Rotary hemming device

摘要

A method and device for hemming metal sheet involving upsetting the sheet metal to form a skirt at an angle to the parent sheet and for hemming the skirt to the parent sheet or another sheet interposed therebetween. Both skirt forming and hemming utilize rotary bending tools to convert perpendicular motion into rotational bending force. The novel device of the present invention is a rotary hemming tool having a cylindrical rocker characterized by a flat extending along its length with two lobes defining the intersection between the flat and the cylindrical surface of the rocker. The flat and the lobes are the surfaces of the rocker which act against the upset metal skirt and against the anvil on which the metal sheet is placed. The rocker and saddle are configured to limit rocker rotation such that skirt bending commences simultaneously with rocker contact rather than interaction between the rocker and the anvil. Skirts are bent at an obtuse angle in the first station to facilitate top-down layering of additional sheets on the parent sheet. The hemming tool in the second station secures in a single bending and coining operation the skirt against the top sheet to hem all layers to one another.