Game racket with incurvate contact surfaces

A game racket (20) having rigid, incurvate contact surfaces (29) with apertures (52) for the passage of air rather than the conventional network of stringing, both contact surfaces (29) having a continuous, smooth corrective curvature able to automatically compensate for the lateral and longitudinal torsional forces that are exerted by an incoming ball (56) onto the racket (20), when a player fails to hit the ball dead center on the racket face. Having no stringing, the racket of the present invention is completely maintenance-free and provides numerous other advantages over conventional racket designs, including: texturable contact surfaces (38); a variety of aperture (52) shapes and patterns with aerodynamic fairing (53); contact surfaces (29) whose playable area extends to their extreme periphery (31 and 33); means for employing vibration-dampening and shock absorbant materials in the racket's construction; and a curvature which aids in the execution of "slice" shots. An alternative design allows the two contact surfaces (43 and 44) to have differentiated curvatures and textures (39, 40, 41, 42, 54 and 55) for forehand and backhand shots. Insofar as the racket (20) itself compensates for all torsional forces, it can be gripped more loosely in the hand, and should reduce the incidence of "tennis elbow."

BACKGROUND OF THE INVENTION 
The invention relates to game rackets of the type having a grip, a handle 
shaft and a head with two contact surfaces, such as for instance a tennis 
racket, a squash racket, a badminton racket or a racket ball racket. 
Game rackets are used in a variety of sports, including tennis, badminton, 
squash, racket ball and ping-pong. The contact surfaces of a conventional 
true racket, as distinguished from the solid surfaces of a paddle, are 
formed by a network of flexible string under high peripheral tension. 
In games such as tennis--where the ball employed is of considerable mass, 
and the velocities achieved, especially in tournament play, are also very 
great--the ball is capable of exerting a significant torsional force on 
the player's wrist, if it is not hit dead center on the racket's face. The 
area which creates a minimal amount of torque and thus allows the player 
to aim the ball with greater precision and force is located in the central 
portion of the racket's face and is referred to as the "sweet spot." Much 
of the prior art relating to improved racket design attempts in various 
ways to enlarge the effective sweet spot area. This has led recently to 
the introduction of a variety of "oversized" racket designs into 
tournament play. 
Some prior art inventions, such as U.S. Pat. No. 4,147,348 (Lee), have 
provided means for increasing the player's ability to counteract the 
torsional forces--in this case by bringing the contact surfaces downward 
such that they are essentially an extension of the forearm itself. 
However, no arrangement can completely do away with the torsional 
forces--they are a physical fact of nature. A combination of such design 
elements as are found in U.S. Pat. No. 4,147,348 (Lee), above, and the 
present invention may represent an optimal solution. 
OBJECTS AND ADVANTAGES 
The present invention provides means for designing a racket with a larger 
sweet spot without expanding the racket's overall size and weight to 
ridiculous proportions. This new design concept opens up many 
possibilities for radically improving upon the conventional form of the 
racket--the shape and texture of its contact surfaces, as well as the 
aerodynamic properties of the racket as a whole. It will also allow many 
of the recently developed plastics, composites and lightweight metal 
alloys to be employed in new ways to greatly improve the racket's 
performance. 
One of the objects of the present invention is to provide a game racket in 
which the contact surfaces are composed of a resilient, lightweight 
material, of a design similar to that found in U.S. Pat. No. 3,934,876 
(Haddad); that is to say, cast or machined into an open cellular network 
or honeycomb-like matrix which derives its strength and resiliency from 
the relative thickness of the matrix itself, and its lightness and minimal 
air resistance from the hollow channels that connect the two contact 
surfaces. This is in contrast to a conventional racket, whose contact 
surfaces are formed by a network of woven gut or synthetic filament 
stringing that gains its resiliency through peripheral tension applied to 
it by a surrounding rigid bow. 
However, instead of the planar or flat contact surfaces indicated in the 
patent cited immediately above, the present invention would give each of 
the front and back contact surfaces a concave, approximately parabolic 
curvature. The purpose of this curvature is to provide means for the 
racket itself to automatically compensate for the torsional forces that 
are exerted upon it by an incoming ball, when the player fails to hit the 
ball dead center. With a conventional racket, these torsional forces cause 
the plane of the contact surface to be shifted away from the intended 
angle of impact, throwing the entire contact surface into severe 
misalignment, and causing the ball to rebound in an unpredictable 
trajectory. 
