LIQUID LEVEL DETECTOR

Abstract: A liquid level detector (25) for detecting the level of a liquid container has a housing (50), a bellows (53), an elastic member (121), a drive mechanism (112) and a sensor (62). The bellows (53) is carried within the housing (50) and divides the housing (50) into a dynamic pressure chamber (56) and a constant pressure chamber (58). The bellows (53) has a top end (88) and a wrinkled sidewall (90). The dynamic pressure chamber (56) contains a gas and communicates the liquid reservoir. The elastic member (121) exerts the force on the top (88) of the bellows (53) to balance a pressure of the dynamic pressure chamber (56). The sensor (62) monitors a movement of the top (88) of the bellows (53). The sensor (62) has a light emitting element (129) and a light receiving element (132). The drive mechanism (112) has a screen member (134) interposed between the light emitting element (129) and a light receiving element (132). The screen member (134) is connected to the top end (88) of the bellows (53).

Description: Liquid Level Detector Field of the Invention The present invention relates generally to a liquid level detector, and more particularly to a optical liquid level detector measuring a residual liquid level contained in a reservoir such as an oil tank or a water tank. Background of the Invention A conventional boiler system for use at home has an oil tank and an indicator showing a residual quantity of fuel contained in the oil tank. The indicator has a transparent tube locating outside of the oil tank and extending vertically. A low end of the tube communicates with the bottom of the oil tank. The level of fuel contained in the oil tank can be seen through the tube. However, it is difficult to look into a residual quantity inside the door and it is inconvenient. An optical liquid level detector is disclosed in Korean Patent Examined Publication No. 96-13254. The detector has an air inlet, a planar rubber membrane, a light emitting element and a light receiving element mounted at the top and a reflect plate mounted on the rubber membrane. The detector may be utilized only in a narrow pressure range, that is, in measuring the liquid level of liquid contained in a liquid tank with a small height because the deflection of the rubber membrane is limited. In addition, it is hard to get an output signal showing a linear relationship between an output signal and a liquid level. Thus, it is difficult to process the output signal into digital signal. Summary of the Invention Accordingly, it is an object of the present invention to provide a liquid level detector capable of being used for measuring a level of liquid contained in a container even though the height of the container is large. It is another object of the present invention to provide an optical liquid level detector capable of obtaining an output signal having a linear relationship with a liquid level. The above and other objects of the present invention are accomplished by providing a liquid level detector for detecting the level of liquid contained in a liquid container comprising: a housing; a bellows having a closed end and a wrinkled side wall attached to the closed end, said bellows dividing the inside of said housing into a dynamic pressure chamber and a constant pressure chamber, the dynamic pressure chamber communicating with the liquid container; a resilient member for resiliently urging said closed end of said bellows: and a sensor for sensing the movement of said closed end of said bellows. In accordance with another aspect of the invention, there is provided a liquid level detector for detecting the level of liquid contained in a liquid container comprising: a housing; a wall having at least a portion of being flexible, said wall and dividing the inside of said housing into a dynamic pressure chamber and a constant pressure chamber, the dynamic pressure chamber communicating with the liquid reservoir; a drive mechanism having a contact member contacting to said wall and a screen member connecting to the contact member; a resilient member for resiliently urging said contact member of the drive mechanism; and a sensor having a light emitting element and a light receiving element opposing each other, wherein said screen member of the drive mechanism is interposed between a light emitting element and a light receiving element. In accordance with a further aspect of the invention, there is provided a fuel supplying system for supplying fuel to a fuel combustion system comprising a fuel tank and a level detector having a feature as described above. Brief Description of the Drawings The above and other objects, advantages and features of the present invention will be apparent from the following description of preferred embodiments taken in conjunction with the accompanying drawings, wherein: Fig. 1 is a block diagram of a boiler system having a liquid level detector in accordance with the present invention: Fig. 2 is a sectional view of an optical liquid level detector in accordance with the present invention; and Fig. 3 is a diagram showing a relationship between an output current and a liquid level. Detailed Description of the Preferred Embodiment Referring to Fig. 1, the boiler system has an oil or fuel tank 12, a combustion device 14, a control panel 16 and an oil supplying pipe or tube 27. The oil tank 12 has an inlet 19. The oil tank 12 is connected with the combustion device 14 to supply fuel contained in the tank 12 through the supplying pipe 27. The combustion device 14 has a burner 22. The supplying pipe 27 extends to the burner 22. The supplying pipe 27 has a valve 29 and a pump 24 to provide fuel to the burner 22. A liquid level detector 25 in accordance with the present invention is mounted on