Locknut

Abstract

The present invention provides a locknut which has a small number of components, has excellent portability and operability, and is suitable for reducing size and weight. A locknut to be screwed onto the thread section 2a of a bolt 2, said locknut having a body section 3 formed by spirally winding a wire material which has a rectangular cross section. A thread groove 5 for engaging the thread section 2a is formed on the inner-circumferential surface 3c of the body section 3 across the entire length thereof in the axial direction. The body section 3 is screwed and mounted onto the thread section 2b of the bolt 2, which passes through fastening targets Wa, Wb. When force is applied to the mounted body section 3 in a releasing direction for loosening the body section 3, the wire material is reduced in diameter by elastic deformation, and as a result, friction is generated between the body section 3 and the thread section 2b, which effectively prevents the body section 3 from loosening.

Description

Locking nuts

[0001] The present invention relates to a locking nut, and more particularly to a technique for preventing a nut attached to the threaded portion of a bolt from loosening or falling off due to loosening.

[0002] Conventionally, as this type of locking nut, a locking nut that uses wedge technology has been known (see, for example, Patent Document 1).

[0003] Figure 4 shows a conventional locking nut a. This locking nut a is composed of a nut body b and a washer c that is used in combination with the nut body b. The nut body b has a recess g on its tightening bearing surface d that is coaxial with the threaded hole e and has a diameter larger than that of the threaded hole e, with the inner peripheral side surface forming a tapered surface f in the shape of a truncated cone.

[0004] On the other hand, the washer c has a tapered surface i in the shape of a truncated cone on the outer peripheral surface of the bolt insertion hole h, and this tapered surface i constitutes a protrusion j that can be fitted into the recess g of the nut body b, but the center line B of this tapered surface i is offset by a small distance L from the center line A of the bolt insertion hole h.

[0005] In the locking nut a constructed in this manner, when washer c is fitted onto the threaded portion q of a bolt p inserted through fastened objects m and n and nut body b is screwed on and tightened, the tapered surface i of the protruding portion j of washer c fitted into recess g of nut body b is eccentric by a distance L from the axis of the threaded hole e, the tapered surface f of recess g, and the bolt insertion hole h of washer c (see center line A in the figure), so that the wedge action between the tapered surface f of nut body b and the tapered surface i of washer c applies a pressing force perpendicular to the axis to the threaded portion q. This pressing force gradually increases until the tightening bearing surface d of nut body b is in tight contact with washer c, thereby providing a powerful locking effect for locking nut a.

[0006] Japanese Utility Model Application Publication No. 57-184308

[0007] However, such conventional locking nuts have the following problems, and improvements are desired.

[0008] (1) The conventional locking nut a is composed of two parts, a nut body b and a washer c, which means that the nut has a large number of parts and is difficult to handle.

[0009] That is, conventional locking nuts a do not function as locking nuts a if either the nut body b or the washer c is missing, so users of locking nuts a must always carry both the nut body b and the washer c, which makes them difficult to carry. In particular, at work sites where this type of locking nut is used (for example, construction sites such as bridges), workers often carry them in their pockets, so there has been a strong demand for easier portability.

[0010] Furthermore, the use of conventional locking nuts a requires two steps: fitting the washer c and then screwing in the nut body b, which makes the installation process laborious and reduces work efficiency.

[0011] (2) Conventional locking nuts a have a structure in which the tapered surface i of the protrusion j formed on the washer c acts as a wedge, so the nut body b and the washer c must be made of a strong material that is not easily damaged or deformed. For this reason, conventional locking nuts a are often made of metal, especially high-strength iron or stainless steel, which tends to make each locking nut heavy.

[0012] Therefore, conventional locking nuts a tend to increase the overall weight of the object to which they are attached, and there was a need to improve this (to provide a lightweight locking nut).

[0013] The present invention has been made in consideration of these problems, and its purpose is to provide a locking nut that has a small number of parts, is easy to carry and use, and is suitable for being small and lightweight.

[0014] In order to achieve the above-mentioned object, the anti-loosening nut of the present invention is a anti-loosening nut that is attached to the threaded portion of a bolt, and is characterized in that it has a main body portion formed by spirally winding a wire rod having a rectangular cross section, and the main body portion has a thread groove formed on its inner surface over its entire axial length that screws into the threaded portion.

[0015] This locking nut has a thread groove formed on the inner circumferential surface of the body along the entire axial length to engage with the threaded portion, so that by aligning the thread groove of the body with the threaded portion of the bolt and rotating the body in the tightening direction (the direction in which the nut is tightened), the body advances along the threaded portion and continues to advance until it abuts against the object to be fastened (including a washer).

