Abstract:
A tennis ball with weight material injected into its interior cavity for use in exercise and sport as a weight bearing device. The weight material adds weight to the tennis ball. The weight material completely or partially fills the interior cavity of the tennis ball. The weight of the tennis ball can be changed based on the amount and type of weight material inside the tennis ball.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention is in the technical field of exercise and sport. More particularly, the present invention is in the technical field of tennis training. More particularly, the present invention is in the technical field of arm and hand exercises. 
         [0002]    Weighted balls of various sizes, materials and weights have been used for centuries by people for performing exercises, gaining strength, and for use in sports and sports training. 
       SUMMARY OF THE INVENTION 
       [0003]    The present invention is a tennis ball filled with weight material comprised of a plurality of either metal balls, metal shot, metal grit, metal sand, metal powder, metal filings or a combination of said material. The advantage of the present invention allows the use of a commonly manufactured tennis ball to be transformed into a weighted ball. The primary purpose is for using one or more weighted tennis balls as an exercise tool. Weighted objects provide resistance to build strength and coordination. The tennis ball in of itself is useful for this purpose as the felt-like exterior of the tennis ball provides surface texture and the rubber interior shell provides flex. One weighted tennis ball tossed up into the air, like one would do while serving in a game of tennis, will build strength and coordination for that movement. Two weighted tennis balls held in one hand and rotated by the fingers will build hand and forearm strength. The Intended use of the present invention can vary from person to person. 
         [0004]    Besides creating a tennis ball with increased weight, the utility of injecting loose weight material like metal balls, metal shot, metal grit, metal sand, metal powder, metal filings or a combination of said material into the tennis ball cavity will also provide the benefit of allowing the tennis ball to give slightly under pressure. A tennis ball filled with a solid (non-rubberized) substance will not give as much under pressure when completely filled. Since a tennis ball is naturally flexible, the injection of loose material, as opposed to a solid core, will maintain that flexibility. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a cross section of a tennis ball being filled with weight material comprised of metal balls. A tube is inserted into an opening of the tennis ball. 
           [0006]      FIG. 2  is a cross section of the present invention. It shows a cross section of a tennis ball filled with weight material comprised of metal balls. 
           [0007]      FIG. 3  is a cross section of the present invention. It shows a cross section of a tennis ball filled with weight material comprised of metal balls. The metal balls are smaller then the balls in  FIG. 2 . This illustrates how weight material of different sizes can be inserted into a tennis ball. 
           [0008]      FIG. 4  is an exterior view of the present invention with a section of the tennis ball cut out to expose the interior containing weight material comprised of small metal balls. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0009]    Referring now to the invention in more detail, a weighted tennis ball is comprised of a tennis ball with weight material injected into it. Weight material can be comprised of a plurality of either metal balls, metal shot, metal grit, metal sand, metal powder, metal filings or a combination of said material. The weight material can vary in size and shape. The weight material does not have to be perfectly round. The weight material can be irregularly shaped (similar to sand).  FIG. 1  shows an example of a tennis ball  10  being filled with weight material comprised of metal balls  12  of about 4.5 millimeters (0.18 inches) in diameter. The way to fill the tennis ball can vary. The simplest concept involves making a small slit into the tennis ball&#39;s shell  14 , and then injecting the weight material into the cavity via a tube  11 . Once filled the filling tube is removed and the slit is sealed with glue.  FIG. 2  shows a cross section of a tennis ball  10  completely filled with the metal balls  12 . 
         [0010]    As shown in  FIG. 2 , if a tennis ball  10  is filled with steel balls  12  it will weigh about 0.45 kilograms (one pound). The overall weight can be slightly more or less depending on the variances of the tennis ball&#39;s interior volume, variances with the size of the weight material, and with the composition of the weight material. A tennis ball&#39;s interior volume space will vary due to the manufacturing process and due to the source manufacturer of the tennis ball. The overall weight of a completely filled tennis ball will be slightly higher with smaller sized weight material than with larger sized weight material.  FIG. 3  shows a cross section of a tennis ball  10  with smaller metal balls  12  inside it than the tennis ball  10  that is illustrated in  FIG. 2 . Smaller diameter metal balls  12  will have less air space  14  between them. Larger weight material, such as metal balls larger than 5 millimeters (0.12 inches) in diameter, can be injected into a tennis ball. However, the size of the weight material will affect how easy or difficult it is to insert the weight material into a tennis ball. The use of weight material larger the 5 millimeters (0.12 inches) in diameter or length may make the tennis ball  10  more difficult to fill. It is up to the manufacturer of the weighted tennis ball to decide about what type of weight material to use and what its dimensions should be. 
         [0011]    As shown in  FIG. 2 , when filling the tennis ball  10  with weight material, such as metal balls  12 , the weight material is injected into the tennis ball  10  until the weight material is touching, or very close to touching, the upper interior surface  13  of the tennis ball  10  near the injection point. Ideally, the weight material should not be jammed in. There should be slight movement. This will enable the tennis ball  10  to compress slightly.  FIG. 4  shows an exterior view of a weighted tennis ball  10  with a cut out exposing metal balls  12  inside the tennis ball  10 . A tennis ball can also be filled with varying amounts of weight material to change the weight of the ball. If a tennis ball is filled half way, then the overall weight of the tennis ball would be close to half as much weight as a completely filled tennis ball. 
         [0012]    Weight material can be composed of various grades of steel, steel alloys, iron, or from various other metals such as zinc, copper, etc. The metals can be coated with other metals or uncoated (steel balls are often coated with zinc or copper). Which metal type used would be based on price, availability, the desired weight, and even toxicity? Although lead has a high weight to volume ratio, the use of lead, or other toxic metals, is not recommended due to health concerns. 
       CONCLUSION, RAMIFICATIONS, AND SCOPE 
       [0013]    Accordingly, the reader will see that inserting weight material into a tennis ball will enable the user of said weighted tennis ball to use the weighted tennis ball to perform exercises where weight is of benefit. The tennis ball in of itself is useful for this purpose as the felt-like exterior of the tennis ball provides surface texture and the rubber interior shell provides flex which may be of benefit to user. 
         [0014]    While the foregoing written description of the invention enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The invention should therefore not be limited by the above described embodiment, method, and examples, but by all embodiments and methods within the scope and spirit of the invention.