Apparatus and method for controlling the amount of coatings on paper or other materials

Abstract

An apparatus and a method for controlling the thickness of coatings on webs at a plurality of cross-directional positions while a coating procedure is taking place. The deflection of the metering element is controlled automatically in response to measurements of the uncoated and coated web that determine the thickness of the coating being applied at a plurality of cross-directional positions. In one preferred embodiment, a bimetallic member having a plurality of separated tongue-like extensions corresponding to cross-directional positions along the blade is used, the tongue-like extensions pressing on the back of the blade at their ends in response to heat applied dependent upon the determined thickness of the coating being applied. In another embodiment, pneumatic actuators whose pressure may be varied in response to the determined thickness are used to adjust the position of the metering element at a plurality of cross-directional positions to locally vary the thickness of the applied coating.

I claim: 
     
       1. In a system for applying a coating material to web material, the system of the type in which web material from a continuous roll on which coating material has been placed is transported through a slot formed between a surface and a metering element, the metering element for pressing the web material on which coating material has been placed against said surface and removing excess coating material, the slot oriented in a cross-direction relative to the direction of transport of the web material and having a width at each cross-directional position that determines the .[.thickness.]. .Iadd.amount .Iaddend.of the web material and coating material at said cross-directional position that is transported through said slot, the improvement, by which a preselected .[.thickness.]. .Iadd.amount .Iaddend.of coating material is applied to the web material with the .[.thickness.]. .Iadd.amount .Iaddend.regulated at a plurality of selected cross-directional positions while web material is being transported through said slot, comprising: a metering element capable of flexion at said plurality of cross-directional positions so that the displacement of said metering element from said surface and hence the width of the slot is adjustable at least to some extent independently at each of said plurality of selected cross-directional positions.Iadd., wherein said metering element includes a bimetallic member whose displacement from the surface at any of the plurality of selected cross-directional positions is dependent upon temperature in the bimetallic member in the area of the selected cross-directional position.Iaddend.;   control means for generating, as web material is transported through said slot, a plurality of control signals corresponding to said plurality of selected cross-directional positions, each control signal having a value dependent upon the difference in .[.thickness.]. .Iadd.the amount .Iaddend.of the web material before it is transported through said slot and the coated web material after it is transported through said slot at one of the plurality of selected cross-directional positions and dependent upon the preselected .[.thickness.]. .Iadd.amount .Iaddend.of said coating material; and   adjusting means coupled to said metering element and coupled to said control means for adjusting, at least to some extent independently, as web material is transported through said slot, the flexion of the metering element and thereby the width of the slot at each of said plurality of selected cross-directional positions, said adjusting means acting in response to the corresponding control signals in order to regulate the .[.thickness.]. .Iadd.amount .Iaddend.of the coating material on the web material as it is transported through said slot .Iadd.and wherein said adjusting means includes a means for varying temperature of the bimetallic member in the areas of the selected cross-directional positions.Iaddend.. .[.2. The system of claim 1 wherein said metering element comprises a bimetallic member whose displacement from the surface at any of the plurality of selected cross-directional positions is dependent upon temperature in the bimetallic member in the area of said selected cross-directional position and wherein said adjusting means includes a means for varying temperature of the bimetallic member in the areas of the   
     
     
        selected cross-directional positions..]. 3. The system of claim .[.2.]. .Iadd.1 .Iaddend.wherein said metering element comprises a blade having an edge which forms one side of said slot and wherein said bimetallic member comprises a plurality of bimetallic tongue-like extensions corresponding to said plurality of selected cross-directional positions, the end of each tongue-like extension engaging said blade in the vicinity of one of the plurality of selected cross-directional positions, said bimetallic tongue-like extensions separated by grooves so that temperature in each bimetallic tongue-like extension can be varied within a range at least to some extent independently of temperature in other bimetallic tongue-like extensions, the end of each bimetallic tongue-like extension moving in response to temperature in said bimetallic tongue-like extension to vary the position of the blade and thereby the width of said slot in the vicinity of the corresponding selected cross-directional position, and wherein said means for varying temperature of the bimetallic member in the area of the selected cross-directional positions comprises separate means 
     
     
        for varying temperature in each bimetallic tongue-like extension. 4. The system of claim .[.2.]. .Iadd.1 .Iaddend.wherein said bimetallic member has a side proximate to said slot, along which said one of the metal layers of said bimetallic member is formed into a blade having an edge forming one side of said slot, and wherein said means for varying temperature of the bimetallic member in the areas of the selected cross-directional positions comprises separately controllable heaters corresponding to each selected cross-directional position and located to provide heat to said bimetallic member in the area of each selected 
     
