Bolt and connection arrangement having such bolt

Abstract

The invention relates to a bolt and a connection arrangement having the same. The bolt is provided with a bolt head, a thread part located at the opposite end of the head and a necking part located between the head and the thread part, the diameter of the necking part is reduced relative to the diameter of the bolt head, and the necking part sequentially comprises a first necking part, a second necking part, a third necking part and a fourth necking part in the direction from the thread head to the thread part. And the third section of necking is provided with a first connecting piece tensioning part of which the diameter is greater than that of the second section of necking, the fourth section of necking and the thread part. The connecting arrangement comprises a first connecting piece, a second connecting piece and the bolt, the first connecting piece and the second connecting piece are connected through the bolt, and the bolt penetrates through the second connecting piece and extends into the hole of the first connecting piece, so that the tensioning part of the first connecting piece of the bolt abuts against the hole of the first connecting piece on the tensioning part. According to the invention, the rigidity of the bolt can be improved without increasing the size of the bolt and the size and the structure of the first connecting piece, the inherent frequency of the bolt is changed, and the conditions of resonance, creep deformation or fatigue failure and the like of the bolt and the first connecting piece are avoided.

Description

Technical Field

[0001] The present invention relates to mechanical connections, such as those used in rail transit gearboxes. In particular, the present invention relates to bolts, particularly long bolts having a length greater than or equal to 10 times the outer diameter of the bolt thread. The present invention also relates to connection arrangements using such long bolts. Background Art

[0002] In the rail transit industry, long bolts are often used to connect gearbox housings. However, increasing bolt length reduces bolt stiffness and affects the natural frequency. On the other hand, increasing bolt stiffness and natural frequency requires increasing the bolt diameter and material, which in turn increases the connection layout dimensions. With limited connection dimensions, it's impossible to simultaneously meet both requirements.

[0003] Therefore, it is desirable to redesign the long bolt so as to maintain the stiffness and natural frequency of the bolt sufficient to meet the requirements without increasing the bolt diameter and material. Summary of the Invention

[0004] The present invention aims to provide a bolt, in particular a long bolt of the above type, which can ensure sufficient strength without increasing the diameter and material of the bolt.

[0005] According to an embodiment of the present invention, the bolt has a bolt head, a threaded portion located at the opposite end of the head, and a necking portion located therebetween, wherein the diameter of the necking portion is reduced relative to the diameter of the bolt head, wherein, along the direction from the threaded head to the threaded portion, the necking portion sequentially includes a first necking section, a second necking section, a third necking section, and a fourth necking section, wherein the third necking section is provided with a first connecting member tightening portion having a diameter greater than that of the second necking section, the fourth necking section, and the threaded portion, which is used for, for example, the first connecting member of a gear box housing.

[0006] Preferably, the third neck section is located in the middle relative to the second neck section and the fourth neck section.

[0007] According to an embodiment, along the direction from the thread head to the threaded portion, an exit guide is provided between the third necking section and the second necking section and the tensioning section of the first connector, and / or an entry guide is provided between the fourth necking section and the tensioning section of the first connector. The exit guide and entry guide are used to guide the bolt out of and into the first connector, respectively. The angle between the axial cross-sectional outer contour of the exit guide and / or entry guide and the axis of the bolt can be between 5 and 20 degrees.

[0008] Preferably, a transition portion is provided between the exit guide portion and the first connector tensioning portion, and / or between the entry guide portion and the first connector tensioning portion. The axial cross-sectional outer contour of the transition portion can be an arc or a straight line to provide a smooth transition. This arrangement can reduce stress concentration.

[0009] The exit guide portion of the third necked section, the transition portion between the exit guide portion and the first connecting member tensioning portion, the first connecting member tensioning portion, the entry guide portion and the transition portion between the first connecting member tensioning portion, and the entry guide portion can be made of materials different from those of the rest of the bolt, including but not limited to aluminum alloy, alloy steel, nylon, plastic, etc.

