Machine for the extrusion of polymers and the like with converging threaded rotors each actuated by means of its own actuating motor

Abstract: Machine for the extrusion of polymers and the like, comprising a pair of threaded rotors (5) with axes which are generally converging with respect to each other and means (7) for synchronized transmission of the movement to the said rotors (5), wherein each rotor (5) is made to rotate by means of its own actuating motor (8).

Description: The present invention relates to a machine for the extrusion of polymers and the like, of the type with two threaded and converging rotors, wherein each rotor is made to rotate by means of its own actuating motor, for example of the hydraulic type. In the technical sector of elastomer and plastomer processing it is known of so-called conical twin-screw extruder machines in which two threaded shafts, known simply as rotors, are arranged with converging axes inside a containment casing. It is also known that said rotors must be made to rotate at a low number of revolutions and must rotate in a synchronized manner with respect to one another so as to maintain the angular phase difference which is predefined during assembly of the machine so as to avoid interference between the threading of the two rotors - interference which would prevent rotation of the latter particularly in the case of rotors of the interpenetrating type. It is also known from the publications EP 0,472,431 and EP 0,598,376 of devices for actuating said rotors respectively based on: transmissions of the endless-screw type, helical wheel and bevel gears for direct transmission of the movement and the synchronism between the low-speed shafts, in the first case; and transmissions with a reducer associated with each rotor and conical drives for transmission of the movement and the synchronism via the high-speed shafts, in the second case. The extruders known in art, therefore, have a single source of movement usually consisting of an electric motor, the output shaft of which is connected by means of suitable transmission devices to the two rotors for the rotational actuation thereof. This configuration, although providing a single source of movement, nevertheless requires the use of devices for reducing the speed of rotation, associated with each rotor, as well as devices for synchronized transmission of the movement, arranged between the high-speed shaft of the motor and the high-speed shaft of the reducer. Said prior art is disclosed into EP-A-0 166 008. This results in the need to provide a structure for supporting and containing the transmission devices, which is of large dimensions and considerable structural complexity, substantially preventing easy assembly during installation and subsequent easy access for the routine maintenance operations. In addition to this, the large number of devices forming the movement transmission system results in an increase in the possibility of malfunctions affecting the machine as a whole. The technical problem posed, therefore, is that of providing a machine for the extrusion of polymers, of the type comprising two threaded and converging rotors, which provides simplified means for synchronized actuation of the rotors themselves allowing a reduction in the component parts, in particular those for transmission of the movement and reduction in the speed thereof, while leaving unaltered the characteristics of working safety and power. Within the scope of this problem, a further necessity is that the extruder structure should have small overall dimensions, while remaining extremely rigid, and that it should be possible to remove the various component parts easily from the machine for the normal maintenance operations without the need for disassembly of most of the transmission system in order to perform said operations. These results are obtained by the present invention which provides a machine for the extrusion of polymers and the like, according to claim 1. The motors for actuating the rotors are of the hydraulic type. Further details and characteristic features of the extruder according to the invention will become clear from the following detailed description of an example of embodiment provided with reference to the accompanying figures, in which: Fig. 1 shows a side view of the extruder according to the invention; Fig. 2 shows a plan view of the extruder partially open in the region of the rotors; Fig. 3 shows a plan view of the extruder partially sectioned in the zone where the two parts forming the rotors are joined together. As shown in Figure 1, the extruder according to the invention comprises a base 1 having arranged on it uprights 2 and 3, the respective upper surfaces 2a and 3a of which are parallel with one another and inclined towards the front part of the machine by a suitable angle. The front uprights 2 support the housing 4 containing the rotors 5, while the rear uprights 3 support a housing 6 containing means 7 for transmission of the movement, associated with each rotor 5. The entire arrangement of the above-described parts which make up the extruder is realized so as to give rise to an angle of convergency of the axes of the two rotors 5 and a downwards inclination of the entire mixing part 4 and extruding part 9 of the machine, corresponding to the front part of the machine itself so as to avoid stagnation of the material during processing. According to a preferred embodiment and as illustrated more clearly in Fig. 3, the said rotors 5 are formed in two separate parts consisting of a shaft 5a for receiving the driving movement and a threaded part 5b, with variable-pitch threading, fixed to the shaft 5a as described in more detail below. The shaft 5a is supported at the rear by associated radial bearings 6a and by a thrust bearing 6c seated in the said housing 6. Said shaft 5a has a front flange 5c with, emerging from it, a conical journal 5d for coupling with a corresponding conical seat 5f formed in the threaded part 5b of the rotor 5, so that insertion of the latter onto the shaft is performed with a self-centering action and with friction which contributes to transmission of the movement. The angular positioning and locking of the threaded part 5b to the shaft 5a is performed by means of pins 11 and screws 12 arranged between respective front-abutting flanges of the parts 5a, 5b of the rotor 5 to be joined. As can be seen from the figures, each rotor 5 is made to rotate by its own motor 8 coaxially and directly mounted on the associated drive shaft 5a. In the example illustrated said motors 8 are of the hydraulic type with a hollow shaft, known per se and therefore not described in detail; said hydraulic motor 8 has a coaxial flange 8a which extends downwards and which is constrained at its bottom end to the free end of a pin 8b, the other end of which is fixed to the upright 3. Said flange 8a and stop 8b form overall anti-rotation means of the motor 8 which without said constraining means could not cause rotation of the rotors 5. Said pin/flange connection may also be realized by means of the intermediate arrangement of an articulation for recovery of any flexing of the rotor due to the loads to which it is subject. As can be seen from Fig. 2, each shaft 5a has mounted on it a respective toothed wheel 7a, 7b radially meshed with the other one so as to form a bevel gearing 7. In a preferred embodiment this gearing consists of gears of the so-called "FACE" type which are simpler to realize. By means of said gearing the simultaneous result of synchronization and a safety check as to correct operation of the two motors 8 is achieved; if, in fact, one of the two motors should jam, the corresponding toothed wheel 7a, 7b which stops is able to stop and keep the other toothed wheel 7b, 7a blocked, preventing impact between the two threaded parts 5b of the rotors 5 which, no longer rotating in a synchronized manner, would not maintain the initial angular difference and would make contact. As shown in Figure 1 in broken lines, the motor shaft may also be provided with a device 10, for example of the type known by the name "encoder", for checking the angular position of the associated rotor 5, i.e. since, if one of the two toothed wheels of the gearing should be damaged, for example losing a tooth, there would be a variation in the initial angle of phase difference between the two rotors 5 which could again result in damage to the rotors 5. From the configuration described above it is therefore obvious how the twin-screw extruder according to the invention has a small number of components forming the mechanical transmission, resulting in greater compactness and reliability of the machine, safe operation of which is ensured both by the particular type of bevel gearing for transmission of the movement between the low-speed shafts, and by any devices for checking the angular position of each rotor. The machine consequently has the characteristic features that it is extremely compact and easy to access and maintain, particularly in the case of rotors consisting of two parts, which allow the threaded part to be replaced without the need for disassembly of the transmission. Many variations may be introduced as regards the realization of the parts which make up the invention, without thereby departing from the protective scope of the present invention as defined by the claims which follow.

