Patent ID: 7520064

Claim:
A laser surveying instrument, comprising a rotating unit for projecting a laser beam by rotary irradiation, a main unit for rotatably supporting said rotating unit, and a sealing means for sealing between said rotating unit and said main unit, wherein said sealing means comprises annular ridges formed on said main unit concentrically to the rotation center of said rotating unit, and annular grooves formed on said rotating unit so that said annular ridges are engaged in said annular grooves and gaps are formed between said annular ridges and said annular grooves, said annular ridges and said annular grooves being arranged concentrically to each other and disposed at least in double arrangement, and wherein said sealing means further comprises a route bent and crooked in a radial direction by said gaps, and a cavity disposed at least at one point along said route and having larger volume than the volume of said gap.