US3670066A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of compression molding a thermoplastic article with walls of variable thickness
Assignee: Individual
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Filing: 1969-11-10
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Granted: 1972-06-13
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Expires: 1989-11-10
Abstract
Abstract A method for molding articles having variable thickness walls from thermoplastic material. An amount of plastic slightly in excess of that required to fill a mold cavity is severed from an extruded quantity and introduced into the cavity. The mold is closed to build up pressure and force the material throughout the cavity. The excess material causes a pressure build up above the necessary molding pressure and causes a plunger in an overflow well to retract under the excess pressure so as to cause the overflow well to receive the excess material. Pressure can be maintained on material in the well during cooling to maintain the cavity filled when shrinkage occurs. Where adjacent thick and thin wall portions are formed in the article, the thick wall forming portion of the cavity may contain another well which receives excess material at a pressure slightly lower than the overflow well and this excess material may then be forced back into the cavity under pressure to insure filling thereof.
Inventors
- 👤 Emery I Valyi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 12:08
CPC Classifications
B; B29; B29C; B29C43/00; B29C43/32; B29C43/34; B29C43/36; B29C43/42; B29C43/54; B29C2043/3272; B29C2043/3283; B29C2043/3433; B29C2043/3444; B29C43/361; B29C2043/3615; B29C43/58; B29C2043/5875; B29C2043/5883; B29C31/00; B29C31/04; B29C31/042; B29C31/048; B29C31/06; B29L; B29L2031/00; B29L2031/712
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
270 words
The method of making an article of thermoplastic material with walls of variable thickness including adjoining thick and thin wall portions which comprises providing a mold defining a cavity having corresponding adjoining thick and thin wall forming portions and further defining an overflow well and a chamber communicating with said cavity, said chamber communicating with said thick wall forming portions thereof, extruding thermoplastic material in flowable form, severing a quantity of the extruded plastic material such that the separated quantity of material is unequal to, and slightly in excess of the capacity of said mold cavity but less than the combined capacity of the mold cavity, overflow well, and chamber, introducing the severed quantity of the material into said mold cavity and subjecting the material in said cavity to an initial molding pressure suited to cause the material to fill said cavity, yieldably closing the entrances to said overflow well and chamber with pressures in excess of said initial mold pressure but less than the pressure exerted due to the excess of material over the capacity of said cavity, the yielding pressure of said chamber being somewhat less than that of said overflow well, whereby the excess material, after the cavity is filled, is first received beyond said cavity in said chamber and builds up pressure therein and is then received beyond said cavity in said overflow well, and, after the material has partly cooled, applying increased pressure on the material in said chamber so as to force the material back into said cavity and maintain the material in said cavity under pressure until the material has cooled and solidified.
Claim 2
Independent Claim
270 words
The method of making an article of thermoplastic material with walls of variable thickness including adjoining thick and thin wall portions which comprises providing a mold defining a cavity having corresponding adjoining thick and thin wall forming portions and further defining an overflow well and a chamber communicating with said cavity, said chamber communicating with said thick wall forming portions thereof, extruding thermoplastic material in flowable form, severing a quantity of the extruded plastic material such that the separated quantity of material is unequal to, and slightly in excess of the capacity of said mold cavity but less than the combined capacity of the mold cavity, overflow well, and chamber, introducing the severed quantity of the material into said mold cavity and subjecting the material in said cavity to an initial molding pressure suited to cause the material to fill said cavity, yieldably closing the entrances to said overflow well and chamber with pressures in excess of said initial mold pressure but less than the pressure exerted due to the excess of material over the capacity of said cavity, the yielding pressure of said chamber being somewhat less than that of said overflow well, whereby the excess material, after the cavity is filled, is first received beyond said cavity in said chamber and builds up pressure therein and is then received beyond said cavity in said overflow well, and, after the material has partly cooled, applying increased pressure on the material in said chamber so as to force the material back into said cavity and maintain the material in said cavity under pressure until the material has cooled and solidified.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-06-13 | 1975-12-13 | 1976-06-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-06-13 | 1979-12-13 | 1980-06-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-06-13 | 1983-12-13 | 1984-06-13 | $7700.00 | Window Closed / Lapsed |