Abstract:
A screw capable of drilling and cutting includes two inclined cutting planes with a cutting edge formed on a convergence of the cutting planes. A tapered positioning member extends from the convergence of the cutting planes, where the cutting edge is divided into dual sub cutting edges by means of the positioning member. Each sub cutting edge has an inclined angle. An included angle included by the sub cutting edges is smaller than 180 degrees. Threads spiral on a shank and extend to the sub cutting edges. Setting the positioning member against on an object permits a steady performance during the first stage of screwing. Subsequently, the sub cutting edges provides a scraping effect on the object during drilling. Torque is reduced and drilling speed is promoted.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a fastener design, particularly to a screw capable of rapidly drilling and cutting. 
     2. Description of the Related Art 
     Referring to  FIG. 1 , a conventional screw  1  comprises a shank portion  11 , a head portion  12  disposed at one end of the shank portion  11 , a drilling portion  13  disposed at the other end of the shank portion  11 , and a plurality of threaded units  14  spirally disposed around the shank portion  11 . Wherein, the drilling portion  13  is formed into a tapered end. Thus, the screw  1  directly enters an object  2  via the tapered drilling portion  13 , and the following threaded units  14  continue entering the object  2  so as to achieve a fastening effect. 
     Afore screw  1  might be smoothly fastened into the object  2  (such as plywood) by means of the drilling portion  13  piercing the object  2 . However, in practice, the object  2  is forcedly pierced by the tapered drilling portion  13 . Thus, it is difficult to completely sever fibers contained in the object  2 . That is to say, the fibers are just simply pushed and thrust by the tapered drilling portion  13 , so the screw  1  would be easily impeded by debris resulted from the object  2  in time of drilling. As a result, the debris can not be timely expelled, and the heaped debris incurs an increasing resistance on the screw  1 . Thereby, the operation of fastening the screw  1  is influenced and the object  2  may be easily broken. 
     Referring to  FIG. 2 , the upright screw  1  in the object  2  might be subject to rustiness since water might pile on the head portion  12 . Therefore, in the practical application, the screw  1  is disposed tilting in the object  2 . Herein, if the cutting debris can not be timely expelled, the head portion  12  easily bulges out of the object  2  after screwing. Such abnormal operation is unbeneficial for further fastening. Therefore, the screw  1  needs improvements. 
     SUMMARY OF THE INVENTION 
     It is therefore the purpose of this invention to provide a screw that is capable of rapidly drilling and cutting so as to promote the screwing speed and the debris-guiding effect but decrease the screwing torque, thereby beneficial for succeeding operation. 
     The screw capable of rapidly drilling and cutting in accordance with the present invention comprises a shank, a head disposed at one end of the shank, a drilling portion disposed at the other end of the shank, and a plurality of threaded units spirally disposed around the shank. Two inclined cutting planes are formed on the drilling portion and the two inclined cutting planes are connected at a cutting edge. Wherein, a tapered positioning member extends outward from a convergence of the cutting planes for dividing the cutting edge into dual sub cutting edges. Each sub cutting edge is disposed by an inclined angle. A first included angle formed by the sub cutting edges is less than 180 degrees. The first included angle of the sub cutting edges is different from a second included angle of a taper of the tapered positioning member. 
     Preferably, a blank area defined on the shank divides the threaded units into a first section and a second section; a first diameter of the blank area is larger than a second diameter of the shank but smaller than a third diameter of the threaded units. 
     Preferably, the second included angle of a taper of the tapered positioning member is smaller than the first included angle of the sub cutting edges. 
     Preferably, the threaded units on the shank are spread to the sub cutting edges for connecting to one end of the sub cutting edges. 
     Preferably, a third section is defined on the shank and includes a plurality of auxiliary threaded units; the auxiliary threaded units are disposed between the threaded units; a fourth diameter of the auxiliary threaded units is smaller than a third diameter of the threaded units. 
     Preferably, a plurality of indented threads are formed on the auxiliary threaded units; a plurality of second guiding channels are partially defined on a part of the threaded units. 
     Preferably, the positioning member is formed by a plurality of inclined walls for structuring a pyramid. 
     Preferably, the positioning member is structured into a cone. 
