Patent ID: 8397838

Claim:
A bore hole rotary reamer comprising: a body having cutters contained in respective recesses formed in the body, each cutter being rotatably mounted by a respective spindle and having a bearing region formed by an inner bearing surface rotatable on an outer bearing surface of the respective spindle; annular seals about the respective spindle, one of which is located at each end of said bearing region to prevent ingress of contaminant to the bearing region; circumferential voids formed between the inner bearing surface and the outer bearing surface of the respective spindle, each of said circumferential voids being located adjacent a respective one of said seals; passageways that each extend in an axial direction of the respective spindle to a respective one of said circumferential voids; and pistons that are each movable in a respective one of said passageway passageways in response to supply of pressure to an outer side of said pistons from the environment which surrounds the reamer, whereby the pistons transfer pressure to fluid in said passageways on an inner side of said pistons to supply pressure to said circumferential voids and thereby to said seals, said pressure being substantially determined by the pressure of the environment surrounding the reamer.