Flow restrictor valve for a downhole drilling assembly

Abstract

An improved drilling assembly of the type comprising a fluid driven motor, a driveshaft operatively connected with the motor, a housing for enclosing the driveshaft and an annular flow passage defined between the driveshaft and the housing for circulating drive fluid therethrough. The improvement comprises a drive fluid flow restrictor device comprising a constricted section in the annular flow passage, an expanded section in the annular flow passage and a valve member positioned in the annular flow passage. The valve member is movable axially in the annular flow passage between the constricted section and the expanded section to define a flow restricting position and a normal flow position When the valve member is in the flow restricting position the circulation of drive fluid through the annular flow passage is restricted. When the valve member is in the normal flow position the circulation of drive fluid through the annular flow passage is relatively unrestricted.

Dependencies are inferred from the claim text.