Claims
- 1. A process for injection molding a hollow plastic tubular article comprising the steps of:
(a) injecting a quantity of plastic material into a mold cavity to at least substantially fill said mold cavity, the mold cavity having a substantially cone-shaped inlet portion, an elongated central portion and an exit portion; (b) injecting pressurized gas into the plastic material in the mold cavity; (c) holding the pressure of the gas and plastic in the mold cavity for a predetermined amount of time; and (d) allowing a portion of the plastic material in the mold cavity to be expelled into at least one secondary cavity coupled to the mold cavity.
- 2. The process as set forth in claim 1 further comprising the steps of:
(e) permitting the plastic material to solidify; (f) exhausting the gas from the mold cavity; and (g) removing the plastic article from the mold.
- 3. The process as set forth in claim 1 wherein said cone-shaped portion has an apex and said gas is injected into the plastic material at said apex.
- 4. The process as set forth in claim 1 further comprising the step of holding constant the plastic material injection pressure in the mold cavity for a predetermined period of time prior to the injection of gas into the plastic material.
- 5. The process as set forth in claim 1 wherein said plastic material is injected into the mold cavity from an injection molding machine with a barrel and nozzle, said method further comprising the step of allowing a portion of the plastic material in the mold to be expelled back into the barrel of the injection molding machine.
- 6. The process as set forth in claim 1 wherein said exit portion comprises a second substantially cone-shaped portion, said cone-shaped exit portion having an apex and said expulsion of plastic material from the mold cavity into the secondary cavity occurs through said apex.
- 7. The process as set forth in claim 1 further calculating the volume of said at least one secondary cavity in order to allow expulsion of a predetermined amount of plastic material from the mold cavity.
- 8. The process as set forth in claim 1 wherein the step of allowing a portion of the plastic material in the mold to be expelled comprises opening a valve member in a conduit connecting the mold cavity with the secondary cavity.
- 9. The process as set forth in claim 1 wherein the plastic material is injected into the mold cavity at said cone-shaped inlet portion and enters the mold cavity along the outer surfaces thereof.
- 10. The process as set forth in claim 9 further comprising a ring gate mechanism for injecting the plastic material into said cone-shaped inlet portion.
- 11. A process for injection molding a hollow plastic tubular article comprising the steps of:
(a) injecting a quantity of plastic material to fill or substantially fill a mold cavity, the mold cavity having a first substantially cone-shaped inlet portion, an elongated central portion and an exit portion; (b) injecting pressurized gas into the plastic material in the mold cavity; (c) holding the pressure of the gas and plastic in the mold cavity for a predetermined amount of time; (d) allowing a portion of the plastic material in the mold cavity to be expelled into at least one secondary cavity coupled to the mold cavity; (e) permitting the plastic material to solidify; (f) exhausting the gas from the mold cavity; (g) removing the tubular-shaped plastic article from the mold; and (h) trimming at least one end of the article to form a tubular article of substantially constant cross-section.
- 12. The process as set forth in claim 11 wherein said cone-shaped inlet portion has an apex and said gas is injected into the plastic material in said apex.
- 13. The process as set forth in claim 11 further comprising the step of holding constant the plastic material injection pressure in the mold cavity for a predetermined period of time prior to the injection of gas into the plastic material.
- 14. The process as set forth in claim 11 wherein said plastic material is injected into the mold cavity from an injection molding machine with a barrel and nozzle, said method further comprising the step of allowing a portion of the plastic material in the mold to be expelled back into the barrel of the injection molding machine.
- 15. The process as set forth in claim 11 wherein said exit portion comprises a substantially cone-shaped portion, said cone-shaped exit portion having an apex and said expulsion of plastic material from the mold cavity in the secondary cavity occurs through said apex.
- 16. The process as set forth in claim 11 further calculating the volume of said at least one secondary cavity in order to allow expulsion of a predetermined amount of plastic material from the mold cavity.
- 17. The process as set forth in claim 11 wherein the step of allowing a portion of the plastic material in the mold to be expelled comprises opening a valve member in a conduit connecting the mold cavity with the secondary cavity.
- 18. A process for injection molding a hollow tubular plastic article utilizing an injection molding machine with a barrel and nozzle and a mold with a mold cavity therein, the mold cavity having a substantially cone-shaped inlet portion, an elongated central portion and an exit portion, said method comprising the steps of:
(a) injecting a quantity of plastic material into said cone-shaped inlet portion of the mold cavity from the injection molding machine; (b) injecting pressurized gas into the plastic material in the mold cavity; and (c) allowing a first portion of the plastic material in the mold cavity to be expelled back into the barrel of the injection molding machine.
- 19. The process as set forth in claim 18 further comprising the step of holding the constant pressure of the gas and plastic material in the mold cavity for a predetermined amount of time before said first portion of the plastic material is expelled back into the injection molding machine.
- 20. The process as set forth in claim 18 wherein a predetermined amount of plastic material is expelled back into the injection molding machine.
- 21. The process as set forth in claim 18 wherein the gas is injected into the plastic material from said exit portion.
- 22. The process as set forth in claim 18 wherein the plastic material is injected into the mold cavity at said cone-shaped inlet portion and enters the mold cavity along the outer surfaces thereof.
- 23. The process as set forth in claim 22 further comprising a ring gate mechanism for injecting the plastic material into said cone-shaped inlet portion.
- 24. The process as set forth in claim 18 wherein the step of allowing a first portion of the plastic material in the mold to be expelled back into the barrel of the injection molding machine comprises opening a shut-off valve member positioned between said mold cavity and said barrel.
- 25. The process as set forth in claim 24 wherein said valve member is included as part of the nozzle.
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent application Ser. No. 09/902,354, filed on Jul. 10, 2001, and entitled “Plastic Expulsion Process.”
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
09902354 |
Jul 2001 |
US |
Child |
09918234 |
Jul 2001 |
US |