GB561053A - Improvements in milling and like machines for copying and reproducing - Google Patents

Abstract

561,053. Milling-machines. BRISTOL AEROPLANE CO., Ltd., and BOLAS, J. T. July 28, 1942, No. 10558. [Class 83 (iii)] In a copying milling machine particularly for milling the ports in a sleeve-valve for an internal combustion engine the cutter is controlled by a follower mounted on the cutter-spindle, the follower being automatically urged round a pattern by fluid pressure acting in mutually perpendicular directions so that the cutter reproduces on the work a port of shape corresponding to the pattern. In Fig. 1 the machine includes a table carrying four cutterheads 11 arranged concentrically around the axis 15 of a work sleeve 13 and movable on circular guides 12 by means of hydraulic cylinders 21. The pattern ports 17, Fig. 4, are formed in the walls of a sleeve 16 concentric with the work. Each cutter-head includes a cutter 18 driven from a motor 19 and a follower 20 concentric with the cutter axis. In addition to its arcuate motion on the guides 12, the cutter has a vertical movement imparted by a hydraulic cylinder 24 to a slide 23. Thus in tracing a port outline 14 by moving the follower 20 round the pattern 17 starting from the point a, Fig. 4, the motors 21, 24, which are supplied by separate variable-delivery pumps 35, 35a, Fig. 6, which are kept flooded by a pump 34, are actuated as follows. The follower is moved from a to b with the motor 21 supplied at high rate and the motor 24 at a low rate to hold the work pattern against the work. During the passage from b to c motor 21 is supplied at a low hold-up rate and motor 24 is supplied at a high rate to move the follower downwardly. From c to d the motor 21 is supplied at low rate to move the follower slowly away from face r and motor 24 supplied at a high rate, and so on until the point a is reached. Relief valves are provided to by pass the delivery of either pump when it is merely holding the follower against the pattern. The changes in speed and direction of the motors are produced by switches actuated by moving cutter-head parts. Switches a<1>, b<1> are respectively actuated by contacts 25, 26 and 27, 28 when the follower is at positions a, b and switches a<11>, c1 d<1> and f<1> are controlled by a switch arm 29 on slide 23 in accordance with the vertical position of this slide. When in its lowest position the slide 23 also controls switches which effect the energising. of solenoids which control the valves of pneumatic motors serving to shift the valves controlling the hydraulic motors 21, 24, the circuits being shown in Fig. 6. The lines 39, 40, supply the motor 21 and the lines 68, 69, the motor 24. Other solenoids control the rate of delivery of the pumps 35, 35a. The valve 36 controlling the direction motor 21 is operated through links 46 by pneumatic cylinders 44, 45, which are selectively opened to pressure from a line 48, by a valve 47 operated by solenoids 54, 55. Similarly solenoids 56, 57 control a pneumatic valve 58, which admits air selectively to pneumatic cylinders 61, 62, acting through links 66 on a hydraulic valve 65 controlling delivery from pump 35a to the motor 24. The rate of delivery of pump 35 is controlled by a lever 83 moved to one of two positions by the plungers of pneumatic cylinders 78, 79, the cylinders being selectively supplied through a valve 76 controlled by solenoids 73, 74. Similar solenoids 88, 89 and valve 90 control the flow to cylinders 95, 96, which control the position of the delivery-determining lever 98 associated with the pump 35a. A master pneumatic valve controls the supply to valves 90, 59, 55 and 76. In order to advance the cutter axially towards the work the vertical slide 23 is 'mounted on a horizontal slide 108 all these slides being first operated to bring the cutters simultaneously up to the work and then to feed the cutters into the work during the orbital copying movement. For the initial feed a master control is provided and this comprises a valve 110 which controls delivery from pump 34 to cylinders 111 thus operating piston rods 113 which engage a cross member 114 to move slide 108 towards the work. The cutting axial feed is produced by a cam 115 engaging a roller 122 on slide 108 and driven from the vertical slide movement from a rack acting through free wheel devices so that the cam is always driven in the same direction and completes its rotation after the pattern has been traced three times. The initial in-feed by cylinders 111 raises the roller to the point 115a after which the cam feed takes control. As the slide 108 is fed, the roller 122 operates a lever 123 controlling a switch rod 124. This carries a contact piece 125 coacting with switch contacts 126, 128. Fig. 6 shows the position of the parts at the end of the in-feed operation. At this point contact 128 has been actuated to energise a solenoid 129 to admit air to motors 133. This returns control 109 to its off position and opens hydraulic cylinder 111 to exhaust 134 as shown. When the roller drops into the trough of the cam 115 the slide 108 is spring returned. This causes contact 126 to energise solenoid 105 and closes valve 102. This cuts off air supply to the above-described pneumatic motors. At the end of the preliminary in-feed by cylinder 111 contacts 125, 127 engage to move valve 102 through its solenoid so as to admit pneumatic pressure to the control devices for the automatic feed round the pattern. A complete sequence of operations is described in detail in the Specification. Any of the cutter heads may be stopped by means of an emergency 'switch 165 in the circuit associated with each head. The machine may also be used for cutting irregular shapes in plane bodies or for cutting irregular cam grooves to a predetermined depth.