Patent GB-1308675-A (GB)
Title: X-ray inspection apparatus
IPC: G01N23/18
Filed: 1970-03-13
Abstract: 1308675 Photo-electric testing of tyres PICKER CORP 13 March 1970 [ 13 March 1969 23 April 1969] 12192/70 Index B7C 75 The splices within each ply P1, P2 of a green tyre being rotated by motor-driven rollers 24 are investigated by monitoring X-radiation that has passed from sources H1, H2 through the tyre using two detector assemblies 36a, 36b and 38a, 38b located below the tyre adjacent opposite axial ends thereof. Splices 88a, 88b in one ply are oriented differently from splices 86a, 86b in the other ply, and the detectors are provided with slits, e.g. 44b, so that each detector in a detector assembly responds only to one orientation of splice. The circuitry for the detectors, which may be scintillation counters, is shown in Fig. 7 for just one detection channel, e.g. detectors 36a and 38a which respond to splices of a given orientation. Each such detection channel comprises five signal channels, as detailed below, each responsive to a different type of splice defect to produce an audio or visual reject signal. A defective tyre may also be marked and/or rejected. The five signal channels are:- (a) An open splice indicating channel 104. An open splice, i.e. one where two ply ends do not meet, produces a positive going pulse from each detector 36a, 38a. The pulse from 36a is delayed in a circuit 116 for a time equivalent to the travel time of the splice from 36a to 38a. The resulting pulse from 38a and the delayed pulse from 36a are supplied to AND gate 118 to produce an output to the rejecting OR gate 122. Joined splices produce negative going outputs from the detectors, which outputs do not produce an output from the open splice detectors 114, 120. (b) A tapered splice detecting channel 106. Pulses corresponding to opposite ends of a splice are fed to a difference amplifier 126 and integrator 128. If the resulting difference signal exceeds a pre-set threshold, indicating an excessive splice taper, a reject signal is generated. (c) Width idicating channel 108. The narrower of the two signals from a splice is passed by an AND gate 132 to an integrator 134 whose output is supplied to three threshold devices 136-140. A reject signal is produced if the splice is too wide or narrow. (d) A splice number indicating channel 110. This comprises a counter 147 which counts the number of splices in a ply and produces a reject signal if this number exceeds two. (e) Spacing indicating channel 112. This employs a differentiator 148 and a delay circuit 150 to measure the spacing between two splices of the same orientation. A signal is produced from AND gate 152 if this spacing is less than a preset amount, and this signal is supplied to the reject OR gate 122. The delaying components of the above circuitry are described in detail, Figs. 8a, 8b (not shown), and include a plurality of astable, monostable and bistable multi-vibrators, among other logic elements. To compensate for variations in the output of each X-ray source, two additional detector arrays 46, 48 are provided, one adjacent each source. Each of these four detectors is paired with one of the detectors outside the tyre in a differential circuit arrangement, Fig.4 (not shown).