Patent ID: 7451684

Claim:
An actuator device comprising an actuator member adapted to move linearly in the motion space of an actuator housing, a microwave position detecting device for detecting the position of the actuator member in the motion space, the actuator member producing a pressure wave acting on the position detecting device on approaching the position detecting device, a high frequency microwave antenna arrangement for emitting and receiving microwaves, which are at least partially reflected by the actuator member, and dielectric guard cover means, arranged in front of the microwave antenna arrangement for the mechanical protection of the microwave antenna arrangement and between the guard cover means and the microwave antenna arrangement for mechanically uncoupling the guard cover means from the microwave antenna arrangement a clearance is maintained to allow pressure wave related deformation of the guard cover means into the clearance, the guard cover means engaging a side wall of the housing and in particular a side wall of a cover and/or a side wall of the motion space, at least one seal being disposed between the side wall of the housing and the guard cover means.