Patent US4923667A successfully refreshed from Google Patents.
US4923667A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method and apparatus for injection moulding
Assignee: Cinpres Ltd
•
Filing: 1988-09-23
•
Granted: 1990-05-08
•
Expires: 2008-09-23
Abstract
Abstract An injection moulded plastics article is produced by introducing a stream of molten plastics material from an injection moulding machine cylinder into an article forming mould space (13). Pressurised gas is supplied into the interior of the molten plastics material to form a gas containing cavity (25) therein. The plastics material is then allowed to solidify and cool sufficiently so that the article can itself sustain the form dictated by the mould surface. The cavity is vented to reduce the pressure within the cavity to ambient pressure prior to opening of the mould. The step of venting the cavity is achieved by providing at at least one position which is separate from the plastics inlet and the gas inlet a vent passage (30) in the mould open at its inner end to a part of the interior of the mould at which the gas containing cavity (25) is formed, and a retractable closure (31) for opening and closing the vent passage at its inner end, maintaining the closure in its closed position during the forming of the article whereby the cavity wall is formed over the inner end of the vent passage and the closure therefor, and subsequently retracting the closure to allow the creation of a vent opening in the cavity wall in the area of the inner end of the vent passage through which vent opening gas from the cavity passes into the vent passage. Apparatus for carrying out the above process is also described.
Inventors
- 👤 Matthew E. Sayer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 22:14
CPC Classifications
B; B29; B29C; B29C45/00; B29C45/17; B29C45/76; B29C45/1703; B29C45/1704; B29C45/26; B29C45/34; B29C45/46; B29C45/57; B29C2045/1729; Y; Y10; Y10S; Y10S425/00; Y10S425/058; Y10S425/812
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
231 words
A method of producing an injection molded plastic article comprising introducing a stream of molten plastic material from an injection molding machine cylinder into an article forming mold space, supplying pressurized gas into the interior of the molten plastic material to form a gas containing cavity therein, allowing the plastic material to solidify and cool sufficiently so that the article can itself sustain the form dictated by the mold surface, and venting the cavity to reduce the pressure within the cavity to ambient pressure prior to opening of the mold, the step of venting the cavity being achieved by providing at at least one position which is separate from the plastic inlet and the gas inlet a vent passage in the mold open at its inner end to a part of the interior of the mold at which the gas containing cavity is formed, and a retractable closure for opening and closing the vent passage at its inner end, maintaining the closure in its closed position during the forming of the article whereby the cavity wall is formed over the inner end of the vent passage and the closure therefor, and subsequently retracting the closure to allow the creation of a vent opening in the cavity wall in the area of the inner end of the vent passage through which vent opening gas from the cavity passes into the vent passage.
Claim 2
Independent Claim
231 words
A method of producing an injection molded plastic article comprising introducing a stream of molten plastic material from an injection molding machine cylinder into an article forming mold space, supplying pressurized gas into the interior of the molten plastic material to form a gas containing cavity therein, allowing the plastic material to solidify and cool sufficiently so that the article can itself sustain the form dictated by the mold surface, and venting the cavity to reduce the pressure within the cavity to ambient pressure prior to opening of the mold, the step of venting the cavity being achieved by providing at at least one position which is separate from the plastic inlet and the gas inlet a vent passage in the mold open at its inner end to a part of the interior of the mold at which the gas containing cavity is formed, and a retractable closure for opening and closing the vent passage at its inner end, maintaining the closure in its closed position during the forming of the article whereby the cavity wall is formed over the inner end of the vent passage and the closure therefor, and subsequently retracting the closure to allow the creation of a vent opening in the cavity wall in the area of the inner end of the vent passage through which vent opening gas from the cavity passes into the vent passage.
Claim 3
Dependent Claim
37 words
A method as claimed in claim 1, wherein on retraction of the closure the cavity wall is unsupported and the pressure of the gas within the cavity ruptures the cavity wall and thereby creates the vent opening.
Claim 4
Dependent Claim
56 words
A method as claimed in claim 1, including immersing a part of the closure in the cavity wall as it is formed to produce weak lines in the cavity wall whereby on retraction of the closure the weak lines assist the pressure of the gas to rupture the cavity wall and thereby create the vent opening.
Claim 5
Dependent Claim
57 words
A method as claimed in claim 1, including immersing a part of the closure in the cavity wall as it is formed to produce weak lines in the cavity wall whereby on retraction of the closure the weak lines assist the removal of a section of the cavity wall and thereby the creation of the vent opening.
Claim 6
Dependent Claim
30 words
A method as claimed in claim 4, wherein the part of the closure to be immersed is undercut whereby retraction of the closure pulls said section from the cavity wall.
Claim 7
Dependent Claim
29 words
A method as claimed in claim 1, including the step of applying heat at the inner end of the vent passage to assist the creation of the vent opening.