[0010] According to an embodiment, the bolt head may be hexagonal, rectangular, cylindrical, or the like.

[0011] According to the embodiment, the tensioning portion of the first connecting member of the third necking section can be a cylindrical structure, a conical structure or an arc structure. In the cylindrical structure, the radial cross-section of the tensioning portion of the third necking section can be circular, elliptical or irregular arc-shaped, and the axial cross-section can be rectangular. In the conical structure, the radial cross-section of the tensioning portion of the third necking section can be circular, elliptical or irregular arc-shaped, and the radial dimension close to the bolt head is larger than the radial dimension away from the bolt head. In the arc structure, the radial cross-section of the tensioning portion of the third necking section can be circular, elliptical or irregular arc-shaped, and the outer contour line of the axial cross-section can be a drum-shaped, arc-shaped, parabolic or other arc-shaped shape with the radial dimension in the middle larger than the radial dimension at both ends.

[0012] Preferably, a first necking transition portion is provided between the bolt head and the first necking section, connecting the bolt head and the first necking section. Preferably, the first necking transition portion is an arc structure to provide a smooth transition. This arrangement can reduce stress concentration.

[0013] According to an embodiment, the first constriction includes, in a direction from the threaded head to the threaded portion, a second connector tensioning portion and a second connector guide portion, the second connector guide portion being connected to the second constriction. The second connector tensioning portion and the second connector guide portion are respectively used to tension the second connector and guide a bolt through the second connector for connection to the first connector.

[0014] According to an embodiment, an angle between an outer contour line of an axial cross-section of the first-section necked guide portion of the second connector and the axis of the bolt is between 5 and 20 degrees.

[0015] Preferably, a transition portion is provided between the first section of the second connector guide portion and the second connector tensioning portion, and the axial cross-sectional outer contour of the transition portion can be an arc or a straight line to achieve a smooth transition. This arrangement can reduce stress concentration.

[0016] According to an embodiment, the first necked second connector guide portion, the transition portion, and the second connector tensioning portion may be made of the same or different materials as the bolt, including but not limited to aluminum alloy, alloy steel, nylon, and plastic.

[0017] The present invention further provides a connection arrangement for connecting, for example, a rail transit gearbox housing, the connection arrangement comprising the above-mentioned bolts and a connecting member connected by the bolts, such as a gearbox housing.

[0018] According to an embodiment of the present invention, a connection arrangement includes a first connector and a second connector, and the aforementioned bolt, which connects the first connector and the second connector, wherein the bolt passes through the second connector and extends into a hole in the first connector, so that a tensioning portion of the first connector and the hole in the first connector abut at a tensioning location. The tensioning portion of the first connector and the tensioning location of the first connector form an interference fit, a transition fit, or a clearance fit.

[0019] According to an embodiment, the hole of the first connecting element is a through hole through which the bolt passes, and the connecting arrangement accordingly has a nut which is screwed onto the threaded portion.

[0020] According to another embodiment, the hole of the first connecting member is a blind hole, into which the bolt is screwed.

[0021] Preferably, the connection arrangement further comprises a first washer and / or a second washer, wherein the first washer is positioned between the bolt head and the second connecting member, and the second washer is positioned between the nut and the first connecting member. With this arrangement, the bolt can be prevented from loosening.

[0022] During connection, the tensioning portion of the first connecting member of the bolt can be guided by the entry guide portion into the tensioning portion of the first connecting member by percussion, pressure, hydraulic pressure, etc. For example, the tensioning portion of the first connecting member of the bolt can be guided by the entry guide portion after cooling the tensioning portion, or the tensioning portion of the first connecting member can be guided by the entry guide portion after heating the tensioning portion of the first connecting member.

