WO2016198896A1

WO2016198896A1 - Vehicle fluid tank cap assembly

Info

Publication number: WO2016198896A1
Application number: PCT/GB2016/051742
Authority: WO
Inventors: James R UNDERWOOD
Original assignee: Micro-Mesh Engineering Limited
Priority date: 2015-06-11
Filing date: 2016-06-10
Publication date: 2016-12-15
Also published as: GB2539244A; GB2539244B; GB201510210D0

Abstract

A cap assembly (10) for a vehicular diesel exhaust treatment fluid tank having a main body (12) defining an enclosure (30), a filter housed within the enclosure (30) and a removable cap for selectively closing a filling opening defining a fluid inlet (18) into the enclosure (30). A filter retaining formation (56) allows the filter to be selectively removed from the enclosure (30), an outlet opening is for connection to an inlet of a vehicle fluid tank, in use. Lockable engagement means is provided for selectively actuating the cap assembly (10) between a first configuration in which the cap assembly (10) is removable from the inlet of the vehicle fluid tank, and a second configuration in which the cap assembly (10) is engaged with the inlet of the vehicle fluid tank, such that the cap assembly (10) remains engaged with the vehicle fluid tank inlet whilst the cap is selectively removable for filling of the tank.

Description

Title - Vehicle Fluid Tank Cap Assembly

The present invention relates to a vehicle fluid tank cap assembly. Various fluid tanks are necessary for the operation and optimal performance of a vehicle. For example, fuel tanks are necessary to supply fuel to the engine of a vehicle, whilst oil tanks are necessary to provide oil that lubricates the engine in use. The ongoing trend toward reducing harmful vehicle engine emissions has seen the introduction of diesel exhaust fluid (DEF, also known as AdBlue®) for use in selective catalytic reduction (SCR) to reduce the concentration of NOx in diesel exhaust emissions from diesel engines. DEF is an aqueous urea solution typically having a composition of 32.5% high-purity urea and 67.5% deionized water, and is typically injected into the exhaust stream of a vehicle by a metering system. Thus, in order to use DEF it is necessary for the DEF to be stored onboard a vehicle in a fluid storage tank separate from the fuel tank.

In order to ensure that DEF achieves its desired function, it is necessary that the DEF solution is kept substantially free from impurities. In particular, it has been found that SCR systems are particularly sensitive to chemical impurities. It has previously been proposed to use filter assemblies in vehicle fluid tanks to filter the fluid prior to its intended use. However such filter assemblies are typically integrated into the fluid tank itself, thereby making maintenance of the filter time consuming and costly, particularly where the entire tank has to be replaced due to degradation of the filter, and further leading to a build-up of impurities within the tank itself.

The above problems are compounded by the variety of different storage solutions that exist for DEF. Whilst some facilities have dedicated pumps for DEF, others make use of more ad-hoc DEF storage and delivery solutions, including

freestanding containers, bottles, cans and the like, which increase the risk of contaminants. There has now been devised a vehicle fluid tank cap assembly which overcomes or substantially mitigates the aforementioned and/or other disadvantages associated with the prior art.

According to the present invention there is provided a vehicle fluid tank cap assembly comprising a main body defining an enclosure, a filter housed within the enclosure, a removable cap for selectively closing a filling opening defining a fluid inlet into the enclosure, a filter retaining formation that allows the filter to be selectively removed from the enclosure, an outlet opening for connection to an inlet of a vehicle fluid tank, in use, and lockable engagement means for selectively actuating the cap assembly, in use, between a first configuration in which the cap assembly is removable from the inlet of the vehicle fluid tank, and a second configuration in which the cap assembly is engaged with the inlet of the vehicle fluid tank for normal use such that the cap assembly remains engaged with the vehicle fluid tank inlet whilst the cap is selectively removable for filling of the tank.

The cap assembly may be engaged with the inlet of a vehicle fluid tank in the second condition such that the cap assembly cannot be removed from the inlet of the vehicle fluid tank without damaging the cap assembly and/or fluid tank. The term "lockable" as used herein may be construed accordingly.

