Abstract:
In some embodiments, devices for measuring strings of a racket include a housing and a button. The devices also include a setting device that determines the frame size of the racket in response to the button being depressed and a spring system that adjusts pre-tension of the strings in response to the button being depressed. The devices further include a calibrated leaf spring having strain gages and an adjustment screw which is affixed to the button and which makes the starting measuring pressure onto the calibrated leaf spring adjustable. The devices still further include a fixing part which becomes fixed to the housing when force is applied to the button that causes the spring system to reach a specified level of compression and a display that reflects pressure on the strings in response to pressure applied to the strain gages.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application claims the priority under 35 U.S.C. § 119 to European Patent Application No. EP06009936, filed May 15, 2006, which is hereby incorporated by reference herein in its entirety. 
   TECHNICAL FIELD 
   The disclosed subject matter relates to devices for measuring strings of a racket and ball quality. 
   BACKGROUND 
   The game of tennis, and similar racket-based games such as racket ball and squash, have wide spread popularity around the world. When playing racket-based games, whether for recreation or professionally, it is important to have a racket with proper string tension. 
   Current devices for measuring string tension are inadequate in that none make a combined measurement of the racket string hardness and the string elasticity of the racket string tension, make a measurement racket string hardness and string elasticity simultaneously and independently of the size of the racket head and its string tension density, have a high measured value resolution and are insensitive with respect to side effects such as the influence of temperature and different conditions when playing, and permit self-adjustment of the device in the event of side effects. 
   SUMMARY 
   Devices for measuring strings of a racket and ball quality are provided. In some embodiments, a device for measuring strings of a racket comprises: a housing; a button; a setting device that determines the frame size of the racket in response to the button being depressed; a spring system that adjustments pre-tension of the strings in response to the button being depressed; a calibrated leaf spring having strain gages; an adjustment screw which is affixed to the button and which makes the starting measuring pressure onto the calibrated leaf spring adjustable; a fixing part which becomes fixed to the housing when force is applied to the button that causes the spring system to reach a specified level of compression; and a display that reflects pressure on the strings in response to pressure applied to the strain gages. 
   In some embodiments, a device for measuring ball quality comprises: a housing; a button; a spring system that adjustments pre-tension on the ball in response to the button being depressed; a calibrated leaf spring having strain gages; an adjustment screw which is affixed to the button and which makes the starting measuring pressure onto the calibrated leaf spring adjustable; a fixing part which becomes fixed to the housing when force is applied to the button that causes the spring system to reach a specified level of compression; and a display that reflects pressure on the ball in response to pressure applied to the strain gages. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross-sectional view of a device for measuring string tension hardness of a racket in accordance with some embodiments. 
       FIG. 2  is a cross-sectional view of a device for measuring the elasticity coefficient of a racket in accordance with some embodiments. 
       FIG. 3  is a cross-sectional view of a mechanical device for measuring string tension hardness of a racket in accordance with some embodiments. 
       FIG. 4  is a cross-sectional view of a device for measuring the quality of balls in accordance with some embodiments. 
       FIG. 5  is a cross-sectional view of a device for measuring string tension hardness of a racket that sits on the strings in accordance with some embodiments. 
       FIG. 6  includes cross-sectional views of details of  FIG. 1  is accordance with some embodiments. 
   

   DETAILED DESCRIPTION 
   Devices for measuring strings of a racket and ball quality are provided. In some embodiments, these devices provide for the measurement of the string hardness and string elasticity of rackets, such as tennis rackets, racket ball rackets, squash rackets, and any other suitable rackets. In some embodiment, a racket may comprise a handle and a frame bounding an area strung with strings. The strings may be woven with one another within the frame boundary such that they form a square mesh network which provides the required contact surface for a game ball. The strings may also be configured to keep the air resistance formed by the strings low when swinging the racket. In some embodiments, devices are used to measure ball quality. 
     FIG. 1  shows a measuring device  100  in cross-section in accordance with some embodiments. For measurement purposes, the base of the device housing  3  is placed on a racket frame  22  with respect to its center. The measurement is started and completed by pressing on switch  9  along slide track  10  until a signal sound is emitted. The measuring device can then be removed from the racket. The values of the racket string tension hardness and of the stretch capability of the strings appear on a digital display  12  of the measuring device. 
   When the measuring device is placed onto the racket frame  22 , the connection part  18  is pressed onto the pressure surface  24  and  25 , whereby the pressure surface  24 ,  25  is in contact with the racket strings  21 . 
   Four paths have to be overcome within the measuring device during the total measuring process: the measuring path  20  via the spring  6 ; the measuring path  23  via the spring  8 ; the measuring path  50  via the spring  51  (shown in  FIG. 6 ); and the lead path via the spring  8  in the device part  18 . 
