Airless bottle is one of the main packaging materials in cosmetics. The airless bottle commonly used in the market is composed of a cylinder into an ellipsoid container and a piston with a settled bottom. Its planning principle is to use the shortening force of a tension spring, and to prevent air from entering the bottle to form a vacuum state, and use atmospheric pressure to push the piston at the bottom of the bottle to travel. However, because the tension spring force and atmospheric pressure cannot give enough strength, the piston cannot fit too tightly with the bottle wall, otherwise the piston will not be able to move up due to excessive resistance; on the contrary, if the piston is to be easy to move, it is easy to leak material. Therefore, the requirements for the professionalism of the manufacturer of the vacuum bottle are very high.

Product structure and assembly requirements
1. Scale control: All assembled products after cooling are controlled within the tolerance range, which shall not affect the assembly function and hinder packaging.
2. The outer cover and inner cover should be assembled in place for cooperation, without tilting or improper assembly;
3. The inner cover will not fall when it is subjected to axial tensile test ≥30N;
4. The inner bottle and outer bottle buckle cooperation should be clamped in place, and the degree of tightness is suitable; the assembling tension of the middle sleeve and the outer bottle is ≥50N;
5. The combination of the inner bottle and the outer bottle cannot conflict with the inner wall to prevent scratches;
6. The screw of the cap and the bottle body rotates smoothly without jamming;
7. Alumina parts are assembled with corresponding caps and bottle bodies, and the tensile force after drying for 24H is ≥50N;
8. The feel of the pump head should be smooth when pressing the test spray, and there should be no obstruction;
9. The gasket will not fall when it bears a pulling force of not less than 1N;
10. After the outer cover and the screw of the corresponding bottle body cooperate, the gap is 0.1～0.8mm.