The filter and/or enclosure may be in the flow path defined by the main body between the filling opening and the outlet opening.

Since the cap assembly is removably attachable to an inlet of a vehicle fluid tank, the assembly may be easily accessed by a user for maintenance purposes. The removable filter located upstream of the inlet of the fluid tank ensures that fluid is filtered, and thus contaminants may be removed, prior to the fluid entering the fluid tank, whilst allowing the filter to be accessed for maintenance and/or replacement. The second configuration of the vehicle fluid tank cap assembly may ensure that the filter assembly cannot be accidentally bypassed in normal use, thereby ensuring the purity of the fluid contained in the vehicle fluid tank. The filter may comprise a filter assembly or cartridge, for example comprising a filter material mounted on a support member or structure. The filter may comprise a fine filter material. The filter may comprise a 100 μιη filter of less, e.g. having a pore size of 100 μιη or less, or else being arranged to filter out particulate material having a diameter of 100 μιη or greater. The filter size may be 50-100 μιη or lower. The filter size may be as low as 10 μιη or in the range 10 to 50 or 100 μιη.

The filter may comprise a pleated filter material.

The cap assembly may be removable from the inlet of a vehicle fluid tank in the first configuration without damaging the cap assembly and/or fluid tank.

The cap assembly may comprise a lock. The lock may be arranged to receive a key, for example such that turning of the key in the lock may actuate the cap assembly from the first configuration into the second configuration, or vice versa. The lock and key formation may comprise a lock which may be a recess or projection, and may comprise a key which may be a projection or recess for engaging a corresponding recess or projection of the lock. The first configuration may be referred to as an unlocked configuration and/or the second configuration may be referred to as a locked configuration. The outlet opening and/or engagement means may comprise at least one projection or recess for engaging a corresponding recess or projection of an inlet of a vehicle fluid tank. The engagement formation may comprise a helical projection or recess for engaging a corresponding helical recess or projection of an inlet of a vehicle fluid tank. The engagement formation may comprise a screw thread for engaging a corresponding screw thread of an inlet of a vehicle fluid tank. The main body and the engagement means or outlet opening may be arranged such that the outlet opening cannot be grasped by a user when the cap assembly is mounted to an inlet of a vehicle fluid tank. The main body may be graspable by a user when the cap assembly is mounted to the inlet of a vehicle fluid tank.

At least a portion of the main body may be hollow, such that the main body comprises an internal chamber. A lowermost region of the main body, in use, may be hollow, such that the lowermost region of the main body, in use, comprises an internal chamber. The internal chamber may house at least a portion of the engagement means. The main body and the engagement means may be concentrically arranged, and may, for example, be arranged such that the main body is located radially outside to the engagement means. The main body may define a cover for the outlet opening and/or engagement means when connected to the fluid tank.

The engagement means may comprise an engagement formation, which may define the outlet opening. The engagement formation may comprise a collar, cuff, or sleeve formation or connector. The main body and the engagement formation may be fixed relative to each other in the first configuration. For example, movement of the main body by a user may result in corresponding movement of the engagement formation. Movement of the main body in the first configuration may move the engagement formation into engagement with an inlet of a vehicle fluid tank and/or remove the engagement formation from engagement with an inlet of a vehicle fluid tank, such that the cap assembly may be attached and/or detached from an inlet of a vehicle fluid tank, for example without damaging the engagement formation and/or fluid tank.

Movement of the main body in the first configuration may screw the engagement formation onto, and/or unscrew the engagement formation from, an inlet of a vehicle fluid tank. At least a portion of the cap assembly may be rotatable relative to an inlet of a vehicle fluid tank in the second configuration, for example without allowing removal of the cap assembly from the inlet of the vehicle fluid tank. The main body and the engagement formation may be movable relative to each other in the second configuration, and may, for example, be rotatable relative to each other in the second configuration. The main body may be movable

independently of the engagement formation in the second configuration. The main body may be movable in the second configuration whilst the engagement formation remains fixed in the second configuration. Movement of the main body in the second configuration may not move the engagement formation into engagement with an inlet of a vehicle fluid tank and/or remove the engagement formation from engagement with an inlet of a vehicle fluid tank, such that the cap assembly cannot be removed from an inlet of a vehicle fluid tank without damaging the cap assembly and/or fluid tank. Movement of the main body in the second configuration may not screw the engagement formation onto, and/or unscrew the engagement formation from, an inlet of a vehicle fluid tank.

