"A thousand mile levee is destroyed by ant nests", a small ant hole can make a thousand foot long levee burst. Screws are known as the rice of industry. Although they are small, they are by no means small. However, there are many accidents caused by ignoring screws in history.
In view of the looseness of threaded fasteners, technicians have taken various positive and effective measures to inject new vitality into the development of threaded fasteners. There are many anti loose technologies and anti loose structures of threaded fasteners. Let's take a look at it with Jinrui.
Control preload
Controlling the pre tightening force of installation is one of the economic and effective measures to prevent the loosening of threaded fasteners. This method uses the self-locking condition of threads and does not need to make any changes to the structure of bolts and nuts, and prevents loosening by ensuring the appropriate pre tightening force. For the application occasions with particularly high requirements for installation control, the direct control method is adopted to measure and control the preload during the installation process. Generally, the direct control of installation preload requires the use of special devices or the mastery of special technology, which is difficult to promote. In order to obtain satisfactory preload in an economical way, more indirect methods of measuring and controlling preload, namely torque control method, are adopted.
The torque control method converts the pre tightening force into assembly torque through torque coefficient, uses the fixed torque or side torque assembly machine or wrench to control the assembly torque, or uses the fastener's own structure to ensure the tightening torque (such as torsion shear bolt connection pair), so as to indirectly achieve the purpose of controlling the pre tightening force.
In order to achieve the expected purpose, it is required that the torque coefficient of the connecting pair can be accurately measured in advance, and ensure that the torque coefficient of the same batch of parts is not discrete. For example, gb/t1231-1991 clearly stipulates that the average value of torque coefficient of the same batch of connecting pairs is 0.110-0.150, and the standard deviation of torque coefficient should be less than or equal to 0.001%. In engineering practice, there are also control methods such as corner method and yield point tightening method.
Effective torque fastener
The effective torque type fastener adds the effective torque part on the basis of the ordinary fastener structure, and its function is to add a resistance torque that does not change with the external force in the connecting pair.
The effective torque part is mainly added to the nut, and the products with effective torque part on the external thread are relatively rare. One kind of all metal effective torque lock nuts is to use the deformation of the nut body after the processing of the thread on the nut body, which causes the axial or radial deformation of the thread, resulting in the local interference of the internal and external threads during assembly and the effective torque. Due to the influence of the deformation amount, the deformation resistance of the blank before deformation and the geometric accuracy, it has high requirements for the processing technology, and it is difficult to control the effective torque; The other is to reduce the effective torque part and close it up or after slotting. At present, it is mainly used in the military industry in China; The third kind is to embed metal elastic elements in the nut body. During assembly, the external thread forces the elastic elements to deform and produce effective torque. This kind of nut has high requirements for the elasticity of the elastic elements and the position of the inserts, and sometimes scratches the surface of the external thread.
Using washers
At present, the washers used mainly include flat washers, spring washers and elastic washers.
The flat washer is mainly used to improve the contact state of the bearing surface, ensure the stability of the friction coefficient of the bearing surface, and play a certain role in preventing looseness; The spring washer uses its elasticity to produce axial force and improve the elasticity of the connection. The transverse vibration test results show that its anti loosening effect is poor under this test condition; The twisted teeth of the elastic washer are flattened by the tightened nut, so that the threaded countershaft body is compressed, and at the same time, it is partially embedded in the bearing surface, which has uniform elasticity and good anti loosening effect, and will scratch the surface of the parts. In some specific occasions, scratching the surface of parts is what people want, such as the terminal on the parts used for surface painting, which can scratch the paint skin and ensure the conductivity.
Directly locked
After tightening the nut, lock the nut and bolt with locking (locking) elements to prevent them from rotating relative to each other. The most commonly used are cotter pins, series wires, and tab washers. The cotter pin is used together with the bolts with holes at the end and slotted nuts, and the locking is reliable. Generally, the slotted angle of the nut is 60 °, and the slotted holes must be aligned during installation, which is inconvenient to assemble; Use low-carbon steel wire to penetrate into the wire hole of the bolt head or nut, so that several bolts or nuts are connected in series to restrict each other, and the locking is reliable; The lock washer against the cushion ring is plastic deformed to block the nut. When disassembling, the washer should be flattened and restored before loosening the nut. It is used for heavy and dynamic load connections that are not often disassembled, such as flywheel nuts.
