| 摘要 |
A self-driving, self-tapping screw for screwing into porous concrete has an outer diameter at least one and half times greater than the diameter of the root. The screw thread profile is asymmetrical about a plane perpendicular to the screw axis. The screw thread flank (7) facing the screw head is delimited by a circular or parabolic generatrix extending at least partially from the outer limits of the screw thread to the root (12). The screw thread flank (9) facing the drilling tip (4) is delimited by an essentially linear generatrix inclined at an angle of approximately 0 to 25 DEG to a plane (11) perpendicular to the screw axis. The screw thread section (5) extends over a part of the screw shaft (2), which also comprises an unthreaded shaft section (6), a screw head (3), and a drilling tip (4). The screw can be screwed directly into porous concrete, and the special screw thread profile permits increased anti-withdrawal values. |
