Patent GB-647123-A (GB)
Title: Arrangement for automatically steering a ship on a predetermined course
IPC: G05D1/02
Filed: 1948-05-14
Abstract: 647,123. Automatic control systems for steering ships. DIAS, J. A. May 14, 1948, No. 23321/45. [Class 38 (iv)] [Also in Group XL (b)] In apparatus for steering a ship on a predetermined course, two magnetic compass needles carrying reflecting mirrors rest against adjustable stops when the craft is on course, and each reflects light from a lamp to illuminate an associated photocell operating a relay. On deviation from course in either direction, one needle is turned with the craft by its adjustable stop while the other remains free to point north, so that one photocell remains illuminated while the other is darkened to release its relay, which operates a further relay, to energize a motor which deflects the rudder in the appropriate direction to correct the course deviation, the rudder movement being arrested by. a limit switch at a predetermined deflection. Compasses 1, 1<SP>1</SP> (Figs. 1A, 1B) have laminated magnetic needles 7, 7<SP>1</SP> on which back-to-back mirrors 8, 8<SP>1</SP> and 9, 9<SP>1</SP> are mounted. Friction rings 10, 10<SP>1</SP> surrounding the compass posts 6, 6<SP>1</SP> carry stops 11, 11<SP>1</SP> which arrest movement of the compass needles, in opposite directions relative to the craft. Adjustable collars 12, 121 surrounding the compass stands respectively carry lamphouses 18, 18<SP>1</SP>, counterweights 20, 20<SP>1</SP>, and photo-electric cells 19, 19<SP>1</SP>. The collars and stops are normally adjusted about the compass axes so that when the ship is on course the compass needles normally rest against their stops and light is reflected from their mirrors to the photocells, whose outputs after D.C. amplification, operate relays 25, 25<SP>1</SP> to open contacts 26, 26<SP>1</SP> and de-energize the rudder motor control switch 36. On deviation of the ship from course to starboard, needle 7 remains freely pointing north, while needle 7<SP>1</SP> (shown dotted) is constrained by its stop 11<SP>1</SP> to turn with the ship. Photocell 19<SP>1</SP> remains illuminated while photocell 19 is darkened, releases relay 25, closes contacts 26, and energizes coil 34<SP>1</SP> through port limit switch 32<SP>1</SP> and switch contacts 29, 29a to close contacts 36a, 36a<SP>1</SP>, 36c, 36c<SP>1</SP> of control switch 36 to energize the reversible motor 2 to drive the rudder to port through change-speed gear-box 60, worm 3, worm-wheel 4, clutch 62 and rudder shaft S. When the rudder deviation reaches a predetermined value the block 74, traversed by lead screw 73 driven by worm 3, opens port limit switch 32<SP>1</SP> and de-energizes coil 34<SP>1</SP> to release the control switch 36. On deviation of the ship from course to port, the apparatus functions oppositely; photocell 19<SP>1</SP> is darkened, relay 25<SP>1</SP> released, coil 34 energized, and contacts 36b, 36b<SP>1</SP>, 36c, 36c<SP>1</SP> are closed to drive the rudder to starboard. The lead screw block 74 may carry a scriber recording deviations from course on a chart. The craft is manually steerable through switches 29, 29<SP>1</SP> which when opened de-energize coils 34, 34<SP>1</SP> and when closed to contacts 29b, 29b<SP>1</SP> energize one coil or the other to deflect the rudder in the desired direction. Plural control units at different positions in the craft may operate a single steering mechanism. Alarm relays 53, 531 are included in each photocell lamp circuit. The apparatus is applicable to steering aircraft.