Supporting A Thin Walled Bottle During Capping

Abstract

In capping a bottle containing a carbonated beverage capable of generating a pressure of from about 15 to 150 psig depending on temperature conditions, wherein a top load is applied to force a closure into sealing engagement with an end section of the bottle, the improvement of circumferentially enveloping a curved, stress minimizing transition zone in the bottle between the side and bottom walls with a restraining member during application of the top load to prevent outward deflection of the transition zone, the bottle being formed of a high barrier, flexible, thermoplastic material having a wall thickness in the area of the transition zone of between 10 to 35 mils. The apparatus comprises a shallow support member for the lower portion of the bottle to resist outward deflection of the thermoplastic during capping.

Description

BACKGROUND OF THE INVENTION

This invention is directed toward filling and capping bottles and more particularly toward capping bottles containing a beverage capable of generating a pressure due to carbonation of from 15 to 150 psig at the extremes of the temperature conditions to which it might be exposed prior to consumption.

Bottled carbonated beverages such as soft drinks and beer have been traditionally marketed in glass containers having relatively thick walls on the order of 1/8 - 1/4 inch. These thicknesses are provided basically in order that the containers be capable of withstanding miscellaneous impact forces without breaking, such as those encountered e.g., during handling, filling and capping. More specifically, the procedure for bottling beverages in such containers customarily involves drawing a beverage portion from a reservoir at a very high rate into the container and then transferring the thus filled container, usually automatically, to a capping machine where a closure is then sealed by various automated techniques to the bottle, such seal being adequate to retain the pressure of the contents until the bottle is opened. The temperature of the beverage during filling and capping is usually quite low, e.g., about 32.degree.-40.degree. F., and consequently the internal pressure from carbonation immediately after capping is also quite low, but eventually the temperature could rise to as high as 120.degree. F. before the bottle is opened by a consumer and at this temperature the internal pressure could reach 150 psig at a level of 5.0 volumes of CO.sub.2 within the container, whereas at the other end of the scale, i.e., at 45.degree. F. and a relatively low carbonation level of 2.6 volumes of CO.sub.2, the pressure of the contents might be as low as 15 psig. Such packages are generally considered to require special pressure resistant closures in contrast to non-pressurized packages where the internal pressure is essentially atmospheric.

Equipment for applying the caps to the bottles usually includes a type of pressure block which is moved axially relative to the closure bearing surface of the bottle at a substantial force, e.g., on the order of 200-1,000 pounds, depending on the equipment, in order to establish a seal of the closure with the upper surface of the bottle finish. As mentioned, because of the relatively thick walls, the base sections of prior art glass bottles readily withstood such top loads without breaking or buckling.

Recently, thermoplastic materials have been developed which have been found especially suitable for pressurized packaging applications primarily because of their attractive carbon dioxide and oxygen barrier properties. Typical of such materials are polymers based on acrylonitrile or methacrylonitrile; vinyl chloride and certain polyesters. Using the prior glass container art as a guide, bottles made from these materials and used in these applications were initially made with rather thick walls, and, accordingly, when we passed such containers through filling and capping equipment of the type just described, the base area to which the relatively high top loads were transmitted was sufficiently heavy to readily withstand the load.

