Shear pin and sensing system

Abstract

To provide a shear pin and a detection system capable of detecting breakage of an outer cylinder.SOLUTION: A shear pin 1 includes a substantially columnar inner pin 2 and a substantially cylindrical outer cylinder 3 into which the inner pin 2 is inserted, the shear pin 1 including a first partial P1 and a second partial P2 formed along an axial direction y, a first gap 6 formed between an outer peripheral surface of the inner pin 2 and an inner peripheral surface of the outer cylinder 3 in the first partial P1, and a second gap 7 formed between the outer peripheral surface of the inner pin 2 and the inner peripheral surface of the outer cylinder 3 in the second partial P2. The first gap 6 is formed larger than the second gap 7.SELECTED DRAWING: Figure 2

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 a detection system including the shear pin. More specifically, the present invention relates to a shear pin and detection system that can detect the breakage of an outer tube. [Background technology]

[0002] The applicant has already proposed a double shear pin configuration having an inner pin and an outer cylinder (see, for example, Patent Document 1). The shear pin described in Patent Document 1 has been able to achieve a long life.

[0003] When checking for fractures in the outer cylinder of the shear pin, the shear pin had to be removed from the crane, etc. It would be desirable to be able to easily check for fractures in the outer cylinder. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-111080 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above problems, and an object of the present invention is to provide a shear pin and a detection system capable of detecting breakage of an outer cylinder. [Means for solving the problem]

[0006] A shear pin for achieving the above-mentioned object is a shear pin having an approximately cylindrical inner pin and an approximately cylindrical outer tube into which the inner pin is inserted, and is characterized in that it has a first portion and a second portion formed along the axial direction, and has a first gap formed between the inner pin and the outer tube in the first portion, and a second gap formed between the inner pin and the outer tube in the second portion, and the first gap is formed larger than the second gap.

[0007] A detection system for achieving the above-mentioned object comprises a shear pin having an approximately cylindrical inner pin and an approximately cylindrical outer tube into which the inner pin is inserted, and a detection device for detecting whether or not the outer tube is broken, wherein the shear pin has a first portion and a second portion formed along the axial direction, and has a first gap formed between the inner pin and the outer tube in the first portion, and a second gap formed between the inner pin and the outer tube in the second portion, and the first gap is configured to be larger than the second gap, and the detection device is characterized by having a target installed on one side of two adjacent members fixed by the shear pin, and a detection unit installed on the other side for detecting the target. [Effects of the Invention]

[0008] According to the present invention, when only the outer cylinder breaks, the member corresponding to the first portion is displaced in accordance with the size of the first gap, and the breakage of the outer cylinder can be easily detected from this displacement. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is an explanatory diagram illustrating an outline of a shear pin in perspective view. [Figure 2] 10 is an explanatory view illustrating a cross section parallel to the axial direction of an outer cylinder and an inner pin. FIG. [Figure 3] FIG. 1 is an explanatory diagram illustrating an outline of a detection device. [Figure 4] 3 is an explanatory view illustrating a state in which the outer cylinder of FIG. 2 is broken. FIG. [Figure 5] 10 is an explanatory diagram illustrating a state of the detection device when the outer cylinder is broken. FIG. [Figure 6] FIG. 3 is an explanatory diagram illustrating a modified example of FIG. 2. [Figure 7] FIG. 10 is an explanatory diagram illustrating a modified example of the detection device. [Figure 8] 10A and 10B are explanatory diagrams illustrating examples of locking portions formed on a collar. [Figure 9] 10A and 10B are explanatory views illustrating examples of locking portions formed on an outer cylinder. DETAILED DESCRIPTION OF THE INVENTION

[0010] The shear pin and the detection system 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 vertical 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 into a generally cylindrical shape overall. The shear pin 1 has a double-tube structure including an inner pin 2 and an outer cylinder 3. The shear pin 1 has a first portion P1 and a second portion P2 formed along the axial direction y. In this embodiment, the shear pin 1 has the first portion P1 formed in the center along the axial direction y, and second portions P2 formed on both sides of the first portion P1. It can be said that the shear pin 1 has the first portion P1 and the second portion P2 formed along the axial direction y.

