method and device for reducing ungleicheverfahren and device to reduce unequal tension in a preferably cylindrical, r tension in a preferably cylindrical, metal sheet existing side wall of metal sheet

摘要

1,204,736. Restoring shape of articles; altering physical properties. VAN LEER (U.K.) Ltd. 6 May, 1969 [14 May, 1968], No. 22931/68. Headings B3Q and B3V. A method of reducing asymmetrical stresses in a cylindrical sheet metal container and restoring its shape by removing any dents comprises expanding the container by radially expanding and retracting inner dies past the yield point of the metal and compressing or shrinking the container by radially movable outer dies while supporting the container interiorly by said inner dies until the yield point is exceeded and the diameter of the cylinder is less than its original diameter and then collapsing the dies to allow the container to return to its original diameter. Apparatus for carrying out the method comprises a base 1, a head 2 and a casing 3 the base and head being connected by tension rods 4. An hydraulic cylinder 7 carried by tension rods 6 operates a conical member 9 which actuates spring-loaded segmental inner dies 10. Hydraulic cylinders 12 mounted in the head 2 reciprocate a conical member 15 which actuates segmental outer dies 17 which extend through slots in the casing 3. In order to prevent thin sheet metal from buckling the axial edges of the dies are serrated to provide zig-zag gaps between the dies.