Patent GB-521471-A (GB)
Title: Apparatus for ascertaining the value of a desired function of one or two variables
IPC: B23Q35/128
Filed: 1938-11-21
Abstract: 521,471. Photo-electric determination of values from graphs. BROIDO, D. Nov. 21, 1938, No. 33796. [Class 106 (i)] [Also in Group XL] An apparatus for ascertaining the value of a desired function of a variable comprises a carrier provided with a two-dimensional graph having optical properties (transparency or reflecting power) different from those of the carrier, a device sensitive to radiant energy for scanning the graph and arranged in co-operation with a beam of radiant energy to produce electrical impulses, means operated by said impulses to operate means for indicating individual values of the variable and means for selectively adjusting in one direction or the other the relative positions of the graph and sensitive device or for selecting a relevant portion of the graph in accordance with a selected value of the variable; and the sensitive device is adapted to be displaced relatively to the graph and the electrical impulses are utilized to regulate the displacement of the sensitive device relatively to the graph in conformity with the varying curvature whereby the sensitive device is caused to follow the graph and the amount of displacement from a zero position represents the value of the desired function.' In the form shown in Fig. 1, a graph carrier 1 can be moved laterally by a screw 11 between a lamp behind and a cell 20 in front. The graph is a line 2, and on each side of that line are limit lines 3, 4 of less transparency. The abscissa x determined by the setting of the screw 11 is indicated by a pointer 14 on a scale 15. The cell 20 has a small aperture 21 and is slidably supported by a rod 23 and rotatably connected to a shaft 26, which is rotated by a pinion 29 through key 30 and and key-way 31 and is formed with a double-handed screw part 28 adapted to be engaged by one of two nuts 35, 48 to cause the shaft to move upwards or downwards to bring the aperture 21 over the graph 2. The displacement of the shaft 26 gives the y ordinate of the graph, and this ordinate may be indicated over a scale. The cell is made to follow the graph automatically as follows : In the position shown, the nut 33 is in mesh and this drives the cell upwards until the aperture comes over the graph 2. When this occurs an amplifier device 50 connected to the cell causes relay 53 to swing switches 54, 55 to the mid position, electromagnet 39 is cut off and nut 33 is removed from screw 28. If now the graph carrier is moved so that the graph rises above the aperture, switches 54, 55 return two position shown and nut 33 again engages to cause cell to ri'se until aperture 21 is again over the graph 2. If the graph carrier is moved so that the graph falls below the aperture, the switches 54, 55 are again returned to the position shown and the nut 33 again makes the cell rise, but this time the aperture 21 is brought over the limit line 3 and the action of this on the amplifier 50 causes switches 54, 55 to be thrown over to the right. Electromagnet 62 is energized through switch 55 and moves a distributer device 67 one step thereby changing connection of switch 54 from electromagnet 39 to electromagnet 41. Nut 48 then engages, and cell is lowered until aperture 21 again reaches graph 2. Similar operations occur at any displacement of the graph carrier. In another construction, a multiple set of a graphs of two dimensions corresponding to successive values of a third dimension are marked on transparent films which are moved one at a time step by step according to the successive values of the third dimensions, and the successive graphs are projected to a larger size on a screen which is scanned by a photoelectric device in the manner of the carrier 1 of the form described above.