Patent GB-585792-A (GB)
Title: Improvements in or relating to projectiles
IPC: F42C9/14
Filed: 1942-04-17
Abstract: 585,792. Photo - electric apparatus. CROW, A. D., KING, E. B., COLES, N., COOPER, A. H., SPENCER, R. E., GAUSS, H. E., BANCROFT, F. E., ELECTRIC & MUSICAL INDUSTRIES, Ltd., and METROPOLITAN - VICKERS ELECTRICAL CO., Ltd. April 17, 1942, No. 5129. [Classes 39 (i), 40 (iii) and 40 (v)]. [Also in Group XXI] Relates to light-sensitive fuzes for projectiles, such as rockets or bombs, which do not rotate in flight, and which are detonated by a relay triggered by a change in the intensity of light falling on a photo-electric cell caused by proximity of the projectile to the target. According to the invention, the fuze comprises a photo-electric device, an optical system limiting the direction from which light can fall on the device and a relay triggered to cause detonation of the projectile charge, the photoelectric device having a cathode in the form of a closed surface symmetrically disposed about the projectile axis, and the optical system comprising an annular window, a toric lens behind the window, and an annular slit between the lens and cathode. The fuze shown in Fig. 1 is arranged in the front of a rocket casing having at its rear (not shown) a cordite propelling charge, the middle casing portion housing the high-explosive charge detonated by the fuze. The fuze casing contains at the front the arming switches 2, the assembly 3 comprising a thermionic amplifier 21, 22, Fig. 4, a gas-discharge relay 4, a self-destruction device, and a low. tension battery 5. At the centre, the fuze casing contains the photo-electric cell 7 and the associated optical system and at the rear the high-tension battery 9 and' the gaine 10 fired by the relay. The central section has a gap for an annular toric lens 11 forming a window for the cell 7. The edges of the lens seat against rubber washers 14, 15. The " look-forward " zone, Fig. 3, is the, space between two cones differing in semi-vertical by 10 degrees, the semi-vertical angle of the rear cone being 57 degrees. The " lookforward " angle depends on the shape of the cell cathode 18 and the positioning of a slitted screen 19 between the lens 11 and cathode 18. This cathode is made in the form of a cylinder, prism, or cone so that the excitation is substantially constant for all directions of incident light. The cell should be sensitive to a 1 per cent change in received light over a wide range of light intensities and its characteristics can be modified so that it is sensitive to light of different wave lengths, for example the blue end of the spectrum and infra-red rays. The cell 7, Fig. 4, is coupled through amplifiers 21, 22 to the grid of the relay 4 in the anode of which is a fusible " puffer " 23 for igniting the projectile charge. A two-stage arming device, Fig. 7 (not shown) comprises mercury acceleration and deceleration inertia switches as described in Specification 581,131, [Group XXXVII]. In place of the mercury acceleration arming switch, a mechanical inertia switch may be provided, Fig. 8 (not shown). This comprises a weighted arm which sets back under the control of a spring and clockwork-geared flywheel to close electric contacts. The acceleration switch completes contacts 24-27 in the filament and anode circuits of the valve amplifier and photo-electric cell, and the deceleration switch closes contacts 28 in the anode circuit of the relay 4 so that the relay does not operate until the rocket decelerates following the combustion of its propelling charge. To ensure self-destruction at a predetermined time after the rocket is discharged if the photo-electric action fails, the relay is triggered through a neon lamp 32 connected to the anode of which is a charging resistance 31 feeding a condenser 30, the voltage across the condenser building up to strike the neon lamp and trigger the relay 4.