EP0028599A1 - Raquette de tennis - Google Patents

Raquette de tennis

Info

Publication number
EP0028599A1
EP0028599A1 EP79901459A EP79901459A EP0028599A1 EP 0028599 A1 EP0028599 A1 EP 0028599A1 EP 79901459 A EP79901459 A EP 79901459A EP 79901459 A EP79901459 A EP 79901459A EP 0028599 A1 EP0028599 A1 EP 0028599A1
Authority
EP
European Patent Office
Prior art keywords
racket
distance
weight
center
centimeters
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP79901459A
Other languages
German (de)
English (en)
Inventor
Jack L. Frolow
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of EP0028599A1 publication Critical patent/EP0028599A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B49/00—Stringed rackets, e.g. for tennis
    • A63B49/02—Frames
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B49/00—Stringed rackets, e.g. for tennis
    • A63B49/02—Frames
    • A63B49/03—Frames characterised by throat sections, i.e. sections or elements between the head and the shaft
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B49/00—Stringed rackets, e.g. for tennis
    • A63B49/02—Frames
    • A63B49/08—Frames with special construction of the handle
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B49/00—Stringed rackets, e.g. for tennis
    • A63B49/02—Frames
    • A63B49/10—Frames made of non-metallic materials, other than wood
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B49/00—Stringed rackets, e.g. for tennis
    • A63B49/02—Frames
    • A63B49/12—Frames made of metal
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B60/00—Details or accessories of golf clubs, bats, rackets or the like
    • A63B60/002—Resonance frequency related characteristics
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B60/00—Details or accessories of golf clubs, bats, rackets or the like
    • A63B60/02—Ballast means for adjusting the centre of mass
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B60/00—Details or accessories of golf clubs, bats, rackets or the like
    • A63B60/06—Handles
    • A63B60/18—Handles with means for cooling, ventilating or sweat-reduction, e.g. holes or powder dispensers
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B60/00—Details or accessories of golf clubs, bats, rackets or the like
    • A63B60/54—Details or accessories of golf clubs, bats, rackets or the like with means for damping vibrations
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B49/00—Stringed rackets, e.g. for tennis
    • A63B49/02—Frames
    • A63B2049/0211—Frames with variable thickness of the head in a direction perpendicular to the string plane
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B49/00—Stringed rackets, e.g. for tennis
    • A63B49/02—Frames
    • A63B2049/0212—Frames with defined weight
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B60/00—Details or accessories of golf clubs, bats, rackets or the like
    • A63B60/48—Details or accessories of golf clubs, bats, rackets or the like with corrugated cross-section

