Drilling signalling system

1. A pressure pulse generator for use in transmitting pressure signals to surface in a fluid-based drilling system, said generator being arranged in use in the path of a pressurized fluid to operate a drilling assembly and being capable of being actuated to generate pressure signals in such fluid for transmission to surface pressure monitoring equipment, in which the pulse generator comprises:

a housing positionable in the path of the supply of pressurized fluid, said housing having an inlet anangement for admitting a portion of the fluid to the interior of the housing, and an outlet arrangement for discharging fluid from the interior of the housing for supply of the drilling assembly;

a control element slidably mounted in the housing for movement between an open and a closed position with respect to said inlet anangement, said control element being operative to generate a pressure pulse in the supply of pressure fluid when the control element takes-up the closed position;

a control passage extending through the control elements and closable by a pilot valve element arranged to be exposed to the pressure of the fluid in the passage; and

an actuator coupled with the valve element and operative, when the pressure generator is activated to generate a pressure signal, to move the valve element to a position closing said passage and thereby to cause movement of the control element towards the closed position;

in which the coupling between the actuator and the valve element includes a yieldable biasing element which provides control of the amplitude of the pressure signals produced by the generator.

2. A pressure pulse generator according to claim 1 , in which the biasing element comprises a spring anangement.

3. A pressure pulse generator for use in transmitting pressure signals to surface in a fluid-based drilling system, said generator being arranged in use in the path of a pressurized fluid to operate a drilling assembly and being capable of being actuated to generate pressure signals in such fluid for transmission to surface pressure monitoring equipment, in which the pulse generator comprises:

a housing positionable in the path of the supply of pressurized fluid, said housing having an inlet arrangement for admitting a portion of the fluid to the interior of the housing, and an outlet anangement for discharging fluid from the interior of the housing for supply of the drilling assembly;

a control element slidably mounted in the housing for movement between an open and a closed position with respect to said inlet arrangement, said control element being operative to generate a pressure pulse in the supply of pressure fluid when the control element takes-up the closed position;

a control passage extending through the control elements and closable by a pilot valve element ananged to be exposed to the pressure of the fluid in the passage; and

an actuator coupled with the valve element and operative, when the pressure generator is activated to generate a pressure signal, to move the valve element to a position closing said passage and thereby to cause movement of the control element towards the closed position;

in which the coupling between the actuator and the valve element includes a yieldable biasing element which provides control of the amplitude of the pressure signals produced by the generator, in which the biassing element comprises a floating piston assembly incorporated within an actuator link between the actuator and the valve element.

4. A pressure pulse generator according to claim 1 in which the inlet anangement comprises a ring mounted internally of the housing at an upstream end thereof, and which defines a restricted inlet passage with the valve element.

5. A pressure pulse generator according to claim 4 , in which a set of rings is provided, having different internal bores, and selectable for use according to by-pass requirements.

6. A pressure pulse generator according to claim 4 , in which the ring includes at least one by-pass port.

7. A pressure pulse generator according to claim 1 , in which the actuator comprises an electromagnetic actuator, and the coupling comprises a first actuator shaft connected to the actuator a second actuator shaft connected to the valve element, and with said yieldable biasing element located between first actuator shaft and the second actuator shaft.

8. A pressure pulse generator according to claim 3 in which the inlet arrangement comprises a ring mounted internally of the housing at an upstream end thereof, and which defines a restricted inlet passage with the valve element.

9. A pressure pulse generator according to claim 8 , in which a set of rings is provided, having different internal bores, and selectable for use according to by-pass requirements.

10. A pressure pulse generator according to claim 8 , in which the ring includes at least one by-pass port.

11. A pressure pulse generator according to claim 3 , in which the actuator comprises an electromagnetic actuator, and the coupling comprises a first actuator shaft connected to the actuator a second actuator shaft connected to the valve element, and with said yieldable biasing element located between first actuator shaft and the second actuator shaft.