Liquid level transducer with pivoting and linear motion

A liquid level transducer includes a mounting head for connection to the wall of a tank and a housing extending into the tank from the mounting head. A float rod is pivotally connected to the housing and a float is connected to the float rod for pivotal movement upon a change of liquid level in the tank. A proximal end of the float rod is connected to an actuator portion and constrained for pivotal movement about two parallel axes so that the actuator portion moves in a linear direction with respect to the housing. The interior of the housing includes a sensor assembly responsive to the linear movement of the actuator portion to thereby determine the level of liquid within the tank.

BACKGROUND OF THE INVENTION

This invention relates to liquid level transducers, and more particularly to a liquid level transducer having a float that moves in response to a change in liquid level.

Transducers for measuring liquid level are often used in vehicles, industrial equipment, as well as other mobile and stationary systems and components. The electrical output of such transducers varies in response to a change in the liquid level being measured and is typically in the form of a change in resistance, capacitance, current flow, magnetic field, and frequency. These types of transducers may include variable capacitors or resistors, optical components, Hall effect sensors, strain gauges, ultrasonic devices, reed switch arrays, and so on.

For reed switch-type devices, a plurality of reed switches are usually arranged in series with a plurality of resistors along the length of a circuit board. The reed switches are normally responsive to the presence and absence of a magnetic field for opening and/or closing the switch. A float rides along the surface of the liquid to be measured and is constrained to move in a linear direction along the circuit board. The float usually includes an embedded magnet to trip one of the reed switches as the float moves in response to a change in liquid level in the tank. Thus, the resistance of the circuit, which is indicative of liquid level, depends on the position of the float and the particular reed switch that has been tripped.

However, such devices typically have several drawbacks. For example, it is known that reed switches suffer from hysteresis effects and may open and/or close prematurely depending on the orientation of the reed switches with respect to the magnet, the magnetic strength of the magnet, the distance between the reed switch and the magnet, and so on. When the reed switches are aligned linearly, each reed switch may open and close up to three times as the float approaches, aligns with, and passes each reed switch, thus leading to improper liquid level indication, undesired switching, and premature failure of the switches. In addition, prior art solutions expose the reed switches to the liquid being measured, which may be corrosive and cause inaccurate liquid level readings and premature failure. It would therefore be desirable to overcome at least some of the disadvantages associated with prior art reed switch-type liquid level transducers.

In addition, prior art liquid level transducers that include a mounting head and an elongate sensor probe, such as a reed switch probe, resistor probe, capacitor probe, and so on, are often difficult and time-consuming to assemble due to the number of individual components and the fastening means associated with each component. It would therefore be desirable to provide a liquid level transducer that is easier to assemble and has relatively fewer parts.

Moreover, prior art liquid level transducers having a float rod that pivots in response to a change of liquid level within a tank suffer from a very limited range of movement, and thus the sensing range as well as the number of sensors, such as reed switches, that can be practically positioned along the range of movement. Accordingly, the measuring resolution can be greatly compromised. In addition, these types of liquid level transducers have limited range of movement due to volume constraints with the tank as well as space constraints of the transducer housing in light of the relatively small opening in the tank for receiving the transducer and other components that may be associated therewith, such as liquid withdrawal and return tubes, pumps, electronics, filters, and so on, that may be associated with various requirements of a tank installations on motorized vehicles or equipment. or stationary structures. associated with installing the liquid level transducer through a relatively small opening in the tank and limitations rotational movement of the float and float arm with respect to the transducer housing.

SUMMARY OF THE INVENTION

In accordance with one aspect of the invention, a transducer for determining the level of liquid within a container comprises a mounting head adapted for connection to the container; a housing extending from the mounting head and having a hollow interior isolated from liquid within the container; and an actuator portion. The actuator portion includes an actuator body connected to the housing that is restrained to travel in a linear direction with respect to the housing. An actuator is connected to the actuator body for movement therewith. A first pivot axis is operably associated with one of the housing and the actuator portion. At least one sensor is located in the hollow interior. The at least one sensor changes in electrical state in response to external input from the actuator. A float rod has a proximal end operably associated with the actuator portion for movement therewith along the linear direction. The float rod is constrained to pivot about the first pivot axis. A float is connected to the float rod to thereby cause pivoting movement of the float rod about the first axis and linear movement of the actuator portion in response to a change in liquid level within the container to thereby change the electrical state of the at least one sensor proportional to the level of liquid within the container.

Other aspects of the invention will become evident upon considering the following detailed description of the preferred embodiments of the invention in conjunction with the accompanying drawings.

It is noted that the drawings are intended to depict only exemplary embodiments of the invention and therefore should not be considered as limiting the scope thereof. It is further noted that the drawings are not necessarily to scale. The invention will now be described in greater detail with reference to the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, and toFIGS. 1-6in particular, a liquid level transducer10in accordance with an exemplary embodiment of the present invention is illustrated. The liquid level transducer10preferably extends into a container12(shown in phantom line inFIG. 1), such as a fuel tank, oil reservoir, radiator, brake fluid chamber, or any other container for holding and/or transporting a liquid (not shown) where it is desirous to determine the level of liquid within the container. The transducer10preferably includes a mounting head14for connection to the container12and a sensor assembly16extending therefrom. Although the transducer10is shown in many of the drawings as being oriented in a horizontal direction, it will be understood that the transducer10can be mounted for extending in a vertical direction or any other suitable angle or orientation, without departing from the spirit and scope of the invention, such angle or orientation being dependent at least partially upon space constraints as dictated by the structure of the vehicle, machine, etc., with respect to the container12and/or the particular shape of the container12.

