Hydraulic circuit leak detector and shut-off mechanism

Abstract

A leak detector and shut-off apparatus shuts off hydraulic fluid downstreamo prevent the hazards attendant hydraulic failure such as loss of fluid and fire. A first sensor is coupled to a supply line for hydraulic fluid to produce pressure differential force F s , which is representative of the flow of hydraulic fluid. A second sensor is coupled to a return line for hydraulic fluid to produce pressure differential force F r that is representative of flow of hydraulic fluid. A compensator creates representation F c of the rate of accumulation of hydraulic fluid in the hydraulic circuit downstream of the device and a safety margin. A shutoff mechanism is connected to the first and second sensors and the compensator to shut off the supply and return lines when F s is greater than the sum of F r and F c . Mechanical and electrical designs shutoff or isolate downstream hydraulic actuators, branches or select components immediately when a leak is detected to prevent loss of fluid and to reduce the hazards of fire.

We claim: 
     
       1. An apparatus for shutting off a hydraulic circuit comprising: a first sensor coupled to a hydraulic fluid supply line to produce force F s  representative of flow of hydraulic fluid;   a second sensor coupled to a hydraulic fluid return line to produce force F r  representative of flow of hydraulic fluid;   a compensator to create force F c  representative of the rate of accumulation of hydraulic fluid in said hydraulic circuit; and   a shutoff mechanism connected to said first and second sensors and said compensator.   
     
     
       2. An apparatus according to claim 1 in which said forces F s  and F r  are representative of pressure differential forces P s  and P r , and consequently, the mass flow difference between supply and return, respectively. 
     
     
       3. An apparatus according to claim 2 in which said shutoff mechanism immediately shuts off said supply line when F s  is greater than the sum of F r  and F c . 
     
     
       4. An apparatus according to claim 3 in which said shutoff mechanism immediately shuts off said return line when F S  is greater than the sum of F r  and F c . 
     
     
       5. An apparatus according to claim 4 in which said first and second sensors include Bernouilli devices providing pressure differential forces P s  and P r . 
     
     
       6. An apparatus according to claim 5 in which said compensator includes a pre-compressed spring. 
     
     
       7. An apparatus according to claim 6 in which said shutoff mechanism comprises: a housing having a plurality of cylindrical compartments separated by walls each having a bore aligned with each another;   a shaft extending through all of the bores to permit reciprocal motion therethrough; and   at least one piston affixed to said shaft in each said compartment.   
     
     
       8. An apparatus according to claim 7 in which said pre-compressed spring is in one of said compartments to displace said shaft in one direction. 
     
     
       9. An apparatus according to claim 8 in which first and second ones of said compartments respectively contain a portion of said supply line and said return line, and first and second pistons are in said first and second compartments, respectively. 
     
     
       10. An apparatus according to claim 9 in which said first and second pistons function as valves to close said supply and return lines when F s  is greater than the sum of F r  and F c . 
     
     
       11. An apparatus according to claim 10 in which said F r  pushes against a third piston in a third one of said compartments to displace it in said one direction, and F s  pushes against a fourth piston in a fourth one of said compartments to displace it in the opposite direction. 
     
     
       12. An apparatus according to claim 11 in which a fifth one of said compartments contains a circumferentially grooved piston, a sleeve having openings on said recessed piston, a spring pre-compressed between said sleeve and said housing, and a series of ball bearings carried in recesses in said housing to extend through said openings. 
     
     
       13. An apparatus according to claim 10 in which a fifth one of said compartments has conduits connected to said supply and return lines and contains a fifth piston. 
     
     
       14. An apparatus according to claim 12 in which said fifth piston closes said conduit to said supply line when F s  is not greater than the sum of F r  and F c  and opens said conduit to said supply line when F s  is greater than the sum of F r  and F c . 
     
     
       15. An apparatus according to claim 1 in which said first and second sensors each include a Bernouilli device and a pressure transducer to produce supply signal V a  representative of said force F s  and return signal V b  representative of said force F r , respectively, said compensator includes an impedance element coupled to each said pressure transducer to produce a voltage drop representative of rate of accumulation of hydraulic fluid in said hydraulic circuit, and said shutoff mechanism includes a relay coupled to a solenoid valve in said supply line and in said return line. 
     
     
       16. An apparatus according to claim 15 in which said relay is actuated to shut said solenoid valves and close said supply and return lines when V a  varies from V b  by a set amount. 
     
     
       17. An apparatus according to claim 16 in which mass flow is converted to voltages V a  and V b . 
     
     
       18. A leak detector and shutoff apparatus comprising: means connected to a hydraulic fluid supply line for sensing pressure differential force P s  representative of flow of hydraulic fluid;   means connected to a hydraulic fluid return line for sensing a pressure differential P r  representative of flow of hydraulic fluid;   means for compensating for rate of accumulation of hydraulic fluid in an interconnected hydraulic element to create a representative pressure force F c  ; and   means connected to said P s  and P r  sensing means for shutting off said supply and return lines.   
     
     
       19. A method for shutting off a hydraulic circuit comprising: sensing a pressure differential P s  representative of flow rate of hydraulic fluid in a supply line to create force F s  ;   sensing a pressure differential P r  representative of flow rate of hydraulic fluid in a return line to create force F r  ;   compensating for rate of accumulation of hydraulic fluid in an interconnected hydraulic element with a force F c  ; and   shutting off said supply and return lines when F s  is greater than the sum of F r  and F c .