Technical problem This invention solves the problem of the optimization of the shape of a racket handle taking into account both anatomical and physiological characteristics of the human hand.

Namely, it is obvious that the efficient holding and shaking of a racket are enabling proper control of a racket and accuracy of a stroke. The size, shape and the quality of a contact surface between the human hand and a racket handle are the critical parameters that determine efficiency of a racket holding and shaking. The more the contact surfaces the greater the efficiency of a racket control and the higher accuracy of a stroke. So, optimization of the shape and the size of the contact surface between the human hand and the racket handle lead to the optimization of the racket control. Both of these parameters must be adapted to conform optimally to the anatomical and natural physiological characteristics of the human hand.

State of the technique Common tennis racket or the like has a handle with an octagonal cross-section whose longest faces are parallel to the racket face and with plastic cap at the butt. The contact surface between conventional racket handle and the human hand consists of flat faces. Despite numerous patented novelties and a certain improvement that has been realized (see U. S. Pat. No. 5,058, 902 for details), neither improved solutions nor conventional straight grip do not optimally conform to the anatomical and physiological characteristics of the human hand. Namely, the solutions prevent the racket from being held and shacked most efficiently and do not enable optimal control of a racket.

Summary of the invention It is the primary object of this invention to provide an optimal shape of the contact surface between a tennis racket handle and human hand that is optimally adapted to conform anatomic and natural physiological characteristics of the human hand. It is evident that the forefingers of a human hand have different lengths and that the central part of the user's palm has the recess, so the most efficient user's finger encircling of the handle is possible only if the thickness of the handle is not uniform along its length. Namely, the contact surface between racket handle and the human hand is the best optimized if the thickness of the handle is minimal in the region where the little finger and the edge zone of the palm (laying in extension of the little finger) are positioned and maximal in the region where the middle finger and the central part of the palm are positioned. In the regions where the ring finger and the index finger are positioned, the thickness of the handle must be larger than in the region where the little finger is positioned and smaller than the thickness in the region where the middle finger is positioned. The such shape of the contact surface between the racket handle and the human hand (which I will call"S"-shape) has the characteristic that it lies uniformly against different grip regions and is best adapted for simultaneously supporting the user's fisted hand. For two hand players it is necessary the existing of two almost identical"S"-shaped parts of the same size (making one totality) that are adapted for being encircled and grasped by both user's hands. The only small difference exists at the very beginning of the first"S"-shaped part (position EEl in Fig. 2) where there is no need for the concave transition region from one part to another existing in the vicinity of the position FFi in Fig. 2. For one-hand players only the one"S"-shaped part of a racket handle is necessary, while the rest of the handle can have arbitrary shaped outer contour of any cross-section of a racket handle.

The thinnest portion of the racket"S"handle is arranged for supporting the user's little finger encircling and the edge zone of the user's palm encircling, lying in the extension of the little finger. The thickest portion of the racket"S"handle is arranged for supporting the user's encircling middle finger and the central part of user's palm encircling the racket"S"handle. The thickness of the region arranged for supporting the user's encircling of the index finger and the thumb is greater that the above-mentioned thinnest region and smaller than the above-mentioned thickest region. Such harmoniously curved"S"-shape of the racket handle is realizable for any outer contour of a cross-section type of a racket handle. The length and variable thickness of each above-mentioned part depend of the size of the user's hand and are different for various grip sizes. An exact optimization for every human hand is possible and the corresponding procedure is described in details here. A suitable tool for realization of that optimization is subject of a separate invention.

Brief description of the drawings Fig. 1 represents a plan view of the palmer side of a human hand Fig. 2 represents a plan view of the tennis racket"S"handles for players playing with two hands Fig. 3 represents a plan view of the tennis racket"S"handles for players playing with one hand Fig. 4 represents the outer contour of the conventional tennis racket handle cross-section.

Fig. 5 represents a perspective view of the tennis racket"S"handle with octagonal flat faces Detailed description of the invention In accordance with Fig. 1 and demand that the contact surface between racket handle and the human hand must be as large as possible, the"S"handle has varying thickness along its length, shown in Fig. 2. The thickness variation is synchronized in accordance both with the length variation of the forefingers of the human hand and palm recess. Namely, as shown in Fig. 2, the thickness of the racket"S"handle is continuously varying from the minimal thickness in the region where the little finger and the edge zone of the user's palm (laying in extension of the little finger) are positioned (position AA1 in Fig. 2) to the maximal thickness in the region where the middle finger and the central part of the user's palm are positioned (position DD, in Fig. 2).

Thickness of the racket"S"handle in the region where the index finger and the thumb are positioned (position BB1 in Fig. 2) is smaller than its thickness in the region where the middle finger and the central part of the palm are positioned (position DD, in Fig. 2) and larger than its thickness in the region where the little finger and the edge zone of the palm laying in the extension of the little finger are positioned (position AA1 in Fig. 2).

