RELATED APPLICATION 
     This is a continuation-in-part of co-pending application Ser. No. 09/574,549 filed May 18, 2000 now U.S. Pat. No. 6,360,613. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to the field of sport balls, such as tennis balls. More particularly, the invention comprises the combination of a container for a plurality of sport balls with a device for testing the playing condition of the balls. 
     BACKGROUND 
     Tennis balls and certain other types of sport balls, such as racquetballs and handballs, are manufactured with a predetermined internal pressure, which imparts resiliency. The pressure is retained within a sphere of elastomeric material; however, the material is not perfectly impermeable. The internal pressure diminishes over time and with extended play. As the pressure diminishes, so does the resiliency of the ball, which has a deleterious effect on the playing characteristics of the ball. 
     Official organizations for tennis and other sports have established specifications for the balls used to play the respective sports. For example, the International Tennis Federation (ITF) Rules of Tennis specify that the ball shall have a bound of more than 53 inches and less than 58 inches when dropped 100 inches upon a concrete base. The Rules also specify that the forward and return deformation of the ball when placed under a load of 18 pounds shall be between 0.220 inch and 0.290 inch. Both of these specifications relate to the resiliency of the ball and hence to its playing characteristics. Recreational players are generally not concerned with whether or not a particular ball meets the precise specifications of an official organization. Such players are more concerned with the general playability of a ball and will often test a ball by squeezing it by hand or bouncing it on pavement. These informal tests are highly subjective. A number of devices have been proposed for objectively testing sport balls, particularly tennis balls. Such devices are shown, for example, in U.S. Pat. Nos. 5,222,391; 5,245,862; 5,291,774; 5,511,410; 5,567,870; 5,639,969; and 5,760,312. 
     Some of the prior art testing devices shown in the above-mentioned patents are intended for laboratory use, while others are intended to be used by individual players. However, all of the known prior art devices are relatively complex and, therefore, relatively expensive. Many of the devices have electronic components and all have one or more moving parts. There remains a perceived need for an inexpensive ball tester that can be provided to consumers at the time that the balls are purchased, analogous to the way that many dry cell batteries are sold with integral devices for testing the condition of the battery. Preferably, such a device would be simple to use and would be incorporated into the package in which balls are sold and stored so that the player would not be burdened with the inconvenience and weight of an additional item to carry. 
     SUMMARY OF THE INVENTION 
     The present invention provides a device for testing the playing condition of sport balls. The invention is preferably configured as a testing device in combination with a container for storing the sport balls; however, the invention may also be configured as a stand-alone testing device. In one embodiment particularly suited for testing tennis balls, the invention comprises a generally cylindrical canister substantially similar to conventional tennis ball canisters. A ball condition test disk is inserted into the canister and supported by means on the inside wall of the canister. The disk has a base portion, which is supported within the canister, and an indicator arm. A ball is placed into the canister where it rests on the indicator arm with a portion of the ball protruding out of the open end of the canister. When the protruding portion of the ball is pressed against a flat surface, the indicator arm is deflected, thereby giving an indication of the playing condition of the ball. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a first type of combination container and tester in accordance with the present invention. 
     FIG. 2 is a side view of the apparatus of FIG. 1 in a ball-testing configuration. 
     FIG. 3 is an end view of the testing device showing the ball condition indicator. 
     FIG. 4 is a perspective view of a second type of combination container and tester in accordance with the present invention. 
     FIG. 5 is a detailed view of the ball condition tester seen in FIG.  4 . 
     FIG. 6 is a top plan view of the ball condition tester. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following description, for purposes of explanation and not limitation, specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of wellknown methods and devices are omitted so as to not obscure the description of the present invention with unnecessary detail. 
     FIG. 1 illustrates a combination ball container and tester  10  in accordance with the present invention. Container/tester  10  comprises a cylindrical tube  12  closed at end  14  and a cap  16 . In the case of a device for tennis balls, cylindrical tube  12  is preferably dimensioned to house three or four balls  20  as is customary. Cylindrical tube  12  is preferably made of a clear plastic material, such as PETE, of sufficient strength to maintain internal pressurization sufficient for extended storage of balls  20  prior to use. A pressure seal (not shown) is provided at end  15  of tube  12  under cap  16 . The pressure seal is removed and discarded by the consumer when balls  20  are first used. 
