LIQUID LEVEL SENSOR WITH INFRARED SENSOR ELEMENT

FIELD OF INVENTION

The present invention relates to liquid level sensor, specifically to a liquid level sensor utilizing infrared elements. More particularly, the present invention relates to liquid level sensing by using infrared sensor elements, in automobiles, industrial and consumer applications. Further, the present invention relates to liquid level sensing arrangement using infrared sensor elements which operate with a float.

BACKGROUND ART

For any tank to indicate its level of the substance present, an instrument namely level indicating gauge is used, for example in automobiles, fuel level indicating gauge is used. The fuel level indicating gauge comprises two main parts namely the sensing unit and the indicator. The output of the sensing device generally fed to a gauge/engine control unit (ECU) to show the level of the fuel in the tank, and use this information to compute other related applications Therefore, sensing unit plays a vital role in measuring the level of the fuel in the tank. The fuel level sensing arrangements presently known in the art have fixed arm with a movable lever attached with a float and hinged to the arm. When the float moves along with fuel level, the lever is moved there by the contact on the lever arm moves on the variable resistor and the output is tapped through the terminals. In reed switch type, a printed circuit board (PCB) mounted with resistor and reed switch is fixed to a tube and has float with magnet to activate the reed switches while fuel level changes. The capacitance type has two electrodes and by using the dielectric strength of the fuel, the level is measured and transmitted to the gauge.

In case of resistor type fuel gauges, the resistors are on the inward side of gauge i.e. inside fuel tank. Sending current through such a resistor has fire hazard associated with it. These resistance sensors are also showing an increased failure rate with the incremental additions of alcohol in automotive gasoline fuel. Alcohol increases the corrosion rate at the potentiometer, as it is capable of carrying current like water. Potentiometer applications for alcohol fuel use a pulse and hold methodology, in that a periodic signal is sent to determine fuel level decreasing the corrosion potential. Therefore, there is demand for another safer method for fuel level sensing. Ongoing developments are taking place in the sensor systems of the sensing unit and it is found that infrared sensor based liquid level sensor will occupy lesser space, less in weight and less expensive. Moreover, liquid level sensing by using infrared sensor elements have enhanced durability since the sensing arrangement eliminates the need for a fixed arm having a movable lever attached with a float and hinged to it.

OBJECTS OF INVENTION

One or more of the problems of the conventional prior art may be overcome by various embodiments of the present invention. It is the primary object of the present invention to provide an apparatus for liquid level sensing used for detecting the level of the liquid present in a tank. It is another object of the present invention to provide an apparatus having infrared elements for sensing the level of the liquid, more particularly the level of the fuel present in the fuel tank. The apparatus comprises of: housing in the form of a tube; one or more infrared sensing elements; printed circuit board (PCB) with an electronic circuit; and float. It is another object of the present invention, wherein the infrared elements are placed on the PCB one after other at a pre-determined distance as per the desired level measuring. It is another object of the present invention, wherein the infrared elements comprises at least two approximately parallel vertical wall portions with pre-determined distance in between them.

It is another object of the present invention, wherein the float comprises a segment portion and a flat portion to slide in between the two vertical wall portions of the infrared elements. It is another object of the present invention, wherein the infrared elements are provided with circuit pins which are soldered to the PCB and routed to top end of the PCB to take output to liquid level indicator. It is another object of the present invention, wherein the electronic circuit provides supply voltage to operate the infrared elements. It is another object of the present invention, wherein when the liquid level varies the flat portion of the float slide in between the two vertical wall portions of the infrared elements corresponding to particular liquid level and a signal is generated which is transmitted to the gauge/the engine control unit (ECU) to indicate the liquid level.

