Patent GB-444207-A (GB)
Title: Apparatus for steering craft along a geographical great circle
IPC: G01C21/02
Filed: 1934-10-08
Abstract: 444,207. Automatic control of a body in motion. BOYKOW, J. M., 2A, Fontanestrasse, Lichterfelde, Berlin. Oct. 8, 1934, No. 28803. Convention date, Oct. 7, 1933. [Class 38 (iv)] [See also Groups XX and XIX] In Fig. 2, NS and A represent the axis of rotation and equator respectively of the terrestrial globe, G a great circle along which it is desired to steer a craft, e.g. the aircraft F, and G<1> the axis of the great circle G. Apparatus is provided for determining whether the angle between the axis G<1> and NS is being maintained. Fig. 1 shows an apparatus in which a sight is maintained on an astronomical fixed point, e.g. the sun. A stabilized platform P carries a vertical tube 1 rotatable about its axis by a worm 2 with a handle 3 and co-operating scale 4. A tube 5 rotatable about its horizontal axis H-H by a worm 6 operated by a handle 7 with a cooperating scale 8 is mounted on an extension of the tube 1. A tube 9 is, in turn, mounted on the tube 5 by a joint 5<a>, 9<a> and may be angularly adjusted by knob 10 and toothed members 11, 9b. The tube 9 carries rotatably about its axis E-E a tube 13 with a Dove prism 19 and a tube 14 supporting a sighting mirror 18. Light from the observed astronomical body passes via mirror 18, prism 19, lens 21, mirror 22 connected to the joint member 9<a>, mirror 23 rotatable about axis 23<a> through half angle of adjustment of tube 9 by gearing 24, 25, lenses 26,'28, and prisms 29, 30 to the image plane 17. In use, the axis H-H (see also Fig. 2) is arranged transversely in the craft and represents the axis G and the tube 9 is adjusted to be parallel to the earth's axis NS. This adjustment is kept unaltered during the journey. The mirror 18 is adjusted about the axis 18<a> in accordance with the declination of the astronomical fixed point used and clockwork mechanism 16 rotates the tube 14 about the axis E-E to neutralize the effect of the earth's rotation and the tube 13 and Dove prism 19 through half the angle of rotation of the tube 14 to erect the image. During the journey the tube 5 is adjusted about the axis H-H in accordance with the travel of the craft around the axis G<1>, a Dove prism 27 being simultaneously rotated through half the angle of adjustment. Failure to adjust the tube 5 about the axis H-H causes the image to be displaced vertically relatively to cross wires in the image plane and this movement may be used to indicate the adjustment necessary. The latter gives an indication of the distance travelled or the land speed. Alternatively, the adjustment of the tube 5 may be effected automatically from a land speed indicator, manual correction means being provided. Deviation of the craft from the desired great circle course is indicated by lateral movement of the image in the image plane. The craft may be steered to maintain the image coinciding with the orosswires or the image may be arranged to co-operate with a number of photo-electric cells controlling apparatus for automatic steering and automatic adjustment of the tube 5. In order to eliminate deviation from the course due to drifting, the tube 1 is appropriately adjusted about the vertical axis by handle 3. When the sun, for example, is obscured by clouds its direction may be determined by a bolometer and the apparatus orientated in accordance with the direction so determined.