[0012] The inner pin 2 is formed in a substantially cylindrical shape. The inner pin 2 has two slits 2a formed along the circumferential direction of its outer circumferential surface. The inner pin 2 has a predetermined shear strength, which is adjusted by the depth of the slits 2a. The shear strength refers to the strength at which the inner pin 2 breaks when subjected to shear forces in the radial directions x and z. The slits 2a are not essential, and the inner pin 2 may be configured without the slits 2a. In this case, the shear strength is preset based on the diameter and material of the inner pin 2. The inner pin 2 is made of machine-forged carbon steel, such as S45C. In this embodiment, the inner pin 2 is configured as a solid cylinder, but is not limited to this configuration. The inner pin 2 may also be configured as a cylindrical member.

[0013] The outer cylinder 3 is formed in a substantially cylindrical shape. The outer cylinder 3 has two slits 3a formed along the circumferential direction of the outer peripheral surface. The outer cylinder 3 has a predetermined shear strength, which is adjusted by the depth of the slits 3a. The slits 3a are not essential, and the outer cylinder 3 may be configured without the slits 3a. In this case, the shear strength is predetermined based on the size of the inner diameter of the outer cylinder 3 and the type of material. The outer cylinder 3 is made of machine-forged carbon steel, such as S25C. The outer cylinder 3 has a cavity 3b into which the inner pin 2 is inserted. For the sake of explanation, FIG. 1 shows the inner pin 2 and the outer cylinder 3 separated from each other.

[0014] As illustrated in FIG. 2, the shear pin 1 is inserted into a through hole formed in two adjacent members (a first member 4 and a second member 5). In this embodiment, one first member 4 is disposed between a pair of second members 5. The first portion P1 of the shear pin 1 is disposed in the first member 4, and the second portion P2 is disposed in a position corresponding to the second member 5. In this embodiment, second portions P2 are formed on both sides of the first portion P1 in the axial direction y, and slits 2a and 3a are disposed at positions that define the boundaries between the first portion P1 and the second portion P2 in the axial direction y. It can be said that the boundaries between the first portion P1 and the second portion P2 of the shear pin 1 are formed by the slits 2a and 3a. In the axial direction y, the first portion P1 and the second portion P2 are formed to be longer or sufficiently longer than the slits 2a and 3a.

[0015] The first member 4 and the second member 5 are constrained by the shear pin 1 from moving relative to each other in a direction perpendicular to the axial direction y. Slits 2a and 3a in the shear pin 1 are formed at positions corresponding to the boundary between the first member 4 and the second member 5. When the shear pin 1 breaks, that is, when both the inner pin 2 and the outer cylinder 3 break, the first member 4 and the second member 5 are released from their fixed position. The shear pin 1 has the function of being inserted into the through hole to secure the adjacent first member 4 and second member 5 together, and the function of breaking when subjected to a predetermined shear force, releasing the first member 4 and the second member 5 from their fixed position.

[0016] As illustrated in FIG. 2 , a first gap 6 is formed between the inner pin 2 and the outer tube 3 in the first portion P1. The first gap 6 is formed over the entire area of ​​the first portion P1 in the axial direction y. Similarly, a second gap 7 is formed between the inner pin 2 and the outer tube 3 in the second portion P2. The second gap 7 is formed over the entire area of ​​the second portion P2 in the axial direction y. The first gap 6 and the second gap 7 refer to gaps formed between the outer peripheral surface of the inner pin 2 and the inner peripheral surface of the outer tube 3 in the radial direction of the shear pin 1. Here, the outer peripheral surface of the inner pin 2 refers to the peripheral surface in the portion that does not include the slit 2a. Therefore, the length from the bottom of the slit 2a to the inner peripheral surface of the outer tube 3 is larger than the first gap 6 and the second gap 7. The sizes of the first gap 6 and the second gap 7 can also be considered the length over which the inner pin 2 can move in the vertical direction z. The first gap 6 is formed larger than the second gap 7.

[0017] The shear pin 1 may include a collar 8 that closes at least a portion of the second gap 7. The collar 8 is formed in a substantially cylindrical shape. In this embodiment, the length of the collar 8 in the axial direction y is formed to be the same length as the second portion P2. In the axial direction y, the collar 8 is arranged in a range that does not overlap with the slits 2a, 3a. In the axial direction y, the length of the collar 8 may be configured to be shorter than the length of the second portion P2. The collars 8 are arranged in the second portion P2, in the region between the inner pin 2 and the outer cylinder 3.