Definitions

  • This invention relates to rackets used to bat a ball in games.
  • Tennis rackets in the prior art weigh from 12 ounces (340.2 gms.) for a light racket to over 14 ounces (396.9 gms.) for a heavy racket.
  • the center of percussion or sweet spot ranges from 17 inches (43.18 cms.) to 18.50 inches (46.99 cms.), from the end of the racket handle. This center does not coincide with the center of the strings, but is closer to the handle end. Thus, when a ball is struck at the center of the racket face, a shock is felt at the handle grip.
  • rackets of the past have utilized wood, aluminum, steel, fiberglass, boron and graphite composites.
  • the overall length of the racket was 26 inches (66.04 cms.) and the striking power was equivalent to a 141 ⁇ 2 ounce (411.08 gms.) racket.
  • This racket was made of wood and the crossectional areas shown were not the best to achieve the results desired.
  • Fig. 1 is a front view of the racket, showing points of application of impulsive forces, axis of rotation, center of gravity and center of percussion.
  • Fig. 2 is a side view of Fig. 1 and a ball traveling with a velocity v toward the racket.
  • Fig. 3 is a view of a pendulum with two weights.
  • Fig. 4 is a front view of an embodiment of the invention.
  • Fig. 5 is a side view of Fig. 4.
  • Fig. 6 is a bottom view of Fig. 4.
  • Fig. 7 is a front view of a sweat absorbent sleeve handle insert.
  • Fig. 8 is an expanded assembly of the component members of Fig. 4.
  • Fig. 9 is a side view of a portion of a component member 9 of Fig. 4 and Fig. 8.
  • Fig. 10 is a crossection view of the section 10-10 of component 9 of Fig. 4 and Fig. 8.
  • Fig. 11 is a crossection view of section 11-11 of member 8 of Fig. 8.
  • Fig. 12 is a crossection view of section 12-12 of member S5 of Fig. 8.
  • Fig. 13 is another crossection view of section
  • Fig. 14 is a side view of the handle member of Fig. 8.
  • Fig. 15 is a front view of an alternate component member 9 of Fig. 4 and Fig. 8.
  • Fig. 16 is a front view of another alternate component member 9 of Fig. 4 and Fig. 8.
  • Fig. 17 is a front view of another embodiment of the invention.
  • Fig. 18 is a side view of Fig. 17.
  • Fig. 19 is a crossection view of section 19-19 of head portion of Fig. 17.
  • Fig. 20 is a crossection view of section 20-20 of the throat portion of the racket shown in Fig. 17.
  • Fig. 21 is a crossection view of section 21-21 of the handle portion of the racket shown in Fig. 17.
  • Fig. 22 is a front view of a racket which is another embodiment of the invention.
  • Fig. 23, Fig. 24, Fig. 25 and Fig. 26 are crossectional views of the sections 23-23, 24-24, 25-25 and 26-26 shown in Fig. 22.
  • Fig. 27 is a front view of a racket which is another embodiment of the invention.
  • Fig. 28 is a crossectional view of the section 28-28 shown in Fig. 27.
  • Fig. 29 is a side view of the embodiment shown in Fig. 27.
  • Fig. 30 is a crossectional view of the section 30-30 of the handle shown in Fig. 29.
  • Fig. 31 is a front view of a racket which is another embodiment of the invention.
  • Fig. 32 is a side view of the racket shown in Fig. 31.
  • Fig. 33, 34, 35, and 36 are crossectional views of the sections 33-33, 33a-33a, 34-34, 35-35, shown in Figs. 31 and section 36-36 shown in Fig. 32.
  • Fig. 37 is a front view of a racket which is another embodiment of the invention, which allows the moment of inertia to be changed by the player.
  • Fig. 38 is a crossectional view of the section
  • Fig. 39 is a crossectional view of the section 39-39 shown in Fig. 37.
  • Fig. 40 is a chart of results of tests made on prior art rackets and rackets fabricated in accordance with the objectives of this invention.
  • Fig. 41 is a chart of results shown in Fig. 40 expressed in the metric system. DESCRIPTION OF INVENTION
  • the racket strings will deform and the ball will deform.
  • the deformation of these bodies result in energy being stored in each and then being dissipated by vibration, heat and some of the energy being given back to the ball in its rebound motion.
  • the energy stored in the strings is mostly given back to the rebound motion of the ball.
  • the energy which remains in the vibration of the strings is a small portion of the energy stored since the weight of the strings is small compared to that of the ball. About 55% of the energy stored in the ball is given back as rebound motion between the ball and the racket.
  • the energy stored in the racket frame due to its bending and torsion under the impact is mostly dissipated in the racket by vibrations.
  • the racket frame in order for the racket frame to give back some energy to the rebound motion of the ball, it must be moving in the direction of the ball's motion when it departs from the racket strings and this would occur infrequently. This action would be similar to a diver using a springboard which requires split second timing. Further, after the diver has left the board, the board vibrates violently, dissipating the energy. This is the job the strings should do , not the frame .
  • deformation of the racket frame reduces the velocity of the ball's rebound and results in vibration of the racket frame after the ball has departed the strings. It is a feature of this invention to reduce this frame deformation in bending and torsion.
  • the velocity of the ball's rebound after striking the racket depends on the moment of inertia of the racket about the pivot axis, the weight of the ball, the velocity of the ball, and the velocity of the racket. If we again return to the racket as shown in Figs. 1 and 2, and a ball b traveling with a velocity, v, with respect to the ground strikes the racket at the center of percussion, C p , the racket will rebound from the impact by rotating about the pivot axis o-o and the velocity of the point C p will be v'.
  • An object of this invention relates to a tennis racket which possesses the same striking power or swing weight as rackets of the prior art, but has a significant reduction in the weight, a significant increase in the center of percussion, a significant decrease in vibration and a significant decrease in flexibility, thereby resulting in a more efficient and accurate racket.
  • This racket will minimize the development and aggravation of tennis elbow.
  • This racket is fabricated of material which has a high stiffness per unit weight. Materials that can be used in descending order of stiffness are graphite composite, boron composite, steel, aluminum, wood and fiberglass. At the present time aluminum is the most cost effective.
  • the crosssections of the racket at various points along its length is designed to provide sufficient stiffness with the minimum amount of material.
  • C p center of percussion in inches (cms.), the distance from the pivot point.
  • C g center of balance or gravity, in inches (cms.) the distance from the pivot point.
  • W the weight of the racket in ounces (gms.)
  • the center of percussion is that point on the racket which, when struck by a force of short time duration, will cause no lateral shock or movement at the pivot point.
  • the distance the center of percussion is from the pivot point is identical to the distance of a pendulum weight to the pivot point, when the pendulum distance is adjusted so as to take the same amount of time to complete one swing as the racket does when it is allowed to swing as a pendulum.
  • the pendulum distance is adjusted so as to take the same amount of time to complete one swing as the racket does when it is allowed to swing as a pendulum.
