Patent GB-198090-A (GB)
Title: Improvements in navigational apparatus applicable generally to ships, aircraft and other vessels
IPC: G01S1/02
Filed: 1922-03-01
Abstract: 198,090. Cooch, H. March 1, 1922. Leader gear.-In apparatus for indicating to a ship, aircraft, &c., whether it is following the marked-out route, or is moving parallel to the route at one side or the other of it or is inclined to it, the magnetic field of the cable acts upon two search coils on the craft, the coils being inclined to one another, to the horizontal, and to the vertical plane of symmetry of the craft, and being connected up to apparatus for indicating the steering direction and, if desired, the height of an aircraft. The steering-controls may also be operated automatically. In the case of an aircraft landing- track, the cable may be laid round the track without corners, so that an aircraft can spiral down by following the course of the cable; the track may have straight landing-stretches, and the cable may be shielded or otherwise adapted to give signal effects at particular points; a plurality of parallel leader cables may be used, or two spaced - cables, energized at different frequencies, may be employed with tuned indicating-apparatus; instead of a continuous cable, there may be spaced charged points or sections; a coil may be placed at a definite position above the cable for testing the strength of the field there in order that the field may be maintained constant notwithstanding variations in the condition of the ground; there may be more than one landing track at the same aerodrome. In the indicating arrangement shown, the port search coil 2 and the starboard search coil 3 are connected through similar apparatus to columns of lamps 32, 32<1> respectively. Shafts 6, 7 are rotated continuously by a motor 5, and each shaft carries a pin 9 on an arm 8 whereby a contact drum 12 is rotated in one direction or the other according as the pin 9 engages a wheel 10 or a wheel 11. When a reversing relay 23 is de-energized, so that the blade 24 engages contact, 21. a solenoid 13 is energized from a battery 10, and the guides 15 are shifted to move the pin 9 into a position in which it engages wheel 10 and rotates the drum 12 in the direction of the arrow x. When the drum has moved sufficiently for its segment 34 to connect contacts a, b, and supposing the control relay 25 to be de-energized, the coil of the reversing relay 23 is energized through blade 26 and circuit 30 from battery 18, its blade 24 engages contact 22, and solenoid 14 is energized from the battery 18 to shift the guides 16 and cause the pin 9 to drive the drum 12 in the direction opposite to that of the arrow x. The drum thus oscillates so as to make and break the circuit 30 at the contacts a, b, and the indicating-lamps are not lighted. If, however, the flux through, say, the port search coil 2 is sufficient to energize the control relay 25, its blade 26 opens the circuit 30 of the reversing relay 23, so that solenoid 13 is energized and the drum 12 rotated in the direction of the arrow x until contact c is engaged by the segment 34 and the top port lamp is lighted. In this position, segment 38 on the drum 12 has connected contacts m, n and placed the whole of the resistance r in shunt across the coil of the control relay 25 through leads 35, 36. If the current through the control relay is now insufficient to keep the circuit 30 open at blade 26, the drum will oscillate so as to connect and disconnect contacts m, n. As the flux through the search coil 2 increases, the drum 12 will be rotated further in the direction of the arrow x, to close, the contacts c - - j of the lamps 32 one after the other, thereby indicating the height and showing the side to which the craft should be steered, and to shunt less and less of the resistance r across the control relay 25. Instead of employing reversing gear 9. 10, 11, &c., the motor may be reversed. The currents in the search coils may be amplified by thermionic valves. The variabLe resistance r may be replaced by a potentiometer, an inductance or a condenser associated with the control relay. The positions of the drum may be calibrated to indicate de-finite potentials in the search coil. In a modified arrangement, the lamps are replaced by slotted discs on the shafts of the drums 12, the height being readable through the slots when they are coincident owing to there being equal fluxes through the search coils, and the slot allowing red or green if one or the other disc has been moved through the greater angle. In another arrangement, two pointers move, over the same dial. In yet another, Fig. 1 (complete), wheels 55, 56 of a differential gear are driven from the respective drums 12 and move an arm 58 to light a white lamp 63 through a contact 59 and close the circuit of a column of heightindicating lamps when the wheels are moved equally, or to light a red lamp 64 or a green lamp 62 through contacts 60, 61 when the wheels are moved unequally.