Abstract:
An improved hot-fill bottle is provided having smooth sides and no heat panels or vacuum panels. The bottle is produced from a plastic pre-form having a mass, PF mass , calculated as a function of the desired volume of the bottle, in litres, according to the following function:  
       97  g/l&lt;PF mass   &lt;135  g/l 
     More preferably, PF mass , is calculated as follows:  
       109  g/l&lt;PF mass   &lt;118  g/l 
     The improved bottle is used in an improved method for hot-filling a beverage container.

Description:
TECHNICAL FIELD  
         [0001]    The present invention relates to blow-moulded plastic containers, and more particularly to containers designed to be filled with a beverage by a “hot-fill” method.  
         BACKGROUND  
         [0002]    Many beverages are packaged in blow-moulded plastic containers, and in particular, in polyethylene terephthalate (PET) bottles. While some beverages are packaged by aseptic means or utilizing preservatives, many other beverages—fruit juices and isotonic drinks, for example—are “hot-filled”. Hot-filling involves the filling of a container with a liquid beverage having some elevated temperature (typically, at about 180-200° F.). The container is capped and allowed to cool, producing a vacuum therein.  
           [0003]    Hot-filling provides various advantages over aseptic or preservative packaging, among them lower capital and operational cost (over aseptic systems), and the elimination of the need for preservatives (the heat of the beverage has a sanitizing effect). The hot headspace in the filled bottle also reduces the carrying capacity of oxygen therein, limiting oxidation of the contents.  
           [0004]    Hot-fillable PET bottles have been well-known for many years, and a variety of such bottles are available today in the market. There are various requirements for such bottles. Most importantly, they must be able to provide thermal resistance against the hot-filled contents. They should also provide an ultraviolet (UV) light barrier and an oxygen (and in some cases a carbon dioxide) barrier to protect the contents from degradation. Their third requirement is that they must be constructed so as to be able to withstand the vacuum created in the bottle as the contents cools, to maintain their intended shape.  
           [0005]    The first two of these requirements are met by manufacturing bottles out of suitable materials, such as PET, and various combinations of such materials. In some instances, the plastics used to produce such bottles may be layered. In other instances, certain additives may be blended directly into the initial resins to provide certain qualitites such as UV resistance.  
           [0006]    The third of these requirements is typically met by constructing the bottles with certain stiffening structures known in the art as “heat panels”, “collapse panels” or “vacuum panels” which typically form a portion of the sides of the bottles. Essentially, these panels, which are described in a variety of patents such as U.S. Pat. Nos. 5,762,221 and 6,375,025, which are incorporated herein by reference, prevent the bottle from collapsing in on itself when the vacuum is generated therein by the cooling of the hot-filled contents.  
           [0007]    However, these stiffening structures adversely affect, in the view of some, the aesthetic look of a bottle, because they prevent the bottle from assuming a traditional round, or cylindrical shape, as a glass bottle would have. Studies have indicated that the configuration and overall aesthetic appearance of a beverage bottle can significantly affect consumer purchasing decisions. A bottle which appears dented or distorted is not necessarily appreciated by consumers, although many manufacturers try to rationalize these distortions as providing “gripping” surfaces for the bottles. Moreover, the panels prevent a label from neatly encircling the circumference of the bottle, since the side of the bottle is not smooth.  
           [0008]    There remains a need, therefore, for a hot-fillable PET bottle with smooth sides and lacking heat panels.  
         SUMMARY OF INVENTION  
         [0009]    The present invention provides an improved hot-fillable bottle, and an improved method for hot-filling a bottle, using the improved bottle.  
           [0010]    More particularly, the improved bottle is made from a pre-form having a certain mass per volume size of the desired bottle, which allows the bottle to be constructed without stiffening structures, and with smooth sides. Specifically, there is described herein a hot-fillable beverage container, comprising a circular base portion; a shoulder portion; a neck portion extending upwardly from the shoulder portion; and a cylindrical body portion extending between the base portion and the shoulder portion. The cylindrical body portion has a circular transverse cross-section along its entire length, and lacks distinct panels formed thereon. The container is constructed from a pre-form of plastic material having a mass, PF mass , as a function of the desired volume of the container, in litres, calculated according to the following function:  
           97 g/l&lt;PF mass &lt;135 g/l. 
