Screw pile

Abstract

The present invention relates to a screw pile comprising a shaft and at least two blades extending outwardly from the shaft. Each blade has a leading edge that contacts earth as the screw pile is screwed into the ground. The leading edge includes a swept back portion adapted to deflect rocks that come into contact with the swept back portion of the leading edge during insertion of the screw pile into the ground. In one embodiment, the leading edge of each blade includes two or more straight edge portions extending at different angles to each other. The straight edge portions may include an inner edge portion extending from the shaft and the swept back portion extending at an angle from the inner edge portion.

1 . A screw pile comprising a shaft, two blades in the form of opposing flat plates extending outwardly from the shaft, each blade having a leading edge that contacts earth as the screw pile is screwed into the ground, each leading edge including a first straight edge portion extending from the shaft and a second straight edge portion forming an obtuse angle with said first straight edge portion. 
     
     
         2 . A screw pile as claimed in  claim 2 , wherein the plates have opposite pitch to each other. 
     
     
         3 . A screw pile as claimed in  claim 1 , wherein a lowermost part of each plate is positioned above a lowermost part of the shaft so that the shaft extends below the plates and can contact the ground prior to the plates. 
     
     
         4 . A screw pile as claimed in  claim 3 , wherein a lower end of the shaft includes an attack bit having two diametrically opposed points at its end. 
     
     
         5 . A screw pile as claimed in  claim 1  wherein, when viewed from above, the first straight edge portion extends radially from the shaft. 
     
     
         6 . A screw pile as claimed in  claim 1 , wherein said straight edge portions include an inner edge portion being the first straight edge portion extending from the shaft, an intermediate swept back edge portion being the second straight edge portion and that sweeps back against the direction of rotation of the blade, and an outer edge portion forming an obtuse angle with the intermediate swept back edge portion. 
     
     
         7 . A screw pile as claimed in  claim 6 , wherein the leading edge of each blade is bevelled or sharpened. 
     
     
         8 . A screw pile as claimed in  claim 6 , wherein each blade is symmetric and a trailing edge of each blade mirrors the leading edge. 
     
     
         9 . A screw pile comprising a shaft, two blades in the form of opposing flat plates extending outwardly from the shaft, each blade having a leading edge that contacts earth as the screw pile is screwed into the ground, each leading edge including a first straight edge portion extending from the shaft and a swept back straight edge portion forming an obtuse angle with said first straight edge portion, the swept back straight edge portion being adapted to deflect rocks during insertion of the screw pile into the ground. 
     
     
         10 . A screw pile as claimed in  claim 9 , wherein said two blades have opposite pitch to each other. 
     
     
         11 . A screw pile as claimed in  claim 10 , wherein a lowermost part of each plate is positioned above a lowermost part of the shaft so that the shaft extends below the plates and can contact the ground prior to the plates, a lower end of the shaft including an attack bit having two diametrically opposed points at its end. 
     
     
         12 . A screw pile as claimed in  claim 9  wherein, when viewed from above, the first straight edge portion extends radially from the shaft. 
     
     
         13 . A screw pile as claimed in  claim 9 , wherein a straight outer edge portion forms and obtuse angle with the swept back straight edge portion. 
     
     
         14 . A screw pile as claimed in  claim 13 , wherein the leading edge of each blade is bevelled or sharpened, each blade being symmetric whereby a trailing edge of each blade mirrors the leading edge. 
     
     
         15 . A blade for a screw pile, the blade having a leading edge that contacts earth as the screw pile is screwed into the ground, the leading edge including a first straight edge portion for extending from a shaft of the screw pile and a second straight edge portion forming an obtuse angle with said first straight edge portion. 
     
     
         16 . A blade as claimed in  claim 15 , wherein a third straight edge portion forms an obtuse angle with the second straight edge portion. 
     
     
         17 . A blade as claimed in  claim 15 , wherein the blade is symmetric and a trailing edge of the blade mirrors the leading edge. 
     
     
         18 . A blade as claimed in  claim 15 , wherein a third straight edge portion forms an acute angle with the second straight edge portion.