Filter assembly for a tank outlet header assembly, e.g. as a bag filter in a def tank

Abstract

A filter assembly (1, 1') includes a sealing portion (10) and a barrier wall (20) having a first permeable portion (30) that extends below the liquid fill line (151) in a tank (110), e.g. a DEF tank. The sealing portion (10) is connected to a sealing surface (113) of the tank assembly (100) so that the barrier wall (20) divides a first part (111') of the internal space of the tank (110) containing a header assembly (130) from a second part (111") external to the first part. In a first aspect, the filter assembly (1) includes a liquid impermeable portion (40) defining a flowpath (42). In a second aspect, the first permeable portion (30) of the filter assembly (F) is made from a non-woven fabric (31), and the barrier wall (20) includes a second permeable portion (60) made from a structured fabric (61), also providing a flowpath (42). The flowpath (42) is arranged to allow gas (160) to flow in the headspace (112) of the tank (110) to equalise pressure across the barrier wall (20). In a third aspect, the filter assembly (1, 1') is tubular and the sealing portion (10) is configured as a flange (11) that is interposed between respective sealing surfaces (132, 113) of the header assembly (130) and the upper wall (116) of the tank (110), e.g. to form a gasket.

Description

[0001] FILTER ASSEMBLY FOR A TANK OUTLET HEADER ASSEMBLY, e g. AS A BAG FILTER IN A DEF TANK

[0002] Technical Field

[0003] This disclosure relates to filter assemblies of the type that are fitted inside a tank of diesel exhaust fluid (DEF) or other liquid so as to enclose the tank outlet opening and other components of the header assembly of the tank.

[0004] Background

[0005] DEF is an aqueous urea solution for use in selective catalytic reduction of nitrogen oxides in the exhaust gas from a diesel engine. The DEF is stored in a tank on the vehicle and pumped to a nozzle where it mixes with the hot exhaust gas before flowing through a downstream catalyst where the reduction reaction occurs.

[0006] DEF freezes at about -11°C, so typically a DEF tank is filled to not more than about 90% capacity, leaving a head space for expansion, and includes a heater to melt the frozen DEF when the vehicle is started up in cold weather.

[0007] The DEF is drawn out of the tank via an outlet opening from which it flows to the nozzle. Typically the outlet opening forms part of a so- called header assembly including various other tank components such as a level sensor for sensing the level of DEF in the tank. The header assembly may also include the heater and / or a pump for supplying DEF to the nozzle.

[0008] DEF is prone to form crystals, not only due to freezing but also when the urea comes out of solution, for example, due to evaporation in a partially full tank.

[0009] DEF tanks are found in diesel engined vehicles including cars, buses, lorries, and work vehicles such as wheeled or tracked excavators, loaders, and other construction vehicles used on off-road worksites. Work vehicles in particular tend to be exposed to dirty conditions which can result in debris entering the DEF tank when it is filled.

[0010] In order to avoid clogging of the DEF supply lines from the tank with crystals of urea or ice or other solid particles that have entered or formed in the tank, it is known to protect the tank outlet header assembly, including the tank outlet opening, with a filter that separates the region of the tank containing the header assembly from the rest of the internal space of the tank.

[0011] The filter can be configured as a tubular structure, or as a bag made from a flexible, permeable fabric, that is immersed at least partially in the DEF within the tank and surrounds the header assembly. For example, the header assembly may have a tubular neck depending from a mounting flange. The lower part of the header assembly is inserted into the open end of the bag filter which is then clamped around the tubular neck of the header assembly, for example, using a band clamp. The assembly is then inserted through an aperture at the top of the tank and fixed in position by the mounting flange of the header assembly which remains external to the tank.

[0012] By way of example, WO2015108826A1 discloses a DEF tank with a header assembly including heating and DEF supply and return lines and a float type level sensor. A coarse inlet filter may be arranged to exclude ice particles at the intake of the DEF supply line. A bag filter is attached to a mounting collar to surround the header assembly. Optionally, the bag filter may be removable and replaceable in service. DEF is filled, optionally via a coarse basket filter, into the tank space surrounding the bag filter. The stored DEF must then pass through the bag filter into the interior space containing the header assembly before it is drawn from the tank via the inlet filter for use.

