Abstract: An automatic tool exchanging apparatus of a machine tool in which a new tool having heavy weight such as 60-100 kg are conveyed with its shank downwardly directed and readily and safely exchanged with a used tool. The apparatus comprises a tool storing magazine, a first tool exchanging mechanism located in front of the magazine, a horizontal tool conveying mechanism connected to the first tool exchanging mechanism, a vertical tool conveying mechanism, a second tool exchanging mechanism located on one side of the vertical tool conveying mechanism, and an intermediate tool pot mechanism for transferring the tool from the second tool exchanging mechanism to the spindle shaft of the machine tool after horizontally rotating the tool.

Abstract: In a bidirectional driving mechanism comprising a rack, two pinions meshing with the rack, and gear trains through which power is transmitted respectively to the pinions from a common driving source, at least one gear of the gear train is formed as a ring gear and a plurality of variable volume oil chambers containing pressurized oil are formed between the ring gear and the shaft thereof so that driving torque is transmitted from the ring gear to the gear shaft through the oil chambers.