Expansion screw is generally said that the metal expansion screw, its fixed principle of the expansion of the screw is fixed using wedge-shaped slope to promote friction to produce friction grip force, to achieve a fixed effect. Screw head is a thread, a taper. (Some steel pipe), metal cylinder (steel pipe) half of the cut, put them together into the hole on the wall, and then lock the nut, the nut pulled out the screw, the taper pulled into the metal Cylinder, metal cylinder was opened, so tightly fixed on the wall, generally used for fence, rain Peng, air conditioning and other cement, brick and other materials on the fastening.
The expansion screw is composed of screw and expansion tube and so on. The screw tail is conical and the large diameter of the cone is larger than the inner diameter of the expansion tube. When the nut is tightened, the screw moves outward and moves the cone part through the axial movement of the thread, Tube of the outer side of the bolt-type composite cable bracket to form a large positive pressure, combined with the angle of the cone is very small, so that the wall, expansion tube and the formation of friction between the cone self-locking, and thus achieve a fixed effect. In fact, expansion screw structure: ① screw (non-standard shape) ② foreskin (ha ha ha is actually surrounded by the metal, the figure can be seen) ③ nut ④ gasket.
What is the working principle of such a complex structure of the expansion screw? First to figure out how many points. 1. The screw is a thread, one with a taper. 2. Half of the metal cylinder has a number of cuts. 3. Tighten the nut --- the squeeze gasket --- the axial extrusion of the metal cylinder (foreskin) at the beginning - the end of the foreskin is screwed with the taper of the head obstruction --- foreskin deformation (simply is the support Open) 4. In addition to the nut part, the entire expansion screw is to be pre-drilled into the hole.
The above points, simply: the nut pulled out the screw, the taper into the metal cylinder, metal cylinder was opened, so tightly fixed on the wall. (A few words from Baidu Encyclopedia --- expansion screw entry) Well, probably the principle of clarity, then talk about how the specific force. Friction is equal to the pressure multiplied by the coefficient of friction, the metal cylinder is opened, due to the taper, the open part is like an open hand, and concrete (assuming that in the concrete wall) in close contact (only abstract description) , Can produce enough force points, but also increase the pressure. It is possible to produce the idea that the taper is coming out and the feeling of the expansion screw will slip out. I: The more tight the screw is screwed, the more the screw is - the greater the taper (associated with the taper of the screw itself), theoretically the taper is big enough, or it will not be designed. II: concrete is not an ordinary mud brick, inside hard as a stone, so that the expansion of the screw shape of the taper can be tightly, as long as the hole does not expand, not loose, theoretically able to withstand more force. The next section to everyone about the expansion screw pull screw installation method. Pull the screw, the nut structure is a section can be deformed, the screw in the tightening of the nut when the nut with the pull of the nut pull the deformation, while the nut riveting tightly on the workpiece, after the nut is fixed on the workpiece. The following are the correct installation steps:
1, first of all, need to install the expansion screw where a hole, hole size, depth and expansion of the outer diameter of the screw, the length of the match, so when drilling drill bit size is essential.
2, the second need to install the flat pad, spring and nuts, and then screw the bolt and the end of the bolt to protect the thread, and then insert the expansion bolt into the hole before the hole.
3, and finally to screw the wrench until the gasket and fixture surface flush, under normal circumstances, after the hand tightened and then wrench three to five turn.
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