System for controlling the stroke of an air-operated double diaphragm pump

Abstract

A system for controlling the stroke of an air-operated double diaphragm pump includes a first control valve and a second control valve disposed in parallel within a drive air outlet conduit. The first flow control valve has a first air flow capacity and the second flow control valve has a second air flow capacity which is less than about 50% of the first air flow capacity.

1 . A system for controlling the stroke of an air-operated double diaphragm pump, the pump having a drive air inlet and a drive air exhaust outlet, the system comprising:
 (a) an air outlet conduit connected in fluid tight communication with the drive air exhaust outlet;   (b) a first flow control valve operatively connected in fluid tight communication with the air outlet conduit, the first flow control valve having a first air flow capacity; and   (c) a second flow control valve operatively connected in fluid tight communication with the air outlet conduit, the second flow control valve being connected in parallel with the first flow control valve and having a second air flow capacity which is less than about 50% of the first air flow capacity.   
     
     
         2 . The system of  claim 1  wherein the second flow control valve has a second air flow capacity which is between about 10% and about 20% of the first air flow capacity. 
     
     
         3 . A method for pumping a precise quantity of fluid using an air-operated double diaphragm pump, the pump having an air inlet and a drive air exhaust outlet, the method comprising the steps of:
 (a) providing the system for controlling the stroke of the air-operated double diaphragm pump of  claim 1 ;   (b) opening the first flow control valve;   (c) pumping greater than about 95% of the precise quantity of fluid at a high rate of flow;   (d) closing the first flow control valve; and   (e) pumping the remainder of the precise quantity of fluid at a reduced rate of flow.   
     
     
         4 . The system of  claim 3  wherein the second flow control valve has a second air flow capacity which is between about 10% and about 20% of the first air flow capacity. 
     
     
         5 . A system for providing liquid coloring agent to concrete delivery vehicles parked in a loading zone, the system comprising:
 (a) a plurality of bulk tanks;   (b) an air operated double diaphragm pump connected in fluid tight communication to each bulk tank, each double diaphragm pump having a drive air exhaust outlet;   (c) an air outlet conduit connected in fluid tight communication with each drive air exhaust outlet;   (d) a fill line connecting each double diaphragm pump to the loading zone; and   (e) a system for controlling the stroke of each air-operated double diaphragm pump comprising (i) an air outlet conduit connected in fluid tight communication with the drive air exhaust outlet, (ii) a first flow control valve operatively connected in fluid tight communication with the air outlet conduit, the first flow control valve having a first air flow capacity, and (iii) a second flow control valve operatively connected in fluid tight communication with the air outlet conduit, the second flow control valve being connected in parallel with the first flow control valve and having a second air flow capacity which is less than about 50% of the first air flow capacity.   
     
     
         6 . The system of  claim 5  wherein the second flow control valve has a second air flow capacity which is between about 10% and about 20% of the first air flow capacity.