  • the pivot point selected was the end of the handle because the butt of the racket is usually resting against the heel of the hand which is very close to the wrist pivot joint. All measurements were taken on different rackets at the handle end for reference purposes. If the pivot point is selected at some other point such as four inches from the end, the center of percussion moves toward the center of the racket face somewhat, but is still below the center of the racket face. As long as comparisons between rackets are done from the same pivot point, the results of the analysis are the same. We can analyze the affect of the removal or the addition of weight along the length of a racket by the following example.
  • the denominator is made smaller by making W smaller and keeping the magnitude of the increase in C g smaller than the magnitude of the decrease in W, thus the product of C g W will be made smaller.
  • Fig. 1 If a particle of material of weight, W 1 in the handle at a distance of l, from the handle end is removed, the moment of inertia is reduced by W, l, 2 If a particle of material of weight W 2 is added at a distance lz. the moment of inertia is increased by W z l z2 .
  • W, l, 2 W 2 l z 2 and there would be no overall net increase in the moment of inertia by the subtraction of W 1 and the addition of W 2 .
  • l z should be made as large as possible, which means that we should be adding the weight to the head end of the racket at approximately 27 inches, which is the length of most rackets.
  • Material is removed from the grip portion A to reduce the overall weight. Sufficient material must be provided to withstand the grip pressure of the hand. Also, a large bending moment occurs at the junction of portions A and B at the instant of impact of the ball. Very little torsion stress is experienced by the material here because the hand cannot exert strong torsion in the short space of time of the ball impact. Reduction in the material from portion A will increase the center of percussion only slightly while the center of gravity will be increased greatly.
  • Material removed from the head portion D and the addition of less material to the head end portion E is also effective in increasing the center of percussion. decreasing the center of gravity, and the overall weight slightly.
  • the stresses in these members consist of a small bending moment when the ball impacts the racket and also the static tension imposed by the racket strings. These members must be sufficiently rigid to prevent movement when the ball impacts the racket and vibration thereafter.
  • portion E should not be removed except to reduce the swing weight to the required value. There is no bending stress except the member must withstand the stress of the string tension. Sufficient material must be provided in the portion E near the axis a-a to withstand the bending stress of the string tension and also the additional tension at the impact of the ball. The material which is removed from the other portions and added to portion E should be added at the outer corners of the racket, at locations N and Q in Fig. 4.
  • the inertia about this axis is important since it determines how far off the longitudinal axis a ball can be hit before rotation of the racket in the hand of the player results in a weakly hit inaccurate return of the ball.
  • P 2 the impulsive force caused by the impact of the ball.
  • I s moment of inertia about the axis o-o
  • the ratio of the angular momentums is, ) ) Y
  • a weight which is added to the racket at a maximum distance from the axis a-a is most effective in increasing this moment of inertia.
  • T 1 period of bar with known moment of inertia
  • T o period of torsional carrier
  • the stiffness of the racket it is noted, that if the racket is designed to obtain the most desired rigidity, it will be strong enough to withstand the stresses required to prevent bending or breaking.
  • Fig. 1 and Fig. 2 when a ball strikes the racket with a force P 1 at point C 1 , the force F 1 at the center of gravity is in the opposite direction. This gives rise to a large bending moment occuring at the center of gravity. If the center of gravity has been moved up to the throat portion C from portion B, a much stronger and rigid crossection exists than the crossection at the top of the handle in the portion B. Hence the racket will be stiffer. When a racket is struck it vibrates in discrete modes at discrete frequencies.
  • the mode of vibration and the frequency is determined by the stiffness, weight, the weight distribution of the racket, and the manner in which the racket is held.
  • the amplitude of a particular mode of vibration also depends upon where the racket is struck.
  • Some modes of vibration have points which do not move with respect to the ground during the vibration. These points are known as nodal points. When a racket is held at a nodal point and the racket is caused to vibrate in the mode associated with this nodal point, the vibration is not affected very much by the means by which the racket is held, .and the vibration lasts longer. The frequency of this free vibration is determined by the stiffness, the weight and the weight distribution alone. It has been observed that the vibration in metal rackets persist for a longer period of time after they are initiated, than the vibrations in wood or composite racket or rackets which employ vibration damping material. The wood and plastic material dampens the vibrations. However, the vibrations are present and can be observed for a short interval of time.
  • One of the modes of vibration of a racket occurs when the center of gravity moves with respect to the racket head end, and the handle end, and both ends are free to vibrate.
  • This mode of vibration can easily be observed by holding the racket handle between the forefinger and thumb at a pivot point so that the pivot axis is parallel to the racket face and then striking the head end perpendicular to the face and noting the strength of the vibration.
  • the point at which the racket handle is held is moved up or down, and the process repeated until the vibration is observed to last the longest length of time.
  • this nodal pivot point is about six inches (15.24 cms.) from the handle end.
  • the strings vibrate also when the center of the racket face is struck by a ball.
  • the strings move perpendicular to the face of the racket frame.
  • the center of the racket face strings is known as a pole or antinode, since when it is struck it moves the most and vibrates the most. Also, if designed properly, the face frame becomes a nodal line for the vibration of the strings, so that very little of the string vibration is transmitted to the frame head when the racket face strings are struck in the center.
  • the racket can be caused to vibrate in a direction parallel to the face of the racket by holding the handle so that the pivot axis is perpendicular to the face of the racket, and the racket head is struck parallel to the racket face.
  • the racket As mentioned when the racket is held at the nodal point near the handle end, and the head end is struck strong vibrations are observed. However, if the racket is held at the nodal point near the handle end and the racket is struck at the nodal point in the center of the racket face or on the nodal points in the head frame opposite the center, the amplitude of the vibration associated with these nodes will not be present in the vibration. Likewise, if the racket is held at one of the nodal points in the head end and the racket is struck at the node at the handle end, the vibration associated with these nodes will not be present.
  • Vibrations perpendicular to the face can be caused by striking the head end in a direction perpendicular to the face and vibrations parallel to the face can be caused by striking the racket in a direction parallel to the face.
