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[EN] 585,791. Wireless systems. CROW, A. D., BUTEMENT, W. A. S., SHIRE, E. S., and THOMSON, A. F. H. April 17, 1942, No. 5123. [Class 40 (v)] [Also in Group XXI] Relates to proximity fuzes for projectiles and like missiles that do not rotate to any substantial extent during flight, such as rockets, bombs dropped from aircraft and remotecontrolled aircraft containing explosive. According to the invention, the proximity fuze comprises a radio transmitter and receiver having a common aerial, the receiver being responsive to radio-frequency energy reflected from a target to trigger a relay which causes operation of the fuze. The transmitter-receiver has a dipole aerial constituted by a part or the whole of the casing of the projectile. The directional characteristics of the aerial are such that maximum sensitivity lies within a conical surface defining a " look-forward " angle within which the target must lie to cause operation of the fuze. The action depends on the " beat " signal set up between the transmitted and reflected waves, and means are provided to eliminate the effect of reflections from the ground. Fig. 1 shows the wireless circuit for a transmitter-receiver apparatus forming part of a rocket and comprising an oscillator-detector valve 1, the oscillator coil 2 being tuned to a wavelength to suit the length of the aerial formed by the rocket casing. The coil 2 is coupled to an aerial coil 3 tuned by a condenser 4. When the target comes within the " look-forward " angle, a low-frequency " beat " signal is developed in the oscillator circuit which is amplified by valves 5, 6, the output serving to trigger a gas-filled ionic relayvalve 7, the anode circuit of which includes a " puffer " 8 for firing the detonator of the explosive charge of the rocket. To prevent detonation by oscillations reflected from the ground, a two-stage arming-device having mercury switches as described in Specification 581,131, [Group XXXVII], is provided for the fuze. The first switch is operated by the acceleration of the rocket and closes contacts 9, 10 to complete the filament and anode circuits respectively, and the second switch closes contacts 11 in the relay which can only operate when deceleration occurs after complete combustion of the propelling-charge of the rocket. As an alternative, a rectifier 15, and a filter-circuit 16, 17, 18 is provided between the amplifier output and the grid of the relay 7 so that signals of decreasing amplitude leak to earth, whilst signals of increasing amplitude build up to trigger the relay. A mechanical form of acceleration arming-switch is shown in Fig. 6 and comprises a weighted arm S' pivoted at S<3> which sets back against the action of a spring S<5> and under the control of a geared fly-wheel S", to close pairs of contacts S<6>, S<8>, the arm being retained in the closing position by a leaf-spring. To ensure self-destruction of the rocket after a, predetermined time, a neon lamp 14 is provided with its anode connected to the junction of a charging-resistance 13 and a condenser 12, the condenser voltage rising .after the set time to a valve sufficient to " strike " the neon lamp and trigger the relay 7. The front part of the rocket casing, Fig. 9, has an insulating-ring 38 to form, with the rest of the rocket casing, the dipole aerial. The front portion of the rocket casing shown which is connected at 34 to the rear portion containing the explosive and propelling charges, comprises a front compartment 31, containing the arming switches 40, low-tension battery 42 and the amplifier unit 41 including valves 5, 6 and relay 7, a central compartment 32 containing the high-tension battery 39, and a rear compartment 33 containing the oscillator-unit 36. This unit shown separately in Fig. 10 is attached to a gaine 35 having a centrifugal-shutter and a detonator fired by the " puffer " 8. Distributer discs 51, 52, 54 facilitate the electrical connections of the units in the casing sections. The oscillator-unit, Fig. 10, comprises discs 45, 46 between which are mounted the valve 1 having rubber caps 48, 49, a former 50 for the coils 2, 3 and the trimmer-condenser 4. Reference has been directed by the Comptroller to Specifications 573,621 and 574,513, [Group XXI]. |
