JP7647159B2 - screw - Google Patents

Description

The present invention relates to screws used in roof construction, etc.

As a roof construction method, a method known as the "covering method" has been proposed in which a metal sheet made of Galvalume steel (registered trademark) is laid over the slate material on a roof made of a wooden base and covered with slate.

Traditionally, impact drivers capable of applying strikes in a rotational direction have been used in roof construction. When using an impact driver in the above-mentioned covering method, the worker using the impact driver must apply a strong pressing force to push the screw through the sheet metal or slate material. In addition, the high rotational load caused by applying strikes in the rotational direction can easily cause the bit to come out of the screw, and a stronger pressing force is required to prevent this.

In order to reduce the pressing force, it is conceivable to apply a screw driving machine equipped with an impact mechanism that drives the screw axially and then tightens it by rotating it, and a screw tightening mechanism, to the cover construction method, as described in Patent Document 1, etc.

JP 2010-23169 A

By using the screw driver described above for the cover construction method, the screws are driven through the sheet metal and slate material using air pressure, which reduces the pressing force required by the worker using the screw driver when driving the screws through.

On the other hand, one characteristic of the cross bits commonly used for screws is that they are prone to cam-out, where the bit comes off the screw when the rotational load is high. However, with the screw driving machine described above, the bit is pressed against the screw using air pressure when the screw is driven, and the screw is pressed against the object to be fastened via the bit. Therefore, even if the operator using the screw driving machine increases the pressing force, it is difficult to prevent cam-out caused by the characteristics of the cross recess.

The present invention was made to solve these problems, and aims to provide a screw suitable for the cover construction method that suppresses the occurrence of cam-out, in which the bit comes off the screw, even when the rotational load is high.

In order to solve the above-mentioned problems, the present invention provides a screw comprising a head having a recess into which a driver bit fits, and a shank having a screw thread, the head having a convex portion protruding in the opposite direction to the shank, and an enlarged diameter portion having a larger diameter than the shank between a seating surface formed on the shank side of the head and the shank, the recess having at least three peaks along the circumferential direction of the head which rotates around the shank as an axis, the portion between the peaks being composed of straight lines or a combination of straight lines and curves that are concave toward the center of the head, or a curve , the diameter of an outer circumferential circle passing through the peaks of the recess is equal to or greater than the diameter of the shank, the depth of the recess is equal to or greater than the thickness of the head, the enlarged diameter portion has a tapered surface whose diameter increases from the shank toward the head, and the length along the axial direction of the shank from the position at which the diameter is the same as the outer diameter of the screw thread to the seating surface of the head is 1.2 mm or more .

In the present invention, a bit is used that has at least three apexes along the circumference of the head that rotates around the shaft, and the apexes are connected to straight lines or a combination of straight lines and curves that are concave toward the center of the head, or a recess that is curved, to fasten the screw.

According to the present invention, it is possible to prevent the bit from coming off the screw, and it is possible to reliably transmit high torque between the bit and the screw. In addition, by providing an enlarged diameter portion between the seat formed on the head and the shank, which has a larger diameter than the shank, it is possible to ensure the strength of the screw.

FIG. 2 is a cross-sectional view showing a main portion of an example of a screw according to the present embodiment. FIG. 2 is a cross-sectional view showing a main portion of an example of a screw according to the present embodiment. 11 is a cross-sectional view of a main portion showing another example of the screw according to the present embodiment. FIG. 11 is a cross-sectional view of a main portion showing another example of the screw according to the present embodiment. FIG. 11 is a cross-sectional view of a main portion showing a modified example of the screw of the present embodiment. FIG. 11 is a cross-sectional view of a main portion showing a modified example of the screw of the present embodiment. FIG. 13 is a cross-sectional view of a main portion showing another modified example of the screw of the present embodiment. FIG. FIG. 2 is a side view showing an example of a screw according to the present embodiment. FIG. 2 is a front view showing an example of a screw according to the present embodiment. FIG. 2 is a perspective view showing an example of a screw according to the present embodiment. 2C is a cross-sectional view of the screw according to an example of the present embodiment taken along line AA in FIG. 2B. 2B is a cross-sectional view of a screw according to an example of the present embodiment. FIG. FIG. 11 is a side view showing another example of the screw according to the present embodiment. 2B showing a cross-sectional view of another example of a screw according to the present embodiment. FIG. 2B is a cross-sectional view of a screw according to another embodiment of the present invention. FIG. FIG. 1 is a perspective view showing an example of a form in which a screw is provided according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a usage pattern of a screw according to an example of the present embodiment. FIG. 11 is a cross-sectional view showing a usage pattern of a screw according to another example of the present embodiment. FIG. 2 is a side view showing an example of a driver bit. FIG. 2 is a front view showing an example of a driver bit. FIG. 1 is a perspective view showing an example of a driver bit; FIG. 4B is an enlarged view of a portion C in FIG. 4A showing an example of a driver bit. 4 is a cross-sectional view showing a state in which a screw and a driver bit are fitted together. FIG. 4 is a cross-sectional view showing a state in which a screw and a driver bit are fitted together. FIG. 13 is a cross-sectional view of a main portion showing still another modified example of the screw of the present embodiment. FIG. 13 is a cross-sectional view of a main portion showing still another modified example of the screw of the present embodiment. FIG. 13 is a cross-sectional view of a main portion showing still another modified example of the screw of the present embodiment. FIG. 13 is a cross-sectional view of a main portion showing still another modified example of the screw of the present embodiment. FIG. 13 is a cross-sectional view of a main portion showing still another modified example of the screw of the present embodiment. FIG. 13 is a cross-sectional view of a main portion showing still another modified example of the screw of the present embodiment. FIG. 13 is a cross-sectional view of a main portion showing still another modified example of the screw of the present embodiment. FIG. 13 is a cross-sectional view of a main portion showing still another modified example of the screw of the present embodiment. FIG. 13 is a cross-sectional view of a main portion showing still another modified example of the screw of the present embodiment. FIG.

