GB2066423A

GB2066423A - Valve and Method of Controlling Fluid Flow Through Valve

Info

Publication number: GB2066423A
Application number: GB8034889A
Authority: GB
Original assignee: Lowe and Fletcher Ltd
Current assignee: Lowe and Fletcher Ltd
Priority date: 1979-11-02
Filing date: 1980-10-30
Publication date: 1981-07-08

Abstract

A valve for use in a fuel tank filler cap. A valve element (19) movable towards and away from a seat (36) is biased against movement from its closed position when in a closed position and is biased against movement from its open position when in the open position. When fitted in filler caps on fuel tank filler necks, the valve closes when fuel surges into the filler neck and also when the vehicle associated with the fuel tank turns over. Biassing of the valve element is carried out magnetically. <IMAGE>

Description

SPECIFICATION Valve and Method of Controlling Fluid Flow Through Valve Description of Invention - From one aspect, the present invention relates to a valve suitable for use in a filler cap which is intended to fit on fuel tank filler necks. In order to avoid significant pressure differentials between the external atmosphere and the interior of the fuel tank, it is known to provide in the filler cap a passageway through which air can be admitted to the tank and through which vapour can escape from the tank. In the case of a fuel tank incorporated in a vehicle, it is desirable to provide in the passageway a valve for preventing the escape of liquid fuel through the filler cap in the event of the vehicle overturning. The invention also provides a method of controlling the flow of fluid through a valve which achieves this result.

Patent Specification No. 1,418,269 discloses a filler cap with a valve normally in a closed state biased thereto by a spring. To ensure an uninterrupted flow of fuel from the tank to the engine, the valve opens when the pressure inside the tank is less than atmospheric pressure. To achieve this the spring must be weak, the valves therefore cannot be relied upon to provide a fluid tight seal when closed.

According to a first aspect of the invention, there is provided a valve for controlling the flow of fluid through a passage defined by the valve, the valve comprising a member which presents a valve seat and an element movable towards and away from the seat between an open position in which there is a gap between the valve element and the seat and a closed position in which the valve element is engaged with the seat, wherein the valve element is biased against movement from its closed position when in a closed position and is biased against movement from its open position when in the open position.

The biasing of the valve element against movement from its open position ensures that the valve is not closed by the slight pressure differentials across the valve which cause flow of gaseous fluids through the passage of the valve at a low rate. The biasing of the valve element in the closed position reduces the risk of leakage through the valve when closed.

The biassing of the element when in the open condition can be overcome by an increase in pressure at the side of the valve which, when the valve is incorporated in a filler cap, is in communication with the tank, as occurs for example when fuel surges.

When closed by a surge of fuel, as may occur when the tank is full and/or the vehicles progress is erratic, the valve may remain closed for longer than the period for which a danger of leakage occurs, due to a residual pressure differential across the valve or the biassing of the element against movement from its closed position. In such circumstances, the pressure of gaseous fluids in the tank may increase for example due to the effect of heat on the tank.

According to a second aspect of the invention, there is provided a valve comprising a member which is movable between two seats defined by the valve, which prevents flow of fluid through a passage of the valve when engaged with either of said seats and which allows flow of fliud through the passage when in an intermediate position in which the member is spaced from each of said seats.

When the member is in the intermediate position, a venting action occurs. When this action is sufficient to remove or significantly reduce a pressure differential across the valve, as is the case when the pressure differential is caused by an expansion of gaseous fluids, the member can engage with one of its seats.

According to a third aspect of the invention, there is provided a method of controlling flow of fluid through a valve wherein a first member of the valve, which is movable relative to a second member of the valve into and out of engagement with a seat of the second member, is, when there is no pressure differential across the valve, restrained by magnetic force against movement onto the seat and wherein the first member is moved, by a pressure differential established across the valve, onto the seat to prevent flow of fluid past the seat.

Preferably, said first member is urged by the magnetic force onto a further seat on the second member to prevent flow of fluid past the further seat when there is no pressure differential across the valve, and the first member is moved momentarily off the further seat by a temporary pressure differential across the valve.

