EP0468263B1 - Racket for ball games, especially tennis racket - Google Patents

Abstract

A racket for ball games, especially a tennis racket, having a strung area provided in a shaft frame made of a profiled bar, a throat zone adjacent thereto and a handle (20) on a racket neck in the longitudinal axis of the racket preferably forming a plane of symmetry, is improved in respect of the so-called impact shock in that the racket has a joint (44) between the throat zone and the front end of the handle (20), the joint axis of which extends parallel to the strung area. This joint (44) is preferably arranged in the vicinity of the handle (20) and is formed by a web part of the handle (20) which is preferably bounded on both sides by groove-type moulded-in channels (40) and is filled by an elastic moulding material (42). <IMAGE>

Description

The invention relates to a racket for ball games, in particular a tennis racket, according to the preamble of claim 1.

Tennis rackets can be found, for example, in DE-A-30 18 354. Clamped in the area of the handle, a natural frequency of 25 to max. 50 Hz detected; unstrung tennis rackets generally show slightly higher values. The frequency of the overall racket / stringing system has a significant influence on the hand that is playing with it and thus also on the creation of the so-called tennis arm.

FR-A 2 547 506 discloses a generic tennis racket. In order to reduce the transmission of vibrations from the racket to the arm of a user, the handle is completely separated from the racket neck, ie the actual striking area. In one embodiment, the racket neck is formed by two end parts of the strip-like profile rod that are parallel and at a distance, between which two other parallel strips of material are inserted, which protrude from the handle. These two pairs of strips are connected by two bolts which carry washers; the latter are located between the inner pair of strips of the handle and the outer pair of strips of the racket frame. Each of these bolts - running parallel to the covering and transverse to the longitudinal axis of the racket - can be described as axis-like, but both bolts together are only connecting means and not articulation points. In the other embodiment of FR-A 2 547 506, the handle and the racket neck are connected by a grip bolt which is axially clamped in the racket grip and is separated from that striking area by two rubber rings; the handle bolt is supported in the two rubber rings, one of which is spaced apart Separating end of the bat neck is provided, whereas the other is in the bat heart. Between these two bearing areas, the handle bolt passes through the racket neck in an axial channel. With this construction, an attempt is made to counteract the transmission of vibrations by interposing coaxial elastic rings between those grip bolts and the club shaft surrounding them.

Knowing this state of the art, the inventor has taken on the task of intercepting or at least mitigating the influences acting on the hand of the player of a generic racket, in particular the so-called shock shock which arises on contact with the ball, without giving up the advantages of a very rigid frame, as they are given, for example, in rackets according to DE-C-33 43 898.

The teaching according to the independent claim leads to solving this problem; the racket has a hinge point in the handle in that there is at least one groove-like indentation on both sides of the racket's longitudinal axis, the lowest point of which ends at a web part of the racket, the web part the position of which - in the prior art laid by a fixed bolt - - Axis determines which forms an articulated axis here. In other words, in the fulcrum that arises when hitting or near this fulcrum, there is an elastic joint in the handle which changes the frequency behavior of the racket and compensates for the shock.

The pivot point of the racket when hitting a ball is referred to in technical terms as "pivot pivot point". No forces occur at this point, but there is torque around it. From this point up to the head of the racket, the racket is influenced by forces in the direction of the incoming ball in the event of a ball impact. Forces, however, contribute from the pivot point to the forehead opposite direction. Therefore, a racket tries to tip out of the hand on a forehand stroke, whereas it hits the palm of the hand on a backhand stroke. This may be the reason why players with a so-called tennis arm can hit the forehand relatively painlessly, but that more pain occurs on a backhand.

The preferred location for the said joint location or the web part is in a range of 60 to 200 mm from the front of the handle. This is also the area in which that pivot lies.

The width, measured in the longitudinal axis of the racket, of the groove-like indentations arranged on that web part, preferably on both sides, can be up to 100 mm, but will generally be considerably shorter. The depth of the web part corresponds approximately to the depth of the recess or groove, which requires a division of the shaft cross section into three sections of approximately the same width.

