Valve for the venting circuit of a liquid tank

Abstract

Valve for the venting circuit of a liquid tank, said valve containing: a) a chamber (3) which opens into the tank and is connected via an aperture to the venting circuit; b) a float containing a head provided with a needle and able to slide vertically inside the chamber; and c) a closure member for closing off the venting aperture and itself having an aperture that can be closed off by the needle of the float, the closure member having a flexible seal which is capable of moving substantially vertically relative to the head of the float, said head being provided with a device for limiting the movement of the seal

Description

REFERENCE TO PRIOR APPLICATIONS

This application claims priority to French patent application 0505195 filed May 24, 2005, incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a valve for the venting circuit of a liquid tank, in particular a fuel tank with which a motor vehicle may be equipped.

Additional advantages and other features of the present invention will be set forth in part in the description that follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from the practice of the present invention. The advantages of the present invention may be realized and obtained as particularly pointed out in the appended claims. As will be realized, the present invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the present invention. The description is to be regarded as illustrative in nature, and not as restrictive.

BACKGROUND OF THE INVENTION

Liquid tanks, in particular fuel tanks for motor vehicles, are nowadays generally provided inter alia with a venting circuit. This circuit allows air to be introduced into the tank in the event of underpressure (especially for compensating for the volume of liquid consumed) or allows the gases contained in the tank to be removed in the event of overpressure (especially in the event of overheating). This circuit also allows the channelling and possible filtering of the gases that have to be discharged into the atmosphere, for the purpose of meeting the ever stricter environmental requirements in this regard.

The venting circuit includes, in a known manner, a valve that prevents, as far as possible, liquid from the tank being expelled in the event of the tank being turned upside down or at an excessively high angle of inclination. This venting valve must provide a rapid and reliable response when these conditions arise, but with minimal sensitivity to abnormal phenomena such as in particular very high flow rates, overpressure in the tank or low-amplitude waves.

Many venting valves employ a float having an upper needle for closing of a connection aperture between the tank and the venting circuit (see for example Patent EP 803671 in the name of the Applicant). Such valves often have the drawback of a delay in opening, which is due to the fact that the force pressing the needle against the aperture (and due to the pressure difference on either side of the aperture) lowers the force that pulls the float downwards (when it redescends owing to the effect of a lowering of the liquid level).

To alleviate this drawback, valves called “2-stage” valves have been developed, such as those described in U.S. Pat. No. 5,944,044. Such valves comprise, in addition to the needle float, a secondary closure member, which can move relative to the float and is fixed to the head thereof. This secondary closure member generally has an aperture that the primary closure member (the needle of the float) closes off in the high position, and which has a smaller cross section than that of the aperture for connection to the venting circuit.

The secondary closure member described in the abovementioned document consists in fact of two parts, namely an upper part (54) based on an elastomeric material, which has a complex shape and acts as a seal during obturation, and a lower part (56) that acts as a support for this seal and also has a complex shape.

Such a part is difficult and expensive to manufacture. The object of the present invention is therefore to provide a two-stage valve of simplified geometry which is easier to manufacture and less expensive.

SUMMARY OF THE INVENTION

The invention relates to a valve for the venting circuit of a liquid tank, said valve comprising:

a) a chamber which opens into the tank and is connected via an aperture to the venting circuit;

b) a float comprising a head provided with a needle and able to slide vertically inside the chamber; and

c) a closure member for closing off the venting aperture and itself having an aperture that can be closed off by the needle of the float, the closure member comprising, consisting essentially or, or consisting of a flexible seal which is “free” (not affixed to a support) and capable of moving substantially vertically relative to the head of the float, said head being provided with a limiter for limiting the movement of the seal.

The valve according to the invention is preferably intended for the circuit for venting a tank, which may contain any liquid. In particular, the liquid may be a fuel, a brake fluid or a lubricant. More particularly, the liquid is a fuel. The tank may be intended for any use, especially for equipping a vehicle and more especially for equipping a motor vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first venting valve according to the invention, in the open position;

FIG. 2 shows the same valve in the closed position;

FIG. 3 again shows the same valve, but in the course of closing; and

FIGS. 4 and 5 show a second version of a valve according to the invention or more precisely only the associated float/needle pair.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The chamber may have any shape, often internally adapted to the sliding of the float. For this purpose, it usually has a constant internal cross section, at least in the part where the float has to be able to slide. In particular, at least in this part, the chamber is internally cylindrical.

