GB429138A - Apparatus for describing and tracing curves - Google Patents

Abstract

429,138. Ellipsographs &c. AFRICANO, E., 2, Via Gaudenzio Ferrari, Turin, Italy. Aug. 11, 1934, No. 23266. Convention date, Aug. 11, 1933. [Class 97 (iii)] [See also Group XXII] Apparatus for describing ellipses, sine curves, cycloids, Archimedean spirals, &c., comprises four cranks 1, 1, 2, 2, arranged on a supporting frame 3 so that the diagonals xx, yy joining their parallel axes of rotation 1<1>, 1<1>, 2<1>, 2<1>, in pairs are at right angles, two rods 5, 6, pivoted each to a pair of cranks at a predetermined distance from the axes of rotation of the cranks, and a member 7 sliding on both rods 5, 6, so that a tracer or tool on it describes a curve identical with that described by the point of intersection of the rods as the cranks are rotated in parallelism. Each crank carries an identical pinion 1<11>, 211 and a toothed wheel 4 rotatably mounted on the plate 3 engages the pinions simultaneously. The pivot pins 1a, 2b, attaching the rods 5, 6 to the cranks 1, 2, are threaded to receive screws which are mounted in the cranks and enable the distance of the pivot pins 1a, 2b from the axes 1<1>, 2<1> to be adjusted in accordance with nature of the ellipse desired. A sleeve 7 with a closed end has in its peripheral wall two pairs of holes to receive the rods 5, 6. A tracing point or a tool, such as a milling cutter, may be secured to the sliding member 7. To adapt the apparatus for describing sine curves, the pivots 2b are made to coincide with the axes 2<1> and the whole apparatus moved in the direction yy proportionally to the angular displacement of the cranks. A slide block fixed to the plate 3 may co-operate with a fixed guide and a rack rigid with the latter may engage a pinion 2<11>. By displacing the pivots 2b as well as the pivots 1a from the corresponding cranks curves of the cycloid type may be described. To enable Archimedean spirals to be described the screws upon which the pivot pins la, 2b are threaded carry bevelled pinions each engaging a bevelled pinion fixed to the plate 3 coaxially with the corresponding crank so that the effective radii of the cranks change proportionally to their angle of rotation. To enable subdivision of the curve described, a pinion 2<11> may be geared to a drum carrying a number of peripheral scales. A slide block movable in an axial direction in accordance with a fixed scale is provided with an index and a window through which the appropriate scale on the drum may be viewed.