Continuous circulation apparatus for air drilling well bore operations

Apparatus for maintaining a continuous circulation of an air stream through a drill string during the drilling of a well bore and comprising housing means secured in the proximity of the surface of the well bore for receiving the drill string therethrough, first and second port means provided in the housing in communication with an internal chamber and for receiving the drill string therethrough, said chamber being disposed around the outer periphery of a portion of the drill string during the well drilling operation and isolating the upper end of the drill string from the atmosphere during separation of the drill string upon an interruption of the drilling operation, flapper means pivotally secured in the housing and disposed within the chamber for engagement with one of said port means in the separated position of the drill string to provide said isolation therefor, by-pass means having one end in communication with the air stream and the opposite end in communication with the chamber for directing the air stream into the chamber during said separation of the drill string for direction of the air stream through the drill string during the interruption of the drilling operation, means connected with said by-pass means for selective closing thereof from said air stream whereby the air stream is directed into the drill string remotely from the housing during a continuation of the drilling operation thus providing a continuous circulation of the air stream through the drill string both during the drilling operation and during an interruption of the drilling operation.