     Accordingly, the positioning member helps the screw stably stand on a screwing object, which allows the sub cutting edges to provide a succeeding scraping effect in time of drilling. Further, the cutting planes guide cutting debris to smoothly enter the channels between the threaded units so as to rapidly expel the cutting debris therefrom. Thereby, the cutting debris does not pile into the vacancy of the threaded units, so that the screwing torque could be decreased but the screwing speed could be enhanced. Moreover, the screw is favorably embedded in a screwing object without any protrudent part. Therefore, such even screwing object is beneficial to be further fastened. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view showing a conventional screw; 
         FIG. 2  is a schematic view showing the conventional screw in screwing; 
         FIG. 3  is a schematic view showing a first preferred embodiment of the present invention; 
         FIG. 4  is an end view of  FIG. 3 ; 
         FIG. 5  is a partial view of the first preferred embodiment of the present invention; 
         FIG. 6  is a schematic view showing the first preferred embodiment of the present invention in screwing; 
         FIG. 7  is a schematic view showing a second preferred embodiment of the present invention; 
         FIG. 8  is a perspective view showing a third preferred embodiment of the present invention; 
         FIG. 9  is a schematic view showing a fourth preferred embodiment of the present invention; and 
         FIG. 10  is a schematic view showing a fifth preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
     Referring to  FIGS. 3 and 4 , a first preferred embodiment of the present invention is shown. In order to clearly show the features of the screw  3 , the screw  3  in this figure and in the following embodiments is presented by one side. A screw  3  comprises a shank  31 , a head  32  disposed at one end of the shank  31 , a drilling portion  33  disposed at the other end of the shank  31 , and a plurality of threaded units  34  surroundingly disposed around the shank  31 . Wherein, a first guiding channel  341  is defined amid the threaded units  34 . 
     Further, two inclined cutting planes  331  are convergently formed on the drilling portion  33 , and a cutting edge  332  is formed on the connective cutting planes  331 . Additionally, a tapered positioning member  333  is integrally bulged outwards from the convergence of the cutting planes  331  to structure a tapered unit for dividing the cutting edge  332  into dual sub cutting edges  3321 . Each sub cutting edge  3321  is disposed by an inclined angle. A first included angle θ 1  formed by the sub cutting edges  3321  is less than 180 degrees. The first included angle θ 1  of the sub cutting edges  3321  is different from a second included angle θ 2  of a taper of the tapered positioning member  333 . Especially, the second included angle θ 2  of the taper of the tapered positioning member  333  is smaller than the first included angle θ 1  of the sub cutting edges  3321  (as shown in  FIG. 5 ). Moreover, the positioning member  333  is assembled by a plurality of inclined walls  333 ′ bulged from the cutting planes  331 . In the figure, there are four inclined walls  333 ′ forming a square pyramid. Alternatively, while the positioning member  333  is structured by a cone that also integrally bulges from the cutting planes  331 , an oblate cone could be especially defined on the cutting planes  331  as preferably shown in  FIG. 6 . Accordingly, however the positioning member  333  is designed outward protrudent from the cutting planes  331 , a precise positioning effect on an object  4  in time of drilling is provided. Continuingly, the sub cutting edges  3321  preferably scrapes the object  4  in time of drilling. Moreover, while the threaded units  34  around the shank portion  31  extend to the sub cutting edges  3321  and connect to an end  3322  of one of the sub cutting edges  3321 , the first guiding channel  341  is formed as an intercommunicated channel amid the threaded units  34 . 
     Referring to  FIG. 7 , in operation, the positioning member  333  props the screwing object  4  (plywood is adopted in the figure) for the screw  3  to achieve a stable positioning effect. Thereby, the head  32  is imparted by a screwing torque for allowing the drilling portion  33  to enter the object  4  by means of the sub cutting edges  3321  scraping the object  4 . Namely, when the positioning member  333  is served as a pivot of the screw  3 , the sub cutting edges  3321  are able to steadily scrape and enter the object  4 . Moreover, since the threaded units  34  extend and connect to the end  3322  of one of the sub cutting edge  3321 , the cutting planes  331  thrust the cutting debris generated in time of drilling, so that the cutting debris further travels into the first guiding channel  341  amid the threaded units  34  that are connected to the end  3322  of one of the sub cutting edges  3321 . Accordingly, the cutting debris is promptly removed, and there is no redundant cutting debris obstructing and compressing the vacancy between the screw  3  and the object  4 , which promotes the screwing speed but decreases the screwing torque. Thus, however the screw  3  is disposed upright or tilting, it could be evenly embedded in the object  4  for a further combination. 
