System for regulation and control of water pressure and flow rate in a high pressure water application

Abstract

A water bypass valve and system for regulation and control of water pressure and water flow rate in high pressure water applications having a water pressure safety relief valve. An operator may select a desired water pressure setting in an operator interface. The water system may be controlled by a computer processor that receives pressure data from a transducer in a high pressure discharge line and a speed sensor at a water pump drive shaft. The water bypass valve, controlled by the computer processor, may regulate water flowing back to the water supply tank, allowing the safety relief valve to remain closed over a wide range of water pump operating speeds.

What is claimed is: 
     
         1 . A system for regulation and control of water pressure and flow rate in high pressure water applications, comprising:
 a variable speed water pump configured for receiving water from a water reservoir;   a discharge conduit configured for passing water from said water pump to a nozzle;   a relief valve in fluid communication with said discharge conduit, said relief valve having a pressure limit, wherein said relief valve is configured to divert water from said discharge conduit to the water reservoir if a water pressure in said discharge conduit exceeds said pressure limit;   a variable flow bypass valve in fluid communication with said discharge conduit, said bypass valve being controllable between a closed position and a fully open position, said bypass valve being configured to divert water from said discharge conduit to the water reservoir when said bypass valve is in an open position;   a speed sensor configured for sensing a speed of said water pump;   a pressure transducer configured for sensing a pressure in said discharge conduit; and   a computer configured for
 setting a preselected water pressure via an operator interface, said preselected water pressure being less than said pressure limit; 
 receiving a speed input signal from said speed sensor; 
 receiving a pressure input signal from said pressure transducer; and 
 in response to said input signals, controlling the speed of said water pump within a range of speeds and controlling said bypass valve in a manner that tends to maintain said pressure in said discharge conduit at said preselected water pressure. 
   
     
     
         2 . The system of  claim 1  further comprising a hydraulic control system comprising:
 a hydraulic drive pump configured for engagement with a power takeoff of a vehicle; 
 a hydraulic drive motor operatively connected to said hydraulic drive pump, said hydraulic drive motor being operatively engaged with said water pump; 
 a hydraulic controller configured for receiving a first output signal from said computer, said hydraulic controller being operatively engaged with said hydraulic drive pump; and 
 a proportional hydraulic pressure control valve configured for receiving a second output signal from said computer, said proportional hydraulic pressure control valve being operatively engaged with said bypass valve; 
 wherein said hydraulic controller is configured for controlling the speed of said water pump via said hydraulic drive pump and said hydraulic drive motor in response to said first output signal; and 
 wherein said proportional hydraulic pressure control valve is configured for controlling said bypass valve in response to said second output signal. 
 
     
     
         3 . The system of  claim 2  further comprising a hydraulic charge pump operatively engaged with said hydraulic drive pump and in fluid communication with said hydraulic controller and said proportional hydraulic pressure control valve. 
     
     
         4 . The system of  claim 1  wherein said water pump comprises a minimum speed, and wherein said computer is further configured to reduce the speed of said water pump if said pressure in said discharge conduit is greater than said preselected water pressure and the speed of said water pump is greater than said minimum speed. 
     
     
         5 . The system of  claim 4  wherein said computer is further configured to divert water from said discharge conduit through said bypass valve if said pressure in said discharge conduit is greater than said preselected water pressure and the speed of said water pump is less than or equal to said minimum speed. 
     
     
         6 . The system of  claim 5  wherein said system is part of a mobile hydroexcavating machine. 
     
     
         7 . The system of  claim 1  wherein said bypass valve is disposed downstream along said discharge conduit from said pressure transducer. 
     
     
         8 . The system of  claim 7  wherein said bypass valve is disposed downstream along said discharge conduit from said relief valve. 
     
     
         9 . An electro-hydraulic water bypass valve for use in a system having a water pressure safety relief valve for regulation and control of water pressure applications, said system comprising an operator interface for setting a preselected water pressure, a computer receiving input from a water pump speed sensor and a water pressure transducer, wherein output from said computer regulates a variable displacement hydraulic drive pump and a proportional pressure control valve, a hydrostatic drive motor operatively connected to said variable displacement hydraulic drive pump and a high pressure water pump, said high pressure water pump being in fluid communication with a water intake conduit extending from a water supply tank, a discharge conduit extending from an output side of said high pressure water pump to a discharge nozzle, said discharge conduit being in fluid communication with said water pressure safety relief valve, a fixed displacement charge pump engaged with said variable displacement hydraulic drive pump and in fluid communication with said proportional pressure control valve, said electro-hydraulic water bypass valve comprising:
 a needle valve having an inlet in fluid communication with said discharge conduit, an outlet in fluid communication with said water supply tank, and a valve stem;   a valve spring configured for urging said valve stem in a first direction; and   a hydraulic cylinder having a cylinder output shaft configured for urging said valve stem in a second direction opposite said first direction, thereby moving said needle valve between an open position and a closed position;   wherein said proportional pressure control valve is in fluid communication with and adapted for controlling said hydraulic cylinder, thereby regulating bypass water from said discharge conduit to said water supply tank in response to output from said computer.   
     
     
         10 . The bypass valve of  claim 9  wherein said needle valve is biased toward said open position by said valve spring. 
     
     
         11 . The bypass valve of  claim 10  wherein said valve spring is compressed by a spring plate, said valve stem comprises a threaded portion having a nut threaded thereon, said nut being engaged with said spring plate, and said valve stem is slidably disposed through said spring plate. 
     
     
         12 . A method of controlling a pressurized water system having a variable speed water pump in fluid communication with a water reservoir and a discharge conduit, a nozzle in fluid communication with the discharge conduit, a safety relief valve in fluid communication with the discharge conduit, the safety relief valve having a pressure limit and being configured to divert water from the discharge conduit to the water reservoir if a pressure in the discharge conduit exceeds the pressure limit, a bypass valve in fluid communication with the discharge conduit, a hydraulic pressure control valve configured for controlling the bypass valve, a hydraulic controller configured for controlling a hydraulic motor, the hydraulic motor being configured for driving the water pump, and a computer in communication with the hydraulic controller and the hydraulic pressure control valve, the method comprising:
 setting a preselected water pressure for said system in said computer via an operator interface, said preselected water pressure being less than said pressure limit;   activating said water pump;   sensing a pressure in the discharge conduit using a pressure transducer;   sending a first signal representative of said pressure as a first input to said computer;   sensing a speed of said water pump using a speed sensor;   sending a second signal representative of said speed as a second input to said computer; and   in response to said first and second signals, sending a first output signal from said computer to said hydraulic controller thereby controlling the speed of said water pump within a range of speeds and sending a second output signal from said computer to said hydraulic pressure control valve thereby controlling said bypass valve in a manner that tends to maintain said pressure in said discharge conduit at said preselected water pressure.   
     
     
         13 . The method of  claim 12  wherein said water pump comprises a minimum speed, and wherein said method further comprises reducing the speed of said water pump if said pressure in said discharge conduit is greater than said preselected water pressure and the speed of said water pump is greater than said minimum speed. 
     
     
         14 . The method of  claim 13  further comprising diverting water from said discharge conduit through said bypass valve if said pressure in said discharge conduit is greater than said preselected water pressure and the speed of said water pump is less than or equal to said minimum speed.