Other considerations however dictate that a more sophisticated approach is necessary to provide a commercially successful carbonated beverage bottle made from these materials. For example, though such thermoplastic bottles have advantages, e.g., in terms of a substantial reduction in weight over glass or metal, if they are to be competitive they must obviously be produced at costs approaching those of the latter. Thus, it is desirable to reduce the wall thickness in order to decrease the amount of the relatively expensive-to-synthesize thermoplastic therein. Also, though these special thermoplastics possess desirable barrier properties, they tend to be somewhat brittle, and especially is this so with polymers wherein the major constituent has been polymerized from a monomer containing at least one nitrile group in its molecular structure. Therefore, the wall thickness cannot be greatly reduced if a high degree of sturdiness is necessary. To compensate for brittleness, it has been suggested that an impact modifier be incorporated into the bottle forming polymer and/or that the polymer be stretched in order to preferentially orient the molecules thereof in the direction of stretch, each of these approaches being for the purpose of improving impact strength. In addition, since the area of maximum stress from internal pressure occurs in the lower portion of an elongated container in the area of the confluence of the sidewall with the base, it has been necessary to very carefully redesign this area versus that previously employed in the less critical, heavy walled containers in order to take maximum advantage of bottle contour in minimizing high stress areas without having to preferentially thicken the wall in such areas. This has involved a rather critical choice between maximum curvature in the area of the lower portion of the bottle and bottle stability or the ability of the container to support itself in an upright position on a flat surface without requiring an auxiliary support. When all of these process and container design changes are made, however, though the strength properties are substantially improved and manufacturing economics competitively approach those of containers made from other materials, we have found that problems occur in the ability of the otherwise desirable thin walled, impact resistant, strong thermoplastic bottles to withstand conventional filling and capping top loads.

One solution to this dilemma is to incorporate means into the capping machine and bottle to prevent the lower end from ever being exposed to the otherwise necessary capping top loads, for example by supporting each bottle at a circumferential ring on its neck below the finish. However, this appears to require that separate means be incorporated into existing or new capping machines which means must be used with thin walled lightweight plastic bottles but which are not required when the bottles are made of other relatively thick walled materials such as glass. In addition, any separate support ring on the bottle would have to be below the finish in order not to interfere with the latter and would, accordingly, detract from the aesthetic appearance of the container.

SUMMARY OF THE INVENTION

Now, however, there has been developed a novel technique for accommodating thin walled, flexible, barrier thermoplastic bottles in carbonated beverage filling and capping machines.

Accordingly, it is a principal object of this invention to provide novel method and means for supporting a thin walled, flexible bottle containing a beverage capable of generating pressures on the order of 15-150 psig at temperatures of from 45.degree. to 120.degree.F., as a cap for resisting such pressures is being applied to the bottle.

An additional object of this invention is to provide method and means for supporting such a container against substantial top loads other than at the neck area thereof.

A further object of this invention is to provide method and means for supporting such a container which has a generously rounded stress minimizing wall portion joining the side and base walls which tends to collapse on itself when axially loaded with forces generated by conventional carbonated beverage filling and capping machine heads.

A specific object of this invention is to provide method and means for supporting such a container which does not require that any revisions at all be made to already existent commercial capping heads.

Yet another object of this invention is to cap such a bottle by application of top loads on the order of 200-1000 pounds without rupturing or in any way permanently deforming the bottle after dissipation of such capping loads.

Other objects of this invention will in part be obvious and will in part appear hereinafter.

These and other objects are accomplished in the method of capping a bottle containing a beverage capable of generating a temperature-dependent pressure of from 15 to 150 psig through imposition of a top load to the bottle to force a closure into sealing engagement with cooperating surfaces on an end section thereof, by providng the improvement which comprises circumferentially enveloping a curved, stress minimizing transition zone in the bottle between the side and bottom walls with a restraining member during application of said top load to prevent outward deflection of said transition zone, said bottle being formed of a high barrier, flexible, thermoplastic material having a wall thickness in the area of said transition zone of between 10 to 35 mils.

The apparatus includes a shallow support member for the lower portion of the bottle to resist outward deflection of the flexible thermoplastic during application of capping forces, the support member preferably having a cavity formed therein which is contoured to match the outer surface of the lower portion of the bottle.

BRIEF DESCRIPTION OF THE DRAWINGS

In describing the overall invention, reference will be made to the accompanying drawings wherein:

FIG. 1 is an elevational view of a bottle and closure useable in the method of the present invention;

FIG. 2 is a vertical sectional schematic view illustrating in solid lines the bottle of FIG. 1 supported according to the present invention just prior to imposition of a top load;

FIG. 3 is a partial, schematic view of the lower end of the bottle of FIGS. 1 and 2 during imposition of a capping top load which is not supported according to the invention;

FIG. 4 is a view similar to FIG. 3 after release of the top load;