[0023] According to the present invention, compared with the traditional long bolt, a connector tensioning portion is added to the neck portion. Therefore, when the bolt is screwed in, only the first connector tensioning portion of the third necked section formed in the middle of the bolt abuts against the through hole or blind hole in the first connector (such as the gearbox housing). Unlike traditional long bolts, this structure does not reduce the rigidity of the bolt after it is screwed in, but still maintains its strength. Therefore, without increasing the size of the bolt and the size and structure of the first connector, the rigidity of the bolt can be increased, the natural frequency of the bolt can be changed, and resonance, creep deformation or fatigue failure between the bolt and the first connector can be avoided. In addition, due to the guiding and tensioning effects of the second connector guide portion of the first necked section and the second connector tensioning portion, even if the bolt is further tightened after it is screwed into place, no shaking will occur between the bolt and the second connector. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Embodiments of the invention will be explained in more detail in the accompanying drawings, in which:

[0025] Figure 1 A schematic diagram showing a bolt according to an embodiment of the present invention;

[0026] Figure 2 A schematic diagram showing a bolt according to another embodiment of the present invention;

[0027] Figure 3 A schematic diagram showing a bolt according to another embodiment of the present invention;

[0028] Figure 4-Figure 6 A schematic diagram showing a connection arrangement according to an embodiment of the present invention, wherein the connection arrangement comprises Figure 1-Figure 3 Bolts shown;

[0029] Figure 7-Figure 9 A schematic diagram showing a connection arrangement according to another embodiment of the present invention, wherein the connection arrangement comprises Figure 1-Figure 3 Bolts shown.

[0030] In the accompanying drawings, for the sake of clarity, embodiments of the present invention are shown in a simplified manner. The accompanying drawings are not necessarily shown to scale. The same reference numerals in the accompanying drawings represent the same components.

[0031] Reference Signs List

[0032] 1 - Bolt

[0033] 2——Bolt head

[0034] 3——First necking transition section

[0035] 4——First necking

[0036] 5——Second necking

[0037] 6——Third necking

[0038] 7——The fourth segment of necking

[0039] 8——Threaded part

[0040] 9——First gasket

[0041] 10——Second connecting piece

[0042] 11——First through-hole connector

[0043] 12——Second gasket

[0044] 13——Nut

[0045] 14——First blind hole connector

[0046] 201——The first connection surface of the bolt head

[0047] 401——Second connecting piece tensioning part

[0048] 402——Transition Department

[0049] 403——Second connecting member guide portion

[0050] 601——Exit guide under the columnar structure

[0051] 602——Transition section under columnar structure

[0052] 603——First connecting piece tensioning part under the columnar structure

[0053] 604——Transition section under columnar structure

[0054] 605——Entry guide under the columnar structure

[0055] 606——Exit guide under the conical structure

[0056] 607——Transition section under the tapered structure

[0057] 608——First connecting piece tensioning portion under the conical structure

