Downhole pressure and/or temperature gauges

In an assembly for monitoring over a required time period down-hole pressure or temperature parameters in an oil or gas well or other remote location accessible only along a narrow bore,

• means defining a sensing element of helical form having a longitudinal axis and two further axes each orthogonal to the longitudinal axis the helical sensing element being subject to angular motion in the direction of the longitudinal axis,
• chart means for recording the said changes in the parameter sensed by the helical sensing element and converted to said angular deflection,
• elongate shaft means coupling the helical sensing element and the chart recording means,
• means for supporting the elongate shaft means at spaced locations along the length of the elongate shaft means, the supporting means including
• an elongate housing, and
• bearing means interposed between the internal housing wall and the elongate shaft means at each of said spaced locations, and
• a selective motion transmitting device interposed along the length of the elongate shaft coupling means, said motion transmitting device exhibiting torsional rigidity such that the angular deflection of the sensing element is transmitted with high precision to the chart recording means while any motion in the direction of said longitudinal axis of the helical sensing element resultant from the parameter being monitored is accommodated by the selective motion transmitting device substantially without transmission of motion along said longitudinal axis to the recording means,
• the assembly serving to record over a predetermined time period the parameter sensed by the said helical sensing element substantially without error resultant from the effect of the said motion of the sensing element in the direction of the longitudinal axis of the helical sensing element.

In an assembly for continuously monitoring over a required period of time down-hole pressure or temperature parameters in an oil or gas well or other remote location accessible only along a narrow passageway,

• a helical Bourdon tube having a longitudinal axis and two further axes each orthogonal to the longitudinal axis, the Bourdon tube being subject to angular deflection over a limited range in response to any change in the parameter being measured and motion in the direction of the longitudinal axis,
• stylus and chart means for recording on a continuous basis the said changes in the parameter sensed by the Bourdon tube,
• an elongate two-part shaft for coupling the Bourdon tube and the stylus,
• means for supporting the elongate shaft at spaced locations along the length of the elongate shaft, the supporting means including
• an elongate hollow, cylindrical housing,
• bearings spaced along the length of the shaft and mounted on the inner wall of the housing, and
• a selective motion transmitting device interposed between the two parts of the shaft, said selective motion-transmitting device exhibiting torsional rigidity such that the angular deflection of the Bourdon tube is transmitted with high precision to the stylus while any motion of the Bourdon tube in the direction of said longitudinal axis is accommodated by the motion-transmitting device substantially without transmission of the axial motion in the direction of the longitudinal axis to the stylus,
• the assembly serving to record over a predetermined time period the parameter sensed by the Bourdon tube substantially without error resultant from the effect of the motion of the Bourdon tube in the direction of the longitudinal axis of the Bourdon tube.