GB592529A - Improvements in or relating to radio scanning a field of view - Google Patents

Abstract

592,529. Directive wireless signalling. SPERRY GYROSCOPE CO., Inc. Oct. 11, 1943, No. 16654. Convention date, April 20, 1942. [Class 40 (v)] [Also in Group XXXVIII] Directional wireless transmitting or receiving apparatus for scanning a rectangular field or a series of such fields comprises an antenna co-operating with a reflector, the antenna and reflector being movable together about a vertical axis whilst the reflector is also independently movable about a horizontal axis. Thus the transmitted 'beam may traverse a pattern A, Fig. 4, comprising two horizontal sides 1, 2; 3, 4 during which the antenna and reflector move together and two vertical sides 2, 3 ; 4, 1 during which the reflector moves alone. Selecting means are provided by which any one of a number of similar rectangular patterns A, B, C may be scanned at will In the apparatus shown, the antenna element comprises a rectangular wave-guide 20, Fig. 1, bent through a right-angle to produce horizontally-polarised waves and terminating adjacent a deflector 22 situated in the focal plane of a parabolic reflector 21. The wave-guide 20 is rotatably connected to a fixed guide 25 through a concentric-line' section 26 in the manner described in Specification 579,764. The reflector 21 is mounted on a yoke 30, the centre of which is fixed to a driving gear 32 for rotating the reflector and the guide 20 together about a vertical axis. The edge of the reflector is mounted on trunnions 34, Fig. 2, and independent rotary movement of the reflector about a horizontal axis is produced by a displaceable rod 37 bearing on a bracket 36. Gear 32 is given an oscillating rotary motion by a sector 33 driven through an eccentric cam 50, Fig. 5, a connecting plate 51 and an eccentric pin 52 from a motor-driven shaft 45. The displacement of the reflector at each end of the rotary movement is produced by a cam surface 61 driven from shaft 45 and engaging a roller 60 on the end of rod 37. In order to provide for scanning a plurality of rectangles as shown in Fig. 4, the cam 61 is movable axially on shaft 63 by a pivoted fork member 72 the other end of which engages a cam member 75 fixed to a ratchet wheel 77. The ratchet wheel is operated to set the cam to a new position by a solenoid 84, the plunger of which is linked to a spring-controlled plate 79 carrying a resilient slotted member 86 engaging the ratchet teeth. In another construction, Figs. 8, 9, the cam 61 is controlled by a bell-crank lever 91 engaging an internal cam 94. Cam 94 is geared to a sleeve 100 and rotates through one-third of a revolution for each revolution of the sleeve. Sleeve 100 is loosely mounted on a shaft 101, driven from main shaft 45, coupling being provided by a pawl 105 on a plate 106 secured to the sleeve and a ratchet 104 secured to the shaft. Normally, the pawl is held out of engagement with the ratchet by the armature 107 of a magnet 108, but at each operation of magnet 108, sleeve 100 makes one revolution and cam 94 moves to another of its three positions corresponding to the three scanning patterns A, B, C. Fig. 9 shows a push-button assembly for controlling the selection of a scanning pattern. If, for example, pattern A is being scanned and push-button C is operated, magnet 108 is operated over momentarilyclosed contacts 116 of button C and again over normal contacts of button B and contacts b, controlled by a cam 111 on shaft 95. When, however, the C position is reached, magnet 108 is not again operated since the circuit over contacts c is open at the normal contacts of button C. A potentiometer 56, providing sweep voltages, is set in synchronism with gear 32 through. a belt 58. In a further construction, Fig. 11, rod 37 is controlled by a cam plate 120 continuously driven through gearing 102 and movable axially by a cam-follower member 130 engaging a spiral groove 129 in a fixed member 128. Gear 99 driving member 130 is coupled to shaft 45 by a pawl and ratchet mechanism similar to that in Fig. 8, but with a solenoid 134 replacing magnet 108. Member 130 carries a cam 137 operating switches a<1>, similar to switches a ... c, Figs. 8 and 9.