GB2191864A

GB2191864A - A device for detecting the level of fuel in a motor vehicle fuel tank

Info

Publication number: GB2191864A
Application number: GB08713410A
Authority: GB
Inventors: Rodolfo Bitetti
Original assignee: Veglia Borletti SRL
Current assignee: Veglia Borletti SRL
Priority date: 1986-06-20
Filing date: 1987-06-09
Publication date: 1987-12-23
Anticipated expiration: 2007-06-09
Also published as: AR240967A1; IT207817Z2; FR2600414B3; MX171251B; IT8653557V0; YU47265B; DE3719555A1; FR2600414A1; ES1002688Y; GB2191864B; GB8713410D0; BR8703503A; YU113587A; AR240967A2; ES1002688U

Description

1 GB2191864A 1

SPECIFICATION

A device for detecting the level of fuel in a motor vehicle fuel tank The present invention relates to a device for detecting the level of fuel in a vehicle fuel tank, of the type comprising a float mounted slidably on a tubular guide element.

In known devices of the type briefly de- 75 scribed the guide element carries a resistor, for example a wire coil, on which slides a contact element fixed to the float. The guide element is normally carried by a flange which can be connected to a wall of the tank, to which a sleeve extending integrally downwardly from the flange itself is fixedly fitted.

The sleeve is usually a hollow cylindrical element having a thickness comparable with the thickness of the flange.

In the case of strong impacts with predominantly transverse loads on the guide element, the high rigidity of the sleeve resists its breakage; the load is transmitted to a portion of the flange adjacent the sleeve itself causing breakage of this with the consequent possibility of the escape of fuel from the tank.

The problem is even more evident in the case in which the guide element also serves as an inlet duct for fuel, and the sleeve passes through it extending from both sides of the flange. If a terminal portion of the guide element, forced within the sleeve, passes the plane of the flange, it directly transfers any transverse forces onto the flange itself.

The object of the present invention is that of providing a device for detecting the level of fuel in a motor vehicle fuel tank which will be free from the disadvantages associated with the known devices specified above.

The said object is achieved by the present invention in that it relates to a device for detecting the level of fuel in a motor vehicle fuel tank, of the type comprising:

a flange for connection of the said device to 110 a wall of the said tank; a guide element fixed to the said flange, provided with a resistor; and a float slidable along the said guide element and provided with a contact element sliding 115 along the said resistor; characterised by the fact that the said guide element is fixed to the said flange by means of a frangible connection which breaks under a pre-established load.

For a better understanding of the present invention a preferred embodiment is described hereinbelow purely by way of non-limitative example and with reference to the attached drawing, in which:

Figure 1 is a partially sectioned side view of a device formed according to the present invention; and Figure 2 is a side view of a detail of Fig. 1 on an enlarged scale and in section.

With particular reference to Fig. 1, the reference numeral 1 generally indicates a device for detecting the level of fuel in a tank.

The device 1 is of the type comprising a flange 2 which can be connected to a wall of the said tank; a tubular guide element 3 provided with a wire coil resistor 4 fixed to the said flange 2; and a float 6 which can be displaced by the hydrostatic thrust of the fuel, slidable along the guide element 3 and provided with electrical contact elements 7 sliding on the resistor 4.

In more detail, the guide element 3 is constituted by a conductive tube 8 the upper end 9 of which is fitted into a cylindrical sleeve 10 extending downwardly from the flange 2; with the exception of its upper end 9 and lower end 11 the conductive tube 8 is clad in a layer of insulating material 12 on which the said resistor 4 is wound.

The flange 2 supports a set of three electrical connectors 13, 14, 15 respectively, the opposite end portions of which extend out from the body of the flange 2. In detail, the connector 13 is connected, by a conductive blade 16, to a certain number of turns of the resistor 4 close to the end portion 9 of the guide element 3. On the other hand, the connector 14 is connected, by means of a con- ductive element 17 wound in a spiral around the guide element 3, to the contact element 7 of the float 6. Finally, a connector 15 is connected by means of an associated conductive blade 18 to the end 9 of the conductive tube 8 of the guide element 3. The connectors 13, 14, 15 can be connected, in use, to a terminal of an indicator instrument, to earth, and to a terminal of a warning lamp (not illustrated) respectively.

The mechanical connection between the flange 2 and the said tank is achieved by means of an internally threaded ring nut 19 which is screwed onto an externally threaded projecting rim 20 of a circular aperture 21 of the said tank and clamps the peripheral portion 22 of the flange 2 onto the upper surface 23 of the said rim with the interposition of an annular sealing washer 24.

