Patent EP0250080A2 successfully refreshed from Google Patents.
EP0250080A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Method for injection molding
Assignee: LADNEY, MICHAEL
•
Filing: 1987-05-05
•
Granted: —
•
Expires: 2007-05-05
Abstract
Abstract A process for producing an injection molded product includes introducing a stream of plastics material into a mold space at a first pressure. A quantity of gas is stored in a storage chamber at a second pressure which is at least as high as the first pressure. The gas is introduced into the molten stream of placstics material immediately after the molten material has passed the position at which the gas is introduced thereby forming a gas cavity in the molten material. The gas exerts pressure on the surrounding plastics material to urge the material toward the surfaces of the mold space. As the feeding of the plastics material into the mold space continues, the injection of the gas is also continued. The supply of molten material is terminated when the surfaces of the mold space are completely covered by the molten material. The pressure within the gas cavity is subsequently maintained as the plastic material cools. An apparatus for producing an injection molded product is also disclosed.
Inventors
- 👤 Indra R. Baxi
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-26 21:35
CPC Classifications
B; B29; B29C; B29C45/00; B29C45/17; B29C45/1703; B29C45/1732; B29C45/46
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
153 words
A process for producing an injection molded product, comprising: introducing a molten stream of a plastics material into a mold space at a first pressure; storing a quantity of gas in a storage chamber at a second pressure which is at least as high as said first pressure; introducing said gas into said molten stream of plastics material immediately after said molten material has passed the position at which the gas is introduced thereby forming a gas cavity in the molten material, the gas exerting pressure on the surrounding plastics material to urge the material toward the surfaces of said mold space; continuing to feed plastics material to said mold space; simultaneously continuing to inject gas into said gas cavity; terminating the supply of molten material when the surfaces of said mold space are completely covered by molten material; and, subsequently maintaining a pressure within the gas cavity as the plastics material cools.
Claim 2
Dependent Claim
153 words
A process for producing an injection molded product, comprising: introducing a molten stream of a plastics material into a mold space at a first pressure; storing a quantity of gas in a storage chamber at a second pressure which is at least as high as said first pressure; introducing said gas into said molten stream of plastics material immediately after said molten material has passed the position at which the gas is introduced thereby forming a gas cavity in the molten material, the gas exerting pressure on the surrounding plastics material to urge the material toward the surfaces of said mold space; continuing to feed plastics material to said mold space; simultaneously continuing to inject gas into said gas cavity; terminating the supply of molten material when the surfaces of said mold space are completely covered by molten material; and, subsequently maintaining a pressure within the gas cavity as the plastics material cools.
Claim 3
Dependent Claim
15 words
A process according to claim 1 wherein the gas is introduced at a mold sprue.
Claim 4
Dependent Claim
14 words
A process according to claim 1 or claim 2 wherein the gas is nitrogen.
Claim 5
Dependent Claim
22 words
A process according to any one of the preceding claims wherein said second pressure is between approximately 4,000 psi and 15,000 psi.
Claim 6
Dependent Claim
71 words
A process according to any one of claims 1 to 4, further comprising the step of replenishing the gas in said storage chamber, said step of replenishing comprising the subsidiary steps of: introducing the gas at a low pressure into a pump; increasing the pressure of the gas by utilizing said pump until the pressure equals said second pressure; and introducing the gas at said second pressure into said storage chamber.
Claim 7
Dependent Claim
22 words
A process according to claim 5 wherein the quantity of said gas that is introduced into said mold space is not measured.
Claim 8
Independent Claim
146 words
An apparatus for producing an injection molded product made of plastics material, the apparatus comprising: means (A) for introducing a molten plastics material into a mold space (11) at a first pressure; a gas supply source (41); gas pressurization means (32) for pressurizing gas to a second pressure which is at least as great as said first pressure; a storage chamber (28) for storing gas at said second pressure so that the gas is immediately available for use; means (29) for initiating gas flow from said storage chamber (28) into said mold space (11) at said second pressure immediately after the molten plastics has passed the position at which the gas is introduced; and, means for maintaining a pressure on the molten plastics material against the surfaces of said mold space as the plastics cools and until it can sustain the form dictated by the mold.
