| 摘要 |
1. A frame structure supporting a plate (3) mounted movably generally in a vertical direction with respect to said frame structure (1) by virtue of any suitable guide means (4, 5), which is intended to support at least two regular superposed layers and which is designed to make it possible to work at each layer at a suitable working level (N), characterized in that at least one pneumatic spring (13, 14 ; 16, 17) having a given extension and retraction travel below and above a given force is interposed between the plate (3) and the frame structure (1), said pneumatic spring or springs (13, 14 ; 16, 17) being selected with an extension-retraction force which corresponds to the total weight of a layer loading the plate and a travel movement which corresponds to the height of said layer. |
