GB2270759A - A fuel level sender assembly - Google Patents

Abstract

A fuel level sender assembly for a vehicle comprises a housing 30 in which a resistor card 28 (e.g. a printed ceramic card) is inserted. A moving contact 34 is connected to a float arm 22 and moves over a track 38 on the card 28 to provide an indication of fuel level. The card 28 is assembled in the housing 30 by sliding it in through a slot 44 at one end of the housing and is thus inserted in a direction which minimises the risk of breaking the card. <IMAGE>

Description

A FUEL SENDER ASSEMBLY This invention relates to a fuel sender assembly for indicating the fuel level in the fuel tank of a motor vehicle.

Fuel sender assemblies are known in which an electrical contact mounted on a float arm moves over a resistor card to produce an electrical signal representative of fuel level in a fuel tank. As the float arm moves up and down, the position of the electrical contact on the resistor card changes so that the resistance in an electrical circuit changes. The resistance in the circuit at any particular time is indicative of the position of the float arm and thus of the level of the fuel.

The resistor cards in such assemblies are conventionally made of a ceramic material on which a resistor track is printed. The card is mounted in a housing and the float arm with its electrical contact moves relative to the housing.

The card must be held accurately in position in the housing and should be capable of being assembled in the housing without risk of breakage. Ceramic resistor cards are particularly brittle and liable to breakage if handled incorrectly.

According to the present invention, there is provided a fuel sender assembly in which an electrical contact mounted on a float arm moves over a resistor card to produce an electrical signal representative of fuel level in a fuel tank, wherein the resistor card is supported in a housing which has location features for locating the 'card in'the housing and a card insertion guide arranged to allow insertion of the card into the housing with the ,card insertion movement being in a plane substantially.-parallel to the plane in which the card will be supported.

By allowing insertion of the card by a sliding movement, the card is not stressed in a way which might cause it to break.

The housing can have a guide track for receiving the card of a depth slightly greater than the thickness of the card, with the bottom face of the track including springs which urge the card against abutments forming the top edge of the track.

The track can have fixed side walls and an end wall which limit movement of the card, and a resilient latch can retain the other end of the card when the card has been fully inserted in position.

The housing, which may be a plastics moulding for example made from acetal, may support the float arm for pivoting movement. The housing with the float arm attached and with the resistor card inserted can then be a sub-assembly which can be supported on a suitable mounting in the tank.

Electrical connections have to be made to the card. These connections can be made by conventional edge connectors, and the housing may incorporate wedge formations located alongside the guide track for the card so that the wedge formations serve to spread open the jaws of an edge connector before the connector encounters the edge of the card. The housing may also include a stop abutment which prevent inadvertent withdrawal of the edge connector from the card.

The invention will now be further described, by way of example, with reference to the accompanying drawing's, in which: Figure 1 is a general view of a fuel tank incorporating a fuel sender assembly in accordance with the invention; Figure 2 is an exploded view of a fuel sender assembly in accordance with the invention; Figure 3 is a detail of parts of the assembly of Figure 2, on a larger scale; Figure 4 is a section through a complete fuel sender assembly, taken on the lines IV-IV from Figure 3; and Figure 5 is another section through a completed assembly on the'lines V-V from Figure 2.

Figure 1 shows a fuel tank 10 which houses an in-tank fuel pump 12 (shown schematically) which pumps fuel out of the tank via a fuel line 14. The pipe 14 and the pump 12 are supported on a tank closure plate 16, and a sender support bracket 18 is also secured to the plate 16 and extends into the tank. A fuel sender assembly generally designated 20 is mounted on the support plate 18 and includes a float arm 22 with a float 24. In Figure 1 the fuel level is indicated at 26 and it will be seen that the float 24 floats on the surface of the fuel. An alternative float arm position 22a is also shown, in dotted lines when the fuel level 26a is near to the top of the tank.

Figure 2 shows the various components of the sender assembly 20. A resistor card 28 is fitted in a housing 30. The float arm 22 is connected to a yoke 32 which carries a moving contact 34. A fixed contact 36 is fitted on the housing 30.

The resistor card 28 has a resistor track 38 and two terminals 40, 42.

The housing 30 has a guide track for the card 28, and this card comprises an entry slot 44, height control lugs 45, 46, 48, side walls 50 and 52 and an end wall 54. The base of the guide track is formed by a floor 56 which, as can be seen particularly in Figure 5, is largely provided by two opposed resilient tongues 58, 60 which bear against the underside of the card 28 and press the card up against the height control lugs 46, 48.

On assembly, the card 28 is introduced to the slot 44 in the direction indicated by an arrow 62 (Figure 3). The leading edge of the card is guided'below the height control lugs 45 and rides along a cam surface 64 pn the tongue 58. This causes the tongue 58 to be forced downwards whilst the card passes. The card is pushed fully into the housing 30, depressing the tongue 60 by passing over the cam surface 66, until the card abuts the end face 54. At this point the trailing end of the card will have passed over the cam surface 64 and a steeper cam surface 68 on the tongue 58 will engage behind the card and tend. to urge it into permanent contact with the end wall 54.At the same time the engagement between the cam surface 68 and the card 28 will lift the card into contact with the height limiting lugs 46, and the cam surface 66 of the tongue 60 will lift the card into contact with the lugs 48.

