In industrial production, some products need to remove the fixing screws; or in the assembly line, the screws that fix the product on the fixture also need to be removed when the product is unloaded. At present, the dismantling of the screws is mainly completed by the manual operation of the operator. However, this method of manually dismantling the screws has low work efficiency and high production cost.
1. Ordinary outer hexagon - widely used, characterized by relatively large tightening force, the disadvantage is that there must be enough operating space during installation, and adjustable wrench, open-end wrench or glasses wrench can be used during installation, all of the above wrenches require a large amount of space. operating space. 2. Cylindrical head hexagon socket - is the most widely used of all screws, because it has a relatively large tightening force, and can be operated with a hexagon wrench. It is very convenient to install and is used in almost all kinds of structures. The appearance is more beautiful and neat. The disadvantage is that the tightening force is slightly lower than the outer hexagon, and the inner hexagon is easily damaged due to repeated use and cannot be disassembled. 3. Pan head inner hexagon - rarely used mechanically, the mechanical properties are the same as above, mostly used in furniture, the main function is to increase the contact surface with wooden materials and increase the ornamental appearance. 4. Headless inner hexagon - must be used in certain structures, such as the top wire structure that requires a large top-tight force, or where the cylindrical head needs to be hidden. 5. Countersunk head hexagon - mostly used in power machinery, the main function is the same as the inner hexagon. 6. Nylon lock nut - a nylon rubber ring is embedded in the hexagonal surface to prevent the thread from loosening, and it is used on strong power machinery. 7. Flange nuts - mainly play the role of increasing the contact surface with the workpiece, mostly used in pipes, fasteners, some stamping parts and casting parts. 8. Ordinary hex nut - the most widely used and one of the most common fasteners.
In chemical production equipment, the cylinder body and the head cover need to be connected and sealed. The traditional sealing structure is to connect the two with a screw, add a non-metallic gasket in the middle and fix it with a nut. However, such a sealing structure only controls the tightening torque, and has the technical defect that the sealing ring will be twisted or even broken during repeated loading and unloading of the cylinder head cover, resulting in poor sealing performance.
Yueluo relates to a self-tapping screw according to the preamble of claim 1. A self-tapping screw is known from EP0623759B1, the ratio of the outer diameter to the smaller diameter of the self-tapping screw is about 1.25-1.5, the ratio of the outer diameter to the pitch lead is about 1.5-1.6 and the thread The flank angles of , are < 50° and ≥ 35°. EP0433484B1 proposes a self-tapping screw whose thread is provided with cutting teeth of approximately arcuate design, and the cutting edge and the thread crest are at the same horizontal position and are set in opposite directions. One purpose of Yueluo is to realize a general type of self-tapping screw so that it can be screwed particularly easily into holes drilled in concrete or other materials such as bricks and the like. According to Yueluo, this object is achieved by the features in the characterizing part of claim 1, and surprisingly, it has been found that the parallel arrangement of the flanks, ie with a flank angle of about 0°, will make screwing particularly easy when screwing in , especially if the diameter of the hole varies within an allowable tolerance. One reason may be due to the fact that there is no lateral pressure on the material screwed into the thread, even if threads of different depths are cut in concrete or other materials such as brick, chipped plywood, or hardwood. The thread cuts into the material over its entire width by cutting grooves. In particular according to the embodiment of claim 11 the result is that the material cut out when screwing in the screw can be discharged without any accumulation, the dependent claims reflecting many advantages of further embodiments.
NPT, PT, G are all pipe threads. NPT is the abbreviation of National (American) Pipe Thread, which belongs to the American standard 60-degree taper pipe thread, which is used in North America. National standards can be found in GB/T12716-1991 PT is the abbreviation of Pipe Thread, which is a 55-degree sealed conical pipe thread, which belongs to the Whitworth thread family and is mostly used in Europe and the Commonwealth of Nations. Commonly used in water and gas pipe industry, the taper is specified as 1:16. The national standard can be found in GB/T7306-2000 G is a 55 degree non-threaded sealing pipe thread, which belongs to the Whitworth thread family. Marked as G stands for cylindrical thread. National standards can be found in GB/T7307-2001 In addition, the 1/4, 1/2, 1/8 marks in the thread refer to the diameter of the pipe, and the unit is inches. People in the industry usually refer to thread size in points, 1 inch equals 8 points, 1/4 inch is 2 points, and so on. G seems to be the general name for pipe threads (Guan), and the division of 55 and 60 degrees is functional, commonly known as pipe circle. That is, the thread is machined from a cylindrical surface. ZG is commonly known as pipe cone, that is, the thread is made of a conical surface. The general water pipe joints are like this. Rc means conical internal thread ZG means taper pipe thread, 3/4 means inch mark, which is 3/4 inch conical pipe Thread, there is in the Hardware Manual. The national standard stipulates that the major diameter of ZG 3/4 thread is 26.44 mm. Please refer to Metric, American and British Thread Standard Manual (Third Edition). Its representation method should be: ZG 3 /4″. Among them (〃) is the representative symbol for inches. One inch is equal to 8 inches. The origin of 3/4 is 6/8=3/4. Commonly known as 6 points. Similarly, the major diameter of ZG 1/2″ thread≈21 mm. Commonly known as 4 points. ZG 1″ thread diameter ≈ 33 mm. Commonly known as 1 inch. ZG 1 1/2″ thread pipe outer diameter ≈ 48 mm. Commonly known as 1 inch and a half. Taper pipe thread is very similar to pipe thread, the difference is Only in the taper. Note that the basic size of the pipe thread and ordinary thread is different. DN is the nominal diameter
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