Patent GB-471802-A (GB)
Title: Improvements in and relating to lapping machines
IPC: B24B5/22
Filed: 1936-02-05
Abstract: 471,802. Lapping cylindrical articles. NORTON CO. Feb. 5, 1936, No. 3450. Convention date, Feb. 6, 1935. [Class 60] Cylindrical work-pieces are lapped between conical abradent surfaces, the ratio of the speeds of the opposed work-engaging portions of which differs at different points of the surfaces, and the work-pieces are moved between the surfaces during the operation so that the ratio of the speeds of the portions engaging them is varied. In the machine shown, a pair of oppositely-arranged rotating abrasive cones, together with a pair of straight parallel workguides extending one on each side of the gap between them, form a throat, from end to end of which the work-pieces pass, the ratio of the surface speeds of the portions of the two cones which engage the work-pieces thus varying from one end to the other, and being unity at the centre of the path. The lower cone 50 is carried by a shaft 40 supported in bearings in heads 38, 46 carried by a table 30, the head 46 being supported on dovetail ways on a plate 49 attached to the table 30 so that it may be detached to allow removal of the shaft and cone. The table 30 is mounted on a central trunnion 31 on a flat-surfaced supporting-plate 28, and is formed at the end with segmental surfaces 33 engaging corresponding overlapping guides 35. It may thus be set over about the axis of the trunnion to skew the axis of the cone in order to give a feed movement to the work. The upper cone 55 is similarly mounted in fixed and removable bearing-heads 68, 76 carried by a table 60 pivotally mounted by means of a trunnion 61 and corresponding segmental end bearing surfaces 63, 64 on the flat underface of an elongated supporting-head 56, so that the axis of the upper cone may also be set in a skew position. To enable the gap between the cones to be adjusted the head 56 extends forwardly from the top of a slide 24, which is vertically-adjustable on a column 21. The adjusting means comprises a nut 109 rotatably mounted in the head and engaging a screw 97 attached at its lower end to the column 21 by a universal joint 95 to ensure smooth operation. The nut is rotated through doublereduction worm gearing by a motor 100, final fine adjustment being effected by a hand wheel 121 which is coupled by a disengageable clutch 123 to the motor shaft. The lower cone 50 is driven through a flexible coupling 84 and worm gearing 41, by a motor 82 carried by a table 81 rigidly secured to the head 38 and slidably supported on a surface 80. The upper cone 55 is driven through worm gearing 71 and a universally jointed and extensible shaft (not shown) from a motor 86, carried on the slide 24. The work guides, Figs. 8 and 17, comprise L-section bars 158 to which removable sectional wear-strips 365 are secured by clamping-plates 368. The strips may be formed of cloth impregnated with artificial resin and compressed, or of harder materials such as boron carbide, Carboloy, tritroloy, or the material known under the Registered Trade Mark " Stellite." Detachable bevel-edged work-receiving guides 370, 370a of similar material may be secured to the ends of the bars, the work-pieces falling on to these guides after leaving the grinding cones. At one end the bars are secured to forked members 157, Fig. 6, by which they are removably supported on a horizontal screwed shaft 155, being maintained at the required distance apart by nuts on the shaft which clamp the forked members. In order to adjust the height of the bars a spindle 137 passing through the shaft 155 is journalled in members 135, 140 slidable on vertical shafts 130, 127, and is formed with teeth engaging rack teeth in these shafts, so that when rotated by a worm gear it causes the shaft 155 to rise or fall. The vertical shaft 130 is vertically adjustable in a split boss 131, fine adjustment being provided by a nut 133 screwed on the shaft. The other ends of the bars. 158 are similarly adjustably supported, the forked supporting members being however pivoted to the ends of the bars to compensate for changes in distance between the horizontal supporting shafts when the angle of slope of the guides is altered to suit cones 50, 55 of different angles. The workpieces are fed down an inclined V-section trough 356 to the starting end of the guides. The cones or abrasive laps are preferably formed of frusto - conical portions cemented together and secured between end-plates. They are preferably of fine-mesh silicon carbide grains in a shellac bond. Means are provided for dressing the cones, which are the same as those described in Specification 471,791.