Patent ID: 8608685

Claim:
A breast pump, comprising: a substantially conically-shaped milking part configured to abut against a breast of a user; a breast pump main body configured to be attached to and detached from a bottle; and a pressure changing apparatus connected with the milking part and configured to alternately generate a first negative pressure state in the milking part and a second negative pressure state having a less negative pressure value than the first negative pressure state in the milking part, wherein the milking part is disposed so as to liquid-tightly separate the pressure changing apparatus from a sealed space in the milking part formed when the milking part abuts against the breast of the user during milking, and the milking part includes a pressure transmission apparatus configured to transmit pressure changed by the pressure changing apparatus to the sealed space, the pressure transmission apparatus having a deformable part configured to change a volume of the sealed space when the deformable part is deformed by a pressure change generated by the pressure changing apparatus, the deformable part including an elastic material that defines an air tight expandable volume and which separates the sealed space from the pressure changing apparatus in a liquid-tight manner, and the pressure transmission apparatus having a case which accommodates the deformable part and is connected with the pressure changing apparatus at one end, and includes attachment structure at an other end of the case configured to communicably attach the case with a portion of the milking part that defines the sealed space, wherein the case is configured to accommodate the deformable part therein, and the attachment structure includes a tubular projecting part, the tubular projecting part projecting from the other end of the case, and the milking part includes a cylindrical connection part extending into the sealed space, and an inner diameter of the cylindrical connection part is slightly larger than an outer diameter of the tubular projecting part of the case so that the case and the sealed space are air-tightly joined to each other when the tubular projecting part is inserted into the cylindrical connection part.