A fastener has a head with a plurality of recesses. Each recess is defined by opposed side surfaces and a floor surface. One or both side surfaces of each recess may be formed of a lower facet which is oriented at an obtuse angle to the floor surface, and an upper facet which is oriented at an acute angle with respect to the floor surface.

The present invention relates to a screw element (1) comprising a threaded shaft (2), a screw tip (4) formed on one shaft end and a screw head (5), formed on an opposite shaft end and with force application means (7), and comprising a screw thread (12) extending on the threaded shaft (2) and on the screw tip (4), wherein the screw tip (4) has a front tip section (4a) tapering toward the screw element end, when viewed in the screwing-in direction (Z), and a section (4b) formed on the threaded shaft with a polygonal cross section, when viewed in cross section, whose enveloping circle diameter (d.sub.h) is greater than a core diameter (d.sub.k) of the screw tip (4), and the polygonal cross section has a corner point (15) lying on the enveloping circle of the section (4b), and a front edge surface (9), radially oriented with respect to a longitudinal center axis (X-X), ends in said corner point in the sense of an increased diameter. The screw tip (4) has a first tapering tip section (4a) with a circular cross section and a second, cylindrical tip section (4c) with a circular cross section formed between the first tip section (4a) and the polygonal section (4b), wherein the screw thread (12) is continuously formed without interruption across the first and second tip sections (4a, 4c) of the screw tip (4).

The present invention relates to a screw element (1) comprising a threaded shaft (2), a screw tip (4) formed on one shaft end and a screw head (5), formed on an opposite shaft end and with force application means (7), and comprising a screw thread (12) extending on the threaded shaft (2) and on the screw tip (4), wherein the screw tip (4) has a front tip section (4a) tapering toward the screw element end, when viewed in the screwing-in direction (Z), and a section (4b) formed on the threaded shaft with a polygonal cross section, when viewed in cross section, whose enveloping circle diameter (d.sub.h) is greater than a core diameter (d.sub.k) of the screw tip (4), and the polygonal cross section has a corner point (15) lying on the enveloping circle of the section (4b), and a front edge surface (9), radially oriented with respect to a longitudinal center axis (X-X), ends in said corner point in the sense of an increased diameter. The screw tip (4) has a first tapering tip section (4a) with a circular cross section and a second, cylindrical tip section (4c) with a circular cross section formed between the first tip section (4a) and the polygonal section (4b), wherein the screw thread (12) is continuously formed without interruption across the first and second tip sections (4a, 4c) of the screw tip (4).

A concrete screw is adapted to be driven into a hole predrilled in a concrete structure and includes a head, a shank extending from the head, a thread formed on the shank, and a plurality of bump units. The shank includes front and rear segments spaced along a longitudinal axis. The bump units are distributed on at least the front segment of the shank and staggered along the longitudinal axis. Each bump unit includes a plurality of bumps constitute an inclined pattern relative to the longitudinal axis. Each bump protrudes from the periphery of the shank. In the course of the screw being driven into the hole, the bumps pulverize concrete debris in the hole, and waste debris accumulates at a segment of the shank on which the bump units are distributed for development of a pressing segment and promotion of anti-pullout strength of the screw.

A self-driving masonry anchor that includes ahead configured to receive a driving bit, a threaded section extending from the bottom of the head, a drilling section following the threaded section, and a drill tip at the end of the drilling section. The threaded section includes alternating high and low threads. The high threads include notches or serrations. The low threads are double low threads such that there are two low threads between each high thread. The drilling section includes at least two flutes for the removal of debris. The drill tip includes an abrasive material which is different than the material of the drilling section such that the drill tip and drill section predrill a hole in a masonry material for the threaded section, the threaded section fastening to the masonry material.

An anti-pullout and low-resistance screw includes a shank, a screw-in portion, a head portion, and a thread. The thread is helically formed around both the screw-in portion and the shank and includes a plurality of thread convolutions. Each thread convolution includes an upper tooth surface facing the head portion and a lower tooth surface facing the screw-in portion. At least one tapered pressing structure is designed on the screw-in portion and/or the shank to define at least one section with its outer diameter tapering towards the screw-in portion gradually. The tapered pressing structure extends from a bottom edge of the lower tooth surface along a longitudinal axis of the shank. The lower tooth surface has a lower tooth surface height that is greater than the thread height. An annular anti-pullout plane is formed on the shank between two adjacent thread convolutions to enhance the anti-pullout strength of the screw

A screw includes a head and a shank extending from the head and defining a longitudinal axis. A thread is provided on the shank. The head includes a top portion and a cone portion located between the top portion and the shank. A plurality of recesses is provided in a peripheral surface of the cone portion and spaced in a circumferential direction of the cone portion. Each recess includes first and second side edges opposite to each other in the circumferential direction and an upper edge connecting the first and second side edges. The first side edge features a maximum recess depth greater than a maximum recess depth of the second side edge. The top edge extending in the circumferential direction of the cone portion is partially arranged between the top portion and the first side edge of an adjacent recess in the longitudinal axis direction.

A screw includes a head having a top face and a conical bottom surface, a shank, and thread convolutions. A chip guiding channel is recessedly formed on the conical bottom surface. On the conical bottom surface are spirally disposed a cutting portion which has a plurality cutting units sequentially arranged in a spiral manner, thereby allowing the chip guiding channel to be surrounded by the cutting units along a spiral track. The spiral arrangement of the cutting units assists the head in cutting fibers of a workpiece which are wound around the head into small chips in a continuous and spiral severing manner to reduce drilling torque and resistance, and the spirally-defined chip guiding channel also facilitates a smooth removal of the chips, thereby allowing the head to fit level with a top surface of the workpiece and increasing a fastening effect.

A member attachment structure, in which a second member is overlapped with the first member while a large diameter hole communicates with a part of small diameter holes, is provided. At a position of the first member where the second member is not overlapped, a male screw portion inserted into the small diameter hole and extending from the small diameter hole to the base portion side is screwed into a first boss. At a position of the first member where the second member is overlapped, a tip end portion of a second boss is inserted into the large diameter hole and brought into contact with the first member, the second member is held while being overlapped with the first member, and the male screw portion inserted into the small diameter hole and extending from the small diameter hole to the base portion side is screwed into the second boss.

The present invention provides compliant screws compatible with standard threaded holes that are self-anchoring via auxetic properties. Once a screw has been twisted in place using a mating screw driver, the screw won't be able to be removed unless it is broken, its surrounding material is torn out with the screw, or unless the screw driver itself is again used to twist the screw in the opposite direction. Thus, although reusable, the screw will never come out of its hole in the presence of vibrations or other cyclic or random loading scenarios. The screws are thereby suitable for critical joint applications where screws must never come loose. Non-limiting examples include satellite fasteners, high-speed vehicle bolts, pedicle screws, and other screws used to secure medical implants within a human body.