Fluidic mud pulse data transmission apparatus

Telemetry apparatus for transmitting data from sensors to the surface during the drilling of a bore hole by generating pressure pulses in a drilling fluid in a drill string, the apparatus comprising:

• a vortex valve means, having a vortex chamber which includes radial main inlet ports through which a first portion of said drilling fluid flows, tangential control inlet ports, and an axial outlet, to create a vortex flow in said vortex chamber and thus a high resistance to flow from said inlets to said outlet when fluid is supplied to said control ports and to create substantially radial flow in said vortex chamber and thus a low flow resistance when no fluid is supplied to said control ports;
• and
• a fluidic feedback oscillator having a power jet supplied by a second portion of said drilling fluid, said oscillator including a first output channel connected to said control inlet ports, a second output channel connected to discharge fluid downstream of said vortex valve, and a means to control the frequency of oscillation of said oscillator in response to signals from said sensors;
• whereby pressure pulses are generated in said drilling fluid in said drill string at a frequency corresponding to the frequency of oscillation of said oscillator and are communicated to the surface.