Abstract:
The spin improvement string pliers is a pivotally secured together plier device used to manually restructure and roughen the surface of a synthetic or a polyester string on a strung tennis racquet by means of plastic deformation. The line grids on the pliers depress the string, leaving a series of indentations on the string surface that increases the friction between the string and the ball so that the tennis player can more easily generate top or under spin on a tennis ball.

Description:
This application is a continuation of application Ser. No. 12/833,981 filed on Jul. 10, 2010. 
    
    
     FIELD OF INVENTION 
     The present invention relates to a pivotally secured together plier device used to manually restructure and roughen the surface of polyester and synthetic gut tennis strings on a strung tennis racquet. The roughened string surface increases the friction between the string and the tennis ball and thus the player can more easily generate spin on a tennis ball while striking the ball. 
     BACKGROUND OF THE INVENTION 
     Many tennis players try many different techniques to generate spin when they hit the tennis balls. With an ultra-high-speed, 10,000-frame-per-second camera, we can now clearly see how strings generate spin during the 4 or 5 milliseconds when the ball is on the strings. Most spin is generated by main strings (vertical strings) slide and snap back movement after they contact with the tennis ball. Thus, the rougher the main string surface is, the more main string slide and snap back with more power for spin generation, and the easier it is for the player to generate spin. Basically, in order to generate more spin, we need two factors: 1. a rough string/ball contact surface, therefore the strings can grasp the ball better, and the ball can push the main strings to slide more over the cross strings(cross strings); as a result, the main strings can generate more spin when they snap back. 2. a smooth main string/cross string contact surface, therefore the main strings can slide farther over the cross strings and snap back efficiently because of less frictions between the strings, this will give an extra kick to the ball and generate more spin. In order to satisfy two factors stated above, you need a main string that has two different surfaces, rough on the top (where it contacts with the ball) and smooth on the bottom (where it contacts with the cross string) in order to generate spin efficiently. 
     Most strings are made of synthetic nylon and polyester, and some of them are made of natural gut. Some string manufacturers provide Octagon or Hexagon shaped polyester strings to increase the friction between the string and ball. It may be effective on the main strings when they are new, after some time, the sharp edge of the Octagon and Hexagon will be worn away by wear and tear between the string and ball. As a result, the main strings can no longer grasp and generate spin as effective as when they are new. Some strings come with a series of small dents on the surface to increase the roughness of the string surface. This is effective when it is new, however, after some time, the small dents will be worn off and the string surface becomes smooth again. 
     BRIEF SUMMARY OF THE INVENTION 
     The primary objective of this invention is to provide a plier device to mechanically and permanently restructure and roughen the surface of a tennis racquet string, section by section on a strung tennis racquet, by means of mechanical deformation on a string to make friction marks. As a result of this process, the friction between the string and ball will be increased, while the friction between the strings will remain the same. This will allow the main strings slide further over the cross strings, and snap back with more power for spin generation. 
     In accordance with the present invention, there is provided a plier device comprising a pair of handle levers including a middle portion pivotally secured together with a pivot shaft. Each lever has a handle on one end and a jaw on the other. The plier device is made of steel or another hard material. Only upper jaw has an elevated pattern of closely adjacent line grids or other shapes, such as diamond. They make friction marks on the strings. The lower jaw is smooth and does not make any friction marks on the strings. The end of the lower jaw has an “L” shaped string locker design with a slot in the middle, which allows the bottom jaw to slide beneath a string by rotating the plier handles. On the bottom of bottom jaw, there is also a slot in the middle. This slot allows the lower jaw to be inserted easily between the main and cross tennis strings. Once the upper jaw is above the string and bottom jaw is beneath the string, close the pliers. A series of elevated line grids will then press and reform the string surface and leave a series of indentations on the string without damaging other characteristics of the string. The roughened string surface increases friction between the string and ball, making it easier for the players to generate spin. After some time, if the indentations on the string are worn because of wear and tear, the pliers can be used again to roughen the string. On the upper jaw, there is an adjustment screw and it can be used to adjust the distance of the gap between the upper and bottom jaws, according to various sizes of string diameters. This device solves two common problems for tennis players: 1. Smooth polyester round strings are slippery, they allow the main string to slide and snap back efficiently for spin generation. However, the smooth round strings cannot grasp the ball well. With this device, the string surfaces where they contact the ball can be roughened, and the strings faces between the strings are kept smooth, therefore strings can grasp the ball better for spin generation. 2. Textured/shaped strings can grasp the ball much better than smooth strings, but they become smooth very quickly and no longer effective in spin generation. They are usually cut and replaced before they break. With this device, the string surface can be roughened again, therefore the string performance can be revived. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of the string pliers in accordance with the present invention. 
         FIG. 2  is another exploded view of the string pliers in accordance with the present invention. 
         FIG. 3  is a close up exploded view of the upper jaw when the pliers are open. 
         FIG. 4  is a close up exploded view of the bottom jaw when the pliers are open. 
         FIG. 5  is a front view of the string pliers when they are closed. 
         FIG. 6  is an exploded view of how to use the string pliers on a strung racquet. 
         FIG. 7  is a close up front view of the tennis strings before string pliers are used. 
         FIG. 8  is a close up back view of string before string pliers are used after the string bed is flipped over. 
         FIG. 9  is a close up front view of string after string pliers are used. 
