Screw capable of cutting and compressing dregs in an object to be drilled

Abstract

A screw capable of cutting and compressing dregs in an object to be drilled comprises: a tapered head with a small lower end; at least one rib being formed on and winds around the tapered area of the head. Each rib is formed with an outer wall having a first slope with respect to an outer wall of a tapered surface of the head and an inner wall with a second slope with respect to an outer wall of the tapered surface. Connection of the inner wall and outer wall is formed as a sharp knife portion. Each rib winds around the tapered surface of the head with an angle being equal to or larger than 360 degrees. By using the structure above said, dregs in screwing are compressed into the object to tighten the screw to the object to be drilled and no dregs expose out.

What is claimed is: 
     
         1 . A screw capable of cutting and compressing dregs in an object to be drilled, comprising:
 a tapered head  1  with a larger upper end and a small lower end; at least one rib  2 , 3  being formed on and winds around the tapered area of the head;   wherein each of the rib  2 , 3  is formed by an outer wall  21 , 31  with a slope A with respect to an outer wall  21 , 31  of a tapered surface of the head and an inner wall  22 , 32  with a slope B with respect to an inner wall  22 , 32  of the tapered surface of the head; the connection of the inner wall  22 , 32  and outer wall  21 , 31  is formed as a sharp knife portion C; a Y axis is defined as an axis parallel to an axis of the head and the stem of the screw and an X axis is an axis vertical to the X axis; outer wall  21 , 31  is in the right upper area divided by the X axis and the Y axis, and the inner wall  22 , 32  is in the left upper area divided by the X axis and the Y axis; and the knife is a spiral knife winding around the tapered surface of the head.   
     
     
         2 . The screw capable of cutting and compressing dregs in an object to be drilled as claimed in  claim 1 , wherein there are two ribs  2 , 3 . 
     
     
         3 . The screw capable of cutting and compressing dregs in an object to be drilled as claimed in  claim 1 , wherein each rib  2 , 3  winds around the tapered surface of the head with an angle being equal to or larger than 360 degrees.