[0058] 609——Transition section under the tapered structure

[0059] 610——Entry guide under the tapered structure

[0060] 611——Exit guide under the arc structure

[0061] 612——Transition section under the arc structure

[0062] 613——The first connecting piece tensioning part under the arc structure

[0063] 614——Transition section under the arc structure

[0064] 615——Entry guide under the arc structure

[0065] 901——First gasket first connection surface

[0066] 902——first aperture portion of the first gasket

[0067] 903——Second connection surface of the first gasket

[0068] 1001——First connecting surface of the second connecting member

[0069] 1002——first aperture portion of the second connecting member

[0070] 1003——Second connecting surface of the second connecting member

[0071] 1101——first connection surface of the first through-hole connector

[0072] 1102——First aperture portion of the first through-hole connector

[0073] 1103——Second connection surface of the first through-hole connector

[0074] 1104——Tightening part of the first through-hole connector

[0075] 1105——Second aperture portion of the first through hole connector

[0076] 1106——third connection surface of the first through-hole connector

[0077] 1201——First connection surface of the second gasket

[0078] 1202——First aperture portion of the second gasket

[0079] 1203——Second connection surface of the second gasket

[0080] 1301——First connection surface of the nut

[0081] 1302——Threaded hole for nut

[0082] 1401——First connection surface of the first blind hole connector

[0083] 1402——First aperture portion of the first blind hole connector

[0084] 1403——Second connection surface of the first blind hole connector

[0085] 1404——Tightening part of the first blind hole connector

[0086] 1405——Second aperture portion of the first blind hole connector

[0087] 1406——Third connection surface of the first blind hole connector

[0088] 1407——the third aperture portion of the first blind hole connector

[0089] 6001——Tensioning part of columnar structure

[0090] 6002——Tightening part of cone structure

[0091] 6003——Curved structure tensioning part DETAILED DESCRIPTION

[0092] The following describes embodiments of the present invention with reference to the accompanying drawings. In the following description, reference is made to a rail transit gearbox.

[0093] Figure 1-Figure 3 The long bolt 1 according to an embodiment of the present invention is shown. Its length is greater than or equal to 10 times the outer diameter of the bolt thread and is generally used to connect the housing of a rail transit gearbox. The bolt 1 has guiding and tensioning functions.

[0094] Figure 4-Figure 6 and Figure 7-Figure 9 The connection arrangement of the screw 1 is shown in each case for use with a first connection element having a through hole and a first connection element having a blind hole.

[0095] As shown in the figure, a bolt 1 comprises a bolt head 2, a first neck transition portion 3, a first neck section 4, a second neck section 5, a third neck section 6, a fourth neck section 7, and a threaded portion 8. In the figure, the diameters of the four neck sections are smaller than the diameter of the bolt head 2, the diameters of the second and fourth neck sections are the same as the diameter of the threaded portion, and the diameters of the first and third neck sections are larger than the diameters of the second and fourth neck sections. However, it is contemplated that the bolt may have a different configuration.

[0096] The bolt head 1 can be in the shape of a hexagonal column, a rectangular column or a cylinder.

[0097] The first necking transition portion 3 connects the bolt head 2 and the first necking section 4 and has an arc structure, which plays a transition role to reduce stress concentration.

[0098] The first section of the neck 4 provides the bolt 2 with a guiding and tightening function for the (second) connecting member, which includes a second connecting member tightening portion 401, a transition portion 402 and a second connecting member guide portion 403. The second connecting member guide portion 403 of the first section of the neck 4 is connected to the second section of the neck 5, and is used to guide the second connecting member tightening portion 401 of the bolt 1 into the first gasket 9 and the second connecting member 10, and guide the second connecting member tightening portion 401 into the first aperture portion 902 of the first gasket 9 and the first aperture portion 1002 of the second connecting member 10 to help the second connecting member tightening portion 401 in the second connecting member 10, wherein the second connecting member tightening portion 401 of the first section of the neck 4 forms an interference fit, a transition fit or a clearance fit with the first aperture portion 902 of the first gasket 9 and the first aperture portion 1002 of the second connecting member 10 in whole or in part.

[0099] Furthermore, the angle between the axial cross-sectional outer contour of the second connector guide portion 403 of the first constriction 4 and the bolt axis 101 is between 5 and 20 degrees. The axial cross-sectional outer contour of the transition portion 402 of the first constriction 4 is an arc or a straight line. The second connector guide portion 403, transition portion 402, and second connector tensioning portion 401 of the first constriction 4 can be made of the same or different materials as the rest of the bolt 1, including but not limited to aluminum alloy, alloy steel, nylon, and plastic.

[0100] The second neck section 5 connects the first neck section 4 and the third neck section 6 and plays a connecting and supporting role.

