GB818628A - An angle measuring or setting instrument - Google Patents

Abstract

818,628. Scale-reading devices; measuring angles. HENSOLDT & SOHNE OPTISCHEWERKE A. G., M. July 18, 1957 [Aug. 2, 1956; Nov. 16, 1956], No. 22742/57. Classes 97(1) and 97(2) An angle measuring or setting instrument includes a rotatable body carrying an annular coarse scale having double line dimensions and a scale reading device movable relative to the coarse scale, said scale reading device having optical elements for forming an image of at least one division of the coarse scale in a reading window, a fine scale mounted to appear in this window, means for moving the fine scale relative to the coarse scale image, and a further rotatable scale mounted to appear in the window and connected with the means for moving the fine scale. The optical dividing head shown comprises a spindle 1 which is rotatable by a handwheel 4 and carries on a cylindrical flange 20 a coarse degree scale 21 having double line divisions Fig. 3, the part of which immediately below an opening 22 is illuminated by rays from a lamp which are reflected by a semi-reflector 25 into an objective 24 and roof prisms 23. These optical elements together with two further prisms 26 and 27 (Fig. 4) and a lens 28 which receive the light reflected by scale and transmitted at 25 form a system which images the illuminated part of coarse scale 21 in a window 29. Adjacent this window is a plate 32 carrying a fine degree scale 39 having single line divisions, the plate 32 being linearly movable by rotating an eccentric 33, spring urged at 50 into constant engagement with a pin projecting from plate 32, and carrying a circular scale 37 which is divided into minutes and is readable against an index mark 38 (Fig. 1). By moving plate 32 until a graduation on scale 39 is enclosed by the image of a double graduation on scale 21, the rotation of spindle 1 is given in degrees and minutes. In a further form of dividing head, the coarse scale 21 is in two parts, one of which carries scale numbers and is rotatable relatively to spindle 1 and the whole optical system is mounted in a housing which can be rotated relatively to the spindle to facilitate zeroing. For the same purpose, the optical system may alternatively be fixedly mounted and include a prism which is slidable under the control of a rotatable cam to displace the image of the coarse scale. The two-part coarse scale 21 may be on spherical surfaces. In the optical turntable of Fig. 9, the table 90 is rotatable by a handwheel and has a coarse degree scale 96 on its underside. An image of this scale is projected on to a window 102 by lenses 99 and prisms 100, 101 so that this image appears superposed on a scale divided into 10 feet intervals carried by a glass plate 103 linearly movable by an eccentric having a peripheral scale divided into 5 inch intervals, so that the rotation of the table can be measured in degrees, minutes and seconds. Specification 643,590 is referred to.