GB1016421A - Weighing apparatus - Google Patents

Abstract

1,016,421. Electric signalling. CARL SCHENCK MASCHINENFABRIK G.m.b.H. June 6, 1962 [June 29, 1961], No. 21947/62. Heading G4H. [Also in Division G1] An automatic weighing machine comprises a balancing mechanism, an adjustable counterbalancing means, means for generating two frequencies dependent upon the momentary differential force between a load and the counterbalancing means, means for converting the frequencies into pulse trains, means for comparing the pulse trains for the purpose of generating difference pulses and means responsive to the difference pulses for determining the state of balance between the load and the counterbalancing means. A load applied at 3 is automatically counterbalanced by weight 4, and crystals 15, 16 are stressed as a result. The crystals are connected to oscillators and under zero load at 3 oscillate at the same frequency. Their outputs are applied to pulse generators 22, 23 which are connected to subtracting elements 24, 25. These elements are interconnected and supply a pulse to storage elements 26, 27 only when a pulse applied to one of the elements 24, 25 is not cancelled by a pulse to the other. Elements 26, 27 clear each other, or may be cleared by a pulse from a selector switch 30, selection depending upon the direction of rotation of a motor 29. As long as a pulse is stored in one of the elements 26, 27 motor 29 is energized through switch 32. The motor operates a pulse generator 28, comprising a toothed wheel 33 and optical detectors illuminated or obscured by areas 34, 35 (Fig. 2). A pulse is generated only when the motor has rotated through about one toothpitch, thus eliminating oscillatory effects. Selection by switch 30 then depends on the illumination sequence of the detectors. The motor drives a sliding counterweight, or operates a weight depositing or removing mechanism, or controls the load. When motor 29 is to be stopped switch 32 may simultaneously provide a braking voltage. In a modification the pulses indicative of the difference between the frequencies of the pulse trains, or between the pulse lengths, from generators 22, 23 are converted to a direct voltage indicative of the magnitude and sense of the difference, which voltage may be used directly for control, or may be compared with a voltage from a tachogenerator coupled to the servomotor shaft, and the difference used to drive the motor via an indicator. Other strain sensitive generators such as tensioned steel wires, membranes, or tuning forks may replace crystals 15, 16. Specification 1,016,422, which is divided from this Specification, is referred to.