AN APPARATUS FOR NON-CONTACT LEVEL SENSING

FIELD OF INVENTION

The present invention relates to a non-contact level sensing used for detecting the level of the substances that flow, particularly liquids and slurries present in a liquid storage. More particularly, the present invention is related to a non-contact level sensing by using magnetic sensor to sense the level of the liquid such as fuel used in automobiles, industrial and consumer applications.

BACKGROUND ART

For any liquid storage 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 gauge works mainly by two main parts of sensing unit and the indicator. The sensing unit helps in sensing the level of the fuel in the tank and transmitting the information to the indicator, which helps in indicating the level of the fuel with the aid of the display unit. So, therefore, sensing unit plays a vital role of measuring the level of the fuel in the tank.

The sensing unit usually uses a float connected to a potentiometer in an automobile. As the tank empties, the float drops and slides a moving contact along the resistor, increasing its resistance. When the resistance is at a certain lower point, it will also turn on a "low fuel" light in display unit of the fuel gauge system. Henceforth, the indicator unit measures and displays the amount of electrical current flowing through the sending unit. For example, when the tank level is high and maximum current is flowing, the needle points to "F" indicating a full tank. When the tank is empty and the least current is flowing, the needle points to "E" indicating an empty tank.

But if an electrical fault opens, the electrical circuit causes the indicator to show the tank as being empty and which will provoke the driver to refill the tank. Likewise, wrong indication would allow the driver to run out of fuel with no prior notification. Corrosion or wear of the potentiometer will provide erroneous readings of fuel level. An electric current is sent through the variable resistor to which a float is connected, so that the value of resistance depends on the fuel level. In most of automotive fuel gauges such 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.

Although these sensors have been well - known already for a long time and within which still ongoing developments are done in the sensor systems of the sensing unit. But, even these kinds of sensor possess demerits of occupying more space, heavy weight, expensive and even low durability.
Some of the prior arts are as follows:

US3709038 discloses a non contact type fuel gauge utilizing magnetic coupling to rotate a follower magnet having a wiper arm attached thereto for sequentially engaging a plurality of circularly spaced electrical contacts. The contacts are connected to fuel level indicator lights positioned, for example, on a snowmobile instrument panel. The drive magnet is attached to a helical element rotatable by the vertical movement of a float assembly in engagement therewith.

WO2005057138 describes a non contact type fuel level sensor for sensing the level of remaining fluid in a container such as a fuel tank for a motorized in which fuel level sensor incorporates a magnetic sensor and magnetic circuit in a rotational sensor configuration for determining the angular position of a hub relative to its pivot base, where the hub is attached to a float-arm member. The magnetic flux sensor positioned between two movable magnets, and critical electronic components are hermetically sealed making the fuel level sensor fully submersible in fuel.

EP1450142 describes a liquid level sensor of non contact type includes a housing, a float attached to a rotary shaft which is rotatably provided in the housing, a magnet which is fixed to the rotary shaft, and rotating together with the rotary shaft, a pair of stators which are disposed so as to face an outer peripheral surface of the magnet, and an electronic circuit which includes at least a set of terminals and a magneto electric transuding element for detecting a change of magnetic flux in the stators caused by rotation of the magnet and for outputting an electric signal. The magneto electric transuding element and the stators are electrically connected and fixed to the set of terminals so that a terminal assembly is formed. The housing is formed by insert molding the terminal assembly with resin so that the terminal assembly is embedded in the housing

EP1437580 relates to anon contact liquid level sensing system in a tank includes a sensor part provided to the tank and for sensing a position of the liquid level in accordance with displacement of a float, and a sensor casing arranged in the tank to be isolated from liquid and for accommodating the sensor part.
Therefore there is demand for another economical, safer non-contact method for fuel level is desired. Whereby, it is desirable to provide an apparatus for non-contact level sensing which will avoid the problems/disadvantages noted above and overcome other problems encountered in conventional methods.

