US Patent 10383439 Swing stool arm

A swing stool arm for use in a swing stool has a horizontal top flange, a horizontal bottom flange, a vertical end flange at a proximal end of the arm, a web extending down from the top flange and up from the bottom flange, and a vertical fillet at the proximal end of the arm. The vertical fillet joins the vertical end flange to the web. The vertical fillet has an open cavity so that the swing stool arm can be made from a cast molten aluminum alloy without forming shrinkage cavities.