Abstract:
A device adapted to be emplaced in a self-securing manner between adjacent strings of a tennis racquet for dampening vibrations caused by impact with a tennis ball produces beneficial sensory effects such as a whistling sound and flashing light.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to strung hand held sports racquets, and more particularly concerns devices for attachment to the strings of such racquets to attenuate vibrational effects produced by impact with a ball. 
   2. Discussion of the Prior Art 
   Most strung hand held sporting racquets have a striking surface or face formed of two intersecting sets of parallel strings suspended by and enclosed by an oval frame. One set of strings extends generally parallel to the handle of the racquet and may be called the longitudinal strings, while the other set of strings extends generally transversely of the handle and may be called the transverse or lateral strings. At their sites of intersection, the strings are interwoven in alternating over and under paths, creating an overall pattern of rectangular apertures, each aperture being defined by two adjacent longitudinal strings and two adjacent transverse strings. 
   In such racquets, vibrations are produced in the racquet face when a ball is struck. The vibrations are transmitted to the frame of the racquet and eventually to the hand and then the arm of the player. It has been shown that a player who has been subject to extensive periods of racquet-induced vibrations can sustain “tennis elbow” injury to his or her arm. It is therefore desirable to reduce such vibrations both for the comfort and protection of the player. 
   Devices for dampening the vibrations in a tennis racquet are well known. Typical devices are shown in U.S. Pat. Nos. 4,180,265; 4,609,194; 4,761,007; 4,776,590; 4,909,509; 5,022,651; 5,106,086; 5,137,769; 5,792,011; 5,871,409; 6,447,411 and 7,014,579. Devices as shown in prior patents have not been entirely successful, since they are sometimes difficult to attach to the racquet face, and can interfere with the flight of the ball if struck by the ball. Also, such devices often fall off the racquet strings during play. 
   U.S. Pat. No. 4,927,143 discloses a vibration dampener device having a rubbery body with a circumferential groove adapted to grip the four strings of a rectangular aperture in the striking surface. The center of the body houses a dampening fluid and interactive ball. Although useful for its intended purpose, it does not serve to enhance the proficiency of the player or the enjoyment of the game. 
   It is accordingly an object of the present invention to provide a vibration absorbing device for use in a strung sports racquet. 
   It is a further object of this invention to provide a device as in the foregoing object which is easily installed onto the strings of a racquet and durably retained therein. 
   It is another object of the present invention to provide a device of the aforesaid nature which produces unique action activated special effects relating to enhancement of playing interest and expertise. 
   These objects and other objects and advantages of the invention will be apparent from the following description. 
   SUMMARY OF THE INVENTION 
   The above and other beneficial objects and advantages are accomplished in accordance with the present invention by a device adapted to be emplaced in a self-securing manner between adjacent strings of a tennis racquet for dampening vibrations caused by impact with a tennis ball and for causing a beneficial sensory effect to be produced by the customary use of said racquet, said device comprising:
     a) a monolithic anchoring base fabricated of a resilient polymer and bounded by parallel substantially flat faces spaced apart by a perimeter wall of oblong contour and a circular cylindrical bore orthogonally bridging said faces, said perimeter wall having recessed therein a continuous circumferential groove extending to a bottom that defines a square shelf configuration surrounding said bore and adapted to be embracingly contacted by said strings,   b) an insert assembly comprised of inner and outer components of rigid plastic construction, each having a circular cylindrical wall bounded by internal and external surfaces and extending between an open distal extremity and a proximal extremity having an outwardly directed flange adapted to abut against a face of said base, the external surface of the wall of said outer component residing in contact with said bore, and the external surface of the wall of said inner component being in contact with the internal surface of said outer component to permit sliding telescopic interaction of said components to form a chamber region within said bore, and   c) an action-activated element located within said chamber region.   

   In a first embodiment of the device, a piezoelectric mechanism is confined within said chamber. As an action-activated element, it emits light when said strings are impacted by a tennis ball. 
   In a second embodiment of the device, a conically shaped surface is associated with the proximal extremity of both components of the insert assembly, and directed toward an aperture positioned within said chamber region. Such construction represents an action-activated element. By virtue of critically dimensioned features of said conical surfaces and apertures, such second embodiment of the device, when installed into the strings of a tennis racquet, produces a whistling sound when the racquet is rapidly swung, the intensity of said sound being greater with faster swing velocities. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing forming a part of this specification and in which similar numerals of reference indicate corresponding parts in all the figures of the drawing: 
       FIG. 1  is an exploded enlarged front perspective view of a first embodiment of the device of this invention. 
       FIG. 2  is a front view of the embodiment of  FIG. 1 . 
       FIG. 3  is a side view of the embodiment of  FIG. 2 . 
       FIG. 4  is a sectional view taken in the direction of the arrows upon the line  4 - 4  of  FIG. 2 . 
       FIG. 5  is an exploded enlarged front perspective view of a second embodiment of the device of this invention. 
       FIG. 6  is a front view of the embodiment of  FIG. 5 . 
       FIG. 7  is a sectional view taken in the direction of the arrows upon line  7 - 7  of  FIG. 6 . 
       FIG. 8  is a further enlarged fragmentary sectional view of the centered components of  FIG. 7  in a separated state. 
