WELL REAMER Russian patent published in 2007 - IPC E21B7/28 

FIELD: drilling equipment, particularly devices for well diameter increase within predetermined interval.

SUBSTANCE: well reamer comprises body with central channel and inclined slots adapted to receive legs with teeth. Spring-loaded rod with annular piston is arranged in central body channel. Annular piston has orifices, which communicate central channel with over-piston cavity. Longitudinal channels are made in the body. Reciprocating bars are installed in the channels. The bars have longitudinal channels for leg flushing and are adapted to transmit piston force to legs during leg projection in working position. Bars are cylindrical and provided with flats mating inclined slots of the body. The bars are restricted from rotation about geometrical axes thereof with fixers made as segmented plates installed at lower ends thereof. Outer annular extension is made on the rod to support rod spring. Hooks to be inserted in radial orifices of legs and used for leg movement in transport position after well reaming operation termination are built in annular extension.

EFFECT: increased working ability.

3 cl, 4 dwg