| 摘要 |
PCT No. PCT/NO90/00164 Sec. 371 Date May 6, 1992 Sec. 102(e) Date May 6, 1992 PCT Filed Oct. 31, 1990 PCT Pub. No. WO91/07566 PCT Pub. Date May 30, 1991.A pressure converter for a drill pipe includes a housing with a header channel therein which is in communication with a drill bit, a drive unit which is driven by a driving drilling fluid flow of the drill pipe, a valve which is operatively connected to and moved by the drive unit, a piston which moves in a reciprocating manner thereby creating a pressure stroke and a return stroke, and a check valve through which a portion of the drilling fluid flow is discharged to the drill bit via the header channel. The reciprocating movement of the piston is controlled by the valve and the piston includes a first piston area which is subjected to the driving drilling fluid flow during the pressure stroke and which is in communication with a returning drilling fluid flow running outside the drill pipe, a second piston area which is opposite the first piston area and which is in communication, during the pressure stroke and the return stroke, with the returning drilling fluid flow, and a third piston area which is opposite to and smaller than the first piston area, and which 1) during the pressure stroke, generates an increased pressure in a portion of the driving drilling fluid flow, and 2) is in communication with the driving drilling fluid flow during the return stroke. The increased pressure portion of the driving drilling fluid flow is discharged via the first check valve and the header channel to the drill bit.
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