GB459008A - Improvements in or relating to automatic heliostats - Google Patents

Abstract

459,008. Heliostats. BENGUE, F. J. M., 24, Fitzroy Street, London. March 10, 1936, No. 7214. [Class 97 (i)] In an automatic heliostat comprising a mirror rotatable about two axes at right angles to each other by means of motors controlled by switches actuated by the sun's rays, so as to stabilize the direction of the rays reflected by the mirror, the rotatable parts supporting the mirror are mounted on anti-friction bearings and have no mechanical connections with external driving forces, these parts being designed so that their moments of inertia about their axes are large. The mirror 1 is carried by a cradle 2 which is rotatable about the horizontal axis H-H<1> in a frame 3 rotatable about the vertical axis V-V<1> in a fixed support 5, the rotary axles being mounted in ball bearings 6 &c. The moments of inertia of the cradle 2 and frame 3 are increased by weights 7, 7<1>, 9, 9<1> and balancing weights 8 are also provided. Rotations of the mirror about its two axes are effected by motors 11, 12 provided with airscrews 13, 14. these motors being secured to the frame 3 and cradle. Each motor is controlled by two independent switches actuated by the sun's rays, one of these switches being arranged to receive direct sunlight and controlling the corresponding motor so as to bring the mirror approximately into its correct position, while the other switch is actuated by light reflected by the mirror and controls the final fine adjustment of the mirror. The switches are of the kind comprising a mercury tube 20, Fig. 3, connecting two hydrogen-filled bulbs 21, 211 between which is a member 24, both surfaces of which are reflecting. The tube has three electrodes 22, 23, 23<1>, and a circuit is cornpleted between the electrode 22 and one or other of the electrodes 23, 23<1> to start the corresponding motor in one direction or the other, according to which of the bulbs receives sunlight from the reflector 24. The switch 25 controlling the initial adjustment about the vertical is mounted on the upper end of the axle 4, while the switch pertaining to the horizontal axis consists of bulbs 28 secured to the frame 3, and a mirror 29 connected by gearing 31, 32, 33 to the horizontal axle of the mirror 1 so as to turn at twice the angular velocity thereof, the mirror 29 being vertical when the mirror 1 is horizontal. The switches controlling the fine adjustment of the mirror are mounted on the frame 3 so as to receive sunlight reflected by the mirror 1, and by a stationary mirror 51, the four bulbs 36, 361, 37, 371 pertaining to these switches being arranged at the corners of a square above reflectors 38. These bulbs may contain heating elements 40a, 40b, Fig. 6, arranged in series in the circuits closed by the switch to prevent the mercury from moving substantially beyond the point at which contact is made. Means are provided for rendering the switches 25, 28 inoperative when the fine adjustment switches come into action.