专利名称：Method and apparatus for improving the
efficiency of a positive displacement motorfor drilling and oil or gas well
发明人：Robert W. Evans申请号：US13787951申请日：20130307公开号：US09255456B2公开日：20160209
专利附图：
摘要：A method and apparatus for improving the efficiency of a drill string thatincludes drilling pipe, a dump valve, a positive displacement motor and a rotary drill bit
driven by the motor utilize a dump valve that does not depend upon a pressure loss tomaintain the dump valve in a position which closes communication between the drillingstring and the annulus between the drilling string and the well bore or casing. The dumpvalve includes a flow sleeve that is axially moved to close outlet passages to the annulusby the flow of fluid through the outlet passages rather than a pressure drop across theflow sleeve.
申请人：Robert W. Evans
地址：Montgomery TX US
国籍：US
代理机构：Tumey L.L.P.
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