     Cap  16  preferably includes a plurality of L-shaped slots  30  which cooperate with protrusions  32  on cylindrical tube  12  to provide a bayonet-type fitting to retain cap  16  in place. Slots  30  may have a spiral configuration to provide a mechanical advantage when securing cap  16  in place. Alternatively, tube  12  and cap  16  may have cooperating screw threads instead of a bayonet-type fitting. Cap  16  allows container/tester  10  to be used for conveniently storing and transporting balls  20  even after the pressure seal has been removed from tube  12 . Cap  16  is preferably made of a clear plastic material, but is preferably somewhat more rigid than tube  12 . Thus, cap  16  may be made of styrene, polycarbonate or similar material. 
     Referring now to FIG. 2, a ball  20  is shown being tested for playing condition. The ball is placed inside cap  16  and the cap is secured over closed end  14  of tube  12  with slots  30  engaging protrusions  34 . Protrusions  34  are spaced from end wall  14  so that ball  20  is slightly compressed when cap  16  is secured in place. As explained above, ITF specifications call for a forward deformation of more than 0.220 inch and less than 0.290 inch under a load of 18 pounds. Thus, if the dimensions are selected so that cap  16  compresses ball  20  by an amount in the specified range, a ball in new condition will exert a force of approximately 18 pounds against cap  16 . In order to ascertain the playing condition of the ball, it is simply necessary to obtain an approximate measure of the force exerted against cap  16 . Any suitable force indicator may be used, such as, for example, a spring-operated indicator or an electronic display coupled to a pressure transducer. 
     In one preferred embodiment, an indicator  18  is attached to the inside of cap  16 . Indicator  18  comprises an opaque fluid enclosed within a pouch of flexible plastic. An indicator of this type is disclosed in U.S. Pat. No. 3,987,699, the disclosure of which is incorporated herein by reference. When the fluid within indicator  18  is displaced as a result of pressure exerted against indicator  18  by compressed ball  20 , a visual indication of the displacement is provided. For example, the fluid may be a dark color, which in the absence of pressure completely obscures an underlying color on one wall of the pouch. When the thickness of the fluid is sufficiently reduced, the underlying color shows through. The degree to which the underlying color appears is directly related to the pressure exerted against indicator  18  and thereby provides a visual indication of the playing condition of ball  20 . 
     FIG. 3 is an end view of cap  16 , through which indicator  18  may be viewed. A ball in good playing condition will exert sufficient force against indicator  18  to displace the fluid therein within a central region  40 . Region  40  will thus have a different hue from surrounding region  42 . A ball in poorer playing condition will exert less force against indicator  18  and the color differentiation between regions  40  and  42  will be diminished. In addition, the diameter of central region  40  will appear reduced. A ball in very poor condition will exert insufficient force against indicator  18  to displace the fluid and the entire face of indicator  18  will appear as a solid hue. 
     FIG. 4 illustrates an alternative embodiment of the invention  100 . A can or canister  102  for storing a plurality, typically three, tennis balls is substantially similar to conventional tennis ball canisters. Canister  102  is preferably made of a clear plastic material, such as PETE. Canister  102  differs from a conventional tennis ball canister in that it is provided with means  104  for supporting a ball-testing disk  106 . As illustrated, supporting means  104  may comprise a circumferential rib on the interior surface of canister  102 . Alternative support means may also be employed, for example, disk  106  may be supported by a plurality of dimples or similar protrusions on the inner surface of canister  102 . Whichever means of support are employed, it is important that they protrude into the interior volume of canister  102  only enough to adequately support disk  106 , but not so much as to interfere with the movement of balls  20  throughout the volume. 
     Referring to FIG. 5, ball-testing disk  106  has a generally conical shape defined by skirt portion  108 . The outer diameter of disk  106  is such that it may be easily inserted into canister  102 , but will be firmly supported by support means  104 . Disk  106  includes an indicator arm  110  with an indicator tip  112 . The indicator arm  110  has as inverted “V” shape with a relatively sharp point  111 . This provides for a small area of contact between the indicator arm and the ball being tested, thereby maximizing the deflection of the indicator arm. 