In this way the final position of the card will be accurately determined which can avoid the need for calibration subsequent to assembly.

It will be noted that the insertion slot 44 has tapered entry walls at 70 so that the card is properly centred on entry through the slot.

Because the card is assembled by a longitudinal sliding movement it is not necessary for there to be any contact between an assembly operator's hand or any assembly tool and the resistor track 38 on the upper surface of the card.

Such contact could result in soiling and/or damage to the resistor track surface. The card can be assembled into the housing completely automatically, merely by providing a component to push against the trailing edge of the card, and this avoids any need to contact the resistor track surface.

The housing 30 is preferably an acetal moulding; acetal being a material which is particularly stable in contact with motor vehicle fuel. The housing includes a journal 72 in which an end part 74 of the rod 22 is inserted, to function as an axle for the pivotal movement of the rod.

However before assembly of the rod 22 to the housing, the moving contact 34 is clipped into the yoke 32, the fixed contact 36 is placed over the top of the journal 72 and the yoke is fitted over the journal so that the contact tip 76 of the moving contact 34 makes contact with the resistor track 38 on the card 28. At the same time the inner part of the moving contact 34 makes sliding/rotational contact with the fixed contact 36 to provide a conductive path. To secure the components together, the end part 74 of the float arm 22 is passed through apertures 78 which are provided on the yoke 32, on the sliding contact 34, on the moving contact 36 and on the journal 72. The arm 22 is then held in place by clipping a straight section 80 of the arm into retaining clips 82 on the yoke 32.

Because of the sliding movement of the card 28 into the housing 30, it is not possible to pre-solder electrical conductors to the terminals 40, 42. Instead the appropriate conductors 84 are connected to the terminals 40, 42 once the card 28 is in position in the housing. Figure 4 shows a conductor 84 with an edge connector 86 fastened to its end.

The connector 86 has two jaws 88, 90 which have to be spread apart to pass over the edge of the card 28. To avoid the connector damaging the edge of the card, the jaws 88, 90 are opened by passing them either side of a wedge-shaped rib 92 which is part of the housing moulding 30. The thickness of the right hand end of the wedge 92 (as viewed in Figure 4) should be substantially equal to the thickness of the card 28, so that the jaws can be opened to the required extent before they encounter the card. The upper jaw 88 will then make contact with the terminal 42 which is printed on the upper surface of the card 28.

To prevent accidental detachment of the connector 86, the connector has a resilient tang 94 which engages behind a wall 96 of the housing 30 on complete insertion of the conductor.

There will normally be two conductors 84 connected to the assembly, one connected to the terminal 40 and the other to the terminal 42. These conductors (wires) can be clipped into a retaining feature 98 before being guided out of the tank through an aperture in the tank closure plate 16.

The sender assembly described here allows the relatively fragile resistor card 28 to be secured in the assembly with very little risk of damaging it or of interfering with the conductive surface of the track 38.

Claims (9)

Claims

1. A fuel sender assembly in which an electrical contact mounted on a float arm moves over a resistor card to produce an electrical signal representative of fuel level in a fuel tank, wherein the resistor card is supported in a housing which has location features for locating the card in the housing and a card insertion guide arranged to allow insertion of the card into the housing with the card insertion movement being in a plane substantially parallel to the plane in which the card will be supported.

2. A fuel sender assembly as claimed in Claim 1, wherein the housing has a guide track for receiving the card of a depth slightly greater than the thickness of the card, with the bottom face of the track including springs which urge the card against abutments forming the top edge of the track.

3. A fuel sender assembly as claimed in Claim 2, wherein the track has fixed side walls and an end wall which limit movement of the card, and a resilient latch which retains the other end of the card when the card has been fully inserted in position.

4. A fuel sender assembly as claimed in any preceding claim, wherein the housing is a plastics moulding.

5. A fuel sender assembly as claimed in ssny preceding claim, wherein the housing supports the float arm for pivoting movement.

6. A fuel sender assembly as claimed in any preceding claim, wherein the housing with the float arm attached and with the resistor card inserted is a sub-assembly which can be supported on a suitable mounting in a fuel tank.

7. A fuel sender assembly as claimed in any preceding claim, wherein electrical connections are made to the card by conventional edge connectors, and the housing incorporates wedge formations located alongside the guide track for the card with the wedge formations ar-ranged to spread open the jaws of an edge connector which is introduced into the housing before the connector encounters the edge of the card.

8. A fuel sender assembly as claimed in any preceding claim, wherein electrical connections are made to the card by conventional edge connectors, and the housing and the edge connectors include a stop abutment to prevent inadvertent withdrawal of the edge connector from the card.

9. A fuel sender assembly substantially as herein described with reference to the accompanying drawings.