FR2791927A1 - Flexible lining for control valve operated by liquid level comprises internal and external parts that make sealed contact according to postion of float relative to predetermined level of petrol in tank. - Google Patents

Abstract

The control valve (100) is used to limit the disharge of vapours from a petrol tank (10) which contains a predetermined level (11) of fuel. The flexible lining is arranged between the float and the vapour outlet. The external flexible lining is in sealed contact when the float reaches a predetermined level, and the interior lining is in sealed contact when the level is above the predetermined level. When the float is in an initial position the valve allows the petrol vapours to flow through it with an initial flowrate. In the intermediate position the lining resticts the flow of vapours. In the final position the lining prevents the flow of vapours through the vapour outlet.

Description

FIELD OF THE INVENTION

  The present invention relates, in general, to gas vapor recovery systems of the "on-board" system type for the fuel tanks of vehicles. The petrol vapors generated during the refueling process are evacuated, in particular, to a two-stroke control valve

  operated by a liquid level.

BACKGROUND OF THE INVENTION

  Managing fuel vapors in a vehicle is an important part of designing fuel systems for modern vehicles. Fuel vapors can be created in the fuel tank by the temperature differences between the fuel tank and the liquid fuel from the fuel pump, or by the agitation and movement of the fuel in the fuel tank. fuel tank during normal vehicle operation. The increase in pressure resulting from the creation of these gasoline vapors must be relieved and it is for this reason that many fuel systems for vehicles are equipped with systems serving to control the draining of the tank. Tank purge control systems are capable of discharging a relatively large amount of gasoline vapors in response to the development of high pressure conditions in the gasoline tank. These systems are sometimes called "fuel regulation" or "stop" valves because their closure creates in the tank a sudden increase in pressure which prevents further refueling. Many pressure actuated control valves also require a filling lance hatch or other sealed structure in the filling pipe. In addition, these control valves can cause fuel to be released and expelled through the inlet of the filler pipe at the end of the refueling operation. Typically, when the fuel tank is full, the fuel rises up the neck of the filling pipe and spurts out of the filling pipe. During the refueling operation, motorists sometimes try to pump fuel even after

  several automatic interruptions of the pump lance.

  The user "clicks" or squeezes the level handle on the pump lance slowly, two or three times in succession after the automatic interruption of the lance, in order to introduce more fuel into the fuel tank. This practice can lead to an overfilling of the fuel tank which can effectively reduce the capacity of expansion of gasoline vapors in the available space.

  for vapors inside the fuel tank.

  A known control valve, sensitive to the fuel level, comprises a two-stroke shut-off valve with an initial "smooth" interruption damping the refueling operation which takes place under high pressure. However, this device is very complex and very expensive to produce. In addition, this device has an annoying tendency to "clog" when the first and second fuel valve structures have successfully closed the secondary bleed ports when the first and second fuel levels are reached. The device becomes blocked when the valve remains closed even though the fuel level in the tank drops, which is due to the fact that the gasket "sticks" to the vapor outlet orifice. This state delays the purging of gasoline vapors despite the

  drop in fuel level in the tank.

  There is therefore a need for a system for controlling the filling limit and the ventilation of the tank which is easy to assemble, capable of evacuating the petrol vapors from the vapor space in the petrol tank during the first moments of refueling, and which also blocks the introduction of any excess liquid fuel exceeding the maximum volume so as to preserve a minimum space for vapors in the fuel tank once it is full of fuel to its maximum capacity. In addition, this control valve system must not become blocked during the filling operation, i.e. must not prevent the flow of vapors through the valve when the

fuel level drops.

SUMMARY OF THE INVENTION

  The present invention is a device for controlling the discharge of petrol vapors from a petrol tank. The device includes a valve body which is mounted in the fuel tank. The valve body is formed to have a vapor inlet opening which communicates with the interior region of the fuel tank. It also includes a vapor outlet opening and a passage connecting the vapor inlet opening to the vapor outlet opening. A float valve element is located in the body. The float valve element is movable between an initial position, when the fuel level in the petrol tank is lower than a predetermined level, an intermediate position, when the fuel level in the petrol tank reaches the predetermined level, and a final position, when the fuel level in the fuel tank is higher than the predetermined level. The float valve element includes an upper part, a side part and a

  passage connecting the upper part and the side part.

