Screw having lock

Abstract

To provide a screw having a lock at a bow capable of obtaining large looseness torque.SOLUTION: A screw has a lock at a bow. The seating face of the bow is formed into an inverted-dish like tapered shape, and protrusions are formed on the outer periphery of the seating face at an almost equal interval in a circumferential direction. When fastened to a locking material, since the seating face is the tapered shape, not the entire seating face, but the outermost peripheral portion of the seating face and round ring-shaped portions of the protrusions in the vicinity of the outermost peripheral portion come into contact with a surface of the locking material and bite. Therefore, a torque loss is reduced, so as to obtain large axial force. When the screw is fastened, force is dispersed ton the entire seating face if the seating face has a planar shape. However, if it has a tapered shape, force due to axial force is concentrated only to the ring-shaped portion of the outermost periphery, and a locking force due to protrusion is improved. Additionally, the ring-shaped portion is at the outermost peripheral position and has a distance from an axial center, so as to obtain large looseness torque.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a screw having an anti-loosening function. More specifically, it relates to a screw having an anti-loosening function on the head of the screw.

Background Art

[0002] In recent years, the outer casings of electronic devices and the like have come to be made of synthetic resin materials such as AS (acrylonitrile-styrene) resin and ABS (acrylonitrile-butadiene-styrene) resin. There are also those made of soft metals such as aluminum and copper materials. Then, while fixing this outer casing to a metal frame or the like with a predetermined tightening torque, there has been a demand for a screw having an anti-loosening function so that the screw does not loosen due to vibrations or impacts during transportation of the electronic device or the like, and as a result, the loosening torque does not significantly decrease.

[0003] Conventionally, as such a screw, a washer-embedded screw (or a small screw with SW+PW embedded), in which a spring washer (SW) and a flat washer (PW) are incorporated into a pan head screw, generally called a Sems screw (registered trademark), has been used. This washer-embedded screw incorporates washers and the like before rolling the thread so that the washers and the like do not fall off after rolling, and it does not require the labor of incorporating washers and the like manually, improving the working efficiency. And when the screw is fastened, the spring washer is compressed to prevent loosening, and it is suitable for places where the screw is repeatedly removed. Incidentally, this washer-embedded screw is also defined in JIS (Japanese Industrial Standard JIS B 1188:2017).

[0004] However, in the washer-embedded screw, the spring washer and flat washer are not fixed to the screw alone, and the flat washer etc. can move within the range incorporated into the screw. Also, the flat washers may overlap each other. Therefore, for example, when attempting to align and supply the washer-embedded screw with an auto parts feeder at a factory etc., there was the inconvenience that it might get jammed in the auto parts feeder midway. For such reasons, a screw having an anti-loosening feature at the head of the screw, rather than the washer-embedded screw, has been demanded.

[0005] As such a screw having an anti-loosening feature at the head of the screw, there is the screw for fixing a resin member disclosed in Patent Document 1. This screw for fixing a resin member is a tapping screw with a cross hole having serrations on the seating surface in the embodiments shown in FIGS. 1 and 3, and is a screw that is screwed into a member made of a resin material while cutting threads to fix the resin member. And it has 18 threads of serrations, and each serration has a locking surface located on the front end side along the tightening direction of the screw and formed substantially parallel to the axis, and an inclined surface formed to incline from the apex of this locking surface toward the rear end side along the tightening direction. If the positional relationship between this locking surface and the inclined surface is configured to be in the opposite direction in the same way as a screw having serrations on a general seating surface, there will be little resistance when tightening the screw, and after tightening, the locking surface will bite into the resin material and function as an anti-loosening feature.

[0006] Also, as such a screw, there is the bolt and nut disclosed in Patent Document 2. This bolt and nut has a plurality of ridges that curve along the thread groove direction radially provided on the lower surface of the head of the bolt or the upper surface of the nut that it screws into, and these ridges are formed to gradually increase in height from the inner side toward the outer peripheral side. When this bolt and nut is rotated and tightened, the ridges bite into the surface of the mating material. Here, since the cross-sectional shape of the ridge is substantially triangular and the tip is sharp, it bites in with a large force. And since the height of the ridge gradually increases from the inner side toward the outer peripheral side, a large torque acts on the outer peripheral side, a large force is locally applied, and it bites in deeper and is fixed, serving as an anti-loosening feature.

[0007] In addition, as a screw having an anti-loosening feature on the head of such a screw, there is a flange bolt disclosed in Non-Patent Document 1. This flange bolt has a conical flange called a flange on the seating surface side of the hexagonal head with a cross hole. On the seating surface side of this flange, there are serrations, and when these serrations bite into the mating material during fastening, the anti-loosening effect is improved. Also, the flange prevents the seating surface from sinking into the mating material. Note that the height of the peaks of these serrations is higher on the outer peripheral part than on the inner peripheral part. Further note that this flange bolt has a conical flange called a flange, but the conical shape is only on the upper surface part of the flange, and the seating surface is flat, and the serrations are formed on this flat part.

[0008] And, as such a screw, there is a screw with a spring-like flange disclosed in Patent Document 3. This screw with a spring-like flange integrally forms an inverted dish-shaped spring-like flange on the lower peripheral edge of the head of the screw. And this flange exhibits spring characteristics by obtaining an appropriate spring constant and deflection amount, and obtains sufficient tightening torque to prevent loosening.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Non-Patent Documents

[0010]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0011] However, in the technique with the orientation of Patent Document 1 reversed, since the seating surface of the screw for fixing the resin member is flat, when the protruding height from the seating surface of the serration is the same for both the outer peripheral part and the inner peripheral part, the part from the outer peripheral part to the inner peripheral part of the serration comes into contact with the fastening surface, resulting in a large seating surface friction torque. Also, when tightening the screw, the serration of the entire seating surface bites into the fastening surface. That is, not only the seating surface friction torque but also the biting torque due to the serration is generated.

[0012] As a result, large torque losses due to friction and biting occurred, and since the seating surface friction torque and the biting torque in the total tightening torque increased, the axial force torque decreased, leading to the disadvantage that the axial force decreased. Also, when tightening the screw, since the entire seating surface comes into contact with the fastening surface, there was the disadvantage that the force due to the axial force applied to the seating surface was dispersed. In any case, in order to prevent the screw from loosening, a screw with serrations that can obtain a large loosening torque has been demanded. Also, when trying to loosen the screw, there was the disadvantage that the bitten surface of the serration was scraped off by the serration, causing whitening on the entire surface.

[0013] By the way, in this screw for fixing the resin member, serrations are provided on the flat seating surface, and the serrations are formed in a substantially radial pattern with respect to the axis. And the circumferential width of each serration is larger at the outer peripheral portion than at the inner peripheral portion. When the serrations are machined, the height of the serration peaks at the outer peripheral portion becomes higher and the depth of the valleys becomes deeper than at the inner peripheral portion. That is, the protrusion height of the serrations from the seating surface at the outer peripheral portion is larger than that at the inner peripheral portion.

[0014] In this case, when tightening the screw, the serrations at the outer peripheral portion first bite into the fastening surface, and then the inner peripheral portion abuts against the fastening surface. And when tightening the screw, not only the outer peripheral portion but also the inner peripheral portion abut against and bite into the fastening surface, so that a large seating surface friction torque and biting torque are generated, and the axial force torque decreases by the amount that the seating surface friction torque and biting torque in the total tightening torque increase, resulting in the problem that the axial force decreases. Also, when the screw is tightened, since the entire seating surface abuts against the fastening surface, there is a problem that the force due to the axial force applied to the seating surface is dispersed.

[0015] Also, in the technique of Patent Document 2 as well, similar to the case of Patent Document 1, when tightening the screw, not only the outer peripheral portion but also the inner peripheral portion abut against and bite into the fastening surface, so that a large seating surface friction torque and biting torque are generated, and it becomes difficult to obtain a large axial force. Also, when the screw is tightened, since the entire seating surface abuts against the fastening surface, there is a problem that the force due to the axial force applied to the seating surface is dispersed.

[0016] In addition, in the flange bolt of the technology of Non-Patent Document 1, serrations arranged substantially radially with respect to the axis are formed on the seating surface, and the protruding height of the serrations on the outer peripheral portion from the seating surface is larger than that of the inner peripheral portion. That is, similar to the case where the height of the serrations on the outer peripheral portion of Patent Document 1 is higher than that of the inner peripheral portion, when tightening the screw, not only the outer peripheral portion but also the inner peripheral portion comes into contact with and bites into the fastening surface, resulting in a large seating surface friction torque and biting torque, and the axial force decreases, which is inconvenient. Also, when the screw is tightened, since the entire seating surface comes into contact with the fastening surface, there is an inconvenience that the force due to the axial force applied to the seating surface is dispersed.

[0017] And in the technology of Patent Document 2, in order for the flange to exhibit spring properties by obtaining an appropriate spring constant and deflection amount, there is an inconvenience that materials and treatments for exhibiting spring properties, such as carburizing treatment being formed on the surface with cold-heading carbon steel wire, are required. Furthermore, as described in paragraph 0050 of Patent Document 2, in order to obtain spring properties, there is an inconvenience that it is necessary to use screws with small or extremely small dimensions and sizes, such as screws used in optical devices such as cameras and video cameras.