           [0011]    In a preferred embodiment, the pre-form has a mass of:  
           109 g/l&lt;PF mass &lt;118 g/l. 
           [0012]    In a preferred embodiment the pre-form is made of PET. In another embodiment, the pre-form is a combination of PET and polyethylene naphthalate (PEN).  
           [0013]    The hot-fillable bottle may have a dimple formed in the base portion thereof which extends into the interior of the bottle, the dimple having a plurality of indicia surrounding its edge, indicating one or more compass points, thereby allowing the bottle to be used as a compass in combination with a thin length of metal.  
           [0014]    In a preferred embodiment of the invention, the neck portion of the bottle has threads, and the bottle has a cap threadable onto the neck portion, the cap having a lower portion having threads for threading the cap onto the neck portion of the bottle, and an upper portion defining a hole therethrough for removably attaching the bottle to an attachment location, for example, onto a back-pack.  
           [0015]    There is also provided, in a known method for hot-filling a bottle, the method comprising the steps of filling a bottle with a heated beverage, capping the bottle, and allowing the bottle and its contents to cool, an improvement which comprises providing a bottle having the characteristics of this new hot-fillable bottle. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0016]    [0016]FIG. 1 is a perspective view of a hot-fillable bottle made in accordance with one embodiment of the invention;  
         [0017]    [0017]FIG. 2 is a side view of the bottle shown in FIG. 1;  
         [0018]    [0018]FIG. 3 is a bottom view of the bottle shown in FIG. 1; and  
         [0019]    [0019]FIG. 4 is a perspective view of a preferred cap for the bottle shown in FIG. 1.  
     
    
     DESCRIPTION  
       [0020]    Throughout the following description, specific details are set forth in order to provide a more thorough understanding of the invention. However, the invention may be practised without these particulars. In other instances, well known elements have not been shown or described in detail to avoid unnecessarily obscuring the invention. Accordingly, the specification and drawings are to be regarded in an illustrative, rather than a restrictive, sense.  
         [0021]    Referring first to FIG. 1, a hot-fillable container or bottle, denoted “ 10 ” throughout this description, has a base portion  12 , a shoulder portion  16 , and a neck portion  18  sitting atop the shoulder portion  16 , in the manner of many traditional bottles.  
         [0022]    The base portion  12  is preferably circular when viewed from the bottom of the bottle, as shown in FIG. 3, as is the shoulder portion  16  and the neck portion  18 , when viewed from the top of the bottle  10 . A cylindrical body portion  14  of the bottle  10  extends between the top of base portion  12  and the bottom of shoulder portion  16 . Bottle  10  may be constructed of any suitable plastic material, but in a preferred embodiment is constructed of polyethylene terephthalate (PET), as described below. In another embodiment, bottle  10  is constructed of a combination of PET and polyethylene naphthalate (PEN). Any other suitable plastic material may be employed.  
         [0023]    As described earlier, many hot-fillable bottles are made of a plastic material such as PET. This allows the production of light-weight bottles which do not break as readily as glass bottles. Such bottles are made from a process known in the art as injection or stretch blow-moulding. In this process, a “pre-form” amount of plastic, again, usually PET, having an neck portion, an interior portion and an exterior portion, is placed into a mould in a heated state. Air or another gas is injected into the interior portion of the pre-form, through the neck portion, forcing the pre-form to expand to the limits of the mould to assume the desired bottle shape. The newly-formed bottle begins to cool within the mould, and is released from the mould to continue to cool.  
         [0024]    Due to cost considerations, bottle manufacturers attempt to limit as much as possible the amount of PET in the bottle (and originally in the pre-form). Limiting the amount of PET which is used to form the bottle may make the bottles too thin, however, to be able withstand the vacuum created within the bottle during the hot-filling process. Hence, manufacturers have been developing stiffening structures for hot-filled bottles as described earlier.  
         [0025]    Although it might be suggested that increasing the amount of plastic in the bottle might increase its strength, thereby avoiding the need for such stiffening structures, there are number of factors which, to date, have prevented manufacturers from successfully making bottles with an increased amount of PET.  
         [0026]    First, most manufacturers attempt to limit the plastic in a bottle to save cost. The focus of bottle manufacturers is thus on methods of reducing the amount of plastic used to make a bottle. Further, from a manufacturing point of view, if too much plastic is used in the production of a PET bottle, the bottle will collapse under its own weight when it is removed from the mould during the manufacturing process. Also, the bottle will not cool properly if too much plastic is used.  
