JPH0338502Y2 - - Google Patents

Description

[Detailed explanation of the idea]

<Industrial Application Field> The present invention relates to improvements in wood screws, particularly self-drilling type wood screws. <Prior art> As shown in FIG. 2, a conventionally used wood screw 2 has a head 21, a shaft 22, and a tapered tip 23.
A thread 24 is formed from the shaft portion 22 to the tip taper 23 . Furthermore, self-drilling screws for metal plates, as shown in FIG. 3, are also used as wood screws. This screw 3 has a head 31, a shaft portion 32, and a drill portion for drilling, and the shaft portion 32 has a thread 34 formed therein. <Problem to be solved by the invention> However, when screwing the wood screw 2 into an object such as wood without drilling a pilot hole, the wood screw 2 does not have a part that performs the drilling function, so it is difficult to tighten it. The required rotational torque becomes extremely large. or,
Cracks may also appear on objects such as trees. On the other hand, when the self-drilling screw 3 shown in FIG. 3 is used for fastening wood, since it has a drill portion 33 at the tip, drilling and fastening can be performed with low rotational torque. However, although the drill portion at the tip has a drilling function, it does not have a propulsion function, so the screw 3 must be pressed against the object with a large force. Therefore, when a tightening test was performed on both screws 2 and 3 with the same driving load, it was confirmed that the self-drilling screw 3 took a longer time to complete tightening. <Means for Solving the Problems> Therefore, the present invention solves the above problems by providing a wood screw having the following configuration. The wood screw of the present invention has a head 11 that receives a tightening tool such as a screwdriver, and a shaft 1 that extends from the head.
2, a drill part 13 formed at the tip of the shaft part,
A tip tapered portion 14 extending from the tip of the drill portion
Equipped with. The shaft portion 12 has a substantially perfect circular cross section with a substantially constant diameter in the axial direction, and a tightening thread 15 is formed on the circumferential surface of the shaft portion 12 . The drill portion 13 has substantially no threads, and two or more cutting blades 131 for drilling are symmetrically formed at substantially the same position in the axial direction. These cutting blades 131, 131 have cutting edges 134,
134 and a land 13 formed on the opposite side of the cutting surfaces 132, 132.
It consists of 3,133. These cutting surfaces 132, 132 are formed by lands 133,
The groove portion 13 is recessed compared to the groove portion 133.
6, 136 are formed, and this groove portion is set back in the radial direction compared to the circumferential surface of the shaft portion 12. The tip tapered portion 14 has a substantially perfect circular cross section, and its diameter gradually decreases toward the tip of the screw, and a propelling screw thread 16 is formed on the circumferential surface of the tip tapered portion 14 . The maximum diameter of the cutting edge 131 of the drill portion is set to be smaller than the outer diameter of the tightening screw thread 15 and approximately equal to or larger than the root diameter of the shaft portion 12 and the maximum diameter of the tip tapered portion 14. <Function> In the wood screw of the present invention, the drill portion is formed in such a manner that the tip tapered portion having the propelling screw thread and the shaft portion having the tightening screw thread are separated. Moreover, this drill part has cutting surfaces 132, 132
are depressed relative to the lands 133, 133 to form groove portions 136, 136, and these groove portions are recessed in the radial direction relative to the circumferential surface of the shaft portion 12. be. That is, this drill part is not just an extension of the shaft part, but has the most appropriate shape to perform the cutting function, and the large space obtained by the groove parts 136, 136 that are retreated in the radial direction allows the cutting There is no risk of the chips being clogged with chips that are generated at times, and the chips that are generated temporarily stay within this large space and are carried toward the head of the screw by the tightening screw thread as screwing progresses. Moreover, since there are virtually no threads formed in this drill part, a large space is secured for forming a cutting blade, and a cutting blade large enough to make a hole can be formed in the axial direction. Two or more can be formed symmetrically and in a well-balanced manner at substantially the same position. This allows the cutting ability to be extremely high. In this way, the drill part does not have substantially any threads, so it cannot apply a driving force to the screw, but the tapered tip with the propelling thread leads the entire screw, making it possible to drive a small drive. Allows perforation by force. Then, the drill part cuts a hole with a diameter larger than the shaft part diameter with low torque, and finally the tightening screw thread tightens the object to be tightened. <Example> An example of the present invention will be described below based on the drawings. FIG. 1A is a side view of the wood screw of one embodiment, the first
Figure B is a sectional view taken along the line B--B in the figure. This wood screw 1 has a head 11 that receives a tightening tool such as a screwdriver, and a shaft 12 that extends from the head.
, a drill portion 13 formed at the tip of the shaft portion, and a tip tapered portion 14 extending from the tip of the drill portion. The shaft portion 12 has a constant root diameter, and the fastening thread 1
5 is formed. The structure of this shaft portion 12 can adopt various structures used in conventional tightening means having threads. The drill part 13 includes a cutting blade 1 that performs a drilling function.
31,131 are formed. This cutting blade 13
1, 131 is composed of cutting surfaces 132, 132 having cutting edges 134, 134 and lands 133, 133. This cutting surface 132,
132 is recessed relative to the lands 133, 133 to form groove portions 136, 136, and these groove portions are set back in the radial direction relative to the circumferential surface of the shaft portion 12. Land 133, 133
It is desirable to apply a second cut. this is,
The lands 133, 133 are prevented from engaging with the perforation 135 cut by the screw rotating in the direction of the arrow,
This aims to reduce rotational torque.
The cutting blades 131, 131 are continuously extended substantially parallel to the axial direction of the screw, but may be extended spirally to give an appropriate rake angle.
Further, the number of cutting blades 131 can be changed as appropriate other than the two in the embodiment. The diameter of the cutting blade 131 (in the embodiment, both cutting edges 13
4 and 134) is set to be equal to or larger than the root diameter of the shaft portion 12 and smaller than the outer diameter of the fastening screw thread 15. This eliminates unnecessary resistance when inserting the shaft portion 12, and
The fastening screw thread 15 reliably bites into the hole to realize complete fastening. The tip tapered portion 14 has a sharp taper angle a (a26° in the embodiment, but is not limited to this), is inserted into an object to be fastened such as wood, and guides the entire screw. A propelling screw thread 16 is formed on the tip tapered portion 14, and when screwed into an object, the rotational force applied to the screw is converted into an axial propulsive force. With this driving force, the driving load required for drilling the hole with the drill portion described above is minimized. The maximum diameter of the tip tapered portion 14 (that is, the diameter of the tip tapered portion 14 on the most proximal side in the embodiment) is set smaller than the diameter of the cutting blade 131 of the drill portion. Further, it is desirable that the outer diameter of the propelling screw thread 16 is set to be equal to or smaller than the diameter of the cutting blade 131, but the present invention is not limited to this. The proximal end of the propelling thread 16 can also be continuous with the tip of the cutting blade 131. Next, a wood screw 1 (hereinafter referred to as a screw) of an illustrated embodiment of the present invention, a wood screw 2 (hereinafter referred to as a screw) of an illustrated conventional example, and a self-drilling screw 3 (hereinafter referred to as a screw) as a comparative example are as follows. Performance test results are shown. (1) Test date: July 24, 1985 (2) Test location: Yamahiro Testing Laboratory (3) Sample screw (screw thread outer diameter) x (total length) Thread 4.0 x 32 mm Thread 3.8 x 32 mm Thread 4.2 ×35mm (4) Test item 4-1 Appearance shape measurement 4-2 Screw-in torque test with manual torque driver 4-3 Screw-in time test with electric screwdriver 4-4 Pull-out test (5) Test direction 5-1 Screw-in torque test is canon Uses an idle-rotating torque screwdriver 20LTDK. 5-2 The screw-in time test was conducted using a Makita screwdriver at 2500 RPM with a load of 13.5 kg and screwing in 22 mm from the screw tip. 5-3 Pull-out test is Shimadzu universal test VEH-10
Screw it 22mm from the tip into the base material 101 used, and perform a pull-out test using test jigs 102 and 103 shown in Figure 4. As is clear from the (6) test results shown on the next page, 6-2
In the screw-in torque test, the wood screw of the present invention (
It was confirmed that the screw) was screwed into the cypress wood with the smallest torque compared to the screw of the comparative example (screw and screw). Next, as is clear from the 6-3 screw-in time test, the wood screw (screw) of the present invention reduces the driving time to 1/3 to 1/4 compared to the self-drilling screw (screw) of the comparative example. This was confirmed. In addition, even when compared to the wood screw (screw) of the comparative example, there is no significant difference, with a time difference of only 0.1 seconds. No significant difference was observed in any of the screws in the 6-4 pullout test. (6) Results

