WATER DETECTOR FOR FUEL SYSTEMS AND METHOD FOR DETECTING WATER IN SAME

Abstract: A water detector apparatus (20) for detecting water in the various reservoirs of a fuel system. The water detector apparatus (20) includes a support housing (22) for supporting control electronics. Electrically interconnected to the electronics by an electrical lead (24) is an electrically conductable probe (26) which is at least partially threaded into the interior of a reservoir (28) of the fuel system. An oscillator (58) is included as part of the electronics for providing the electrically conductive probe (26) with an AC signal. The electronics further includes circuitry for comparing the resultant resistance of the electrically conductive probe (26) with a known resistance and further providing an output signal representative of the resultant resistance of the electrically conductive probe (26). A green LED (36) is electrically interconnected to the output so as to be lit when a low output is provided, indicating the absence of water and a red LED (38) is electrically interconnected to the output to intermittently blink when a high output is detected, indicating the presence of water.

Description: WATER DETECTOR FOR FUEL SYSTEMS " AND METHOD FOR DETECTING WATER IN SAME BACKGROUND OF.THE INVENTION The present invention relates to a water detector apparatus for fuel systems and method for detecting water in such fuel systems. More par¬ ticularly, the present invention provides an apparatus and method for detecting water in the carburetor bowl, fuel sumps, gasgulator, water separators, etc. of a fuel system. Moisture has a tendency to collect in the car¬ buretor bowl and other reservoirs in a fuel system. Since the accumulation of moisture is undetectable in normal conditions, it can cause an engine to eventually stop. A reliable method and apparatus is required to monitor such reservoirs for the presence of water to provide an indication before an engine shutdown occurs. The present invention solves this problem and others. SUMMARY OF THE INVENTION The present invention relates to a water detector apparatus for fuel systems. The water detec¬ tor apparatus includes an electrically conductive probe inserted into a fuel holding reservoir of the fuel system. AC signal means is electrically interconnected to the probe for supplying an AC signal thereto. The probe exhibits a resultant resistance when the AC signal is so applied. The resultant resistance is indicative of the presence or absence of water in the fuel holding reservoir. Circuitry means is electri¬ cally interconnected to the probe for comparing the resultant probe resistance with a known resistance, the circuitry means including an output means for providing an output signal representative of the resultant resistance of the probe. Indicator means is electri¬ cally interconnected to the output means of the cir¬ cuitry means for receiving the output signal. The indicator means is responsive to the output signal received, the indicator means having a first state indicative of the presence of water and a second state indicative of the absence of water. The present invention further relates to a method for detecting water in fuel systems. The method comprises applying an AC signal via an electrical interconnection to an electrically conductive probe inserted into a fuel holding reservoir of the fuel system, the probe exhibiting a resultant resistance when the AC signal is so applied, the resultant resistance being indicative of the presence or absence of water in the fuel holding reservoir. The method further includes monitoring via an electrical intercon¬ nection the resultant resistance of the probe and com¬ paring the probe resistance with a known resistance. An electrical signal representative of the resultant resistance of the probe is then output to an indicator via an electrical interconnection, the indicator being responsive to the output signal. The indicator has a first state indicative of the presence of water and a second state indicative of the absence of water. The present invention is particularly advan¬ tageous in that it provides a system to detect water in the carburetor bowl, fuel sumps, gasgulator, and other reservoirs of an aircraft fuel system. The present invention has particular utility in aircraft fuel -3- systems where it is important to detect the presence of water before engine shutdown occurs, which * could be a life threatening situation. In one embodiment of the present invention, a selector switch is utilized to enable switching between probes at different locations in the fuel system. In yet another embodiment of the present invention, a test switch is provided such that the operation of the indi¬ cator means can be verified. Still yet another embodiment provides for simultaneous monitoring of two or more reservoirs. The present invention provides a water detec¬ tor apparatus which is fairly sensitive and relatively inexpensive to incorporate into a fuel system whether it be