Preform With Geodesic Reinforcement Ring

The present invention is directed to a preform for a free-standing, one piece plastic bottle, preferably of PET (polyethylene terephthalate), for carbonated beverages having a champagne bottle type shaped base of controlled thickness to provide an annular chime to provide stable upright standing ability wherein the thickness of the bottom is controlled to provide adequate resistance to internal pressure, that thickness being derived from a varying thickness in the preform. More particularly, the base of the present invention incorporates an integral geodesic ring that runs horizontally of the bottle in the hoop direction. The reinforcing ring is placed in a location within the base of the bottle that has a moment arm trying to invert the base and provides sufficient strength to withstand that moment arm and keep the push up of the bottom intact. A feature is that the shape of the preform's interior and exterior walls are ever decreasing in diameter from the neck to the base so that it may be easily removed from a suitable core and injection mold cavity thereby avoiding the need for a split mold as in the Makowski teaching.

Referring first to FIG. 1 through 10, a first embodiment of the present invention consists of a preform injection molded from PET for blow molding, in a blow mold 12, to produce a bottle 114 of a self-standing champagne bottle type base suitable for carbonated beverages and having a half-litre capacity with a weight of 27.5 grams. The preform consists of a neck portion 16 from which the neck 118 of the bottle is produced, a shoulder portion 20 from which the shoulder 122 of the bottle is blown, a sidewall portion 24 of substantially constant thickness from which the sidewall 126 of the bottle is 10 blown and a base structure 28 terminating in a closed end 32 from which the base 130 of the bottle is blown. The neck portion 16 is connected to the sidewall portion 24 by way of the shoulder portion which forms a transition between the neck portion (which remains substantially unchanged during the blow molding process) and the sidewall portion which, after temperature conditioning, is stretched longitudinally in the blow mold before the blowing operation takes place in most case. In the shoulder portion 20, the thickness of the material increases progressively from the neck portion to the sidewall portion, which is of a substantially constant thickness and diameter. The sidewall portion 24 terminates remote from the shoulder portion 20 at a transition to the base structure which itself terminates in the closed end 32, from which the center of the base of the bottle is produced. The base structure between the sidewall portion and the closed end consists of an annular wall portion 34 on the interior wall face 35 of which are integrally formed a plurality of longitudinally extending reinforcing filets 36 six in number in this embodiment, symmetrically disposed around the interior wall face 35 of wall portion 34 in contact with one another to form a geodesic reinforcement ring 38 defined on its outside by the circular wall face 35 of the wall portion 34 and on its interior by a hexagonal line 40 symmetrically disposed about and normal to the axis 42 of the preform. Apart from the filets 36, the preform is of a circular cross-section, normal to axis 42, having interior and exterior surfaces which are of ever decreasing diameter from the neck to the base. This ever decreasing diameter need only be sufficient to facilitate removal of the preform from the mold, in which it is injection molded, and the associated core pin. The filets 36 extend from the transition of the base portion with the sidewall portion to the closed end of the preform which consists of a substantially flat end lYing transversely of the axis 42 and joined to the base structure 28 by a rapid transition 44 which may be curved or angled depending on the particular preform design and blow mold configuration. The wall thickness of the sidewall portion 24 and the wall portion 34 of the base portion are substantially the same with the filets 36 forming a variable thickness reinforcement ring 38 circumscribing the interior of the base structure of the preform. Toward the closed end 32 from adjacent the reinforcement ring 38, the interior and exterior wall faces 35, 39 of the wall portion 34 taper inwardly toward the axis 42 at an angle of 4 degrees. The exposed surfaces of the filets 36 comprise triangular flat surfaces or facets 46 extending from the reinforcement ring 38 to the closed end 32 substantially parallel to the axis 42 whereby the filets are of ever decreasing thickness and width from the reinforcement ring 38 to the closed end 32. Similar triangular flat surfaces 48 extend from the reinforcement ring 38 to the transition with the sidewall portion 24 with these angled outwardly from the reinforcement ring 38 at an angle of 4 degrees to the axis 42 thereby to cause each filet to taper downwardlY both in thickness and width from the reinforcement ring 38 to the transition with the sidewall portion 24. In the area of the triangular surfaces 48, both the interior and exterior wall faces 35, 39 of the wall portion 34 are essentially cylindrical.

Portions 50 of the interior wall face 35 of the wall portion 34 are exposed between the triangular surfaces 46 and 48. The triangular surfaces 46 and 48 are flat and the filets 36 contact one another only at the reinforcement ring 38 there to form straight edges or ridges. This contact between the filets 36 coupled with the material provided by the filets defines the reinforcement ring and the reinforcement ring acts as a geodesic structure resulting from continuous nature of the ring and the triangulation of forces operating both circumferentially and longitudinally within the filets around the reinforcement ring. The tapering down of the filets in both directions away from the reinforcement ring longitudinally of the preform serves to provide the necessary additional strength either side of the reinforcement ring for preventing the champagne base of the bottle from inverting under the influence of pressure of a beverage contained therein.

