Abstract:
The present invention pertains to a high-speed fastening screw comprising a plurality of concavities on the threads connected in sequence in a single helix. Further, the concavities separately located adjacent to the screw head and to the drilling portion are disposed at relative positions for aligning with an imaginary line, hence efficiently cutting and severing the object fibers to enhance a screwing efficiency.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a screw, in particular, a high-speed fastening screw. 
   2. Description of the Related Art 
   Referring to  FIG. 1 , a conventional screw  1  comprises a screw head  10 , a shank  11  extending from the head  10  along a shank axis “θ”, a drilling portion  13  disposed at the distal end of the shank  11 , and a plurality of threads  12  disposed on the shank  11 ; wherein each of the threads  12  provides with a notch  121  disposed around the outer edge thereof, and a plurality of the notches  121  are assumed to be sequentially joined by an imaginary line “a”, started from an initial notch “c” located adjacent to the drilling portion  13  to a final notch “d” located adjacent to the screw head  10 , which results in the line “a” being inclined with respect to the shank axis “θ” by an angle “ρ”. 
   While screwing, the screw  1  is initially drilled into the object through the drilling portion  13  and the threads  12 , and further the notches  121  assist to cut the fibers and receive the debris (not shown in the figures). By means of the inclination of the imaginary line “a” and the smaller angle “ρ” in  FIG. 1 , the notches  121  solely spread around part of the shank  11  (shown in end view of  FIG. 2 ) and can not thoroughly cut off the fibers of the object. Thereafter, the unsevered fibers would be facilely twisted round the shank  11 , which increases the screwing resistance and affects the screwing efficiency. 
   To solve the aforementioned problems, some manufacturers may intend to dispose a plurality of notches  221  on each of the threads  22 , as shown in  FIG. 3 . However, the more notches  221  are on the threads  22 , the less dimension of each notch  221  is. The notches  221  with smaller dimensions would not substantially cut and sever the fibers, which causes fibers to be twisted round the shank and accumulated within the object and furthers the object easily to be destroyed. In addition, the configuration of multiple notches  221  on the threads  22  may also cause injuries to the operators while screwing. Thus, screw  1  and  2  still requires further improvements. 
   SUMMARY OF THE INVENTION 
   Therefore, the object of the present invention is to provide a screw comprising a plurality of concavities disposed on the threads for being sequentially connected as a state of a single helix, thereby assisting to thoroughly and sequentially sever fibers for reducing the screwing resistance and for reducing potential injury to the operators. 
   The screw in accordance with the present invention comprises a screw head, a shank, a drilling portion and a plurality of threads; wherein a plurality of concavities on the threads are sequentially connected to transversely form a single helix around the shank with an initial concavity longitudinally aligning with respect to a final concavity by an imaginary line. With the help of the concavities to cut and sever the fibers, the present invention increases the screwing efficiency by reducing screwing resistance and also introduces a more user-friendly interface for the operators. 
   The advantages of the present invention over the known prior art will become more apparent to those of ordinary skilled in the art upon reading the following descriptions in junction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view showing a conventional screw; 
       FIG. 2  is an end view showing the screw of  FIG. 1 ; 
       FIG. 3  is a perspective view showing another conventional screw; 
       FIG. 4  is a perspective view showing a screw of a first preferred embodiment of the present invention; 
       FIG. 5  is an end view showing the screw of  FIG. 4 ; 
       FIG. 6  is a perspective view showing a screw of a second preferred embodiment of the present invention; 
       FIG. 7  is a schematic view showing the screw of the first preferred embodiment to be screwed into the object; and 
       FIG. 8  is a schematic view showing a screw of a third preferred embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Like elements in the present invention are denoted by the same reference numerals throughout the disclosure. 
   Referring to  FIG. 4 , a screw  3  of a first preferred embodiment comprises a screw head  30 , a shank  31  longitudinally extending from the screw head  30 , a drilling portion  33  disposed on the distal end of the shank  31 , opposite to the screw head  30 , and a plurality of threads  32  disposed on the shank  31 ; wherein each of threads  32  consists of a thread bottom  324  joined to the shank  31  and a thread crest  325  outwardly protruded from the shank  31 . Further, a concavity  321  is defined from a periphery of the thread crest  325  toward the thread bottom  324  to form a bottom wall adjacent to the thread bottom  324  (shown in a second preferred embodiment of  FIG. 6 ). It is adopted in the preferred embodiments of the present invention that the each of the concavities  321  is extensively depressed to contact with the surface of the thread bottom  324  (shown in  FIG. 4 ), which results in that the concavity  321  has the bottom wall corresponding to the thread bottom  324  and defines two flanks  327  and  328  separately extending to meet the thread bottom  324 . In this manner, the cross-sectional view of a concavity  321  would be presented as a trapezoid contour shown in the figures of the present invention. 
   Still further, the concavities  321  on the threads  32  are sequentially connected in the shape of a single helix around the shank  31  in cross section, started from an initial concavity “s” located adjacent to the drilling portion  33  and terminated at a final concavity “t” located adjacent to the screw head  30 . Moreover, the initial concavity “s” and the final concavity “t” are disposed at relative positions, whereby the initial concavity “s” is accurately aligned with the final concavity “t” by an imaginary line “β”, so that the threads  32  with respect to the imaginary line “β” are not interrupted, and the concavities  321  are defined to be overall spread around the shank  31  (shown in the end view of  FIG. 5 ). 
   Referring to  FIG. 7 , in manipulation, an operator holds the screw  3  by steadily gripping the shank  31  and the threads  32  and further transfers a force upon the screw head  30 , so that the screw  3  is drilled into the object  4  by the drilling portion  33  with the threads  32  for cutting the fibers of the object  4 . In the mean time, by means of the concavities  321  on threads  32  spreading around the shank  31 , the flanks  327  and  328  of the concavity  321  thus aid in continuously cutting and severing the fibers of the object  4  and gradually guiding the debris out, so as to prevent the unsevered fibers from being twisted round the shank  31  and causing the destruction of the object  4 . Further, the configuration of the concavities  321  connected as a state of a single helix would also improve the problem of the injuries to the operator, for instance of reducing the cases of hurting the operator&#39;s hands while gripping the screw  3 . 
   Referring to  FIG. 8 , a screw  3  of a third preferred embodiment comprises a similar configuration like the first preferred embodiment. Specifically, the concavities  321  are disposed at an interval of one thread  32  between any of the two threads  32  and still connected in a single helix around the shank  31 , which helps cutting the fibers by reducing screwing resistance with a higher screwing speed and hence enhancing the screwing stability. Also, the fewer amounts of the concavities  321  on threads  32  facilitate to decrease the possibility of the injuries to the operators. 
   To sum up, the present invention takes advantages of the concavities on the threads overall spreading around the shank, so as to cooperate with threads to sequentially sever the fibers into debris and to prevent the fibers from being twisted round the shank. As a result, the present invention reduces the screwing resistance for a higher screwing efficiency and avoids hurting the operators while screwing. 
   While we have shown and described the embodiment in accordance with the present invention, it should be clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.