Patent GB-1016422-A (GB)
Title: Improvements in or relating to automatic weighing apparatus
Inventor: FRICKE HERBERT
IPC: G01G1/26
Filed: 1962-06-06
Abstract: 1,016,422. Indicating count; transfer mechanism; electric signalling. CARL SCHENCK MASCHINENFABRIK G.m.b.H. June 6, 1962, No. 23983/65. Divided out of 1,016,421. Headings G4D and G4H. [Also in Division G1] Automatic weighing apparatus comprises a balancing mechanism, an adjustable counterweight, a force detecting member constrained so as to be subjected only to deformation or strain by the momentary differential force existing between the load force and the counterbalancing force, means for converting the deformation or strain into an electrical output, and a control device to which the output is fed for the continuous determination of the state of balance. A weighbridge, Fig. 1, includes adjustable counterwieght 73, moved by servomotor 72 during a taring operation, two strain gauge load cells 64, 67, and weight-lifting mechanism 69, 70. The output of load cell 64 when a load is moved on to platform 60 is converted to binary form and weights 68 are deposited on, or removed from, lever 65 by activation of magnets 70, until the load is substantially balanced, the remaining difference being indicated by the output from load cell 67. Sliding or pendulum weights may be used instead of loose weights 68. In a modification four strain gauges are arranged on a leaf spring connecting the balance arm to a support, or on the arm itself, the gauges being bridge connected. A second embodiment includes a beam 100, a counterweight 106 and a slidable tare weight 107, the load being applied at 105. One end of the beam is attached to the centre of a vibrating wire 114, tensioned by weight 117. The vibrations of the two halves are sensed by coils 119, 120 and the voltages or frequencies of the induced currents are compared in control unit 121. Sets of weights 108, 109 and 110 normally rest on one arm of the beam and are selectively lifted by bell-crank levers 123, a chain 111 being provided for fine weighing, for example 200 kg. in 10 kg. steps, the other weights being 100, 1000 and 10,000 kg. Weights 112 on the other arm are 9000, 900,145, and 5 kg. and are raised by bell-crank lever 124. Levers 123, 124 bear against cams 125, 139, and cams 125 each rotate with individual ratchet wheels 127 and stepped feeler discs 126, and are actuated through spring-loaded slip couplings by gearwheels 133. Pawls 129 are disengaged from ratchet wheels 127 by respective magnets 130. Cam 139 rotates with cam 147 and gear sectors 134, 135, 136 and 137 which engage with respective gear-wheels 133. Sector 137, which meshes with gear-wheel 133 associated with chain 111, has a smaller radius so that the chain is adjusted slowly. Cam 147 is engaged by a stirrup 146 attached to a shaft 142 carrying levers 141. Each lever 141 carries a stop lever 148 engaging with a feeler disc 126, and an indicating scale 143 visible through window 144. On application of a load at 105 the control unit 121 starts a motor driving shaft 138 through 300 degrees. Bell-crank lever 124 first deposits all the weights 112, reducing the load to be balanced by 10,050 kg., then gear-wheel 133 associated with the 10,000 kg. weights 108 is engaged by sector 134 to lift weights 108 one at a time until the equilibrium position is passed, whereupon magnet 130 is de-energized and ratchet 127 locked. Cam 139 then causes 9000 kg. weight 112 to be lifted, then sector 135 causes weights 109 to be adjusted until equilibrium is again passed. Similarly, 900 kg. weight 112 is lifted and weights 110 are adjusted, 145 kg. weight 112 is lifted, and chain 111 is adjusted, and then 5 kg. weight 112 is lifted. Finally stirrup 146 is lowered and stop levers 148 rest on portions of discs 126 corresponding to the load 105, and an indication is displayed in window 144. A tens transfer is provided by a further cam 149 (Fig. 6) connected to feeler disc 126. When the ninth position is passed in the lowest order digit a lever 150 drops and pushes stop lever 148 of the next higher order digit to the right. In addition, if this causes a change from 9 to 0 in the higher order digit, a pin on lever 148 enters a recess in a further spring-biased lever 153 (Fig. 7) allowing it to move to the right and deflect stop lever 148 of the next higher order decimal. Push rods 145 may transmit the final reading to a printing mechanism. A circulating weight machine is shown in Figs. 8 and 9, and includes a balance lever 200 pivoted at 204 and anchored by link 206 to measuring element 201. Disc 207 carries a weight 209, and marks 210 on the disc can be sensed by photo-electric detector 214, while a supplementary mark 216 co-operates with a further detector 215 for zero indication. Tare balance is first established by motor 217 positioning weight 219. The load is then applied at 205 and motor 211 rotates disc 207 to restore equilibrium. Detector 214 is then actuated and the marks 210 are counted while the disc is returned to its zero position. Alternatively, pulses may be counted during rotatibn towards equilibrium, where counting is stopped, and the disc may then be rotated to its second equilibrium position where a check count is indicated. As a further alternative the second count may be made while the disc rotates from its 180 degrees position to the second equilibrium point, the sum of the two counts equalling the full weighing range if weighing is correct. A disc having markings as shown in Fig. 11 may replace or supplement disc 207. This disc has pulse generating marks 231, a scale 232, and positional marks 233 indicating tens, hundreds and thousands. The marks may be grouped in a binary-decimal, cyclically permutated or other code. Marks 233 may be sensed by a stationary or a radially or tangentially movable photo-electric transducer. Weighings may be carried out in rapid succession so that the disc rotates almost continuously, the scale being stroboscopically illuminated and projected into a fluorescent screen having a long afterglow. The construction of bearings 204 is described. Fig. 14 shows a sliding weight machine having a beam 301 with a tare weight 335 and displaceable weight 311 mounted on a carriage 310 running on rollers 312, 314. One end of beam 301 is attached by steel band 307 to measuring unit 308. Carriage 310 is moved by a linear induction motor having as its armature an aluminium blade 320 attached to the carriage. Tare balance is first established by weight 335. A load at 300 upsets the balance, which the induction motor then restores. When balance is approximately reached a magnet 318 is energized to deflect pawl 317 into engagement with rack 316. If the balance point has been passed magnet 329 is energized to reduce by one digit the indication in windows 326 by moving marking plate 327 to the right. A rack 332 co-operates with a trip member 333 to generate pulses corresponding to the weight measured. The final pulse may be suppressed when over-running occurs. An eddy current brake 334 steadies the motion of the carriage. A plurality of similar carriages may be provided, displaceable alternately in opposite directions. An arrangement is also referred to in which coarse adjustment is made by lifting loose weights, and fine adjustment by adjusting sliding weights. The rate of adjustment of the sliding weights may be proportional to the amount of unbalance. The invention is also applicable to the weighing of predetermined quantities of loose materials. The electrical measuring units may be of the variable resistance, inductance or capacitance type, or may generate a variable frequency, or may be of magnetostrictive or piezo-electric type. In all the embodiments the coarse digital indication may be corrected by a fine indication derived from the electrical measuring unit at the coarse equilibrium position.