  • the torsional vibration can be caused by striking one side of the head frame opposite the center of the face and holding the head end of the racket with the tip of the forefinger to dampen out other modes of vibration.
  • the frame can vibrate in a direction perpendicular to the face of the racket, in a direction parallel to the face of the racket, and the head end of the frame can vibrate in torsion with respect to the racket handle.
  • each frequency of vibration can have related overtone frequencies of vibrations and modes. These modes of vibration can be observed by placing a piezo-electric crystal pickup, which generates a voltage when stressed, at various points on the racket frame, and feeding the voltage generated by the vibration at that particular point to the vertical plates of a cathode ray oscilloscope.
  • a calibrated variable audio voltage oscillator is fed to the horizontal plates of the oscilloscope.
  • the frequency of the crystal voltage and the audio voltage oscillator are the same, a visual elliptical pattern is observed on the oscilloscope cathode ray tube.
  • the crystal is placed near the handle end and the racket is struck at the head end. The racket is held between the forefinger and the thumb at the node near the handle end.
  • the crystal pickup is placed at one of the nodes in the frame head, and the center of the strings is struck.
  • the racket handle is held in one hand. Vibration of the center of gravity will be minimized and the voltages caused by the string vibration will be emphasized.
  • the frame is struck in a direction perpendicular to the face.
  • the handle, end is held in a heavy vise.
  • the racket is struck at the other node in the head frame opposite the face center, in a direction perpendicular to the racket face.
  • the center of the head end is held with the tip of the forefinger to dampen out vibrations other than the torsion vibration.
  • the crystal pickup is placed at one of the nodes in the head frame opposite the center of the racket face, and the racket is struck at the other node in the head frame.
  • the racket is held by the handle in the other hand.
  • D g the deflection of the center of gravity under its own weight.
  • K 1 a factor which is dependent on the racket weight and also the weight distribution along its length.
  • the factor K 1 is somewhat different for each racket; hence, the frequency will not be exactly inversely proportional to the square root of the deflection from racket to racket.
  • the deflection of the racket as a beam under its own weight can be related to the deflection of the racket as a beam, when additional static weight is placed over the center of gravity, and the racket is supported at the node near the handle end and the nodes near the head end, by appropriate beam deflection formula. Measurement of this deflection at the center of gravity when a weight is placed over the center of gravity is related to the performance of the racket at the instant of impact, and the subsequent vibrations of the racket which occur. When a racket is held in a player's hand and it strikes a ball, the racket is also stressed as a cantilever.
  • the head end of the racket deflects with respect to the handle end held by the player, and the racket end vibrates subsequently as a cantilever.
  • the deflection of the racket head end when the handle end is held in a heavy vise six inches (15.24 cms.) from the handle end, and a weight is placed at the center of the racket face is related to the performance of the racket at the instant of the ball impact and the subsequent vibration of the racket.
  • the frequency of vibration of the racket head end with respect to the handle end can be approximated by the formula
  • f 3 the frequency of vibration.
  • g the acceleration of gravity.
  • D 3 the deflection of the racket head end.
  • l 4 the distance of the racket head end from the cantilever base.
  • w 3 the weight added to the racket face center.
  • l 3 the distance of the racket face center to the cantilever base.
  • I c the moment of inertia of the racket about the cantilever base.
  • the hand acts more as a pivot point and a weight at the pivot point.
  • the vibrations measured when the racket is caused to vibrate freely and holding the racket at the node near the handle end is closely related to the frequency measured when the racket is held in a player's hand, and the racket is struck at the head end by a ball.
  • the nodal point of a racket does not move with respect to the ground when a racket vibrates in a mode that is associated with that node.
  • the racket is held between the forefinger and thumb, and the racket is struck at the head end.
  • the point at which the racket is held is shifted up and down until the vibrations caused by the impact of a small rubber hammer at the head end persist the longest.
  • the position at which the racket is held is the node in the handle end.
  • Rackets made in accordance with the objectives of this invention have nodal points much further away from the handle end.
  • the nodal pivot near the handle end does not move in space when the racket bends from a concave arc to a convex arc when vibrating in this mode.
  • the nodal pivot acts as a fulcrum in a see-saw as the racket vibrates. As in a see-saw the further one moves away from the pivot, the less force is required to balance the force on the other end of the see-saw.
  • Y represents a Yonex aluminum racket of prior art.
  • H represents a Headmaster aluminum racket of prior art.
  • D represents a Dunlop steel racket of prior art.
  • TA represents a TAD wood racket of prior art.
  • TE represents a Tensor aluminum racket of prior art.
  • W represents a Wilson steel racket of prior art. 1, represents a racket similar to the embodiment of Fig. 31 without the openings 36.
  • FIG. 2 represents a racket similar to the embodiment in Fig. 17, but provided with an attached tubular aluminum handle with a fiberglass grip.
  • 3 represents a racket similar to the embodiment in Fig. 27.
  • FIG. 6 represents a racket similar to the embodiment in Fig. 17, but repaired due to breakage in fabrication.
  • Col. 1 the racket under test.
  • Col. 2 Test 2 for the length of the racket.
  • Col. 4 Test 4 for the center of percussion.
  • the racket is supported at a pivot at the handle end.
  • the racket is caused to swing as a pendulum having a small amplitude for more than 10 consecutive swings.
  • the time T in seconds is measured for the pendulum to complete 10 swings.
  • Col. 5 Test 5 for the difference of Col. 3 and Col. 4 divided by Col. 4.
  • Col. 6 Test 6, for the center of gravity.
  • Col. 7, Test 7 for the weight in ounces, or grams.
  • Col. 8 Test 8 for the ratio of Col. 6 to Col. 4.
  • Col. 9 Test 9, for the product of Col. 6 and
  • Col. 10, Test 10 for the moment of inertia about the axis o-o, in ounce-in 2 or kgm-cm. 2 , shown in
  • Col. 13, Test 13 for the frequency, f 1 , in cycles per second, of vibration perpendicular to the racket face with the ends free, and the racket is held at the nodal point at the handle end.
  • This mode of vibration has a node near the handle end and a node in each side of the head portion of the frame near the head end of the racket.
  • Col. 14, Test 14 for the deflection perpendicular to the racket face, D 1 , in inches or cms. of the middle of the racket between the ends when a weight of 80 ounces (22.68 kgms.) is applied to the middle of the racket, and the racket is supported six inches (15.24 cms.) from the handle end, and the head frame sides are supported at points opposite the center of the face.
  • Col. 15, Test 15 for the distance of the node closest to the handle end, associated with the frequency f 1 , from the handle end. The racket is held between the forefinger and thumb in the vicinity of the node located in one side of the head portion of the frame.
