CA2551314A1

CA2551314A1 - A plastic container or a preform

Info

Publication number: CA2551314A1
Application number: CA 2551314
Authority: CA
Inventors: Thomas E. Nahill
Original assignee: Graham Packaging Pet Technologies, Inc.; Thomas E. Nahill
Current assignee: Graham Packaging Pet Technologies Inc
Priority date: 2003-12-24
Filing date: 2004-12-23
Publication date: 2005-07-21
Also published as: WO2005066034A1; CN1898134A; EP1706329A1; MXPA06007081A; US20050142311A1; AU2004312420A1; BRPI0418108A

Abstract

A finish assembly for a plastic container or preform includes a plastic neck having an open end surrounded by an external flange (22). The flange has an open axially facing channel proximal to an outer surface of the neck. A
plastic finish ring has an annular body, an inner surface opposed to the outer surface of the neck, an outer surface with at least one external thread, bead or other means for attachment of a closure, and an annular lip (36) extending into the channel. The channel may be formed in part by a radially inwardly extending conical surface on the flange, and the lip has a radially outwardly extending conical surface in facing engagement with the radially inwardly facing conical surface on the flange to seal the finish ring against the flange against entry of liquid between the finish ring and the neck.

Description

A PLASTIC CONTAINER OR A PREFORM
FIELD OF THE INVENTION
[01] The present invention is directed to finishes for plastic containers or preforms, to preform assemblies for blow molding plastic containers, to plastic containers blow molded from such preform assemblies, and to methods of making such finishes, preform assemblies and containers.
BACKGROUND OF THE INVENTION

[02] In the manufacture of plastic containers, it is conventional to injection mold or compression mold a container preform having a body and a finish with one or more external threads or other closure attachment means. The preform finish typically is molded to its final geometry, while the body of the preform subsequently is blow molded to the desired geometry of the container body. The preform may be of monolayer construction, or may be of multilayer construction in which one or more intermediate layers in the preform body may or may not extend into the finish area of the preform. U.S. Patent Nos. 4,609,516, 4,710,118 and 4,954,376 illustrate injection molding of multilayer container preforms.

[03] Molding the finish portion of the container as part of the preform presents a number of problems. For example, when the preforms are formed by injection molding, the plastic material typically is injected into a mold cavity at the closed end of the preform body and must first flow in the area along the sides of the preform cavity, to form the relatively thin walled preform body, and then into the area in which the finish is molded, to form the substantially thicker finish portion. Because it is located at the end of the flow path, it can be difficult to completely fill the relatively thicker and more contoured finish portion. Also, the finish typically requires more accurate and stable dimensioning than the body of the preform, which can lengthen the cycle time of the molding process. Furthermore, where the finish portion of the preform is of the same material as at least the outer layers of the preform body, this may limit the ability to obtain more desirable performance characteristics in the finish. For example, when the preform is of polyester construction, such as polyethylene terephthalate (PET), the finish portion of the preform can be wholly or partially crystallized to improve the operating characteristics of the finish area, particularly in higher temperature container applications (e.g., hot-fill, pasteurization, refill, etc.). However, the requirement that the finish be of the same material as at least the outer layers of the preform body (in a multilayer preform) may limit the design, manufacture and/or performance characteristics of the preform or container.
[04] U.S. Application Serial Nos. 10/351,671, 10/375,376, 10/375,758 and 10/403,415, assigned to the assignee of the present application, disclose finish assemblies for preforms and containers in which the preform neck has an external flange around its open end, and a separate plastic finish ring is assembled over the preform neck in abutment with the external flange. The finish ring has one or more external threads or other means for securement of a closure, and can be of a plastic construction different from the plastic construction of the preform. The preform body and neck may be of relatively thin plastic construction, while the finish ring (alone or together with the neck) forms a thickened construction. However, liquid that spills on the finish during filling of the container can flow between the finish ring and the preform flange, and collect between the finish ring and the preform neck. Such fluid is unsightly and can encourage the growth of mold. It would be desirable to provide a finish assembly for a plastic preform or container, a method of making a plastic preform or container, and a preform assembly that reduce or eliminate the likelihood of leakage of fluid between the finish ring and the preform/container neck.
SUMMARY OF THE INVENTION

