Patent ID: 7541068

Claim:
A method for dispensing a liquid onto a substrate, comprising: providing first and second positive displacement pumps intermediate a liquid reservoir and a dispenser for substantially continuously metering of said liquid, said positive displacement pumps being connected in parallel such that each pump is capable of independently drawing said liquid from said liquid reservoir and independently metering said liquid to said dispenser; metering a predetermined quantity or flow rate of said liquid using one of said first and second positive displacement pumps; supplying said metered quantity or flow rate of said liquid to said dispenser to form droplets of a predetermined size and/or size distribution which are deposited onto said substrate; regulating the metering of said liquid and operation of said dispenser so that the liquid flow rate, droplet frequency, droplet volume and/or droplet velocity is controlled substantially independently of the particular flow characteristics of said liquid; and operating said positive displacement pumps in alternating succession such that while one of said positive displacement pumps meters said liquid to said dispenser the other positive displacement pump can draw additional liquid from said liquid reservoir to allow for substantially continuous and uninterrupted dispensing.