Linear motor-driven table apparatus capable of operating both in fine-feed and large-feed modes

Claim 1

A linear motor-driven table apparatus capable of operating both in a fine-feed mode and large-feed mode, comprising: a base having an upper surface with a recess in said surface extending in a longitudinal direction over its entire length; first linear bearing means, said first linear bearing means including individual bearing units secured in said recess on opposite walls facing one another, said bearing units extending parallel along said recess and provided with first ball rolling grooves on the facing sides away from said walls; a carriage having a surface on the side away from said base with a recess in said surface extending in said longitudinal direction over its entire length, said carriage mounted on said base by said first linear bearing means and movable in said longitudinal direction, said carriage also provided with first ball rolling grooves on opposite side surfaces, said ball rolling grooves of said first side surfaces facing said ball rolling grooves of said first linear bearing means; first rolling ball elements rolling through passages formed by said first ball rolling grooves in said first linear bearing means and said carriage, respectively such that the angle of contact between the rolling balls and each of the first ball rolling grooves is substantially 45° with respect to the horizontal plane; second linear bearing means, said second linear bearing means also including individual bearing units secured in said carriage recess on opposite walls facing one another, said bearing units extending parallel along said recess and provided with second ball rolling grooves on the facing sides away from said walls; a table mounted by said second bearing means and movable relative to said carriage in the same or opposite direction of the movement, said table also provided with second ball rolling grooves on opposite side surfaces, said second ball rolling grooves of said side surfaces facing said ball rolling grooves of said second linear bearing means; second rolling ball elements rolling through passages formed by said second ball rolling grooves in said table and said second linear bearing means, respectively such that the angle of contact between the rolling balls and each of the second ball rolling grooves is substantially 45° with respect to the horizontal plane; a first linear motor means acting between said base and said carriage, said first linear motor including a first fixed member secured to a lower surface of said intermediate carriage and extending in the longitudinal direction thereof, and a first movable member secured to said upper surface of said base in position opposite said first fixed member; and a second linear motor means acting between said carriage and said table, said second linear motor including a second fixed member secured to an upper surface of said carriage and extending in the longitudinal direction thereof, and a second movable member secured to a lower surface of said table in position opposite said second fixed member, said first fixed member having teeth arranged at a pitch different from the pitch of teeth of said second fixed member.