     
        cross-directional position. 5. .[.The system of claim 1 wherein said metering element comprises.]. .Iadd.In a system for applying a coating material to web material, the system of the type in which web material from a continuous roll on which coating material has been placed is transported through a slot formed between a surface and a metering element, the metering element for pressing the web material on which coating material has been placed against said surface and removing excess coating material, the slot oriented in a cross-direction relative to the direction of transport of the web material and having a width at each cross-directional position that determines the amount of the web material and coating material at said cross-directional position that is transported through said slot, the improvement, by which a preselected amount of coating material is applied to the web material with the amount regulated at a plurality of selected cross-directional positions while web material is being transported through said slot, comprising.Iaddend.: a linear .Iadd.metering element .Iaddend.member having one side forming a side of said slot.Iadd., the linear member being capable of flexion at said plurality of cross-directional positions so that the displacement of the linear member from said surface and hence the width of the slot is adjustable at least to some extent independently at each of said plurality of selected cross-directional positions.Iaddend.; and   a bimetallic .Iadd.metering element .Iaddend.member corresponding to each selected cross-directional position, each bimetallic member having an end coupled to said linear member at one of the selected cross-directional positions, said end controllably displaceable to move said linear member so that said one side of said linear member is displaced at said one of the selected cross-directional positions to vary the width of the slot;   .Iadd.control means for generating, as web material is transported through said slot, a plurality of control signals corresponding to said plurality of selected cross-directional positions, each control signal having a value dependent upon the difference in the amount of the web material before it is transported through said slot and the coated web material after it is transported through said slot at one of the plurality of selected cross-directional positions and dependent upon the preselected amount of said coating material; and   adjusting means coupled to said control means for adjusting, at least to some extent independently, as web material is transported through said slot, the flexion of the linear member and thereby the width of the slot at each of said plurality of selected cross-directional positions, said adjusting means acting in response to the corresponding control signals in order to regulate the amount of the coating material on the web material as it is transported through said slot, .Iaddend..[.and.]. wherein said adjusting means includes means for controllably applying heat to each   
     
     
        bimetallic member to controllably displace said end. 6. The system of claim 5 wherein said linear member is a blade having an edge and said one 
     
     
        side of said linear member is the edge of said blade. 7. The system of 
     
     
        claim 5 wherein said linear member is a rod. 8. .[.The system of claim 1.]. .Iadd.In a system for applying a coating material to web material, the system of the type in which web material from a continuous roll on which coating material has been placed is transported through a slot formed between a surface and a metering element, the metering element for pressing the web material on which coating material has been placed against said surface and removing excess coating material, the slot oriented in a cross-direction relative to the direction of transport of the web material and having a width at each cross-directional position that determines the amount of the web material and coating material at said cross-directional position which is transported through said slot, the improvement, by which a preselected amount of coating material is applied to the web material with the amount regulated at a plurality of selected cross-directional positions while web material is being transported through said slot, comprising: a metering element capable of flexion at said plurality of cross-directional positions so that the displacement of said metering element from said surface and hence the width of the slot is adjustable at least to some extent independently at each of said plurality of selected cross-directional positions;   control means for generating, as web material is transported through said slot, a plurality of control signals corresponding to said plurality of selected cross-directional positions, each control signal having a value dependent upon the difference in amount of the web material before it is transported through said slot and the coated web material after it is transported through said slot at one of the plurality of selected cross-directional positions and dependent upon the preselected amount of said coating material; and   adjusting means coupled to said metering element and coupled to said control means for adjusting, at least to some extent independently, as web material is transported through said slot, the flexion of the metering element and thereby the width of the slot at each of said plurality of selected cross-directional positions, said adjusting means acting in response to the corresponding control signals in order to regulate the amount of the coating material on the web material as it is transported through said slot, .Iaddend.wherein said adjusting means comprises a pneumatic actuator corresponding to each selected cross-directional position, the pneumatic actuator including a member responsive to pneumatic pressure, said member coupled to said metering element at said cross-directional position to press on said metering element with a force dependent upon pneumatic pressure applied to said member and to thereby vary the width of the slot at said selected cross-directional position, the displacement of said metering element at each selected cross-directional position dependent upon the pneumatic pressure applied   
     
     
        to the corresponding member. 9. The system of claim 8 wherein each said member responsive to pneumatic pressure comprises a pneumatic chamber, at least a portion of the wall of which is elastically displaceable in 
     
     
        response to pneumatic pressure within the chamber. 10. The system of claim 
     
     
        9 wherein said chamber is formed of an elastomer material. 11. The system of claim 10 wherein a plurality of said chambers corresponding to adjacent 
     