The two grooves or indentations are preferably filled by a molding compound of low flexural rigidity, in particular when the two grooves or indentations are provided in the grip area and must be covered by the grip leather.

The object according to the invention is also achieved by a racket with a plurality of parallel axes of adjacent articulation points directed transversely to the longitudinal axis of the racket. The deflection in the elastic area of the racket, which is firmly clamped to the first joint point on the handle under the action of a force that acts headwards in 400 mm sand from the joint axis, should be 1.2 to 9 times as large as the deflection of a jointless - otherwise but appropriately designed - racket with firm clamping on the handle up to the hinge axis.

The joint point (s) advantageously reduces the frequency of a racket firmly clamped to the first joint on the handle by √ 1.2 up to √9 compared to an identical racket without a joint.

Even tennis rackets with an open heart zone delimited by two profile sections with a frame web connecting them, as well as a cross-section that is excessive in their area, which have proven to be exceptionally effective in practice, can be made even more efficient by at least one such joint.

Of additional importance for the invention is the possibility of providing the racket neck and a racket shaft forming the handle with at least one shaft gap which extends into the heart zone and which at least in sections contains an elastic mass lying on both sides of the shaft gap as an intermediate layer or intermediate element between the shaft rods . According to a further feature of the invention, the intermediate layer - seen in cross section - can also consist of several strips or strands which leave hollow spaces or gaps between them. In a special embodiment, a round strand is provided which keeps the two associated shaft rods at a distance and the remaining sections of the shaft gap free.

In addition, it has proven to be advantageous that the elastic mass rests on both sides of the surfaces delimiting the shaft gap and that the shaft rods can be moved - at least partially - laterally relative to one another in the direction of impact.

The handle is separated in the case of a symmetrical racket construction parallel to the striking direction or perpendicular to the striking surface and preferably along the longitudinal axis of the racket. If the dividing shaft gap lies outside the center line, is curved, oblique or jagged, the achievable damping results are not quite as good, but still acceptable. According to a further feature of the invention, the generally rectangular cross-section of the shaft gap runs linearly in the plane or surface, but the cross-section can also be wave-shaped or jagged.

The elastic connecting elements of properly separated shaft or handle bars can - e.g. B. from a silicone rubber layer - be continuous. However, it is also conceivable to arrange them in punctiform or strip-like fashion, for example at the cutting edge or the gap ends. These connecting elements can be made from pieces of tubing, round rubber cords or otherwise resilient. A partial opening, for example slots, which can also be unfilled, is also conceivable; a firm connection could only remain at the end of the handle and the slot above could contain a damping material.

It has proven to be advantageous to form the surface described. In a special embodiment, the surface is curved in cross section, and several surfaces can be assigned to one another.

Depending on the design of the racket according to the invention, linear or curved flat bars made of elastic mass are used which, as described, can completely or only partially fill the shaft gap.

An elastic connection - or interruption - is therefore placed in the handle or in its center line, which absorbs and dampens the torsion in the lower area of the racket. This prevents, among other things, the disadvantages of foamed grips with almost elastic behavior, namely a "softening" of the racket in its longitudinal direction, as a result of which the vibration conditions change, the impact precision deteriorates as well as the listed positive properties of a super hard racket are lost. If the otherwise made of more or less inelastic materials - such as wood, metal, pressed fibers in the plastic bed, plastics or rigid foam - handle along the center line or axis of symmetry or close to it separated approximately perpendicular to the face and z. B. is reconnected with an elastic mass such as silicone rubber, this changes the hardness of the racket in its longitudinal direction just as little as the vibration behavior of the racket. The latter is not changed even if the ball is hit in the longitudinal axis of the racket. In the case of balls that hit the striking surface outside of this axis, torsional vibrations occur which, although superimposed on the longitudinal vibration, are then damped and suppressed by the resulting relative movement of the shaft and handle bars against each other via the elastic intermediate layer and less able to reach the striking arm . The connection of the handle ends through the handle cap, which is primarily not divided or also consists of elastic material, and the influence of a wrapped grip leather must be taken into account when selecting the required interlayer elasticity. Tests have confirmed that rackets constructed in this way reduce the impact shock when the balls are hit off-center and impart an improved "ball feel". With this invention, the disadvantages of super hard rackets can be largely eliminated, but their advantages can be retained.