[0013] The filter must be fine enough to effectively exclude particulate contaminants from the header assembly. However, a fine filter fabric can slow down the rate at which the liquid level rises in the interior space of the filter containing the header assembly. Where the header assembly includes a level sensor, this can delay the response of the level sensor to the rising liquid level in the tank when it is filled.

[0014] In order to exclude contaminants, the filter must also be sealed effectively to the tank assembly, which however can complicate assembly. In practice, it is found that a band clamp does not always provide a satisfactory seal, since the fabric of the bag filter can become pleated between the clamp and the supporting surface of the header assembly.

[0015] Summary of the Disclosure

[0016] First Aspect

[0017] In a first aspect, the disclosure provides a filter assembly for use as part of a tank assembly.

[0018] The tank assembly further includes a tank, and a header assembly extending into an internal space of the tank. The internal space contains a liquid in use, and includes a headspace above a maximum fill level of the liquid. The header assembly includes an outlet for the liquid to flow out of the tank.

[0019] The filter assembly includes a sealing portion, and a barrier wall.

[0020] The barrier wall includes a first permeable portion including a first permeable material, and a liquid impermeable portion including a liquid impermeable material.

[0021] The sealing portion is sealingly connected or connectable to a sealing surface of the tank assembly to locate the filter assembly in a use position. In the use position, the barrier wall is arranged in the internal space of the tank to enclose a first part of the internal space containing the header assembly, and to separate the first part of the internal space from a second part of the internal space external to the first part. The first permeable portion extends below the maximum fill level of the liquid to filter the liquid flowing, in use, through the first permeable portion from the second part of the internal space to the first part of the internal space. The liquid impermeable portion extends within the headspace and defines a liquid impermeable barrier to prevent the liquid from sloshing, in use, through the liquid impermeable barrier between the first and second parts of the internal space.

[0022] A flowpath is formed through the liquid impermeable barrier. The flowpath has a smallest total cross-sectional area A through which, in the use position, gas in the headspace can flow between the first and second parts of the internal space, wherein the first and second parts of the internal space are not in fluid communication through the liquid impermeable barrier except via the flowpath.

[0023] Second Aspect

[0024] In a second aspect, the disclosure provides a filter assembly for use as part of a tank assembly.

[0025] The tank assembly further includes a tank, and a header assembly extending into an internal space of the tank. The internal space contains a liquid in use, and includes a headspace above a maximum fill level of the liquid. The header assembly includes an outlet for the liquid to flow out of the tank.

[0026] The filter assembly includes a sealing portion, and a barrier wall.

[0027] The barrier wall includes a first permeable portion including a first permeable material, and a second permeable portion including a second permeable material different from the first permeable material.

[0028] The sealing portion is sealingly connected or connectable to a sealing surface of the tank assembly to locate the filter assembly in a use position.

[0029] In the use position, the barrier wall is arranged in the internal space of the tank to enclose a first part of the internal space containing the header assembly, and to separate the first part of the internal space from a second part of the internal space external to the first part. The first permeable portion extends below the maximum fill level of the liquid to filter the liquid flowing, in use, through the first permeable portion from the second part of the internal space to the first part of the internal space. The second permeable portion extends within the headspace and defines a permeable barrier between the first and second parts of the internal space within the headspace.

[0030] The first permeable material is a non-woven fabric made from randomly interconnected fibres without a regular structured pattern.

[0031] The second permeable material is a structured fabric made from strands or fibres arranged in a regular structured pattern to define a regular pattern of intersticial spaces extending through a thickness of the structured fabric between adjacent ones or groups of the strands or fibres, the first and second parts of the internal space within the headspace being in fluid communication via said intersticial spaces.

[0032] Third Aspect

[0033] In a third aspect, the disclosure provides a filter assembly for use as part of a tank assembly.

[0034] The tank assembly further includes a tank, and a header assembly extending through an aperture in an upper wall of the tank into an internal space of the tank. The internal space contains a liquid in use, and includes a headspace above a maximum fill level of the liquid. The header assembly includes an outlet for the liquid to flow out of the tank, and a mounting surface. The mounting surface is sealingly mounted to the upper wall of the tank to seal the header assembly in the aperture.

[0035] The filter assembly includes a sealing portion, and a barrier wall.

[0036] The barrier wall extends along an axis and includes a first permeable portion.

[0037] The first permeable portion includes a first permeable material and extends along the axis to define a first tubular portion of the barrier wall.