Below, an embodiment of the screw of the present invention will be explained with reference to the drawings.

<Example of the screw configuration according to this embodiment>
1A and 1B are cross-sectional views of a main part showing an example of the screw of this embodiment, and FIG. 1B shows the dimensional relationship of the screw shown in FIG. 1A. Also, FIG. 1C and FIG. 1D are cross-sectional views of a main part showing another example of the screw of this embodiment, and FIG. 1D shows the dimensional relationship of the screw shown in FIG. 1C. Furthermore, FIG. 1E and FIG. 1F are cross-sectional views of a main part showing a modified example of the screw of this embodiment, and FIG. 1G is a cross-sectional view of a main part showing another modified example of the screw of this embodiment. Also, FIG. 2A is a side view showing an example of the screw of this embodiment, FIG. 2B is a front view showing an example of the screw of this embodiment, and FIG. 2C is a perspective view showing an example of the screw of this embodiment. Furthermore, FIG. 2D is a cross-sectional view of line A-A of FIG. 2B showing the example of the screw of this embodiment shown in FIG. 2A, and FIG. 2E is a cross-sectional view of line B-B of FIG. 2B showing the example of the screw of this embodiment shown in FIG. 2A. Fig. 2F is a side view showing another example of the screw of this embodiment, Fig. 2G is a cross-sectional view taken along line A-A in Fig. 2B showing the screw of the other example of this embodiment shown in Fig. 2F, and Fig. 2H is a cross-sectional view taken along line B-B in Fig. 2B showing the screw of the other example of this embodiment shown in Fig. 2F. Fig. 2I is a perspective view showing an example of a provision form of the screw of this embodiment. Fig. 3A is a cross-sectional view showing a usage form of the screw of the example of this embodiment shown in Fig. 1A, and Fig. 3B is a cross-sectional view showing a usage form of the screw of the other example of this embodiment shown in Fig. 1C.

Furthermore, FIG. 4A is a side view showing an example of a driver bit used with the screw of the present embodiment shown in FIG. 1A, FIG. 1B, FIG. 1C, FIG. 1D, FIG. 1E, and FIG. 1F, FIG. 4B is a front view showing an example of a driver bit, FIG. 4C is a perspective view showing an example of a driver bit, and FIG. 4D is an enlarged view of part C in FIG. 4A showing an example of a driver bit. Also, FIG. 5A and FIG. 5B are cross-sectional views showing the engagement state of the screw and the driver bit.

As shown in Figures 3A and 3B, the screw 1A is used in a roof construction method known as a covering method, in which a first plate material, slate material 102 (or a roof material called cement board) is attached to a wooden base 101 on a roof, and a waterproof sheet 103 is sandwiched on top of the slate material 102, and then a second plate material, sheet metal 104 made of galvalume steel (registered trademark), is layered on top of the slate material 102.

Traditionally, impact drivers capable of applying impact in the rotational direction have been used in roof construction. When using an impact driver in the above-mentioned covering method, a strong pressing force is required to penetrate the metal plate 104 and slate material 102 and fasten the screw 1A to the base 101.

As described in JP 2010-23169 A, the screw 1A is driven in the axial direction, and then fastened using a screw driving machine equipped with a striking mechanism that fastens the screw by rotating, and a screw tightening mechanism. By using a screw driving machine, the load required to penetrate the screw 1A into the metal plate 104 and the slate material 102 can be reduced.

On the other hand, a characteristic of the cross bits commonly used for screws is that they are prone to cam-out, where the bit comes off the screw, when the rotation load is high. As described above, when a screw driver uses air pressure to press the bit against the screw, and the screw is pressed against the object to be fastened via the bit, it is difficult to prevent cam-out due to the characteristics of the cross recess, even if the pressing force of the operator using the screw driver is increased. Therefore, the screw 1A is configured so that it can be fastened with a driver bit 201 equipped with a bit 200 in a form called a hexalobular, as shown in Figures 4A to 4D, which has a recess shape that does not generate a force in the direction of separating the screw and the bit, even when the rotation load is high.

The screw 1A will be described in detail below. The screw 1A has a head 3 in which a recess 2A is formed into which a driver bit provided in a screw driving machine fits, and a shaft 4 in which a thread 40 is formed on the outer circumferential surface.

The screw 1A also has an enlarged diameter section 5 between the head 3 and the shank 4, which has a larger diameter than the shank 4, in order to ensure a sufficient thickness around the sides and bottom of the recess 2A. As shown in FIG. 2I, the screw 1A used in the screw driving machine is provided in a form in which multiple screws 1A are connected by connecting members 10A in a direction perpendicular to the axial direction of the shank 4 and wound in a spiral shape from the inner circumference to the outer circumference.

The recess 2A is configured as a concave portion with an opening on the top surface 30 of the head 3 to match the shape of the bit 200 of the driver bit 201. The recess 2A, which has a shape called a hexalobular shape, has six apexes 20A along the circumferential direction of the head 3, which rotates around the shaft 4, and the space between each apex 20A is configured with a curve that is concave toward the center of the head 3. Each apex 20A is configured with a curve that is convex toward the outer periphery of the head 3.