[0101] The third section necking 6 provides the bolt 1 with a guiding and tightening function for the (first) connecting member (i.e., the gearbox housing). The first connecting member tightening portion of the third section necking 6 can be a columnar structure 6001 ( Figure 1 ), cone structure 6002( Figure 2 ) or arc structure 6003( Figure 3 The radial cross-section of the cylindrical structure 6001 can be circular, elliptical, or an irregular arc, and the axial cross-section can be rectangular. The radial cross-section of the conical structure 6002 can be circular, elliptical, or an irregular arc, and the radial dimension of the conical structure near the bolt head 2 is larger than the radial dimension away from the bolt head 2. The radial cross-section of the arc structure 6003 can be circular, elliptical, or an irregular arc, and the outer contour of the axial cross-section can be a drum, arc, parabola, or other arc shape, with the radial dimension in the middle larger than the radial dimensions at both ends.

[0102] In the columnar structure 6001, the third constriction section 6 includes an exit guide 601, a transition section 602, a first connector tensioning section 603, a transition section 604, and an entry guide 605. The entry guide 605 guides the first connector tensioning section 603 into the tensioning areas 1104 and 1404 of the first connectors 11 and 14. The transition section 604 connects the entry guide 605 and the first connector tensioning section 603, providing a smooth transition. The exit guide 601 guides the first connector tensioning section 603 out of the tensioning areas 1104 and 1404 of the first connectors 11 and 14, exiting the first gasket 9 and the first aperture 902 and first aperture 1002 of the second connector 10. The transition section 602 connects the exit guide 601 and the first connector tensioning section 603, providing a smooth transition.

[0103] In the tapered structure 6002, the third section of the necking 6 includes an exit guide portion 606, a transition portion 607, a first connector tensioning portion 608, a transition portion 609, and an entry guide portion 610. The entry guide portion 610 guides the first connector tensioning portion 608 into the tensioning portions 1104 and 1404 of the first connectors 11 and 14. The transition portion 609 connects the entry guide portion 610 and the first connector tensioning portion 608, providing a smooth transition. The exit guide portion 606 guides the first connector tensioning portion 608 to exit the tensioning portions 1104 and 1404 of the first connectors 11 and 14, exiting the first gasket 9 and the first aperture portion 902 and the first aperture portion 1002 of the second connector 10. The transition portion 607 connects the exit guide portion 606 and the first connector tensioning portion 608, providing a smooth transition.

[0104] In the arc-shaped structure 6003, the third section of the necking 6 includes an exit guide portion 611, a transition portion 612, a first connector tensioning portion 613, a transition portion 614, and an entry guide portion 615. The entry guide portion 615 guides the first connector tensioning portion 613 into the tensioning portions 1104 and 1404 of the first connectors 11 and 14. The transition portion 614 connects the entry guide portion 615 and the first connector tensioning portion 613, providing a smooth transition. The exit guide portion 611 guides the first connector tensioning portion 613 to exit the tensioning portions 1104 and 1404 of the first connectors 11 and 14, exiting the first gasket 9 and the first aperture portion 902 and the first aperture portion 1002 of the second connector 10. The transition portion 612 connects the exit guide portion 611 and the first connector tensioning portion 613, providing a smooth transition.

[0105] The entry guide portions 605, 610 and 615 of the third section necking 6 respectively guide the first connector tensioning portions 603, 608, 613 into the first gasket 9, the second connector 10, the first through-hole connector 11 or the first blind hole connector 14, and guide the first connector tensioning portions 603, 608, 613 into the tensioning portion 1104 of the first through-hole connector 11 or the tensioning portion 1404 of the first blind hole connector 14, so that the first connector tensioning portions 603, 608, 613 fully or partially form an interference fit, a transition fit or a clearance fit with the tensioning portion 1104 of the first through-hole connector 11 or the tensioning portion 1404 of the first blind hole connector 14, thereby helping the first connector tensioning portions 603, 608, 613 to complete the tensioning process.

