GB842045A - Pneumatic gauges - Google Patents

Abstract

842,045. Pneumatic gauge-photo-electric control. TOLIMIT GAUGES Ltd., WILLS, S. A., and GATHERCOLE, E. F. J. Feb. 26, 1958 [Nov. 26, 1956], No. 36152/56. Class 40(3). In a pneumatic gauge the rate of flow of gas through the measuring head is determined by means, including a photo-electric cell, and responsive either to the pressure measured by a monometer at the throat of a venturi placed upstream of the head, or to the position of a plug in a transparent divergent passage through which the air flows and whose vertical displace-. ment is a measure of the gas flow. In Fig. I the gas compressed air flows from a constant pressure source via the venturi 17 to the measuring head 18. The difference in pressure between the Venturi throat 17 and the point 16 upstream thereof is a measure of the gas flow and this difference is measured by the monometer comprising tubes 21 and 18 and the tank 20. In addition to the calibrated scale 19 two photoelectric detectors are provided comprising the lamps 25 and 30 and associated phototransistors 26 and 31 which are energized when there is no liquid between them and the source. The detectors are slideably mounted so that they can be set to any position on the scale 19, the output of each photo-transistor is amplified by a further transistor and operates a relay. In operation the relays associated with each detector can be arranged to operate visual indicating devices which indicate whether an article being gauged is within required dimension limits, or arranged, in conjunction with a machine tool, to cease a machining operation when the size of the article being machined reaches a required dimension.