[05] In accordance with one embodiment of the invention, a method is provided for making a preform assembly. A plastic preform is provided having a body with a closed end, and a neck extending from the body, the neck having an open end and a radially outwardly extending flange surrounding the open end.
The flange has an open channel proximal to the outer surface of the neck. A finish ring is provided having an annular body and an outer surface with an attachment portion for securing a closure. An annular lip extends from the body of the finish ring.
The finish ring and. preform are assembled such that the ring is received over the outer surface of the neck and the annular lip is received in and engages at least a portion of the channel.

[06] In accordance with another embodiment of the invention, a finish assembly is provided for a plastic container or preform. The assembly includes a plastic neck having an open end surrounded by an external flange, the flange having an open channel proximal to an outer surface of the neck. The assembly further includes a plastic finish ring having an annular body with an inner surface positioned opposite the outer surface of the neck, and an outer surface having an attachment portion for securing a closure. An annular lip on the finish ring extends into and engages at least a portion of the channel.

[07] In a further embodiment, a preform assembly is provided for blow molding a plastic container. The assembly includes a plastic preform having a body with a closed end which is blow molded to form a container, and a neck extending axially from the body and having an open end with a radially outwardly extending flange. The flange has an annular undercut forming an open channel on an underside of the flange. The assembly further includes a finish ring having an annular body disposed over the neck of the preform, and an outer surface having at least one external thread. An annular lip on the ring extends into and engages at least a portion of the channel.

(08] In various described embodiments of the invention, the engaging portions of the lip and channel comprise one or more facing surfaces which enable sealing of the finish ring against the flange. The channel, which may be extracted from or molded into the underside of the flange, produces a radially-extending top flange portion and a downwardly projecting outer flange projection or lip. The outer flange lip is generally axially aligned with the channel (and with the preform neck central axis). This lip on the flange has at least one facing surface which matches an opposed facing surface on the annular lip of the finish ring, to seal the ring and flange. The facing surfaces may, for example, form mating conical surfaces.
The facing surfaces may extend to the outer surfaces of the finish ring and flange, to thereby retard or prevent the entrance of any fluid between the preform neck and finish ring. The finish ring lip and preform channel may be in complete abutment, or there may be a gap between at least a portion of the lip and channel so long as another portion seals the lip and channel. The lip and channel may alternatively have stepped facing surfaces.

[09] Generally, each of the finish ring and preform neck are annular bodies have axially elongated inner and outer annular engaging surfaces, respectively. The finish ring thus forms a collar around the preform neck.

[10] The finish ring may be used to provide a substantially thicker finish portion to the neck of the preform or container, compared to a sidewall of the container. The finish ring may be of a different plastic material than the preform or container neck, thus, providing different performance characteristics. The finish ring may be treated (e.g., thermally) either prior to or subsequent to its assembly with the neck, to provide different properties (even if made of the same material as the neck).
The finish ring may be slid over the bottom end and onto the neck of the preform, followed by blow molding of the preform body to form a container.

[11] Other various embodiments of the invention can be understood from the following description and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS

[12] FIG. 1 is an elevational view of a preform assembly in accordance with one embodiment of the invention;

[13] FIG. 2 is an exploded perspective view of the preform assembly illustrated in FIG. 1;

[14] FIG. 3 is a fragmentary sectional view taken substantially along the line 3-3 in FIG. 1;

[15] FIG. 3A is a fragmentary sectional view on an enlarged scale of the upper end of the preform neck illustrated in FIG. 3;

[16] FIG. 3B is a fragmentary sectional view on an enlarged scale of the upper end of the finish ring illustrated in FIG. 3;

[17] FIGS. 4 and 5 are fragmentary sectional views, similar to that of FIG. 3, but illustrating modified embodiments of the finish ring and preform neck;

