Device for a top drive drilling machine for continuous circulation of drilling mud

A method of continuously supplying drilling mud by the use of a top drive drilling machine said method comprising the following steps:

• establishing a borehole with a drill string and a circulation circuit for the drilling mud, a drive shaft arranged for the drilling machine being connected to the drilling mud plant and drill string, and the drilling mud being supplied to the borehole through a centre bore in the drive shaft arranged for fluid communication with the drill string;
• activating a first pressure seal around the drive shaft in a first chamber of a connection housing, and forming a second pressure seal around the drill string in a second chamber in the connection housing;
• supplying drilling mud to the second chamber through a drilling mud inlet;
• stopping the drill string rotation and disconnecting the drive shaft from the drill string;
• pulling the drive shaft out of the second chamber;
• closing, in a pressure-sealing manner, a valve forming an interface between the first and the second chambers;
• stopping the supply of drilling mud through the drive shaft;
• pulling the drive shaft out of the first chamber;
• connecting a drill pipe to the drive shaft;
• inserting the drill pipe and drive shaft into the upper chamber;
• activating the first pressure seal;
• opening the valve;
• stopping the supply of drilling mud through the drilling mud inlet;
• connecting the drill pipe to the drill string;
• and
• resuming the drill string rotation.