As best shown inFIGS. 4-6, the sensor assembly16preferably senses liquid by translating arcuate sliding motion of a float44and float rod32with respect to a sensor housing18as the liquid rises and falls within the container, and translates the arcuate sliding motion into linear movement along a length of the housing18, so that a significant increase in measurement range and/or resolution can be realized without the significantly increasing the size of the sensor assembly.

With this feature in mind, and referring now toFIGS. 1-3, 7, and 9, the sensor assembly16preferably includes the housing18with a first housing section20that is preferably integrally formed with the mounting head14and a second housing section22that extends from the first housing section20. The first and second housing sections are preferably constructed of a plastic material that is chemically resistant to the liquid being measured.

In accordance with a further embodiment of the invention, the housing18can be separated from the mounting head14by a variable length support, such as by support rails (not shown) that extend from the mounting head and through supporting structure (not shown) in the housing18so that the housing18can slide with respect to the mounting head and thus be adjustable in length for accommodating different space constraints and sizes of containers. Where it is desirous to keep the interior of the housing18sealed from the contents of the tank, a flexible membrane complementary in shape with both the housing and mounting head can be connected therebetween. Moreover, in accordance with yet a further embodiment of the invention, the housing18can be formed of multiple sections sealingly connectable together so that a desired housing length can be formed. Thus, it will be understood that the housing18can be a fixed size or adjustable in length and/or distance with respect to the mounting head to accommodate a wide variety of tank configurations and sizes.

A first pivot mount24is integrally formed or otherwise connected to the second housing section22and is in the form of an elongate, tubular member that extends transverse to a sensor wall25of the first housing section20when connected thereto. The sensor wall25extends between a movable actuator portion40and an electronic sensor unit52located within a hollow interior50of the first housing section20. A first pivot pin26extends through a bore23of the first pivot mount24and is pivotally secured thereto via a push-nut or washer28that is press-fit over one end of the pivot pin26after installation in the pivot mount24within the bore23. It will be understood that the push-nut or washer can be eliminated and other means used for pivotally securing the first pivot pin26to the first pivot mount24can be used. An opening30is formed in the opposite end of the first pivot pin26and is sized to slidably receive a float rod32so that the float rod both slides through the first pivot pin26and rotates about a first pivot axis34coincident with a central axis of the first pivot mount24during float movement, such as when the level of liquid within the container changes, and thus the height of the float with respect to the container.

The float rod32has a proximal end36slidably connected to a second pivot pin38associated with an actuator portion40and a distal end42that receives a float44. The float44is connected to the distal end42of the float rod32via a central bore45formed in the float in a conventional manner, with bearing washers46positioned on either side of the float44and a push nut or washer48pressed onto the distal end42of the float rod32. As shown, the float rod32can be bent to accommodate the float rod mounting and the configuration of a particular tank or container. However, it will be understood that the float rod can be straight or configured in any desired shape to accommodate different containers and liquid level measurement configurations.

The first housing section20is preferably of unitary construction with the mounting head14so that the hollow interior50of the first housing section20is isolated from the liquid in the tank or container being measured. However, it will be understood that the mounting head14and first housing section20can be separately formed and connected together without departing from the spirit and scope of the invention. The electronic sensor unit52, including one or more sensing and processing circuit board(s)54, one or more sensors56(FIG. 10), and/or one or more sensors58(shown in phantom line inFIG. 10), and suitable processing circuitry (not shown) are located in the hollow interior50and are also isolated from the contents of the tank.

As shown, the first housing section tapers inwardly and away from the mounting head14and is received in a similarly shaped hollow interior60of the second housing section22. Due to the unitary construction of the housing section20, the hollow interior50and its contents, including the electronic sensor unit52, are completely isolated from the liquid being measured to advantageously increase the measurement reliability of the transducer10and extend its useful life over prior art arrangements where measurement components are directly exposed to the liquid being measured. Since many liquids are corrosive in nature and could cause deterioration of the measurement components and their electrical connections in prior art solutions, isolation of the sensor unit52in accordance with the present invention prevents deterioration of both the measurement components as well as their electrical connections, thereby providing a liquid level transducer10that is more robust, reliable, and longer lasting than prior art solutions.

Reinforcing ribs62(FIG. 7) are preferably formed on one side of the second housing section22. As best shown inFIG. 8, a support ledge or platform64is formed on an opposite side of the second housing section22and may include reinforcing ribs66to add structural support to the ledge64.

Guide members, shown by way of example as guide rods or rails68,70preferably extend between the ledge64of the second housing section22and rod support structure73(FIG. 11) formed with the mounting head14. The guide rods are preferably cylindrical in shape and are operable to guide linear movement of the actuator portion40during use. Although two guide rods are shown, it will be understood that a single guide rod, or more than two guide rods, may be provided without departing from the spirit and scope of the invention. Moreover, in accordance with a further embodiment of the invention, one or more guide rods or rails can be formed integrally with the housing18and/or the mounting head14. The guide rods can also be of any suitable cross sectional shape, such as T-shaped, L-shaped, oval, square, rectangular, triangular (dovetail-shaped), and so on.