     
        said selected cross-directional positions are integrally formed. 12. The system of claim 1 wherein said control means includes: a first web material .[.thickness.]. monitoring means for monitoring the .[.thickness.]. .Iadd.amount .Iaddend.of the web material at each selected cross-directional position before the web material is transported through said slot and generating a first signal whose value is dependent upon the monitored .[.thickness.]. .Iadd.amount.Iaddend.;   a second coated web material .[.thickness.]. monitoring means for monitoring the .[.thickness.]. .Iadd.amount .Iaddend.of the .Iadd.coated .Iaddend.web material at each selected cross-directional position after the web material is transported through said slot and generating a second signal whose value is dependent upon the monitored .[.thickness.]. .Iadd.amount.Iaddend.; and   a computer means for computing, using the values of said generated first and second signals and the value of said preselected .[.thickness.]. .Iadd.amount .Iaddend.of said coating material, the values of said control   
     
     
        signals. 13. The system of claim 12 wherein: said first web material .[.thickness.]. monitoring means includes a first basis weight gauge and a means for sequentially translating said first basis weight gauge in a cross direction proximate to said web material so that said first basis weight gauge sequentially monitors the .[.thickness.]. .Iadd.basis weight .Iaddend.of said web material at each selected cross-directional position before the web material is transported through said slot; and   said second web material .[.thickness.]. monitoring means includes a second basis weight gauge and a means for sequentially translating said second basis weight gauge in a cross direction proximate to said web material so that said second basis weight gauge sequentially monitors the .[.thickness.]. .Iadd.basis weight .Iaddend.of said coated web material at each selected cross-directional position after the web material is   
     
     
        transported through said slot. 14. A method for applying a uniform .[.thickness.]. .Iadd.amount .Iaddend.of a coating material to a web material from a continuous roll comprising .Iadd.the steps of.Iaddend.: selecting .[.a thickness.]. .Iadd.an amount .Iaddend.of the coating material to be applied to said web material at each of a plurality of selected cross-directional positions;   monitoring the .[.thickness.]. .Iadd.amount .Iaddend.of the web material at said plurality of selected cross-directional positions across said web material before coating material is placed on said web material and producing first signals representative thereof;   placing coating material on said web material;   transporting web material from said roll on which said coating material has been placed through a slot formed by a surface and a metering element to remove excess coating material placed on said web material, the separation of said metering element and said surface at each of the selected cross-direction positions determining the .[.total thickness.]. .Iadd.amount .Iaddend.of said web material and coating material passing through said slot at that selected cross-directional position.Iadd., said metering element including a bimetallic member whose temperature sensitive movement controls the width of the slot at each of the selected cross-directional positions.Iaddend.;   monitoring the .[.thickness.]. .Iadd.amount .Iaddend.of said web material and coating material at said plurality of selected cross-directional positions after said web material has been transported through said slot and producing second signals representative thereof;   comparing in a device the corresponding first and second signals to determine the .[.thickness.]. .Iadd.amount .Iaddend.of coating material applied at each selected cross-directional position and producing third signals representative thereof;   generating fourth signals representing the said selected .[.thicknesses.]. .Iadd.amounts.Iaddend.;   comparing in a device the corresponding third and fourth signals to determine the difference between the .[.thickness.]. .Iadd.amount .Iaddend.of the coating material applied at each selected cross-directional position with the .[.thickness.]. .Iadd.amount .Iaddend.of the coating selected to be applied, and producing control signals therefrom for each selected cross-directional position; and   applying said control signals to corresponding means for controlling the .[.separation.]. .Iadd.temperature .Iaddend.of said .[.metering element and said surface.]. .Iadd.bimetallic member .Iaddend.at each selected cross-directional position while web material is being transported through said slot to change the .[.thickness.]. .Iadd.amount .Iaddend.of the coating material applied in order that the coating material applied be the selected .[.thickness.]. .Iadd.amount .Iaddend.at each selected   
     
