Koordinatenvermessungsgeraet

摘要

1,193,168. Selective signalling. FERRANTI Ltd. 3 Dec., 1968 [9 Dec., 1967], No. 56073/67. Heading G4H. To determine the x, y co-ordinates of the centre of a circular hole or stub on a workpiece, a frame 14 is moved on a gantry (not shown) to the correct position of the centre, and with probe 22 in a datum position (aligned with axis 12 of shaft 11, in the case of a hole), the frame 14 is lowered and probe carriage 21 is released so that it is biased along arm 16 towards the edge of the hole or stub by springs 25, 27. Shaft 11 and arm 16 are rotated by hand to a starting position L or L1, Fig. 2, defined by a stop, and the arm 16 is then rotated away from the stop so that probe 22 follows the periphery of the hole or stub. Consequential movement of carriage 21 along arm 16 is detected by optical gratings and photo-detectors 33 producing a pulse on a lead 34 or 35 for each increment of movement. Divider 48 halves the numbers of pulses on leads 34, 35 since the coordinates of the actual centre H of the hole or stub are represented by the equations x = ¢ (OB-OA) and y=¢ (OD-OC). Associated with shaft 11 is a reflective block 42 and photocell array 44 providing signals which control network 47 to feed pulses to the X counter 51 only during movement of the probe round the arc ACB or ADB and to the Y counter 52 only during movement of the probe round the arc CBD or DBC. The signals on channels 45, 46 also effect switch-over of the add and subtract inputs of the counters as becomes necessary when the various co-ordinate axes are crossed. Block 42 is essentially square in plan, its vertical faces evenly illuminating a pair of horizontally-spaced photo-cells when arm 16 is aligned with one of the co-ordinate axes, the phase of the photo-cell outputs indicating the direction of rotation of shaft 11. The upper and lower edges of block 42 are bevelled to selectively illuminate two vertically-spaced photocells to provide a 2-bit signal indicating the identity and sign of the axis being crossed. Network 47 is illustrated in detail in Fig. 6 (not shown). Counters 51 and 52 may have an associated quadrant indicator controlled by sign stages 511, 521. The apparatus may also be used for determining the dimensions of a workpiece.