   As the measuring process progresses, the spring  8  presses onto connection part  18  and thus onto pressure surfaces  24  and  25  because of the pressure onto switch  9 , and path  20  is closed simultaneously by overcoming compression spring  6 . During this process, the connection part  18  is closed with the function part  7  causing the housing part  2  to press clamping ball  4  onto the track  3 A via the spring  1 , whereby device part  5  is fixed in the housing  3 . The lead path  20  is thus closed and the ball  4  fixes the part  5  of the device within the framework of the height variation between the device housing  3  and the racket frame  22 , with the spring  6  and spring  18 B passing the built-up pressure onto the pressure surface  24  and  25  and further onto the racket strings  21 . This pressure as a result provides the required pre-tensioning for the pre-adjustment by means of the contact part  24  and  25  on the racket strings for the following main measurement process. 
   The basic measuring process starts after the pre-procedure. In this procedure, the counter-pressure of the racket strings  21  is directly transferred via the pressure surface  24  and the compensation rocker  25  onto calibrated leaf springs with affixed strain gages  17  and the measuring process is thus initiated. Strain gages  17  may use a compensation rocker  16  (shown in  FIG. 6 ) for pressure transmission and may be adjusted using an adjustment screw  14  (also shown in  FIG. 6 ). The measuring process is maintained by temporary pressing on the push-button  9  until the measuring path  23  is closed and the setting device for the racket head size  19  contacts the sensor  18 A, which signifies that all paths and measurement paths have finished closing and thus that the measuring process is completed. 
   As will be apparent to one of skill in the art, any suitable circuitry  15  can be used to measure the stress on strain gages  17  and reflect that stress on a display  12  visible through a transparent window  13 . These electronics may be powered by a battery in a compartment  11 . 
     FIG. 2  shows the measuring device as in  FIG. 1  with an expanded measurement range for the measurement of the elasticity coefficient. The total measuring path  23 B is affixed in accordance with  FIG. 2  between the setting device of the racket head size  19  to be measured with part  5  and sensor  26  over a larger path  26 A which also takes account of the run-out path  27  and  28 . The final stage of the measurement of the string tension hardness of the racket head strings is designed such that it will take place between the function part  18  and  18 A and the measuring path  23 B and the run-out path part  28 . On the measurement of the elasticity coefficient of the strings  21  after the measurement of the string tension hardness in accordance with  FIG. 1 , the parts  19  and  26  from the total path  26 A are brought into contact with one another and the end of the total measurement is transmitted to the electronic system by this closure. In this measuring process, the parts  18 A and  28 , which are closed, are designed via the spring  27  so that the required run-out path for the measurement of the elasticity coefficient extends over a longer path, as shown by  26 A. The measurement result of the elasticity coefficient takes place by means of an electronic evaluation circuit  15  and display  12 . 
     FIG. 3  shows a modification in accordance with a mechanical functional principle on the basis of  FIG. 1  in accordance with some embodiments. The measuring procedure starts as described by  FIG. 1  with the pressing of the switch  9  temporarily until a signal sounds. When the measuring device  3  is placed onto the racket head frame  22 , the connection part  18  is pressed via the spring  8  onto the pressure surface  24  and  25  so that the pressure surface lies on the racket strings  21 . During the measuring procedure, four paths have to be overcome within the measuring device: measuring path  20  via the spring  6 ; measuring path  44  via the spring  8 ; measuring path  50  via the spring  51  (shown in  FIG. 6 ); and the lead path via the spring  18 B in part  18 . On the progressing of the measuring procedure, the spring  8  of the part  18  is pressed via pressure on switch  9  onto the pressure surface  24  and  25  and the path  20  is closed by overcoming the pressure on spring  6 . As a consequence, the part  18  comes into contact with the function part  46  and the ball  4  is pressed onto the fixing track  3 A by spring  1  and part  2 , whereby a clamping process is exerted onto the housing  3 . The lead path is thus simultaneously closed and ball  4  fixes the part  5  for the vertical adjustment between  3  and the racket head frame  22 , with the spring  6  passing on the built-up pressure to  21  via  24  and  25 . The pressure of springs  6  and  51  provides the required pre-tension for the pre-adjustment onto  21  via  24  and  25  for the measuring procedure. The latter part of the measuring procedure starts when part  5  is fixed by temporary pressing on the switch  9 . The end of measurement takes place via the mechanical build-up of the positions  19  and  45  and is reached by a signal sound via the sensory signal transducer  48 . The altered path distance is transferred as the measuring path via the gear  42  onto the sliding device  36  and then onto the display  41 . The function for mechanical and automatic measuring procedures in a measuring device is reached. 