         [0027]    The present inventors have discovered the fine line which exists between having too little plastic in a bottle (forcing the requirement for stiffening structures and their attendant problems), and having too much plastic in a bottle (with the limitations discussed above). This line may be more clearly defined by way of the following formula:  
         97 g/l&lt;PF mass &lt;135 g/l 
         [0028]    wherein PF mass  is the mass (in grams) of the plastic pre-form which should be used to make a hot-fillable PET bottle which will not require stiffening structures, per desired volume of the bottle, in litres. In a preferred embodiment, this range may be more narrowly defined in accordance with the following function:  
         109 g/l&lt;PF mass &lt;118 g/l. 
         [0029]    In a preferred embodiment of the bottle, for example, a bottle having a volume of 620 ml (21 oz.) may be produced using a pre-form having a mass of between approximately 68 g and 73 g. A typical hot-fill bottle requiring heat panels has, by way of contrast, a mass of about 35 g, or only about half of the mass of the present bottle.  
         [0030]    The inventors have found that using this amount of plastic in the production of a hot-fillable bottle allows the bottle  10  to be moulded with the body portion  14  thereof having a circular transverse cross-section along its entire length, without the need for any distinct panels formed along its length. This allows bottle  10  to present a pleasing, rounded shape to the consumer, and also allows a label  35  (FIG. 2) to be applied to bottle  10 , label  35  showing a smooth face without dimpling.  
         [0031]    The inventors have also determined that using this amount of PET will also provide bottle  10  with enough thickness in body portion  14  to provide an appropriate UV barrier without the requirement for extra, UV-blocking layers of plastic. A bottle produced in accordance with the present invention will also provide an appropriate oxygen barrier. In practise, it has been determined that a bottle produced in accordance with the present invention has a typical thickness of between approximately 0.025″ and 0.055″. By contrast, a typical hot-fillable bottle employing heat panels has a thickness of approximately 0.008″-0.020″. The relative thickness of the bottle also conveniently provides the bottle with better insulative properties—beverages tend to warm up less slowly in the present bottle than in known PET bottles.  
         [0032]    In a preferred embodiment, the present bottle  10  also has a dimple  30  formed in base portion  12 , extending into the interior of bottle  10 . It will be appreciated that dimple  30  may strengthen bottle  10 , but one of its purposes is to allow bottle  10  to be used as a compass in combination with a thin length of metal, such as a pin. In particular, dimple  30  may be provided with a plurality of indicia  50   a ,  50   b  surrounding its edge, indicating one or more compass points. When bottle  10  is inverted, and dimple  30  filled with a liquid, a pin may be placed on top of this liquid and, as is well known, the pin will tend to indicate magnetic North. The bottle user turns the bottle so as to align the “North” indicia with the pin, and thereby may gain a sense of direction.  
         [0033]    Bottle  10  may of course be capped with any suitable cap, but it being foreseen that bottle  10  will be reusable (given its strength), bottle  10  may be provided with a specialized cap  40  (shown in FIG. 4), which allows bottle  10  to be removably attached to an attachment point (for example, onto a back pack, not shown). Cap  40  has a lower portion  42  having inner threads for threading cap  40  onto neck portion  18  of bottle  10 , and an upper portion defining a hole  44  therethrough for removably attaching bottle  10  to an attachment location with any suitable attachment means (for example, a carabineer).  
         [0034]    Bottle  10  may, as is known in the art, be moulded with various trade-marks and other indicia  20   a ,  20   b.    
         [0035]    The new bottle may be produced by an improved method. In a known method, a hot-fillable bottle is produced by the steps of providing a pre-form of PET material having as little mass as possible to provide a one-time use container, and injecting a gas into the pre-form, thereby expanding it within a mould to a desired size and shape. The improved step involves the provision of a PET pre-form having a mass, PF mass , calculated as a function of the desired volume of the bottle, in litres, according to the following function:  
         109 g/l&lt;PF mass &lt;118 g/l, 
         [0036]    which allows the production of a bottle which can be reused many times.  
         [0037]    This improved bottle  10  may be used in a known method for hot-filling a bottle, the method having the steps of filling bottle  10  with a heated beverage, capping the bottle with cap  40 , and allowing the bottle and its contents to cool.  
         [0038]    As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.