The square nut is a fastener that needs to be used in the installation of the cable tray. In the prior art, the square nut 1 is pressed by the elastic force of the spring 2 below it and the opening of the C-shaped steel 3 (as shown in Figure 1, Figure 2), in the absence of external force, through the interaction of pressure and static friction, the C-shaped steel 3 will not move vertically or horizontally, which can facilitate engineering installation. The advantage of this installation method is that it can slide anywhere on the C-shaped steel 3, but the disadvantage is that it occupies the bottom space of the C-shaped steel 3, and the spring 2 will interfere with the installation hole of the square nut I, which affects the installation.
Spring washers are widely used in the load-bearing and non-load-bearing structures of general mechanical products. They are characterized by low cost and easy installation. They are suitable for parts with frequent assembly and disassembly. Quick and easy automatic selection of washers is included, but the anti-loosening ability of spring washers is very low! Especially in European and American countries that require high reliability, the adoption rate is extremely low, especially the important load-bearing structural connection parts have long been abandoned. Our country still has some applications in the military industry, but it has been improved to stainless steel. Steel spring washers have long been banned in CASC! It is also said to be very unsafe, because there are two reasons: 1 is circle rise and 2 is hydrogen embrittlement.
The defect of the existing press-fit solution is: when the retaining ring is placed in the chamfering section or the guide section of the shaft head, the retaining ring cannot be accurately fixed, and the retaining ring is easy to tilt or fall, especially when the shaft head is located inside the bearing chamber depression, The inclination of the retaining ring will make it difficult to press the retaining ring, affect the production efficiency, and even cause the product to be scrapped.
Several concepts about high-strength bolts 1. According to the specified performance level of bolts above 8.8, they are called high-strength bolts. The current national standard only lists M39. For large-size specifications, especially those with a length greater than 10 to 15 times High-strength bolts, domestic production is still short-term. The difference between high-strength bolts and ordinary bolts: High-strength bolts can withstand larger loads than ordinary bolts of the same specification. High-strength outer hexagon bolts High-strength outer hexagon bolts are made of Q235 (ie A3). The material of high-strength bolts is 35# steel or other high-quality materials, which are heat-treated after being made to improve the strength. The difference between the two is the difference in material strength. From raw materials: High-strength bolts are made of high-strength materials. The screws, nuts and washers of high-strength bolts are all made of high-strength steel, such as No. 45 steel, 40 boron steel, 20 manganese titanium boron steel, 35CrMoA, etc. Ordinary bolts are usually made of Q235 (equivalent to A3 in the past) steel. In terms of strength grades: high-strength bolts are increasingly used. Two strength grades are commonly used, 8.8s and 10.9s, of which 10.9 is the majority. The strength level of ordinary bolts is lower, generally 4.4, 4.8, 5.6 and 8.8. High-strength bolts High-strength bolts are viewed from the force characteristics: high-strength bolts apply pretension and transmit external forces by friction. Ordinary bolt connection relies on the shear resistance of the bolt and the bearing of the hole wall to transmit the shear force. When the nut is tightened, the pre-pressure is very small, and its influence can be ignored. In addition to its high material strength, high-strength bolts also exert a large amount of pressure on the bolts. The pre-pressure generates extrusion force between the connecting components, so that there is a large friction force perpendicular to the direction of the screw, and the pre-pressure, anti-slip coefficient and steel type directly affect the bearing capacity of high-strength bolts. According to the force characteristics, it is divided into pressure type and friction type. The calculation methods of the two are different. The minimum specification of high-strength bolts is M12, and M16~M30 are commonly used. The performance of super-large bolts is unstable and should be used with caution in design.
When checking the finished blind rivet, check: the diameter of the rivet body, the length of the rivet body, the thickness of the rivet body cap, the diameter of the cap, the total length of the mandrel, the exposed size of the mandrel, the size of the nail cap, and the outer diameter after assembly can be considered. In the actual inspection, the weak links of the product can be measured, such as: tensile force, shear resistance, and core pull-out resistance. The key is to pay attention to the rivets, if the rivets are insufficient, whether they are riveted in place; or because the cap of the mandrel is too large, so that the mouth of the rivet body cannot be pulled down; and there are jump heads, that is, the mandrel is too low or broken. The size is too small etc. Length measurement of closed blind rivets
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