Patent GB-830461-A (GB)
Title: Improvements in or relating to plugs or closures
Inventor: CAIL ROLAND ALLAN
IPC: G05B19/4105
Filed: 1954-07-03
Abstract: 830,461. Electric copying machines. ELECTRIC & MUSICAL INDUSTRIES Ltd. July 21, 1955 [July 3, 1954; July 30, 1954], Nos. 19543/54 and 22251/54. Class 40 (1). [Also in Group XXXVI] In a machine tool in which a record automatically controls the relative displacement between a tool-holder and a work carrier compensating means are provided for superimposing an additional displacement to take account of a dimension or dimensional error of the tool held by said tool holder. The machine described is similar to the cam-profiling machine described in Specification 807,643 in which a milling cutter 1 shapes a workpiece 4 which is rotated by a motor 6 and traversed by a servomotor 14 under instructions from a perforated record in a reader and digital-to-analogue converter 23, all the analogue signals being represented by the amplitude of an alternating voltage derived from a common source. A synchro transmitter 9 driven by the motor 6 controls a synchro receiver 10 to rotate a shaft 11 in synchronism with the rotation of the workpiece 4. The servomotor 14 is controlled by an error detector 16 receiving one signal from a lead 17 representing the desired displacement between the axis of the tool 1 and workpiece 4 and another, of opposite polarity, representing the actual displacement and derived from a potentiometer 20 driven by the motor 14 through a gear-box 15. The potentiometer 20 may be replaced by a linear interpolator as described in Specification 802,472. The instructions from the reader 23, which are in the form of angularly-displaced ordinates, are applied to a pair of quadratic interpolators 21, 22, which may be of the type described in Specification 796,994, the output from which is derived from the brushes 25, 26 of a rotary switch driven by a shaft 24 coupled to the shaft 11. The output of the brushes 25, 26 is applied to the auto-transformer 27 of a linear sub-interpolator, as described in Specification 796,994, which injects modifying signals into transformers 31, 33, whose secondaries are in the output leads of the quadratic interpolators 21, 22. The modified signal representing the required ordinate before correction for tool dimension is derived from the centre point 27a of transformer 27 and fed to an adding circuit 36. The correction for the tool dimension comprises a component a which is added to the ordinate derived from the reader 23 and a component d which is used to modify the angular displacement between the tool and work axes, these quantities being derived from a computer 43 (see Group XXXVI). The inputs to the computer are a quantity e which is the difference in the lengths of adjacent ordinates and a quantity s which is the length of arc between adjacent ordinates and the correction is based on the equations a=r cos #, d=a sin # and e/s=d/a where # is the angle between the desired cutting line and the normal to the starting ordinate, Fig. 1 (not shown). The quantity a from computer 43 is fed to the adder 36, the sum of whose inputs is fed to the lead 17. The quantity e is fed to the computer 43 from a secondary winding 44 coupled to the auto-transformer winding 27 and the quantity 8 (= r ##) from a potentiometer 41 driven by motor 14 and supplied with a voltage whose value is set by a switch 39 whose position depends on the gear ratio of a gear-box 37 between shafts 11 and 24. This ratio depends upon the angular separation, ##, between adjacent ordinates and may be set manually or automatically as described in Specification 807,644. The quantity d is fed from the computer 43 to an error detector 46 where it is compared with the product r.## of the modification of the angular displacement ## and the ordinate r. This angular modification is introduced by a differential gear 38, between shaft 11 and gear-box 37, controlled by a servomotor 47 from the error detector 46. The product r.## is derived from the output of a potentiometer 50 driven by motor 14 and supplied from the output of a potentiometer 49 driven by the motor 47. In practice, the potentiometers 19, 41, 49, 50, are auto-transformers and the error detectors 16, 46 include rectifiers. The perforated record may be replaced by a continuous record, such as a prototype and the invention is stated to be applicable to three-dimensionally controlled machines or those such as described in Specification 830,462.