Self-locking nut

Abstract

This utility model relates to fastening and connecting devices and components, specifically to a self-locking nut. The self-locking nut comprises recesses of gradually increasing depth formed on its internal threaded surface, each of which contains a locking element secured at the maximum depth of the recess. The locking element is a cylindrical metal pin positioned transversely to the threads. The length of the metal pin spans at least two threads, and the diameter corresponds to the maximum depth of the recess, measured relative to the bottom of the threaded root. The metal pin is secured in the recess using magnetic force. This utility model improves the reliability of threaded connections.

Description

[0001] Field of technology to which the utility model belongs

[0002] The utility model relates to the field of devices and parts for fastening and connecting, namely to a self-locking nut.

[0003] Technology Level

[0004] The main advantage of threaded fasteners is that they can be dismantled and reused. However, this property also creates a serious problem for both machinery and metal building structures. This problem is the unintentional and spontaneous loosening (self-loosening) of a threaded connection. In most threaded fasteners, the strength of the connection is ensured by creating a large tensile load within it. This tensile load is created through controlled tightening. Loosening of a threaded connection is the subsequent loss of a portion of this tensile load.

[0005] Currently, a large number of fasteners are known that prevent self-loosening, the operating principle of which is based on rigid, elastic, frictional and other locking methods.

[0006] For example, threaded connections are known where a spring-loaded split washer (Grover washer) is placed under the nut. Its ends are axially spaced and equipped with sharp edges. When tightened, this washer deforms axially, and the edges cut into the bearing surfaces of the nut and the component being fastened, ensuring locking of the nut "on the housing." The disadvantage of this locking method is that the cutting is noticeable only when the bearing surfaces are not too hard (at least less than the hardness of the washer). Otherwise, only purely elastic locking is effective, reducing the reliability of the locking (locking).

[0007] Various types of nuts with inserts are also known, but their main drawback is the possibility of cutting off the threads of the insert, low radial tension in the mating parts and an insufficiently high coefficient of friction.

[0008] Nuts with an elastic threaded rim are known (see https: / / inzhener-info.ru / razdely / konstruirovanie / sposoby-stoporeniya-krepezhnykh-detalej / samokontryashchiesya-gajki.html?ysclid=m8zze9e0ik571446458). The rim is slightly compressed after the thread is cut. When the nut is tightened, the threaded end of the bolt or stud lifts the rim, creating axial tension in the thread. This design has disadvantages, including technological complexity of manufacture and the risk of the rim breaking off when tightening the nut.

[0009] A self-locking nut (see patent RU2347119C1) is known, containing holes with plastic pins inserted into them. The holes are designed so that the pins penetrate the nut's threads to 50-75% of the thread profile height. A drawback of this design is that the plastic pins are susceptible to deformation and failure, especially under extreme operating conditions (specifically, at low and high temperatures), and therefore may not provide reliable locking of the nut.

[0010] The closest technical feature to the claimed utility model is a nut (CN 201884437 U) containing involute recesses formed in the internal threaded surface of the nut. Balls are placed in the recesses and secured in place by a plastic insert, which is removed when the nut is screwed onto the bolt. When attempting to loosen the nut, the ball locks the shank of the bolt or stud by deforming the thread. Because the ball has a linear dimension comparable to the thread pitch, it contacts one, maximum two, threads during locking, which does not provide sufficient frictional locking due to the small contact area between the ball and the thread. Therefore, under certain operating conditions, such as vibration, thermal expansion, or improper installation of the nuts, the nut may become loose.Additionally, improper preparation of the joint surfaces or selection of inappropriate beads can also contribute to loosening or creep.

[0011] The technical problem is to eliminate the shortcomings of the prior art and develop a self-locking nut that provides reliable locking after installation on a mating fastener with external thread.

[0012] The technical result is to increase the reliability of locking (locking) of the threaded connection.

[0013] Disclosure of the essence of the utility model

[0014] A self-locking nut contains recesses of gradually increasing depth on its internal threaded surface, each of which contains a locking element secured at the maximum depth of the recess. The technical problem is solved, and the technical result achieved, by using a cylindrical metal pin positioned transversely to the threads. The length of the metal pin spans at least two threads, and its diameter corresponds to the maximum recess depth, measured relative to the bottom of the threaded cavity. The metal pin is secured in the recess by magnetic force.

