GB417612A - Improvements in and relating to the grinding of curved surfaces - Google Patents

Abstract

417,612. Grinding curved surfaces. ALLMANNA SVENSKA ELEKTRISKA AKTIEBOLAGET, Vasteras, Sweden. April 18, 1933, No. 11365. Convention date, April 22, 1932. [Class 60.] In the grinding of curved surfaces by the copying principle, in order to obtain an exact copy of the templet irrespective of scale, the desired curved surface is divided into a number of arc shaped elements, and the surface of the templet, which is engaged by a guide roller or other guide member, also is divided into the same number of arcs, of which the individual centres of curvature coincide with those of the corresponding elements of the work surface, and the grinding disc and the work and templet are so moved that the disc will at every moment touch the required surface at a point situated on the line joining the centre of the disc to the centre of curvature of the templet surface for the time being in action. In the example shown in Fig. 2, the surface to be ground is divided into arcs 3a, 3b, 3c, and the templet is divided into corresponding arcs 4a, 4b, 4c, the arcs having centres of curvature a, b, c respectively. The work and templet are rotated about the centre b, the grinding-disc rotates about centre O, and a guide roller 2 contacting with the surface 4a ... is provided. During the grinding of the arc 3b, the required conditions are fulfilled, but during the grinding of the arc 3a, the centre of curvature a moves off the line O, b by an amount x. In order to keep the point a on the line O, b, the templet is moved, during rotation through the arc 3a, by an amount x by the use of a cam 10 also rotating on the axis b and engaging a roller 11, the part 10a of the cam corresponding to the arc 3a of the work ; similarly the cam 10 has a part 10c corresponding to the arc 3c and giving a vertical movement to the work and templet of the amount y. A machine for carrying out the above process is shown in Fig. 3, and comprises a grinding-disc 1 rotated in fixed bearings 21 on a table 22 by an electric motor 20, and a holder 25 slidable in guides 24 on the table ; the table also supports a guide roller 2. The holder 25 has a vertical rack 26 reciprocated by a link 27 and crank disc 28 driven from an electric motor 30, and the rack engages a toothed arc 31 on a disc 5 connected to a shaft 32 carried by a slide movable in guides 36 in the holder 25. The disc carries the templet 4 and the cam 10 resting on a roller 11 carried by the holder 25, and the holder is pressed towards the grinder 1 and the roller 2 by a weight 37. In operation, as the disc 5 rotates it is moved by the templet 4 and by the cam 10. In a modification, the centre of the roller 2 may be above or below the line O, b, the arcs 4a &c. being turned through corresponding angles, and the surface of the templet then not being continuous; in further modifications, the roller 2 or the grinder may be moved instead of, or in addition to the movements of the work and templet. Specification 135,401, [Class 60], is referred to.