a new fuel system or an existing fuel system. Further, the present invention provides for detection of the presence of water, not necessarily the level of water. For example, the present invention is capable of detecting pockets of water in a flow of fuel or when the fuel is being agitated or unsettled. These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advan¬ tages, and objects attained by its use, reference should be had to the drawings which form a further part hereof and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention. BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, in which like reference numerals and letters indicate corresponding parts throughout the several views; Figure 1 is a diagramatic view of an embodi¬ ment of a water detector apparatus in accorance with the principles of the present invention; Figure 2 is a cross-sectional view of an embo- diment of a probe assembly utilized in the embodiment shown in Figure 1; Figure 3 is a schematic of an embodiment of the detection circuitry of the embodiment shown in Figure 1; Figure 4 is a diagramatic view of a fourteen lead dual inline plastic package containing the cir¬ cuitry generally shown in Figure 3, the external con¬ nector pins being numbered 1-14, wherein the presence or absence of water is determined by comparing the loaded probe resistance with an internal resistance; Figure 5 is an alternate embodiment of a four¬ teen lead dual inline plastic package containing generally the circuitry shown in Figure 3, the external connector pins being numbered 1-14, wherein the pre- sence or absence of water is determined by comparing loaded probe resistance with an external resistance; Figure 6 is a partial electrical block diagram/schematic of the embodiment shown in Figure 1; Figure 7 is a diagramatic view of an alternate embodiment of the present invention providing for water detection at multiple locations in the fuel system; Figure 8 is a front elevational view of a front panel of the alternate embodiment shown in Figure 7; Figure 9 is a schematic diagram of an alter¬ nate embodiment of the present invention which provides for simultaneous monitoring at two locations in the fuel system; and Figure 10 is a front elevational view of a front panel of the embodiment shown in Figure 9. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, there is shown in Figure 1 a preferred embodiment of the water detec¬ tor apparatus of the present invention, generally being designated by reference numeral 20. As illustrated, the water detector apparatus includes a support housing 22, which in the embodiment shown is a printed circuit board supporting the necessary electronics. Electrically interconnected to the electronics of the circuit board 22 by an electrical lead 24 is an electrically conductive probe assembly 26 which is at least partially threaded into the interior of a reser¬ voir 28 of the fuel system. For example, the reservoir might be the carburetor bowl, fuel sump, gasgulator, water separator, etc. of the fuel system. The electro¬ nics of the printed circuit board 22 are further inter¬ connected by an electrical lead 29 to an electrical ground ' 30 and by an electrical lead 31 to a power supply 32 such as the vehicle's battery. The printed circuit board 22 is mounted behind a face place 34 which supports a green light-emitting diode (LED) 36 and a red light-emitting diode (LED) 38 as well as a button test switch 40 which when pressed lights the red LED 38 to verify its operation. As illustrated in Figure 2, a preferred embo¬ diment of the electrically conductive probe assembly 26 includes a brass threaded male fitting 42 having a collar portion 42a and a threaded portion 42b extending into the reservoir and a threaded portion 42c extending externally of the reservoir. The threaded male fitting 42 includes an aperture extending generally longitudi¬ nally thereof. An electrically conductive cylindrical brass rod 44 having an insulating sleeve 49 con¬ centrically positioned on the outside thereof is fitted -6- into the aperture of the male fitting 42 so as to form a fluid tight seal • with the male fitting 42 and be generally flush with the male fitting 42 on an inside end 45 thereof and extend beyond an outside end 43 of the male fitting 42. A hole is drilled into the electrically conductive brass rod 44 from an outside end 47 thereof which is adapted for receipt of a bare electrically conductive lead wire 46. The lead wire 46 is suitably soldered onto the electrically conductive brass rod 44 and interconnected to a portion 24a of the electrical lead 24 which might be terminated with a male connector 48 to enable releasable attachment to the electrical lead 24 from the printed circuit board 22. A threaded female fitting 52 is slideably posi- tioned over the outside end 47 of the electrically con¬ ductive brass rod 44 so as to enable the female fitting 52 to be threaded onto the threaded portion 42c of the male fitting. Concentrically positioned about the electrically