| 摘要 |
A vehicle or cart for movement in mutually perpendicular directions includes two sets of driving chains both in contact with the floor at the same time, one set for driving in one direction includes rollers whose axes are parallel to the direction of movement and thus provide gripping with the floor when moving in that direction and the corresponding rollers on the oppositely directed chain links have their axes perpendicular to the direction of movement and thus roll along the floor without impeding, significantly, the movement of the vehicle in the first direction. When the vehicle or cart moves in the second direction the rollers on the second set of chain links engage the floor while the rollers of the chains in the first links roll without impeding the movement.
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