The external (lateral) shape of the float is obviously matched to that of the inside of the chamber in which it has to be able to slide. Therefore in general it has a cylindrical external shape.

The float of the valve according to the invention has a head with which a needle is associated in any manner. Preferably, the needle is integral with the head of the float. The head and the needle may be produced as a single part or produced separately and assembled. The term “needle” is understood to mean a tip of appropriate shape for closing off the aperture in the seal.

The valve according to the invention also includes a seal favouring the sealing of the valve in the closed position (that is to say when the seal closes off the venting aperture of the valve and when the needle closes off the aperture of the seal) and itself fulfilling the role of secondary closure member, giving the valve a two-staged effect (hence the expression “closure member . . . essentially consisting of a seal”). By this is meant in particular that the seal is “free”, that is to say it is not affixed to a support.

The seal may have any shape. A substantially flat seal (such as a portion of a diaphragm) gives good results and is simple to produce in practice. This flat seal may have an outline of any shape. A flat seal of substantially circular shape (that is to say a washer) is particularly simple and gives good results. This seal may be made of any material but preferably a material that is sufficiently flexible, (preferably having a Shore hardness of 60 to 80) to ensure sealing. Elastomers are very suitable as constituent materials for the seal, in particular fluoroelastomers (FPM).

According to the invention the seal is pierced by an aperture that can be closed off by the needle of the float. This aperture must therefore have a shape complementary to/compatible with that of the needle. It may have a cross section of any shape, whether constant or not, but preferably one that is similar (in shape and in size) to the cross section of the needle in that region of the latter serving to close off the aperture in the closed position of the valve. Cross sections that are almost identical with this region give good results in terms of sealing.

According to the invention, the head of the float is provided with a limiter for limiting the movement of the seal. Preferably, this limiter forms an integral part of said head (and/or of its needle), that is to say the head/needle has (have) a geometry allowing the seal to move essentially vertically relative to said head (and in its entirety, i.e. the seal does not remain in permanent contact with the needle), but with a limited travel. In other words, this geometry must allow a clearance between the movement of the needle and that of the seal, so as to obtain the desired two-staged effect. This geometry is preferably such that it favours the equalization of the pressures on either side of the seal when the valve starts to descend and clears the aperture in the seal. It is also such that the lateral movements of the seal are limited, so that its aperture remains aligned with the needle of the float.

According to a first embodiment of the invention, the needle has, at its upper end (or tip), a larger cross section than that of the aperture in the seal. Within the context of the invention, such a geometry means that the needle also has a cross section generally smaller than the cross section of the aperture in the seal. In this way, the seal can slide freely over a large portion of the needle, but is stopped in its travel by the tip. In this embodiment, the lower end of the needle (or its base for anchoring onto the head of the float) preferably has a cross section substantially equal (in shape and size) to that of the aperture of the seal so as to ensure perfect sealing in the closed position of the valve.

Consequently, a needle geometry that is very suitable for this embodiment is that in which the needle is essentially conical but is provided with a stop device at its tip. This stop device preferably has a conical lateral surface so as to make it easier to pass through the aperture of the seal (by deforming the latter, taking advantage of its elasticity) when fitting the seal onto the head of the float. In this embodiment of the invention, the stop device preferably has at least one passage for the gases, so as to allow the two-staged device to rebalance the pressures after the needle has been disengaged from the aperture of the closure member. For this purpose, the closure member is advantageously in the form of a cross, the branches of which limit the displacement of the closure member while providing a passage for the gases between them.

One drawback of this embodiment lies in the fact that part of the aperture of the seal is occupied by the needle, which retards the flow of gases and delays the equalization of the pressures on either side of the seal when the valve opens.

