PATENT ABSTRACT
A training device which interactively guides a tennis racquet by exerting a towing force on a card which is connected to the tennis racquet. The device includes a vertically adjustable support connected with a guide pole fixed to a wall. A swivel arm is movably supported on the support and has a distal end which suspends a ball therefrom. The cord extends along the swivel arm and the support, and one end thereof is connected to the racquet through a stirrup.

PATENT DESCRIPTION
SUMMARY OF THE INVENTION 
     The basic purpose of the invention is to provide a training device for interactively guiding a tennis racquet by means of exercising a towing force on a cord, which is connected with the tennis racquet, in the sequence corresponding to some certain points and phases of the swing during the execution of the strokes. In particular, for the serve, fore-, and backhand smash, fore-, and backhand slice, and volley strokes. 
     This is achieved according to the invention with a training device, which includes a vertically adjustable support that is telescopically connected with a vertical guide pole that is fixed on the wall. On the upper part of the support is arranged a frame for supporting a shaft of a swivel-arm that is constructed such that the swivel-arm is slanted upward. 
     On the proximal end of the swivel-arm, a weight-balance is fixed that turns the swivel-arm into the upper position in which the swivel-arm is automatically arrested by means of an arresting mechanism fixed on the frame. On the distal end of the swivel-arm is fixed a ring, which includes a suspension arrangement to hang a ball. 
     On the support and the swivel-arm are arranged some pulleys and devices to exercise the towing force on the cord, which is connected with the tennis racquet through a stirrup. The mechanisms for exercising the towing force on the cord are adjustable to define the parameters such as direction, quantity, and timing of the towing force according to the kind of stroke, the body height of the player and the player&#39;s skill level. 
     The motto of the present training device is “Practice slowly, learn quicker”. That means: the player is not under pressure to respond quickly and can thereby feel and sense the whole movement involved. 
     The ball being placed in the ideal hitting zone gives even a beginner the possibility of hitting the ball in the very first practice. The player is able to watch in slow motion the way in which the racquet face comes to the ball. In particular, it is very important to watch the difference between the flat-, slice- and topspin serve swing at the meeting point. 
     The prescribed position of the hanging ball is defined by means of a stepping plate with marked footprints placed at certain distances from the hanging ball or from the ring. During serve training, the ring allows the player to visualize the ideal tossing zone, and both the direction and the height of the toss for the different kinds of serves, i.e., flat-, slice-, and topspin serves. 
     During training of the fore- and backhand slice and volley, the marked footprints give the player the possibility of training or learning the footwork in the sequence corresponding to the swing. 
     The cord, by being connected with the tennis racquet distinguishes the present training device, in particular by the interactive guiding of the tennis racquet during the swing. 
     The other portion of the cord runs through some pulleys and a moveable releasing device to an anchor point on the support. The towing force on the cord is exercised by means of an elastic rope that is fixed in the moveable releasing device. In addition, a trigger is mounted on the support to fix and release a bead that is pressed on the cord at a certain distance from the anchor point. 
     At the waiting stance for serve training, the bead is fixed in the trigger and the portion of the cord between the anchor point and the bead is strained by means of the elastic rope, the proximal end of the swivel-arm is free from the arresting mechanism to let it turn and thereby let a player pull the racquet down. 
     From the waiting stance to the end of the back swing (the upper, at-rest position of the swivel-arm), the weight-balance on the proximal end of the swivel arm exercises a relatively weak force on the cord to let same guide the tennis racquet in the correct way to the end of the back swing at which the proximal end of the swivel-arm is arrested. 
     Thus, the tennis player is forced to go through the prescribed position on the end of the back swing because the defined length of the cord does not allow dropping the right elbow lower than shoulder height and tilting the racquet shaft to the wall. 
     At the end of the back swing, there is no hindrance from the cord so as to allow the player to execute the next phase of the swing (i.e. a loop) in the correct direction back, downward. The construction of the stirrup does not allow the racquet and arm to go in the wrong direction, but rather allows the arm to drop the head of the racquet in the correct way, that is, to the small of the back. 
     At the lowest point of the loop, after a short plucking of the cord which releases the trigger, the towing force will be activated overall on the cord and a player will be interactively led to the next prescribed position of the swing, which includes the full stretching of the arm and body. 
     At the full stretching of the arm and body (the point is adjustable), the moveable releasing device enters into a releasing port that is adjustably mounted on the lower part of the support, and through this interaction the cord will be set free from the releasing device so as to allow the player to hit the hanging ball and follow-through without hindrance from the cord. 