[0015] The metal pin has a length that covers at least three threads.

[0016] The self-locking nut contains more than two recesses evenly distributed around the circumference of the inner surface of the nut.

[0017] The hardness of the metal pin is lower than the hardness of the nut.

[0018] The metal pin is pre-magnetized.

[0019] The self-locking nut is pre-magnetized.

[0020] Brief description of drawings

[0021] Fig. 1 shows an axonometric view of the proposed self-locking nut.

[0022] Fig. 2 shows a longitudinal section of the proposed self-locking nut.

[0023] Fig. 3 shows a cross-section of the proposed self-locking nut.

[0024] The figures indicate the following positions:

[0025] 1 - recess; 2 - metal pin.

[0026] Implementation of a utility model

[0027] The proposed technical solution aims to improve the reliability of threaded connection locking by locking the nut on the mating fasteners through increased radial tension and friction in the mating surfaces when the nut thread and the fastener thread are locked. This solution ensures secure fixation of the nut on the mating fastener and prevents its loosening.

[0028] The problem of nut locking is solved by completely locking it on the thread of the mating fastener (bolt, shaft, stud, etc.), due to which the threaded connection becomes permanent and a reliable locking effect is achieved.

[0029] The threaded connection comprises a fastener with an external thread (not shown in the figure) and a self-locking nut screwed onto the fastener with an external thread.

[0030] The self-locking nut (Fig. 1-3) has a central threaded hole defining an internal threaded surface. The internal threaded surface is provided with recesses 1 (for simplicity, one recess 1 is shown in the figures) of a twisted (involute) shape with a smoothly increasing depth with axial shift. In particular, the bottom of recess 1 in longitudinal section (see Fig. 2) is formed by a curve, for example, a portion of a spiral, extending from a point on the internal surface of the threaded hole of the self-locking nut (the point of zero depth of recess 1) and penetrating into the body of the nut (to the point of maximum depth of recess 1). The depth of recess 1 smoothly increases in the direction of thread twist.

[0031] In each recess 1, at its deepest point, a locking element, a cylindrical metal pin 2, is positioned across the nut's threads and secured there. The length of pin 2 is selected based on the nut's size and is preferably chosen to overlap at least two nut threads, ensuring reliable frictional contact and thus secure locking. More preferably, the length of pin 2 is chosen to overlap at least three nut threads, ensuring even more reliable frictional contact and thus secure locking.

[0032] Unlike plastic locking elements, metal pin 2 is not subject to destruction under extreme operating conditions, and its service life is comparable to the service life of the threaded connection as a whole.

[0033] The diameter of the metal pin 2 corresponds to the maximum depth of the recess 1, measured relative to the bottom of the threaded root. In the context of this application, "correspondence of the diameter of the metal pin 2 to the maximum depth of the recess 1" means that the diameter of the metal pin 2 is equal to or slightly greater than the maximum depth of the recess 1 so that the pin 2 protrudes slightly relative to the bottom of the thread root to ensure the possibility of screwing the mating fastener onto the nut when the metal pin 2 is located in the area of ​​the maximum depth of the recess 1.

[0034] The diameter of metal pin 2, and therefore the maximum depth of recess 1, is selected based on the nut diameter, thread pitch, and thread depth. For example, the diameter of metal pin 2 can be selected within the range of 0.4 to 0.8 standard thread pitch or 0.2 to 0.5 standard thread depth (specifically, according to GOST 5915-70).

[0035] The material of metal pin 2 is selected so that its hardness is equal to or, preferably, less than the hardness of the nut and, accordingly, the mating fastener. If the hardness of metal pin 2 is lower than that of the nut, during locking, metal pin 2 deforms and the threads penetrate the body of metal pin 2, completely locking pin 2 in the threaded connection and preventing any movement, thereby further enhancing the locking effect.

[0036] The number of recesses 1 is preferably two to four, evenly spaced around the circumference of the internal threaded surface of the nut's threaded hole. Specifically, the presence of a single recess 1 may not ensure reliable locking, as it will result in uneven radial tension. Increasing the number of recesses 1 with locking elements improves locking reliability. However, using more than four recesses 1 is impractical, as it will not provide a significant increase in tension force. Furthermore, it is physically problematic to place a large number of recesses 1 around the circumference of the internal threaded hole of a self-locking nut.

