GB701954A - Improvements in hardness measuring apparatus - Google Patents

Abstract

701,954. Hardness testing : pneumatic gauges. SOC. D'APPLICATIONS ET DE CONSTRUCTTONS POUR MATERIEL AUTOMOBILE. S.A.C.M.A. March 13, 1952 [March 17, 1951], No. 6575/52. Class 106 (2) In an apparatus for measuring the hardness of a piece by means of a ball or cone &c. driven into the piece by the action of a diaphragm subiected to the pressure of a gaseous fluid, hardness is determined by measuring, by means of a pneumatic device, the displacement of the diaphragm under the effect of a given pressure, and is characterized in that the same source of gaseous fluid at constant pressure supplies the fluid acting upon the diaphragm and feeds the pneumatic measurement device. A supply of compressed air is maintained at constant pressure in a pipe 74, Fig. 2, by a head of water H. After passing through a calibrated nozzle 82, the air is fed by a pipe 36 to a chamber 16 beneath a diaphragm 19, Fig. 1. which incorporates a ball 20, supporting a rod 21 embodying a conical diamond 22 which is applied to the surface of the workpiece 9. Two air leakages are provided in the chamber 16 ; a small calibrated leakage 33, Fig. 2, and a larger aperture 38, Fig. 1, which, when closed by manually depressing a lever 40, causes pressure to build up beneath the diaphragm 19 and force the conical point 22 into the workpiece. The pressure in the chamber 16 is indicated by a hydrostatic gauge 79. Pneumatic gauging of the depth of the impression is performed by a device 29 incorporating a plunger 28 spring-urged to maintain contact with a plunger 27 which follows the movement of the ball 20. This movement adjusts the effective leakage aperture to atmosphere between the conical end 54 of the plunger 28 and its seating 55. Compressed air is supplied to the gauge via a calibrated nozzle 71 and the pressure in the chamber 58-which is related to the size of the leakage aperture and therefore to the depth of the impression in the workpiece -is indicated by a hydrostatic gauge 72. Means are described for adjusting the position of the gauge for zeroizing, and for adjusting the height of the workpiece support 8.