GB1265143A - - Google Patents

Abstract

1,265,143. Apparatus for horizontal and vertical alignment. NATIONAL RESEARCH DEVELOPMENT CORP. Feb. 25, 1969 [Feb. 7, 1968], No. 6100/68. Heading G2J. [Also in Division G1] A method of establishing the vertical position of an object in relation to a horizontal line comprises projecting a light beam on to a vertical surface, adjusting the beam until it is reflected along its incident path and relating the position of the object to the horizontal beam. The horizontal position of an object may be established by reference to a vertical beam formed by deflecting the horizontal beam through 90 degrees by a prism. As shown the light beam 11 is produced by a laser having three adjustable levelling feet and a mirror 12 mounted on a pendulum 13 to reflect the beam back through the laser 10 to a photo-electric cell 14 connected to a meter and amplifier unit 15 measuring beam intensity, the maximum reading of which defines a horizontal beam. The pendulum 13 comprising a bob 24 which has adjustable weights 26, 27 and is housed within walls 29, 30 to form the piston of an air-damper, is suspended by a ligament 25 to form the piston of an air-damper, is suspended by a ligament 25 from a bridge 23 supported by pillars on a turn-table 20 pivotally supported on a base 35.having three adjustable levelling feet. The mirror 12 is rendered vertical by appropriately adjusting the feet of the base 35 in conjunction with a circular level 39 and weights 26, 27 so that a horizontal reference beam reflected by the mirror 12 registers a constant meterreading upon rotation of a pendulum turn-table 20 through 180 degrees. Alignment detectors for various instruments may be placed in the beam 11 and may comprise four rectangular photo-sensitive devices arranged to form a cross-shaped space therebetween, Fig.4(not shown) or arranged so that each device faces a surface of a pyramid-shaped mirror which may have the beam directed thereto by a corner cube formed from mirrors (50), Fig. 6 (not shown), and a semi-reflector (51). The devices are appropriately coupled together to form two pairs each of which is connected with the two halves of a centre-tapped resistor in a bridge connected to a centre zero meter. Liquid or eddy current damping may be employed for the weights 26, 27 and an alignment telescope,autocollimator or a rodolite may replace the laser 10.