The actuator portion40preferably includes an actuator body72with a second pivot mount74that is integrally formed or otherwise connected to the body72and is in the form of an elongate, tubular member. The second pivot pin38extends through a bore76of the second pivot mount74and is pivotally secured thereto via a push nut or the line (not shown) that is pressed over one end of the second pivot pin38after installation in the pivot mount24within the bore23. A split sleeve or collar78can also be installed in the bore76and surround the second pivot pin38to ensure smooth rotational movement of the second pivot pin38with respect to the second pivot mount74. The second pivot pin38preferably includes an enlarged head80with an opening82extending therethrough and is sized to slidably receive the proximal end36of the float rod32so that the proximal end36of the float rod rotates about a second pivot axis84coincident with a central axis of the second pivot mount74and parallel with the first pivot axis34, and also slides through the opening82during pivoting movement of the float, when the liquid level within the container changes height.

The actuator portion40also includes guide bores86and88formed in the body72that extend perpendicular to the pivot axis84. Each guide bore86,88is preferably sized and complementary shaped to slidably receive one of the guide rods68,70so that the actuator portion40moves linearly along the guide rods with respect to the housing18, as represented by opposing arrows85and87inFIG. 11, in response to pivotal and sliding movement of the float rod32. It will be understood that where only one guide rod is provided, as previously described, the actuator portion40can have a single guide bore or more than one guide bore in series coincident with the same axis. It will be further understood that the guide bores may include linear guide bearings or the like or be constructed of a bearing material, such as nylon or brass for example, in order to ensure smooth movement of the actuator portion40with respect to the guide rod(s). It will be further understood that where the guide rod(s) have a particular cross-section, the guide bore(s) can also be complementary in cross sectional shape or of a cross sectional shape that would be suitable for the guide rod. By way of example, for a guide rod with a T-shaped cross section, the guide bore can also be an open T-shaped slot. As a further example, when the guide rod is dovetail-shaped, the guide bore can also be dovetail-shaped for receiving the guide rod. Thus, a wide variety of different guide rod and guide bore configurations are within the purview of the present invention.

As best shown inFIGS. 7 and 11, a cylindrical pocket or depression90(shown in hidden line) is formed in the body72of the actuator portion40for receiving a cylindrically-shaped actuator92that also moves linearly with the actuator portion40and changes one or more states of the sensors56and/or58. Preferably, the sensors56comprise reed switches in series with resistors57(FIG. 10) that change state between open and closed positions depending on the location of the actuator92with respect to the sensors56(see the dashed circles inFIG. 10that represent different positions of the actuator92along the length of the sensor board(s)54). To that end, the actuator92preferably comprises a permanent magnet that changes the state of the reed switches and causes a voltage change in the circuitry depending on the location of the actuator and which reed switch(es) is/are actuated, as is well known.

In accordance with a further embodiment of the invention, the sensors94(in phantom line inFIG. 10) represent one or more Hall-effect sensors or similar devices that measure the strength of a magnetic field generated by the permanent magnet92as the magnet travels towards and away from one or more of the sensors58.

As best shown inFIGS. 10 and 11, the sensor board54is preferably in the form of one or more printed circuit boards (PCB), located in the hollow interior or pocket50of the first housing section20. The PCB preferably extends along a substantial height and width of the interior pocket50. A grommet or retainer55(FIG. 8) is connected to a proximal end of the PCB for retaining the PCB in a centered position within the interior pocket50when the transducer10is assembled. Although the PCB is shown extending a substantial length or height of the hollow interior50to take full advantage of the entire linear travel of the actuator portion40, the PCB, as well as the first housing section20, can be shorter than the length of linear travel when the entire travel is not needed, such as when the arcuate movement of the float between full and empty conditions does not require the entire travel length of the actuator portion40. The plurality of sensor elements56, preferably in the form of normally-open reed switches56, (or one or more Hall-effect sensors58) are mounted on the PCB54and can be connected in series with the plurality of resistors57in a well-known manner. The reed switches56are preferably oriented in a linear pattern along the length of the PCB so that linear movement of the magnetic actuator92is coincident with the linear array of reed switches56and/or Hall-effect sensor(s) in response to rotational movement of the float44. Preferably, the reed switches56are positioned parallel to a mounting flange116of the mounting head14and parallel to each other, as shown inFIG. 10, in order to position a greater number of reed switches56into a relatively small housing, thereby increasing resolution of the liquid level transducer10.

The reed switches56are responsive to the magnetic field generated by the magnetic actuator92, which passes through the side wall98of the first housing section20as the magnet travels along the linear pathway in response to float movement due to a change in the level of liquid within the container. When a magnetic field is present on one of the reed switches56, the reed switch closes and, in conjunction with its associated resistor57, creates a liquid level signal. As the magnet travels away from the reed switch, it will return to its normally open position and another reed switch will close under the magnetic field. In this manner, liquid level sensing can advantageously occur without exposing the reed switches to the liquid being measured to thereby advantageously increase the measurement reliability of the transducer10and extend its useful life over prior art arrangements. As best shown inFIG. 2, a first stop100is formed on the first housing section20and a second stop102is formed on the second housing section to limit rotational movement of the float arm32, and thus the linear travel of the actuator portion40under full tank and empty tank conditions.

