Patent GB-785361-A (GB)
IPC: G05B19/4105
Abstract: 785,361. Programming for machine tools. MULLARD RADIO VALVE CO., Ltd. March 9, 1955 [March 15, 1954], No. 7442/54. Class 83 (3). [Also in Group XXXVIII] In a milling machine for generating a shape from analogue interpolation, information is provided on a record in the form of digital input data and supplied therefrom at intervals to means wherein analogue interpolation is carried out automatically during each interval by bending, within its elastic limit, a leaf-spring &c. between two selected mounting points positioned in relation to each other in a manner related to the positions on a curve of datum points determining the ends of the intervals, both the positioning of the mounting points and the bending of the flexible member being effected automatically in response to the information contained on the record, and the desired interpolation information being obtained during each interval by following the flexible member between its mounting points. As shown in Fig. 7, a leaf spring E is held firmly in a rotatable mount A and has a sliding fit in a second rotatable mount B, the slopes fl(n), fl(n + 1), at the ends of the interpolation interval, being set by gearing at A and B and the increment #y(n) being set by a rack and pinion C. A follower D is driven in the direction x following the strip E and thus measuring the distance #y, which when applied to a profile milling machine, Fig. 5, is transferred to the y co-ordinate drive of the machine. The tool T is provided with x and y drives together with measuring systems for both co-ordinates, providing indications of tool position through lines 10, 11, the work-table being driven independently in the x direction. The input information, in the form of punched tape or the like, is applied at 7 and provides as parameters f<SP>1</SP>(n), f<SP>1</SP>(n, + 1), #y(n) and x(n) together with either #x(n) or x(n + 1) when successive intervals are not equal, and by means unspecified, controls the interpolator 6. A subtractor 1 compares the measured position of the table with the initial value x(n) and supplies a difference signal #x to the follower of the interpolator 6. Subtractor 1 also supplies a signal to control 3 at the end of an interval to open momentarily the four gates which allow the data for a new interval to pass to units 6 and 4. The interpolation is carried out from A to B by making xn = yn = 0, i.e. placing the origin of the axes at A, and the instantaneous value #y is obtained from the interpolator for varying values of #x and added to y(n) in the unit 4. The output from 4 is fed to a differential unit D and compared with the position of the tool in the y direction, the error signal being used to operate the y drive. A unit 9 may be provided with a signal proportional to the slope f<SP>1</SP>(n) whereby the speed of the x drive is maintained inversely proportional to the slope. In a modification, Fig. 6 (not shown) the interpolators are used, one being sensed while the other is being reset, and the sensing means changing over at the end of each interval. The flexible member may be in the form of a closed loop with supporting arms adjustable about a common centre, and one or more sections may be set up while any given section is being explored by a continuously-moving follower. Alternatively a flat flexible disc or annular strip may be used. Specification 773,494, [Group XXXVIII], is referred to.