     Referring to  FIG. 8 , a third preferred embodiment is shown. In order to clearly show the features of the screw  3 , the screw  3  in these figures and in the following embodiments are shown by another sides different from those of afore embodiments. Wherein, the screw  3  similarly comprises the shank  31 , the head  32 , the drilling portion  33 , and the threaded units  34 . Differently, a blank area  311  defined on the shank  31  divides the threaded units  34  into a first section A 1  and a second section A 2 . A first diameter R 1  of the blank area  311  is larger than a second diameter R 2  of the shank  31  but smaller than a third diameter R 3  of the threaded units  34 . Further, the second section A 2  of the threaded units  34  is spread to the sub cutting edges for connecting to one end  3322  of the sub cutting edges  3321 . 
     In operation, the positioning member  333  helps the screw  3  stably situates on the object  4  (not shown), and a screwing torque is imparted on the head  32  for bringing the drilling portion  33  to go through the object  4 . Herein, when the sub cutting edges  3321  contact the object  4 , the second section A 2  gradually gets in the object  4 . Thereby, cutting debris generated in time of drilling arrive at the second section A 2  along the cutting planes  331 . After that, the cutting debris are expelled rapidly through the first guiding channel  341  amid the threaded units  34 , the blank area  311 , and the first section A 1 . Obviously, no redundant cutting debris will accumulate and press the vacancy between the screw  3  and the object  4 . Moreover, the screw  3  could firmly stay in the object  4  since the first diameter R 1  of the blank area  311  is larger than the second diameter R 2  of the shank  31 . Preferably, the fastened screw  3  also promotes a subsequent combination. 
     Referring to  FIG. 9 , a fourth preferred embodiment is shown. The screw  3  similarly comprises the shank  31 , the head  32 , the drilling portion  33 , and the threaded units  34  as those in the first and the second embodiments. Differently, a third section B is defined on the shank  31  and includes a plurality of auxiliary threaded units  35 . The auxiliary threaded units  35  are disposed between the threaded units  34 . A fourth diameter R 4  of the auxiliary threaded units  35  is smaller than the third diameter R 3  of the threaded units  34 . Whereby, the threaded units  34  and the auxiliary threaded units  35  contribute to a high-low threaded section on the shank. Accordingly, the screw  3  is able to sever the cutting fibers and expel the cutting debris faster and more efficient. Obviously, the screwing resistance is decreased since the vacancy between the object and the screw  3  is clear and not obstructed. Thus, the screw  3  provides a smooth screwing effect and a stable combination after fastened. 
     Referring to  FIG. 10 , a fifth preferred embodiment is shown similar to that of fourth preferred embodiment. Differently, a plurality of indented threads  351  are formed on the auxiliary threaded units  35 . Moreover, a plurality of second guiding channels  342  are partially defined on a part of the threaded units  34 . Wherein, a drilling effect and a concurrent severing function could be brought about by the second guiding channels  342  and the indented threads  351 , which enhances the drilling effect of the drilling portion  33  and promotes the cutting efficiency as well as the fastening performance. Favorably, the cutting debris is still timely expelled, which allows the friction and the torque in time of drilling to be largely reduced. Thus, the screw  3  is preferably embedded in the object  4 , and a firm and stationary fastening performance is achieved. 
     To sum up, the present invention in particularly utilizes the positioning member formed on the cutting planes of the drilling portion to render a stable positioning effect. Namely, dual sub cutting edges are provided by the positioning member dividing the cutting edge of the drilling portion. Thereby, the positioning member properly positions the screw for proceeding to subsequent drilling, and the sub cutting edges as well as the cutting planes help guide the cutting debris generated in time of screwing for a speedy expelling via the cutting planes and the guiding channels amid the threaded units. Accordingly, no redundant cutting debris would pile the vacancy between the screw and the object, so the drilling torque could be decreased, but the drilling speed could be enhanced. Thus, the screw of the present invention could be firmly and smoothly embedded in the object for a further combination. 
     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.