Patent GB-772014-A (GB)
Title: Improvements in or relating to automatic computing apparatus
IPC: G06J1/00
Filed: 1954-06-02
Abstract: 772,014. Electric analogue calculating systems. SCHLUMBERGER WELL SURVEYING CORPORATION. June 2, 1954 [June 2, 1953], No. 16335/54. Addition to 732,878, [Group XL (b)], and 745,403. Class 37. [Also in Group XL (b)] In a computer of the kind described in Specification 745,403, the linearly movable belt, having plural frames inscribed with families of curves representing a predetermined function u=f (x, y) referred to transverse x and longitudinal y axes intercepting a beam of light traversed proportionately to x to fall on a linear transverse photo-cell, and also having parallel frames inscribed with triangular timing patterns intercepting a second beam of light traversed proportionately to y to fall on the same photo-cell, is replaced by a transparent circular disc 10 (Fig. 1), rotatable at constant speed by motor 16 which carries on segmental half-section 11 an opaque inscribed family of curves 12 representing a predetermined function u=f (x, y) of independent variables x, y. A beam of light from a source 13 is reflected on to the disc face by mirror galvanometer 14 responsive to a voltage representing x to deflect the beam radially of the disc, and the emergent light is received by linear radial photo-cell 17. The remaining segmental half section 22 of the disc is partially covered by an opaque region 23 and a second beam is reflected on to the disc face from source 19 by mirror galvanometer 20 responsive to a voltage representing y, to deflect the beam radially of the disc and collinearly with the x beam deflection but on the opposite side of the rotational axis; emergent light being received by a linear radial photocell 24 and the opaque region being contoured so that the time interval of the interruption of the beam thereby is proportional to the instantaneous value of y. The x-output of photo-cell 17 and the y-output of phto-cell 24 are applied to electronic switches 32, 33, triggered by the output of photocell 30 responsive to illumination by an auxiliary light beam from source 28 interrupted by the alternatively opaque and transparent semi-circular borders 26, 27 of the disc respectively embracing the segmental halfsections 11 and 22, so that the switches are operative when photo-cell 30 is darkened and inoperative when it is illuminated; their respective outputs being connected over pulse amplifier 36 to pulse counter 37 having an output indicator or responsive device 38. Trains of pulses 40 (Fig. 2a) and 43 (Fig. 2b) due to the intersection of beams 15, 21 and the family of curves 17, whose adjacent pulse time displacements are dependent on the instantaneous values of variable x according to the function u=f (x, y), appear on the outputs of photo-cells 17, 24 interspersed with rectangular pulses 42, 41 due to the intersection of opaque region 23 and beams 15, 21, whose time durations are proportional on the instantaneous values of variable y. Operation of electronic switches 32, 33 in response to the pulse output 44 of photo-cell 30 (Fig. 2 (c)) select the pulse groups 40 and the pulses 41 only excluding pulse groups 43 and pulses 42 for transmission to pulse amplifier 36, which is biased to pass pulse groups 40 only during the occurrence of pulses 41 superimposed thereon. The integrated grouped numbers of pulses 45 selected from each group 40 (Fig. 2 (d)) are shown to represent the instantaneous values of the function u=f (x, y) for corresponding instantaneous values of (x, y) for each revolution of the disc, and are registered and indicated in succession by output device 38. Interchangeable discs may represent different functions of the independent variables (x, y), while the electronic switches may be controlled by mechanically generated impulses synchronized with the disc rotation. In a modification (Fig. 3, not shown), the outputs of photo-cells 17, 24, 30 are additively combined at the input of a single shot multivibrator biased to operate responsively to pulse trains from photo-cell 17 only in the presence of rectangular pulses from photo-cells 24 and 30, so that the pulse counter is supplied with varying numbers of pulses selected from pulse group 40 as above. Alternatively the three photo-cells shown in Fig. 1 may be replaced by a single linear photo-cell which is completely saturated by any incident light to yield output pulses only when all three light beams are simultaneously obscured. The disc may be opaque and bear transparent inscribed markings with appropriate modifications of the photo-cell circuits, and markings 12 and 23 may be inscribed in alternate quadrants while the markings may alternatively be inscribed on a rotating drum or moving belt in the predetermined alternating sequence. The disc may also be provided with a peripheral track of alternate transparent and opaque sections, co-operating with an additional light beam and photo-cell to derive a rotational speed voltage applied to control the gain of an amplifier between counter 37 and indicator 38 so as to compensate speed variations.