Patent ID: 8302941

Claim:
A micro-bubble generating device comprising: a liquid flow body in the form of a cylindrical column having a flow passage formed in its outer circumferential surface so as to extend in its axial direction so that a liquid flows through the flow passage, an inlet opening which is formed in one of its opposite axial end portions and through which the liquid flows into the flow passage, and an outlet opening which is formed in the other axial end portion and through which the liquid is discharged from the flow passage, wherein the outer circumferential surface is covered by a gas-permeable film so as to close an opening of the flow passage open in the outer circumferential surface; and a casing in the form of a cylindrical sleeve which is open at its opposite ends and which has a gas inlet hole formed through its cylindrical wall and accommodates therein the liquid flow body, the casing and the outer circumferential surface of the liquid flow body define therebetween an internal space accommodating a pressurized gas introduced into the cylindrical sleeve through the gas inlet hole, wherein the flow passage is helically formed in the outer circumferential surface, and the gas-permeable film has a structure which normally has a low degree of gas permeability, and permits generation of micro-bubbles in the liquid by forced permeation of the pressurized gas therethrough.