Abstract:
A racket assembly having a racket head that is supported by a handle. A string is strung across the racket head forming a string face. The string used in the string face is statistically likely to fail after the string face has been impacted a precalculated number of times. At least one sensor is provided for sensing when the racket head experiences a change in acceleration that exceeds a predetermined threshold level. A logic circuit creates a count corresponding to the number of times the sensor detects a change in acceleration in excess of the predetermined threshold level. An indicator is provided that creates an indication when the count approaches the precalculated number. In this manner, a person is warned when the string of the racket is statistically likely to fail.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to rackets that are used in sports activities such as tennis, racquetball, squash, badminton and the like. More particularly, the present invention relates to rackets and electronic devices that attach to rackets and gather data from the strings of the racket. 
   2. Description of the Prior Art 
   There are many sports that are played with a racket. One of the most popular of these sports is tennis. In the game of tennis, the racket includes an oblong head section supported by a handle. A string is strung back and forth through the head section of the racket, thereby producing a mesh structure. The mesh structure creates the surface that is used in the game to contact the ball. 
   In the prior art, the head sections of rackets have been typically manufactured with periodic apertures. To create the mesh structure across the head of the racket, a single unbroken string is woven through the various apertures. As the string is being woven through the apertures in the head section of the racket, the string is kept at a preset tension that is desired by the player. 
   Since the stringing of a racket with a single string is a complicated process, most players have their rackets professionally strung. A professional stringer typically has a stringing machine that assists in weaving the string through the various apertures in the head section of the racket at the appropriate tension. One problem associated with having a racket professionally strung is that it is expensive and inconvenient. If the racket string breaks during a game, the player cannot fix the racket string and continue with the game. Rather, a player must either change rackets or stop playing. 
   Recreational tennis players often own inexpensive rackets. Commonly, a recreational player can buy an inexpensive new pre-strung racket for less money than it would cost to have their old racket professionally pre-strung. However, players with expensive rackets have little choice but to restring their rackets if the string breaks. 
   When the racket string of a conventional racket breaks, the string becomes loose and leaves the weave pattern. Since only one string is used, the broken string eventually unwinds to a point where the racket is no longer functional. 
   The primary reason that a string in a racket breaks is due to fatigue. When a ball strikes a racket, the string is stretched. Once the ball rebounds from the racket, the string again contracts. The stretching and contracting cycles of the string cause fatigue in the material of the string. Depending upon the tension of the string, the material of the string and the diameter of the string, the string may break between a few hundred strikes and a few thousand strikes. 
   In the prior art, there are several electronic devices that attach to rackets. Many of these electronic devices are used to count calories or to keep score of the game. Consider, for example, the score keeping device in U.S. Pat. No, D458,171 to Lin, entitled Racket Counter. Consider also the calorie counter in U.S. Pat. No. 6,409,616 to Lin, entitled Calorie Counter Racket. 
   In U.S. Pat. No. 4,822,042 to Landsman, entitled Electronic Athletic Equipment, a system is shown where sensors are attached to various strings in a racket. The sensors are used to determine if a player is striking a ball with the proper portion of the racket. Although this system does collect data from the strings relating to ball impact, the system requires a specialized racket head having sensors placed around the periphery of the string field. Such systems do not track impacts for the purpose of determining string fatigue and the statistical probability that the string will break. 
   A need exists in the art for a system that can be added to standard racket designs that counts how many times the racket has been used to impact a ball and provides some indication of when a racket&#39;s strings are approaching failure. In this manner, a racket can be serviced prior to the failure of the string and the string will not fail during play. This need is met by the present invention as described and claimed below. 
   SUMMARY OF THE INVENTION 
   The present invention is a racket assembly such as that used in the game of tennis, racquetball, squash, badminton and the like. A racket assembly has a racket head that is supported by a handle. A string is strung across the racket head forming a string face. The string used in the string face is statistically likely to fail after the string face has been impacted a precalculated number of times. 
