Importance

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Abstract

A valve means to be installed in a string of drill pipe above a bottom hole positive displacement motor comprises a hollow housing (1) having an inlet and an outlet for the passage of a drilling fluid therethrough, the wall of the housing having through holes (4) to communicate the interior of the housing with the annular space of the well bore. Secured in the housing (1) substantially above the through holes is a transverse plate or partition (5) provided with a plurality of calibrated openings (6) intended to produce a pressure drop. The housing (1) further accommodates a chamber (7) communicating with the through holes (4) and provided with an open face in the upper portion thereof, the chamber (7) being arranged such that through passages (10) are formed between the chamber (7) and the housing (1). The housing further comprises a sealing couple (12) intended to prevent the through holes (4) from communicating with the interior of the housing (1) in the course of drilling operation. A valve seat (13) of the couple is adapted to fit the circumference of the open face in the upper portion of the chamber (7), whereas a spring-loaded valve element (14) of the couple is capable of being moved axially under the action of the pressure drop, the valve element having a tail-piece (15) the end of which is adapted at least to level with the upper surface of the partition (5).

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First Claim