Plastic article or earthenware shaping or treating: apparatus – Female mold and charger to supply fluent stock under... – With means to heat or cool
Reexamination Certificate
2000-02-08
2001-10-30
Heitbrink, Tim (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Female mold and charger to supply fluent stock under...
With means to heat or cool
C264S328150
Reexamination Certificate
active
06309207
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an injection molding nozzle assembly. More particularly, the present invention relates to an injection molding nozzle assembly which has a relatively wide operating temperature window and/or which can be easily removed and installed without requiring removal of the mold from an injection molding machine.
BACKGROUND OF THE INVENTION
Injection molding nozzles for injection molding are known. For example hot runner injection machines feed liquefied plastic material from the bushing of an injection molding machine to an injection gate of a mold cavity to mold the desired article therein. Examples of prior U.S. Patents relating to injection molding nozzles and machines include 4,173,448; 4,588,367; 4,662,837; 4,682,945; 5,374,182; and 5,533,882, all of which are assigned to the assignee of the present invention and the contents of all of which are incorporated herein by reference.
While injection molding and nozzle assemblies are well known, problems still exist with prior art injection nozzles. For example, leaking of liquefied plastic from various connection points within the nozzle assembly, the manifold and the injection machine is a continuing problem. In particular, such leaked material can remain within the nozzle assembly, being heated for time periods in excess of those intended within normal processes, resulting in crystallization and other deleterious effects in the material. This leaked material can contaminate ongoing injection operations and generally results in difficulty in servicing nozzle assemblies and machines. Further, some materials are corrosive or otherwise aggressive to materials within the nozzle assembly and their continued presence within the nozzle assembly due to leaking can result in decreased service lifetimes.
The problem of leaking has proven to be a difficult one to address due to the wide range of operating temperatures which can be required, depending upon the plastic material and/or injection process. As the nozzle assembly is formed of components subject to thermal expansion and contraction, and in fact such components can have different thermal expansion coefficients, generally a nozzle assembly is designed for use within a relatively narrow operating temperature window such as 20° C. or, at best, 30° C. about the designed operating temperature. While the materials, design and clearances within the nozzle assembly are carefully selected to reduce leaking within the operating temperature window, operation outside this operating temperature window often results in unacceptable leaking.
As will be apparent, a narrow operating temperature window limits use of the nozzle assembly to specific processes and/or configurations. To supply nozzle assemblies with different required operating windows, a supplier must maintain a wide inventory of components with different designs, dimensions and/or which are formed of different materials.
Another difficulty with prior art injection nozzles is that, with the exception of the invention disclosed in the above-mentioned U.S. Pat. No. 5,533,882, injection nozzles can only be serviced by removing the mold from the injection molding machine and then disassembling the mold to remove the nozzle assemblies from the back side of the mold.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a novel injection molding nozzle assembly and method of assembling an injection molding nozzle assembly which obviates or mitigates at least one disadvantage of the prior art.
According to a first aspect of the present invention, there is provided a nozzle assembly comprising:
an elongate nozzle body having a head and a nozzle tip and a melt channel extending along a longitudinal axis between said head and said tip;
a heater located about said nozzle body to heat said body;
a first spacer connected to said nozzle body and having a first response characteristic to pressure applied thereto in parallel to said axis;
a second spacer to act between said first spacer and an injection mold, said second spacer having a second response characteristic which differs from said first response characteristic, said first and second spacers co-operating to provide a sealing force between said head and a manifold of an injection mold when said nozzle assembly is installed therein and within a selected range of operating temperatures.
According to another aspect of the present invention, there is provided a nozzle assembly having an enhanced operating temperature window, comprising:
an elongate nozzle, body having a head and a nozzle tip and a melt channel extending between said head and said tip along a longitudinal axis;
a heater located about said nozzle body to heat said body;
a first spacer connected to said nozzle body and having a first response characteristic to pressure applied parallel to said longitudinal axis;
a second spacer to act between said first spacer and an injection mold, said second spacer having a second response characteristic to pressure applied parallel to said longitudinal axis which differs from said first response characteristic, said first and second spacers cooperating to provide a contact force to seal a connection between said head and a manifold of said injection mold when said nozzle assembly is installed therein and operated within a temperature window of up to 50° C. from a preselected operating temperature.
According to yet another aspect of the present invention, there is provided a method of assembling an injection nozzle assembly in an injection mold comprising the steps of:
(i) placing a heater element in thermal contact with the exterior of a nozzle body having a head, a nozzle and a melt channel therebetween;
(ii) providing a first spacer at the head of said body and surrounding said melt channel;
(iii) providing a second spacer about said body and routing electrical leads from said heater through an aperture provided through said second spacer;
(iv) inserting said nozzle body and spacers into said injection mold such that said melt channel at said head contacts a melt outlet in a manifold of said injection mold; and
(v) mounting said nozzle body to a manifold plate of said mold such that a sealing contact force is produced by said second spacer acting between said manifold plate and said first spacer and by said first spacer acting between said second spacer and said manifold.
The present invention provides a nozzle assembly with several advantages. The use of two or more spacers with different resilient and/or thermal expansion characteristics results in an acceptable seal between the nozzle body melt channel and the manifold over a relatively wide thermal operating window. The nozzle assembly is particularly compact, allowing center spacings between adjacent nozzles of as little as eighteen millimetres. Further, the nozzle assemblies can be mounted, removed or otherwise accessed easily, from the cavity side of the manifold plate, without requiring removal of the mold from an injection molding machine.
REFERENCES:
patent: 4173448 (1979-11-01), Rees et al.
patent: 4333608 (1982-06-01), Hendry
patent: 4588367 (1986-05-01), Schad
patent: 4662837 (1987-05-01), Anderson
patent: 4682837 (1987-07-01), Schad
patent: 5049062 (1991-09-01), Gellert
patent: 5374182 (1994-12-01), Gessner
patent: 5533882 (1996-07-01), Gessner
patent: 6062846 (2000-05-01), Kalemba
patent: 1153523 (1983-09-01), None
patent: 2060282 (1970-12-01), None
patent: 2137430 (1971-07-01), None
patent: 29501450.4 (1995-01-01), None
patent: 1373040 (1974-11-01), None
German Paper Kunststoffe 75 (1985) 12, p. 880.
Heitbrink Tim
Husky Injection Molding Systems Ltd.
Spencer Eric
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