[0038] The sealing portion is sealingly connectable to a sealing surface of the tank assembly to locate the filter assembly in a use position.

[0039] In the use position, the barrier wall is arranged in the internal space of the tank to enclose a first part of the internal space containing the header assembly, and to separate the first part of the internal space from a second part of the internal space external to the first part. The first permeable portion extends below the maximum fill level of the liquid to filter the liquid flowing, in use, through the first permeable portion from the second part of the internal space to the first part of the internal space.

[0040] The sealing portion includes a flange extending radially outwardly, with respect to the axis, from an upper end of the barrier wall in the use position. The flange is configured to be interposed, in the use position, between the mounting surface of the header assembly, and the upper wall of the tank defining said sealing surface.

[0041] Brief Description of the Drawings

[0042] Further features and advantages will become apparent from the illustrative embodiments that will now be described, purely by way of example and without limitation to the scope of the claims, and with reference to the accompanying drawings, in which:

[0043] Fig. 1 shows a tank assembly including a first filter assembly having a first permeable portion formed from a nonwoven fabric, and a liquid impermeable barrier with a single discrete vent hole forming a flowpath in the headspace.

[0044] Fig. 2 is an enlarged view of part of Fig. 1.

[0045] Fig. 3 is a further enlarged view of part of the first filter assembly showing the opening of the vent hole through the outer surface of the liquid impermeable barrier.

[0046] Fig. 4 shows the first filter assembly in a variant having a pair of diametrically opposed vent holes, wherein the assembly is shown in side and end view and in longitudinal section at [IV] - [IV] of the same figure.

[0047] Fig. 5 shows part of the first filter assembly in a further variant having a flowpath screened by a structured fabric, wherein the assembly is shown in side view and in longitudinal section at [V] - [V] of the same figure. Fig. 6 shows a piece of the nonwoven fabric alongside a piece of the structured fabric.

[0048] Fig. 7 is a longitudinal section through part of the first filter assembly in a further variant having a flowpath protected by a check valve.

[0049] Fig. 8 is a longitudinal section through part of the first filter assembly in a further variant having a flowpath protected by a semipermeable membrane.

[0050] Fig. 9 is a longitudinal section through part of the first filter assembly in a further variant having a nonlinear flowpath.

[0051] Fig. 10 shows a second filter assembly in which the barrier wall has first and second permeable portions made respectively from the nonwoven fabric and the structured fabric, wherein the assembly is shown in side and end view and in longitudinal section at [X] - [X] of the same figure.

[0052] Fig. 11 shows the time taken for the liquid level to equalise across the barrier wall in a tank assembly similar to that of Fig. 1, respectively with and without a flowpath through the liquid impermeable barrier.

[0053] Reference numerals and characters that appear in more than one of the figures indicate the same or corresponding elements in each of them.

[0054] Detailed Description

[0055] A Brief Summary of the Differences between the Three Aspects of the Disclosure

[0056] Although the following description is divided by subheadings for ease of reference, it will be understood that many of the features of the embodiments described are common to all three aspects of the disclosure, and so are only described once. The essential features of each of the three aspects are as defined in the respective independent claim.

[0057] In each of the three aspects, the filter assembly 1 or 1' includes a barrier wall 20 having a sealing portion 10 and a first permeable portion 30 that filters the liquid 150 flowing through it into the first part 111' of the internal space of the tank. The sealing portion 10 is sealingly connected or connectable to a sealing surface 113 of the tank assembly to mount the filter assembly 1 in its use position.

[0058] The first filter assembly 1 illustrates the first aspect of the disclosure, wherein the barrier wall 20 also includes a liquid impermeable portion 40 having a flowpath 42 in the headspace 112 of the tank.

[0059] The second filter assembly T (Fig. 10) illustrates the second aspect of the disclosure, wherein the barrier wall 20 also includes a second permeable portion 60 in the headspace 112 of the tank. The first and second permeable portions 30, 60 are made respectively from different, first and second permeable materials 31, 61.

[0060] Both the flowpath 42 of the first filter assembly 1 and the second permeable portion 60 of the second filter assembly 1' allow gas to flow through the barrier wall 20 in the headspace 112 to equalise the pressure across the barrier wall 20.