FIGS. 5 and 6 are vertical, sectional, schematic views of alternative forms of bottle support according to the present invention; and

FIG. 7 is an enlarged, sectional, schematic view of the upper end of the bottle of FIGS. 1 and 2 during capping;

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Referring now to the drawings, there is illustrated in FIG. 1, a one piece bottle 10 for containing a carbonated beverage which is formed of a high barrier, flexible, thermoplastic material, such as a polymer comprising from 60 to 80 weight percent polymerized acrylonitrile monomer and 40 to 20 weight percent of another monomer, such as styrene, copolymerized therewith. it should be understood, however, that this composition represents a preferred embodiment and that alternative yet highly selective types of thermoplastics are useable in packaging the carbonated beverages, such as soft drinks and beer, toward which the present invention is directed. To accomplish this, it is necessary that the thermoplastic exhibit high barrier properties toward oxygen and carbon dioxide, materials having permeabilities of less than 20 (O.sub.2) and 30 (CO.sub.2) cc./day/100 sq.in./mil./atm. at 73.degree.F. being considered herein as qualifying for this application.

Bottle 10 comprises sidewall 12, the upper portion of which converges inwardly to eventually form central opening 14 through which the contents is discharged, the inwardly tapered end section 16, in the illustrated embodiment, having a finish constituting threads 18 integrally formed on its outer surface. Alternative types of finishes, however, may be provided on bottle 10 for accommodating different types of closures, e.g., crown, rip cap, or crown-twist off. Bottle 10 includes a rounded transition zone 20 at the lower end thereof which smoothly connects sidewall 20 with base 22. Base portion 22 includes a raised inwardly convex central area 24 and a relatively flat annular seating ring portion 26 for supporting bottle 10 in an upright position on a flat surface without requiring an auxiliary coaster-like support member. Transition zone 20 is rather critical in the design of bottle 10 in that this is the area of the bottle in which maximum stresses are developed due to the pressure of the beverage contents 28, when the bottle is capped and the contents are increased in temperature, e.g., to the temperature of the particular surroundings to which the filled and capped bottle is exposed during handling, storing, etc., which temperature is considered to lie anywhere within the range of from about 45.degree. to 200.degree.F., with the corresponding internal pressure, depending on the carbonation level, being within the range of 15 to 150 psig. Of course the beverage temperature, because of consumer preference, most likely will have been reduced again to around 32.degree. F. at the time of consumption.

Bottle 10 in the area of transition zone 20 has a relatively thin wall of between 10 to 35 mils as shown at 78 in FIG. 1, which has been molecularly oriented during molding by stretching the plastic forming transition zone 20 both axially in the direction of axis 62 and either subsequently or simultaneously in the radial direction perpendicular to axis 62. For the high nitrile plastic of bottle 10 of the illustrated embodiment, stretching should be carried out above the glass transition temperature of the polymer and preferably within the temperature range of from 250.degree. to 325.degree. F. Though bottle 10 (with cap 32 sealed thereon) can successfully contain contents 28 without being molecularly oriented, the ability of the bottle to withstand impact is greatly improved by orienting the plastic of transition zone 20 in the sense that the plastic tends to yield when exposed to a critical yield stress such as an impact force, whereas the bottle is prone to fail at transition zone 20 under exposure to similar force conditions with an unoriented plastic.

Closure 32 is provided for bottle 10 and comprises flattened end wall 34 and skirt 36 depending from the periphery of wall 34. In the illustrated embodiment, closure 34 is made of thin walled deformable aluminum metal having a liner 56 (FIG. 7) therein which is inert to contents 28, though obviously closure 32 could be formed of other materials such as plastic.

Contents 28 in the illustrated embodiment comprises a cola beverage to which 3.75 volumes of carbon dioxide has been added, but which is at a temperature sufficiently low, e.g., on the order of 32.degree. F. to avoid generation of the pressures otherwise encountered due to carbonation on subsequent increase of the temperature. By a volume of CO.sub.2 gas under these circumstances is meant one volume of CO.sub.2 gas measured under standard conditions for gases dissolved in one volume of the liquid. Though bottling the beverage at low temperature is preferred since the pressures encountered are lower, it should be realized that the beverage temperature during bottling can be higher, e.g., 70.degree. F., and such may be desirable to reduce refrigeration requirements. Contents 28 has been added to bottle 10 by conventional filling equipment preferably while supported within support member 30, (FIG. 2) the significance of which will be described hereafter.