  The device also includes an elastomeric element at the top of the float valve element. The elastomeric element includes an interior portion, an exterior portion, an interior trim adjacent to the interior portion and an exterior trim adjacent to the exterior portion. The interior of the packing communicates in a manner allowing circulation with the passage in the valve body. The outer seal contacts the vapor outlet opening when the float valve member reaches the predetermined level and the inner seal contacts the vapor outlet opening when the float member float valve is above the predetermined level. Thus, when the float valve element is in the initial position, it allows the flow of gasoline vapors with a first high flow rate. In addition, when the float valve element is in the intermediate position, the interior of the packing allows gasoline vapors to flow through the vapor outlet opening with a second flow rate less than the first flow rate. In addition, when the float valve member is in the final position, the inner lining and the outer lining of the elastomeric member are in sealing contact with the vapor outlet opening so as to prevent the flow of vapors. gasoline through

the vapor outlet opening.

  It is therefore an object of the present invention to provide a float valve with a flexible packing which initially reduces the area of the vapor outlet opening so as to obtain a much smaller outlet opening. Vapors can be vented through the small opening until more liquid is added to the fuel tank. The float rises, causing the wide lip of the flexible gasket to flex, and as the fuel continues to rise, the small diameter lip touches the top of the vapor outlet opening to prevent flow through

the vapor outlet opening.

  Another object of the present invention is to provide a flexible lining which allows reopening of the vapor outlet when the tank is completely closed and the fuel in the tank increases with temperature. As the temperature in the tank increases, it increases the pressure in the tank; the pressure acts against the float and the wide lip so as to create a force which keeps the seal closed even when the liquid level drops. Yet another object of the present invention is to provide a flexible gasket with a small inner lip which reduces the force required for contact with the vapor outlet opening. Once the liquid is lowered into the tank, the weight of the float and the bending of the wide flexible lip create a force which makes it possible to break the contact between the float and the outlet opening

  vapors to lower the pressure in the tank.

  These features of the present invention, and others

  again, will appear on reading the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

  Figure 1 is a schematic representation of a vehicle fuel system comprising an on-board vapor recovery system according to the present invention; Figure 2 is a schematic representation of a vehicle fuel system comprising a vapor recovery system on board, during the refueling operation; Figure 3 is a perspective view of the device according to the preferred embodiment of the present invention Figure 4 is a side view of Figure 3; Figure 5 is a sectional view along line 5-5 of Figure 4, where the valve is in the open position; Figure 6 is a sectional view along line 5-5, but where the float is in the closed position; Figure 7 is a perspective view of the valve body; Figure 8 is a top view of the valve body shown in Figure 7; Figure 9 is a sectional view of the valve body along line 9-9 of Figure 8; Figure 10 is a sectional view along line 10-10 of Figure 8; Figure 11 is a perspective view of the float; Figure 12 is a top view of the float; Figure 13 is a side view of the float; Figure 14 is a sectional view along line 14-14 of Figure 13; Figure 15 is a sectional view along line 15-15 of Figure 13; Figure 16 is a partial sectional view of the float; Figure 17 is a top view of the packing; Figure 18 is a sectional view of the packing along the line 18-18 of Figure 17; Figure 19 is a bottom view of the vapor outlet opening of the preferred embodiment of the invention; Figure 20 is a sectional view of an alternative embodiment of the present invention, where the valve is in the open position; Figure 21 is a sectional view of the alternative embodiment, where the valve is in the closed position; and Figure 22 is a bottom view of the packing according to the

  alternative embodiment of the invention.

  DETAILED DESCRIPTION OF THE PRIVILEGED EXECUTION

  As shown in Figure 1, the device for controlling the discharge of petrol vapors from a petrol tank is identified by the number 100. The device 100 comprises a tank 10, a filling pipe 12 provided with an inlet 14 which is selectively closed by a plug 16, and a vapor absorber 18 connected to the tank 10 by a purge line 17. During refueling, that is to say when the fuel is pumped at high speed from the filling lance in the filling hose, a vacuum hose fitting adjacent to the outlet of the filling lance prevents gasoline vapors from escaping from the inlet of the filling hose. The petrol vapors coming from the tank 10 are evacuated via line 17 to an absorber 18 o the petrol vapors are absorbed and purged periodically in response to a purge solenoid valve 19 leading to a motor for combustion . The evacuation of petrol vapors from the tank 10 by means of line 17 to the absorber 18 is controlled by a control valve 100 sensitive to the fuel level which is mounted in an appropriate opening in the petrol tank 10, where the control valve 100 is closed by the liquid fuel when it reaches or exceeds a predetermined level indicated by the reference number 11. When the liquid fuel in the tank 10 is below the predetermined level 11, the valve remains open for vent gasoline vapors into

the absorber 18.