[0037] The initial fixation of pin 2 in recess 1 is achieved by magnetic force. For this purpose, pin 2 and nut are made of magnetic materials, specifically ferromagnetic ones. The nut and / or pin must be pre-magnetized and connected to each other by magnetizing pin 2 to the material of the nut in recess 1. The magnetization of pin 2 and / or nut is carried out in such a way as to ensure secure fixation of pin 2 in recess 1.

[0038] Alternatively, the initial locking of pin 2 in recess 1 can be achieved by any other suitable method, in particular, by using a plastic mounting cap inserted into the threaded hole of the nut. The plastic mounting cap preferably fits into the threaded hole with an interference fit, for which its diameter corresponds to the diameter of the threaded hole of the nut. The plastic mounting cap is removed (pushed out) from the nut when it is screwed onto the mating threaded fastener.

[0039] In another embodiment, pin 2 can be fixed in recess 1 using a soft elastic adhesive, for example, silicone, cyanoacrylate or epoxy based, which will not damage the thread when deformed by screwing on the nut.

[0040] The utility model operates as follows. When tightening the nut onto the mating fastener, metal pin 2 is positioned within the maximum depth of recess 1 due to the depth of recess 1 gradually increasing in the direction of thread tightening, and the nut is screwed onto the fastener without resistance. When a return force (loosening) is applied, pin 2 shifts in the direction of decreasing recess 1 and jams the thread, creating radial deformation in the contact area. The nut's return movement is blocked, preventing its movement (loosening). The cylindrical shape of pin 2 creates a large contact area and greater plastic deformation during loosening, thus ensuring a secure locking of the connection.

[0041] For initial axle fixation in the deep recess area 1, an internal plastic mounting cap is used. This cap protects pin 2 from falling out and the threads from contamination during transport. It is then pushed out when the nut is screwed onto the mating fastener. Alternatively, soft, elastic adhesives based on silicone, cyanoacrylate, or epoxy can be used for initial axle fixation. These adhesives will not damage the threads during deformation caused by screwing on the nut.

[0042] No design modifications to the fastener interacting with this nut are required. The nut is compatible with standard or any typical mating fastener.

[0043] As an implementation example, let's consider an M24 nut. For this size, the maximum depth of recess 1 is 1.8 mm, and the diameter of pin 2 is 1.8 mm. Pin 2, when located within the maximum depth of recess 1, does not protrude relative to the thread root and, when screwed onto the mating fastener, allows it to move freely along the thread. When loosened, the contact point of pin 2 begins to move along recess 1 toward a smaller depth, locking the thread by deformation. Tightening torque should be applied by hand. Generally, tightening torque depends on the material, heat treatment, presence of lubricant, strength class, and other factors and is calculated for each specific case. Recommended tightening torque values ​​are specified, for example, in ISO 898 / 1.

[0044] Thus, thanks to the presence of recesses 1 with gradually increasing depth, in which locking elements in the form of cylindrical metal pins 2 are placed and secured using magnetization. The length of these pins covers at least two thread turns and the diameter corresponds to the maximum depth of recess 1. This improves the reliability of the nut's locking on the mating fastener, preventing the nut from loosening. Furthermore, the required tightening torque for the connection is reduced severalfold.

Claims

1. A self-locking nut, on the internal threaded surface of which there are recesses of smoothly increasing depth, in each of which a locking element is placed, fixed in the section of the maximum depth of the recess, characterized in that the locking element is a cylindrical metal pin located across the thread turns, and the length of the metal pin covers at least two thread turns, and the diameter corresponds to the maximum depth of the recess, measured relative to the bottom of the threaded cavity, and the metal pin is fixed in the recess using a magnetic force.

2. A self-locking nut according to paragraph 1, characterized in that the metal pin has a length that covers at least three thread turns.

3. A self-locking nut according to claim 1, characterized in that it contains more than two recesses, evenly distributed around the circumference of the inner surface of the nut.

4. A self-locking nut according to claim 1, characterized in that the hardness of the metal pin is lower than the hardness of the nut.

5. A self-locking nut according to claim 1, characterized in that the metal pin is pre-magnetized.

6. A self-locking nut according to paragraph 1, characterized in that it is pre-magnetized.

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