JP3246522U - Wood screws - Google Patents

Abstract

[Problem] To provide a wood screw with improved screwing performance and pull-out resistance. [Solution] A double-start thread with a large-diameter first thread 5a and a small-diameter second thread 5b is provided on the outer periphery of a shaft portion 2 with a sharp tip 3 at its tip, and the lead L of the thread is formed such that L/D1 is 0.80 or more and 0.90 or less with respect to the outer diameter D1 of the first thread 5a, and a plurality of slits are provided from the sharp tip 3 in the axial direction across the first thread 5a and the second thread 5b, forming groove edges on the first thread and the second thread by the slits. [Selected Figure] Figure 2

Description

This invention relates to a wood screw with improved screwing performance.

A wood screw has a sharp tip at the tip and a head at the tail end, with a spiral thread formed around the outer circumference of the shaft. When screwed into wood, the thread taps and penetrates into the wood.

When tapping with the screw, the shaft pushes the wood apart to penetrate, so there is a lot of resistance when screwing in and there is a risk of cracks in the wood.

For this reason, coarse threads with widely spaced threads are available, and are designed so that they can be screwed directly into the wood material without drilling pilot holes, and then rotated with a powered driver such as an impact driver, allowing the screw to be screwed in all at once.

Utility Model Registration No. 3173168 Utility Model Registration No. 3218609 JP 2006-329254 A

In order to quickly screw a wood screw into the inside of a wooden material, it is preferable to increase the lead of the thread so that the screw advance distance per rotation is large.

However, in that case, the pitch of the thread also becomes larger, which reduces the bonding strength of the shaft inside the wood material, making it difficult to ensure sufficient pull-out resistance.

In this regard, for example, if the thread diameter is made larger relative to the diameter of the shaft, the pull-out resistance can be increased, but this raises the problem that a large torque is required when screwing in.

The present invention has been found to solve the above problems by forming a larger thread lead than conventional methods, increasing the screw threading distance per rotation, while at the same time giving each thread its own characteristics by adopting a double-start thread, and by providing a slit that extends in the axial direction of the shaft from the sharp tip across multiple threads, and by configuring the grooved blades formed on the threads to cut wood material.

Furthermore, by exploring the optimum ratio of the diameters of the large and small threads that make up the double-thread screw to the diameter of the shank (the portion of the shank that does not have threads), it was discovered that sufficient pull-out resistance could be ensured without any reduction in pull-out resistance.

The present invention is configured as a means to provide a wood screw having a double-thread screw with a large diameter first thread and a small diameter second thread, the screw thread extending in a spiral shape around the outer circumference of a shaft having a sharp tip at the tip and a head at the tail end, the outer diameter D1 of the first thread and the outer diameter D2 of the second thread are formed so that D1/S is 1.35 or more and 1.45 or less, and D2/S is 1.08 or more and 1.13 or less, with respect to the outer diameter S of the shaft, the lead L of the screw is formed so that L/D1 is 0.80 or more and 0.90 or less, and a plurality of slits are provided from the sharp tip in the axial direction across the first thread and the second thread, and the slits form groove edges on the first thread and the second thread.

The slits are preferably arranged at an angle to the axis of the shaft portion and intersect with the helical direction of the helix.

It is preferable that the ridge angle θ1 of the first thread and the ridge angle θ2 of the second thread are such that θ1 < θ2.

The wood screw 1 of the present invention has a larger lead L than conventional screws, and a larger screwing distance per rotation, allowing for quick screwing. On the other hand, the height of the outer diameter D1 of the first thread 5a and the outer diameter D2 of the second thread 5b that constitute the double thread from the surface of the shaft 2 is ensured, so that the pull-out resistance after screwing is sufficient. In order to reduce the screwing torque, a slit 6 is provided that extends from the sharp tip 3 to the multiple threads 5 in the axial direction of the shaft 2, forming groove blades 6a, 6b on the threads 5a, 5b, and cutting the wood material when screwing. Therefore, even when screwing in all at once by rotating with a powered driver such as an impact driver, the wood material can be screwed in while being appropriately cut, so there is no risk of cracking the wood material.

