Patent GB-712904-A (GB)
Title: Improvements in or relating to machine tools
IPC: B23C3/18
Filed: 1951-04-13
Abstract: 712,904. Control of several motors. EX-CELLO CORPORATION. April 13, 1951 [Oct. 10, 1950]. No. 8649/51: Class 38(3) [Also in Group XXII] A machine for milling workpieces (see Group XXII) has three electric motors M, M1, M2, Fig. 13, arranged respectively to rotate the tool, index the workspindle, and drive a pump for circulating pressure fluid in a system for clamping the work holder and workpiece in position and effecting the traverse and other movements of the workholder. The workpiece W, Fig. 4, is carried between the work spindle 53 and a tailstock 72 on the underside of a frame 40 which is mounted so that it can be swung about a horizontal axis to and from the tool 30 and traversed along this axis with the tool operating on the workpiece. The control circuit includes solenoids SV1, SV2, SV3, SV4, SV5, SV6 for actuating valves in the pressure fluid system. For automatic operation, the closure of a starting switch S1 energizes a relay MR so as to close a switch MR1 and thereby operate the pump motor M2. The closure of a cycle-start switch CS then energizes a relay CR2 which closes a switch CR2-2 to energize a relay CR1 and solenoid SV1 which acts in the pressure fluid system to cause the tailstock to be advanced on to the workpiece. When this engagement reaches a pre-determined pressure, a pressure-responsive device PR1 closes a switch PR1-1 and thereby energizes the cutterspindle motor M through a relay SP and switch SP-1; various valves in the pressure fluid system are then successively operated to cause clamping of the work spindle, tailstock, and workpiece, swing- ing of the frame to bring the workpiece into engagement with the tool, and traverse of the frame through a cutting stroke. Near the end of this stroke, the frame acts through limit switches LS1, whereby, when the frame is stopped by a bracket, the appropriate valve acts to release the clamps and the motor M1 is energized to rotate the work spindle through an indexing cycle. For this purpose, the motor M1, Fig. 4, is carried on the frame 41 so as to drive the work spindle 53 through gearing, and a control disc 101 on the work spindle is provided with a ring of apertures for the reception, where desired, of control pins 104 co-operating with limit switches LS2. The work spindle is therefore rotated until the next pin 104 actuates the switches LS2 so as to open the circuit of the motor M1 and act through the pressure fluid system to traverse the frame to its initial position where the limit switches LS1 again act to cause a further indexing motion of the work spindle followed by another traverse of the frame. The operation continues until, at the last index step, a control pin 104a, actuates a switch LS3 whereby the pressure fluid system releases the clamps, raises the frame to inoperative position and stops the motor M1. The control circuit provides also for cutting to occur only on alternate strokes of the frame, in which case the work spindle is indexed only when the frame is at one end of its stroke. Specifications 712,969 and 712,970, [both in Group XXII], are referred to.