[0018] Here, consider the case where the shape of the screw described in Patent Document 2 is used, without using materials and treatments for exhibiting spring properties, and using materials for ordinary screws and having ordinary screw sizes. When fastening with such a screw, since the flange has no spring properties, it becomes a screw without anti-loosening function. That is, it is possible to make a screw with a shape of the screw described in Patent Document 2 using a material without spring properties, but in that case, an inconvenience occurs that, despite having a complex shape, it becomes a screw without anti-loosening function and the loosening torque becomes small.

[0019] An object of the present invention is to provide a screw having anti-loosening function on the head of the screw, which can obtain a large loosening torque.

Means for Solving the Problems

[0020] In order to solve the above problems, the present invention adopts the following configuration.

[0021] The present invention relates to a screw having a head provided with a tool engaging portion for rotating the screw, a screw portion integrally formed with the head, and having a locking function on the head. The seating surface of the head is formed in an inverted dish-shaped tapered form, and at least in the vicinity of the outermost circumference of the seating surface, there are formed protruding portions that protrude in the direction of the locking object and are arranged at substantially equal intervals in the circumferential direction. The locking object is made of a synthetic resin material or a soft metal such as aluminum or copper. When the screw having a locking function is fastened to the locking object, the outermost peripheral portion of the seating surface is brought into contact with the surface of the locking object, and the protruding portions near the outermost peripheral portion are configured to bite into the locking object.

[0022] Further, the protruding portion is characterized in that it has a front inclined surface with a small angle in the portion in front of the protruding portion in the direction of tightening the screw.

[0023] Further, the protruding portion is characterized in that it has a locking surface that engages with the locking object at a large angle in the portion behind the protruding portion in the direction of tightening the screw.

[0024] Further, the protruding portion is characterized in that it has a rear inclined surface with a small angle in the portion behind the protruding portion in the direction of tightening the screw.

[0025] Further, the angle of the seating surface with respect to the plane is 3 degrees or more and 10 degrees or less.

[0026] Further, the outer diameter of the head is substantially the same as the outer diameter of a flat washer corresponding to the nominal diameter of the screw.

[0027] Further, the protruding portion is formed in a shape that extends radially with respect to the axis.

[0028] Further, the protruding portion has a flat planar portion where the ridge line portion at the tip of the front inclined surface and the locking surface is flattened, and the corner portion between the front inclined surface and the planar portion is not rounded but angular.

[0029] And the protruding portion is characterized in that at least a part of the front inclined surface has a substantially arc-shaped surface bulging in the direction of the locking object, and at least a part of the rear inclined surface also has a substantially arc-shaped surface bulging in the direction of the locking object.

Advantages of the Invention

[0030] According to the present invention, since it has the above-described features, the following can be achieved.

[0031] A screw having a head provided with a tool engaging portion for rotating the screw, a screw portion integrally formed with the head, and having an anti-loosening function in the head, wherein the seating surface of the head is formed in an inverted dish-shaped taper shape, and at least in the vicinity of the outermost circumference of the seating surface, protruding portions protruding in the direction of the locking object and arranged at substantially equal intervals in the circumferential direction are formed. The locking object is made of a synthetic resin material or a soft metal such as aluminum or copper. When the screw having the anti-loosening function is fastened to the locking object, the outermost peripheral portion of the seating surface abuts against the surface of the locking object, and the protruding portions near the outermost peripheral portion are configured to bite into the locking object. Therefore, when the screw is tightened, since the seating surface has a taper shape, not the entire seating surface but only the outermost peripheral portion of the seating surface and the ring-shaped portion of the protruding portion in the vicinity thereof abut against and bite into the locking object, a large axial force can be obtained. Further, when the screw is tightened, if the seating surface is planar, the entire seating surface abuts against the locking object and the force is dispersed. However, when there is a taper on the seating surface, the force due to the axial force is concentrated only on the outermost peripheral ring-shaped portion, so the locking force by the protruding portion is improved. Moreover, since the ring-shaped portion is located at the outermost peripheral position, there is a distance from the axis, and as a result, a large loosening torque can be obtained.

[0032] In addition, since the protruding portion has a front inclined surface with a small angle at the portion in front of the protruding portion in the direction of tightening the screw, when the screw is tightened, the seating surface friction torque and the biting torque between the protruding object and the surface of the locking object are reduced, and a large axial force can be obtained.

[0033] In addition, since the protruding portion has a locking surface that engages with a locking object having a large angle at the portion behind the protruding portion in the direction of tightening the screw, a large locking force can be obtained by the locking surface, and the loosening torque can be increased.

[0034] In addition, since the protruding portion has a rear inclined surface with a small angle at the portion behind the protruding portion in the direction of tightening the screw, when the screw is loosened after tightening the screw, the surface of the locking object bitten into the locking surface can be shaved and whitening can be eliminated.

[0035] In addition, since the angle of the seating surface with respect to the plane is 3 degrees or more and 10 degrees or less, the inclination is gentle and the difference from the plane is small, and by forming the seating surface in an inverted dish shape exceeding 10 degrees, the process becomes difficult or it becomes difficult to manufacture. It was possible to prevent this.

[0036] In addition, since the outer diameter of the head is substantially the same as the outer diameter of the flat washer corresponding to the nominal diameter of the screw, it was possible to easily replace it with a washer-embedded screw.

[0037] In addition, since the protruding portion is formed in a shape extending radially with respect to the axis, it has become possible to easily make a mold for forming the protruding portion.

[0038] In addition, the protruding portion has a flat planar portion where the ridge line portion at the tip of the front inclined surface and the locking surface is flattened, and the corner portion between the front inclined surface and the planar portion is not rounded but angular. Therefore, when the locking object is a metal with paint or plating, the paint or the like is peeled off at the corner portion for preventing loosening, bites into the internal metal, connects the outer shell of the metal and the frame, etc., and can be electrically conducted.

[0039] And, since the protruding portion has a substantially arc-shaped surface that bulges in the direction of the locking object at least in part on the front inclined surface and also has a substantially arc-shaped surface that bulges in the direction of the locking object at least in part on the rear inclined surface, when the screw is tightened, the seating surface friction torque and the biting torque between the protruding object and the surface of the locking object are reduced, a large axial force can be obtained, and when the screw is loosened, whitening on the surface of the locking object can be prevented.

Brief Description of the Drawings

[0040]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

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Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Embodiments for Carrying Out the Invention

[0041] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, when the head of the screw having an anti-loosening feature is upward and the threaded portion is downward, it will be referred to as the vertical direction. However, the front-back and up-down directions shown below are for convenience of explanation, and the present technology is not limited to and applied in these directions.

[0042] Here, the screw having an anti-loosening feature of the present invention is a screw for fastening a synthetic resin material having an anti-loosening feature, a soft metal such as an aluminum material or a copper material, to the head of the screw. And the seat surface is in an inverted dish-shaped taper shape, and protrusions are formed side by side in the circumferential direction at least near the outermost periphery of the taper-shaped seat surface. By making the seat surface in a taper shape, when the screw is tightened to the object to be locked, not the entire seat surface but the outermost peripheral portion of the seat surface and the protrusions of that portion come into contact with and bite into the object to be locked.

[0043] Here, when the seat surface is flat, as the screw is tightened, the entire seat surface comes into contact with the fastening object, and due to serration or the like biting in, a large seat surface frictional torque or biting torque is generated by the entire seat surface. On the other hand, in the screw with a locking function of the present invention, the seat surface has a tapered shape and is inclined itself. Therefore, unlike the case where the seat surface is flat, only the ring-shaped portion at the outermost periphery of the seat surface and the protruding portion of that portion come into contact with and bite into the locking object. Therefore, the seat surface frictional torque and biting torque during screw fastening are smaller than those in the case where the entire seat surface comes into contact and is flat. According to the Motosh formula showing the relationship between the tightening torque and the axial force described later, the decrease in the axial force is reduced, and as a result, a large axial force can be obtained. Also, when the screw is tightened, if the seat surface is flat, the entire seat surface comes into contact with the locking object and the force is dispersed. However, if there is a taper on the seat surface, the force due to the axial force is concentrated only on the outermost peripheral ring-shaped portion, so the surface pressure increases and the locking force due to the protruding portion is improved. That is, the protruding portion in the ring-shaped portion is pressed against the locking object with a strong force, and the protruding portion firmly bites into and engages with the locking object, generating a large locking force. Moreover, since the ring-shaped portion is located at the outermost periphery, there is a distance from the axis, and a large loosening torque can be obtained.

[0044] That is, the present invention not only simply makes the seat surface tapered, but also forms protrusions arranged in the circumferential direction at least in the vicinity of the outermost periphery of the tapered seat surface to serve as a locking function. The shape of this protrusion may be a small hemispherical shape or a square protrusion-like convex portion, or a convex portion protruding in a continuous rectangular parallelepiped shape or a kamaboko shape arranged substantially radially with respect to the axis.