[0018] The collar 8 can be made of the same material as the inner pin 2 or the outer cylinder 3. The collar 8 may also be made of engineering plastic. The collar 8 is desirably made of a material that is resistant to deformation when subjected to external forces during use of the shear pin 1. In the embodiment illustrated in FIG. 2, the collar 8 fills at least a portion of the second gap 7, making the second gap 7 smaller than the first gap 6. In the direction perpendicular to the axial direction y, the second gap 7 is smaller by the area occupied by the collar 8. This collar 8 prevents bending forces from occurring in the inner pin 2.

[0019] In this embodiment, the collar 8 is loosely fitted to the outer cylinder 3. Therefore, the size of the second gap 7 is not zero, but is made as small as possible. The collar 8 may be tightly fitted to the outer cylinder 3, so that the size of the second gap 7 is zero. In other words, the shear pin 1 of this invention includes a range in which the size of the second gap 7 is zero.

[0020] The inner pin 2 is disposed inside the collar 8. The inner pin 2 is held by the collar 8. A second gap 7 is formed between the inner pin 2 and the collar 8. The inner pin 2 and the collar 8 may be a clearance fit or an interference fit. When the collar 8 is provided, the second gap 7 is the sum of the gap formed between the inner pin 2 and the collar 8 in the radial direction of the shear pin 1 and the gap formed between the collar 8 and the outer cylinder 3.

[0021] Closing members 9 may be arranged on both ends of the shear pin 1 in the axial direction y. The closing members 9 can prevent the inner pin 2 and the collar 8 from slipping out of the outer tube 3. The shear pin 1 may have one or both ends open in the axial direction y.

[0022] 3, a detection system can be configured by combining a detection device 10 that detects whether or not the outer cylinder 3 is broken with the above-mentioned shear pin 1. The detection device 10 has a target 10a installed on one side of the first member 4 or the second member 5, and a detection unit 10b installed on the other side.

[0023] 3, the target 10a is made of, for example, a metal material processed into an arc shape. The target 10a is formed of, for example, a steel plate or an aluminum plate having an arc shape centered on the central axis C of the shear pin 1. The target 10a is fixed to the first member 4.

[0024] The detection unit 10b is configured, for example, by a proximity sensor that measures the distance to the target 10a. The detection unit 10b is fixed to the second member 5. The proximity sensor that constitutes the detection unit 10b measures the distance to the target 10a and emits a signal or the like when this distance exceeds a preset threshold value. The detection device 10 can detect changes in the relative position between the first member 4 and the second member 5.

[0025] Either the target 10a or the detection unit 10b may be fixed to the first member 4, and the other may be fixed to the second member 5. Alternatively, the target 10a may be fixed to the second member 5, and the detection unit 10b may be fixed to the first member 4.

[0026] As shown in the example of Figure 4, when the outer cylinder 3 breaks due to fatigue, the first member 4 moves, for example, upward in Figure 4, relative to the second member 5. The amount of this relative displacement corresponds to the size of the first gap 6. For the sake of explanation, in Figure 4, the position of the first member 4 before displacement is shown by a dashed line, and the displacement direction of the first member 4 is shown by a white arrow.

[0027] As shown in FIG. 5, displacement of the first member 4 relative to the second member 5 causes the target 10a to move away from the detection unit 10b. The proximity sensor that constitutes the detection unit 10b emits a signal when the distance to the target 10a exceeds a predetermined threshold. This signal is sent to, for example, the crane's cab to notify the operator that the outer cylinder 3 has broken. The operator can learn of the breakage of the outer cylinder 3 using the detection device 10 without removing the shear pin 1.

[0028] 5, even when the first member 4 and the second member 5 tilt around the shear pin 1, the detection device 10 can accurately detect fracture of the outer cylinder 3. Because the target 10a is formed in an arc shape centered on the shear pin 1, whether or not the first member 4 tilts relative to the second member 5 does not affect the distance between the target 10a and the detection unit 10b. Therefore, the detection device 10 can accurately detect the relative position of the first member 4 and the second member 5, regardless of whether or not the first member 4 tilts.