The recess 2A has an inner side surface 21A parallel to the axial direction in which the shaft portion 4 extends. Furthermore, the recess 2A shown in Figs. 1A, 1B, 1C, 1D, 1E, and 1F has a guide recess 22A that guides the bit 200 of the driver bit 201 shown in Figs. 4A to 4D. In the examples shown in Figs. 1A, 1B, 1C, and 1D, the guide recess 22A has a shape that is curved in a direction that convexly curves inward so that the diameter becomes smaller toward the bottom of the guide recess 22A in accordance with the shape of the conical protrusion 202 whose peripheral surface protrudes from the tip of the bit 200 of the driver bit 201 and is curved concavely. In the example shown in Fig. 1E, the guide recess 22A has a side surface that is linearly inclined so that the diameter becomes smaller toward the bottom of the guide recess 22A. Furthermore, in the example shown in Fig. 1F, the guide recess 22A has a cylindrical shape into which the protrusion 202 of the driver bit 201 fits.

In the screw driving machine shown in JP 2010-23169 A and the like, the screw 1A is supplied in a connected form, and the bit 200 needs to fit into the recess 2A when the driver bit 201 drives the screw 1A in the axial direction or when the driver bit 201 rotates. Therefore, the guide recess 22A of the recess 2A guides the convex portion 202 protruding from the tip of the bit 200 of the driver bit 201, so that the bit of the driver bit 201 can be reliably fitted into the recess 2A of the screw 1A, as shown in Figures 5A and 5B. That is, as shown in Figs. 1A, 1B, 1C, 1E, and 1F, the guide recess 22A has a shape in which the diameter becomes smaller toward the bottom of the guide recess 22A, for example, as shown in Figs. 1A, 1B, 1C, and 1D, the side surface of the guide recess 22A is curved to match the shape of the convex portion 202 of the driver bit 201 shown in Fig. 4D, or as shown in Fig. 1E, the side surface of the guide recess 22A is a linear inclined surface, so that the radial centers of the bit 200 and the recess 20A are guided in a direction to match each other when the bit 200 of the driver bit 201 and the recess 2A of the screw 1A are fitted together. This allows the bit of the driver bit 201 to be reliably fitted into the recess 2A of the screw 1A as shown in Fig. 5B. The recess 2A shown in Fig. 1G does not have a guide recess. In this case, a driver bit having no convex portion at the tip of the bit is used.

Now, the performance required for the screw used in the above-mentioned sheet metal cover construction method is to reliably fix the sheet metal 104, and when reliably fixing the sheet metal 104, it is important that the head of the screw does not float from the sheet metal 104 and does not sink into the sheet metal 104. In order to reliably fix the sheet metal 104, while suppressing the increase in load during the operation of fastening the screw 1A, in order to ensure the strength that the shank 4 does not break, it is preferable that the diameter D1 of the shank 4 of the screw 1A is 2.7 mm or more and 3.3 mm or less. That is, in order to ensure the strength that the shank 4 does not break, it is preferable that the lower limit value of the diameter D1 of the shank 4 of the screw 1A is 2.7 mm or more. On the other hand, if the diameter of the shank 4 becomes thicker, the driving load and the rotation load during screwing increase, and the workability deteriorates, so it is preferable that the upper limit value of the diameter D1 of the shank 4 is 3.3 mm or less. In addition, to prevent the shank 4 of the fastened screw 1A from coming out of the base 101, the outer diameter D2 of the thread 40 is preferably 4.0 mm or more, but considering the driving load and the rotation load during screwing, it is preferable that it is 4.5 mm or less.

Furthermore, in order to hold the metal plate 104 by the head 3 so that it does not come loose, it is preferable that the diameter D3 of the head 3 is 8.1 mm or more. On the other hand, the diameter of the head 3 of the screw 1A needs to be smaller than the inner diameter of the nose through which the screw passes in the screw driving machine. Furthermore, in order to suppress the angle at which the screw 1A tilts within the nose, it is better not to make the difference between the diameter D2 of the thread 40 of the shank 4 of the screw 1A and the diameter D3 of the head 3 too large. Therefore, in the case of the screw 1A with the outer diameter D2 of the thread 40 of about 4.0 mm, it is preferable that the upper limit of the diameter D3 of the head 3 is 8.7 mm or less.

When the recess 2A has a shape known as a hexalobular shape, a driver bit with a size (nominal) of T20 or T25 is used for a screw 1A with an outer diameter D2 of the thread 40 of approximately 4.0 mm. The recess 2A corresponding to a driver bit with a size T20 has a spacing A1 of 3.84 mm between the apexes 20A located on a diagonal line passing through the center of the head 3, and the recess 2A corresponding to a driver bit with a size T25 has a spacing A1 of 4.40 mm between the apexes 20A located on a diagonal line.

In addition, as shown in Figures 1A, 1B, 1C, 1D, 1E, and 1F, in a configuration in which the recess 2A has a guide recess 22A, the diameter A2 of the guide recess 22A is 2.85 mm or less in the recess 2A corresponding to a driver bit having a size of T20, and the diameter A2 of the guide recess 22A is 3.3 mm or less in the recess 2A corresponding to a driver bit having a size of T25.

In the above-mentioned covering method, the next metal plate 104 is placed on top of the metal plate 104 fixed by the screw 1A. Therefore, the top of the head 3 of the screw 1A exposed on the surface of the metal plate 104 fixed on the lower side is covered by the next metal plate 104.

The head 3 has a protrusion 33 that protrudes along the axial direction of the shaft 4 in the direction opposite to the side where the enlarged diameter portion 5 is provided. Therefore, it is preferable that the thickness T1 of the head 3 of the screw 1A is 1.2 mm or more and 2.4 mm or less . If the thickness T1 of the head 3 is 2.4 mm or less, even if a force is applied to the metal sheet 104 placed on the head 3 of the screw 1A, deformation of the metal sheet 104 caused by being pressed against the head 3 of the screw 1A is suppressed.

