GB2191297A

GB2191297A - A device for detecting the level of a liquid in a tank

Info

Publication number: GB2191297A
Application number: GB08712714A
Authority: GB
Inventors: Rodolfo Bitetti
Original assignee: Veglia Borletti SRL
Current assignee: Veglia Borletti SRL
Priority date: 1986-05-30
Filing date: 1987-05-29
Publication date: 1987-12-09
Anticipated expiration: 2007-05-29
Also published as: BR8703245A; ES2005884A6; FR2599497A1; PL265975A1; YU47264B; YU96787A; DE3718199C2; AR240504A1; IT8667452A0; IT1203567B; PL155531B1; DE3718199A1; GB8712714D0; FR2599497B1; GB2191297B

Description

GB2191297A 1 SPECIFICATION wall of the said tank; - a float which can be

displaced by the said A device for detecting the level of a liquid liquid and carrying an electrical contact ele in a tank ment; 70 - a guide for the said float supporting a The present invention relates to a device for resistor on which, under the hydrostatic thrust detecting the level of a liquid in a tank and, exerted by the said liquid, said contact ele particularly, to a device for detecting the level ment carried by the said float slides in use; of fuel in a vehicle tank. - characterised by the fact that it comprises:

The device formed according to the present 75 - a cup-shape body having an end wall and invention is of the type comprising a flange a substantially cylindrical side wall defining a which can be fixed to a wall of the tank, a chamber in which the said float and the said float which can be displaced by the liquid con- guide are contained; the said end wall sup tained in the tank and carrying an electrical porting a lower end of the said guide and contact element which slides, in use, on a 80 having at least one through hole operable to resistor wound on a float guide element and put the said chamber into communication with supported by the said flange. The float and the interior of the said tank, the said side wall the associated guide are enclosed within a being able to translate perpendicularly with re chamber externally delimited by a cylindrical spect to an end wall of the said flange be tube which is mounted coaxially around the 85 tween a first and a second position in such a guide and fixed at its opposite ends respec- way that the distance between the end walls tively by the said flange and by a disc having of the said cup shape body and of the said a through hole and convieniently fixed to the flange can vary, Cespectively, between a first guide itself. In use, the measurement of the value and a second value greater than the said liquid present in the tank is achieved by taking 90 first value; and account of the position assumed by the float - resilient means substantially interposed be with respect to the above mentioned guide; tween the said cup-shape body and the said since this latter is fixed, by means of the re- flange and operable to exert an elastic thrust spective flange, to the upper wall of the tank, tending to make the said cup-shape body it is obvious that the measurement of the level 95 translate from the said first position towards of the liquid is referred to the upper wall of the said second position.

the said tank. For a better understanding of the present Devices of the above described type are invention a preferred embodiment is described preferred to other indicator devices since, as in the following purely by way of non-limita well as the advantage of eliminating oscilla- 100 tive example and with reference to the at tions of the float, and therefore of the index tached drawings, in which:

of the instrument connected to the resistor, Figure 1 is a view in section and in eleva they also offer the advantage of a more pre- tion of a device formed according to the pre cise indication of the level of the liquid as a sent invention; consequence of the extent of the resistor (in 105 Figure 2 is a sectional view taken on the general, resistive wire) over the whole longitu- line 11-11 of Fig. 1 with some parts removed for dinal extent of the guide and therefore essen- clarity; and tially over the whole of the height of the tank. Figure 3 illustrates, in schematic form on a A large part of this latter advantage is lost, reduced scale, the device of Fig. 1 in three however, in some tanks, particularly those 110 different working conditions.

made of plastics material in which the bottom With particular reference to Fig. 1, a device of the tank tends to drop by the effect of the for detecting the level of a liquid in a tank, weight of liquid contained in it and/or by the particularly the fuel tank of a motor vehicle, is effect of pressure variations which take place generally indicated with the reference numeral within the tank and which are a result of vari- 115 1. The upper and lower walls of this tank are ations in ambient temperature. It is therefore indicated, in particular, with the reference evident that a displacement of the lower wall numerals 3 and 4 respectively, and the tank is of the tank involves an error in the indication conveniently made of plastics material.

of the level of the liquid measured by means The device 1 essentially comprises:

of known devices of the type specified above. 120 - a flange 5 provided with a radial annular The object of the present invention is that projection which rests, by means of a seal 7, of providing a device for indicating the level of also of annular form, on the outer surface of liquid in a tank which is able to overcome the the upper wall 3 of the tank 2; disadvantages presented by devices of the - a float 8 which can be displaced by the known type listed above. 125 said liquid and which carries an electrical con The said object is achieved with the present tact element 9; invention in that it relates to a device for de- - a guide 10 for the float 8 supporting a tecting the level of a liquid in a tank, the said helically wound resistive wire 11 on which, in device being of the type comprising: use, slide conductive shoes 12 of the contact - a flange which can be fixed to an upper 130element 9 when the float 8 slides along the 2 GB2191297A 2 guide 10 by the effect of the hydrostatic wire 37 (see also Fig. 2) to a terminal portion thrust exerted by the said liquid. of a shaped plate 39. This latter is electrically According to the present invention the de- connected, as illustrated in Fig. 2, to a con vice 1 is provided with a cup-shape body 15 nector 40 which, in a manner not illustrated, having an end wall 16 and a substantially 70 projects out from the flange 5.

