Process for injection molding a hollow plastic article
OwnerSiebolt Hettingainventor
Life of this patent
Estimating the term…
Abstract
A process for injection molding a hollow plastic article in which a low pressure heat-activated gas is injected in combination with a plastic material into a mold cavity of a plastic injection mold unit. When the plastic material and heat-activated gas enter the mold cavity, the gas expands to outwardly exert pressure on the plastic material thereby urging the plastic material towards the walls of the mold cavity to, in turn, form the hollow portions of the hollow plastic article. The gas remains within the hollow plastic article and continues to exert outward pressure until the plastic article has substantially cooled and hardened at which time the gas becomes dormant. Accordingly, no venting of the gas from the plastic article is necessary.
Claims27
A process of injection molding for forming a plastic article which is hollow in at least a portion thereof, said process comprising:
- A. providing a mold apparatus, including a first section and a second section opposite to an in mated alignment with said first section, said mold apparatus further having an inlet for receiving an injection material;
- B. clamping said first mold section and said second mold section together to form an injection mold cavity for said plastic article;
- C. introducing a substance into contact with a molten plastic material, said substance and said plastic material forming said injection material;
- D. injecting said injection material through said inlet and into said mold cavity, said plastic material heating said substance to its gasification temperature to form a heat-activated gas, said substance expanding in its heated gaseous form to urge said plastic material towards the walls of said mold cavity to form said hollow portion of said plastic article therein;
- E. allowing said plastic material to at least partially cool and harden with said gaseous substance remaining therein, said gaseous substance becoming dormant as said plastic material cools and hardens;
- and
- F. removing said resultant plastic article from said mold cavity.
A process of injection molding for forming a plastic article which is hollow in at least a portion thereof, said process comprising:
- A. providing a mold apparatus, including a first section and a second section opposite to and in mated alignment with said first section, said mold apparatus further having an inlet for receiving an injection material;
- B. clamping said first mold section and said second mold section together to form an injection mold cavity for said plastic article;
- C. injecting said injection material comprising a heat-activated gas in confluence with a plastic material for flowing movement together through said inlet and into said mold cavity, said heat-activated gas formed by introducing a substance with said plastic material thereby heating said substance to its gasification temperature, said heat-activated gas being compressed to a pressure below 500 p.s.i., said heat-activated gas expanding upon injection into said mold cavity thereby urging said plastic material towards the walls of said mold cavity to form said hollow portion of said plastic article therein;
- D. terminating the injection of said heat-activated gas;
- E. injecting a final portion of said plastic material through said inlet and into said mold cavity, said final portion of said plastic material thus sealing said heat-activated gas within said hollow portion of said plastic articles;
- F. allowing said plastic material to at least partially cool and harden with said heat-activated gas remaining therein, said gas becoming dormant as said plastic material cools and hardens;
- and
- G. removing said resultant plastic article from said mold cavity.
A process of injection molding for forming a plastic article which is hollow in at least a portion thereof, said process comprising:
- A. providing a mold apparatus, including a first section and a second section opposite to and in mated alignment with said first section, said mold apparatus further having an inlet for receiving an injection material;
- B. clamping said first mold section and said second mold section together to form an injection mold cavity for said plastic article;
- C. drawing a liquid from a supply reservoir;
- D. urging said liquid into means for pressurizing said liquid to a pressure below 500 p.s.i.;
- E. introducing said pressurized liquid into contact with said plastic material, said liquid introduced in substantially the same direction as the flow of said plastic material, said plastic material thereby heating said liquid to its gasification temperature to form a heat-activated gas;
- F. injecting said heat-activated gas in combination with said plastic material into said mold cavity, said heat-activated gas expanding upon injection into said mold cavity thereby urging said plastic material towards the walls of said mold cavity to form said hollow portion of said plastic article therein;
- G. terminating the introduction of heat-activated gas;
- H. injecting a final portion of said plastic material through said inlet and into said mold cavity, said final portion of said plastic material thus sealing said heat-activated gas within said hollow portion of said plastic article;
- I. removing said resultant plastic article from said mold cavity;
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- J. allowing said plastic material to cool and harden, said heat-activated gas continuing to expand and urge said plastic material towards said outer walls of said mold cavity until said gas becomes dormant upon substantial cooling and hardening of said plastic material.
Dependencies are inferred from the claim text.