Diaphragm vacuum pump

A diaphragm vacuum pump having a plurality of check valves for allowing flow into and out from a suction chamber having a diaphragm-piston assembly for creating suction therein wherein each check valve comprises:

• a valve body made of plastic material in a mushroom configuration having a circular cap and a neck portion including an annular groove,
• a plate member including a flat valve seat surface to be engaged with the annular rim of the cap portion of said valve body,
• a circular assembling hole to be coupled with the neck portion of said valve body, and
• a plurality of circular openings disposed symmetrically on a circular path concentric with said assembling hole so as to be normally closed by the annular rim of the cap portion of said valve body, the neck portion of said valve body being assembled within said assembling hole so that said groove is registered with said assembling hole through said plate, said neck portion being under an axially and radially compressed condition to air-tightly engage the annular rim of the cap portion of said valve body against said valve seat surface of said plate member, the ratio of the radius of said circular path to the radius of the cap portion of the valve body being in the range from about 0.5 to about 0.65, the ratio of the width of said plate to the width of said annular groove being in the range from about 1.2 to about 1.4, and the ratio of the diameter of the assembling hole to the normal diameter of the neck portion of the valve body being about equal to or less than 1.1.