| 摘要 |
A switch point (20) is alternatively raised and lowered. An upper comb structure (22) has a switch point (20) on its upper surface and teeth (23) on a lower surface. A lower comb structure (24) has compatible teeth (25) on its upper surface. The upper comb (22) moves only vertically. The lower comb structure (24) moves only horizontally. The combs may assume a raised configuration wherein the upper comb teeth (23) are supported on the lower comb teeth (25), or alternatively, a lowered configuration wherein the upper and lower comb teeth are nested. The comb structures (22, 24) have either laterally or longitudinally disposed teeth, and may be either linear or curvilinear with respect to a longitudinal axis. The combs and switch point are enveloped within containment walls (36) and end plates (38) so as to be a largely sealed unit. |
