Patent ID: 6857441

Claim:
A fluid metering device comprising: a first gear; a second gear disposed adjacent said first gear so that said second gear intermeshes with said first gear; a third gear disposed adjacent said second gear so that said second gear is intermediate said first gear and said third gear, and so that said third gear intermeshes with said second gear; a fourth gear disposed adjacent said third gear so that said third gear is intermediate said second gear and said fourth gear, and so that said fourth gear intermeshes with said third gear; a liquid inlet port that is in liquid communication with both a portion of said second gear and a portion of said third gear; a first liquid discharge port that is in liquid communication with both a portion of said first gear and a portion of said second gear; a second liquid discharge port that is in liquid communication with both a portion of said third gear and a portion of said fourth gear; and a pressure balance port disposed adjacent said first gear, said pressure balance port being in liquid communication with a portion of said first gear, wherein: said second gear is configured to move liquid from said liquid inlet port to said first liquid discharge port at a first flow rate, said third gear is configured to move liquid from said liquid inlet port to said second liquid discharge port at a second flow rate, and said fluid metering device is configured so that: (1) liquid passing through said first liquid discharge port exerts a first force on said first gear in a first direction; (2) liquid within said pressure balance port exerts a second force on said first gear in a second direction, said second force substantially offsetting at least a portion of said first force; and (3) the liquid within said pressure balance port is substantially stagnant.