[0045] Here, if a front inclined surface with a gentle angle is arranged on the protrusion in front of the portion in the direction of tightening the screw, it becomes easier to tighten compared to the case without the front inclined surface, the seating surface friction torque and the biting torque are reduced, and further the axial force increases. Also, if a locking surface with a large angle is arranged on the protrusion behind the protrusion, after tightening, the locking surface biting into the fastening object will act as a locking prevention. That is, if a protrusion having a front inclined surface and a locking surface is provided on the tapered seating surface, due to the synergistic effect of a large axial force and the locking force generated by the locking surface at the outermost peripheral end of the seating surface with a large distance from the axis biting into the fastening object, a large loosening torque can be obtained. However, when trying to loosen the screw, the portion where the locking surface bites into the surface of the fastening object will be scraped off and whitening will occur.

[0046] Also, it may be configured to have a rear inclined surface with a gentle angle on the portion behind the protrusion in the direction of tightening the screw together with the front inclined surface on the protrusion. Since there is no locking surface, the locking force decreases, but since the locking surface does not bite into the surface of the fastening object, it is possible to prevent the surface of the fastening object from being scraped off or whitening from occurring. In this case, since the seating surface is tapered, a large axial force can be obtained, and even with the reduced locking force, a firm loosening torque can be obtained. And for those with serration, they can be used appropriately according to the purpose of using the screw. Then, first, the details of the screw with loosening prevention having serration will be described.

[0047] (First Embodiment) Referring to FIGS. 1 to 4, the screw 1 with loosening prevention (screw with loosening prevention) according to the first embodiment of the present invention will be described. The screw of this embodiment has a protrusion having a front inclined surface 62 (front inclined surface) and a locking surface 61 (locking surface), and has a tapered seating surface provided with serration 6 (protrusion) as the protrusion.

[0048] Figs. 1(A), 1(B), and 1(C) are perspective views showing the configuration of the head 2 (head) and the threaded portion 3 (threaded portion) of the screw 1 having an anti-loosening feature. Fig. 1(A) is a perspective view seen from the upper surface side, Fig. 1(B) is a perspective view seen from the lower surface side, and Fig. 1(C) is a partial enlarged view of part A in Fig. 1(B). Also, Figs. 2(A), 2(B), and 2(C) are three views of the screw 1 having an anti-loosening feature. Fig. 2(A) is a front view, Fig. 2(B) is a top view, and Fig. 2(C) is a bottom view. Also, Fig. 2(D) is a cross-sectional view taken along line BB in Fig. 2(B).

[0049] As shown in Figs. 1 and 2, at the center of the upper surface of the head 2 of the screw 1 having an anti-loosening feature, there is a cross recess as a screw rotation tool engaging portion 4 (tool engaging portion), and the head 2 has a shape of a substantially truss screw. The outer diameter of the head 2 is 5.3 mm when the screw diameter is M5, and it is formed to be substantially the same as the outer diameter of the corresponding flat washer. In this way, the outer diameter of the head 2 is set to a value near the outer diameter of the corresponding flat washer in order to obtain a large-diameter seating surface and to enable easy replacement with a washer-embedded screw.

[0050] Also, the seating surface 5 (seating surface) of the head 2 is formed in an inverted dish-shaped taper shape with an angle of about 6 degrees with respect to the plane, and the seating surface 5 has 24 serrations 6 extending radially from the center portion. The height of the peaks of the serrations 6 is 0.13 mm when the screw diameter is M5. And each serration 6 has a locking surface 61 (locking surface) with a large inclination angle located on the rear end side with respect to the tightening direction of the screw on the screw loosening direction side. Also, on the tightening direction side, it has a front inclined surface 62 (front inclined surface) formed with a gentle and small inclination angle toward the front end side with respect to the tightening direction from the ridge line of this locking surface 61. That is, it is easy to tighten due to the front inclined surface 62, and since the locking surface 61 bites in, it is difficult to loosen.

[0051] First, a screw 1 with an anti-loosening feature is formed by plastic working such as upset forging into a screw having a substantially truss-screw shape with a tapered seating surface 5 having an angle of about 6 degrees with respect to a plane. Next, it is formed by transferring the serration 6 portion, and then surface-treated for manufacturing. Also, the material of the screw 1 with an anti-loosening feature is formed from the same steel material as ordinary screws, but of course, it may be made of other metals if necessary.

[0052] Here, as shown in FIG. 1(C), the locking surface 61 and the front inclined surface 62 of each serration 6 are configured such that their surfaces intersect at approximately 90 degrees. This is to facilitate cutting and the like with a cutting tool or the like when creating a mold for transferring the serration 6 portion, thereby facilitating the creation of this mold. Also, when transferring the serration 6 portion, it functions in the same way as a draft angle in so-called injection molding to make it easier to create the locking surface 61. Of course, the angle of the locking surface 61 may be made steeper, for example, an angle parallel to the axis.

[0053] FIG. 3 is a cross-sectional view showing a state where a screw 1 with an anti-loosening feature is fastened to a locking object 100 (locking object) made of a synthetic resin material. That is, the threaded portion 3 of the screw 1 with an anti-loosening feature is passed through the fastening hole 110 of the locking object 100 and screwed into a threaded hole 210 with burring applied to a frame 200 made of a metal plate, and is in a fastened state.

[0054] As shown in FIG. 3, when the screw 1 with an anti-loosening feature is rotated and tightened, since the seating surface 5 is formed in a tapered shape, only the outermost peripheral portion of the seating surface 5 abuts against the locking object surface 120 which is the surface of the locking object 100. Then, the ring-shaped portion near the outermost peripheral portion of the seating surface 5 of the serration 6 bites into the locking object surface 120, and the outermost periphery of the seating surface 6 abuts against the surface of the locking object 100. Here, the portion of the serration 6 at the outermost periphery of the seating surface 5 bites deepest into the locking object 100.

[0055] Figure 4 is a photograph of the fastening mark 130 on the surface 120 of the locking object 100 when the locking object 100 is an ABS (acrylonitrile-butadiene-styrene) resin plate with a thickness of 6 mm, the screw 1 with anti-loosening using a nut is screwed at a predetermined torque, and then the nut is loosened and removed. As shown in the photograph of Figure 4, the fastening mark 130 has an annular mark 140 which is a circular groove formed by the outermost peripheral part of the seating surface 5 and 24 recessed marks 150 which are recesses formed by the serration 6 of the outermost peripheral part.

[0056] Thus, since the seating surface 5 is formed in an inverted dish-shaped tapered form, as shown in the photograph of Figure 4, when screwing, only the outermost peripheral part of the seating surface 5 and the serration 6 of the outermost peripheral part are pressed against and bite into the surface of the locking object 100. On the other hand, when the seating surface is formed in a flat planar shape, the entire seating surface and its serration will be pressed against the surface 120 of the locking object. Then, compared with the serration screw with a flat seating surface, the screw 1 with anti-loosening has the frictional torque of the seating surface against the locking object and the biting torque by the serration 6 reduced when screwing.

[0057] And when the frictional torque of the seating surface and the screwing torque during screwing are reduced, as will be described later, the axial force torque is improved. Also, when the screw is tightened, if the seating surface 5 is planar, the entire seating surface 5 abuts against the locking object 100 and the force is dispersed, but if there is a taper on the seating surface 5, the force due to the axial force concentrates only on the outermost ring-shaped part, so the locking force by the serration 6 is improved.

[0058] That is, the serration 6 at the outermost peripheral part is pressed against the locking object 100 with a strong force, and the serration 6 bites firmly into the locking object 100, generating a large locking force. Moreover, since the ring-shaped part is at the outermost peripheral position, there is a distance from the axis of rotation. As a result, by using the screw 1 with anti-loosening of this embodiment, a large anti-loosening torque can be obtained.

[0059] Incidentally, there is also a thought that the effect of the outer peripheral portion biting deeply is the same as that of providing serrations 6 on the tapered seat surface 5 and that of providing serrations on the flat seat surface such that the ridges at the outer peripheral portion are higher than those at the inner peripheral portion. Here, in the case of the tapered one, since the seat surface itself has an angle, the serrations near the outer peripheral portion bite in at a large angle, and the ring-shaped portion at the outermost periphery of the seat surface 5 abuts against the surface of the locking object 100. On the other hand, in the case of the flat one, although it surely bites in from the serrations at the outer peripheral portion, eventually the entire seat surface abuts against and bites into the locking object, so as described above, a large difference occurs in the loosening torque. Also, there is a limit to forming the serrations of the flat one high. Note that a tapered surface is provided on a part of the flat seat surface and serrations are provided thereon is also included in the present invention.

[0060] In addition, in the present embodiment, the angle of the seat surface 5 with respect to the plane is set to about 6 degrees, but it may be 3 degrees or more and 10 degrees or less. If it is less than 3 degrees, the inclination is gentle and there is no difference from the plane, and if it exceeds 10 degrees, the process becomes difficult because the seat surface 5 is formed in an inverted dish shape and it becomes difficult to manufacture. Also, the angle of the seat surface 5 with respect to the plane may be 4 degrees or more and 8 degrees or less. If it is 4 degrees or more, the effect of the taper is further increased, and if it is 8 degrees or less, it becomes easier to manufacture.

[0061] In addition, the screw 1 having anti-loosening means is first formed by plastic working such as forging, and then the serration 6 portion is transferred to form it. This is to enable easy manufacturing using conventional techniques. Also, it is not limited to this. For example, when performing plastic working, it is of course possible to form it in a shape such that the outermost peripheral portion of the head 2 is restrained and the outermost peripheral portion is cut with a cylindrical surface. And in this case, by providing the serrations 6 up to the end of the seat surface 5, a larger loosening torque can be obtained.