It will be appreciated that due to a curvature of the interior wall face 35 the filets will taper down progressively, continuously and gradually circumferentially from the radially thickest region to the circumferential location of their point contact meeting along the reinforcement ring.

In the figures illustrating the bottle, the portions of the bottle derived from and corresponding to various portions of the preform are identified by reference numbers which are exactly 100 higher than the reference numerals for the corresponding portions in the figures illustrating the preform. This distinction will be utilized throughout the description of the other embodiments. Additionally, reference numerals used in the other embodiments will be the same as those used with reference to the first embodiment where the features concerned are similar.

Reference numerals identifying features on the various embodiments of core pin will be exactly 200 higher than the reference numerals used with respect to the corresponding features of the associated preform.

With reference now to the second embodiment illustrated in FIGS. 11 through 14 the geodesic reinforcement ring 38 here has a discrete width W resulting from an overlap of the triangular surfaces 46 whereby the circumferential width of the surfaces 46 is somewhat truncated. The triangular surfaces 48 in this second embodiment are essentially identical to those of the first embodiment. By virtue of this the reinforcement ring 38 with a discrete width, a chime reinforcement ring 138 will have a discrete width which will render less critical the placement of that reinforcement ring relative to the chime 152 for satisfactory performance of the bottle.

The third embodiment as illustrated in FIGS. 15 through 22 is quite similar to that of the second embodiment. However, in this third embodiment the filets 36 have superimposed on them ribs 54 extending longitudinally of the preform for the full longitudinal extent of the filets. The purpose of these ribs 54 is to provide additional control of the longitudinal stretching of the preform in preparation for the introduction of gas under pressure for the blow molding operation and provides additional strength. By the use of these ribs, the desired relatively large longitudinal stretching of the sidewall portion 24 can take place while the desired restriction of the longitudinal stretching of the base structure 28 is facilitated. Additionally, in this third embodiment, the junction between filets in the region of the reinforcement ring 38 is filled by a small filet 56 to provide a gently curved concave junction between filets.

A variation of the third embodiment is found in the fourth embodiment illustrated in FIGS. 23 through 31 in which ribs 58 are formed in the interior surface of the wall portion 34 between filets 36. These ribs 58 which extend longitudinally for the full extent of the filets 36 serve exactly the same purpose as do the ribs of 54. It will be appreciated by those skilled in the art that the arrangement of the third and fourth embodiments could be combined to double or otherwise modify the number of longitudinally extending ribs for greater control of the stretching of the base portion 28 relative to the sidewall portion 24.

The fifth embodiment illustrated in FIGS. 32 and 33 involves a preform in which two tiers of filets 36 are disposed longitudinally of one another relative to the longitudinal axis 42 of the preform. By this design two spaced concentric reinforcement rings 138 are formed in a bottle blown from the preform thereby allowing greater flexibility of bottle design and potentially greater material savings.

The sixth embodiment illustrated in FIGS. 34 through 36, the seventh embodiment illustrated in FIGS. 37 through 39 and the eighth embodiment illustrated in FIGS. 40 through 42 illustrate variations of the preform and bottle of the earlier described embodiments all of which utilized a symmetrical arrangement of six filets 36. The sixth, seventh and eighth embodiments disclose arrangements for 3 8 and 12 filets, respectively. Apart from the different numbers of filets involved, it will be appreciated by those skilled in the art that within the limits imposed by machining of core pin and the need to provide sufficient extra material to produce an effective triangulation in the geodesic reinforcement ring, the number of filets may be varied as desired. However, it is believed that a preferred range of numbers of filets is from 3 to 12 filets symmetrically arranged about the axis 42 of the preform and that for half-litre bottles, the preferred number of filets is six.

The ninth embodiment of the invention is illustrated in FIGS. 43 through 48. In this embodiment, the triangular surfaces 48 are eliminated in favor of a curved surface 60 by way of which the triangular surfaces 46 are joined to the interior wall face 35 of the preform in an area of the base portion extending toward the transition with the sidewall portion 24. The curved surface 60 comprises six surfaces, one for each filet 36 which are exposed toward the neck portion 16 and which are suitable, if desired, to be contacted by a stretch rod to selectively stretch the sidewall portion in preparation for the blowing operation whereby the stretch rod will, upon its extension into the blow mold, stretch the sidewall as desired without significant stretching of the base portion 28.

