CROSS REFERENCES TO RELATED APPLICATIONS 
     This application is a continuation-in-part of application Ser. No. 29/100,237, filed Feb. 8, 1999, and is also a continuation-in-part of application Ser. No. 29/094,324, filed Sep. 30, 1998, the disclosures of both of said applications are hereby incorporated by reference herein. 
     STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to specialized containers in general, and more particularly to packages for retail display of round cell batteries. 
     By universal agreement, a number of battery types have been defined in terms of voltage, current, and dimensional criteria. Most common among these defined battery types are the round cells, readily available sources of direct current packaged in cylindrical canisters. These round cells have been given letter designations and range, in physical size, from AAAA, AAA, AA, C to D. 
     Although the battery chemistries, available power, and recharging options may vary, the dimensions and electrical properties are confined within agreed-upon tolerances. These standardized battery properties allow consumers to replenish the battery compartments of their electronic devices from the stocks of thousands of convenience stores, hardware stores, and electronic shops throughout the world. 
     Advancements in microcircuitry, optics, and micro-machinery, have resulted in a proliferation of portable electronic devices which rely on standard round cells for power. Whereas a hundred years ago a consumer might possess only one or two lanterns or flashlights calling for batteries, the modern household, in addition to flashlights, may have portable radios, CD and tape players, intercoms, cellular phones, computers, musical devices, camcorders, interactive toys, remote control cars, calculators, or any of a multitude of home electronic devices. 
     To anticipate the immediate need for replacement batteries, the modern consumer is called on to maintain a stockpile of batteries of various sizes ready at hand. To address this need, manufactures package multiple batteries in a single container, usually offering a reduced unit price for quantity purchases. Multiple batteries have been offered on blister cards, such as those shown in U.S. Pat. No. Des. 408,732; in front-to-back plastic clamshell packages, and in paperboard containers, such as those shown in U.S. Pat. No. 5,823,350. 
     Although a consumer may desire to purchase multiple batteries in a single package, often a single replenishment of an electrical device will not fully deplete the multi-battery package. In these cases, the unused batteries will be unconstrained unless the battery package itself serves as a container after the package has been opened. The problem presented by unconstrained batteries is particularly acute with round cells, which will tend to roll along any flat surface. 
     What is needed is a multi-battery package which presents batteries for attractive retail display while at the same time restraining a subset of the batteries within the package to serve as a container after it has been opened. 
     SUMMARY OF THE INVENTION 
     A retail package for round cell batteries is a transparent single sheet thermoformed clam shell having a cover connected along a perforated hinge to a base which receives an array of upwardly extending batteries. The base has a side wall which extends upwardly from a flat bottom wall. The side wall has a lower section which is substantially perpendicular to the bottom wall and has a zero degree draft angle. Semicylindrical pockets are defined by the base wall lower portion and batteries are positioned in the pockets two abreast. Thus, each battery is engaged by a portion of the side wall and another battery. Hence, a partially emptied container will still retain most of the batteries upright. The cover has a downwardly extending skirt with an inwardly extending semicircular closure tab which engages beneath a lip formed on the base side wall. The lid closure may be released by pressing the base side wall. 
     It is an object of the present invention to provide a retail display package for multiple batteries which prominently displays the package contents. 
     It is also an object of the present invention to provide a container for multiple batteries which retains batteries in an upright position after removal of a subset of the batteries. 
     It is an additional object of the present invention to provide a battery container which is readily loaded by automatic machinery. 
     It is another object of the present invention to provide a package for multiple batteries with a closure which is readily opened. 
     Further objects, features and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top view of the battery package of this invention in an open configuration held tilted on its side with a single battery removed. 
     FIG. 2 is a cross-sectional view of the battery package of FIG. 1, in a closed configuration, taken along section line  2 — 2 , with the thickness of the package wails exaggerated for clarity. 
     FIG. 3 is a fragmentary isometric view of the package of FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring more particularly to FIGS. 1-3, wherein like numbers refer to similar parts, a multiple battery package and container  20  is shown in FIG.  1 . The container  20  is a single-sheet thermoformed thermoplastic package. In the single-sheet thermoforming process, a single sheet of thermoplastic material is heated and then brought into contact with a molding tool having a plurality of ports through which air is drawn to cause the semi molten plastic to conform to the shape of the molding tool. The container  20  may be formed of PVC plastic, or alternatively of polyethylene, polyurethane, polypropylene, PET, RPET, or other suitable thermoplastic materials. The sheet is a thin sheet of thermoplastic, for example about 0.02 inches thick. 