The head 3 is provided with a seat 31 on the outer periphery of the enlarged diameter portion 5, which contacts and holds the sheet metal 104 fixed to the base 101 via the slate material 102. Here, when the screw 1A is fastened to fix the sheet metal 104, the seat 31, which is the surface of the head 3 that faces the sheet metal 104, may be configured as a flat surface, or as a tapered surface consisting of a slope or curved surface whose diameter increases from the shaft 4 toward the outer periphery of the head 3, as in the form called a countersunk screw. When the seat 31 is configured as a flat surface, the screw 1A is screwed in until the entire surface of the seat 31, including the outer periphery of the head 3, is in contact with the surface of the sheet metal 104, so that the head 3 of the screw 1A does not float above the surface of the sheet metal 104. In contrast, when the seat 31 is configured as a tapered surface whose diameter increases from the shaft 4 toward the outer periphery of the head 3, it protrudes from the outer periphery of the head 3 toward the shaft 4 along the axial direction of the shaft 4, so that the screw 1A is screwed in until the outer periphery of the head 3 comes into contact with the surface of the sheet metal 104 while a part of the seat 31 presses against the sheet metal 104, so that the head 3 of the screw 1A does not float above the surface of the sheet metal 104. Therefore, when the head 3 of the screw 1A does not float above the surface of the sheet metal 104, the outer periphery of the seat 31, which is the outer periphery of the head 3, comes into contact with the surface of the sheet metal 104.

The outer periphery of the seat 31 is referred to as the seat reference surface 32. In a configuration in which the head 3 has a convex portion 33, the thickness T1 of the head 3 is the length along the axial direction of the shaft 4 from the top surface 30 of the head 3 to the seat reference surface 32. Note that, in the case where the seat 31 is a flat surface, the thickness T1 of the head 3 is the length along the axial direction of the shaft 4 from the top surface 30 of the head 3 to the seat 31.

For screw 1A with recess 2A size corresponding to a driver bit with T20, it is preferable that thickness T1 of head 3 is 1.2 mm or more and 2.3 mm or less, and it is more preferable that the upper limit of thickness T1 of head 3 is 2.0 mm or less. For screw 1A with recess 2A size corresponding to a driver bit with T25, it is preferable that thickness T1 of head 3 is 1.6 mm or more and 2.3 mm or less, and it is more preferable that the upper limit of thickness T1 of head 3 is 2.0 mm or less.

In order to ensure a sufficient contact area between the driver bit and the inner surface 21A of the recess 2A, the depth Dep1 of the recess 2A is preferably 1.6 mm or more. If the depth Dep1 of the recess 2A is 1.6 mm or more, the occurrence of cam-out, in which the driver bit comes out of the recess 2A when fastening the screw 1A with the driver bit, is suppressed, and the driver bit can apply a force to the screw 1A that is necessary and sufficient for fastening.

As shown in Figures 1A, 1B, 1C, 1D, 1E, and 1F, in a configuration in which the recess 2A includes a guide recess 22A, it is preferable that the depth Dep2 of the guide recess 22A is 1.2 mm or more and 2.1 mm or less. In the case of a screw 1A in which the recess 2A size corresponds to a T20 driver bit, it is preferable that the depth Dep2 of the guide recess 22A is 1.2 mm or more and 2.1 mm or less. In the case of a screw 1A in which the recess 2A size corresponds to a T25 driver bit, it is preferable that the depth Dep2 of the guide recess 22A is 1.5 mm or more and 2.1 mm or less.

As described above, the recess 2A corresponding to the driver bit of size T25 has a diameter of an outer circumference passing through each apex 20A, in this example, the distance A between the diagonally positioned apexes 20A is 4.4 mm, and the radial size of the recess 2A is larger than the diameter D1 of the shank 4. On the other hand, the thickness T1 of the head 3 of the screw 1A is preferably 2.0 mm or less, while the depth Dep1 of the recess 2A is preferably 1.6 mm or more.

The thickness of the sides and bottom of the recess 2A is preferably 0.7 mm or more. In contrast, with the above dimensional relationship, if the seat 31 is flat and the shank 4 is shaped to connect to the seat 31 at approximately the same diameter without the enlarged diameter portion 5, the thickness between the bottom of the recess 2A and the seat 31 of the head 3 can be secured at most 0.4 mm, which does not satisfy the value stipulated in the present invention. Therefore, with a screw in which the shank 4 is shaped to connect to the seat 31 at approximately the same diameter without the enlarged diameter portion 5, the required thickness cannot be secured around the sides and bottom of the recess 2A.

Therefore, in order to ensure the thickness around the sides and bottom of the recess 2A, the screw 1A has an enlarged diameter portion 5 between the head 3 and the shank 4, the diameter of which is larger than that of the shank 4. By providing the enlarged diameter portion 5 between the head 3 and the shank 4, the depth Dep1 of the recess 2A can be made equal to or greater than the thickness T1 of the head 3 of the screw 1A.

In this case, when the recess 2A has a shape called hexalobular and is provided with a guide recess 22A as shown in Figs. 1A, 1B, and 1C, the thickness T2 between the recess 2A and the enlarged diameter portion 5 around the sides and bottom of the recess 2A is the thinnest between the top 20A of the recess 2A and the enlarged diameter portion 5, or between the guide recess 22A of the recess 2A and the enlarged diameter portion 5. When the recess 2A is not provided with a guide recess as shown in Fig. 1D, the thickness T2 between the recess 2A and the enlarged diameter portion 5 is the thinnest between the top 20A of the recess 2A and the enlarged diameter portion 5. It is preferable that the thinnest part of the thickness T2 between the recess 2A and the enlarged diameter portion 5 is 0.7 mm or more.

