Collapsible bottle
BACKGROUND OF THE INVENTION 
     The field of the invention pertains to collapsible plastic bottles and in particular to collapsible plastic bottles for foods and beverages, such as soda pop. Such bottles are constructed of plastics approved by the Food and Drug Administration for intimate and prolonged contact with foods and beverages. These bottles are commonly used for a variety of brands of soda pop and are formed of a clear plastic in a two-stage molding process. Typically, the two-stage molding process comprises an injection molded preform that is subsequently positioned in a bottle mold and blown to the full size of the bottle. In so doing, the side wall of the preform as the bottle is blown is stretched and tensioned to create an exceptionally sturdy thin-walled plastic bottle. Because the end of the preform, which eventually forms the bottom of the bottle, is not stretched axially as is the side wall, the bottom of the bottle does not possess the same strength as the side wall. Therefore, a separate plastic cup is fitted and affixed to the bottom of the bottle in a subsequent operation to reinforce the bottom of the bottle and prevent cracking or leakage in the handling of the filled bottle. 
     SUMMARY OF THE INVENTION 
     Applicant&#39;s invention comprises further improvements in the configuration of the finished bottle and in the manufacture of the finished bottle to provide a collapsible bottle. The purpose of a collapsible bottle is to substantially eliminate the air space in the top of the bottle as the contents are partially used. In the case of soda pop, a previously opened and partially filled bottle, upon storage for a few hours, goes flat or dead to the taste. In large part this is due to the escape of carbon dioxide dissolved in the soda pop into the air above the pop and in the bottle. By permitting the user to collapse the vertical height of the bottle as the soda is used or just before the cap is reattached, the air space above the partially filled bottle is substantially eliminated. With the cap on the bottle the carbon dioxide in the soda pop has no air space in which to escape. 
     Applicant&#39;s bottle provides a side wall circumferentially shaped in the manner of bellows. The bellows are formed to overcenter as the bottle is collapsed thus preventing the bottle from returning to its full height before or after the cap is placed on the bottle. The bellows are formed in the preferred embodiment by adding a third step to the manufacture of the blown bottle. After the preform is made and then is blown and stretched in the bottle mold, additional air or nitrogen is suddenly injected into the bottle at higher pressure to drive the already stretched side wall into the grooves of the mold that form the bellows. This sudden increased pressure further stretches the side wall and thins it; in particular, over the inner circumferential ridges of the mold to form folding points or folding sections of the side wall. Thus, the bottle can be easily and quickly folded as the liquid is withdrawn therefrom. The bellows also permit the bottle to be bent over to one side thus simulating a spout for easier pouring of the liquid inside. 
     The cap placed on the bottom of the bottle is slightly larger and deeper than the conventional bottle bottom cap and is attached to the bottom of the collapsible bottle both to reinforce the bottom of the bottle and to provide a pocket for the bottle to fold into. The new cap is substantially smooth sided on the outside side wall thereof to form a suitable surface for the bottle labels in substitution for placing the labels on the bottle side wall. The bellows configuration makes difficult the placing of labels on the bottle itself, and the labels would interfere with the proper folding of the bottle. Thus, the folded bottle fits generally within the extended bottom cup of the bottle. The cup also provides a convenient hand grip when the bottle is partially or fully collapsed. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partial side cross-sectional view of the collapsible bottle; and 
     FIG. 2 is a partial side cross-sectional view of the collapsible bottle fully collapsed, and 
     FIG. 3 is a top view of the collapsible bottle. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In FIG. 1 the bottle, generally denoted by 10, includes an upper hemispherical portion 12 having a central neck 14 for a cap 16 that may be attached and detached. The bottle 10 is formed with generally bellows-shaped sidewalls 18 and includes a separate bottom cup 20 affixed to the bottom of the bottle 10. The cup 20 side wall 22 is generally smooth to provide a suitable surface for the labels that are affixed to the bottle. Labels may also be affixed to the generally smooth hemispherical portion 12 at the top of the bottle. As illustrated in FIG. 1, the bellows-shaped side wall 18 of the bottle extends down within the cup side wall 22 as illustrated at 24. Typically the bellows extend almost to the bottom of the bottle and cup and the cup side wall extends generally toward the middle of the vertical height of the bottle. 
     Each bellow here indicated by 26 comprises a downwardly and outwardly extending conical portion 28 and a downwardly and inwardly extending conical portion 30 which is substantially smaller and at a much greater angle to the axis of the bottle. In the figure six bellows are shown; however, in actual practice a very large number of bellows, each of which is much smaller in proportion to the size of the bottle, is preferred. Thus, as shown, the bellows are greatly enlarged in proportion to the typical soda bottle in which the bellows are incorporated. 
