Precision measuring apparatus having a measuring interval sealed from environmental influences

An improved precision measuring apparatus defining a measuring interval sealed from environmental influences, the apparatus comprising:

• a shielding housing surrounding the measuring interval, the housing defining within its wall a slit oriented along the measuring interval, the housing further defining within its outer wall an inner annular channel encircling the slit, the housing further defining within its outer wall at least one outermost channel encircling at least in part the inner annular channel;
• a movable member attachable to a measured object and movable along the measuring interval, the movable member positioned over the housing, the movable member defining within its wall adjacent to the housing an outer annular channel, the inner and outer annular channels and the at least one outermost channel arranged such that the outer annular channel encircles the inner annular channel and the at least one outermost channel surrounds at least in part the outer annular channel;
• a carrying member attached to the movable member, the carrying member extending through the slit;
• means for introducing bearing fluid between the movable member and the shielding housing, the bearing fluid introducing means arranged to create a bearing gap between the movable member and the housing, the bearing fluid forming a bearing within the bearing gap, the bearing movably supporting the movable member on the housing substantially without friction;
• means for supplying sealing fluid to the bearing gap, the inner annular channel arranged to distribute the sealing fluid through the bearing gap to form a seal around the slit, the outer annular channel and the at least one outermost channel arranged to collect the sealing fluid in the bearing gap;
• means for draining sealing fluid from the at least one outermost channel;
• means for draining sealing fluid from the inner annular channel into the housing;
• and
• means for evacuating and draining the housing.