Finish assembly for a plastic container or preform

Abstract

A finish assembly for a plastic container or preform includes a plastic neck having an open end surrounded by an external flange. The flange has an open axially facing channel adjacent to the 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 extending into the channel. The channel is 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

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 AND SUMMARY OF THE INVENTION

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. Pat. Nos. 4,609,516, 4,710,118 and 4,954,376 illustrate injection molding of multilayer container preforms.

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, so that the material must flow along the sides of the preform cavity into the area in which the finish is molded. The finish typically requires more accurate and stable dimensioning than the body of the preform, which can limit the cycle time of the molding process. Furthermore, the finish portion of the preform is of the same material as at least the outer layers of the preform body, which limits the ability to obtain the most desirable characteristics at the finish. 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 hot-fill container applications. 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) still limits the design capabilities of preform manufacture.

U.S. application Ser. 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 thin plastic 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 is a general object of the present invention 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.

A method of making a preform assembly for blow molding a container, in accordance with a first aspect of the present invention, includes providing a plastic preform having a body with a closed end and a neck extending from the body. The neck has an open end and a radially outwardly extending flange surrounding the open end. The flange has an open axially facing channel adjacent to the outer surface of the neck. A finish ring has an annular body, an outer surface with at least one external thread, bead or other means for securing a closure, and an annular lip extending axially from the body. The finish ring is assembled to the preform until the ring abuts the flange, such that the finish ring is received over the outer surface of the neck and the annular lip is received in the neck flange channel to seal the finish ring against the flange. In the preferred embodiments of the invention, the channel in the flange is formed in part by a radially inwardly and axially facing conical surface, and the lip on the finish ring has a radially outwardly and axially facing conical surface in facing engagement with the radially inwardly facing conical surface on the flange to seal the finish ring against the flange and retard or prevent entry of liquid between the finish ring and the neck of the preform.

A finish assembly for a plastic container or preform in accordance with a second aspect of the invention includes a plastic neck having an open end surrounded by an external flange. The flange has an open axially facing channel adjacent to the 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 extending axially into the channel. In the preferred embodiments of the invention, the channel is formed in part by a radially inwardly and axially facing conical surface on the flange, and the lip has a radially outwardly and axially facing 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.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with additional objects, features, advantages and aspects thereof, will be best understood from the following description, the appended claims and the accompanying drawings, in which:

FIG. 1 is an elevational view of a preform assembly in accordance with one presently preferred embodiment of the invention;

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

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

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

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

FIGS. 4 and 5 are fragmentary sectional views that are similar to that of FIG. 3 but illustrate respective modified embodiments of the invention; and

FIG. 6 is a partially sectioned elevational view of a blow molded plastic container in accordance with another aspect of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1-3B illustrate a preform assembly 10 in accordance with one presently preferred embodiment of the invention as including a preform 12 having a finish ring 14 assembled thereto. 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 preferably is of cylindrical construction, and flange 22 preferably is circumferentially continuous and perpendicular to the axis of neck 20. An open channel 24 (FIGS. 3 and 3A) is formed on the undersurface of flange 22, such as by being molded into the flange or formed in the flange in a post-molding operation. As best seen in FIG. 3A, channel 24 has a radially outwardly facing surface 26 that preferably is a continuation of the radially outwardly facing surface 28 of preform neck 20, an axially facing annular undersurface 30 adjacent to surface 26, and a generally radially inwardly and axially facing surface 32 extending from the radially outer edge of surface 30. Surface 32 preferably is of conical construction. Surfaces 26, 30 and 32 are circumferentially continuous, and preferably are coaxial with the axis of neck 20 and with each other. Conical surface 32 preferably is at an angle of about 30° to the axis of preform neck 20. Annular undersurface 30 preferably lies in a plane perpendicular to the axis of neck 20.

Finish ring 14 preferably is of molded plastic construction, having an annular body 34 with an integrally formed axially extending 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 axially facing end surface 42, which preferably lies in a plane perpendicular to the axis of ring 14, and a radially outwardly and axially facing conical surface 44 that extends from the outer edge of surface 42. Conical surface 44 preferably is complementary to surface 32 on preform flange 22, preferably at an angle of about 30°. A second axially facing surface 46, which may be parallel to or angled with respect to 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. 6). 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.

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, is assembled over the closed end of the preform so that the radially inner surface 40 of preform body 34 is in close sliding engagement with the outer surface 28b 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. The assembly of finish ring 14 over preform neck 20 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 of channel 24 preferably is coordinated with the axial dimension of finish ring lip 36 so that there is a gap 56 (FIG. 3) between preform neck flange 22 and neck ring surface 46 in assembly, which helps ensure that surfaces 44, 32 are in seating engagement.

FIGS. 4 and 5 illustrate 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 dimensioned so that there is axially abutting engagement between the axially facing surfaces 30, 33 (FIG. 3A) on flange 22a and surfaces 42, 46 (FIG. 3B) on neck ring 14a. In other words, the neck flange and/or the neck ring lip is dimensioned to eliminate gap 56 in FIG. 3. There can be a gap between surfaces 30, 42 (FIGS. 3A and 3B) in the embodiment of FIG. 4. In FIG. 5, neck flange 22b has an axially facing channel in which conical surface 32b extends to the outer edge of the flange, and conical surface 44b on neck ring lip 36b extends to the outer surface of the neck ring, which is to say that axially facing surfaces 33 (FIG. 3A) and 46 (FIG. 3B) are eliminated. FIG. 6 illustrates a container 64 that includes a body 16a blow molded from body 16 of preform 12 (FIGS. 1 and 2), and a finish assembly 66 in accordance with any of the embodiments illustrated in FIGS. 1-5.

