JP7290290B2 - bolts and nuts - Google Patents

Description

The present invention relates to bolts and nuts. More particularly, it relates to bolts and nuts utilized in environments where sand adheres to the bolts and for clamping objects between the bolt head and nut.

As an example of a rolled screw, the following patent document 1 is known. The document points out that even a slight chipping impairs the function of the screw. Here, chipped fragments are caught in the meshing part of the screw, and the balance between tightening torque and axial force is lost. Therefore, it is described that a predetermined axial force cannot be obtained. Moreover, it is also described that fragments are seized on the flanks during tightening, and excessive force is required to loosen the screws, making it difficult to loosen the screws.

On the other hand, in making castings, bolts and nuts are used to fasten the mold. In addition to the above-mentioned inconveniences, this type of bolt and nut has a problem in that sand rubs against the troughs of the bolt and nut, which impairs the durability of the bolt and nut.

Japanese Patent Application Laid-Open No. 2001-317518

In view of such conventional circumstances, it is an object of the present invention to provide a bolt and nut which can be tightened more easily than before even in an environment where foreign matter such as sand exists and which has excellent durability.

To achieve the above objects, the bolt and nut features of the present invention are utilized in environments where sand adheres to the bolt, and in a configuration for clamping an object between the head and nut of the bolt. The crest of the screw thread is formed in a trapezoidal shape, the nut is formed by cutting, and the bolt is formed by rolling. and a straight flank and a straight trough, at least the flank of the trough of the bolt has a more obtuse angle than the flank, and the trough of the bolt forms a corner at the bottom. be.

According to this configuration, the bolt is formed by rolling, and the surface hardness and surface roughness are improved by pressing with the rolling dies, so that the bolt is less likely to be worn by sand than a machined bolt. Since at least the vicinity of the flank of the root portion of the bolt has a more obtuse angle than the flank, the root portion can be formed shallower, the root diameter of the bolt can be made as large as possible, and the strength of the bolt as a whole can be prevented from decreasing. In addition, the bottommost corner of the bottom of the bolt becomes more obtuse, and the decrease in strength due to the shape is alleviated.

The crests of the bolt and nut are trapezoidal, and due to the presence of the corners, flattened triangular areas are formed by the trapezoidal crests and the flanks around the corners. In the triangular area, sand with a larger grain size moves to the center, and as a result, sand with different grain sizes can be reasonably accommodated in this area, and sand biting into the flank can be reduced. Moreover, since the bolt has a corner at the bottom of the valley, it is sufficient to use a die having a corner that fits the corner, which facilitates the rolling process. Moreover, the nut is easy to cut a thread groove suitable for the rolled bolt, and the problem of tension is less likely to occur, so there is little problem with strength. Therefore, it can be manufactured at a low cost as a whole, and a long life can be achieved by strengthening the bolt by rolling.

Note that the corners and triangular areas exist at least at the bottom of the bolt. Therefore, when sand is removed from the crest of the bolt and a nut with no sand attached is used, the bolt can be tightened using the triangular area even if sand remains in the bottom of the bolt.

In the nut having the above configuration, it is preferable that the crest width, which is the distance between the crest-side ends of the pair of flanks in the screw thread of one tooth, is larger than the flank length. In this way, the width of the triangular area is increased, making it easier for sand to flow in. Moreover, the ratio of the flank length is smaller than that of conventional bolts and nuts, so the friction area on the flank is reduced, and the flank due to fine sand particles is reduced. Frictional force can be reduced, and the nut can be tightened to a predetermined position more easily.

Furthermore, in the above, it is preferable that the average clearance between the bolt flank and the nut flank is 340 μm or more. The average grain size of No. 6 silica sand, which is frequently used in casting, is 340 μm. Since the relaxation takes place in the triangular area, the probability of large grains of sand getting caught in the clearance between the flanks is reduced, resulting in smoother rotation.