       FIG. 9  is a front view of a tennis racquet having installed therein the device of this invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to  FIGS. 1-4 , a first embodiment  10  of the invention is shown comprised of a monolithic anchoring base  11  fabricated of a resilient polymer such as plasticized polyvinyl chloride, silicone, or other moldable elastomeric composition having a Shore A Durometer Hardness in the range of 20 to 50. Said base is bounded by parallel substantially flat faces  12  spaced apart by a perimeter wall  13  which defines the thickness of the base. Said wall is of oblong contour, having a longitudinal long axis  14  which terminates in slightly rounded first apices  15 , and a transverse short axis  16  that terminates in greatly rounded second apices  17 . The portions  18  of perimeter wall  13  which intervene between said apices may be substantially straight, causing the base to have a substantially trapezoidal shape. A circular cylindrical bore  19  extends orthogonally between and opens upon both faces  12 . Perimeter wall  13  has recessed therein a continuous circumferential groove  20  extending to a bottom  21  that defines a square shelf configuration  22  surrounding bore  19  and adapted to be embracingly contacted by the strings of the racquet. Said square configuration is oriented such that two opposed straight sides are parallel to said long axis, and the other opposed straight sides are parallel to said transverse axis. 
   In order to securely engage the strings of the racquet, the dimensional features of the base are of critical importance. In particular, said thickness should be about 11 millimeters. The longitudinal length should be about 24 millimeters, and the transverse length should be about 17 millimeters. The depth of groove  20 , measured between its bottom  21  and perimeter wall  13 , will vary along the path of the groove, but its width remains constant at about 1.6 mm. 
   An insert assembly  35  is comprised of inner and outer components  26  and  27 , respectively, of rigid plastic construction. Each component is comprised of a circular cylindrical wall  28  bounded by internal and external surfaces  29  and  30 , respectively. Said wall extends between an open distal extremity  31  and a proximal extremity  32  having an outwardly directed flange  33  adapted to abut against a face  12  of said base. The external surface of the wall of said outer component has a diameter of 9.5 mm, and resides in contact with bore  19 . External surface  30  of the wall of inner component  26  has a diameter of 8.5 mm and resides in contact with the internal surface  29  of said outer component to permit telescopically sliding interaction between the two components, as shown by the arrowed lines in  FIG. 8 , to form a chamber region  34  within said bore. 
   In said first embodiment of the device, an action-activated element in the form of a piezoelectric mechanism  35  is confined within said chamber region. Suitable piezoelectric mechanisms are commercially available in various sizes. As an action-activated element, mechanism  35  emits flashing light when the strings are impacted by a tennis ball. Such effect adds a pleasurable element of interest to the playing of the game. 
   In said second embodiment of the device, as shown in  FIGS. 5-8 , a conical or funnel shaped nozzle surface  37  is emergent from the proximal extremity of each component of insert assembly  25 , and is convergently directed toward the interior of chamber region  34 . Each nozzle surface terminates in a circular aperture  38  located within chamber region  34 . The apertures  38  of the nozzle surfaces of both components are in axial alignment and spaced apart by 2.5 to 3.5 mm. Such construction represents an action-activated element. 
   By virtue of critically dimensioned features of said nozzle surfaces and apertures, such second embodiment of the device, when installed into the strings of a tennis racquet, produces a whistling sound when the racquet is rapidly swung, the intensity of said sound being proportionately greater with faster swing velocities. In view of such functionality, the device serves as a training means to enhance the player&#39;s competence in playing the game of tennis. 
   In order for the aforesaid nozzle construction to produce a whistling sound, several parameters must be optimized. In particular, circular aperture  38  should have a diameter of 3.5 to 4.5 mm, and the diameter of circular entrance  46  of the nozzle surface should be between 10 and 11 mm, causing the preferred ratio of the diameter of aperture  38  to the diameter of entrance  42  to be between 0.32 and 0.45. The angle of convergence of nozzle surface  37  should be between 43 and 47 degrees, and the axial length of said nozzle surface should be between 4 and 6 mm. It is to be noted that the proximal extremity of outer component  27  contains an annular shelf region  40  which receives the distal extremity of inner component  26 . This permits a close fitting complete insertion of inner assembly  26  into outer assembly  27  while enabling both nozzle surfaces to be of identical dimensions. 
   When attached to a tennis racquet  40 , as shown in  FIG. 9 , the device of this invention is preferably caused to engage a rectangular aperture in the racquet face formed by two center strings  43  and two uppermost transverse strings  41  adjacent the frame  44 . The device is inserted into said aperture with the longitudinal axis of the device initially oriented with the longitudinal strings, then twisted a quarter turn so that said longitudinal axis becomes aligned with said transverse strings. Such action locks the device in place because the four strings comprising said rectangular aperture enter groove  20  and abut against the bottom  21  of square shelf  22 . Certain modifications of the device of this invention may also be usefully attached to the extremities of other sporting equipment, such as baseball bats and golf clubs, where high velocity swinging motion and impact with a ball are involved. 
   While particular examples of the present invention have been shown and described, it is apparent that changes and modifications may be made therein without departing from the invention in its broadest aspects. The aim of the appended claims, therefore, is to cover all such changes and modifications as fall within the true spirit and scope of the invention.