A pressure differential sufficient to move the first member onto the first mentioned seat can be established across the valve, when for example a vehicle having a fuel tank filler cap incorporating the valve overturns. When this occurs, gravity drives the fuel into the valve and a pressure differential due to the weight of the column of fuel above the valve is set up. When slight movement of the first member off the further seat is capable of significantly reducing a pressure differential across the valve, the first member will return to the further seat upon reduction or cessation of such a temporary pressure differential.

According to a fourth aspect of the invention, there is provided a valve or filler cap substantially as herein described with reference to and as illustrated in the accompanying drawings.

According to a fifth aspect of the invention, there is provided a valve comprising a main member which defines a valve orifice and a closure member for closing the valve orifice, the main member and the closure member being relatively movable to close and open the valve, wherein at least one of said members is permanently magnetised and comprises particles of magnetic material which are dispersed in a matrix of plastics material.

The magnetic field of said one member can be used to influence the condition of the valve, for example to establish a required contact pressure between the valve and its seat when the valve is engaged with the seat.

One example of a valve in accordance with the first, second, fourth and fifth aspects of the invention for use in a method according to the third aspect, will now be described, with reference to the accompanying drawings wherein: Figure 1 shows a perspective view of part of a filler neck; Figure 2 shows a perspective view of a filler cap for application to the filler neck; Figure 3 shows a cross-section through the valve and adjacent parts of the cap in positions adopted for a normal working condition; Figure 4 shows a cross section of the valve in a surge condition.

Figure 5 shows a cross-section of the valve in a roll-over condition.

The filler neck 50 shown in Figure 1 is provided on a vehicle fuel tank and has at its outer end an inwardly directed flange 51, from the inner edge of which there depends a pair of ramps, one of which is shown at 52. A respective notch 53 in the flange leads to each ramp. Radially outwardly of the notches 53, the flange 51 provides an annular seat for engagement by a rubber seal 54 on the filler cap.

The filler cap comprises a disc-like body 55 having a hollow central boss 56 which projects from the body inwardly of the filler neck. The seal 54 is mounted on the body near to its periphery.

Radially inwardly of the seal, the body is provided with a pair of depending lugs 57 which engage in the notches 53 to constrain the body against rotation relative to the filler neck. The body further includes valve housing 11 disposed between the boss 56 and the seal 54. In the housing 11 there is a valve through which there extends two flanges, an inner flange 6 and an outer flange 7, both of which, when the cap is fitted to the filler neck, lead from the interior of the filler neck through the body.

The filler cap further comprises a cover 58 which covers the face of the body 55 which is remote from the filler neck but is generally spaced from the body to provide communication between the atmosphere outside the cap and the passage through the valve housing 11. The cover is mounted for limited rotation on the body 55 by a stem 59 which extends through the boss 56. An O-ring seal (not shown) is provided between the stem and the boss. On an end portion of the stem 59 which protrudes from the boss 56, there are provided two retaining arms 60 for engaging with the ramps 52 to secure the cap on the filler neck.

A compression spring (not shown) is interposed between the cover 58 and the body 55 for urging the body towards the flange 51 of the filler neck.

When the cap is applied to the filler neck, the arms 60 are aligned with the lugs 57 and pass through the notches 53. Rotation of the cover then drives the arms down the ramps 52 to stress the compression spring and establish pressure contact between the seal 54 and the filler neck flange. Rotation of the cover relative to the body is limited by a stop 61.

If required there may be provided in the boss 56 a cylinder lock mechanism whereby the arms 60 can be locked against rotation relative to the body.

In normal operating conditions, the filler cap adopts a generally upright orientation and the valve housing 11 is shown in this orientation in Figure 3. The tubular housing is symmetrical about an axis 12 and the interior is stepped along the length of the axis. A lower end portion 10 of the housing communicates with the part of the filler neck which leads to the fuel tank. An upper end portion 9 of the housing is mounted in fluidtight relation in or is integral with, the body 55.