  As shown in Figure 2, when the tank has a low level 13, fuel is introduced at a high rate through line 12 into the tank 10. The vapors in the fuel tank are discharged through the valve 100 to allow for the fuel to fill the tank 10 quickly without this being accompanied by an increase in the pressure in the tank 10. The gasoline vapors evacuated by the valve 100 go into the vapor absorber 18 until a fuel level corresponding to the approximate full is reached. The valve 100 essentially reduces the evacuation of gasoline vapors from the tank but without abruptly interrupting it. Instead, the valve 100 still provides limited evacuation of a small volume of vapors when the level of

  fuel in the fuel tank reaches the predetermined level.

  The result is an initial interruption of the fuel when the latter reaches a predetermined level in the tank so as to prevent too rapid reflux of the fuel in the filling pipe and a possible rejection on the person who actuates the filling lance. When the first interruption occurs, the resulting increase in tank pressure forces the fuel going up in the filling pipe to cover the mouth of the filling lance, activating an internal stop mechanism in the lance filling, which is well known in the art. After a short time, the stagnant fuel in the filling pipe returns to the petrol tank. If the person actuating the filling lance continues to fill the tank after being alerted by the first interruption, the valve closes at the maximum level in order to trigger a final interruption and put an end to the refueling activity. Returning to FIG. 1, when the control valve 100 closes to close the reservoir and the filling ceases, a plug 16 in the filling tube closes positively and the

  fuel in the tank is sealed.

  Figure 1 illustrates the fuel system for a vehicle immediately after filling the tank to its maximum level after refueling has ended. In this condition, the control valve 100 is closed, the plug 16 in the filling pipe is closed and a fuel column

  liquid may stagnate in the filling pipe.

  The control valve 100 of the present invention is normally opened both during refueling and during normal vehicle operation as long as the fuel level in the tank is below the predetermined level. This predetermined level may vary slightly due to differences in pressure in the tank and the composition of the fuel in the system. The vapors are discharged to the absorber 18 on a relatively continuous basis. The electronic purge solenoid valve 19 is connected downstream of the absorber 18 so as to periodically allow the vacuum of the vehicle intake manifold

  "purge" the vapors of the absorber 18 to bring them to the engine.

  The fuel level sensitive valve 100 is unaffected by pressure extremes and freely discharges until the tank is full and the fuel level in the tank reaches the predetermined level. Thus, when the tank is full and the fuel reaches the predetermined level, the damped interruption provided by the control valve provides initial protection which reduces rejection and expulsion for a refueling operation taking place under

high pressure.

  The control valve 100 is mounted in a suitable opening in the fuel tank 10. As shown in Figures 3, 4, 5 and 6, the valve 100 essentially comprises a hollow valve body 30. The lower half 32 of the valve is located inside the fuel tank and communicates with an upper half 34 outside the fuel tank. The valve 100 is fixed to the fuel tank 10 and sealed so as to allow communication of liquid and vapors by a connection flange 36, for example by ultrasonic welding, a gasket

  made of elastomer or other well known techniques.

  The lower half 32 of the valve 100 defines a cavity 38 which is open at its lower end in order to receive the liquid fuel when the level of fuel in the tank rises to the level of the full of fuel. Radial orifices 37 in the side of the lower half 32 and holes or slots 39 in the lower end of the lower half 32 ensure the circulation of vapors and liquid between the reservoir 10 and the float tank 40. The tank float 40 is provided, at its upper end, with a vapor outlet opening 80 which opens in the upper half 34 of the valve and communicates with an outlet 33 which is connected to a

  vapor absorber 18 through a conduit or pipe 17.

  As seen more clearly in Figures 7, 8, 9 and 10,

  the valve 100 is provided with a baffle structure and walls 44.

  Those skilled in the art will recognize that the walls 44 form, in connection with the baffles 42, the float tank 40. Openings 46 are formed between the baffles 42 and the walls 44 near the top of the lower half 32. The bottom of the openings 46 is located below the bottom of the radial holes 37 so as to establish communication

  allowing a circulation of gasoline vapors between the two.