Fig. 1:

die teilweise wiedergegebene Draufsicht auf einen Tennisschläger mit einem Kopf aus einem hohlen Profilstab sowie mit einem Handgriff an einem Schlägerhals;;

Fig. 2:

die Seitenansicht zu Fig. 1;

Fig. 3:

den vergrößerten Querschnitt durch Fig. 1 nach deren Linie III - III;

Fig. 4:

den vergrößerten Querschnitt durch Fig. 1 nach deren Linie IV - IV;

Fig. 5,6:

zwei teilweise geschnittene Draufsichten auf gegenüber Fig, 1,2 vergrößerte Handgriffe;

Fig. 7,8:

verschiedene -- teilweise geschnittene -- Seitenansichten von vergrößerten Handgriffen;

Fig. 9:

einen vergrößerten Ausschnitt aus Fig. 1 zu einer weiteren Ausführung;

Fig. 10:

einen Abschnitt der Fig. 9 um 90° gedreht;

Fig. 11: bis Fig. 15:

vergrößerte Querschnitte durch den Griff gemäß Linie XI - XV in Fig. 10 zu unterschiedlichen Ausführungen.

Further advantages, features and details of the invention result from the following description of preferred exemplary embodiments and from the drawing; this shows in:

Fig. 1:

the partially reproduced plan view of a tennis racket with a head from a hollow profile bar and with a handle on a racket neck ;;

Fig. 2:

the side view of Fig. 1;

Fig. 3:

the enlarged cross section through Figure 1 along the line III - III.

Fig. 4:

the enlarged cross section through Figure 1 along the line IV - IV.

Fig. 5,6:

two partially cut top views of handles enlarged compared to FIG. 1, 2;

Fig.7.8:

various - partially cut - side views of enlarged handles;

Fig. 9:

an enlarged section of Figure 1 to another embodiment.

Fig. 10:

a portion of Figure 9 rotated 90 °.

Fig. 11: to Fig. 15:

enlarged cross sections through the handle according to line XI - XV in Fig. 10 for different versions.

A tennis racket 10 shown by way of example in FIGS. 1 to 4 has an oval racket head or clamping frame 14 formed by a correspondingly curved profile bar 12. The profile rod 12 of the club head 14 ends on both sides of the longitudinal axis M in - profile arms 16 which laterally delimit an open heart zone H - which are connected by a frame web 18 and merge into a club neck 19.

A handle 20 with a thickness h of approximately 26 to 32 mm adjoins the racket neck 19; this thickness h is measured on the handle 20 without wrapping leather 21 and without taking into account a handle cap 22 which is covered by this in FIG.

The racket head 14 and the frame web 18 determine a stringing surface Q from cross strings 24 and these cross-stringing longitudinal strings 25. The preferred point of impact A for a tennis ball (not shown) lies in FIG. 1 approximately at the point of intersection of the racket longitudinal axis M with the section line III-III and in FIG in a line K.

The club head 14 or its hollow profile rod 12 is i.w. of elongated oval cross-section, the side walls 26 of which run at an inner distance a of, for example, 8 mm (outer width m about 10 mm) and merge into curved sections 27 with an inner profile height b of 20 mm and an outer profile height n of about 25 mm here.

This profile rod 12 is formed from a tubular blank 30, in which 27 longitudinal fiber strands 31 are arranged in the arc sections. The ends of the blank 30 are brought together on the bat neck 19 so that two chambers 29 are formed in this and in the handle 20. 4, the two ends of the blank 30 form the octagonal cross section of the handle 20.

5, the handle 20 is made of two parts 32, 32a, which are connected at a distance e by an elastic intermediate piece 34. The latter comprises two transverse plates 36 made of metal or another suitable material as well as a rubber block 38 vulcanized onto them. This forms a limited flexible joint, the joint axis B of which extends at a distance t of 60 to 220 mm to the end face 23 of the grip cap 22 as the grip end. The distance of this hinge axis B from the end 15 of the club head 14 is denoted by g.