conductive brass rod 44 is a washer 50. The washer 50 provides a seal between the male fitting 42 and the electrically conductive rod 44 to assure that there is no leakage of fluid from the reservoir 28. Although, in the preferred embodiment, the male fitting 42 is electrically conductive, it will be appreciated that the male fitting 42 might be made of a thermo plastic or some other electrically nonconducting material thereby doing away with the need for the insu¬ lating sleeve 49. However, this type of fitting might be less resistive to fire. Mounted on the printed circuit board of the preferred embodiment is a monolithic bipolar integrated circuit including fluid detection circuitry 100 as generally illustrated in Figure 3. (In the preferred embodiment, the circuitry 100 is packaged in a fourteen lead dual inline package 60 as illustrated in Figure 4 wherein the connector pinds ■ are consecutively numbered 1-14.) The fluid detection circuitry 100 includes four basic circuits; a voltage regulator circuit, an oscillator circuit, an oscillator level detector cir- cuit, and an output drive circuit, each circuit being generally designated by the broken lines 102, 104, 106 and 108, respectively. In the figures, the numerical values of the resistors and capacitors are indicated, the respective units being ohms and microfarads. The voltage regulator circuit 102 includes a seven volt zenner diode 110 which establishes a fairly constant voltage for the transistor Q5 so as to set a stable Vcc for the circuit. A diode 112 prevents reverse con¬ nection of the power supply Vcc from damaging the cir- cuit. The oscillator circuit 104 includes transistors Q2 and 06 which act as a driver for transistor Ql. This multi vibrator circuit is driven by a connection across connector pins 5 and 7 via a .01 microfarad (uf) capacitor 118 as is generally illustrated in Figure 4 so as to alternately provide base drive for the tran¬ sistors Q2 and Q6 forming a square wave output at con¬ nector pin 6 at approximately 2500 Hz. The output of the oscillator circuitry 104 is fed through an 18k ohm resistor 114 to connector pin 8 and through an external connection to connector pin 9 via a .1 microfarad (uf) capacitor 116 as illustrated in Figure 4. The probe 26 as illustrated in Figure 4 is connected to the connec¬ tor pin 9 through a fluid medium 27 to an electrical ground. As the current from the connector pin 9 to ground is increased decreasing resistance the voltage level to the base at transistor 3 and an emitter follower resistor (270 ohms) 120 is decreased turning off the transistor Q3 thereby allowing the transistor 4 to conduct. A decoupling capacitor 122 intercon- necting connector pins 10 and 11 tends to stabilize the output of transistor Q4 thereby providing a bistable switch "on/off" action. A decoupling capacitor 123 is also interconnected to the connector pin 12. The out¬ put driver circuitry 108 provides a load driven output on connector pins 1 and 14. When the transistor Q4 is conducting or "on", the transistors Q7 and Q8 are "off" thus allowing the output at the connector pins 1 and 14 to go high. As previously discussed, the integrated cir- cuit might be packaged in the fourteen lead dual inline plastic package 60 diagramatically illustrated in Figure 4. In particular, the integrated circuit might be the ULN-2429A Fluid Detector sold by Sprague Products Company, North Adams, Massachusetts 01247. The fluid detection circuitry is interconnected to a supply voltage Vcc of preferably ten to sixteen volts and most preferably twelve volts which is provided by the power supply 32. The circuitry includes the oscillator circuitry 104 for driving the electrically conductive probe 26 with an AC signal so as to prevent plating problems or the like. Upon application of the AC signal the probe 26 exhibits a resultant resistance which is indicative of the presence or absence of water in the fuel holding reservoir. The resultant resistance will depend on whether an electrically con¬ ductive fluid is sensed such as water with impurities therein or a non-conductive fluid such as fuel. The resultant probe resistance is compared with an internal resistance as previously discussed and as generally illustrated in the embodiment of Figure 4 or an exter¬ nal resistance as generally illustrated in the alter¬ nate embodiment of Figure 5 wherein corresponding parts are designated by primed reference numerals. The fluid detection system provides an output signal represen- tative of the resultant resistance of the electrically -9- conductive probe 26. In the case of the embodiment shown in Figure 4, the probe 26 is connected to the connector pin 9. A decrease in resistance at probe 26 causes transistor Q3 to turn "off" thereby turning "on" transistor Q4 and "off" transistors Q7 and Q8 thus allowing the output at connector pins 1 and 14 to go high. In Figure 5, the probe 26 is replaced by an 18k ohm resistor 124 to ground at connector pin 9. Under normal conditions wherein there is no