A positioning device comprising a first part and a second part which is displaceable relative to the first part by means of a system of Lorentz-force motors, whereby, relative to the first part, the second part is supported in a Z-direction by means of at least one gas cylinder, said gas cylinder comprising...http://www.google.de/patents/US6337484?utm_source=gb-gplus-sharePatent US6337484 - Positioning device and lithographic projection apparatus comprising such a device
