GB773160A - Improvements relating to pneumatic gauging devices for effecting linear measurements - Google Patents

Abstract

773,160. Pressure gauges for effecting linear measurements. MERCER, Ltd., T., and WEATHERBY, D. J. Dec. 22, 1955 [Jan. 31, 1955], No. 2839/55. Class 106 (2). In a device for effecting linear measurement comprising a source of gas fed through a filter 1, a pressure regulator 3, a control orifice, e.g. the needle valves 14, 15 to a gauging head 17 having a second orifice governed by the linear dimensions of the workpiece, the pressure gauge includes an indicator tube 27 containing a liquid column 30, one end of which is subjected to the back-pressure, dependent on the dimensions being gauged, at the valve 14, and the other end of which communicates with a pressure-sensitive device 35 having a predetermined, preferably linear, pressure-displacement characteristic such that displacement of the first end of the column 30 from a predetermined level indicates the back-pressure and hence the required dimension. As shown, the pressure-sensitive device comprises a metallic bellows 36 containing gas raised to a predetermined standing pressure by means of a sealing plug 38 and has stop surfaces 39, 40, 41, 42 to limit its deflection. The predetermined liquid level may be varied by means of a screwed plug 32. A flow restrictor 22 is provided between the gas in duct 18 and the liquid in the column 27. The liquid may be water coloured with a chemically inert dye and the internal surface of the tube 30 may be rendered water-repellant.