[0106] Furthermore, in the cylindrical structure 6001, the exit guide 601, transition section 602, first connector tensioning section 603, transition section 604, and entry guide 605 of the third constriction 6 can be constructed from materials different from those of the rest of the bolt 1, including but not limited to aluminum alloy, alloy steel, nylon, plastic, etc. The angle between the axial cross-sectional profile of the exit guide 601 and entry guide 605 of the third constriction 6 and the bolt axis 101 is between 5 and 20 degrees. The axial cross-sectional profile of the transition sections 602 and 604 of the third constriction 6 can be either circular arcs or straight lines. In the other two structures, the aforementioned construction of the third constriction 6 can be the same as that of the cylindrical structure.

[0107] The fourth neck section 7 connects the third neck section 6 and the threaded portion 8 and plays a connecting and supporting role.

[0108] The threaded portion 8 is connected to the fourth necking section 7 and has an external thread so as to be connected to the nut 13 by engaging with the internal thread of the threaded hole 1302 of the nut 13 in the case of the first through-hole connector 11, or to be fixed in the first blind hole connector 14 by engaging with the internal thread of the blind hole end in the case of the first blind hole connector 14.

[0109] In the connection arrangement of the first through hole connector 11, the first connecting surface 201 of the bolt head 2 and the first connecting surface 901 of the first washer 9, the second connecting surface 903 of the first washer 9 and the first connecting surface 1001 of the second connector 10, the second connecting surface 1003 of the second connector 10 and the first connecting surface 1101 of the first through hole connector 11, the second connecting surface 1106 of the first through hole connector 11 and the first connecting surface 1201 of the second washer 12, and the second connecting surface 1203 of the second washer 12 and the first connecting surface 1301 of the nut 13 are abutted against each other. During connection, the bolt 1 is passed through the first aperture portion 902 of the first gasket, the first aperture portion 1002 of the second connecting member 10, the first aperture portion 1102 of the first through-hole connecting member 11, the second aperture portion 1105 of the first through-hole connecting member 11, the first aperture portion 1202 of the second gasket 12, and fixed at the nut 13, and the first connecting member tensioning portion 603, 608 or 613 is tightened at the tensioning portion 1104 of the first through-hole connecting member 11.

[0110] In the connection arrangement of the first blind hole connector 14, the first connection surface 201 of the bolt head 2 abuts against the first connection surface 901 of the first washer 9, the second connection surface 903 of the first washer 9 abuts against the first connection surface 1001 of the second connector 10, and the second connection surface 1003 of the second connector 10 abuts against the first connection surface 1401 of the third blind hole connector 14. During connection, the bolt 1 passes through the first aperture 902 of the first washer 9, the first aperture 1002 of the second connector 10, the first aperture 1402 of the first blind hole connector 14, and the second aperture 1405 of the first blind hole connector 14. It is then secured at the third aperture 1407 of the first blind hole connector 14, and the first connector tensioning portion 603, 608, or 613 is tightened at the tensioning location 1404 of the first blind hole connector 14.

[0111] The first aperture portion 1002 of the second connector 10 may be made of a material different from that of the rest of the second connector 10, including but not limited to aluminum alloy, alloy steel, nylon, plastic, etc. The tensioning portion 1104 of the first through-hole connector 11 and the tensioning portion 1404 of the first blind hole connector 14 may be made of a material different from that of the second connector 10, including but not limited to aluminum alloy, alloy steel, nylon, plastic, etc.

[0112] In all embodiments, the threaded portion 8 of the bolt 1 has a right-hand thread. In addition, due to strength requirements, 42CrMo material and 10.9 grade bolts are usually used, with a Geomet coating of 10-15 microns and an anti-corrosion treatment of more than 1000 hours.

[0113] The bolt 1 of the present invention can be guided into the tensioning portion of the first connecting member through the entry guide portion by percussion, pressure, hydraulic pressure, etc. For example, the tensioning portion of the first connecting member of the bolt 1 can be guided into the tensioning portion of the first connecting member through the entry guide portion after cooling, or the tensioning portion of the first connecting member can be heated and then guided into the tensioning portion of the first connecting member through the entry guide portion.

