| 摘要 |
A screw comprising a head part (50), a pointed insert part (52) and a shank part disposed between said head part and said pointed insert part and having a shank axis (A). The shank part comprising a first shank segment (53) adjacent to said head part and having a first radius (r0) relative to the shank axis, and a second shank segment (54) adjacent to said pointed insert part and having a surface that is formed with a helical screw thread (55) including interconnected thread sections that have a second radius (ii) relative to the shank axis and larger than the first radius. The second shank segment is provided with one lengthwise groove (56) having a curvature so that the depth of said groove is larger than zero but smaller than the outer diameter of said threads, and the length of said groove is larger than zero but smaller than the whole length of said shank part, said lengthwise groove extends upward from the pointed end. The surface of the second shank segment being further formed with at least one projecting element (57) between two neighbouring interconnected ones of said thread sections, said projecting element having a greatest radial dimension (r2) with respect to the shank axis that is greater than the first radius (r0) and less than or equal the second radius (r1), |