OBJECTS OF INVENTION

One or more of the problems of the conventional prior art may be overcome by various embodiments of the present invention.

The primary object of the present invention is directed to provide an apparatus of non-contact level sensing used for detecting the level of the liquids and slurries present in a liquid storage.

It is another object of the present invention to provide an apparatus of non-contact level type using magnetic sensor for sensing the level of the liquids and slurries present in a liquid storage.

It is another object of the present invention, wherein according to the level of liquids, the float assembly moves upwards or downwards and creates variation in air gap between the sensing element and a ferromagnetic wall arranged at an inclination thereby obtaining output variations.

It is another object of the present invention, wherein the output variations can be discrete or linear based on the ferromagnetic material design.

It is another object of the present invention to provide an apparatus for non-contact level sensing with a contact-less principle, which will not prone to wear.

It is yet another object of the present invention to provide an apparatus for non-contact level sensing which can be used in high temperature application.

It is another object of the present invention to provide an apparatus for non-contact level sensing for automobiles, industrial and consumer applications.

SUMMARY OF INVENTION

Accordingly there is provided a non-contact level sensing device for sensing liquid level in
a liquid storage comprising of:

a float assembly housed within a guide;
and
a wall,

wherein the guide and the wall are fitted to a flange of the sensing device,

wherein the float assembly comprises of a float, a magnet and a sensing element,

wherein the sensing element is placed adjacent to the magnet and positioned within the float thereby preventing the sensing element and the magnet from contact with the liquid,

wherein the guide is provided for guiding the float assembly without tilting during its upward and downward movement and retaining it in position ,

wherein the wall of the sensing device is arranged at an inclination in the vertical axis, and

wherein the wall is made of ferromagnetic material.

According to another aspect of the invention the device the sensing element is hall effect type / magneto resistive element type.

According to another aspect of the invention the sensing element is positioned with face to face contact to the magnet.

According to another aspect of the invention the sensing element measures the air gap between its face and the wall of the sensing device.

According to another aspect of the invention the right side wall of the guide is provided with an opening , thereby enabling the sensing element to sense the air gap between its face and the wall of the sensing device.

According to another aspect of the invention the sensing element is electrically connected with an external circuit to determine the level of the liquid present inside the liquid storage.

BRIEF DESCRIPTION OF THE DRAWINGS:

Figure 1: Schematically illustrates the cross sectional front view of the apparatus for non-contact level sensing according to the present invention.

Figure 2: Schematically illustrates the front view of the float of the non-contact level sensing device according to the present invention.

Figure 3: Schematically illustrates the cross sectional top view of the guide of the non-contact level sensing device according to the present invention.

Figure 4: Schematically illustrates the cross sectional top view showing the guide housed within the guide.

Figure 5: illustrates graphical representation of output variations with different positions of sensing element according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING FIGURE

The present invention provides an apparatus for measuring liquid level that present in a liquid storage. This system utilizes a mechanical float mechanism and position sensor to detect the direction and magnitude of movement of the float. The sensor generates electrical / electronic signals that are used to calculate the updated level of the float and thus the liquid level.

The invention is described in detail with reference to figure 1 to 4 of the accompanying drawings.

The sensing device according to the invention essentially provided with a float assembly (1) comprising a float (2), a magnet (3) and a sensing element (4). The sensing element (4) is of hall effect type / magneto resistive element type and placed adjacent to the magnet (3) with face to face contact and positioned within the float (2).

The float assembly (1) may be molded using synthetic material for example poly propylene, nylon with the magnet (3) and the sensing element (4) in a pre-determined location and configuration. The float (2) may be of any shape, for example, in one of the embodiments the float (2) is provided with flat surface (2a) and (2b) and a spherical surface (2c).

