GB1025615A - Check weigher - Google Patents

Abstract

1,025,615. Electric selective signalling. LINDONS AUTOMATION Ltd. Dec. 6, 1963 [Dec. 7, 1962], No. 46215/62. Heading G4H. [Also in Division G1] Relates to a check weigher for checking the deviation in the weight of an article from a desired value, by determining the period of oscillation, using pulse counting circuitry, of a resiliently supported weigh platform due to an article thereon. In Fig. 2 a weigh platform 12 is carried by a vertical spindle 6 resiliently supported by crossed leaf springs 10. In operation a projection 15 of the spindle is forced against an upper limit stop 8a by a pneumatic actuator cylinder 16. An article is placed on the platform, air is released from the cylinder allowing the spindle to drop against the restraint of the springs 10. The spindle oscillates vertically and a voltage output will be produced by a coil 17 attached thereto, moving in the field of magnets 18. The voltage will be zero at the upper and lower limits of movement and the interval of time between successive zero outputs showing the same polarity change sense is equal to the period of oscillation T1 of the platform. The relationship between a known mass M2, having a period T2, and the unknown mass M1 is given by The period of oscillation may be measured by utilizing the output of the coil to open a gate circuit (not shown) which then admits pulses of high constant frequency to a pulse counting circuit. The input gate is arranged to open at the first desired signal output voltage and close at the second. The interval between the gate operations is thus equal to one period T1. The pulse frequency may be controlled by a crystal oscillator.