Abstract: A control for an excavator controls the position of the bucket cutting edge to a desired depth accurately by a calibrating laser receiving mounted on the excavator stick member and passed through a stationary laser plane wherever the stick is moved into or out of a trench. Linear position encoders monitor the length that the actuating cylinders are extended and lookup tables convert the encoder outputs to angle representations for determining the positions of the laser receiver and the cutting edge. Other lookup tables are utilized to avoid time-consuming iterative calculation procedures to provide real-time digital process solutions of trigonometric functions. The apparatus includes a unique laser receiver comprising a plurality of linearly aligned photo receptors with associated circuitry for producing an output representative of the receptor illuminated or, if a group of receptors are illuminated, the centermost receptor illuminated.

Abstract: A control for an excavator controls the position of the bucket cutting edge to a desired depth accurately by a calibrating laser receiver mounted on the excavator stick member and passed through a stationary laser plane wherever the stick is moved into or out of a trench. Linear position encoders monitor the length that the actuating cylinders are extended and lookup tables convert the encoder outputs to angle representations for determining the positions of the laser receiver and the cutting edge. Other lookup tables are utilized to avoid time-consuming iterative calculation procedures to provide real-time digital process solutions of trigonometric functions. The apparatus includes a unique laser receiver comprising a plurality of linearly aligned photo receptors with associated circuitry for producing an output representative of the receptor illuminated or, if a group of receptors are illuminated, the centermost receptor illuminated.

Abstract: A control for an excavator controls the position of the bucket cutting edge to a desired depth accurately by a calibrating laser receiver mounted on the excavator stick member and passed through a stationary laser plane wherever the stick is moved into or out of a trench. Linear position encoders monitor the length that the actuating cylinders are extended and lookup tables convert the encoder outputs to angle representations for determining the positions of the laser receiver and the cutting edge. Other lookup tables are utilized to avoid time-consuming iterative calculation procedures to provide real-time digital process solutions of trigonometric functions. The apparatus includes a unique laser receiver comprising a plurality of linearly aligned photo receptors with associated circuitry for producing an output representative of the receptor illuminated or, if a group of receptors are illuminated, the centermost receptor illuminated.

Abstract: A reference light beam projector of the type which produces a modulated plane of light for use as a reference in many different applications such as for aligning railroad tracks. This modulated reference plane is formed by projecting a collimated light beam along a predetermined path and providing means for variably refracting the beam so to effectively variably bend the beam back and forth along a plane. Specifically, the means for variably refracting the beam is a rotating optical element comprising a window through which the beam is transmitted and variably refracted as the optical element is rotated.

Abstract: Self-leveling light beam projection apparatus for projecting and maintaining a beam of light along a predetermined path relative to the earth's vertical. A housing adapted for mounting in a predetermined plane includes a light source such as a laser generator for generating a collimated beam of light. A lens system including a pendulum mounting at least one lens is mounted for movement about mutually perpendicular axes to seek the vertical and to maintain the projected beam along the predetermined path despite the relative positions of the housing and light source.