Patent GB-471246-A (GB)
Title: Improvements in copying metal cutting machines
IPC: B23Q35/18
Filed: 1936-01-27
Abstract: 471,246. Fluid-pressure servomotor-control systems. KAIN, C. H. Jan. 27, 1936, No. 20461 /37. Divided out of 471,108. [Class 135] [Also in Group XXII] In a metal-cutting copying- machine having a tool and tracer traversed over the surface of the work and pattern, hydraulically controlled means are provided actuated by movement of the tracer relatively to its carrier to cause movement of the carrier to or from the pattern, and separate hydraulic means actuated by movement of the carrier are provided to move the tool to or from the work. As applied to a milling or boring machine, the pattern 6 and work 7, Fig. 1, are mounted on a common support 5 capable of being traversed along a carriage 3 which is movable to and from a fixed column 2 carrying the tracer 21 and cutter 15. The saddle 14 carrying the tracer and cutter spindles is movable vertically on the column 2 by a screw 12, this screw and the mechanism for traversing the support 5 and carriage 3 being controlled by hand levers 8 ... 11. The cutter spindle 16 is driven through a splined shaft 17 from a motor 18. The tracer casing 27 is secured to a slide 20 adjustable relatively to the saddle 14 to vary the distance between tracer and cutter according to the size of pattern and work by means of a screw jack 22 locked by a nut 24. The tracer tip 21, Fig. 3, is mounted on a shank 60 slidable in a tube or carrier 61 and is pressed towards the pattern by a spring 89, the tube 61 being universally mounted by means of a ball joint 62 in a tube 26 slidable within an extension 46 of the casing 27. A rod 66 is attached at one end to the shank 61 and at the other to a piston valve 70 slidable within a piston 41 which is slidable within the casing 27 and is attached to a tube 40 carrying a head 39, Fig. 1, on the projecting end. Oil is supplied by a pump 32, from a tank 29 by means of pipes 33, 38 to the head 39 and thence to a space between the interior of the tube 40 and the exterior of a tube 42 secured to the piston 41 and sliding with the tube 40. The pump supplies more oil than the maximum required and the surplus is returned to the tank through a weighted relief valve 35 and pipe 30, thus ensuring a constant supply pressure. Oil is returned to the tank from the interior of the tube 42 by a pipe 31 connected to the head 39, and the pipes 31, 38 have flexible connections to allow for sliding movement of the head. During traverse of the work and pattern past the cutter and tracer, if the tracer meets a protuberance on the pattern it is depressed against the pressure of the spring 89 and slides the rod 6 rearwardly, thus moving the valve 70 to the right from the neutral position shown in Fig. 3 and allowing oil which has flowed into a central annular recess 79 in the valve by way of passages 85, 86 in the piston from the tube 40, to pass into an annular recess 72 in the piston and thence by a passage 88 to the left end of the piston, moving the piston to the right. This movement of the piston 41 to the right restores the neutral position of the valve 70 therein and cuts off the supply of oil to the passage 88, thus preventing further axial movement of the cutter spindle unless the tracer tip is further depressed by the pattern. If the tracer meets a cavity in the pattern, the tip 21 is pressed to the left in Fig. 3 by the spring 89 and draws the valve 70 to the left within the piston 41, thereby admitting oil by a passage 87 in the piston 41 to the right of the piston which is then moved to the left. The head 39 is connected by a link 94 to a rod 93 carrying a valve within a piston 50 similar to the valve and piston 70, 41, which are supplied with fluid by pipes 91, 92, and a head 90 similar to the head 39, so that movement of the piston 41 and tube 40 will cause fluid to be admitted to one side or the other of the piston 50 to move it in the same direction. The rod 93 is attached to a bracket 54 connected by thrust bearings 58, as described in Specification 471,108, to the tool spindle sleeve 56 which is thus fed axially in conformity with the axial movements of the tracer. The saddle 14 may be traversed vertically and the support 5 given a step-by-step feed after each traverse, or the support 5 may be traversed horizontally and the saddle 14 given a vertical step-by-step feed. The tracer may be removed from the pattern at any time by opening a valve 96, Fig. 1, in a pipe 95 leading from the pressure supply 91 to a piston 99, Fig. 2, attached to the rod 66, thereby drawing the valve and tracer to the right. The piston 99 is not packed so that the oil therein will readily pass to the exhaust line 31 when the valve 96 is closed. If tilting movements of the tracer are not required, the tracer shank and rod 66 are slidably mounted directly in the casing 27, as shown in Fig. 1. Surmounting abrupt surfaces on the pattern.- If the tracer tip 21 encounters an abruptly rising surface on the pattern it may be tilted about the ball joint 62, Fig. 3, thereby displacing laterally the rear end of the shank 61. The rod 66 is made flexible to allow this displacement to take place. A valve 105 fitting on the end of the shank 61 is thus displaced from the neutral position shown to allow oil under pressure, which has passed into the casing 26 on the outside of the tube 68 by means of the passage 85 in the piston 41, to proceed through channels 112, 113 and past the displaced edge of the valve to a passage 118 leading to a cylinder 109 at the left of a piston,110 thus moving the piston to the right. This piston is loose on the rod 66 and is normally pushed to the left by oil passing by a small channel 115, through the right-hand end of the cylinder and then by the interior of the tube 68 to exhaust. When the piston 110 moves to the right, however, it engages a shoulder on the rod 66 and carries it to the right, thus operating the piston valve 70 to cause axial withdrawal of the cutter from the work in the same manner as by axial pressure of the pattern on the tracer tip 21. The tracer shank 61 is normally maintained in a neutral position about the ball joint 62 by means of four radial springs 103, and pressure oil is delivered to both sides of the valve 105 by passages 112a so that this valve will be balanced and will move freely. Any oil which leaks into the chamber a of the tube 26 passes through the channel 118 and then to exhaust through the interior of the tube 68. Reversing band of reproduction.--The tool may be moved in a direction opposite to that of the tracer for forming a surface which is the reverse of the pattern.