Further, it is preferable that the root portion of the nut has the same cross-sectional shape as the root portion of the bolt. According to this configuration, since the triangular area can be formed in the root portion of the nut, fastening is facilitated even if sand adheres to the thread groove of the nut. This configuration is extremely effective, for example, in an environment such as mold fastening where sand enters the hole of a slightly screwed nut.

In addition, it is preferable that the clearance between the bottom of the bottom of the bolt and the top of the nut is 850 μm or more. Since the maximum particle size of No. 6 silica sand is about 850 μm, if this clearance is secured, even if it is difficult to remove the sand of about the maximum particle size, it can be stored in the triangular area and practical problems are unlikely to occur.

Similarly, it is more preferable that the clearance between the bottom of the root of the bolt and the top of the nut and the clearance between the bottom of the bottom of the nut and the top of the bolt are 850 μm or more. . With this shape, the clearance of the triangular area can be formed not only at the root of the bolt but also at the root of the nut.

The present invention is useful in environments prone to sand, i.e. for fastening molds or for fastening on construction sites. In particular, it is useful in an environment where it is difficult to wash bolts and nuts with water or the like.

In carrying out the present invention, a washer may be fixed to the bolt head formed on the bolt, and a detent may be fixed to a corner between the washer and the barrel of the bolt. A frictional force is generated in the washer by the axial force due to tightening of the bolt, and the bolt head and the anti-rotation portion are fixed to the washer to generate torque durability. Moreover, since the anti-rotation portion is fixed to the corner portion between the washer and the barrel portion of the bolt, it has sufficient rotational durability against the tightening torque.

In practicing the present invention, the following conditions should be observed.
Thread diameter of bolt ≧ 24mm
Thread pitch ≧ 9mm

According to the features of the present invention, it is possible to provide a bolt and nut that can be easily fastened even in an environment where foreign matter such as sand exists, and which is superior in durability.

Other objects, configurations and effects of the present invention will become apparent from the following detailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS The perspective view of the bolt and nut which concern on this invention is shown, (a) is the perspective view looked up from the lower side, (b) is the perspective view looked down from the upper side, (c) is a side view. 1 shows a bolt and nut according to the present invention, (a) is a side view of the first embodiment, (b) is a cross-sectional view of (a), (c) is a cross-sectional view of the second embodiment, and (d) is 5 is a cross-sectional view showing Comparative Example 1. FIG. It is a figure which shows the rolling process of the bolt which concerns on this invention, Comprising: (a) is a cross-sectional view, (b) is a longitudinal cross-sectional view, (c) is the elements on larger scale of (b). 1 shows an enlarged vertical cross-sectional view of a bolt and a nut according to the present invention, (a) is a cross-sectional view showing a first embodiment, (b) is a cross-sectional view showing a second embodiment, and (c) shows Comparative Example 1. FIG. 8D is a cross-sectional view showing Comparative Example 2; BRIEF DESCRIPTION OF THE DRAWINGS It is an enlarged vertical cross-sectional view for demonstrating the effect of the bolt and nut which concern on this invention, (a) is sectional drawing which shows 1st embodiment, (b) is partial enlarged sectional view of (a). Photographs of the bolt and nut used in the confirmation test of the effect of the present invention are shown, (a) is the bolt and nut of the first embodiment, (b) is the state where sand is attached to the bolt of the first embodiment, ( c) is the bolt and nut of the first embodiment; It is a table|surface which shows the test result of 1st embodiment. 4 is a table showing test results using the first and second embodiments and Comparative Example 2. FIG.

Next, the present invention will be described in further detail with reference to the accompanying drawings as appropriate. The bolt and nut 1 according to the present invention show an example of use for fastening molds, and the first embodiment is shown in FIGS. 5(a).

