Method and apparatus for adjusting laser instruments Z axis

#Laser leveling instruments sweep a horizontal beam over the area. The instrument is adjusted by projecting the beam at a target located at least 10 meters away, preferably more since accuracy of the adjustment increases with distance to the target. It is convenient to reflect the beam back towards the vicinity of the instrument since it is easier for the technician to make readings, etc.

#In the normal operating mode a laser leveling instrument is leveled in the X and Y axes and is used principally in that mode. When the instrument is used to establish a vertical plane (Z axis) it is tipped on its side so the (normally horizontal) beam will sweep in a vertical plane. The Z axis must be adjusted initially to a plane normal to the earth's surface. Normally the instruments are calibrated/adjusted in rooms having 3-4 meter ceilings which does not give enough room the locate a target far enough above the instrument to permit accurate adjustment.

#This invention is directed to apparatus for enabling adjustment of the Z axis in laser instruments while using a target preferably located 10 or more meters from the instrument. A new adjustment method is used and takes less time than prior methods while giving excellent results.

#FIG. 1 is a perspective view of a self leveling laser instrument supported in the present adjusting fixture for adjusting the Z axis of the instrument by projecting the "vertical" laser beam horizontally to a target located a considerable distance from the fixture.

#FIG. 2 is another perspective view of the instrument and cradle.

#FIG. 3 is a side elevation view of the instrument in the fixture.

#To put this invention in perspective it should be noted that the details of the self leveling laser instrument are not critical and this invention can be used to adjust instruments having various construction details. This invention provides an apparatus, hereinafter referred to as a fixture in which the instrument is cradled while adjustments are made to the Z axis calibration. The fixture provides means for holding the instrument with its normally vertical axis in a nearly horizontal position so adjustments can be made to the Z axis level vial.

#Before the instrument 10 is mounted in the fixture 12 the X and Y level vials in the instrument are adjusted in the usual manner. This is carried out with the center part 12 of the protective housing removed to expose the adjusting means for the electronic level sensing devices (vials) which are adjustably mounted to the gimbaled portion of the internal mechanism. For clarity and to keep the drawings simple the cover 12 is shown in place with a portion cutout to show the interior (the details of which are unimportant here)... if the cover was removed a lot of detailed, irrelevant parts would be exposed without adding anything of value to this disclosure.

#There are three level vials (X,Y,Z) orthogonally arranged of the mechanism of the instrument. When the instrument is used in the vertical mode only the Z axis vial is active. Initially the instrument is adjusted on a different fixture which provides a truly horizontal surface and the X and Y axis vials are adjusted. Each vial assembly is mounted on the gimbaled portion of the instrument with two screws passing through oversize holes in the vial assembly into tapped holes in the gimbaled assembly. Midway between the mounting holes and in line with them there is a dowel pin which serves as a pivot for the vial adjustment. Perpendicular to each of the two mounting screws and in line with them are adjusting screws which impinge on the body of the mounting screw and are used as fine adjustments to pivot the vial assembly within the clearance of the oversize holes. In use of the instrument tilting the vial assembly causes an electrical signal to be sent to an electric motor which, in turn, drives the gimbaled assembly via a cam arrangement in the direction to null out the signal from the vial assembly. The vial is adjusted by means of the vial adjusting screws until the gimbaled assembly is positioned to produce a horizontal laser sweep when the instrument is in the fixture. These adjustments are made with the cover removed. After the adjustments have been completed the cover is replaced. This makes the instrument more rigid and likely results in changing the vial adjustments slightly. The instrument is then fine tuned...i.e., electric potentiometers accessible from outside the instrument are adjusted to change the electrical bias on each of the vials.