[18] FIG. 6 is a perspective view of a preform and finish ring for providing a preform assembly in accordance with another embodiment;

[19] FIG. 7 an enlarged fragmentary sectional view of the preform neck and finish ring taken substantially along the line 7-7 in FIG. 6; and [20] FIG. 8 is a fragmentary sectional and partially schematic view of a finish ring and preform neck, similar to the preform assembly shown in FIGS. 6-7, and further illustrating a blow molded container portion made from the body portion of the preform.
DETAILED DESCRIPTION

[21] FIGS. 1-3B illustrate a preform assembly 10 in accordance with one embodiment of the invention. The assembly 10 includes a preform 12 and a finish ring 14 assembled thereto.

[22] Preform 12 includes a body 16 with a closed lower end 18 and an integrally formed neck 20 with an external flange 22 extending radially outwardly from the open end of the neck. Neck 20 is generally of cylindrical construction, and flange 22 is circumferentially continuous and substantially perpendicular to the central longitudinal axis of the preform neck 20 (shown by line 3-3 in FIG. 1 ). An open channel (or undercut) 24 (FIGS. 3 and 3A) is formed on the undersurface 33 of flange 22, such as by being molded into the flange or formed in the flange in a post-molding operation, thus leaving a top portion 25 above the channel and a downwardly extending projection or lower lip 23 on the flange 22. As best seen in FIG. 3A, channel 24 has a generally radially outwardly facing surface 26 that preferably is a continuation of the radially outwardly facing surface 28 of preform neck 20, an annular undersurface 30 adjacent (and substantially perpendicular) to surface 26, and an inclined (at less than 90° with respect to the central neck axis) radially inwardly facing surface 32 (see Fig. 3A) extending from the outer edge of channel undersurface 30. In this example, the inclined surface 32 is of conical construction with respect to the longitudinal neck axis. Conical surface 32 preferably is at an angle of about 30° to the central axis of the preform neck 20.
The annular undersurface 30 of channel 24 preferably lies in a plane substantially perpendicular to the axis of neck 20. Similarly, the annular undersurface 33 of the outer flange lip 23 preferably lies in a plane substantially perpendicular to the axis of neck 20.

[23] Finish ring 14 preferably is of molded plastic construction, and may be of a different or the same plastic material as preform 12. If the same material is used, the molded finish ring may be processed differently than the preform to provide different properties. The finish ring 14 has an elongated annular body 34 with an integrally formed axially extending upper lip 36. Ring body 34 and lip 36 preferably are circumferentially continuous. Lip 36 has an inner surface 38 (FIG. 3B) preferably formed as an extension of the inner surface 40 of ring body 34, both preferably being cylindrical. Lip 36 also has an upper end surface 42, which preferably lies in a plane perpendicular to the longitudinal axis of ring 14 (same as the neck axis), and a radially outwardly facing conical surface 44 that extends from the outer edge of upper surface 42. Conical surface 44 preferably is complementary to conical surface 32 on preform flange lip 23, preferably at an angle of about 30°, so that the two facing surfaces will abut one another in sealing engagement. A second upper surface 46 on ring 14, which may be parallel to or angled with respect to uppermost surface 42, extends from conical surface 44 to the radially outer surface 48 of ring body 34. Ring body 34 also includes at least one external thread, bead or other means 50 for securing a closure to the final container (FIG. 8). In the exemplary embodiments illustrated in the drawings, ring body 34 also includes an annular bead 52 for engagement by tamper-indicating means on the closure, and a support flange 54 to facilitate subsequent handling of the preform and container.

