Vacuum preloaded bearings
Bearing principle: The pressurized part of the
bearing can be considered as a collar bearing. This
collar bearing is loaded internally by the action of
vacuum acting on the inner part of the bearing. The
groove connected to ambient pressure is applied to
reduce the flow through the vacuum system.
The pressure in the center part of the bearing where
vacuum is drawn is constant, independent of the flying
height, resulting in a constant
preload. With increased flying height the pressure force in
the collar bearing decreases resulting in a net pulling
action. It follows that equilibrium between the preload and
the pressure force in the bearing can be established for a
specific flying height.