GB663760A - Improvements in weighing device - Google Patents

Abstract

663,760. Automatic weighing machines. MERCK & CO., Inc. July 29, 1948. [Aug. 1, 1947] No. 20225/48. Class 40 (i). [Also in Groups XXXVI, XL (b) and XL (c)] A weighing machine gives an instantaneous indication of weight and/or controls the feed of material to the balance so that a predetermined quantity is weighed out before the balance has settled, dependent on the displacement of the balance beam from the neutral position, and its acceleration. The specification shows mathematically that this is substantially correct when the weight is small compared with the mass of the balance system. A vane 1 attached to the beam 2 of a laboratory balance moves between a light source 3 and a photo-cell 4 so that the cell output is proportional to the displacement of the beam from its neutral (steady) position. The cell is connected to a cathode-follower 6 feeding a two channel amplifier (see Group XL (c)) which gives an output comprising the sum of the input and its second differential i.e. displacement plus acceleration. This output may operate an indicator, as shown, or be used in suitable proportions to control two A.C. energised thyratrons so that they cease to fire consecutively thereby reducing and finally cutting of the supply to an electromagnetic vibrofeeder supplying material to the balance Fig. 2 (not shown). It is stated that the device will automatically weigh out 100 + 1m.g. in 5 or 6 seconds on a balance having a natural period of 8 secs. The Specification also states that a voltage proportional to the displacement may be generated by use of change in capacitance, inductance or mutual inductance and the acceleration may be obtained from the first differential of a velocity component generated by relative movement of a magnet and coil.