Patent Publication Number: US-2005137034-A1

Title: Method for manufacturing a robust tethered ball

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
      This application is a continuation-in-part of U.S. patent application Ser. No. 10/813,641 filed on Mar. 29, 2004 for METHOD FOR MANUFACTURING A ROBUST TETHERED BALL, which is a continuation of U.S. patent application Ser. No. 10/319,398 filed on Dec. 12, 2002 for METHOD FOR MANUFACTURING A ROBUST TETHERED BALL and U.S. patent application Ser. No. 09/563,305 filed on May 2, 2000 for METHOD FOR MANUFACTURING A ROBUST TETHERED BALL, which applications are hereby fully incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention is in the field of sporting goods and specifically it relates to a method for producing a composite article that includes a ball and an elastic tether. In a preferred embodiment, the ball has the size and shape of a baseball, and sounds like a baseball when struck by a bat.  
      2. Description of Related Art  
      In the United States, baseball has been a popular sport for well over a century, and so it is not surprising that a very large number of patents have been granted for batting practice devices. These devices are intended to permit a sole individual to perfect his swing without the need to retrieve each ball that is hit. To cause the ball to return to the vicinity of the batter, it is known to tether the ball to a stationary object, such as an upstanding post, a horizontal arm, or other structure.  
     SUMMARY OF THE INVENTION  
      In an exemplary embodiment, a method includes steps of: 
          (a) providing an elastic tether;     (b) cutting the tether to a desired length so that the tether has an end portion that extends from an inner portion of the tether to an end of the tether;     (c) folding the end portion of the tether straight back upon the inner portion of the tether so that the end portion of the tether including the end of the tether lies parallel to the inner portion of the tether;     (d) securing the end portion of the tether to the inner portion;     (e) coating the end portion of the tether including the end of the tether and the inner portion of the tether with an adhesive to provide adhesion between the tether and a liquid polymer; and     (f) forming a solid ball on the end portion of the tether from the liquid polymer that completely includes the end portion of the tether, the end of the tether, and the inner portion of the tether.        

      In another embodiment, an article of manufacture includes a tether having an end portion that extends from an inner portion of the tether to an end of the tether. The end portion of the tether is folded straight back upon the inner portion so that the end portion of the tether including the end of the tether lies parallel to the inner portion of the tether. The end portion of the tether, the end of the tether, and the inner portion are coated with an adhesive to provide adhesion between the tether and a cured liquid polymer. A solid ball is formed from the cured liquid polymer so that the solid ball completely includes the end portion of the tether, the end of the tether, and the inner portion of the tether.  
      In accordance with one embodiment, a length of elastic shock cord, also known as bungee cord or stretch cord, is used for the tether. The shock cord includes a core of rubber threads enclosed within one or more layers of braided nylon. In the preferred embodiment, the core of the shock cord is approximately one-half inch in diameter and is surrounded by a single layer of braided nylon.  
      An anchor is formed at one end of the tether by folding an end portion of the tether back upon the remainder of the tether and fastening the end portion to the remainder by a hog ring.  
      Next, the end of the tether on which the anchor has been formed is inserted into a mold that will be used for producing the ball. The mold includes a lower part and an upper part, which are clamped together with the tether held between them. Each part of the mold includes a hemispherical cavity.  
      A liquid composed of an activated urethane is poured into the mold to produce a high density urethane foam. After about 30 minutes, the mold is opened, the ball and tether are removed from the mold, and any rough edges are trimmed off. Thereafter, the ball and tether are permitted to cure for about 24 hours.  
      The novel features which are believed to be characteristic of the invention, both as to organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description considered in connection with the accompanying drawings in which a preferred embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The embodiments described herein are illustrated by way of example and not limitation in the accompanying figures, in which like references indicate similar elements throughout the several views of the drawings, and in which:  
       FIG. 1  illustrates a perspective view of the shock cord used for the tether after the anchor has been formed at one end of the shock cord;  
       FIG. 2  illustrates a cross sectional view of the lower part of the mold used to form the solid ball;  
       FIG. 3  illustrates a cross sectional view of the lower part of the mold used to form the solid ball including the tether anchor of  FIG. 1 ;  
       FIG. 4  illustrates a cross sectional view of the mold used to form the solid ball with the upper part of the mold;  
       FIG. 5  illustrates a perspective view of the solid ball after it has been removed from the mold; and  
       FIG. 6  illustrates a flow chart for a method of making the solid ball; and  
       FIG. 7  illustrates a flow chart for a method of making the solid ball with an adhesive coating to extend wear life. 
    
    
      Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some elements in the figures may be exaggerated relative to other elements to point out distinctive features in the illustrated embodiments of the present invention.  
     DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS  
      A serious problem with previous batting practice devices is that they cannot successfully withstand a large number of hits. Depending on the specific apparatus, the tether may come loose from the ball, the tether may become damaged and eventually break, or the ball may disintegrate. The use of metal parts, such as a screw eye, is undesirable because of the likelihood of damaging the bat. Not only should the tethered ball be able to survive thousands of hits, but also the sound made when the bat strikes the ball should simulate the sound of a real bat striking a real baseball. Also, the optimum product should be manufacturable in quantity.  
      The first step in making the tethered ball is to cut the tether to a desired length. In a preferred embodiment of the invention, the tether is composed of a length of elastic shock cord, also known as a bungee cord or stretch cord. In the preferred embodiment, the cord is manufactured by the HNW Company of North Vale, N.J., and is designated as their 0.5 inch single nylon cover bungee cord.  
       FIG. 1  illustrates a perspective view of the shock cord used for the tether after the anchor has been formed at one end of the shock cord. It includes a core  12  consisting of a bundle of strands of rubber. The core  12  is surrounded by an inner layer  14  of braided nylon, which, in turn is surrounded by an other layer  16  also of braided nylon. The use of an electric hot knife is advisable for cutting the shock cord to a desired length because it seals the edges of the nylon braid, thereby resisting unraveling. An end portion  18  is bent back 180 degrees, so as to lie against the remainder  20  of the length of cord, and the end portion  18  is secured in that position by affixing a No. 2 hog ring  22 . The diameter and stiffness of the shock cord used in the preferred embodiment make it impractical to tie a knot at the end of the tether. Also, the size of the knot would make the ball weaker because the ball would consist of less foam material. In an alternative embodiment, the folded back end portion  18  is lashed to the remainder  20  of the tether by a strong cord or wire. The folded back end portion  18  forms an anchor  23  that helps to prevent the tether from becoming detached from the ball in use.  
      The ball  26  is formed by a molding process. For this purpose, a mold, best seen in  FIG. 4  is used. The mold includes a lower part  28 , an upper part  30 , and plug  32 . The lower part and upper part of the mold include respectively portions  34  and  36  that closely surround and sealingly engage the outer layer  16  of the tether.  
       FIG. 2  shows the lower part  28  of the mold. It includes a hemispherical cavity  38  that defines the size and shape of the ball. To help the ball to cure more evenly, the mold is preheated to a temperature between 80° F. and 100° F. A household electrical bread warmer works well for this purpose. Next, both halves of the spherical cavity of the mold are sprayed with a silicone mold release liquid, and the prepared shock cord is positioned in the mold as shown in  FIG. 3  with the anchor portion  23  centrally located within the mold. The upper part  30  of the mold is clamped in place in the position shown in  FIG. 4 .  
       FIG. 3  illustrates a cross sectional view of the lower part of the mold after the prepared tether has been inserted. Shown in  FIG. 3  are an anchor portion  23 , an inner portion  302  of the tether, an end portion  304  of the tether, an end  306  of the tether, an adhesive coating  308 , a wear resistant coating  310 , and an outer portion  312  of the tether.  
      In  FIG. 3 , the end portion  304  of the tether extends from the inner portion  302  of the tether to the end  306  of the tether. The end portion  304  of the tether is folded straight back upon the inner portion  302  of the tether so that the end portion  304  of the tether including the end  306  of the tether lies parallel to the inner portion  302  of the tether to minimize the amount of foam material displaced by the tether. The end portion  304  of the tether is secured to the inner portion  302  of the tether, for example, by crimping a hog ring on the end portion  304 . The end portion  304  of the tether, the end  306  of the tether, and the inner portion  302  of the tether are coated with an adhesive to provide adhesion between the tether and a liquid polymer used to form a solid ball around the end portion  304  of the tether. The liquid polymer completely includes the end portion  304  of the tether, the end of the tether  306 , and the inner portion  302  of the tether.  
      In a preferred embodiment, the ball  26  is composed of a cured high density urethane foam. For example, a formulation identified as IPS6168-20F (20 pounds per cubic foot) made by Innovative Polymer Systems, Inc. of Ontario, Calif., has been found to achieve optimum results. The material is supplied in the form of two liquid components which are stable until mixed. Appropriate quantities of each component are measured, using 40 parts by weight of component A and 60 parts by weight of component B. These components should be at approximately 80° F. The components are mixed throughly, and a chemical reaction begins. During an early phase of the reaction, the mixture remains pourable, and at that stage the mixture is poured into a pour opening  42  in the upper part  30  of the mold.  
      The reaction continues after the mixture has been poured into the mold, and the mixture begins to foam, thereby expanding. The plug  32  of  FIG. 4  is not set in place until the air has escaped from the mold and foam begins to flow from the pour opening  42 . At that point, the plug  32  is installed in the pour opening  42 . Thereafter, it takes from 15 to 30 minutes for the foam to set up so that the ball  26  will hold its shape when the mold is opened. During this time, the mold should be maintained at a temperature of 80°. At the end of this time, the mold is opened and the ball is removed from it. At this time it is desirable to remove any mold marks from the ball. Thereafter, the ball is allowed to rest at room temperature for 24 to 48 hours, during which the curing of the material is completed. The same process can also be used to produce a tethered softball, which is larger than a baseball.  