1 is a front view of a wood screw according to an embodiment of the present invention; 1 shows the characteristic configuration of a wood screw, in which (A) is an enlarged front view, and (B) is a table showing the shapes and values of the wood screws adopted in Examples 1 to 4. 13 shows the configuration regarding the slit, where (A) is an enlarged front view and (B) is an enlarged view of the A-A cross section.

The following describes an embodiment of the invention with reference to the drawings.

As shown in Figures 1 and 2, the wood screw 1 has a shaft 2 with an outer diameter S, a sharpened portion 3 at the tip of the shaft 2, a head 4 at the tail end, and a thread 5 extending helically around the outer periphery of the shaft 2.

The head 4 has an engagement portion 4a for rotary tools, which is made up of a cross hole. The pointed portion 3 is sharply formed with an angle α toward the tip in the range of 25° to 28°, which makes it possible to screw wood screws directly into the surface of the wood material without drilling a pilot hole in the surface of the wood material, with the pointed portion 3 standing upright on the surface of the wood material. However, for better screwing, it is preferable to provide a drill portion 3a, known as a split foot, as shown in the figure.

As shown in FIG. 2(A), the screw thread 5 is configured as a double-threaded thread with a large-diameter first thread 5a and a small-diameter second thread 5b, and the outer diameter D1 of the first thread 5a, the outer diameter D2 of the second thread 5b, which are the nominal diameters of the wood screw 1, the thread pitch P, and the lead L are configured as described below.

In other words, the wood screw 1 of the present invention is configured to have a larger lead L than conventional screws, and to increase the screwing distance per rotation. On the other hand, the height of the outer diameter D1 of the first thread 5a and the outer diameter D2 of the second thread 5b that make up the double thread from the surface of the shaft 2 is ensured, ensuring sufficient pull-out resistance.

Example 1
The wood screw according to Example 1 is formed with D1 = 3.80 mm, D2 = 3.00 mm, S = 2.70 mm, P = 1.69 mm, and L = 3.38 mm. The lead L relative to the nominal diameter D1 is formed to be larger than that of the prior art, such as L/D1 = 0.88. The outer diameter D1 of the first thread 5a and the outer diameter D2 of the second thread 5b are D1/S = 1.40 and D2/S = 1.11, respectively, and the thread height from the shank 2 is ensured, providing sufficient pull-out resistance.

Example 2
The wood screw according to Example 2 is formed with D1 = 4.20 mm, D2 = 3.30 mm, S = 2.95 mm, P = 1.81 mm, and L = 3.62 mm. The lead L relative to the nominal diameter D1 is formed to be larger than that of the prior art, such as L/D1 = 0.86. The outer diameter D1 of the first thread 5a and the outer diameter D2 of the second thread 5b are D1/S = 1.42 and D2/S = 1.11, respectively, and the thread height from the shank 2 is secured, providing sufficient pull-out resistance.

Example 3
The wood screw according to Example 3 is formed with D1 = 4.50 mm, D2 = 3.50 mm, S = 3.20 mm, P = 1.81 mm, and L = 3.62 mm. The lead L relative to the nominal diameter D1 is formed to be larger than that of the prior art, such as L/D1 = 0.80. The outer diameter D1 of the first thread 5a and the outer diameter D2 of the second thread 5b are D1/S = 1.40 and D2/S = 1.09, respectively, and the thread height from the shank 2 is secured, providing sufficient pull-out resistance.

