GB755052A - Improvements in or relating to apparatus for controlling a machine tool in response to dimensional changes of a workpiece - Google Patents

Abstract

755,052. Size gauging. SIGMA INSTRUMENT CO., Ltd. Nov. 23, 1954 [June 4, 1954], No. 16645/54. Class 60 A control apparatus comprises means 1 responsive to dimensional changes of a workpiece W undergoing treatment in a grinding machine for correspondingly varying the pressure in a pneumatic pressure responsive element 14, an electric switch device 15, 16 operable by said element and means for initiating a control signal to the machine tool when said switch device is operated to vary the action of the machine on the workpiece. The means 1 consists of an orifice 5 connected to a supply 8 of air under pressure and controlled by a valve 4 which is in turn controlled by a spring-loaded stylus 2 bearing against the workpiece W. The back pressure at the orifice 5, which is dependant upon the position of the valve 4 and hence upon the size of the workpiece, is communicated by a conduit 12 to the element 14. The latter carries one element 15 of the switch device and is in the form of a flexible capsule mounted inside a chamber 13 which is also connected to the supply 8. Two adjustable valves 18, 22 determine the pressure inside this chamber and hence the pressure required to expand the capsule 14 and to operate the switch device 15, 16. As the diameter of the workpiece is reduced the valve 4 approaches the orifice 5 until the pressure in the conduit 12 is raised sufficiently to close the switch 15. 16 which energizes a relay 24. The latter closes contacts 28 in a holding circuit and contacts 30 to energize an electromagnet 60B for ending a first stage of operation of the machine. After contacts 28 have closed, contacts 27 open to disconnect the relay 24 from the switch 15, 16 and contacts 26 close to place a second relay 25 under control of the switch 15, 16 which is simultaneously opened by an increase of pressure in the chamber 13 with corresponding collapse of the capsule 14. This increase in pressure is produced by a valve 21 which is controlled by the relay 24 and cuts off the escape of air through the valve 22. Further reduction of the workpiece diameter now takes place until the capsule 14 is again expanded to energize the relay 25 which closes contacts 32 in a holding circuit and contacts 34 to energize an electromagnet 60A for ending the second stage of operation. The relay 25 also opens contacts 31 to de-energize the relay 24 which in turn opens contacts 26 to isolate the relay 25 from the switch 15, 16 and contacts 30 to de-energize the electromagnet 60B. De-energization of the relay 24 also permits the valve 21 to open and thus restores the pressure in the chamber 13 to its original value. After a new workpiece has been inserted in the machine, a push-button switch 55 is actuated to break the holding circuit for the relay 25 so that the control apparatus is ready to commence the first stage of operation upon the new workpiece. A switch 47 enables the switch 55 to be isolated and the relay 25 to remain under the control of the switch 15, 16 so that if desired, the circuit may be re-set bv the insertion of the new workpiece which moves the stylus 2 and hence the valve 4 to a position in which the capsule 24 collapses and opens the switch 15, 16. Warning lamns 70, 72 are also operated by the relays 24, 25. The collapse of the capsule 14 is limited by a rod R.