FR2599497A1 - DEVICE FOR DETECTING THE LEVEL OF A LIQUID IN A TANK - Google Patents

Abstract

THE DEVICE 1 OF THE INVENTION INCLUDING A FLANGE WHICH CAN BE ATTACHED TO A WALL OF A TANK IS OF A TYPE IN WHICH A FLOAT 8 IS MOUNTED SO AS TO SLIDE ALONG A GUIDANCE ELEMENT 10 BEARING A RESISTANCE 11 ON WHICH AN ELECTRICAL CONTACT ELEMENT SLIDES 9, 12 CARRIED BY THE FLOAT ITSELF 8. THE GUIDANCE ELEMENT 10 AND THE FLOAT 8 ARE ENCLOSED IN A BODY IN THE SHAPE OF CUP 15 OF PLASTIC MATERIAL WHICH INCLUDES A WALL OF ' END 16 AND A SIDE WALL 17. THE END WALL 16 SUPPORTS THE LOWER END 22 OF THE GUIDING ELEMENT 10 AND HAS AT LEAST ONE THROUGH HOLE 19 TO ALLOW THE LIQUID CONTAINED IN TANK 2 TO PASS OVER THE FLOAT. THE SIDE WALL 17 IS SENSITIVELY CYLINDRICAL AND IS SLIDINGLY CONNECTED TO THE FLANGE 5 BY THE INTERPOSITION OF AN ELASTIC MEDIUM 33 TENDING TO SEPARATE FROM THE FLANGE 5 THE END WALL 16 OF THE CUP-SHAPED BODY 15.

Description

1. The present invention relates to a device for detecting the level

  of a liquid in a tank and, more particularly a device for detecting the level of fuel

in a vehicle tank.

  The device of the present invention is of a type comprising a flange which can be fixed to a wall of the tank, a float which can be moved by the liquid contained in the tank and contains a sliding electrical contact element, during operation, on a resistor wound on a float guide element supported by the flange. The float and the associated guide are housed in a chamber delimited externally by a cylindrical tube which is mounted around the guide along the same axis and fixed at its opposite ends, respectively, on the flange and on a disc having a hole 15 passing through and conveniently attached to the guide itself. In use, the measurement of the liquid present in the tank is made taking into account the position taken by the float relative to the 2. guide. As the latter is fixed, by means of the respective flange, to the upper wall of the tank, it is obvious that the

  liquid level measurement is reported to the upper wall of the tank.

  Devices of the type just described are preferred to the other indicators, because in addition to the advantage of eliminating the oscillations of the float and consequently of the index of the instrument connected to the resistor, they offer l another advantage of a more precise indication of the level of the liquid due to the extent of the resistance (in general, a resistant wire) over the entire longitudinal length of the guide and therefore essentially over the entire height of the tank. However,

  a large part of this latter advantage is lost in certain tanks, in particular in those made of plastic materials in which the bottom of the tank tends to collapse under the effect of the weight of the liquid which it contains and / or under .

  the effect of pressure variations occurring inside the tank which are caused by changes in the ambient temperature. It is therefore obvious that a displacement of the lower wall of the tank implies an error

  in the indication of the level of the liquid, measured by known devices of the type specified above.

  The object of the present invention is to provide a device for indicating the level of a liquid in a reservoir, which is capable of overcoming the drawbacks which suffer

  devices of the known type that have just been exposed.

  According to the present invention, this object is achieved with a device making it possible to detect the level of a liquid in a tank, this device comprising: - a flange which can be fixed to the upper wall of the tank; - A float which can be moved by the liquid, and which carries an electrical contact element; - A guide for the float supporting a resistor on which, under the effect of the hydrostatic thrust 3. exerted by the liquid, slides the contact element carried by the float during operation; which is characterized in that it comprises: - a cup-shaped body having an end wall and a substantially cylindrical side wall defining a chamber which encloses the float and the guide; the end wall supporting a lower end of the guide and having at least one through hole which can be used to place the chamber in communication with the interior of the tank, the side wall being able to be moved in a perpendicular translational movement at the end wall of the flange between a first and a second position so that the distance between the end walls of the cup-shaped body and the flange can vary, respectively between a first value 15 and a second value greater than the first; and - an elastic means practically interposed between the cup-shaped body and the breeze and which can be used to exert an elastic thrust taking care to cause the

  translation of the cup-shaped body between the first position 20 and the second position.

  The present invention will be well understood during the

  following description made in conjunction with the attached drawings

  in which: Figure 1 is a sectional elevation of a device according to the present invention; Figure 2 is a sectional view taken along line II-II of Figure 1 with portions removed to make it clearer; and Figure 3 illustrates in schematic form and at

  reduced scale, the device of Figure 1 in three different service conditions.

  More particularly in connection with FIG. 1, an outline is shown by the reference 1 of a device for detecting the level of a liquid in a tank, in particular in the fuel tank of a motor vehicle. The upper and lower walls of this tank are represented, in particular, by the references 3 and 4 respectively, and the tank is conveniently

made of plastic material.