     FIG. 2 illustrates the bottle substantially collapsed for a volume approximately one-half that of the expanded bottle. Thus, the bottle substantially eliminates the air volume over the liquid beverage down to the point where the bottle is half full. As shown, the individual bellows 26 are collapsed or folded over such that the short portion 30 of each bellow is folded over the long portion 28 of the adjacent bellow. In FIG. 2 as in FIG. 1 the size of each bellow in proportion to the size of the bottle is greatly exaggerated. 
     In actual practice the increase in diameter of the bottle attributed to the bellows is so limited as to not substantially increase the diameter of the bottle with the cup attached. The cup side wall 22 interior diameter need only be sufficient 23 to permit the bellows to fold over and become overcentered as shown in FIG. 2. The flexibility of the cup material assists in permitting the bellows to fold and snap over. Once snapped over as shown in FIG. 2, because of the cylindrical configuration of the bottle and bellows, the bellows will not expand despite the failure to replace the cap 16 on the bottle. The close proximity 21 of the sidewall 22 of the cup also assists in preventing the collapsed bellows from expanding. 
     The cup side wall 22 is substantially smooth to assist in attaching labels and the like to the cup and bottle combination. The cup is adhesively affixed to the bottom of the bottle as shown at 32 in both figures. It is preferred that the bellows be generally shaped as shown to obtain the overcentering action that holds the bottle collapsed. However, even without the overcentering action, the attachment of the cap to the collapsed bottle prevents the bottle from expanding due to the external atmospheric air pressure. It is envisioned that in a vast majority of instances the plastic utilized for the bottles will be a very strong flexible plastic such as acrylonitrile or similar plastic approved by the Food and Drug Administration. In some instances a relatively soft plastic may be utilized for the bottle in which case the overcentering action would not be completely satisfactory and the replacement of the cap on the bottle required to retain the partially full bottle in the collapsed state. 
     To assist in the folding and collapsing of bottles manufactured from stretched plastics such as are typically used currently for the more popular brands of soda pop in two liter bottles, such stretch plastics are typically formed into bottles by first creating an injection molded or blow molded preform having a relatively thick plastic wall and bottom and generally in the shape of a common laboratory test tube. The preform, heated above the heat distortion temperature of the plastic, is then blown in a bottle mold to the full bottle size and wall thickness. In the process of blowing the bottle the side wall of the bottle is stretched, which in combination with the particular plastic adds significantly to the tensile strength of the bottle side wall. After removal from the bottle mold, the bottom cup is adhesively affixed to the bottom of the bottle to reinforce the bottle bottom. 
     Applicant&#39;s bottle is manufactured in a similar manner; however, the cup 20 is sized in depth and inside diameter to accommodate the collapsed bellows as shown in FIG. 2. Typically, the cup will be two or more times the depth of the plastic cup on the bottom of a conventional two liter soda pop bottle. In blowing the bottle, subsequent to blowing the bottle within the bottle mold and before removal from the bottle mold, additional high pressure air or nitrogen gas is suddenly admitted to the interior of the bottle to expand the side wall of the bottle into the bellows forming grooves of the mold. The sudden expansion with the high pressure air or gas stretches the side wall further at the lesser diameters of the bellows such as 34 thereby forming a stretched circular thin spot or fold ring in the bottle wall. In addition, the conical portions 28 and 30 will be slightly stretched further as blown from the bellowless wall indicated at 36 to the final bellows configuration. 
     The additional thinning of the wall permits the bellows action to more easily take place with the plastic materials currently utilized and the wall thicknesses currently utilized. The additional thinning of the wall beyond that of the conventional uncollapsible bottle is not detrimental to the strength of the bottle because the ribbing effect created by the bellows configuration adds additional rigidity in all directions with the exception of the collapsing direction of the bottle. Thus, the fold rings and thinned sections of the side wall assist in creating an easily collapsible bottle that remains convenient for handling and storing. 
     Fully collapsed into the cup, the bottle remains easy to use and when completely emptied and stored, only takes approximately half the volume of the conventional uncollapsible soda pop bottle. In States such as Michigan, the storage of empty bottles for return to the bottling plants and distributors is a significant problem. Collapsible bottles can significantly assist in lessening the storage volumes required for large quantities of empty bottles in storage rooms before they are returned to the reprocessor of the bottles.