GB759150A - Improvements in and relating to measuring or gauging apparatus - Google Patents

Abstract

759,150. Gauge - - testing apparatus. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Aug. 16, 1954 [May 14, 1953], No. 13578/53. Class 106 (2). Apparatus for testing, e.g. dial gauges comprises means which apply a continuously variable displacement to the driving link of the gauge under test and which produces a relative movement between a reference mark and the gauge such that the mark indicates the position the pointer of the gauge should occupy if the gauge is accurate, throughout the displacement of the driving link. As shown, the gauge 21, Fig. 1, to be tested is mounted on a supporting plate 18 which can be rotated on a shaft 14 relative to the base 11 of the apparatus. The shaft 14 is coaxial with a stationary helical gear 13 which engages with a helical pinion 33 secured on or integral with a lead screw 29 pivoted at its ends in lugs 27, 28, Fig. 2, formed at the bifurcated end of the supporting plate 18. With the screw meshes a nut formed in two portions 34, 35 on opposite sides of the pinion 33 to permit a considerable traverse along the screw, the nut being formed in or secured to a saddle 36 whose rotation relative to the screw is checked by a screw 37 carried in a cross-bar 39 joining the lugs 27, 28. Against a flat surface 42 of the saddle 36 are pressed two piles of slip gauges 43, 44 upon which are seated two balls 45, 46 carried at an accurately known distance apart on the underside of a bar 47. A block 48 secured to the plate 18 carries a plunger 49 having a round end riding on the bar and the other end actuating the plunger 22, i.e. driving link of the dial gauge under test. During a test the dial gauge supporting plate is rotated by means of gearing 55, 56 and its plunger is continuously displaced as it moves relatively to the sine-bar 47 which is traversed by the engagement of the nut 34, 35 with the leadscrew. The pitch of the screw, the ratio of the gears 13, 33 and the slope of the sine-bar are so chosen that during the rotation of the dial guage its indicator, if the gauge is accurate, should remain stationary with respect to a datum mark 26 secured to the apparatus frame. As shown, the mark 26 is in double form which straddles the correct position so as to show whether the instrument under test is within a tolerance corresponding to the spread of the double mark. In another embodiment the gauge to be tested is mounted on a base board with a similar instrument of high accuracy and by means of a lead-screw and a cross-bar the same displacement is given to the plungers of both gauges. The gauges are spaced at a suitable distance apart and are observed as a stereoscopic pair so that any deviation of the gauge under test may be visually detected.