Subterranean drilling and slurry mining

A close coupled foot valve and eductor nozzle unit of a pipe strint comprising:

• an apertured foot valve seat defining a system pressure zone on one side and a cavity pressure zone on the other side thereof when said valve seat is closed;
• means defining a dash pot having a housing communicating with said system pressure zone, a centrally apertured foot valve plug on the lower end of said housing for substantially sealing said foot valve aperture when closed and resilient means normally urging said foot valve plug to its open position;
• means defining an eductor nozzle having a nozzle seat, a nozzle plug-piston unit, a nozzle cylinder means including a cylindrical bore for receiving said plug-piston unit and including a cylinder base having a transverse bore therein, and resilient means urging said plug-piston unit towards its nozzle closing position;
• and tubular conduit means concentric with and connected to said cylinder means and slidably receiving said dash pot housing, said tubular conduit means establishing flow communication between said cavity and one of said bores in said nozzle cylinder means when said valve is closed.

A close coupled foot valve and eductor nozzle unit of a pipe string comprising an apertured foot valve seat, means defining a system pressure zone in the pipe string subjected to variable system pressures and flow rates on one side of said seat, means defining a cavity pressure zone in the pipe string on the other side of said seat subject to pressure varying from slightly less than system pressure to cavity pressure depending upon flow rate and the position of the foot valve, a centrally apertured foot valve plug movable between an open position permitting flow of liquid through said valve seat and a closed position at least substantially terminating flow through said valve seat, a dash pot disposed in the system pressure zone and associated with said plug to reduce the rate of closure of said plug;

• said dash pot including a housing rigid with said valve plug and communicating with said system pressure zone through bleed passage defining means for allowing liquid to enter said housing, a tubular piston rod slidably received in said housing, a piston connected to said piston rod and disposed within said housing, resilient means disposed between a portion of said housing and said piston for urging said foot valve plug toward its open position, means defining a bleed passage extending from one side of said piston to the other which passage gradually decreased in size as the plug moves toward the closed position thereby maintaining a controlled closing rate in the face of increasing pressure drag across the foot valve;
• an eductor nozzle seat secured to the pipe string, an eductor nozzle cylinder rigidly secured to said seat, an eductor nozzle plug slidable in said eductor cylinder between open and closed positions, and resilient means disposed between said eductor nozzle cylinder and said eductor nozzle plug for urging said piston toward said closed position, said tubular piston rod establishing communication between said eductor nozzle cylinder and said cavity pressure zone when said foot valve is closed, a predetermined pressure drop across said foot valve being effective to close said foot valve thus creating a pressure differential between system pressure and cavity pressure that is sufficiently high to cause system pressure acting on the external surfaces of the eductor nozzle plug to open the eductor nozzle.