The joint shown in FIGS. 6, 7 is defined by grooves 40 of the greatest width z formed on both sides in the handle 20 - tapering towards the grip axis M -. The grooves 40 are filled, for example, by plastic blocks 42 with low bending stiffness. The depth i of the grooves 40 is somewhat shorter in FIG. 7 than the thickness c of a stopped intermediate web 44 of the handle 20; the surfaces of the intermediate web 44 each form the deepest groove 41. Furthermore, longitudinal strands 31 of the blank 30 are wrapped around the grooves 40, that is to say not interrupted at the joint point.

In FIG. 8, the joint point from the intermediate web 44 flanked by the grooves 40 lies near the end of the racket neck 19.

If the thickness c of the intermediate web 44 formed by the grooves 40 over the length z - which must not only have the shape shown in the exemplary embodiment - measures approximately half the thickness h of the handle 20, the deflection is due to an acting force due to the lower moment of inertia in the cross-section of the bar per unit length about 4.3 times as high as the deflection with a full handle cross-section, if the modulus of elasticity is assumed to be unchanged; otherwise the deflection is inversely proportional to the product of the moment of inertia x modulus of elasticity.

If the web thickness c is only a third of the thickness h of the handle 20, the corresponding value is 12.5 and finally becomes 20 times as high as a quarter. These initially calculated values are confirmed in measurements on corresponding racket designs, a preferred measure of the web thickness c being given when it measures approximately 4 to 6 mm, that is to say the thickness h of the handle 20 is five to eight times the web thickness c.

The articulation point 34 must act fairly elastic in order to bring about small frequency changes. This will be explained using an example for the embodiment according to FIGS.

The thickness c of the web 44 should be half the handle thickness h of the tennis racket 10, the width z is 20 mm. The distance t from the handle end 23 is set at 120 mm. The ball hits the covering Q at point A, which in the selected example is 400 mm away from the articulation axis B. For the sake of simplicity, it is assumed that the moment of inertia for the full grip cross-section is unchanged for all racket cross-sections - that is to say over the entire racket length - no torsional moments occur and the modulus of elasticity remains constant. The calculation shows that the deflection of the tennis racket 10 with the described joint 34 under the acting ball force is 1.22 times as high as that of an identical racket without a joint. The frequency of the tennis racket 10 would then vary with the reciprocal change from the root of the deflection. If the tennis racket 10 had a frequency of 80 Hz, the racket provided with this joint would have a frequency of 80 x 1 / _1.22 Hz, i.e. 72.5 Hz.

Another example should show how a larger frequency reduction is possible.

The web height c is chosen with a quarter of the handle thickness h. The width z is 100 mm. Otherwise, the data of the first example apply.

In this case, the required deflection would be six times as large and the desired frequency root six times lower, i.e. instead of 80 Hz only 33 Hz. This frequency relates to a tennis racket 10 firmly clamped to the first joint on the handle 20.

In the embodiment of FIGS. 9, 10 the racket neck 19 and the subsequent shaft of the handle 20 are symmetrically divided in the direction of the longitudinal axis M of the racket, ie each of the profile arms 16 continues with its own shaft rod 46 _a in the handle 20, both shaft rods 46 _a together determine the outer contour of a handle shaft 46 and delimit a shaft gap 48 between them, which receives an elastic intermediate layer 50 in FIG. 9 and determines a plane E which crosses the covering surface Q - approximately perpendicular in FIGS. 11 to 14.

In the exemplary embodiment of FIGS. 9 to 11, the shaft rods 46 _a - apart from the articulation point 40/44 - are symmetrical full profiles with an interposed strip of elastic mass as a filling intermediate layer 50 in the shaft gap 48, which is linear in cross section here, whereas FIG. 12 cross-sectional differently designed shaft rods 46 _b , 46 _c with between them - at different distances f, g to the side contours 52 - approximately undulating shaft gap 48 _c , which is completely filled by the elastic intermediate layer 50 _c .