         FIG. 10  is a close up back view of string after string pliers are used after the string bed is flipped over. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 ,  FIG. 2  and  FIG. 3 , the tool of the present invention can be seen to include two plier handles  10 - 10  which pivot about pivot pin  11 . One of the handles  10 - 10  is rigidly connected to upper jaw  22  and the other handle is rigidly connected to lower jaw  21 . When handles  10 - 10  are spread apart, the jaws open, as shown in  FIG. 1 ,  FIG. 2 ,  FIG. 3  and  FIG. 4 , and when the handles  10 - 10  are closed, the jaws close, as indicated in  FIG. 5 . Upper jaw  22  contains an elevated pattern of adjacent diamond shaped line grids  18 , as indicated in  FIG. 3 . The line grids  18  can come with different shapes, a rectangular block, a pyramid, a triangle, diamond, cylinder or a half cylinder. Lower jaw  21  surface  19  is smooth, as indicated in  FIG. 4 . 
     The upper jaw  22  and lower jaw  21  are shown in greater detail in  FIG. 3  and  FIG. 4 . The upper jaw  22  has an elevated L shaped jaw tip  25  at the end. An elevated pattern of elements  18  is on the top of elevated L shaped jaw tip  25 . Right beneath the elevated L shaped jaw tip  25  on the upper jaw  22 , a recessed indentation  24  is located on the lower jaw  21 . The indentation  24  is about ⅛″-½″ wide and 3/16″ to 5/16″ deep. The top of the recessed indentation  24  is smooth, as indicated in  FIG. 4 . The recessed indentation  24  is to lock the string in place once the lower jaw  21  slides beneath the string. Upon closure of the upper jaw  22  and the lower jaw  21 , a gap  12  is formed between the upper jaw  22  and the lower jaw  21 , as indicated in  FIG. 5 . The formed gap  12  is about 1/32″ which prevents the string from being overly deformed by the upper jaw  22  and lower jaw  21  respectively. Adjustment screw  26  can be used to adjust the distance of gap  12  between upper jaw  22  and lower jaw  21 . 
     The lower jaw  21  has  2  elevated L shaped string lockers  23  at the end, which are extruded from upper jaw  22 , as indicated on  FIG. 3  and  FIG. 4 . Between these two L shaped string lockers  23 , at the end of lower jaw  21 , a slot  16  about ⅛″ in width and ½″ in depth is located in the center. A polished slot  27  on the bottom of lower jaw  21  allows the lower jaw  21  to be easily inserted between tennis strings  14  and  15 , and allows lower jaw  21  to be easily pivoted about the string  14  and push down string  15  after lower jaw  21  is inserted under string  14 . 
     In  FIG. 5 , it can be seen that the surfaces of upper jaw  22  and lower jaw  21  are not parallel to the center line of the handles  10  of the pliers. Instead, it forms an angle A 1 . This feature makes the tool of the present invention much easier to operate than if it had the surfaces of upper jaw  22  and lower jaw  21  in direct alignment with the center line of the plier handles  10 . Angle A 1  indicated in  FIG. 5  may vary from about 20° to about 35°, or more preferably from about 25° to 30°. 
     The manner in which the tool of the present invention is used to deform and roughen the surface of the string on a strung racquet is shown in  FIG. 6-10 . In  FIG. 6 , the player intends to make a series of indentations on a main string  14  on a strung racquet. The player first puts the elevated L shaped string lockers  23  located at the end of lower jaw  21  under the cross string  14 , while the main string  15  is inserted in the slot  16  located in the center of lower jaw  21 . The L shaped string lockers  23  and the slot  16  lock both the cross string  15  and the main string  14  in place. The player then pushes down the plier handles  10 , so the plier pivots about the main string  14 , As a result, the cross string  15  is pushed down by the slot  16  and slot  27 , and the lower jaw  21  is pushed under the main string  14 . Main string  14  is then pushed on the recessed indentation  24  on lower jaw  21 , and indentation  24  locks the main string  14  in place. Finally, the player can close the pliers and leave a series of indentations on the main string  14 , as indicated in  FIG. 9 .  FIG. 7  and  FIG. 8  show the front and the back of main string  14  before the pliers are used.  FIG. 9  and  FIG. 10  show the front and the back of main string  14  after the pliers are used to depress the main string  14 .  FIGS. 9 and 10  also show that a series of indentation is only put on the upper surface of main string  14 , but not on the bottom surface of main string  14 . This process increases only the friction between main string  14  and tennis ball, but does not change the friction between main string  14  and cross string  15 , therefore main string  14  can slide and snap back over the cross string  15  efficiently for spin generation. After the string is pressed, the pliers can then be opened and rotated upward to release the main string  14  and cross string  15 . 
     The same manner can be repeated to put a series of indentations on the rest of the main string  14 . The player needs to turn over the racquet and work on the other side of the racquet to complete roughening the string surface. It is not necessary to roughen all the strings on the racquet, it is sufficient to roughen the string in the “sweet spot” on the main strings only, where the string makes contact with the balls most often. This covers about ⅓ the racquet area, in the center. The players can repeat the same process to roughen the cross string  15 . Roughening cross string  15  will allow cross string  15  grasp tennis ball better, however, it also increase the friction between main string  14  and cross string  15  and prevent main string  14  from sliding and snapping back efficiently over the cross string  15 . 
     The tool of the present invention is made from any suitable common metal such as steel alloy, aluminum alloy, plastic with high hardness and the like. The handles  10 - 10  of the tool may preferably be covered with soft material such as plastic or rubber, or the like. 
     Although a preferred embodiment of the invention has been disclosed for the purpose of illustration, it will be understood that various changes, modifications, and substitutions may be incorporated in such embodiment within the scope of the invention without departing from the spirit of this invention.