GB2046403A - Valves - Google Patents

Abstract

A vent valve for a petrol filler cap includes a passageway 50 within which a solid ball 51 is free to move gravitationally between a venting position in which the passageway is open and a closed position in which the ball engages a seating 55 to prevent the outflow of fuel. If desired, a hollow plastics ball 52 may also be provided to act as an additional shut-off element. <IMAGE>

Description

SPECIFICATION Venting means for a vehicle fuel tank or for a filler cap for such a tank This invention relates to venting means for motor vehicle fuel tanks and to filler caps.

The filler caps of motor vehicle fuel tanks normally include vent holes for ensuring that the interior of the tank is maintained at atmospheric pressure.

However, if a vehicle overturns, the outflow of fuel through the vent hole or holes will create a fire hazard condition and a number of proposals have accordingly been made for limiting the rate at which liquid fuel can escape through the vent hole or holes.

It is an object of the present invention to provide an improved venting arrangement.

According to the present invention there is provided venting means for a vehicle fuel tank or for a filler cap for such a tank, said venting means comprising a ball freely movable along a passageway which, in use, is not horizontal such that, when the vehicle is upright, the ball moves gravitationily into a portion of the passageway which is of greater cross-sectional area that the ball so asto permit free flow of air past the ball whereas, if the vehicle is tilted, the ball is displaced along the passageway to engage a seating and thereby close the passageway thus preventing the escape of liquid fuel from the tank.

The passageway may be of generally frustoconical form, the seating being at the smaller diameter end of the frustum and of generally tapered form. Alternatively, the passageway may be cylindrical, of radius greater than the ball, with the seating again of generally tapered or otherwise restricted form. The inclination of the axis of the passageway to the horizontal may be of the order of 15 with the seating at the higher end thereof and with a conduit extending from a position centrally of the seating to atmosphere.The ball may be of solid steel or glass (or some other solid material such as a polyacetal resin which is corrosion-resistant and is not affected by hydrocarbons), the ball typically being 6mm in diameter with the diameter of the passageway at the end thereof remote from the seating 8mm, and the travel of the ball between its two limiting positions being between 2mm. and 10mm.

In addition to the solid ball referred to above, the venting means preferably also includes a hollow ball of less diameter than the solid ball and formed from a synthetic plastics material such as a polyacetal resin. The hollow ball is conveniently located between the solid ball and the conduit leading to atmosphere with the arrangement such that, if air or vapour is caused to flow through the passageway (as could arise under certain accident conditions, the hollow ball is moved into position in which it closes said conduit to prevent flow of liquid fuel through the conduit.

As applied to a filler cap, the passageway may be formed within a moulded plastics body which carries a metal locking plate shaped to interengage with co-operating formations on the fuel filler tube. The body may be attached, for example by a snap-fit coupling, to a protective cover which carries a resilient sealing element which seals against the end face of the fuel filler tube. Alternatively, the moulded plastic body may be contained within a resilient bush snap-fitted in position in an aperture in a cap which carries a locking plate for interengagement with formations on the fuel filler tube. As a further alternative, the passageway is formed within a moulded plastics cap which has a threaded portion for engagement with a rolled thread formation of the fuel filler tube.

In a further arrangement, in which the venting means is separate from the filler cap, the filler tu be has a branch into the end of which is fitted a breather assembly comprising a moulded plastics body in which the passageway is formed, the moulded body being contained within a resilient bush snap-fitted in position in the end of the branch pipe which is so disposed as to ensure that the passageway is at the required inclination to the horizontal. As a further alternative, a breather assembly may be mounted directly in an aperture in the fuel filler tube, the breather assembly then including a moulded plastics body within which the passageway is formed at the required inclination, and a resilient sealing element acting between the body and the surround of the aperture.

The invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a sectional view of a filler cap, Figure 2 is a scrap view of an alternative form of filler cap, Figure 3 shows a locking plate forming part of the filler cap of Figure 2, Figure 4 is a sectional view of a further form of filler cap, Figure5shows a vehicle fuel tankfillertankhaving a branch pipe fitted with a vent assembly, Figure 6 is a sectional view of a vent assembly for a filler cap or branch pipe, and Figure 7 is a sectional view of a further form of filler cap.