Claim 8
Dependent Claim
16 words
A method as claimed in claim 6, wherein the heat is applied by heating the closure.
Claim 9
Dependent Claim
145 words
Apparatus for producing an injection molded plastic article comprising means for introducing a stream of molten plastic material from an injection molding machine cylinder into an article forming mold space, means for supplying pressurized gas into the interior of the molten plastic material to form a gas containing cavity therein, and at at least one position which is separate from the plastic inlet and the gas inlet a vent passage in the mold open at its inner end to a part of the interior of the mold at which the gas containing cavity is to be formed, a retractable closure positioned in the inner end of the vent passage for movement between an extended position in which the vent passage is closed and a retracted position in which the vent passage is open, and means for moving the closure between its extended and retracted positions.
Claim 10
Dependent Claim
145 words
Apparatus for producing an injection molded plastic article comprising means for introducing a stream of molten plastic material from an injection molding machine cylinder into an article forming mold space, means for supplying pressurized gas into the interior of the molten plastic material to form a gas containing cavity therein, and at at least one position which is separate from the plastic inlet and the gas inlet a vent passage in the mold open at its inner end to a part of the interior of the mold at which the gas containing cavity is to be formed, a retractable closure positioned in the inner end of the vent passage for movement between an extended position in which the vent passage is closed and a retracted position in which the vent passage is open, and means for moving the closure between its extended and retracted positions.
Claim 11
Dependent Claim
22 words
Apparatus as claimed in claim 8, wherein the inner end of the vent passage is open to the article forming mold space.
Claim 12
Dependent Claim
34 words
Apparatus as claimed in claim 8, wherein the inner end of the vent passage is open to a part of the interior of the mold which is upstream of the article forming mold space.
Claim 13
Dependent Claim
37 words
Apparatus as claimed in claim 8, wherein the closure has a conical surface which engages a correspondingly shaped valve seat in the vent passage when the closure is in its extended position thereby closing the vent passage.
Claim 14
Dependent Claim
26 words
Apparatus as claimed in claim 8, wherein a part of the closure, in its extended position, becomes immersed in the cavity wall as it is formed.
Claim 15
Dependent Claim
23 words
Apparatus as claimed in claim 12, wherein said part of the closure, in its extended position, protrudes into the interior of the mold.
Claim 16
Dependent Claim
30 words
Apparatus as claimed in claim 12, wherein said part of the closure is shaped to assist the removal of a section from the cavity wall when the closure is retracted.
Claim 17
Dependent Claim
26 words
Apparatus as claimed in claim 12, wherein the closure is undercut to provide a head which becomes immersed in the cavity wall as it is formed.
Claim 18
Dependent Claim
18 words
Apparatus as claimed in claim 8, wherein the closure is a pin extending lengthwise of the vent passage.
Claim 19
Dependent Claim
19 words
Apparatus as claimed in claims 8, including means for applying heat at the inner end of the vent passage.
Claim 20
Dependent Claim
16 words
Apparatus as claimed in claim 17, wherein the heating means are provided internally of the closure.
Claim 21
Dependent Claim
18 words
Apparatus as claimed in claim 8, wherein the means for moving the closure is a piston and cylinder.
Claim 22
Dependent Claim
18 words
Apparatus as claimed in claim 8, wherein the outer end of the vent passage is open to atmosphere.
References Cited (Backward Citations)
US2105704A
Cited
US2331688A
Cited
US3366993A
Cited
US3021559A
Cited
GB996186A
Cited
US3114931A
Cited
DE1265395B
Cited
GB945234A
Cited
GB1076047A
Cited
US3378612A
Cited
GB1106567A
Cited
US3358062A
Cited
GB1167513A
Cited
US3575949A
Cited
US3793421A
Cited
DE2106546A1
Cited
US3793415A
Cited
US3873661A
Cited
US4017225A
Cited
US3899278A
Cited
FR2256021A1
Cited
US4129635A
Cited
US4101617A
Cited
US4033710A
Cited
US4115491A
Cited
DE2655255A1
Cited
US4201742A
Cited
US4136220A
Cited
US4070429A
Cited
DE2800482A1
Cited
US4140672A
Cited
JPS54123173A
Cited
US4247515A
Cited
US4234642A
Cited
US4389358A
Cited
GB2122130A
Cited
US4474717A
Cited
US4555225A
Cited
US4498860A
Cited
GB2139549A
Cited
GB2139548A
Cited
EP0127961A2
Cited
GB2158002A
Cited
US4740150A
Cited
US4740150B1
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-05-07 | 1993-11-06 | 1994-05-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-05-07 | 1997-11-06 | 1998-05-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-05-07 | 2001-11-06 | 2002-05-08 | $7700.00 | Window Closed / Lapsed |