It will be understood that normally closed reed switches can be used without departing from the spirit and scope of the invention. It will be further understood that the reed switches or other sensors can be located on either side of the PCB without departing from the spirit and scope of the invention, as the magnetic field can be made sufficiently strong to pass through the housing wall(s), the PCB, and any potting material contained within the pocket50.

Moreover, in accordance with a further aspect of the invention, reed switches56can be located on opposite sides of the PCB in a staggered relationship to thereby increase the number of sensors and thus the measuring resolution of the liquid level transducer10.

Although not shown, insulating material, such as potting material, and so on, can be located in the pocket50, surrounding the PCB, reed switches, and other components to insulate and protect the components against shock, vibration, and other harsh conditions to which the transducer10may be exposed.

Although a particular number of reed switches are shown, it will be understood that more or less reed switches can be provided without departing from the spirit and scope of the invention. Electrical wires104,106, and108(best shown inFIGS. 7 and 8) preferably extend from the sensor board54and through a strain relief or grommet110located in an opening112of an annular side wall114of the mounting head14. Alternatively, in accordance with a further aspect of the invention, the grommet110can be in the form of an electrical connector or plug for receiving a complementary connector or plug associated with further processing and/or display circuitry (not shown) of the vehicle or other device with which the container is associated. Moreover, the grommet110can be used for sealing only, and a separate strain relief provided inside the mounting head14. Where an electrical connector or plug is used, or depending on the particular structure of the mounting head14and the manner in which the electrical wires are connected to the PCB, the grommet and/or strain relief can be eliminated.

In addition, although reed switches have been described with respect to this embodiment, it will be understood that other magnetic sensing devices can be used without departing from the spirit and scope of the invention. For example, other devices can include, but are not limited to, one or more solid state magnetic flux field sensors, the afore-mentioned Hall effect sensors, magnetoresistive (MR) sensors, anisotropic MR (AMR) sensors, giant magnetoresistance (GMR) sensors, solid state Micro-Electro-Mechanical Systems (MEMS), magnetic switches, as well as nonmagnetic sensing technologies such as proximity detectors using capacitance, optical, or other measurement technologies, and so on. With the use of the above sensors, it may not be necessary to have the sensor in alignment with the linear pathway of the magnet, or a plurality of sensors, since a single Hall effect IC may be sufficient to determine the position of the magnet and thus the level of liquid within the container. In addition, the actuator need not be cylindrical in shape as shown, but may be of other suitable shapes such as rectangular, square, and so on.

Likewise, the actuator can be in the form of one or more magnets, LED's, optical fibers or other light source, or other contactless actuator/sensor arrangements to remotely change the electrical state of the sensor elements. In the event that optical sensors are used, the housing can be formed of a material that is translucent or transparent to the wavelength of the light source so that the sensor elements can readily detect movement of the light source as the liquid level in the container rises and falls.

Referring now toFIGS. 7 to 9, the mounting head14preferably includes a mounting flange116extending radially outwardly from the annular side wall114, and an annular groove118formed in the annular side wall114. The mounting head14is preferably formed as a unitary structure with the first housing section20through injection molding, but may alternatively be formed by machining, die-casting, or other known forming means. The mounting flange116is preferably disk-shaped and includes a plurality of mounting holes120that extend axially through the mounting flange and in proximity to its outer peripheral edge122. The mounting holes120are adapted to receive threaded studs (not shown) associated with a tank or other container in a well-known manner. A cover or cap124has an internal annular ridge (not shown) for mating with the annular groove118(FIG. 10) formed in the side wall114in a snap-fit engagement to retain the cap124on the mounting head14and enclose the hollow interior50. An O-ring126or other sealing arrangement is sandwiched between the cap124and the side wall114so that the hollow interior50is isolated from the environment outside of the container. A gasket128can be provided between the mounting flange116and the container for sealing the opening (not shown) in the container through which the transducer10extends.

It will be understood that the mounting head14is not limited to a flange mounting arrangement as shown, other means for mounting the liquid level transducer10to a tank or other container can be used, including NPT type threads, clamping, welding, and so on, without departing from the spirit and scope of the invention.

The head14and housing sections20,22are preferably constructed of a molded material, such as plastic, through injection molding or other techniques. However it will be understood that the mounting head14and/or the housing sections20and22, are not limited to plastic material, but may be constructed of metal, composites, ceramics, combinations thereof; or any other suitable nonmagnetic material. Moreover, although the first housing section20and second housing section22of the housing18are shown as separate units, they can be integrally formed. In accordance with a further embodiment of the invention, the second housing section22can be eliminated and the first housing section either alone or together with the mounting head14can include all necessary structure to support the various components of the liquid level transducer10.

