Patent GB-1139881-A (GB)
Title: Weighing scales
IPC: G01G23/42
Filed: 1965-12-31
Abstract: 1,139,881. Calculating apparatus; selective signalling. HOBART MFG. CO. 31 Dec., 1965 [31 Dec., 1964], No. 54709/65. Headings G4A and G4H. A weighing system includes programme means responsive to detection of a balance condition to transfer groups of pulses representing the digits of the weight to corresponding counters. The system described is a development of the systems described in Specifications 695,635, 808,235, 809,719 and 1,059,681 and it differs from the earlier systems in four main respects, namely the way in which the weight digits are transferred from a coded scale to a set of counters, the way in which multiplication of the weight by the unit price is effected, the way in which the contents of various counters are read out to the printer, and a touch responsive tare adjusting arrangement. Detailed negative logic drawings of all four features are described-the preferred hardware being solid state-and the last three features are claimed in Specifications 1,139,882, 1,139,883 and 1,139,884, respectively. Derivation of weight digits.-The position of the weigh pan is digitized by a photoelectrically sensed scale employing a cyclic-binary coded bi-quinary cyclic decimal code. Precise details of this coding are given in the Sepcification: basically each digit of the usual reflected decimal code is coded by two digits, the first being 0 or 1 and the second 0, 1, 2, 3 or 4 and the second digit of each of these bi-quinary pairs is coded in cyclic binary. In order to transfer the weight into a pure decimal register having a pure binary coded counter for each decimal denomination, the decimal digits from the scale are examined successively, starting with the most significant, and an appropriate number of pulses entered into the corresponding denominational counter of the register, using the technique of entering either the digit from the scale, or its nine's complement, in accordance with the parity of the corrected next more significant digit. This is effected by the use of a buffer register of four bi-stables FF45, ... FF48 (Fig. 6, not shown), to which the outputs from the sensing photocells A, B, ... N (Fig. 11, not shown), are successively transferred in groups of four. Before any transfer takes place the weigh pan must come to rest, then being detected, as in Specification 1,059,681, by examining two of the lower bits, and it must be reading more than zero and less than the maximum capacity of the system, this being detected by examining the highest two bits. Multiplication.-Multiplication of the decimal weight WXYZ (e.g. 14.96; Fig. 3, not shown), by the decimal price PQR (e.g. 1À26) to produce a rounded-up product decimal STUV is effected by evaluating and summing the following partial products: Each partial product (e.g. RZ) is obtained and summed by gating a repeatedly occurring pulse train containing a number of pulses equal to the second digit (Z) into a decade counter (N) for a number of times equal to the first digit (R). This is done successively for each of the twelve partial products in the order RZ, RY, RX, RW, QZ, ... PZ, ... PW, the resulting pulses being gated into the appropriate denominations of a decimal product accumulator comprising four decade counters STUV. In oder to effect correct rounding-up, the two most significant denominational counters S and T are borrowed to act as counters M and N respectively during the initial stages of the calculation: once they have achieved this purpose, which for N is after RZ has been evaluated, and for M after QZ has been evaluated, they are zeroized with suppressed carry, and revert to their main function. The calculation is controlled by a programme counter (Figs. 6, 7 and 8, not shown), comprising three groups DCU-1, DCU-2, DCU-3, of four bistables, the first two groups being constrained by conventional feed-back to count to 10, so that a complete cycle contains 1600 bit periods, numbered 000 to 1599. Each partial product is allotted 100 bit periods; thus RZ extends from 000 to 099, RY from 100 to 199 and so on, the final partial product PW extending from 1100 to 1199. The price PQR is hand set on three ten-position rotary switches 33, 32, 31 respectively (Fig. 7, not shown), so connected to the programme stage DCU-2 that the wiper of each switch is marked for 10r bit periods in every successive 100 bit periods, where r is the switch setting, e.g., a switch set to the digit 6 has its wiper marked (negative) for 60 bit periods in every 100 bit periods: thus the wiper of such a switch is marked from 40 to 90, 140 to 190, 240 to 290 and so on. For a switch set to the digit 8 the marked periods are 00 to 70, 100 to 170 and so on. The weight WXYZ is set in four decode counters DCU-W, DCU-X, DCU-Y, DCU-Z (Fig. 15, not shown). These counters, by means of appropriate gates, each produce in every group of ten bit positions, a pulse train containing a number of pulses equal to the number they register. The conjunction of the price deviation signals, and the weight pulses, and the routing of the resulting product pulses to the product accumulator DCU-S, DCU-T, DCU-U, DCU-V (Fig. 10, not shown), is controlled by other stages of the programme counter, as are the initial entry of the rounding 5 into DCU-S, which acts as the "M" stage, the zeroising with suppressed carry of DCU-T (time 120-139) when acting as "N". and the zeroising with suppressed carry of DCU-S (time 520-539). Read-out to printer.-The contents of every decode counter are "rolled-out" to set type wheels by entering ten pulses produced by a rotary switch coupled to the printer drive shaft, and suppressing interdenominational carry. The pulses are produced by connecting all the odd contacts of the switch to one input of a bistable and all the even contacts to the other, and by differentiating the output of the bistable. In this way, errors, which might be carried by contact bounce, are avoided. Touch responsive tare adjuster.-In order to reduce the risk of error, whenever the weighing system is turned on an indicator lights to call attention to a tare adjusting knob. However, on many occasions the tare may not need to be changed and in order that the operator shall not need to twiddle the knob and then return it to its original position so as merely to acknowledge that he has considered the tare, the knob is made of metal, and so arranged in conjunction with an oscillator, that a mere touch of the knob by the operator, without any twiddling, is sufficient to effect the necessary acknowledgment without which the system will not start.