MAGNETIC CATCHER Russian patent published in 1995 - IPC

FIELD: well drilling equipment. SUBSTANCE: magnetic catcher has magnetic system which includes central magnetic circuit, external magnetic circuit made of magnetically soft material, and permanent magnets with radially directed magnetic texture. Height of permanent magnets in direction of magnetic texture is determined by relation h=KD, where D is external diameter of catcher body, mm; K is coefficient depending on magnet material, K= 0.15-0.17 provided condition _мH_c≥ 0,5B_r/μ_o is observed, where _мH_c is coercive force of permanent magnets in magnetizing A/m; B_r is residual induction; T; μ_o is magnetic permeability of vacuum μ_o=4π·10^-7 H/m. External surface of permanent magnets is made in form of regular prism whose face number n satisfies relation 5≅ n≅ 12, and flushing channels are made in external magnetic circuit. Number of flushing channels corresponds to the number of faces of permanent magnetic system. EFFECT: higher efficiency in catching ferromagnetic particles, broken pieces of tool and hard alloy teeth of cones with simultaneous increase of load lifting capacity. 3 cl, 3 dwg