Method and apparatus for controlling the thickness of a lamina of a coextruded laminate

Claim 2

Apparatus for controlling the average thickness (T 1 ) of a film lamina of thermoplastic material having a known density (D 1 ) and coextruded at a variable extrusion rate with a foam lamina of similar thermoplastic material having a thickness (T 2 ) and a density (D 2 ) to form a thermoplastic laminate comprising: a first gauge for sensing the thickness of the laminate which is equal to (T 1 +T 2 ) and for providing a caliper signal (C) corresponding to the thickness sensed; a second gauge for sensing the mass/unit-area of the laminate which is equal to (T 1 )(D 1 )+(T 2 )(D 2 ) and for providing a mass signal (M) corresponding to the mass/unit-area sensed; a third gauge for sensing a response to said thermoplastic material and its distribution in the laminate and for providing a dielectric signal (W) corresponding to the response which is equal to [(a)(T 1 )/(b+T 1 )][K-(D 2 /D 1 )] where (K) is a ratio of the dielectric effect of the solid material in each lamina and (a) and (b) are coefficients approximated to best fit empirical data measured by said gauge, said gauge being positioned adjacent the film lamina and the sensitivity of said gauge decreasing with the distance therefrom; a computer having a memory containing the value of the density (D 1 ) of the film lamina, the value of the ratio (K) and the values of the coefficients (a) and (b), said computer being connected to said first, second, and third gauges and being responsive to successive sets of signals comprising the caliper signal (C), the mass signal (M) and the dielectric signal (W) for calculating the thickness (T 1 ) of the film lamina according to the formula: ##EQU6## combined from the equalities associated with each signal received, and then for comparing an average thickness (T 1 ) of the calculated thicknesses (T 1 ) to a desired thickness (T 0 ) and providing a first control signal (DEC) when the average thickness (T 1 ) is greater than the desired thickness (T 0 ) and a second control signal (INC) when the average thickness (T 1 ) is less than the desired thickness (T 0 ); and means connected to said computer and responsive to the first control signal (DEC) for decreasing the extrusion rate of the film lamina and responsive to the second control signal (INC) for increasing the extrusion rate of the film lamina.

Claim 3

Apparatus as recited in claim 1 wherein said third gauge comprises an electrically conductive plate having a surface contiguous with the film lamina, said conductive plate having a longitudinal slot extending therethrough, an electrically conductive bar positioned within said slot of said conductive plate but physically spaced from both the conductive plate and the film lamina, and means electrically connected to said plate and said bar for providing the dielectric signal (W).

Claim 4

Apparatus as recited in claim 1 wherein said caliper signal (C), mass signal (M) and dielectric signal (W) are analog and said apparatus further comprises an analog multiplexer connected to said first, second and third gauges for receiving the signals provided therefrom and an analog-to-digital converter connected between said multiplexer and said computer whereby the analog signals (C), (M) and (W) are sequentially presented to said computer in parallel binary form.

Claim 5

Apparatus as recited in claim 1 further comprising a carriage on which said gauges are mounted to scan the laminate while traversing the width thereof, and wherein said multiplexer during the scan provides said converter with successive sets of sequential signals from said gauges, and said computer calculates the thickness (T 1 ) of the film lamina for sets (L) of signals comprising a segment of the scan and then computes the average thickness (T 1 ) for a predetermined number (N) of segments of the scan.

Claim 6

Apparatus as recited in claim 1 further comprising means for displaying the calculated thickness (T 1 ) for each segment of said scan.

Claim 9

The method as recited in claim 6 wherein the step for sensing a response to the dielectric material is accomplished adjacent the film lamina with a decreasing sensitivity for increasing distance.

Claim 10

The method as recited in claim 6 or 7 wherein the step for sensing a response to said thermoplastic material includes the steps of positioning the surface of an electrically conductive plate having a longitudinal slot extending therethrough contiguous with the film lamina, positioning an electrically conductive bar within said slot of said conductive plate but physically spaced from both the conductive plate and the film lamina, and electrically connecting the plate and the bar to the computer for providing the dielectric signal (W) thereto.

