Abstract: One aspect of the invention provides a rail arrangement in which a rail is releasably supported in an inner shell, and the inner shell and rail are received within an outer shell. This provides flexibility in that the design of the inner shell can be varied to provide different relative positioning of the rail with respect to the outer shell. Thus, the inner shell can be used to take account of sinking of the outer shell, which is typically cast into the rail foundations.

Abstract: A transmission is provided for converting rotary input into an oscillating output. The transmission includes a housing with an input shaft and an output shaft, and a series of gears interconnecting the shafts. The gears include a pair of rack gears on opposite sides of an output pinion mounted on the output shaft. The rack gears are held in meshing engagement with the output pinion by a carrier which is mounted upon a floating bushing on the output shaft. The floating bushing allows the rack gears and rack carrier to move side-to-side relative to the output shaft, thereby equalizing the load on the rack gears and preventing binding between the teeth of the rack gears and the teeth of the output pinion.