     Disk  106  is preferably made of a relatively rigid plastic material, such as Delrin or the like. The disk is preferably made by an injection molding process and may be engraved with a product logo, etc. Due to the generally conical shape of the disk, a plurality of the disks will naturally tend to nest and can be easily stacked in a shipping container or a dispenser for placing the disks into tennis ball canisters. 
     FIG. 6 is a top plan view of ball-testing disk  106 . While the disk has a generally circular outer perimeter corresponding to the circular cross-section of canister  102 , it can be seen that the sides  114 ,  115  of disk  106  are somewhat flattened. This facilitates the insertion of disk  106  through the opening of canister  102 . The outer perimeter of disk  106  bulges outwardly slightly at  116 ,  117  and  118  to ensure that the disk will be securely supported by support means  104 . These bulges also hold disk  106  in place when canister  102  is inverted. It should be noted that indicator tip  112  is set back slightly from the outer perimeter of the disk to ensure that it will not strike the support means  104  when indicator arm  110  is deflected during a test of ball condition. 
     Referring again to FIG. 4, the playing condition of a ball  20  is tested by first placing disk  106  on support means  104  and then inserting ball  20  into canister  102  to rest upon indicator arm  110 . A portion of ball  20  protrudes from the opening of canister  102 . The canister is grasped and the protruding portion of ball  20  is placed against a flat surface, such as a wall or tabletop. Pressure is applied on the canister until the rim of the opening contacts the flat surface. The pressure causes the indicator arm  110  to be deflected. The amount of deflection is a function of the rigidity of ball  20 . This, in turn, is a function of the internal pressure in ball  20 . A fresh ball, having an internal pressure established at the time of manufacture, will provide the greatest deflection of indicator arm  110 . Over the life span of the ball, the pressure decreases and the amount of deflection is correspondingly less. At some point, the pressure decreases to an extent that the ball is no longer considered playable. The playing condition of ball  20  is thus ascertained by the deflection of indicator arm  110  as seen by the position of indicator tip  112  viewed through the transparent wall of canister  102 . The wall of canister  102  may be provided with a scale or other indicia by which the deflection of indicator arm  110  may be measured. The scale may provide a quantitative measure of ball condition or may simply provide a pass/fail indication. In one embodiment, canister  102  may be provided with a frosted ring or band surrounding support means  104 . The frosted band may extend down the side of canister  102  far enough to obscure indicator tip  112  in all positions except when deflected by a ball in playable condition. Thus, when a ball is tested, the appearance of indicator tip  112  below the frosted band provides an indication that the ball is in playable condition. 
     An individual ball  20  may be easily tested for playing condition as described above. The invention also facilitates rapid testing of a plurality of balls, such as may be required, for example, by a pro shop. This is easily accomplished by placing the balls to be tested on a flat surface, such as a tabletop. Canister  102 , with ball-testing disk  106  installed, is then simply pressed down on each of the balls in succession. The playing condition of the ball is observed with indicator tip  112  and the ball may then be kept or discarded in accordance with its indicated playing condition. Pressure on the canister may be released to roll the ball around on the supporting surface to bring the point  111  of disk  106  into contact with the ball at multiple locations on the surface of the ball. Thus, a ball may be tested at the multiple locations to determine an “average” playing condition. This also allows the ball to be tested at an optimum location, such as on a seam. Optionally, the sport balls may be provided with a marking, either at the time of manufacture or subsequently, to indicate a test location so as to enhance repeatability of the test. 
     It will be recognized that the above-described invention may be embodied in other specific forms without departing from the spirit or essential characteristics of the disclosure. Thus, it is understood that the invention is not to be limited by the foregoing illustrative details, but rather is to be defined by the appended claims.
A container for storing sport balls incorporates a device for testing the playing condition of the balls. The test device is in the form of a disk with a base portion supported within the container and an indicator arm. A ball to be tested is placed into the container where it rests on the indicator arm with a portion of the ball protruding out of the open end of the container. The exposed portion of the ball is pressed against a flat surface. This deflects the indicator arm and provides a visual indication of the playing condition of the ball.