Liquid delivery system

Abstract

A liquid delivery system comprises a tank containing a supply of a first liquid. A positive displacement pump operates to withdraw the first liquid from the tank via a suction conduit and to deliver a pressurized flow of the first liquid via a delivery conduit. An adjustable metering orifice in the delivery conduit serves to control the flow of the first liquid through the delivery conduit. A normally closed first valve located in the delivery conduit between the pump and the metering orifice is opened in response to a pressure of the first liquid exceeding a threshold level, and is operative when open to deliver the first liquid to the metering orifice at a substantially constant pressure. A bypass conduit communicates with the tank and with the delivery conduit at a location between the pump and the first valve. A second valve in the bypass conduit is adjustable to accommodate a controlled return flow of the first liquid from the delivery conduit to the tank, thereby modulating the pressure of the first liquid being delivered to the first valve.

1 . A system for delivering a metered flow of a first liquid, said system comprising:
 a tank containing a supply of the first liquid;   a positive displacement pump, said pump being operable to withdraw said first liquid from said tank via a suction conduit and to deliver a pressurized flow of said first liquid via a delivery conduit;   a metering orifice in said delivery conduit, said metering orifice being adjustable to control the flow of said first liquid through said delivery conduit;   a valve located in said delivery conduit between said pump and said metering orifice, said valve being normally closed, being opened in response to a pressure of said first liquid exceeding a threshold level, and being operative when open to deliver said first liquid to said metering orifice at a substantially constant pressure;   a bypass conduit communicating with said tank and with said delivery conduit at a location between said pump and said first valve; and   a flow restrictor in said bypass conduit, said flow restrictor serving to moderate a return flow of said first liquid from said delivery conduit to said tank.   
     
     
         2 . The system of  claim 1  wherein said flow restrictor comprises a second valve that is adjustable to accommodate a controlled return flow of the first liquid from said delivery conduit to said tank. 
     
     
         3 . The system of  claim 1  wherein said flow restrictor comprises a second metering orifice sized to accommodate a set return flow of the first liquid from said delivery conduit to said tank. 
     
     
         4 . The system of  claim 1  further comprising a pressure gauge for visually displaying the pressure of the first liquid being delivered to said first valve. 
     
     
         5 . The system of  claim 1  wherein said metering orifice includes a visual display of the volume of said first liquid flowing through said delivery conduit. 
     
     
         6 . The system of  claim 1  further comprising at least one delivery hose having first and second hose conduits leading to a handgun, said first hose conduit being connected to said delivery conduit, and said second hose conduit being connected to a pressurized source of a second liquid, said handgun being adapted to alternatively deliver only said second liquid, or a mixture of said first liquid and said second liquid.