  The device 1 essentially comprises - a flange 5 having a radial annular projection which rests, by means of a seal 7, also of annular shape, on the external surface of the upper wall 3 of the tank 2; - A float 8 which can be moved by the liquid and which carries an electrical contact element 9; - A guide 10 for the float 8 supporting a resistant wire 11 wound in a spiral, on which slide while the conductive brushes 12 of the contact element tact 9 when the float 8 slides along the guide 10 under

  the effect of the hydrostatic thrust exerted by the liquid.

  According to the present invention, the device 1 comprises a cup-shaped body 15 having an end wall 16 and a substantially cylindrical side wall 17 defining a chamber 18 in which are contained, in the axial position, the float 8 and the associated guide 10. In more detail,

  the end wall 16 has through holes 19 capable, during operation, of bringing the chamber 18 into communication with the interior of the reservoir 2. In addition, the end wall 16 has, in an axial position, a convex part 20 defining a sleeve 21 inside which a lower part 22 of the guide 10 is fitted tightly.

  In addition, between the sleeve 21 and the part 22, is interposed an end pair of a spiral spring 23 which can be used to compensate, in a known manner, for part of the weight of the float 8 when the latter is located very

  near the bottom wall 4 of the tank 2.

  The flange 5 has a substantially cup-shaped structure, with an end wall 25 and a substantially cylindrical side wall 26. More particularly, the 5. outside diameter of the side wall 17 of the body 15 is slightly less than the inside diameter of the side wall 26 of the flange 5. The body 15 is slidably mounted inside the flange 5 and has more particularly a longitudinal outer rib 27 in which is engaged a tooth 28 extending radially from the side wall 26 in order to limit the downward translational movement of the body 15 relative to the flange, as well as the rotation

  relative from one to the other.

  It will further be noted that on an end portion 30 of the guide 10, on the side opposite to the lower end portion 22, is mounted in a tight fit a cap 31 from which extends radially an annular portion 32, of which the outside diameter is slightly smaller than the inside diameter 15 of the side wall 17 of the body 15. In this way, the guide 10 is correctly placed inside the associated body 15. Between the facing surfaces of the end wall 15 of the flange 5 and the annular portion 32 of the cap 31 is interposed a conical spring 33, the function of which is to exert an elastic thrust tending to cause the translation of the body 15 perpendicular to the wall 25 of the flange 5. In the example illustrated, the resistant wire 11 is used as a rheostat, more particularly for measuring the distance present between the terminals placed near the upper portion 25 of the guide 10 and the zone over which the brushes 12 of the contact element 9. For this purpose, this element is connected by means of a conducting wire 35 wound in a spiral

  an intermediate connector 36 carried by the annular portion 32. The connector 36 is in turn connected by means of another conductive wire 37 wound in a spiral (see also FIG. 2), to a connection part of a shaped plate 39 .

  The latter is electrically connected, as illustrated in FIG. 2, to a connector 40 which, in a manner not illustrated,

protrudes from the flange 5.

  The end of the resistant wire 11 close to the upper portion 6. of the guide 10 is connected by a connector 41 to one end of the spring 33 conveniently made of conductive material. The latter rests on the opposite side on a conductive plate 42 which is fitted tightly on an axis 43 projecting from the end wall 25 of the flange 5. The plate 42 is also connected to an associated electrical connector 44

  (see Figures 1 and 2) which is also projecting from the flange 5.

  The operation of the device 10 1 will be described below in conjunction with FIG. 3, in which three different positions taken by the device are illustrated as a function of the three respective positions occupied by the end wall 4 of the tank 2 In particular, in FIG. 3a, the distance between the facing surfaces of the upper and lower walls of the tank 2 is minimum, which allows the positioning of the device 1. In fact, the flange 5 of the latter is correctly anchored to the upper wall 3 of the tank 2, while the surface of the end wall 16 of the body 15 rests on the corresponding surface of the lower wall 4 of the tank 2, when the cap 31 rests on the axis 43. By therefore, the device 1 has a length

  minimum in the axial direction of this configuration.

  Figure 3c illustrates the device of Figure 1 in the opposite operating condition to that illustrated in Figure 3a. Indeed, in this condition, the bottom wall 4 of the reservoir 2 is located below the end wall 16 of the body 15 which, however, under the effect of the elastic thrust exerted by the spring 33 takes the extension maximum in the axial direction. More specifically, it is driven in a translational movement relative to the flange 5 over a distance slightly less than the length of the groove 25 and precisely until the tooth 28 intercepts part of the wall 17 of the body. 15 delimiting the top of the groove 27. It is obvious that the operating conditions of the device 11 il35 illustrated in FIGS. 3a and 3c are boundary conditions which, in general, do not occur. The most frequent operating configuration is that illustrated in FIG. 3, in which the body 15 partially moves from the flange 5 under the elastic thrust exerted by the spring 33 until the associated end wall 16 rests on the bottom wall 4 of the tank 2. In this position, the body can move in an identical fashion along its axis, in both directions so as to follow perfectly the movements of the bottom wall 4 of the tank 2 which can 10 occur as a result of both the increase in weight due to fuel and a possible increase in pressure

  air inside the tank 2.

