Drive arrangement in a pneumatic power tool

A drive arrangement in a pneumatic power tool which includes a pneumatic motor, said drive arrangement comprising:

• a spindle for mounting a cutting element, said spindle being drivingly connected to said pneumatic motor and said spindle externally including a thread and an axial groove;
• a drive gear for driving a drive rotation of said spindle, said drive gear being engaged with the axial groove on said spindle and being drivingly connected to the pneumatic motor so as to rotate at a constant rotational speed with respect to a motor output shaft;
• and
• a feed gear threaded upon said spindle, said feed gear being rotatable with respect to the spindle to advance and retract said spindle, and said feed gear being driven by an intermediate feed gear which is interchangeably drivingly connectable to the pneumatic motor via a first and a second gear connection, respectively;
• wherein the intermediate feed gear is arranged to drive the feed gear at a slightly higher rotational speed than the constant rotational speed of the drive gear so as to advance the spindle with respect to the feed gear in the first gear connection, and to drive the feed gear at a lower rotational speed than the constant rotational speed of the drive gear so as to retract the spindle with respect to the feed gear in the second gear connection, and
• wherein an intermediate drive gear is drivingly connected to the pneumatic motor and journalled around a first gear shaft to rotate freely with respect to the first gear shaft, said intermediate drive gear being in toothed engagement with the drive gear, and said intermediate feed gear being in toothed engagement with the feed gear and lodged to slide coaxially along said first gear shaft between a first gear position in which it is engaged to the first gear shaft and a second gear position in which it is engaged to the intermediate drive gear, and wherein the first and second gear position of the intermediate feed gear correspond to the first and second gear connection, respectively.