The parabolic curvature of the lateral portions of the contact surfaces of 
the present invention provide an automatic compensation for the lateral 
torsional force caused by an inaccurate hit in the following manner. The 
racket is shaped such that an incoming ball, hitting the contact surface 
somewhat off center, expends its kinetic energy applying a torsional force 
which twists the racket away from the intended plane of contact. Once all 
of the ball's kinetic energy is expended, however, the racket will have 
been automatically readjusted by the torsional force itself such that it 
will be presenting its curved surface to the ball at a point whose tangent 
plane is once again identical to the intended plane of contact. 
A ball hit dead center would cause no lateral torque, and thus the angle of 
presentation in this area would be the same as for a conventional 
racket--it would be perfectly flat. The farther from the central 
longitudinal axis the ball is hit, the greater the torsional force that is 
encountered--the more precipitous would be the curvature, and the more the 
racket would automatically compensate. Effectively, the sweet spot has 
been expanded to include the entire surface of the racket. 
In designing the correct curvature for the present invention, many factors 
must be taken into consideration. Theoretically, the torsional force is 
equal to the force applied by the ball times the length of the lever arm 
(in this case the distance from the point of contact to the central 
longitudinal axis of the racket face). Therefore, one might assume that a 
simple linear increase in the angle of the tangent plane to the curved 
surface as a function of the distance of the point of contact from the 
central longitudinal axis of the racket face would be ideal. 
However, discovering the optimal design, in practice, will require a 
thorough analysis of the interrelationship between all of the forces 
involved: the mass and average velocity of the ball, the momentum of the 
racket and the forces applied to the grip by the wrist and forearm. Even 
such minute forces as the slight spin which will be put on the ball as it 
contacts the curved surface and the physiological response time of the 
player must be taken into account. Therefore, it will only be through 
extensive empirical testing and a great deal of trial and error that the 
ideal curvature will be determined. It may be determined that a 
considerable portion of the center of the racket face should remain 
perfectly flat, and that the corrective curvature should begin closer to 
the lateral edges. 
Additionally, the present invention includes a similar compensatory 
curvature in the contact surface for a secondary torsional force which 
increases as the point of contact approaches the extreme end of the racket 
farthest from the grip--the distance along the longitudinal axis from the 
grip to the point of contact representing the lever arm in this case. The 
exact curvature to adequately compensate for this longitudinal torque 
force must also be determined empirically through experimentation. 
Although one might not assume that a single racket could be designed to 
provide adequate compensation for every player from rank beginner to 
advanced tournament competitor, there are some indications that this may 
indeed be so. Assuming that we are speaking only of games between players 
of roughly equal strength, one can see that both the velocity that the 
ball achieves during play (and the consequent torsional forces that it can 
exert on the racket) as well as the ability of the players to resist those 
torsional forces (with the muscles of their forearm and wrist) depend upon 
the same variable: the physical strength of the players involved. 
Consequently, a weaker player's racket will twist more easily in his hand, 
but the slower moving ball will create a proportionally weaker torsional 
force. 
One great advantage of the present invention which is not at first apparent 
arises from the fact that the player no longer has to try so desperately 
to counter the torsional forces acting upon his racket by maintaining an 
excessive tension in his wrist and forearm. The player will be able to 
hold the racket in a much more relaxed manner, secure in the knowledge 
that the twisting of the racket is part of its normal process of 
self-correction. This may decrease the intensity of the muscular stresses 
which often result in the painful and debilitating condition known as 
"tennis elbow." 
One distinct advantage of doing away with the conventional string surface 
is that there is no longer a need for the massive peripheral bow which 
supports it. Since in a conventional racket the bow must necessarily 
extend a considerable height above the contact surfaces, a large area of 
the racket head, including the bow itself and the inch or so of peripheral 
string surface abutting it, is completely unusable. A ball hitting 
anywhere in this area rebounds in a wild, unpredictable trajectory. In the 
present invention, since the entire contact surface can be designed to be 
completely self-supporting, with all structural members occupying the 
space between the two concave faces, the parabolic curvature can extend to 
the very edge of the racket, maximizing the effective playing area. 