[0016] After the main body contacts the workpiece, when a force is applied to the main body in the tightening direction, the spirally wound wire expands while deforming against elasticity. This expansion temporarily loosens the engagement between the main body and the threaded portion, but when the force applied to the main body is released, the expanded wire in the main body returns to its original shape and contracts in diameter due to elastic deformation. At this time, the friction generated between the inner surface of the main body and the threaded portion tightens and fixes the main body to the threaded portion.

[0017] Once the main body is tightened and fixed in this way, even if a force is subsequently applied in the opposite direction to the tightening direction, i.e., in the removal direction (the direction to loosen the nut), the force will reduce the diameter of the main body and increase the friction between the inner surface of the main body and the threaded portion, so that the main body is firmly tightened to the threaded portion.

[0018] Therefore, with the anti-loosening nut of the present invention, once the main body is screwed onto the threaded portion of the bolt inserted into the object to be fastened and tightened to a position where it abuts against the object to be fastened, the nut will not loosen even if a force is applied to the main body in the direction of removal.

[0019] The present invention has the following features as preferred embodiments: (1) The main body is characterized in that it is formed by tightly winding the wire material. By tightly winding the wire material in this manner, the thread groove formed on the inner peripheral surface of the main body can be formed continuously without interruption, and the main body can be smoothly attached to the threaded portion (rotated in the tightening direction).

[0020] (2) The main body is made of a wire rod made of metal or resin. In other words, the locking nut of the present invention prevents the nut from loosening by utilizing the diameter-reducing action of the main body (tightening of the threaded portion) caused by the application of a force in the direction of removal to the main body. Therefore, resin other than metal can be used as the material for the main body, and the locking nut can be made lighter.

[0021] (3) The main body is formed by forming a thread groove on the inner peripheral surface of a square spring. In this invention, the main body is formed by forming a thread groove on a square spring, so the main body can be formed using, for example, a commercially available square spring. Therefore, the main body can be manufactured inexpensively, and the locking nut can be provided at a low price.

[0022] (4) The main body has a hexagonal outer circumferential surface. In this invention, the main body has a hexagonal outer circumferential surface, so that when the main body is attached to the threaded portion of the bolt, it can be rotated in the tightening direction using a spanner or wrench, just like a hex bolt.

[0023] According to the present invention, the main body portion attached to the threaded portion of a bolt inserted into the object to be fastened reduces in diameter and is firmly fastened to the threaded portion when a force in the direction of removal is applied to the main body portion, thereby effectively preventing the main body portion from rotating in the direction of removal, i.e., preventing the main body portion attached to the threaded portion from loosening.

[0024] Furthermore, the locking nut according to the present invention is constructed from only one body, so the number of parts is small, making it possible to provide a locking nut that is easy to carry and use.

[0025] Furthermore, it is easy to manufacture a small body that can accommodate small-diameter bolts.Furthermore, the body of the locking nut according to the present invention can be made of resin, making it possible to provide a small and lightweight locking nut.

[0026] 1(a) is a front view showing an example of the external configuration of a locking nut according to the present invention, and FIG. 1(b) is a plan view. It is a cross-sectional view showing the locking nut attached to the threaded portion of a bolt. It is a plan view showing another example of the locking nut. It is a cross-sectional view showing a conventional locking nut attached to the threaded portion of a bolt.

[0027] The locking nut 1 according to the present invention is a fastener used together with a bolt 2 to fix or tighten objects Wa and Wb, and as shown in Figure 1, is formed by winding a wire rod in a spiral shape.

[0028] Here, we will first briefly explain the bolt 2 with which the locking nut 1 is used. As is well known, the bolt 2 is a fastener used together with a nut to secure and tighten fastened objects Wa, Wb, and includes a threaded portion (shank) 2a with threads formed thereon and a head 2b. In the example shown in Figure 2, the bolt 2 is illustrated as a hexagonal bolt with a hexagonal head 2b, but the locking nut 1 according to the present invention can also be applied to bolts other than hexagonal bolts (for example, hexagon socket head bolts, eye bolts, etc.).

[0029] In contrast, the locking nut 1 is composed of a main body 3 made of a wire wound in a spiral shape, as shown in Figure 1. In this embodiment, the main body 3 is made of a metal wire having a rectangular cross section tightly wound in a spiral shape of the same diameter, and has a through hole 4 formed in its center that passes through in the axial direction.

[0030] In the locking nut 1 of this embodiment, the wire constituting the main body 3 has a rectangular cross section, and this wire is tightly wound so that the inner circumferential surface 3c of the main body 3 is a substantially flush cylindrical surface, which makes it easy to form the thread groove 5 (thread cutting), which will be described later. In the illustrated example, adjacent wires are shown with a slight gap between them to clearly show that the wire is wound spirally, but the wire of the main body 3 in this embodiment is wound so that adjacent wires are tightly wound.

