US3889849A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Shot volume and cushion point control for injection molding apparatus
Assignee: General Electric Co
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Filing: 1973-12-26
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Granted: 1975-06-17
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Expires: 1993-12-26
Abstract
Abstract A simplified process controller for effecting the continued operation of an injection molding machine in a predetermined mode. A timer is started when the injection ram begins an injection stroke. When a first predetermined time has elapsed, it is assumed that the initial cushion point has been reached and the ram injection pressure is reduced to a holding value. At a subsequent time a comparison is made between a signal representing an actual final ram cushion point position, and another signal representing the desired position. An error signal is then generated and utilized to change the screwback and pullback positions of the ram. Simultaneous modification of the screwback and pullback points maintains a constant shot volume for each injection stroke. In another embodiment the transition from injection to holding pressure is accomplished as a function of ram position rather than time. The error signal is then also utilized to control the point at which the pressure change occurs.
Inventors
- 👤 Jr Robert F Chandler
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 05:00
CPC Classifications
B; B29; B29C; B29C45/00; B29C45/17; B29C45/76
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
137 words
A control system for an injection molding machine including a ram and having drive means for rotating, and hydraulic means for advancing and withdrawing said ram, said control system comprising: position sensing means for producing a position signal indicative of ram position; reference means for producing a first position reference signal; circuit means connected to receive said position signal and said reference signal for producing an error signal representing the difference therebetween; first control means for causing pressure applied by said hydraulic means upon said ram to decline from a first, higher value to a second, lower value; second control means responsive to said error signal for establishing a point for termination of operation of said drive means; and third control means responsive to said error signal for establishing a point of maximum withdrawal of said ram.
Claim 2
Dependent Claim
137 words
A control system for an injection molding machine including a ram and having drive means for rotating, and hydraulic means for advancing and withdrawing said ram, said control system comprising: position sensing means for producing a position signal indicative of ram position; reference means for producing a first position reference signal; circuit means connected to receive said position signal and said reference signal for producing an error signal representing the difference therebetween; first control means for causing pressure applied by said hydraulic means upon said ram to decline from a first, higher value to a second, lower value; second control means responsive to said error signal for establishing a point for termination of operation of said drive means; and third control means responsive to said error signal for establishing a point of maximum withdrawal of said ram.
Claim 3
Dependent Claim
30 words
The invention defined in claim 1, wherein said first control means comprises a timer for effecting a decline in said applied pressure a predetermined time after initiation of ram advancement.
Claim 4
Dependent Claim
56 words
The invention defined in claim 2, wherein said second control means comprises a comparison circuit coupled to said circuit means and to said position sensing means and operative to terminate the screwback operation in response to the achievement by said ram position signal of a predetermined relationship with a second reference signal comprising said error signal.
Claim 5
Dependent Claim
58 words
The invention defined in claim 3, wherein said third control means comprises a comparison circuit coupled to said circuit means and to said position sensing means and operative to terminate the pullback of said ram in response to the achievement by said ram position signal of a predetermined relationship with a third reference signal comprising said error signal.
Claim 6
Dependent Claim
69 words
The invention defined in claim 1, wherein said first control means comprises a comparison circuit coupled to said circuit means and to said position sensing means and operative to reduce said hydraulic pressure upon said ram from a first, higher value to a second, lower value in response to the achievement by said ram position signal of a predetermined relationship with a third reference signal comprising said error signal.
Claim 7
Dependent Claim
56 words
The invention defined in claim 5, wherein said second control means comprises a comparison circuit coupled to said circuit means and to said position sensing means and operative to terminate the screwback operation in response to the achievement by said ram position signal of a predetermined relationship with a second reference signal comprising said error signal.
Claim 8
Dependent Claim
42 words
The invention defined in claim 6, wherein said third control means comprises a comparison circuit operative to terminate the pullback of said ram in response to the achievement by said ram position signal of a predetermined relationship with a third referenced signal.
Claim 9
Dependent Claim
189 words
A control system for controlling the operation of an injection molding machine including a ram and having drive means for rotating, and hydraulic means for advancing and withdrawing said ram comprising; position sensing means for producing a signal indicative of ram position; reference means for producing a first reference signal representative of a desired final ram position; comparison means coupled to said position sensing means and said reference means for producing a ram position error signal; an integrate-and-hold circuit coupled to said comparison means for periodically receiving a signal representative of ram position error and outputting a signal representative of accrued position error; first timer means for periodically energizing said integrate-and-hold circuit; first control means for causing pressure exerted by said ram to decline from a first, higher value to a second, lower value; second control means coupled to said integrate-and-hold circuit for terminating the operation of said drive means in response to a signal outputted by said integrate-and-hOld circuit; and third control means coupled to said integrate-and-hold circuit for establishing a point of maximum withdrawal of said ram in response to a signal outputted by said integrate-and-hold circuit.
Claim 10
Dependent Claim
189 words
A control system for controlling the operation of an injection molding machine including a ram and having drive means for rotating, and hydraulic means for advancing and withdrawing said ram comprising; position sensing means for producing a signal indicative of ram position; reference means for producing a first reference signal representative of a desired final ram position; comparison means coupled to said position sensing means and said reference means for producing a ram position error signal; an integrate-and-hold circuit coupled to said comparison means for periodically receiving a signal representative of ram position error and outputting a signal representative of accrued position error; first timer means for periodically energizing said integrate-and-hold circuit; first control means for causing pressure exerted by said ram to decline from a first, higher value to a second, lower value; second control means coupled to said integrate-and-hold circuit for terminating the operation of said drive means in response to a signal outputted by said integrate-and-hOld circuit; and third control means coupled to said integrate-and-hold circuit for establishing a point of maximum withdrawal of said ram in response to a signal outputted by said integrate-and-hold circuit.
Claim 11
Dependent Claim
16 words
The invention defined in claim 8, wherein said final ram position comprises a final cushion point.
Claim 12
Dependent Claim
31 words
The invention defined in claim 9, wherein said first control means comprises second timer means for effecting a decline in said applied pressure a predetermined time after initiation of ram advancement.
Claim 13
Dependent Claim
43 words
The invention defined in claim 9, wherein said first control means comprises a comparison circuit coupled to said integrate-and-hold circuit for establishing a point at which pressure exerted by said ram is reduced from a first, higher value to a second, lower value.
Claim 14
Dependent Claim
41 words
The invention defined in claim 11, wherein said first, second, and third control means comprise comparison circuits, each of said comparison circuits having a first input coupled to said position sensing means and a second input coupled to said integrate-and-hold circuit.
Claim 15
Dependent Claim
44 words
The invention defined in claim 12, further including first, second, and third summing means coupled to the second inputs of said first, second and third control means respectively for combining the signal outputted by said integrate-and-hold circuit and first, second, and third reference signals.
References Cited (Backward Citations)
US3436443A
Cited
US3632246A
Cited
US3647309A
Cited
US3666141A
Cited
US3797808A
Cited
US3693946A
Cited
US3728058A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-06-16 | 1978-12-16 | 1979-06-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-06-16 | 1982-12-16 | 1983-06-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-06-16 | 1986-12-16 | 1987-06-17 | $7700.00 | Window Closed / Lapsed |