GB2374669A

GB2374669A - Float type liquid level sensing mechanism

Info

Publication number: GB2374669A
Application number: GB0109582A
Authority: GB
Inventors: Roy David Tyler; Bernard Catherall; Colin Edward Mack; John Clinton Hall; James Richard Norton; Robert John Byrne
Original assignee: Visteon Global Technologies Inc
Current assignee: Visteon Global Technologies Inc
Priority date: 2001-04-19
Filing date: 2001-04-19
Publication date: 2002-10-23
Also published as: GB0109582D0

Abstract

It is particularly but not exclusively intended for sensing the fuel level in a vehicle fuel tank. The arrangement of the mechanism allows it to work within a relatively confined space in a tank by varying the distance between the float (28) and the pivot point (16) of the float arm (18) as the float (28) rises and falls. The float arm (18) is made in two parts (24, 26) and (19). One part (19) is fixed in a pivot bearing (16) and the second part (24, 26) is slidable relative to the first part (19). Part (24, 26) has a follower (30) which engages in a track (20) mounted in a fixed position relative to the pivot (16). The radial distance of the track (20) from the pivot (16) varies at different arcuate positions around the pivot (16). Arcuate movement of the float arm (18) results in movement of the follower (30) along the track (20) which in turn results in relative sliding movement between the first part (19) and the second part (24, 26), thereby varying the distance between the float (28) and the pivot point (16). The float arm (18) moves relative to a resistor card (22), the instantaneous resistance being used to signal the liquid level in the tank. Further embodiments include a mechanism having a straight float arm and non-linear track paths.

Description

A LIQUID LEVEL SENSING MECHANISM This invention relates to a liquid level sensing mechanism, to be mounted within a liquid container, to sense the level of liquid in the container. Such a mechanism is particularly (but not exclusively) intended for sensing fuel level in a motor vehicle fuel tank.

Conventional fuel level senders have a main body mounted at a fixed position within the fuel tank, and a float arm which is pivoted on the body. An electrical wiper contact carried by the arm moves over an electrical resistance track supported on the body, so that as the fuel level varies and the float moves up and down in accordance with the fuel level, a corresponding liquid level signal is produced from the electrical components, indicative of the liquid level.

For maximum sensitivity and accuracy, it is desirable that the float arm should be as long as possible. The arm must also be long enough to reach the liquid surface when the tank is filled to its maximum level, and to reach the floor of the tank. In modern vehicles, the fuel tank is often moulded from plastics materials and is of an irregular shape to fit in with other vehicle components. This can make it difficult to design a mechanism where the float arm is long enough to perform its proper functions.

According to the invention, there is provided a liquid level sensing mechanism comprising a body to be mounted within a liquid container, a float arm having a buoyant float at one end and being mounted at the other end for pivoting movement relative to a pivot point on the body so that the float will float on the surface of liquid in the container and cause the rod to pivot about the pivot point

when the level of liquid in the container changes, wherein the float arm has two mutually telescopic parts which can retract and extend to vary the distance between the pivot point and the float, and wherein the body carries a track, the distance of which from the pivot point varies with angular position relative to the pivot point, one part of the rod being pivotally mounted to the body, and the other part of the rod having a track follower which engages with the track so that as the rod pivots about the pivot point, the engagement of the follower in the track results in telescopic movement of the parts to vary the distance between the float and the pivot point.

The use of a two-part rod, together with a track and follower which enables the length of the rod to change as it rises and falls with the liquid level, allows the sensor mechanism to be designed to work within a relatively confined space in a tank.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic view of a sensing mechanism in accordance with the invention, in position in a motor vehicle fuel tank; Figure 2 is an enlarged view of the mechanism of Figure 1; and Figures 3 and 4 show alternative embodiments of the mechanism.

Figure 1 shows part of a motor vehicle fuel tank 10. In the drawing, only one half of the tank 10 is shown. The

tank could for example be a so-called saddle tank, which has two chambers, one either side of a central vehicle underbody region through which a transmission shaft and/or an exhaust pipe can pass. As a result of this tank configuration, the space within each half of the tank is relatively restricted (when compared with a single chamber tank).

