| 摘要 |
The modular top frame has a plurality of rails that are interconnected with corner members and has a top and a bottom surface between the inner and outer perimeter of the top frame. The corner members are assembled with two corner parts which have an outer side, a central rib and reinforcing ribs. The corner members have retainer pins in pin receiving apertures positioned along and adjacent to the outer side and the central rib so that when the corner parts are positioned one over the other, the retainer pins and the pin receiving apertures join the corner parts. The corner members have improved resistance to torsional and bending stresses. The top frame has an outside and an inside perimeter and the provides an area between the outside and inside perimeter equal to or greater than 48% of area of the outside perimeter. |
