US Patent 7575633 Fluid dispenser with positive displacement pump

Fluid dispensing apparatus uses positive displacement of the fluid for accurate metering of the quantity of liquid applied to a surface. Positive displacement includes a metering volume that is filled and emptied so that each cycle corresponds to an accurate volume of material dispensed independent of viscosity. In one embodiment, a positive displacement pump is used with a variable speed air motor. The air motor drives the pump. A variable output air regulator supplies air pressure to run the air motor based on a position signal. A profile may be used to relate position with motor speed and to control quantity to be dispensed.