SUMMARY OF INVENTION

Accordingly there is provided an apparatus for liquid level sensing comprising of: an housing; a printed circuit board (PCB) comprising an electronic circuit; one or more infrared sensing elements; and a float, wherein the housing is disposed to accommodate the infra red elements which are mounted on the PCB one above the other at a pre-defined spacing between them and soldered, wherein bottom of the housing is closed and provided with a tiny hole for entry of the liquid, wherein the housing comprising the PCB is positioned inside the tank, wherein the infra red elements comprises a first and a second vertical wall which are arranged approximately parallel to each other defining a pre-determined distance in between them and one of the walls accommodate an emitter and the other wall accommodate a receiver, wherein the float comprises an outwardly extending flat portion is disposed within the housing to move in a first and second direction in vertical plane according to variation in the liquid level of the tank, and wherein the flat portion of the float intercept the infrared element's receiver corresponding to particular level and a signal is generated and transmitted to a gauge/engine control unit (ECU) to indicate the liquid level.

According to another aspect of the invention an air vent is provided at top end of the housing. According to another aspect of the invention the housing is cylindrical in shape and is made of stainless steel or plastic or aluminum or brass. According to another aspect of the invention the housing comprises one or more PCB holding part provided to hold the PCB. According to another aspect of the invention the housing further comprises one or more float guide portions having lip portion provided to facilitate point contact for the float in order to have reduced friction while the float move in the first/second direction according to the variation in the liquid level inside the tank. According to another aspect of the invention the float is limited by the lips portion of the float guide portion. According to another aspect of the invention supply voltage to operate the infrared elements are provided by the electronic circuit. The details for the invention, its aspect and advantages are explained hereunder in greater details in relation to non-limiting exemplary illustration as per the accompanying figures as detailed hereunder.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1: schematically illustrates the apparatus for sensing the liquid level according to the present invention.

Figure 2: schematically illustrates the cross sectional top view of the apparatus for sensing the liquid level according to the present invention.

Figure 3: schematically illustrates circuit diagram of the apparatus for sensing the liquid level according to the present invention.

Figures 4: schematically illustrates infrared element of the apparatus for sensing the liquid level according to the present invention.

Figures 5: schematically illustrates the float of the apparatus for sensing the liquid level according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING FIGURES

Referring to Figure 1 of the drawings, the apparatus according to the present invention comprises a housing (1) with a closed bottom with tiny hole (Id) which is provided for entry of the liquid. The top of the housing is also closed and an air vent is provided.

As shown in Figure 2, in a preferred embodiment, the housing (1) is cylindrical in shape and of pre-defined height. The housing (1) is made of material which posses sufficient resistance against corrosion caused by the fluid, for example stainless steel, plastic, aluminum, brass. Pre-determined numbers of infrared elements (3) are mounted on a printed circuit board (PCB) (2) which comprises an electronic circuit. The infra red elements (3) are mounted on the PCB (2) at a pre-defined spacing between them and soldered.

As shown in Figures 1 and 2 of the drawing, the printed circuit board (PCB) (2) is mounted inside the housing (1) such that the infra red elements (3) are one above the other. The PCB (2) mounted with the infrared elements (3) are placed inside the housing (1) and held by a PCB holding part (la) arranged at 4 locations. The housing (1) further provided with a float guide portion (lb) arranged at 2 locations and comprises lip portion (lc) to limit the radial movement of float (5). The lip portion (lc) also facilitate point contact for the float (5) in order to have reduced friction while float move in the first/second direction according to the variation in the liquid level inside the tank (4). The PCB holding part (la) and float guide portion (lb) comprises the lip portion (lc) are the integral part of the housing (1) and extend to the entire height of the housing. The housing may be formed as an extruded part. The ends of the housing (1) is sealed such that while the infra red elements mounted portion of the PCB (2) is exposed to the liquid in the tank (4), the opposite side of the PCB (2) is prevented from the contact with the liquid inside the tank (4). The housing (1) mounted with the PCB (2) is placed inside the liquid tank (4) at a pre-defined position and fastened. The tiny hole (Id) provided for the entry of the liquid at the bottom of the housing (1) permits the flow of the fluid inside the housing (1) such that the infrared elements mounted area are prevented from the effect of liquid sloshing.