cylindrical side wall 17 defining a chamber 18 The end of the resistive wire 11 close to in which are contained, in an axial position, the upper portion 30 of the guide 10 is con the float 8 and the associated guide 10. In nected by means of a connector 41 to one more detail, the end wall 16 has through end of the spring 33 conveniently made of a holes 19 able, in use, to put the chamber 18 75 conductive material. This latter rests on the into communication with the interior of the opposite side on a conductive plate 42 which tank 2. Moreover, the end wall 16 has, in an is force fitted over a pin 43 emerging from axial position, a convex portion 20 defining a the end wall 25 of the flange 5. The plate 42 sleeve 21 within the interior of which is force is also connected to an associated electrical fitted a lower portion 22 of the guide 10. 80 connector 44 (see Figs. 1 and 2) which also Moreover, between the sleeve 21 and the projects out from the flange 5.

above mentioned portion 22 there is inter- The function of the device 1 is described posed a terminal portion of a coil spring 23 hereinbelow by making reference initially to operable to compensate, in a known way, Fig. 3 in which are illustrated three different part of the weight of the float 8 when this 85 positions assumed by the device 1 as a func latter is located close to the lower wall 4 of tion of the three respective positions assumed the tank 2. by the end wall 4 of the tank 2. In particular, The flange 5 has a substantially cup-shape in Fig. 3a, the distance between the facing structure with an end wall 25 and a substan surfaces of the upper and lower walls of the tially cylindrical side wall 26. In particular, the 90 tank 2 is a minimum, which allows the posi outer diameter of the side wall 17 of the cup- tioning of the device 1. In fact, the flange 5 shape body 15 is slightly less than the internal of this latter is correctly anchored to the up diameter of the side wall 26 of the flange 5. per wall 3 of the tank 2, whilst the surface of This cup-shape body 15 is slidably mounted the end wall 16 of the cup- shape body 15 within the flange 5 and in particular has a 95 rests on the corresponding surface of the longitudinal outer groove 27 which is engaged lower wall 4 of the tank 2, when the cap 31 by a tooth 28 extending radially from the side rests on the pin 43. Consequently, the device wall 26 of the flange 5 for the purpose of 1 presents a minimum length in an axial sense limiting the downward translation of the cup- in this configuration.

shape body 15 with respect to the flange 5, 100 Fig. 3c illustrates the device of Fig. 1 in the as well as the relative rotation of one with opposite working condition to that illustrated respect to the other. in Fig. 3a. In fact, in this condition the lower It is moreover observed that on an end por- wall 4 of the tank 2 is beneath the end wall tion 30 of the guide 10, on the side opposite 16 of the cup-shape body 15 which, however, the lower end portion 22, is force fitted a cap 105 by the effect of the resilient thrust exerted by 31 radially from which extends an annular porthe spring 33, assumes the maximum exten tion 32 the outer diameter of which is slightly sion in the axial sense. That is to say, it tran less than the inner diameter of the side wall slates with respect to the flange 5 for a dis 17 of the cup-shape body 15. In this way the tance slightly less than the length of the guide 10 is correctly positioned within the as- 110 groove 27 and precisely until the tooth 28 sociated cup-shape body 15. Between the intercepts a portion of the side wall 17 of the facing surfaces of the end wall 25 of the cup-shape body 15 delimiting the top of the flange 5 and the annular portion 32 of the cap above mentioned groove 27. It is evident that 31 is interposed a cone spring 33 the princi- the operating conditions of the device 1 illus ple purpose of which is that of exerting a 115 trated in Figs. 3a and 3c are limit conditions resilient thrust tending to cause the cup-shape which, in general, do not occur. The most body 15 to translate perpendicularly with re- frequent operating configuration is that illus spect to the wall 25 of the flange 15. In the trated in Fig. 3, in which the cup-shape body illustrated example the resistive wire 11 is util- 15 translates partially from the flange 5 under ised as a rheostat in particular for measuring 120 the resilient thrust exerted by the spring 33 the resistance which it presents between the until the associated end wall 16 rests on the twrninals placed in proximity to the upper por- lower wall 4 of the tank 2. In this position the tion 30 of the guide 10 and the zone on cup-shape body 15 can equally displace along which the shoes 12 of the contact element 9 its axis in both directional senses in such a slide. For this purpose this latter is connected 125 way as perfectly to follow the displacements by means of a helically wound conductive of the lower wall 4 of the tank 2 which can wire 35 to an intermediate connector 36 car- take place both by the effect of the increase ried by the above mentioned annular portion of weight due to the fuel and because of a 32. The connector 36 is in turn connected, by possible increase in the pressure of air within means of a further helically wound conductive 130 the tank 2 itself.