[0062] In addition, in the embodiment described above, the head 2 has a cross recess, but it goes without saying that it may have a minus-shaped grooved shape, a hexagonal recess, or a star-shaped hexagonal hexalobular recess. Also, although the shape of the head is substantially that of a carriage bolt, it goes without saying that it may be, for example, the shape of a socket head cap screw with a flange, the shape of a binding screw, the shape of a round screw, or the shape of a hexagonal flange bolt.

[0063] Furthermore, although the thread portion 3 of this embodiment shows the form of a normal screw, it goes without saying that it is not limited to this and may be a tapping screw or the like. Also, it goes without saying that the length of the thread portion 3 may be made longer or shorter.

[0064] Also, although the thread pitch 6 of these embodiments has 24 threads or is provided, it goes without saying that this number may be, for example, changed to 16 threads, increased, or decreased. Also, for screws with a large outer diameter, the number of threads of the thread pitch 6 may be decreased, and for small screws, the number may be decreased to make it easier to manufacture.

[0065] Also, in this embodiment, the thread pitch 6 extends radially from the center of the seating surface 5. The reason the bulging portion 7 extends from the center is that, for example, when fastening a locking object 100 made of a soft material such as a rubber sheet-like elastic body, the seating surface 5 will deeply bite into the locking object 100. At this time, the bulging portion 7 near the center also bites into the locking object 100, and a greater anti-loosening effect can be obtained. However, it goes without saying that the thread pitch 6 may not extend from the center, and the thread pitch 6 may not be provided at the center of the seating surface 5, but may be provided, for example, from the middle or only near the outermost peripheral portion of the seating surface 5. This is because when the locking object 100 is made of resin or the like, a sufficient effect can be obtained.

[0066] Also, although the head 2 is a head with a flange and the outer diameter of the flange portion 22 is set to be near the outer diameter of a flat washer corresponding to the screw diameter, this flange may be made wider. The wider flange not only prevents the seating surface from sinking into the locking object 100, but in the case of the present invention, the position where the bulging portion 7 bites in becomes farther from the axis of the screw, and a greater anti-loosening effect can be obtained. It is also effective in improving the axial force.

[0067] In addition, in the case of this embodiment, although there is only one type of height of the crest of the serration 6, a screw 1 having a second anti-loosening feature with a higher crest height may be prepared. When there is a serration 6 on the seating surface 5, if the screw 1 having an anti-loosening feature is loosened after tightening, the surface of the locking object 100 is scraped off by the serration 6. Then, even if the same screw 1 having an anti-loosening feature is tightened again, since the surface of the locking object 100 has been scraped off, the serration 6 does not bite into the locking object 100, and sufficient anti-loosening torque cannot be obtained. In such a case, by using the screw 1 having a second anti-loosening feature, the serration 6 bites deeper into the surface of the locking object 100, so that sufficient anti-loosening torque can be obtained again.

[0068] (Second Embodiment) Referring to FIGS. 5 to 6, a second embodiment of the present invention will be described. The screw of this embodiment is also a protrusion having a front inclined surface and a locking surface, similar to the first embodiment, and has a tapered seating surface provided with a serration 6 (protrusion) as the protrusion. In this second embodiment, the shape of the upper part of the head 2 and the seating surface 5 of the first embodiment is changed. In particular, the front inclined surface 62 of the serration of the seating surface is changed from a planar shape to a substantially arc-shaped curved surface shape. Hereinafter, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted, and only the different parts will be described.

[0069] FIGS. 7(A), (B), and (C) are perspective views showing the configuration of the head 2 and the screw portion 3 of the screw 1 having an anti-loosening feature. FIG. 5(A) is a perspective view seen from the upper surface side, FIG. 5(B) is a perspective view seen from the lower surface side, and FIG. 5(C) is a partially enlarged view of part C of FIG. 5(C). FIGS. 6(A), (B), and (C) are three views of the screw 1 having an anti-loosening feature. FIG. 6(A) is a front view, FIG. 6(B) is a top view, and FIG. 6(C) is a bottom view. FIG. 6(D) is a cross-sectional view taken along line DD of FIG. 6(B), and FIG. 6(E) is a partially enlarged view of part E of FIG. 6(A).

[0070] As shown in FIGS. 5 and 6, the upper part of the head 2 has a cross hole similar to that of the first embodiment. However, in this embodiment, it has a substantially hemispherical shape and is similar in shape to a breather screw or a truss screw. The outer diameter of the head 2 is formed to be substantially the same as the outer diameter of the flat washer corresponding to the screw diameter. This is because it can be easily replaced with a washer-embedded screw.

[0071] As shown in FIGS. 5(B)(C) and 6(D)(E), the surface at the position connecting the valleys of the serrations 6 of the head 2 is formed in an inverted dish-shaped taper with an angle of about 6 degrees with respect to the plane. On the seating surface 5, there are 16 ridges extending radially from the center, and serrations 6 with a ridge height of 0.2 mm are formed. Each serration 6 is formed with a locking surface 61 at a large angle located on the rear end side with respect to the tightening direction of the screw, and a front inclined surface 62 having a substantially arc-shaped curved surface located on the front end side. In this embodiment, the surface at the position connecting the valleys is referred to as the seating surface 5.

[0072] As shown in FIG. 6(E), when each serration 6 is viewed from the outer peripheral side of the screw head 21, there is a locking surface 61 having an angle of approximately 70 degrees with respect to the seating surface 5 indicated by the two-dot chain line, and a front inclined surface 62 having a substantially arc-shaped surface formed to bulge from the top of the ridge toward the locking object side.

[0073] Here, since the front inclined surface 62 near the top of the ridge of the serration 6 is a flat surface or a gently sloping and loose-angle surface close to the horizontal plane, the locking force decreases due to the lack of an angle. However, the seating surface 5 has a taper, and the outermost peripheral portion of the serration 6 bites into the surface 120 of the locking object at the taper angle, so a predetermined locking force is ensured. In addition, because there is a smooth surface, it becomes easier to slide, the seating surface friction torque and the biting torque during screw fastening are further reduced, the decrease in axial force is less, and the effect of improving the axial force occurs.

[0074] It should be noted that although the locking surface 61 has been described as having an angle of approximately 70 degrees with respect to the seating surface 5, it is not limited to this, and of course, the angle of the locking surface 61 can be made steeper, for example, an angle parallel to the axis.

[0075] Also, here, the small angle and gentle angle of the front inclined surface 62 mean that the angle formed between the front inclined surface 62 and the surface of the locking object 100 is preferably 0 degrees or more and 40 degrees or less, but any angle at which the front inclined surface 62 functions may be used. Further, the large angle of the locking surface 61 means that the angle formed between the locking surface 61 and the surface of the locking object 100 is preferably 60 degrees or more and 90 degrees or less, but any angle at which the locking surface 61 functions may be used.

[0076] (Third Embodiment) Referring to FIGS. 7 and 8, a third embodiment of the present invention will be described. The screw of this embodiment is also a protruding portion having a front inclined surface and a locking surface, similar to the first embodiment, but a flat surface portion is provided between the front inclined surface and the locking surface. Here, such a protruding portion will also be referred to as a serration 6 (protruding portion). This third embodiment is mainly used for an outer casing made of a soft metal such as an aluminum plate or the like that has been anodized, such as an aluminum material or a copper material, and whose surface has been painted or plated. Hereinafter, the same parts as those in the first embodiment will be denoted by the same reference numerals, and the description thereof will be omitted, and only the different parts will be described.

[0077] FIGS. 7(A), (B), and (C) are perspective views showing the configuration of the head 2 and the screw portion 3 of the screw 1 having an anti-loosening function. FIG. 7(A) is a perspective view seen from the upper surface side, FIG. 7(B) is a perspective view seen from the lower surface side, and FIG. 7(C) is a partially enlarged view of the F portion in FIG. 5(B). Further, FIGS. 8(A), (B), and (C) are three views of the screw 1 having an anti-loosening function. FIG. 8(A) is a front view, FIG. 6(B) is a top view, and FIG. 8(C) is a bottom view. Further, FIG. 8(D) is a cross-sectional view taken along the GG line in FIG. 8(B), and FIG. 8(E) is a partially enlarged view of the H portion in FIG. 8(A).

[0078] As shown in FIGS. 7 and 8, the upper part of the head 2 has the same shape as that in the second embodiment, has a cross-shaped hole, and has a shape similar to a Phillips screw or a truss screw. The outer diameter of the head 2 is formed to be substantially the same as the outer diameter of a flat washer corresponding to the screw diameter. This is because it becomes possible to easily replace it with a screw with a built-in washer.

[0079] As shown in FIGS. 7(B) and (C) and FIGS. 8(D) and (E), the surface at the position connecting the valleys of the serrations 6 of the head 2 is formed in an inverted dish-shaped tapered form with an angle of approximately 6 degrees with respect to the plane. On the seating surface 5, there are 16 ridges extending radially from the center, and serrations 6 with a ridge height of 0.2 mm are formed. In this embodiment, the surface at the position of the valley connecting the valleys is referred to as the seating surface 5.

