US3797808A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Plastication control system for injection molding machines
Assignee: Milacron Inc
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Filing: 1972-11-17
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Granted: 1974-03-19
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Expires: 1992-11-17
Abstract
Abstract A plastication control system for controlling the shot size and plastication time of an injection molding machine. The control system includes a computer which calculates the screw speed based on the operating conditions of the immediately preceding cycle in order to control the plastication time to a predetermined value. Additionally, the system controls the back pressure applied to the rotating screw in order to maintain the melt temperature of the plastic at the forward end of the barrel at a predetermined value.
Inventors
- 👤 C Ma
- 👤 J Peter
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 17:25
CPC Classifications
B; B29; B29C; B29C45/00; B29C45/17; B29C45/46; B29C45/461; B29C45/76
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
122 words
A method of controlling the operation of an injection molding machine which includes a plastication system comprising a plastication screw rotatably and translatably positioned within a barrel, said method comprising: a. rotating said screw at a constant speed until the desired volume of plasticated material has been processed; b. measuring the plastication time within which said screw has been rotated to provide said desired volume of plasticated material; c. comparing the measured plastication time with a desired plastication time and generating a time correction signal proportional to the difference therebetween; d. computing a new screw rotational speed for the next succeeding operating cycle based on said time correction signal to provide the desired volume of plasticated material within the desired plastication time.
Claim 2
Independent Claim
122 words
A method of controlling the operation of an injection molding machine which includes a plastication system comprising a plastication screw rotatably and translatably positioned within a barrel, said method comprising: a. rotating said screw at a constant speed until the desired volume of plasticated material has been processed; b. measuring the plastication time within which said screw has been rotated to provide said desired volume of plasticated material; c. comparing the measured plastication time with a desired plastication time and generating a time correction signal proportional to the difference therebetween; d. computing a new screw rotational speed for the next succeeding operating cycle based on said time correction signal to provide the desired volume of plasticated material within the desired plastication time.
Claim 3
Dependent Claim
30 words
The method of claim 1 including the additional step of applying a back pressure to said rotating screw to maintain the temperature of said plasticated material at a predetermined level.
Claim 4
Dependent Claim
74 words
The method of claim 1 wherein said speed computation is based on the following formula: N A Xs/tp ( B + Pb ) where N is the screw rotational speed in rpm Xs is the desired shot size in inches of screw retraction tp is the calculated trial plastication time in seconds Pb is the back pressure on the screw in psi and A and B are constants for a given screw and material.
References Cited (Backward Citations)
US3693946A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-03-18 | 1977-09-17 | 1978-03-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-03-18 | 1981-09-17 | 1982-03-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-03-18 | 1985-09-17 | 1986-03-19 | $7700.00 | Window Closed / Lapsed |