the supplying pipe 27. The control panel 16 for controlling the combustion device 14 has a display panel 32 for showing a level of fuel. Wires 33 connect electrically between the detector 25 and the control board 16 so as to supply an electric power to the detector 25 and transmit a signal generated by the detector 25 to the control board 16. The control board 16 has an electronic circuit which processes the transmitted signal into a display signal and displays it on the display panel 32. Fig. 2 shows the detector device 25 in accordance with the present invention. The detector device 25 has a housing 50, a bellows type boundary wall or bellows 53. a drive mechanism 112, and a sensing portion or sensor 62. The detector 25 has a constant pressure chamber or atmospheric pressure chamber 56 and a dynamic pressure chamber 58 divided by the boundary wall or bellows 53. The gas such as air is contained in the dynamic pressure chamber 58. The housing 50 includes an upper case 68 and a lower case 70. The lower case 70 has a circular bottom 71 and a cylindrical sidewall 73 which is extended upwardly from the edge of the bottom 71. A flange 75 is formed on a top of the sidewall 73. The lower case 70 has a bore 79 at the center of the bottom 71 and a boss 82 surrounding the bore 79. A screw thread is formed on the outer surface of the boss 82. The boss 82 of the lower case 70 is secured to a connecting pipe 66 through which the dynamic pressure chamber 58 communicates with the supplying pipe 27 (see Fig. 1). The connecting pipe 66 has a screw thread at an inner surface of the top portion so that the connecting pipe 66 is secured to the lower case 70 by way of engagement of the screw threads of the connecting pipe 66 and the boss 82. A annular seal 83 is inserted between the connecting pipe 66 and the lower case 70. Also a screw thread is formed at an inner surface of a bottom portion of the connecting pipe 66. The supplying pipe 27 has a branch 86. A screw thread is formed at an outer surface of the branch 86. The connecting pipe 66 is mounted on the supplying pipe 27 by engagement of the screw threads of the branch 86 with the screw thread of a bottom portion of the connecting pipe 66. Therefore, the supplying pipe 27 communicates with the dynamic pressure chamber 58 of the inside of the housing 50. An annular seal is inserted between the connecting pipe 66 and the branch 86. It is preferable that the sectional area of the connecting pipe 66 is uniform along the length of the connecting pipe 66 and the top of oil always locates between the top and the bottom of the connecting pipe 66. The bellows 53 is positioned above the lower case 70. A top end 88 of the bellows 53 is planar and circular and the bottom end is open. A wrinkled sidewall 90 is extended downwardly from the edge of the top 88. A flange 92 is formed at the bottom of the sidewall 90. The flange 92 contacts the flange 75 of the lower case 70. It is preferable that a material of the bellows 53 is a rubber. The upper case 68 includes a circular top 98 and a cylindrical sidewall 96 extended from the edge of the top 98. The upper case 68 has a bore formed at the center of the top 98 and a boss 105 surrounding the bore. A screw thread is formed on the inner surface of the boss 105. The upper case 68 includes a flange 102 formed at the bottom of the sidewall 96. The flange 92 of the bellows 53 is interposed between the flange 102 of the upper case 68 and the flange 75 of the lower case 70. The housing 50 has an annular band 104. The upper case 68 and the lower case 70 are joined by the band 104. The connecting band 104 is made of metal. The constitution fixing the upper and lower cases is not limited by the above. Alternatively, bolts and nuts may be used for securing the flange 102 of the upper case 68 to the flange 75 of the lower case 70. Adhesive may be used for bonding among the flange 102 of the upper case 68, the flange 92 of the bellows 53 and the flange 75 of the lower case 70. A annular seal 103 is provided at a upper corner of the upper case 68. The seal 103 prevents oil from leaking by cooperation with the drive mechanism 112 when the bellows 53 is damaged, as will be described below. The drive mechanism 112 has a circular contact plate or member 113 and a rod 115 secured to a center of the circular plate 113. The bottom surface of the circular plate 113 contacts to the top 88 of the bellows 53 so that the pressure of the dynamic pressure chamber 58 is applied to the plate 1 13. The circular plate 113 and the top of the bellows 53 may be secured integrally. A guide bush 118 is inserted into and secured to the boss 105 of the upper case 68 by engagement between a screw thread formed on the outer surface of the guide bush 1 18 and a screw thread formed on the inner surface of the boss 105. The rod 115 is slidablv inserted through the bore of the guide bush 1 18 and the rod 1 15 can move upwardly or downwardly. The constant pressure chamber 56 communicates with the outside of the housing 50 through the guide bush 1 18. A bore may be formed on the top 98 of the upper case 68 to provide a path between the constant pressure chamber and the outside of the housing. A resilient member or compression spring 121 is interposed between the guide bush 118 and the circular plate 1 13 to resiliently urge the circular plate 113. The rod 115 has a blind hole formed on the top of the rod 115. A screw thread is formed on the inner surface of the blind hole 123. The drive mechanism 1 12 has a screen member or light blocking member 134 for blocking selectively the light transmitted from the light emitting element 129 to the light receiving clement 132 as will be described below. The screen member 134 has a screen portion 135 extending vertically and a coupling