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Patent US3741700A successfully refreshed from Google Patents.
US3741700A
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US
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Time monitored injection molding cycle with timed pressure control
Assignee: Pennwalt Corp
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Filing: 1971-03-01
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Granted: 1973-06-26
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Expires: 1991-03-01
Abstract
Abstract Injection molding process control in which the viscosity index of a shot being injected is measured by timing the advancement of the ram, preferably at constant hydraulic pressure, from the moment of opening of the relief valve to a predetermined ram position before the molds are filled. Variations from a normal interval empirically determined to produce good parts are compensated in the same shot being injected by automatically increasing or decreasing the length of time of imposition of primary high pressure through an electronic clock and then reducing the pressure level for the duration of the injection stroke.
Inventors
- 👤 H Hutchinson
- 👤 V Arpajian
- 👤 R Malcomson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 08:18
CPC Classifications
B; B29; B29C; B29C45/00; B29C45/17; B29C45/76; B29C45/768; B29C45/7646
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
213 words
Automatic control apparatus for an injection molding machine having a reciprocable ram for injecting plasticized material from an extrusion cylinder into a mold comprising: means for advancing the ram under hydraulic pressure to inject a prepared shot of plasticized material into the mold, including a hydraulic system, means for applying a hydraulic pressure upon the ram during the initial portion of the injection stroke until the pressure reaches a predetermined value, including means to maintain a constant primary pressure level at said predetermined value, means for changing the hydraulic pressure to a secondary pressure level during the terminal portion of the stroke, and a timer for actuating the means for changing the hydraulic pressure to the secondary level after lapse of a selected time period, sensing means for time monitoring a predetermined portion of the ram injection stroke prior to complete filling of the mold, including comparator means for measuring the degree of variation when the monitored interval falls outside predetermined limits determined to produce satisfactory molded parts, and, compensation means responsive to said comparator means automatically varying the time period of said timer to modify the duration of the primary pressure level in the same shot being injected corresponding to the degree of variation from the prescribed limits during the monitored interval.
Claim 2
Dependent Claim
213 words
Automatic control apparatus for an injection molding machine having a reciprocable ram for injecting plasticized material from an extrusion cylinder into a mold comprising: means for advancing the ram under hydraulic pressure to inject a prepared shot of plasticized material into the mold, including a hydraulic system, means for applying a hydraulic pressure upon the ram during the initial portion of the injection stroke until the pressure reaches a predetermined value, including means to maintain a constant primary pressure level at said predetermined value, means for changing the hydraulic pressure to a secondary pressure level during the terminal portion of the stroke, and a timer for actuating the means for changing the hydraulic pressure to the secondary level after lapse of a selected time period, sensing means for time monitoring a predetermined portion of the ram injection stroke prior to complete filling of the mold, including comparator means for measuring the degree of variation when the monitored interval falls outside predetermined limits determined to produce satisfactory molded parts, and, compensation means responsive to said comparator means automatically varying the time period of said timer to modify the duration of the primary pressure level in the same shot being injected corresponding to the degree of variation from the prescribed limits during the monitored interval.
Claim 3
Dependent Claim
40 words
The automatic control apparatus of claim 1 wherein said primary pressure is at a higher level than said secondary pressure level, and said means for changing constitutes a means for reducing the hydraulic pressure to the lower secondary pressure level.
Claim 4
Dependent Claim
70 words
The automatic control apparatus of claim 1 including pressure relief means in the hydrauLic system actuated at a predetermined pressure level during ram advancement and operative when actuated to maintain said means for applying hydraulic pressure at a substantially constant level, and said sensing means monitors the time interval between the actuation of said pressure relief means and a predetermined position of the ram prior to filling of the mold.
Claim 5
Dependent Claim
48 words
The automatic control apparatus of claim 3 wherein the position of the ram at actuation of the pressure relief means is determined by the tripping of a pressure switch and the position of the ram at the end of the monitored interval is determined by a limit switch.
Claim 6
Dependent Claim
91 words
The automatic control apparatus of claim 3 wherein said comparator means includes a plurality of step counting means for determining in increments the relative degree to which the apparent viscosity of the shot being injected is respectively less and greater than the prescribed limits when the measured interval is correspondingly less and greater than a selected band, and said compensating means includes a step correction means actuated by a corresponding one of said step counting means for respectively subtracting and adding corresponding decrements and increments of time to said timing means.
Claim 7
Dependent Claim
19 words
The automatic control apparatus of claim 5 wherein said timer constitutes an electronic resistance - capacitance time delay circuit.
Claim 8
Dependent Claim
20 words
The automatic control apparatus of claim 5 wherein said step counting means are adjustable for varying sensitivity of measured interval.
Claim 9
Dependent Claim
34 words
The automatic control apparatus of claim 5 wherein said step counting means includes means for signaling an alarm when the viscosity of the shot being injected is beyond the capability of the compensating means.
Claim 10
Dependent Claim
41 words
The automatic control apparatus of claim 5 wherein said step correction means are each adjustable for varying the incremental degree of correction in time which is applied to said timing means as a result of actuation of any step counting means.
Claim 11
Dependent Claim
20 words
The automatic control apparatus of claim 4 wherein said timer begins to time at the start of the injection stroke.
Claim 12
Dependent Claim
20 words
The automatic control apparatus of claim 4 wherein said timer begins to time at the end of the monitored interval.
References Cited (Backward Citations)
US3330003A
Cited
US3628901A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-06-25 | 1976-12-25 | 1977-06-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-06-25 | 1980-12-25 | 1981-06-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-06-25 | 1984-12-25 | 1985-06-26 | $7700.00 | Window Closed / Lapsed |