| 摘要 |
PURPOSE:To bend a metallic square pipe without causing fold and collapse, etc., by forming the cross sectional shape of a groove of at least one bending die between two dies into a specified concave surface. CONSTITUTION:In the grooves 6, 7 of dies 1, 2, the width W1 of respective groove bottoms 6a, 7a is made approximately equal to the width W in the direction perpendicular to the internal-external X-X direction with respect to the bending direction of a blank square pipe material P, and each depth d1 is made a little smaller than the 1/2 length of the thickness D in the X-X direction with respect to said bending direction. At least the groove 6a, at the inside in bending, between both of the grooved bottoms 6a, 7a is formed into the smoothly concave surface so that its depth becomes gradually deeper d2 toward the center, and the other groove bottom 7a is formed into the approximately plane surface. Further, both side walls 6b, 7b of respective grooves 6, 7 are formed, if required, into taper surfaces gradually enlarging toward the opening side. Thus, the bending of a square pipe is performed without causing fold and collapse, etc. |
