Patent GB-300697-A (GB)
Title: Improvements in or relating to direction- or position-finding and recording apparatus
IPC: G01S1/02
Filed: 1927-08-18
Abstract: 300,697. Wheatley, C. H. P. Aug. 18, 1927. Determining bearings and distances acoustically. - Relates to directionfinding systems wherein an energycollecting device, such as a loop aerial, explores the field of an incoming wave, or is traversed by a radiated beam, so that the effect of the received energy varies in pulsations. and consists in providing an indicator which is operated synchronously with the collecting-device and registers the critical point of maximum reception. The apparatus may be arranged to work with a number of different transmitting stations spaced apart, and to give separate indications of the direction of each station. The system is also applicable to the automatic navigation of a vessel along a predetermined course under the control of the received' energy. Fig. 1 illustrates one form of apparatus adapted to indicate the direction of two separate transmitters. Energy received on a continuously-rotating loop aerial 11 is applied through an amplifier 19 to the grid circuit of a relay valve 21, so arranged that when the current in the winding 20 exceeds a certain predetermined value, a reed 25 intermittently closes a contact 26, to reduce the negative grid-charge, and so operate a detent 31 through an electromagnet 27 included in the plate circuit of the valve 21. The aerial shaft 12 is driven by worm gearing 14, 15, and carries with it the electromagnet 27, detent 31, and a disc 33 with which the detent engages, together with an actuating rack member 36 which serves to operate planet-gears 38, 39 freely mounted on the main shaft 12 as follows: Cam projections 50 and 51 are carried by the gear 38 and similar projections 52, 53 by the gear 39, whilst the actuating-member 36 is provided with three radial arms 54, 55, 56, Figs. 1 and 3. As the main shaft 12 rotates, the upper gear 38 makes an initial movement until the cams 50 and 53 are nearly in line simultaneously rotating a carrier wheel 40, Fig. 3. As the incoming energy increases in strength the moment comes when the detent 31 is moved in a peripheral slot in the disc 33 so as to allow the latter to rotate. This frees the rack 36 and so allows the radial arm 54 to ride over the cam projection 50 on the gear 38 and leave this gear, together with the gear 39, stationary. This movement of the disc 33 coincides with what may be called the first phase, i.e. the amount at which the received energy on the loop aerial begins to approach the point of maximum reception. The extent of the movement of the disc 33 is determined by the form or outline of the peripheral slot co-operating with the detent 31. The arm 55 next engages the cam 53 on the gear 39 and so continues the rotation of the carrier-wheel 40 at half the speed of normal rotation. This brings the carrier wheel to a mean position equal to half the angular traverse of the loop aerial between the times when the valve relay 21 comes into and out of operation. At this position the arm 56 on the actuating-member 36 operates a spring plunger (not shown) to centre the upper of two rings 45, 46 in a position corresponding to the point of maximum signal strength. The release of the disc 33 from constraint by the detent 31, in the first place allows the member 36 to move longitudinally and thus free the gear pinions 38, 39 for alternate periods, and in the second place allows the disc 33 to be rotated by a pinion so as to operate a change-over switch 66, 67 which functions to tune the receiving loop to the wavelength of a second transmitting station. The operation is then repeated on the second wavelength so that finally the arm 56 operates a spring plunger 44 to centre the second ring 46 along the line of the second bearing. The two rings 45, 46 are chain-geared to a separate indicator 74 where the two readings are duplicated and registered against a magnetic-compass card. In a modified construction, means are provided for varying the position of the actuating-member 36 relatively to the shaft driving the aerial in order to compensate for any change in the course of the ship or other vessel, particularly when the bearings are being recorded by means of an indicating stylus moving over a map. In this case the shaft carrying the electromagnet 27 and associated parts may be spaced apart from the rotating aerial shaft, in order to prevent any undesirable inductive effect between the electromagnet and the compass needle used for determining the appropriate setting of the actuating member. The two rotating systems are driven in synchronism through electromagnetic ratchets. The compensating movement may be derived from an electromagnetic ratchet co-operating with setting-cams and a friction clutch on the main shaft. Or either the separate shaft, or the shaft carrying the aerial, may be aligned with the compass needle through an intermittent coupling-device, or through a clamp fitted with centring or aligning cams. The arrangement shown in Fig. 13 is used with a non-directional receiving aerial co-operating with two rotating beams of energy, transmitting a synchronizing signal which controls the setting of the indicator shaft. In order to synchronize the rotation of the disc 107, which is mounted on the shaft 12, Fig. 1, with the speed of the rotating beam, two magnet windings 27, 130 inserted in the plate circuit of the relay valve 21, are energized alternately by a pivoted switch arm 132, the other end of which engages a cam 139 on the ratchet wheel 107. If the wheel is rotating at a speed slightly faster than the rotating beam it is arrested intermittently as follows. The primary drive is through a vibrator switch 140 which feeds two ratcheting magnets 105 from a battery 141 so long as the contact 137 is closed. When the cam 138 engages the cam 139, the contact 137 is broken and the wheel 107 is held stationary. Simultaneously the winding 130 is connected in the plate circuit of the valve 21, until the synchronizing signal is received whereupon the winding 130 restores the rotation of the wheel 107 through a time lag corresponding to the flattened portion of the cam 139. A neon lamp 146 simultaneously gives a visible indication of the zero point between the beam signal and the synchronously driven gear. The speed of the main shaft may alternatively be controlled by automatic regulation of the speed of the driving motor through an iron plate which is moved so as to increase or decrease the magnetic flux through the armature of the motor. In applying the apparatus to navigate a vessel automatically, a raised guide-rail corresponding to the predetermined course is used to control the movement of a carriage mounted at the intersection of the two indicator or stylus arms, the position of which is determined by the direction of the incoming waves. The carriage is in turn coupled to the steering-mechanism through switch means which automatically correct any tendency to deviate from the set course. Fig. 17 illustrates an arrangement in which the directional apparatus is combined with means for ascertaining the velocity and direction of wind, in an aircraft, and also the propeller-slip. For this purpose the controlled slider 185 is associated with a magnetic needle 196, which carries two electrodes 198 co-operating with two arcshaped electrodes 107 energized by an induction coil. Sparks pass between the two electrodes at regular intervals governed by the speed of the propeller, and so make a trace of the air-miles on a map whereby this speed can be compared with the land miles per hour. The same trace indicates the degree to which the craft is turned into the wind to maintain its course so enabling the direction of the wind as well as its velocity to be ascertained.