| 摘要 |
<p>The head (1) has cutting line (12) attached to it in a number of relatively short sections, each section being folded to form two parallel projecting lines (12a, 12b) of the same length, lying in the same plane and perpendicular to the axis (2) of the head. Each doubled section of line is fitted through a radial slot in the head between a central cavity and its periphery, and is held in place by the bulge (13) formed by the fold in the line. The outer end of each slot is formed by curved surfaces which reduce the lateral forces in the line sections.</p> |