   At least one sensor is provided for sensing when the racket head experiences a change in acceleration that exceeds a predetermined threshold level. A logic circuit creates a count corresponding to the number of times the sensor(s) detect a change in acceleration in excess of the predetermined threshold level. Finally, an indicator is provided that creates an indication when the count approaches the precalculated number. In this manner, a person is warned when the string of the racket is statistically likely to fail. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a better understanding of the present invention, reference is made to the following description of an exemplary embodiment thereof, considered in conjunction with the accompanying drawings, in which: 
       FIG. 1  is a front view of one preferred embodiment of a racket in accordance with the present invention; 
       FIG. 2  is a graph that plots acceleration forces for a series of impact events; 
       FIG. 3  is an enlarged view of the electronic module shown in  FIG. 1 ; and 
       FIG. 4  is a schematic of an exemplary embodiment of the electronics module. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Although the present invention assembly can be used in association with any strung racket, such as a racquetball racket, a squash racket, a badminton racket or the like, the present invention assembly is particularly well suited for use as a tennis racket. Accordingly, the exemplary embodiment of the present invention assembly will be described in an application as a tennis racket. However, it will be understood that any other type of racket can be substituted for the tennis racket described. 
   Referring to  FIG. 1 , a tennis racket assembly  10  is shown in accordance with the present invention. The tennis racket assembly  10  includes an elliptical head section  12  that supports a string  14  that is interwoven into vertical and horizontal rows. The interweaving of the string  14  in the head section  12  creates the string face  16  of the tennis racket assembly  10 . It is the string face  16  of the tennis racket assembly  10  that is used to strike a tennis ball  17 . 
   The head section  12  is attached to a handle  18  by a tapered neck  22 , such as is standard in the industry. 
   An electronics module  20  is set into the tennis racket assembly  10  within the area of the tapered neck  22 . As such, the electronics module  20  is supported on the tennis racket assembly  10  above the point where a player grips the handle  18 . The electronics module  20 , therefore, always experiences a swinging movement when the tennis racket assembly  10  is swung. 
   When the tennis racket assembly  10  is swung, the head  12  of the racket assembly  10  experiences both positive and negative G-forces. Referring briefly to  FIG. 2 , it can be seen that the G-forces experienced by the head section of the tennis racket assembly fluctuate as the tennis racket assembly is swung in the air or changed from hand to hand by a player. These mild fluctuations are shown by the low amplitude sinusoidal pattern  25 . However, when the tennis racket assembly is swung hard and actually impacts a tennis ball, an impact spike  26  is created that shows a dramatic change in acceleration. A threshold level  28  is set. The threshold level  28  is not reached during normal manipulations of the tennis racket assembly. Rather, the threshold level  28  is set high enough so that only the impact spike  26  of a solid ball impact during play will surpass the threshold level  28 . 
   Smaller spikes  29  in acceleration may occur if a player is using the tennis racket assembly to bounce a ball. However, these smaller spikes  29  do not reach the threshold level  28 . Accordingly, only a solid impact during play will create an acceleration event, such as the impact spike  26 , that surpasses the set threshold level  28 . 
   Returning to  FIG. 1 , it will be understood that as the tennis racket assembly  10  experiences changes in acceleration, the string face  16  deforms. Deformation of the string face  16  that is caused by the tennis racket assembly  10  being swung through the air is negligible. The only deformations that count toward the fatigue failure of the string face  16  are accelerations that surpass the threshold level  28  shown in  FIG. 2 . This type of acceleration only occurs when a player strikes the tennis ball  17  firmly with the racket assembly  10  during play. As a tennis ball  17  contacts the tennis racket assembly  10 , the string face  16  deforms. The deformation cycles the string  14  thereby causing that string  14  to come closer to failing from fatigue. 
