Shear Pin

Abstract

To provide a shear pin realizing a long life by suppressing deterioration.SOLUTION: A generally columnar shear pin 1 has a function of fixing members 4a and 4b by being inserted in through-holes 5 formed on the adjacent two members 4a and 4b, and a function of breaking when receiving predetermined shear force to release the fixing of the two member 4a and 4b. The shear pin is equipped with an inside pin 2 having a predetermined shear strength, and a generally cylindrical outer cylinder 3 that has a cavity 3b in which the inside pin 2 is inserted.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a shear pin that is installed on a crane or the like to protect the equipment by breaking, and more particularly to a shear pin that achieves a long life by suppressing deterioration. [Background technology]

[0002] Various configurations of shear pins have been proposed (see, for example, Patent Document 1). Patent Document 1 discloses a configuration of a shear pin that is used by being inserted into a through hole formed in two adjacent members. Shear pins are arranged, for example, in seismic isolation devices for cranes. Also, shear pins are arranged, for example, as overload (snug load) protection devices for cranes.

[0003] When a shear pin is inserted into the through holes of two adjacent components, the two adjacent components are fixed together. The shear pin maintains the fixation of the two components together without breaking even when subjected to loads (hereinafter referred to as normal loads) that occur during normal loading and unloading operations. For example, when a crane tries to lift a container fixed to a ship, an excessive load (hereinafter referred to as overload) occurs on the shear pin that is placed as an overload protection device. When an abnormal load, which is a force exceeding the specified shear force, occurs on the shear pin, the shear pin breaks and the rope lifting the container loosens. When the crane lifts the ship, the shear pin prevents accidents such as the crane collapsing or tipping over.

[0004] There was a defect where the shear pin broke even though no overload had occurred. It was found that the shear pin had deteriorated due to repeated bending stress caused by vibrations and other factors occurring in the two adjacent components. It was also found that fretting wear had increased the gap between the through hole in which the shear pin is placed and the shear pin, making it more susceptible to bending stress occurring in the shear pin. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2016-147752 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a shear pin that achieves a long life by suppressing deterioration. [Means for solving the problem]

[0007] The shear pin for achieving the above object is a generally cylindrical shear pin, comprising an inner pin having a preset shear strength, and a generally cylindrical outer cylinder having a cavity into which the inner pin is inserted. and a gap is provided between the inner pin and the outer cylinder and formed over the entire axial direction of the shear pin. It is characterized by: Effect of the Invention

[0008] According to the present invention, the shear pin is formed in a double tube shape of an inner pin and an outer cylinder. Since only the outer cylinder comes into contact with the through hole into which the shear pin is inserted, deterioration of the inner pin can be suppressed. This is advantageous for realizing a long life of the shear pin. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is an explanatory diagram illustrating an outline of a shear pin in perspective view. [Diagram 2] 1 is an explanatory diagram illustrating a cross section parallel to the axial direction of an outer cylinder and an inner pin. FIG. [Diagram 3] 1 is an explanatory diagram illustrating a cross-section of a state in which a shear pin is disposed in a through hole of a member; [Figure 4] 4 is an explanatory diagram illustrating a state in which the outer cylinder of FIG. 3 is bent. FIG. [Diagram 5] FIG. 4 is an explanatory diagram illustrating a cross section perpendicular to the axial direction of the shear pin. [Figure 6] 5 is an explanatory view illustrating a state in which the outer cylinder of FIG. 4 is broken. FIG. [Figure 7] 7 is an explanatory view illustrating a state in which the inner pin in FIG. 6 is broken. FIG. [Figure 8] 3 is an explanatory diagram illustrating a modified example of the inner pin in FIG. 2. [Figure 9] 9 is an explanatory diagram illustrating a modified example of the inner pin in FIG. 8. [Figure 10] 3 is an explanatory diagram illustrating a modified example of the outer cylinder of FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The shear pin will be described below based on the embodiment shown in the drawings. In the drawings, the axial direction of the shear pin is indicated by arrow y, the lateral direction perpendicular to the axial direction y is indicated by arrow x, and the up-down direction perpendicular to the axial direction y and the lateral direction is indicated by arrow z.

