The present invention relates to a kneading machine or a mixing machine in which two rotors are respectively housed in two cavities of a chamber.
Heretofore, as an apparatus for kneading natural or synthetic rubber or for mixing and kneading the rubber and various kinds of additive agents to disperse them uniformly in the rubber, or for mixing and kneading various thermoplastic elastomer or high viscous fluid with powder material or liquid material, or for dispersing materials, has been known a kneading machine in which blade-like rotors are rotatably supported within a sealed container (chamber) and kneading objects put into the chamber are moved from the axial direction of the rotor to the radial direction of the rotor to be circulated. For example, in the sealed type kneading machine disclosed in JP-A-8-24833 (corresponding to U.S. Pat. No. 4,834,543), spiral blades having spiral angles extending in the same direction are respectively formed on circumferences of shafts of two rotors and the two rotors are respectively arranged in disengaged condition in two parallel cylindrical cavities communicated with each other at their side faces. The rotors are rotated in opposite directions and the kneading objects are moved in the axial direction in each of the cavities and are interchanged between the cavities.
FIG. 7 is a side view showing the rotors described in the above described Patent Document, and FIGS. 8-10 are schematic views showing flows of the kneading objects in the kneading machine in which the rotors are incorporated. A pair of rotors 1 are horizontally arranged in the right and left cavities of the chamber 3 of the kneading machine with a predetermined distance between them while keeping parallel relationship with each other. Neck portions of the shafts of the rotors la are rotatably supported by both sides of the chamber 3, and end portions of the rotor shaft at one side are connected to a drive motor via a gear system (not shown). The rotors are rotated in the opposite directions at the same speed. These rotors 1 each are formed with a long blade 5 and a short blade 6 extending in the axial direction with a predetermined spiral angle. The rotors are assembled in the machine to shift phases of rotating angle so that the rotors cannot interfere with each other at rotation and in the example, the rotors are assembled in the machine with a phase difference 90.degree. at a position.
In this example, the spiral directions of the blades of the right and left rotors 1 are the same. Therefore, when the rotors 1 are rotated in opposite directions, the movements of the kneading objects in the axial direction in the respective cavities 2 become opposite direction as schematically illustrated in FIGS. 8 and 9, so that the movement of the kneading objects in the axial direction in the cavities becomes good condition. Further, interchanging of the kneading objects are performed near the end of both cavities 2 in the axial direction.
Kneading machines of the above described type in which spiral directions of the blades portions of the right and left rotors are the same and the rotors are rotated in opposite directions can improve the movability of the kneading objects in the axial direction in the chamber. However, when an operation in which the raw materials of kneading objects are continuously supplied into the chamber and simultaneously the product is simultaneously taken out from a discharge outlet of the chamber, so-called continuous operation, is performed, resulted is a disadvantageous phenomenon, so-called short pass, in which the raw materials entered a material supply inlet of the chamber immediately move to the discharge outlet without being uniformly mixed in the radial direction (see FIG. 10) because of the high movability in the axial direction of raw materials, so that uniformly kneaded product cannot be obtained. Therefore, the conventional kneading machines can do only batch treatment, and they have a problem on the productivity.
Further, in the conventional kneading machines, because the right and left rotors of which spiral directions of the blade portions the rotors are the same are rotated in opposite directions, phases of the right and left rotors during rotation are shifted at the positions in the axial direction. Therefore, quantity of interchanging of the kneading objects between the cavities in the chamber changes. In case where the length of the chamber in the axial direction is short, the phase shift is limited to a small range and its influence is negligible. However, in case of the length of the chamber in the axial direction is longer, i.e. the ratio L/D of the length L with the diameter D of the chamber is larger, its influence cannot be ignored.