| 摘要 |
An auger assembly is provided which includes a core, the surface of which increases in diameter from the upstream end towards the downstream end. The auger flighting upon the core, however, maintains a constant diameter from the upstream end towards the downstream end so that the depth of flighting gradually decreases to zero at the downstream end. This means that the maximum thrust against the concrete being augered occurs at a negative angle of approximately 105.degree., said thrust being at right angles to the surface of the core. This produces a negative flow of the concrete thus contradicting the free concrete flow required in order to provide the necessary bond between the concrete and the cables. The present invention reduces this surface angle to an angle of approximately 90.degree. or having the surface substantially parallel to the longitudinal axis. The forming mandrel is preferably provided with an inclined surface formed by the diameter of the mandrel decreasing slightly from the upstream end to the downstream end. If a finishing mandrel is included, this also tapers towards the down stream end because of the diameter decreasing from the upstream end towards the downstream end all of which give improved performance of the auger assemblies in such machines. |