The bolt and nut 1 in FIG. 1 show a state in which a nut 20 is screwed onto a bolt 30. The nut 20 has an internal threaded portion 25 and a hexagonal portion 26 for tightening with a tool such as an electric tool. there is The bolt 30 has a shaft portion 36 and a bolt head portion 37 integrally formed continuously with a male threaded portion 35 to which the nut 20 is fastened. The washer 38 has the shaft portion 36 penetrated through the through hole 38a and the bolt head portion 37 is brought into contact therewith. Configure. The bolt head 37 and the washer 38 are connected at the first welded portion m1, the shaft portion 36 and the detent portion 39 are connected at the second welded portion m2, and the washer 38 and the detent portion 39 are connected at the third welded portion m3. are fixed by welding. The nut 20 is formed by cutting, and the bolt 30 is formed by rolling, which will be described later.

In this embodiment, the object to be clamped 200 is a mold flask, and has, for example, a lower mold frame 201 and an upper mold frame 202 . Specifically, while the bolt 30 is inserted through the through hole 202 a of the upper mold 202 , the nut 20 is temporarily fixed, and the lower part of the bolt 30 is inserted through the U-shaped notch 201 a of the lower mold 201 . In the U-shaped notch 201a, the nut 20 is tightened from above with an electric tool while the rotation-preventing portion 39 of the bolt 30 abuts against the wall of the U-shaped notch 201a to prevent rotation. As a result, the tightening object 200 is tightened between the lower portion of the nut 20 and the upper portion of the head 40 . After fastening, a reaction force U is transmitted to the bolt 30 through the nut 20, and the bolt is stretched in the axial direction, and an axial force D is generated.

2(a)(b), 4(a) and 5(a), the thread 24 of the female threaded portion 25 of the nut 20 and the thread 34 of the male threaded portion 35 of the bolt 30 I will elaborate. The screw thread 24 of the nut 20 has a trapezoidal crest portion 21, a trapezoidal root portion 22, and a linear flank 23 connecting them in a vertical cross section along the bolt axis P. As shown in FIG. Further, the thread 34 of the bolt 30 has a trapezoidal crest portion 31, a trapezoidal root portion 32, and a linear flank 33 connecting them in a vertical cross section along the bolt axis P. As shown in FIG.

As shown in FIGS. 5A and 5B, the valley bottom 32 of the bolt 30 near the flank 33 has a more obtuse angle than the flank 33, and the valley bottom 32 forms a corner 32a at the bottom. In the nut 20, the crest width B, which is the distance between the crest 21 side ends of the pair of flanks 23, 23 in the thread of one tooth, is formed larger than the flank length A. In the first embodiment, the root portion 22 of the nut 20 is formed to have the same cross-sectional shape as the root portion 32 of the bolt 30 .

In this embodiment, the third clearance C3 (corresponding to the average clearance) between the flank 33 of the bolt 30 and the flank 23 of the nut 20 is desirably 340 μm or more, and both flanks 23, 33 are in close contact. is 2*C3=680 μm at maximum, but the distance between both flanks 23 and 33 depends on how the sand S bites.

Further, in the present embodiment, the first clearance C1 between the bottom corner 32a of the root 32 of the bolt 30 and the crest 21 of the nut 20 is desirably 850 μm or more, and 1.33 mm in the following experimental example. is. Similarly, the second clearance C2 between the lowest corner 22a of the root 22 of the nut 20 and the crest 31 of the bolt 30 is desirably 850 μm or more, and 1.33 mm in the experimental example below.

In rolling the bolt 30 , as shown in FIG. 3 , a pair of rolling dies 210 are used to sandwich the rolling bolt 3 between them for plastic working. The rolling die 210 has a helical thread on its cylindrical outer circumference. A cross-section along the central axis of rotation of the rolling die 210 has a peak portion 211 and a valley bottom portion 212 each having a corner portion 211a. The rolling bolt 3 initially has a bolt head portion 3c and a shaft portion 3b, and a rolling die 210 is pressed against the shaft portion 3b to form the male thread portion 3a.

