HYDRAULIC CENTRALIZER Russian patent published in 1995 - IPC

FIELD: mining industry. SUBSTANCE: hydraulic centralizer has: hollow body 1; radial canals, made in body walls; U-shaped form pushers, located in the canals; rollers 11, located on U-shaped form pushers horizontal axes 10. Being in initial position rollers 11 are sunk in the body 1 and during contact with borehole walls in operational position are protruded beyond limits of body 1 by value, that does not exceeds half of rollers 11 diameter. Radial canals are made at different level of body 1 and with angular shift in respect to each other along helical line of body. Bush 14 is located in cavity of body 1. Spring-loaded ring-type piston 17 is mounted between the bush and body 1. In the case cavity 16 between bush 14 and body 1 is filled with lubricant 19. During pressure increase in axial canal 2 of body 1 helical piston 17, pressing spring 18, is going upward and increases pressure in cavity 16. As a result of it pushers are pressing roller 11 to borehole walls and so rigid centering of drilling string lower part is exercised in transverse section. In process of borehole becoming deeper rollers 11 are rolling on walls of borehole, normalize bore hole and make up for bottom hole engine reactive force moment. During pressure decrease in string space spring 18 shifts ring-type piston 17 downward, pressure in cavity 16 also decreases and pushers with rollers 11 are sinking in radial canals. EFFECT: hydraulic centralizer is used for centering of borehole drilling strings. 2 cl, 3 dwg