Rotating gas drilling head

Claim 1

A GAS DRILLING HEAD FOR WELL CASING AND ADAPTED TO RECEIVE A POLYGONAL CROSS SECTION KELLY EXTENT OF A DRILL STRING THROUGH WHICH PRESSURIZED GAS IS INTRODUCED TO THE WELL AND CASING, COMPRISING A TUBULAR STATIONARY BODY INCLUDING MEANS FOR ATTACHMENT TO THE CASING, A METALLIC TUBULAR DIAMETRICALLY SPLIT PACKING HOLDER WITHIN SAID BODY AND EXPOSED TO CASING PRESSURE INSIDE THE BOTTOM OF THE BODY, SAID HOLDER HAVING A POLYGONAL KELLY-PASSING OPENING EXTENDING THERETHROUGH COAXIALLY OF THE BODY AND HAVING SUCH SIZE THAT THE HOLDER IS ROTATABLY DRIVEN BY THE KELLY, PACKING MEANS CARRIED BY THE INSIDE AND OUTSIDE OF SAID HOLDER FOR ROTATION THEREWITH AND HAVING SEALING ENGAGEMENT WITH THE KELLY AND BODY WALL, SAID HOLDER AND PACKING BEING MOVABLE UP AND DOWN RELATIVE TO BOTH THE BODY AND KELLY, STOP MEANS CARRIED BY THE BODY AND NORMALLY SPACED ABOVE THE HOLDER AND PACKING WHEREBY THE HOLDER AND PACKING ARE SIMULTANEOUSLY ROTATABLE IN THE BODY AND UPWARDLY DISPLACEABLE THEREIN BY THE CASING GAS PRESSURE.