      Simple equipment may be used to evaluate the durability of the article produced by the above process, for example, a clay target throwing machine, normally used in trap shooting. The target slinger was replaced by a metal bat, which created a force equal to that employed by a college level baseball player. The tether was attached to a stand with a length of rubber tubing extending vertically from the stand, surrounding the tether and supporting the ball. The length of the rubber tubing was sufficient to maintain the tether under a small degree of tension, so that after each hit, the ball returned to its original position resting on the upper end of the rubber tube. Using this test setup, the ball was repeatedly struck by the bat.  
      As a result of this testing, it was found that the ball and tether produced by the above process had a life expectancy in excess of 5,000 hits.  
      The testing also demonstrated that the sound produced when a bat strikes the ball varies with the density of the cured urethane foam. The most realistic sound resulted when the density was between 18 and 32 pounds per cubic foot.  
      The tether may be, for example, a piece of commercially-available elastic shock cord having a central core of numerous strands of rubber surrounded by an inner cover of braided nylon and an outer cover of braided nylon. An anchor is formed at one end of the elastic cord by folding it back upon itself and securing the portion folded back by means of a hog ring or by lashing it with wire or cord. A mold having a spherical cavity is used to form the ball, and the anchor portion of the cord is placed in the mold before the mold is filled. A two component mixture is used, which initially is liquid. The liquid is poured into the mold, and as the reaction progresses, a foam is formed, preferably a high density 100 percent urethane foam. After the foam has set up, the solid ball is removed from the mold as shown in  FIG. 5  and allowed to cure at room temperature.  
       FIG. 7  illustrates a flow chart  700  for a method of making the solid ball with an adhesive coating to extend wear life.  
      Step  702  is the entry point of the flow chart  700 .  
      In step  704 , an elastic tether, for example, a bungee shock cord including a bundle of elastic bands (which may or may not be twisted or woven), in a fibrous sheath, such as a nylon fiber sheath, is provided to make the tethered ball as described above.  
      In step  706 , the tether is cut to a desired length so that the tether has an end portion that extends from an inner portion of the tether to an end of the tether.  
      In step  708 , the end portion of the tether is folded straight back upon the inner portion of the tether so that the end portion of the tether including the end of the tether lies parallel to the inner portion of the tether as shown in  FIG. 3 .  
      In step  710 , the end portion of the tether is secured to the inner portion, for example, by a hog ring, a wire, or a cord.  
      In step  712 , the end portion of the tether, the end of the tether, and the inner portion of the tether are coated, for example, on their exterior surface, that is, on the fibrous sheath and the end surfaces, for example, of the elastic bands, in the case when a bungee cord is used, with an adhesive to provide adhesion between the tether and a liquid polymer. The adhesive is preferably absorbed, at least in part, into the exterior surface, so as to further promote adhesion. The adhesive may be, for example, isocyanate catalyst, which is a mixture of methylene bisphenyl dirsocyanate, polymethyleneolyphenol, and methylone bispheylene isocyanate. Preferably, the proportions of the mixture by weight are about 15 percent methylene bisphenyl dirsocyanate, 50 percent polymethyleneolyphenol, and 35 percent methylone bispheylene isocyanate.  
      In step  714 , a solid ball is formed on the end portion of the tether from the liquid polymer that completely includes the end portion of the tether, the end of the tether, and the inner portion of the tether. Preferably, the liquid polymer is absorbed, in part, into the exterior surface, so as to further promote adhesion.  
      In step  716 , a wear resistant coating  310  may be applied, for example, to an exterior surface of an outer portion  312  of the tether that extends outside the solid ball as shown in  FIG. 3 . The wear resistant coating, may be, for example, a mixture of tetrahydrofuran, polyurethane polymer, and methyl ethyl ketone that is painted or sprayed on the outer portion  312  while stretching the outer portion  312  to increase the surface area during the application of the wear resistant coating  310 . Preferably, the wear resistant coating  310  is absorbed, at least to some degree, into the exterior surface of the outer portion  312 . Preferably, the proportions of the mixture by weight are about 15 percent tetrahydrofuran, 20 percent polyurethane polymer, and 65 percent methyl ethyl ketone. The addition of the wear resistant coating has been found to increase the life of the tethered ball substantially.  
      Step  718  is the exit point of the flow chart  700 .  
      Although the method illustrated by the flowchart description above is described and shown with reference to specific steps performed in a specific order, these steps may be combined, sub-divided, or reordered without departing from the scope of the claims. Unless specifically indicated herein, the order and grouping of steps is not a limitation of other embodiments within the scope of the claims.  
      The foregoing detailed description is illustrative of one embodiment of the invention, and it is to be understood that additional embodiments thereof will be obvious to those skilled in the art. The embodiments described herein together with those additional embodiments are considered to be within the scope of the invention.