     All points and phases of the swing are adjustable by means of shifting both the trigger and the releasing port. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be discussed in detail hereinafter in connection with the drawings, whereby the individual aspects and advantages of the invention, whether or not they have been discussed above, can be recognized more clearly. All figures of the drawings relate to the same preferred exemplary embodiment of the training device of the invention, whereby: 
     FIG. 1 is a side view of the device for serve training, 
     FIG. 2 is a top view of FIG. 1, 
     FIG. 3 shows the tennis player in position with a racquet at the lowest point of the loop of the serve swing, 
     FIG. 4 is an opposite side view of the device for slice, volley, and smash training, 
     FIG. 5 is a top view of FIG. 4 of the stepping plate for slice, volley and smash training, 
     FIG. 6 is a side view of FIG. 7, 
     FIG. 7 is a front view of the grip of the tennis racquet with the stirrup, 
     FIG. 8 is an enlarged fragmentary view of a top part of the holder shown in FIG. 1, 
     FIG. 9 is a cross-sectional view along the line IX—IX of FIG. 8, 
     FIG. 10 is an enlarged, fragmentary view of a lower part of the holder shown in FIG. 1, 
     FIG. 11 is a cross-sectional view along the line XI—XI of FIG. 10, 
     FIG. 12 is a longitudinal cross-sectional view along the line XII—XII of FIG. 13, 
     FIG. 13 is an enlarged, fragmentary front view of the lower part of the holder shown in FIG. 1, 
     FIG. 14 is an enlarged, fragmentary view of the top part of the holder shown in FIG. 4, 
     FIG. 15 is an enlarged, fragmentary front view of the releasing port shown in FIG. 14, and 
     FIG. 16 is a side view of FIG.  15 . 
    
    
     DETAILED DESCRIPTION 
     According to the basic design illustrated in FIGS. 1,  2 ,  4  and  5 , the training device illustrated in the drawings includes a vertically adjustable support  1 , which is telescopically connected with a vertical guide pole  2  that is fixed by means of two pylons  3  on a wall  4 . 
     The support  1  can be moved along the guide pole  2  and fixed by hand at the desired height by means of a fixture  5 . Smooth sliding of the support  1  is provided by means of two plastic cuffs  6  which are firmly fixed on both ends of a telescopic tube  7  of the support  1  (see FIGS.  1  and  10 ). 
     On the upper part of the telescopic tube  7  is arranged a three-cornered frame  8  that is constructed such that the upper side of the triangle is slanted upward. The free end of the frame  8  has a support  9  for a shaft  10  of a vertically swiveling arm  11  which has on a proximal end an adjustable fixed balance-weight  12  that turns the swivel-arm  11  into the upper at-rest position  11  that is defined by a catch  13  arranged on the frame  8 . The swivel-arm  11  can be set free by pulling a releasing cord  14  to disengage the catch  13  (see FIGS. 1,  8  and  9 ) 
     On a distal end of the swivel-arm  11 , a ring  15  is fixed asymmetrically relative to the long axis of the swivel-arm to train the user with respect to tossing the ball during serve training. The ring  15  includes a suspension  16  for hanging a ball  17  in the desired hitting zone, which comprises two pieces of Velcro™ fastening  18  being hung on two threads  19  in such a way as to enable the ball to fly by hitting it with a tennis racquet  20  (see FIGS.  1  and  2 ). 
     According to FIG. 2, the position of the tennis player P relative to the ring  15  and correspondingly to the ball  17  and to a pulley  25  is defined by means of a pair of footprints  21  on a stepping plate M, which is placed on the ground  43 . On the stepping plate M are marked three pairs of footprints  21 ,  21   a ,  21   b  with the base line markings  22 ,  22   a ,  22   b  at different distances relative to a point F, which is the vertical projection of the ring center (see FIG.  1 ), to define the position of the player P depending upon the different kinds of serve (flat, slice, topspin serve). 
     According to FIGS. 1,  6  and  7  a stirrup  23  is fixed on the tennis racquet  20 , which is connected with a cord  24  that runs upwards to the pulley  25  fixed on the distal end of the swivel-arm  11 , through the pulley  25 , to a further pulley  26  fixed on the top of the telescopic tube  7 , and then downwards through a trigger mechanism  33  to a moveable releasing device  27 , which has a releasing pulley  28 . After turning around the pulley  28 , the cord  24  runs upwards along the tube  7  to an anchor point  29 . 
