The principle of the lotion pump is to use the atmospheric pressure

When using it, we first push out the air in the liquid storage chamber (that is, the plastic tube that can absorb the shampoo) by pressing. When the air is exhausted, press the pump head again. To restore the original state, a vacuum will be formed in the liquid storage chamber, and negative pressure will be generated. At this time, the pressure in the container is consistent with the atmospheric pressure. Then, the pressure in the liquid storage chamber is small and the pressure in the container is large. At this time , Due to the pressure difference, the atmosphere will press the liquid around the mouth of the liquid storage cavity into the liquid storage cavity, giving people the feeling that the liquid is sucked up by the pump head.