Now, in the case of a screw 1A having an enlarged diameter portion 5 between the head 3 and the shank 4, if the length along the axial direction of the shank 4 from the starting point 51 of the enlarged diameter portion 5, where the diameter (diameter) is larger than that of the shank 4, to the seat reference surface 32 (seat 31) of the head 3 is equal to or less than the combined thickness of the metal plate 104 and the waterproof sheet 103, which in this example is 1.35 mm, then even if the screw 1A is screwed in until the seat reference surface 32 (seat 31) of the head 3 is in close contact with the metal plate 104, the enlarged diameter portion 5 will not reach the slate material 102.

However, in this case, if the enlarged diameter portion 5 is configured as a tapered surface whose diameter increases from the starting point 51 of the enlarged diameter portion 5 toward the seating surface reference surface 32, the thickness T2 between the recess 2A and the enlarged diameter portion 5 will be less than 0.7 mm at its thinnest point.

In response to this, we are considering a configuration in which the length along the axial direction of the shaft portion 4 from the starting point 51 of the enlarged diameter portion 5 to the seat reference surface 32 (seat surface 31) of the head portion 3 exceeds the combined thickness of the metal plate 104 and the waterproof sheet 103.

In this case, the expanded diameter portion 5 reaches the slate material 102. However, in the hole in the slate material 102 where the thread 40 passes during the tightening operation of the screw 1A, the slate material 102 is destroyed at the part inside the outer diameter D2 of the thread 40 on the opening side facing the waterproof sheet 103 when the thread 40 penetrates. Therefore, in the vicinity of the side of the slate material 102 facing the waterproof sheet 103, even the part of the expanded diameter portion 5 that is thicker than the diameter D1 of the shaft portion 4 can penetrate into the slate material 102.

Therefore, in the expanded diameter portion 5, the length L1 along the axial direction of the shaft portion 4 from position P1, where the diameter is the same as the outer diameter D2 of the thread 40, to the seat reference surface 32 (seat 31) of the head 3 is preferably approximately equal to the combined thickness of the metal plate 104 and the waterproof sheet 103, and is preferably 1.2 mm or more, and in this example is approximately 1.35 mm to 1.65 mm. In this example, since the outer diameter D2 of the thread 40 is 4.2 mm, it is preferable that the diameter of the expanded diameter portion 5 at position P1, which is 1.2 mm or more away from the seat reference surface 32 (seat 31) of the head 3 along the axial direction of the shaft portion 4, is 4.2 mm or less.

In order to ensure that the thickness T2 between the recess 2A and the enlarged diameter portion 5 is 0.7 mm or more at its thinnest point, it is preferable that the length L2 from the starting point 51 of the enlarged diameter portion 5 to the seat reference surface 32 (seat surface 31) of the head 3 is 1.5 mm or more and 3.5 mm or less.

When the recess 2A is configured to have a guide recess 22A, the length L2 from the starting point 51 of the enlarged diameter portion 5 to the seat reference surface 32 (seat surface 31) of the head 3 is preferably 1.7 mm or more and 2.6 mm or less. In the case of a screw 1A in which the recess 2A size corresponds to a driver bit of T20, the length L2 from the starting point 51 of the enlarged diameter portion 5 to the seat reference surface 32 (seat surface 31) of the head 3 is preferably 1.7 mm or more and 2.6 mm or less. In the case of a screw 1A in which the recess 2A size corresponds to a driver bit of T20, the length L2 from the starting point 51 of the enlarged diameter portion 5 to the seat reference surface 32 (seat surface 31) of the head 3 is preferably 1.7 mm or more and 2.6 mm or less.

When the recess 2A does not have a guide recess 22A, the length L2 from the starting point 51 of the enlarged diameter portion 5 to the seat reference surface 32 (seat surface 31) of the head 3 is preferably 1.5 mm or more and 3.5 mm or less. In the case of a screw 1A in which the recess 2A size corresponds to a driver bit of T20, the length L2 from the starting point 51 of the enlarged diameter portion 5 to the seat reference surface 32 (seat surface 31) of the head 3 is preferably 1.7 mm or more and 3.5 mm or less. In the case of a screw 1A in which the recess 2A size corresponds to a driver bit of T20, the length L2 from the starting point 51 of the enlarged diameter portion 5 to the seat reference surface 32 (seat surface 31) of the head 3 is preferably 1.7 mm or more and 2.9 mm or less.

In addition, the expanded diameter section 5 is in contact with the metal sheet 104 between position P1, where the diameter is the same as the outer diameter D2 of the thread 40, and the seat reference surface 32 (seat 31) of the head 3. In order to prevent the head 3 of the screw 1A from floating above the surface of the metal sheet 104, the seat reference surface 32, which is the outer periphery of the head 3, must be in contact with the surface of the metal sheet 104. For this reason, in order to deform the metal sheet 104 and the waterproof sheet 103, the expanded diameter section 5 is provided with a tapered surface 50 whose diameter increases from the shaft 4 toward the head 3, between position P1, where the diameter is the same as the outer diameter D2 of the thread 40, and the seat reference surface 32 (seat 31) of the head 3.

When the recess 2A is configured with a guide recess 22A and the diameter D3 of the head 3 is 8.4 mm, the angle α of the tapered surface 50 is preferably 70° or more and 115° or less. When the screw 1A has a recess 2A size that corresponds to a T20 driver bit, the angle α of the tapered surface 50 is preferably 76° or more and 115° or less. When the screw 1A has a recess 2A size that corresponds to a T25 driver bit, the angle α of the tapered surface 50 is preferably 70° or more and 115° or less.