[0031] The reason for using a wire made of metal (for example, iron, stainless steel, aluminum, etc.) for the main body 3 is that the main body 3 can be configured to be elastically deformable and can have sufficient strength compared to other materials such as resin. Therefore, in cases where strength as high as that of metal is not required, the main body 3 (wire) can also be configured using a material other than metal (for example, synthetic resin such as plastic, etc.).

[0032] In this embodiment, the upper end surface 3a and the lower end surface 3c of the main body 3 are each formed flat. This is because the upper end surface 3a or the lower end surface 3b of the main body 3 forms a bearing surface that abuts against the fastened objects Wa, Wb when the main body 3 is used as a locking nut 1. Therefore, for example, if only one of the upper end surface 3b or the lower end surface 3c is used as the bearing surface, it is sufficient to form only the side to be used as the bearing surface (the upper end surface 3a or the lower end surface 3b) flat.

[0033] The through hole 4 constitutes a threaded hole in the locking nut 1 according to the present invention, and a thread groove 5 is formed over the entire length in the axial direction (see the vertical direction in FIG. 1( a)) on the inner peripheral surface 3c of the main body 3 that forms the through hole 4. The thread groove 5 is set in a shape that allows it to be threaded onto the threads of the bolt 2 to be used. In other words, the specific shape of the thread groove 5 (nominal diameter, pitch, etc.) is determined in accordance with the specifications of the threads of the bolt 2 (thread diameter, pitch, etc.).

[0034] 1(a) shows a locking nut 1 in which the number of turns N of the wire in the main body 3 is 5.5, but the number of turns N and the thickness (axial thickness) L1 of the wire constituting the locking nut 1 can be changed as appropriate. As will be described later, the locking nut 1 of the present invention achieves its locking effect by utilizing the friction generated between the threaded portion 2a and the wire (the inner peripheral surface 3a of the main body 3). Therefore, by increasing or decreasing the number of turns N of the wire or the wire thickness L1, the frictional force generated between the threaded portion 2a and the wire can be adjusted. In other words, increasing the number of turns N or the wire thickness L1 increases the frictional force acting between the threaded portion 2a and the wire, thereby improving the locking effect of the locking nut 1.

[0035] In addition, in the illustrated example, the overall shape of the main body 3 is shown to be a slightly flattened shape in which the radial length L3 is slightly longer than the axial length L2, but it is also possible to configure the main body 3 so that the axial length L2 is longer than the radial length L3 by changing the settings of the number of turns N of the wire and the thickness L1 of the wire.

[0036] Next, a method for manufacturing the locking nut 1 configured in this manner will be described. As described above, the locking nut 1 according to this embodiment is mainly configured with the main body 3, which is tightly wound metal wire having a rectangular cross section, and therefore, for example, a commercially available square spring can be used as the wire. Since commercially available square springs are inexpensive, using a square spring as the material for the main body 3 can keep the manufacturing cost of the locking nut 1 low.

[0037] Then, a thread groove 5 is formed on the inner surface of a purchased, commercially available square spring using a metalworking tool for thread cutting, such as a tap, to complete the anti-loosening nut 1 (main body 3) of the present invention.

[0038] In this way, the locking nut 1 of the present invention can be completed by purchasing a commercially available square spring and forming the desired thread groove 5 in the purchased square spring, so the locking nut 1 can be manufactured with fewer steps and at low cost.

[0039] Next, how to use the locking nut 1 configured in this manner will be explained with reference to Figure 2. When fastening and fixing objects Wa, Wb using the locking nut 1 according to the present invention, first the positions of the mounting holes ha, hb for inserting the bolt drilled in the objects Wa, Wb are aligned, and the bolt 2 is inserted through the mounting holes ha, hb. In the illustrated example, the bolt 2 is inserted upward from below the object Wb, which is located on the lower layer, through the mounting holes ha, hb, with the tip of the threaded portion 2a protruding outside the object Wa.

[0040] The main body 3 of the locking nut 1 is then screwed onto the threaded portion 2a protruding from the workpiece Wa. That is, the thread groove 5 formed on the inner peripheral surface 3c of the main body 3 is aligned with the threads formed on the threaded portion 2a of the bolt 2, and the main body 3 is rotated in the tightening direction (the direction in which the nut is tightened, usually clockwise). This causes the main body 3 to move forward along the threaded portion 2a until the lower end surface 3b, which forms the seating surface, abuts against the workpiece Wa.

[0041] When the main body 3 is advanced until it abuts against the workpiece Wa, a force in the tightening direction is applied to the main body 3 from that position, tightening the workpieces Wa, Wb. As a result, the workpieces Wa, Wb are firmly tightened, and at the same time, a force that expands the spirally wound wire acts on the main body 3 against the elasticity of the wire. When the tightening of the workpieces Wa, Wb is completed and the tightening operation is stopped, the force that expanded the wire is released, and the expanded wire of the main body 3 returns to its original shape and contracts in diameter due to elastic deformation. At this time, friction is generated between the inner peripheral surface 3c of the main body 3 and the threaded portion 2a, and the main body 3 is tightened and fixed to the threaded portion 2a.