The main body and engagement formation may be de-coupled or unlocked in the second configuration. The main body may be connected to, or coupled to, the engagement formation in the first configuration, and/or the main body may be disconnected from the engagement formation in the second configuration. The main body and/or engagement formation may comprise a retaining formation for preventing relative longitudinal motion between the main body and the

engagement formation in the first and second configurations. Thus the main body and engagement formation may not be completely separated from one another in either the first or the second configurations.

The main body may comprise at least one projection or recess for selectively engaging or disengaging a corresponding recess or projection of the engagement formation. The engagement means may comprise a lock between the main body and engagement formation. Turning of a key in the lock may remove the at least one projection from engagement with the corresponding recess of the engagement formation or main body.

The filter retaining formation may comprise a maintenance closure, for example a closable maintenance opening.

The fluid inlet may be spaced apart from the closable maintenance opening, such that the fluid inlet and the closable maintenance opening are separate or distinct openings. This may allow the fluid inlet to be shaped and dimensioned to correspond to a desired fluid delivery device, whilst allowing the closable maintenance opening to be shaped and dimensioned to allow removal of the filter assembly.

The fluid inlet opening may be of smaller width/diameter than the maintenance opening and/or outlet.

The maintenance closure may fit to the closable maintenance opening via any conventional fitting, for example a snap-fit, push-fit, or screw-fit. The maintenance closure may be releasably fastenable relative to the closable maintenance opening such that a key or other tool is required to remove the closure from the closable maintenance opening. This may prevent accidental or intentional removal of the maintenance closure, which may result in contamination and/or tampering of the filter assembly. The tool may comprise a head formation shaped to engage a corresponding shaped formation in the maintenance closure, and may, for example, comprise a hex key (also referred to as an Allen® key).

The closable maintenance opening and/or the maintenance closure may comprise a seal for preventing contaminant entry into the enclosure when the closable maintenance opening is closed by the closure. The sealing arrangement may comprise any conventional sealing arrangement, and may, for example, comprise an O-ring seal trapped between the closure and maintenance opening. The fluid inlet cap may fit to the fluid inlet via any conventional fitting, for example a snap-fit, push-fit, or screw-fit. The cap may be freely removable from the closable filling opening, for example devoid of a lock, such that a user is freely able to fill the vehicle fluid tank. The closure may be connected to a portion of the main body, for example by a tether, such that the closure remains connected to the main body when the closure does not close the closable filling opening.

The filter assembly and/or the enclosure may comprise the filter retaining formation. The retaining formation may comprise a projection or recess on the filter assembly for engaging a corresponding recess or projection of an internal wall of the enclosure. The filter assembly may be received within the enclosure by a push-fit or a snap-fit. The filter assembly may comprise a porous filter material for filtering contaminants, for example particulate material, from a fluid to be stored in a vehicle fluid tank. At least a portion of the filter assembly may be replaceable and/or disposable, and, for example, the filter material may be removable and/or disposable.

The main body may be shaped such that the fluid inlet comprises a branch or angled passageway relative to the enclosure. The fluid inlet may be obliquely angled relative to an axis of the enclosure and/or outlet opening. The inlet opening may be angled relative to the maintenance opening.

The cap assembly may comprise a fluid level indicator for indicating the level of fluid contained within a vehicle fluid tank in use. The fluid indicator may comprise visual indicia for indicating the level of fluid to a user, and may, for example, comprise a light which indicates when the fluid level within a vehicle fluid tank is at a desired or maximum level. The fluid indicator may comprise an indicating member which extends into a vehicle fluid tank in use, which may, for example, comprise a wire or rod. The fluid level indicator may be mounted on an underside of the main body, for example extending through the outlet opening. The cap assembly may comprise sealing arrangements located at interfaces between any of its components, for example between the main body and the engagement formation, or between the filter assembly and the enclosure. The cap assembly may comprise a secondary filter assembly, which may be located in a region of the closable filling opening. This may provide further filtering of a fluid before it is delivered to a vehicle fluid tank.