[0080] As shown in FIG. 8(E), when each serration 6 is viewed from the outer peripheral side of the screw head 21, it has a shape cut by a top plane 63 such that the pointed top portion of the substantially saw blade-shaped tip is flattened. In other words, each serration 6 has a flat top plane 63 where the leading edge portion of the ridge line between the front inclined surface 62 and the locking surface 61 is flattened. That is, when each serration 6 is viewed from the outer peripheral side, it has a substantially trapezoidal shape with the seating surface 5 as the lower base and the top plane 63 as the upper base. And each serration 6 has a locking surface 61 located on the rear end side with respect to the tightening direction of the screw of the top plane 63 and formed at a large angle of approximately 70 degrees, and a front inclined surface 62 located on the front end side and inclined at an angle of approximately 20 degrees.

[0081] Here, the ridge between the front inclined surface 62 and the top plane 63 is not rounded and remains angular. When tightening the screw, due to the taper on the seating surface 5, the outermost corner portion first comes into contact with the surface of the locking object 100. And when the locking object 100 is an anodized aluminum plate, the anodized coating on the surface is peeled off at this corner and bites directly into the inner aluminum plate. The same applies when it is painted.

[0082] This is for grounding a part of the outer casing of an electronic device or the like when the outer casing is made of metal by means of a locking screw. That is, an anodized film or the like is a good electrical insulator, and it is difficult to electrically connect the outer casing and the frame simply by fixing the outer casing with a screw. Therefore, the screw 1 with anti-loosening function of the present embodiment is used to peel off the anodized film or the like at the corner part of the anti-loosening, bite directly into the internal aluminum plate, connect the outer casing and a metal frame or the like, and make them electrically conductive.

[0083] Here, although the locking surface 61 and the front inclined surface 62 are in a substantially orthogonal relationship, this is to facilitate the manufacture of the mold for processing the serration 6. Here, although it has been described that the locking surface 61 has an angle of approximately 70 degrees with respect to the seating surface 5, it is not limited thereto, and of course, the angle of the locking surface 61 can be made steeper, for example, an angle parallel to the axis.

[0084] Also, the top plane 63 of the present embodiment may be omitted, and it may be in the form of a normal serration with only the front inclined surface 62 and the locking surface 61. If the inclination of the front inclined surface 62 is relatively large, the plating and painting can be peeled off by the sharp top, and the top can be bitten into the base metal.

[0085] (Fourth Embodiment) Referring to FIGS. 9 to 12, a fourth embodiment of the present invention will be described. The protruding part of the present embodiment is configured to have a rear inclined surface 64 (rear inclined surface) with a gentle angle at the part behind the protruding part in the direction of tightening the screw, together with the front inclined surface.

[0086] In this embodiment, the front inclined surface 62 is formed in a substantially arc shape that bulges in the direction of the locking object 100, and the rear inclined surface 64 is also formed in a substantially arc shape that bulges in the direction of the locking object 100. The protruding portion is formed in a continuous substantially arc shape combining the front inclined surface and the rear inclined surface, and has a shape that protrudes so as to bulge in the direction of the locking surface. That is, the front inclined surface 62 and the rear inclined surface 64 are integrated into a curved surface and are formed in a substantially arc shape that protrudes so as to bulge from the seating surface. Therefore, such a protruding portion will be referred to as the bulging portion 7 (protruding portion). Hereinafter, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted, and only the different parts will be described.

[0087] FIGS. 9(A) and 9(B) are perspective views showing the configuration of the head 2 and the screw portion 3 of the screw 1 having an anti-loosening function. FIG. 9(A) is a perspective view seen from the upper surface side, and FIG. 9(B) is a perspective view seen from the lower surface side. Further, FIG. 9(C) is an enlarged view of the J portion of FIG. 9(B). As shown in FIG. 9(A), at the center of the upper surface of the head 2 of the screw 1, there is a cross-shaped hole as the screw rotation tool engaging portion 4, and the screw 1 as a whole has a shape of a substantially binding screw with a large diameter.

[0088] As shown in FIG. 1(B), the seating surface 5 of the head 2 is formed in an inverted dish-shaped taper shape, and the seating surface 5 has six bulging portions 7 with a predetermined width that bulge downward and extend radially from the center portion. The circumferential cross-section of the bulging portion 7 at the portion of the predetermined width is formed in a substantially arc shape continuous from the seating surface 5, and the tip portion at the outer peripheral portion also has a substantially arc surface.

[0089] Here, the angle of the inverted dish-shaped taper-shaped seating surface 5 with respect to the plane is about 6 degrees. When the diameter of the screw portion 3 is 5 mm, the bulging surface of the portion with the predetermined width is a large arc surface with a radius of about 5 mm, and is a substantially arc-shaped surface that bulges with a large radius.

[0090] As shown in Fig. 9(C), the leading end portion of the outer peripheral portion of the bulging portion 7 is shaped as if it were cut by the outermost peripheral surface continuous with the upper surface of the head portion 2. And at the outermost peripheral portion of the bulging portion 7, a bulging tip portion 8 that bulges downward from the seating surface 5 is formed.

[0091] Fig. 10 is a cross-sectional view showing a state where a screw 1 having an anti-loosening function is fastened to a locking member 100 made of a synthetic resin material. That is, the screw portion 3 of the screw 1 having an anti-loosening function is passed through the fastening hole 110 of the locking member 100 and screwed into the screw hole 210 with burring provided on the frame 200 made of a metal plate, and is in a fastened state.

[0092] As shown in Fig. 10, when the screw 1 having an anti-loosening function is rotated and tightened, since the seating surface 5 has an inverted dish shape, first, the bulging portion 7 of the outer peripheral portion abuts against and digs into the surface of the locking member 100. And then, the leading end portion of the seating surface 5 abuts against the surface of the locking member 100.

[0093] The photograph in Fig. 11 shows the state of the fastening marks 130 attached to the surface of the locking member 100 when the screw is loosened and removed after the screw 1 having an anti-loosening function is fastened. As shown in Fig. 11, the fastening marks 130 include an annular mark 140 which is a circular groove shape formed by the outermost peripheral portion of the seating surface 5 and six recessed marks 150 which are six recesses formed by the six bulging portions 7. Also, at the outermost peripheral position of the fastening marks 130 facing the tip bulging portion 7, six tip bulging portion marks 160 which are recesses formed by the tip bulging portion 7 are attached.

[0094] Thus, since the seating surface 5 is formed in an inverted dish-shaped tapered form, as shown in Figs. 10 and 11, the six bulging portions 7 at the outer peripheral portion far from the axial center of the screw dig into the locking member 100, so that it is an anti-loosening with a large torque. And the outermost peripheral portion of the seating surface 5 abuts against the surface of the locking member and is firmly held by the axial force. In this way, a screw for fastening a synthetic resin material capable of obtaining an axial force while preventing loosening of the screw was obtained.

[0095] In addition, since the portion of the bulging portion 7 facing the locking member 100 is formed in a substantially arc shape, the loosening prevention force is weaker than that of serration with claws. However, by forming the seating surface 5 in an inverted dish shape, sufficient loosening prevention could be achieved. Further, since the portion of the bulging portion 7 biting into the surface of the locking member 100 when the screw is fastened is formed in a substantially arc surface shape, as shown in FIG. 3, it was possible to prevent the surface of the locking member from being scraped and whitened when the screw was loosened.

[0096] And since the bulging tip portion 8 located at the outermost peripheral position of the seating surface bulges downward from the seating surface, it bites into the locking member 100, and the tip bulging portion mark 150 is formed at the outermost peripheral portion of the annular mark 130. Therefore, it is possible to firmly bite into the locking member 100 at the position farthest from the axis of the screw and to prevent loosening with a larger torque.

[0097] FIGS. 12(A) to (F) schematically show the screw 1 with anti-loosening in the present embodiment. In FIG. 12, (A) is a front view, (B) is a plan view, (C) is a bottom view, and (D) is a right side view. Further, in FIG. 4, (E) shows a cross section taken along line HH in (C), and (F) shows a cross section taken along line JJ in (C). Note that the rear view is the same shape as the front view, and the left side view is the same shape as the right side view, and the description thereof is omitted.

[0098] In the above description, it was assumed that the bulging portion 7 bites into the locking member 100 to prevent loosening, and the outermost peripheral portion of the seating surface 5 abuts against the surface of the locking member to obtain an axial force. This is mainly in this sense. Of course, the axial force is also obtained by the bulging portion 7 and the like.

[0099] In addition, in the present embodiment, the angle of the seating surface 5 with respect to the plane is about 6 degrees, but it may be 3 degrees or more and 10 degrees or less. If it is less than 3 degrees, the inclination is too gentle and there is no difference from the plane. If it exceeds 10 degrees, the process becomes difficult to form the seating surface 5 in an inverted dish shape, making it difficult to manufacture.

[0100] In addition, when the diameter of the threaded portion 3 is 5 mm, the portion of the bulging portion 7 having a predetermined width has an arc surface with a width of about 3.4 mm and a radius of about 5 mm. That is, the radius of the arc surface in the cross section cut by a plane perpendicular to the straight line passing through the axis on the seat surface 5 is about 5 mm. An arc surface is also formed at the outermost peripheral portion of the portion having the predetermined width, and the bulging portion 7 protrudes about 0.2 mm below the lowermost end of the seat surface 5.

