Capacitance sensor for measuring thickness of blown film including a collapsing frame and a pair of linear motor assemblies
AssigneeModern Controls, Inc.
InventorDaniel W. Mayer
Life of this patent
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Abstract
A sensor system for measuring the thickness of blown film, by mounting a linear motor system on either side of a collapsing frame to permit the linear travel of a forcer element substantially across the width of the collapsing frame. A sensor is affixed to the forcer element and is positioned in close contact with blown film surface, to provide a plurality of measurement samples of thickness during the traversal of the linear motor across the blown film surface.
Claims7
A system for measuring thickness of blown film in a blown film machine utilizing a collapsing frame having two inclined surfaces to transform a cylindrical film bubble shape to a flattened film bubble shape, comprising:
- a) a first linear motor platen affixed across one inclined surface of the collapsing frame in a direction normal to the direction of film travel, and a second linear motor platen affixed across the other inclined surface of the collapsing frame in a direction normal to the direction of film travel;
- b) a linear motor forcer element engaged to each of said first and second linear motor platens;
- c) a movable carriage coupled to each of said forcer elements, said carriages being movable substantially across the entire width of the collapsing frame inclined surface by said forcer elements;
- d) a capacitance sensor affixed to each of the movable carriages, said sensor having a measurement head for making film thickness measurement in contact with said bubble;
- and
- e) means for moving each of said linear motor forcer elements at a rate of travel of about 15 inches per second.
A system for measuring thickness of blown film in a blown film machine utilizing an A-shaped collapsing frame to transform a rotating cylindrical film bubble shape to a flattened film bubble shape, comprising:
- a) a pair of linear motor assemblies, each motor assembly affixed to a different side of the A-shaped collapsing frame, each assembly having a fixed platen element and a movable forcer element;
- b) a capacitance sensor mounted to each of said forcer elements, said capacitance sensor having a sensor head for making film thickness measurement facing toward said flattened film bubble shape;
- and
- c) means for moving said forcer elements along said fixed platen to substantially traverse each side of said collapsing frame in a time increment substantially less than the time required for a complete rotation of the cylindrical film bubble.
Dependencies are inferred from the claim text.