Patent US4013745A successfully refreshed from Google Patents.
US4013745A
Expired / Lapsed
US
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Process for the extrusion of a plastic foil having small variations in thickness
Assignee: Dynamit Nobel AG
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Filing: 1975-05-20
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Granted: 1977-03-22
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Expires: 1995-05-20
Abstract
Abstract A process for extruding a film having small variations in thickness by regulating the quantities fed to a worm press and by regulating the extrusion process. Marginal strips and waste products of extruded film are re-processed by returning these materials, slicing them and directly weighing them before being fed to the filling bin of the screw press. In order to regulate the quantities fed to the screw press, the weighed material per unit of time is continually subtracted from a nominal value set by a volume regulator associated with the raw material seeder devices. The filling degree of the screw press is measured as the mass pressure between the screw press and a constant volume pump such that the filling degree is maintained constant during the extrusion process.
Inventors
- 👤 Hans Brinkmann
- 👤 Gottfried Eisele
- 👤 Helmut Gormar
- 👤 Horst Pabst
- 👤 Helmut Putz
- 👤 Hans Jurgen Schrick
- 👤 Uwe Sommermeyer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 12:20
CPC Classifications
B; B29; B29B; B29B17/00; B29B17/0005; B29B7/00; B29B7/30; B29B7/34; B29B7/38; B29B7/58; B29B7/60; B29B7/603; B29B7/72; B29B7/726; B29B7/728; B29B7/80; B29B7/88; B29B7/885; B29C; B29C31/00; B29C31/04; B29C31/06; B29C31/10; B29C48/00; B29C48/03; B29C48/07; B29C48/08; B29C48/25; B29C48/275; B29C48/277; B29C48/285; B29C48/286; B29C48/288; B29C48/2888; B29C48/36; B29C48/365; B29C48/37; B29C48/92; B29C2948/00; B29C2948/92; B29C2948/92009; B29C2948/92019; B29C2948/92085; B29C2948/92104; B29C2948/92114; B29C2948/92161; B29C2948/9218; B29C2948/92219; B29C2948/92314; B29C2948/92323; B29C2948/92333; B29C2948/92361; B29C2948/9238; B29C2948/92504; B29C2948/9258; B29C2948/926; B29C2948/92609; B29C2948/92657; B29C2948/92809; B29C2948/92819; B29C2948/92828; B29K; B29K2031/00; B29K2031/04; B29K2105/00; B29K2105/0005; B29L; B29L2031/00; B29L2031/778; B29L2031/7782; Y; Y02; Y02P; Y02P70/00; Y02P70/10; Y02W; Y02W30/00; Y02W30/50; Y02W30/62
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
167 words
A process for extruding a film from materials including virgin polymer and returned scrap, said film having small variations in thickness, comprising: feeding virgin polymer to an extruder screw inlet and measuring the feed rate thereof; moving said virgin polymer and returned scrap through an extruder screw press and then moving said materials at a constant rate from the screw press and through a pump having a constant volume output per unit of time; then extruding said materials through a sheeting die, forming film; severing margins of said film and recycling the severed margins as scrap to said screw inlet; measuring the weight per unit time of recycled material returned to said screw inlet; subtracting the measured quantity of said severed margins from a nominal feed rate for said extruder and controlling the rate at which virgin polymer is fed according to differences between the amount of scrap returned and the nominal feed rate; and maintaining the pressure constant at an inlet to said constant volume pump.
Claim 2
Dependent Claim
167 words
A process for extruding a film from materials including virgin polymer and returned scrap, said film having small variations in thickness, comprising: feeding virgin polymer to an extruder screw inlet and measuring the feed rate thereof; moving said virgin polymer and returned scrap through an extruder screw press and then moving said materials at a constant rate from the screw press and through a pump having a constant volume output per unit of time; then extruding said materials through a sheeting die, forming film; severing margins of said film and recycling the severed margins as scrap to said screw inlet; measuring the weight per unit time of recycled material returned to said screw inlet; subtracting the measured quantity of said severed margins from a nominal feed rate for said extruder and controlling the rate at which virgin polymer is fed according to differences between the amount of scrap returned and the nominal feed rate; and maintaining the pressure constant at an inlet to said constant volume pump.
Claim 3
Dependent Claim
21 words
A process according to claim 1, including weighing the amounts of said virgin polymer and scrap fed per unit of time.
Claim 4
Dependent Claim
35 words
A process according to claim 1, further including the step of delaying a measuring signal produced by measuring the severed material so as to synchronize the discharge of the returned material with the measured materials.
Claim 5
Dependent Claim
52 words
A process according to claim 3, wherein measuring of the raw materials is effected by feeders, a volume regulator within which the nominal value is set being operatively associated with the feeders, and an idle-time means operatively associated with the volume regulator for delaying the measured signal corresponding to the severed material.
Claim 6
Dependent Claim
43 words
A process according to claim 1, including controlling by an automatic controller the speed of a feeder for said virgin polymer and a feeder for plasticizer, and biasing the controller according to a function of pressure at an outlet of the extruder screw.
Claim 7
Dependent Claim
19 words
A process according to claim 5, wherein the returned materials comprise marginal strips and waste from the extruded film.
Claim 8
Dependent Claim
14 words
A process according to claim 6, wherein the materials comprise polyvinyl butyral and plasticizer.
Claim 9
Dependent Claim
50 words
A process according to claim 1, wherein the filling degree of the screw press is measured as a function of the pressure between the screw press and the constant volume pump, and further including the step of varying the nominal value within a small range to maintain the pressure constant.
Claim 10
Dependent Claim
12 words
A process according to claim 8, wherein the range is ±10 percent.
Claim 11
Dependent Claim
30 words
A process according to claim 8, wherein the varying of the nominal value is effected by means of a controller receiving the value of measured pressure at the screw outlet.
Claim 12
Dependent Claim
67 words
A process according to claim 1, wherein the total quantity of raw materials and returned materials supplied to the screw press is somewhat greater than the quantity discharged from the constant volume pump, and further including the step of ejecting the differential quantity between the total quantity and the discharged quantity from an outlet opening so as to maintain the filling degree of the screw press constant.
Claim 13
Dependent Claim
21 words
A process according to claim 11, wherein the outlet opening is located between the screw press and the constant volume pump.
Claim 14
Dependent Claim
21 words
A process according to claim 11, further including the step of measuring the pressure in the vicinity of the outlet opening.
Claim 15
Dependent Claim
33 words
A process according to claim 13, wherein the outlet opening is provided with a regulating valve for maintaining the pressure constant and the pressure is measured by means of a pressure sensing element.
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) | 1980-03-21 | 1980-09-20 | 1981-03-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-03-21 | 1984-09-20 | 1985-03-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-03-21 | 1988-09-20 | 1989-03-22 | $7700.00 | Window Closed / Lapsed |