Finish for injection blow molded container

Abstract

An injection molded finish portion of a container preform has an annular wall with an end sealing surface. A set of ratchet teeth are located at a lower end of the annular wall on a flange having upper and lower surfaces including radially inward edges coterminous with the annular wall. A threaded portion is located below the sealing surface and above the ratchet teeth that includes sets of inclined threads extending part way around the annular wall, the threads having crest portions that terminate at planes tangent to the annular wall along parting lines on opposite sides of the finish. Lugs project outward from the annular wall in the vicinity of the parting lines to ensure correct interaction between the ratchet teeth and a cooperating flexible closure.

Description

BACKGROUND

1. Technical Field

The present invention is directed generally to neck structures of containers and preforms that are particularly adapted to receiving flexible closures that include a tamper indicating band.

2. General Background

Flexible closures that include a tamper indicating band are commonly employed on extrusion blow molded plastic jugs typically used in the dairy industry. Closures of this general type are disclosed, for example, in U.S. Pat. Nos. 3,980,195; 5,480,045 and 6,003,701. Another similar closure in common use is a Super Quad ASP-100 available from Blackhawk Molding Co., Inc., of Addison, Ill. Closures of this general type are typically made of low density polyethylene and are therefore very flexible and unsuitable for use to contain carbonated beverages. Such closures generally include an end panel having an interior surface that can include various sealing elements. The end panel is surrounded by a skirt having an interior surface including threads or other container engaging structures. The tamper indicating band can be connected to the lower edge of the skirt by a plurality of circumferentially spaced frangible webs. The tamper indicating band can include a series of inward projections designed to interact with a related structure on the container. Closures of this general type are suitable for use to contain still liquids in addition to dairy products, such as distilled water, mineral water, filtered water, and natural spring water. While such products can be marketed in the extrusion blow molded plastic jugs typically used in the dairy industry, enhanced market acceptance might be enjoyed by adopting more stylish containers that can more easily be manufactured using the injection blow molding procedure on polyethylene terephthalate and other similarly performing resins.

Injection blow molding procedures for forming articles such as containers are well known. The injection blow molding procedure can be accomplished as a continuous process in a single machine or can be divided into two distinctly different processes accomplished in two separate machines that need not be located at the same facility. In a typical injection blow molding procedure, a preform is first formed in an injection mold. The injection molded preform includes a body portion and a finish portion. The finish portion of the preform includes the geometry that cooperates with the structure of a pre-selected closure. While the body portion of the preform is deformed during a subsequent blow molding step of the procedure, the finish portion of the preform generally remains unchanged. Thus, the geometry of the finish created by the injection molding of the preform is generally the same geometry as exists in the completely formed container. This is quite different from the finish portion of extrusion blow molded containers, such as plastic jugs typically used in the dairy industry, wherein the finish is formed during the blow-molding step of the process.

The finish portion of extrusion blow molded containers designed for use with flexible closures that include a tamper indicating band typically have an end sealing surface defining the opening into the interior of the container. A closure retaining structure, typically in the form of a plurality of threads, projects outward from a cylindrical surface below the end sealing surface. A tamper evident band retaining bead is situated below the closure retaining structure. The retaining bead generally has a minimum diameter that exceeds the outermost projection of the closure retaining structure. Typically, an essentially radially extending surface connects the cylindrical surface at the lower end of the closure retaining structure to the retaining bead minimum diameter. The retaining bead is typically characterized by a corrugated surface designed to interact with inward projections on the tamper indicating band so that any attempt to remove the closure from the finish will generally result in separation of the tamper indicating band from the remainder of the closure.

The finish portion of extrusion blow molded containers typically has a substantially uniform wall thickness with the interior of the finish portion reflecting, more or less, the exterior features. While the wall thickness of the finish portion can be somewhat thicker than the body portion of the container, it is generally still quite flexible, which facilitates removal of the molded article from the mold in which it is formed. By contrast, the interior of the finish portion of an injection blow molded container is usually uniformly cylindrical or slightly outwardly tapered toward the mouth of the container. Further, the finish portion can be quite rigid so that removal of the molded article from either the injection mold or the blow mold generally cannot require any flexing on the part of the molded finish. Any attempt at a straight reproduction of the exterior finish geometry of a given extrusion blow molded container into an injection blow molded container would result in a very heavy, and thus overly expensive, finish, probably containing flaws due to the general inability of the injection molded finish to flex as the molded article is removed from the mold.

