OVERFLOW VALVE Russian patent published in 1995 - IPC

FIELD: drilling equipment. SUBSTANCE: overflow valve includes body with radial holes, seat installed in body and having conical and axial peripheral channels and elastic collar installed for overlapping seat peripheral channels. Valve has bushing located in body under seat to form closed circular space, and filter separating circular space into two concentric parts to prevent large rock cuttings from getting on seat working surface. Seat periphery holes are communicated with part of circular space formed by outer surface of bushing and filter inner surface. Body radial holes are communicated with circular space part formed by inner surface of body and filter outer surface in the upper and lower parts. EFFECT: higher efficiency. 2 cl, 1 dwg