US 6,293,778 B1 · Automatically balancing a blower in a blown film extrusion line

Abstract

The present invention is directed to an apparatus for startup of extruded film tubes. A controller member is utilized to provide control signals to a supply blower which supplies air to the extruded film tube in an amount corresponding to a supply control signal, and an exhaust blower which exhausts air from the extruded film tube in an amount corresponding to an exhaust control signal. The controller member executes program instructions which define at least one control routine for automatic and coordinated control of the supply blower and the exhaust blower during starting of the extruded film tube, by directing a series of supply control signals to the supply blower and exhaust control signals to the exhaust blower. When a valve is utilized to control the flow of air from the supply blower to the extruded film tube, the controller is also utilized to adjust the supply blower and the exhaust blower in order to optimize operation of the valve by placing the valve in a substantially linear operating range. Additionally, the controller member may be utilized to execute program instructions in order to implement a bubble break detection routine which utilizes software timers in combination with monitoring of a position signal in order to determine collapse or break of the extruded film tube.

Claims43

Dependent claims

In a blown film extrusion apparatus in which film is extruded as a tube from an annular die and then pulled along a path, an apparatus for startup of said extruded film tube, comprising:

(a) means for varying a quantity of air within said extruded film tube, including:
(1) a supply blower which supplies air to said extruded film tube in an amount corresponding to a supply control signal, and
(2) an exhaust blower which exhausts air from said extruded film tube in an amount corresponding to an exhaust control signal;
and
(b) a controller member including executable program instructions which define at least one control routine for automatic and coordinated control of said means for varying during starting of said extruded film tube by directing a series of supply control signals to said supply blower and exhaust control signals to said exhaust blower in order to independently and concurrently control said supply blower and said exhaust blower;
and
(c) a valve member, under control of said controller, for varying admission of air into said extruded film tube for controlling the circumference of said extruded film tube;
(d) wherein at least one control routine includes a valve optimization routine during which:
(1) said controller member determines a current closure condition for said valve member;
(2) based upon said current closure condition of said valve, said controller sends at least one of (a) said supply control signals and (b) said exhaust control signals to at least one of (a) said supply blower and (b) said exhaust blower, in order to establish operating rates which allow said valve member to operate in a substantially linear portion of its range of closure conditions.

7 more elements

An apparatus for extruding a film tube, comprising:

(a) a die member;
(b) means for supplying molten film to said die member;
(c) a supply blower for supplying air to said extruded film tube in an amount corresponding to a supply control signal;
(d) an exhaust blower for exhausting air, from said extruded film tube in an amount corresponding to an exhaust control signal;
(e) a valve for controlling air flow from said supply blower to said extruded film tube in response to a valve control signal;
(f) a position sensor for providing a signal indicative of the size of said extruded film tube;
(g) a controller member including executable instructions which define at least one control routine;
(h) a control interface for receiving operator instructions;
and
(i) said at least one control routine including:
a valve optimization routine during which:
(1) said controller member determines a current closure condition for said valve member;
(2) based upon said current closure condition of said valve, said controller sends at least one of (a) said supply control signals and (b) said exhaust control signals to at least one of (a) said supply blower and (b) said exhaust blower, in order to establish operating rates which allow said valve member to operate in a substantially linear portion of its range of closure conditions.

10 more elements

In a blown film extrusion apparatus in which film is extruded as a tube from an annular die and then pulled along a path, an apparatus for controlling said blown film extrusion apparatus, comprising:

(a) an air supply subsystem for varying a quantity of air within said extruded film tube, including:
(1) a supply blower which supplies air to said extruded film tube in an amount corresponding to a supply control signal, and
(2) an exhaust blower which exhausts air from said extruded film tube in an amount corresponding to an exhaust control signal;
and
(3) a valve member for controlling air flow from the supply blower to the extruded film tube;
and
(b) a controller member including executable program instructions which define at least one control routine for automatic and coordinated control of said air supply subsystem by;
(1) examining the closure condition of said valve member;
(2) based upon the determined closure condition of said valve member, automatically directing at least one of a series of supply control signals to said supply blower and exhaust control signals to said exhaust blower in order to independently and concurrently control said supply blower and said exhaust blower, in order to maintain automatically said supply blower and said exhaust blower in operating ranges which allow said valve member to operate in a linear range of operation.