[0042] Once the body 3 has been fastened to the threaded portion 2a in this way, if a force is subsequently applied in the opposite direction to the tightening direction, i.e., in the direction to loosen the nut (removal direction), the force acts to reduce the diameter of the spirally wound body 3, thereby increasing the friction caused by contact between the threaded portion 2a of the bolt 2 and the inner peripheral surface 3c of the body 3. As a result, the body 3 is prevented from loosening in the removal direction, and the locking effect of the locking nut 1 is exerted.

[0043] Thus, according to the present invention, the main body 3 attached to the threaded portion 2b of the bolt inserted through the fastened objects Wa, Wb contracts in diameter and is firmly fastened to the threaded portion 2b when a force in the direction of removal acts on the main body 3, thereby effectively preventing loosening of the main body 3 attached to the threaded portion 2b.

[0044] Furthermore, because the locking nut 1 of the present invention is composed only of the main body 3, it is composed of fewer parts than conventional locking nuts that use wedge technology (locking nuts that use washers).As a result, the locking nut 1 of the present invention is more portable than conventional products, and can be used more easily because the process of attaching a washer can be omitted.

[0045] Furthermore, the locking nut 1 according to the present invention is suitable for miniaturization due to its simple structure, and it is possible to provide a locking nut 1 that can be applied to small bolts and screws, for example.

[0046] Furthermore, the locking nut 1 of the present invention allows the number of turns N and thickness L1 of the wire in the main body 3 to be adjusted depending on the strength of the locking effect required, and the material used to construct the main body 3 can also be selected, so that it is possible to provide, for example, a small, lightweight locking nut 1.

[0047] Next, another embodiment of the locking nut 1 according to the present invention will be described with reference to Fig. 3. The locking nut 1 shown in Fig. 3 has a modified shape of the outer peripheral surface 3d of the main body 3, but the rest of the structure is the same as that of the above-described embodiment 1. Therefore, parts that have the same configuration are given the same reference numerals and will not be described again.

[0048] In the locking nut 1 shown in this embodiment, the outer peripheral surface 3d of the main body 3 is formed into a hexagonal prism shape that is hexagonal in plan view. By forming the outer peripheral surface 3d of the main body 3 in this hexagonal shape, the locking nut 1 can be tightened using tools (such as spanners and wrenches) that are used to tighten hexagonal nuts, improving the ease of installation of the locking nut 1. Note that, because the locking nut 1 shown in this embodiment has the outer peripheral surface 3d of the main body 3 shaped to be suitable for manipulation with tools, it is of course also possible to configure the outer peripheral surface 3d in a polygonal prism shape other than a hexagonal prism.

[0049] The above-described embodiments are merely preferred embodiments of the present invention, and the present invention is not limited to these, and various design modifications are possible within the scope of the present invention.

[0050] For example, in the above-described embodiment, the main body portion 3 is configured by tightly winding adjacent wire rods in close contact with each other, but if it is possible to form a screw groove 5 on the inner surface 3c of the main body portion 3, the main body portion 3 may be configured such that a fixed gap is provided between adjacent wire rods.

[0051] Furthermore, in the above-described embodiment, a square spring is used to manufacture the main body 3, but it is of course possible to manufacture the main body 3 using wire material other than a square spring.

[0052] In addition, in the above-described embodiment, when fastening the fastened objects Wa and Wb, a structure is shown in which the anti-loosening nut 1 is directly abutted against the upper fastened object Wb, but it is also possible to interpose a part such as a washer between the fastened object Wb and the anti-loosening nut 1, for example.

[0053] REFERENCE SIGNS LIST 1 Locking nut 2 Bolt 2a Threaded portion of bolt 2b Head portion of bolt 3 Main body 3a Upper end surface of main body 3b Lower end surface of main body 3c Inner peripheral surface of main body 3d Outer peripheral surface of main body 4 Through hole 5 Thread groove Wa, Wb Fastened object

Claims

1. A locking nut to be attached to the threaded portion of a bolt, characterized in that it has a main body made of a wire rod with a rectangular cross section wound in a spiral shape, and the main body has a thread groove formed on its inner surface over its entire axial length to thread onto the threaded portion.

2. The locking nut according to claim 1, wherein the main body is made by tightly winding the wire.

3. A locking nut according to claim 1 or 2, characterized in that the main body is made of a wire material made of metal or resin.

4. A locking nut as described in claim 1 or 2, characterized in that the main body is constructed by forming a screw groove on the inner surface of a square spring.

5. A locking nut according to claim 1 or 2, characterized in that the outer surface of the main body is formed in a hexagonal shape.

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