Patent GB-561818-A (GB)
Title: Improvements in or relating to the automatic electrical control of metal cutting or like machine tools
IPC: B23C9/00
Filed: 1943-02-08
Abstract: 561,818. Electric motor control systems. JONES, W. H., and LYONS, W. H. Feb. 8, 1943, Nos. 766, 5200 and 9680. [Class 38 (iii)] [Also in Group XXII] In the electric control of machine tools such as milling-machines a control member is rotated in conformity with the traverse of each slide of the machine, each member carrying adjustable dogs which actuate switches to control the respective motors driving the slide traversing mechanism. As applied to a milling-machine for automatically generating a profile such as that shown in Fig. 2, the cutter d, Fig. 1, is carried by a head c vertically movable on a carriage a movable horizontally on guides b. Three electric motors are provided for driving the two traversing mechanisms and for rotating the cutter. A control member e is rotatably mounted on the carriage and is connected to a pinion f engaging a fixed rack g so as to be rotated whenever the carriage is traversed in either direction. A helical groove h on the member e engages a roller i on a switch j to slide the switch along a guide k during its rotary movements and thus allow a series of strikers m adjustably secured in a T-slot, &c. on the member to actuate the switch in sequence. A second control member n on the carriage engages a rack o moving with the head c through a pinion and ratchet so that it will only be rotated in one direction during downward movement of the head, and adjustable strikers 16, 24 are secured in a circular T-slot therein to engage switches 17, 25, Fig. 5. The switches actuated by the control members energize solenoids operating one of two ratchet wheels connected to a cam drum u on the carriage a consisting of a number of discs each having a tooth for engagement with one of the switches 8, 12, 15, 20. The discs have polygonal central apertures engaging the spindle and may be arranged in any order to cause the teeth thereon to actuate their switches in sequence and thus control the motor switches 2 .. 7. The operation of the machine in producing a work piece such as A, Fig. 2, is started by depressing the button w, Fig. 5, thus closing contactor x, which maintains itself, and also contactor y for . the cutter-rotating motor (not shown). A cycle then commences and the traverse motor 39 starts at slow speed forward by closure of contactor 3 due to switch 8 being closed by the first disc on the cam drum. When the striker 9 on the control member e closes switch 10, coil 11 is energized to operate the ratchet for the cam drum which is thereby rotated to allow switch 8 to open and to close switch 12 through the second disc thereon. This closes the high speed contactor 4 for motor . 39 and subsequent rotations of the cam drum cause 12 to open and 8 to close for slow traverse to machine the part U and then 8 opens and 15 closes to close the down feed contactor 6 for motor 40, thus feeding the cutter into the work. Downward feed causes rotation of the control member n and, when the required depth has been reached, striker 16 thereon closes switch 17 to energize solenoid 18 and operate the cam-rotating ratchet, thus opening switch 15 and closing 8 for slow traverse to machine the part V. The next rotation of the cam by switch 10 opens switch 8 and closes 20 to close contactor 7 and raise the cutter until a stop 21 on the cutter head engages a switch 22 to release and re-energize solenoid 18, thus rotating the cam to start slow traverse again. The traverses and feeds alternate until the work has been completed, and during the final raising of the cutter head, the switch 25 is held open by striker 24 on the disc n to short circuit switch 22 and thus allow the head to rise clear of the work until the stop 21 engages a switch 26 to. energize a relay 27. This breaks the circuit to switch 20 to bring the cutter head to rest, stops the drive for the cutter and closes contactor 2 for slow reverse traverse. A time lag switch 32 opens contactor 2 and closes the fast reverse contactor 5 which continues to function until striker 35 on member e trips a switch 31 to bring the machine to rest. For restarting, contactor 6 is closed by a push-button 36 which also breaks the circuit to switch 27 to restore switches 28-30 to their original positions and the disc n is reset by hand. The switches 8, 12, 15 and 20 may be operated by push-button 37 and reverse contactors 2, 5 by push-button 38 when setting up the machine, the cam drum u being then rotated by hand. The control member e may be replaced by a disc having a spiral groove for receiving the strikers m.