[0114] Specifically, when the bolt 1 is to be fixed to the first through-hole connector 11, first fix the first through-hole connector 11, and then fit one side of the second connector 10 to the opening on one side of the through-hole of the first connector 11 and align them axially so that the two connectors are in a fitted state. Then, fit the bottom end of the first gasket 9 to the second connector 10 and align them axially. Then, freeze the bolt 1 to a certain temperature so that the bolt 1 is successively extended into the first gasket 9, the second connector 10 and the first connector 11 until the first connector tensioning portion of the third section necking 6 fits the inner wall of the through-hole. Next, slowly press the bolt 1 into the appropriate position by applying pressure, and then fit the second gasket 12 to the opening on the other side of the through-hole of the first connector 11, so that the bolt 1 passes through the second gasket 12, and then tighten the nut 13 onto the threaded portion 8. When tightened, the first constriction 4 guides the second connector 10, while the third constriction 6 forms a grip with the inner wall of the through-hole, creating resistance and increasing strength. To remove the bolt 1, first heat the first connector 11 (i.e., the gearbox housing), then rotate the bolt 1 in the opposite direction until the tensioning portion of the first connector on the third constriction 6 releases the grip from the inner wall of the through-hole. Simultaneously, loosen the nut 13 to release the retaining force, and then remove the bolt 1, first washer 9, second connector 10, and second washer 12.

[0115] When the bolt 1 is to be fixed into the first blind hole connector 14 , the process is similar, except that the second washer 12 and the nut 13 are not required, but the bolt 1 is screwed into the blind hole.

[0116] The neck portion of the bolt of the present invention is formed with a tensioning section, whereas conventional long bolts do not have a tensioning section. In the present invention, this tensioning section is formed approximately in the middle of the neck portion of the conventional long bolt, forming a fulcrum. This section extends from the second neck portion of the bolt toward the fourth neck portion with a large-angle rounded transition. Consequently, there is a significant diameter difference and transition between the second neck portion and this neck portion. To manufacture such a bolt, the following method is used: a portion forming the fourth neck portion is pre-set on both sides of a pair of dies for rolling the bolt, and the blank is rolled while being rotated 180 degrees between the dies. Simultaneously, the other end is precision-turned multiple times to a predetermined value.

[0117] Furthermore, the third constriction extends a portion of the bolt's length, for example, by 4.9% of the bolt's machined area. This third constriction 6 is formed by partially thickening the constriction. Furthermore, the diameter of the third constriction 6 is set to 104.8% of the constriction's diameter, making the tensioning portion slightly larger than the constriction. For a standard M20 x 2.5 bolt, the constriction's diameter is 20.948 mm, and the interference fit is set to approximately 65% of the thread height. In comparison, the thread interference fit of the bolt of the present invention is smaller.

[0118] In some cases, features disclosed in the present invention may be used independently of other features. On the other hand, when necessary, features disclosed in the present invention may be combined to provide various combinations.

[0119] The terms and expressions used in this disclosure are illustrative rather than restrictive, and thus their use is not intended to exclude from the scope of the present disclosure any equivalents of the features illustrated and described. Various modifications, variations, and alternatives are possible within the scope of the claims. For example, the description in this specification is directed to a long bolt for a rail transit gearbox, but it is understood that the long bolt of the present disclosure can be used in other applications. Therefore, the claims are intended to encompass all such equivalents.

Claims

1. A bolt having a bolt head, a threaded portion at opposite ends of the head, and a constricted portion therebetween, wherein the diameter of the constricted portion is reduced relative to the diameter of the bolt head, wherein: Along the direction from the thread head to the threaded portion, the neck portion includes the first necking section, the second necking section, the third necking section and the fourth necking section in sequence, wherein the third necking section is provided with a first connecting piece tightening portion having a diameter larger than that of the second necking section, the fourth necking section and the threaded portion.

