accordance with fig2 fig5 the driving mechanism 30 consists of a case body 31 which is inserted in the bracket 11 of the truck 10 a motor 32 including an oil pressure motor an induction motor and the like which become the driving source the said driving source is secured at the end of rear side of this case body 31 a shaft 33 which a rotating drive is performed by a motor 32 in accordance with installing rotatably in the case body 31 and a differential gear mechanism 34 which is disposed within an expanding diameter portion 31a formed at the end of the rear side of the case body 31 the shaft 33 is disposed in concert with an axial center of the inside processing apparatus the said shaft 33 and an output axis 32a of the motor 32 are connected through a sleeve coupling 35 a gear portion 33a is formed in the end of rear side of the shaft 33 and this gear 33a is constituted as the sun gear 33a in the differential gear mechanism 34 also the rear mentioned working head 20 is arranged in the front side of the shaft 33 the differential gear mechanism 34 is constituted by the two planet gear mechanisms namely the first planet mechanism is constituted by an inner teeth gear 34a which is secured in the expanding diameter portion 31a a first planet gear 34b which engages with the sun gear 33a in company with a fact which engages with this inner teeth gear 34a and an outside sleeve 34c which installs firmly a shaft 34c 39 the said shaft 34c 39 supports this first planet gear 34b rotatably further the second planet gear mechanism is constituted by an inner teeth gear 34d which is disposed.