The filler cap shown in Figure 1, includes a main body 10 which is moulded from a synthetic plastics material such as nylon or an acetal homopolymer, a cap 11 moulded from polypropylene, an annular sealing element 12 formed from a nitrile rubber, and a locking plate 13 formed from mild steel. The body 10 is attached to the cap 11 by means of screws 14 which also attach the locking plate 13 to the body 10, the locking plate 13 having cranked end portions 15 which interengage with co-operating formations on the fuel filler tube to hold the filler cap in position.An effective seal between the end of the filler tube and the filler cap is ensured by arranging for the nitrile sealing element 12 to be biassed towards the end face of the filler tube by means of a pair of resilient legs 16 formed integrally with the body 10, the construction being such as to ensure that there is a leakage path for the flow of air or vapour from a position at the centre of the interface between the cap 11 and the body 10 to atmosphere.

A passageway 17 extends along the axis of the body and, as shown, has a lower end portion adjacent the locking plate 13 which is of greater cross-sectional area than the end portion thereof adjacent the cap 11, the two end portions being interconnected by a part having a tapered wall surface 18 providing a seating for a ball 19 which is moulded from a polyacetal resin and is of such dimensions that, when the filler cap is inverted or partially inverted, the ball 19 seals against the wall surface 18to close the passageway 17.In use, the filler cap is mounted on the end of the filler tube with the axis of the passageway 17 inclined at an angle of about 15 to the horizontal, i.e. the arrangement is as indicated in outline in Figure 5 so that the ball 19 is at the end of the passageway 17 adjacent the locking plate 13 to permit the free flow of air around the ball 19 through the passageway 17. A venting action is thus provided.

If, however, the vehicle should tilt in the direction indicated by the arrow 20 in Figure 5, a condition will be reached in which the end of the passageway 17 adjacent the cap 11 is at a sufficiently lower level than the end of the passageway 17 adjacent the locking plate 13 for the ball 19 to roll along the passageway 17 into engagement with the seating afforded by the wall surface 18. As shown, the part of the passageway 17 adjacent the locking plate 13 is of cylindrical form so that the ball 19 will commence to roll as soon as the angle between the axis fof the passageway 17 and the horizontal is sufficient for the frictional restraints on the ball to be overcome.

Alternatively, this part of the passageway 17, may be of frusto-conical form and, in such case, the angle through which the vehicle will tilt before the ball 19 commences to roll will be greater by an amount dependant on the semi-apical angle of the cone.

In the modification shown in Figures 2 and 3, the cap 11 is attached to the body 10 by means of a snap-fit interengagement, the cap 11 being provided with projecting tangs 21 which are pressed through apertures in the body 10 so that shoulders on the rangs 21 locate against the surrounds of the apertures. The locking plate 13 is provided with two keyhole-shaped apertures 22 (Figure 3) which are arranged to receive projections 23 on the body, the method of assembly being such thatthe locking plate 13 is moved towards the body 10 so that the projections 23 pass through the larger portions of the apertures 22 and then the locking plate 13 is pushed sideways so that a snap action is obtained and the projections 23 are located relative to the locking plate 13 in the positions shown in broken lines in Figure 3.

The further embodiment shown in Figure 4, includes a one-piece moulding 24 of polypropylene which combines the functions of the parts 10 and 11 of the previous embodiments and has an aperture in which a vent assembly 25 is fitted, the detailed construction of the vent assembly 25 being as shown in Figure 6. The moulding 24 includes an outer skirt 26, an intermediate wall 27 on which a nitrile sealing element 28 is mounted and a central boss 29 to which a locking plate 30 is attached by means of screws 31. Upon tilting of the tiller cap so that the axis of the passageway in the vent assembly 25 is appropriately inclined to the horizontal, the passageway will be closed as described below in more detail with reference to Figures 5 and 6.

Figure 5 shows an arrangement in which the vehicle fuel tank filler tube 32 is closed by a non-vented filler cap 33 and there is a branch pipe 34 the end of which contains a vent assembly 25 corresponding to that fitted in the filler cap shown in Figure 4. The detailed construction of the vent assembly 25 is as shown in Figure 6 which, however, illustrates an assembly fitted in a filler cap having an outer plastics cover 35 of, for example, polypropy lene, and an inner sealing lining 36 of, for example, nitrile rubber.