In use, when the liquid level changes height in the container12for example, the float44will also change in height, causing the float rod32to pivot about the first pivot axis34. Due to the linear restraint of the actuator portion40, the float rod will also slide through the first pivot pin26, and will also slide through the second pivot pin38, while pivoting about the second pivot axis84, thereby causing the actuator portion40to travel in a linear path along the guide rods68,70connected to the housing18thereby causing linear translation of the magnetic actuator92and change the electrical state of one or more sensors indicative of the liquid level. In this manner, a larger number of sensors and/or greater measurement resolution can be obtained without significantly increasing the size of the housing when compared to prior art transducers that have a float rod with only a pivoting motion upon a change in the liquid level. In addition, a wider variety of tank sizes and shapes can be accommodated.

Referring now toFIGS. 12 to 21, a liquid level transducer140in accordance with a further exemplary embodiment of the present invention is illustrated. As in the previous embodiment, the liquid level transducer140is preferably mounted to the wall142(FIGS. 17 to 19) of a container144and extends through a hole146formed in the wall and into the tank for determining the level of liquid within the container.

The transducer140preferably includes a mounting head148for connection to the wall142of the container144and a sensor assembly150extending from the mounting head148. Although in this embodiment the transducer140is shown as being oriented in a vertical direction, it will be understood that the transducer140can be mounted for extending in a horizontal direction or any other suitable angle or orientation, and can be adapted for use with any suitable tank or the like without departing from the spirit and scope of the invention, as discussed above with respect to the liquid level transducer10.

As best shown inFIGS. 12 and 17-19, the sensor assembly150preferably senses liquid in the container144by translating arcuate motion (represented by arrows152) of a float rod166and attached float168about a first axis154(FIG. 12) associated with a sensor housing156as the liquid rises and falls within the container12, and translates the arcuate motion152into both rotational movement (represented by arrows158) of an actuator portion162associated with the sensor assembly150about a second or central axis160(FIG. 12) of the actuator portion162that is parallel with the first axis154, and linear movement (represented by arrows164) of the actuator portion162along a length of the sensor housing156, so that a significant increase in measurement range and resolution can be realized when compared to the prior art without significantly increasing the size of the sensor assembly or the need to enlarge the size of the hole146of the container144for installation of an otherwise larger sensor assembly.

Referring now toFIGS. 12-16 and 20, the sensor assembly150preferably includes the sensor housing156with a first housing section170that is preferably integrally formed with the mounting head148and a second housing section172that extends from the first housing section170. The first and second housing sections170,172are preferably constructed of a plastic material that is chemically resistant to the liquid being measured, but may be constructed of any suitable material or combinations of materials including, but not limited to, metals, ceramics, composites, and so on. As in the previous embodiment, although the housing156is shown having a fixed length or “depth” into the tank, it will be understood that the housing156can be adjustable in length and/or distance with respect to the mounting head to accommodate a wide variety of tank configurations and sizes.

A first pivot mount174is integrally formed or otherwise connected to the second housing section172and is in the form of an elongate, tubular member that extends transverse to a sensor wall175of the first housing section170when connected thereto and coaxial with the first pivot axis154. The sensor wall175extends between the movable actuator portion162and the electronic sensor unit52(FIGS. 10and11) located within the hollow interior of the first housing section170. A pivot pin176extends through a bore178(FIG. 20) of the first pivot mount174and is pivotally secured thereto via a push nut or washer (not shown) that press-fits over one end of the pivot pin176after being inserted into the bore178of the first pivot mount174, as in the previous embodiment. It will be understood that the push-nut or washer can be eliminated and other means used for pivotally securing the first pivot pin176to the first pivot mount174can be used.

A transverse opening180(FIG. 20) is formed in the pivot pin176and is sized to slidably receive a proximal or connection end182of the float rod166so that the float can slide through the pivot pin176and rotate about the first pivot axis154with the pivot pin176during movement of the float, such as when the level of liquid within the container changes.

The connection end182of the float rod166is also slidably connected to the actuator portion162for pivoting and sliding movement therewith. A distal or float end184of the float rod166receives the float168. The float168is connected to the distal end184of the float rod166via a central bore186(FIG. 20) formed in the float in a conventional manner, with push-nuts or washers188pressed onto the distal end184of the float rod166on either side of the float168. As with the previous embodiment, the float rod166can be bent to accommodate the float rod mounting and configuration of a particular tank or container. However, it will be understood that the float rod can be straight or configured in any desired shape to accommodate different containers and liquid level measurement configurations. It will be further understood that the float168is not limited to the cylindrical shape as shown, but may encompass any shapes or configuration without departing from the spirit and scope of the invention.

As in the previous embodiment, the first housing section170of the present embodiment is preferably of unitary construction with the mounting head148so that a hollow interior (not shown) of the first housing section170is isolated from the liquid in the tank or container being measured. However, it will be understood that the mounting head148and first housing section170can be separately formed, connected, and sealed together without departing from the spirit and scope of the invention. An electronic sensor unit52(FIG. 20), including one or more sensing and processing circuit board(s)54, one or more sensors56(FIG. 10), and/or one or more sensors58(shown in phantom line inFIG. 10), as well as suitable processing circuitry (not shown) are located in the hollow interior of the first housing section170and are also isolated from the contents of the tank.