Thus, according to a preferred second embodiment of the invention, the head of the float comprises vertical hooked fingers that surround the needle and have an upper end higher than the needle. In this way, the seal can slide vertically between the hooked end of the fingers and a position where it bears on the head of the float. The term “hooked” is understood in fact to mean any shape allowing the seal to be retained. This shape may for example be that of an “L” on its tip.

In this embodiment, there are preferably at least three fingers so as to prevent the seal from leaking between two consecutive fingers. Most particularly preferably, there are at least four of them so as to limit this risk. These fingers are preferably placed symmetrically on the head of the float, and therefore in the form of a cross with equal branches when there are four of them. Most particularly preferably, these fingers guide the seal during its vertical travel, so as to minimize its lateral movements.

Again according to this embodiment, the venting aperture preferably consists of the end of a venting duct. This duct makes it possible for the aperture to be located inside the fingers when the float is in the high position, this being necessary in order to allow the needle and the seal to close off said aperture.

Advantageously, the head of the float has a shape (domed or conical) so as to prevent the seal from sticking on the head in the event of liquid being deposited at this point.

The head of the float may also, or in addition, include ribs on the surface (for example arranged in the form of a cross), so as to facilitate drainage of the liquid in line with the seal and to prevent liquid entrainment when the valve reopens.

The chamber of the valve according to the invention preferably includes a support for the float when the latter is in the low position. The support for the float may be of any known type. Advantageously, it is an apertured plate or apertured frustoconical dish. The term “apertured” is understood to mean having several openings that allow liquid to flow through the dish in order to allow the float to fulfil its function. In particular, the frustoconical dish or the plate includes a central aperture. When the liquid level rises in the tank, this liquid penetrates the valve via the lower part, through the openings in the frustoconical dish or the plate, forces the float upwards and also causes the needle to close off the aperture located in the head of the valve.

In a preferred embodiment, the chamber of the valve according to the invention has, in its upper part, one or more lateral openings for flow of the gases, and therefore providing the degassing/venting function of the valve. Advantageously, these lateral openings are small in size, so as to prevent the flow of substantial volumes of liquid, in particular by throttling. These openings may for example be made on a circuit provided with one or more baffles or in the form of a labyrinth. In particular, these openings have an elongate rectangular cross section. Advantageously, the number of these openings is at least two, more advantageously at least four. Preferably they do not exceed eight in number. These openings preferably have together a total flow area of at least 35 mm², more preferably still at least 45 mm². Good results have been obtained when these openings together have a total flow area not exceeding 100 mm².

The term “gas” is understood in particular to mean the external air that has to be introduced into the tank or the gas mixtures contained in the tank, the removal of which has to be possible. In the case of a fuel tank, these gas mixtures comprise essentially air, and fuel vapour.

Positioning gas flow openings in the upper part of the chamber very substantially reduces the possible impact on these openings of the liquid level and of its movements, thus allowing venting in certain critical situations. This impact may also, when required, be reduced by the use of at least one baffle placed facing some of the openings and preferably all of them. This may be a single baffle having a substantially annular cross section, surrounding the head of the valve. Or alternatively, it is possible to use a succession of baffles, each facing one or more openings. This or these baffles may be located on the inside and/or on the outside of the chamber.

Preferably, there is both at least one baffle internal to the chamber and at least one baffle external to the chamber. The fact of having an external baffle, protecting the abovementioned venting openings, enables the size of the openings to be increased. The fact of also having an internal baffle makes it possible to increase the tortuosity of the path followed by the gases and therefore to further reduce the risks of entrainment. However, the shape and the size of the internal baffle must be such that it does not disturb the movements of the float.

The embodiment with an internal (or double) baffle is consequently preferably used in conjunction with a conical float head, as described above. In this case, the internal baffle advantageously surrounds the conical part of the float when the latter is in the high position. It should also be noted that this embodiment may be used with good results outside the scope of the invention, for any valve provided with an aperture intended for a flow of gas without any risk of liquid entrainment.

The valve according to the invention allows a liquid tank to be vented. It does not have, as such, the function of preventing ingress of liquid in the event of a vehicle rolling over or being excessively tilted (ROV or Roll-Over Valve function), the function of fixing the maximum fill level (FLVV or Fill Limit Venting Valve function) and/or the function of preventing overfilling (OFP or Overfilling Prevention function). These functions must therefore, where appropriate, be provided by independent devices or by additional means combined with the valves.

