Borehole deformation gage

Claim 2

In a borehole deformation gauge having LVDT transducers positioned in a substantially tubular casing in alignment with different longitudinal planes radiating from a longitudinal axis of the casing, and having contacts interconnecting with the LVDT transducers for measuring deformation acting along different radial lines within a borehole, the improvement comprising: a plurality of pivotally mounted cantilever arms positioned within the casing, a plurality of contact means arranged in alignment with a single plane perpendicular to the longitudinal axis, each contact means extending through the casing and positioned for interconnecting a small area of a borehole wall with one of the plurality of cantilever arms for pivoting the one arm toward and away from the longitudinal axis when deformation of the borehole occurs, a plurality of LVDT transducers positioned within the casing and spaced from one another in the direction of the longitudinal axis, each transducer including a relatively movable coil and core, and means interconnecting each LVDT transducer with a cantilever arm for relative movement between the coil and core of the transducer when the cantilever arm is pivoted in response to deformation.

Claim 3

A borehole deformation gauge as claimed in claim 1 in which: each contact means contacts the one of the plurality of cantilever arms at a distance from a fulcrum plane of the cantilever arm which has the same proportional relationship to the total effective length of the cantilever arm for all cantilever arms and contact means, and the fulcrum planes of at least two cantilever arms are displaced from one another in the direction of the longitudinal axis.

Claim 4

A borehole deformation gauge as claimed in claim 2 in which: the coil and core of each LVDT transducer are each independently connected to different cantilever arms which have a common fulcrum plane and are positioned on opposite sides of the longitUdinal axis in alignment with a single longitudinal plane extending through the axis.

Claim 5

In a borehole deformation gauge having LVDT transducers positioned in a substantially tubular casing, and having external contacts interconnecting with the LVDT transducers for measuring deformation within a borehole, the improvement comprising a sensing element including: a rigid support having a longitudinal axis, a plurality of cantilever arms arranged in an arcuate array, each arm fixed at one end to the support and extending outward from a fulcrum plane on the support in a direction substantially parallel to the longitudinal axis with the fulcrum planes of at least two cantilever arms displaced from one another along the longitudinal axis, a plurality of LVDT transducers mounted substantially within the arc defined by the plurality of cantilever arms and spaced in the direction of the longitudinal axis, each transducer including a relatively movable coil and core, means for relatively moving the coils and cores of the LVDT transducers in response to flexing movement of the cantilever arms, and a plurality of contact means arranged in an arcuate array in alignment with a single plane perpendicular to the longitudinal axis, each contact means connecting with a distinct location on a cantilever arm for flexing the arm in response to an external deformation, the distance of the distinct location on a cantilever arm from the fulcrum plane of the arm having the same proportional relationship to the total effective length of the arm for all cantilever arms, whereby a mechanical deformation affecting a contact means produces the same effect in the associated LVDT transducer, regardless of the length of the cantilever arm through which the stimulus is transmitted.

Claim 6

In a borehole deformation gauge having LVDT transducers positioned in a substantially tubular casing, and having external contacts interconnecting with the LVDT transducers for measuring deformation within a borehole, the improvement comprising a sensing element including: a rigid support having a longitudinal axis, a plurality of cantilever arms arranged in an arcuate array, each arm fixed at one end to the support and extending outward from a fulcrum plane on the support in a direction substantially parallel to the longitudinal axis with the fulcrum planes of at least two cantilever arms displaced from one another along the longitudinal axis, a plurality of LVDT transducers mounted substantially within the arc defined by the plurality of cantilever arms and spaced in the direction of the longitudinal axis, each transducer including a relatively movable coil and core, means for relatively moving the coils and cores of the LVDT transducers in response to flexing movement of the cantilever arms, and a plurality of contact means arranged in an arcuate array in alignment with a single plane perpendicular to the longitudinal axis, each contact means connecting with a distinct location on a cantilever arm for flexing the arm in response to an external deformation, the distance of the distinct location on a cantilever arm from the fulcrum plane of the arm having the same proportional relationship to the total effective length of the arm for all cantilever arms, whereby a mechanical deformation affecting a contact means produces the same effect in the associated LVDT transducer, regardless of the length of the cantilever arm through which the stimulus is transmitted.

Claim 7

A sensing element as claimed in claim 4 in which: the coil of at least one LVDT transducer is fixed relative to the rigid support, and the core is connected to move with a cantilever arm for movement of the core relative to the coil as the cantilever arm flexes.

Claim 8

A sensing element as claimed in claim 4 in which: the core of at least one LVDT transducer is fixed relative to the rigid support and the coil is connected to move with a cantilever arm for movement of the coil relative to the core as the cantilever arm flexes.

Claim 9

A sensing element as claimed in claim 4 in which: the coil of at least one LVDT transducer is connected to one cantilever arm and the core of the same transducer is connected to another cantilever arm aligned in the same plane with the one arm and the longitudinal axis, with the longitudinal axis extending between the one and the other cantilever arms.