US Patent 11867166 Piezoelectric pump with annular valve arrangement

A piezoelectric pump includes a first top board, a second top board, a diaphragm, a first side wall, a second side wall, a first valve, and a second valve. The first valve has an annular shape to surround the first aperture while being spaced apart from the first aperture and the second aperture, and is disposed in the first pump chamber between the first aperture and the second aperture when viewed in a plan. The second valve has an annular shape to surround the third aperture while being spaced apart from the third aperture and the fourth aperture, and is disposed in the second pump chamber between the third aperture and the fourth aperture when viewed in a plan.