a tubular prepreg (4, 6), which define a double-walled circumferential transverse web (40) extending approximately in parallel to the striking surface (12) approximately at the height of the striking surface (12), wherein the fastening portions (22) of the retainers (20; 23) are each embedded between the wall portions (42) of the two tubular prepregs (4, 6) defining the double-walled transverse webs (40) and are therefore fixedly anchored.
7. The ball-striking device according to claim 1, characterized in that the inner radius (21) of the retainers (20; 23) is in a range from 0.5 to 1.9 mm.
8. The ball-striking device according to claim 1, characterized in that the length of each of the retainers (20; 23) in the circumferential direction of the head frame is in the range from 5-30 mm, in particular the first predetermined length (L1) of the first number of retainers is in a range from 9-11 mm and/or the first number of retainers in the first predetermined length (L1) is 12 to 20, in particular 16, and/or the second predetermined length (L2) of the second number of retainers is in a range from 10-11 mm and/or the second number of retainers of the second predetermined length (L2) is 6 to 14, in particular 10, and/or the third predetermined length (L3) of the third number of retainers is in a range from 11-13 mm and/or the third number of retainers of the third predetermined length (L3) is 2 to 10, in particular 6, and/or the fourth predetermined length (L4) of the fourth number of retainers is in a range from 16-18 mm and/or the fourth number of retainers of the fourth predetermined length (L4) is 2 to 8, in particular 4, and/or the fifth predetermined length (L5) of the fifth number of retainers is in a range from 20-22 mm and/or the fourth number of retainers of the fourth predetermined length (L5) is 1 to 4, in particular 2.
9. The ball-striking device according to claim 1, characterized in that the retainers (20; 23) of predetermined length are each identified with a character provided for the purpose of typing, in particular visually and/or haptically recognizable characters or also characters readable in any other readable or automatically analyzable form, which indicate the type of the retainer of predetermined length (L1; L2; L3; L4; L5).
10. The ball-striking device according to claim 1, characterized in that a lateral gap (S) is defined between the free end of a retainer (20; 23) and the portion of the head frame (2) facing toward it, wherein the width of this gap is in the range from 1.0 to 2.0 mm, in particular in a range from 1.5 to 1.7 mm.
11. The ball-striking device according to claim 1, characterized in that the frontal ends (29) of the retainers (20; 23), via each of which the string (8) defining the striking surface is deflected, are rounded.
12. A method for producing a ball-striking device according to claim 1, wherein the retainers (20) are positioned in relation to a mold, within which a head frame (2) of a ball-striking device is produced, such that the fastening portions (14) of the retainers (20; 23) each protrude therein during the production of the head frame and are enclosed by the material thereof.
13. The method for producing a ball-striking device according to claim 12, characterized by the following method steps: positioning a first prepreg tube (4) in a first, for example, lower head frame mold (50); positioning a second prepreg tube (6) in a second, for example, upper head frame mold (52); positioning a holding device (30) for the retainers (20; 23) held in the correct position therein between upper and lower head frame molds such that the fastening portions of the retainers (20; 23) protrude into a region between the first and second prepreg tube (4; 6); forming and curing the prepreg tubes (4; 6) in the closed head frame mold while embedding the retainer fastening portions (22); and cooling and demolding the finished produced head frame having retainers (20; 23) fixedly anchored on the frame inner side.
14. The method for producing a ball-striking device according to claim 12, in which the frame, which consists of head frame (2) having retainers (20; 23), and also shaft (17) with grip (16) and optionally throat (18), is produced in one method step.
