Apparatus for providing directional control of bore drilling equipment

1. An apparatus to provide directional control of bore drilling equipment, the apparatus comprising:

a hydraulic pump comprising an input shaft configured to receive an input torque from a drill pipe and configured to connect to a drilling head; and

a control arrangement configured to vary a rate of fluid flow through the hydraulic pump;

wherein the control arrangement comprises:

a closed loop oil-filled system comprising the hydraulic pump and a main valve, wherein, within the closed loop oil-filled system, an outlet of the hydraulic pump leads to the main valve and the main valve includes an exit pipe that leads to an inlet of the hydraulic pump; and

an orifice control system comprising a gearbox and an electrical generator, wherein the gearbox is configured to produce a mechanical output torque to control a position of the main valve in response to an input signal from a control processor, and wherein the electrical generator is current loaded from the output of the control processor.

2. The apparatus of claim 1 , wherein the orifice control system comprises a control valve provided in the closed loop system and connected to the main valve;

wherein the control valve is configured to control the position of the main valve.

3. The apparatus of claim 2 , wherein the control valve is configured to alter the position of the main valve based on a pressure variation across the control valve.

4. The apparatus of claim 3 ,

wherein the gearbox includes a mechanical input configured to be driven by the drill pipe, and a differential output that is configured to drive the electrical generator; and

wherein the mechanical output torque of the gearbox is configured to alter the pressure variation across the control valve.

5. The apparatus of claim 4 , wherein the mechanical output torque of the gearbox is proportional to an input/output differential torque of the gearbox.

6. The apparatus of claim 4 , wherein the gearbox is epicyclic in form.

7. The apparatus of claim 6 , wherein the control valve is a flap valve.

8. The apparatus of claim 4 , wherein the control processor is configured to produce an output that provides a load to the generator.

9. The apparatus of claim 2 , wherein the control valve is a ball valve.

10. The apparatus of claim 1 , wherein the main valve comprises a spool valve.

11. The apparatus of claim 1 , further comprising a roll sensor system configured to provide inputs to the control processor.

12. The apparatus of claim 1 , wherein the control processor is configured to calculate an output signal to limit drill bit torque and/or provide damping against stick-slip oscillations.

13. The apparatus of claim 1 , wherein the input shaft is configured to connect to the downhole end of the drill pipe via a rotatable joint; and

wherein the apparatus further comprises a downhole end that is configured to be coupled to a bottom hole assembly.

14. A method of providing directional control to a bore drilling arrangement, the method comprising:

providing a hydraulic pump, wherein a downstream end of the hydraulic pump is connected to a bottom hole assembly, and wherein an upstream input shaft of the hydraulic pump is indirectly coupled to a down hole end of a drill pipe;

providing a closed-loop oil system including: the hydraulic pump, a main valve through which oil is pumped before returning to the pump; and an orifice control system for varying the position of the main valve;

receiving inputs relating to the orientation and position of the bottom hole assembly and drill pipe into a control processor;

calculating an output signal with the control processor for limiting drill bit torque and/or to provide damping against stick slip oscillations;

feeding the output signal to the orifice control system;

driving a differential gearbox with the drill pipe;

driving an electrical generator with the gearbox; and

applying a mechanical output torque of the gearbox to a control valve of the orifice control system to alter the position of the main valve.

15. The method of claim 14 , wherein the control valve is connected to the main valve; and

wherein applying a mechanical output torque of the gearbox to the control valve further comprises:

altering a pressure variation across the control valve as a result of the mechanical output torque; and

altering the position of the main valve as a result of the altered pressure variation across the control valve.

16. The method of claim 14 , further comprising:

electrically converting the output signal to a proportional current sink; and

current loading the electrical generator with the proportional current sink.