Screw

Abstract

To provide a screw capable of improving the bending and torsional strength of a shaft part by increasing a section modulus of the shaft part, and preventing generation of bending and breakage during screwing.SOLUTION: In a screw 1, a sharp end 5 is formed at the other end of a shaft part 3 having a head part 4 at one end, and a screw thread 2 is provided on the outer periphery of the shaft part 3. On both sides of a root side of the screw thread 2 of the shaft part 3, a slope 6 that spread out on both sides is provided. Further, in valleys 7 of the screw thread 2, a ridge 8 is provided so that a height from the valley 7 is lower than a height of the screw thread 2. A section modulus of the shaft part 3 is increased by the slopes 6 and the ridges 8.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This invention relates to a screw used for fastening wooden structures, and more particularly to a screw having an increased section modulus of the shank to make the shank resistant to bending and torsional stress. [Background technology]

[0002] The basic structure of a screw used to fasten wooden structures is a threaded shank with a head at one end and a sharp tip at the other end.When the screw is screwed into a wooden structure with a rotary tool, it rotates along the threads and penetrates, tightly fastening the wooden structure.However, such screws are required to have sufficient strength in the shank to withstand bending and torsional stresses, not only to prevent cracks in the wood when screwed in and to improve the efficiency of the screwing process so that the screw can be screwed in smoothly, but also to prevent the shank from bending or breaking when screwed in.

[0003] Generally, when a screw is screwed in, a linear load is applied to the threads, and the torsional load acting on the shank increases as the screw is driven into the wooden material. Under such circumstances, the load is concentrated at the corner of the shank between the root and the valley of the thread, which can cause the shank to crack or bend, and in the worst case, break. This is particularly noticeable when the wooden material is hard or the screw is long, and as a result, the required fastening strength for the wooden structure cannot be achieved, or the fastening can fail.

[0004] To prevent such cracks, bending, or breakage in the shank of a screw, it is necessary to increase the strength of the corners between the root and root of the threads in the shank, and at the same time, increase the section modulus between the threads in the shank to increase the stress against bending and twisting.

[0005] In conventional screws, in order to improve the strength of the corner portion between the root and valley of the thread in the shank, as in Patent Documents 1 and 2, it has been proposed to provide slopes on both sides of the root side of the thread provided in the shank, starting halfway up the side of the thread and descending from this base point towards the valley formed between the threads, and arranged in a widening pattern on both sides of the thread, thereby increasing the thickness on the root side of the thread and thereby increasing strength.

[0006] Next, as an example of a screw that aims to make the screwing process more efficient, as in Patent Documents 3 and 4, a ridge that is lower in height than the thread is provided midway along the thread, and when the screw is screwed, this ridge cuts and stirs the wood tissue between the threads, softening it, and the threads proceed through this softened tissue, preventing cracks in the wood material and reducing resistance when the screw is screwed. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-7723 [Patent Document 2] Jikko No. 48-2908 [Patent Document 3] Japanese Patent Application Publication No. 9-217722 [Patent Document 4] Japanese Patent Application Laid-Open No. 2000-2218 Summary of the Invention [Problem to be solved by the invention]

[0008] Incidentally, the screws shown in the above-mentioned Patent Documents 1 and 2 simply thicken the base portion of the threads and reinforce the portion of the shank between the threads, so that only the shank portion exists between the inclined surfaces, and the shank portion between the inclined surfaces does not have structural strength improvement against bending or twisting stress. As a result, when the screw is screwed in, the load is concentrated on the shank portion between the inclined surfaces, which poses the problem that it is not possible to sufficiently prevent bending or breakage of the shank portion when the screw is screwed in.

[0009] Furthermore, the screws shown in the above-mentioned Patent Documents 3 and 4 are intended to improve the efficiency of the driving work by utilizing the function of ridges provided between the threads, but because the ridges are provided at a partial position along the entire length of the threads, there is no attempt to improve the strength of the entire length of the shank, and there is a problem in that it is not possible to prevent bending or breakage of the shank due to torsional stress that increases as the screwing amount progresses.

[0010] Therefore, an object of the present invention is to provide a screw that can prevent bending or breakage of the shank by increasing the section modulus between the threads of the shank as much as possible, thereby increasing the stress against bending and twisting over the entire length of the shank. [Means for solving the problem]

[0011] In order to solve the above-mentioned problems, the invention of claim 1 provides a shaft portion having a head at one end and a sharp end at the other end, and a screw thread and a screw thread axially extending from the outer periphery of the shaft portion. On both sides of the shaft located in the axial direction, At the base position, on the side of this thread Height direction It starts halfway and goes down from this starting point to the solstice point on the valley between the threads. Clamp the threads Slopes that transition to a widening pattern on both sides In a screw provided with The grooves between the threads are parallel to the axial direction of the shank or inclined in a direction along the lead angle of the threads, and, The height from the root is set to be lower than the height of the thread. A protrusion is provided, one end of which reaches one of the slopes facing each other across the valley, and the other end of which reaches the other of the slopes.

[0012] The invention of claim 2 is the invention of claim 1, The ribs are arranged at equal intervals in the circumferential direction of the shaft. This is what was done.