The device 1 further includes a containment body 25 having a bottom wall 26 and a cylindrical side wall 27, in which the guide element 3 and the float 6 are contained. The bottom wall 26 has a through hole (not shown) which permits the ingress of fuel into the contain- ment body 25. The bottom wall 26 is further provided with an annular conductive element 28 electrically connected to the lower end of the conductive tube 8, on one end of which is fixed a conductive coil spring 29. The cylindri- cal wall 27 is fitted at the top into an annular seat 30 of the flange 2.

With reference to Fig. 2, the sleeve 10 is, according to the present invention, dimensioned in such a way as to constitute a frangi- ble coupling; in the case of strong transverse 2 GB2191864A forces on the device 1 and therefore on the guide element 3, the sleeve 10 breaks close to the connecting portion 31 leaving the flange 2 whole; to ensure that this takes place the characteristic dimensional ratios between the critical sections must be respected.

For example, for a sleeve of moulded plastics material in which a=7-8 millimetres and d>2.5 millimetres, the pedetermined breakage condition is obtained with b=9-10.5 millimetres and c= 12-15 millimetres.

The functional behaviour of the device is substantially known. The wire coil resistor 4 is used as a rheostat having a fixed terminal connected to an indicator instrument and a cursor slidable in dependence on the level of fuel and connected to earth by means of the conductive element 17. Consequently the variation of the fuel level involves a variation of resistance in series with the indicator instrument and therefore of the current measured by the instrument itself.

When the float 6 reaches a position close to the bottom wall 26 the contact element 7 establishes an electrical contact with the conductive spring 29 and, by means of the element 28, with the conductive tube 8 which is in turn connected to the connector 15 and the warning lamp. Consequently the warning lamp is activated when the float 3 reaches a minimum position.

From a study of the characteristics of the device formed according to the present invention the advantages which it allows to be ob- tained are evident. In particular the possibility of escape of fuel from the tank by breakage of the flange connecting the fuel level detector device, in the event of strong transverse forces on the device, is avoided Finally, it is clear that the device 1 de- 105 scribed above can have modifications and vari ations introduced thereto without by this de parting from the protective ambit of the pre sent invention. In particular the sleeve can have a circumferential groove close to the connecting portion 31, or else one or more longitudinal slots for the purpose of creating weakened sections for preferential initiation of the breakage of the sleeve itself. Moreover, the attachment of the device to the tank can be of any type, for example by bayonet coupling. Finally, the guide element 3 can also function as a fuel inlet duct.

Claims

1. A device for detecting the level of fuel in a motor vehicle fuel tank, of the type comprising:

a flange for connecting the said device to a wall of the said tank; a guide element fixed to the said flange and provided with a resistor; and a float slidable along the said guide element and provided with a contact element sliding along the said resistor; characterised by the fact that the said guide element is fixed to the said flange by means of a frangible connection.

2. A device according to Claim 1, charac- terised by the fact that the said frangible connection is constituted by a tubular sleeve extending integrally from the said flange, into the interior of which the said guide element is inserted under pressure; a portion of the said sleeve connected to the said flange being dimensioned to withstand a maximum transverse load less than the transverse load which causes breakage of the said flange.

3. A device according to Claim 2, charac- terised by the fact that the said flange and the said sleeve are made of plastics material, the said flange having a thickness not less than 2.5 millimetres; and the said sleeve having an internal diameter lying between 7 and 8 millimetres, an external diameter lying between 9 and 10. 5 millimetres, and an axial length lying between 12 and 15 millimetres.

4. A device according to any preceding Claim, characterised by the fact that the said flange is connected to the said fuel tank by means of a threaded nut.

5. A device according to any of Claims from 1 to 3, characterised by the fact that the said flange is connected to the said tank by means of a bayonet coupling.

6. A device according to any preceding Claim, characterised by the fact that the said guide element is tubular and functions as a fuel inlet tube.

7. A device according to any preceding Claim, characterised by the fact that the said sleeve has an outer circumferential groove close to the said portion fitting into the said flange.

8. A device according to any preceding Claim, characterised by the fact that the said sleeve includes at least one longitudinal slot.

9. A device for detecting the level of fuel in a vehicle fuel tank substantially as described with reference to the attached drawing.

Printed for Her Majesty's Stationery Office by Burgess & Son (Abingdon) Ltd, Dd 8991685, 1987. Published at The Patent Office, 25 Southampton Buildings, London, WC2A l AY, from which copies may be obtained.