DE1602521

1,195,278. Stamping. NETHERLANDS, APPLIED SCIENTIFIC RESEARCH FOR INDUSTRY, TRADE & COMMERCE. 30 Oct., 1967 [31 Oct., 1966], No. 49170/67. Heading B3Q. Apparatus for deep drawing circular, square &c., blanks to form cylindrical articles or articles having a rectangular, square, elliptical &c., cross-section comprises a drawing ring 3, Fig. 3, having a ribbed upper surface and a hold-down 2, Fig. 2, with a corresponding profile and an allowance for the thickness of the blank. As illustrated, the hold-down 2 has a flat base surface 4 and four projections 7 forming part of a concave conical surface. Surfaces 11 between the ribs 14 of the drawing ring are part of a convex conical surface. The arms 14 protrude less than the projections 7. Instead of a plane base 4, it may be conical, the upper surface 14 then being conical or flat. The flanks 16, 9 may be parallel or convergent, and the ring may have six ribs 13. Exchangeable ribs 13 and projections 7 may be used experimentally to determine the best shape for a particular article. Operation.-The ribs and projections divide a blank into zones engaged by the ribs 13 and zones engaged by the projections 7, the zones being separated by axially-bent sections of the blank which, during descent of the drawing punch (not shown), increase tangential compression and thus radial extension in the zones engaged by the projections. This property is utilized in drawing square blanks by positioning the diagonals of the blank on the ribs 13 where they are substantially free from tangential deformation. If the material of the blank is liable to form ears, due to having different yielding properties in different directions, the blanks should be so cut that ear formation occurs between the corners. Round blanks of earforming material should be located so that any ears are formed over the ribs 13.