Claim 9
Independent Claim
146 words
An apparatus for producing an injection molded product made of plastics material, the apparatus comprising: means (A) for introducing a molten plastics material into a mold space (11) at a first pressure; a gas supply source (41); gas pressurization means (32) for pressurizing gas to a second pressure which is at least as great as said first pressure; a storage chamber (28) for storing gas at said second pressure so that the gas is immediately available for use; means (29) for initiating gas flow from said storage chamber (28) into said mold space (11) at said second pressure immediately after the molten plastics has passed the position at which the gas is introduced; and, means for maintaining a pressure on the molten plastics material against the surfaces of said mold space as the plastics cools and until it can sustain the form dictated by the mold.
Claim 10
Dependent Claim
34 words
Apparatus as claimed in claim 7 further comprising a means for continuously feeding gas at said second pressure into said mold space as long as said molten plastictis being fed to said mold space.
Claim 11
Dependent Claim
18 words
Apparatus according to claim 7 or 8 wherein said second pressure is approximately 4,000 psi to 15,000 psi.
Claim 12
Dependent Claim
15 words
Apparatus according to any one of claims 7 to 9, wherein the gas is nitrogen.
Claim 13
Dependent Claim
130 words
A process for producing an injection molded product, comprising: introducing a molten stream of a plastics material, at a first pressure, into a mold space; storing a quantity of gas in a storage chamber at a second pressure which is at least as high as said first pressure; introducing the gas into the molten stream of plastics material immediately after the molten material has passed the position at which the gas is introduced thereby forming a gas cavity in the molten material, wherein the gas exerts a pressure on the surrounding plastics material to urge the material toward the surfaces of the mold space; continuing to introduce both gas and molten material into said mold space; terminating the supply of gas; and immediately thereafter terminating the supply of molten material.
Claim 14
Dependent Claim
130 words
A process for producing an injection molded product, comprising: introducing a molten stream of a plastics material, at a first pressure, into a mold space; storing a quantity of gas in a storage chamber at a second pressure which is at least as high as said first pressure; introducing the gas into the molten stream of plastics material immediately after the molten material has passed the position at which the gas is introduced thereby forming a gas cavity in the molten material, wherein the gas exerts a pressure on the surrounding plastics material to urge the material toward the surfaces of the mold space; continuing to introduce both gas and molten material into said mold space; terminating the supply of gas; and immediately thereafter terminating the supply of molten material.
Claim 15
Dependent Claim
41 words
A process according to claim 11 further comprising the step of maintaining a pressure lower than said first and second pressures within said gas cavity to urge the molten plastics material against the surfaces of the mold space as the plasticscools.
Claim 16
Dependent Claim
23 words
A process according to claim 11 or 12 wherein the quantity of gas that is introduced into said mold space is not measured.
Claim 17
Dependent Claim
30 words
A process according to any one of claim 11 to 13 wherein the pressure of gas that is introduced into said mold space is substantially maintained at said second pressure.
Claim 18
Dependent Claim
35 words
A process according to any one of claims 11 to 14 wherein the pressurized gas is introduced into the molten stream of plastics material after the mold space is over half occupied with molten plastics.
Claim 19
Dependent Claim
23 words
A process according to any one of claims 11 to 15 wherein said second pressure is between approximately 4,000 psi and 15,000 psi.
Claim 20
Dependent Claim
54 words
A process according to any one of claims 11 to 16 further comprising the step of maintaining the gas in said storage chamber at said second pressure when gas at said second pressure is introduced into the molten stream of plastics material by introducing additional gas at said second pressure into the storage chamber.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.