GAS EXPELLING EQUIPMENT FOR USE IN A VISCOUS-MATERIAL KNEADER OR THE LIKE

Abstract: A device for expelling the gas liberated within a viscous-material treating apparatus such as a kneader, an extruder or the like. The device basically consists of a cone-shaped rotor (4) and a cone-shaped cover member (3) covering the rotor (4). The cone-shaped rotor (4) is provided with volute protrusions (7), while the cone-shaped cover member (3) is provided with a gas exhaust orifice (8) to which a vacuum system is to be connected. With the cone-shaped rotor (4) kept rotating, the volute protrusions (7) act so as to prevent the viscous material from being swallowed up together with the liberated gas to be pumped out.

Description: The present invention relates to a gas expelling equipment for use in a viscous-material treating apparatus such as a kneader, extruder or the like. In such an apparatus as an extruder of molten plastic to be molded as a plastic mold product, it is inevitably necessary to expel from the material the gas included in or generated from the same to keep the product free from vacuoles. For example, in a conventional rotary screw type extruder with this problem taken into consideration, the screw is designed to have the pitch made unequally spaced with the coarsely spaced portion localized at the practically central portion of the whole length of the screw, while the barrel or cylinder encasing the screw is provided with a gas exhaust pipe (leading to an exhaust pumping system) at the position corresponding to the above coarsely pitched portion of the screw. With the extruder thus constituted, an external pumping system can exhaust only the gas liberated into a broadened space formed at the coarsely pitched portion of the screw without swallowing up the viscous material being transferred toward the outlet of the extruder. However, an extruder of this type has a decisive disadvantage that the extruder is made unnecessarily long. In another type of extruder, instead of providing the extruder screw with a coarsely pitched portion to form there a gas stagnating space, there is equipped, near the gas exhaust pipe, a viscous material restoring device to prevent the viscous material being swallowed up through the gas exhaust pipe. The device is, for example, made up of a pair of screws roughly engaged with each other, and mounted on the extruder barrel or cylinder with the screw axes kept vertical to the axis of the extruder screw. Such a device is described in DE 1 201 041. The rotation of the paired screws pushes back the viscous material having a tendency to be drawn out by an external gas exhaust system through the gas exhaust pipe. In the case of this extruder it is a disadvantage that the viscous-material restoring device, which is relatively tall, protrudes vertically from the extruder body. Another disadvantage is the device has a complex constitution. It has been desired to provide an improved gas expelling device applicable to a viscous material treating apparatus such as a viscous material kneader, extruder or the like in which the above-mentioned disadvantages are substantially eliminated. According to the present invention there is provided a gas expelling device for use in a viscous material treating apparatus such as a kneader, an extruder or the like, the device comprising a rotor for restraining a viscous material and a cover member for covering the rotor, the cover member being provided with a gas exhaust orifice out of which is pumped gas liberated within the apparatus, characterised in that the rotor is a cone-shaped rotor having a plurality of volute protrusions on its outer conical surface, and in that the cover member is cone-shaped. The device is mounted on the outer barrel, for example, of an extruder so as to keep the axis of the cone-shaped rotor perpendicular to the axis of the extruder screw. By applying the gas expelling device to a viscous-material treating apparatus such as an extruder, kneader or the like, the apparatus as a whole is made compact; when applied to a screw type extruder, the need for a long screw, provided with a coarsely pitched portion, is avoided and the gas expelling device itself is short of stature. The present invention will be further described by way of example with reference to the accompanying drawings, in which: Fig. 1 shows a cross-sectional view of a screw type extruder to which an embodiment of the present invention is applied; Fig. 2 shows a close-up of the embodiment of Fig. 1; Fig. 3 illustrates, in another embodiment of the present invention, the relationship between a protrusion pattern provided on the upper surface of the cone-shaped rotor and that provided on the inner surface of the cone-shaped cover member; and Figs. 4(A) and (B) schematically show flat projections of cross-sections illustrating the cross-sectional protrusion patterns on the cone-shaped rotor and the cone-shaped cover member. Detailed Description of the Invention Referring to Fig. 1, which shows the application of an embodiment of the present invention to a screw type extruder, the embodiment consists basically of a cone-shaped cover member 3 and a cone-shaped rotor 4. The cover member 3 is provided with a gas exhaust orifice 8, and the rotor 4 is connected to a motor 9 through a shaft 6 and is rotatable by that motor 9. On the other hand the extruder to which the present invention is applied comprises a material hopper 10, a barrel or cylinder 2, a material mixing and transferring screw 1 and an arrangement of extruding nozzles 11. Further referring to Fig. 2 which shows a close-up of the above embodiment, the cone-shaped rotor 4 is provided with a plurality of volute (swirl-shaped) protrusions 7 on its upper surface. With the rotor 4 rotating, the volute protrusions 7 act so as to push back and prevent the viscous material from being swallowed up, and thus only the gas liberated within the extruder can be removed by being pumped out through the gas exhaust orifice 8 to which a vacuum system (not shown) is to be connected. Incidentally, it is preferrable that the vertical angle of the geometrical imaginary cone made by an averaged form of the cone-shaped rotor 4 is obtuse reaching about 110°. The present invention can be embodied by providing volute protrusions also on the inner surface of the cone-shaped cover member 3, as is illustrated with dotted lines in Fig. 3. These volute protrusions 12 curves inversely to the volute protrusions 7 provided on the upper surface of the cone-shaped rotor 4. Figs. 4(A) and 4(B) show the examples of the cross-sectional pattern of the above two kinds of volute protrusions. As may be seen in Fig. 4(B), the protrusions 7 of the cone-shaped rotor 4 may be formed to have a saw-tooth cross section.

Claims: A gas expelling device for use in a viscous material treating apparatus such as a kneader, an extruder or the like, the device comprising a rotor (4) for restraining a viscous material and a cover member (3) for covering the rotor, the cover member (3) being provided with a gas exhaust orifice (8) out of which is pumped gas liberated within the apparatus, characterised in that the rotor (4) is a cone-shaped rotor (4) having a plurality of volute protrusions (7) on its outer conical surface, and in that the cover member (3) is cone-shaped. A gas expelling device according to claim 1, in which the inner conical surface of the cone-shaped rotor (4) is provided with a plurality of volute protrusions (12) curving inversely to the volute protrusions (7) provided on the outer conical surface of the cover member (3). A gas expelling device according to claim 1 or 2, in which the vertical angle of an imaginary cone obtained by averaging the forms of the cone-shaped rotor (4) and the cone-shaped cover member (3) is obtuse.

Inventors: MORIYAMA, MASAO
Applicants: MORIYAMA, MASAO
Application year: 1988
Main classification: B29B7
IPC codes: B29C47, B29B7