SELF-TAPPING SCREW WITH DRILLING WING

Abstract

A self-tapping screw with drilling wing includes a head, a shank extending therefrom, a plurality of threads spirally disposed on the shank, a drilling portion opposite to the head, and at least one winged reaming unit formed on the drilling portion and extending outwards therefrom. At least one supporting rib protrudes from at least one surface of the reaming unit for increasing the strength of the reaming unit, allowing the reaming unit to bear the larger drilling stress during a screwing operation and provide the greater cutting action, and preventing the reaming unit from wearing or breaking. The combination of the supporting rib and the reaming unit allows the reaming unit to provide a suitable thickness which facilitates a preferable cutting speed without affecting the drilling capability of the screw.

Claims

1. A self-tapping screw with drilling wing comprising a head, a shank extending downwards from said head, a plurality of threads spirally formed around said shank, a drilling portion connected to an end of said shank opposite to said head, and at least one reaming unit disposed on said drilling portion, wherein said drilling portion has a drilling body connected to said shank and tapering off to a tip, a drilling blade formed at an end of said drilling body connected to said tip, two evacuation flutes formed on opposite sides of said drilling body, and two cutting edges each formed at a convergence of each of said evacuation flutes and said drilling body, said at least one winged reaming unit extending outwards from said drilling body, at least one supporting rib projecting from at least one surface of said reaming unit to reinforce strength of said reaming unit.

2. The self-tapping screw with drilling wing as claimed in claim 1, wherein said at least one supporting rib extends in a direction different from an axis of said shank.

3. The self-tapping screw with drilling wing as claimed in claim 1, wherein said at least one supporting rib is connected to an outer periphery of said at least one reaming unit.

4. The self-tapping screw with drilling wing as claimed in claim 2, wherein said at least one supporting rib is connected to an outer periphery of said at least one reaming unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 is a schematic view showing a conventional fastener;

[0010] FIG. 2 is a schematic view showing that reaming units of the conventional fastener snap when reaming a wood object;

[0011] FIG. 3 is a schematic view showing that reaming units of the conventional fastener obstruct a screwing operation;

[0012] FIG. 4 is a schematic view showing a first preferred embodiment of this invention;

[0013] FIG. 4A is a perspective view showing a partial element of FIG. 4;

[0014] FIG. 5 is a schematic view showing that reaming units cut a wood object;

[0015] FIG. 6 is a schematic view showing that reaming units reach a metal object; and

[0016] FIG. 7 is a schematic view showing that reaming units snap to allow the self-tapping screw to penetrate and engage with the metal object.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Referring to FIG. 4, a first preferred embodiment of a self-tapping screw 3 with drilling wing of this invention is disclosed. The self-tapping screw 3 includes a head 31, a shank 32 extending downwards from the head 31, a plurality of threads 33 spirally disposed on the shank 32, a drilling portion 34 fitted at an end of the shank 32 and opposite to the head 31, and at least one reaming unit 35 fitted on the drilling portion 34. The drilling portion 34 has a drilling body 341 connected to the shank 32 and tapering off to a tip 342, a drilling blade 343 formed at an end of the drilling body 341 and connected to the tip 342, two evacuation flutes 344 relative to each other and recessed on opposite sides of the drilling body 341, and two cutting edges 345 each of which is formed at a convergence of each evacuation flute 344 and the drilling body 341. The winged reaming unit 35 extends outwards from the drilling body 341. Referring to FIG. 4A, at least one supporting rib 36 projects from at least one surface of the reaming unit 35. Here takes an example that there are two reaming units 35 formed on the drilling portion 34 and each reaming unit 35 has one supporting rib 36 extending in a direction different from an axis R of the shank 32.

[0018] Referring to FIG. 4 and FIG. 5, the self-tapping screw 3 is aimed at screwing an object to a metal object, such as steel structures or iron plates. Here takes an example that the self-tapping screw 3 is applied to screw a wood object 41 to a metal object 42. During the screwing operation of the self-tapping screw 3, the tip 342 of the drilling portion 34 is positioned against a surface of the wood object 41 firstly. Then, the head 31 receives the rotation force to carry out the cutting action of the cutting edges 345 of the drilling portion 34 to cut a hole 411 in the wood object 41. When the drilling portion 34 gradually moves downwards into the hole 411, the reaming unit 35 starts reaming the hole 411. Because the reaming unit 35 is provided with the supporting rib 36 formed thereon, the supporting rib 36 can sustain the reaming unit 35 whereby the strength of the reaming unit 35 is increased to execute the cutting and reaming operation of the wood object 41 smoothly. Further, with the support of the supporting rib 36, the reaming unit 35 can be formed with smaller thickness to increase the sharpness and enhance the cutting capability while maintaining enough strength for cutting the wood object 41. Referring to FIG. 6 to FIG. 7, when the reaming unit 35 contacts the metal object 42, the reaming unit 35 snaps immediately because the reaming unit 35 is formed with smaller thickness and the support of the supporting rib 36 is insufficient forbearing the drilling stress derived from cutting the metal object 42. After the reaming unit 35 snaps, the drilling portion 34 and the threads 33 continue cutting the metal object 42 whereby the self-tapping screw 3 engages the wood object 41 with the metal object 42 effectively to achieve the preferable screwing effect.

[0019] Furthermore, the supporting rib 36 enhances the strength of the reaming unit 35, thereby allowing the reaming unit 35 to bear the larger drilling stress during the screwing operation, solving the problem of the insufficient strength of the reaming unit 35 caused by reducing the thickness of the reaming unit 35, and preventing the reaming unit 35 from breaking when executing the reaming operation of the wood object 41. Hence, the combination of the supporting rib 36 and the reaming unit 35 allows the reaming unit 35 to provide a suitable thickness. In other words, the reaming unit 35 can be formed with less thickness to increase the cutting speed while maintaining the sufficient strength for cutting the wood object 41. On the other hand, the reaming unit 35 breaks instantly when reaming the metal object 42. Besides, the reaming unit 35 is formed by pressing the drilling portion 34 whereby parts of the drilling portion 34 extend outwards to form the reaming unit 35. Hence, the strength of the drilling portion 34 is not weakened because the reaming unit 35 is formed thinner, namely, less parts of the drilling portion 34 in comparison of the conventional fastener 1 are taken to form the reaming unit 35. Therefore, the drilling potion 34 maintains the preferable strength. Thus, the production quality and the screwing capability of the self-tapping screw 3 are increased effectively.

[0020] To sum up, the self-tapping screw with drilling wing of this invention takes an advantage of at least one supporting rib formed on one surface of the reaming unit and extending outwards from the drilling body to increase the strength of the reaming unit, thereby allowing the reaming unit to bear larger drilling stress during the screwing operation, allowing the reaming unit to make thinner while keeping enough strength for cutting the wood object, preventing the reaming unit from wearing or breaking before reaching the metal object, and ensuring the preferable screwing effect of the self-tapping screw.

[0021] While the embodiments of this invention are shown and described, it is understood that further variations and modifications may be made without departing from the scope of this invention.