Claim 11

The method as recited in claim 6 or 7 wherein said caliper signal (C), said mass signal (M) and said dielectric signal (W) are analog and said method further comprises the steps of multiplexing the sensed analog signals (C), (M) and (W) and converting the sequential signals received therefrom to binary signals in parallel form for presentation to the computer.

Claim 12

The method as recited in claim 9 further comprising the steps of scanning the width of the laminate while being extruded, multiplexing successive sets of sensed sequential signals, and enabling the computer upon receipt of the binary signals to calculate the thickness (T 1 ) of the film lamina for sets (L) of signals comprising a segment of the scan and then compute the average thickness (T 1 ) for a predetermined number (N) of segments of the scan.

Claim 13

The method as recited in claim 10 further comprising the step of displaying the calculated thickness (T 1 ) for each segment of said scan.

Claim 14

In a system for controlling the average thickness (T 1 ) of a film lamina of a thermoplastic material having a known density (D 1 ) and coextruded at a variable extrusion rate with a foam lamina of similar thermoplastic material having a thickness (T 2 ) and a density (D 2 ) to form a thermoplastic laminate having a thickness (T 1 +T 2 ) providing a caliper signal (C), apparatus comprising: means for sensing a response to said thermoplastic material and its distribution in the laminate, said sensing means being positioned adjacent the film lamina with a decreasing sensitivity for increasing distance therefrom and an electrically conductive plate having a surface contiguous with the film lamina and a longitudinal slot extending therethrough, an electrically conductive bar positioned within the slot of said plate adjacent but physically spaced from both the conductive plate and the film lamina; and means electrically connecting said plate and said bar for providing a dielectric signal (W).

Claim 15

In a system for controlling the average thickness (T 1 ) of a film lamina of a thermoplastic material having a known density (D 1 ) and coextruded at a variable extrusion rate with a foam lamina of similar thermoplastic material having a thickness (T 2 ) and a density (D 2 ) to form a thermoplastic laminate having a thickness (T 1 +T 2 ) providing a caliper signal (C), apparatus comprising: means for sensing a response to said thermoplastic material and its distribution in the laminate, said sensing means being positioned adjacent the film lamina with a decreasing sensitivity for increasing distance therefrom and an electrically conductive plate having a surface contiguous with the film lamina and a longitudinal slot extending therethrough, an electrically conductive bar positioned within the slot of said plate adjacent but physically spaced from both the conductive plate and the film lamina; and means electrically connecting said plate and said bar for providing a dielectric signal (W).

Claim 16

Apparatus as recited in claim 12, wherein said sensing means provides a dielectric signal equal to (K)[f(T 1 )]+(D 2 /D 1 )[f(C)-f(T 1 )] where (K) is a ratio of the dielectric effect of the solid material in each lamina and both f(C) and f(T 1 ) are functions derived to approximate empirical data measured by said sensing means.

Claim 17

Apparatus as recited in claim 13 wherein said function f(T 1 ) is equal to aT 1 /(b+T 1 ) and said function f(C) is equal to aC/(b+C) where (a) and (b) are approximated to best fit empirical data measured by said third gauge.

Claim 18

Apparatus as recited in claim 13 wherein said function f(T 1 ) is equal to m(1-e -T .sbsp.1 /n ) and said function f(C) is equal to m(1-e -C/n ) where (m) and (n) are approximated to best fit empirical data measured by said third gauge.

Claim 19

Apparatus as recited in claim 13 wherein said function [f(C)-f(T 1 )]/D 1 is equal to a constant (Q) approximated to best fit empirical data measured by said third gauge.

