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Ball game racquet, especially tennis racquetRelated Patent Categories: Games Using Tangible Projectile, Player Held And Powered, Nonmechanical Projector, Per Se, For Projecting Aerial Projectile By Striking; Part Thereof Or Accessory Therefor, Racket Or Paddle; Accessory Therefor (e.g., A Tennis Racket, Tennis Racket Press, Etc.)Ball game racquet, especially tennis racquet description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060199680, Ball game racquet, especially tennis racquet. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] The invention relates to a ball sport or ball game racquet, in particular a tennis racquet, with a racquet frame for holding the stringing and with a shaft extending from the racquet frame and with a racquet grip. The racquet frame and the racquet shaft both feature a hollow frame profile made up of a plurality of walls or wall sections. The invention also relates to a method for manufacturing a hollow frame profile for such a ball sport racquet. [0002] Modern ball sport or ball game racquets, in particular tennis racquets, consist among other things of a racquet frame and a racquet shaft extending from and connected with this racquet frame. The racquet frame and the racquet shaft are manufactured from an outwardly closed hollow frame profile, which normally is made from a plurality of prepreg layers that are pressed together to form closed hollow frame profile. [0003] Prepreg layers are layers of synthetic or plastic material reinforced by fibers, such as carbon fibers, glass fibers and also other fibers, which are pre-impregnated with resin. Prepreg layers can be designed as woven prepreg layers, which are pre-impregnated in form of unidirectional and multi-axial layers. Depending on the requirements for the component to be manufactured, various resins are used, especially epoxide or epoxy resins and phenolic resins, both of which hardly flow at room temperature. In order to manufacture a hollow frame profile from such prepreg layers, the prepreg layers are placed in cold condition in a pre-defined mold and hardened under pressure and application of heat. Especially the application of heat causes the resin to liquefy temporarily so that it impregnates the fibers before it begins to harden. [0004] Various methods, in particular the blow molding methods, are known for manufacturing a racquet frame and racquet shaft featuring a hollow frame profile with a pre-defined wall thickness and fiber orientation and a defined outer contour and surface. In the blow molding method, a plurality of prepreg layers or prepreg layer windings are placed carefully and load-oriented on or around a core, which for example is covered with a tube, and pressed under high pressure into a female mold and hardened to achieve a defined surface and outer contour. In heavily stressed zones, it is possible to include additional prepreg layers at particular locations, in order to achieve different wall thicknesses while maintaining the same outer diameter, if required. [0005] Furthermore, the wall thicknesses and the outer diameters of the hollow frame profile have a significant influence on the playability of a tennis racquet, so that especially tennis racquets for amateur and hobby use have a very high and wide hollow frame profile with a wall thickness of less than 1 mm in order to achieve a very high degree of stiffness in combination with low weight (less than 200 g). The hollow frame profile of the racquet frame and of the racquet shaft comprises for example four opposing walls in pairs, which can have one left and right opposing wall, each with a height of up to 30 mm or more and one upper and lower opposing wall, each with a width of up to 15 mm or more, to form a honeycomb cross section. [0006] Individually, neither the upper and lower walls nor the left and right walls of the hollow frame profile are stiff; rather, they receive the necessary stiffness by suitably connecting the corresponding walls. [0007] It is an object of the present invention is to provide for a ball sport racquet of the type mentioned at the outset featuring a sufficiently high degree of stiffness despite a high and wide hollow frame profile. SUMMARY OF THE INVENTION [0008] This object is achieved by a ball sport or ball game racquet, in particular tennis racquet, with a racquet frame for holding the stringing and with a shaft extending from the racquet frame and with a racquet grip, wherein the racquet frame and the racquet shaft both feature a hollow frame profile made up of a plurality of walls or wall sections, and wherein at least one of the walls of the racquet frame and/or of the racquet shaft features at least in some sections at least one spacing layer for increasing the stability of the ball sport racquet. [0009] The increase of stability is not or only to a small extend obtained by the stability or strength of the material of the spacing layer itself, but mainly by the fact that prepreg layers or the windings of the wall or wall section are spaced from another by the spacing layer and that by that the moment of inertia of the wall and the stiffness the wall are increased without substantially increasing the weight of the ball sport racquet. [0010] The use of a spacing layer in at least one of the walls of the hollow frame profile of a ball sport racquet according to the invention, on at least one or more wall sections, significantly increases the stiffness of the overall racquet frame. Preferably the spacing layer is provided in-between the wall layers forming the wall or wall section, that means in-between two windings in the shaft area and in the upper and lower wall sections of the hollow frame profile, if the hollow frame profile is made by winding the prepreg material around a core. [0011] The spacing layer is manufactured from a porous or honeycomb material, which is for example known from airplane construction. Alternatively, various foam materials can be used for manufacturing the spacing layer, due to their low volume weight. The density of the material used should be considerably below the density of the prepreg layers, which have a density of approx. 1.9 g/cm.sup.3. The materials used preferably have a density of less than 1.0 g/cm.sup.3 while also featuring a high degree of compressive strength. This is of particular importance, since when applying the blow molding method for manufacturing the hollow frame profile of the tennis racquet, pressures of more than 8 bar can occur, so that the material used as the spacing layer must be able to withstand such high pressures during the production process. BRIEF DESCRIPTION OF THE DRAWINGS [0012] Exemplary embodiments of the invention are described below with reference to the drawings, in which: [0013] FIG. 1 shows a simplified representation in top view of a ball sport racquet in the form of a tennis racquet; [0014] FIG. 2 shows a simplified representation in cross section corresponding to the line 1-1 of FIG. 1; [0015] FIG. 3 shows a simplified representation in cross section corresponding to the line 11-11 of FIG. 1; [0016] FIG. 4 shows a simplified representation of shaft area of the ball sport racquet in the form of a tennis racquet; and [0017] FIG. 5 shows a simplified representation of single selected production steps for a hollow frame profile manufactured according to the blow molding process. DETAILED DESCRIPTION OF THE INVENTION [0018] The tennis racquet depicted in the drawings and generally designated 1 consists essentially of a racquet frame 2 forming the racquet head, of the stringing 3 located there, which comprises a plurality of crisscrossing string lengths 4', 4'' or strings 4, and of a racquet shaft 6 connecting to the racquet frame 2 by means of a throat or heart 5 and on which (shaft) a racquet grip 7 is provided. The throat 5 is connected with the racquet frame 2 in the connecting areas 5', 5''. [0019] The racquet frame 2 features an outwardly closed hollow frame profile 8, which is manufactured for example from a plurality of prepreg layers according to the blow molding process. [0020] To exemplify the structure of the hollow frame profile 8 of the racquet frame 2 and of the racquet shaft 6, FIG. 2 shows a cross section corresponding to the line 1-1 of FIG. 1. The hollow frame profile 8 features by way of example an oval cross section flattened on two opposing sides each being at a distance form the stinging and parallel or nearly parallel with the stringing. The hollow frame profile 8 features a hollow space 9, which is surrounded by the walls of a plurality of prepreg layers or windings 10. Continue reading about Ball game racquet, especially tennis racquet... Full patent description for Ball game racquet, especially tennis racquet Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Ball game racquet, especially tennis racquet patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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