Patent ID: 8529223

Claim:
A pump assembly comprising: a housing defining a working chamber, a first pump chamber and a second pump chamber; a first diaphragm disposed in the housing, the first diaphragm separating the first pump chamber and the working chamber; a second diaphragm disposed in the housing, the second diaphragm separating the second pump chamber and the working chamber; a driven member interconnecting the first diaphragm and the second diaphragm, the driven member disposed within the housing for reciprocal movement; a first inlet check valve in fluid communication with the first pump chamber, the first inlet check valve having a first diameter; a first outlet check valve in fluid communication with the first pump chamber, the first outlet check valve having a second diameter; a second inlet check valve in fluid communication with the second pump chamber, the second inlet check valve having a third diameter, the third diameter greater than both the first diameter and the second diameter; a second outlet check valve in fluid communication with the second pump chamber, the second outlet check valve having a fourth diameter, the fourth diameter greater than both the first diameter and the second diameter; and a drive member coupled to the driven member for reciprocating the driven member; the driven member configured such that movement of the driven member in a direction toward a first position creates a positive pressure in the first pump chamber and a negative pressure in the second pump chamber and movement of the driven member in a direction toward a second position creates a negative pressure in the first pump chamber and a positive pressure in the second pump chamber; wherein the second pump chamber includes a generally L-shaped cross section having a horizontally extending portion and a vertically extending portion, the horizontally extending portion bounded on a lower side thereof by a wall, an upper end of the vertically extending portion in fluid communication with the horizontally extending portion, a lowermost portion of the vertically extending portion in fluid communication with the second outlet check valve such that movement of the driven member to the second position substantially empties the horizontally extending portion into the vertically extending portion to allow drainage out of the second outlet check valve.