Guiding device

A guiding device comprising at least one base portion, at least one aerostatically journalled carriage portion displaceable with respect to the at least one base portion and a drive for the at least one carriage portion,

• said at least one base portion being provided with guide tracks,
• said at least one carriage portion being provided with a plurality of bearing feet, which cooperate with the guide tracks and in which ducts are provided for the supply of pressurized air for generating and maintaining air cushions, which act as air bearings,
• said guiding device further comprising means for pre-stressing the air bearings, wherein
• the guide tracks define first and second guide planes enclosing an angle with each other,
• and the means for pre-stressing the air bearings includes a magnet system comprising a permanent magnetic part and a ferromagnetic part, which are arranged with opposite surfaces facing each other on the base portion and the carriage portion, respectively
• the plane of symmetry through the centre line of the magnet system enclosing first and second acute angles with the first and second guide planes, respectively
• said opposite surfaces of said permanent magnet part and said ferromagnetic part enclosing third and fourth acute angles with said first and second guide planes, said third and fourth acute angles being the complementary angles of said first and second acute angles, respectively.