Thus, there remains a need for a low cost injection moldable finish, which can be incorporated into containers made by an injection blow molding process, that can accommodate a flexible closure that includes a tamper indicating band as are commonly employed on extrusion blow molded plastic jugs typically used in the dairy industry, such as the Blackhawk closure.

SUMMARY OF THE INVENTION

Accordingly, an injection molded finish portion of a container preform of the present invention includes an annular wall having an outside surface and an end sealing surface on an upper end of the annular wall. A set of ratchet teeth are located at a lower end of the annular wall. A threaded portion is located below the sealing surface and above the ratchet teeth. The threaded portion includes two sets of inclined threads extending part way around the annular wall. The threads have crest portions that terminate at planes tangent to the annular wall along parting lines on opposite sides of the container preform finish.

The finish portion can also include lugs projecting outward from the annular wall in the vicinity of the parting lines. The lugs can extend equally on each side from the parting lines. The lugs can be parallel to the sealing surface or aligned with the adjacent ends of the threads of the threaded portion. Each lug can include a base portion adjacent to the annular wall, defined by a first vertical cross-sectional geometry, and a radially outward crown portion, defined by a second vertical crow-sectional geometry. The first vertical cross-sectional geometry can include arcuate surfaces above and below a midline of the lug, while the second vertical cross-sectional geometry can include a wedge extending outward from a middle sector of the first geometry.

The ratchet teeth of the finish portion can be disposed on a flange having an upper surface and a lower surface. The flange upper and lower surfaces can include radially inward edges coterminous with the annular wall of the finish. The flange upper and lower surfaces can taper outwardly. The ratchet teeth can include a radial surface and an outer surface inclined with respect to the radial surface. Outer ends of adjoining radial and outer surfaces can be joined by a curved portion while the inner ends of adjoining radial and outer surfaces can be joined by a segment parallel to the annular wall of the finish portion. The outer surface of each ratchet tooth is preferably inclined at about 75° with respect to the radial surface of the same tooth.

One feature of a finish portion molded in accordance with the present invention is the termination of the crest portions of the threads in planes tangent to the parting lines so that the threads are not deformed by the outwardly moving mold surfaces upon release of the finish portion from the corresponding mold.

Another feature of a finish portion molded in accordance with the present invention is the incorporation of lugs in the region of the parting lines so that a cooperating closure is inhibited from flexing enough to permit the closure to be removed without tearing the tamper indicating band from the skirt of the closure.

A further feature of a finish portion molded in accordance with the present invention is the placement and configuration of the ratchet teeth so that interaction with the tamper indicating band in maximized.

Still further features and advantages of an injection molded finish portion of a container preform will become apparent to those skilled in the art from a consideration of the following description of the preferred embodiments illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of an injection molded preform including a finish according to the present invention.

FIG. 2 is a sectional detail view of a portion of FIG. 1 showing a preferred thread cross-section.

FIG. 3 is a plan view of the finish of FIG. 1 showing the threads and lugs of a preferred finish.

FIG. 4 is a schematic view of an entire thread development around the finish shown in FIG. 3.

FIG. 5 is another sectional view of the finish of the previous Figures taken along line 5-5 of FIG. 3.

FIG. 6 is a sectional detail of the lugs.

FIG. 7 is a sectional view taken along lines 7-7 of FIG. 1 showing the ratchet toothed flanges and support ring.

FIG. 8 is a detail view of two adjacent ratchet teeth.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a vertical sectional view of an injection molded preform 10 including a finish portion 12 according to the present invention and a body portion 14. The body portion 14 can have a wide variety of shapes that generally is a function of the size and shape of the container that is to be formed from the preform in any subsequent blow molding operation. The body portion 14 is typically rotationally symmetric about a vertical axis Y of the preform. The body portion 14 and finish portion 12 are generally formed in a single unitary process, which is well known, in an injection mold that typically includes a core unit, a cavity unit, and a pair of thread splits. The core unit defines the interior surface 16 of the preform 10 including the interior surface 18 of the finish portion 12. The cavity unit defines the exterior surface 20 of the body portion 14. The thread splits define the outside configuration of the finish portion 12. As suggested by the name, the thread splits are generally formed in pairs that can reciprocate laterally with respect to the vertical axis Y. The juncture of the two thread splits defines parting lines, which are generally vertically oriented, located on opposite sides of the finish portion 12. The finish portion 12 includes an annular wall 22 having an outside surface 24 and an end sealing surface 26 on an upper end of the annular wall 22. A threaded portion 28 is located below the sealing surface 26. The finish portion 12 also includes a set of ratchet teeth that are located on an outward protruding flange 30 located below the threaded portion 28. A support ring 32 can be located below the ratchet teeth bearing flange 30.