When the recess 2A does not have a guide recess 22A and the diameter D3 of the head 3 is 8.4 mm, the angle α of the tapered surface 50 is preferably 38° or more and 115° or less. When the screw 1A has a recess 2A size that corresponds to a T20 driver bit, the angle α of the tapered surface 50 is preferably 38° or more and 115° or less. When the screw 1A has a recess 2A size that corresponds to a T25 driver bit, the angle α of the tapered surface 50 is preferably 57° or more and 115° or less.

When the angle α of the tapered surface 50 is the above value, the thickness T2 between the recess 2A and the enlarged diameter portion 5 can be set to 0.7 mm or more at the thinnest part, and the depth Dep1 of the recess 2A can be set to 1.6 mm or more. Furthermore, by providing the enlarged diameter portion 5, the depth Dep1 of the recess 2A can be set to be equal to or greater than the thickness T1 of the head 3 of the screw 1A, with a configuration in which the thickness T1 of the head 3 of the screw 1A is 1.2 mm or more and 2.4 mm or less.

For this reason, it is preferable that the depth Dep1 of the recess 2A is 1.6 mm or more and 2.5 mm or less. In the case of a screw 1A in which the recess 2A size corresponds to a driver bit of T20, it is preferable that the depth Dep1 of the recess 2A is 1.6 mm or more and 2.5 mm or less. In the case of a screw 1A in which the recess 2A size corresponds to a driver bit of T25, it is preferable that the depth Dep1 of the recess 2A is 1.6 mm or more and 2.0 mm or less.

On the other hand, if the angle α of the tapered surface 50 exceeds the above value, the area of the seat 31 may become small or a flat surface that becomes the seat 31 may not be formed. In order to ensure the area of the seat 31 without making the outer diameter of the head 3 larger than the above value, a seat lower connecting surface 50a may be provided between the tapered surface 50 and the seat 31, and the tapered surface 50 and the seat 31 may not be directly connected to each other, forming a so-called stepped shape. The angle β (half angle) of the seat lower connecting surface 50a is preferably 0° or more and 35° or less, and may be configured with a tapered surface with an angle different from that of the tapered surface 50 as shown in Figures 1A and 1B, or may be configured with a straight surface along the axial direction of the shaft portion 4 as shown in Figures 1C and 1D. In addition, the length L3 of the seat lower connecting surface 50a along the axial direction of the shaft portion 4, i.e., the length from the seat reference surface 32 (seat 31) of the head 3 to the connecting point P2 between the seat lower connecting surface 50a and the tapered surface 50, is preferably 0.3 mm or more and 1.3 mm or less. Furthermore, as shown in Figures 1A and 1B, between the tapered surface 50 formed of a linear inclined surface and the starting point 51 of the enlarged diameter portion 5, in this example, between the position P1 and the starting point 51 of the enlarged diameter portion 5, may be formed of a curved surface 50b that is concave toward the center of the shaft portion 4. By configuring the area between position P1 and the starting point 51 of the enlarged diameter portion 5 with a curved surface 50b that is concave toward the center of the shaft 4, the length L2 from the starting point 51 of the enlarged diameter portion 5 to the seat reference surface 32 (seat surface 31) of the head 3 can be extended within a specified range while suppressing an increase in load when fastening the screw 1A, ensuring the thickness T2 between the recess 2A and the enlarged diameter portion 5 and deepening the depth Dep1 of the recess 2A.

6A to 6I are cross-sectional views of the main part showing yet another modified example of the screw of this embodiment. In the expanded diameter portion 5, if the diameter between position P1, where the diameter is the same as the outer diameter D2 of the thread 40, and the starting point 51 of the expanded diameter portion 5 is smaller than the outer diameter D2 of the thread 40, it can penetrate the slate material 102. Therefore, the expanded diameter portion 5 may have a tapered surface between position P1, where the diameter is the same as the outer diameter D2 of the thread 40, and the starting point 51 of the expanded diameter portion 5, whose diameter increases from the starting point 51 to position P1, where the diameter is the same as the outer diameter D2 of the thread 40. In the enlarged diameter portion 5, the tapered surface 52a provided between the position P1 where the diameter is the same as the outer diameter D2 of the thread 40 and the starting point 51 of the enlarged diameter portion 5 may have the same angle as the tapered surface 50, or as shown in Fig. 6A, the angle α1 (half angle) of the tapered surface 50 and the angle α2 (half angle) of the tapered surface 52a provided between the position P1 and the starting point 51 of the enlarged diameter portion 5 may be different angles. In this case, the position where the tapered surface 50 and the tapered surface 52 are connected may not coincide with the position P1 where the diameter is the same as the outer diameter D2 of the thread 40. A virtual circle C1 is shown by a two-dot chain line, with the recess 2A side as the center and the minimum value (0.7 mm in this example) obtained as the wall thickness T2 between the recess 2A and the enlarged diameter portion 5 as the radius. If the angle between each tapered surface is such that each tapered surface does not fall inside an imaginary circle C1 centered on an arbitrary point O on the recess 2A side, then the thickness T2 between the recess 2A and each tapered surface will be equal to or greater than the desired value.

