| 摘要 |
<p>The backrest comprises a frame (10, 12) of portal-like shape with two substantially parallel uprights (10), interconnected by a main cross-piece (12) at the upper ends thereof. and one or more stiffening cross-pieces (14). The uprights (10) and cross-pieces (12, 14) form a single hollow body of plastics material which is charged with glass fiber, and defines a cross-section, the moment inertia whereof is such as to impart to the framework (10, 12) the required stiffness in relation to the elastic moduius of the plastics material. The cross-section of the uprights (10) is preferably tapered from the base toward the upper ends thereof. The framework (10, 12) is preferably produced by rotatively molding a plastics material charged with 30% glass fibers, having an average length of 10 mm.</p> |
