Patent GB-559275-A (GB)
Title: Improvements in or relating to apparatus for recording photographically the indication of instruments whilst testing aircraft in flight
IPC: G03B17/24
Filed: 1942-09-16
Abstract: 559,275. Photographic recording apparatus. HAWKER AIRCRAFT, Ltd., and BETTERIDGE, P. D. Sept. 16, 1942. Nos. 13088/42 and 1407/43. [Classes 97 (i) and 98 (i)] Apparatus for recording the readings of aircraft instruments during test flights comprises a camera with means including a plurality of telephone selector switches, for giving a series of exposures at variably predetermined timed intervals. In one form the number of exposures may also be predetermined. The apparatus shown comprises a box 10 having at one end a duplicate set of the instruments of which the readings are to be recorded, or alternatively adapted to be fitted over the actual instruments of the aircraft. At the other end is fitted a camera 12, the filmwinding and shutter-setting spindle of which is operated by a rack and pinion 14, 16. When a starting button 34 is pressed a circuit is completed through the actuating winding of a relay 42, which closes contacts to complete the circuit of a holding winding and of a motor 18 which then moves the rack 14 to the right to wind the film and set the shutter. As the rack begins to move it allows a contact arm 38 to move opening the circuit of the actuating winding of the relay 42 and closing contacts in a circuit through the holding winding of a second relay 56 and a motor 22. On completion of the winding, a block 45 on the end of the rack engages a contact arm to open contacts 48 which break the circuit of the motor 18 and close contacts 62 which complete the circuit of the motor 22 to return the rack. During the return movement a projection 28 on the rack engages one arm of a bell-crank lever 26 to operate the shutter release. The operations are repeated as long as the button 34 is pressed. The rack may alternatively be returned by a spring instead of the motor 22. Lamps for illuminating the instruments are arranged in casings 70 on the upper and lower sides of the box. The apparatus further comprises automatic mechanism for giving a series of exposures at one of a number of different frequencies, pre-selected by a switch 86, and for pre-selecting the number of exposures to be given by operation of a telephone dialling switch 84. Four automatic line selector switches, housed in a control unit 74, are used, two serving to control the frequency of the exposures and two to determine the number. The circuits are indicated in Fig. 4a (not shown). Each switch comprises eight banks of twenty-five contacts each and a set of eight brushes, one for each bank, which may be driven simultaneously step-by-step, over the contacts by ratchet-mechanism operated by an electromagnet, the complete passage taking about two seconds. Of the two used to control the frequency of the exposure, one operates continuously and transmits at every revolution a current impulse to the actuating magnet of the second, the brushes of which therefore move once every two seconds to the next contacts. In the first bank all contacts are connected together, in the second, every second, and so on up to the fifth bank; in the sixth bank every eighth is connected and in the seventh only the second and fourteenth. One bank is brought into circuit by operation of the switch 86, and as the corresponding brush reaches each connected contact an impulse is emitted which energises the relay 42 and causes an exposure to be made. Exposures may be thus made automatically at intervals of 2, 4, 6, 8, 10, 16, or 24 seconds. The number of exposures, up to 25, is pre-selected by operation of the dial 84, which sends a corresponding number of impulses to the operating electromagnet of a line selector switch and moves the brushes to the corresponding set of contacts. The contacts of one bank are connected to the corresponding contacts of a bank on another selector switch. As each photograph is taken the operating electromagnet of this latter switch is energized, moving the brushes on one contact at each exposure until they arrive at the set of contacts corresponding to those to which the brushes of the first switch have been set. This completes a circuit through the connected contacts and corresponding brushes of the two switches which stops further operation, after which the brushes of all four switches are returned automatically to their starting positions. A dial lamp in parallel with the operating magnet of the selector switch first referred to is lit as long as the switch is operating and photographs being taken. In a modification, Figs. 5, 6a, 6b (not shown), a " single-shot " kinematograph camera is used, in which the release lever is moved upwards to make a single exposure and downwards for kinematographic operation. A control unit carries a twoway and a multi-contact exposure-frequency determining switch, by adjusting which the pressure of a starting button on the aircraft control column may be made to cause either (a) a single exposure, (b) a series of exposures at a predetermined frequency, or (c) kinematographic operation. The release lever of the camera is operated by an armature which is moved upwardly or downwardly by the energization of the appropriate one of a pair of electromagnets. In case (b) energization is by impulses derived from either of two telephone selector switches, mounted at the side of the camera, each comprising eight banks of twenty-four contacts. The first switch rotates continuously at about one revolution a second, and transmits at each revolution an impulse to the operating magnet of the second, which thus rotates once in 24 seconds. Any one of four banks of contacts on each switch can be brought into use by the exposure-frequency determining switch, certain only of the contacts in each bank being connected, whereby impulses at intervals of 1/6, 1/3, 1 or 2 seconds may be derived from the first switch and of 4, 8, 12, or 24 seconds from the second. Operation continues as long as the starting button is depressed there being no provision for pre-determinmg the number of exposures. Signal lamps on the control unit indicate the operation of the camera.