Patent GB-803412-A (GB)
Title: Improvements relating to mechanical triangle solving mechanism
IPC: G01C21/20
Filed: 1955-04-29
Abstract: 803,412. Angles measuring. MINISTER OF NATIONAL DEFENCE OF HER MAJESTY'S CANADIAN GOVERNMENT. April 29. 1955 [Oct. 1, 1954], No 12561/55. Class 97(2) The invention relates to an automatically actuated mechanical triangle computer for the solution of navigational problems, especially interception problems, where the "wind speed" side of the triangle is nearly equal to the ''airspeed" side, and the triangle may become locked in line. To enable the triangle to be unlocked, the pivot at one end of the unknown arm has a limited, spring-restrained, displacement. Theh Specification describes the mechanical construction of the triangle and actuating means in detail, and a navigational computing system (employing the triangle) which may be used in association with an RO dead-reckoning computor as described in Specification 803,411. Construction of mechanical triangle. (i) (Wind speed and angle side and spring- loaded pivot, Figs. 6 and 7). Gear wheels 66, 83 are mounted on a pin 81 providing the fixed apex of the triangle; slots 67, 68 in wheel 66 define the direction of one side (wind angle) relative to the base; pins 69, 73 pass through slots 67, 68 to engage a scroll in the wheel 83 whereby they can be moved along the slots to determine the length of the side (wind speed magnitude) whose end is a cursor carrying pin 50 described below. Pins 69, 73 are mounted on a plate 63 carrying a pin 54 on which is pivoted a further plate 52, which is normally constrained to move with the plate 63 by spring-loaded arms 55, 56, engaging studs 62, 64 on the plates 63, 52 respectively, but can pivot about pin 54 against the action of a spring 61 joining the arms 55, 56, in order to unlock the triangle. A cursor 57 sliding on the "ground-speed" arm is pivoted on a pin 50 carried by plate 52. (ii) Unknown side (ground-speed) and base (airspeed) Figs. 6 and 8. The unknown side comprises a double-ended arm 90 pivoted in the middle on a pin 102 and carrying a potentiometer 100 engaged by the cursor. The cursor-pin is moved relative to the fixed-apex-pin 81 by a worm and nut to determine air speed Electrical connections to the potentiometer 100 and contact bars 114, 115 on the arm 90 are made through slip rings and brushes Whenever the cursor is in the half of the arm containing bar 115, relays 107, 121 are energized to feed current in the correct sense to the potentiometer and the fieldwinding of the drift-differential-synchro, Aircraft navigation system, Fig. 6 (and Fig. 9, not shown). The magnetic variation (set by hand) is added to the compass heading signal in a differential synchro 150, to control an R.P.C. servo system (154, 159...161) driving one input 164 of a mechanical-differential-gear in accordance with true heading. True wind direction is set into another input of the differential 165 to give relative-wind-angle as an output. The wind speed (i.e. magniture of the wind-angle-vector) is set in at knob 177. The true-airspeed signal from a measuring unit controls a servo system 182...187, to drive a worm co-operating with a nut carrying the pivot 102 of the potentiometer arm, and determines the length of the base of the triangle. The groundspeed signal from the potentiometer controls a servo system 188, 189, 195 to turn an output shaft at R.P.M. proportional to ground-speed.