Patent GB-599795-A (GB)
Title: Method and apparatus for controlling the operation of a machine tool
IPC: B23Q15/00
Filed: 1944-05-08
Abstract: 599,795. Lathes. WINTERMUTE, G. J., and BENCH, D. E. May 8, 1944, No. 8663. [Class 83(iii)] [Also in Group XXXVII] A method of operating a machine tool in which the work piece is rotated and in which the tool is fed at a constant speed, includes the steps of controlling the length of the cut by electrically timing each feed movement to a predetermined duration. In one arrangement, Fig. 2, the lead screw of a lathe is driven by a synchronous motor 1 through a magnetic clutch having foward and reverse windings 4a, 4b, respectively, and the cross-feed screw is driven by a synchronous motor 2 through a magnetic clutch with forward and reverse windings 6a, 6b. To start the lathe, the operator presses a button 7a. This completes a holding circuit through a solenoid 12 and starts up the motors 1 and 2 and also smaller motors 16 associated with a timing mechanism to be referred to later. To begin the first operation, the operator then presses a button 8a. This energizes a solenoid 13a of a switch which is actuated to complete a holding circuit through the solenoid, to energize the clutch 17 of the timing mechanism and also to energize any one of the clutch windings 4a, 4b, 6a, 6b, according to the setting of a selector switch 15a. After a predetermined time a rotary arm 52 driven through the motor 16 and clutch 17 will engage contacts 18 to break the holding circuit through the solenoid 13a and so stop the operation. The second operation is then begun by depressing button 8b which controls members similar to those already described with reference to the first operation. Preferably a single starter button would be employed and moved around a circular track to the various operational stations. Alternatively, the rotary arm 52 could, in addition to breaking the contact 18, also make contact so as to energize the solenoid 13b and start the second operation. In another form a single synchronous motor 26 may drive all the timing units from a shaft 27 as shown in Fig. 11. Each unit comprises a clutch part 56 keyed to the shaft and movable by a solenoid 53 operating through a bell-crank lever 55 to engage the part 57 carrying the rotary arm 52. The breaker points 18 are carried by an arm 60 having a zero mark to register with a scale marked on a scale 51. After setting, the arm 60 may be clamped by a knurled screw 62 and clamping plate 63. If desired, the whole of the machine may be driven from a single synchronous motor through suitable gearing and a single timing unit may be employed. In this form of control the relays are replaced by double pole switches 30a, b, c, and d, Fig. 6. The operation of a switch establishes a circuit through the clutch 17 of the timer and another circuit through two lines from the selector switch 31, thus selecting either forward or reverse movement of the cross-feed screw or of the lead screw. The operator's control for a circuit of the kind shown in Fig. 2 and referred to above, comprises a push button unit slidable around a circular track 35 (not shown) to positions where the button 36, Fig. 8, may be depressed to actuate plungers 42 co-operating with fixed contacts 42, 43. In the position shown the end of an arm 44 engages the side of the plunger 42 so as to position the button. When the button is depressed, the arm 44 moves under the action of a spring 45, over the head of the plunger 42 so as to shield it against a second accidental actuation. In addition the depending end 50 of the arm hooks over the plunger 42 to prevent a backward movement of the button unit 36 along the circular track. On a forward movement of the button the arm engages the next contact, correctly positioning the button as before and preventing the operator from passing the contact and so missing one of the machining operations.