A composite screw includes a tapping end portion that includes a circular bottom surface, a peripheral surface and a main thread. The peripheral surface extends from the circular bottom surface. The main thread is formed around the peripheral surface. A reception recess is recessed from the circular bottom surface and the peripheral surface. The main thread has a discontinuation where the reception recess opens at the peripheral surface. A rigid body and a weld material fill the reception recess. The rigid body has an outer surface and an auxiliary thread. The outer surface is exposed from the reception recess. The auxiliary thread is formed on the outer surface and connected to the main thread to fill the discontinuation.

A screw anchor for a trussed foundation system to support single-axis trackers and other structures and related methods of driving such a screw anchor into underlying ground. A hollowed tube of uniform diameter is open at both ends with a thread form beginning at one end and circumscribing a portion the tube, the thread form having a tapered lead-in. The open-ended geometry allows a mandrel or rock drill to be inserted and operated through the anchor during driving to expedite the driving process. The tapered thread form provides a lead-in for driving the anchor into a rock bore.

A method for producing a composite screw includes: providing a screw body a circular bottom surface, a peripheral surface and a main thread; processing the screw body to format least one reception recess indented upwardly from the circular bottom surface and inwardly from the peripheral surface; providing at least one composite unit including a weld material and a rigid body of high stiffness material; disposing the weld material in the at least one reception recess and subsequently inserting and moving the rigid body into the at least one reception recess; and melting the weld material to secure the rigid body to the screw body.

A fastening member includes a screw thread formed therein. A portion including a crest portion of the screw thread is formed of a first alloy material and includes: a thick portion where the portion is maximized in thickness in a circumferential direction; and a thin portion where the portion is minimized in thickness in the circumferential direction. A portion including a root of the screw thread is formed of a second alloy material having a tensile strength higher than that of the first alloy material.

A screw anchor for a trussed foundation system to support single-axis trackers and other structures and related methods of driving such a screw anchor into underlying ground. A hollowed tube of uniform diameter is open at both ends with a thread form beginning at one end and circumscribing a portion the tube, the thread form having a tapered lead-in. The open-ended geometry allows a mandrel or rock drill to be inserted and operated through the anchor during driving to expedite the driving process. The tapered thread form provides a lead-in for driving the anchor into a rock bore.

A machine for rotary driving screw anchors into underlying ground and related. The machine has a mast with a rotary driver and a mandrel driver oriented on a common axis. The mandrel driver passes a mandrel through the rotary driver and the screw anchor to allow the mandrel to be actuated ahead of the screw anchor while the rotary driver drives the screw anchor into the ground. Alternatively, the mandrel driver may also drive a hammering drill through the screw anchor to clear a path ahead of it through subsurface rocks.

A screw includes a shank where a thread helix receiving groove winds around the shank and is disposed in the shank. A thread helix is disposed in the thread helix receiving groove where the thread helix has an expandable helix section. The shank has, at the thread helix receiving groove, a wedge flank for radially expanding the expandable helix section as the shank is moved relative to the expandable helix section. The expandable helix section has a helical back and a plurality of expansion fingers projecting axially from the helical back towards the wedge flank. The wedge flank of the thread helix receiving groove is configured for radially displacing the plurality of expansion fingers outwardly as the shank is moved relative to the plurality of expansion fingers.

A machine for rotary driving screw anchors into underlying ground and related. The machine has a mast with a rotary driver and a mandrel driver oriented on a common axis. The mandrel driver passes a mandrel through the rotary driver and the screw anchor to allow the mandrel to be actuated ahead of the screw anchor while the rotary driver drives the screw anchor into the ground. Alternatively, the mandrel driver may also drive a hammering drill through the screw anchor to clear a path ahead of it through subsurface rocks.

The invention relates to a two-steel screw comprising a top part and a cutting part, the top part consisting of a corrosion-resistant material and having a screw head and a shank portion, and the cutting part consisting of a hardenable material, the top part being permanently connected to the cutting part in the region of the shank portion by way of impact extrusion.

The present invention relates to a fastener (10) for a non-threaded bore (50), which fastener comprises: a first member (12) with a head (18), an externally threaded shank (20) extending from the head, and an axially extending projection (22) at the opposite end (24) of the shank compared to the head; and a second at least partly deformable member (14) attached to the axially extending projection, wherein the second member comprises a plurality of longitudinally extending outer ridges (40a-d). The present invention also relates to a method of mounting a first object (46) to a second object (48) using such a fastener, and to a method of manufacturing a fastener (10).