A spigot 13 is mounted in the lower end portion 10 of the housing 11, in co-axial relation thereto, by radially extending arms 14 which engage with the sides of the housing. The spigot does not significantly impede flow of fluid through the housing, which may take place between the arms. A gauze 8 between the arms segregates particles from the fluid passing through the housing. A valve body 1 5, which is also co-axial with the housing, rests on a shoulder 1 6 of the spigot. A downwardly extending sleeve 17 of the body 1 5 is a sliding fit on the spigot, and the lowermost end 1 8 of the sleeve rests on said shoulder. The spigot and body are substantially symmetrical about the axis 12 of the housing; the spigot guides the body for movement along the axis of the housing and the shoulder limits this movement in one direction.

A valve element 19 rests in turn on an upwardly facing surface 20 of the body 1 5. The element is comprised of a first part 22 which is of generally greater radius than a second part 23, the second part protruding towards the upper end portion 9 of the housing. The first part is enclosed by upwardly extending protuberances 24 of the body 1 5. These may form a continuous ring about the first part of the element or, as shown in the diagrams, consist of a plurality of discrete protuberances. Lobes 25 on the first part of the element are a sliding fit within the protuberances which constrain movement of the valve element in the housing to an axial direction. It will be noted that the area of the downwardly facing surface of the body 15 is a plurality of times greater than that of the element 1 9.

An annulus 26 is mounted in the housing 11 at a position between the end portions 9 and 1f1 thereof and sealed to the inwardly facing surface of the housing. A surface on the annulus which faces generally towards the upper end portion of the housing and which is inclined with respect to the axis 1 2 of the housing forms a frusto conical seat 29 for a movable valve member 30. The member has an elastomeric O-ring 28 for engagement with the seat which limits movement of the member 30 in a downward direction and compression of the O-ring between the inclined surface and a shoulder on the movable member forms a seal against passage of fluid past the seat. The valve member is free to move between the seat 29 and a seat 31 which limits movement of the member in an upward direction.This seat is of a similar form with an inclined surface on the housing and an elastomeric O-ring 33 on the movable member.

With the movable components of the valve, namely body 15, element 19 and movable member 30, adopting the positions shown in Figure 3, the inner passage 6, between the inwardly facing surface of the movable member 30 and parts of the surface of the valve element is open. The valve element is shown in an open position.

The valve element 19, movable member 30 and fixed annulus 26 are magnetic, with the North and South poles on these elements indicated in Figure 3. South poles of the valve element are formed on the lobes 25 of the first part 22, the second part 23 of the element comprises the corresponding North pole. A lower part of the movable member forms a North pole and an upper part forms the South pole. Magnetic attraction between the North pole of the movable member and the South poles of the element overcomes attraction between the South pole on the movable member and the North pole on the element to bias the element against movement from an open position when in the open position.

Similarly, an upper part of the fixed annulus forms a North pole and a lower part a South pole.

Magnetic attraction between the North pole of the annulus and the South pole of the movable member biases the member against movement from seat 29.

Figure 4 shows the positions adopted by the elements of the valve when fuel surges into the lower part of the housing 11 and against the downwardly facing side of the valve body 1 5. The fuel exerts pressure on the body in an upward direction towards a seat 34. This seat is of a similar form to seats 29 and 31 and is formed by an inclined surface on the movable member 30.

An O-ring 35 on the body engages the seat 34 to seals the valve against the flow of fuel through the passage between the member 30 on the one hand and the valve element and body on the other hand.

As the body 1 5 is driven upwardly, the valve element 1 9 is carried with it and thereby prevented from remaining in its closed position.

The second part 23 of the element passes into a narrow opening 40 of the valve member 30 at the upper part 9 of the valve housing 11. The element reaches a position where the magnetic attraction 'between the North pole of the second part of the element and the South pole of the movable valve member is sufficient to overcome the magnetic attraction which biases the element towards its open position, and the element is lifted clear of the upwardly facing surface 20 of the body. The element impinges on a seat 36 formed on the member 30 so that further upward movement is prevented. Seat 36, like seats 29,31 and 34, is co-axial with the valve housing, with an O-ring 37 on the element held in pressure contact with an inclined surface on the member 30 when the valve element is in its closed position.