portion or connecting part 139 extending from the top end of the screen portion 135. The connecting part 139 is substantially perpendicular to the screen portion 135. The screen portion 135 has a hole formed on the end portion of the connecting part 139. A adjusting screw 142 is inserted into the hole of the screen member 134 and the screen member 134 is secured to the screw 142 by means of a retaining ring 143. The screw 142 with the blocking member 134 is inserted into the blind hole 123 of the rod 1 15. The sensing portion or sensor 62 has a circuit board 126, a light emitting element 129 and a light receiving element 132 mounted on the circuit board 126. The light emitting element 129 and the light receiving element 132 are mounted on the circuit board 126 to oppose each other. It is preferable that the light emitting element 129 is LED and the light receiving element 132 is CdS cell. The screen portion of the blocking member 134 is interposed between the light emitting element 129 and the light receiving element 132. The circuit board 126 has conductive wires 130 so as to connect the sensing portion 62 to the control panel. Thus, the electric power can be supplied to the sensing portion 62 and the signal produced at the sensing portion 62 can be transmitted to the control panel. The detector 25 has a cap 146. The cap 146 is mounted at the top of the upper case 68. The cap 146 is made of the opaque material to block a light from the outside of the detector 25. The cap 146 has a hole 148 through which the wires 130 pass. The hole 148 allows the constant pressure chamber 56 communicating with the outside of the detector 25. Referring to Fig. 1 and Fig. 2, the operation of the optical liquid level detector in accordance with the present invention will be explained below. The level of fuel contained in the tank 12 becomes higher, the pressure of the dynamic pressure chamber 58 increases. A increased pressure of the chamber 58 causes the top wall 88 of bellows 53 and the circular plate 113 to move upwardly until the pressure balances a resilient force of the spring 121. The blocking part 134 rises along with the circular plate 113. Then, tine quantity of light which is received by the light receiving element 132 increases. So. an electric signal corresponding to the increased quantity of light received by the light receiving element 132 is generated and transmitted to the control board 16. When die level of oil lowers, the pressure of the dynamic pressure chamber 58 lowers. So, the blocking part 134 moves downwardly and the quantity of light which is transmitted to the light receiving element 132 decreases. The change of a residual quantity of oil contained in the oil tank is indicated on the display panel 32 of the control board 16. The guide bush 118 is screwed into the boss 105 so that, when the bush 118 is rotate, it moves either upwardly or downwardly. The force of the spring 121 urging resiliently to the contact plate 113 may be adjusted. And then, the pressure of the dynamic pressure chamber 58 is adjusted. Thus, this adjustment function of the guide bush 118 allows the detector 25 being adjusted for various height of liquid tanks. T e guide bush 118 may be rotated and disengaged from the upper case 58. Then, the spring 121 is easily replaced with another resilient member having a different elastic coefficient. When the adjusting screw 142 may be rotated, the screen 134 moves upwardly or downwardly. Thus, when the tank is almost vacant, the zero point of the display panel can be adjusted. As shown in Fig. 3, the linear relationship between the output signal generated by the sensor 62 and the level of fuel contained in the tank can be obtained. According to another embodiment of the present invention, the detector device 25 may have an elongated connecting pipe attached to the lower case and be mounted on the top of tiie fuel tank. The connecting pipe extends from the bottom of the lower case 70 of the detector 25 to the bottom of the fuel tank. Although it is described in the above embodiments that the detector is used for the boiler system for home having the oil tank, the detector in accordance with the present invention may be used for detecting a level of any kind of liquid contained in the container, the detector in accordance with the present invention may be used in, for example, a washing machine, an fuel reservoir in a gas station, and so on. Also, the detector device in accordance with the present invention may be used for detecting a level of fuel contained in a fuel reservoir of a vehicle. The detector device is mounted on the top of the fuel tank. It is preferable that the detector is positioned at the geometrical center point in horizontal plane. The bottom of the connecting pipe of the detector extends to the bottom of the fuel tank. It is shown in Fig. 2 that the sensor 62 is mounted on the top of the upper case 68. In a further embodiment, alternatively, the sensor 62 may be attached to and hung from the ceiling of the cap 146. The light emitting and receiving elements 129 and 132 extend from the circuit board downwardly. The screen plate extends upwardly from the end of the coupling portion 139. In another further embodiment, the pressure adjusting member may be mounted in place of the lower case for adjusting the pressure of the dynamic pressure chamber. For example, the lower case have a hole and a plug for blocking the hole. The plug can be selectively opened. Then, the pressure of the dynamic pressure chamber can be adjusted. Although the invention has been shown and described with respect to the exemplary embodiments, it should be understood that various changes, modifications and additions maybe made without departing from the spirit and scope of the invention.

