Head assembly for multiposition borehole extensometer
AssigneeThe United States of America as represented by the United States Department of Energy
InventorDonald N. Frank
Life of this patent
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Abstract
A head assembly for a borehole extensometer and an improved extensometer for measuring subsurface subsidence. A plurality of inflatable anchors provide discrete measurement points. A metering rod is fixed to each of the anchors which are displaced when subsidence occurs, thereby translating the attached rod. The head assembly includes a sprocket wheel rotatably mounted on a standpipe and engaged by a chain which is connected at one end to the metering rod and at the other end to a counterweight. A second sprocket wheel connected to the standpipe also engages the chain and drives a connected potentiometer. The head assembly converts the linear displacement of the metering rod to the rotary motion of the second sprocket wheel, which is measured by the potentiometer, producing a continuous electrical output.
Claims7
A head assembly for a borehole extensometer, comprising:
- a vertical hollow standpipe;
- a first sprocket wheel rotatably mounted to the standpipe;
- a chain passing over and engaging the first sprocket wheel;
- a member movably mounted to the standpipe;
- a second sprocket wheel rotatably mounted to the member;
- means connected to the standpipe and to the member for maintaining the second sprocket wheel in engagement with the chain;
- and
- a potentiometer connected to and driven by the second sprocket wheel.
A borehole extensometer for measuring ground subsidence around a borehole in an earth formation, comprising:
- a casing embedded in the borehole at the top of the borehole;
- a conduit aligned with and extending down the borehole;
- a radially expandable anchor mounted to the conduit and adapted to be firmly fixed at a position in the earth formation;
- a metering rod aligned with and extending down the conduit in the borehole, the metering rod being connected at its lower end to the anchor;
- a vertical hollow standpipe mounted to the casing and connected to the conduit;
- a first sprocket wheel rotatably mounted to the standpipe;
- a chain passing over and engaging the first sprocket wheel, the chain being connected at one end to the top of the metering rod;
- a counterweight attached to the opposite end of the chain;
- a member movably mounted to the standpipe;
- a second sprocket wheel rotatably mounted to the member;
- means connected to the standpipe and the member for maintaining the second sprocket wheel in engagement with the chain;
- and
- a potentiometer connected to and driven by the second sprocket wheel.
Dependencies are inferred from the claim text.