6B, the area between position P1 and the starting point 51 of the enlarged diameter portion 5 may be configured with a curved surface 52b that is convex toward the center of the shaft portion 4 so as not to enter inside the imaginary circle C1 centered on an arbitrary point O on the recess 2A side. Furthermore, as shown in FIG. 6C, the enlarged diameter portion 5 may be configured to have a tapered surface 50 that increases in diameter from the shaft portion 4 toward the head 3 on the side closer to the shaft portion 4 and does not enter inside the imaginary circle C1 centered on an arbitrary point O on the recess 2A side, between position P1 where the diameter is the same as the outer diameter D2 of the thread 40 and the seat reference surface 32 (seat 31) of the head 3, and a straight surface 53a along the axial direction of the shaft portion 4 on the side closer to the seat 31 so as not to enter inside the imaginary circle C1 centered on an arbitrary point O on the recess 2A side. In addition, the enlarged diameter portion 5 may have a step portion between the position P1 where the diameter is the same as the outer diameter D2 of the thread 40 and the starting point 51 of the enlarged diameter portion 5, the diameter of which increases from the starting point 51 to the position P1 where the diameter is the same as the outer diameter D2 of the thread 40. Furthermore, as shown in FIG. 6D, the enlarged diameter portion 5 may have a step portion 53b that follows the shape of the recess 2A between the position P1 where the diameter is the same as the outer diameter D2 of the thread 40 and the bearing reference surface 32 (bearing surface 31) of the head 3, so that the thickness T2 between the recess 2A and the enlarged diameter portion 5 is approximately uniform.

As shown in FIG. 6E, the expanded diameter portion 5 may be configured such that the section between the seat 31 of the head 3 and the position P1 where the diameter is the same as the outer diameter D2 of the thread 40, and the section between the position P1 and the starting point 51 of the expanded diameter portion 5, is made up of an arc C2 of a single diameter or a combination of arcs of multiple different diameters, and the curved surface 54a does not fall inside the imaginary circle C1 centered on an arbitrary point O on the recess 2A side. As shown in FIG. 6F, the expanded diameter portion 5 may be configured such that the seat 31 is made up of a tapered surface consisting of an inclined surface or a curved surface whose diameter increases from the shaft portion 4 toward the outer periphery of the head 3, and the section between the seat reference surface 32 of the head 3 and the position P1 where the diameter is the same as the outer diameter D2 of the thread 40, and the section between the position P1 and the starting point 51 of the expanded diameter portion 5, is made up of an arc C2 of a single diameter or a combination of arcs of multiple different diameters, and the curved surface 54b does not fall inside the imaginary circle C1 centered on an arbitrary point O on the recess 2A side.

As shown in Figure 6G, the screw 1A may be configured with a head 3 in a form called a button head, as long as the tapered surface 50 in the enlarged diameter portion 5 that faces the guide recess 22A of the recess 2A does not enter inside the imaginary circle C1 centered on an arbitrary point O on the recess 2A side. Furthermore, as shown in Figure 6H, even if the tapered surface 50 in the enlarged diameter portion 5 extends to the outer periphery of the head 3 and the seat surface 31 is configured as a tapered surface whose diameter increases from the shank 4 toward the outer periphery of the head 3, the screw 1A may be configured with a head 3 in a form called a button head.

Also, as shown in FIG. 6I, if the head 3 does not have a convex portion 33 and the screw 1A is in the form of a flat head screw, the bearing surface 31 is formed by a part of the tapered surface 50, but if the depth Dep1 of the recess 2A is 1.6 mm or more, the tapered surface 50 facing the recess 2A and the guide recess 22A does not fall inside the imaginary circle C1 centered on an arbitrary point O on the recess 2A side, and further, a part of the tapered surface 50 presses against the sheet metal 104, and the screw 1A can be screwed in until the outer periphery of the head 3 (bearing surface reference surface 32) comes into contact with the surface of the sheet metal 104, then the screw 1A may be in the form of a flat head screw.

As described above, the screw 1A has a recess 2A into which the driver bit fits that has at least three apexes 20A along the circumferential direction of the head 3 that rotates around the shank 4, and the spaces between the apexes 20A are composed of straight lines or a combination of straight lines and curves that are concave toward the center of the head 3, or curves, and an enlarged diameter section 5 with a larger diameter than the shank 4 is provided between the seat 31 of the head 3 and the shank 4, thereby ensuring the strength of the screw 1A while suppressing the occurrence of cam-out.

It is preferable that the dimensions of each part of the screw 1A satisfy the values stipulated in the present invention described above. That is, the diameter D3 of the head 3 is 8.1 mm or more and 8.7 mm or less, the thickness T1 of the head 4 is 1.2 mm or more and 2.4 mm or less, the depth Dep1 of the recess 20A is 1.6 mm or more and 2.5 mm or less, the diameter D1 of the shank 4 is 2.7 mm or more and 3.3 mm or less, the diameter D2 of the thread 40 of the shank 4 is 4.1 mm or more and 4.35 mm or less, the thickness T2 between the recess 2A and the enlarged diameter portion 5 is 0.7 mm or more, and the length L2 along the axial direction of the shank 4 from the starting point 51 of the enlarged diameter portion 5 where the shank 4 and the enlarged diameter portion 5 intersect to the bearing surface 31 (bearing surface reference surface 32) of the head 3 is 1.5 mm or more and 3.1 mm or less.

The angle α of the tapered surface 50 is 38° or more and 115° or less, and when the guide recess 22A is provided, the angle α of the tapered surface 50 is 70° or more and 115° or less.

Furthermore, the diameter of the enlarged diameter portion 5 is 4.2 mm or less at a position P1 that is 1.2 mm or more away from the seat surface 31 (seat surface reference surface 32) of the head 3 along the axial direction of the shaft portion 4.

By having the dimensions of each part of the screw 1A satisfy the values stipulated in the present invention, it is possible to realize that when the metal plate 104 is fixed in the above-mentioned cover construction method, the head 3 of the screw 1A does not float above the metal plate 104, and the head 3 of the screw 1A does not sink into the metal plate 104.