The procedure to determine the exact shape of the racket"S"handles is as follows : The first step is to record the palmer side of an open human hand with outstretched forefingers and open thumb. First frame should be recorded with index finger in the neutral position (full line in Fig. 1) and than on the same frame should be recorded the same hand position changing only the position of the index finger by its moving in the maximal aside position (shown with broken line in Fig. 1). All next steps should be done on the resulting figure. The second step is to determine on the resulting figure (Fig. 1) the along axes of the middle finger (broken line LL, in Fig. 1). The third step is to determine the line (broken line KM in Fig. 1) that is normal to the along axes of the middle finger and that contains the bordering point of the open thumb and the palm (point K in Fig. 1). The fourth step is to measure the normal distances from the fingertips to that line (line KM in Fig. 1) in order to determine the lengths a, b, c and d, shown in Fig. 1. The fifths step is to put the line from the very outer bordering point of the edge zone of the palm and the little finger (point Eo in Fig. 1) that is parallel to the along axes of the middle finger, in order to determine the position of the beginning of the buttcap (position EEl in Fig. 2). The length a (the normal distance from the little fingertip to the line KM in Fig. 1) is equal to the circumference of the outer contour of the cross-section of the racket"S"handles at the position of the little fingertip (position AA1 in Fig. 2). The length b (the normal distance from the index fingertip to. the line KM in Fig. 1) is equal to the circumference of the outer contour of the cross- section of the racket"S"handles at the position of the index fingertip (position BB1 in Fig. 2).

The length c (the normal distance from the ring fingertip to the line KM in Fig. 1) is equal to the circumference of the outer contour of the cross-section of the racket"S"handles at the position of the ring fingertip (position CC1 in Fig. 2). The length d (the normal distance from the middle fingertip to the line KM in Fig. 1) is equal to the circumference of the cross-section of the outer contour of the racket"S"handles at the position of the middle fingertip (position DDI in Fig. 2).

The next step is to determine the position of the very end of the part of the racket"S"handles (position FFI in Fig. 2) that is suited for one user's hand (part EFF, EL in Fig. 2). First it should be determined the position of the very outer point of the second joint of the index finger that is maximal aside open (point Fo in Fig. 1). Through the point Fo one can putt the line that is parallel to the along axes of the middle finger (line LL1 in Fig. 1) in order to determine the position where the circumference of the outer contour of the cross-section of the racket"S"handles (position FF, in Fig. 2) is equal to the circumference of the outer contour of the cross-section of the racket"S" handles at the position of the beginning of the buttcap (position BEi in Fig. 2). The circumferences of the outer contours of the cross-sections of the racket"S"handles at the positions AA1, CC1, DD, and BB1 can be calculated by using a simple mathematical procedure, that is specific for every type of an outer contour of a corresponding cross-section. The outer contour of the cross-section of the racket"S"handles can be arbitrary. Knowing that the circumferences of the outer contour of the cross-section of the racket"S"handles at positions AA1, CC1, DD1 and BB1 (shown in Fig. 2) are equal to one of the values a, b, c and d, respectively, one can fit a wanted (or predetermined) ratio (between the widths of the octagon faces, in the case of the octagonal outer contour of the cross-section shown in Fig. 4) in order to fulfill the above-mentioned demand of equality. The same procedure can be applied for every other type of an outer contour of the racket"S"handle cross-section. At all other positions between the positions EEl and FFi (including that positions), the values of the circumferences of the outer contours of the corresponding cross-sections of the racket"S"handles can be determined by best-fitting procedure applying the demand that the corresponding circumferences should be changing smoothly from one position to the next. Depending on the type of the outer contour of the cross-section of a racket handle, the best-fit calculation can be performed under assumption of the smoothly changing of the thickness of the racket"S"handles along its axes.

The second part of the racket"S"handle FGGFL (in Fig. 2) must be the same as the first part EFFlEl and is suited for the user's second hand. The only small difference exists at the very beginning of the second part (FGGiFi in Fig. 2) where the small concave part in the vicinity of the position FF1 in Fig. 2 does not exist in the vicinity of the position EE, in Fig. 2. The rest of the racket"S"handle can have the cross-section with arbitrary outer contour (at position U, in Fig. 2 is shown conventional octagonal cross-section).

For the players playing only with one hand, the"S"-shape of the racket handle is necessary only for the first part of the racket handle, as it is shown in Fig. 3. The rest of the racket"S"handle can have either conventional octagonal outer contour of the cross-section (position JJI in Fig. 3) or any other arbitrary outer contour of the cross-section.

A perspective view of the tennis racket"S"handles with octagonal flat faces is shown in Fig. 5.