Patent GB-580165-A (GB)
Title: Position indicator for vehicles
IPC: G01C21/12
Filed: 1941-03-24
Abstract: 580,165. Position indicators for vehicles. SCOPHONY, Ltd., and GALE, A. J. March 24, 1941, No. 3949. [Class 97 (ii)] Relates to position indicators for vehicles of the kind adapted to operate from electrical log signals provided from the speedometer of the vehicle, the signals comprising short pulses. each of which is generated when a prodotermined distance has been traversed, such indicator including a compass to give readings indicative of the geographical position of the vehicle such as the latitude and longitude. In such an indicator, the positive or negative increment to be added to the latitudinal counter at each log signal will be proportional to the cosine of the angle made by the direction of vehicle movement with the true north-south direction whilst in that of the longitudinal counter the increment is proportional to the product of the cosine of the angle made by the direction of vehicle movement with the true east-west direction and the secant of the latitudinal reading. As shown, the compass shaft 1 rotates a cam 2 to a position indicating the direction of travel of the vehicle thereby displacing a member 3, 3a against a spring 5 so that a stop 4 is displaced from a fixed stop 9 permitting the movement of a stop 8 for a distance determined by the compass bearing. The stop 8 is carried by a rack 6 gearing with a split gear 7 connected to a coil 11 and forming part 15 of an electromagnet clutch, the other part 16 of which operates, through gear 17, the latitudinal counter 18. The coil 11 is mounted in relation to polepieces and is rotated each time a log signal arrives, the log signal also closing the electromagnetic clutch 15, 16. A similar arrangement is provided in the case of the longitudinal counter 34, the log signal operating the coil 27, gear 24, rack 23, clutch 31, 32 and gear 33. In this case, however, it is necessary to provide for that portion of the increment due to the secant of the latitudinal reading and to this end the compass cam 19 has a curved profile which, in addition to its angular position, determines the distance through which the rack is permitted to travel. This is accomplished by mounting the coil 27, rack gear 24, and clutch member 31 rotatably on a sleeve 39 which is moved endwise by a nut wheel 36 in gear with the latitudinal counter 18. Fig. 5 shows the circuits for the log signals and for operating the latitudinal counter, similar arrangements being provided' for the longitudinal counter. Terminals A, B are provided for the log signals which, on arrival, close the clutch 15, 16. A source of supply, say of 24 volts, is applied to terminals C, E having a centre tapping D which is connected to one end of the coil 11, the other end of which is connected to either terminal C or E through contacts 41 ... 44, fixed contacts 49, 50 and a movable contact 51 operated by the clutch part 16. Reversal of direction of travel of the vehicle reverses the switching arrangement by means of a cam 47 on the compass shaft 1 as shown. Movement of the contact 51 on the operation of the clutch permits the C, E supply of current to operate the coil 11 and move the rack away frorn the stop against which it is previously held.