2. The bolt according to claim 1, characterized in that The third neck section is located in the middle relative to the second neck section and the fourth neck section.

3. The bolt according to claim 1 or 2, characterized in that Along the direction from the thread head to the thread portion, the third necking section is provided with an exit guide portion between the second necking section and the first connector tightening portion, and / or an entry guide portion is provided between the fourth necking section and the first connector tightening portion.

4. The bolt according to claim 3, characterized in that The included angle between the outer contour line of the axial section of the exit guide portion and / or the entry guide portion and the axis of the bolt is between 5 and 20 degrees.

5. The bolt according to claim 3, characterized in that A transition portion is provided between the exit guide portion and the first connecting piece tensioning portion, and / or a transition portion is provided between the entry guide portion and the first connecting piece tensioning portion.

6. The bolt according to claim 5, characterized in that The outer contour line of the axial cross section of the transition portion is an arc or a straight line.

7. The bolt according to claim 1 or 2, characterized in that: The tightening portion of the first connecting member of the third neck section is a columnar structure, a conical structure or an arc structure.

8. The bolt according to claim 7, characterized in that In the cylindrical structure, the radial cross-section of the tightening part of the third necking section is circular, elliptical or irregular arc-shaped, and the axial cross-section is rectangular; in the conical structure, the radial cross-section of the tightening part of the third necking section is circular, elliptical or irregular arc-shaped, and the radial dimension close to the bolt head is larger than the radial dimension away from the bolt head; in the arc structure, the radial cross-section of the tightening part of the third necking section is circular, elliptical or irregular arc-shaped, and the outer contour line of the axial cross-section is drum-shaped, arc-shaped or parabolic, with the radial dimension in the middle being larger than the radial dimensions at both ends.

9. The bolt according to claim 1 or 2, characterized in that: A first necking transition portion is provided between the bolt head and the first necking section, connecting the bolt head and the first necking section. The first necking transition portion is an arc structure.

10. The bolt according to claim 1 or 2, characterized in that: Along the direction from the thread head to the thread portion, the first necking section sequentially includes a second connector tensioning section and a second connector guiding section, and the second connector guiding section is connected to the second necking section.

11. The bolt according to claim 10, characterized in that The included angle between the outer contour line of the axial section of the first-section necked second connecting member guide portion and the axis of the bolt is between 5 and 20 degrees.

12. The bolt according to claim 10, wherein A transition portion is provided between the first necked second connector guide portion and the second connector tensioning portion. The outer contour line of the axial cross section of the transition portion is an arc or a straight line.

13. A connection arrangement, characterized in that The connection arrangement includes a bolt according to any one of claims 1 to 12 and a first connecting member and a second connecting member, wherein the bolt connects the first connecting member and the second connecting member, wherein the bolt passes through the second connecting member and extends into the hole of the first connecting member, so that the tensioning portion of the first connecting member of the bolt abuts against the hole of the first connecting member at the tensioning position.

14. The connection arrangement according to claim 13, characterized in that The tensioning portion of the first connecting member forms an interference fit, a transition fit or a clearance fit with the tensioning part of the first connecting member.

15. A connection arrangement according to claim 13 or 14, characterised in that The hole of the first connecting piece is a through hole through which the bolt passes, and the connecting arrangement further has a nut which is screwed onto the threaded portion.

16. A connection arrangement according to claim 13 or 14, characterised in that The hole of the first connecting member is a blind hole, and the bolt is screwed into the blind hole.

17. A connection arrangement according to claim 13 or 14, characterised in that The connection arrangement further includes a first washer positioned between the bolt head and the second connection member.

18. The connection arrangement according to claim 15, characterized in that The connection arrangement further comprises a second washer positioned between the nut and the first connection member.

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