[0011] As illustrated in FIG. 1, the shear pin 1 is formed in a generally cylindrical shape as a whole. The shear pin 1 has a double-tube structure including an inner pin 2 and an outer cylinder 3. The inner pin 2 has a preset shear strength. In the embodiment illustrated in FIG. 1 and FIG. 2, the inner pin 2 is formed in a generally cylindrical shape. The inner pin 2 also has a slit 2a formed along the circumferential direction of the outer circumferential surface. The shear strength of the inner pin 2 is adjusted by the depth of the slit 2a. The depth of the slit 2a refers to the length of the slit 2a in the radial direction perpendicular to the axial direction y of the inner pin 2. The inner pin 2 breaks when subjected to a shear force exceeding the preset shear strength. The shear strength refers to the force at which the inner pin 2 breaks when subjected to a shear force in the radial direction. The shear strength is indicated by the load per unit area, and is expressed in N / mm 2 The slit 2a is not essential, and the inner pin 2 may have a configuration without the slit 2a. In this case, the shear strength is set according to the diameter of the inner pin 2 and the type of material.

[0012] In the embodiment illustrated in Figs. 1 and 2, the outer cylinder 3 is formed in a substantially cylindrical shape. The outer cylinder 3 has a slit 3a formed along the circumferential direction of the outer peripheral surface. The shear strength of the outer cylinder 3 is adjusted by the depth of the slit 3a. As with the inner pin 2, the outer cylinder 3 may also be configured without the slit 3a. The outer cylinder 3 has a cavity 3b into which the inner pin 2 is inserted. The cavity 3b is formed in a substantially cylindrical shape with the axial direction y coinciding with that of the outer cylinder 3. For the sake of explanation, Figs. 1 and 2 show a state in which the inner pin 2 and the outer cylinder 3 are separated. For the sake of explanation, Fig. 1 shows the inner pin 2 when placed in the cavity 3b by a broken line.

[0013] 2, both ends of the cavity 3b in the axial direction y are open, and the inner pin 2 can be inserted and removed from the cavity 3b from either end. The cavity 3b may have a structure in which one or both sides in the axial direction y are closed. In the case of a structure in which both sides are closed, at least one side is configured to be openable and closable for inserting and removing the inner pin 2.

[0014] In this embodiment, the inner pin 2 and the outer cylinder 3 each have two slits 2a and 3a, respectively, but are not limited to this configuration. Each of the slits 2a and 3a may be one.

[0015] 3, the shear pin 1 is inserted into a through hole 5 formed in two adjacent members 4a and 4b. In this embodiment, one member 4b is disposed between a pair of members 4a. A configuration in which one member 4a and one member 4b are disposed adjacent to each other and the shear pin 1 is inserted into a through hole 5 formed in the members 4a and 4b may also be used.

[0016] The shear pin 1 fixes one member 4a to the other member 4b. The members 4a and 4b are constrained from relative movement in a direction perpendicular to the axial direction y of the shear pin 1. The shear pin 1 is configured in such a way that the slits 2a and 3a are located at positions corresponding to the boundaries between the two members 4a and 4b. When the shear pin 1 breaks, that is, when both the outer tube 3 and the inner pin 2 break, the fixation between the one member 4a and the other member 4b is released. The shear pin 1 has the function of being inserted into the through hole 5 formed in the two adjacent members 4a and 4b to fix the members 4a and 4b, and the function of breaking when a predetermined shear force is applied to release the fixation between the two members 4a and 4b.

[0017] Since the shear pin 1 has a double tube structure, only the outer tube 3 comes into contact with the through hole 5 into which the shear pin 1 is inserted. Therefore, wear due to contact with the through hole 5 occurs only on the outer tube 3, not on the inner pin 2. This is advantageous for suppressing deterioration of the inner pin 2. This is advantageous for realizing a long life for the shear pin 1 as a whole.

[0018] This avoids the problem of the inner pin 2 breaking due to fatigue at a shear force smaller than the preset shear strength. The shear pin 1 as a whole is unlikely to break under normal load. Even if the shear pin 1 is used for a long period of time, it is possible to avoid problems such as the shear pin 1 breaking unintentionally during normal loading and unloading operations, causing the rope to loosen and the container to fall.

