US Patent 7631596 Screw device

A choke for a screw device include a choking plug comprising a plurality of choking plug segments, and a choking ring cooperating with the choking plug, the choking ring comprising a plurality of choking ring segments. The plug segments may be releasably mounted to a hub is releasably mounted to a shaft of the screw device, and the choking ring segments releasably mounted to the barrel.