     The container  20  is a clamshell package having a base  22  with a cover  24  connected to the base along a perforated plastic hinge  26 . The base  22  has a generally flat bottom wall  28  with an upwardly extending encircling side wall  30 . The encircling side wall  30  has a lower side wall  32  which extends nearly perpendicular to the bottom wall  28  and an upper side wall  34  which extends from the lower side wall at a generally horizontal transition wall  36 . The lower side wall  32  is formed as a “zero draft” segment of the part, while the upper side wall  34  is inclined outwardly from the perpendicular at conventional draft angles, for example from 3 degrees to 7 degrees, and preferably about 5 degrees. Although the container  20  may be formed for any desired round cell, the unit illustrated in the figures is specially configured to receive eight C cell batteries. Whereas the total height of the base is approximately 4.5 centimeters, the lower side wall is approximately 1 cm tall. In general, the lower side wall may be about one fifth the height of the base. 
     As shown in FIG. 2, the lower side wall  32  engages the cylindrical exterior of a battery  38 , while the upper side wall  34  diverges away from the battery  38 . As shown in FIG. 1, the lower side wall is composed of a sequence of semicylindrical segments  40 , each segment being separated from the next by an inward protrusion  42 . Together, the semicylindrical segments  40  and inward protrusion  42 , define an array of battery pockets  44  rising up from the bottom wall  28 . A separate pocket  44  will correspond to each battery  38  received within the container  20 . The array of pockets  44  will be no more than two batteries deep in one dimension, and at least two batteries wide in the other dimension. The number of batteries in the long dimension of the array will vary depending on the desired size of the package, but will generally be in the range of four to six. For purposes of discussion herein, each battery position defined by the eight pockets  44  has been designated in FIG. 1 with a Roman numeral. 
     The semicylindrical segments  40  located at the opposite ends  46  of the base side wall  30  wrap approximately 180 degrees of the circumference of the batteries  38  in the pockets I, II, VII, and VIII. The semicylindrical segments  40  on the long portions  48  of the side wall  30  each wrap approximately ninety degrees of the batteries positioned within pockets III, IV, V, and VI. As shown in FIG. 3, the inward protrusions  42  which separate the semicylindrical segments  40  are confined to the lower side wall  32 . However, similar full height protrusions  50  are provided on the ends  46  of the side wall  30  which extend the full height of the upper side wall  34  and which terminate at an outwardly extending peripheral lip  52  which encircles the upper edge of the upper side wall. 
     As shown in FIG. 2, the transition wall  36  provides a radiused inlet  54  to each pocket  44 . The radiused inlets  54  assist the loading of the container  20 , as discussed below. 
     The upper side wall  34  may be provided with an outwardly protruding security tag bubble  56  which extends away from the contained batteries  38 . As disclosed in U.S. Pat. Nos. 5,586,657 and 5,871,100, the disclosures of which are incorporated by reference herein, a battery container can be configured to operate with a security tag sensing detector by spacing a security tag  58  on the container  20  a determined distance away from the batteries. As shown in FIG.  2 ,the security tag  58  is positioned on the bubble  56  which, like the upper side wall from which protrudes, is inclined outwardly, thus obtaining maximum spacing of the security tag  58  from the batteries. 
     The hinge  26  is defined by a score line or fold line extending along the base peripheral lip  52 . The cover  24  extends from the hinge  26  at a cover lip  60  which, in the cover open position extends in approximately the same plane as the hinge  26 . In the cover closed position, shown in FIG. 2, the cover lip  60  overlies the base peripheral lip  52 . A skirt  62  extends downwardly from the cover lip  60  to encircle the three sides of the base  22  not including the hinge  26  side. A cover side wall  64  extends upwardly from the cover lip  60  and is positioned inwardly of the cover skirt  62 . A top wall  66  extends inwardly from the cover side wall  64 . Two nesting protrusions  68  extend upwardly from the top wall  66 . The nesting protrusions  68  are positioned and shaped to extend inwardly to engage a similar container  20  stacked on the top wall  66 . The overlying container  20  may be positioned so that the inward protrusions  42  on the ends  46  of the lower side wall  32  meet with the nesting protrusions  68 , thereby permitting secure stacking of multiple loaded containers  20 . 
     As shown in FIG. 1, the cover  24  is preferably provided with two semi-circular closure tabs  70  which extend inwardly from the cover skirt  62 . The closure tabs  70  are positioned at the corners of the cover spaced from the hinge  26 , and are positioned to engage beneath the base peripheral lip  52  when the cover is closed on the base as shown in FIG.  2 . As shown in FIG. 3, the closure tabs  70  extend inwardly from a cover flange  72  which extends outwardly from the cover skirt  62 . The cover flange  72  is spaced from the hinge  26  on three sides of the cover, but connects to the cover lip  60  by ramped sections  74  adjacent the hinge side of the base  22 . This arrangement allows the cover to be pivoted about a hinge axis which lies in the same plane as the cover lip  60  and the base lip  52 . 
     Multiple battery packages serve several functions. First, they contain and display batteries in a retail environment. The container  20  performs advantageously as a retail display package, especially when it is formed of substantially transparent plastic sheet material. The flat bottom wall, top wall, and long segments of the side wall provide minimal optical impediments to customer perception of the product contained within. The graphics on the contained round cells themselves provide the predominant graphic message of the container. The package is readily sealed by an adhesive label, not shown, which extends over the cover and onto the base side wall. In addition, the protrusions  68  of the cover permit multiple similar battery containers to be stacked one upon the other. 