water present, this will cause the output at connector pins 1 and 14 to go high. If the probe 26 is connected through a .01 microfarad (uf) capacitor 125 to the connector pin 6, as the probe resistance is decreased the transistor Q3 is turned "on" causing the transistor 4 to turn "off" and allowing forward bias current to flow to tran¬ sistors Ql and 8 thus causing the output at connector pins 1 and 14 to go low. The output is typically a square wave signal which might be used with an LED, incandescent lamp, or loudspeaker. As illustrated in Figure 6, in the embo¬ diment of the present invention shown, the green LED 36 will be lit when a low output is provided and the red LED 38 will intermittently blink when a high output is provided by the integrated circuit. The green LED 36 is associated with a resistor 69 and the red LED 38 is associated with a resistor 71. As previously discussed in connection with the embodiment shown in Figure 4, with no water detected the resistance to the probe 26 is high causing the output to be low. The blinking is caused by use of conventional oscillator/driver cir¬ cuitry as generally referenced by reference numeral 70. Indeed, in one embodiment of the present invention an integrated circuit having nomenclature 74C14 and being manufactured by National Semiconductor Corp., 2900 Semiconductor Drive, Santa Clara, California 95051 -10- might be utilized. Each stage 70a,b,c of the integrated circuit acts as an invertor. The 74C14 integrated circuit is used since it has a high hystere¬ sis. When the input to the first section 70a is pulled down, the output of the last section 70c will be high thus keeping the red LED 38 "off". When water is detected the output of the connector pins 1 and 14 go high so as to turn "off" the green LED 36. When the input of the first section 70a of the 74C14 integrated circuit goes high, the output of the last section 70c is driven low turning "on" the red LED 38. When the output of the first section is low, a discharge path is formed for a capacitor 126. When a predetermined level is reached, the output of the last section 70c switches "high" causing the red LED 38 to turn "off". A 330k ohm resistor 128 then charges the capacitor 126 and after approximately one-half second switches the out¬ put. In this manner the red LED 38 continues to flash until the probe resistance is increased. In yet another embodiment of the present invention as generally illustrated in Figures 7 and 8, a rotary selector switch 80 might be provided enabling detector apparatus to be switched between various ones of the probes 26 at differing locations in the fuel system and/or a test position wherein the function of the red LED 38 is verified. Furthermore, an on-off switch 82 might be provided for selectively intercon¬ necting the detector apparatus to the power supply 32 with a fuse 84 being inserted in the line. Yet another embodiment of the present inven¬ tion is illustrated in Figures 9 and 10. This embodi¬ ment includes two integrated fluid detector circuits 130, 132 similar ' to the integrated circuit 60 illustrated in Figure 4, interconnected to two indepen- dent probes. Each of the integrated fluid detector -11- circuits is in turn interconnected to oscillator/driver circuitry 150, 152 similar to the oscillator/driver circuitry 70. As discussed previously, the oscillator/driver circuitry 150, 152 might be included in a single integrated circuit, such as the IC 74C14. The oscillator/driver circuitry each includes three sections 150a,b,c and 152a,b,c respectively, a 2.7 megaoh resistor 154, 156 respectively, a .1 microfarad capacitor 158, 160 respectively, and a Ik ohm resistor 162, 164 respectively, associated with the yellow LEDs 134, 136 respectively. Under normal conditions, that is no water, the probe resistance is high and thus the output at connector pins 1 and 14 is low. This causes the output of oscillator/driver circuits 150, 152 to be low such that the yellow LEDs 134, 136 are continuously "on". When water is detected, the output pins 1 and 14 go high. This enables the oscillator to flash the LEDs 134 and 136 as discussed * above. Pushing a test 'button 138 removes power from the integrated circuits 130, 132 but allows power to be delivered via electrical inter¬ connect 139 to the oscillator/driver circuitry 150, 152 thereby enabling the LEDs 134, 136 to flash so as to test the operativeness of the circuitry. Illustrated in Figure 10 is a front panel view of the embodiment shown in Figure 9. It is to be understood, however, that even though numerous characteristics and advantages of the invention have been set forth in the foregoing descrip¬ tion, together with details of the structure and func- tion of the invention, disclosure is illustrative only, and changes may be made in detail, especially in mat¬ ters of shape, size and arrangement of parts within the principles of the invention, to the full extent indi¬ cated by the broad general meaning of the terms in which the appended claims are expressed.

