Such oscillatingly driven machine tools are known in various designs. They are driven by means of a mechanical oscillatory gear transforming the rotating drive motion of a drive motor into a rotary oscillatory drive motion of the tool spindle about its longitudinal axis.
According to EP 1 428 625 A1 to this end an eccentric is provided which works together with an eccentric fork for oscillatingly driving the tool spindle. The eccentric is driven rotatingly by an eccentric shaft which is mounted in parallel to the tool spindle.
According to EP 2 283 979 A1 an oscillatingly driven machine tool comprises a drive motor with a motor shaft as well as a tool spindle which is rotatingly oscillatingly driven about its longitudinal axis, wherein a coupling element rotatingly driven by the motor shaft and comprising a closed guide surface circulating about a guide axis, wherein the guide surface is coupled by means of transfer means to at least one entrainer for driving the latter, wherein the at least one entrainer is held movably with respect to the work spindle and engaging within a circumferential region of the work spindle for driving the latter rotatingly oscillatingly.
Such mechanical oscillatory gears are known in various embodiments, for transferring the rotating drive motion of a motor shaft into the rotatingly oscillatingly movement of the tool spindle.
Due to the constantly increasing demands for the performance of oscillatory tools herein high demands are present with respect to the mechanical oscillatory gears. These are subject to a high mechanical load due to the oscillatory load and therefore may be subject to wear in long-time operation. In case of high load also the noise generation increases. Finally the oscillatory gears lead to more or less vibrations depending on the load which partially is sensed disadvantageously by the user.