A cross section along the central axis has a peak portion 3d and a valley bottom portion 3e, and the peak portion 211 of the rolling die 210 is pressed to deform and move the metal material of the valley bottom portion 3e in the direction of the arrow to roll. A metal material is raised on the valley bottom 212 of the die 210 to form the peak 3d. Since the peak portion 211 of the rolling die 210 has a corner portion 211a, there is an advantage that the metal material can be easily raised. Further, as will be described later, since the angle of the corner portion 3f is obtuse than the flank angle, the effect of notching the shape of the corner portion 3f is reduced, which has the advantage of preventing the strength of the rolled bolt 3 from deteriorating.

The second embodiment and comparative examples will be described below, and the results of comparative experiments using these will be described.

2(c) and 4(b) are sectional views showing the second embodiment, and FIGS. 2(d) and 4(c) are sectional views showing Comparative Example 1. FIG. In the second embodiment shown in FIGS. 2(c) and 4(b), the bottom 22' of the nut 20' has a trapezoidal shape, and the corner 22a is absent. The configuration is similar to that of the first embodiment. In Comparative Example 1 shown in FIGS. 2(d) and 4(c), both the root portion 22' of the nut 20' and the root portion 32' of the bolt 30' are trapezoidal, and the corner portions 22a and 32a are formed in a trapezoidal shape. does not exist. These are comparisons to confirm the effectiveness of the corners 22a, 32a on both the root 22 of the nut 20 and the root 32 of the bolt 30. FIG.

FIG. 6 shows photographs, in which (a) is the bolt and nut of the first embodiment, (b) is the state where sand is attached to the bolt of the first embodiment, and (c) is the first bolt for conducting the following test. A bolt and nut of one embodiment, (d) shows a state in which the nut such as (c) is sanded, respectively. This bolt has a thread diameter of M24, a thread pitch of 9 mm, and is made of SCM435H which has been quenched and tempered. The material of the nut is SCM435H, which is machined and quenched and tempered.

On the other hand, FIG. 4(d) is a sectional view showing Comparative Example 2, showing a conventional metric thread. The nut 120 has a crest portion 121 , a root portion 122 and a flank 123 , and the bolt 130 has a crest portion 131 , a root portion 132 and a flank 133 . FIG. 6(e) is a photograph of the bolt and nut of Comparative Example 2. The bolt has a thread diameter of M24, a thread pitch of 3 mm, and is made of SCM435H, which has been quenched.

Here, the conditions and results of the comparative experiment are shown. Under the following conditions, we changed the grain size of the sand, put the sand into the nut screwed to the bolt, and performed the experiment by manual rotation. The sand was sieved to make the particle size uniform as much as possible, and sand having average particle sizes of 53, 173, 222, 284, 723 and 1139 µm was used. The types of sand used as raw materials are Tohoku Silica Sand No. 4, Tohoku Silica Sand No. 7, and Tohoku Silica Sand No. 8. The amount of sand added was constant in all the examples and was 0.1, 0.3, 0.8, 1, 2, 3, 5 and 10 g.

A first clearance portion Ga corresponding to the triangular area is formed between the corner portion 32a, which is the bottommost portion of the root portion 32 of the bolt 30, and the crest portion 21 of the nut 20. In the first and second embodiments, A second clearance C2 in the height direction of the thread is 1.33 mm.

A second clearance portion Gb corresponding to the triangular area is provided between the corner portion 22a, which is the bottommost portion of the root portion 22 of the nut 20, and the crest portion 31 of the nut 30 in the first embodiment. The second clearance C2 in the longitudinal direction is 1.33 mm. On the other hand, between the root portion 22' of the nut 20' and the crest portion 31 of the nut 30 in the second embodiment is a second clearance portion Gb' different from the triangular area, and the clearance in the height direction of the screw thread is 550 μm. For reference, in Comparative Example 1 of FIG. 4(c), both the first clearance portion Ga' and the second clearance portion Gb' are narrower than in the first embodiment.

