Gear Wheel Single Screw Extruder
An extruder plant includes a gear wheel single screw extruder having a reduced length and including only a feed zone of the extruder plant and a gearwheel twin screw extruder connected downstream of the worm extruder and including a plasticizing and pressure build-up zone of the extruder plant.
The present sheet production extruder relates to an extruder plant for processing rubber mixtures or thermoplastics which includes a feed zone, a plasticizing zone and a pressure build-up zone. The extruder plant is equipped with a worm extruder and with a gearwheel extruder connected to the worm extruder downstream in the extruding direction and to which an extruding die for shaping the extrudate is capable of being connected.
According to the present invention, a a worm extruder is connected to a gearwheel extruder in a series connection such that the gearwheel extruder simultaneously plasticizes the material and generates the static pressure while the worm extruder merely supplies the material. The worm extruder in the present invention is restricted in its overall length merely to the feed zone of a conventional worm extruder. That is, the worm extruder does not itself have any plasticizing zone. This type of extruder, which is designated hereafter as a short extruder, requires only a low structural outlay because the short extruder is not equipped with heating or cooling equipment.
The short extruder is a highly robust material draw-in assembly which can be fed with any desired physical embodiments of the raw material to be supplied. Accordingly, any type of raw material may be supplied including strip-like materials, the uniformity of which is no longer of any importance, granulates and even so-called puppets (rolls produced from strip-like material and having a diameter of, for example, 100 mm). The extruder plant according to the present invention may be used for processing high-viscosity materials such as, for example, rubber mixtures and thermoplastics. Furthermore, the inventive extruder plant is extremely simple to control and regulate.
To further reduce plant outlay, the short extruder and the gearwheel twin screw extruder may be driven by a common motor. In principle, the motor may comprise any desired type of motor but it is preferably designed as an electric motor. This simplification of the drive is readily possible because experience has revealed that the ratio of the necessary rotational speeds of the two extruders remains substantially constant for most materials over a wide range of rotational speeds. There are very few materials for which it is necessary to adapt the rotational speeds to optimal values at which the rotational speed ratio changes. Experience has shown single screw extruder that the range of variation is approximately from 1:1 to 1:0.9.