US3695800A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Time monitored injection molding control apparatus
Assignee: Pennwalt Corp
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Filing: 1970-07-30
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Granted: 1972-10-03
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Expires: 1990-07-30
Abstract
Abstract Process control for injection molding machines in which the viscosity of the plasticized material in a shot being prepared is monitored as a function of ram injection speed (rate of melt flow) at constant hydraulic pressure. The interval is measured during ram advancement between the time at which a pressure relief valve opens and the time that the mold cavities are substantially filled (when ram is at end of stroke). If the time period exceeds or falls below predetermined limits, either (1) the heat input to subsequent shots being prepared may be respectively raised or lowered in increments, (2) high pressure injection time may be respectively added or subtracted in increments to increase or decrease the point in time at which lower secondary hydraulic pressure is applied, or (3) injection pressure may be respectively raised or lowered.
Inventors
- 👤 Herman R Hutchinson
- 👤 Vasken F Arpajian
- 👤 Robert S Malcomson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 13:54
CPC Classifications
B; B29; B29C; B29C45/00; B29C45/17; B29C45/76; B29C45/7646
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
222 words
An automatic control system for injection molding machines having a reciprocable ram for injecting plasticized material from an extrusion barrel into a mold comprising: hydraulic means for advancing the ram by build up of hydraulic pressure and injecting a shot into the mold, pressure sensing means associated with said hydraulic means actuated at a predetermined pressure level during advancement of said ram and operative thereafter to maintain substantially constant pressure upon the shot being injected into the mold such that the rate of flow of the material is proportional to apparent melt viscosity, first triggering means responsive to the actuation of said pressure sensing means and signalling a point in time at the start of the constant pressure portion of the stroke, second triggering means responsive to ram position when the mold is substantially filled and signalling a point in time before the end of the constant pressure portion of the stroke, monitoring means for measuring as a function of apparent melt viscosity the elapsed interval of time signalled by the respective actuation of said first and second triggering means, and control means responsive to said monitoring means and, when the elapsed time interval measured by said monitoring means varies from predetermined band limits set for producing satisfactory molded parts, providing compensation for such variations in melt viscosity in subsequent injection shots.
Claim 2
Dependent Claim
222 words
An automatic control system for injection molding machines having a reciprocable ram for injecting plasticized material from an extrusion barrel into a mold comprising: hydraulic means for advancing the ram by build up of hydraulic pressure and injecting a shot into the mold, pressure sensing means associated with said hydraulic means actuated at a predetermined pressure level during advancement of said ram and operative thereafter to maintain substantially constant pressure upon the shot being injected into the mold such that the rate of flow of the material is proportional to apparent melt viscosity, first triggering means responsive to the actuation of said pressure sensing means and signalling a point in time at the start of the constant pressure portion of the stroke, second triggering means responsive to ram position when the mold is substantially filled and signalling a point in time before the end of the constant pressure portion of the stroke, monitoring means for measuring as a function of apparent melt viscosity the elapsed interval of time signalled by the respective actuation of said first and second triggering means, and control means responsive to said monitoring means and, when the elapsed time interval measured by said monitoring means varies from predetermined band limits set for producing satisfactory molded parts, providing compensation for such variations in melt viscosity in subsequent injection shots.
Claim 3
Dependent Claim
41 words
The automatic control system of claim 1 wherein said control means respectively raises and lowers heat input to subsequent shots being prepared in response to greater and lower elapsed time intervals from the predetermined band limit measured by said monitoring means.
Claim 4
Dependent Claim
24 words
The automatic control system of claim 2 wherein the raising and lowering heat input to subsequent shots comprises respectively elevating and decreasing barrel temperature.
Claim 5
Dependent Claim
22 words
The automatic control system of claim 3 wherein the respective elevation and decreasing of barrel temperature is in predetermined increments and decrements.
Claim 6
Dependent Claim
33 words
The automatic control system of claim 2 wherein the raising and lowering of heat input to subsequent shots is effected by respectively increasing and decreasing the rate of screw rotation during shot preparation.
Claim 7
Dependent Claim
36 words
The automatic control system of claim 2 wherein the raising and lowering of heat input to subsequent shots is effected by respectively increasing the decreasing the degree of back pressure exerted on the shot being prepared.
Claim 8
Dependent Claim
38 words
The automatic control system of claim 1 wherein said control means respectively increases and decreases the total injection time in response to greater and lower elapsed time intervals from the predetermined band limit measured by said monitoring means.