A practicable embodiment of the invention is described in further detail below with reference to the accompanying drawings, of which:

Figure 1 is a perspective view of an embodiment of a vehicle fluid tank cap assembly according to the present invention; Figure 2 is a front view of the vehicle fluid tank cap assembly of Figure 1 ;

Figure 3 is a cross-sectional view along the line A-A shown in Figure 2;

Figure 4 is a front view of a further embodiment of a vehicle fluid tank cap assembly according to the present invention; and

Figure 5 is a cross section of a further embodiment of a filter and main body closure according to the present invention. A vehicle fluid tank cap assembly according to the present invention, generally designated 10, is shown in Figures 1 to 3. The vehicle fluid tank cap assembly 10 has a main body 12, a filter assembly 14, an engagement formation 16, a fluid inlet 18, a fluid inlet closure 20, a main body closure 22, and a locking formation 24. The main body 12 has upper 26 and lower 28 portions. The upper main body portion 26 is substantially cylindrical in form, and is hollow, thereby defining an enclosure 30 for receiving the filter assembly 14. A lower wall of the enclosure 30 has an aperture for receiving a corresponding connecting formation 38 of the filter assembly 14. An uppermost region of the upper portion 26 defines an aperture for receiving the main body closure 22. An uppermost region of the inner wall of the enclosure 30 has a screw thread 32 for engaging a corresponding screw thread 72 of the main body closure 22, and a seal 34 for preventing ingress of contaminants into the enclosure 30.

The lower main body portion 28 is substantially cylindrical in form, and is substantially hollow, thereby defining an internal chamber 36 for housing the engagement formation 16. The upper 26 and lower 28 main body portions are integrally formed, with the lower main body portion 28 being shorter, and having a larger diameter, than the upper main body portion 26. Thus the main body portion 12 has a generally inverse-T shaped cross-sectional profile, as seen in Figure 3.

An intermediate internal wall 53 separates the interior of the upper 26 and lower 28 portions of the main body 12. The filter assembly 14 is seated atop the intermediate wall 53 when mounted for use. The intermediate wall 53 has an opening to allow flow from the upper 26 to the lower 28 portion of the main body in use. The filter assembly 14 is substantially cylindrical in form, and is dimensioned to be received within the enclosure 30 when the cap assembly 10 is assembled. The filter assembly has a downwardly depending cylindrical connecting formation 38 which is shaped and dimensioned to be received within an aperture of a lower wall of the enclosure 30 when the cap assembly 10 is assembled. The connecting formation 38 comprises a seal 40 which engages with the inner wall of the aperture in the lower wall of the enclosure 30.

The filter assembly 14 has a filter material 42 which allows the passage of fluid whilst preventing the passage of particulate matter, and an internal fluid

passageway 44 which is in fluid communication with the fluid inlet 18 and a fluid outlet 54 of the cap assembly 10. The filter material 42 is disposed around a central cylindrical member 43 of the filter assembly 14, with the central cylindrical member 43 comprising apertures which allow fluid to pass to the internal fluid passageway 44.

The engagement formation 16 is substantially cylindrical in form, and is

substantially hollow in nature, such that the engagement formation 16 can receive an inlet of a vehicle fluid tank in use. An inner wall of the engagement formation 16 has a screw thread 46 for engaging a corresponding screw thread of an inlet of a vehicle fluid tank in use. The engagement formation 16 has an upstanding circular connection formation 48 for receiving a corresponding downwardly depending wall portion 50 of the internal chamber 36. The connection formation 48 comprises a seal 52 for sealing against the downwardly depending wall portion 50 when the cap assembly 10 is assembled.