[0029] By configuring the first gap 6 to be larger than the second gap 7, it becomes easier to distinguish whether the displacement of the first member 4 is due to bending of the outer tube 3 or due to breakage of the outer tube 3. It becomes easier to check whether the outer tube 3 is broken or not based on the amount of displacement of the first member 4 relative to the second member 5. Depending on the size of the first gap 6, it may even be possible for an operator to visually determine whether the outer tube 3 is broken or not. If a detection device 10 is installed, breakage of the outer tube 3 can be detected with even greater accuracy.

[0030] The configuration in which the second gap 7 is smaller than the first gap 6 makes it possible to suppress bending of the outer tube 3 relative to the inner pin 2 at the second portion P2. This makes it possible to avoid a problem in which the detection device 10 mistakenly detects bending of the outer tube 3 as a breakage of the outer tube 3.

[0031] If the outer tube 3 breaks due to fatigue, the detection device 10 can quickly detect this breakage. This prevents the inner pin 2 from fatigued and the shear pin 1 from breaking unintentionally if the breakage of the outer tube 3 is left unattended for a long period of time. The shear pin 1 can accurately fix and protect the first member 4 and the second member 5. Since the breakage of the outer tube 3 can be detected without removing the shear pin 1, the maintainability of the shear pin 1 can be improved.

[0032] 4, after the outer cylinder 3 is broken, the closing member 9 is removed first. Then, the collar 8 is pulled out in the axial direction y from the outer cylinder 3, and the inner pin 2 is pulled out in the axial direction y. In this embodiment, the diameter of the inner pin 2 is the same in the first portion P1 and the second portion P2, so that the inner pin 2 can be pulled out in the axial direction y relatively easily.

[0033] When the inner pin 2 is pulled out, the outer tube 3 has already broken, so the constraint between the first member 4 and the second member 5 is released. The outer tube 3 is then pulled out from the first member 4 and the second member 5. After aligning the first member 4 and the second member 5, a new shear pin 1 is inserted into the through hole of the first member 4, etc. This completes the shear pin 1 replacement work.

[0034] The configuration in which the collar 8 is disposed in the second portion P2 makes it easier to adjust the size of the second gap 7 in the shear pin 1. Even when the outer diameter of the inner pin 2 and the inner diameter of the outer cylinder 3 are formed to be uniform in the axial direction y, the use of the collar 8 makes it possible to make the second gap 7 smaller than the first gap 6. This is advantageous in reducing the manufacturing cost of the shear pin 1.

[0035] The shear pin 1 may have a configuration in which the first gap 6 is formed larger than the second gap 7. The larger the first gap 6, the greater the displacement of the first member 4 when the outer tube 3 breaks. It is easier to confirm the breakage of the outer tube 3 from the outside. On the other hand, the smaller the second gap 7, the more effectively the bending force generated in the inner pin 2 inside the outer tube 3 can be suppressed. By suppressing the bending of the inner pin 2, it is possible to precisely fracture the inner pin 2 with a predetermined shear strength. For this reason, it is desirable that the second gap 7 is entirely filled with the collar 8.

[0036] The shear pin 1 is not limited to a configuration in which a collar 8 is disposed. As illustrated in Fig. 6, the outer cylinder 3 may be machined so that the inner diameter of the outer cylinder 3 is larger in the first portion P1 than in the second portion P2. By machining the inner peripheral surface of the outer cylinder 3, a configuration in which the first gap 6 is formed larger than the second gap 7 can be realized.

[0037] This configuration provides the same effect as the embodiment in which the collar 8 is provided. Since it is necessary to process the inner peripheral surface of the outer cylinder 3, the configuration in which the collar 8 is provided is advantageous in terms of reducing the manufacturing cost of the shear pin 1.

[0038] The outer diameter of the first portion P1 of the inner pin 2 may be smaller than the outer diameter of the second portion P2. By machining the outer peripheral surface of the inner pin 2, a configuration can be realized in which the first gap 6 is formed larger than the second gap 7. Because the size of the outer peripheral surface of the inner pin 2 is not uniform, when the outer tube 3 breaks, the inner pin 2 may not be able to be pulled out in the axial direction y. In this case, it is necessary to forcibly break the inner pin 2 and release the constraint between the first member 4 and the second member 5, and then remove the inner pin 2 and the outer tube 3.

