GB723822A - Improvements relating to apparatus for indicating and/or controlling a dimension of articles moving in the direction of such dimension - Google Patents

Abstract

723,822. Measuring length. METROPOLITAN VICKERS ELECTRICAL CO., Ltd. May 27, 1953 [July 24, 1952], No. 18799/52. Class 40 (1) [Also in Group XL (b) ]. An apparatus for measuring the deviation from a standard length of articles moving in the direction of their length, comprises two detector devices spaced apart in the line of motion, giving impulses in response respectively to the passage of the leading and trailing edges of an article, and means for integrating a current proportional to speed over the time interval between the impulses to give a measure of length. The deviation measured may be indicated and/or may control the length of the articles. In the first embodiment described (Fig. 1) for red-hot steel billets, two photoelectric cells PC1 and 2 equipped with collimators are at a distance apart equal to the standard length and feed pulse generators P.GENS 1 and 2 which give simultaneous short rectangular pulses b, b1 of opposite sign which sum to zero if the billet is standard. If it is not the pulses are no longer simultaneous and the sum consists of two consecutive pulses of opposite sign which are integrated in INT 1 to give a rectangular pulse C of duration equal to the pulse interval and of sign dependent on the order of occurrence of pulses b, b1. This pulse actuates an electronic switch ES which according to its sign switches on one of a pair of integrator circuits in INT 2 for the duration thereof, the integrator circuits being supplied with the output of a tachometer generator TG connected to the billet conveyer to give an integrated voltage of sign dependent-on whether the deviation is positive or negative proportional to the deviation in length. The circuit RS, tripped by the leading edge of wave C effects transitron resetting of the integrator circuit after a fixed time interval. In a modification (Fig. 2) the amplified outputs of the photo-electric cells trigger circuits, which may be of the flip-flop type having a stable and an unstable state or having two stable states, producing outputs d, d1 which have steps of opposite sign differing in time so that the summated output is again a rectangular pulse C of duration equal to this time difference, this pulse directly operating the electronic switch ES. If the circuits are of the flip-flop type the resetting time must exceed the maximum period between pulses, whilst if they have two stable states the integrator resetting device is arranged to give a resetting pulse to both a fixed time after the occurrence of the first step. The output voltage of the device may be used for resetting the shearing machine to reduce the deviation in length.