Patent GB-953317-A (GB)
Title: Improvements in or relating to gauging devices
Inventor: ADAMS JOHN REGINALD
IPC: G01B5/08
Filed: 1959-05-27
Abstract: 953,317. Measuring dimensions. RANK PRECISION INDUSTRIES, [trading as TAYLOR, TAYLOR & HOBSON]. May 19,1960 [May 27, 1959], No.18062/59. Headings G1M and G1N. A gauge for a cylindrical workpiece comprises elements contacting the workpiece in a plane at right angles to its axis so that the points of contact define a basic circle, one element being displaceable out of this circle to contact the workpiece when the diameter of the latter differs from that of the basic circle, and a transducer responsive to the displacement of the element, coarse and fine means being provided to adjust the diameter of the basic circle by appropriate movement of the contacting elements. In Fig. 3 (a side view of the device) the interior of a hollow workpiece is contacted by two raised bars C<SP>3</SP> on plugs C<SP>1</SP>, and by a stylus E on a bar D projecting through a hole in the casing A. The bar D has a right-angled extension piece D<SP>1</SP> and is mounted on a fixed bracket A<SP>3</SP> by means of crossed spring ligaments G<SP>1</SP>G<SP>2</SP>. Displacement of the stylus E causes the bar D to pivot and move an arm H<SP>4</SP> which is suspended from the bracket A<SP>3</SP> by further spring ligaments LH<SP>1</SP>H<SP>3</SP> and suspension arms HH<SP>2</SP>. Movement of the arm H<SP>4</SP> in turn moves the armature J of a differential transformer to give an output signal from the secondaries. A spring K urges the stylus E downwards into contact with the workpiece. The plugs C<SP>1</SP> are carried on arms C mounted on the front of equally-inclined slides B (see also front view in Fig. 2) which can be moved lengthwise by a knob F via the worm F<SP>1</SP>, pinions F<SP>3</SP> and racks B<SP>2</SP>. The diameter of the basic circle formed by the three contacting elements can thus be pre-set, and the transducer output will be a measure of the deviation of the workpiece internal diameter from this pre-set value. A plurality of such calibrated values may be provided, and the arms C may be changed to extend the range. Fine adjustment of the basic circle is provided by a knob N which rocks a right-angled lever M which presses against the arm H (Fig. 3) and moves the whole framework H<SP>2</SP>H<SP>4</SP>D<SP>1</SP> relative to the casing, thus producing a resultant vertical movement of the stylus E. The device is suitable for controlling a grinding machine to make a plug which will fit a hollow workpiece with predetermined clearance. The coarse and fine adjustments are used to set the transducer output to zero with a master bore in position, and a caliper gauge (not shown) is similarly set to zero against a master plug. The bore to which the plug is to be matched is then substituted, and the transducer output signal is used in conjunction with the caliper gauge to control the grinding of the plug to the required size. Modifications. The worm F<SP>1</SP> for effecting the coarse adjustment may be replaced by a screw and nut. The spring K can be omitted if the crossed ligaments are suitably biased, or the stylus E can be moved into engagement with the workpiece by a screw stud. The slides B need not move in the direction of their common intersection. The bars C<SP>3</SP> may be replaced by studs and need not engage the workpiece in the same vertical plane as the stylus E. The whole device can be modified to determine the external diameter of a cylindrical workpiece.