As shown in Figure 4, the infrared element (3) comprises a first and a second vertical wall which are arranged approximately parallel to each other defining a pre-determined distance between them. The infrared element (3) further includes an emitter (3a) and receiver (3b) which are arranged each in one of the walls, for example while the emitter (3a) is arranged in the first wall of the infrared element (3), the receiver (3b) is arranged in the second wall. The supply voltages to operate infrared elements (3) are provided by the electronic circuit by suitable means. The float (5) is disposed within the housing (1) and the float (5) moves in a first and second direction in vertical plane according to the variation in the liquid level in the tank. Shown in Figure 5, the float (5) comprises a segment portion (5a) and an outwardly extending flat portion (5b) of pre-defined thickness. The float (5) is constructed in a suitable material that is buoyant in the liquid present in the tank (4). The flat portion (5b) is capable of freely sliding in between the two vertical wall portions of the infrared elements (3) comprising the emitter (3a) and the receiver (3b).

the float (5) moves in the first/second direction, according to the fluid level, the flat portion (5b) intercepts one of the infrared element's receiver (3b) corresponding to particular liquid level and a signal is generated and transmitted to the gauge/the engine control unit (ECU) to indicate the liquid level. Each one of the infrared sensing element (3) corresponds to particular level and is calibrated to the liquid level of the tank by the electronic circuit. So that the manner in which the features, advantages and objects of the invention, as well as others which will become apparent, may be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiment thereof which is illustrated in the appended drawings, which form a part of this specification. It is to be noted, however, that the drawings illustrate only a preferred embodiment of the invention and is therefore not to be considered limiting of the invention's scope as it may admit to other equally effective embodiments.

WE CLAIM:

1. An apparatus for liquid level sensing comprising: an housing (1); a printed circuit board (PCB) (2) comprising an electronic circuit; one or more infrared sensing elements( 3); and a float (5), wherein the housing (1) is disposed to accommodate the infra red elements (3) which are mounted on the PCB (2) one above the other at a pre-defined spacing between them and soldered, wherein bottom of the housing (1) is closed and provided with a tiny hole (Id) for entry of the liquid, wherein the housing (1) comprising the PCB (2) is positioned inside the tank (4), wherein the infra red elements (3) comprises a first and a second vertical wall which are arranged approximately parallel to each other defining a pre-determined distance in between them and one of the walls accommodate an emitter (3a) and the other wall accommodate a receiver (3b), wherein the float (5) comprises an outwardly extending flat portion (5b) is disposed within the housing (1) to move in a first and second direction in vertical plane according to variation in the liquid level of the tank, and wherein the flat portion (5b) of the float (5) intercept the infrared element's receiver (3b) corresponding to particular level and a signal is generated and transmitted to a gauge/ engine control unit (ECU) to indicate the liquid level.

2. The apparatus as claimed in claim 1, wherein an air vent is provided at top end of the housing (1).

3. The apparatus as claimed in claim 2, wherein the housing (1) is cylindrical in shape and is made of stainless steel or plastic or aluminum or brass.

4. The apparatus as claimed in claims 2 and 3, wherein the housing (1) comprises one or more PCB holding part (la) provided to hold the PCB (2).

5. The apparatus as claimed in claims 2 to 4, wherein the housing (1) further comprises one or more float guide portions (lb) having lip portion (lc) provided to facilitate point contact for the float (5) in order to have reduced friction while the float (5) move in the first/ second direction according to the variation in the liquid level inside the tank (5).

6. The apparatus as claimed in claims 1 and 5, wherein radial movement of the float (5) is limited by the lip portion (lc) of the float guide portion (lb).

7. The apparatus as claimed in claim 1, wherein supply voltage to operate the infrared elements (3) is provided by the electronic circuit.