Example 4
The wood screw according to Example 4 is formed with D1 = 4.80 mm, D2 = 4.00 mm, S = 3.55 mm, P = 1.95 mm, and L = 3.90 mm. The lead L relative to the nominal diameter D1 is formed to be larger than that of the prior art, such as L/D1 = 0.81. The outer diameter D1 of the first thread 5a and the outer diameter D2 of the second thread 5b are D1/S = 1.35 and D2/S = 1.12, respectively, and the thread height from the shank 2 is secured, providing sufficient pull-out resistance.

When these Examples 1 to 4 are evaluated comprehensively, the outer diameter D1 of the first thread 5a and the outer diameter D2 of the second thread 5b are formed so that D1/S is 1.35 or more and 1.45 or less, and D2/S is 1.08 or more and 1.13 or less, relative to the outer diameter S of the shaft portion 2, and the lead L of the thread is formed so that L/D1 is 0.80 or more and 0.90 or less, relative to the outer diameter D1 of the first thread 5a, thereby achieving the above-mentioned objectives of increasing the screw advance distance per rotation and ensuring the pull-out resistance of each thread that constitutes the double-thread thread.

Throughout all the embodiments, the ridge angle θ1 of the first thread 5a and the ridge angle θ2 of the second thread 5b are set to θ1 < θ2, specifically, θ1 = 40° and θ2 = 60°, and are formed to bite well into the wood material.

However, wood screws that have a large threading distance per rotation and also have a large pull-out resistance require a large torque to be screwed in. If a powered driver such as an impact driver is used to screw in the screw in one go, there is a risk that the wood material will crack.

Therefore, in order to improve the screwing performance of the wood screw 1, it is preferable to provide a slit 6 that extends in the axial direction of the shaft portion 2 from the sharp tip 3 across multiple threads 5, as shown in Figures 2 and 3, and it is desirable to form V-shaped groove blades 6a, 6b by cutting out the threads 5a, 5b with the slit 6, so that the wood material is cut when the screw is screwed in.

As shown in FIG. 3(A), the slit 6 is inclined at an angle β with respect to the axis of the shaft portion 2, preferably β=15°. Moreover, the inclination direction is opposite to the screw-in rotation direction R of the wood screw 1. In other words, as shown in the figure, the slit 6 is arranged to intersect with the helical direction of the screw thread 5.

In a preferred embodiment, three slits 6 are formed at equal intervals around the circumference of the shaft portion 2. The angle G at which each slit 6 expands into a V shape is preferably set to G = 75°, so that while being screwed into the wood material, the first thread 5a and the second thread 5b are screwed into the wood material and fastened while the groove blades 6a, 6b appropriately cut the fibers of the wood material.

1 Wood screw 2 Shank 3 Sharp portion 3a Drill portion 4 Head 4a Engagement portion 5 Screw thread 5a First thread 5b Second thread 6 Slits 6a, 6b Groove blade

Claims (3)

A wood screw having a pointed portion (3) at the tip and a head portion (4) at the tail end, the screw extending helically around the outer periphery of the shaft portion (2) is constituted by a double thread having a first thread (5a) with a large diameter and a second thread (5b) with a small diameter,
With respect to the outer diameter S of the shaft portion (2), an outer diameter D1 of the first thread (5a) and an outer diameter D2 of the second thread (5b) are formed such that D1/S is 1.35 or more and 1.45 or less, and D2/S is 1.08 or more and 1.13 or less,
The lead L of the first thread (5a) relative to the outer diameter D1 of the first thread (5a) is formed so that L/D1 is 0.80 or more and 0.90 or less,
A wood screw characterized in that a slit (6) is provided axially from the sharp portion (3) across a plurality of first threads (5a) and second threads (5b), thereby forming groove edges (6a, 6b) on the first threads and the second threads by the slit. The wood screw according to claim 1, characterized in that the slit (6) is inclined with respect to the axis of the shaft and is arranged so as to intersect with the helical direction of the screw. 3. The wood screw according to claim 1, wherein a thread angle θ1 of the first thread (5a) and a thread angle θ2 of the second thread (5b) satisfy the relationship θ1<θ2.

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