Claims: WHAT IS CLAIMED IS: 1. A water detector apparatus for detecting the pre¬ sence of water in a fuel system, comprising: a. an electrically conductive probe at least par- tially inserted into a fuel holding reservoir of the fuel system; b. AC signal means electrically interconnected to the probe for applying an AC signal thereto, the probe exhibiting a resultant resistance when the AC signal is supplied, the resultant resistance indicative of the presence or absence of water in the fuel holding reser¬ voir; c. circuity means electrically connected to the probe for comparing the resultant probe resistance with a known resistance, circuitry means including output means for providing an output signal representative of the resultant resistance of the probe; and d. indicator means being electrically intercon¬ nected to the output means of the circuitry means for receiving the output signal, the indicator means being responsive to the output signal received, the indicator means having a first state indicative of the presence of water within a nonconductive fluid of the fuel holding system and a second state indicative of the absence of water. 2. A water detector apparatus in accordance with claim 1, wherein the water detector apparatus includes multiple ones of the probes, the probes being used in differing ones of the fuel holding reservoirs of the fuel system, switch means being electrically intercon¬ nected to the circuitry means; the AC signal means and the probes for interconnecting individual ones of the probes to the circuitry means and the AC signal means whereby multiple ones of the fuel holding reservoirs can.be selectively and individually monitored. 3. A water detector apparatus in accordance with claim 1, further including manual test switch means electri- cally interconnected to the circuit means for manually switching the indicator means to its first state. 4. A water detector apparatus in accordance with Claim 1, wherein the electrically conductive probe includes a non-conductive housing including threaded end portion means for threaded insertion into a threaded aperture of a wall of the fuel holding reservoir, an electri¬ cally conductve member axially extending through the center of the non-conductive housing, the electrically conductive member forming a water-tight seal with an inside wall of the non-conductive housing, an inner end of the probe being positioned on the inside of the fuel holding reservoir and an outer end of the electrically conductive probe being interconnected to an electrical lead which in turn is electrically interconnected to the circuitry means. 5. A water detector apparatus in accordance with claim 4, wherein the electrically conductive member is press fitted into the non-conductive housing. 6. A water detector apparatus in accordance with claim 5, wherein the electrically conductive member has a recess axially extending from the outer end, the electrical lead being inserted into the aperture and securedly soldered in place so as to extend away from the electrically conductive member, the electrical lead being electrically interconnected to the circuitry means. 7. A water detector apparatus in accordance with .claim 1, wherein the indicator means includes audible alert means for producing sound when in the first state. ' 5 8. A water detector apparatus in accordance with claim 1, wherein said AC signal means includes oscilla¬ tion circuitry means for providing an AC output signal from a DC input signal. 9. A water detector apparatus in accordance with 0 claim 1, wherein the indicator means includes a green LED interconnected to the circuitry for receiving the output signal so as to be lit when the indicator means is in the second state, the indicator means further including a red LED interconnected to the circuitry 5 for receiving the output signal so as to be lit when the indicator means is in the first state. 10. A water detector apparatus in accordance with claim 9, wherein the indicator means is interconnected to oscillator/driver circuitry means for intermittently 0 being lit when the indicator means is in the first state. 11. A water detector apparatus in accordance with claim 1, wherein the electrically conductive probe includes an electrically conductive housing including 5 threaded end portion means for threaded insertion into a threaded aperture of a wall of the fuel holding reservoir, an electrically conductive member axially extending through the electrically conductive housing, the electrically conductive member being surrounded by 0 an electrically nonconducting sleeve member and forming a water tight seal with an inside wall of the electri- -15- cally conductive housing, an inner end of the probe being positioned on the inside of the fuel holding reservoir and an outer end of the electrically conduc¬ tive probe being interconnected to an electrical lead which in turn is electrically interconnected to the circuitry means. 