     
        cross-directional position. .Iadd.15.  A method for applying a uniform amount of a coating material to a web material from a continuous roll comprising the steps of: selecting an amount of the coating material to be applied to said web material at each of a plurality of selected cross-directional positions;   monitoring the amount of the web material at said plurality of selected cross-directional positions across said web material before coating material is placed on said web material and producing first signals representative thereof;   placing coating material on said web material;   transporting web material from said roll on which said coating material has been placed through a slot formed by a surface and a pneumatically controlled metering element to remove excess coating material placed on said web material, the separation of said metering element and said surface at each of the selected cross-directional positions determining the amount of said web material and coating material passing through said slot at that selected cross-directional position;   monitoring the amount of the web material and coating material at said plurality of selected cross-directional positions after the web material has been transported through said slot and producing second signals representative thereof;   comparing in a device the corresponding first and second signals to determine the amount of coating material applied at each selected cross-directional position and producing third signals representative thereof;   generating fourth signals representing the said selected amounts;   comparing in a device the corresponding third and fourth signals to determine the difference between the amount of the coating material applied at each selected cross-directional position with the amount of the coating selected to be applied, and producing control signals therefrom for each selected cross-directional position; and   applying said control signals to corresponding means for controlling the separation of said pneumatically controlled metering element and said surface at each selected cross-directional position while web material is being transported through said slot to change the amount of the coating material applied in order that the coating material applied be the selected amount at each selected cross-directional position. .Iaddend. .Iadd.16. A method for applying a uniform amount of a coating material to a web material from a continuous roll comprising the steps of:   selecting an amount of the coating material to be applied to said web material at each of a plurality of selected cross-directional positions;   monitoring the amount of the web material at said plurality of selected cross-directional positions across said web material before coating material is placed on said web material and producing first signals representative thereof;   placing coating material on said web material;   transporting web material from said roll on which said coating material has been placed through a slot formed by a surface and one side of a flexible coater blade to remove excess coating material placed on said web material, the separation of said one side and said surface at each of the selected cross-directional positions determining the amount of said web material and coating material passing through said slot at that selected cross-directional position;   monitoring the amount of the web material and coating material at said plurality of selected cross-directional positions after the web material has been transported through said slot and producing second signals representative thereof;   comparing in a device the corresponding first and second signals to determine the amount of coating material applied at each selected cross-directional position and producing third signals representative thereof;   generating fourth signals representing the said selected amounts;   comparing in a device the corresponding third and fourth signals to determine the difference between the amount of the coating material applied at each selected cross-directional position with the amount of the coating selected to be applied, and producing control signals therefrom for each selected cross-directional position; and   applying said control signals to corresponding means for preferentially heating the side of the blade opposite the first side so that the blade bends toward the surface at each selected cross-directional position while web material is being transported through said slot to change the amount of the coating material applied in order that the coating material applied be the selected amount at each selected cross-directional position.   
     
     
        .Iaddend. .Iadd.17.  A device for controlling the movement of a material, comprising: a flexible metering element; and   a plurality of independently controllable pneumatic actuators, each actuator engaging the metering element at a selected cross-directional position along the length of the element for at least to some extent independently controlling the movement of the element at the selected cross-directional positions, wherein each pneumatic actuator includes a member responsive to pneumatic pressure, said member engaging the metering element at the selected cross-directional position to act on the element with a force dependent upon the pneumatic pressure applied to the member. .Iaddend. .Iadd.18. The device of claim 17, wherein the metering element is a coater blade adapted to control the amount of coating material applied to a sheet, the device further comprising:   a coating sensor adapted to sense the amount of coating material adhering to a sheet at a plurality of cross-directional positions across the sheet, wherein the sensor is further adapted to generate signals having values dependent upon the sensed coating amounts; and   adjusting means, operatively coupled to the sensor and to the pneumatic actuators, for adjusting, in response to the signals and at least to some extent independently, the pneumatic pressure applied to each member. .Iaddend. .Iadd.19. The device of claim 18, wherein the sensor includes a basis weight gauge and a means for sequentially translating the basis weight gauge in a cross-direction proximate to the sheet so that the basis weight gauge sequentially monitors the amount of coating at each selected   
     
     
        cross-directional position after the sheet is coated. .Iaddend. .Iadd.20. A device for controlling the movement of a material, comprising: a blade having a first major surface and a second major opposing surface, wherein the blade is a coater blade adapted to control the amount of coating material applied to a sheet;   a plurality of individually controllable heaters disposed at intervals along the length of the blade, at least one heater disposed adjacent to the first surface for preferentially heating the first surface relative to the second surface;   a coating sensor adapted to sense the amount of coating material adhering to the sheet at a plurality of cross-directional positions across the sheet, wherein the sensor is further adapted to generate signals having values dependent upon the sensed coating amounts; and   adjusting means, operatively coupled to the coating sensor and to the heaters, for adjusting, in response to the signals and at least to some extent independently, the heat generated by each of the heaters. .Iaddend. .Iadd.21. A device for controlling the movement of a material, comprising:   a blade having a first major surface and a second major opposing surface, wherein the blade is a coater blade adapted to control the amount of coating material applied to a sheet;   a plurality of individually controllable heaters disposed at intervals along the length of the blade, at least one heater disposed adjacent to the first surface for preferentially heating the first surface relative to the second surface;   a coating sensor adapted to sense the amount of coating material adhering to the sheet at a plurality of cross-directional positions across the sheet, wherein the sensor is further adapted to generate signals having values dependent upon the sensed coating amounts;   adjusting means, operatively coupled to the coating sensor and to the heaters, for adjusting, in response to the signals and at least to some extent independently, the heat generated by each of the heaters; and   wherein the sensor includes a basis weight gauge and a means for sequentially translating the basis weight gauge in a cross-direction proximate to the sheet so that the basis weight gauge sequentially monitors the amount of coating at each cross-directional position after   
     
