Auger with Butterfly Flighting

Abstract

An auger for digging holes in soil is coupled to a gearbox and powered by the power take-off of a tractor. The auger comprises a shaft with a cutting head disposed near its bottom end. The cutting head comprises a plurality of cutting (i.e. digging) blades that cut into soil. Flighting disposed above the cutting head moves and lightens soil, but the flighting does not extend far above the cutting head. The majority of the shaft is free from protrusions that may ensnare a user of the auger during use.

What is claimed is: 
     
         1 . An auger comprising:
 a cylindrical shaft;   an upper end coupled to a gearbox and rotatable by a power take-off of a tractor;   a cutting head disposed near a lower end of the shaft, the cutting head comprising a plurality of blades, the blades extending downwardly and angularly from a blade disc, the blade disc comprising an opening associated with each blade, the blade angled downwardly into the opening, the cutting head comprising a substantially circular outer edge;   an auger tip releasably affixed to and extending beneath the lower end of the shaft, the auger tip extending substantially parallel to the shaft and comprising at least one boring blade;   a plurality of flights rigidly affixed to the shaft and extending helically around the shaft, the flights disposed above the cutting head and below the upper end, the flights comprising substantially flat plates rigidly affixed to the shaft at an angle to the shaft, the flights comprising curved outer edges substantially aligned with the outer edge of the cutting head, upper ends of the flights aligned in substantially a same horizontal plane, lower ends of the flights aligned in substantially a same horizontal plane, each flight extending more than 180 degrees and less than 270 degrees around the shaft.   
     
     
         2 . The auger of  claim 1 , wherein the shaft comprises a smooth portion above the upper ends of the flights, the smooth portion being substantially free of protrusions. 
     
     
         3 . The auger of  claim 2 , wherein the ratio of the smooth portion to a length of the shaft from its upper end to its lower end is greater than 66%. 
     
     
         4 . The auger of  claim 1 , wherein the upper end of the shaft comprises a coupler, the coupler comprising internal threads mateable to the gearbox. 
     
     
         5 . The auger of  claim 1 , wherein the upper end of each flight comprises a substantially straight trailing edge extending radially from the shaft and then curving towards the curved outer edge. 
     
     
         6 . The auger of  claim 5 , wherein the plurality of flights comprises a first flight and a second flight, wherein the first flight is clocked 180 degrees from the second flight with respect to the shaft. 
     
     
         7 . The auger of  claim 6 , wherein the trailing edge of the first flight and the trailing edge of the second flight are aligned with each other and with the center of the shaft. 
     
     
         8 . The auger of  claim 7 , wherein the first flight is angled with respect to the second flight at an angle of substantially 40 degrees. 
     
     
         9 . The auger of  claim 1 , wherein the plurality of blades in the cutting head are oriented such that they face in the same direction when the shaft rotates. 
     
     
         10 . An auger comprising:
 a cylindrical shaft;   an upper end coupled to a gearbox and rotatable by a power take-off of a tractor;   a cutting head disposed near a lower end of the shaft, the cutting head comprising a plurality of blades, the blades extending downwardly from a blade disc, the blade disc comprising an opening associated with each blade, the blade angled downwardly into the opening, the cutting head comprising a substantially circular outer edge;   an auger tip releasably affixed to and extending beneath the lower end of the shaft, the auger tip extending substantially parallel to the shaft and comprising at least one boring blade;   a first flight and a second flight rigidly affixed to the shaft and extending helically around the shaft, the flights disposed above the cutting head and below the upper end, the flights comprising substantially flat plates rigidly affixed to the shaft at an angle to the shaft, the flights comprising curved outer edges substantially aligned with the outer edge of the cutting head, upper ends of the flights aligned in substantially a same horizontal plane, lower ends of the flights aligned in substantially a same horizontal plane, each flight extending less than 360 degrees around the shaft, the first flight clocked with respect to the second flight at substantially 180 degrees.   
     
     
         11 . The auger of  claim 10 , wherein the shaft comprises a smooth portion above the upper ends of the flights, the smooth portion being substantially free of protrusions. 
     
     
         12 . The auger of  claim 11 , wherein the ratio of the smooth portion to a length of the shaft from its upper end to its lower end is greater than 66%. 
     
     
         13 . The auger of  claim 10 , wherein the upper end of the shaft comprises a coupler, the coupler comprising internal threads mateable to the gearbox. 
     
     
         14 . The auger of  claim 10 , wherein the upper end of each flight comprises a substantially straight trailing edge extending radially from the shaft and then curving towards the curved outer edge. 
     
     
         15 . The auger of  claim 14 , wherein the trailing edge of the first flight and the trailing edge of the second flight are aligned with each other and with the center of the shaft. 
     
     
         16 . The auger of  claim 10 , wherein the first flight is angled with respect to the second flight at an angle of substantially 40 degrees. 
     
     
         17 . The auger of  claim 10 , wherein the plurality of blades in the cutting head are oriented such that they face in the same direction when the shaft rotates.