The clearance in the height direction of the thread at the first clearance portion ga between the root portion 132 of the bolt 130 and the crest portion 121 of the nut 120 in Comparative Example 2 of FIG. 4D is 474 μm. Further, the clearance in the height direction of the thread of the second clearance portion gb between the root portion 122 of the nut 120 and the crest portion 131 of the nut 130 is 509 μm. Additionally, the average clearance between both flanks 123, 133 is 70 μm.

The test method is to put each weight of sand into the internal thread of the nut that is temporarily fixed to the bolt and turn it by hand three times, and evaluate the test from the viewpoint of whether the nut can be easily turned by hand. did

FIG. 7 shows test results of the first embodiment. Only where the amount of sand is 5 g, the results of three tests are shown, and elsewhere only the conclusions of the three tests are given. In the case of 723 μm sand, trouble occurred in the case of 10 g, and in the case of 5 g, twice out of three times. In the case of 1139 μm, it was only in the cases of 3, 5 and 10 g. Other average particle sizes and g numbers below these did not cause any problems.

As shown in FIG. 7, when a failure occurs even once out of three times, the results of the comparison test between the first and second embodiments and Comparative Example 2 are as shown in FIG. Both the area of the first embodiment (indicated by the solid line) and the area of the second embodiment (indicated by the dashed line) can be used in an environment where sand S of various grain sizes exists compared to the area of the comparative example 2 (indicated by the dashed line). I can tell something. In addition, the first embodiment differs from the second embodiment in that it is easy to rotate even when the amount of sand having a particle size of 723 μm or more is 1 g or more. , the third clearance C3 of the flank is the same in the first and second embodiments. Therefore, the presence of the second clearance portion Gb facilitates rotation even when the amount of sand is large, and its effect was confirmed.

Moreover, when the nut is fastened with sand adhering to the valleys between the threads of the bolt (in this case, it is difficult for sand to enter the valleys of the nut), a problem occurs in Comparative Example 2. However, in the first and second embodiments, no problem occurred, and the effect of only the first clearance Ga was confirmed.

Considering the above results, the following phenomena are observed.

The clearance between both flanks 23 and 33 is 2C3=680 μm at maximum, and in the first embodiment, it is possible to rotate up to 3 g at 723 μm, which exceeds this, and up to 2 g at 1139 μm, which exceeds this. It is considered that the particles are pulverized by these flanks 23, 33 and the like and move to the first and second clearance portions Ga, Gb.

As shown in FIG. 5B, when the crest width B of the nut 20 is set to a width Bx smaller than the flank length A, the first corner T1 moves to the second corner T2, and the first imaginary clearance C11 becomes It becomes smaller than the one clearance C1, and the volume of the first clearance portion Ga is also reduced. As a result, the grain size of the sand received in the first clearance portion is small and the volume of the sand is also small, so it is expected that the rotation will become more difficult.

On the other hand, the vicinity of the flank 33 of the valley bottom 32 has a more obtuse angle than the flank 33. It becomes sharper than T1 and the second corner T2, and the durability against the axial force of the bolt is lowered due to its shape. In addition, since the root diameter Dc of the square portion T4 is smaller than the root diameter Db of the first corner T1, even in terms of the tensile stress per unit cross-sectional area, the sharp square portion T4 is the axial force of the bolt. durability against

From the above, the durability against the axial force of the bolt 30, the improvement of the shape strength by configuring the first corner T1 with a more obtuse angle, and the crest width B of the bolt 30 is made larger than the flank length A. As a result, the volume of the first clearance portion Ga is increased, so that the bolt 30 having the above-described structure can be easily rotated even when sand is bitten, and the durability is further improved. Also, by designing the nut 20 in the same shape, the same effect can be obtained.

From the viewpoint that even if sand of about the maximum particle size adheres to the bottom 32 of the bolt 30, it can be stored in the triangular area, the first clearance Ga between the bottom of the bottom of the bolt 30 and the top of the nut 20 and the clearance of the second clearance portion Gb are preferably 850 μm or more. In view of practicality, it is desirable that the pitch on the pitch line PL is 9 mm and the thread diameter Da of the bolt 30 is 24 mm or more. A pitch of 9 mm is more rapid for fastening, and a bolt thread diameter is less than 24 mm when rolling bolts with a pitch of 9 mm or more. ) becomes an acute angle, making rolling difficult.

