Patent GB-544203-A (GB)
Title: Improved method of and means for producing generated forms for use in connection with machine tools
IPC: B23Q35/10
Filed: 1941-01-04
Abstract: 544,203. Milling-machines ; copying mechanism. GHAYE, A. L. J. Jan. 4, 1941, Nos. 148 and 7395. [Class 83 (iii)] In a method of and apparatus for producing a master form for use in a copying, milling, grinding, turning, filing or like machine tool movements of considerably greater magnitude than those required in the copying machine for making the workpieces w, Fig. 2 are obtained from a large replica W of the work and the scale of these movements then reduced and introduced as components of the motion required to generate by a tool GT the desired master form on a blank B of larger size than the work pieces to be made. Thus for the production of small square workpieces w from a circular blank b by means of a rotary milling cutter c the maximum radial movement of the cutter relative to the rotating blank is that indicated at x, Fig. 2, and this movement is obtained from a large master cam f coacting with a roller r, the said cam having a dimension z equal to x. In order to generate the cam a rotary cutter GT, Fig. 1, of the same diameter as the roller r may be used and a spindle a carries a circular blank B and also an enlarged pattern W of the workpiece. This pattern imparts a magnified movement X to a roller C carried by a rack bar 2 connected by a segment 3 to a shaft 8 driving a pinion 5 which imparts movement to the table 1 carrying the cutter. If the pattern W has 10 times the linear dimensions of the work w to be produced then the diameter D of roller C is also ten times that of the cutter c and there is a 10 to I reduction in the gearing between the rack 2 and the table 1 so that the cutter movement y is the same as the dimensions x and z. In some cases the template W may be replaced by segmental pieces such as that shown in Fig. 3 at F, the segment being rotated together with the blank through 90 degrees and then turned back through 90 degrees on its spindle and relocked. The comers of the segment may be rendered obtuse to prevent undue wear. The method may also be employed for forming a master cam for the cutting of a number of small components arranged around a rotary carrier. In some cases such components may be removed after finishing from the carrier and fresh blanks substituted so that the profiling is a continuous one. Thus a number of valve rockers VR may be arranged on a table RT and the outside profiles D formed in succession by a cutter PC. By providing a second cutter PC<SP>1</SP> controlled by a second cam and arranged in staggered relation with the first and inside edges may be cut at the same time as the outer edges. Or the inner edges may be cut during one revolution and the outer edges during a second revolution with the same cutter. In a machine for cutting the master cams a main spindle 14 rotating in ball bearings 12, 13 carries a master cam blank B and is driven by worm gearing 20, 21 and belt gearing 33 from a motor 31, the speed of rotation being about 1/5 R.P.M. The rear end of the spindle 14 carries an adapter for the mounting of an enlarged template, W of the work which is adjustable with reference to the spindle 14 by means of an indexing plate which is used when segmental patterns are employed. The template co-operates with a disc C mounted on a vertically movable rack slide 2 which is urged upwardly by a weight 43 or by spring or fluid pressure means. This slide carries a rack 4 engaging a toothed segment 3. Adjustment is provided for the disc C and the disc may be readily interchanged. The segment 3 is mounted on a spindle 43 connected by chain gearing 8, 9 to a pinion 5 which imparts reduced movement to a table 1 carrying a cutter GT dnven by a motor 57. Instead of transmitting motion directly from the template W to the disc C an optical projection apparatus may be employed for manually controlling the movement of disc C. Thus in Fig. 11 a sample pattern 67 of the work piece may be mounted on an extension 64 of the spindle 14 and may have its outline projected on to a screen 69. A follower disc C<SP>1</SP> is mounted on the slide 2 and by means of a handwheel 74 and gearing 71 the edge of the follower disc is maintained in contact with the edge of the shadow of the pattern 67 as the latter rotates. A microscope 75 may be provided to observe the conjunction of the disc C<SP>1</SP> and the shadow. In a modification of this optical arrangement the projector 68 is mounted on a vertical slide controlled by a cam similar to the pattern 67 so that the projector movement follows the edge of the rotating pattern.