Patent GB-467241-A (GB)
Title: Improvements in or relating to milling machines adapted for die-sinking operations
IPC: B23Q35/18
Filed: 1935-12-14
Abstract: 467,241. Fluid-pressure servomotorcontrol systems. STEVENS, A. H. (Cincinnati Milling Machine Co.) Dec. 14, 1935, No. 34780. [Class 135] [Also in Group XXII] In a milling-machine for performing diesinking operations from a pattern, the work and pattern are mounted on a slide moved past the cutter and tracer by a hydraulic cylinder and the cutter and tracer are carried by a slide moved in and out by a hydraulic cylinder and constantly acting means such as a weight, spring or fluid pressure, and given an intermittent vertical feed after each reciprocation of the work slide, the hydraulic cylinders being controlled by the tracer in such manner that small in or out feeds of the cutter alternate with small advance movements of the work, one being stopped when the other has its maximum speed. The machine comprises a base 10 on which the work and pattern table 11 is fed by a hydraulic cylinder 22 and which is provided with a pillar 12 on which a carriage 14 is fed vertically by means of a screw 28, the cutter and tracer slide 16 being movable on horizontal ways 15 on the carriage by means of a hydraulic cylinder 25 and a weight 90. Copying-mechanism.-The tracer 17, Figs. 1 and 7, carries a flange 61 provided with an annular groove engaging, in the neutral position a ridge on a cover 65 of the tracer casing 64, these parts being kept in contact by means of a cup-shaped flange 138 on a rod 140 carrying a bell-crank lever 139 which is pressed upwards by the plunger 59 of the tracer valve 58 and a spring 60. Oil is supplied to the valve 58 by a constant displacement pump 76, Fig. 3, and a pipe 75. An annular port in the valve casing is slightly wider than a piston 71 so as to provide restricted passages 81, 82 on opposite sides of the piston. In the neutral position these passages are equal and serve to supply oil at equal pressures through pipes 77, 78 to opposite ends of a control valve 31. Oil is supplied to the valve 31 from a constant displacement pump 35, which may be supercharged from the pump 76, through a speed regulating device 43, and a pipe 44, excess oil being led to the sump a by a pipe 50. The plunger 51 of the valve 31 has five positions, that shown in Fig. 3 allowing a full supply of oil by pipe 55, through a depth limiting valve 116 and a balancing valve 83 to the cylinder 25 for feeding the cutter and tracer towards the pattern and work and simultaneously shutting off a pipe 56 for supply to the work traversing cylinder 22. In the next position of the valve, Fig. 9, the port 33 leading to pipe 55 is partly closed and the port 34 leading to pipe 56 is partly opened, thus advancing the cutter to the work and traversing the work past the cutter at the same medium speed. In the next position, the port 33 is closed and the port 34 fully opened causing feed of the cutter to be stopped and traversing the work at maximum speed, whilst in the fourth position, Fig. 11, the port 33 is partially opened to exhaust, permitting the weight 90 to withdraw the cutter and partially restricting the flow to the cylinder 22 by means of a piston 53. In the final position, the port 33 is fully opened to exhaust and the port 34 is completely closed, allowing the weight 90 to withdraw the cutter at maximum speed and stopping the traverse of the work. The work table 11 and cutter slide 16 are thus fed alternately, one being stopped when the other has its maximum speed. The plunger 51 is moved from the position of Fig. 3 to the final right-hand position, and vice versa, by causing a difference in pressure at opposite ends of the plunger by means of the tracer valve 58, the spring 60 normally establishing a difference which causes the cutter to be fed rapidly to the work, as shown in Fig. 3. When the tracer 17 is displaced, however, by axial or lateral pressure of the pattern thereon, the plunger 59 is moved to shift the plunger 51 to the right and execute the cycle described above. The balancing valve 83 is actuated by the oil flowing to the cylinders 22, 25, to shut off the supply to one when the other is being operated, and thus maintain the division of flow in the pipes 55, 56 which is determined by the valve 31. The oil from the pipes 77, 78 to opposite ends of the valve 31 passes to exhaust through fluid resistances 79, 80, Fig. 3, which maintain pressure in the tracer valve 58. The depth limiting valve 116 is used when it is desired to copy a deep pattern in a number of steps or contours and operates by contacting with an adjustable stop 123, Fig. 1, on the cutter slide when the required depth has been reached. This moves the plunger 117 against a spring 122 to shut off the supply to the cutter cylinder 25 and connect the pipe 55 to the pipe 56, thus traversing the work past the cutter until the tracer again makes contact with the pattern on the other side of a deep depression. For producing the next contour or step the stop 123 is set to engage the plunger 117 at a greater depth, and in this way the necessity for a number of shallow successive patterns to produce a deep impression is obviated. The cylinder 25 exhausts through a non-return valve 89. When the plunger 51 of valve 31 is in the right-hand position and the cutter is withdrawing from the work, the oil supply pipe 44, Fig. 3, is completely cut off from the ports 33, 34 and the pump 35 consequently discharges through a relief valve 39. In a modification which avoids heating of the oil passing through the relief valve, a second inlet port and an exhaust port are supplied in the valve 31 and are controlled by an additional piston on the plunger 51 so as to pass the supply freely to exhaust when the plunger is in the right-hand position, a balancing valve similar to the valve 83 being incorporated to maintain the set condition. In another modification, the cylinder 25 is made double acting and the weight 90 is dispensed with, the supply to the bottom end of the cylinder being controlled by the additional piston on the plunger 51 and the balancing valve above referred to. Work-table feeds; reversing-mechanism.-The work traversing cylinder 22 has its supply and exhaust reversed at opposite ends of each traverse by means of the valve 98, Fig. 3, which is actuated by adjustable trip dogs 101, Fig. 1, on the table 11 which act on a rotatable shaft 100 connected to the valve through a load and fire device. A hand lever 102 provides for reversing the traverse at any intermediate time. Intermittent feeds; gauging devices.-At each end of a traverse of the work-table 11 the carriage 14 carrying the cutter slide 16 is given a vertical feed by means of a dog 115, Figs. 1 and 2, on the table engaging one of the collars 113, 114 on a rod 112. The rod is connected by a bell-crank lever to toggle links 107, 110, the former carrying pawls 109 engaging a ratchet wheel 103 attached to a shaft 104 geared at 106 to the vertical feed screw 28. By changing the positions of the collars 113, 114 so as to engage the dog 115 at different times in relation to the operation of the table reversing valve 98, the amount of vertical feed may be varied.