US Patent 9239046 Air pump for measuring an air pressure

An air pump that measures an air pressure including a base, a one-way valve, a pump pipe, a piezometer, a scale plate, a cylinder, a piston, and a driving stem. The base has a chamber room. The one-way valve has an inlet chamber and a vent. The scale plate has an air-guiding hole so that a cylinder hole of the cylinder is communicated with the air-guiding hole. A piston is driven to pump gas in the cylinder hole, thereby forcing the gas to enter the inlet chamber, rendering the vent to deliver the gas unidirectionally, and allowing the scale plate to display an air pressure value.