A preferred embodiment of the threaded portion 28 can be seen in FIG. 2 to include threads having an upper wall 52 and a lower wall 54. The upper and lower walls 52 and 54 extend radially outward from the annular wall 22. A tapered surface 56 extends downwardly from the upper wall 52 outer extremity. A curved surface 58 joins the tapered surface 56 to the lower wall 54. The curved surface 58 defines a thread crest 44. FIG. 3 shows a plan view of the upper part of the finish portion 12 including the sealing surface 26, the interior surface 18, and the outside surface 24. The sectional view shown in FIG. 1 is taken along the diameter line 1-1 of FIG. 3. The orthogonal diameter line 5-5 is located in alignment with the vertical axis Y and the parting lines 34 created by the thread splits during the molding process. A set of four thread segments 36, 38, 40 and 42 are located on each side of the diameter line 5-5. The four thread segments 36-42 protrude outward from the outer surface 24 of the annular wall 22 to a radially outer edge of each thread segment defining the crest 44 of the threads. The crests 44 of the threads 36-42 terminate at planes W-W that are tangent to the outer surface 24 of the annular wall 22 along the parting lines 34. The termination of the crests 44 of the threads 36-42 in planes W-W tangent to the parting lines 34 ensures that the freshly molded threads are not deformed by the outwardly moving thread split mold surfaces upon release of the finish portion 12 from a corresponding thread split mold at the completion of the injection molding step. Lugs 46 project outward from the annular wall 22 in the vicinity of the parting lines 34. The lugs 46 can extend equally on each side of the parting lines 34.

FIG. 4 is a schematic view of an entire thread development around the finish portion 12 of the preform 10 extending from one parting line 34 at the left edge of the diagram to the same parting line 34 at the right edge of the diagram. The four thread segments 36-42 can be seen to form four discontinuous threads A, B, C, and D, which are composed of two thread segments each. An upper end of the threads A-D can be uniformly spaced below the sealing surface 26 of the finish portion 12. Each of the threads A-D can include a lead-in section 48 and a locking section 50. The thread crest 44 in the locking section 50 can project outward from the annular wall 22 by a greater distance than does the lead-in section 48, as shown in FIGS. 2 and 3. The difference in vertical cross-section between the lead-in section 48 and the locking section 50 can be seen in FIG. 2.

FIG. 5 is another sectional view of the finish 12 taken through diameter 5-5 of FIG. 3 at right angles to the view shown in FIG. 1. The sectional view of FIG. 5 is aligned with the parting lines 34 and passes through lugs 46. A detail view taken from FIG. 5 and shown in FIG. 6 reveals a preferred cross-sectional shape for the lugs 46 in which each lug 46 can include a base portion 52 adjacent to the annular wall 22 and a radially outward crown portion 54. The lug base portion 52 can exhibit a first vertical cross-sectional geometry including arcuate surfaces 60 and 62 above and below a middle sector 64 of the lug 46. The radially outward crown portion 54 can be defined by a second vertical cross-sectional geometry including a wedge 66 extending outward from the middle sector 68 of the first geometry 56. It is to be noted that the ratchet toothed flanges 30 do not protrude outward from the annular wall 22 in the cross-sectional view of FIG. 5. The incorporation of lugs 46 in the region of the parting lines 34 inhibits a cooperating flexible closure from flexing enough to allow the closure to be removed without tearing the tamper indicating band from the skirt of the closure. While the lugs 46 are shown in FIGS. 3-5 to be generally aligned with the ends of the adjacent threads, the lugs 46 could be situated at other locations on the annular wall 22 of the finish portion 12 so long as the lugs 46 did not interfere with the application of the selected closure.

