Method of extruding, using a self-adjusting mandrel

Claim 1

APPARATUS FOR EXTRUDING HOLLOW SHAPES IN METALS TO CONTROLLED AND CONSTANT DIMENSIONS, SAID APPARATUS TO BE USED IN GENERAL WITH CONVENTIONAL EXTRUSION EQUIPMENT, SAID APPARATUS CONSISTING OF A CYLINDRICAL MIXING CHAMBER WITH AN OPENING IN ONE END FOR THE ENTRANCE OF MATERIAL TO BE EXTRUDED, THE OPPOSITE OR DOWNSTREAM END SLOPING INWARDLY TO A CENTRAL OPENING CONTAINING A DIE MEANS, WEBBING BARS PROJECTING INWARDLY FROM THE DOWNSTREAM PORTION OF THE WALLS OF THE MIXING CHAMBER AND IN SO DOING PREVENTING LONGITUDINAL MOVEMENT OF A MANDREL, THE TIP OF WHICH PROTRUDES THROUGH THE DIE MEANS, THERE BEING AT LEAST ONE OF SUCH MANDRELS, EACH SAID MANDREL HAVING A HEAD WHICH IS WIDER THAN ANY SINGLE OPENING BETWEEN THE WEBBING BARS, EACH SAID HEAD BEING FASHIONED WITH SPHERICAL CURVATURE ON AT LEAST THE DOWNSTREAM FACE THEREOF, AND EACH MANDREL STEM DEFINING BY ITS PRECISE SHAPE AND DIMENSIONS A CAVITY OF THE HOLLOW EXTRUDED PIECE, SAID WEBBING BARS SO FASHIONED AS TO LEAVE BETWEEN THEM PORTS WHICH IN THEIR SEVERAL CROSS SECTIONAL AREAS ARE PRECISELY PROPORTIONAL TO THE DESIRED LATERAL DISPLACEMENT IN A CONSTANT ATTITUDE OF THE MANDREL STEM, SAID DISPLACEMENT TO BE A POSITION OF EQUILIBRIUM WITH THE RHEOLOGICAL FORCES PRESENT.