As indicated in FIG. 2, in capping bottle 10, cylindrical closure 32 is placed, either automatically or manually, loosely on the neck of bottle 10 such that end wall 34 overlies opening 14 and depending skirt 36 surrounds the threads 18 on the outer surface of neck 16. According to the present invention, at some time prior to application of the top load, as indicated by the dotted line position of head 48 in FIG. 2, bottle 10 is placed within shallow support member 30, or alternatively, support member 30 may be brought up around the bottom portion of bottle 10 while the latter is held in fixed position by a suitable means (not shown). This latter placement could be accomplished, for example as illustrated in FIG. 6, by means of piston rod 38 reciprocable in conventional fluid actuated cylinder 40 which has at its outer end, carrier platform 42 with a continuous side portion 43 extending upwardly from its periphery, as illustrated in FIG. 6. In the preferred embodiment of FIG. 1, support member 30 has an upwardly facing cavity 44 formed therein, the sidewall 46 of which is contoured to exactly match the outer surface configuration of transition zone 20 of bottle 10, i.e., wall 46 is curved at a radius or radii equivalent to that of R of the bottle (FIG. 1). For good thin walled, flexible thermoplastic pressurized container design, R should be maintained at between 0.125 to 0.7 inch.

As illustrated in FIG. 2, conventional capping head 48 is supported above the cap-bearing bottle 10, and includes a pressure block 52, having a bottle facing cavity formed in its lower end which includes a vertical surface 54, the diameter of which is equivalent to that of the outside diameter of bottle neck 16 plus the thickness of sidewall 36 of closure 32 as well as that of liner 56, should the latter extend partially down along wall 36. Roller 58, resiliently supported by means such as springs 60 is positioned beneath head 48 and beside closure 34 and bottle neck 16.

Next, capping head 48 and the closure-containing bottle are brought together under an axial pressure of from 200 to 1,000 pounds in order to swage or bend the metal (and optionally the liner) of the closure around the outer upper corner of the bottle wall around the periphery of opening 14 so as to frictionally engage and seal the closure to the bottle. These rather substantial top loads are necessary for such deformation to occur. Thus, an annular band 64 of the flattened section 34 of closure 32 is sealed against end face 50 of the bottle neck and with the upper end of the sidewall forming a corner with surface 50, except that in the illustrated embodiment where closure 32 has a liner therein, the seal on the top surface is formed between face 50 and an annular surface portion of liner 56. This loaded position is depicted in the outline form of head 48 in FIG. 2 and in detail in FIG. 7. While this axial pressure is maintained by suitable means either pushing upwardly on support member 30 or downwardly on pressure block 52, resiliently supported rollers such as that shown at 58 are moved radially inwardly against the thin wall 36 of closure 32 so as to deform it inwardly around and against the threaded finish 18 so as to sealingly frictionally engage the opposing surfaces of the threads and sidewall against internal carbonation pressure after release of the axial pressure and subsequent increase of the beverage temperature. During deformation of sidewall 36, either bottle 10 or rollers 58 are rotated circumferentially to cause the sidewall to engage the threads on the neck. It is preferable also that this action of the roller(s) crimp end portion 65 of the closure sidewall under ledge 66 at the base of neck 16 so as to provide the sealed container with a tamper proof feature, though a separate roller can be provided to accomplish this.

As can be appreciated from FIG. 2, the relatively thin, molecularly oriented deformable wall 78 (FIG. 1) of transition zone 20 is circumferentially enveloped by member 30 and therefore supported against outward deflection during application of the axial sealing pressure. The wall thickness of the bottle in the region of the neck finish and upper portion of sidewall 12 is shown as somewhat thicker than that of transition zone 20 in the illustrated embodiments of FIGS. 1 and 7, but this increased thickness tends to be somewhat of a limitation of the blow molding manner of forming the bottle and need not necessarily exist. After the closure sidewall has been deformingly engaged with the bottle neck finish, the pressure block and supported bottle are separated from each other and the thus tightly capped container extricated from support member 30.

