Patent GB-576856-A (GB)
Title: Improvements in and relating to cutting, grinding or polishing machines for diamondsor other stones and the like
IPC: B24B9/16
Filed: 1944-05-12
Abstract: 576,856. Grinding. JEARUM, F. C.. May 12, 1944, No. 9112. [Class 60] A machine for grinding &c. diamonds and other hard stones &c., and for shaping cutting-tools of hard metal, comprises a dop mounting oscillable in a predetermined arcuate path and a modifying device which, during the oscillation may effect a displacement of the axis of oscillation so as to generate a desired shape on the stone &c. The machine comprises a stand 1 carrying, in a mounting 2, a planetary abrading-disc 3 and a dop mounting 5 on a slide 6 adjustable on a radial arm 7 carried at the upper end of a hollow shaft 8, oscillable about a vertical axis A-A lying normally in the cutting plane of the disc 3. The shaft 8 is coupled at its lower end to a sleeve 9 by means of an Oldham coupling 10-12 adapted to be rotated through a friction disc 15 by the sleeve 9 ; pressure between the disc 15 and the coupling element 10 is applied by a spring 16. The sleeve 9 is oscillable in a bearing 20, carried by a bar 22 in a casing 23, and is movable by a rod 21 having thereon a handle 24, so as to oscillate the arm 7 to an extent limited by adjustable stops 7a. The shaft 8 is supported by the arm 7, being secured thereto by a flange 25, and the arm 7 is supported by an antifriction bearing 27 on a table 28, and is located laterally in the table by a split. coned bearing 29, 30. The table is mounted, for free movement towards and from the disc 3, by a parallel link suspension comprising two frames 33, 34 secured to upper shafts 35, 36 mounted in ball bearings in the casing 23, and secured also to lower shafts 38, 39, upon which rest, on ball bearings, depending legs 40, 41 forming part of the table 28. The table is provided with counterweight means, comprising an arm 46 pivoted at 47 to the casing and having a slot engaged by a pin on the shaft 39, the upper end of the arm carrying an adjustable weight 50 ; a bar 51 secured to the arm 46 also carries adjustable weights 52, whereby the table may be biassed towards the cutting-disc 3. The movements of the table are modified, to pro. duce desired shapes on the stone &c. by means of a former 54 carried by a forked member 56 pivoted at 60 in a bracket 61 secured to the shaft 8 through an intermediate sleeve 162 ; the former may be canted about the pivot to an extent determined by scales, carried respectively by an arm 62 on the pivot 60, and by a plate 63 on the bracket 61. The former engages an abutment member in the form of a bar 55 of square section mounted by pointed screws 170 in a frame carried on ball bearings by the shafts 38, 39, and comprising levers 67, 68 pivotally connected by link members 70. The frame 68 has pivoted thereon a U-shaped block to which a plate 75 is secured, the plate having two holes 78 therein to receive the stems 79, 80 of micro-screws 81, 82, the stems carrying collars 83 to engage the rear face of the plate 75 ; the screw 81 controls the rate of table feed, and the screw 82 is set to stop the feed movement of the table to control the finished size of the stone &c., whilst a visual indication of the table movement is given by a dial gauge 84, and a microscope 91 allows observation of the stone. For grinding conical and spherical shapes, the dop is rotated by a flexible drive 89 and a motor mounted on a support 90, the machine being set up for grinding by the use of the screws 81, 82 and adjustment of the slide 6 by a screw 6a, and the handle 24 being swung during the grinding operation. For grinding an elliptical form on the tip of the stone, for example to produce a tool with front clearance and required to cut a circular arcshaped work-piece, for example, as shown in Figs. 13a and 13b, the tool is set with the line, EF vertical, and the former 54 is canted, so that as the arm 7 is swung to carry the tool tip over the disc 3, the axis of the shaft 8 moves towards and from the cutting-face of the disc. In a modification, the displacements given to the stone by the former may be smaller than those given to the abutment member, a system of reducing levers being used, and the former may be of a shape to give the required form to the stone, no canting of the former being necessary. Means may be provided for automatically removing the stone from the disc at the ends of the arc of oscillation, this means being additional to, or in place of the adjustable stops 7a. Specifications 565,399 and 576,857 are referred to.