[0013] The invention of claim 3 is the invention of claim 1 or claim 2, wherein the protrusions are: The thread is provided over the entire length of the thread, from the position excluding the sharp end of the shank to the end of the head. This is what was done.

[0017] Here, the inclined surfaces provided on both sides of the thread described above start from a position lower than half the height dimension on the side of the thread, and slope downward from this start point to a point on the root portion, increasing the root diameter of the shank on both sides of the thread, and as a result, increasing the thickness of the root side of the thread.

[0018] Furthermore, the ridges provided between the threads have a cross-sectional shape that is, for example, trapezoidal, and the ridges located between each thread are arranged in a spiral that is parallel to the axial direction of the shank or continues with a lead angle in the same direction as the threads, and these ridges and the above-mentioned inclined surfaces increase the cross-sectional modulus of the shank between the threads to the greatest extent possible. [Effects of the Invention]

[0019] According to the screw of this invention, A screw having a thread and slopes that start midway along the height direction of the side of the thread at a position on the base side that connects to the shank on both sides of the thread located in the axial direction of the shank of the thread, and that descend from this starting point to a point on the valley between the threads while widening on both sides of the thread, A protrusion is provided in the valley between the threads, which is parallel to the axial direction of the shank or inclined in a direction following the lead angle of the thread, and whose height from the valley is set to be lower than the height of the thread, and one end of this protrusion reaches one of the inclined surfaces facing each other across the valley, and the other end reaches the other inclined surface, The inclined surface and ridges increase the section modulus between the threads of the shank, which increases the stress against bending and twisting of the shank, preventing bending or breakage when screwed in and ensuring that the fastened state is maintained reliably.

[0020] Furthermore, in nails equipped with screws, the ridges between the threads scrape the wooden material when the nail is screwed into a wooden structure, thereby improving the efficiency of screwing in. In this case, if the height of the ridges between the threads from the valley is set lower than the outer diameter of the threads and equal to or lower than the starting point of the slope on the side of the thread, it is possible to prevent the ridges from scraping the wooden material between the threads excessively. This makes it possible to increase the cross-sectional modulus between the threads of the shank while ensuring the degree of engagement of the threads into the wooden material, resulting in a strong fastening of the wooden structure. [Brief explanation of the drawings]

[0021] [Figure 1] A front view showing the overall shape of the screw according to the present invention. [Figure 2] FIG. 1 is an enlarged horizontal front view of a shank of a screw according to the present invention. [Figure 3] Enlarged horizontal cross-sectional view along arrow aa in Figure 2 [Figure 4] Cross section along arrow bb in Figure 2 [Figure 5] A horizontal cross-sectional view of the threads and ridges cut vertically at a position close to the arrow aa in Figure 2. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0023] As shown in Figures 1 to 3, the screw 1 has a structure in which a shank 3 has a thread 2 on its outer periphery, a head 4 equipped with an engaging portion for a rotary tool at one end, and a sharp tip 5 for screwing at the other end, and the thread 2 has slopes 6 on both sides in the axial direction at the base side, and a ridge 8 is provided in the valley 7 between adjacent threads 2, extending from the part of the shank 3 excluding the sharp tip 5 side of the thread 2 to the end on the head 4 side.

[0024] The height, pitch, lead angle, diameter and overall length of the shank 3 of the thread 2 are not particularly limited and may be set appropriately depending on the conditions of the wooden structure to be fastened. For example, as shown in Figure 5, the thread 2 has a 45° cross section, a height H1 from the root 7 of 1.0 mm, and the pitch P between the threads 2 is slightly more than three times the height of the thread 2. The inclined surfaces 6 on both sides of the thread 2 start halfway up the side of the thread 2 to a starting point a, descend from this starting point a to a point b on the root 7 between the threads 2, and then spread out toward the root 7 on both sides of the thread 2. The base point a of the inclined surface 6 on the side of the thread 2 is set at a height H2 of 0.3 mm from the root 7, and the axial distance L from this base point a to the point b where the inclined surface 6 reaches the root 7 is 0.7 mm.

[0025] In the illustrated example, the cross-sectional shape of the slope 6 connecting the starting point a and the ending point b is a straight line, but it may also be formed as a curved slope that is concave in an arc. By providing such slopes 6 on both sides of the thread 2, the thickness of the base portion of the thread 2 increases, and as a result, the diameter of the valley portion 7 in the shank 3 increases on both sides of the thread 2, improving not only the strength of the thread 2 but also the bending and torsional strength of the shank 3.

[0026] The height of the ridges 8 from the valleys 7 can be set arbitrarily as long as it is lower than the height of the threads 2 from the valleys 7. By setting the height lower than the outer diameter of the threads 2, it is possible to ensure that the threads 2 are threadedly engaged with the wooden object when the ridges 8 are screwed into the wooden object. Specific examples of the height of the ridges 8 under such conditions include setting the height of the ridges 8 to the same height as the starting point a of the slope 6 on the side of the threads 2, or setting the height H3 slightly lower by about 0.2 mm, as shown in Figure 5. As shown in Figures 1 and 2, the ridges 8 are inclined relative to the axial direction of the shank 3 in a direction that is parallel to the lead angle of the threads 2, at a lead angle that is steeper than the lead angle. Furthermore, as shown in the cross-sectional view of Figure 4, multiple ridges 8 are provided at equal intervals around the circumferential direction of the shank 3.

