Geometrical instruments – Area integrators – Electrical
Patent
1975-05-29
1977-01-11
Phillips, Charles E.
Geometrical instruments
Area integrators
Electrical
33 1H, 73 88E, G01B 500
Patent
active
040019420
ABSTRACT:
A rod extensometer which can be inserted into a hole drilled into the roof or floor of an underground excavation to monitor the shifting of material surrounding the excavation. The extensometer has a head which is anchored in the inner end portion of the hole by a hardened synthetic plastic substance, an annular section which is inserted into the outer end portion of the hole and is bonded to surrounding material, and a set of interconnected coaxial cylindrical rods one of which is rigid with the head and another of which extends through the annular section. Changes in distance between the outer end of the other rod and the annular section are indicative of movement of material surrounding the inner end portion of the hole relative to material surrounding the outer end portion of the hole and/or vice versa. The head has an externally threaded member which is bonded to the surrounding material and a blade-like or conical breaker member located forwardly of the externally threaded member and serving to break a cartridge which contains separate supplies of a hardenable synthetic plastic bonding substance and a hardening agent for such substance. The annular section of the extensometer has a nut and washer which abuts against the exposed surface of material bounding the outer end portion of the hole, and the outer end of the other rod has flats which can be engaged by a torque transmitting device serving to rotate the rods and the head. Two identical or dissimilar extensometers can be installed in two coaxial holes to facilitate additional measurements, such as changes in the distance between the two heads, changes in the distance between the two nuts, as well as changes in the distance between each head and the respective nut.
REFERENCES:
patent: 3404460 (1968-10-01), Livingston et al.
patent: 3885423 (1975-05-01), Schuermann et al.
Boddicker Horst
Muller Herbert
Schuermann Fritz
Bergwerksverband GmbH
Phillips Charles E.
Striker Michael J.
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