As best shown inFIG. 20, the first housing section170tapers inwardly and away from the mounting head148and is received in a similarly shaped hollow interior190of the second housing section172. Due to the unitary construction of the housing section170with the mounting head148, the hollow interior (not shown) of the first housing section170and its contents, including the electronic sensor unit52, are completely isolated from the liquid being measured. This feature advantageously increases the measurement reliability of the transducer140and extend its useful life over prior art arrangements where measurement components are directly exposed to the liquid being measured. Since many liquids are corrosive in nature and could cause deterioration of the measurement components and their electrical connections in prior art solutions, isolation of the sensor unit52in accordance with the present invention prevents deterioration of both the measurement components as well as their electrical connections, thereby providing a liquid level transducer140that is more robust, reliable, and longer lasting than prior art solutions. The sensor unit52in the present embodiment is substantially similar in construction to the sensor unit in the previous embodiment, and therefore will not be further described, with the exception that instead of a three-wire system associated with the liquid level transducer10, which can be used for power, ground and liquid level signal associated with active electronic components on the PCB for converting the sensor output to a voltage for operating an indicator or the like, the transducer140of the present embodiment comprises two wires171and173for powering one or more passive devices, such as parallel reed switches each in series with a resistor for changing the voltage as more or less reed switches are activated in response to a change in liquid level and the corresponding change in linear position of the actuator portion162with respect to the housing150and the passive electronics positioned therein.

In order to secure the first and second housing sections together, and with particular reference toFIG. 21, a reinforced opening191is formed in a bottom wall193of the second housing section172and a complementary-shaped protrusion195formed on a bottom wall197of the first housing section172. When the first housing section170is inserted into the second housing section172, the protrusion195will extend through the opening191and downwardly from the bottom wall193of the second housing section172. A locking cap199is then inserted over the protrusion195to prevent the protrusion from exiting the reinforced opening191, thereby securing the housing sections together. It will be understood that other means for securing the housing sections together can be used without departing from the spirit and scope of the invention, including but not limited to, adhesive bonding, staking, mechanical clamping or fastening, ultrasonic welding, and so on. Moreover, in accordance with a further embodiment of the invention, the second housing section172can be eliminated and the described features, such as the first pivot mount174and ledge196, can be formed on or otherwise connected to the first housing section170. As best shown inFIGS. 15 and 16, a stop195is formed on the second housing section172to limit rotational movement of the float arm166, and thus the linear travel of the actuator portion162when the container approaches an empty condition.

Reinforcing ribs194(FIGS. 12, 15, 16, and 21) can be formed on the second housing section172. A lower support ledge or platform196extends outwardly from a side198of the second housing section172. Lower rod support apertures or depressions200(FIG. 12) are formed in the lower platform196for receiving and supporting guide members, shown by way of example as cylindrical guide rods or rails202and204.

The guide members202,204preferably extend between the lower platform196of the second housing section172and the mounting head148and are secured therebetween when the second housing section172is connected to the first housing section170during assembly, as described above. Upper rod support apertures or depressions206,208, as best shown inFIG. 20, are formed in the mounting head148for receiving the guide members202,204, respectively. The guide rods are preferably cylindrical in shape and are operable to guide linear movement of the actuator portion162during use. Although two guide rods are shown, it will be understood that a single guide rod, or more than two guide rods, may be provided without departing from the spirit and scope of the invention. Moreover, in accordance with a further embodiment of the invention, one or more guide rods or rails can be formed integrally with the housing150and/or the mounting head148. The guide rods can also be of any suitable cross sectional shape, such as T-shaped, L-shaped, oval, square, rectangular, triangular, dovetail-shaped, and so on.

Turning now toFIGS. 12 and 22-30, the actuator portion162preferably includes a generally cylindrical bearing body210with a front surface212, rear surface214, and a circular side surface216having the central or second pivot axis160(as previously described) extending between the front and rear surfaces. An annular guide groove or raceway218is formed in the side surface216and is shaped and sized for receiving the guide rods202,204(FIGS. 12 and 20) of the transducer140. The annular groove218functions as both a second pivot mount for the actuator portion162and the float rod166and float168and as a linear slide for linear movement of the actuator portion162along the guide rods202,204during movement of the float168and float rod166. Preferably, the annular groove218is formed proximal to the rear surface214and is coaxial with the second pivot axis160. An actuator bore220is formed in the rear surface214of the actuator portion162and extends into the body210coincident with the second pivot axis160.

As shown inFIG. 20, an actuator222is received in the actuator bore220and is fixed to the body210within the bore220so that the actuator222moves in a linear direction (denoted by arrows154inFIGS. 12-19) while rotating in a clockwise or counterclockwise direction (denoted by arrows158inFIGS. 12-19). When one or more sensors responsive to the presence of a magnetic field are used, such as one or more solid state magnetic flux field sensors, Hall effect sensors, magnetoresistive (MR) sensors, anisotropic MR (AMR) sensors, giant magnetoresistance (GMR) sensors, solid state Micro-Electro-Mechanical Systems (MEMS), magnetic switches such as reed switches, and so on, the actuator222is preferably in the form of a magnet with sufficient strength to create a difference in measurement in at least one of the afore-mentioned sensors during movement of the actuator portion162in response to changes in liquid level within the container.

Although the preferred embodiment utilizes a centrally-located and cylindrically-shaped magnet for the actuator222, it will be understood that the actuator may be offset from the second pivot axis160and may be of any shape or configuration without departing from the spirit and scope of the invention. Moreover, as mentioned earlier, other non-contact sensors and actuators can be used without departing from the spirit and scope of the invention, such as proximity detectors using capacitance, optical, or other measurement technologies, and so on.

