| 摘要 |
A hand truck for moving sheet material has a laterally extending shelf and a generally upright frame, which extends upwardly from the shelf. The frame may be formed by tubular metal of generally inverted U-shape and together with the frame support a load. The hand truck has a pair of inline primary wheels, mounted on fixed parallel axes, near the two ends of the shelf and the lower ends of the two sides of the frame. The two primary wheels lie in a common plane. A turning wheel, also mounted for rotation about a fixed axis, is situated midway between the two primary wheels but slightly out of line therewith. The turning wheel is of smaller diameter than the two primary wheels, and the plane in which it is mounted forms a small acute angle with the plane of the primary wheels. The turning wheel is out of contact with a supporting surface when both primary wheels touch the supporting surface. For movement of the hand truck in a straight path, both primary wheels touch a supporting surface and the turning wheel is out of contact with the supporting surface. For turning movement, one of the two primary wheels and the turning wheels are in contact with the supporting surface, while the other primary wheel is raised slightly above the supporting surface so as to be out of contact. The turning wheels may be adjustably mounted by a hand or foot operated lever.
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