[0019] By pulling out the inner pin 2 from the outer tube 3, the inner pin 2 can be easily inspected. If no cracks or the like are generated in the inner pin 2, the defect that the shear pin 1 as a whole breaks at a shear force equal to or less than a predetermined value can be avoided. Even when the outer tube 3 is disposed in the through hole 5, the inner pin 2 can be pulled out and inspected. This is advantageous for improving the workability of inspecting the inner pin 2. Even when the outer tube 3 is disposed in the through hole 5, the presence or absence of cracks in the outer tube 3 can be inspected from the cavity 3b side. This is advantageous for improving the workability of inspection. Since the workability of inspecting the shear pin 1 is improved, the frequency of inspection can be increased. This is advantageous for realizing a long life of the shear pin 1.

[0020] 3, the shear pin 1 may have a gap 6 formed between the inner pin 2 and the outer cylinder 3. The shear pin 1 may have no gap 6. In other words, the inner diameter d1 of the outer cylinder 3 and the outer diameter d2 of the inner pin 2 may be substantially the same. For example, the inner pin 2 may be disposed in the cavity 3b of the outer cylinder 3 without any gap by shrink fitting or the like.

[0021] Providing the gap 6 in the shear pin 1 is advantageous in improving the efficiency of inspection work because it makes it easier to pull out the inner pin 2 from the outer tube 3. In this case, the gap 6 only needs to be large enough to allow the inner pin 2 to be pulled out from the outer tube 3.

[0022] As illustrated in FIG. 4, even if bending stress occurs in the outer tube 3 due to the relative displacement of the members 4a and 4b, the shear pin 1 may have a gap 6 large enough to prevent this force from being transmitted to the inner pin 2. The size of the gap 6 can be said to be a size that allows the inner pin 2 to maintain a state without receiving any bending stress from the outer tube 3 when the outer tube 3 is in a bent state just before it breaks. For the sake of explanation, in FIG. 4, the displacement direction of the member 4b is shown by a white arrow, and the initial position of the member 4b before the displacement is shown by a dashed line. The shear pin 1 of this embodiment has a gap 6 large enough to prevent stress from occurring in the inner pin 2 even if the outer tube 3 is bent. Therefore, unless the outer tube 3 breaks, stress does not occur in the inner pin 2. Even if the outer tube 3 is repeatedly subjected to bending stress due to vibration of the members 4a and 4b, or friction occurs between the outer tube 3 and the through hole 5, the inner pin 2 is not affected. This is even more advantageous in avoiding the problem of the inner pin 2 deteriorating due to bending stress.

[0023] When the shear pin 1 has a relatively large gap 6, stoppers 7 may be disposed on both ends of the outer tube 3 to prevent the inner pin 2 from falling out. The stoppers 7 only need to be large enough to prevent the inner pin 2 from jumping out of the cavity 3b. At least one of the stoppers 7 is configured to be removable or openable / closable to allow the inner pin 2 to be inserted and removed from the cavity 3b.

[0024] As shown in Fig. 5, it is desirable that the width Δd of the gap 6 in the radial direction is 0.5 to 30.0% of the inner diameter d1 of the outer cylinder 3. Here, the width Δd of the gap 6 can be expressed as the difference between the inner diameter d1 of the outer cylinder 3 and the outer diameter d2 of the inner pin 2. In other words, Δd = d1 - d2. Moreover, the width Δd of the gap 6 satisfies 0.005 × d1 ≦ Δd ≦ 0.300 × d1.

[0025] If the width Δd of the gap 6 is too small, bending stress will be generated in the inner pin 2 when the outer tube 3 is bent. This may cause the inner pin 2 to deteriorate. If the width Δd is too large, bending stress may be generated in the inner pin 2 when the outer tube 3 breaks and shear force is generated in the inner pin 2. This bending stress increases the possibility that the inner pin 2 will break even if the shear force is less than a certain level. The smaller the width Δd, the more shear force will be generated in the inner pin 2 in a direction perpendicular to the axial direction y of the inner pin 2, and the larger the width Δd, the more bending stress will be generated in the inner pin 2, for example, centered on the lateral direction x of the inner pin 2. The width Δd of the gap 6 can be appropriately changed taking into account the length of the shear pin 1 in the axial direction y and the ease of bending of the outer tube 3.