     Although an attractive package is helpful at the point-of-sale in drawing the customer&#39;s attention to the product, once purchased the customer has more utilitarian demands. Although a stockpile of multiple batteries readily available within the home or workplace is desired by the purchaser of a multiple battery product, frequently batteries will be drawn from this stockpile in quantities less than the total number contained within the package. The lower side wall  32  of the container  20 , by providing discrete pockets  44  for each battery, contributes to the convenient and organized storage of less than the full complement of batteries. 
     As shown in FIG. 1, each battery  38  is engaged by the bottom wall  28 , the lower side wall  32 , and at least one other battery. When the container  20  is fully loaded with its complete complement of batteries  38 , each battery is restrained on four sides in addition to the bottom wall. The batteries  38  in positions I, II, VII, and VIII are engaged by the lower side wall end portions  46  and the long portions  48 , as well as two other batteries. The batteries  38  in positions III, IV, V, and VI are engaged by long portions  48  of the lower side wall  32  and three other batteries. However, as batteries are extracted from the container  20 , support for the remaining batteries is decreased. Nevertheless, the configuration of the inward protrusions  42  defining the pockets  44  allows the container  20  to provide significant support for any pair of batteries positioned between the long portions  48  of the lower side wall  32  and adjacent one another. 
     As shown in FIG. 2, the two batteries positioned between the long portions  48  of the lower side wall  32  are engaged against each other and against the zero draft perpendicular semicylindrical segments  40  of the lower side wall  32 . This engagement restricts the tipping of the batteries towards one or the other of the ends  46  of the container  20 . As shown in FIG. 1, the removal of an adjacent battery, for example of the battery in position III, while removing some support for the batteries in positions I, IV, and V, will not leave the batteries in positions I and V unsupported. The two protrusions  42  which engage the pair of batteries in positions I and II prevent those batteries from sliding within the package. Furthermore, the lower side wall  32  extends upwardly sufficiently to restrict the tilting of the batteries in those positions. In the partially depleted package of FIG. 1, the battery in position IV will not be restricted from sliding between the long portions  48  of the side wall, although the remaining batteries will restrain it within the space defined by positions m and IV. Thus, although when an odd number of batteries are present within the container, at least one battery will be loose, in most cases, the majority of the remaining batteries will be retained in an upright condition within the container  20  ready for access. 
     As shown in FIG. 3, the container, while snugly engaging the loaded batteries, also provides easy access to each battery due to the diverging upper side walls  34 . The result of the outward inclination of the upper side walls  34  is that a clear margin unoccupied by battery or plastic material is defined around the tops of the batteries, thereby allowing the user to grasp a battery with two fingers and extract it by pulling upwardly. 
     The thin plastic of the container  20  is somewhat resilient, with the result that the package tends to return to its original shape after it is temporarily twisted or distorted. In addition, the perforated hinge  26  functions like a spring, tending to restore the cover to its original, molded, open, configuration. Thus the closure tabs  70  are preferably configured to engage with the base peripheral lip  52  in such a way that the upper side wall may be depressed inwardly to engage the batteries and to be removed from engagement with the closure tabs, causing the cover to spring open. In some sizes of packages it may thus be possible to open the container with one hand. 
     The container  20  is also amenable to effective and economical filling with batteries. The diverging upper side wall directs the loaded batteries downwardly into engagement with the radiused inlets  54  at the transition to the lower side wall four smooth entry into the pockets  44 . Because the bottom wall  28  of the container  20  is flat and featureless between the lower side wall, it presents minimal impediments to accurate loading of a full complement of batteries. Typically, batteries will not be loaded sequentially, but will be loaded together. 
     It should be noted that, although a perforated hinge has been shown, other conventional hinge structures may be employed, including molded hinges of various sizes. Furthermore, although a C cell battery package has been disclosed, the invention may also be dimensioned to accommodate AAAA, AAA, AA, D, or other round cells. 
     It is understood that the invention is not limited to the particular construction and arrangement of parts herein illustrated and described, but embraces such modified forms thereof as come within the scope of the following claims.
A retail package for round cell batteries is a transparent single sheet thermoformed clamshell having a cover connected along a hinge to a base which receives an array of upwardly extending batteries. The base has a side wall which extends upwardly from a flat bottom wall. The side wall has a lower section which is substantially perpendicular to the bottom wall and has a zero degree draft angle. Semicylindrical pockets are defined by the base wall lower portion and batteries are positioned in the pockets two abreast. Thus, each battery is engaged by a portion of the side wall and another battery. Hence, a partially emptied container will still retain most of the batteries upright. The cover has a downwardly extending skirt with an inwardly extending semicircular closure tab which engages beneath a lip formed on the base side wall. The lid closure may be released by pressing the base side wall.