Manufacture of refractory metal tubes

Claim 1

THE METHOD OF MAKING A TUBE OF A METAL OF THE GROUP CONSISTING OF MOLYBDENUM, TUNGSTEN AND ALLOYS OF ONE OR BOTH OF SAID METALS WITH SMALL PROPORTIONS OF OTHER METALS, COMPRISING CLOSELY WINDING A WIRE OF THE SELECTED METAL, HELICALLY AROUND A MANDREL OF READILY MACHINABLE CHEAP METAL, SO THAT EACH TURN CLOSELY ABUTS ITS NEIGHBOR, SECURING THE ENDS OF SAID WIRE TO SAID MANDREL, APPLYING BRAZING MATERIAL TO THE COIL OF WIRE ALONG THE LENGTH OF THE WOUND MANDREL, PLACING THE ASSEMBLY IN AN UPRIGHT POSITION WITH ONE END SUPPORTED IN A CUP OF SIMILAR MATERIAL, ENCLOSING SAID ASSEMBLY AND CUP IN AN AIR-TIGHT ENVELOPE, EVACUATING SAID ENVELOPE, HEATING SAID ASSEMBLY IN SAID ENVELOPE, THEREBY CAUSING THE BRAZING MATERIAL TO MELT AND FLOW INTO THE NARROW SPACE BETWEEN THE TURNS OF WIRE, SO THAT ANY EXCESS COLLECTS IN THE SUPPORTING CUP AND IF ALL THE SPACE BETWEEN THE TURNS IS NOT INITIALLY FILLED, SAID MATERIAL FLOWS BY CAPILLARY ACTION UP ALONG THE HELICAL PATH BETWEEN SAID TURNS, DISCONTINUING THE HEATING WHEN THE DESIRED BRAZING HAS BEEN EFFECTED, ALLOWING THE MATERIAL TO COOL, AND REMOVING SAID MANDREL FROM THE FORMED TUBE, WHEREBY SAID TUBE HAS RELATIVELY GREAT CIRCUMFERENTIAL STRENGTH, IN ACCORDANCE WITH THE LONGITUDINAL STRENGTH OF THE WIRE FROM WHICH MADE.