Patent GB-643596-A (GB)
Title: Improvements in or relating to three-dimensional engraving and the like machines
IPC: B44B1/04
Filed: 1948-02-25
Abstract: 643,596. Copy-milling machines. GORTON MACHINE CO., G. Feb. 25, 1948, No. 5671. Convention date, Nov. 15, 1947. [Class 83 (iii)] [Also in Group XX] A milling or engraving machine for producing a copy of a master in a desired scale relation comprises tracer and cutter heads TH, CH movable with their axes in the same plane in a straight-line path which is swingable bodily, together with the means for causing the cutter head to reproduce in scaled relation the movements of the tracer head, in a plane containing the axes of the heads and also in a plane at right angles to such plane, the two pivotal axes about which swinging occurs being in a common plane. As shown in Figs. 2 and 4, the cutter and tracer heads CH, TH are carried by slides CS, TS which are movable along guides provided on the lower horizontal beam 15 of a composite beam structure B. The beam 15, which is of channel cross-section and provided with spaced stiffening webs, is supported at its ends from an upper arched bar 16 of I cross-section, the connection at the pivoted end of the structure being on an offset part 16c of a depending leg 16b on the bar 16 so that the longitudinal axes of the members 15, 16 are slightly inclined to each other. The members 15, 16 may be of aluminium or aluminium alloy, and, if desired, be formed as a single casting. The pivotal support for the composite beam is provided by an L-shaped member 17 which at its lower end is hingeable about a horizontal shaft 19 mounted on a bracket 18 on the machine column 10; the upper end of the member 17 carries a shaft 16e which is in line with the connection between the inner ends of the beam 15 and bar 16 and serves as a hinge for the composite beam on the member 17. The axes of the shafts 16e, 19 are arranged in the same plane. In order to counterbalance the weight of the composite beam overhanging the work and pattern arranged on the tables W, P, a tension spring 21, Fig. 2, is connected between the column 10 and the lower end of the member 17; variation of the counterbalancing effect is obtained by an oppositely-acting compression spring 24 adjustable by a bolt 25. The guides on the beam 15 for the cutter and tracer slides are formed by a pair of adjustably-mounted rails 30, 31, Fig. 6, each of which has a longitudinal groove 30a, 31a for receiving endless sets 45, 46 of anti-friction balls associated in the slides as shown in Fig. 10, Each of these slides is built up of a central plate 40 and end plates 41, the central plate being provided with two longitudinal passages 42 for co-operation with semicircular passages 43, 44 in the end plates and longitudinal grooves 40a in the upper and lower edges of the plate 40 so as to provide housings for two continuous sets 45, 46 of balls. Lubrication of the guides 30, 31 and balls 45, 46 is effected by providing near one end of each plate 41 a pair of graphite or similar wipers 50 which are pressed outwardly by a spring 52 so that their V-shaped ends engage the rails 30, 31; the wipers 50 also serve to prevent dust and cuttings reaching the balls 45, 46. The cutter and tracer slides each carry a base-plate 551, Fig. 6, which is provided with a semicircular recess 57<SP>1</SP> so as to form with a similar recess in the head CH a space for the reception of the cutter or tracer unit; the head CH is pivoted on a vertical axes 58, Fig. 4, on the slide so as to permit fitting and withdrawal of the unit. A hinged and spring-loaded locking member 59 clamps the head in position, and a spring-pressed pin 59c, Fig. 6, is mounted in the head for engaging a locating recess in the unit. A projection 73, Fig. 4, on the slide TS co-operates with a stop 74 on the rail 30 to prevent over-running. The cutter unit C includes a rotary cutting spindle 64, Fig. 6, which is disposed in a casing 65 and is urged upwardly by spring pressure; the vertical position of the spindle may be adjusted by means of a screw-threaded pin 63 which is mounted in an arm 62a on a bracket 62 mounted on the cutter slide and bears against a pin 64a. The drive for the cutter spindle 64 is by a belt 71, Fig. 4, passing over a stepped pulley 66 on the spindle and a stepped pulley 70a carried by a horizontally-swingable arm 70 pivoted on the bracket 18 to which the arm 17 is pivoted. The pulley 70a is driven by a belt 70b which passes downwardly over pulleys 70c to a pivoted and counter-balanced motor. The arm 70 positions the pulley 70a generally centrally of the length of the beam 15, and an adjustable radius rod 72 connects the outer end of the arm with the cutter unit in order to maintain the correct spacing of the pulleys 70a, 66. The linkage between the cutter and tracer slides is constructed and arranged so as to ensure that these members move relatively in the same selected scale ratio when they move, with the beam, vertically and horizontally or when they move longitudinally of the beam. In the form shown in Fig. 4, a long link 80 is adapted to be clamped in any adjusted position in a slide block E pivoted on an upstanding pin 61 on the slide CS. The outer end of the link 80 is coupled by a link 81 with an upstanding pin 56 on the slide TS, and its inner end is connected to a link 84 which can be clamped in adjusted position in a clamp block H pivoted to the underside of the beam 15; the pivot of the block H may be offset from the axis of the shaft 16e, and to compensate for this, the axes of the pins 56, 61 are similarly offset from the axes of the tracer and cutter. By adjustment of the position of the links 80, 84 in the slide blocks E, H, a wide range of scale ratios is obtainable for the movements of the cutter and tracer. In the construction shown in Fig. 19, the linkage is modified by the provision of an additional link 87 parallel to the link 80<SP>1</SP> and coupled between the link 84<SP>1</SP> and an extension of the link 811 so that, after release of the links 801, 841 from the blocks E, H, the setting of the link 80<SP>1</SP> in its new position in the block E will automatically set the position of the link 84<SP>1</SP>. With the cutter and tracer slides positioned as shown, the movement of the cutter will be in the selected reduced ratio of the movement of the tracer. An enlarged ratio may be obtained by interchanging the cutter and tracer units in the respective slides, the belt drive permitting drive of the cutter spindle in its new position. In operation, the work-piece and pattern are mounted on tables W, P which are adjustable vertically and horizontally on the column 10, and the operator then scans the pattern P with the tracer S; the point of the rotating cutter is adjusted initially so as to lie in the same horizontal plane as the point of the tracer S. When it is desired to engrave or reproduce on a curved surface from a flat master, the bracket 62, Figs. 2 and 6, may be removed from the cutter slide, and a suitably-curved surface may be mounted on the beam structure for cooperating with the pin 64a and so controlling the vertical position of the cutter spindle. When employed for two-dimensional copying, the arm 17 is locked by a bolt 26, Fig. 4, against movement in a vertical plane.