The downwardly depending wall portion 50 depends from the intermediate wall 53 of the internal chamber 36, and extends into the hollow interior of the engagement formation 16 when assembled. The downwardly depending wall portion 50 defines a fluid outlet 54 of the cap assembly, with the fluid outlet 54 being in fluid communication with the internal fluid passageway 44 of the filter assembly 16, the fluid inlet 18, and a vehicle fluid tank inlet in use. The downwardly depending wall portion 50 comprises an annular retaining formation 56 which abuts against an internal wall of the engagement formation 16.

The engagement formation 16 is housed concentrically within the internal chamber 36, and abuts the retaining formation 56 and an underside of the intermediate wall 53 of the internal chamber 36, such that longitudinal separation of the main body 12 and engagement formation 16 is prevented.

The fluid inlet 18 is substantially cylindrical in form, and is hollow in nature, ie tubular, thereby defining a fluid passageway. The fluid inlet 18 extends at an oblique angle from the upper main body portion 26, and is in fluid communication with the enclosure 30. The fluid inlet 18 is dimensioned to receive a desired fluid delivery device, such as a fluid nozzle or spout, therein. An uppermost end of the fluid inlet 18 has a screw thread 58 for engaging a corresponding screw thread 62 of the fluid inlet closure 20, and a seal 60 for sealing against the fluid inlet closure 20.

The fluid inlet closure 20 is substantially cylindrical in form, and is dimensioned to fit over the uppermost end of the fluid inlet 18. Thus the fluid inlet closure 20 takes the form of a cap. The fluid inlet closure 20 has a screw thread 62 for engaging the corresponding screw thread 58 of the fluid inlet 18. The fluid inlet closure 20 has an upstanding projection 64 for engaging a retaining strap 66. The restraining strap 66 is adjacent to, or fixedly connected to, the engagement formation 16 such that one end of the strap 66 is trapped on the inlet of a fluid tank to which the cap assembly 10 is applied in use. The strap 66 is releasably connected to the projection 64 at its free end, such that the restraining strap 66 can optionally be used to prevent the fluid inlet closure 20 from being completely removed from the cap assembly 10 when the fluid inlet closure 20 is unscrewed from the fluid inlet 18.

The main body closure 22 has a shoulder formation 68 and a downwardly depending plug formation 70. The shoulder formation 68 is shaped and

dimensioned to abut a rim of the aperture defined by the uppermost region of the upper main body portion 26 when the main body closure 22 closes the aperture. The plug formation 70 is shaped and dimensioned to be received in the aperture defined by the uppermost region of the upper main body portion 26 when the main body closure 22 closes the aperture. The plug formation 70 has a screw thread 72 for engaging a corresponding screw thread 32 of the upper main body portion 26. The plug formation 70 has recesses 74 for engaging the filter material 42, such that the filter material 42 is securely held in place in the filter assembly 14.

The plug formation 70 is integrally formed with the central cylindrical member 43 of the filter assembly 14, such that removal of the main body closure 22 from the upper main body portion 26 removes the filter assembly 14 from the enclosure 30.

The main body closure 22 has a tightening/release formation 76 that is upstanding from an upper surface of the shoulder formation 68. The formation 76 comprises a recess 78 of hexagonal cross-section for receiving a corresponding hex key. The hex key may be required to remove the main body closure 22 from the upper main body portion 26. The main body closure 22 is thus typically a friction fit on the upper portion 26 of the main body 12 by tightening the friction engagement of the screw thread formations therebetween using a suitable tool.

In use, the main body 12 and the engagement formation 16 are fixed relative to each other, such that movement of the main body 12 effects movement of the engagement formation 16. The main body 12 is grasped by a user, and is rotated so that the screw thread 46 of the engagement formation 16 engages a

corresponding screw thread of an inlet of a vehicle fluid tank. When the cap assembly 10 is attached to the inlet of the vehicle fluid tank, the locking formation 24 is actuated so that the cap assembly 10 is fixed to the inlet of the vehicle fluid tank, such that the cap assembly 10 cannot be removed without causing damage to the cap assembly 10 and/or vehicle fluid tank. The main body 12 is now rotatable relative to the engagement formation.

