Self-proportional fluid metering device actuated by a pressurized fluid

Claim 1

A fluid metering device, comprising, detecting means for detecting the flow rate of a first fluid in a conduit; amplifier means operatively connected to said detecting means for delivering a pneumatic pressure which is dependent on the flow rate of said first fluid as detected by the detecting means; a control unit having a control diaphragm, a control shaft and a first spring, said control diaphragm being exposed to and urged by said pneumatic pressure against said first spring, said control shaft being connected to said control diaphragm; a motor unit having a motor diaphragm, a motor shaft and a second spring, said motor diaphragm having one face thereof exposed to a hydraulic fluid which periodically urges the diaphragm against the action of said second spring; said motor shaft being connected to said diaphragm and being operatively engageable by said control shaft; a pumping unit having a pump diaphragm and a stop member, said pump diaphragm being connected to the motor shaft, said stop member being positioned to abut the motor shaft when the motor shaft is given a maximum displacement by said control shaft and said first spring means; said control shaft comprising a variable stop member whose position is dependent upon the flow rate of said first fluid, said position determining the displacement of said pump diaphragm; and a continuously operating modulating means operating at a substantially constant speed for periodically supplying hydraulic pressure to said motor unit to cause said pump diaphragm to pump a second fluid with a pumping action which is dependent on said pneumatic pressure and thus on the flow rate of said first fluid.