Method and device for producing a plastic part, especially a plastic part for an automobile, by an injection molding method

Patent metadata

Field	Value
Publication number	US-9944003-B2
Application number	US-201314413735-A
Country	US
Kind code	B2
Filing date	Jun 18, 2013
Priority date	Jul 17, 2012
Publication date	Apr 17, 2018
Grant date	Apr 17, 2018

Abstract

The invention relates to a method for producing a plastic part, especially a plastic part for an automobile, by an injection molding method comprising the steps: Using an injection molding device, plastic in a flowable state is injected into the mold cavity of an injection mold, gas under pressure is injected through a gas inlet opening in the injection mold into the mold cavity of the injection mold by means of a gas injection device so that a gas bubble forms within the still flowable plastic, the plastic is heated and kept flowable, at least in a region neighboring the gas inlet opening while the plastic is hardening in the mold cavity, wherein pressure is exerted on the plastic being kept flowable so that an opening in the plastic in the region of the gas inlet opening is sealed, and the plastic part is removed from the injection mold after reaching a sufficient dimensional stability. In addition, the invention relates to a corresponding device.

First claim

The invention claimed is:

1. A method for producing a plastic part, with an injection molding method comprising the steps:
Plastic is injected in a flowable state by means of an injection molding device into a mold cavity of an injection mold,
Gas under pressure is injected through a gas inlet opening of the injection mold into the mold cavity of the injection mold by means of a gas injection device so that a gas bubble forms within the still flowable plastic,
The plastic is heated and kept flowable, at least in a region neighboring the gas inlet opening, while the plastic is hardening in the mold cavity, wherein pressure is exerted on the plastic being kept flowable so that an opening in the plastic in the region of the gas inlet opening is sealed,
The plastic part is removed from the injection mold after reaching sufficient dimensional stability, wherein
at least one of:
(i) the plastic is heated at least in the region neighboring the gas inlet opening by means of an ultrasonic welding device, and wherein the pressure is exerted on the plastic being kept flowable by means of a sonotrode of the ultrasonic welding device;
(ii) the heating device comprises a heated sleeve and a plunger that can be moved in an axial direction and guided in the sleeve; or
(iii) the plastic is heated at least in the region neighboring the as inlet opening by means of an electrical heating device.

2. The method according to claim 1 , wherein the plastic is heated at least in the region neighboring the gas inlet opening by means of the ultrasonic welding device.

3. The method according to claim 2 , wherein the pressure is exerted on the plastic being kept flowable by means of the sonotrode of the ultrasonic welding device.

4. The method according to claim 3 , wherein the sonotrode forms a part of the mold surfaces forming the mold cavity.

5. The method according to claim 3 , wherein at least a part of the injection mold is distanced from the sonotrode before the sonotrode is excited to vibrate ultrasonically to heat the plastic, at least in the region neighboring the gas inlet opening.

6. The method according to claim 1 , wherein the heating device comprises the heated sleeve and the plunger that can be moved in the axial direction and guided in the sleeve.

7. The method according to claim 6 , wherein the sleeve is supplied hot gas from a hot gas source.

8. The method according to claim 7 , wherein the sleeve is provided with at least one additional heating element.

9. The method according to claim 6 , wherein the plunger forms a part of the surfaces forming the mold cavity when the flowable plastic and the gas are being injected into the mold cavity.

10. The method according to claim 9 , wherein the gas injection device supplies the gas through the sleeve, wherein the plunger is at least partially withdrawn from the sleeve while the gas is being injected so that a part of the still flowable plastic enters the sleeve in which it is kept flowable by means of the heated sleeve.

11. The method according to claim 10 , wherein the plunger is then moved in an axial direction into the sleeve, wherein the pressure is exerted that is necessary to close the opening in the plastic in the region of the gas inlet opening.

12. The method according to claim 1 , wherein the plastic is heated at least in the region neighboring the gas inlet opening by means of an electrical heating device.

13. The method according to claim 12 , wherein the electrical heating device comprises an electrically heated hot plunger which, after the gas is injected, can move in an axial direction toward the gas inlet opening so that the plastic is heated and kept flowable at least in the region neighboring the gas inlet opening, and wherein the pressure is exerted that is necessary to close the opening in the plastic in the region of the gas inlet opening.

14. The method according to claim 12 , wherein the hot plunger forms a part of the surfaces forming the mold cavity when the flowable plastic and the gas are being injected into the mold cavity.

15. The method according to claim 12 , wherein at least a part of the injection mold can be distanced from the hot plunger before the hot plunger is moved in an axial direction toward the gas inlet opening.

16. The method according to claim 12 , wherein, after closing the opening in the plastic located in the region of the gas inlet opening, a cooling gas, is conducted through the hot plunger toward the closed opening in the plastic.

17. The method according to claim 1 , wherein the plastic part is chrome-plated after being removed from the injection mold.

18. A device for producing a plastic part, with an injection molding method comprising:
an injection mold with a mold cavity and an injection molding device that is designed to inject plastic in a flowable state into the mold cavity of the injection mold,
a gas injecting device that is designed to inject gas under pressure through a gas inlet opening of the injection mold into the mold cavity of the injection mold,
a heating device that is designed to heat the plastic hardening in the mold cavity, at least in a region neighboring the gas inlet opening, and keep it flowable,
a pressurizing device that is designed to exert pressure on the plastic that is being kept flowable so that an opening in the plastic in the region of the gas inlet opening is sealed, and
a removing device by means of which the injection mold can be opened to remove the plastic part from the injection mold, wherein
at least one of:
(i) the heating device is an ultrasonic welding device, and wherein the pressurizing device comprises a sonotrode of the ultrasonic welding device;
(ii) the heating device comprises a positioning device that is designed to distance at least a part of the injection mold from the sonotrode before the sonotrode is excited to vibrate ultrasonically to heat the plastic, at least in the region neighboring the as inlet opening;
(iii) the heating device comprises a heated sleeve and a plunger that can be moved in an axial direction and guided in the sleeve;
(iv) the heating device comprises a chrome plating device for chrome plating a plastic part after being removed from the injection mold; or
(v) the heating device comprises an electrical heating device.

19. The device according to claim 18 , wherein the heating device is the ultrasonic welding device.

20. The device according to claim 19 , wherein the pressurizing device comprises the sonotrode of the ultrasonic welding device.

21. The device according to claim 20 , wherein the sonotrode forms a part of the mold surfaces forming the mold cavity.

22. The device according to claim 18 , wherein the device comprises the positioning device that is designed to distance at least the part of the injection mold from the sonotrode before the sonotrode is excited to vibrate ultrasonically to heat the plastic, at least in the region neighboring the gas inlet opening.

23. The device according to claim 18 , wherein the heating device comprises the heated sleeve and the plunger that can be moved in the axial direction and guided in the sleeve.

24. The device according to claim 23 , wherein the sleeve is connected to a hot gas source.

25. The device according to claim 24 , wherein the sleeve is provided with at least one additional heating element.

26. The device according to claim 23 , wherein the plunger, in a first ax

Assignees

• Illinois Tool Works

Inventors

• Fries Elmar

Classifications

• B29C45/7337

  using gas or steam (B29C45/7331 takes precedence) · CPC title

• B29C35/0261

  using ultrasonic or sonic vibrations · CPC title

• B29C45/33

  having transversely, e.g. radially, movable mould parts · CPC title

• B29C45/1704 Primary

  the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles (B29C45/1732 and B29C45/1734 take precedence; injection blow-moulding B29C49/06) · CPC title

• B29C2045/1718

  sealing or closing the fluid injection opening · CPC title