【table】

【table】

【table】

【table】

[Table] <Effects of the invention> The wood screw of the present invention has the following effects due to the joint action of the propulsive action of the tapered part and the drilling action of the drill part.
In addition to reducing the rotational torque required for screwing, it also reduces the large axial load required for drilling, thereby realizing screwing in a short time with low torque. Moreover, since the hole is drilled by the drill part, it is possible to prevent cracks from forming in the wood when screwing into an object to be fastened, such as wood, as with conventional wood screws. Although the present invention was developed primarily for screwing into wood, it is of course possible to use it for objects made of other materials.

[Brief explanation of the drawing]

FIG. 1A is a side view of a wood screw according to an embodiment, FIG. The side view and FIG. 4 are explanatory views of the pull-out test. DESCRIPTION OF SYMBOLS 11... Head, 12... Shaft part, 13... Drill part, 14... Tip taper part, 15... Tightening thread, 16... Propulsion thread, 131... Cutting blade.

Claims (1)

[Scope of claim for utility model registration] Head 11 that receives a tightening tool such as a screwdriver
and a shaft portion 12 extending from the head, a drill portion 13 formed at the tip of the shaft, and a tip tapered portion 14 extending from the tip of the drill portion, the shaft portion 12 comprising: The shaft portion 12 has a substantially perfect circular cross section with a substantially constant diameter in the axial direction, and a tightening thread 15 is formed on the circumferential surface of the shaft portion 12, and the drill portion 13 is substantially free of threads. In addition, a cutting blade 131,1 for drilling
31 are formed symmetrically at approximately the same position in the axial direction, and the cutting edges 134,
134 and a land 13 formed on the opposite side of the cutting surfaces 132, 132.
3,133, and this cutting surface 132,132 is composed of lands 133,
The groove portion 13 is recessed compared to the groove portion 133.
6, 136 are formed, this groove portion is set back in the radial direction compared to the circumferential surface of the shaft portion 12, and the tip tapered portion 14 has a substantially perfect circular cross section;
The diameter gradually decreases toward the tip of the screw, and a propelling screw thread 16 is formed on the circumferential surface of the tip tapered portion 14, and the maximum diameter of the cutting blade 131 of the drill portion is set to the outside of the tightening screw thread 15. A wood screw characterized in that it is smaller than the diameter of the shaft portion 12 and is approximately equal to or larger than the root diameter of the shaft portion 12 and the maximum diameter of the tapered tip portion 14.