STEP-BY-STEP TRAVEL HYDRAULIC DRIVE Russian patent published in 2003 - IPC

FIELD: construction and repair of oil mains. SUBSTANCE: invention provides traveling of earth-moving, cleaning and isolating equipment along oil mains. Proposed step-by-step travel hydraulic drive of earth-moving machine along line contains two hydraulic cylinders secured on machine housing coaxially to pipeline whose rods are provided with units for longitudinal thrusting against pipeline. Rod spaces of hydraulic cylinders are interconnected by bypass main line with make-up unit from pressure main line. Hydraulic cylinders are furnished with hydraulic selector for alternate connection of piston spaces with pressure and drain main lines operated from machine step completion sensors. Makeup unit is made in form of check valve and restrictor connecting bypass main line with pressure main line and installed in series and connected with drain line by excess pressure valve. Make-up unit can be coupled with pressure main line through one of outlet channels of said hydraulic selector. EFFECT: facilitated operation of hydraulic drive, increased efficiency and reliability under automatic conditions. 2 cl, 1 dwg