Claims: Machine for the extrusion of polymers and the like, comprising a pair of threaded rotors (5) with axes generally converging with respect to each other and means (7) for synchronized transmission of the movement to the said rotors (5), characterized in that each rotor (5) is made to rotate by means of an own actuating motor (8), of the hydraulic type coaxially and directly mounted on the respective drive shaft (5a) of the rotor (5). Machine according to Claim 1, characterized in that said hydraulic motor (8) is provided with external means (8a, 8b) for preventing rotation of the casing of the motor itself. Machine according to Claim 1, characterized in that said system for synchronized transmission of the movement consists of a bevel gearing (7). Machine according to Claim 3, characterized in that said gearing (7) is of the FACE type. Machine according to Claim 1, characterized in that said rotors are formed as two separate parts (5a, 5b) which are removably joined by means of associated centering means (5d, 5f), angular positioning means (11) and locking means (12), one of said parts consisting of a shaft (5a) for receiving the driving movement and the other part (5b) comprising the variable-pitch threading. Machine according to Claim 1, characterized in that devices (10) for checking the angular position of each rotor (5) are also provided.

Inventors: GIANI MAURO MATTEO, GIANI, MAURO MATTEO
Applicants: TECHINT SPA, TECHINT COMPAGNIA TECNICA INTERNAZIONALE S.P.A.
Application year: 1996
Main classification: B29C47
IPC codes: B29C47