Internally driven earth anchor having small diameter anchor rod

Abstract

An improved modular screw anchor is provided which is adaptable for use with many sizes of elongated anchor rods, is inexpensive to manufacture, can be installed in a wide variety of soil conditions including rocky soils, and permits use of a number of wrench tubes having different internal dimensions. The anchor preferably includes two main components, namely an elongated anchor rod having an obliquely oriented, beveled earth-penetrating lead at one end, and a polygonal in cross-section drive boss separated from the lead by an enlarged, annular flange, and, secondly, an anchor member having a bore-defining hub, an outwardly extending, helical blade circumferentially secured to the hub, and an apertured plate affixed across the bore of the hub. The anchor rod and anchor member are interfitted for installation by inserting the rod through the apertured plate of the hub until the drive boss extends through the aperture and the flange abuts the apertured plate. A polygonal in cross-section tubular anchor wrench is then telescoped over the rod and inserted into the hub bore; the wrench tube is complementally configured for establishing a driving engagement between the outer faces of the wrench and the hub, and between the inner faces of the wrench and the drive boss. Axial rotation of the wrench thus effects rotation of the anchor for installation. The engagement of the flange to the apertured plate is particularly advantageous because this arrangement allows the lead, flange, and drive boss to be dimensioned for use with a smaller diameter rod.