  A float 50 is contained inside the float tank 40 so as to be able to effect an axial displacement, that is to say an upward and downward movement; it is guided by walls 48 as the float tank 40 fills with liquid fuel through the holes 39. The density of the float 50 is studied so that it floats in the fuel so as to prevent the flow of liquid fuel through valve 100, whether in situations where the vehicle is straight or overturned. The float 50 may have a density less than, equal to or greater than that of the fuel, depending on what is desired for the

  filling control functions and overturning cases.

  As shown in Figures 11-16, the upper end of the float

  is provided with an opening 51 which communicates with the notch 52.

  The notch 52 extends radially from one side to the other of the float passing through its center and communicates with the opening 51. The petrol vapors coming from the tank 10 pass through the notch 37,

  the opening 46, pass through the notch 52 and then through the opening 51.

  The float 50 is also provided with at least one groove which extends axially and is intended to cooperate with the walls 48 in the float tank 40 to guide the float 50. At the top of the float 50 is a support element 58. The support element is provided with a lip 59 which extends radially with respect thereto 58 and is located at an axial distance from the top of the float 50 so as to

  form a draft at its outside diameter.

  An elastomeric lining 60, shown in FIGS. 17 and 18, is fixed, blocked, linked or attached to the top of the float 50. The elastomeric lining 60 has an outside diameter 62 and an inside diameter 64. A concentric draft 66 by compared to the diameter 64 is studied to adapt to the lip 59, the draft and the support element 58 on the float. Those skilled in the art will recognize that the lining 60 is thus captured, at the top of the float, thanks to the lip 59 of the lining 60 which cooperates with the draft formed in the support element. Alternatively, the liner 60 can be adhesively bonded to the float 50 by conventional means. The lining 60 comprises an outer lining 68 which moves away from the central axis of the lining 60. The outer lining 68 has a cross-sectional area and properties of elastomeric material such that the lip 59 can flex essentially under all conditions of operation of the valve 100, while preventing the opening 80 of the valve outlet from becoming blocked or the seal sticking thereto. Similarly, a garnish

  inner 69 is formed adjacent to the inner diameter 64.

  The top of the outer liner 68 is offset axially from the top of the inner liner 69 for a purpose that

we will study later.

  As shown in Figure 19, the outlet opening 80

  vapor is formed in the upper half 34 of the hollow body 30.

  The vapor outlet opening 80 has at least one opening 82 which extends from the solid central portion 83 of the vapor outlet opening in a truncated sector configuration. The central part 83 is connected by a series of spokes 84 to the solid central body 85 outside the outlet opening 80. The opening 82 communicates with the passage 31 in the fitting 33. Alternatively, the opening 82 can be round, elliptical, polygonal,

  square, rectangular, triangular or any other suitable shape.

  During normal vehicle operation, the float 50 remains in the lower half of the float tank 40 and is away from the vapor outlet opening 80 as long as the fuel level is below a predetermined level. When the fuel reaches a predetermined level close to the full level, the float 50 rises in the tank 40, forcing the outer lining 68 located on the top of the float 50 to come into contact with the opening 80 for the vapor outlet. . As the fuel continues to enter the tank, the float continues to rise in the axial direction and the outer lining 68 comes into tight contact with the outer body 85 of the opening 80 of the vapor outlet. However, since the top 67 of the outer liner 68 is offset in the axial direction relative to the top of the inner liner 69, the inner diameter 64 is not in contact with the solid central portion 83 in this condition. The flow of gasoline vapors continues through the opening 80 with a lower flow rate since it is restricted by the area of the section of the opening 51 and by the area of the section formed by the axial interval between the inner lining 69 and the central part 83. The possibility is therefore given of an evacuation of gasoline vapors through the notches 37 in the tank 40, the baffles 42 in the hollow valve body 30, the notch 52, the opening 51, the opening 82 and through the passage 31, with a lower flow rate than when the fuel level is lower than the predetermined level. This results in a significant reduction in the vapor discharge rate, which causes a rapid but controlled increase in pressure at the top of the tank. This in turn forces the fuel to go up into the filling pipe at a controlled speed, which activates the mechanism of the filling lance to obtain an initial "smooth" interruption without rejection of fuel on the user. This initial interruption is a

  signal warning the user that the tank is almost full.

  After the initial smooth interruption and the rise in pressure in the tank inducing this interruption, the vapor pressure in the tank dissipates fairly quickly, in a few seconds for example, through the secondary evacuation path defined by l flow of gasoline vapors through the diameter

  interior 64, the openings 82, the passage 31 and then in the absorber 18.

