output the first and second fluids; monitoring the amounts of the first and second fluids output by the first and second pumps during each proportioning cycle; stopping operation of the first pump in each proportioning cycle while the second pump continues to operate, operation of the first pump being stopped each time the first pump outputs a selected amount of the first fluid; and restarting the first pump once the second pump has output enough of the second fluid in a current proportioning cycle to achieve the selected mix ratio.
In another aspect of the invention, a system for proportion metering fluids, comprises first and second pumps for pumping first and second fluids, respectively. Each pump includes a drive motor, and the fluid displacement of the first pump isless than the fluid displacement of the second pump. A sensor associated with each drive motor senses revolutions of each pump. Control circuitry is provided for determining the amounts of the first and second fluids output by the first and second pumps based upon the sensed revolutions during a series of repeating proportioning cycles. The control circuitry is designed to stop operation of the first pump when a predetermined amount of the first fluid has been output in each proportioning cycle. The control circuitry is further designed to restart operation of the first pump to begin the next proportioning cycle when the second pump outputs enough of the second fluid to achieve a desired mix ratio between the first and second fluids in each proportioning cycle.
In yet another