   The electronics module  20  counts only acceleration events that surpass the threshold value  28  shown in  FIG. 2 . Thus, the electronics module  20  counts how many times the tennis racket assembly  10  has firmly struck a ball, and thus how many times the string face  16  has been significantly deformed. 
   The number of deformation cycles until failure are known by racket designers. The number of cycles until failure is programmed into the electronics module  20 . The electronics module  20  compares the number of acceleration events detected to the predicted cycles until failure. As the number of detected acceleration events approaches the predicted number of cycles until failure, a warning indication is provided. 
   Referring to  FIG. 3  in conjunction with  FIG. 4 , it can be seen that the electronics module  20  has a logic circuit  30 , a digital display  32 , light indicators  34 , a speaker  36  and input controls  38 . The logic circuit  30  counts the number of acceleration events that have occurred and compares that number to the predicted failure number. The number of acceleration events that have occurred, or the number of acceleration events that are left to occur are displayed upon the digital display  32 . 
   The light indicators  34 , in the shown embodiment, include a green light indicator  41 , a yellow light indicator  42  and a red light indicator  43 . If the number of acceleration events is less than seventy five percent (75%) of the number predicted to failure, then the green light indicator  41  is lit. If the number of acceleration events exceeds seventy five percent (75%) but is less than ninety five percent (95%) of the predicted failure number, then the yellow indicator light  42  is lit. Lastly, if the number of acceleration events surpasses ninety five percent (95%) of the predicted maximum, then the red indicator light  43  is lit. 
   The use of the three light indicators  34  can be supplemented or replaced by the use of a tone generator  44 . The tone generator  44  is coupled to the speaker  36 . The tone generator  44  can produce tones, either periodically, or after each acceleration event, that are indicative of the status of the string. The tone can change pitch, frequency, volume and/or melody as the number of acceleration events approaches the predicted failure number. 
   The input controls  38  preferably include a mode select switch  46 . The mode select switch  46  is used to adjust the direction of count. By using the mode select switch  46 , the logic circuit  30  can be caused to either count up to a predicted failure number or count down from a predicted failure number. 
   A count set switch  48  is also provided. The count set switch  48  enables a person to input the predicted failure number. The failure number is a function of string diameter, string material, string tension and racket head configuration. The predicted failure number may be predetermined by the racket manufacturer and preprogrammed into the logic circuit  30 . Alternatively, a person can be able to find the predicted failure number by referencing a precalculated reference chart. 
   A reset switch  50  is provided that enables the electronics module  20  to restart the count sequence when the string of the tennis racket assembly is replaced. 
   Returning to  FIG. 1 , it can be understood that to use the present invention, the following steps are followed. First, a tennis racket assembly  10  is provided that contains the electronics module  20 . The tennis racket assembly  10  can be manufactured with the electronics module  20  or the electronics module  20  can be retroactively added to the tennis racket assembly  10 . 
   Second, the predicted failure number for the string  14  used in that tennis racket assembly  10  is programmed into the electronics module  20 . 
   Third, the count sequence is started. Once the count sequence is started, only acceleration events that significantly deform the string  14  are counted. As the number of acceleration events approaches the predicted failure number, some indication is provided. 
   The indications can be visual and/or audible and enables a person to determine when the string  14  used in the tennis racket assembly  10  is statistically predicted to break. The person using the tennis racket assembly  10  will therefore have the opportunity to change the string before it breaks during a game. As a result, the player will have his/her racket fail less often during play. 
   It will be understood that the figures described above illustrate only one exemplary embodiment of the present invention. A person skilled in the art can make numerous alterations and modifications to the shown embodiment utilizing functionally equivalent components to those shown and described. For example, the colored light indicators can be replaced by a diminishing bar graph or histogram that is displayed on the digital display. Furthermore, the location and type of input controls can be varied to the needs of the manufacturer. The tone generator and input controls are also optional and the invention can be practiced without these features. All such modifications are intended to be included within the scope of the present invention as defined by the appended claims.