| 摘要 |
<p>The one-piece safety helmet gives increased strength and has two halves which have toothed edges, with triangular, rectangular or semicircular teeth, by which they fit together. That part of a tooth protruding beyond the symmetrical plane of the row of teeth rests against a strip which is joined to the other half of the helmet. The strips are joined in one piece with the appropriate halves. The row of teeth runs crosswise to the plane of symmetry.</p> |
