Patent GB-600193-A (GB)
Title: Improvements in and relating to metal cutting and like copying machines
IPC: B23Q35/18
Filed: 1944-06-01
Abstract: 600,193. Copying by milling and turning. THURSTON, A. P. (Bailey Meter Co.)..June 1, 1944, No. 10519. [Class 83 (iii)] [Also in Group XXIX] In a copying machine such as a lathe or milling-machine a tracer engages a pattern and, by its deflections, varies the escape to atmosphere of a constant pressure air supply so as to cause variations in the pressure of the air line which are utilised to actuate hydraulic valves controlling the relative feeds of the tool and work and also the speed of movement. As applied to a lathe, the work 16, Fig. 1, is mounted between a headstock 2 and a tailstock 3 and is rotated by a hydraulic motor 46. The tool 10 is carried by a rest 9 on a transverse slide 8 fed by a hydraulic cylinder 11 on a saddle 7 which is fed longitudinally by a hydraulic cylinder 14. The pattern 17 is mounted on a support 18 attached to the bed 1 and coacts with a tracer 19 on the slide 8. An air supply passes through a regulator 22, Fig. 2, and a volume chamber 23 to an orifice 26 from which it passes into the constant pressure line 25, connected to the tracer 19, Figs. 2 and 4. A lever 53 in the tracer body 21 is pressed by a spring 58 against a knifeedge pivot 54 and carries the tracer finger 20 at its free end. The finger is interchangeably secured to the lever by head 70 and is angularly adjustable in the head, and the body 21 is angularly adjustable on the slide 8 by means of a clamp engaging a recess 52, the preferred position being that in which the knife edges 54 are inclined at about 15 degrees to the axis of the work. This allows the tracer to surmount abrupt rises on the pattern. A flat spring 57 biasses the lever to a neutral position in which a valve 55 attached to its lower end is positioned with its head 63 closing the outer end of a stationary sleeve 56. Air at a pressure of about 35 lbs. per sq. in. enters a chamber 64 in the sleeve from the line 25 and bleeds past a double conical portion 61 of the valve to centralize and lubricate the valve. The saddle is traversed to the left in Fig. 2 for a copying operation by oil from a pump 31 passing to the cylinder 14 through pipe 41, valve 40 and pipe 43, the exhaust passing through valves 40, 39 and a tracer-controlled throttle valve 30 to the sump 33. On deflection of the lever 53 by pressure against the pattern the valve 55 is moved to the right in Fig. 4 to allow air to escape past the edge 65 of the valve, thus lowering the pressure in the line 25. A bellows 27, Fig. 2, is connected to line 25 by pipe 83 so that the reduced pressure will allow a spring 88 to partially collapse the bellows and draw a valve 86, Fig. 11, connected thereto by ball joints 94, upwardly into a neutral position. This permits oil from the pump 31 to pass by pipe 34 to both sides of a piston 96 and thence bleed back to the sump 33 through the ends of triangular ports 101, 102, thus maintaining equal pressures on both sides of piston 96 which is communicated by pipes 35, 36 to opposite ends of the cylinder 11 to hold the cross slide 8 stationary. If pressure of the pattern on the tracer is further increased the air pressure in line 25 is further reduced, the valve 86 moves upwardly to cut off flow of oil through port 102 and allow an increased flow through port 101, thereby allowing oil to flow by pipe 35 to cylinder 11 and move the slide 8 and tool away from the work. Conversely, relief of pressure of the pattern on the tracer raises the pressure in line 25 and moves valve 86 downwardly to supply oil to pipe 36 and feed the tool towards the work, the speed of the feeds being controllable by a valve 38 adjusted by hand. Variations of pressure in line 25 are also communicated by pipe 109 to a bellows 29 connected by ball joints 94, Fig. 14, to a valve 110 in the casing 30 having pistons 113, 114 provided with pressure equalizing grooves 113<SP>1</SP>. In the neutral position of valve 86 (i.e. when the slide 8 is locked against movement), the valve 110 is in the central position shown with the tapered ends of the pistons providing equal clearances with ports leading to pipes 44, 45 in the oil supply from pump 31 to cylinder 14. When the slide 8 moves in or out due to fall or rise of pressure in line 25 the valve 110 will be raised or lowered and in each case will throttle the flow from pipe 44 to pipe 45 and so slow down the rate of traverse of the saddle 7 to allow the tool to surmount abrupt changes in the contour of the work. The rate of flow of oil through valve 110 may be adjusted, to vary the rate of traverse of the saddle, by rotating the valve about its axis by means of a handle acting through gearing on a crank attached to the valve through a spring 120 which does not impede axial movement of the valve, or alternatively the pistons 113, 114 may have opposed helical surfaces aligned with the ports to provide similar adjustment. When a cutting traverse of the saddle has been completed the operator pulls a handle at the front of the saddle connected to a rod 72, Fig. 4, on a pin 80 attached to a yoke 78 on a diaphragm 73 pressed upwardly in the tracer valve by a spring 77. This causes a tongue 74 on the diaphragm to displace a hooked spring 75 attached to the tracer lever 53 and thereby move valve 55 to the right and withdraw the tool from the work. The valve 39, 40 may then be rotated manually from the position shown in Fig. 2 to that shown in Fig. 3 in which oil is supplied from pump 31 to cylinder 14 by pipe 42 to traverse saddle 7 to the right and exhaust proceeds to the sump 33 through pipes 43, 45 without passing through throttle valve 110 so that the traverse is at a rapid rate. Tracer control may be applied to either the cross feed only or the longitudinal traverse only. The speed of rotation of the headstock motor 46 may also be varied in accordance with the work diameter at which the tool is operating by providing another connection 50, Fig. 2, from the air chamber 23 through an orifice 50<SP>1</SP> to a tracer 19A mounted on the saddle 7 and co-operating with a wedge-shaped cam 47 on the cross slide. The position of slide 7 thus determines the air pressure in the line 50 which is communicated to a bellows 51 controlling a throttle valve 30A in either the supply pipe 48 or exhaust pipe 49 to the motor 46: Milling.-As applied to a milling machine the work 133, Fig. 18, is mounted on a holder 134 rotated by a hydraulic motor on a vertical axis on a table 124 movable longitudinally by a hydraulic cylinder 118 on a saddle 126 adjustable transversely on a knee 128 which is adjustable vertically on a column 123. A pattern 137 is formed on the work support 134 and co-operates with a tracer 19B, similar to the tracer 19, on the saddle 126 to control oil supply to the cylinder 118 by a valve similar to valve 86. The speed of rotation of the pattern and work is varied in accordance with the radius of the work which is being operated upon by a stationary milling cutter 125 by means of a tracer 19c on the table 124 cooperating with a second rotating pattern 139 to control a throttle valve for the work-driving motor. Catching and removing cuttings.-Chip guards are provided for the tracers at 69, 71, Fig. 4, the air escaping from valve 55 passing under the guards to assist in excluding chips &c. A raised flange 138 on the pattern 137, Fig. 18, prevents scattering of chips from the work 133.