The diaphragm pump has one of the simpler operating mechanisms of any mechanical pump. A flexible metal or polymeric sheet material seals a small, usually cylindrical, chamber at one end. At the other end are two spring-loaded valves: one opening when the chamber pressure falls below the pressure outside the valve and the other opening when the chamber pressure exceeds the pressure outside the valve. A cam on a motor shaft rapidly flexes the diaphragm, causing gas to transfer in through one valve and out through the other.