Extruder viscosity control system and method
AssigneeHarrel, Inc.
InventorHolton E. Harris
Life of this patent
Estimating the term…
Abstract
An extruder control system and method controls melt temperature to maintain viscosity of the melt at the die. A constant volumetric flow to the die is delivered by a gear pump, the die is a fixed orifice, and pressure between the gear pump and the die is indicative of viscosity. Changes in pressure are sensed and compensating changes in temperature are effected to return the pressure and, hence, the viscosity to its previous value.
Claims26
A method of extruder viscosity control for an extruder used in the manufacture of continuously extruded articles including the steps of providing a controlled volumetric flow of thermoplastic material to be extruded to a die by provision of a controlled volumetric flow means upstream of the die with respect to the flow of the material to be extruded, detecting pressure variations in the flowing material intermediate the controlled volumetric flow means and the die, and altering the temperature of the material flowing to the die to be extruded to hold the pressure relatively constant, whereby the viscosity of the material to be extruded is held substantially constant at the die.
An extruder control system for use on an extruder for the production of continuously extruded articles and having a barrel, a screw within the barrel to move towards a die material in the barrel from which extruded articles are formed, means for delivering a constant volumetric flow of the material to the die, and means in heat exchange relation with the barrel for regulating the temperature of the material moving in the barrel towards the die;
- the control system including controller means for electrically controlling the means in heat exchange relation with the barrel to establish a predetermined temperature of the material in the barrel;
- and
- means responsive to an electrical input thereto indicative of viscosity of the material in the flow path proximate and preceding the die for electrically revising the predetermined temperature, in response to a change in said viscosity.
An extruder for continuous production of extruded articles of thermoplastic material including feed means for introducing material to be extruded, a barrel defining a bore, a screw for moving the material in the bore, a screw drive, a series of temperature altering means in heat exchange relation to the barrel to establish the temperature of the material in the bore, means downstream of the screw and communicating with the bore for delivering a constant volumetric flow of the material from the bore, a die, a passage in material delivery communication between the constant flow means and the die, sensing means responsive to a viscosity representative characteristic of the material in the passage, electrical control means having temperature sensors in zones along the barrel at which are located the means in heat exchange relation to the barrel, means for comparing the temperatures sensed by said temperature sensors with at least one preselected temperature to develop signals controlling said means in heat exchange relation with the barrel, and viscosity correcting means connected with said sensing means responsive to a viscosity representative characteristic and connected in controlling relation to at least one of said screw drive and said means for comparing the temperatures to correct viscosity in the passage leading to the die by alteration of heat imparted to the material in the barrel.
An extruder according to claim I5 wherein the viscosity correcting means is connected with said screw drive and provides a screw drive speed adjusting output to adjust the heat imparted by the screw to material in the barrel to control viscosity.
An extruder viscosity control system for use on an extruder for production of continuous articles of thermoplastic material having a barrel, a screw within the barrel to move material in the barrel towards a die, means for controlling the volumetric flow of material to the die, and means in heat exchange relation with the barrel for regulating the temperature of the material moving in the barrel towards the die;
- the control system including means responsive to an indication of the pressure of the material between the volumetric flow control means and the die for producing a temperature alteration output;
- and
- said temperature alteration output of the pressur indication responsive means being connected in controlling relation to at least one of a screw drive speed control and the means in heat exchange relation with the barrel.
Dependencies are inferred from the claim text.