  This allows the fuel discharged into the filler pipe to flow into the tank. As a result, a small additional amount of fuel can be added to adjust the filling of the tank by "clicking" on the lance operating handle.

filling.

  If it happened that the user of the filling lance chooses to add fuel after the initial interruption, the float 50 and the lining are forced, under the effect of the rise in the fuel level, to move upwards against the vapor outlet opening 80 until the top of the interior lining 69 comes into contact with the central part 83 of the vapor outlet opening 80, as shown in FIG. 6. This completely closes the vapor outlet opening 80 and prevents any evacuation of the fuel tank to the absorber 18 via the control valve 100. This constitutes a final interruption signal for the filling lance. If the user persisted in trying to add fuel beyond the initial interruption and a few "clicks" of adjustment of the full allowable by valve 100 before a final interruption signal, the fuel would be all simply

  pumped out of the inlet of the filling pipe.

  The smooth, two-stage interruption, with its initial damped interruption and its controlled tolerance for full adjustment, can be adjusted as desired thanks to the relative dimensioning of the internal diameter 64 and the external diameter 62 of the lining 60, the 82 vapor outlet opening, model and density of float

  and by other means which will be obvious to those skilled in the art.

  The valve 100 remains completely closed until the level of liquid fuel in the tank drops, the interior lining 69 then being pulled by the weight of the float 50 as the load-bearing capacity of the latter 50 decreases, and the bending of the outer lining 68 due to the movement of the vehicle or to the pulling of the weight of the float 50 allows the inner lining 69 to move away from the vapor outlet opening 80 in the axial direction. When this happens, the petrol vapors have the possibility of passing through the internal diameter 64, which allows the external lining 68 to detach completely from the vapor outlet opening 82 in the

  axial direction and float 50 to descend with the fuel level.

  Due to the small contact surface of the inner lining 69, the force holding the float 50 and the outer lining 68 against the vapor outlet opening 80 is reduced to a level which may be less than the weight of the float 50. Thus , when the liquid level drops in the tank, the weight of the float and the bending of the external lining 68 reduce the force holding the lining 60 against the vapor outlet opening 80 and reduce the force necessary to allow the interior lining 69 to move away or

  detach from the vapor outlet opening 80.

  The flexible elastomeric lining 60 also allows the reopening of the vapor outlet opening in a condition where the tank is completely closed and the fuel pressure in the tank increases due to the temperature and the limited expansion of the tank. The increase in temperature can cause an essential increase in the pressure in the tank, the pressure then acts against the float 50 and the lining 60. As a result, the external lining 68 is pressed against the opening 80 for vapor outlet so keep the seal closed even when the liquid level drops, until the flexion of the outer seal 68 and the weight of the float 50 overcome the pressure force which presses the seal 60 against the opening 80 of

steam outlet.

  Those skilled in the art will recognize that the lower half 32 can be formed of a fuel-resistant material, such as the thermoplastic polyolefin Acetyl, which is a registered trademark of BASF, or a similar material such as the thermoplastic polyketone Carilon), which is a trademark of Shell, and the upper half 34 may be formed of a high density polypropylene thermoplastic material or the like. The lining 60 is formed from a thermoset polymer resistant to fuel, such as fluorosilicone,

  fluoroelastomer or similar material.

  In the preferred embodiment, the control valve according to the present invention is shown in Figures 20, 21 and 22 and is identified by the reference number 200. When the elements are identical to those which have been described above, they are identified by the same reference numbers in this form

privileged execution.

  The float 50 is located in the float tank 40, the lower half of which is provided with walls, baffles and openings, as described above. The lower half 32 is also provided with a cavity 38, radial holes or notches 37 in its side, and holes 35 and slots 39 at its lower end. The lower half 32 is connected to the upper half 34 by a means

  conventional. The float 50 is provided with an upper surface 158.

  In the preferred embodiment, the float 50 is identical, under

  all other reports, to the float 50 previously described.