To provide the abovementioned ROV function, the means generally employed consist of a heavy ball and/or a preloaded spring. A heavy ball gives good results, in particular in combination with an apertured frustoconical dish (or perforated plate in combination with a float having a concave frustoconical bottom). In the event of the tank being inclined, this ball moves in the frustoconical dish, drives the float upwards and causes the venting aperture to be closed off by the needle and the seal of the head of the valve even before the liquid level rises in the valve, thus completely preventing liquid from flowing into the venting circuit. In the event of the tank rolling over, the ball of heavy material also pushes the float towards the closed position of the valve and, through gravity, keeps it in this position.

The FLVV function, also mentioned above, may be provided by any known means, for example by using lateral apertures in the chamber, these being placed so as to be closed off by the liquid when this reaches a certain level in the tank. These apertures must be dimensioned so that the reduction in venting flow rate resulting from their being closed off is sufficient to trip the filling nozzle a first time (as a result of the pressure rise generated). After several successive trips, the nozzle will trip a final time as soon as the float and its seal have closed off the venting aperture.

As regards the OFP function, this may be provided, where required, by any of the devices known for fulfilling this function. Heavy-ball OFP devices closing off the venting aperture by gravity give good results.

Preferably, the OFP device chosen is housed in the upper part of the valve, inside the chamber, above the float. It then rests on a wall separating the valve into a top part, fulfilling the OFP function, and a bottom part, fulfilling the venting function. This wall is pierced by an aperture that is closed off by the ball below a certain pressure level in the tank. This wall is advantageously moulded as a single part with the chamber of the valve.

The constituent elements of the valve may be made of any material. Preferably, they are based on a thermoplastic. In this case, it is obviously convenient to choose the material or materials in such a way that they withstand the operating stresses. Of course, the materials chosen must be inert with respect to the liquids with which they have to be in contact, in particular inert with respect to fuels.

In particular in the case in which the liquid tank is a fuel tank made of plastic, most of the constituent elements of the valve according to the invention are also made of plastic. The term “plastic” is understood to mean any polymeric synthetic material, whether thermoplastic or thermosetting, which is in the solid state under ambient conditions, as well as blends of at least two of these materials. The intended polymers comprise both homopolymers and copolymers (especial binary or ternary copolymers). Examples of such copolymers are, non-limitingly: random copolymers, linear block copolymers, non-linear block copolymers, and graft copolymers. Thermoplastic polymers, including thermoplastic elastomers, and blends thereof are preferred.

Any type of thermoplastic polymer or copolymer, the melting point of which is below the decomposition temperature, is suitable. Thermoplastics having a melting range spread over at least 10 degrees Celsius are particularly suitable. Examples of such materials include those that exhibit polydispersion in their molecular weight.

In particular, the valve according to the invention may be made of polyolefins, grafted polyolefins, thermoplastic polyesters, polyketones, polyamides and copolymers thereof.

One polymer often used in plastic fuel tanks is polyethylene, in particular high-density polyethylene (HDPE) possibly in a multilayer structure including a barrier layer (for example based on EVOH, or hydrolysed ethylene/vinyl acetate copolymer) or one with a surface treatment (fluorination or sulphonation for example) for the purpose of making it impermeable to the fuels for which it is intended. Consequently, when the valve according to the invention includes a cover, this is preferably based on HDPE, so as also to be welded to the tank. As for the other parts of the valve, these are preferably based on at least one hydrocarbon-impermeable plastic. Examples of such hydrocarbon-impermeable plastics are, non-limitingly: polyethylene terephthalate or polybutylene terephthalate, polyamides, polyketones and polyacetals. It should be noted that all these parts, the cover included, may be multilayer structures, comprising, for example, at least one high-density polyethylene layer and optionally a hydrocarbon barrier layer (on the surface or within said structures).

In the case of a plastic fuel tank, and in particular one based on HDPE, good results have been obtained with valves, including a cover, based on HDPE, a chamber and a float made of POM (polyoxymethylene) or PBT (polybutylene terephthalate), and a seal made of a fluoroelastomer.