  • the racket is tapped repeatedly with a rubber tipped hammer along the longitudinal axis of the racket in a direction perpendicular to the face of the racket, in the vicinity of the node located near the handle end.
  • the location at which the minimum amplitude of vibration occurs when tapped, having the frequency f 1 is the precise location of the node.
  • Col. 16, Test 16 for the frequency, f 2 , in cycles per second, of the vibration parallel to the racket face when the ends are free and the racket is held at node near the handle end.
  • This mode of vibration has a node near the handle end and a node in each side of the head portion of the frame near the head end of the racket.
  • Col. 17, Test 17 for the deflection parallel to the racket face, D 2 , in thousandths of an inch (cm.) at the middle of the racket frame between the ends when a weight of 80 ounces (2268 kgms.) is applied at the middle of the racket frame, and the racket is supported as a beam six inches (15.24 cms.) from the handle end, and also at head frame side at a point opposite the center of the face.
  • This mode of vibration has no nodes, the base of the entil ever is not considered a node.
  • Col. 19 Test 19 for the deflection D 3 in thousandths of an inch or cm. of the head end of the racket perpendicular to the face, when the racket is held as a cantilever as described in Col. 18 when a weight of 15.62 ounces (442.83 gms.) is applied at the center of the racket face.
  • Col. 20, Test 20 for the frequency, f 4 , in cycles per second, of the vibration of the racket parallel to the racket face when the racket is held in a heavy vise six inches (15.24 cms.) from the handle end.
  • This mode of vibration has no nodes.
  • the base of the cantilever is not considered a node.
  • Col. 21, Test 21 for the deflection, D 4 , in inches or cms. of the head end of the racket parallel to the face of the racket, when a weight of 15.62 ounces (442.83 gms.) is applied to the center of the racket face.
  • Col. 22, Test 22 for the frequency, f 5 , in cycles per second, of the racket in torsion, when the racket is held in a heavy vise as a cantilever six inches (15.24 cms.) from the handle end.
  • the torsional mode of vibration is initiated by striking the racket on one side of the head frame opposite the center of the face. The frame is held at the center of the head end with the tip of the forefinger to dampen out vibrations other than the torsional vibration. This mode of vibration has no nodes.
  • the base of the cantilever held by the vise is not considered a node.
  • Test Numer 5 indicates the distance between the center of percussion and the center of the face divided by the distance of the center of percussion.
  • the center of the face has the softest deflection to the impact of the ball compared to other impact points on the face of the strings. This results in the most efficient rebound of the ball from the strings, since the strings are doing more work at this point, and they are more efficient than the deformation of the ball.
  • the ideal racket would have all its weight concentrated at the point which contacts the ball.
  • the handle and frame would weigh nothing and be perfectly rigid.
  • the strings would weigh nothing.
  • the ratio of is a measure of how ideal the weight distribution of the racket is.
  • K 2 .75 whereas for the weight concentrated at a point
  • Test Number 9 indicates the product of the weight W in ounces or grams, times the distance of the center of gravity, in inches or cms. If a player holds the racket in his hand with the handle parallel to the ground, this product indicates the static bending moment the player feels at his wrist. The smaller this moment is the less strain on the player's wrist and arm. Further for a given moment of inertia about the axis, o-o, the smaller this product is the larger the distance the center of percussion will be from the handle end.
  • the handle 1 of the racket is formed of type 7075 T6 aluminum, .020 inches (.0508 cms.) thick.
  • the handle end grip portion A is formed to be six sided polygon, with the upper and lower faces of S 1 and S 2 in Fig. 5 to be larger.
  • the surface of the portion A is perforated with holes 2 to provide for air circulation, cushioning for shocks to reduce the weight, and to provide for drainage holes for sweat from the player's hands.
  • the surface may be covered with a thin epoxy coating to present a warm feeling for the hand, or with a light porous nylon sleeve, or a perforated leather or rubber sleeve.
  • a sweat absorbing sleeve 3 in Fig. 6 may be inserted inside the handle contacting the inside surface, and the sweat drainage holes.
  • the handle extends into portion B which must withstand bending when the racket is swung and also when the ball is struck.
  • Portion B has the sides perforated with openings 4 as shown in Fig. 5, to remove material and reduce the weight.
  • the edges of the openings 4 are bent inward to provide for more rigidity to keep the upper and lower surfaces S 3 and S 4 in Fig. 5. in place when the racket is stressed.
  • throat portion C has the plates S 5 and S6 riveted to the handle by the use of steel "pop" rivets, 7.
  • the surfaces of the plates and handle which are in contact are cleaned thoroughly and then coated with an epoxy glue.
  • These plates are fabricated of type 7075 T6 aluminum, .020 inches thick (.0508 cms.). They may be perforated with holes, 2, again to reduce the weight.
  • Fig. 12 and Fig. 13 are views of the crossection 12-12 and 13-13 shown in Fig. 8 of the member S 5 .
  • Fig. 8 is an expanded assembly of Fig. 4. Shown in Fig. 8 is a curved member 8 which is also shown in Fig. 4 and Fig. 5. The crossection 11-11 of this member in Fig. 8 is shown in Fig. 11. This curved member
  • the crossection 10-10 of Fig. 8, of the extruded aluminum frame 9 is shown in Fig. 10. Since the main stress is compression and tension in the upper and lower surfaces, as much of the material as possible should be placed there. To increase the resistance to warping the upper and lower areas are made in hollow tubes which give the crossection more strength in torsion.
  • the crossection used in this embodiment is shown in Fig. 10. Many other crossections may be used.
  • the weight of the extruded tubing prior to reducing the weight by putting openings in the central web area was 0.16 oz/inch (1.758 gms./ cm.).
  • Fig. 14 shows a side view of the handle 1.
  • Fig. 4 is shown a strip 12 of sticky mastic material with a vinyl plastic outer coating on one side placed upon the strings. It has been found that when a ball is struck the strings vibrate and give rise to a loud audio sound, such as a "bong." Placing the mastic tape at various locations dampens this sound. The more the strip is lengthened, and with the use of additional strips at the head end, sides and center, the sound can be caused to be quite dead. The ball bounces from the racket with a dull sound.
  • the use of the strip is at the desire of the player. It is easily applied and removed by the player, by placing two strips face to face from opposite sides of the racket strings.
  • Fig. 15 Shown in Fig. 15 is an embodiment wherein the frame 9 in Fig. 4 has been modified and is shown as 9a.
  • Weight is removed from the locations N and Q and by addi tional openings 11, as shown in Fig. 5.
  • Additional weights 13a and 14a are placed opposite the center of the racket face at the locations J and M.
