Patent GB-1536558-A (GB)
Title: Apparatus for measuring weight of bulk material conveyed by conveying apparatus
IPC: G01G11/18
Filed: 1975-12-22
Abstract: 1536558 Weighing belt-conveyed material KUBOTA Ltd 22 Dec 1975 [20 Dec 1974 3 Dec 1975 4 Dec 1975] 52491/75 Heading G1N Apparatus for weighing material 1 conveyed on a belt 13 includes a device 20 generating from a load cell 22 an analog weight-representative signal for the material on that portion of the belt between the rollers 11, 12 and a pulse generator 30 providing a pulse train whose repetition frequency represents belt speed. These pulses are shaped, 40, and fed to a three digit decimal counter 110 having three four-bit counters 111, 112, 113, from which the outputs are fed to a full-scale detector 130 and to a conditioning circuit 120. The weight-representative signal is amplified 60, converted to a corresponding pulse duration and fed to an AND gate 250 also receiving pulses from a clock 240, the resulting pulse count passing to the counter 220 being proportional to the instantaneous weight when the enabling signal γ is fed to the converter 210 from the full-scale detector 130. This signal is provided when 1000 pulses have been fed from the generator 30 i.e. at predetermined intervals of length of belt. The counter 220 feeds a parallel bit digital output signal to the latch circuit 230, which is also enabled by the signal γ from the full-scale detector. Figs. 2A and 3A (not shown) indicate the operation of the pulse-number modifying means whereby assuming the inputs R A  and R C  are logic ones the outputs OA, OC of the AND gates 121A,C are as shown at (7), (8) in (Fig. 3A) yielding the resultant four as at (9) from the OR gate 121E. This resultant pulse train four has a reduced number of pulses, compared to f in , in a given time, the reduction being determined by the value of the weightrepresenting digital signal. R A , R B , R C , R D  are the outputs from the latch circuit 233. The output from the circuit 120 is counted in an eight digit cumulative counter 300. In an alternative embodiment Fig. 4 (not shown) a flip-flop (50), AND gate (70), OR gate (90), binary counter (260) and binary latch (270) are provided to extend the resolution of the weight since the count in counters 110 and 220 has a maximum of 2000 instead of 1000. Also a non-linearity correcting circuit (400) is provided between the latch circuit 230 and the conditioning circuit 120 to compensate for non-linearities in the response of the load cell 22. According to a further embodiment, Fig. 5 (not shown) the load cell output voltage (E x ) is roughconverted to a digital signal (D1) which is D/A converted back to an analog signal (E DA ). The difference between the original voltage (E x ) and the re-converted signal (EDA) is evaluated and A/D converted by a second A/D converter (200B). The bit-parallel coded digital outputs from the converters (200A,B) are fed to respective pulse number modifying means (100A,B) whereby the speed-representing pulse output from the generator 30 is multiplied by a volume less than unity and determined by the coded digital outputs representing the weight conveyed. In a further embodiment, Fig. 6 (not shown) the distinction from the embodiment of (Fig. 5) is that the first pulse member modifiying means (100A) is arranged to provide pulses each representing a count of one whereas in the (Fig. 5) embodiment one pulse output from the means (100A) was weighted so that it represented a count of 1000.