Patent GB-512739-A (GB)
Title: Improvements in or relating to milling machines
IPC: B23Q35/18
Filed: 1938-08-19
Abstract: 512,739. Milling machines. CINCINNATI MILLING MACHINE CO. Aug. 19, 1938, No. 24443. Convention date, Sept. 3, 1937. [Class 83 (iii)] A copy-milling machine has a number of hydraulic cylinders associated with a cutter which is fixed with respect to a control valve assembly, and the tracer may be moved in a number of directions with respect to the control valve assembly to shift individual control valves for the cylinders away from normally closed positions whereby the cylinders are actuated to cause cutter movements corresponding to the tracer movements. The bed 10, having a part 11 on which the work and pattern tables are stationarily supported carries a saddle. 13 movable horizontally by means of a cylinder 19 sliding on a fixed piston 20. Guides 15 on the saddle carry a horizontal cross slide 16 which in turn receives the vertically movable-slide 18 carrying the cutter and tracer which can thus be moved in three mutually perpendicular directions. The flow to cylinder 19 may be controlled selectively by either of two servo valves 22, 23, Fig. 7, the former being actuated by a servo screw 24 and the latter by the tracer. A selector valve operated by a knob 25 selects the method of control and sections of this valve are shown at 26-28, Fig. 7. A variable delivery pump 29 delivers to a line 34 and a cross bore 37 of the selector valve may deliver fluid either, as shown, to line 49 and tracer-controlled valve 23 or to line 81 and valve 22. The connections of cross bore 62 of section 27 and cross, bore 71 of section 28 are similarly changed over when the selector valve is moved from the position shown to bring valve 22 into operation. When the operative servo-valve plunger is moved from its mid position, fluid may flow to one end or other of the cylinder 19, the opposite end being connected to exhaust through a common return line 57. The end of plunger 44 of valve 22 carries a segmental nut 77 which is normally disengaged by a spring but when pressure is admitted to line 81, a cylinder 80 engages the nut segment with the screw 24. The screw carries a hand wheel 83 for direct actuation. Intermittent feed may also be imparted to the screw by means of a lever 84 actuated by a hydraulic cylinder 87, Fig. 7, to 'which fluid may be admitted by operation of a push button valve 89. controlled by the operator. At each actuation of the button, the lever 84 rotates shaft 85 connected to a gear 98 carrying a pawl engaging a ratchet wheel on the servo screw. The amount of each movement may be regulated by an adjustable guard carried by a sleeve 99 operated from a graduated knob 106. After release of valve 89 fluid in cylinder 86 leaks away through a bleeder coil 108. This control is mainly used to effect a spacing movement between tool and work in a direction normal to path of cutting. The cross slide 17 is actuated by a cylinder 110 controlled by a pair of selective servo valves 113, 114 in a manner similar to that described above and the vertical slide is similarly actuated by a cylinder 119 controlled by servo valves 122, 123. The vertical slide carries a cutter-spindle 132 mounted in a quill 133 actuated from a graduated dial 140 through bevel and rack-and-pinion gearing. The spindle is driven by belts from a hydraulic motor 146. Automatic control for duplicating is derived from the tracer 147 connected by a Hookes joint to a lever 149 pivoted at 150 and connected to the plunger of servo valve 123. The tracer is also connected, as by rod 158, Fig. 4 to the plungers of servo-valves 23 and 114. All the servo-valves are normally neutralised by springs 156 adjusted by nuts 157 and free movement of the plungers is, facilitated by ball bearings 152. When the tracer is moved axially the flexibility of rods 158 allows the plungers of valves 114, 23 to remain unaffected while the plunger of servo 123 is operated by lever 149 to cause corresponding vertical movement. Similarly movement of the tracer in a horizontal plane operates the rods 158 to cause movement of one or both of the plungers of servos 114 and 23 and corresponding movement of the horizontal slides. In order to limit the speed of movement the tracer movements are limited both laterally and vertically by an upper conical portion 166 engaging in an adjustable conical sleeve 164. By means of the selector valves one or more of the slides may be disconnected from the tracer so that for instance the vertical slide may be disconnected and a profiling operation performed in a horizontal plane after which a vertical spacing movement may be effected by operation of push button 90. Similarly one of the horizontal slides may be disconnected and the other slide may be fed, and the cutter moved vertically as determined by the pattern. After one stroke across the pattern in this way a horizontal spacing movement is effected by operation of the push button. Only the ratchet plungers whose selectors are set to the "screw" position will be effective. The cutter-driving motor 146 is arranged in a closed circuit, Fig. 7, with a variable delivery pump 171 supplied from a line 175 the pressure in which is determined by resistances 176, 177. Make-up fluid is supplied to either side of the circuit through check valves 174.