Vacuum sizing apparatus with controlled vacuum
First Claim
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1. Apparatus for cooling and sizing a molten plastic extrudate comprising:
- a vacuum chamber containing water;
an entry passage into said vacuum chamber for said plastic extrudate;
an exit passage from said vacuum chamber for said plastic extrudate;
seal means sealing said entry passage and said exit passage while said plastic extrudate is passing through said passages;
a variable speed motor driven vacuum pump to reduce the atmospheric pressure within said vacuum chamber;
an adjustable vent valve to admit atmospheric pressure to said vacuum chamber in varying amounts depending upon the amount said vent valve is open;
a pressure transducer to sense the level of pressure within said vacuum chamber; and
an electrical circuit that controls the speed of said vacuum pump motor and the position of said adjustable vent valve to control the level of pressure within said vacuum chamber in response to signals from said pressure transducer.
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Abstract
A vacuum sizing apparatus with a controlled vacuum is provided. The vacuum is precisely controlled by the use of a variable speed motor driven vacuum pump and a step motor controlled vent valve. An electrical circuit containing a microprocessor coordinates the speed of the motor driven vacuum pump with the position of the vent valve to give precise vacuum control within the vacuum chambers of the sizing apparatus. A closed sump tank contains water for the water system of the apparatus and is maintained at the same vacuum level as the vacuum chambers within the sizing apparatus.
48 Citations
20 Claims
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1. Apparatus for cooling and sizing a molten plastic extrudate comprising:
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a vacuum chamber containing water; an entry passage into said vacuum chamber for said plastic extrudate; an exit passage from said vacuum chamber for said plastic extrudate; seal means sealing said entry passage and said exit passage while said plastic extrudate is passing through said passages; a variable speed motor driven vacuum pump to reduce the atmospheric pressure within said vacuum chamber; an adjustable vent valve to admit atmospheric pressure to said vacuum chamber in varying amounts depending upon the amount said vent valve is open; a pressure transducer to sense the level of pressure within said vacuum chamber; and an electrical circuit that controls the speed of said vacuum pump motor and the position of said adjustable vent valve to control the level of pressure within said vacuum chamber in response to signals from said pressure transducer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. Apparatus for cooling and sizing a molten plastic extrudate comprising:
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a vacuum chamber having a main chamber, an entry sub-chamber at the inlet end of said main chamber and a water seal chamber adjacent the exit end of said vacuum chamber, said vacuum chamber containing water; an entry passage into said entry sub-chamber for said plastic extrudate; an exit passage from said main chamber into said water seal chamber for said plastic extrudate; seal means sealing said entry passage and said exit passage while said plastic extrudate is passing through said passages; a variable speed motor driven vacuum pump to reduce the atmospheric pressure within said vacuum chamber, said variable speed motor being a pulse width modulated AC motor; an adjustable vent valve comprising a needle valve operated by an electrical step motor to admit atmospheric pressure to said vacuum chamber in varying amounts depending upon the amount that said vent valve is open; a pressure transducer to sense the level of pressure within said vacuum chamber; and an electrical circuit including a microprocessor that controls the speed of said vacuum pump motor and the position of said adjustable vent valve to control the level of pressure within said vacuum chamber in response to signals from said pressure transducer, said microprocessor coordinating the speed of said vacuum pump motor and the position of said adjustable vent valve. - View Dependent Claims (12, 13, 14, 15)
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16. Apparatus for cooling and sizing a molten plastic extrudate comprising:
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a vacuum chamber having a main chamber, an entry sub-chamber at the inlet end of said main chamber and a water seal chamber adjacent the exit end of said vacuum chamber; a water system to provide water into said vacuum chamber, said water system including a water pump, a closed sump tank, a make-up tank to provide make-up water to said closed sump tank, water lines containing control valves to convey water from said closed sump tank to said main vacuum chamber, to said entry sub-chamber and to said water seal chamber, and drain lines to return water to said closed sump tank and said make-up tank; an entry passage into said entry sub-chamber for said plastic extrudate; an exit passage from said main chamber into said water seal chamber for said plastic extrudate; seal means sealing said entry passage and said exit passage while said plastic extrudate is passing through said passages; an air drying chamber following said water seal chamber in the direction of movement of said plastic extrudate whereby said plastic extrudate is subjected to drying air after leaving said water seal chamber; a variable speed motor driven vacuum pump to reduce atmospheric pressure within said vacuum chamber, said variable speed motor being a pulse width modulated AC motor; an adjustable vent valve comprising a needle valve operated by an electrical step motor to admit atmospheric pressure to said vacuum chamber in varying amounts depending upon the amount that said vent valve is open; a pressure transducer to sense the level of pressure within said vacuum chamber; a vacuum system including said variable speed motor driven vacuum pump, said adjustable vent valve, and said pressure transducer; and an electrical circuit including a micro-processor that controls the speed of said vacuum pump motor and the position of said adjustable vent valve to control the level of pressure within said vacuum chamber in response to signals from said pressure transducer, said micro-processor coordinating the speed of said vacuum pump motor and the position of said adjustable vent valve. - View Dependent Claims (17, 18, 19, 20)
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Specification