When it is desired to fill the vehicle fluid tank, the fluid inlet closure 20 is unscrewed from the fluid inlet 18, and a fluid delivery device may be inserted into the fluid inlet 18. Fluid flows from the fluid delivery device, through the fluid inlet, and is filtered by the filter material 42 of the filter assembly 14. The filtered fluid passes through the internal fluid passageway 44 of the filter assembly 14, and out of the fluid outlet 54, into the vehicle fluid tank.

When maintenance of the filter assembly 14 is required, the lock formation 76 is used to unscrew the main body closure 22 from the upper main body portion 26 via the use of an appropriate hex key. The filter assembly 14 may be removed from the enclosure 30, either so that maintenance of the filter assembly 14 can be carried out and the filter assembly 14 can be reinserted into the enclosure 30, or so that the filter assembly 14 can be replaced by a new filter assembly. This can be achieved whilst the remainder of the cap assembly 10 remains in place on the vehicle fluid tank inlet. If it becomes necessary to remove the cap assembly 10, then the locking formation 24 is actuated so that the cap assembly 10 can be unscrewed from the inlet of the vehicle fluid tank.

A further embodiment of the cap assembly 10 is shown in Figure 4, and is identical to the cap assembly shown in Figures 1 -3 other than the presence of the fluid level indicator 80, the power source 82, and the light emitting diode (LED) 84. The fluid level indicator 80 is a hollow tube depending downwardly from a lowermost region of the cap assembly 10, and comprises a float 86 and a switch 88 contained within the hollow tube. The switch 88 is electrically connected to the power source 82, which is in turn electrically connected to the LED 84. It will be recognised that the power source 82 is mounted internally of the main body 12.

When the cap assembly 10 is mounted to an inlet of a vehicle fluid tank, the fluid level indicator 80 extends through the inlet of the vehicle fluid tank and into the main body of the tank. As the fluid level within the tank rises when it is being filled, the float 86 rises within the hollow tube until it contacts the switch 88. When the switch 88 is tripped, the power source 82 is activated, which in turn lights the LED 84. Thus a user is provided with an indication that the fluid level within the tank has reached a certain level.

When the fluid level within the tank drops, the float 86 disengages the switch 88, thereby causing the LED 84 to be turned off.

It will be recognised that alternative forms of fluid level indicator 80 may be used. For example, the fluid level indicator 80 may comprise two conductors depending downwardly from an underside of the cap assembly 10, or mounted within the tube 80, such that when both conductors are contacted by fluid within the tank the electrical circuit is completed and the LED 84 is lit. Various other conventional fluid level detectors/sensors may be used which may or may not require the presence of the tube 80. Whilst an LED is provided in this example as a visual indicator of fluid level, alternative indicators could be used, including visual and/or audio indicators, such as for example a buzzer, speaker or the like. A non-electric indicator could for example include a float within the tube 80 that is visible in a window of the cap assembly when the tank is full or nearly full. Thus a battery may potentially be avoided if desired.

An alternative embodiment of a filter assembly 14 and main body closure 22 for use with the present invention is shown in Figure 5. This embodiment is

substantially the same as previous embodiments and differs only in the presence of a breathing passageway 90 and a breathable filter 92.

The breathing passageway 90 extends between the hexagonal recess 78 of the main body closure 22 and the internal fluid passageway 44 of the filter assembly. The breathable filter 92 has a substantially hexagonal profile, and is dimensioned to be received within the hexagonal recess 78. In use, the combination of the breathing passageway 90 and the breathable filter 92 allows air to escape from the internal fluid passageway 44 of the filter assembly 14, whilst the breathable filter 92 prevents particulate material, for example contaminants, from passing into the internal fluid passageway 44 of the filter assembly 14. In alternative embodiments, the breathing passageway 90 may be provided with its own internal filter. The breathable filter 92 may be removable in order to allow removal of the main body closure 22 via use of an appropriate hex key, or alternatively the breathable filter 92 may be resiliently deformable so that the breathable filter 92 can be

compressed within the recess 78 to allow insertion of an appropriate hex key within the recess 78.

