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

When using, we first press the air in the reservoir cavity (that is, the plastic tube that can absorb shampoo), when the air is discharged, press the pump head again, because after letting go, the spring in the pump head to return to its original state, then the vacuum will be formed in the reservoir, generating negative pressure, at this time, the pressure in the container is consistent with atmospheric pressure, then, it causes the pressure in the reservoir cavity is small, the pressure in the container is large, at this time, due to the pressure difference, the atmosphere will press the liquid around the reservoir cavity into the reservoir chamber, It feels like the pump head is sucking the liquid up.