Stretch blow-molded stackable tumbler

Abstract

The inventive drinking vessels are prepared by stretch blow-molding a preform and exhibit increased Rigidity as well as elevated, preferably relatively uniform crystallinity. A preferred method of making blow-molded stackable drinking vessels includes expanding a preform both axially and radially to make an intermediate article with a neck, a transition portion and a tumbler portion. The transition portion and neck are severed from the tumbler which is then fortified around its upper aperture which is larger than its base.

Description

CLAIM FOR PRIORITY [0001] This application claims the benefit of the filing date of U.S. Provisional Patent Application Ser. No. 60 / 402,314, filed Aug. 9, 2002. This application also claims priority to U.S. patent application Ser. No. 10 / 635,722, filed Aug. 6, 2003. The disclosures of each of these applications are incorporated herein in their entireties by this reference.TECHNICAL FIELD [0002] The present invention relates generally to drinking vessels and in preferred embodiments to a stretch blow-molded tumbler formed from an injection molded preform which is expanded radially and axially to form the tumbler. The tumblers exhibit high Rigidity, orientation and relatively high crystallinity. BACKGROUND [0003] In quick service restaurants, one of the highest margin items offered is the fountain beverage. In many cases, it is possible for the quick service restaurant owners to boost their sales of beverages by providing promotional cups either with printing tied to some media phenom...

AI Technical Summary

Benefits of technology

[0011] The tumblers typically exhibit a Rigidity of at least 4 or 5 lbf at ⅔ cup height and 1 inch sidewall deflection as is seen in Table 6 hereinafter. A weight to volume ratio of less than about 1.2 gram / oz. is preferred; the volume being the contained volume of the tumbler. Weight to volume ratios of about 1 g / oz. or less are still more preferred. The inventive process provides relatively high crystallinity in the sidewall as will be seen from the calorimetry data which follows. Crystallinities of 20%, 25% and higher may readily be achieved with PET. The high Rigidity makes the process especially suitable for large tumblers of low weight. Tumblers of 20 fluid oz. volumes, 30 fluid oz. volumes and more are advantageously fabricated in accordance with the invention.

[0013] One preferred method of making a blow-molded tumbler includes: (a) injection-molding a preform provided with a neck portion, a body portion and a bottom portion; (b) blow-molding the preform to form a first intermediate article therefrom wherein the preform is expanded radially as well as axially, the intermediate article being characterized by having a neck portion corresponding to the neck portion of the preform, a transition portion adjacent the neck portion of the first intermediate article and a tumbler portion adjacent the transition portion thereof, the tumbler portion of the first intermediate article being further characterized by having a base formed from the bottom portion of the preform and a sidewall formed from the body portion of the preform; (c) severing the tumbler portion of the first intermediate article from its transition portion to form a second intermediate article having a base corresponding to the base of the first intermediate article and a sidewall extending upwardly therefrom to define an upper aperture, the aperture being generally larger in area than the base of the second intermediate article such that the tumbler portions are stackable; and (d) fortifying the sidewall of the second intermediate article around the upper aperture to form the tumbler. Typically the step of blow-molding the preform includes, reheating the preform after it is injection molded, stretching the preform with a solid or hollow stretch rod prior to blow-molding, and then blow-molding the bottle, usually first with a low pressure and then with high pressure. Alternatively, uniform pressure may be used, but this is not preferred for the present invention. Generally, the first intermediate article has an axial stretch ratio of 1.5 to 7 and a hoop stretch ratio of 1.5 to 10. In some cases, the first intermediate article has an axial stretch ratio of 2.0 to 3.5 times and a hoop stretch ratio of 1.5 to 4. A blow-up ratio (hereinafter defined) of at least 3 is desirable, typically a blow-up ratio of at least 5 is used. Blow-up ratios of from about 7.5 to about 14 with respect to the preform are preferred in some cases; for instance, the first intermediate article may have a blow-up ratio of from about 9 to about 12. The tumblers or cups of the invention are stackable because their bases have a perimeter that is smaller than the inner perimeter of their upper apertures and of suitable shape, such that one tumbler may be stacked with a like tumbler. Preferably, the tumbler's perimeter from its base up to about 60% of its height is likewise smaller than the interior of its upper aperture so that the lower 60% at least fits within a lower adjacent tumbler in a stack. In many cases, it is desirable that the tumbler's perimeter at its base and its perimeter up to at least 90 or 95% of its height is smaller than the interior of its upper aperture such that the tumblers are compactly stackable.

[0020] The tumbler portion of the first intermediate article may be provided with a flange projecting inwardly or outwardly from its sidewall joining the tumbler portion of the first intermediate article to the transition portion thereof. The flange may project downwardly as well and is generally configured to be incorporated into the fortified rim of the tumbler and facilitate formation of the tumbler rim.

[0025] The multilayer preform may contain two contiguous layers of polymer with different compositions, but including a common monomeric repeat unit to improve compatibility and adhesion of the various layers while providing for a spectrum of properties. For example, there could be provided an interior layer of polypropylene copolymer which is relatively stiff and an outer layer of polypropylene copolymer which is relatively soft to improve “hand feel” of the tumblers.

[0027] In some embodiments, the tumblers of the invention can be made relatively thick-walled, e.g., a wall thickness of greater than 25 thousandths of an inch such that it is not necessary to fortify the rim; rather the tumbler portion may simply be severed from the upper portion of the intermediate article and the rim optionally smoothed with a flame treatment, abrasive, or other honing technique. Of course, curling the rim or flanging it with a hot tool will likewise provide the needed smoothness after cutting the tumbler from the transition section.

Problems solved by technology

However, the ability to offer cups in unusual configurations or shapes is greatly limited by the technology currently used to produce such cups.

In particular, injection-molding is relatively inefficient in use of materials when cups are formed from polymeric resins, while injection blow-molding is best applied to only a limited range of polymers and vacuum thermoforming produces a relatively weak cup.

The cups produced by these methods are usually limited to traditional straight taper designs and are usually not transparent, particularly in large sizes as are typically employed in connection with promotional cups.

Stretch blow-molding is perhaps one of the most widely employed methods for making blow-molded bottles; however, the method is not believed to have been employed to make stackable drinking vessels.

This process is more intricate to coordinate than stretch blow-molding processes and does not utilize generally available molding equipment since the injection-molding and blow-molding operations are practiced concurrently.

Moreover, the process of the '543 patent does not extend the length of the injection molded parison and thus generally requires a relatively thin-walled parison which, in turn, restricts the selection of polymer material utilized in the process.

So also, the process of the '543 patent does not include heating the parison sufficiently to relieve molded-in stress.

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