Patent ID: 7867123

Claim:
A drive apparatus for an extruder comprising: a speed reduction mechanism unit comprising a planetary gear speed reduction mechanism, the planetary gear speed reduction mechanism including: a hollow gear connected in mesh with a main input shaft connected to a main motor on an outer periphery of the planetary gear speed reduction mechanism through a gear ratio changing mechanism, wherein a gear ratio of the gear ratio changing mechanism can be selectively switched to change a speed of the hollow gear; a sun gear; a supporting shaft of the sun gear which constitutes an auxiliary input shaft connected to an auxiliary motor; and a planetary frame of planetary gears which constitutes an output shaft; an output distributing mechanism unit, which is separated from the speed reduction mechanism unit, and which comprises a screw; and an output shaft joint connecting the speed reduction mechanism unit and the output distributing mechanism unit; wherein the gear ratio changing mechanism comprises: an intermediate gear shaft and the main input shaft that are arranged in parallel to a center of a shaft of the hollow gear; a first intermediate gear, a second intermediate gear and a third intermediate gear; a first main input gear and a second main input gear that are mounted on the main input shaft; a switching cam mechanism arranged between the first intermediate gear and the second intermediate gear; and a switching lever that is connected to the switching cam; wherein the first intermediate gear and the second intermediate gear are respectively meshed with the first main input gear and the second main input gear; wherein the third intermediate gear is mounted on the intermediate gear shaft and is meshed with the hollow gear; wherein the first gear ratio between the first intermediate gear and the first main input gear is different from a second gear ratio between the second intermediate gear and the second main input gear; wherein the intermediate gear shaft is capable of being fixed to or released from the first intermediate gear and the second intermediate gear such that the intermediate gear shaft is selectively connected to the first intermediate gear or the second intermediate gear by the switching cam mechanism operated by the switching lever; wherein the main motor for driving the screw has a constant speed; and wherein the auxiliary motor for driving the sun gear has a variable speed.