The extruding helix
The mass which is made flowable (rendered plastic) must be degassed on its way to the outlet. In order to make the degassing section free of pressure a diaphragm, through which the mass flows, is provided further upstream. The extruding helix is provided with at least one helical flute, the free flow passage of which is blocked, and the diaphragm is provided with an adjustable throughput area. The diaphragm can simply consist of two perforated disks, which are rotatable with respect to each other around their axes. Each perforated disk has a fixed throughput area. The holes of both perforated disks overlap more or less, or not at all. The throughput rate of the mass through the extruding device can therefore, according to the state or the kind of mass, be regulated independently of the rotation speed of the extruding helix. Different masses can be extruded with one and the same helix, in a way hitherto not possible. One can also use an extruding helix which is shorter than was hitherto possible. The perforated disks can be easily exchanged.
Extruding device comprising a casing, a passage through the casing for a flowable mass, the passage having an outlet, and an extruding helix in the passage for urging the flowable mass in the passage towards the passage outlet, a restraining diaphragm placed alongside the helix in the passage, the diaphragm having an adjustable size throughput area through which the flowable mass flows, means for selectively adjusting the size of the throughput area for controlling the flow of the flowable mass, and a degassing section downstream of the diaphragm.
Wherein twin screw extruder comprises two perforated disks positioned facewise next to the other in the flow path of the flowable mass, the disks being mutually movable with respect to each other within their respective planes, each disk having a respective fixed throughput area which is shaped and placed such that when the two perforated disks are moved with respect to each other, their throughput areas overlap selectively more or less, or not at all. The invention relates to an extruding device with an extruding helix for urging a flowable mass towards an outlet, a diaphragm through which the flowable mass flows being provided alongside the helix, and there being provided a degassing section downstream of the diaphragm. In a first section of the extruding helix (as seen in its direction of travel) a mass is rendered plastic, i.e. flowable, by heating. During this passage into the plastic state gases are formed (water vapor and other gases) which are then evacuated from the device into a degassing section. A diaphragm is provided upstram of the degassing section, so that the latter is situated in a zone with no pressure.