The method and the position for fastening the valve to the tank may be chosen in any standard manner suitable for the specific conditions. Preferably, the valve is joined directly to the upper wall of the tank and preferably by welding its cover (see above).

The invention also relates to a tank comprising a valve as defined above.

The invention is illustrated non-limitingly by the following figures:

FIG. 1 shows a first venting valve according to the invention, in the open position;

FIG. 2 shows the same valve in the closed position;

FIG. 3 again shows the same valve, but in the course of closing; and

FIGS. 4 and 5 show a second version of a valve according to the invention or more precisely only the associated float/needle pair.

FIG. 1 shows a venting valve comprising a cover (1) incorporating a venting tube (2), and a chamber (3) which opens into the tank (not shown). A float (4), shown in the low position, may slide vertically in the chamber (3) and includes a needle (5), (produced as a single part with the float) on which a seal (6) provided with an aperture rests. The upper part of the chamber (4) is in the form of a frustoconical dish (11) and includes a moving OFP ball (8). The float (4) can be made to move by the rise of the liquid in the valve through an apertured plate (9) or, in the case of the tank being inclined, by displacement of an ROV ball (10) of heavy material. The chamber (3) includes, in its upper part, small lateral openings (11) allowing the gases to flow but preventing substantial volumes of liquid flowing. The chamber also includes an internal baffle (12) of annular shape, for the purpose of stopping any liquid entrained by the gases through the openings (11). It should be noted that the cover (1) is extended downwards by an annular part, also acting as a baffle, but an external one. The head of the float (4) is provided with hooked fingers (13) defining a kind of hollow cage around the needle (5), in which cage the seal (6) can move.

FIG. 2 illustrates this same valve, but with the float (4) in the high position, when the needle (5) closes of the aperture in the seal (6) and when said seal closes off the lower end of a venting duct (14) opening in to the frustoconical dish (7).

To pass from the position illustrated in FIG. 1 to that illustrated in FIG. 2, the float (4) is moved vertically (in the direction indicated by the arrow in FIG. 2) through the effect of the rise of the liquid (not shown). Throughout this movement, the seal (6) remains integral with the needle (5). This position is then occupied by the float (4) in the event of roll-over and/or waves.

The maximum fill level of the tank is such that the float (4) occupies a lower position, allowing the OFP ball (8) to vent the tank after filling, even when full. However, the OFP ball (8) is preloaded so as not to vent the tank during filling (hence its names OFP). This type of valve is generally used in combination with another accessory for fixing the maximum fill level (in Europe, typically a tube, terminating in the upper part of the filling nozzle, while in the United States this is typically an FLVV valve). In order for this accessory to function, it is necessary for the valve not to vent during filling (in order to take part in a pressure rise at the end of filling, when said accessory is in the closed, obstructed, position and to cause the nozzle to trip).

FIG. 3 illustrates the same valve but when the fuel level has started to descend, entraining the float (4), but not yet the seal (6), which remains attached to the venting duct (14). The needle of the float (4).is however disengaged from the aperture of the seal (6), thereby allowing progressive balancing of the pressures on either side of the seal.

To return to the low position illustrated in FIG. 1, the liquid level must again fall (in the direction of the arrow indicated in FIG. 1) so that the float (4) is now retained only by the seal (6) still in contact with the lower end of the venting duct (14). Thus, as soon as the pressures on either side of the seal are balanced, the float will be free to descend. The final lift-off of the seal (6) by gravity is then assisted by the fingers (13).

FIGS. 4 and 5 illustrate an alternative geometry of the float head (4)/needle (5) pair, in which the needle (5) has a substantially conical shape and a tip in the form of a cross (13). In this embodiment, it is this cross (13) that allows the relative movement of the seal (6) with respect to the float (4) (which is not shown in its entirety in these figures, but only symbolized by its upper part) to be limited.

FIG. 4 shows a schematic view of only the upper part of the head of the float and FIG. 5 shows two sections illustrating two successive positions of the float relative to the venting duct (14).