Returning to FIG. 1, it will be seen that the ratchet toothed flanges 30 can include upper and lower surfaces 80 and 82 that can include radially inward edges 84 and 86, which can be coterminous with the outer surface 24 of annular wall 22 of the finish 12. The flange upper and lower surfaces 80 and 82 can taper outwardly to ensure quick mold release. FIG. 7 is a sectional view taken along lines 7-7 of FIG. 1 showing a preferred embodiment of the ratchet toothed flanges 30 and support ring 32. In this preferred embodiment, the flanges 30 are confined essentially to occupy two opposite quadrants 70 and 72 of the finish 12. A lateral surface 74 of each flange 30 is situated parallel to the planes W-W that are tangent to the annular wall 22 at the parting lines 34. Each of the teeth 76 can be related to its nearest neighbors by a fixed geometric relationship shown in detail in FIG. 8. The ratchet teeth 76 can include a radial surface 88 and an outer surface 90 that is inclined with respect to the radial surface 88. Outer ends of adjoining radial and outer surfaces can be joined by a curved portion 92. The inner ends of adjoining radial and outer surfaces can be joined by a segment 78 that is arranged to be generally parallel to the outer surface 24 of annular wall 22. In the illustrated preferred embodiment, the outer surface 90 of each ratchet tooth 76 is preferably inclined at about 75° with respect to the radial surface 88 of the same tooth. The placement and configuration of the ratchet teeth 76 as previously described maximizes the interaction of the ratchet teeth 76 with the tamper indicating band on a flexible closure such as the Blackhawk Super Quad ASP-100.

The foregoing detailed description should be regarded as illustrative rather than limiting, and the following claims, including all equivalents, are intended to define the spirit and scope of this invention.

Claims

1. An injection molded finish portion of a container preform comprising: an annular wall having an outside surface, an end sealing surface on an upper end of the annular wall, a set of ratchet teeth located at a lower end of the annular wall, and a threaded portion located below the sealing surface and above the ratchet teeth, the threaded portion including two sets of inclined threads extending part way around the annular wall, the threads including crest portions terminating at planes tangent to the annular wall along parting lines on opposite sides of the container.

2. The injection molded finish portion of claim 1 further comprising lugs projecting outward from the annular wall in the vicinity of the parting lines.

3. The injection molded finish portion of claim 2 wherein the lugs extend equally on each side from the parting lines.

4. The injection molded finish portion of claim 2 wherein the lugs are aligned with adjacent ends of the threads.

5. The injection molded finish portion of claim 4 wherein each lug includes a base portion adjacent to the annular wall defined by a first vertical cross-sectional geometry and a radially outward crown portion defined by a second vertical cross-sectional geometry.

6. The injection molded finish portion of claim 5 wherein the first vertical cross-sectional geometry includes arcuate surfaces above and below a midline of the lug, and the second cross-sectional geometry comprises a wedge extending outward from a middle sector of the first geometry arcuate surfaces.

7. The injection molded finish portion of claim 4 wherein the lugs comprise an upper lug and a lower lug straddling each parting line, the lower lug crown portion extending radially outward further than the upper lug crown portion.

8. The injection molded finish portion of any of claims 1, 2, 3, 4, 5, 6 or 7 wherein the ratchet teeth are disposed on a flange having an upper surface and a lower surface, the flange upper and lower surfaces including radially inward edges meeting with said annular wall.

9. The injection molded finish portion of claim 8 wherein the ratchet teeth include a radial surface and an outer surface inclined with respect to the radial surface, outer ends of adjoining radial and outer surfaces being joined by a curved portion and inner ends of adjoining radial and outer surfaces being joined by a segment parallel to said annular wall.

10. The injection molded finish portion of claim 9 wherein the outer surface of each ratchet tooth is inclined at about 75° with respect to the radial surface of the same tooth.

11. The injection molded finish portion of claim 8 wherein the flange upper and lower surfaces are outwardly tapered so that the flange is thickest at the radially inward edges of the upper and lower surfaces.

12. The injection molded finish portion of any of claims 1, 2, 3, 4, 5, 6 or 7 wherein each of the threads is defined by an upper wall and a lower wall, the upper and lower walls extending radially outward from said annular wall, a tapered surface extending downwardly from the upper wall outer extremity, and a curved surface joining the tapered surface to the lower walls, the curved surface defining said thread crest portion.