Screw dowel for fastening rails

Abstract

Screw dowel for concreting into a railway sleeper or ballastless track and frictionally connecting to a sleeper screw, containing a threaded portion ( 14 ) with external thread flights ( 18 ) arranged on the outside of the screw dowel ( 10 ) and with internal thread flights ( 19 ) arranged on the inside of the screw dowel; and an upper subportion ( 16 ) without external thread that is situated close to the dowel opening ( 26 ) in the installed state; the screw dowel containing two constituent parts made of different materials, namely a basic body made of plastic and a cylindrical ring ( 20 ) made of a steel material and mounted with a form fit and/or force fit.

1 . Screw anchor for concrete attachment into a railroad tie or non-ballasted track and force-fit connection using a rail screw comprising:
 a threaded section comprising external threads disposed on an exterior of the screw anchor and internal threads disposed on an interior of the screw anchor; and   an upper partial section without external threads which is disposed in an installed state close to an anchor opening;   
       characterized in that
 the screw anchor further comprises two components made of different materials, a base body made of plastic, 
 and a cylindrical ring made of a steel material, which is attached to the base body in a form and/or force fit manner; and 
 wherein a linear coefficient of thermal expansion of the steel material of the cylindrical ring does not exceed 3·10 −5  l/K. 
 
     
     
         2 . Screw anchor according to  claim 1 , characterized in that, in the installed state, the cylindrical ring with the base body extends upwards to a region of the anchor opening for a the rail screw and is covered by a plastic collar comprising a further component of the screw anchor. 
     
     
         3 . Screw anchor according to  claim 1 ,
 characterized in that the attachment of the cylindrical ring is achieved by an adjustment of an internal diameter of the cylindrical ring.   
     
     
         4 . Screw anchor according to a  claim 1 , characterized in that the cylindrical ring has a wall thickness between 0.5 mm and 5 mm. 
     
     
         5 . Screw anchor according to  claim 2 , characterized in that, in the installed state, the cylindrical ring extends to an upper start of the external threads. 
     
     
         6 . Screw anchor according to  claim 1 , characterized in that the linear coefficient of thermal expansion of the steel material of the cylindrical ring is at least ten times smaller than that of the plastic material of the base body. 
     
     
         7 . Screw anchor according to  claim 1 , characterized in that the linear coefficient of thermal expansion of the steel material of the cylindrical ring is approximately equivalent to that of concrete. 
     
     
         8 . Screw anchor according to  claim 6 ,
 characterized in that the steel material of the cylindrical ring is characterized by a modulus of elasticity high enough that the cylindrical ring attached to the anchor does not substantially expand when heated within the temperature range in which it is used.   
     
     
         9 . Screw anchor according to  claim 1 ,
 characterized in that the external thread of the threaded section comprises a round thread.   
     
     
         10 . Screw anchor according to  claim 1 ,
 characterized in that the cylindrical ring is coated with plastic.   
     
     
         11 . Railroad tie or non-ballasted track with at least one screw anchor according to  claim 1 . 
     
     
         12 . Screw anchor according to  claim 8  wherein the maximum modulus of elasticity is 150 GPa. 
     
     
         13 . Screw anchor according to  claim 10  wherein the plastic coating has a thickness between 0.1 mm and 1 mm.