Grade setting and calibration arrangement for laser beam projection device

摘要

An arrangement for use in a laser beam projection device for controlling the orientation of a support frame upon which a laser beam source is mounted includes a base frame, a support frame, and a pivot for mounting the support frame on the base frame. A level arm is pivotally supported at one point by the support frame and carries a level vial which provides an electrical indication of the orientation of the level arm. A positioning arrangement engages the support frame and the level arm and adjusts their relative position. The positioning arrangement includes a threaded shaft having a first threaded portion engaging the support frame and a nut engaging a second threaded portion of the shaft. The nut contacts the level arm. By rotating the nut, the relative position of the level arm and the support frame are adjusted. Differing thread pitches for the two threaded portions are provided and rotation of the threaded shaft while holding the nut stationary thus allows very fine adjustments to be made in relative positions between the parts, thus facilitating calibration. A flexible cable extending from the nut to a knob mounted on the base frame and a spline attached to the end of the cable and received within an appropriately shaped opening on the knob permit the nut to be rotated for appropriate setting without hindering movement of the support frame or the level arm.