It will be recognised that the embodiment of Figure 5 may be used with any of the previous embodiments of the present invention. In other examples, the breathing passageway 90 could be provided in another portion of the main body 12 or filter assembly 14, provided it offers breathing communication with the 'clean' side of the liquid filter 44.

Claims

1. A vehicle fluid tank cap assembly comprising a main body defining an enclosure, a filter housed within the enclosure, a removable cap for selectively closing a filling opening defining a fluid inlet into the enclosure, a filter retaining formation that allows the filter to be selectively removed from the enclosure, an outlet opening for connection to an inlet of a vehicle fluid tank, in use, and lockable engagement means for selectively actuating the cap assembly, in use, between a first configuration in which the cap assembly is removable from the inlet of the vehicle fluid tank, and a second configuration in which the cap assembly is engaged with the inlet of the vehicle fluid tank for normal use such that the cap assembly remains engaged with the vehicle fluid tank inlet whilst the cap is selectively removable for filling of the tank.

2. A cap assembly as claimed in Claim 1 , wherein the cap assembly comprises a lock, and turning of a key in the lock actuates the cap assembly from the first configuration into the second configuration, and vice versa.

3. A cap assembly as claimed in any preceding claim, wherein the

engagement means comprises an engagement formation.

4. A cap assembly as claimed in Claim 3, wherein the main body and the engagement formation are fixed relative to each other in the first configuration.

5. A cap assembly as claimed in any of Claim 3 or Claim 4, wherein the main body and the engagement formation are rotatable relative to each other in the second configuration.

6. A cap assembly as claimed in any of Claims 3 to 5, wherein the main body is connected to the engagement formation in the first configuration.

7. A cap assembly as claimed in any of Claims 3 to 6, wherein the main body is disconnected from the engagement formation in the second configuration.

8. A cap assembly as claimed in Claim 6 or Claim 7, wherein the cap assembly comprises means for disconnecting the main body from the engagement formation.

9. A cap assembly as claimed in Claim 8, wherein the main body comprises at least one projection or recess for engaging a corresponding recess or projection of the engagement formation, and the means for disconnecting the main body from the engagement formation comprises means for removing the at least one projection or recess of the main body from engagement with the corresponding recess or projection of the engagement formation.

10. A cap assembly as claimed in Claim 9, wherein the cap assembly

comprises a lock, and turning of a key in the lock removes the at least one projection or recess of the main body from engagement with the corresponding recess or projection of the engagement formation and/or engages the at least one projection or recess of the main body with the corresponding recess or projection of the engagement formation.

1 1. A cap assembly as claimed in any preceding claim, wherein at least a portion of the cap assembly is rotatable relative to the inlet of the vehicle fluid tank in the second configuration, without allowing removal of the cap assembly from the inlet of the vehicle fluid tank.

12. A cap assembly as claimed in any preceding claim, wherein the cap assembly comprises a maintenance opening spaced apart from the filling opening, such that the filling opening and the maintenance opening are separate and distinct openings.

13. A cap assembly as claimed in any preceding claim, wherein the cap assembly comprises a maintenance opening, and a closure for the maintenance opening, the closure being releasably fastenable to the maintenance opening, such that a tool or key is required to remove the closure from the maintenance opening.

14. A cap assembly as claimed in any preceding claim, wherein the cap is freely removable from the closable filling opening.

15. A cap assembly as claimed in any preceding claim, wherein the filter is replaceable and/or disposable.

16. A cap assembly as claimed in any preceding claim, wherein the filter retaining formation comprises an aperture extending between the interior and exterior of the cap assembly, such that the aperture allows the passage of gas between the interior and exterior of the vehicle fluid tank when the assembly is attached thereto in use.

17. A cap assembly as claimed in Claim 16, wherein the aperture comprises a breather filter which prevents the passage of particulate material and/or liquids.

18. A cap assembly as claimed in any preceding claim, wherein the filter comprises a fine and/or pleated filter material having an average filter pore size of 100 μιη or less.

19. A diesel exhaust treatment fluid tank cap assembly according to any preceding claim.