Avoidance of resonance in the inflatable sport ball by limiting the critical ratio

Abstract

A sport ball having an internal device such as an internal pump has a critical ratio that insures that rebound characteristics or coefficient of restitution of the ball, such as a basketball, will be acceptable for use. The invention also includes the method for evaluating design and/or quality control of a sport ball by measuring the internal vibration and determining the critical ratio of the sport ball.

1 . A ball comprising: 
 a carcass having at least one layer of material, the carcass defining an exterior surface and a generally hollow interior;    a device having an top and a bottom, wherein the device extends into the generally hollow interior of the carcass; and    a housing having an upper end with a flange extending therefrom and a lower end, the housing defining a central opening extending between the upper end and lower end of the housing, wherein the device is received by the central opening of the housing and extends therefrom, wherein the flange is coupled to the at least one layer of material and the lower end is disposed within the hollow interior of the carcass, and wherein the natural frequency of oscillation of the housing with the device coupled thereto is not in resonance with a predetermined loading force such that the performance characteristics of the ball are within an allowable range from specified performance characteristics for a second ball, the second ball defining a second housing that does not include a second device therein.    
   
   
       2 . The ball of  claim 1 , wherein the housing defines a groove circumscribing the housing.  
   
   
       3 . The ball of  claim 1 , wherein the ball is a basketball having a coefficient of restitution in the range of 0.750 to 0.813.  
   
   
       4 . The ball of  claim 3 , wherein the ball has multiple values for the coefficient of restitution, and wherein the difference between the largest and smallest values of coefficient of restitution for the ball is equal to or less than 0.051.  
   
   
       5 . The ball of  claim 4 , wherein the ball has multiple values for the coefficient of restitution, and wherein the difference between the largest and smallest values of coefficient of restitution for the ball is equal to or less than 0.036.  
   
   
       6 . A method of testing a hollow ball, the method comprising the steps of: 
 providing a carcass, the carcass defining an exterior surface and a generally hollow interior, wherein the carcass includes at least one layer of material;    providing a device;    coupling the device to the at least one layer of material, wherein the device extends generally inward from the one layer of material and is substantially disposed into the generally hollow interior; and    providing a loading force that deforms at least a portion of the ball; and    determining whether the device oscillates at a frequency that is in resonance with the loading force.    
   
   
       7 . The method of  claim 6 , further including the steps of: 
 responsive to determining whether the device oscillates at a frequency that is in resonance, altering the natural frequency of oscillation of the device.    
   
   
       8 . The method of  claim 7 , wherein the natural frequency of oscillation of the device is altered by changing the mass of the device.  
   
   
       9 . The method of  claim 7 , wherein the natural frequency of oscillation of the device is altered by changing the distribution of the mass of the device.  
   
   
       10 . The method of  claim 7 , wherein the natural frequency of oscillation of the device is altered by changing the coupling of the device to the at least one layer of material.  
   
   
       11 . The method of  claim 7 , wherein device is coupled to the at least one layer using a housing having the device extending therethrough, wherein the coupling is altered by changing the housing.  
   
   
       12 . The method of  claim 1   1 , wherein the change in the housing involves a change in at least one of the flex modulus, bulk modulus, tension modulus, and compression modulus of the housing.