  An elastomeric packing element 160 is fixed, linked or attached to the lower end 81 of the outlet opening 80 of the valve by conventional means. The elastomeric packing element 160 is provided with an outside diameter 167, openings 162 and an inside packing 169. The outside diameter 167 comprises a sealing lip 168 provided with an outside part which moves away from the central axis of the float 150 which is variable, that is to say as a function of the force exerted on the lining 160 by the float 150. As the float 150 rises in the axial direction towards the opening 80 vapor outlet, the lip 168 is compressed. The contact area of the lining 160 in contact with the upper surface 158 of the float 150 varies as the lip 168 rolls. This does not affect the sealing characteristics of the lining 168 since it is designed to flex and roll, while remaining in contact with the top 158 of the float 150. As the force exerted on the lining 160 increases due the rise in the fuel level and the bearing force of the float 150 which presses against the lining 160, as well as the pressure of the vapors acting on the lip of the lining 160, the latter 160 will bend and roll while remaining in contact with the top 158 of the float 150 until the top 158 comes into contact with the interior trim 169 to stop the flow of gasoline vapors through the vapor outlet opening 80. The interior trim 169 is surrounded by openings 162 which

  correspond to the openings 182 in the opening 80 of the valve.

  The inner lining 169 has an axial height, from its top to the lower end surface 81, which is less than the axial height

  from the lip 168 from its top to the lower end 81.

  When the fuel in the tank reaches the predetermined level, that is to say the level of full, the float 150 rises in the tank 40 and the top 158 comes into contact with the sealing lip 168 on the opening 80 vapor outlet. As the fuel level increases, the float continues to rise in the axial direction and the sealing lip 168 comes into sealing contact with the top 158. However, since the axial height of the lip 168 relative to the surface 81 is greater than the axial height of the interior lining 169, the interior lining 169 is not yet in contact with the top 158 of the float 150. The flow of vapors through the openings 182 in the opening 80 of the valve, and through the openings 162 of the lining 160 in the vapor outlet opening 80, is restricted by the area of the section of the opening 51 in the float 150. In addition, the flow of vapors is restricted because of the axial interval existing between the interior lining 169 and the top 158 of the float 150. Thus, the petrol vapors are evacuated through the notches 37, enter the tank 40, passing through the baffles in the body valve 30 hollow, the notch 52, the opening 51, the openings 162, the opening 182 and the

passage 31.

  As the user adds fuel to the tank, the float 150 rises axially in the tank 40 due to the increase in the fuel level. Thus, the top 158 exerts an axial pressure against the area of the external surface of the lining 160, so that the sealing lip 168 rolls on the top and allows an additional axial movement of the lining so that the top 158 also comes into contact with the interior trim 169. This completely stops the flow of vapors through the opening 51 in the float 150 and prevents any evacuation of gasoline vapors from the tank to

  gasoline to the absorber 18 through the control valve 200.

  In all other respects, the operation of the valve

  is identical to that of the other embodiment.

  The previous description of the valve device

  command according to the present invention is given by way of example and the invention cannot be limited unless otherwise indicated in the

following claims.

Claims (20)