[0026] The shear strengths of the inner pin 2 and the outer cylinder 3 are set to be equal or nearly equal. The outer cylinder 3 deteriorates due to the effects of vibration, friction, and the like received from the members 4a and 4b. As a result, the outer cylinder 3 often breaks before the inner pin 2. Furthermore, when the shear pin 1 receives a shear force exceeding its shear strength, the inner pin 2 and the outer cylinder 3 break almost simultaneously. The shear strengths of the inner pin 2 and the outer cylinder 3 are set so that at least the inner pin 2 does not break before the outer cylinder 3.

[0027] The shear strength of the outer tube 3 may be set to be smaller than the shear strength of the inner pin 2. Even if the outer tube 3 is not deteriorated, it will break before the inner pin 2. After the outer tube 3 breaks, the inner pin 2 will break when it receives a shear force exceeding a predetermined shear strength. The shear strength of the shear pin 1 as a whole can be set with high precision by the shear strength set for the inner pin 2. The undeteriorated inner pin 2 can control the timing at which the shear pin 1 as a whole breaks.

[0028] The second moment of area may be set to be larger for the outer cylinder 3 than for the inner pin 2. The inner pin 2 and the outer cylinder 3 may be made of the same material. Specifically, the inner pin 2 and the outer cylinder 3 may be made of, for example, chromium molybdenum steel or ferritic stainless steel. Desirably, the inner pin 2 is made of a material that is tougher than the outer cylinder 3. Even if the inner pin 2 bends together with the outer cylinder 3, the inner pin 2 is less likely to deteriorate.

[0029] The above conditions of shear strength, moment of inertia, and toughness of the material need only be set at least in the parts that are sheared, such as the slits 2a and 3a. The parts of the inner pin 2 and the outer cylinder 3 that are not sheared do not need to satisfy the above conditions. In order to adjust the above conditions of shear strength, moment of inertia, and toughness of the material, the material and the depth of the slits 2a and 3a may be changed, or the surface hardness of the inner pin 2 and the outer cylinder 3 may be changed by ceramic spraying.

[0030] As shown in FIG. 6, the outer tube 3 may deteriorate and break under normal loads generated in normal loading and unloading operations. In this embodiment, the outer tube 3 breaks at the slit 3a. Even in this case, the inner pin 2 can support loads smaller than the preset shear strength. In other words, the inner pin 2 supports normal loads generated in normal loading and unloading operations. This can avoid problems such as the shear pin 1 breaking, the rope loosening, and the container falling. As long as the inner pin 2 does not experience an overload exceeding the preset shear strength, the crane can continue loading and unloading operations. If a break in the outer tube 3 is confirmed during inspection, the shear pin 1 (the inner pin 2 and the outer tube 3) can be replaced. By pulling out the inner pin 2, the presence or absence of a break or crack in the outer tube 3 can be easily confirmed from the cavity 3b side. If the shear pin 1 has a gap 6, the gap 6 may be used to check the presence or absence of a break in the outer tube 3. When the shear pin 1 is replaced, only the outer tube 3 may be replaced.

[0031] As shown in the example of Fig. 7, when a load (overload) larger than a preset shear strength occurs on the inner pin 2, the inner pin 2 breaks. Since the inner pin 2 is not affected by bending stress, friction, etc. and does not deteriorate, it breaks with precision at the preset shear strength. Since the shear pin 1 breaks when an overload occurs, such as when lifting a container fixed to a ship, equipment such as cranes can be protected.

[0032] As illustrated in Fig. 8, the inner pin 2 may be formed in a substantially cylindrical shape. The upper part of Fig. 8 shows a cross section of the inner pin 2 formed in a substantially cylindrical shape, and the lower part of Fig. 8 shows a cross section of a solid inner pin 2 (see Fig. 2) formed in a cylindrical shape for comparison. In this embodiment, the inner pin 2 has an inner cavity 2b. The inner cavity 2b is formed in a substantially cylindrical shape with the axial direction y coinciding with that of the inner pin 2. The inner pin 2 has a slit 2a formed along the circumferential direction of the outer circumferential surface, similar to the inner pin 2 illustrated in Fig. 2.