[0027] In the case of Figure 1, the ribs 8 between the threads 2 are shown as being spirally arranged in a continuous manner with the threads 2 sandwiched between them in the axial direction of the shank 3, but the ribs 8 may not only be spirally arranged in this manner, but may also be arranged in a linear manner along the axial direction of the shank 3.

[0028] This ridge 8 is formed, for example, with a cross-sectional shape of a 60° trapezoid, and both ends thereof reach onto the slope 6 and become integrated with said slope 6, thereby also serving to reinforce the base portion of this thread 2, and if the end of the thread 2 on the head 4 side is an incomplete thread, the ridge 8 located at the end on the head 4 side is also provided on this incomplete thread portion.

[0029] In the case of Figure 1, the screw 1 is shown as an example of a full thread, in which the threads 2 are provided over almost the entire length from the sharp tip 5 of the shank 3 to the under-neck portion of the head 4. However, it may also be a half-thread, in which the threads 2 are provided in the range from the sharp tip 5 to partway along the shank 3, and the sharp tip 5 may not only be simply conical, but also have a structure equipped with a cutting edge.

[0030] Furthermore, in the case of Figure 1, the positions and range in which the ridges 8 are provided on the threads 2 are all within the range from a position several threads away from the sharp end 5 of the threads 2 toward the head 4 to the end on the head 4 side, but the ridges may also be provided in a scattered arrangement at several locations in the axial direction of the shank 3, and the cross-sectional shape of the ridges 8 and the number of ridges arranged circumferentially around the shank are not limited to those shown in the illustration.

[0031] The screw 1 of this invention is configured as described above. When the screw 1 is screwed into a wooden structure from the sharp end 5, the threads 2 act to penetrate the wooden structure, and a load is applied to the threads 2 in the axial direction of the shank 3. However, the section modulus of the shank 3 is increased by the slopes 6 located on both sides of the threads 2 and the ridges 8 provided in the valleys 7 between the threads 2, improving the bending and torsional strength of the shank and allowing the screw 1 to be screwed in smoothly without bending or breaking.

[0032] In addition, the slope 6 located on the forward side of the screw 1 slopes upward from the valley 7 toward the middle of the thread 2, so by guiding the wood material from the valley 7 toward the outer periphery of the thread 2, the forward load applied to the thread 2 is reduced, making it possible to screw in smoothly.

[0033] Furthermore, when the shank 3 is screwed in, the ribs 8 provided between the threads 2 rotate, and these ribs 8 scrape and soften the wooden material between the threads 2, thereby reducing the resistance to screwing in the shank 3 and making the screwing smoother.In addition, since the height of the ribs 8 is set lower than the height of the threads 2, the threads 2 can be securely screwed into the wooden material, thereby achieving the pull-out resistance strength of the screw 1.

[0034] In this way, by providing a slope 6 at the base of the thread 2 and providing a protrusion 8 in the valley 7 between the threads 2, the cross-sectional modulus of the shaft 3 is increased, thereby improving the bending and torsional strength of the shaft 3 and preventing damage to the shaft 3 when screwing in or after fastening a wooden structure.

[0035] In addition, in the fastened state after screwing in the screw 1, the protrusion 8 located between the threads 2 is positioned in the wooden object at a lead angle different from that of the threads 2, thereby preventing the screw 1 from loosening and ensuring that the fastened state of the wooden structure can be maintained reliably. [Explanation of symbols]

[0036] 1 screw 2 threads 3 Shaft 4 head 5 Sharp tip 6. Slope 7 Valley 8 ridges a Starting point of the slope b Slope solstice

Claims

1. A screw (1) has a shank (3) with a head (4) at one end and a sharp tip (5) at the other end, and on the outer periphery of the shank (3) is provided a thread (2), and on both axial sides of the thread (2) on the shank (3) at a position on the base side where it connects to the shank (3), a slope (6) is provided which starts midway in the height direction on the side of the thread (2) with a starting point (a) and descends from the starting point (a) to a point (b) on a valley (7) between the threads (2) while widening on both sides of the thread (2), A screw characterized in that a ridge (8) is provided in a valley (7) between the threads (2), the ridge (8) being parallel to the axial direction of the shank (3) or inclined in a direction following the lead angle of the thread (2), and the height from the valley (7) is set to be lower than the height of the thread (2), and one end of this ridge (8) reaches one of the inclined surfaces (6) opposing the valley (7) and the other end reaches the other inclined surface (6) on the same side.

2. 2. The screw according to claim 1, wherein a plurality of the ridges are provided at equal intervals in the circumferential direction of the shank.

3. 3. The screw according to claim 1 or 2, characterized in that the ridges (8) are provided over the entire length of the threads (2) from a position on the shank (3) excluding the sharp end (5) side to an end on the head (4) side.

Images