[0061] Optionally in embodiments in accordance with the first and second aspects, and as illustrated, the liquid impermeable portion 40 or the second permeable portion 60 may be arranged between the first permeable portion 30 and the sealing portion 10, so that the sealing portion 10 can be mounted at the upper wall of the tank.

[0062] The first and second filter assemblies 1, 1' both illustrate the third aspect of the disclosure, wherein the first permeable portion 30 extends along an axis X of the barrier wall 20 to define a first tubular portion 30' of the barrier wall, and the sealing portion 10 includes a flange 11 that is interposed between the mounting surface 132 of the header assembly 130 and the upper wall 116 of the tank which in the third aspect defines the sealing surface 113.

[0063] As illustrated, these features of the third aspect of the disclosure may be included as optional features in embodiments in accordance with the first and second aspects. The Tank Assembly 100

[0064] Referring to Fig. 1, a first filter assembly 1 is shown in its use position as part of a tank assembly 100.

[0065] The tank assembly 100 includes a tank 110, and a header assembly 130 that extends through an aperture 115 in an upper wall 116 of the tank into an internal space 111 of the tank 110. The internal space 111 contains a liquid 150 in use, and includes a headspace 112 above a maximum fill level 151 of the liquid 150.

[0066] The headspace 112 contains gas 160 which may be a mixture of air and vapour from the liquid in the tank. The maximum fill level is the maximum level to which the tank is designed to be filled, and as shown may be between about 80% and less than 100% of the volume of the internal space, with the remaining volume of the tank forming the headspace. The tank may be filled via a filler inlet 117 via an inlet filter 118. In use, when the tank is mounted on a vehicle (not shown), the movement of the vehicle will agitate the liquid so that it sloshes (moves about) in the headspace 112.

[0067] The header assembly 130 includes an outlet 131 through which the liquid 150 can flow out of the tank, and a mounting surface 132 that is sealingly mounted to a sealing surface 113 of the upper wall 116 of the tank to seal the header assembly 130 in the aperture 115 as shown.

[0068] The mounting surface 132 may be arranged as shown on a mounting flange 139 extending around the part of the header assembly external to the tank, with the internal (submerged) part of the header assembly extending down from the flange into the tank. The header assembly can be assembled to the tank by inserting its internal part into the tank through the aperture 115 and then fixing the mounting flange to the upper wall of the tank, e.g. with screws 140 that engage in threaded holes formed in a thickened portion 141 of the upper wall that extends down from the upper wall 116 into the internal space of the tank proximate the aperture 115. The header assembly 130 includes an outlet 131 for the liquid 150 to flow out of the tank 110, which may be protected by an outlet filter 133.

[0069] The header assembly may also include a pump 135 for pumping the liquid from the tank via the outlet 131. A recirculation inlet 134 may be provided so that a proportion of the liquid that flows out of the tank via the outlet 131 can be returned to the tank via inlet 134. The tank may be mounted on a vehicle to contain DEF that is pumped to or recirculated through a dispensing system in the engine exhaust treatment system via flow and return lines 136.

[0070] The header assembly may include a heater or heat exchanger 137 that extends below the fill level close to the bottom of the tank to liquefy the DEF or other liquid in cold weather. The heater may be an electric heater or a heat exchanger carrying a flow of engine coolant or other hot fluid via heater lines 138. As illustrated, the heat exchanger 137 may be configured as a coiled tube that supports the permeable material of the filter.

[0071] The header assembly may include a level sensor 142, which may be of the type having a float 143 as illustrated. The level sensor senses the level of the liquid 150 in the first part 111' of the internal space of the tank inside the filter assembly, and sends a signal indicative of the liquid level, e.g. via signal line 144 to an indicator or control system of the vehicle or liquid supply system.

[0072] The lower body 145 of the header assembly 130 is smaller in diameter than the inner surface of the barrier wall 20 of the filter assembly 1, 1', so that the inner surface of the barrier wall 20 at the top of the filter assembly is in fluid communication with the first part 111' of the internal space of the tank containing the gas 160 in the headspace 112 inside the barrier wall 20.

[0073] The Filter Assembly 1, 1*

[0074] Referring to Fig. 1, Fig. 4 and Fig. 10, in each aspect of the disclosure, the filter assembly 1, 1' includes a sealing portion 10 and a barrier wall 20. The sealing portion 10 is sealingly connected or connectable to the sealing surface 113 of the tank assembly 100 to locate the filter assembly 1, 1' in its use position. The barrier wall 20 includes a first permeable portion 30 which includes or consists of a first permeable material 31, which filters the liquid flowing through the barrier wall 20 into the filter assembly.