3 GB2191297A 3

Claims

From a study of the characteristics of the 2. A device according to Claim

1, charac- device formed according to the present inven- terised by the fact that the said flange is tion the advantages which it allows to be obessentially cup-shape and has a substantially tained are evident. First of all, since the cup- cylindrical side wall extending perpendicuarly shape body 15 is maintained in contact with 70 of the said end wall and housing within it an the surface of the lower wall 4 of the tank

2 upper portion of the side wall of the said cup supporting the cup-shape body and the sensi- shape body.

tive part of the device 1 (float 8, guide 10

3. A device according to Claim 2, charac and associated resistive wire 11), the detec- terised by the fact that the said side wall of tion of the level of liquid is effected with ref- 75 the said cup-shape body has on its outer side erence to the lower wall 4 of the tank 2. a longitudinal groove engaged by a corre Consequently, the indication of the liquid con- sponding tooth extending radially from the tent is rendered more precise and is affected said side wall of the said flange.

in only an extremely limited way by the defor- 4. A device according to any preceding mations of the lower wall 4 of the tank 2. 80 Claim, characterised by the fact that an upper Finally, it is clear that the device 1 de- end of the said guide carries a radially extend scribed above can have modifications and vari- ing spacer element a lateral edge of which ations introduced thereto without by this de- cooperates with an inner surface of the side parting from the scope of the present invenwall of the said cup-shape body to maintain tion. For example, wide modifications can be 85 the said guide directly positioned with respect introduced to the way in which electrical con- to the said cup-shape body.

nection is made between the connectors 40, 5. A device according to Claim 4, charac 44 and respectively, the contact element 9 terised by the fact that the said resilient sliding by means of its shoe 12 on the resismeans are interposed between the said spacer tive wire 11 and the terminal fixed to this 90 element and the said end wall of the said resistive wire can be close to the upper pori- flange.

ton 30 of the guide 10. 6. A device according to Claim 5, charac terised by the fact that the said resilient CLAIMS means are constituted substantially by a 1. A device for detecting the level of a 95 spring the opposite end portions of which rest liquid in a tank, the said device being of the respectively on the surface of the said end type comprising: wall of the said flange and on the opposite - a flange which can be fixed to an upper surface of the said spacer element.

wall of the said tank; 7. A device according to Claim 6, charac - a float which can be displaced by the said 100 terised by the fact that the said spring has a liquid and carrying an electrical contact ele- frusto-conical structure.

ment; 8. A device according to Claim 6 or Claim - a guide for the said float supporting a 7, characterised by the fact that the said resistor on which, in use, the said contact spring is made of electrically conductive ma- element carried by the said float slides under 105 terial and constitutes one of the electrical co the hydrostatic thrust exerted by the said nection elements between a terminal of the liquid; said resistor and an electrical connector ex - characterised by the fact that it comprises: tending externally of the said flange.

- a cup-shape body having an end wall and 9. A device according to any of Claims a substantially cylindrical side wall defining a 110 from 4 to 8, characterised by the fact that it chamber in which the said float and the said includes a pair of conductive wires having a guide are contained; the said end wall sup- first terminal connected in common and sub porting a lower end of the said guide and stantially in correspondence with the said spa having at least one through hole operable to cer element, and a second terminal respec- put the said chamber into communication with 115 tively connected to the said electrical contact the interior of the said tank; the said side wall element carried by the said float and an elec being able to translate perpendicularly with re- trical connector an end portion of which pro pect to an end wall of the said flange be- jects from the said flange.

tween a first position and a second position in 10. A device according to any preceding such a way that the distance between the end 120 Claim, characterised by the fact that it in- walls of the said cup-shape body and the said cludes a spring fixed to the said end wall of flange respectively can vary between a first the said cup-shape body and around the said value and a second value greater than the said guide; the said spring being able to transmit a first value; and resilient upward thrust to the said float when - resilient means substantially interposed be- 125 this latter is located close to the said end wall tween the said cup-shape body and the said of the said cup-shape body.

flange and operable to exert a resilient thrust 11. A device according to any preceding tending to make the said cup-shape body (15) Claim, characterised by the fact that the said translate from the said first position towards flange and the said cup- shape body are made the said second position. 130 of plastics material.

4 GB2191297A 4 12. A device for detecting the level of a liquid in a tank substantially as described with reference to the attached drawings.

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 'I AY, from which copies may be obtained.