Nanjing GIANT Machinery Co.,Ltd.

Gear system for driving screws of a single screw extruder with two parallel drive shafts (1, 2) of different length, of which the longer drive shaft (1) bears a drive gear wheel (3). The shorter drive shaft (2) has rotationally fixed connection by way of a pinion (6) to three distributor twin screw extruder (13, 14, 15), which can be driven from the longer drive shaft (1) by way of an annular gear wheel (20) which has internal teeth (19) and, on the distributor shafts (13, 14, 15), gear wheels (16, 17, 18) intermeshing with these teeth. On the longer drive shaft (1), there is a pinion (5) directly intermeshing with the pinion (6) of the shorter drive shaft (2). In order to achieve good division of the loads, the annular gear wheel (20) also has outer teeth (21) which intermesh with gear wheels (22, 23) of two intermediate shafts (24, 25), which intermesh by way of further gear wheels (26, 27) with the drive gear wheel (3).

The problem with driving single screw extruders lies in the fact that two drive shafts that are very close to each other have to transfer very high torques. Both drive shafts of the transmission have different lengths. A drive gear of virtually any size can be put on the long drive shaft so that the forces effective on this drive gear (as a result of its large diameter) can be kept within reasonable limits in spite of the high torque. Only a gear with relatively small diameter can be put on the short drive shaft, as it would otherwise interfere with the long drive shaft. The forces on this gear are extremely large with high torque. The pressure on the teeth of the gear can only be mitigated in a limited manner by making the gear longer (longitudinally of the drive shaft), but since the drive shaft will twist at high torque, only one portion of the length of the gear will then actually transmit force. Maximum torque is the result of the force the teeth of the gear are sustaining, that is to say the radial forces the radial bearings can absorb on one hand, and the diameter of the gear on the other hand, which can be transferred to the short drive shaft.

All the gears are—in a known manner—designed as helical gears in order to partially compensate for axial forces transferred to the short drive shaft from the corresponding screw and thus take load off the axial bearing 9 , which is limited in diameter sheet production extruder.

Due to the design of the transmission according to twin screw extruder to 5, the loads on the individual gears and shafts are kept low so that high torques can be transferred via the transmission to the screws of both the drive shafts 1 and 2 . Thus the high load-bearing capacity of the screws can be utilized fully without the danger of failure of the single screw extruder.