| 摘要 |
A rail support form an upwardly directed generally planar slide face, a longitudinally extending running rail secured to the support and having a foot. A longitudinally extending switch blade adjacent the rail is shiftable above the slide face between an inner position closely transversely juxtaposed with the running rail and an outer position transversely spaced from the running rail. A frame defines a longitudinal outer axis spaced transversely along the slide face from the running rail, a longitudinal middle axis between the outer axis and the running rail, and an inner axis between the middle axis and the running rail. Respective outer, middle, and inner rollers are carried on the frame and rotatable about the respective axes. The middle roller is axially offset from the inner and outer rollers and is of such a diameter that it radially overlaps the inner and outer rollers.
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