Figure 4 shows the valve element 19 on seat 36 and the valve body 1 5 held in pressure contact with seat 34. The inner passage 6 is sealed against an upward surge of fuel at the seats 29, 34 and 36. As the fuel surges into the lower part of the housing 11, a pressure differential is created against the seats. The magnetic force holding the element on seat 36 ensures that the retaining of the element on the seat is less dependent on changes in pressure differential than is the retaining of the valve body on seat 34.

Seat 36 provides a second point at which the inner passage is sealed. If the inner passage is not sealed at seat 34, for example if particles should hold the valve body clear of the seat, seat 36 improves the effectiveness of the valve.

When the passage is sealed, during or shortly after a surge of fuel into the lower part of the housing 11 , the pressure of gaseous fluids in the tank may increase due, for example, to external heating of the tank. Movement of the movable member 30 can provide a venting action when this occurs. A sufficient pressure differential across the valve will urge the member just clear of seat 29 against the force of magnetic attraction between the member and the fixed element 26.

When member 30 occupies an intermediate position between seats 29 and 31, the outer passage 7 is opened through the valve between the outwardly facing surfaces of the member and the inwardly facing surfaces of the housing 11.

The outer passage is annular and substantially coaxial with the inner passage 6 and the housing.

The member may occupy such an intermediate position until the pressure differential across the valve has decreased sufficiently, i.e. significantly, to enable magnetic attraction to draw the member back onto seat 29. The minimum pressure differential necessary to move the member 30 from its seat 29 onto its seat 31 exceeds the minimum pressure differential which causes the body 15 and the valve element 19 to move to their closed positions.

The movable components of the valve housing 11 will usually return to their normal operating positions when the fuel surges back down the filler neck 50. The return surge of fuel may be sufficient to draw the valve body 1 5 back onto shoulder 1 6 or the body may drop back after a venting action has decreased the pressure differential across the valve. Furthermore, use of fuel by the vehicle engine establishes a pressure differential to draw the body onto the shoulder. As the body moves downwardly, abutments 39 on the protuberances 24 engage with the lobes 25 on the first part of the element to draw the element to a position where the magnetic attraction biasing the element towards the open position is sufficient to overcome the magnetic attraction biasing the element towards the closed position. The element then slides down onto surface 20.

In the event of a vehicle to which the filler cap shown in the drawings is fitted being overturned, the effect of gravity on the fuel drives body 1 5 and thereby element 1 9 onto their respective seats 34 and 36. The pressure differential across the valve is sufficient to drive the movable member 30 from seat 29, against the magnetic attraction between the member and fixed annulus 26, onto seat 31. Both passages through the valve are then sealed against leakage of fuel, as shown in Figure 5.

Each of the element 19, the fixed annulus 26 and the movable member 30 is formed of a composite material comprising particles of magnetic material which are dispersed in a matrix of a plastics material. In the particular example illustrated, the particles consist of iron oxide and the plastics material is nylon. Typically, the weight of the particles is four times that of the plastics material. The element, fixed annulus and movable member are formed separately by moulding a mixture of iron oxide particles and plastics material whilst the mixture is subjected to the influence of a magnetic field. The resulting mouldings are permanently magnetised and have a surface layer wherein the proportion of iron oxide particles is less than the proportion in the remainder of the moulding. It may be noted that other forms of biasing, such as is provided by springs for example, may be used in preference to part or all of the magnetic biasing described herein. The body is formed of plastics material without any magnetic particles dispersed therein.

Claims

1. A valve for controlling the flow of fluid through a passage defined by the valve, the valve comprising a member which presents a valve seat and an element movable towards and away from the seat between an open position in which there is a gap between the valve element and the seat and a closed position in which the valve element is engaged with the seat, wherein the valve element is biased against movement from its closed position when in a closed position and is biased against movement from its open position when in the open position.

2. A valve according to Claim 1 wherein parts of the valve are magnetised to establish a magnetic field which opposes movement of the valve element from its closed position when in the closed position and which opposes movement of the valve element from its open position when in the open position.