Fig. 13 illustrates a handle 20 with symmetrically in the plane E in shaft rods 46 _d divided hollow profile with elastic round strand 50 _d . The embodiment of FIG. 14 corresponds to that of FIG. 11 with the difference that the shaft rods 46 _{e are} hollow profiles, each with an all-around limited profile chamber 47.

Finally, FIG. 15 shows a three-part handle shaft 46 _f made up of two flank bars 54 and a core or central bar 55, between which intermediate layers 50 _k curved in the shape of a circle can be seen. Instead of the plane E described, two curved surfaces F can be seen here.

Claims (14)

1. Racket (10) for ball games, especially tennis racket, comprising stringing (24, 25) provided in a frame (14) consisting of a shaped bar (12) and a frame web (18) completing the latter, and a handle (20) on a racket shaft (19) along the longitudinal axis (M) of the racket preferably forming a straight line of symmetry, the free end of the handle (20) being defined by a handle end face (23) and the racket (10) having a region between the frame (14) and the handle end (23) of the handle (20) with an axis extending parallel to the stringing (Q) and transversely to the longitudinal axis (M) of the racket, characterised in that at least one groove-like recess (40) is provided in the handle (20) on either side of the longitudinal axis of the racket, the bottom of which ends in a web portion (44) of the racket, the web portion defining the position of the axis forming a hinge axis (B).
2. Racket according to claim 1, characterised in that the centre of the web portion (44) or the hinge axis (B) is arranged at a distance (t) of 60 mm to 220 mm from the handle end (23).
3. Racket according to claim 1 or claim 2, characterised in that the width (Z) of the groove-like recess (40) as measured along the longitudinal axis (M) of the racket is up to 100 mm.
4. Racket according to one of claims 1 to 3, characterised in that the thickness (c) of the web portion (44) is no more than half the thickness (h), and preferably corresponds approximately to the depth (i) of the groove-like recess (40).
5. Racket according to one of claims 1 to 3, characterised in that the thickness (h) of the handle (20) corresponds to four to ten times, preferably five to eight times the thickness (c) of the web portion (44) or that the thickness (c) of the web portion (44) corresponds to a quarter of the handle thickness (h).
6. Racket according to one of claims 1 to 5, characterised in that the groove-like recess/es (40) is/are filled with a moulding compound (42) with low bending strength.
7. Racket according to one of claims 1 to 6, characterised by a plurality of axially adjacent groove-like recesses (40).
8. Racket according to one of claims 1 to 7, characterised in that the groove-like recess/es (40) taper/s towards the handle axis (M).
9. Racket according to one of claims 1 to 8, characterised in that the sag in the elastic region of the racket (10) firmly tensioned up to the first hinge point (34, 44) by the handle (20) under the action of a force acting towards the head at a distance of approximately 400 mm from the hinge axis is 1.2 to 9 times as great as the sag of a racket which is hingeless but which otherwise corresponds thereto with firm tensioning at the handle (20) to the hinge axis (B).
10. Racket according to one of claims 1 to 9, characterised in that the racket shaft (19) and the racket shaft portion forming the handle (20) have a shaft gap (48, 48c, 48k) passing through to the throat zone (H), containing at least in portions an elastic compound (50) bearing on either side against the surfaces defining the shaft gap as an intermediate element between the shaft bar portions (46a to 46e; 54, 55).
11. Racket according to claim 10, characterised in that the shaft bar portions (46a to 46e; 54, 55) can move at least partially relative to one another in the direction of impact.
12. Racket according to claim 10 or claim 11, characterised in that the shaft gap (48) defines a surface (E, F) extending transversely to the stringing surface (Q), the surface (E) extending transversely to the stringing plane optionally defining a plane of symmetry.
13. Racket according to one of claims 10 to 12, characterised in that the surface (F) defined by the shaft gap (48k) has a curved cross section and/or that the cross section of the shaft gap (48c) has an undulating or zig-zag configuration.
14. Racket according to one of claims 1 to 13, characterised by a handle (20) consisting of at least one hollow profile section and/or by a plurality of surfaces (E, F) or shaft gaps (48, 48c, 48k) in the cross section of the handle (20).

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