In the present invention, the possibility of the contact surface and the 
surrounding frame being made of different materials, joined by an 
intermediate layer of vibration-dampening material, has also been 
explored. In such a case, the contact surface could have some "give" to 
it, approximating the "trampoline effect" of a conventional racket, while 
maintaining the advantages of the compensatory curvature. The racket 
itself would be made of a stiffer material, and a vibration-dampening 
layer in between them would help to minimize the deleterious effects of 
excessive vibrations on the joints of the wrist and arm. 
A further variation of the design outlined in the last paragraph is 
possible in which the contact surface is a pliant membrane of variable 
thickness conforming to the above mentioned curvature, which is kept taut 
by being joined to the surrounding frame structure under high peripheral 
tension. 
The racket of the present invention can of course also utilize any of the 
recently developed materials which are now commonly used in the 
manufacture of game rackets, many of which possess excellent shock 
absorbency characteristics and others that are actually able to sense the 
velocity of an incoming ball and respond with an appropriate amount of 
"give." 
A further improvement vis-a-vis U.S. Pat. No. 3,934,876 (Haddad) in the 
present invention is the shape of the cross-section of the strips which 
form the cellular network. Instead of the squared-off lozenge shape which 
is indicated in the prior art claims, those of the present invention have 
an aerodynamic ovoid cross-section, like that of an airplane wing. This 
helps stabilize the swing and greatly reduces air resistance. 
Alternatively, if one desires to leave more of the contact surface solidly 
intact by decreasing the size of the apertures, it can then be textured in 
various ways to facilitate the execution of certain trick shots, such as 
adding top spin or backspin to the ball. It may be found through 
experimentation that it is beneficial for the lateral areas to be textured 
differently from the center, or for the extreme end to be textured 
differently from the area near the throat. It is also believed that the 
parabolic curvature of the contact surface itself can be exploited to 
allow more prolonged contact with the ball and thus greater control when 
one is attempting to put backspin or top spin on the ball with a slice 
shot. In this case the apertures could be of any conceivable shape and 
have leading edges with aerodynamic fairing. 
A further object of an alternative design of the present invention is to 
provide a racket whose two contact surfaces are designed with different 
curvatures and textures--one to be used exclusively for forehand shots and 
the other to be used for backhand. Again, the specific design details for 
such a racket could only be determined through experimentation, although 
it is obvious that the muscles used in the execution of backhand shots are 
considerably weaker than those employed in forehand shots and would 
necessitate a greater compensatory curvature. 
It is clear from the text of the section entitled "Background of the 
Invention" in U.S. Pat. No. 3,934,876 (Haddad) that the inventor intended 
nothing more than a method of producing inexpensive, long-lasting, easily 
manufactured rackets. However, it is now possible, using today's panoply 
of lightweight, high tensile strength polymers and metallic alloys (such 
as graphite composites, carbon reinforced plastics and ceramics), to 
fabricate a racket with this corrective curvature which far surpasses 
those of the conventional configuration. Additionally, this new generation 
of rackets would be completely maintenance-free, with no need for periodic 
restringing to counter the inevitable slackening of the string surface due 
to the constant tension under which it is held--an inconvenient and 
expensive drawback to all conventional racket designs. Nor would there be 
a need for players to continually readjust the meshwork of stringing as it 
works its way out of alignment during play. 