The float assembly (1) is housed within a guide (5) and arranged such that it is capable of moving upward and downward direction inside the liquid storage according to the level of the liquid present. The guide (5) is disposed for guiding the float assembly (1) without tilting during its upward and downward movement according to the varying level of the fluid present inside the liquid storage and may be fitted with the flange (7) of the sensing device. For example in one of the embodiments the guide is of rectangular in shape and having left side wall (5a), right side wall(5b) ,front side wall (5c) and rear side wall (5d).. Preferably the upper side of the housing is having a opening for the passage of the float assembly (1). The horizontal bottom portion (5f) of the guide (5) that connects the vertical walls (5a, 5b, 5c and 5d) is provided with opening (5g) for the entry of the liquid to reach the float assembly (1) located inside the guide (5). The guide (5) may be fabricated from sheet metal or made of plastic material.

During the upward and downward motion, flat surface (2a) and (2b) of the float (2) is guided by the left side wall (5a) and right side wall (5b) such that the float assembly (1) is guided without tilting.

The float assembly (1) is retained in position within housing (5) by the spherical surface (2c) of the float (2) which is guided by the front side wall (5c) and the rear side wall (5d)). The side wall (5b) of the guide (5) is provided with opening (5e) so as to enable the sensing element (4) to sense the air gap from its face to the wall (6) of the sensing device.

The wall (6) of the sensing device according to the invention is made of ferromagnetic material and is arranged at an angle in the vertical plane which depend upon the construction detail like the working length of the float .The wall (6) is fitted to the flange (7) of the sensing device. The flange (7) comprises integral mounting features such that the sensing device can be conveniently kept inside the liquid storage at the required location and fastened. The flange (7) further comprises integral electrical connectors to provide connection to the sensor electronics.

The shape of the float (2) and the guide (5) is illustrated as an exemplary embodiment. However, it is to be understood that it is possible to construct the float (2) and the guide (5) in different shapes and all such obvious modifications are well within the scope of the claimed invention. It is possible to construct the guide such that the wall is fitted inside the guide itself instead keeping the same outside the housing.

The sensing element (4) and the magnet (3) are located within the float (2) and during working of the sensing device the float assembly (1) always floats above the liquid surface. Due to this the sensing element (4) and the magnet (3) are free from contact with the liquid.

The float assembly (1) moves in upward / downward direction as the liquid level changes. The sensing element (4) attached to the float assembly (1) measures the air gap (distance) between its face and the wall (6). As shown in the figure the air gap (AG1 , AG2) between the face of the sensing element (4) and the wall(6) varies continuously according to the position of the float assembly(l). The sensor element (4) is electrically connected with an external circuit that determines the level of the liquid in the form of electrical voltage which feed to the indicating device for the display of the fuel level.

WE CLAIM:

1. A non-contact level sensing device for sensing liquid level in a liquid storage comprising of:
a float assembly (1) housed within a guide (5); and

a wall (6),

wherein the guide (5) and the wall (6) are fitted to a flange (7) of the sensing device,

wherein the float assembly (1) comprises of a float (2), a magnet (3) and a sensing element(4),

wherein the sensing element (4) is placed adjacent to the magnet (3) and positioned within the float (2) thereby preventing the sensing element (4) and the magnet (3) from contact with the liquid,

wherein the guide (5) is provided for guiding the float assembly (1) without tilting during its upward and downward movement and retaining it in position ,

wherein the wall (6) of the sensing device is arranged at an inclination in the vertical axis, and

wherein the wall (6) is made of ferromagnetic material.

2. The device as claimed in claim 1, wherein the sensing element (4) is hall effect type / magneto resistive element type.

3. The device as claimed in claim 1, wherein the sensing element (4) is positioned with face to face contact to the magnet (3).

4. The device as claimed in claim 3, wherein the sensing element (4) measures air gap between its face and the wall (6) of the sensing device.

5. The device as claimed in claim 1, wherein the right side wall (5b) of the guide (5) is provided with an opening (5e) , thereby enabling the sensing element (4) to sense the air gap between its face and the wall (6) of the sensing device.

6. The device as claimed in claim 3, wherein the sensing element (4) is electrically connected with an external circuit to determine the level of the liquid present inside the liquid storage.