  1. A device for controlling the discharge of petrol vapors from a petrol tank containing a predetermined level of fuel, said device comprising: a valve body adjacent to the petrol tank, said valve body having an inlet opening a vapor which communicates with the interior region of the fuel tank, a vapor outlet opening and a passage connecting said vapor inlet opening and said vapor outlet opening; a float valve element disposed in said body, said float valve element being movable between an initial position, when the fuel level in the fuel tank is lower than the predetermined level, an intermediate position, when the fuel level in the fuel tank reaches the predetermined level, and a final position, when the fuel level in the tank is higher than the predetermined level, said float valve member comprising an upper part; and an elastomer element interposed between said float valve element and said vapor outlet opening, said elastomer element comprising an internal part, an external part, an internal lining adjacent to said internal part and an external lining adjacent to said external part, said inner portion communicating in a manner allowing circulation with said passage in said valve body, said outer packing coming into sealing contact with said vapor outlet opening when said float valve member reaches the predetermined level and said inner packing sealingly contacting said vapor outlet opening when said float valve member is above the predetermined level, so that when said float valve member is in said initial position, said valve member pearl float t the flow of gasoline vapors with a first flow and, when said float valve member is in said intermediate position, said elastomeric member allows gasoline vapors to flow through said vapor outlet opening with a second flow rate which is less than said first flow rate and, when said float valve member is in said final position, said inner liner and said outer liner of said elastomeric member are in sealing contact with said vapor outlet opening so as to prevent flow of gasoline vapors to   through said vapor outlet opening.   2. Device according to claim 1, wherein said upper part of said float valve element is provided with a fixing part, said fixing part comprising a cylindrical part extending axially and a part extending radially located at a distance. of said upper part so as to form a lock to prevent said   elastomeric element is detached from said upper part.   3. Device according to claim 1, in which said elastomeric element comprises a lower part, a hollow cavity part adjacent to said lower part and a passage extending from said lower part towards said lining. outside.   4. Device according to claim 1, wherein said outer part comprises a flexible lip seal and said lip seal is provided with a sealing contact part. 5. Device according to claim 1, wherein said elastomeric lining is an elastomer selected from the group   composed of fluoroelastomer and fluorosilicone.   6. Device according to claim 4, wherein said interior lining comprises a passage communicating in a manner allowing circulation with said vapor inlet opening. 7. Device according to claim 1, wherein said elastomeric lining is provided with an outside diameter, an inside diameter and a draft which comes into contact with said   upper part of said float valve part.   8. Device according to claim 2, in which said elastomeric element comprises a part of a cavity in a draft in order to   cooperate with said fixing element.   9. Device according to claim 4, in which said flexible lip seal comes into leaktight contact with the vapor outlet opening when said float valve element reaches the predetermined level and said flexible lip seal maintains tight contact with said float valve member when said interior gasket contacts said vapor outlet opening to prevent   the flow of petrol vapors out of the petrol tank.   10. Device according to claim 4, in which said contact portion of the lining is brought into variable contact with the closed area of said vapor outlet opening so as to come into sealed contact with said vapor outlet opening. when said float element is located   in said intermediate position and in said final position.   11. A device for controlling the discharge of petrol vapors from a petrol tank, said petrol tank containing a predetermined level of fuel, said device comprising: a valve body mounted in the petrol tank, said valve body comprising a vapor inlet opening which communicates with the interior region of the fuel tank, a vapor outlet opening and a passage connecting said vapor inlet opening and said vapor outlet opening; a float valve element disposed in said passage, said float valve element being movable between an initial position, when the fuel level in the fuel tank is lower than the predetermined level, an intermediate position, when the fuel level reaches the predetermined level, and a fully extended position, when the fuel level is higher than the predetermined level, said float valve element comprising an upper part and an elastomer element comprising an internal lining part and an external diameter part, said outer diameter being provided with a flexible lip, said flexible lip having a variable contact area, said flexible lip seal being located at a distance from said vapor outlet opening and the flow of gasoline vapors being effected with a first flow, and when said flexible lip seal is in contact with said vapor outlet opening and said interior lining is remote from said vapor outlet opening, the flow of gasoline vapors through said vapor outlet opening takes place at a second flow rate which is less than said first flow rate , and when said flexible lip seal and said interior seal are in leaktight contact with said vapor outlet opening, the flow of gasoline vapors through said vapor opening vapor outlet is prevented.   The device according to claim 11, wherein said upper part of said float valve member is provided with a fixing part, said fixing part comprising a cylindrical part extending axially and a part extending radially located at a distance from said upper part so as to form a lock to prevent said   elastomeric element is detached from said upper part.   13. Device according to claim 11, in which said elastomeric element comprises a lower part, a hollow cavity part adjacent to said lower part and a passage extending from said lower part towards said external lining. 14. Device according to claim 1 1, wherein said elastomeric lining is an elastomer selected from the group   composed of fluoroelastomer and fluorosilicone.   15. Device according to claim 11, wherein said interior lining comprises a passage connected to said inlet opening. vapors.   16. Device according to claim 11, in which said elastomeric lining is provided with an outside diameter, an inside diameter and a recessed cavity part which comes into contact with said upper part of said valve part. float.   17. Device according to claim 11, in which said flexible lip of the lining comes into sealing contact with said float valve element and said outlet opening of   vapors when said float valve member is above   above the predetermined level and said float valve is in an intermediate position.   18. Device according to claim 11, in which said internal lining and said flexible lip of the lining come into sealing contact with said float valve element when said float valve element is above the level.   predetermined and is in a final position.   19. Device according to claim 11, in which said flexible lip seal is in leaktight contact with said vapor outlet opening until the level of fuel drops in the petrol tank and the weight of the element of float and bending of the lip seal overcome the force exerted by the pressure of the petrol vapors against the garnish.   20. Device according to claim 11, in which said flexible lip seal cannot become blocked due to the flexing of the seal when the liquid level moves axially in response to the progression of the fuel level towards the predetermined level. .