linear motion feedthrough


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Linear motions can be coupled into the vacuum system by using flexible welded bellows as in the picture below. For this particular device, the distance between the left and the right flange can be changed such that an evaporator or something else can be moved in and out of the chamber.



Using bellows allows motion without actually breaking the vacuum anywhere and without the need for any kind of differential pumping. A design challenge is that one usually wants to be able of doing quite precise movements while dealing with big forces at the same time. Keep in mind that, for mechanical purposes, the pressure inside the chamber is zero and so there is a big force trying to compress the bellows. It is therefore necessary to have a rather bulky mechanical construction to keep the bellows stretched and the flanges parallel to each other.