Description
[0029] In the figures:
[0030] FIG. 1: shows the head frame of a ball-striking device according to the invention within a production mold in cross section and enlarged scale;
[0031] FIG. 2: shows a top view of an exemplary embodiment of a ball-striking device designed according to the invention, specifically a tennis racket;
[0032] FIG. 3: shows a detail view of a retainer embedded in the head frame in a top view;
[0033] FIG. 4: shows a perspective in a top view and a side view in each case of two retainers of different predetermined length L;
[0034] FIG. 5 shows an enlarged view (perspective, top view, side view) of an exemplary retainer according to FIG. 4;
[0035] FIG. 6: shows a perspective of a lower part of a holding device for retainers;
[0036] FIG. 7: shows a perspective of a fully assembled holding device for retainers;
[0037] FIG. 8: shows a perspective of a lower mold half for the production of a ball-striking device according to the invention with positioned holding device for retainers;
[0038] FIG. 9: shows a perspective of a ball-striking device lying in a lower mold half with holding device after removal of an upper mold half;
[0039] FIG. 10: shows an alternative embodiment of a head frame having semi-oval retainers embedded inside a transverse web, in cross section; and
[0040] FIG. 11: shows insertion devices for the positioning of the retainers in a perspective view.
[0041] The elements essential for the immediate understanding of the invention will now be shown.
[0042] FIG. 1 shows a cross section A-A through the head frame 2 of a ball-striking device 1 according to the invention inside a production mold. In this case, a retainer 20 is embedded between two halves 4, 6 of a head frame 2. The head frame 2 is formed by two frame halves 4, 6, which are each made of two tubular prepregs 4, 6. Approximately at the height of the striking surface 12, the section shows a double-walled circumferential transverse web 40, which extends approximately in parallel to the striking surface 12. The retainers 20 are held for positioning between an upper holding tool 34 and a lower holding tool 32. The upper and the lower holding tools 32, 34 form a holding device 30. The holding device 30 is used for holding the retainer(s) 20 in the correct position between an upper 52 and a lower 50 head frame mold such that the retainers 20 are enclosed with the fastening portions 22 thereof in a region between the two prepreg tubes 4, 6. The two prepreg tubes 4, 6 are then formed and cured with the supply of pressure and heat between an upper mold 52 and a lower mold 50. The fastening portions 22 of the retainers 20 are each embedded between the wall portions 42 of the two tubular prepregs 4, 6, which define the double-walled transverse webs 40, and fixedly anchored. Of course, the two wall portions 42 of the two prepregs 4, 6 fuse together during the production of the head frame to form a unified material transverse web 40, wherein in this case the fastening portions 22 of the retainers are fixedly embedded and anchored in this transverse web 40, which then has unified material.
[0043] As already mentioned above, each retainer 20 has a fastening portion 22 embedded in the head frame 2. The fastening portion 22 essentially consists of a longitudinal structure 26 and a transverse structure 27. At the intersection of the longitudinal and transverse structures 26, 27 of each fastening portion 22, a character 14 applied for the purposes of typingthe number 2 in FIG. 1is provided. The character 14 applied for the purpose of typing corresponds to the type and/or the length (L1 to L5) of the retainer 20 in the circumferential direction of the head frame. The applied character is essentially used for the identification and later placement in the holding device 30. For this purpose, a plurality of retainers 20 is fixed in the holding device 30 and subsequently positioned on the first prepreg tube 4 in the first, lower head frame mold 50. Subsequently, the mold 50, 52 is closed and the retainers 20 are thus positioned between the first and a second prepreg tube 4, 6, from which the head frame 2 is produced. Subsequently, forming and curing of the prepreg tubes 4, 6 is performed in the closed head frame mold with the supply of pressure and heat, whereby the fastening portions 22 of the retainers 20 are embedded in a friction-locked and formfitted manner between the two head frame halves formed from the prepreg tubes 4, 6. After cooling, the finished produced head frame 2 can be demolded having the retainers 20 fixedly anchored on the frame inner side.