Accordingly, several objects and advantages of the present invention are: 
(a) to provide a game racket composed entirely of one or several resilient, 
lightweight materials such as graphite composites, carbon reinforced 
plastics, ceramics or metallic alloys, obviating the need for 
string-webbed contact surfaces; 
(b) to provide a game racket with a larger "sweet spot" area without 
further expansion of the racket'overall size or weight; 
(c) to provide a game racket whose open cellular, honeycomb-like contact 
surface structure ensures low swing weight (torsional inertia) and minimal 
wind resistance; 
(d) to provide a game racket whose honeycomb-like contact surfaces are 
formed from interconnected strips with an aerodynamic, ovoid 
cross-section; 
(e) to provide a game racket whose incurvate contact surfaces are able to 
automatically compensate for the torsional forces applied to the racket by 
an incoming ball hitting anywhere on either contact surface; 
(f) to provide a game racket with a secondary compensatory curvature in the 
lengthwise direction to automatically adjust for the secondary torsional 
force encountered when the ball is hit too far toward the extreme end of 
the playing surface from the racket's grip end; 
(g) to provide a game racket whose compensatory properties allow the same 
or a similar design to be used by players of all levels of expertise, 
regardless of their strength; 
(h) to provide a game racket which can be held in a more relaxed manner, 
since the player no longer needs to resist the torsional forces in order 
to aim accurately, thus decreasing the muscular stresses which often 
result in injury; 
(i) to provide a game racket which does not necessitate a cumbersome frame 
extending above the contact surfaces, able to withstand the extreme 
peripheral tension of the stringing; 
(j) to provide a game racket whose contact surfaces extend to the very edge 
of the racket face and whose supporting structures occupy the space 
between the concave surfaces; 
(k) to provide a game racket whose solid contact surfaces can be textured 
in any conceivable manner to assist the player in the execution of shots 
involving backspin and top spin; 
(l) to provide a game racket in which the contact surface is made of a 
material with more elasticity than the frame of the racket and is joined 
to the racket frame by an intermediate layer of vibration-dampening 
material; 
(m) to provide a game racket of an alternative design whose contact surface 
is a pliant membrane of variable thickness conforming to the above 
mentioned curvature, held taut by being fastened to the surrounding frame 
structure under high peripheral tension; 
(n) to provide a game racket of an alternative design in which the two 
contact surfaces have different curvatures and textures--one optimally 
designed for forehand shots and the other for backhand; 
(o) to provide a game racket whose parabolic curvature can be exploited to 
allow a smoother and more prolonged contact with the ball and thus greater 
control in the execution of shots involving backspin and top spin; and 
(p) to provide a game racket which is maintenance-free, with no need for 
periodic restringing or for a player to be continually readjusting the 
crisscrossing string as it works its way out of alignment during play. 
Further objects and advantages will become apparent from a consideration of 
the ensuing description and drawings.

REFERENCE NUMERALS IN THE DRAWINGS 
20: game racket 
21: grip 
22: handle shaft 
23: throat 
24: head 
25: generally ovoid peripheral bow 
26: incurvate open cellular network 
27: rectangular, lozenge-shaped or ovoid strips 
28: top and bottom edges 
29: contact surfaces 
30: central longitudinal axis 
31: extreme lateral edges 
32: greatest thickness 
33: extreme end 
34: central area 
35: central locus 
36: maximal surface area 
37: minimal aperture area 
38: texturable contact surface 
39: barbs or cusps 
40: striated ridges and grooves 
41: small, rounded protuberances 
42: grainy, roughened surface 
43: front contact surface 
44: back contact surface 
45: alternative embodiment of game racket 
46: enlarged peripheral bow 
47: concave outer edge 
48: rigid, resilient material 
49: interposed vibration-dampening material 
50: relatively more pliant material 
51: alternative contact surfaces 
52: apertures 
53: aerodynamic fairing 
54: variable height 
55: rounded texture knobs 
56: ball 
57: arrow indicating direction of movement of incoming ball 
58: general plane of the head portion of the game racket 
59: tangent plane to incurvate contact surface at point of contact 
60: point of contact. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring first to FIG. 1, wherein the general features of the present 
invention are best illustrated, the game racket 20 has the shape and 
dimensions of a tennis racket, and the invention will be described in 
relation to a tennis racket. However, it is understood that the invention 
is applicable to any other game racket such as a racket ball racket or a 
squash racket. 
The game racket 20 comprises a grip 21, a handle shaft 22, a throat 23 and 
a curvilinear head 24 comprising a generally ovoid peripheral bow 25 and 
an incurvate open cellular network 26 rigidly held with respect to the bow 
25, said incurvate open cellular network in the preferred embodiment being 
formed by a plurality of intercommunicating rectangular, lozenge-shaped or 
ovoid strips 27, whose top and bottom edges 28 form the contact surfaces 
29. The compensatory curvature of each contact surface 29 continues 
uninterupted across the top and bottom surfaces of the surrounding 
peripheral bow 25, which effectively forms the peripheral portions of the 
contact surfaces 29. Said compensatory curvature provides graded 
correction for the misalignment of the contact surfaces 29 by the lateral 
torsional force exerted by an incoming game ball, the lever arm of said 
lateral torsional force being the distance from the point of contact to 
the central longitudinal axis 30. The compensatory curvature is greatest 
at the extreme lateral edges 31 of the peripheral bow 25 farthest from the 
central longitudinal axis 30. Here also are the points of greatest 
thickness 32 of the racket head 24. 