Claim 20

Apparatus for controlling the average thickness (T 1 ) of a film lamina of thermoplastic material having a known density (D 1 ) and coextruded at a variable extrusion rate with a foam lamina of similar thermoplastic material having a thickness (T 2 ) and a density (D 2 ) to form a thermoplastic laminate, comprising: a first gauge for sensing the thickness of the laminate which is equal to (T 1 +T 2 ) and for providing a caliper signal (C) corresponding to the thickness sensed; a second gauge for sensing the mass/unit-area of the laminate which is equal to [(T 1 )(D 1 )+(T 2 )(D 2 )] and for providing a mass signal (M) corresponding to the mass/unit-area sensed; a third gauge for sensing a response to said thermoplastic material and its distribution in the laminate and for providing a dielectric signal (W) corresponding to the response which is equal to (K)[f(T 1 )]+(D 2 /D 1 )[f(C)-f(T 1 )] where (K) is a ratio of the dielectric effect of the solid material in each lamina, said function f(T 1 ) is equal to aT 1 /(b+T 1 ) and said function f(C) is equal to aC/(b+C) where (a) and (b) are approximated to best fit empirical data measured by said third gauge; said third gauge being positioned adjacent the film lamina and the sensitivity of said gauge decreasing with the distance therefrom; a computer having a memory containing the value of the density (D 1 ) of the film lamina, the value of the ratio (K) and the values associated with each of the functions f(C) and f(T 1 ), said computer being connected to said first, second, and third gauges and being responsive to successive sets of signals comprising the caliper signal (C), the mass signal (M) and the dielectric signal (W) for calculating the thickness (T 1 ) of the film lamina according to the formula: ##EQU8## combined from the equalitites associated with each signal received, and then for comparing an average thickness (T 1 ) of the calculated thicknesses (T 1 ) to a desired thickness (T 0 ) and providing a first control signal (DEC) when the average thickness (T 1 ) is less than the desired thickness (T 0 ); and means connected to said computer and responsive to the first control signal (DEC) for decreasing the extrusion rate of the film lamina and responsive to the second control signal (INC) for increasing the extrusion rate of the film lamina.

Claim 21

Apparatus for controlling the average thickness (T 1 ) of a film lamina of thermoplastic material having a known density (D 1 ) and coextruded at a variable extrusion rate with a foam lamina of similar thermoplastic material having a thickness (T 2 ) and a density (D 2 ) to form a thermoplastic laminate, comprising: a first gauge for sensing the thickness of the laminate which is equal to (T 1 +T 2 ) and for providing a caliper signal (C) corresponding to the thickness sensed; a second gauge for sensing the mass/unit-area of the laminate which is equal to [(T 1 )(D 1 )+(T 2 )(D 2 )] and for providing a mass signal (M) corresponding to the mass/unit-area sensed; a third gauge for sensing a response to said thermoplastic material and its distribution in the laminate and for providing a dielectric signal (W) corresponding to the response which is equal to (K)[f(T 1 )]+(D 2 /D 1 )[f(C)-f(T 1 )] where (K) is a ratio of the dielectric effect of the solid material in each lamina, said function f(T 1 ) is equal to aT 1 /(b+T 1 ) and said function f(C) is equal to aC/(b+C) where (a) and (b) are approximated to best fit empirical data measured by said third gauge; said third gauge being positioned adjacent the film lamina and the sensitivity of said gauge decreasing with the distance therefrom; a computer having a memory containing the value of the density (D 1 ) of the film lamina, the value of the ratio (K) and the values associated with each of the functions f(C) and f(T 1 ), said computer being connected to said first, second, and third gauges and being responsive to successive sets of signals comprising the caliper signal (C), the mass signal (M) and the dielectric signal (W) for calculating the thickness (T 1 ) of the film lamina according to the formula: ##EQU8## combined from the equalitites associated with each signal received, and then for comparing an average thickness (T 1 ) of the calculated thicknesses (T 1 ) to a desired thickness (T 0 ) and providing a first control signal (DEC) when the average thickness (T 1 ) is less than the desired thickness (T 0 ); and means connected to said computer and responsive to the first control signal (DEC) for decreasing the extrusion rate of the film lamina and responsive to the second control signal (INC) for increasing the extrusion rate of the film lamina.

