What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
In addition, the angle aluminum connection structure itself has structural defects of poor torsional and shear resistance, and many projects use larger insulating glass to meet the requirements of architects, resulting in a larger self-weight. In the event of a natural disaster such as an earthquake that will cause the curtain wall to shake violently, the bolts on the angle aluminum are prone to breakage, and the seismic performance is not good. Especially for the beam with the open structure, since the angle aluminum is installed in the opening cavity of the beam, the inertia moment of the beam is small, and the torsion resistance and shear resistance performance of the force are worse.
The key connection is a typical mechanical connection, which is usually used to connect the parts on the shaft and to fix them circumferentially and realize torque transmission. Key connection can be divided into flat key connection, semicircular key connection, wedge key connection and tangential key connection, among which flat key connection is widely used in practical engineering because of its simple structure, good alignment and convenient manufacturing. During operation, torque is transmitted through the contact between the sides of the key and the sides of the shaft and hub grooves. In order to ensure the transmission accuracy, the flat key structure generally adopts the transition fit. Due to its structural characteristics and working conditions, it is difficult to use ordinary mechanical tools to lift and pull out during the maintenance process. If forcibly removed, the key and the mating shaft will be destroyed.
flat washer is a part that is placed between the connected part and the bolt to protect the surface of the connected part from being scratched by the nut and to disperse the pressure of the nut on the connected part. At present, a flat washer in the prior art generally includes a washer body; the washer body has a bolt hole in the middle for a bolt to pass through. Although the flat washer of the above structure has a simple structure, it still has a disadvantage. When the flat washer is cushioned between the connected part and the bolt, the bolt head is usually exposed outside the connection part, so the bolt head is easy to It is damaged under the impact of external force, thus affecting its fixing effect.
As my digital TV technology becomes more and more mature, more and more people with digital-to-analog signal conversion function enter people's lives. Therefore, the number of production and processing is also increasing day by day. There are many requirements for the form, reliability and cost of PCB fixing screws in production. One of the existing fixing methods is to fix by means of bolts and nuts. The operation steps are to place the PCB board on the inner threaded copper column connected to the casing, and pass through the bolts with fine teeth. Screw holes on the PCB board, and then fix them on the copper posts with nuts. The connection method of this solution is reliable, but its manufacturing cost is high, and the copper column and the metal shell need to be screwed together, resulting in low production efficiency and high cost. In addition, there is also a common way that the PCB is supported by a plastic column, and the self-tapping screw is passed through the screw hole on the PCB board, and the PCB board and the metal bottom shell are connected by the self-tapping thread on the screw. The main disadvantage of this solution is that after the screw is fixed on the metal shell, the screw head is exposed at the bottom of the machine. If the user is not careful during use, the hand scratching phenomenon will occur, which will bring changes and harm to the user's use. . And when the machine slides on the desktop, if the screw head is too exposed, it will scratch the desktop. Therefore, how to provide a PCB fixing method with convenient operation, reliable connection and low production cost is a technical problem to be solved urgently in the industry.
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