The strength of lightweight bottles is not only related to the glass composition and microscopic and macroscopic defects in the glass, but also has a lot to do with the shape of the bottle. Reasonable structural design can make stress distribution uniform, cooling uniform and increase the "elasticity" of the container, so that the internal pressure resistance and impact strength can be improved. Therefore, as long as the bottle shape and wall thickness distribution are reasonably designed, lightweight bottles will not cause strength reduction.
When designing the bottle shape, it is mainly based on the principle that the closer the glass product is to a sphere, the less likely it is to produce stress concentration, thereby increasing the strength. The bottle shape is designed to be connected with a rounded spherical connection at the shoulder and the root to improve the strength of the bottle.
The general principles of lightweight bottle shape design are as follows.
1 Shrink the bottle root, which can increase the strength of the bottle and improve the distribution of glass in this area.
2 Avoid special-shaped bottles, preferably a cylinder with the so-called "tapered bottom". The bulge at the bottom of the bottle should be as shallow as possible.
3 Try not to use long-necked bottles, which only increase the height of the bottle but not the capacity of the bottle. In addition, the bottleneck is easy to break, and it is not easy to reduce the amount of neck glass.
4 Avoid sharp angles on the bottle shoulder. Use a tapered high shoulder with a smooth transition.
5 Avoid seams at corners, otherwise it will make mold maintenance difficult, increase bottle defects, make blank design difficult, and make the glass distribution uneven at the corners.
6 Use a bottle mouth with the smallest wall thickness to avoid excessive overlap of threads. The bottle mouth reinforcement ring should be as small as possible or even not at all.
7 The distance from the top of the bottle mouth to the beginning of the thread should be as small as possible. The bottle mouth height should also be as small as possible.
8 Reduce the overall height of the bottle.
From the lightweight bottle shape of Owens-Brockway in the United States (Figure 2-40), it can be seen that the bottle body reaches or approaches the minimum cylindrical structure per unit volume, reducing the bottle height, and adopts appropriate arc smooth transition between the bottle body and the bottle bottom and bottle neck, and the shoulder gradually shrinks toward the bottle mouth, making the bottle neck as short as possible, and the center of the bottom slightly bulges upward. The convex bottle bottom can make the center of gravity downward, increase the stability of the bottle, have great benefits in resisting internal stress and water impact, and increase its anti-inversion strength. This bottle shape can also effectively reduce the weight of the bottle.