     FIG. 4  shows the measuring device as in  FIG. 1  which is suitable for measuring tennis ball quality as modified by means of elements  29 ,  30 ,  32  and  33 . Part  32  holds tennis ball  31 . The counter-pressure base is the pressure surface  24 ,  25 . The measuring procedure takes place as with  FIG. 1 . 
     FIG. 5  shows as an example the measuring device as in  FIG. 1 , with the exception of the modification of the measuring device base  3 , which does not lie on the tennis racket frame  22 , but directly on the strings  21 . 
     FIG. 6  shows detailed representations of the pressure surface  24  and  25  and of the compensation rocker  16 . 
   As shown, various embodiments of the invention provide a significant enrichment of ball games using rackets with a net-strung racket head, in particular, for tennis, whether for amateurs or professionals. The string tension hardness and string elasticity of the racket head strings can be optimized by means of the device, thereby saving the replacement of racket material which is still good and relieving physical strain on users (which may result in relief of cases of tennis elbow). 
   The following reference numerals are used throughout the figures:  1 —spring for the vertical adjustment for the lead path of the measuring procedure;  2 —fixing part for the vertical regulation;  3 —device base with roughened surface  3 A for the purpose of fixing the ball  4 ;  4 —clamping ball for the fixing of the vertical position;  5 —compensation rocker  25  relative between the racket frame height and the string tension moving part for the vertical compensation with different racket frame height;  6 ,  8 —springs of different tensioning force for the lead path and adjustment of the measuring procedure;  7 —function part and sensor of the lead path boundary and switching on of the electronics;  9 —switch button for the switching on and temporary switching of the measuring procedure;  10 —slide track for pressure button;  11 —compartment for battery;  12 —measured value display which is contained within transparent window  13 ;  14 —adjustment screw—starting point setting for the measuring procedure;  15 —container for electronics;  16 —compensation rocker for the pressure transmission;  17 —calibrated leaf springs with strain gages;  18 ,  18 A,  18 B—function contact part for lead path and measurement path boundary with sensor  18 A and spring  18 B for the lead path;  19 —device for racket head size adjustment;  20 —distance path for the pre-adjustment and electronic activation;  21 —racket head strings;  22 —racket head frame, which may have different heights and strengths;  23 ,  26 A—total measuring path, plus electrical and mechanical end stops for the measuring procedure;  23 B—in  FIG. 2 , replaces the electrical function of  23  in accordance with  FIG. 1 ;  24 —pressure contact surface of the device on the racket head strings;  25 —compensation rocker as pressure transfer to the racket head strings;  26 ,  19 —mechanical end stops of the total measurement path—as in  FIG. 1 , plus sensory electronic contact for the end of the measurement of the string elasticity coefficients in the case in accordance with  FIG. 2 ;  26 A—measurement path for elasticity coefficient;  27 —springs for the run-out path for the measurement of the elasticity coefficient;  28 —run-out path function part for the measurement of the elasticity coefficient;  29 —device modification for the measurement of the tennis ball quality;  30 —anti-slip soft rubber stoppers;  31 —tennis ball;  32 —counter-pressure surface and centering of the tennis ball;  33 —fixing element for the measuring device and the tennis ball containment;  34 —toothed bolt for the transfer of the measuring path onto the scale band;  35 —adjustment device for the adjustment of the measurement display;  36 —sliding device for the movement of the measurement display  41 ;  37 —starting adjustment point for the scale band, with calibrated display in Kp;  38 —calibrated display of the measured results in Kp;  39 —longitudinal compensation spring for the sliding device  36 ;  40 —position  36  slides  41  up to and into the end position;  41 —display pin that measures maximum value and is resettable after the measurement;  42 —gear for the measurement path transfer to the display field;  43 —linear compression spring for the triggering of different measuring paths in dependence on the counter-pressure and the running paths;  44 —default path for the fixing of the measuring stop process;  45 —sensor-triggered electrical stop contact for the bounding of the path on a signal sound;  46 —automatic pre-adjustment path for the measuring procedure;  47 —battery for electronics and signal transducer;  48 —signal trigger;  49 —adjustment element;  50 —path for adjustment of the measuring pressure transfer;  51 —bias spring for adjustment;  52 —vertical adjustment part for different frame heights of the rackets; and  53 —counter-piece for the receiving of the spring  51  in accordance with  FIG. 3 . 
   Although the invention has been described and illustrated in the foregoing illustrative embodiments, it is understood that the present disclosure has been made only by way of example, and that numerous changes in the details of implementation of the invention can be made without departing from the spirit and scope of the invention, which is only limited by the claims which follow. Features of the disclosed embodiments can be combined and rearranged in various ways.