Patent GB-440454-A (GB)
Title: Self regulating heliostat
IPC: F21S11/00
Filed: 1934-11-23
Abstract: 440,454. Heliostats. ARTHEL (SOC. D'EXPLOITATION DES BREVETS J. ARTHUYS), 29, Rue d'Artois, Paris. Nov. 23, 1934, No. 33749. Convention date, Nov. 23, 1933. [Class 97 (i)] A self-adjusting heliostat comprises a mirror rotatable about two independent axes lying respectively along, and at right-angles to, the direction of the reflected ray, the rotation being effected by motors controlled by relays actuated by solar radiation. The relays are mounted in a casing which rotates with the mirror about the first-mentioned, or primary axis, and at twice the angular velocity of the mirror about an axis parallel to the secondmentioned, or secondary, axis. The casing also contains a plane element referred to as an " orientation face " which operates to stop the orientation motors when the mirror is correctly adjusted, this element being so disposed that its surface is parallel to that of the mirror when the latter is at right-angles to the primary axis. As shown, the mirror 1 is rotatably mounted on a shaft 3 within a frame 12 extending from a shaft 2 rotatably mounted within a socket 10 which is attached to a fixed support by a ball and socket joint so that the shaft 2 can be set in any desired direction. The shafts 2, 3 constitute the above-mentioned primary and secondary axes. The spring motors 17, 17<1> effecting rotation of the mirror about the axes 1, 2, respectively, are mounted in casings 5, 5<1> carried by a shaft 4 parallel to the shaft 3. The motor 17 drives a pinion 16 gearing with a rack 15 on a ring 14 extending from the upper end of the socket 10, so that the pinion rolls over the rack carrying with it the frame 12. The motor 17 also drives the casing 36 of a differential 37, one shaft 38 of which drives, through multiplying gearing, a small wheel 40, while the other shaft 41 is coupled to a shaft 13 extending through the shaft 4 and driving a wheel 40<1>. The wheels 40, 40<1> are contained within glass covers 35, 35<1> and their rotations are controlled by thermal elements 21, 21<1>, each of which is adapted to be operated by solar radiation so as to release a brake 29 and allow the corresponding wheel to turn. Each element 21, 211 consists of three bimetallic members 22, 22<1>, 22<11>, Figs. 10 and 11, each having two limbs between which extends a partition 27, so that when one limb is exposed to radiation the other is shielded. The free ends of these members extend through a casing 30<1> and are clamped by a nut 30 against a cup 32 which normally, under the action of a spring 31, presses the brake 29 against the wheel 40. The bending of the members 22 &c. due to their exposure to radiation, pushes back the cup and releases the wheel. When either wheel 40, 40<1> is so released the motor 17 is enabled to turn owing to its connection to the differential 36. The rotation is stopped when the mirror 1 and shaft 3 have been brought to the appropriate position about the axis 2 by means of a thermal element 43 acting as a brake to a wheel 42 geared to the motor 17. The member 43 is of the form shown in Fig. 12, comprising a slotted bimetallic element 22 as in Figs. 10 and 11, over which is mounted a prism 33, the angle of which is such that light incident on the face A B C D in or parallel to the principal section M N P Q meets the faces A B A<1> B<1>, CD C<1> D<1> at the critical angle. Thus, rays not parallel to the said plane are totally reflected by one of the faces and transmitted by the other. The face A<1> B<1> C<1> D<1> is blackened. The motor 171 for rotating the mirror about the secondary axis 3 is contained in the casing 5<1> and is adapted to drive a pinion 20, Fig. 14, fixed to the frame 12 so that rotation of the motor causes the casing to turn bodily about the shaft 4. This rotation is transmitted by gearing 7, 8, 9 to the mirror 1 so as to cause the mirror to rotate about the shaft 3 at half the speed of rotation of the casing about the shaft 4. The motor 171 is geared to the pinion 20 through a reversing arrangement comprising two differentials 45, 451, the input shafts of which are driven by gearing 47, 47<1> from the motor so as to rotate in opposite directions while the output shafts are connected by gearing 49, 49<1> and an idler 50 so as to rotate in the same direction, the wheel 49 being geared to the wheel 20. The cages of the differentials are geared to wheels 54, 541 adapted to be selectively released by thermal elements 56, 56<1> and are also geared to wheels 55, 551 adapted to be stopped, when the casing has reached the appropriate position in relation to the sun, by thermal elements 57, 571, associated with prisms 58, 58<1> as above described. Means may be provided for automatically rewinding the spring motors 17, 17<1>.