GB365905A - Improvements in machines for working marble - Google Patents

Abstract

365,905. Copying and reproducing mechanism. CROQUET, R., La Buissiere, Hainaut, Belgium. April 24, 1931, No. 12189. Convention date, April 29, 1930. [Class 83 (iii).] A machine for working marble comprises a rotary table and two tool carriages which carry grinding or polishing tools or chisels and have simultaneous vertical and horizontal feed movements and means are provided for shaping oval work pieces. The machine frame comprises an upper plate 3 which carries a partcylindrical support 40 having ball bearings 39 for the rotary work-table 38. The work piece is mounted on a circular plate 36 secured to the work table which is driven through bevel gearing 42, and belt pulleys 44, 46 from a main belt-driven power shaft 47. The front of the frame carries on a member 12 the spindle of a grinding-wheel 23, which is adjustable in a vertical plane. The frame also carries a vertical guide 25 for the lower grinding-wheel carriage 26 carrying a grinding-wheel 34, which may operate on the lower side of the work-piece. The operation of the grinding carriages is effected from a worm 51 on the main driving-shaft which through sprung gears 54, 55, 56 drives a horizontal shaft carrying cams 60, 61. The cam 60 operates a bar 62 pivoted at 5 and connected by links 67, 66 to the vertical and horizontal slides respectively of the upper grinding-carriage. The cam 61 similarly operates a pivoted bar 63 connected by links 69, 68 to the vertical and horizontal slides respectively of the lower grinding-carriage. For the production of oval work pieces the table 38 is replaced by a second table 74, Figs. 8 and 9, having an eccentric circular opening 75 in which is carried, on ball bearings, a circular plate 78 carrying the working holding plate 80, the plate 78 being slotted to receive an adjustably fixed pivot 85 located at a distance from the centre of the table 74 equal to a quarter of the difference between the major and minor diameters of the ellipse to be shaped. This distance is also equal to the eccentricity of the plate 78. The lower face of the plate 78 carries two pins 90, 91 engaging a guide 92 fixed to the member 82, the guide being so shaped that as the table 74 rotates, the pins remain in contact with the guide and the eccentric plate 78 is constrained by the engagement of its slot with the fixed pivot 85 to rotate about its centre at half the angular speed of the table 74 to produce the desired elliptical profile on the work.