APPARATUS FOR FORMING SHARPLY BENT BRANCHES Russian patent published in 2007 - IPC B21D9/12 B21C37/28 

FIELD: plastic working of metals, possibly manufacture of parts from tube blanks by cold forming process.

SUBSTANCE: apparatus includes sleeve with punch, two die-halves forming draw die, and rigid inner mandrel. The last has inner working portion with working surface having minimum curvature radius, outer working portion with working surface having maximum curvature radius and locking members for fixing inner mandrel in working position. Locking members are arranged in front and rear ends of mandrel. In working position mandrel is arranged with guaranteed gap Sz between its working surface and working surface of draw die. Inner and outer working portions of mandrel are mutually spaced by distance H. Values of said guaranteed gap Sz and distance H are determined according to next expressions: Sz = (1.1 -1.2)S; H = (3.5 - 4.%)S, where S - thickness of initial tube blank. Outer working portion of mandrel is stationary one. Inner working portion may be moved at absence of front and rear locking members in direction of outer portion till closing with it.

EFFECT: possibility for using universal sheet forming equipment during increased useful life period.

2 dwg