The gradual increase in curvature toward the extreme end 33 of the contact 
surfaces 29 farthest from the grip 21 compensates for the secondary 
torsional force whose lever arm is the distance along the central 
longitudinal axis 30 from the point of contact to the grip 21. 
The incurvate open cellular network 24 is thinnest in the central area 34 
where, in this embodiment, there is no corrective curvature; and hence the 
contact surfaces are parallel to each other as well as to the general 
plane of the peripheral bow. 
As shown in the cross-sectional view in FIG. 2 taken on the line II--II of 
FIG. 1, the thickness of the open cellular network 26 and peripheral bow 
25 varies from one laterl edge 31 to the other. FIG. 2 also shows the 
generally rectangular strips 27 which form the incurvate open cellular 
network 26 and whose top and bottom edges 28 make up the contact surfaces 
29. In this embodiment there is a relatively large central area 34 which 
has no corrective curvature. 
FIG. 3 shows a cross-sectional view along the central longitudinal axis 30 
taken on the line III--III of FIG. 1 and illustrates the compensatory 
curvature for the secondary torsional force, said compensatory curvature 
producing the greatest thickness between the extreme edges 33 of the 
contact surfaces 29 farthest from the grip. Also shown are the unplayable 
throat 23 and a portion of the handle shaft 22. 
FIG. 4 shows a cross-sectional view similar to FIG. 2 of an alternative 
embodiment with approximately parabolic contact surfaces 29 and an 
incurvate open cellular network 26 composed of aerodynamic ovoid strips 
27. In this embodiment, there is only one central locus 35 at which planes 
tangent to both contact surfaces would be parallel. 
FIG. 5 is similar to FIG. 4 and illustrates a further alternative 
embodiment with maximal surface area 36 and minimal aperture area 37, 
producing a greater area of texturable contact surface 38. 
FIG. 6 is a close-up cross-sectional view of the lateral portion of the 
racket head indicating in no particular sequence several possible surface 
textures including: barbs or cusps 39; striated ridges and grooves 40; 
small, rounded protuberances 41; and a grainy, roughened surface 42. 
FIG. 7 is similar to FIG. 6, illustrating a further alternative embodiment 
wherein the front contact surface 43 and the back contact surface 44 have 
differentiated corrective curvatures and textures such as may be 
determined to be optimal for forehand and backhand respectively. 
In FIG. 8 an alternative embodiment of a game racket is indicated generally 
at 45. The game racket 45 has the general shape and dimensions of a racket 
ball racket. However, it is understood once again that the present 
invention is applicable to any other game racket such as a tennis racket 
or squash racket. This game racket 45 is similar to the one described in 
detail in the description of FIG. 1 and has the following additional 
features: an enlarged and stronger peripheral bow 46 and a concave outer 
edge 47 which pares away unnecessary material and decreases the swing 
weight of the game racket 45. 
A further improvement which is intended to mimic the "trampoline effect" of 
conventional stringing is illustrated in FIG. 9, which shows in 
cross-section the three materials which are bonded together to make up 
this embodiment: the rigid, resilient material 48 of the racket frame 
itself; the interposed vibration-dampening material 49 and the relatively 
more pliant material 50 forming the incurvate open cellular network. 
Alternatively, the same figure can be used to illustrate an embodiment 
wherein a pliant material membrane of variable thickness 50 forming the 
incurvate open cellular network is held taut by being fastened or bonded 
to the interposed vibration-dampening material 49 and the surrounding 
rigid, resilient material 48 of the racket frame under high peripheral 
tension. 
FIGS. 10 and 11 show possible configurations for alternative contact 
surfaces 51 and apertures 52 for the incurvate open cellular network. Many 
such configurations comprising patterns of hexagons, triangles, squares, 
rectangles, circles and ovals are all possible and fall within the scope 
of the present invention. FIG. 11 also indicates that the apertures can 
have aerodynamic fairing 53. 
In FIG. 12 the preferred embodiment of the incurvate open cellular network 
is illustrated in a detailed perspective view and shows clearly many of 
the advantages of the present invention. The ovoid strips 27 are shown in 
cross-section to illustrate their aerodynamic profile and are of variable 
height 54 to show another way in which texturing can be added to the 
contact surfaces. The rounded protruberances 55 at the intersections of 
the ovoid strips 27 show further means for adding texture. 