FIG. 3 illustrates the appearance of the transition zone with respect to the remainder of the lower portion of a bottle 10 under an axial capping load as just described when the transition zone is not supported against outward deflection, the bottle merely resting on flat surface 74. As illustrated, portion 68 has been rather dramatically deformed outwardly primarily because of the generous curvature of transition zone 20. In the illustrated embodiment, this effect is accentuated because of the differences in diameter in the cylindrical bottle from that at 70 versus that at transition zone 20. This creates sort of a hinge effect at 72 causing the wall to collapse downwardly on itself when loaded. If the container as illustrated in FIG. 3 does not rupture under the imposition of capping forces as is the case more often than not, it can retain a permanent set after dissipation of such force which resembles its deformed shape under load, such shape being illustrated at ridge 76 in FIG. 4. Ridge 76 acts as an area of high stress concentration, and also tends to detract from the aesthetic appearance of the lower portion of the bottle.

Support member 30 of the present invention may alternatively be provided in two or more complementary pieces such as 78a and 78b in FIG. 5, which are moved toward each other in the direction of 82 preferably until they abut the surface of the lower portion of the bottle. Each portion 78 is preferably, though not necessarily, contoured as at 84 to match the outer contour of transition zone 86 in bottle 80.

The above description and particularly the drawings are set forth for purposes of illustration only and are not to be taken in a limited sense.

Various modifications and alterations will be readily suggested to persons skilled in the art. It is intended, therefore, that the foregoing be considered as exemplary only and that the scope of the invention be ascertained from the following claims.

Claims

We claim:

1. In the method of capping a bottle containing a beverage capable of generating a temperature-dependent pressure of from 15 to 150 psig by applying a top load to the bottle to force a closure into sealing engagement with cooperating surfaces on an end section of the bottle, the improvement which comprises circumferentially enveloping a curved, stress-minimizing transition zone only in the body of the bottle between the side and bottom walls with a restraining member and resisting outward deflection of said transition zone with said restraining member during application of said top load to avoid damaging said bottle, said bottle being formed of a high barrier, flexible, thermoplastic material having a wall thickness in the area of said transition zone of between 10 to 35 mils.

2. The method of claim 1 wherein the thermoplastic at least in the area of the transition zone is molecularly oriented.

3. In the method of capping a bottle containing a beverage capable of generating a pressure due to carbonation of from 15 to 150 psig at temperatures within the range of from 45.degree. to 120.degree.F. which comprises placing a closure loosely on an outer end section of the bottle such that a flattened region of the closure overlies the bottle mouth and a depending skirt surrounds a threaded portion on the outer surface of the bottle neck, while said beverage is at a temperature on the order of 32.degree. to 40.degree. F., then bringing a capping head and the bottle with the closure thereon together under an axial pressure of from 200 to 1,000 pounds to seal an annular band of the flattened section of the closure against the end face of the bottle neck and thereafter deforming the closure sidewall inwardly about the threaded portion of the bottle neck to sealingly engage the threaded portion and closure sidewall against said carbonation pressure after release of said axial pressure and increase of the beverage temperature to within said range, the improvement which comprises moving a support member having a cavity formed therein contoured to match the outer surface of a curved transition zone in the lower portion of said bottle relative to said bottle prior to application of said axial pressure so as to support said transition zone against outward deflection during application of said axial pressure, said bottle being formed of a high barrier, flexible molecularly oriented thermoplastic material having a wall thickness in the area of said transition zone of between 10 to 35 mils.

4. The method of claim 3 wherein the thermoplastic comprises a polymer, the major portion of which has been polymerized from a monomer having at least one nitrile group in its molecular structure.

5. The method of claim 4 wherein the thermoplastic has been stretched axially and circumferentially to develop said molecular orientation.