The tenth embodiment of the invention is illustrated in FIGS. 49 and 50. In this embodiment, the triangular surfaces 48 are eliminated in favor of a curved surface 60 by way of which the triangular surfaces 46 are joined to the interior wall face 35 of the preform in an area of the base portion extending toward the transition with the sidewall portion 24. The curved surface 60 comprises six surfaces, one for each fillet 36, which are exposed toward the neck portion 16 and which are suitable, if desired, to be contacted by a stretch rod to selectively stretch the sidewall portion in preparation for the blowing operation whereby the stretch rod will, upon its extension into the blow mold, stretch the sidewall as desired without significant stretching of the base portion 28. In this embodiment, two tiers of fillets 36 are disposed longitudinally of one another relative to the longitudinal axis 42 of the preform. By this design, two spaced concentric reinforcement rings 138 are formed in a bottle blown from the preform thereby allowing greater flexibility of bottle design and potentially greater material savings. In this embodiment, the fillets of the two tiers are circumferentially offset from one another by half of the angles subtended by each fillet 36 so that the triangular point of each fillet of the tier closest to the neck of the preform meets the reinforcement ring 38 between the two tiers at junctions between the fillets of the tier of fillets adjacent the closed end of the preform. Additionally, this embodiment illustrates the option of providing additional reinforcement by forming the faces 46 as convex faces to increase the depth of material of the fillets at the reinforcement rings they create at the center of the angles subtended for each fillet.

The eleventh embodiment of the invention is illustrated in FIGS. 51 through 54. This embodiment is quite similar to that described with reference to the tenth embodiment differing substantially only in that the faces 46 are folded to increase the depth of material at the center of each fillet with a consequence that a central longitudinally extending fold line is centrally located in each face 46. As a result of this, the curved surface 60 also may be formed with a central fold. With reference to FIG. 53, the sequence of operations in the blow mold is illustrated with the eleventh embodiment preform first being stretched by a stretch rod (not shown) until its base is closely adjacent the innermost end of the blow mold. This stretching is carried out in a manner to stretch the sidewall of the preform without significantly stretching or deforming the base portion thereof. Once this stretching is completed, the preform is blown to unfold the base and stretch the sidewall with the base first assuming a position and shape as shown at 200 and subsequently completely being formed as shown at 201 to form a champagne base with a geodesic reinforcement forming a chime and inwardly extending area capable of resisting the unrolling stresses applied by carbonated beverages which might be contained in the bottle. The dashed lines with arrows indicate the general movement of the material from the geodesic reinforcement area to the chime area of the finished bottle. FIG. 54 illustrates the shape of the interior base of the finished bottle when blown as illustrated in FIG. 53.

The twelfth through fourteenth embodiments as illustrated in FIGS. 55, 56 and 57 have folded faces 46 much like those of the eleventh embodiment. However, in these embodiments, the two tiers of fillets overlap one another to bring the reinforcement rings closer together and, in some of the embodiments, to add additional intermediate fillets to provide a third reinforcement ring. In these embodiments, the surfaces 60 are curved surfaces without the fold lines mentioned in the description relating to the eleventh embodiment.

Ignoring the ever decreasing diameter of the interior and exterior walls of the preform (which is dimensionally minor), the preform of the first embodiment for the manufacture of a half-litre bottle will have an interior diameter in the sidewall portion of 0.550 inches and an interior diameter at the closed end of 0.480 inches. The longitudinal extension of the filets 36 is approximately 1 inch. Additionally, the closed end 32 may be thinner by approximately 20 percent than the thickness of the sidewall portion 24 and the remainder of the base portion 28.

It will be appreciated that the closed end 32 need not necessarily be a substantially flat disc-like closure and that other shapes may be utilized without departing from the concept of the present invention.

Similarly, other shoulder portion designs and neck portions might be utilized as these do not play a direct part in the inventive advance provided by the present invention which advance revolves around the manner of providing a reinforcement ring based on the circumferential and longitudinal triangulation of forces of a geodesic structure in the bas portion of the preform to form a reinforcement in the base of a champagne type self-standing, one-piece bottle for carbonated beverage following blowing in a blow mold. Reference to FIG. 1 will illustrate with the directional lines 62 the distribution of material from the preform to the blown bottle. This distribution results from the shape of the preform, the shape of the blow mold, the extent of the stretching of the preform in preparation for blow molding and the temperature conditioning and temperature distribution in the preform during blow molding. These are matters well-known to those skilled in the art and will not be described in detail here.

It will further be appreciated as reference to the aforementioned U.S. Pat. No. 4,785,948 will show that it will be readily apparent to a man skilled in the art that the filets could be replaced with similar reinforcing structures forming a geodesic reinforcement ring on the exterior of the preform and that such an arrangement is considered to be within the scope of the present invention. However, this is not believed to be the best mode of performing the present invention as there are many technical problems in putting such an arrangement into practical effect. These involving the problems of forming the injection mold cavity for the preform including the desirable use of a single cavity injection mold to avoid the need for the expensive and complex two-part molds which are required for example in Mankowitz, the need for corresponding shapes in the blow mold and the problems of orienting an exteriorally reinforced preform to match the shaped blow mold. Consequently, it is believed that the most practical form of the present invention involves the provision of filets 36 as described in the interior of the preform.

It will also be appreciated that while the preferred description has been made with reference to half-litre bottles, the invention is applicable to other sizes for example, one-litre and two-litre sizes.