What is the purpose of the notch in the screw of the soda bottle cap?

Update:15 Apr 2021

Coke, mineral water, and ice tea bottles have such gaps in the spirals of the bottles. The spirals are not connected, and there are gaps in the corresponding positions on the caps. Why is there such a design? I guess it is thermal expansion and cold contraction or gas overflow, but I can’t figure out why there are these two situations.
One of the main functions of this gap is to make it easier for the water to rinse the bottle mouth to flow down, otherwise the content remaining in the bottle mouth will breed mold (shown as black spots) and attract small bugs. Now someone will ask, if there is no such gap for hot charging, wouldn’t it be difficult for the water to flow down the bottle?

Let us return to the hot filling process. After filling and locking the cap, it will pass through a long spray cooling chamber to cool the product temperature below the dew point and continue to rinse the bottle mouth. The spray cooling method is to use a lot of spray nozzles like showers, from top to bottom, spraying at the bottle in all directions without dead corners. Don't think that by spraying from top to bottom, the water cannot enter the gap between the cap and the bottle head.
Therefore, the spray water also plays a considerable role in flushing the bottle mouth during the cooling process. Since the aseptic filling does not have this cooling spray, the bottle mouth must be rinsed after the filling is completed. This gap is indispensable. That's it.
In addition, Zhang Maizi asked if the detergent rushed into the bottle when washing the mouth of the bottle. Okay, serious boy. After filling, the water used to rinse the mouth of the bottle is for beverages, which is RO water that is purer than pure water, and does not contain detergent. There is no need to worry too much about water splashing into the bottle. The existing technology has been able to wash the mouth of the bottle without splashing water into the bottle.