  • the additional weights that are placed at locations J and M increase the moment of inertia of the racket about a longitudinal axis a-a shown in Fig. 4. This additional weight also increases the overall weight of the racket from the minimum weight which is required to attain the required moment of inertia about the axis o-o.
  • a racket having a minimum weight for a given moment of inertia about the axis o-o, and also a large moment of inertia about the longitudinal axis a-a would have as much weight located in the corners N and M as permissible.
  • the moment of inertia of the racket about the longitudinal axis a-a may be increased by removing material from the corner locations N and M of the frame which are 27 inches (68.58 cms.) from the handle end and adding weights 13a and 14a to the frame sides at the locations J and M, which are 21.5 inches (54.61 cms.) from the handle end, opposite the center of the racket face.
  • the weight of the material added at the locations J and M must be times greater than the weight of the material removed, from the locations N and Q.
  • Fig. 16 shows another shape for the racket frame as 9b.
  • the shape of the frame 9b removes more weight from the locations N and Q than does the frame 9a, and allows the weights 13b and 14b to be greater.
  • Shown in Figs. 17 and 18 is a racket fabricated by the assembly of two metal formings of aluminum 15 and 16. In Fig. 19, the crossection 19-19 of Fig. 17 is shown.
  • the racket is made of aluminum, .020 inches (.0508 cms.) thick.
  • the formings are assembled by the application of epoxy glue to the mating surfaces. Holes utilizing pop rivets 7 are used as feed through holes for the strings and also to assist in fastening the two halves 15 and 16 together.
  • the shape of the racket, weight, weight distribution and stiffness conform to the objectives given for the previous embodiments.
  • material is formed at the locations U, V, and W, to improve the stiffness. It is known that crossections which have thin walled material have greater strength and rigidity per unit weight, than solid or thicker crossections. The material may have the wall thickness reduced to gain this advantage, until a point is reached wherein the material is too easily dented. Further, as the wall becomes thinner, the ability of the crossection to maintain its shape under stress is diminished.
  • Fig. 20 is a view of section 20-20 of Fig. 17.
  • Fig. 21 is a view of section 21-21 of Fig. 17.
  • openings 18 and 19 are provided to reduce the weight of the handle and the grip.
  • Another embodiment is shown in Fig. 22.
  • a racket is fabricated of a composite material such as epoxy with fiberglass, epoxy with graphite fibers, or epoxy with boron fibers.
  • the racket frame 20 molded over a core made of Woods metal which has previously molded to shape. The core is removed by heating to a relatively low temperature at which the Woods metal melts.
  • the racket frame 20 is molded so as to provide ribs and thicker crossections as required by the stresses. Such crossections are shown in Figs.
  • Fig. 26 shows the crossection 26-26 of Fig. 22.
  • the weight distribution and the use of reinforcement material, the frame 20, is in accordance with the objectives given for the previous embodiments.
  • the use of epoxy with graphite fibers or epoxy with boron fibers as the fabrication material for the frame 20 should provide for approximately a twenty percent reduction in weight for the same stiffness and swing weight over a racket fabricated of aluminum.
  • the use of epoxy with fiberglass material should weigh more than aluminum. The use of these composite materials provide that vibrations are damped out quickly.
  • Fig. 27 Shown in Fig. 27 is another embodiment of the invention.
  • the crossection 28-28 of Fig. 27 is shown in Fig. 28.
  • the frame 21 is fastened to the plates 22a and 22b by the use of steel pop rivets 7The mating surfaces are cleaned and glued with epoxy.
  • These plates 22a and 22b are made of 7075 T6 aluminum, .020 inches (.0508 cms.) thick and holes 28 are provided to reduce the weight with a minimum reduction in rigidity.
  • Yoke 23 is also fastened to the frame 21 and the plates 22a and 22b by pop rivets 7 and epoxy glue. Holes 24a are provided for the racket strings.
  • the frame 21 in Fig. 29 shows openings 24 to feed the racket strings through and openings 25 and 26 to reduce the weight.
  • the section of the handle 30-30 of Fig. 29 is shown in Fig. 30.
  • the handle 27 is mode of 7075 T6 aluminum, 0.020 inches (.0508 cms.) thick and is perforated with holes 28.
  • the handle 27 is fastened to the spread frame 21 by the use of steel pop rivets 7 and the use of epoxy glue on the mating surfaces.
  • the weight distribution and the rigidity is in accordance with the objectives given for the previous embodiments.
  • Shown in Fig. 31 is another embodiment of the invention.
  • the frame members 29, 30a, 30b, 31a, 31b, 32a, 32b, 33a, 33b and 34 are made of 7075 T6 aluminum, 0.020 inches (.0508 cms.) thick.
  • Fig. 33 The metal is formed as shown and fastened together by the use of the pop rivet 7.
  • a plastic tube 38 is used in the holes as a guide for the racket strings and prevents the metal edges from cutting the strings.
  • Shown in Fig. 34 is the crossection 34-34 shown in Fig.
  • Fig. 35 shows the crossection 35-35 shown in Fig.
  • Fig. 36 shows the crossection of the handle grip 36-36 in Fig. 31.
  • openings 35 are provided for the plastic tube 38
  • openings 36 are provided in the handle to reduce the weight yet maintain bending and torsional rigidity.
  • Openings 37 are provided in the handle end to reduce the weight.
  • the weight, weight distribution, and rigidity is in accordance with the objectives given for the previous embodiments. Shown in Fig. 37 is an embodiment which allows the moment of inertia of the racket to be changed.
  • 38 is the extruded frame.
  • Cross member 39 in Fig. 37 is fastened to member 38 by rivets.
  • Member 49 is a handle suitably fastened to member 38.
  • Fig. 38 is a view of the section 38-38 of Fig.
  • the member 38 has tubular openings 40a and 40b and a central portion 41.
  • Fig. 39 is a view of the section 39-39 of a portion of member 38 as shown in Fig. 37.
  • Shown in Fig. 39 are lead pellets 42 located in the tubular openings 40a and 40b. These lead pellets may move in these tubular openings but are stopped by the pins 50 shown in Fig. 37. These lead pellets can be restrained in their movement by the spring 44 shown in Fig. 39. When the spring 44 is in the normal position shown, the lead pellets cannot move in the direction shown past the spring end. However, they can move in the opposite direction past the spring end, since the movement of the weight forces the spring to swing out. of the way.
  • the flexible nylon string 45 is pulled through the hole 46 so as to pull the ends of the spring 44 out of the way of the pellets.
  • the spring 44 is shaped as shown in Fig. 39, and is fastened to the central portion 41 of frame member 38 by a rivet 47.
  • the members 38, 45, 44 and the hole 46 constitutes a valve which allows the player to lock a group of lead pellets between the stops 50 and the ends of the spring 44. Valves are positioned at locations K, L, H and J shown in Fig. 37. Thus, the player can hold the racket vertical and allow the pellets to be locked between the locations H and J and the stops 50.
  • the string 45 may be pulled releasing the lead pellets under centrifugal force to lodge between locations K and L and the stops 50 and be locked there until released.
  • the player may also shift the pellets without swinging the racket by raising or lowering the racket head vertically and operating the valves.
  • the weight, weight distribution, and rigidity of the rest of the embodiment conforms to the objectives of this invention shown in the previous embodiments.