There have thus been disclosed a method of making a preform assembly, a finish assembly for a plastic container or preform, and a preform assembly that fully satisfy all of the objects and aims previously set forth. The invention has been disclosed in conjunction with several exemplary presently preferred embodiments, and a number of additional modifications and variations have been discussed. Other modifications and variations will readily suggest themselves to person of ordinary skill in the art. The invention is intended to embrace all such modifications and variations as fall within the spirit and broad scope of the appended claims.

Claims

1. A method of making a preform assembly for blow molding a container, which includes the steps of:

(a) providing a plastic preform having a body with a closed end and a neck extending from said body, said neck having an open end and a radially outwardly extending flange surrounding said open end, said flange having an open axially facing channel adjacent to an outer surface of said neck,

(b) providing a finish ring having an annular body, an outer surface with at least one external means for securing a closure, and an annular lip extending axially from said body, and

(c) assembling said finish ring to said preform until said ring abuts said flange such that said ring is received over said outer surface of said neck and said annular lip is received in said channel to seal said finish ring against said flange.

2. The method set forth in claim 1 wherein said channel in said flange is formed in part by a radially inwardly and axially facing conical surface on said flange, and said lip has a radially outwardly and axially facing conical surface in facing engagement with said radially inwardly facing conical surface on said flange.

3. The method set forth in claim 2 wherein said flange has an axially facing surface disposed radially outwardly of said channel, and wherein said finish ring has an axially facing surface opposed to said axially facing surface on said flange and disposed radially outwardly of said lip.

4. The method set forth in claim 3 wherein said axially facing surfaces are spaced from each other following said step (c).

5. The method set forth in claim 3 wherein said axially facing surfaces are in abutment following said step (c).

6. The method set forth in claim 2 wherein said channel in said flange is formed in part by an axially facing surface between said conical surface and said outer surface of said neck, and wherein said lip on said finish ring has an axially facing surface within said conical surface on said ring and opposed to said axially facing surface on said flange.

7. The method set forth in claim 6 wherein said axially facing surface on said flange and said lip are in opposed abutment.

8. The method set forth in claim 1 wherein said finish ring is circumferentially continuous.

9. The method set forth in claim 1 wherein said step (a) is carried out by injection or compression molding.

10. A finish assembly for a plastic container or preform, which includes:

a plastic neck having an open end surrounded by an external flange, said flange having an open axially facing channel adjacent to an outer surface of said neck, and

a plastic finish ring having an annular body, an inner surface opposed to said outer surface of said neck, an outer surface with means for attachment of a closure, and an annular lip extending into said channel to seal said finish ring against said flange.

11. The finish assembly set forth in claim 10 wherein said channel in said flange is formed in part by a radially inwardly and axially facing conical surface on said flange, and said lip has a radially outwardly and axially facing conical surface in facing engagement with said radially inwardly facing conical surface on said flange.

12. The finish assembly set forth in claim 11 wherein said flange has an axially facing surface disposed radially outwardly of said channel, and wherein said finish ring has an axially facing surface opposed to said axially facing surface on said flange and disposed radially outwardly of said lip.

13. The finish assembly set forth in claim 12 wherein said axially facing surfaces are spaced from each other.

14. The finish assembly set forth in claim 12 wherein said axially facing surfaces are in opposed abutment.

15. The finish assembly set forth in claim 11 wherein said channel in said flange is formed in part by an axially facing surface between said conical surface and said outer surface of said neck, and wherein said lip on said finish ring has an axially facing surface within said conical surface on said ring and opposed to said axially facing surface on said flange.

16. The finish assembly set forth in claim 15 wherein said axially facing surface on said flange and said lip are in opposed abutment.

17. The finish assembly set forth in claim 10 wherein said neck is cylindrical, and wherein said finish ring is a circumferentially continuous cylindrical ring.

18. The finish assembly set forth in claim 10 wherein said means includes at least one external thread.

19. A preform assembly for blow molding to form a plastic container, which includes:

a plastic preform having a body with a closed end for blow molding to form a container, and a neck extending integrally from said body having an open end surrounded by a radially outwardly extending flange, said flange having an annular undercut forming an axially facing channel, and

a finish ring having an annular body externally surrounding said neck, an outer surface with at least one external thread, and an annular lip extending axially from said body into said channel in sealing engagement with said flange.

20. The preform assembly set forth in claim 19 wherein said channel in said flange is formed in part by a radially inwardly and axially facing conical surface on said flange, and said lip has a radially outwardly and axially facing conical surface in facing engagement with said radially inwardly facing conical surface on said flange.

21. The preform assembly set forth in claim 20 wherein said flange has an axially facing surface disposed radially outwardly of said channel, and wherein said finish ring has an axially facing surface opposed to said axially facing surface on said flange and disposed radially outwardly of said lip.

22. The preform assembly set forth in claim 21 wherein said axially facing surfaces are spaced from each other.

23. The preform assembly set forth in claim 21 wherein said axially facing surfaces are in opposed abutment.

24. The preform assembly set forth in claim 20 wherein said channel in said flange is formed in part by an axially facing surface between said conical surface and said outer surface of said neck, and wherein said lip on said finish ring has an axially facing surface within said conical surface on said ring and opposed to said axially facing surface on said flange.

25. The preform assembly set forth in claim 24 wherein said axially facing surface on said flange and said lip are in opposed abutment.

26. The preform assembly set forth in claim 19 wherein said finish ring is circumferentially continuous.

27. The preform assembly set forth in claim 19 wherein said neck is cylindrical, and wherein said finish ring is a circumferentially continuous cylindrical ring.