FIGS. 13 and 14 show the present invention in operation. In FIG. 13 the 
incoming ball 56 is shown with an arrow 57 indicating its direction of 
movement. The broken line at 58 indicates the general plane of the head 
portion of the game racket 20 before the incoming ball 56 has struck the 
contact surface 29. Thus the broken line 58 in FIG. 13 also represents the 
intended plane of contact. Another broken line at 59 indicates the tangent 
plane to the incurvate contact surface 29 at the imminent point of contact 
60. 
FIG. 14 shows the displacement of the general plane 58 of the head portion 
of the game racket 20 away from the intended plane of contact as a result 
of the torsional force exerted upon it at the point of contact 60 by the 
ball 56. Although the general plane 58 of the head portion of the game 
racket 20 is now out of alignment, the tangent plane 59 to the contact 
surface 29 at the point of contact 60 has automatically realigned itself 
and is once again parallel with the intended plane of contact. 
CONCLUSION, RAMIFICATIONS, AND SCOPE OF THE INVENTION 
Accordingly, the reader will see that the game racket of the present 
invention introduces a range of innovations not feasible in any prior art 
racket with conventional strung contact surfaces. By replacing the 
stringing with two concave, approximately parabolic, open cellular contact 
surfaces made of one or several resiliant, lightweight materials such as 
graphite composites or metalic alloys, a game racket is provided which is 
able to automatically compensate for the torsional forces applied to the 
racket by an incoming ball hitting anywhere on either contact surface, 
effectively enlarging the sweet spot area to include the entire racket 
face. A secondary compensatory curvature in the lengthwise direction 
adjusts for the secondary torsional force encountered when the ball is hit 
too far toward the extreme end of the playing surface from the racket's 
grip end. The parabolic curvature of the racket face can also be exploited 
to allow smoother and more prolonged contact with the ball and thus 
greater control in the execution of "sliced" shots involving backspin and 
top spin. In an alternative design, the two contact surfaces have 
different curvatures and textures--one optimally configured for forehand 
shots and the other for backhand. Without the conventional racket's 
requirement of a cumbersome supporting frame extending some distance above 
the string surfaces, and with all supporting structures in the present 
invention being located between the two concave surfaces, the playing 
surfaces are capable of being extended to the very edges of the racket 
face. 
In addition, the invention provides a racket whose honeycomb-like contact 
surfaces are made up of aerodynamic strips with ovoid cross-sections, thus 
decreasing wind resistance as well as swing weight. Alternatively, the 
ratio of solid contact surface area to aperture area can be increased 
(said apertures having any conceivable shape and their leading edges 
having aerodynamic fairing), allowing the surface to be textured in any 
conceivable manner to assist the player in the execution of shots 
involving backspin and top spin. Furthermore, the present invention has 
additional advantages in that 
it allows rackets with a corrective curvature of the same or a similar 
design to be used by players of all levels of expertise, regardless of 
their strength; 
it provides a racket which can be held in a more relaxed manner, since the 
player no longer needs to resist the torsional forces in order to aim 
accurately, thus decreasing the muscular stresses which often result in 
injury; 
it provides a racket of an alternative design in which the contact surface 
is made of a material with more elasticity than the frame of the racket 
and is joined to the racket frame by an intermediate layer of 
vibration-dampening material; 
it provides a further alternative racket design in which a pliant membrane 
of variable thickness conforming to the above mentioned curvature is held 
taut by being fastened to the surrounding frame structure under high 
peripheral tension; and 
it provides a game racket which is maintenance-free, as there is no 
necessity for the racket to be restrung every four to six months, as with 
a conventional racket, or for a player to be continually readjusting the 
crisscrossing string as it works its way out of alignment during play. 
Although the description above contains many specificities, these should 
not be construed as limiting the scope of this invention but as merely 
providing illustrations of some of the presently preferred embodiments of 
the invention. It is obvious that minor changes may be made in the form 
and construction of the invention without departing from the material 
spirit thereof. For example, the racket face can have other shapes, such 
as circular, rectangular, hexagonal, trapazoidal etc.; the racket can be 
designed without the secondary compensatory curvature in the longitudinal 
direction; textures can be added to the racket face in various ways, such 
as by sand-blasting, spraying the contact surfaces with a liquid texturing 
medium, adhering textural elements to the surfaces with glue, etc. 
Thus the scope of the invention should be determined by the appended claims 
and their legal equivalents, rather than by the examples given.