Control system and method for continuous mixer with moving surface discharge device

An improved apparatus for continuously processing thermoplastic material under controllable power, the apparatus including a barrel forming at least one substantially cylindrical material working chamber having material charging orifice adjacent one end and a material discharge orifice adjacent the other end, means for substantially continuously feeding material to said chamber through said charging orifice at a controllable rate, a mixing rotor extending axially in said chamber, a rotor drive motor, said rotor having axially extending blade portions, means on said rotor between said charging orifice and said blade portions for substantially continuously pushing material fed to said chamber toward said discharge orifice, a discharge control device having a moving surface and an inlet connecting to said discharge orifice for engaging moving material entering therein through said inlet, and means for adjusting said discharge control device at a variably controlled rate for applying a variable back pressure to the material fed through said orifice, the improvement comprising:

• means for measuring actual amperage drawn by the rotor drive motor;
• means for comparing said actual amperage drawn by the rotor drive motor with a target amperage to be drawn by said motor;
• means responsive to said comparing means for producing a control signal indicative of the difference between said actual amperage and said target amperage;
• means for sending said control signal to the means adjusting the rate of said discharge control device to adjust said adjusting means in response to said control signal to maintain, said amperage drawn by the rotor drive motor at a chosen level.

An apparatus for the continuous processing of thermoplastic material under controllable power comprising:

• a barrel forming at least one substantially cylindrical material working chamber having a material charging orifice adjacent to one end and a material discharge orifice adjacent the other end,
• means for substantially continuously feeding material to said chamber through said charging orifice at a controllable rate;
• a mixing rotor extending axially in said chamber and means for rotating said rotor, said rotor having axially extending blade portions means on said rotor between said charging orifice and said blade portions for substantially continuously pushing material fed to said chamber towards said discharge orifice;
• a discharge control device having a moving surface and an inlet connected to said discharge orifice for engaging moving material entering therein through said inlet and means for adjusting said discharge control device at a variably controlled rate for applying a variable back pressure to the material fed through said orifice;
• means for measuring torque produced by said means for rotating said rotor;
• means for comparing said measured torque with a target torque and for generating an adjustment signal indicative of the difference between said measured torque and said target torque;
• means for adjusting a discharge rate of the discharge control device in response to said adjustment signal.

An apparatus for the continuous processing of thermoplastic material under controllable power comprising:

• a barrel forming at least one substantially cylindrical material working chamber having a material charging orifice adjacent to one end and a material discharge orifice adjacent the other end,
• means for substantially continuously feeding material to said chamber through said charging orifice at a controllable rate;
• a mixing rotor extending axially in said chamber and means for rotating said rotor, said rotor having axially extending blade portions means on said rotor between said charging orifice and said blade portions for substantially continuously pushing material fed to said chamber towards said discharge orifice;
• a gear-type pump having an inlet connected to said discharge orifice for engaging moving material entering therein through said inlet and means for rotating said gear-type pump at a variably controlled rate for applying a variable back pressure to the material fed through said orifice, the improvement comprising:
• processor means for accepting input values of a production rate, a specific energy and a mixer RPM, said processor means calculating a horsepower value from the production rate and the specific energy, and then calculating a target torque from the mixer RPM and the calculated horsepower value;
• means for providing a feedback signal to said processor means indicative of actual torque produced by said means for rotating said rotor, said processor means comparing said feedback signal and said target torque and then generating a correction signal indicative of the difference between said target torque and said actual torque, said processor applying said correction signal to a proportional, integral and derivative control loop to produce an adjustment signal which is applied to said discharge control device to thereby adjust the gear pump RPM so as to maintain said actual torque equal to said target torque.

A method for continuously processing thermo-plastic material under controllable power in a continuous mixer including a barrel forming at least one substantially cylindrical material working chamber having a material charging orifice adjacent one end and a material discharge orifice adjacent the other end, means for substantially continuously feeding material to said chamber through said charging orifice at a controllable rate, a mixing rotor extending axially in said chamber, means for rotating said rotor, said rotor having axially extending blade portions, means on said rotor between said charging orifice and said blade portions for substantially continuously pushing material fed to said chamber toward said discharge orifice, a discharge control device having a moving surface and an inlet connecting to said discharge orifice for engaging moving material entering therein through said inlet, and means for adjusting said discharge control device at a variably controlled rate for applying a variable back pressure to the material fed through said orifice, said method comprising the steps of:

• measuring torque produced by the means for rotating said rotor;
• comparing said measured torque with a target torque and generating an adjustment signal indicative of the difference between said measured torque and said target torque;
• adjusting a discharge rate of the discharge control device in response to said adjustment signal.

A method for continuously processing thermoplastic material under controllable power in a continuous mixer including a barrel forming at least one substantially cylindrical material working chamber having a material charging orifice adjacent one end and a material discharge orifice adjacent the other end, means for substantially continuously feeding material to said chamber through said charging orifice at a controllable rate, a mixing rotor extending axially in said chamber, means for rotating said rotor, said rotor having axially extending blade portions, means on said rotor between said charging orifice and said blade portions for substantially continuously pushing material fed to said chamber toward said discharge orifice, a discharge control device having a moving surface and an inlet connecting to said discharge orifice for engaging moving material entering therein through said inlet, and means for adjusting said discharge control device at a variably controlled rate for applying a variable back pressure to the material fed through said orifice, said method comprising the steps of:

• inputting values of a production rate, a specific energy and a mixer RPM to a processor means;
• caclutating a horsepower value from the production rate and the specific energy, and then calculating the target torque from said mixer RPM and said calculated horsepower value;
• providing a feedback signal to said processor means indicative of actual torque produced by said means for rotating said rotor;
• comparing said feedback signal and said target torque and generating a correction signal indicative of the difference between said target torque and said actual torque;
• applying said correction signal to a proportional, intergral and derivative control loop to produce an adjustment signal which is applied to said discharge control device to thereby adjust a discharge rate of said discharge control device so as to maintain said actual torque equal to said target torque.