Within the tank 10 is a structure 12 which supports a body 14 of the level sensing mechanism. The structure 12 can house a fuel pump and/or a fuel filter and possibly other components required for the passage of fuel between the vehicle engine and the fuel tank.

The body 14 defines a pivot point 16 at which a float arm 18 is supported. The float arm comprises a base component 19, and a rod 21. A track 20 runs alongside the pivot point 16. An electrical resistance track 22 is mounted on the body and a wiper contact (not shown) carried on the arm 18 moves over the track 22 as the arm rotates about the pivot point 16 to vary the resistance in an electrical circuit of which the resistance 22 forms a part.

Figure 2 shows this in more detail. In this figure, the float arm 18 is shown in three different positions, indicated by 18a, 18b and 18c.

The arm has an inner portion 24 and an outer portion 26, at the outer end of which is a float 28. The inner and outer portions are cranked at approximately 900 to one another. At the outer end of the inner portion 24 is a follower 30 which runs in the track 20. The track 20 is (in Figures 1 and 2) a straight track, the distance of which from the pivot point 16 is not constant around an arc centred on the point 16.

The angular position of the float 28 varies with the liquid level in the tank. As the float rises and falls, the float arm 18 rotates about the pivot 16. As the arm rotates, the follower 30 is constrained to move along the track 20, and this causes the inner portion 24 of the float arm to slide within the base portion 19, to shorten the length of the rod between the pivot point and the track. As a result, the arc through which the float moves is no longer an arc centred at the pivot point 16, but is a modified arc, as shown at 32 in Figure 2.

In Figure 2, 18a shows the float arm near to its lowest position, representing a nearly empty tank. 18b shows the rod in a raised position, close to its maximum level. 18c shows the position which the rod would take up when raised, without the variable length feature of the present invention. It will be seen that the length variation provided by the present invention, together with the cranked form of the rod, results in the rod being able to sense liquid levels which are higher by the distance'h' than would be the case without the features of the invention.

The modified arc also has the effect that the float 28 does not need so much room to the right of the pivot as would be the case if the length of the float arm was constant. The mechanism can thus be used in a smaller tank and/or can be mounted closer to a tank wall than was previously possible.

The configuration of the track can be designed in accordance with the particular requirements, in particular the internal shape of a fuel tank. Figures 3 and 4 show two alternative track forms which will produce different

arcs of movement of the float 28. In Figure 3, the major part of the track 20a is straight, with a tight curve 34 at the upper end which will bring the float closer to the pivot at the upper extreme of float arm movement.

Figure 4 shows a track with a sinusoidal profile which might be required to make the float move along a path as close as possible to an irregular tank wall.

In the drawings, the arm 24,26 is shown with a cranked configuration. A cranked configuration is not essential, and the invention is applicable to straight rods, curved rods or rods of other configurations.

Claims

Claims 1. A liquid level sensing mechanism comprising a body to be mounted within a liquid container, a float arm having a buoyant float at one end and being mounted at the other end for pivoting movement relative to a pivot point on the body so that the float will float on the surface of liquid in the container and cause the rod to pivot about the pivot point when the level of liquid in the container changes, wherein the float arm has a first part mounted at the pivot point and a second part connected to the float with the second part being slidable relative to the first part to vary the distance between the pivot point and the float, and wherein the body carries a track, the distance of which from the pivot point varies with angular position relative to the pivot point, and the second part of the rod having a track follower which engages with the track so that as the rod pivots about the pivot point, the engagement of the follower in the track results in sliding movement of the second part relative to the first part to vary the distance between the float and the pivot point.
2. A mechanism as claimed in Claim 1, wherein the float arm is straight.
3. A mechanism as claimed in Claim 1, wherein the second part of the float arm, which engages with the track, is bent between the track follower and the float.
4. A mechanism as claimed in any preceding claim, adapted to sense fuel level in a motor vehicle fuel tank.
5. A mechanism as claimed in any preceding claim,

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wherein the first part of the arm is a plastic moulding mounted for pivoting movement on the body, and the second part of the arm is a rod which is retained in the first part and is slidable therethrough.
6. A liquid level sensing mechanism substantially as herein described with reference to any one embodiment shown in the accompanying drawings.