     
        the sheet is coated. .Iaddend. .Iadd.22.  A device for controlling the movement of a material, comprising: a bimetallic blade having first and second opposing major surfaces, wherein the side of the blade defined by the first surface is formed of one type of metal and the opposite side of the blade is formed of a different type of metal, wherein the blade is a coater blade adapted to control the amount of coating material applied to a sheet;   a plurality of individually controllable heaters disposed at intervals along the length of the blade, at least one heater disposed adjacent to the first surface for heating the blade;   a coating sensor adapted to sense the amount of coating material adhering to the sheet at a plurality of cross-directional positions across the sheet, wherein the sensor is further adapted to generate signals having values dependent upon the sensed coating amounts; and   adjusting means, operatively coupled to the coating sensor and to the heaters, for adjusting, in response to the signals and at least to some extent independently, the heat generated by each of the plurality of   
     
     
        heaters. .Iaddend. .Iadd.23.  A device for controlling the movement of a material, comprising: a bimetallic blade having first and second opposing major surfaces, wherein the side of the blade defined by the first surface is formed of one type of metal and the opposite side of the blade is formed of a different type of metal, wherein the blade is a coater blade adapted to control the amount of coating material applied to a sheet;   a plurality of individually controllable heaters disposed at intervals along the length of the blade, at least one heater disposed adjacent to the first surface for heating the blade;   a coating sensor adapted to sense the amount of coating material adhering to the sheet at a plurality of cross-directional positions across the sheet, wherein the sensor is further adapted to generate signals having values dependent upon the sensed coating amounts, wherein the sensor includes a basis weight gauge and a means for sequentially translating the basis weight gauge in a cross-direction proximate to the sheet so that the basis weight gauge sequentially monitors the amount of coating at each selected cross-directional position after the sheet is coated; and   adjusting means, operatively coupled to the coating sensor and to the heaters, for adjusting, in response to the signals and at least to some extent independently, the heat generated by each of the plurality of   
     
     
        heaters. .Iaddend. .Iadd.24.  A device for controlling the movement of a material, comprising: a coater blade adapted to control the amount of coating material applied to a sheet;   bimetallic members disposed at selected cross-directional positions along the length of the blade, each bimetallic member having an end engaging the blade at one of the selected cross-directional positions, the end being controllably displaceable to move the blade so that the blade is displaced at one of the selected cross-directional positions;   an independently controllable heater, associated with each member, for controllably applying heat to each member to displace the end;   a coating sensor adapted to sense the amount of coating material adhering to the sheet at a plurality of cross-directional positions across the sheet, wherein the sensor is further adapted to generate signals having values dependent upon the sensed coating amounts; and   adjusting means, operatively coupled to the coating sensor and to the heaters, for adjusting, in response to the signals and at least to some extent independently, the heat generated by each of the heaters. .Iaddend. .Iadd.25. A device for controlling the movement of a material, comprising:   a coater blade adapted to control the amount of coating material applied to a sheet;   bimetallic members disposed at selected cross-directional positions along the length of the blade, each bimetallic member having an end engaging the blade at one of the selected cross-directional positions, the end being controllably displaceable to move the blade so that the blade is displaced at one of the selected cross-directional positions;   an independently controllable heater, associated with each member, for controllably applying heat to each member to displace the end;   a coating sensor adapted to sense the amount of coating material adhering to the sheet at a plurality of cross-directional positions across the sheet, wherein the sensor is further adapted to generate signals having values dependent upon the sensed coating amounts, and wherein the sensor includes a basis weight gauge and a means for sequentially translating the basis weight gauge in a cross-direction proximate to the sheet so that the basis weight gauge sequentially monitors the amount of coating at each selected cross-directional position after the sheet is coated; and   adjusting means, operatively coupled to the coating sensor and to the heaters, for adjusting, in response to the signals and at least to some extent independently, the heat generated by each of the heaters. .Iaddend.