[0044] FIG. 2 shows a top view of a ball-striking device 1 of an exemplary embodiment according to the invention. The racket 1 substantially consists of the head frame 2, the stringing arranged therein, which defines a striking surface 12 (formed from a plurality of intersecting string portions), and also a racket shaft 17, which comprises a grip 16 and a so-called throat 18, via which the shaft is connected to the head frame. The throat 18, which is produced from two webs or prepreg tubes 4, 6 (see FIG. 1), which originate from the shaft 17 and diverge in a fork shape, results in an integral racket 1 jointly with the shaft 17 and the head frame 2. The illustrated embodiment, which comprises a hollow profile closed to the outside, consists of a material suitable for the intended field of use of a piece of sports equipment, for example, of fiber-reinforced plastic. The striking surface 12 is formed by a string 8 (see FIG. 3), which is held on the head frame 2 under predetermined tension. The string is typically fastened and tensioned by means of a tensioning device on the frame. Inside the main striking region 13, the striking surface 12 has a checkerboard stringing pattern consisting of substantially identical squares. The goal of a racket produced according to the invention is a higher degree of accuracy in the positioning of the retainers 20 (see FIG. 1), so that the above-mentioned stringing pattern is obtainable. Outside the main striking region 13, the stringing pattern deviates from the checkerboard shape. The intersecting string portions then delimit rectangles of greater or lesser length.
[0045] FIG. 3 shows an enlargement of a retainer 20 embedded in the head frame 2. The fastening portion 22, which is located inside the head frame 2 and is fixedly anchored in the head frame 2, is indicated accordingly. A string 8 is wrapped around the two ends of the retainer portion 24, which protrudes out of the head frame, of the retainer 20. The retainer has in particular, but not exclusively, rounded corners 29 in the region of frontal ends. The rounded corners prevent rubbing of the string 8 and unintentional damage thereto by sharp edges, as is typical in conventional rackets having boreholes in the head frame. The string deflection surface 46 of the retainer portion 24 of the retainer 20 protruding out of the head frame, against which the deflected portion of a string presses, drops off slightly on both sides in the circumferential direction of the head frame from a plane of symmetry 47 of the retainer 20. This deflection surface is preferably curved toward the striking surface or away from the inner side of the head frame in the circumferential direction of the head frame, wherein the radius is in the range from 80-150 mm.
[0046] FIG. 4 shows a first type of retainer 20 and a fifth type of retainer 20, each of different predetermined length L1 and L5. To produce a uniform and substantially checkerboard string stringing of the ball-striking device 1, the different length L is used for the adaptation to various frame geometries, which are generally substantially ellipsoidal, and can be of different sizes. In general, a larger number of retainers of a shorter predetermined length and a smaller number of retainers of a longer predetermined length are required for this purpose.
[0047] FIG. 5 shows a perspective of a retainer 20, a frontal view having a frontally attached typing character 2, and a top view of this retainer 20. The top view shows a line of symmetry 47 and the rounded corners 29 of the retainer portion 24 (see FIG. 3). A character 14 applied for the purpose of typingnumber 2 hereis provided at an intersection of the longitudinal and transverse structures 26, 27 of the fastening portion 22 of the retainer 20. The character 14, which is applied for the purpose of typing, indicates the type or the length L1, etc., of a retainer 20. The applied character 14 is essentially used for identification and later processing in a positioning and holding device 30 (see FIG. 7). The longitudinal and transverse structures 26, 27 of the fastening portion 22 (see FIG. 3) are used for the friction-locked and formfitted anchoring of the retainer 20 in the head frame and are optimized and adapted with respect to the shaping thereof to the material of the plastic used, in particular a prepreg tube which is used, and the wall thickness thereof. It is substantially important that the plastic presses in a formfitted manner, without shrinkage cavities or gas bubbles, against the outer side of the retainer 20. For this purpose, the pressure during inflation of the prepreg tube together with the curing temperature used also has to be selected such that this is ensured. Furthermore, the above-mentioned parameters have to be selected accordingly so that force transmission, which is required for typical stresses of a ball-striking device, between head frame and the retainers 20 embedded therein can thus be absorbed in a friction-locked and formfitted manner.
