Structure of screw

Abstract

A screw includes a screw cap and a shank extending downward from the screw cap. The shank has an outer circumferential surface on which a thread is formed. The shank has a lower end forming a tip section. The screw cap is extended downward to form a conic section. The conic section is provided thereon with a reverse prevention mechanism, which is constructed to include at least one step structure. After the screw is screwed into a workpiece, in an attempt to screw the screw out of the workpiece, the reverse prevention mechanism providing a blocking and resisting effect to prevent the screw from being readily screwed out of the workpiece and thus, a reverse prevention effect of the screw can be enhanced to thereby improve overall performance of use of the screw.

I claim: 
     
         1 . A screw, comprising a screw cap and a shank extending downward from the screw cap, the shank having an outside circumferential surface on which a thread is formed, the shank having a lower end forming a tip section, the screw cap being extended downward to form a conic section, the conic section being provided with a reverse prevention mechanism, which is constructed to comprise at least one step structure. 
     
     
         2 . A screw, comprising a screw cap and a shank extending downward from the screw cap, the shank having an outside circumferential surface on which a thread is formed, the shank having a lower end forming a tip section, the screw cap being extended downward to form a conic section, the shank located below the screw cap comprising a neck section that is free of thread, the thread-free neck section being provided with a reverse prevention mechanism, which is constructed to comprise at least one step structure. 
     
     
         3 . A screw, comprising a screw cap and a shank extending downward from the screw cap, the shank having an outside circumferential surface on which a thread is formed, the shank having a lower end forming a tip section, the screw cap being extended downward to form a conic section, the tip section being provided with a reverse prevention mechanism, which is constructed to comprise at least one step structure. 
     
     
         4 . The screw according to  claim 1 , wherein the screw cap has a top on which a rotating section is formed. 
     
     
         5 . The screw according to  claim 2 , wherein the screw cap has a top on which a rotating section is formed. 
     
     
         6 . The screw according to  claim 3 , wherein the screw cap has a top on which a rotating section is formed. 
     
     
         7 . The screw according to  claim 1 , wherein the thread is provided with a reverse prevention mechanism, which is constructed to comprise at least one step structure. 
     
     
         8 . The screw according to  claim 2 , wherein the thread is provided with a reverse prevention mechanism, which is constructed to comprise at least one step structure. 
     
     
         9 . The screw according to  claim 3 , wherein the thread is provided with a reverse prevention mechanism, which is constructed to comprise at least one step structure. 
     
     
         10 . The screw according to  claim 1 , wherein the conic section of the screw is provided with a reverse prevention mechanism, which extends to a top surface of the screw cap. 
     
     
         11 . The screw according to  claim 2 , wherein the reverse prevention mechanism is arranged between a lower end of the conic section of the screw cap and an end of the thread and the reverse prevention mechanism comprises at least one step structure arranged in a longitudinal direction of the shank. 
     
     
         12 . The screw according to  claim 2 , wherein the reverse prevention mechanism is arranged between a lower end of the conic section of the screw cap and an upper end of the thread and is constructed to comprise at least one step structure that is inclined with respect to a longitudinal direction of the shank. 
     
     
         13 . The screw according to  claim 2 , wherein the reverse prevention mechanism is arranged between a lower end of the conic section of the screw cap and an upper end of the thread and extends upward from the upper end of the thread and does not extend into the conic section of the screw cap, wherein an upper end of the reverse prevention mechanism and the lower end of the conic section of the screw cap define therebetween a thread-free portion of the neck section. 
     
     
         14 . The screw according to  claim 1 , wherein the shank comprises a cylindrical or triangular prismatic body or, alternatively, the shank comprises both a cylindrical body and a triangular prismatic body, the thread being an umbrella-shaped thread, on which the reverse prevention mechanism is provided, the reverse prevention mechanism being constructed to comprise at least one step structure. 
     
     
         15 . The screw according to  claim 2 , wherein the shank comprises a cylindrical or triangular prismatic body or, alternatively, the shank comprises both a cylindrical body and a triangular prismatic body, the thread being an umbrella-shaped thread, on which the reverse prevention mechanism is provided, the reverse prevention mechanism being constructed to comprise at least one step structure. 
     
     
         16 . The screw according to  claim 3 , wherein the shank comprises a cylindrical or triangular prismatic body or, alternatively, the shank comprises both a cylindrical body and a triangular prismatic body, the thread being an umbrella-shaped thread, on which the reverse prevention mechanism is provided, the reverse prevention mechanism being constructed to comprise at least one step structure. 
     
     
         17 . The screw according to  claim 2 , wherein the neck portion of the shank located below the screw cap is provided therein with a neck thread, the neck thread having an outside diameter that is equal to or slightly greater than an outside diameter the reverse prevention mechanism. 
     
     
         18 . The screw according to  claim 14 , wherein the shank below the screw cap is provided with a neck section, which comprises a neck thread, the neck thread having an outside diameter that is equal to or slightly greater than an outside diameter the reverse prevention mechanism. 
     
     
         19 . The screw according to  claim 14 , wherein the shank below the screw cap is provided with a neck section, which comprises a neck thread, the thread of the shank extending from the screw cap to the tip section, the neck thread and a thread extending from the reverse prevention mechanism to the tip section are both of a regular tooth shape of thread, wherein the neck section of the screw above the umbrella-shaped thread and the thread from the umbrella-shaped thread to the tip section are both of a regular tooth shape of thread, the thread of the regularly shaped screw tooth having an outside diameter equal to or slightly greater than an outside diameter of the reverse prevention mechanism.