The actuator portion162also includes a guide bore224formed in the body210that extends through the side surface216for receiving the proximal or connection end182of the float rod166so that the float can slide within the bore224of the actuator portion162and rotate therewith about the second pivot axis160during movement of the float, such as when the level of liquid within the container rises or falls. The guide bore224has a central axis226(FIGS. 25 and 30) oriented perpendicular to the second pivot axis160. The guide bore224is also axially offset from the annular guide groove218while extending through the center of the body210, as best shown in hidden line inFIG. 25. In this manner, sliding and pivotal movement of the proximal end182of the float rod166is centered at the second pivot axis160. A step228can formed in the front surface212of the actuator portion162for reducing the weight of the actuator portion.

It will be understood that the guide bore224may include linear guide bearings, low friction coatings, or the like to ensure smooth movement between the float rod166and the actuator portion162. Preferably, the actuator portion162is constructed of a single piece of material with bearing or lubricating properties, such as, but not limited to, nylon, acetal, Teflon™, brass, and so on, in order to ensure smooth angular and linear sliding movement of the actuator portion162with respect to the guide rods202and204, as well as smooth sliding movement with respect to the float rod166. It will be further understood that where the guide rods and/or the float rod have a particular cross-section, the guide groove218and/or guide bore224can also be complementary in cross sectional shape or of a cross sectional shape that would be suitable for relative angular and/or linear movement of the components. Thus, a wide variety of different guide rod, float rod, and guide groove and guide bore configurations are within the purview of the present invention.

Referring toFIGS. 12 and 20, the mounting head148is similar in construction to the mounting head148previously described, and includes a mounting flange230integrally formed with the first housing section170and extending radially outwardly therefrom. The mounting head148is preferably formed as a unitary structure with the first housing section170through injection molding, but may alternatively be formed by machining, die-casting, or other known forming means. The mounting flange230is preferably disk-shaped and includes a plurality of mounting holes232that extend axially through the mounting flange and in proximity to its outer peripheral edge234. The mounting holes232are adapted to receive threaded studs (not shown) associated with a tank or other container in a well-known manner. A cover or cap236has an internal tabs235for mating with an annular groove (not shown) formed in the side wall (not shown) of the mounting head148in a snap-fit engagement to retain the cap236on the mounting head148and enclose the hollow interior of the first housing section170, as previously described with respect to the mounting head14(FIG. 7). An annular gasket238(FIGS. 12 and 17-19) can be provided between the mounting flange230and the wall142of the container144for sealing the opening146(FIGS. 17-19) in the container through which the transducer140extends. Alternating ribs240and depressions242are formed in the bottom of the mounting head to reduce the weight and material costs, while maintaining sufficient strength and rigidity of the mounting head148.

It will be understood that the mounting head148is not limited to a flange mounting arrangement as shown, other means for mounting the liquid level transducer140to a tank or other container can be used, including NPT type threads, clamping, welding, and so on, without departing from the spirit and scope of the invention.

The head148and housing sections170,172are preferably constructed of a molded material, such as plastic, through injection molding or other techniques. However it will be understood that the mounting head148and/or the housing sections170and172, are not limited to plastic material, but may be constructed of metal, composites, ceramics, combinations thereof; or any other suitable nonmagnetic material. Moreover, although the first housing section170and second housing section172of the housing150are shown as separate units, they can be integrally formed.

Referring now toFIGS. 31-33, a liquid level transducer250in accordance with yet another embodiment of the invention is illustrated. The transducer250is substantially similar to the transducer140previously described, with the exception that the actuator portion162of the previous embodiment is replaced with an actuator portion250that functions in a similar manner. As illustrated inFIG. 31, the transducer250is oriented for mounting in a horizontal position, e.g. on a vertical wall of a container, tank or the like. Likewise inFIG. 32, the transducer250is oriented for mounting in a vertical position, e.g. on a horizontal wall of a container, tank or the like. Accordingly, it will be understood that the present invention is readily adaptable to any orientation where movement of the float can occur in response to a change in liquid level within the container.

With particular reference toFIG. 33, the actuator portion252preferably includes a generally cylindrical bearing body254with an annular wall256and an annular flange258extending radially outwardly from and around the periphery of the annular wall256. A central opening260is formed by the annular wall256and extends through the body254. The annular wall256forms a central axis266, similar to the second axis of the previous embodiment, about which the actuator portion252will rotate during movement of the float168and float rod166(FIGS. 31 and 32). An actuator retainer262also includes an annular wall264with a central opening268for receiving an actuator270, such as a magnet or the like, as previously described. The retainer262also includes an annular stop flange272that extends radially outwardly from and around the periphery of the annular wall256. Holes274and276extend through the annular wall in a direction perpendicular to a central axis280of the annular wall264. The holes274and276are configured for slidably receiving the proximal or connection end182of the float rod166.

