Preform assembly, container assembly, and method of manufacture
A method of making a preform assembly including providing a finish ring of plastic construction, placing the finish ring onto a core pin, introducing a preform polymer into a mold cavity that includes the core pin, and compression molding the preform polymer to the finish ring. A resulting preform assembly, and container assembly blow-molded from the preform assembly, are also disclosed.
The present invention is directed to preform assemblies for blow molding plastic container assemblies, to plastic container assemblies blow molded from such preform assemblies, and to methods of making such preform assemblies and container assemblies.
BACKGROUND AND SUMMARY OF THE INVENTIONIn the manufacture of plastic containers, it is conventional to injection mold or compression mold a container preform having a body and a neck finish with one or more external threads or other closure attachment means. The preform neck 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 neck finish 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 neck finish portion of a container as part of the container 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 mold cavity into the area in which the neck finish is molded. The neck finish typically requires more accurate and stable dimensioning than the body of the preform, which can limit the cycle time of the preform molding process. Furthermore, the neck finish of the preform is of the same material as a monolayer preform body, and of the same material as at least the outer layers of a multilayer preform body, which limits the ability to obtain the most desirable material characteristics at the neck finish. When the preform is of polyester construction, such as polyethylene terephthalate (PET), the neck finish of the preform can be wholly or partially crystallized to improve the operating characteristics of the neck finish area, particularly in hot-fill container applications. However, the requirement that the neck finish be of the same material as at least the outer layers of a multilayer preform body still limits the design capabilities of preform manufacture.
A method of making a preform assembly in accordance with one aspect of th present invention includes providing a finish ring of plastic construction, placing the finish ring onto a core pin, introducing a preform polymer into a mold cavity that includes the core pin, and compression molding the preform polymer to the finish ring.
In accordance with a second aspect of the present invention, there is provided a preform assembly for blow molding a container assembly, which includes a molded plastic finish ring and a plastic preform compression molded to the finish ring such that a neck portion of the plastic preform radially interengages the finish ring.
In accordance with a third aspect of the invention, there is provided a container assembly blow molded from a preform assembly which is produced from compression molding a preform to a molded plastic finish ring. The container assembly includes the molded plastic finish ring, and a plastic container having a neck portion thereof radially interengaging said finish ring.
BRIEF DESCRIPTION OF THE DRAWINGSThe 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:
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With one or more of the embodiments described above, the present invention provides a number of advantages. The present invention facilitates production of preform assemblies and container assemblies wherein a finish ring is composed of a material different from that of a preform or container to which the finish ring is radially interengaged. Likewise, the present invention facilitates application of finish rings of various sizes and/or materials, to a common size preform and/or container. Moreover, the present invention enables a decrease in the cycle time required to produce a preform because the constraint of the process—forming the neck finish portion—can be subordinated to a separate, parallel production process for producing just finish rings. In the same vein, the present invention enables a reduction in the piece price of each preform because the mold tooling can be simplified, and reduced in cost, to omit the complex thread split features typically required for the threaded finish portion of the preform.
There have thus been described preform assemblies for blow molding plastic container assemblies, plastic container assemblies blow molded from such preform assemblies, and methods of making such preform assemblies and container assemblies that fully satisfy all of the objects and aims previously set forth. The present invention has been disclosed in conjunction with presently preferred embodiments thereof, and a number of modifications and variations have been discussed. Other modifications and variations will readily suggest themselves to persons of ordinary skill in the art in view of the foregoing description. Indeed, the invention is intended to embrace all modifications and variations as fall within the spirit and broad scope of the appended claims.
Claims
1. A method of making a preform assembly, said method including:
- (a) providing a finish ring of plastic construction,
- (b) placing said finish ring onto a core pin,
- (c) introducing a preform polymer into a mold cavity,
- (d) placing said core pin and finish ring into said mold cavity around said core pin, and
- (e) compression molding said preform polymer to said finish ring.
2. The method of claim 1 wherein said step (a) includes providing said finish ring with an internal surface having at least one radial interengagement feature, such that a portion of said preform polymer flows during said step (e) into interengagement with said at least one radial interengagement feature during said compression molding step.
3. The method of claim 2 wherein said step (a) includes said at least one radial interengagement feature being at least one radial recess, such that a portion of said preform polymer flows into said at least one radial recess during said compression molding step.
4. The method of claim 3 wherein said step (a) also includes said at least one radial recess being at least one annular groove, such that a portion of said preform polymer flows into said at least one annular groove during said compression molding step.
5. The method of claim 1 wherein said step (a) includes providing said finish ring with an internal surface having at least a portion thereof greater in diameter than said core pin, such that a gap is formed during said step (e) between said at least a portion of said internal surface, said core pin, and a forward edge of said preform polymer, said gap being provided to accommodate within-tolerance variation of a molten charge of said preform polymer to prevent overpacking of said preform polymer into said finish ring.
6. A preform assembly produced by the method of claim 5.
7. A preform assembly produced by the method of claim 1.
8. A method of making a container assembly includes blow molding the preform assembly of claim 7.
9. A container assembly produced by the method of claim 8.
10. A preform assembly for blow molding a container assembly, which includes:
- a molded plastic finish ring, and
- a plastic preform compression molded to said finish ring such that a neck portion of said plastic preform radially interengages said finish ring.
11. The preform assembly set forth in claim 10 wherein said finish ring includes at least one internal surface with at least one radial interengagement feature formed therein, further wherein said neck portion of said plastic preform radially interengages with said at least one radial interengagement feature.
12. The preform assembly set forth in claim 10 wherein said finish ring includes at least one tapered internal surface, at least one straight internal surface, and a transition point therebetween, and wherein there is an open gap between said transition point and a forward edge of said neck portion of said plastic preform to prevent said neck portion of said plastic preform from being overpacked into said finish ring.
13. A container assembly blow molded from a preform assembly produced from compression molding a preform to a molded plastic finish ring, said container assembly includes:
- said molded plastic finish ring, and
- a plastic container having a neck portion thereof interengaging said finish ring.
14. The container assembly set forth in claim 13 wherein said finish ring includes at least one internal surface with at least one radial interengagement feature formed therein, and wherein said neck portion of said plastic container interengages with said at least one radial interengagement feature.
15. The container assembly set forth in claim 14 wherein said finish ring includes at least one tapered internal surface, at least one straight internal surface, and a transition point therebetween, and wherein a gap is defined between said transition point and a forward edge of said neck portion of said plastic container to prevent said neck portion of said plastic container from being overpacked into said finish ring.
Type: Application
Filed: Apr 1, 2004
Publication Date: Oct 6, 2005
Inventors: Keith Barker (Candia, NH), Bassam Kalmouni (Pembroke, NH), Brian Lynch (Merrimack, NH), Nikhil Mani (Billerica, MA), Thomas Nahill (Amherst, NH)
Application Number: 10/816,500