Japanese Direct4K & Direct8K fastening systems
Since the 1960s, Japan has been pioneering the study of non-ballasted track systems, leading to the development and implementation of various fastening systems. Among these, the Direct4 and Direct8 fastening systems were initially introduced, followed by the improved Direct4K and Direct8K systems, which are currently the main types in use.
The Direct8K fastening system features a separated structure with the tie plate, utilizing pre-embedded plastic dowels on the sleeper instead of metal dowels. Oval holes on the tie plate allow for gauge distance adjustment by moving the tie plate, with a range of ±10mm. Height adjustment, achieved through rail pads, tie plates, and adjusting lining pads, spans from 0 to 70mm.
On the other hand, the Direct4K fastening system consists of a single elastic layer structure without a tie plate. In this system, the blade clamps directly onto the rail, with the clamping force varying depending on the tightness of the bolts. Height adjustment in this system ranges from 0mm to 10mm, with a gauge adjustment range also of ±10mm.
The Improved Direct4K fastening system incorporates tee hexagon bolts, spherical washers, and double-deck adjustment pads. This system offers an expanded adjustment range, with height adjustment from 0mm to 50mm and a gauge adjustment range of ±10mm. These advancements enhance the flexibility and performance of the fastening system, catering to the diverse requirements of railway infrastructure.