The upper part of FIG. 5 shows the venting duct (14) closed off by the seal (6) and the needle (5), as is the case upon a roll-over, a wave, etc.

The lower part of FIG. 5 (which corresponds to the position of the seal illustrated in FIG. 4) shows that, when the float (4) starts its descent, the seal (6) firstly remains attached to the duct (14). However, thanks to the cross (13) shape of the top of the needle (5), pressure is balanced on either side of the seal (6), which finally allows, by gravity, the seal to separate (not shown). The direction of flow of the gases during this pressure balancing is illustrated by an arrow in these figures.

The above written description of the invention provides a manner and process of making and using it such that any person skilled in this art is enabled to make and use the same, this enablement being provided in particular for the subject matter of the appended claims, which make up a part of the original description, and including a valve for a venting circuit of a liquid tank, said valve comprising:

• a chamber (3) which opens into the tank and is connected via an aperture (14) to the venting circuit (2);
• a float (4) comprising a head provided with a needle (5) and able to slide vertically inside the chamber (3); and
• a closure member (6) for closing off the venting aperture (14) and itself having an aperture that can be closed off by the needle (5) of the float (4),
• the closure member (6) having a flexible seal (6) which is “free” (not affixed to a support) and capable of moving substantially vertically relative to the head of the float (4), said head being provided with a limiter device (13) for limiting the movement of the seal (6), where element numbers (Figure references) denote preferred embodiments of the more general terms.

As used above, the phrases “selected from the group consisting of,” “chosen from,” and the like include mixtures of the specified materials. Terms such as “contain(s)” and the like as used herein are open terms meaning ‘including at least’ unless otherwise specifically noted. The 6^th paragraph of 35 U.S.C. 112 is not implicated herein unless the specific term “means” is used.

All references, patents, applications, tests, standards, documents, publications, brochures, texts, articles, etc. mentioned herein are incorporated herein by reference. Where a numerical limit or range is stated, the endpoints are included. Also, all values and subranges within a numerical limit or range are specifically included as if explicitly written out.

The above description is presented to enable a person skilled in the art to make and use the invention, and is provided in the context of a particular application and its requirements. Various modifications to the preferred embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the invention. Thus, this invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.

Claims

1. A valve for a venting circuit of a liquid tank, said valve comprising:

a) a chamber which opens into the tank and is connected via an aperture to the venting circuit;

b) a float comprising a head provided with a needle and able to slide vertically inside the chamber; and

c) a closure for closing off the venting aperture and itself comprising an aperture that can be closed off by the needle of the float,

the closure member comprising a flexible seal which is not affixed to a support and capable of moving substantially vertically relative to the head of the float, said head being provided with a limiter that limits the movement of the seal.

2. The valve according to claim 1, in which the seal is a flat seal of substantially circular shape.

3. The valve according to claim 1, in which the needle comprises a tip having a larger cross section than that of the aperture in the seal.

4. The valve according to claim 1, in which the needle is substantially conical and its tip is in the form of a cross.

5. The valve according to claim 1, in which the head of the float comprises vertical hooked fingers that surround the needle and have an upper end higher than the needle.

6. The valve according to claim 5, in which the fingers are four in number and are arranged in the form of a cross with equal branches.

7. The valve according to claim 1, in which the head of the float is of convex, domed or conical shape and/or includes drainage ribs on the surface thereof.

8. The valve according to claim 1, in which the chamber has an upper part provided with lateral openings and in which at least one baffle is placed facing these openings.

9. The valve according to claim 8, comprising two baffles, one placed on the inside of the chamber and the other on the outside of said chamber.

10. The valve according to claim 1, which further comprises a cover comprising high-density polyethylene, and wherein said chamber and float are independently made of POM (polyoxymethylene) or PBT (polybutylene terephthalate), and wherein said seal is made of an elastomer.

11. The valve according to claim 1, wherein the closure member consists essentially of a flexible seal which is not affixed to a support and capable of moving substantially vertically relative to the head of the float.

12. The valve according to claim 1, wherein the closure member consists of a flexible seal which is not affixed to a support and capable of moving substantially vertically relative to the head of the float.