Patent GB-911336-A (GB)
Title: Optical equipment for the accurate setting and reading of the amount of displacementof a slide
IPC: B23Q17/22
Filed: 1960-09-26
Abstract: 911,336. Tilt compensators. HENSOLDT & SOHNE, OPTISCHE WERKE A.G., M. Sept. 26, 1960 [Oct. 3, 1959; March 11, 1960], No. 32933/60. Class 97 (1). [Also in Groups XIX, XXII, XXIX and XXXVIII) For eliminating the effects of tilt (pitch) and rotation (yaw) of a slide 4 in a machine tool, length-measuring device, or the like, on the accuracy of measurement of the slide position by a scale M on the slide and a scale reading device 7, 8, 9, 10, 11 on the fixed part of the machine, or vice versa, a collimator 12 is attached to the slide to provide a reference mark for lining up an alignment telescope 13 mounted in gimbals 15 attached to the fixed part, or vice versa. The adjustment of the alignment telescope, about axes which are orthogonal to each other and to the slide guideway axis, to follow displacement of the collimator mark as the slide pitches and/or yaws, is effected by two mutually orthogonally aligned screws 16, 17 and the telescope movement is transmitted by controlling means to an optical compensating member 8, supported in gimbals 46 in the image-forming ray path of the scale-reading device, which so displaces the scale image as to compensate for the effect of pitch and/or yaw. The controlling means are adjustable to selectively vary the transmission ratio between the amount of movement of the telescope and that of the optical compensating member in dependence on the height of a workpiece. (For a given angle of pitch u and/or yaw v, the linear displacement (a, b) of a point in the working plane is assumed proportional to the height of this plane from the measuring scale.) As shown in Fig. 2, a lever 14 carrying the alignment telescope 13, is fixed at one end to gimbals 15 allowing pivoting of the lever 14 in two mutually orthogonal planes. Adjustment of telescope 13 by screws 16, 17 to follow the mark of collimator 12 as the latter is displaced with the slide 4 causes a spherical part of lever 14 to bear against either or both of mutually orthogonal spring-loaded piston rods 21, 21<SP>1</SP>, which are hydraulically connected, respectively, with output pistons 42, 43<SP>1</SP>, Fig. 4, actuating a gimbal-mounted lever 45 carrying a pentag prism 8 which serves as the optical compensating element. Displacement of pentag prism 8 in the direction of either of the piston rods 42 or 43<SP>1</SP> will produce a shift of the scale image along the same line. The hydraulic linkage between each pair of " input " and " output " pistons includes three piston-and-cylinder systems of different diameter arranged in parallel which can be selectively isolated by 3-way stop-cocks to vary the ratio of input/output piston movement. In other embodiments, there is a single output piston which imparts the sum of both. transmitted movements to the optical compensating element which is mounted to be pivotable only in a single plane. The optical compensating element may comprise two prisms (Fig. 10) suspended in parallelogram linkages, or a Boskowitch wedge. The hydraulic system may be replaced by an electric motor that tilts the compensating element 115 (Fig. 17) by means of a rack and pinion device in response to the out-of-balance current in a bridge circuit (Fig. 18) whose arms include condensers (e.g. 132, 134), resistors or inductances which are varied by movement of the alignment telescope. Instead of being applied to an optical compensating element, movement of the alignment telescope may be transmitted directly to the graticule of the scale-reading device.