Patent GB-711526-A (GB)
Title: Device for computing the maximum range of variation of a physical characteristic in a group
IPC: B07C5/28
Filed: 1952-06-13
Abstract: 711,526. Photo-electric counting. EXACT WEIGHT SCALE CO. June 13, 1952 [June 26, 1951], No. 14929/52. Class 40 (3). [Also in Groups XXXVI and XXXVIII] In apparatus for testing a series of successive groups of processed articles for a measurable physical characteristic thereof which may vary in value for each individual article, an electronic measuring device produces an output voltage for each article representing the difference between the value of the characteristic and an arbitrary norm, which output voltage is applied as input to an electronic memory circuit which develops a group-range voltage representing the difference between the most dissimilar input voltages (and thus the greatest dissimilarity of the physical characteristic being measured) for each successive group of articles ; such group-range voltage being supplied to a comparison circuit together with a predetermined standard voltage to produce an indication of the deviation of the group-range voltage from normal, for each successive group, and/or to operate an alarm circuit. Packages A moving along a conveyer line S are successively filled with material by a controlled dispenser D and checkweighed by passing over a conveyer section P, carried by a continuous weighing machine wherein it is mounted on one end of a balance beam B having a predetermined counterweight W at the other end, and the deflection of the beam from balance varies the capacitance of a condenser C which detunes an oscillatordiscriminator O to produce a unidirectional output voltage on lines 18, 19 representing in magnitude and sense the weight deviation from standard of each package ; positive and negative polarities respectively denoting underweight and overweight. The voltage is applied through normally closed contact 21 of relay 41 to condenser 30 in the paralleled grid circuit C of resistance coupled triode amplifiers, 23, 24 whose outputs are connected over normally open contacts 35, 36 of relay 41 to the anode of a diode 37 and the cathode of a diode 39, the respective cathode and anode thereof being connected to the cathode return of the amplifiers through equal condensers 46, 47 which are initially charged equally and oppositely. Each package of a sample group passing the weighing section momentarily breaks a light beam falling on a photocell E, whose output pulses the relay 41 and the actuating coil 106 of a stepping switch 100. Assuming that the first package is e.g. overweight to an extent producing an input voltage of -2, a corresponding charge is placed on condenser 30, and the passage of the package pulses relay 41 to open contacts 21 and close contacts 35, 36 whereby an amplifier positive voltage from triodes 23, 24 proportional to the input across condenser 30 is applied to the anode and cathode, respectively, of diodes 37, 39. Due to the opposite charges on condensers 46, 47 the anode of diode 37 is initially more positive than its cathode, and the cathode of diode 39 is more negative than its anode, so that currents will flow through the diodes until condensers 46, 47 are charged equally in the same direction to a value corresponding to the input. On passage of a second package of e.g. exact weight, the relay 41 and stepping switch 106 are pulsed as before, but since the input voltage is now zero, a lower positive voltage corresponding thereto is applied to diodes 37, 39 from triodes 23, 24. The cathode of diode 37 is now positive with regard to its anode and the anode of diode 39 is positive with regard to its cathode, so that the charge on condenser 46 remains unchanged white that on condenser 47 assumes a value corresponding to zero input, whereby a difference in potential arises between the anode of diode 39 and the cathode of diode 37 proportional to the range of variation between the weights of the first two packages. The passage of the third package operates similarly and the fourth object positions the contact arm 107 of the stepping switch on contact 104 to operate relay 71 and close contact 69 to discharge condenser 66. The passage of the fifth object positions contact arm 107 on contact 105 to release relay 71 and operate relay 78 to close contacts 52, 53, 75. The potential existing between the cathode of diode 37 and the anode of diode 39 across condensers 46, 47 after the passage of the fifth package represents the maximum range of weight variation in the sample group, charges condenser 66 and after a time delay due to resistance 74 and condenser 73 relay 60 operates to change over contacts 56, 57 and charge condensers 46, 47 equally and oppositely from battery 65 to a voltage greater than any possible voltage from triodes 23, 24 in preparation for the next cycle. The charge on condenser 66 biases triode 81, which is in series with triode 83 and connected with potentiometer 84 in a bridge circuit energized by battery 86, to produce an unbalance voltage between the potentiometer slider and the anode of triode 81 which is measurable at a jack point 90 to indicate the range of variation and energizes triode 92 to operate relay 95 and alarm lamp 98 when a predetermined range value is reached. The stepping switch 100 and contacts 21, 35, 36 may be mechanically operated by the passage of successive packages, and system may be actuated in response to other characteristics, eg. linear dimensions, E.M.F., colour and the like, of successively tested objects.