Landscapes

  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Physical Education & Sports Medicine (AREA)
  • Pulmonology (AREA)
  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Golf Clubs (AREA)

Abstract

Une raquette de tennis possede le meme poids de balancement que les raquettes de tennis de la technique anterieure mais possede une reduction importante du poids et une augmentation notable de la distance du centre de percussion (Cp) et de la distance du centre de gravite (CG) a l'extremite du manche (1). On obtient une reduction notable de la deflection et de la vibration de la raquette causees par l'impact de la balle. La tendance de la raquette a tourner dans la main du joueur lorsqu'une balle frappe la raquette en un point (C2) en dehors de l'axe longitudinal (a-a) de la raquette, est reduite. Ces ameliorations sont obtenues par la distribution du poids et de la rigidite de la raquette obtenue par la distribution du materiau, la forme, et la forme en coupe transversale sur la longueur, la largeur et la profondeur de la partie de la tete (9), de la partie de coeur (C) et de la portion du manche (1) ainsi que par l'utilisation de materiaux ayant une forte rigidite et une forte resistance par unite de poids. Des procedes sont proposes pour estimer une raquette par son poids de balancement mesure physiquement, son poids, sa frequence de vibration, la localisation du centre de gravite, la localisation du centre de percussion et les localisations des pivots nodaux associes a la frequence de vibration.
EP79901459A 1979-05-17 1980-12-01 Raquette de tennis Withdrawn EP0028599A1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US1979/000328 WO1980002510A1 (fr) 1979-05-17 1979-05-17 Raquette de tennis