Destroy the relationship between sports pairs
Use a punch to deform the thread of the bolt and nut locally, deviate from the original tooth profile, and make it locally unable to engage with the normal thread, destroy the motion relationship of the original motion pair, and form a connection that cannot be reused. If you want to disassemble, you must use a large torque to screw out the nut or destroy it. This method is rarely used at present.
bond
Bonding is to bond bolts and nuts or connected parts together to achieve the purpose of locking. For bonding bolts used in mass production, anaerobic glue is generally applied to parts in the fastener manufacturer and dried to form microcapsules. The surface of such microcapsules is dry and has no viscosity. During assembly, the microcapsules are crushed and broken, the glue overflows, and the bolts and nuts are firmly bonded. As long as enough torque is applied during disassembly, generally, it can be reused for a limited number of times within a certain period of time.
Display of some products of Jinrui Jiangsu Jinrui metal products Co., Ltd. is the production base of Shanghai Jinrui standard parts. The factory covers an area of more than 20000 square meters, with a registered capital of 50million yuan, a total investment of more than 100million yuan, and an annual output of more than 20000 tons. Its products are exported to more than 40 countries overseas. Since its establishment in 2001, Jinrui company has developed into a new layout with Jiangsu Haian as its production base and Shanghai Baoshan and Henan Nanyang as its sales centers after more than 20 years of unremitting efforts. At present, Jinrui's main products include the following six categories: 1. The main products of bolts include: metric and American round head oval neck bolts (also known as fishtail bolts), inner and outer hexagon bolts, hexagon flange bolts, carriage bolts, wheel hub bolts, etc 2. Stud products: full thread thread thread, double headed studs, etc 3. Nut products: Hexagon nuts, flange nuts, heavy nuts, square nuts, butterfly nuts, etc 4. Screw products: self tapping screws, self tapping and self drilling screws, wood screws, various machine screws, etc 5. Washer products: flat washer, spring washer, square washer, locking washer, etc 6. Fasteners related non-standard products Jinrui's wire drawing plant also provides processing services such as fine drawing, coarse drawing and spheroidization of wires, and supplies finished wires from various domestic big brand steel mills. Based on the business philosophy of "pioneering and innovative, pursuing excellence", Jinrui has successively introduced many models of heading and forming machines, threading machines, nut machines, hot heading and rolling machines, lathes, large hot heading machines and their supporting testing equipment, such as magnetic particle flaw detectors, metallographic analyzers, salt spray testing machines, direct reading spectrometers and optical screening machines, tensile machines, Vickers hardness testers, Rockwell hardness testers, etc., and has an independent R & D department, It can produce all kinds of high-quality fasteners such as national standard (GB), German standard (DIN), American Standard (ANSI), Japanese standard (JIS) and ISO international standards. The products are widely used in petroleum, chemical industry, boilers, wind power generation, highway guardrails, elevator guide rails, machinery manufacturing, construction sites, auto parts and medical devices. Since its establishment, Jinrui has developed vigorously. It integrates the strengths of each family, carefully designs and strictly selects materials, so that the products are more durable and are highly praised by the majority of users. Jinrui won ISO9001:2000 international quality system certification in 2001, special equipment manufacturing license in 2010, TS16949 automobile quality management system certification in 2012, and the products are underwritten by the people's Insurance Company of China "global product liability insurance", ensuring that every screw should be used with confidence, firmness and peace of mind for customers! No matter now or in the future, Jinrui will always grasp the core service concept of "quality first, revitalizing the enterprise through science and technology, user first, and considerate service", and sincerely provide you with high-quality services and high-quality products. Jinrui will also become your most loyal and long-term partner.
