Drilling unit with automatic drill shaft feeding, and method and means thereto

Means for changing a drill shaft rotation velocity of a gearbox in a drilling unit, wherein:

• said gear box is provided with an output axle and an input axle;
• a cassette is provided which comprises at least two meshed gearings with a certain gear ratio;
• said cassette has one input axle and one output axle each connected to one of said gearings;
• said cassette is detachably mounted on an outside of said gearbox;
• and
• said cassette further comprises interconnecting means for connecting said input axle and said output axle thereof to said output axle and said input axle of said gearbox, respectively, for adapting a total gear ratio of said gearbox to different unit applications.

A drilling unit comprising:

• a motor;
• a drilling shaft;
• and
• a gear box coupling the motor to the drilling shaft;
• wherein the gearbox comprises an output axle and an input axle;
• wherein a gearing cassette is mounted to an outside of the gearbox;
• wherein said gearing cassette comprises a gearing with a certain gear ratio and is arranged to connect said output axle to said input axle;
• and
• wherein said gearing cassette comprises one of a number of exchangeable gearing cassettes with different gear ratios for adapting a total gear ratio of the gearbox to different unit applications.