Publications (1)

Publication Number Publication Date
EP0028599A1 true EP0028599A1 (fr) 1981-05-20

Family

ID=22147591

Family Applications (1)

Application Number Title Priority Date Filing Date
EP79901459A Withdrawn EP0028599A1 (fr) 1979-05-17 1980-12-01 Raquette de tennis

Country Status (2)

Country Link
EP (1) EP0028599A1 (fr)
WO (1) WO1980002510A1 (fr)

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2585256B1 (fr) * 1985-07-29 1988-08-19 Leyssene Bruno Systeme antivibration pour raquette de tennis
US4761214A (en) 1985-11-27 1988-08-02 Airfoil Textron Inc. ECM machine with mechanisms for venting and clamping a workpart shroud
JPH0429624Y2 (fr) * 1987-11-17 1992-07-17
US4903967A (en) * 1989-01-27 1990-02-27 Ferrari Importing Company, Inc. Racket frame having holes for tailoring frame stiffness
GB2259020A (en) * 1991-08-29 1993-03-03 Kuni Tseng Badminton racket
US5219165A (en) * 1991-12-30 1993-06-15 Gencorp Inc. Tennis racquet
US5249799A (en) * 1992-07-24 1993-10-05 Chang Chen Chung Racket including a metal reinforced throat section
DE102013011174B4 (de) * 2013-07-04 2016-08-18 Head Technology Gmbh Magnesiumschläger

Family Cites Families (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE605166C (de) * 1934-11-05 Richard Berthold Tennisschlaeger mit metallenem Saitenrahmen
GB107660A (en) * 1916-07-17 1917-07-12 Morton Rallinshaw Improvements in or relating to Tennis Rackets.
US1587919A (en) * 1922-04-26 1926-06-08 Spalding & Bros Ag Racket
US1539019A (en) * 1924-02-07 1925-05-26 John P Nikonow Tennis racket
GB284754A (en) * 1926-11-01 1928-02-01 Harold Willing Norton Improvements in or relating to rackets for tennis and like games
FR800262A (fr) * 1935-04-05 1936-07-01 Raquette pour tennis et autres jeux, en métal léger et procédé de fabrication
US2164631A (en) * 1937-01-16 1939-07-04 Abell Rollin Racket
US2224567A (en) * 1939-06-20 1940-12-10 Milton B Reach Racket or the like
GB547946A (en) * 1941-03-10 1942-09-18 Roland Gwynne Davies Improvements in or relating to frictional anti-slipping means
US3147012A (en) * 1961-11-14 1964-09-01 Louis F Muccino Slip resistant grip for handles of golf clubs
US3809402A (en) * 1969-01-02 1974-05-07 Dunlop Holdings Ltd Tennis rackets and frames therefor
US3647211A (en) * 1970-06-08 1972-03-07 James H Doessel Plastic tennis racket having predetermined cross sections effecting flexibility
US3751034A (en) * 1970-11-02 1973-08-07 True Temper Corp Game racket
US3752478A (en) * 1971-03-26 1973-08-14 Questar Corp Racket frame
US3724850A (en) * 1971-04-12 1973-04-03 R Stevens Racket with string tension adjusting means
US3801099A (en) * 1971-06-23 1974-04-02 J Lair Tennis racquet
US3941380A (en) * 1972-07-31 1976-03-02 Patentex S.A. Tennis rackets and similar implements with vibration damper
US3986716A (en) * 1974-09-23 1976-10-19 Arundale Manufacturers, Inc. Composite racquet structure

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO8002510A1 *

Also Published As

Publication number Publication date
WO1980002510A1 (fr) 1980-11-27

Similar Documents

Publication Publication Date Title
US4165071A (en) Tennis racket
US4291574A (en) Tennis racket
USRE31419E (en) Tennis racket
US4192505A (en) Game racket
US4690405A (en) Tennis racket
US4353551A (en) Tennis racket with frame mounted oscillatable weights
US20030145686A1 (en) Impact instrument
EP0317711B1 (fr) Raquettes pour jeux de balles
US4057250A (en) Tennis racket construction
EP2777776B1 (fr) Raquette de tennis ayant des caractéristiques de jeu améliorées
EP0028599A1 (fr) Raquette de tennis
Cross Flexible beam analysis of the effects of string tension and frame stiffness on racket performance
US5816963A (en) Sports bats
EP0032506A1 (fr) Raquette de tennis.
JP2505667B2 (ja) スカッシュラケット
JP2651565B2 (ja) 打球具
Russell Hoop frequency as a predictor of performance for softball bats
US4367874A (en) Tennis racquet and method of making same
US6059674A (en) Racquetball racquet
US5599018A (en) Strung racket
JP2636721B2 (ja) テニス用ラケット
JPH0515617A (ja) テニスラケツトフレーム
Vedula et al. An experimental and finite element study of the relationship amongst the sweet spot, cop and vibration nodes in baseball bats
JP2003093548A (ja) ラケットフレーム
JP2667788B2 (ja) テニスラケット

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): CH DE FR GB LU SE

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 19810513