Linear bearing arrangement

A bearing arrangement comprising:

• a first support element,
• a second support element spaced from and generally opposite said first element,
• an intermediate element interposed between said first and second support elements and moveable relative to said support elements,
• one of said first support element and said intermediate element having a first guide surface facing the other of said first support element and said intermediate element, said first guide surface being formed to run extremely true to the desired path of movement of the intermediate element relative to the support elements, one of said second support element and said intermediate element having a second guide surface facing the other of said second support element and said intermediate element,
• a first antifriction bearing means comprising rotatable bearing elements connected to the other of said first support element and said intermediate element and in movable engagement with said first guide surface in directions parallel to said first guide surface,
• a second antifriction bearing means comprising rotatable bearing elements connected to the other of said second support element and said intermediate element and in movable engagement with said second guide surface in directions parallel to said second guide surface, and
• preload means on the opposite side of said intermediate element as said first guide surface for exerting pressure along a preload direction thereby yieldably pressing said second bearing means and said second guide surface together, said preload means including an expansible chamber device connected between said second bearing means and said the other of said second support element and said intermediate element such that expansion of the expansible chamber device presses said second bearing means and said second guide surface together thereby exerting a reaction force on said the other of said first support element and said intermediate element urging it toward the first guide surface, and means for supplying pressurized fluid to said expansible chamber device, said first bearing means being substantially immovably and non-yieldably supported by the other of said first support element and said intermediate element against movement relative thereto along the direction of the preload pressure when preload pressure is applied, there being preload means only on the side of said intermediate element opposite said true guide surface.