This invention relates to a self-leveling device used, for example, to provide a level surface to support a laser or other light source for construction or other purposes.
Electronic levels for use e.g. in carpentry and construction are well known; examples are shown in U.S. Pat. No. 4,912,662 issued to Butler, et al., U.S. Pat. No. 5,313,713 issued to Charles E. Heger, et al., U.S. Pat. No. 5,083,383 issued to Charles E. Heger, and U.S. Pat. No. 5,259,118 issued to Charles E. Heger, all incorporated by reference. Also, projecting a level line on a vertical surface may be provided by emitting a leveled plane of light from a laser. The laser light may be leveled (relative to the Earth's gravity) by positioning, calibrating and adjusting the laser's orientation. Some levels project a level line by attaching a laser line generator to the shaft of a pendulum. Some levels provide a level line by floating a laser line generator on a liquid. Alternatively, some levels provide a level line by placing a laser light generator on a level surface. These surfaces may be leveled by requiring a user to manually adjust the orientation of the surface until a pair of bubbles (as in a conventional bubble level) is properly aligned. Other levels provide a level surface by using fluid sensors that provide signals to control leveling motors.
However, it has been found by the present inventor that such approaches to provide a level surface to support the laser line generator require costly sensors, demand user interactions or utilize liquids. There is a need for a better automatic electronic sensor for electronic levels.