[0039] The detection device 10 is not limited to a combination of a metal material processed into an arc shape and a proximity sensor. As illustrated in FIG. 7, the target 10a is made of, for example, a display member showing an arc-shaped pattern. The target 10a may be, for example, a pattern drawn directly on the first member 4 with ink or the like, or may be a sticker or the like showing an arc-shaped pattern attached to the first member 4. The detection unit 10b is made of, for example, a metal material with an observation window 11 formed therein. The detection unit 10b is fixed to the second member 5.

[0040] When the outer cylinder 3 is not broken, as illustrated on the left side of Fig. 7, the target 10a can be seen through the viewing window 11 of the detection unit 10b. When the outer cylinder 3 breaks and the first member 4 moves, as illustrated on the right side of Fig. 7, the target 10a cannot be seen through the viewing window 11 of the detection unit 10b. Whether the outer cylinder 3 is broken or not can be detected depending on the state of the target 10a that can be seen through the viewing window 11.

[0041] The shape of the target 10a is not limited to an arc shape. When the first member 4 and the second member 5 do not tilt around the shear pin 1, the target 10a only needs to have a configuration that can detect the same length as the first gap 6 in one direction.

[0042] As illustrated in FIG. 8, the shear pin 1 may have a locking portion 12 that prevents the collar 8 from entering the first portion P1. In this embodiment, the locking portion 12 is formed of an annular member that protrudes from the outer peripheral surface of the collar 8. The locking portion 12 contacts the end of the outer cylinder 3 in the axial direction y, thereby preventing the collar 8 from moving from the second portion P2 toward the first portion P1. This can prevent the shear strength of the inner pin 2 and the outer cylinder 3 from changing due to the collar 8 moving to the first portion P1.

[0043] 9, the locking portion 12 may be formed of a member that protrudes inward from the inner circumferential surface of the outer tube 3. In this embodiment, the locking portion 12 is formed near the boundary between the first portion P1 and the second portion P2 of the outer tube 3. The locking portion 12 makes the radius of the inner circumferential surface of the outer tube 3 larger in the second portion P2 than in the first portion P1. The step formed by the locking portion 12 prevents the collar 8 from moving from the second portion P2 toward the first portion P1. [Explanation of symbols]

[0044] 1 shear pin 2 inner pins 2a Slit 3 Outer cylinder 3a Slit 4 First member 5 Second member 6 First Gap 7 Second gap 8 colors 9 Closure member 10. Detection Device 10a Target 10b Detection unit 11 Peephole 12 Locking part x horizontal direction y-axis direction z Vertical direction P1 first part P2 second part

Claims

1. A shear pin having a substantially cylindrical inner pin and a substantially cylindrical outer cylinder into which the inner pin is inserted, The shaft has a first portion and a second portion formed along an axial direction, a first gap formed between the outer peripheral surface of the inner pin and the inner peripheral surface of the outer cylinder in the first portion, and a second gap formed between the outer peripheral surface of the inner pin and the inner peripheral surface of the outer cylinder in the second portion, wherein the first gap is larger than the second gap.

2. The inner pin has two slits formed along its outer periphery, 2. The shear pin according to claim 1, wherein the second portion is formed on both sides of the first portion in the axial direction, and the slit is disposed at a position that is a boundary between the first portion and the second portion in the axial direction.

3. The shear pin of claim 1 or 2, further comprising a generally cylindrical collar disposed in the second gap.

4. A detection system including a shear pin having a substantially cylindrical inner pin and a substantially cylindrical outer cylinder into which the inner pin is inserted, and a detection device that detects whether or not the outer cylinder is broken, the shear pin has a first portion and a second portion formed along an axial direction, a first gap formed between an outer peripheral surface of the inner pin and an inner peripheral surface of the outer cylinder in the first portion, and a second gap formed between the outer peripheral surface of the inner pin and the inner peripheral surface of the outer cylinder in the second portion, and the first gap is larger than the second gap, The detection system is characterized in that the detection device has a target installed on one side of two adjacent members fixed by the shear pin, and a detection unit installed on the other side to detect the target.

5. The inner pin has two slits formed along its outer periphery, The detection system according to claim 4 , wherein the second portions are formed on both sides of the first portion in the axial direction, and the slit is disposed at a position that is a boundary between the first portion and the second portion in the axial direction.

6. The detection system according to claim 4 or 5, wherein the target is formed in an arc shape centered on the central axis of the shear pin.

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