GB782691A - Differential pneumatic linear dimension comparator gauge - Google Patents

Abstract

782,691. Pneumatic linear-dimension gauges. FORTIER, A. Nov. 8, 1954, No. 32222/54. Class 106 (2). A pneumatic linear dimension gauge whose operation is independent of the pressure of the air supply comprises a casing 1, 2 having two chambers 10, 12 separated by a flexible diaphragm 3 operating a dial indicator 28 and disposed between a pair of perforated concave members 36, 37, the diaphragm being substantially non-elastic and of such surface area that it can conform to the concave surfaces without tension. A source 14 supplies compressed air through a passage 4 which is connected by ports 7 to the chamber 10 and by ports 5 to the chamber 6, and through a passage 11 connected by ports 13 to the chamber 12, there being two inlets 16, 17 and two outlets 23, 19, the outlet 23 being controlled by a valve 27a operated by the diaphragm, which may be of thin leather, and the outlet 19 being disposed at a short distance from the object 21 to be gauged. The dimension of the object 21 to be gauged determines the pressure in the chamber 12 and if this exceeds the pressure in the chamber 10 the diaphragm 3 will move upwards, acting on the rods 33, 27b so that the valve 27a will decrease the escape of air through outlets 23 and 26, raising the pressure in the chamber 10 until there is equilibrium. Thus the reading of the dial 28 connected by a rod 30 to the member 27a is a function of the dimension. A weak spring 31 keeps the member 33 in contact with the diaphragm 3. In another embodiment an additional outlet is provided which may be used in conjunction with a series of calibrated nozzles to permit comparison within a number of ranges of measurement. In place of the dial gauge 28 a rack and pinion device engaging a series of micro-switches which operate a corresponding series of lamps may be incorporated to indicate whether the dimensions of objects placed on the bracket 20 are within, above or below specified limits. Fig. 5 is a cross-sectional view of a cylindrical gauging head with diametrically opposed openings in place of the members 19, 20 of Fig. 1 for checking the internal diameter of a ring. By connecting a further gauging head at 22 the gauge can be used for checking angles of conicity. The valve 27a can be modified to control the inlet of air to the upper chamber.