3. A valve according to Claim 1 or Claim 2 wherein either said member or a further member of the valve is movable between two further seats defined by the valve, said movable member prevents flow of fluid thorugh a further passage of the valve when the member is engaged with either of said further seats, said movable member is biased against movement from one of the further seats and said movable member allows flow of fluid through the further passage when the movable member is in an intermediate position in which it is spaced from both of said further seats.

4. A valve according to Claim 3 as appendant to Claim 2 wherein the magnetic field biases said member against movement from said one of the further seats.

5. A valve according to any preceding claim further comprising a body which is movable relative to said member between a closed position in which the body engages a fourth seat also to prevent flow of fluid through the first said passage and an open position in which the body is spaced from the fourth seat and wherein there are provided on the valve element and on the body respective abutments which co-operate to prevent the valve element remaining in its closed position when the body moves to its open position and to prevent the valve element remaining in its open position when the body moves to its closed position.

6. A valve according to Claim 5 wherein the arrangement is such that, when the body moves into its closed position, the body moves the valve element to a position where it is subjected to a magnetic force urging the valve element into its closed position.

7. A valve according to Claim 2 wherein both of said member and said valve element are permanently magnetised.

8. A valve according to Claim 3 wherein said movable member is permanently magnetised and interacts magnetically with a permanently magnetised element which is fixed with respect to a housing of the valve.

9. A valve according to Claim 5 wherein the body is formed of non-magnetic material.

10. A valve according to Claim 3 wherein the further passage is annular and lies at the periphery of the movable member.

11. A valve according to Claim 10 wherein the passages are coaxial.

12. A valve according to Claim 5, Claim 6 or Claim 9 wherein the surface area of the body, as viewed in the direction of movement of the body from its open position to its closed position, is a plurality of times greater than the corresponding surface area of the valve element.

13. A valve according to Claim 3 wherein the valve element is moved into its closed position whenever there is established across the valve in the appropriate direction a pressure differential which is less than the minimum pressure differential across the valve in the same direction which will move the movable member from said one of its seats to the other of its seats.

14. A valve comprising a member which is movable between two seats defined by the valve, which prevents flow of fluid through a passage of the valve when engaged with either of said seats and which allows flow of fluid through the passage when in an intermediate position in which the member is spaced from each of said seats.

1 5. A valve according to Claim 14 wherein parts of the valve are magnetised to establish a magnetic field which urges said member into engagement with one of the seats at least when the member is nearer to said one seat than to the other seat.

16. A filler cap comprising a valve according to any preceding claim.

1 7. A method of controlling the flow of fluid through a valve wherein a first member of the valve which is movable relative to a second member of the valve into and out of engagement with a seat on the second member is, when there is no pressure differential across the valve, restrained by magnetic force against movement onto the seat and wherein the first member is moved, by a pressure differential established across the valve, onto the seat to prevent flow of fluid past the seat.

18. A method according to Claim 17 wherein said first member is urged by the magnetic force onto a further seat on the second member to prevent flow of fluid past the further seat when there is no pressure differential across the valve and wherein the first member is moved momentarily off the further seat by a temporary pressure differential across the valve.

1 9. A valve or a filler cap substantially as herein described with reference to and as illustrated in the accompanying drawings.

20. A method of controlling the flow of fluid through a valve substantially as herein described with reference to and as illustrated in the accompanying darwings.

21. A valve comprising a main member which defines a va!ve orifice and a closure member for closing the valve orifice, the main member and the closure member being relatively movable to close and open the valve, wherein at least one of said members is permanently magnetised and comprise particles of magnetic material which are dispersed in a matrix of plastics material.

22. A valve according to Claim 21 wherein said one of the members is formed by moulding a mixture of the magnetic particles and the plastics material.

23. A valve according to claim 22 wherein the mixture is subjected to a magnetic field during moulding.

24. A valve according to any one of Claims 21, 22, and 23 wherein said one of the members has a surface layer in which the proportion of particles of magnetic material is less than the proportion of particles of magnetic material in a part of the member covered by the surface layer.