     On the tube  7 , between the frame  8  and the fixture  5 , vertically adjustable clamp  32  is arranged, which includes the trigger mechanism  33  fixed on a plate  34 . The trigger  35  turns on a stub axle  36  through a torsion spring  37  from a level position  35   f  into a vertical position  35   v , which are defined or limited by a stop  38  (see FIGS. 1,  8 ,  10 ,  13 ). 
     In FIG. 8, the trigger  35  is shown in the working, level position  35   f  being stopped on the stop  38  under the pressure of a bead  39 , which bead  39  is steadily clamped on the cord  24  at a certain distance from the anchor point  29 . 
     The pressure on the bead  39  is exercised through the cord  24  by means of an elastic rope  30  one end of which is fixed on the moveable releasing device  27 , then the elastic rope  30  runs through three pulleys  31  fixed on the lower and middle parts of the tube  7  to another moveable releasing device  70  (see FIGS. 1,  4 ,  8 ,  10 ,  13 ). 
     The elastic rope  30 , being prestretched in the trigger position  35   f , exercises the towing force through the releasing device  27  only on the part of the cord between the bead  39  and the anchor point  29 . 
     The working level position of the trigger  35   f  corresponds to the execution of the serve swing from a waiting stance of the player P A  (shown on FIG. 1 as the racquet  20   A  with a hand), through a position of the player P B  (see FIG. 1) up to a lowest point of the loop of the serve swing, and through a position of the player P C  (see FIG.  3 ). 
     Only at the lowest point of the loop, i.e. the position of the player P C  (FIG.  3 ), the towing force will be activated overall on the cord  24 , correspondingly on the racquet  20 , by means of the plucking the cord  24  and moving the bead  39  shortly upwards to let the trigger  35  turn or move via the torsion spring  37  into the vertical position  35   v  and move the bead  39  out of contact with a fork-like cutting  40  of the trigger  35  (see FIG.  13 ). 
     On FIG. 8 in large scale, the upper part of the support  1  is shown with the frame  8 , on which the catch  13  is arranged to fix the swivel-arm  11  in the upper attest position. A pin  41  fixed on the proximal end of the swivel-arm  11  will be automatically arrested with the catch  13 , this turns with a torsion spring  42  on an axle  45 . In the waiting stance, the catch  13  is stopped by means of a stop  44  (see FIG.  9 ). 
     The moveable releasing device  28  includes a carrying member  46  to fix the elastic rope  30  between two clamping screws  47 , an offset hinged folding-bracket  48  and a releasing mechanism  49 . 
     As shown on FIG. 13, the folding-bracket  48  is offset hinged relative to the cord  24 , on a joint-pin  50  in the carrying member  46  in order to provide the moment arm for secure folding out after releasing the stub axle  51 , bearing the turn-pulley  28 , out of the contact with two rotary latches  52  of the releasing mechanism  49 . 
     The rotary latches  52  with flange cheeks  53  turn on an axle  54  with a torsion spring  55  partly overlapping a hold  56  in the carrying member  46  and being in a groove  57  of the stub axle  51  in the closed position, which is defined by means of a stop  56  and a cutting  57  in the latches  52  (see FIGS.  12  and  15 ). The releasing port  58  is fixed on a vertically adjustable clamp  60 , which is placed on the down part of the tube  7  (see FIGS. 10,  11  and  13 ). 
     By entering into a releasing port  58 , the rotary latches  52  with flanged cheeks  53  will be turned through the contact with flanged cheeks  59  of the releasing port  58  letting the folding-bracket  48  fold out and thereby set the cord  24  free. After releasing the cord  24 , the releasing device  27  is stopped on a rubber shock absorber  61 , which is fixed on the releasing port  58  (see FIGS. 12,  13  and  15 ). 
     FIGS. 6 and 7 show the connection of the cord  24  with the tennis racquet  20  by means of the stirrup  23 , which is fixed on two flanges  62 ,  63  bridging the grip of the tennis racquet  20 . The stirrup  23  includes a round rod  64 , an adjustable member  65 , protecting rubber rings  66 , and a glide ring  67  to connect the cord  24 . 
     The flanges  62 ,  63  are clamped on the grip by means of two demountable yokes  68 . The form of the rod  64 , the adjustable member  65  and the glide ring  67  provide the shifting of the point of connection accordingly the point of the exerting of the towing force on the tennis racquet  20 , which is a necessary condition during the swing. 
     Although a particular preferred embodiment of the invention has been disclosed in detail for illustrative purposes, it will be recognized that variations or modifications of the disclosed apparatus, including the rearrangement of parts, lie within the scope of the present invention.