Piezoelectric pump with annular valve arrangement

A piezoelectric pump comprising:

• a first top plate having a first opening;
• a second top plate arranged as spaced from the first top plate and having a second opening;
• a diaphragm arranged between the first top plate and the second top plate and having a piezoelectric element attached thereto;
• a first side wall coupling the first top plate and the diaphragm together and defining a first pump chamber between the first top plate and the diaphragm;
• and
• a second side wall coupling the second top plate and the diaphragm together and defining a second pump chamber between the second top plate and the diaphragm, wherein
• the diaphragm has a vibrating part having the piezoelectric element attached thereto, a frame part enclosed between the first side wall and the second side wall, and a connecting part connecting the vibrating part and the frame part,
• the connecting part defines a third opening, and the third opening communicates the first pump chamber with the second pump chamber,
• the frame part has a fourth opening, and the fourth opening communicates with the third opening and also communicates with outside, and
• the piezoelectric pump further includes
• in the first pump chamber, an annular first valve provided as spaced from the first opening in in a planar view from a main surface of the first top plate toward a main surface of the second top plate so as to surround the first opening, and
• in the second pump chamber, an annular second valve provided as spaced from the second opening in the planar view from a main surface of the first top plate toward a main surface of the second top plate so as to surround the second opening.