[24] Preform 12 preferably is formed in a compression or injection molding operation. Finish ring 14, which preferably is itself formed in a suitable plastic molding operation, can be slid over the closed end of the preform so that the radially inner surface 40 of finish ring 14 is in close sliding engagement with the radially outer surface 28 of preform neck 20. The above-noted pending applications disclose various techniques for assembling finish ring 14 over neck 20 and securing the finish ring to the neck, such as by interference press fit, alone or enhanced by adhesive and/or ultra-sonic welding. The assembly of finish ring 14 over preform neck continues until lip 36 on finish ring 14 is received within channel 24 on preform neck flange 22 and conical surfaces 44, 32 are brought into abutting facing engagement.
Such abutting facing engagement of surfaces 44, 32 helps prevent any flow of liquid between the opposing surfaces of the finish ring and the preform neck. The axial dimension (depth) of channel 24 may be less than the axial dimension (height) of the finish lip 36 so that there is a gap 56 (FIG. 3) between preform flange 22 and finish ring surface 46 when assembled, which helps ensure that conical facing surfaces 44, 32 are in seating engagement. In FIG. 3, the gap 56 is between the lower lip 23 (see FIG. 3A) of flange 22 and upper surface 46 (see FIG. 3B) of finish ring 14.

[25] FIGS. 4 and 5 illustrate other preform assemblies 60, 62 in accordance with respective modified embodiments of the invention. Reference numerals in FIGS. 4 and 5 that are identical to those in FIGS. 1-3B indicate identical or related components. The primary difference between preform assembly 60 in FIG. 4 and preform assembly 10 in FIGS. 1-3 is that preform flange 22a and/or finish ring lip 36a is/are dimensioned so that there is abutting engagement for both of lower surfaces 30, 33 (FIG. 3A) on flange 22a and upper surfaces 42, 46 (FIG. 3B), respectively, on finish ring 14a. In other words, the channel flange and the finish ring lip are dimensioned to eliminate gap 56 in FIG. 3. As a further alternative, there can be a gap provided between surfaces 30, 42 (FIGS. 3A and 3B) in the embodiment of FIG.
4. In FIG. 5, neck flange 22b has a channel in which conical surface 32b extends to the outer edge of the flange, and conical surface 44b on finish ring lip 36b extends to the outer surface of the finish ring, which is to say that engaging surfaces 33 (FIG.
3A) and 46 (FIG. 3B) are eliminated.

[26] FIGS. 6-8 illustrate a further embodiment wherein the assembled preform and neck finish are used to form a blow molded container 64. FIG. 6 illustrates a finish ring 14c, shown separately below, and assembled with a preform 12c in the upper portion of the figure. FIG. 7 is an enlarged fragmentary sectional view of the assembled preform neck 20c and finish ring 14c of FIG. 6. FIG. 8 shows the assembly of FIGS. 6-7 after blow molding of the preform body 16c to form a container body 60c. The resulting container 64 thus includes the unexpanded preform neck 20c integral with container body 60c, and finish ring 14c positioned over neck 20c.

[27] Preforms may be of any suitable plastic construction, such as monolayer PET or multilayer construction of PET layers alternating with layers of barrier resin such as ethylene vinyl alcohol (EVOH) or nylon. Preforms may be injection molded or compression molded. Likewise, finish rings may be of injection or compression molded plastic construction. By providing finish rings separate from preforms, the finish rings may be of any desired material construction, either the same as.or more preferably different from the material construction of the preform.
For example, the finish ring can be of PET, post consumer resin (PCR), process regrind (REG), polypropylene (PP), polyethylene (PE) or polyethylene naphthalate (PEN) construction. Where the finish ring is of polyester construction (e.g., PET, PEN or process regrind), the finish ring may be wholly or partially crystallized as molded. This may be accomplished by employing fast-crystallizing materials, or suitably setting process conditions for manufacture of the finish ring, such as high mold temperature, slow mold cooling, heated areas in the mold cavity, etc. The finish ring alternatively may be wholly or partially crystallized in a post-molding operation. In other words, the material and conditions of fabrication of the finish ring may be selected separately from the material and manufacturing conditions of the preform to achieve desired operating characteristics at the finish area of the preform and the final container. Furthermore, the preform can be molded with thin wall sections without having to accommodate flow of material into a thicker finish area, which reduces material cost and mold cycle time. The finish ring is secured to the neck of the preform by interference fit (e.g., press fit or shrink fit), adhesive or welding. The finish ring and/or the preform neck can be provided with suitable means for preventing rotation of the ring on the neck.