[0048] FIGS. 6 and 7 show a lower holding tool 32 and an upper holding tool 34, which together form a holding device 30. The retainers 20 can be inserted, preferably in a precisely fitted manner, between the holding tools 32, 34. For this purpose, a defined number of retainers 20 is inserted into the lower holding tool 32, for example, and subsequently the upper holding tool 34 is laid over it in a precisely fitted manner. The lower holding tool 32 has multiple threaded boreholes 35, whereby the upper and lower holding tools can be screwed together with one another, and the retainers 20 are held against mechanical stress in a desired position. The holding tool can have multiple material recesses 38. After the production of a ball-striking device in a forming and curing method according to the teaching according to the invention, the screw connection 36 of the holding device 30 can be detached again. This offers the advantage that the holding device 30 is reusable and can be used in the scope of a mass production method.
[0049] FIG. 8 shows a lower mold 50 for producing a ball-striking device 1 having an inserted holding device 30 having retainers 20. At the lower end of the lower mold 50, compressed air inlets 54 are provided, via which the prepreg tubes 4, 6 (see FIG. 1) can be inflated during the production method according to the invention. FIG. 9 shows a perspective illustration of a ball-striking device 1, which is still to be demolded but is substantially finished, having head frame 2, throat 18, and shaft 17 including grip 16, and also retainers 20 fixedly anchored in the head frame 2.
[0050] It is to be noted here that instead of the above-mentioned one-piece construction, constructions having head frame, on the one hand, and separately formed-on shaft and/or grip and/or open or closed throat are also conceivable. The above-described measures according to the invention are applicable for all of these constructions.
[0051] FIG. 10 shows an alternative embodiment of a retainer 23, which is embedded inside a transverse web 40 of the head frame 2, in cross section. The retainer 23 is designed as semi-oval shaped in cross section, wherein the longer branch having the larger curve radius is used as the fastening portion and the shorter branch having smaller curve radius is used as the retainer portion which protrudes freely beyond the inner side of the head frame. This retainer portion is freely accessible from one side of the striking surface, i.e., the stringing of the ball-striking device, for example, tennis racket, takes place via this free access or via the gap between the free end of the retainer portion and the inner side of the head frame facing toward this free end. Otherwise, the production of the above alternative is performed similarly to the production of the embodiment according to FIGS. 1 to 8. FIG. 11 also shows an example of an insertion device 44, by means of which the retainers are held securely in position and introduced into the holding device 30, so that during the screwing together of the holding tools 32, 34, the retainers 20 cannot change the predetermined position thereof. The insertion device 44 facilitates the positioning of the retainers 20 in the holding device 30.
LIST OF REFERENCE NUMERALS
[0052] 1 ball-striking device
[0053] 2 head frame
[0054] 4 first prepreg tube
[0055] 6 second prepreg tube
[0056] 8 tensioned string
[0057] 10 ends of the string portions
[0058] 12 striking surface
[0059] 13 main striking region
[0060] 14 character
[0061] 16 grip
[0062] 17 shaft
[0063] 18 throat
[0064] 20 retainer
[0065] 21 inner radius
[0066] 22 fastening portion
[0067] 23 retainer
[0068] 24 retainer portion
[0069] 25 retainer inner surface
[0070] 26 longitudinal structure
[0071] 27 transverse structure
[0072] 28 end of the retainer
[0073] 29 rounded corners
[0074] 30 holding device
[0075] 32 lower holding tool
[0076] 34 upper holding tool
[0077] 35 threaded borehole
[0078] 36 screw connection
[0079] 38 material recesses
[0080] 40 double-walled transverse web
[0081] 42 wall portions
[0082] 44 insertion device
[0083] 46 string deflection surface of the retainer
[0084] 47 line of symmetry/plane of symmetry
[0085] 50 lower mold
[0086] 52 upper mold
[0087] 54 compressed air inlets
[0088] S gap
[0089] L1-L5 five different predetermined lengths of the retainers 20, 23 according to the invention