In this way, in the cover construction method, by using a screw driving machine equipped with an impact mechanism that fastens the screw 1A by rotating after driving the screw 1A in the axial direction and a screw tightening mechanism, the load required to penetrate the screw 1A into the sheet metal 104 and slate material 102 can be reduced. In addition, even if the rotation load is high, the occurrence of cam-out, in which the bit 200 comes off the screw 1A, can be suppressed.

In addition, in the screw 1A, the recess 2A is not limited to the shape called hexalobular, but may be a rectangle having four apexes 20A along the circumferential direction of the head 3, with straight lines between each apex 20A, and each side of the rectangle having an inner surface 21A parallel to the axial direction of the shank 4, or a hexagon having six apexes 20A along the circumferential direction of the head 3, with straight lines between each apex 20A, and each side of the hexagon having an inner surface 21A parallel to the axial direction of the shank 4, etc.

Now, in order to join materials that are subject to high tightening loads, such as fastening hard wood together, and to make connections that require high torque when turning the screw, it is essential that the torque generated by the tool be transmitted reliably to the screw without camming out, and that the screw be strong enough so that it will not break even when tightened with high torque.

To prevent cam-out, it is effective to form a deep recess in the screw. If the thickness of the screw head is increased in order to form a deep recess, the amount by which the screw head protrudes from the surface of the object to be fastened increases. On the other hand, if the recess is made deep without increasing the thickness of the screw head, due to the relationship between the size of the recess and the diameter of the shank where the threads are provided, it becomes necessary to form an enlarged diameter section on the underside of the head that is larger in diameter than the shank.

However, the enlarged diameter portion provides resistance when the screw sinks into the object being fastened during the fastening operation, so the larger the diameter of the enlarged diameter portion is made to ensure the strength of the screw, the higher the torque required to fasten the screw, making it difficult to achieve the effect of ensuring the strength of the screw.

In contrast, in the screw 1A of this embodiment, the shape of the recess 2A, the diameter of the enlarged diameter portion 5, and the length along the axial direction of the shaft portion 4 are specified, which minimizes the increase in load when the enlarged diameter portion 5 sinks into the object to be fastened during the fastening operation of the screw 1A, enabling reliable torque transmission from the driver bit 201 to the screw 1A. This achieves the goals of reliable transmission of high torque, ensuring the strength of the screw 1A, and suppressing the increase in torque required to fasten the screw 1A, without increasing the thickness of the head 3. Therefore, the applications to which the screw 1A can be applied are not limited to the above-mentioned cover construction method, and it is effective in fastening members that have a high tightening load, such as fastening hard wood pieces together.

1A...screw, 2A...recess, 20A...top, 21A...inner surface, 22A...guiding recess, 3...head, 30...top surface, 31...seat, 32...seat reference surface, 33...projection, 4...shaft, 40...thread, 5...expanded portion, 50...tapered surface, 50a, seat lower connection surface, 50b...curved surface, 51...starting point, 101...base, 102...slate material, 104...sheet metal, 200...bit, 201...driver bit

Claims (11)

a head portion having a recess into which a driver bit is fitted;
a shaft portion on which a screw thread is formed,
The head portion includes a protrusion protruding in a direction opposite to the shaft portion,
an enlarged diameter portion having a diameter larger than that of the shaft portion is provided between the shaft portion and a seat surface formed on the head portion on the shaft portion side;
The recess has at least three apexes along a circumferential direction of the head which rotates about the shaft portion,
The recess is formed between the apexes by a straight line or a combination of straight lines and curves that are concave toward the center of the head, or by a curve , and the diameter of an outer circumferential circle passing through the apex of the recess is equal to or greater than the diameter of the shaft portion;
The depth of the recess is equal to or greater than the thickness of the head,
The enlarged diameter portion has a tapered surface whose diameter increases from the shank toward the head, and the length along the axial direction of the shank from a position at the enlarged diameter portion where the diameter is the same as the outer diameter of the thread to the seat surface of the head is 1.2 mm or more . The screw according to claim 1 , wherein the recess has an inner surface parallel to the axial direction of the shank. 3. The screw according to claim 1 , wherein the depth of the recess is not less than 1.6 mm and not more than 2.5 mm . The screw according to any one of claims 1 to 3 , wherein the recess is provided with a guide recess for guiding a bit of a driver bit into the recess . The screw according to any one of claims 1 to 3 , wherein the angle formed by the tapered surfaces is equal to or greater than 70° and equal to or less than 115° . The enlarged diameter portion has a tapered surface whose diameter increases from the shaft portion toward the head portion,
The screw according to claim 4 , wherein the angle between the tapered surfaces is equal to or greater than 38° and equal to or less than 115°. The screw according to any one of claims 1 to 6 , wherein a length along the axial direction of the shank from a starting point of the enlarged diameter portion where the shank and the enlarged diameter portion intersect to the seat surface of the head is 1.5 mm or more and 3.5 mm or less . The recess has six apexes along the circumferential direction of the head, and each apex is formed by a curve that is convex toward the outer periphery of the head, and the space between each apex is formed by a curve that is concave toward the center of the head.
The screw according to any one of claims 1 to 6. The screw according to any one of claims 1 to 8, wherein the thickness of the head portion is 1.2 mm or more and 2.4 mm or less . The screw according to any one of claims 1 to 9, wherein the head has a seat provided on an outer periphery of the enlarged portion, and the seat is configured as a flat surface . The screw according to any one of claims 1 to 10 , wherein the plurality of screws are connected by a connecting member in a direction perpendicular to the axial direction of the shaft portion and wound in a spiral shape from the inner circumference side to the outer circumference side .

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