[28] Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the invention being indicated by the following claims.

Claims

1. A method of making a preform assembly comprising the steps of:
(a) providing a plastic preform having a body with a closed end and a neck extending from the body, the neck having an open end and a radially outwardly extending flange surrounding the open end, the flange having an open channel proximal to an outer surface of the neck, (b) providing a finish ring having an annular body, an outer surface with an attachment portion for securing a closure, and an annular lip extending from the body, and (c) assembling the finish ring to the preform such that the ring is received over the outer surface of the neck and the annular lip is received in and engages at least a portion of the channel.

The method of claim 1, wherein the lip and the channel have facing surfaces which are engaged when the lip is received in the channel.

3. The method of claim 2, wherein the facing surfaces are inclined with respect to a central axis of the neck.

4. The method of claim 3, wherein the channel and lip having conical facing surfaces.

5. The method of claim 3, wherein the facing surfaces extend to the outer surfaces of the finish ring and flange.

6. The method of claim 1, wherein there is a gap between at least a portion of the flange and finish ring following the step (c).

7. The method of claim 1, wherein the lip and channel are in complete abutment following the step (c).

8. The method of claim 2, wherein the lip and channel have stepped facing surfaces.

9. The method of claim 1, wherein the finish ring and preform neck have inner and outer annular engaging surfaces, respectively.

10. The method of claim 1, wherein the attachment portion of the finish ring comprises a radially thickened threaded portion.

11. The method of claim 1, wherein the step (a) is carried out by injection or compression molding.

12. The method of claim 1, followed by the step of:
(d) blow molding a container from the preform.

13. A finish assembly for a plastic container or preform comprising:
(a) a plastic neck having an open end surrounded by an external flange, the flange having an open channel proximal to an outer surface of the neck;
and (b) a plastic finish ring having an annular body, an inner surface-opposed to the outer surface of the neck, an outer surface with an attachment portion for securing a closure, and an annular lip extending into and engaging at least a portion of the channel.

14. The finish assembly of claim 13, wherein the lip and channel have facing surfaces engaged to seal the finish ring to the flange.

15. The finish assembly of claim 14, wherein the facing surfaces are inclined with respect to a central axis of the neck.

16. The finish assembly of claim 15, wherein the channel and lip have conical facing surfaces.

17. The finish assembly of claim 13, wherein there is a gap between at least a portion of the flange and finish ring.

18. The finish assembly of claim 13, wherein the lip and channel are in complete abutment.

19 The finish assembly of claim 14, wherein the lip and channel have stepped facing surfaces.

20. The finish assembly of claim 13, wherein the attachment portion of the finish ring comprises a radially thickened threaded portion.

21. The finish assembly of claim 13, wherein the finish ring and neck are in press fit engagement.

22. A preform assembly for blow molding a plastic container, comprising:
(a) a plastic preform having a body with a closed end for blow molding a container, and a neck extending integrally from the body having an open end with a radially outwardly extending flange, the flange having an annular undercut forming an open channel on an underside of the flange; and (b) a finish ring having an annular body disposed over the neck, an outer surface with at least one external thread, and an annular lip extending into and engaging at least a portion of the channel.

23. The preform assembly of claim 22, wherein the lip and channel have facing surfaces engaged to seal the finish ring to the flange.

24 The preform assembly of claim 23, wherein the facing surfaces are inclined with respect to a central axis of the neck.

25. The preform assembly of claim 23, wherein the channel and lip have conical facing surfaces.

26. The preform assembly of claim 22, wherein there is a gap between at least a portion of the flange and finish ring.

27. The preform assembly of claim 22, wherein the lip and channel are in complete abutment.

28 The preform assembly of claim 23, wherein the lip and channel have stepped facing surfaces.

29. The preform assembly of claim 22, wherein the attachment portion of the finish ring comprises a radially thickened threaded portion.

30. The preform assembly of claim 22, wherein the finish ring and neck are in press fit engagement.