Patent GB-669986-A (GB)
Title: Improvements in and relating to calculating machines for performing division
IPC: G06F7/46
Filed: 1948-06-21
Abstract: 669,986. Digital electric calculating - apparatus. BRITISH TABULATING MACHINE CO., Ltd. June 21, 1948 [June 21, 1947], No. 16624/48. Class 106 (i). In a dividing machine, one-half the divisor is entered in a dividend accumulator, prior to division, in the appropriate denominations to obtain a quotient rounded-off to a predetermined number of digits. As described, the machine comprises electrical circuits including relay magnets and cam-operated contacts which automatically perform the following operations: (1) the addition of half the divisor to the dividend; (2) estimation of quotient digits from comparison of the first two digits of divisor and dividend; (3) multiplication by partial products of the estimated quotient digit and the divisor, and the subtraction of the resulting product from the dividend; (4) correction of under- or over-estimation of quotient digits; (5) stopping the machine when the required number of correct quotient digits have been found. Accumulating or totalizing mechanism. The dividend, divisor and quotient are registered on accumulators, similar to that described in Specification 636,967, of which one denomination is shown in Fig. 12. A continuously rotating main-shaft 10 drives through gearing a ratchet 12 which is engaged by a pivoted dog 15 when a lever 17 is rocked out of engagement of a disc 18 by an electrical impulse sent to a start magnet 25. Normally, this impulse is sent at a time determined by the digit to be entered and the dog 15, disc 18 and a wheel 14 then rotate until at a fixed point in the revolution of shaft 10 a pin 19 rocks the lever 17 back into disc-engaging position. When the wheel 14 is in in its " 9 " position electric contacts 21 are closed and as the wheel moves from " 9 " to " 0," contacts 22 are closed instead. Transfer is effected during the same revolution of shaft 10 by another impulse sent to start magnet 25, the lever 17 being returned by a pin 23. The lever 17 may also be rocked back by an impulse sent to a stop magnet 25 which is used when the nines complement of a digit is to be entered. Each wheel 14 has a brush 26, e.g. see Fig. 14c, which moves over ten contact segments 27 (shown in a developed view) connected to a common conductor 28. The divisor accumulator has a double set of brushes 26, segments 27 and conductors 28. Multiplying mechanism. The mechanism for multiplication by partial products disclosed in Specification 614,054 is used for multiplying the divisor by an estimated quotient digit. This mechanism comprises a drum 32, Fig. 11, having sets of openings 33, those shown being for the right-hand digits of each product of a multiplicand digit (represented by the selected set of openings) and a multiplier digit (represented by a vertical line within the set). Associated with each set of openings is a spring-pressed finger (not shown) of a pair of contacts 36R. The drum is rotated through a half-revolution clutch from shaft 10, Fig. 12, when an impulse is sent to magnets 30 (not shown), and whenever a finger enters an opening 33 the corresponding contacts 36R close to send a timed impulse to an accumulator magnet 25. The drum and contacts are relatively moved as indicated by arrows, Fig. 11, by energization of magnets 40L, 40R and 52L, 52R, Fig. 14c, to align the contact fingers on the appropriate vertical lines. The openings 33 for the left-hand partial product digits (not shown) are associated with contacts 36L, Fig. 14e, and since, as the drum rotates, contacts 36L, 36R will successively operate with both left and right-hand openings 33, contacts 53 are alternately opened and closed during successive half-revolutions of the drum by a cam on the drum shaft. Denominational shift mechanism. During each half-revolution of the multiplying drum, a cam on the drum shaft allows a plate to rock until stopped by the armature of one of four energized magnets 73, Fig. 14d, as described in Specification 614,054. As the " 1 " magnet 73 may be energized with delay, this gives five positions for the plate which is connected to a commutator. Two such commutators are provided for directing entries to the dividend accumulators, one commutator comprising tabs 87 and wipers 88, being shown in Fig. 14f. Division; preliminary operations. Suppose that it is desired to find 5,314,270¸2743, correct to three figures, Fig. 13. The brushes 26 of the dividend and divisor accumulators, Figs. 14d, e and g, are initially set, e.g. manually, to the nines complements of these numbers, and a connection 103, Fig: 14a, is made from the " In " to the " 3 " socket 104. If there are any decimal places, the entry in the dividend accumulator is shifted to the left to cause proper registration in the quotient accumulator. Electric current is supplied over main lines 100, 101 and, to start operation, a switch is closed to energize several relay magnets through contacts operated by