12. A water detector apparatus in accordance with claim 1, wherein the water detector apparatus includes two or more of the probes and circuitry means for pro- viding simultaneous monitoring of two or more of the fuel holding reservoirs. 13. A method for detecting the presence of water in a fuel system, comprising: a. applying an AC signal via an electrical connection to an electrically conductive probe inserted into a fuel holding reservoir of the fuel system, the probe exhibiting a resultant resistance when the AC signal is so applied, the resultant resistance being indicative of the presence or absence of water in the fuel holding reservoir; b. monitoring via an electrical connection the resultant resistance of the probe and comparing the probe resistance with a known resistance; and c. outputting an electrical signal represen- tative of the resultant resistance of the probe to an indicator via an electrical interconnection, the indi¬ cator being responsive to the output signal, the indi¬ cator having a first state indicative of the presence of water and a second state indicative of the absence of water. 14. A water detector apparatus for detecting the presence of water in a fuel system, comprising: -16- a. an electrically conductive probe assembly, the electrically conductive pr.obe assembly further including an elongated electrically conductive member mounted in a housing, the housing including threaded end means for at least partial threaded inser¬ tion into a fuel holding reservoir of the fuel system; b. power supply means,- c. control circuitry means electrically interconnected to the electrically conductive probe assembly and the power supply means, the control cir¬ cuitry means including: i. voltage regulator circuitry means for providing a regulated voltage output; ii. oscillator circuitry means intercon- nected to the output of the voltage regulator circuitry means for providing an alternating current (AC) output signal; iii. oscillator level detector circuitry means, interconnected to the oscillator circuitry means for receiving the AC output signal, and for outputting the AC output signal to the electrically conductive member of the electrically conductive probe assembly, the oscillator level detector circuitry means including means for detecting current flow from the electrically conductive probe assembly through the fluid in the fluid holding reservoir to an electrical ground and for providing a bistable output having one of two states indicative of the presence or absence of water in the fuel holding reservoir; and iv. output driver circuitry means inter¬ connected to the oscillator level detector circuitry means for receiving the bistable output and for out- putting an output signal indicative of the state of the bistable output; and -17- d. indicator means interconnected to the output driver circuitry means for receiving the output signal from the output driver circuitry means, the indicator means being responsive to the output signal received, the indicator means having a first state indicative of the presence of water within a nonconduc- tive fluid of the fuel holding reservoir and a second state indicative of the absence of water. 15. A water detector apparatus in accordance with claim 14, wherein the water detector apparatus includes two or more of the electrically conductive probe assemblies, the indicator means, and the control cir¬ cuitry means, each of the electrically conductive probe assemblies being interconnected to individual ones of the control circuitry means and the indicator means to enable simultaneous monitoring of two or more fuel holding reservoirs. 16. A water detector apparatus in accordance with claim 15, wherein the water detector apparatus further includes switch means for disconnecting the power supply means from the control circuitry means, the power supply means being interconnected to the indica¬ tor means when the control circuitry means is so disconnected, thereby causing the indicator means to be placed in the first state for test purposes.

Inventors: BROWN RICHARD W, BROWN, RICHARD, W.
Applicants: AQUATROL CORP, AQUATROL CORPORATION
Application year: 1985
Main classification: G08B21
IPC codes: F02D33, F02M37, G01F23