Patent GB-693445-A (GB)
Abstract: 693,445. Calculating-apparatus. BROIDO, D. April 30, 1951 [July 20, 1950], No. 18199/50. Class 106 (i). In dividing on a direct-multiplying machine, a quotient digit is estimated by comparing the initial three dividend digits with ten precomputed maximum values selected according to the initial two divisor digits and corresponding to the ten quotient digits. Repeated division with successive estimated quotient digits is then carried out in the manner described in Specification 577,330 in order to arrive at the complete quotient and final remainder. The comparison values are given by b+bq+q, where b represents an initial two divisor digits and q a quotient digit; the quotient digits they yield will, occasionally, prove to be one less than the correct value necessitating correction by the operator and subtraction of the divisor from the dividend. In the mechanism shown, the comparison values are embodied in a set of nine tables marked on a set of nested drums 200 incorporated in the multiplying-machine described in Specification 687,582. A drum and table is selected according to the first divisor digit and a line of the table according to the second digit. The line for the divisor digits 17 is shown in Fig. 2 behind a reading aperture 210 in the machine casing for visual comparison with the dividend set up on the totalizer 146. The quotient digits 260 are marked on the casing along the reading aperture. As in the machine described in Specification 687,582, denominational slides 35 on a step-wise movable carriage 21 are differentially adjusted in turn by operating the ten setting keys, and mechanism is provided in the present machine by which the initial two slides 35 select and adjust the drums 200 after setting the divisor. For this purpose two further slides 213, 239 are mounted on the machine frame above the carriage 21 and have depending lugs 212, 238 which engage slotted parts 211, 237 of the two slides 35 concerned when in setting position. The setting is therefore also applied to the slides 213, 239 and spring-actuated pawls 233, 248, released by cams 236, 249 on the carriage 21, lock them in their set positions. The slide 213 is adapted to select the appropriate drum 200 and has a stepped portion 216 engaged by a feeler lever 218 when released to a spring 231 by downward (Fig. 3) movement of a " subtract lever 250. The forward end of the lever 218 differentially adjusts a collar 223 along the shaft 201 of the drums, and the collar slides a key 224 along a groove in the shaft to engage an extended lug 227 thereon with slots 228 in one or more end hubs 207 of the drums. One or more of the drums, starting from the innermost, are thus coupled to the shaft 201 for rotation, the remainder being held by engagement of a pin 226 on the collar 223 in bores in their hubs 207. All but the innermost drum have longitudinal slots 209 (Fig. 7) normally in register with the reading aperture 210 so that the lines of the table on the selected drum will be visible as it is rotated. For differentially rotating the shaft 201 and selected drum, the slide 239 has a stop 241 adapted to be engaged by a stepped plate 242 biased counterclockwise by a spring 247 but normally held by a stud 259 on a bracket 254 engaging under a toothed segment 245 sleeved to the plate 242. The bracket 254 supports the " subtraction " lever 250 which, following the movement referred to above, is rocked counterclockwise (Fig. 1) in a gate opening (Fig. 2) of the casing, so releasing the plate 242 and segment 245 to the spring 247 to be differentially positioned by the stop 241 of slide 239. The segment 245 meshes with a pinion 246 on the drum shaft 201 so that the selected drum is rotated to reveal the appropriate line of its table in the reading aperture 210. In operation, the dividend is first entered on the totalizer 146. The divisor is next entered on the setting carriage and the subtraction lever 250 operated to select a line of the tables according to the two first set divisor digits. The three first dividend digits on the totalizer are then compared with the maximum values showing in the aperture 210 to ascertain the probable first quotient digit. The machine is then operated (see Specification 577,330) to subtract the product of this digit and the divisor from the dividend on the totalizer. Further similar operations are made until the remainder standing on the totalizer is less than the, divisor and all the. quotient digits have been ascertained. If, after an operation, the first three digits on the totalizer exceed the divisor, the latter is subtracted from the totalizer and one added to the quotient digit. As an alternative to visual comparison of the actual and precomputed dividend values, this may be done automatically. by, representing the values by means of notches, contacts, magnetic spots or other physically discernible means.