Claims: Claims 1. A liquid level detector for detecting the level of liquid contained in a liquid container comprising: a housing: a bellows having a closed end and a wrinkled side wall attached to the closed end, said bellows dividing the inside of said housing into a dynamic pressure chamber and a constant pressure chamber, the dynamic pressure chamber communicating with the liquid container; a resilient member for resiliently urging said closed end of said bellows; and a sensor for sensing the movement of said closed end of said bellows. 2. The detector of Claim 1, further comprising a drive mechanism having a contact member contacting to said wall and a screen member connecting to the contact member; and said sensor having a light emitting element and a light receiving element opposing each other, λvherein said screen member of the drive mechanism is interposed between a light emitting element and a light receiving element. 3. The detector of Claim 2, further comprising a position adjusting device for adjusting the relative location of the screen member to the light emitting and receiving elements. 4. The detector of Claim 2 or 3, wherein said contact member of the drive mechanism has a shape corresponding to the inside of the housing, and the housing has an annular seal. 5. The detector of one of Claim 2 to 4, Λvherein said light emitting element is LED and said light receiving element is CdS cell. 6. The detector of one of Claim 1 to 5, further comprising a pressure adjusting device for adjusting the pressure of the dynamic pressure chamber. 7. A liquid level detector for detecting the level of liquid contained in a liquid container comprising: a housing; a wall having at least a portion being flexible, said wall dividing the inside of said housing into a dynamic pressure chamber and a constant pressure chamber, the dynamic pressure chamber communicating with the liquid reservoir; a drive mechanism having a contact member contacting to said wall and a screen member connecting to the contact member; a resilient member for resiliently urging said contact member of the drive mechanism; and a sensor having a light emitting element and a light receiving element opposing each other, wherein said screen member of the drive mechanism is interposed between a light emitting element and a light receiving element. 8. The detector of Claim 7, wherein said wall having a closed end and a flexible side, and the contact member of the drive mechanism contacts to the closed end. 9. The detector of Claim 7 or 8, further comprising a position adjusting device for adjusting the relative location of the screen member to the light emitting and receiving elements. 10. The detector of one of Claim 7 to 9, wherein said contact member of the drive mechanism has a shape corresponding to the inside of the housing, and the housing has an annular seal. 11. The detector of one of Claim 7 to 10. wherein said light emitting element is LED and said light receiving element is CdS cell. 12. The detector of one of Claim 7 to 1 1. further comprising a pressure adjusting device for adjusting the pressure of the dynamic pressure chamber. 13. The fuel supplying system for supplying to a fuel combustion system comprising a fuel tank and a level detector, said detector including: a housing; a bellows having a closed end and a wrinkled side wall attached to the closed end, said bellows dividing the inside of said housing into a dynamic pressure chamber and a constant pressure chamber, the dynamic pressure chamber communicating with the liquid container; a resilient member for resiliently urging said closed end plate of said bellows; and a sensor for sensing the movement of the closed end plate of the bellows. 14. The system of Claim 13, further comprising a tube connecting the tank and the combustion system and wherein die detector is mounted on the tube. 15. The fuel supplying system for supplying to a fuel combustion system comprising a fuel tank and a level detector. said detector including: a housing; a wall having at least a portion being flexible, said wall dividing the inside of said housing into a dynamic pressure chamber and a constant pressure chamber, the dynamic pressure chamber communicating with the liquid reservoir; a drive mechanism having a contact member contacting to said wall and a screen member connecting to the contact member: a resilient member for resiliently urging said contact member of the drive mechanism; and a sensor having a light emitting element and a light receiving element opposing each other, wherein said screen member of the drive mechanism is interposed between a light emitting element and a light receiving element.

Inventors: KIM UI-GYO, MOK DO-GYUN, KIM, UI-GYO, MOK, DO-GYUN
Applicants: KIM UI GYO, MOK DO GYUN, KIM, UI-GYO, MOK, DO-GYUN
Application year: 1998
Main classification: G01F23
IPC codes: G01F23, G01F25