The vent assembly shown in Figure 6 comprises a moulded plastics body 37 surrounded by a bush 38 of nitrile rubber which includes a neck portion and an adjacent flange 39 to ensure a fluid-tight sealing engagement between the vent assembly and the part in which it is mounted. The body 37 has an axial passageway which is of circular cross-section and includes portions of three different diameters; there is thus 9 first portion 40 of the greatest diameter, a second portion 41 of intermediate diameter and a third portion 42 of least diameter.The first and second portions 40 and 41 are connected by a tapered wall surface affording a seating for a solid steel ball 43 whilst the second and third portions are connected by a second tapered wall surface affording a seating for a hollow ball 44 of a polyacetal resin, the diameter of the hollow ball 44 being approximately half that of the solid bail 43. The vent assembly 25 is shown in its sealed condition (which it will occupy when the vehicle is inverted), with the two balls 43 and 44 in engagement with their respective seatings. Normally, however, the two balls 43 and 44 will be displaced downwardly from the position shown in Figure 6 so that air can flow freely through the passageway and the interior of the fuel tank will remain at atmospheric pressure.

When, however, the vehicle tilts sufficiently to generate an outgoing flow of air vapour, the hollow ball 44 will be lifted by the flow into engagement with its seating. As tilting continues, a position is reached in which, as described above, the solid ball 43 will roll along the passageway to ensure its seating and close the passageway, thereby, preventing the outflow of fuel.

Turning next to Figure 7, this shows a moulded plastics cap 45 which may be moulded from polyacetal resin or polypropylene but can consist of chromium-plated acrylonitrile-butadiene-styrene copolymer. The cap 45 has an H-shaped fingergrip formation 46 with the cross-piece 47 of the H formed with a bore 48 which communicates with a passageway 49 leading to the interior of a fuel tank to which the cap 45 is fitted. The passageway 49 leads to a chamber 50 within which are disposed a solid steel ball 51 and a hollow polyacetal ball 52, the two balls 51 and 52 being retained in position by means of a steel pin 53. The chamber 50 is shaped to provide two frusto-conical seatings 54 and 55, the first seating 54 being disposed adjacent the passageway 49 and arranged to co-operate with the smaller ball 52 whereas the second seating is arranged to co-operate with the larger ball 51.

In normal usage, the filler cap is attached to the filler tube with the axis of the passageway 49 inclined to the horizontal so that the steel ball 51 rests on and is supported by the transverse steel pin 53 and the two balls 51 and 52 are spaced away from their respective seatings 55 and 54 to allow the free flow of air through the passageway 49 and thereby ensure that the interior of the fuel tank reamins at atmosphereic pressure. When, as described above, there is an outgoing flow of air from the tank, the hollow ball 52 will be pressed into engagement with seating 54 and, when the vehicle tilts by a predetermined amount, the solid ball 51 will roll as to engage the larger seating 55 and prevent the outflow of fuel from the tank.

In the particular arrangement shown in Figure 7, the plastics moulding includes a peripheral skirt 56 and an externally threaded boss portion 57 which screws into the end of the filler tube which terminates in a roll-threaded neck 58 having an outwardly extending flange 59 which carries a nitrile rubber sealing element 60 which bears against the adjacent face of the cap 45.

Claims (10)

1. Venting means for a vehicle fuel tank or for a filler cap for such a tank, said venting means comprising a ball freely movable along a passageway which, in use, is not horizontal such that, when the vehicle is upright, the ball moves gravitationally into a portion of the passageway which is of greater cross-sectional area than the ball so as to permit free flow of air past the ball whereas, if the vehicle is tilted, the ball is displaced along the passageway to engage a seating and thereby close the passageway thus preventing the escape of liquid fuel from the tank.

2. Venting means according to claim 1, wherein the passageway is of frusto-conical form and the seating is at the smaller diameter end of the frustum.

3. Venting means according to claim 1,wherein the passageway is cylindrical, of greater radius than the ball, and the seating is of frusto-conical form.

4. Venting means according to claim 1,wherein said ball is solid and wherein the passageway also contains a hollow ball of less diameter than the solid ball.

5. Afillercap incorporating venting means according to any one of the proceeding claims wherein the passageway is formed within a moulded plastics body.

6. Afiller cap according to claim 5, wherein the plastics body carries a metal locking plate shaped to interengage with co-operating formations on a fuel filler tube.

7. A filler cap according to claim 5, wherein the moulded plastics body is contained within a resilient bush snap-fitted in position in an aperture in a cap.

8. Afiller cap according to claim 5, wherein the moulded plastics body has a threaded portion for engagement with a rolled thread formation on a fuel filler tu be.

9. Venting means for a vehicle fuel tank substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

10. A petrol filler cap substantially as hereinbefore described with reference to Figure 1, Figures 2 and 3, Figure 4, Figure 6 or Figure 7 of the accompanying drawings.