Geometrical instruments – Straight-line light ray type – Level
Patent
1977-03-15
1979-04-17
Stephan, Steven L.
Geometrical instruments
Straight-line light ray type
Level
356249, G01C 500, G01C 918
Patent
active
041493214
ABSTRACT:
These three new types of leveling instruments do not rely on spirit-level-bubbles in glass vials used in dumpy-levels and in tilting-levels, nor on the so called self-leveling pendulums used in the automatic levels. These new types of leveling instruments use a free mercury surface as a mirror to assure that the line of sight through the center of the cross hairs is horizontal, or has a very small but constant inclination from the true horizontal for all pointings to the leveling rods. In the most precise model, the mercury surface is used to autocollimate the line of sight through the center of cross hairs to be horizontal for every pointing. In the less elaborate models, the mercury surface is used to guarantee that the line of sight through the center of cross hairs has only a very small but constant inclination with the true horizontal. It is important that this inclination stays constant, and it can be adjusted to be less than one tenth of one second of arc if so desired. The mercury levels itself correctly with great precision and consistency, and it has a superior performance if compared to hanging pendulums with friction, or to bubbles with surface tension in level vials, and therefore using mercury as described in this disclosure in leveling instruments will produce better leveling instruments.
REFERENCES:
patent: 921773 (1909-05-01), Wild
patent: 1089480 (1914-03-01), Korrodi
patent: 3807869 (1974-04-01), Hartley
patent: 3905707 (1975-09-01), Feist et al.
patent: 3910704 (1975-10-01), Richarme
patent: 3918813 (1975-11-01), Rossiter
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