Apparatus for signalling within a borehole while drilling
First Claim
1. A down-hole signal transmitter for a mud-pulse telemetry system, comprising a flow constrictor defining a throttle orifice for the mud flow passing along a drill string, a throttling member displaceable with respect to the throttle orifice to vary the throughflow cross-section of the throttle orifice, a pump for displacing the throttling member against the mud flow, and valve means switchable between a first state in which the throttling member is displaceable by the output pressure of the pump against the mud flow and a second state in which said output pressure is relieved so as to enable the throttling member to be moved in the direction of the mud flow by the pressure of the mud flow acting on the throttling member, whereby the pressure of the mud flow may be modulated, wherein the valve means comprises a hydraulic amplifier incorporating a main, pressure relief valve and a subsidiary, control valve for controlling a main flow of fluid through the main valve by acting on a subsidiary flow of fluid of relatively low magnitude, the pressure relief valve being adapted to open when the control valve is opened and comprising a spring-biased valve member having a bore extending therethrough for the subsidiary flow of fluid towards the control valve, and the valve member being movable by pressure of fluid acting against the spring force when the control valve is opened, to open the pressure relief valve.
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Accused Products
Abstract
A down-hole signal transmitter for a mud pulse telemetry system comprises a flow constrictor defining a throttle orifice for the mud flow, a throttling member displaceable to vary the throughflow cross-section of the throttle orifice, and a pump for displacing the throttling member against the mud flow in order to modulate the mud flow. The displacement of the throttling member is controlled by a hydraulic amplifier, comprising a main pressure relief valve and a subsidiary control valve, and a solenoid to which the output signal of a measuring instrument is supplied. When the main valve is close, the pump displaces a ram, coupled to the throttling member, upwardly. However, when the signal supplied to the solenoid is such as to magnetically attract an armature, the control valve is opened to conduct a small flow of oil between the pump input and the pump output, and this in turn causes the main valve to open thus conducting a much larger flow of oil from the pump input to the pump output and allowing the throttling member to be displaced downwardly by the pressure of the mud flow. The power required to modulate the mud flow with this arrangement is very low and is easily provided by a down-hole electrical generator.
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Citations
16 Claims
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1. A down-hole signal transmitter for a mud-pulse telemetry system, comprising a flow constrictor defining a throttle orifice for the mud flow passing along a drill string, a throttling member displaceable with respect to the throttle orifice to vary the throughflow cross-section of the throttle orifice, a pump for displacing the throttling member against the mud flow, and valve means switchable between a first state in which the throttling member is displaceable by the output pressure of the pump against the mud flow and a second state in which said output pressure is relieved so as to enable the throttling member to be moved in the direction of the mud flow by the pressure of the mud flow acting on the throttling member, whereby the pressure of the mud flow may be modulated, wherein the valve means comprises a hydraulic amplifier incorporating a main, pressure relief valve and a subsidiary, control valve for controlling a main flow of fluid through the main valve by acting on a subsidiary flow of fluid of relatively low magnitude, the pressure relief valve being adapted to open when the control valve is opened and comprising a spring-biased valve member having a bore extending therethrough for the subsidiary flow of fluid towards the control valve, and the valve member being movable by pressure of fluid acting against the spring force when the control valve is opened, to open the pressure relief valve.
- 2. A down-hole signal transmitter for a mud-pulse telemetry system, comprising a flow constrictor defining a throttle orifice for the mud flow passing along a drill string, a throttling member displaceable with respect to the throttle orifice to vary the throughflow cross-section of the throttle orifice, and control means for displacing the throttling member to modulate the mud pressure, wherein the control means is disposed in a mud-free environment within a mud pulse telemetry tool, and incorporates a pump for displacing the throttling member aginst the mud flow, and change-over means switchable between a first state in which the output pressure of the pump is applied to the throttling member so as to displace the throttling member against the mud flow and a second state in which the pressure applied to the throttling member is relieved so as to enable the throttling member to be moved in the direction of the mud flow by a pressure of the mud flow acting on the throttling member and without application of output pressure from the pump in said direction, whereby the pressure of the mud flow may be modulated.
Specification