6 more elements

An apparatus for extruding a film tube, comprising:

(a) a die member;
(b) means for supplying molten film to said die member;
(c) a supply blower for supplying air to said extruded film tube in an amount corresponding to a supply control signal;
(d) an exhaust blower for exhausting air from said extruded film tube in an amount corresponding to an exhaust control signal;
(e) a valve for controlling air flow from said supply blower to said extruded film tube in response to a valve control signal;
(f) a position sensor for providing a signal indicative of the size of said extruded film tube;
(g) a controller member including executable instructions which define at least one control routine;
(h) a control interface for receiving operator instructions;
and
(i) said at least one control routine including:
(1) a blower control routine for automatic and coordinated control of said supply blower and said exhaust blower during startup of said extruded film tube in order to independently and concurrently control said supply blower and said exhaust blower;
and
(2) a valve optimization routine during which:
(a) said controller member determines a current closure condition for said valve;
and (b) based upon said current closure condition of said valve, said controller automatically establishes an operating rate for at least one of said supply blower and said exhaust blower in order to allow said valve to operate in a substantially linear portion of a range of closure conditions.

12 more elements

An apparatus for extruding a film tube, comprising:

(a) a die member;
(b) means for supplying molten film to said die member;
(c) a supply blower for supplying air to said extruded film tube in an amount corresponding to a supply control signal;
(d) an exhaust blower for exhausting air from said extruded film tube in an amount corresponding to an exhaust control signal;
(e) a valve for controlling air flow from said supply blower to said extruded film tube in response to a valve control signal;
(f) a position sensor for providing a signal indicative of the size of said extruded film tube;
(g) a controller member including executable instructions which define at least one control routine;
(h) a control interface for receiving operator instructions;
and
(i) an inlet variable speed drive for receiving control signals from said controller member and for determining an operating speed for said supply blower;
(j) an outlet variable speed drive for receiving control signals from said controller member and for determining an operating speed for said exhaust blower;
(k) wherein at least one control routine comprises a valve optimization routine which automatically establishes an operating speed for at least one of said supply blower and said exhaust blower in order to allow said valve member to operate in a substantially linear range of closure conditions.

9 more elements

In a blown film extrusion apparatus in which film is extruded as a tube from an annular die and then pulled along a path, an apparatus for controlling said blown film extrusion apparatus, comprising:

(a) an air supply subsystem for varying a quantity of air within said extruded film tube, including:
(1) a supply blower which supplies air to said extruded film tube in an amount corresponding to a supply control signal, and
(2) an exhaust blower which exhausts air from said extruded film tube in an amount corresponding to an exhaust control signal;
and
(3) a valve member for controlling air flow from the supply blower to the extruded film tube;
(4) an inlet variable speed drive for receiving control signals and for determining an operating speed for said supply blower;
(5) an outlet variable speed drive for receiving control signals and for determining an operating speed for said supply blower;
(b) a controller member including executable program instructions which define at least one control routine for automatic and coordinated control of said air supply subsystem by directing a series of supply control signals to said inlet variable speed drive for said supply blower and said outlet variable speed drive for said exhaust control signals to said exhaust blower in order to independently and concurrently control said supply blower and said exhaust blower in order to maintain automatically said supply blower and said exhaust blower in operating ranges which allow said valve member to operate in a linear range of operation.

5 more elements

An apparatus for extruding a film tube, comprising:

(a) a die member;
(b) means for supplying molten film to said die member;
(c) a supply blower for supplying air to said extruded film tube in an amount corresponding to a supply control signal;
(d) an exhaust blower for exhausting air from said extruded film tube in an amount corresponding to an exhaust control signal;
(e) a valve for controlling air flow from said supply blower to said die member in response to a valve control signal;
(f) a position sensor for providing a signal indicative of the size of said extruded film tube;
(g) a controller member including executable instructions which define at least one control routine;
(h) said at least one control routine including:
a valve optimization routine during which, based upon current closure condition of said valve, said controller sends at least one of (a) said supply control signals and (b) said exhaust control signals to at least one of (a) said supply blower and (b) said exhaust blower, in order to establish operating rates which allow said valve member to operate in a substantially linear portion of its range of closure conditions.

6 more elements

Dependencies are inferred from the claim text.

Automatically balancing a blower in a blown film extrusion line

Life of this patent

Automatically balancing a blower in a blown film extrusion line

Life of this patent

Abstract

Claims43