[0101] Here, the radius of the arc surface of the parallel portion is preferably about 2 mm to 8 mm. This is because when the radius of the arc surface is small, whitening is likely to occur, and when the radius is large, it is difficult to be a loosening stopper. That is, if the diameter of the screw is D, the radius of the arc surface of the portion having the predetermined width of the bulging portion 7 is preferably 2 / 5D to 8 / 5D.

[0102] In addition, in the present embodiment, the bulging portion 7 extends radially from the central portion of the seat surface 5. The reason why the bulging portion 7 extends from the central portion is that, for example, when fastening a locking object 100 made of a soft material such as a rubber plate-like elastic body, the seat surface 5 will bite deeply into the locking object 100. At this time, the bulging portion 7 near the central portion also bites into the locking object 100, and a greater loosening prevention effect can be obtained. In addition, there is also an effect that the mold for molding the screw is easy to make.

[0103] In addition, since only the outer peripheral portion of the bulging portion 7 actually abuts against and bites into the locking object 100, it may be shaped by removing the portion having a predetermined width extending radially. Of course, for example, a substantially elliptical bulging portion 7 may be provided, and only the outermost peripheral portion thereof may be configured to abut against and bite into the locking object 100.

[0104] (Fifth and Sixth Embodiments) Referring to FIG. 13, the fifth and sixth embodiments of the present invention will be described. The protruding portion 9 (protruding portion) of these embodiments has a small convex shape protruding from the seat surface near the outermost peripheral portion. Hereinafter, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted, and only the different parts will be described.

[0105] Figure 13 is an enlarged partial perspective view of the screw 1 having an anti-loosening feature as seen from the bottom side. As shown in Figure 13, the screw 1 having an anti-loosening feature has a cross-hole (not shown) as a screw rotation tool engagement portion 4, and has a head 2 in the shape of a flanged head composed of a screw head portion 21 having a shape of a substantially pan-head screw and a flange portion 22. The outer diameter of the head 2 is formed to be substantially the same as the outer diameter of the corresponding flat washer, and the seating surface 5 is formed in an inverted dish-shaped taper shape with an angle with respect to the flat surface of about 6 degrees.

[0106] Figure 13(A) shows the fifth embodiment, and has a protruding portion 9 that protrudes substantially hemispherically on the seating surface near the outermost peripheral portion. When the screw is tightened, the protruding portion 9 bites into the surface of the locking object 100 and acts as a locking force. If the tip of the protruding portion 9 is formed, for example, in a conical shape or a pointed shape, it will work effectively when the locking object 100 is made of a soft metal with paint or plating as described in the third embodiment. That is, by the protruding portion 9 peeling off the paint or plating and biting in, the outer casing and the frame can be electrically connected.

[0107] Note that the shape of the protruding portion 9 is substantially hemispherical, but it is not limited to this, and for example, it may be a short cylindrical shape. The main point is that as long as the seating surface near the outermost peripheral portion is not simply a tapered shape but a protruding protruding portion 9 is formed, it is possible to bite into the surface of the locking object 100 when the screw is tightened and exert a strong locking force. Also, it goes without saying that the number of the protruding portions 9 may be reduced or increased, and the same applies to the following embodiments.

[0108] Further, FIG. 13(B) shows the sixth embodiment, in which the protruding portion 9, which is a convex portion in the shape of kamaboko (fish cake) obtained by vertically cutting a cylinder in half, is configured such that one end is along the outermost circumference and they are arranged radially. Also in this case, when the screw is tightened, the protruding portion 9 bites into the surface of the locking object 100 and acts as a locking force. Since one end of the protruding portion 9 is configured to be along the outermost circumference, the distance from the axis is large, and a locking force larger than that in the fifth embodiment acts. If the shape of the protruding portion 9 is a triangular prism or a prismatic shape, the metal outer casing and the frame or the like can be electrically connected.

[0109] Note that although the protruding portions 9 are arranged radially, the present invention is not limited to this. They may be arranged at a predetermined angle with respect to the outermost peripheral portion, or the shape of the protruding portions 9 may have a curve when viewed from the locking object side, or may be configured in a spiral shape.

[0110] (Seventh and Eighth Embodiments) With reference to FIG. 14, the seventh and eighth embodiments of the present invention will be described. The protruding portion 9 (protruding portion) in these embodiments is formed in a protruding shape having a front inclined surface 62 and a locking surface 61. Hereinafter, the same parts as those in the seventh embodiment are denoted by the same reference numerals, and the description thereof is omitted, and only the different parts will be described.

[0111] FIG. 14(A) shows the seventh embodiment, in which the protruding portions 9 having a front inclined surface 62 with an arcuate surface bulging toward the locking object 100 side and a locking surface are arranged at substantially equal intervals on the seating surface near the outermost peripheral portion. Here, since the front inclined surface 62 has an arcuate surface bulging outward, as in the second embodiment, the resistance force received from the locking object 100 is weakened, it becomes easier to tighten, and a larger axial force can be obtained.

[0112] Further, FIG. 14(B) shows the eighth embodiment, in which projecting portions 9 each having a front inclined surface 62 with an arcuate surface that is concave inward on the seating surface near the outermost peripheral portion and a locking surface 61 are arranged at substantially equal intervals. Here, since the front inclined surface 62 has an arcuate surface that is concave inward, the ease of tightening is reduced, but the tip of the projecting portion 9 becomes sharper and bites firmly into the locking object, so that the locking force can be improved.

[0113] (Ninth and Tenth Embodiments) Referring to FIG. 15, the ninth and tenth embodiments of the present invention will be described. The projecting portion 9 (projecting portion) of these embodiments has a rear inclined surface 64, which is an inclined surface with a gentle angle, arranged at the rear portion of the projecting portion 9 in the direction of tightening the screw, together with the front inclined surface 62. Hereinafter, the same parts as those in the seventh embodiment will be denoted by the same reference numerals, and the description thereof will be omitted, and only the different parts will be described.

[0114] FIG. 15(A) shows the ninth embodiment, which has a projecting portion 9 having a front inclined surface 62 along the outermost periphery, a top plane 63, and a rear inclined surface 64. That is, when viewed from the side, it has a substantially trapezoidal shape, and the two oblique sides of the trapezoid are formed to have a gentle inclination. Here, it is assumed that the ridge lines between the top plane 63, the front inclined surface 62, and the rear inclined surface 64 are joined by a curved surface rather than an angle. Since the top plane 63 has the rear inclined surface 64 instead of the locking surface 61 at the rear portion of the projecting portion 9, when the screw is loosened, there will be no shaving or whitening of the surface of the locking object 100 by the locking surface 61.

[0115] Further, FIG. 15(B) shows the tenth embodiment, in which the front inclined surface 62 is formed in a substantially arcuate surface shape that bulges in the direction of the locking object 100, the rear inclined surface 64 is also formed in a substantially arcuate surface shape that bulges in the direction of the locking object 100, the projecting portion is formed in a continuous substantially arcuate surface shape combining the front inclined surface and the rear inclined surface, and has a shape that projects so as to bulge in the direction of the locking surface.

[0116] That is, the portion of the seat surface 5 is formed by connecting the front inclined surface 62, the top flat surface 63, and the rear inclined surface 64 with a substantially arc-shaped curved surface that is continuous, and the valley portion is also connected with a curved surface. When viewed from the side, it has the shape of a protruding portion 9 that protrudes in a wavy shape. Since the seat surface 5 is configured in a tapered shape, the outermost peripheral portion bites into the surface of the locking object 100, but there is no shaving or whitening due to the locking surface 61.

[0117] This tenth embodiment and the fourth embodiment are examples of those having a substantially arc-shaped surface that bulges in the direction of the locking object at least partially on the front inclined surface 62, and also having a substantially arc-shaped surface that bulges in the direction of the locking object at least partially on the rear inclined surface. That is, here, the front inclined surface 62, the top flat surface 63, and the rear inclined surface 64 are connected with a substantially arc-shaped curved surface that is continuous. Of course, it is also possible to leave a part of the top flat surface 63 instead of a continuous surface.

[0118] Here, the shape of the protruding portion 9 is wavy when viewed from the side, but it is not limited to this. Of course, for example, when viewed from the side, it may have a jagged shape or the like.

[0119] By the way, products with the screw 1 having anti-loosening are transported, stored, unloaded, and used in a vehicle interior or a container, etc., from a scorching place to a frigid place. Also, at that time, they are subjected to many vibrations and impacts. Under such harsh conditions, experiments and measurements were conducted to see if the screw 1 having anti-loosening has sufficient loosening torque or a loosening torque and can be used. Therefore, the report is as follows. In the following experiments, the locking object 100 was made of resin.