timing cams on the continuously rotating shaft 10, Fig. 12. In particular, a row of magnets R530 to R555, Fig. 14e, is selectively energized depending on the order of magnitude of the divisor. In the present example, magnets R530, R525 are energized corresponding to 6 nines to the left of the divisor, Fig. 13. Similarly, magnets R500, R501, R546, R549, Fig. 14g, are selected for energization to represent the order of magnitude of the dividend. The magnets R530, R525 direct a circuit through the divisor accumulator to energize temporarily the " 7 " magnet R906 representing the digit in the second highest order or denomination of the divisor. Later, a circuit is completed through the highest order of the divisor and contacts of the selected " 7 " magnet R906, Fig. 14k, to energize a magnet R810 to represent the two highest divisor digits throughout the subsequent computation. There are 23 magnets R810 representing predetermined values, and the one selected (" 28 " in the example) has the same value as the divisor digits or the next highest value. In addition, divisor magnets R530, R525 and the corresponding dividend magnets jointly control a circuit network, Fig. 14b (not shown), to energize a number (6 in the example) of magnets R141, Fig. 14a, depending on the number of digits in divisor and dividend. These magnets close contacts to cause the permanent energization of corresponding magnets R566. A circuit then extends through connection 103 and a network of b contacts of magnets R566 to energize the " 9 " magnet R141, thus completing a circuit near the end of the revolution of shaft 10 through cam contacts C84, Fig. 14d, to the " 1 " magnets 73 which are energized with delay so that the commutators move five steps. This determines the denominational position of the subsequent entry of half the divisor into the dividend accumulator. A circuit is also completed to the drum clutch magnets 30 (not shown) to start revolution of the multiplying drum. Entering half the divisor into the dividend accumulator. This is effected during a single cycle or revolution of the main shaft 10 (cycle 3, Fig. 13) following the energization of magnets 30 described immediately above. At the beginning of this cycle a magnet R413 is energized, and at the point in the cycle corresponding to the entry of digit " 9 " (see " Accumulating or totalizing mechanism " above), a circuit is completed through cam contacts C112 and a contacts of magnet R413, Fig. 14f, to all the start magnets 25 of the dividend accumulator. At the same time, for every odd digit in the divisor (even complementary digit in divisor accumulator), a circuit is completed through contacts C160, Fig. 14d, a contacts of energized magnet R178, brushes 26 of the divisor accumulator, contacts of normal magnet R608, wires 132 (10 and 8 in the example), contacts of energized magnet R233, Fig. 14f, tabs 87 and wipers 88 (1 and 3) of commutator (shifted five steps), and contacts of energized magnet R214 and normal magnet R218 to b contacts of the magnet R413 and the first and third stop magnets 25. Thus the accumulator wheels in the first and third orders will not start to rotate, as indicated in Fig. 18. At the " 4 " time in the cycle similar circuits are completed through contacts C161, Fig. 14d, to wires 136, Fig. 14f, and a contacts of energized magnet R418 to the first and third start magnets 25, thus starting to add the complement of " 5 " to the corresponding accumulator wheels, this representing the right-hand partial product components of 0.5 times the divisor, Fig. 18. The wheels are stopped by impulses from the multiplying drum representing the left-hand components. For example, in the fifth denomination an impulse is sent at the " 1 " time through " 2 " contacts 36L (representing divisor digit 2), Fig. 14e, d contacts 53, contacts of magnet R190, "7 " wire 118, brush 26, socket 139, socket 141, Fig. 14f, contacts of normal magnet R233, fourth tab 87 and wiper 88, and contacts of magnets R214, R218 (both normal) to b contacts of energized magnet R413 (as before) and the fifth stop magnet 25. As magnet R214 is no longer energized, a denominational shift to the left is effected for entry of the left-hand partial product components. If a " tenths " quotient digit is estimated, as described below, the whole entry is shifted to the right by energization of magnet R608, Fig. 14d. Magnet R413 is energized before the " O " time at which all the accumulator wheels still rotating are arrested. Later in the cycle, an impulse is sent through contacts C111 and the closed carry contacts 21, 22 to start magnets 25 to effect transfer, and the fugitive one is entered through a connection 143. Estimating quotient digits. A first quotient digit is estimated, before the entry of half the divisor described above, according to the first two digits of the divisor, represented by energization of the " 28 " magnet R810, Fig. 14k, and the first two digits of the dividend. Just after the selected magnet R810 is energized, as described above, a magne