[0033] When the preset shear strength of the inner pin 2 is the same, the depth t of the slit 2a can be made smaller in the roughly cylindrical inner pin 2 than in the inner pin 2 that is formed as a solid body. The roughly cylindrical inner pin 2 has a larger second moment of area at the slit 2a than the inner pin 2 that is formed as a solid body, and is more resistant to deterioration due to bending stress. This is advantageous in suppressing deterioration of the inner pin 2. In addition, because the depth t of the slit 2a is smaller, cracks that occur in the slit 2a are easier to find during inspection.

[0034] As shown in FIG. 9, slits 2a may be formed along the circumferential direction of the inner peripheral surface of the inner cavity 2b. The second moment of area of ​​the slits 2a is larger than that of the inner pin 2 formed as a solid body, making it more resistant to deterioration due to bending stress. This is advantageous for suppressing deterioration of the inner pin 2. In addition, the outer peripheral surface of the inner pin 2 is formed smooth without slits 2a. This makes it difficult for resistance to occur when inserting the inner pin 2 into the outer tube 3, making it easier to insert and remove the inner pin 2. This is advantageous for improving the efficiency of inspection work.

[0035] The shear pin 1 may be composed of only the inner pin 2 having a substantially cylindrical shape without the outer cylinder 3. The shear pin 1 composed of only the inner pin 2 can obtain the same effect as above. In other words, since the inner pin 2 is formed in a substantially cylindrical shape, the second moment of area at the slit 2a is larger than that of a conventional shear pin formed as a solid body, and the shear pin 1 is more resistant to deterioration due to bending stress. The shear pin 1 may also be composed of only the inner pin 2 formed in a substantially cylindrical shape with the slit 2a formed in the inner cavity 2b. This shear pin 1 composed of only the inner pin 2 can also obtain the same effect as above.

[0036] As illustrated in FIG. 10, the outer cylinder 3 may have an oil supply port 8 penetrating from the inner cavity 3b to the outer peripheral surface. The outer cylinder 3 may have an oil supply passage 8a formed along the circumferential direction of the outer peripheral surface and connected to the oil supply port 8. When lubricating oil is supplied to the gap 6 between the inner pin 2 and the outer cylinder 3, the lubricating oil is supplied to the outer peripheral surface of the outer cylinder 3 via the oil supply port 8. Wear of the through hole 5 formed in the members 4a and 4b and the outer cylinder 3 can be suppressed by the lubricating oil. This is advantageous in suppressing deterioration of the outer cylinder 3. In FIG. 10, the movement path of the lubricating oil is indicated by arrows for the purpose of explanation.

[0037] Even when lubricating oil such as grease is applied to the outer peripheral surface of the inner pin 2, the lubricating oil moves to the outer peripheral surface of the outer cylinder 3 via the oil supply port 8 and the oil supply passage 8a. This can suppress deterioration of the outer cylinder 3. This is advantageous for realizing a long life of the shear pin 1. [Explanation of symbols]

[0038] 1 Shear pin 2 Inner Pin 2a Slit 2b inner cavity 3. Outer cylinder 3a Slit 3b cavity 4 Two adjacent members 4a Materials 4b Materials 5 Through hole 6. Gap 7 Stopper 8 Fuel filler 8a Fuel supply line x Horizontal y-axis direction z Vertical direction Δd (gap) width d1 (Outer cylinder) inner diameter d2 (Outer diameter of inner pin) t Depth

Claims

1. In a shear pin having a substantially cylindrical shape, The present invention provides a method for manufacturing a gyro fitting, comprising: providing an inner pin having a preset shear strength; and providing an outer cylinder having a generally cylindrical shape and a cavity into which the inner pin is inserted. A shear pin comprising a gap between the inner pin and the outer cylinder and formed along the entire axial direction of the shear pin.

2. The shear pin of claim 1 , wherein the inner pin has a slit formed along a circumferential direction of an outer periphery of the pin.

3. 3. The shear pin according to claim 1, wherein the shear strength of the outer cylinder is set to be smaller than the shear strength of the inner pin.

4. The shear pin according to any one of claims 1 to 3, wherein the inner pin has an inner cavity formed on the inside and a slit formed along the circumferential direction of the outer circumferential surface.

5. 2. The shear pin of claim 1, wherein the inner pin has an inner cavity formed therein and a slit formed along a circumferential direction of the inner cavity.

6. The shear pin according to any one of claims 1 to 5, wherein the outer cylinder has an oil supply port penetrating from the cavity on the inside to an outer peripheral surface on the outside.

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