Claim 22

Apparatus for controlling the average thickness (T 1 ) of a film lamina of thermoplastic material having a known density (D 1 ) and coextruded at a variable extrusion rate with a foam lamina of similar thermoplastic material having a thickness (T 2 ) and a density (D 2 ) to form a thermoplastic laminate, comprising: a first gauge for sensing the thickness of the laminate which is equal to (T 1 +T 2 ) and for providing a caliper signal (C) corresponding to the thickness sensed; a second gauge for sensing the mass/unit-area of the laminate which is equal to [(T 1 )(D 1 )+(T 2 )(D 2 )] and for providing a mass signal (M) corresponding to the mass/unit-area sensed; a third gauge for sensing a response to said thermoplastic material and its distribution in the laminate and for providing a dielectric signal (W) corresponding to the response which is equal to (K)[f(T 1 )]+(D 2 /D 1 )[f(C)-f(T 1 )] where (K) is a ratio of the dielectric effect of the solid material in each lamina, said function f(T 1 ) is equal to m(1-e -T .sbsp.1 /n ) and said function f(C) is equal to m(1-e -C/n ) where (m) and (n) are approximated to best fit empirical data measured by said third gauge; said third gauge being positioned adjacent the film lamina and the sensitivity of said gauge decreasing with the distance therefrom; a computer having a memory containing the value of the density (D 1 ) of the film lamina, the value of the ratio (K) and the values associated with each of the functions f(C) and f(T 1 ), said computer being connected to said first, second, and third gauges and being responsive to successive sets of signals comprising the caliper signal (C), the mass signal (M) and the dielectric signal (W) for calculating the thickness (T 1 ) of the film lamina according to the formula: ##EQU9## combined from the equalities associated with each signal received, and then for comparing an average thickness (T 1 ) of the calculated thicknesses (T 1 ) to a desired thickness (T 0 ) and providing a first control signal (DEC) when the average thickness (T 1 ) is greater than the desired thickness (T 0 ) and a second control signal (INC) when the average thickness (T 1 ) is less than the desired thickness (T 0 ); and means connected to said computer and responsive to the first control signal (DEC) for decreasing the extrusion rate of the film lamina and responsive to the second control signal (INC) for increasing the extrusion rate of the film lamina.

Claim 23

Apparatus for controlling the average thickness (T 1 ) of a film lamina of thermoplastic material having a known density (D 1 ) and coextruded at a variable extrusion rate with a foam lamina of similar thermoplastic material having a thickness (T 2 ) and a density (D 2 ) to form a thermoplastic laminate, comprising: a first gauge for sensing the thickness of the laminate which is equal to (T 1 +T 2 ) and for providing a caliper signal (C) corresponding to the thickness sensed; a second gauge for sensing the mass/unit-area of the laminate which is equal to [(T 1 )(D 1 )+(T 2 )(D 2 )] and for providing a mass signal (M) corresponding to the mass/unit-area sensed; a third gauge for sensing a response to said thermoplastic material and its distribution in the laminate and for providing a dielectric signal (W) corresponding to the response which is equal to (K)[f(T 1 )]+(D 2 /D 1 )[f(C)-f(T 1 )] where (K) is a ratio of the dielectric effect of the solid material in each lamina, said function f(T 1 ) is equal to m(1-e -T .sbsp.1 /n ) and said function f(C) is equal to m(1-e -C/n ) where (m) and (n) are approximated to best fit empirical data measured by said third gauge; said third gauge being positioned adjacent the film lamina and the sensitivity of said gauge decreasing with the distance therefrom; a computer having a memory containing the value of the density (D 1 ) of the film lamina, the value of the ratio (K) and the values associated with each of the functions f(C) and f(T 1 ), said computer being connected to said first, second, and third gauges and being responsive to successive sets of signals comprising the caliper signal (C), the mass signal (M) and the dielectric signal (W) for calculating the thickness (T 1 ) of the film lamina according to the formula: ##EQU9## combined from the equalities associated with each signal received, and then for comparing an average thickness (T 1 ) of the calculated thicknesses (T 1 ) to a desired thickness (T 0 ) and providing a first control signal (DEC) when the average thickness (T 1 ) is greater than the desired thickness (T 0 ) and a second control signal (INC) when the average thickness (T 1 ) is less than the desired thickness (T 0 ); and means connected to said computer and responsive to the first control signal (DEC) for decreasing the extrusion rate of the film lamina and responsive to the second control signal (INC) for increasing the extrusion rate of the film lamina.

