Extrusion Method And Single Screw Extruder
An extrusion method and single screw extruder, the material to be extruded being fed with a material feeding device (1) into a radial pump unit included in the twin screw extruder. The radial pump unit comprises conical gearwheels (2) which are adjacently positioned and rotate in opposite directions. The radial pump unit transfers the material in an annular flow into the extruder's nozzle (4). Additional material (20) can be supplied into the product through the radial pump unit.
A product of the sheet production extruder, in turn, is characterized in that the product comprises a basic material and an additional material supplied through the radial pump unit.
An essential idea of the single screw extruder is that the material feeding device supplies the material to be extruded in a melted form into the radial pump unit of the equipment, the radial pump unit comprising a plural number of conical gearwheels which are adjacently positioned and provided with helical gears, or a plural number of screws which are adjacently positioned and rotate in opposite directions. The radial pump unit transfers the material in an annular flow into the extruder's nozzle. A preferred embodiment is based on the idea that at least one gearwheel in the radial pump unit receives its rotational energy via the material feeding device. The idea of a second preferred embodiment is that the material feeding device is a melting screw. A third preferred embodiment is based on the idea that a continuous solid material, a liquid or gas, or a combination of these, is supplied through the gearwheel. A fourth preferred embodiment is based on the idea that there is a plural number of material feeding devices and that the material to be extruded is supplied into the material feeding devices through a ring channel where their input ends are connected to. A fifth preferred embodiment is based on the idea that the equipment is provided with a plural number of radial pump units, which allows a plural number of material layers arranged one inside the other to be supplied into the extruder's nozzle to produce multilayer products.
An advantage of the twin screw extruder is that an extremely uniform yield is obtained using the equipment. In addition, it provides a simple means for ensuring an excellent centricity of the product, thereby allowing products with extremely good centricity and radial thickness profile to be produced. Furthermore, an excellent thickness profile is achieved in multilayer products. The solution of the invention further allows the material or materials to be extruded to be most effectively melted and mixed, a most homogeneous material flow being thereby obtained. Further still, products produced by applying the solution of the single screw extruder can be reinforced in various different ways.