In recent years a maintenance technique for long wave track irregularity has been introduced to improve riding comfort. This, however, may cause problems of insufficient adjustment allowance in the rail type 4 fastener for ballastless track used in slab track sections. For purposes of environmental protection and track maintenance cost reduction though, the adoption of ballastless track such as D-type track with direct-connect sleepers is expanding. There has therefore been a growing demand for the development of a rail fastener for ballastless track that allows greater adjustment allowance of the rail in both vertical and horizontal directions.
      A cost-effective direct seat fastening system without tie plate was therefore developed for ballastless tracks. This can generally be used both for ballastless tracks with pre-stressed concrete sleepers and for slab tracks; its vertical and horizontal rail adjustment capacity is equivalent to or greater than that of ballastless track type 4 (Table 1, Fig. 1). The fastener uses a spherical seat hexagon-headed bolt and a spherical washer to adapt to the variable spring clip position, and the spherical washer bottom rib resists any loosening rotation of the spherical seat hexagon-headed bolt. This allows adjustment plate A to vertically adjust the rail up to 20 mm and adjustment plate B up to 30 mm. Adjustments of up to 20 mm are supported by changes of the position of the spring clip. If the adjustment exceeds 20 mm, the clip-supporting wedge is also adjusted (Fig. 2).
      The current fastening interval on the slab track is 625 mm, but with improved lateral pressure resistance and rail creepage resistance, fastening intervals can now be extended to 715 mm in consideration of the recent needs of cost reduction.
      By using this fastener, initial costs and maintenance costs for rail adjustments can be reduced by about 30%.