Telescopic driving mechanism

The utility model discloses a telescopic driving mechanism which comprises a hollow fixing cylinder with one end open, a driving seat used for being connected with a mechanical arm is movably arranged in the fixing cylinder, a rack and a plurality of guide rods are arranged on the inner side wall of the fixing cylinder in the extending direction, and the driving seat is arranged on the guide rods in a sliding and sleeved mode at the same time. A driving motor is arranged on the driving seat, a gear is arranged on a rotating shaft of the driving motor, the gear is meshed with the rack, the driving seat is provided with a limiting mechanism, and the mechanical arm and the driving motor are both electrically connected with the controller; according to the scheme, the mechanical arm can be fed from the flushing hole position through the driving base, the high-pressure spray head at the front end of the mechanical arm is close to the back face of the cutter head, and therefore kinetic energy loss of the high-press