GB767969A - Transverse scale device for the precision reading of scales - Google Patents

Abstract

767,969. Machine-tool details. HEIDENHAIN, J., [trading as WENCZLER & HEIDENHAIN]. April 21, 1954 [April 21, 1953], No. 11584/54. Class 83 (3). [Also in Group XIX] A device for reading the position of e.g. the 100 graduation-line S of a scale, moving with the slide of a machine-tool, comprises, as in Fig. 2, an array of identical, equally spaced rectangles R, m+1 in each column, stepped in succeeding columns in a ratio 1/n. As shown, m=n=10 and the line S cuts the rectangle lying between the fifth and sixth space in the first column and lies most evenly between two rectangles in the fifth column so that the scale reading is 100.55. The scale graduation-lines S may be optically projected on to the device and if the width of the line S is suitably chosen with relation to the magnification ratio and length, along a column, of the rectangles and spaces, the accuracy of the reading may be increased. To determine the kth part of an m, nth part of a graduation, a series of vernier lines may be provided between the line S and in Fig. 5, where m=n=k=10, the image 165 S<SP>1</SP> cuts the rectangle between the second and third spaces in the first column, lies most evenly between two rectangles in the fifth column, and in the fifth column the image of the third vernier line R<SP>1</SP> lies most evenly between two rectangles so that the reading is 165.253. If the geometrical figures of the transverse scale are circles, the graduation-lines are in the form of rows of smaller circles and symmetry balancing is obtained by observing where a small circle is most nearly concentric with a larger one. In an alternative form the graduation-lines are stepped, instead of the rows of geometrical figures being stepped.