Continuous positive displacement metering valve

A positive displacement piston pump for dispensing an adhesive onto a work surface, comprising:

• a metering block defining first and second cylinders;
• a valve block coupled to said metering block and defining a first metering chamber portion and a second metering chamber portion, said first metering chamber portion communicating with and having a smaller cross-section than said first cylinder and said second metering chamber portion communicating with and having a smaller cross-section than said second cylinder;
• first and second pistons disposed within said cylinders for reciprocation therein, said first piston having a first metering tip at one end and a first rack toward an opposing end, and wherein said first tip is configured to substantially conform to the geometry of said first metering chamber portion and said second piston having a second metering tip at one end and a second rack toward an opposing end, and wherein said second tip is configured to substantially conform to the geometry of said second metering chamber portion;
• a motor in meshing engagement with said first rack and said second rack, such that angular displacement of said motor causes a linear displacement of said first and second pistons in simultaneous opposing dispensing and reloading directions;
• a motor controller configured to precisely control the angular displacement of said motor;
• and
• wherein the pump is configured to dispense adhesive through a fluid outlet onto a work piece moving relative thereto.