Claim 24

Apparatus for controlling the average thickness T 1 ) of a film lamina of thermoplastic material having a known density (D 1 ) and coextruded at a variable extrusion rate with a foam lamina of similar thermoplastic material having a thickness (T 2 ) and a density (D 2 ) to form a thermoplastic laminate, comprising: a first gauge for sensing the thickness of the laminate which is equal to (T 1 +T 2 ) and for providing a caliper signal (C) corresponding to the thickness sensed; a second gauge for sensing the mass/unit-area of the laminate which is equal to [(T 1 )(D 1 )+(T 2 )(D 2 )] and for providing a mass signal (M) corresponding to the mass/unit-area sensed; a third gauge for sensing a response to said thermoplastic material and its distribution in the laminate and for providing a dielectric signal (W) corresponding to the response which is equal to (K)[f(T 1 )]+(D 2 /D 1 )[f(C)-f(T 1 )] where (K) is a ratio of the dielectric effect of the solid material in each lamina and [f(C)-f(T 1 )]/D 1 is a function equal to a constant (Q) approximated to best fit empirical data measured by said third gauge; said third gauge being positioned adjacent the film lamina and the sensitivity of said gauge decreasing with the distance therefrom; a computer having a memory containing the value of the density (D 1 ) of the film lamina, the value of the ratio (K), the value of the constant (Q) and the values associated with each of the functions f(C) and f(T 1 ), said computer being connected to said first, second, and third gauges and being responsive to successive sets of signals comprising the caliper signal (C), the mass signal (M) and the dielectric signal (W) for calculating the thickness (T 1 ) of the film lamina according to the formula: ##EQU10## combined from the equalities associated with each signal received, and then for comparing an average thickness (T 1 ) of the calculated thicknesses (T 1 ) to a desired thickness (T 0 ) and providing a first control signal (DEC) when the average thickness (T 1 ) is greater than the desired thickness (T 0 ) and a second control signal (INC) when the average thickness (T 1 ) is less than the desired thickness (T 0 ); and means connected to said computer and responsive to the first control signal (DEC) for decreasing the extrusion rate of the film lamina and responsive to the second control signal (INC) for increasing the extrusion rate of the film lamina.

Claim 25

Apparatus for controlling the average thickness T 1 ) of a film lamina of thermoplastic material having a known density (D 1 ) and coextruded at a variable extrusion rate with a foam lamina of similar thermoplastic material having a thickness (T 2 ) and a density (D 2 ) to form a thermoplastic laminate, comprising: a first gauge for sensing the thickness of the laminate which is equal to (T 1 +T 2 ) and for providing a caliper signal (C) corresponding to the thickness sensed; a second gauge for sensing the mass/unit-area of the laminate which is equal to [(T 1 )(D 1 )+(T 2 )(D 2 )] and for providing a mass signal (M) corresponding to the mass/unit-area sensed; a third gauge for sensing a response to said thermoplastic material and its distribution in the laminate and for providing a dielectric signal (W) corresponding to the response which is equal to (K)[f(T 1 )]+(D 2 /D 1 )[f(C)-f(T 1 )] where (K) is a ratio of the dielectric effect of the solid material in each lamina and [f(C)-f(T 1 )]/D 1 is a function equal to a constant (Q) approximated to best fit empirical data measured by said third gauge; said third gauge being positioned adjacent the film lamina and the sensitivity of said gauge decreasing with the distance therefrom; a computer having a memory containing the value of the density (D 1 ) of the film lamina, the value of the ratio (K), the value of the constant (Q) and the values associated with each of the functions f(C) and f(T 1 ), said computer being connected to said first, second, and third gauges and being responsive to successive sets of signals comprising the caliper signal (C), the mass signal (M) and the dielectric signal (W) for calculating the thickness (T 1 ) of the film lamina according to the formula: ##EQU10## combined from the equalities associated with each signal received, and then for comparing an average thickness (T 1 ) of the calculated thicknesses (T 1 ) to a desired thickness (T 0 ) and providing a first control signal (DEC) when the average thickness (T 1 ) is greater than the desired thickness (T 0 ) and a second control signal (INC) when the average thickness (T 1 ) is less than the desired thickness (T 0 ); and means connected to said computer and responsive to the first control signal (DEC) for decreasing the extrusion rate of the film lamina and responsive to the second control signal (INC) for increasing the extrusion rate of the film lamina.