CENTRIFUGAL DEBRIS CATCHER

A debris catcher comprising a conical screen (filter) in a drill string which defines an annular accumulation space between the screen and the inner wall of the drill string is presented. The central portion of the screen is open to establish an unimpeded flow path. A centrifugal deflector, impeller or similar device above (upstream from) the screen establishes a helical flow pattern in the drilling mud whereby debris entrained in the mud is forced outwardly by centrifugal action. The debris is then caught in the annular accumulation space between the screen and the drill string wall when the mud flows through the screen. If the accumulator fills or the screen becomes clogged, mud will still flow through the center flow passage. The debris catcher of the present invention is preferably positioned within a drill string upstream of a mud powered turbine or other device in the mud stream, the operation of which may be jeopardized by debris in the mud stream.