Example

[0120] Vibration was applied in a vibration test after a heat cycle test, and then the loosening torque was measured, so the results are reported. That is, we examined whether the serrated tapered screw (first embodiment) and the tapered screw with a bulging portion (fourth embodiment) of the product of the present invention can correspond to a washer-embedded screw (or a small screw with SW+PW embedded) called a Sems screw, in which a spring washer and a flat washer are incorporated into a small pot screw. In addition, for comparison, a small pot screw and a screw with only a taper (Comparative Example 1) were added, and actual experiments and measurements were conducted. The serrated tapered screw (first embodiment) has 24 serrations as described in the first embodiment, and has a head shape of a serrated head composed of a screw head 21 having a shape substantially similar to that of a small pot screw and a flange portion 22. However, in the following examples, it is expressed as the first embodiment.

[0121] As the screw with only a taper (Comparative Example 1), a screw having a tapered seating surface 5 formed by plastic working was used without transferring the serration 6 portion. A tapered screw without serration 6 was created for the screw 1 having a locking function and used in this test.

[0122] First, five pieces each of the small pot screw, the washer-embedded screw (small screw with SW+PW embedded), the screw of Comparative Example 1, the screw 1 with a locking function of the fourth embodiment, and the screw 1 with a locking function of the first embodiment, all of M5×12, were prepared. Then, these screws were fixed to an ABS resin plate with a thickness of 6 mm having a drilled pilot hole using an M5 hexagon nut with a tightening torque of 15 kgf·cm to prepare test pieces for this experiment.

[0123] Then, as a heat cycle test, these test pieces were placed in an environment of -20°C over 10 minutes from room temperature and held for 60 minutes, then placed in an environment of 80°C over 25 minutes and held for 60 minutes, and then left at room temperature for 24 hours or more. Next, as a vibration test, vibration was applied to each of the XYZ axes by a vibration testing machine. That is, vibration was applied for 3 hours in the X-axis direction (vertical direction), and for 1.5 hours each in the Y-axis direction (left-right direction) and the Z-axis direction (front-back direction). Then, a loosening test was conducted. For this loosening test, a PC torque analyzer (registered trademark) manufactured by Vectorix Co., Ltd. and a screw torque graphic analysis system were used. Incidentally, the subsequent tightening tests and loosening tests were also conducted using the same equipment.

[0124] The data of the results of this loosening test accompanied by the vibration test are shown in Table 1 of Fig. 16. As shown in Table 1 of Fig. 7, first, in the case of the small pan head screw, compared with the washer-inserted screw, the loosening torque (TL) is small and the loosening work amount (EL) is also small. This is presumably because the diameter of the head of the screw is small and the seating surface is flat, so the frictional force between the seating surface of the screw and the surface of the locking object 100 becomes small, resulting in the screw being loosened significantly by vibration. In any case, it is inappropriate to use the small pan head screw as an alternative to the washer-inserted screw.

[0125] Next, when the locking screw is the washer-inserted screw, the loosening torque (TL) is larger than that in the case of the small pan head screw. This is presumably because the diameter and area of the flat washer in contact with the surface of the test piece are large, and the frictional force with the surface of the test piece becomes large. However, the loosening torque with respect to the tightening torque is small. Incidentally, the reason why the loosening work amount (EL) is very large is presumably that due to the spring force of the spring washer, after the screw is loosened once, the work amount is increased to prevent the screw from loosening further and falling off. And in order to be used as an alternative to the set screw, it is necessary to be at least larger than this loosening torque (TL).

[0126] In the case of the tapered screw of Comparative Example 1, the loosening torque (TL) is better than that of the pot small screw, but less than half of that of the washer-embedded screw. This is because although the outer diameter of the tapered screw is larger than that of the pot small screw, due to the taper on the seating surface 5, only the portion near the outermost circumference is in contact with the surface of the locking object 100, resulting in a small frictional force. Therefore, it is considered that this is the reason why the screw loosened significantly due to vibration. In any case, it is inappropriate to use the tapered screw as an alternative to the washer-embedded screw.

[0127] In the case of the tapered screw with a bulging portion of the fourth embodiment and the serrated tapered screw of the first embodiment, the loosening torque (TL) is more than twice that of the washer-embedded screw in the case of the fourth embodiment and about four times that of the first embodiment, which is extremely large. That is, from this experiment, the products of the fourth embodiment and the first embodiment can be used as alternatives to the washer-embedded screw. Also, as the data after applying heat cycle and vibration, it is considered that they have sufficient values for use in fastening products.

Example

[0128] In Example 1, vibration was applied in the vibration test after the heat cycle test. In Example 2, after the same heat cycle test, instead of the vibration test, impact was applied in the impact resistance test, and the results are reported. This time, the pot small screw was not measured, and experiments and measurements were actually conducted using the washer-embedded screw (or SW+PW embedded small screw), the screw with only a taper (Comparative Example 1), the tapered screw with a bulging portion (the fourth embodiment), and the serrated tapered screw (the first embodiment).

[0129] First, five pieces each of the washer-embedded screw (SW+PW embedded small screw), Comparative Example 1, the fourth embodiment, and the first embodiment, all of M5×12, were prepared. Then, these screws were fixed to a 6-mm-thick ABS resin plate with a drilled pilot hole using an M5 hex nut with a tightening torque of 15 kgf·cm to prepare test pieces for this experiment.

[0130] First, as a heat cycle test, in the same manner as in Example 1, these test pieces were placed in a -20°C environment over 10 minutes from room temperature, held for 60 minutes, placed in an 80°C environment over 25 minutes, and held for 60 minutes, and then left at room temperature for 24 hours or more. Next, as an impact resistance test, impacts of 50G, 100G, and 500G were applied by an impact tester in the X-axis, Y-axis, and Z-axis directions of the screw, that is, in the up-down, left-right, and front-back directions, respectively, for testing. And then, a loosening test was conducted. The data of the results of this loosening test are shown in Table 2 of FIG. 17. Here, the maximum torque required to loosen the screw was compared with the tightening torque during tightening, and how much it loosened as a result of the test was expressed as a loosening rate.

[0131] As shown in Table 2 of FIG. 8, first, in the case where the locking screw is a washer-embedded screw (or a small screw with SW + PW embedded), the loosening torque with respect to the tightening torque is small, and the loosening rate is large. This is considered to be the influence of the impact test. In order to replace the washer-embedded screw, at least it is necessary to be smaller than the loosening rate of this loosening torque (TL) and not have a large loosening.

[0132] In the case of the screw with only a taper in Comparative Example 1, although the loosening rate drops significantly from -41% to -28%, it shows a good value compared to the washer-embedded screw. The screw with only a taper showed bad values in the test with the vibration test of Example 1, but showed relatively strong results in the test with the impact test.

[0133] In the case of the tapered screw with a bulging portion of the fourth embodiment, the loosening rate is about -10%, which is an extremely good value without even comparing with the value of the washer-embedded screw. In the impact test, it was found that the bulging portion of the seat surface of the second invention product effectively acts on the loosening of the screw.

[0134] In the serrated tapered screw of the first embodiment, the loosening rate is from 18% to 34%, and the loosening torque when the screw is loosened is greater than the tightening torque when the screw is tightened. Moreover, the ratio is larger when it is 500G. It is considered that by applying an impact, the serration bites deeper into the surface of the locking object and adheres tightly, resulting in such values. That is, from the results of this experiment, those of the fourth embodiment and the first embodiment can be substituted for the washer-embedded screw. Also, it is considered that the values are sufficient for use in fastening products.

[0135] Thus, in the screws with anti-loosening of the fourth embodiment and the first embodiment, a much larger loosening torque (TL) is obtained compared to the washer-embedded screw, and it is difficult to loosen. Furthermore, it eliminates the problems in the production site of the washer-embedded screw. Therefore, it was confirmed that the screw with anti-loosening of the product of the present invention can replace the washer-embedded screw.

[0136] The tapered screw with a bulging portion of the fourth embodiment and the serrated tapered screw of the first embodiment have a plurality of bulging portions, serrations, that is, irregularities, at least on the outermost peripheral portion of the seating surface of the tapered screw. It can be seen that the irregularities on the outermost peripheral portion are also long in the distance from the axis of the screw, and it is easy to obtain a large torque. However, considering that this large loosening torque (TL) is obtained, it is thought that it may be related to the axial force when the screw is tightened, and an experiment was conducted in Example 3 next.

Example

[0137] As Comparative Example 2, a commercially available screw with a serration and a flat seat surface described in Non-Patent Document 1 was obtained, and an experiment was conducted to compare it with the tapered screw with serration of the first embodiment, and the results are reported. The height of the serration crest is 0.3 mm for the commercially available screw of Comparative Example 2, while it is 0.13 mm for that of the first embodiment. Also, the height of the serration crest is higher at the outer peripheral portion than at the inner peripheral portion. First, as an axial force test for these screws, the tightening axial force when tightened with a predetermined torque was measured, and the results are summarized in Table 3 of FIG. 18. Then, the loosening torque was measured and summarized in Table 4 of FIG. 19.

[0138] As shown in Table 3 of FIG. 18, the tightening axial force when tightened with a predetermined tightening torque was measured. As a result, the tightening axial force of the commercially available screw with a serration and a flat seat surface of Comparative Example 2 is about 0.65 kN, while that of the tapered screw with serration of the first embodiment is about 1.1 kN, and the first embodiment obtained a tightening axial force about 70% larger.