INDUSTRIAL APPLICABILITY The present invention can be used as bolts and nuts for casting (for fastening molds). In addition, it can be effectively used in environments where sand adheres, for example, for fastening at civil engineering and construction sites, especially in environments where it is difficult to remove sand with water or air.

1: bolt and nut, 3: rolled bolt, 3a: male screw portion, 3b: shaft portion, 3c: bolt head portion, 3d: crest portion, 3e: root portion, 3f: corner portion, 20: nut, 21: crest part, 22: root part, 22a: corner part, 23: flank part, 24: screw thread, 25: internal thread part, 26: hexagonal part, 30: bolt, 31: crest part, 32: root part, 32a: corner part, 33: Flank, 34: Thread, 35: Male screw portion, 36: Shaft portion, 37: Bolt head, 38: Washer, 38a: Through hole, 39: Detent portion, 40: Head, 120: Nut, 121: Peak 122: Valley bottom 123: Flank 130: Bolt 131: Peak 132: Valley bottom 133: Flank 200: Object to be tightened 201: Lower formwork 201a: U-shaped cut 202: upper formwork, 202a: through hole, 210: rolling die, 211: crest, 211a: corner, 212: root, 20': nut, 22': root, 24': thread, 30 ': bolt, 32': root, 34': thread, A: flank length, B: crest width, C1: first clearance, C2: second clearance, C3: third clearance, C11: first virtual clearance, C12: second virtual clearance, C13: third virtual clearance, Da: bolt crest diameter, Db: bolt root diameter, Dc: bolt root diameter, Ga, ga, Ga': first clearance portion, Gb, gb , Gb': second clearance portion, Gc, gc: third clearance portion, m1: first welded portion, m2: second welded portion, m3: third welded portion, P: bolt axis, PL: pitch line, S: sand, T1: first corner, T2: second corner, T3: third triangular part, T4: fourth square part

Claims (9)

A bolt and nut used in an environment where sand adheres to the bolt and for tightening an object between the bolt head and nut,
The crests of the threads of the bolt and nut are formed in a trapezoidal shape,
The nut is formed by cutting,
The bolt is formed by rolling,
The screw thread of the bolt and nut is formed by the crest portion, the linear flank and the root portion in a longitudinal section along the axis of the bolt,
At least the vicinity of the flank of the root portion of the bolt has an obtuse angle than the flank,
The bottom of the bolt is the bottom and the bolt and nut form the corner. 2. The bolt and nut according to claim 1, wherein, in said nut, a crest width, which is a distance between crest-side ends of a pair of said flanks in said screw thread of one tooth, is formed larger than said flank length. 3. The bolt and nut according to claim 1, wherein the average clearance between the bolt flank and the nut flank is 340 [mu]m or more. The bolt and nut according to any one of claims 1 to 3, wherein the root portion of the nut is formed to have the same cross-sectional shape as the root portion of the bolt. 5. The bolt and nut according to any one of claims 1 to 4, wherein the clearance between the bottom of the bottom of the bolt and the top of the nut is 850 μm or more. 5. The set forth in claim 4, wherein the clearance between the bottom of the root of the bolt and the top of the nut and the clearance between the bottom of the root of the nut and the top of the bolt are 850 μm or more. bolts and nuts. The bolt and nut according to any one of claims 1 to 6, which are used for fastening molds or for fastening at civil engineering and construction sites. 8. The bolt according to any one of claims 1 to 7, wherein a washer is fixed to the bolt head formed on the bolt, and a detent part is fixed to a corner between the washer and the barrel of the bolt. nut. A bolt and nut according to any one of claims 1 to 8, subject to the following conditions.
Thread diameter of bolt ≧ 24mm
Thread pitch ≧ 9mm

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