Patent GB-318587-A (GB)
Title: Improvements in or relating to the electrical operation and control of metal cutting and like machine tools
IPC: B23Q35/32
Filed: 1929-08-22
Abstract: 318,587. Keller Mechanical Engineering Corporation, (Assignees of Shaw, J. C., and Shaw, R. D.). Sept. 6, 1928, [Convention date]. Milling-machines.-A tracer which is adapted to follow the outline of a model or pattern and control electro-magnetic clutches which operate forward and reverse feeds in two rectilinear directions for a carriage supporting the tracer and a milling-cutter so as to cause the cutter to reproduce the model, has four fixed contacts effaced in a plane 90‹ apart and connected in circuits controlling the four clutches and four movable tracer-controlled contacts, cooperating therewith, two selected pairs of contacts being normally closed so as to produce a selected normal direction of motion of the cutter The tracer comprises a head 9, Fig. 1, in which is secured a tubular body 1 baving a ball joint 2 for supporting the spindle 5 which has an interchangeable end 4 for engaging the pattern. The head 9 carries four radial screws 20 mounted adjutably in insulated bushes 26 and connected as shown in Fig. 9 to four electro-magnets 70, 71 which form relays to control switches 60, 61 for the clutches 56, 57 operating the feed motions. The ends of the screws 20 form electrical contacts 21 - - 24, which co-operate with four contacts 32 - - 35 on a ring 31 slidable vertically on a ring 38 slidable horizontally in the head. Vertical and horizontal keys and slots 37, 41 allow universal movement of the ring 31 in a plane, pins 43 screwed in the head serving to keep the rings in place. The central aperture 30 of the ring 31 receives a collar 29 on the rear end of the spindle 5 and is moved thereby to bring one or two adjacent contacts against the screws 20. A spring 49 is anchored to the extreme rear end of the spindle and to a ring 52 which is rotatable on the head by hand so as normally to close any two pairs of contacts. The elecltrical supply for the relay circuits is desired from a low-tension generator 66, Fig. 9, one lead being earthed through the frame of the machine to the tracer spindle at 68, and the high tension supply for the electro-magnetic clutches is derived from supply mains 58, 59. The four clutches S. N. W. E. are each connected to one of the feeding means so that when two are energized, such as S, and W, the resultant motion will be a 45‹ one, or to the SW. In operation, to copy a pattern A, Fig. 10, the ring 52 carrying the spring 49 is rotated to cause the handle 55 to occupy the position shown in the figure thus closing the contacts at N and E and causing clutches. N, E, to be energized. This will traverse the cutter and tracer in a NE direction, as shown by the arrow 4, until the tracer encounters the pattern and rocks the spindle to break the K contacts. The tracer &c. will then travel E until it begins to leave the curved edge of the pattern, whereupon the N contacts will be closed again and NE and E feeds will alternate round the curve. As the tracer passes round the curve, the handle 55 may be rotated slowly anti-clockwise but when the NE feed becomes tangential to the curve the handle must be moved to the NW quadrant, as shown in Fig. 12, so that the NW feed will cause the W contacts to be opened, and N and NW fesds will alternate until the NW feed becomes tangential to the curve. The handle is then moved into the SW quadrant and the tracer will then follow the pattern to the upper left-hand corner. At this point the handle is moved to the SE quadrant, whereupon the tracer will travel S to the lower left-hand corner, and moving the handle to the NE quadrant again will return the tracer along the lower edge of the pattern to the starting point. The tracer may be used in a similar manner for following round the inside of a pattern comprising re-entrant angles or curves. Balancing parts.-In order to balance the tracer spindle 5, particularly when different tracer points 4 are used, a counterweight or a spring 15, Fig. 1, adjusted by a screw 16, is provided. Specifications 233,747 and 275,479 are referred to.