Claim 9
Dependent Claim
89 words
The automatic control system of claim 1 including pressure reducing means operative upon being actuated for reducing the pressure on said hydraulic means from a predetermined primary level to a lower secondary level and timing means for actuating said pressure reducing means upon lapse of a selected time period after application of hydraulic pressure upon said ram wherein said control means respectively increases and decreases primary injection time in response to corresponding greater and lower elapsed and time intervals from the predetermined band limit measured by said monitoring means.
Claim 10
Dependent Claim
38 words
The automatic control system of claim 1 wherein said control means respectively increases and decreases primary injection pressure in response to corresponding greater and lower elapsed time intervals from the predetermined band limit measured by said monitoring means.
Claim 11
Dependent Claim
169 words
An automatic control system for injection molding machines having a reciprocable ram for injecting plasticized material from an extrusion barrel into a mold comprising: hydraulic means for advancing the ram and applying injection pressure upon the plasticized material in a shot from a starting position to the end of the injection stroke, means constituting a pressure relief valve associated with said hydraulic means actuated at a predetermined pressure level during advancement of said ram and operative thereafter to maintain substantially constant pressure upon the material being injected into the mold whereby the rate of flow of material at constant pressure is proportional to melt viscosity, monitoring means for measuring as a function of apparent melt viscosity the elapsed interval from the time of actuation of said pressure relief valve to a point in time when the mold is substantially filled, and control means responsive to and actuated by said monitoring means compensating in subsequent shots for variations in melt viscosity from prescribed band limits set for producing satisfactory parts.
Claim 12
Dependent Claim
169 words
An automatic control system for injection molding machines having a reciprocable ram for injecting plasticized material from an extrusion barrel into a mold comprising: hydraulic means for advancing the ram and applying injection pressure upon the plasticized material in a shot from a starting position to the end of the injection stroke, means constituting a pressure relief valve associated with said hydraulic means actuated at a predetermined pressure level during advancement of said ram and operative thereafter to maintain substantially constant pressure upon the material being injected into the mold whereby the rate of flow of material at constant pressure is proportional to melt viscosity, monitoring means for measuring as a function of apparent melt viscosity the elapsed interval from the time of actuation of said pressure relief valve to a point in time when the mold is substantially filled, and control means responsive to and actuated by said monitoring means compensating in subsequent shots for variations in melt viscosity from prescribed band limits set for producing satisfactory parts.
Claim 13
Dependent Claim
60 words
The invention of claim 10 wherein said control means raises heat input to the subsequent shots being prepared in the barrel in response to greater elapsed time intervals than the set prescribed band limits and lowers heat input to the subsequent shots being prepared in the barrel in response to lesser elapsed time intervals than the set prescribed band limits.
Claim 14
Dependent Claim
22 words
The invention of claim 11 wherein the respective raising and lowering of heat input is produced by raising and lowering barrel temperature.
Claim 15
Dependent Claim
25 words
The invention of claim 11 wherein the respective raising and lowering of heat input is produced by increasing and decreasing the speed of screw rotation.
Claim 16
Dependent Claim
23 words
The invention of claim 11 wherein the respective raising and lowering of heat input is produced by raising and lowering screw back pressure.
Claim 17
Dependent Claim
36 words
The invention of claim 19 wherein said control means respectively increases and decreases the total injection time in response to greater and lower elapsed time intervals from the predetermined band limit measured by said monitoring means.
Claim 18
Dependent Claim
90 words
The invention of claim 10 including pressure reducing means operative upon being actuated for reducing the pressure on said hydraulic means from a primary level to a lower secondary level, timing means for actuating said pressure reducing means upon lapse of a selected time period after ram hydraulic pressure has been instituted, and means actuated by said control means for respectively adding and removing predetermined incrementS of time to said timing means in response to greater and lower elapsed time intervals from the band limits set by said monitoring means.
Claim 19
Dependent Claim
34 words
The invention of claim 10 wherein said control means respectively increases and decreases primary injection pressure in response to greater and lower elapsed time intervals from the band limits set by said monitoring means.
References Cited (Backward Citations)
US3330003A
Cited
US3354501A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-10-03 | 1976-04-03 | 1976-10-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-10-03 | 1980-04-03 | 1980-10-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-10-03 | 1984-04-03 | 1984-10-03 | $7700.00 | Window Closed / Lapsed |