  The study of the characteristics of the device formed according to the present invention highlights the advantages which it makes it possible to obtain. First of all, since the cup-shaped body 15 is kept in contact with the surface of the lower wall 4 of the reservoir 2 supporting this body and the sensitive part of the device 1 (float 8, guide 10 and associated resistant wire 11), the detection of the level of the liquid is carried out by reference to the bottom wall 4 of the reservoir 2. Consequently, the indication of the content of liquid is made more precise and is only affected in an extremely limited manner.

  by the deformations of the lower wall 4 of the tank 2.

  Finally, it is clear that the device 1 which has just been described can be subjected to modifications and variants without departing from the scope of the present invention. For example, large modifications can be introduced as to the way in which the electrical connections are made between the connectors 40 and 44 and, respectively, the contact element 9 sliding by means of its brush 12 on the resistant wire 11, and the terminal attached to this resistant wire can

  be close to the upper part 30 of the guide 10.

  The present invention is not limited to the embodiments which have just been described, it is on the contrary subject to modifications and variants which

will appear to those skilled in the art.

259? 497

8.

Claims (9)

  1 - Device (1) for detecting the level of a liquid in a tank (2), the device being of the type comprising: - a flange (5) which can be fixed to the upper wall (3) of the tank (2) ; - - a float (8) which can be moved by the liquid and which supports an electrical contact element (9); - a guide (10) for the float (8) supporting a resistance (11), on which, during operation, the contact element (9) carried by the float (8) slides under the effect of the thrust hydrostatic exerted by the liquid; characterized in that it comprises: a cup-shaped body (15) having an end wall (16) and a substantially cylindrical side wall (17) defining a chamber (18) in which the float (8) is contained and the guide (10), the end wall (16) supporting the lower end (22) of the guide (10) and comprising at least one through hole (19) which can be used to put the chamber (18 ) in communication with the interior of the tank (2); the side wall (17) being able to be moved in a translation movement perpendicular to the end wall (25) and the flange (5) between a first position and a second position so that the distance between the end walls (16, 25) of the body (15) and the flange (5), respectively, can vary between a first value and a second value greater than the first value; and - an elastic means (33) substantially interposed between the body (15) and the flange (5) and which can be used to exert an elastic thrust tending to cause a   translational movement of the body (15) from the first position to the second position.   2 - Device according to claim 1, characterized in that the flange (5) has essentially the shape of a neck 35 pe and has a substantially cylindrical side wall (26) 9. which extends perpendicular to the end wall ( 25) and contains an upper portion of the side wall (17) of the cup-shaped body (15).   3 - Device according to claim 2, characterized in that the side wall (17) of the cup-shaped body (15) has on its outer side a longitudinal groove (27) in   which engages a corresponding tooth (28) extending radially from the lateral wall (26) of the flange (5).   4 - Device according to any one of the preceding claims, characterized in that the upper end (30) of the guide (10) carries a spacer element which extends radially (31), of which a lateral edge cooperates with the inner surface of the side wall (17) of the shaped body   cup (15) in order to hold the guide (10) directly in place relative to the cup-shaped body (15).   - Device according to claim 4, characterized   in that the elastic means (33) is interposed between the spacer element (31) and the end wall (25) of the flange (5).   6 - Device according to claim 5, characterized in that the elastic means (33) consists substantially of a spring, the opposite end portions of which respectively rest on the surface of the end wall (25) of the   flange (5) and on the opposite surface of the spacer element 25 (21).   7 - Device according to claim 6, characterized   in that the spring (33) has a frustoconical structure.   8 - Device according to claim 6 or claim 7, characterized in that the spring (33) is of electrically conductive material and constitutes one of the elements of   electrical connection between a terminal of the resistor (11) and an electrical connector (44) extending outside the flange (5).   9 - Device according to any one of claims 4 to 8, characterized in that it comprises a pair of wires 10. conductors (35, 37) having a first terminal connected in common and substantially in correspondence with the forming element spacer (31), and a second terminal connected respectively to the electrical contact element (9) carried by the float (8) 5 and an electrical connector (40) including an end portion is projecting from the flange (5).   -A device according to any one of the preceding claims, characterized in that it comprises a spring   (23) fixed to the end wall (16) of the neck-shaped body 10 pe (15) and around the guide (10), the spring (23) being capable of transmitting to the float (8) a directed elastic thrust   upwards when the latter is located near the end wall (16) of the cup-shaped body (15).   11 - Device according to any one of the preceding claims, characterized in that the flange (5) and the   cup-shaped bodies (15) are made of plastic material.