Device, preferably for underground purposes, to transfer information out of a drilling hole

A choker valve assembly for a target drill rod, said drill rod having an outer pipe, an inner pipe within said outer pipe and measuring means in said outer pipe for measuring functions of said drill rod, said measuring means having channels for transmitting hydraulic signals in response to the measurement data, said inner pipe having wall means for defining a flushing fluid passage axially through which flushing fluid flows in a predetermined direction, said valve assembly comprising:

• means defining a tapered restriction portion of said wall means;
• a valve housing within said passage axially spaced from said restriction portion;
• connecting means for non-rotatably connecting said housing to said wall of said inner pipe;
• a valve element supported by said housing and displaceable axially in said passage;
• drive means for causing axial movement of said valve element in response to said hydraulic signals;
• a first streamlined cap on one end of said valve element facing the direction of flushing fluid flow, said cap extending outside the perimeter of said housing;
• and
• a second streamlined cap on a second end of said valve element facing away from the direction of flushing fluid flow of said second cap positioned within the perimeter of said housing.