PUMP METERING SYSTEM

摘要

A fluid delivery system (10) and method for dispensing precisely metered quantities of a fluid, comprising fluid supply means (16); pump means (22); a conduit (14) interconnecting said fluid supply means and pump means; a first valve (18) in said conduit positioned intermediate said fluid supply means and pump means; a nozzle (28) for discharging said fluid from said system; a further conduit (24) connecting said nozzle with said pump means and with said conduit; a second valve (26) in said further conduit; means (44) for selectively applying a vacuum and a superatmospheric pressure to said pump means; and control means (50) operatively interconnecting said first and second valves and said selecive pressure applying means for aspirating predetermined quantities of fluid from said fluid supply means through said conduit to said pump means and thereafter conveying said quantities of fluid from said pump means to said nozzle, the system being so arranged as to cause formation of a fluid flow-occluding air bubble in said nozzle upon termination of discharge of fluid from said nozzle so as to inhibit discharge of residual droplets of said fluid from said nozzle.