When assembled, the actuator270is fixedly connected within the bore268of the retainer262and the annular wall264of the retainer is received through the opening260of the bearing body254. The annular flange272rests against the annular flange258and can be fixedly secured thereto. During assembly of the transducer250, the actuator portion252is first placed on the sensor side wall175of the sensor housing156, then the rods202and204are installed and secured in place, thereby trapping the flange258between the rods and the side wall of the housing. In this position, the annular wall256is located between and contacts the inner surfaces of the rods202and204during rotational and linear sliding movement in response to arcuate and sliding movement of the float rod and float, such as when the level of liquid in the container increases or decreases. The annular side wall256therefore functions as both a second pivot mount for the actuator portion252and the float rod166and float168and as a linear slide for linear movement of the actuator portion252along the guide rods202,204during movement of the float168and float rod166.

From the above-described configurations, it can be seen that various configurations can be implemented for achieving linear movement of the actuator in response to pivotal movement of the float, thereby increasing the travel distance of the actuator with respect to one or more sensors within the housing, over prior art solutions where the float and actuator move only along arcuate pathways. Accordingly, the present invention advantageously increases the size of the measurement area and the number of sensors and/or distance over which the sensor(s) can detect movement of the actuator, thereby increasing liquid level measurement accuracy while minimizing the size of the liquid level transducer.

It will be understood that the term “preferably” as used throughout the specification refers to one or more exemplary embodiments of the invention and therefore is not to be interpreted in any limiting sense. It will be further understood that the term “connect” and its derivatives refers to two or more parts capable of being attached together either directly or indirectly through one or more intermediate members. In addition, terms of orientation and/or position as may be used throughout the specification denote relative, rather than absolute orientations and/or positions.

It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof.

By way of example, the first and second pivot mounts can be located on the first housing section rather than divided between the first and second housing sections. Moreover, as previously described, the second housing section can be eliminated and the structure and components of the liquid level transducer can be formed and installed on the first housing structure and/or the mounting head. In addition, the guide rods or rails can be located along the top, bottom, or any side or position and at various angles with respect to a direction the housing extends or is suspended in from the mounting flange. If the housing is circular or cylindrical in shape, the guide rods can be mounted at any location along the periphery or bottom of the housing. The guide rods may be retained by blind holes in the housing and end cap or may be retained by staking, push-nuts or other hardware for connecting the guide rods to the housing and and/or mounting head. Moreover, the guide members can be of any suitable cross sectional shape and formed separately from the housing as shown, or can be integrally formed with the housing. In addition, the guide members can be one or more integral tracks or slots formed in the housing with complementary structure on the actuator portion for sliding along the tracks or slots. The guide members Single guide members . . . can be integrally formed as round, Rails can be round rods or other shaped separate parts, single or multiple rails can be used.

In addition, the actuator portion can slide or rotate between, behind, in front of, and/or to the side of the guide members. The actuator portion may be of one-piece construction as in the second embodiment or in multiple parts as in the first and third embodiments. The actuator portion can also vary in size and shape, can partially or fully enclose the guide members or rods. The actuator portion can also be in the form of a wheel-shaped member or a double wheel-shaped member that encompasses opposite sides of the guide rods.

Moreover, the actuator, when embodied as a magnet, can be constructed of various materials, including ferrite, alnico, Samarian Cobalt or other magnetic material that is capable of generating a magnetic field, whether permanent or temporary. The magnet can be of various shapes and sizes, including cylindrical, disk, cube, rectangular, triangular, and so on. The magnet can also be positioned at various offsets to adjust the distance from the reed switches and/or other magnetic field sensors that may be required travel to actuate the sensor(s). The actuator may be retained in the actuator portion by push-nuts, staking, or rolling over material from the actuator body. The actuator can alternatively be insert-molded into the body of the actuator portion or epoxied into position for retention and protection from harmful liquids such as fuels that may be located within the container. The actuator can also be inserted from various directions and oriented at various positions to maximize the magnetic field towards the one or more sensors.

The body of the actuator portion can rotate about an axis perpendicular to the rails, and thus the PCB, as shown in the second and third embodiments, or can rotate about an axis parallel to the rails. The actuator portion can include an extension to allow the connection end of the float rod to be shorter. The actuator portion can also be counterbored to ensure the end of the float rod or rod extension slides freely through the body of the actuator portion. The float rod can also extend part way or completely through the guide bore of the actuator portion and can be constructed of any suitable configuration to ensure free pivoting and sliding movement throughout the range of empty to full conditions of the container. The actuator portion can also be integrally constructed with the actuator portion, such as through insert-molding or the like

Furthermore, the hollow interior of the first housing section can be oriented horizontally, vertically, or at any other suitable angle to fit within the confines of the container and any surrounding structure associated with the vehicle or machine on which the container is mounted. The hollow interior can also include features to either center or offset the PCB with respect to the hollow interior to thereby accommodate the position or changing positions of the actuator. The hollow interior can also contain insulating fluid or potting material to protect the PCB and its associated sensors and other electronic components. Strain relief for the electrical wires can be provided by pins or bosses formed integrally with the hollow interior of the housing, or by separate hardware or wire wrapping or potting material. The end cap and housing can also be configured for aligning and retaining the end cap thereon through the use of one or more bosses that accept push-nuts, screws, and/or other retaining hardware.

It will be understood, therefore, that the invention is not limited to the particular embodiments disclosed, but is intended to cover all modifications and variations within the spirit and scope of the present invention as defined by the appended claims.