[0139] Also, as shown in Table 4 of FIG. 17, when the loosening torque was measured, a larger value was obtained for the loosening torque than for the tightening torque for both screws. The loosening torque of the commercially available screw with a serration and a flat seat surface of Comparative Example 2 is about 19.4 kgf·cm, while that of the tapered screw with serration of the first embodiment is about 29.6 kgf·cm, and the first embodiment obtained a loosening torque about 50% larger. That is, the first embodiment had a tightening axial force about 70% larger and a loosening torque about 50% larger than Comparative Example 2.

[0140] By the way, generally, in the case of a screw with a serration and a flat seat surface, since the seat surface is flat, a large number of serrations can be provided on both the outer peripheral portion and the inner peripheral portion, and the serrations can bite deeply into the fastening surface, so it is considered that a large loosening torque can be obtained. On the other hand, in the tapered screw with serrations of the present invention, since the seating surface is tapered, only the round ring-shaped portion at the outermost periphery of the seating surface contacts the fastening surface, and only the serrations in this portion bite into the fastening surface. At first glance, this seems to reduce the number of serrations biting into the seating surface, resulting in a smaller loosening torque. However, the experimental results showed that the screw of the present invention with fewer biting serrations obtained a larger loosening torque.

[0141] First, let's consider why the axial force of Comparative Example 2 is lower than that of the tapered screw with serrations of the first embodiment. First, in Comparative Example 2, as the screw is tightened, since the seating surface is flat, not only the outer periphery but also the inner periphery contacts and bites into the fastening surface, generating a large seating surface friction torque and biting torque. On the other hand, in the product of the present invention, as the screw is tightened, due to the taper of the seating surface, only the round ring-shaped portion at the outermost periphery of the seating surface and the serrations in this portion contact and bite into the surface of the locking object, rather than the entire seating surface. Therefore, it is considered that the friction torque and biting torque of the seating surface are reduced.

[0142] Then, it is considered that the seating surface friction torque and biting torque of Comparative Example 2 are larger than those of the first embodiment. Here, there is an equation called the Motosh equation that shows the relationship between the tightening torque and the axial force. According to this equation, the total tightening torque applied from the outside can be decomposed into three components: the friction torque at the seating surface, the friction torque at the thread surface, and the axial force torque. It is considered that the friction torque at the thread surface is constant among these three torques. Then, when the seating surface friction torque increases, the axial force torque decreases, and as a result, the axial force decreases. And when there are serrations on the seating surface, in addition to the seating surface friction torque, the torque reduction due to the serrations biting into the fastening surface is also added. So, the torque reduction by the seating surface is the combined action of these seating surface resistance torques. And in this case, it is considered that in Comparative Example 2, this seating surface resistance torque acts greatly, resulting in a decrease in the axial force.

[0143] Next, consider the relationship between the axial force and the loosening torque. In Comparative Example 2, when the screw is tightened, since the seating surface 5 is flat, the entire seating surface 5 abuts against the locking member 100 and the force is dispersed, so the force pressing the serration 6 on the entire seating surface 5 against the locking member 100 becomes weak. On the other hand, in the product of the present invention, since the seating surface 5 has a taper, the force due to the axial force is concentrated only on the outermost peripheral ring-shaped portion, and the locking force by the serration 6 is improved. That is, the serration 6 in the ring-shaped portion is pressed against the locking member 100 with a strong force, and the serration 6 bites firmly into the locking member 100, generating a large locking force. Moreover, since the ring-shaped portion is located at the outermost periphery, there is a distance from the axis, and it is considered that a large loosening torque can be obtained.

[0144] Then, regarding the screw 1 with anti-loosening in the first embodiment and the fourth embodiment, as a higher concept combining the two, it can also be expressed as follows. A screw having a head provided with a tool engagement portion for rotating the screw, a screw portion integrally formed with the head, and having anti-loosening with loosening prevention in the head, wherein the seating surface of the head is formed in an inverted dish-shaped taper shape, and at least the outermost peripheral portion of the seating surface has a protruding portion, the locking member is made of a synthetic resin material, and when the screw having loosening prevention is fastened to the locking member, the portion near the outermost periphery of the seating surface abuts against the surface of the locking member and bites in, and the outermost peripheral portion of the seating surface abuts against the surface of the locking member so that an axial force is obtained, and the protruding portion bites into the locking member so as to be loosening-prevented. A screw having loosening prevention, characterized in that it is configured as such.

[0145] With such a configuration, when the screw is tightened, since the seating surface has a tapered shape, only the outermost peripheral portion of the seating surface and the convex portion in its vicinity come into contact with and bite into the locking object, rather than the entire seating surface. The seating surface friction torque and biting torque during screw tightening are smaller than those of a flat seating surface, and the decrease in axial force is reduced. As a result, a large axial force can be obtained. Due to this large axial force, the serration 6 and the bulging portion 7 on the outermost periphery of the seating surface, which are at a large distance from the axis center, bite into the locking object, and a large loosening torque can be obtained by this synergistic effect. This can be considered the same even if the serration is the protruding portion 9.

[0146] In the above description, it was assumed that the protruding portion near the outermost periphery bites into the locking object to prevent loosening, and the outermost peripheral portion of the seating surface abuts against the surface of the locking object to obtain the axial force. However, this is mainly in the sense that the axial force is also obtained by the protruding portion near the outermost periphery, and it goes without saying that the outermost peripheral portion of the seating surface also abuts against the surface of the locking object to prevent loosening. Also, although the screw 1 with anti-loosening of the first embodiment and the fourth embodiment was used, it goes without saying that the anti-loosening of other embodiments can also be expressed in this way.

[0147] Also, in the embodiments described so far, the anti-loosening of the head is all arranged on the seating surface, and the protruding portion protruding in the direction of the locking object has been described. However, it goes without saying that it is not limited to this. For example, when looking at the shape of the seating surface from below, it may be made into a substantially star shape with many corners, and the jagged portion on the outer periphery may be used as the protruding portion. This protruding portion protrudes in the direction of the locking object because the seating surface is tapered and oblique, bites into the locking object, and exhibits an anti-loosening effect. That is, such a protruding portion is also included in the protruding portion of the present invention that protrudes in the direction of the locking object.

[0148] The screw with anti-loosening of the present invention is not limited to the embodiments described above and shown in the drawings, and various modifications can be made without departing from the gist thereof. For example, in the above description, the locking member is made of a synthetic resin material or a soft metal. However, for example, it may also be used for a laminated steel plate or a vinyl steel plate in which resin is coated on the surface of a galvanized steel plate or the like, which is used in an outdoor unit of an air conditioner or the like.

Explanation of Signs

[0149] 1 Screw with anti-loosening 2 Head 21 Screw head 22 Flange part 3 Thread part 4 Screw rotation tool engagement part 5 Seat surface 6 Serrations 61 Locking surface 62 Front inclined surface 63 Top flat surface 64 Rear inclined surface 7 Bulge part 8 Bulge tip 9 Protrusion 100 Locking member 110 Fastening hole 120 Locking member surface 130 Fastening mark 140 Annular mark 150 Concave mark 160 Tip bulge mark 200 Frame 210 Screw hole

Claims

1. A screw having a head provided with a tool engagement portion for rotating the screw, a screw portion integrally formed with the head, and having a locking function in the head, wherein the seating surface of the head is formed in an inverted dish-shaped tapered form, at least in the vicinity of the outermost circumference of the seating surface, protrusions are formed that protrude in the direction of the locking object and are arranged at substantially equal intervals in the circumferential direction, the locking object is made of a synthetic resin material or a soft metal such as aluminum or copper, when the screw having the locking function is fastened to the locking object, the outermost peripheral portion of the seating surface is brought into contact with the surface of the locking object, and the protrusions near the outermost peripheral portion are configured to bite into the locking object A screw having a locking function, characterized by the above.

2. The protrusion has a front inclined surface at a small angle in the portion in front of the protrusion in the direction of tightening the screw. A screw having a locking function according to claim 1, characterized by the above.

3. The protrusion has a locking surface at a large angle in the portion behind the protrusion in the direction of tightening the screw. A screw having a locking function according to claim 2, characterized by the above.

4. The protrusion has a rear inclined surface at a small angle in the portion behind the protrusion in the direction of tightening the screw. A screw having a locking function according to claim 2, characterized by the above.

5. The angle of the seating surface with respect to the plane is 3 degrees or more and 10 degrees or less. A screw having a locking function according to claims 1 to 4, characterized by the above.

6. The outer diameter of the head is substantially the same as the outer diameter of a flat washer corresponding to the nominal diameter of the screw. A screw having a locking function according to claims 1 to 4, characterized by the above.

7. The protrusion is formed in a shape extending radially with respect to the axis. A screw having a locking function according to claims 1 to 4, characterized by the above.

8. The protrusion has a flat surface portion where the ridge line portion at the tip of the front inclined surface and the locking surface is flattened, and the corner portion between the front inclined surface and the flat surface portion is not rounded but angular. A screw having a locking function according to claim 3, characterized by the above.

9. The protrusion has a substantially arc-shaped surface that bulges in the direction of the locking object at least in part of the front inclined surface, and also has a substantially arc-shaped surface that bulges in the direction of the locking object at least in part of the rear inclined surface. A screw having a locking function according to claim 4, characterized by the above.

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