[0075] In the use position as shown in Fig. 1, the barrier wall 20 is arranged in the internal space 111 of the tank 110 to enclose a first part 111' of the internal space containing the header assembly 130, and to separate the first part 111' of the internal space from a second part 111" of the internal space external to the first part. The first permeable portion 30 extends below the maximum fill level 151 of the liquid 150 to filter the liquid 150 flowing, in use, through the first permeable material 31 of the first permeable portion 30 from the second part 111" of the internal space to the first part 111' of the internal space inside the barrier wall.

[0076] The barrier wall 20 may be configured as shown to extend along an axis X with a generally conventional, tubular shape to define a so-called bag or sock filter, with an open (e.g. upper) end 21 through which the internal (submerged) part of the header assembly 130 is inserted into the space 111' inside the filter assembly, and a closed (e.g. lower) end 22 as shown. The barrier wall 20 may include a conventional supporting frame or carrier (not illustrated) that supports the permeable material(s) 31, 61. Alternatively, the permeable material(s) 31, 61 may be supported (as illustrated) by a helical heat exchanger 137, or by another functional element of the header assembly; for example, as described in WO2015108826A1.

[0077] The First and Second Permeable Materials 31, 61

[0078] In this specification, a "non-woven fabric" means a fabric that is made from randomly interconnected fibres without a regular structured pattern.

[0079] In this specification, a "structured fabric" means a fabric that is made from strands or fibres arranged in a regular structured pattern to define a regular pattern of intersticial spaces extending through a thickness of the structured fabric between adjacent ones or groups of the strands or fibres. The first permeable material 31 may be (and in accordance with the second aspect of the disclosure, is) a non-woven fabric. The second permeable material 61 is a structured fabric.

[0080] Fig. 6 illustrates the difference between the two materials.

[0081] The non-woven fabric 31 is made from randomly interconnected fibres 32 without a regular structured pattern. For example, a non-woven fabric could be a felted or spunbonded or spunlace (hydroentangled) fabric.

[0082] A non-woven fabric filter is sometimes termed a 3D (three dimensional) filter, because the interstices between the fibres 32 are nonlinear (i.e. twisted or convoluted) in the thickness dimension, since multiple fibres are overlaid and entangled together in the thickness dimension (which is imperfectly illustrated in Fig. 6 but will be well understood by those familiar with such fabrics.) For this reason such fabrics make good filters, excluding particles even in the form of fine filaments that would tend to pass through the interstices of a structured fabric. The fibres may be synthetic, e.g. polypropylene.

[0083] The non-woven fabric 31 may be about 99% efficient at 40p, which is to say, it excludes about 99% of 40p particles.

[0084] The structured fabric 61 is made from strands or fibres 62 arranged in a regular structured pattern to define a regular pattern of intersticial spaces 63 extending through a thickness T2 (Fig. 5, Fig. 10) of the structured fabric 61 between adjacent ones or groups of the strands or fibres 62. For example, the structured fabric 61 could be a woven fabric.

[0085] A structured fabric filter is sometimes termed a 2D (two dimensional) filter, because the interstices 63 between the fibres 62 extend all the way through the fabric in a regular pattern. For this reason, ceteris paribus, the structured fabric 61 tends to be less efficient than the non-woven fabric. The fibres may be synthetic, e.g. polypropylene.

[0086] The structured fabric 61 may be about 95-96% efficient at 40p. Where the second permeable material 61 is a structured fabric, the first and second parts 111', 111" of the internal space within the headspace 112 are in fluid communication via the intersticial spaces 63.

[0087] As further discussed below, it is found that a nonwoven fabric 31 will become nearly impermeable to gases when saturated with liquid, while a structured fabric 61, even when wet, will remain sufficiently gas permeable to allow rapid pressure equalisation across the barrier wall, due to the intersticial spaces 63 between its fibres 62.

[0088] The First Filter Assembly 1 (First Aspect)

[0089] Referring to Fig. 1 and Fig. 4, as illustrated, the first permeable portion 30 of the first filter assembly 1 may extend along the axis X of the barrier wall 20 to define a first tubular portion 30' of the barrier wall 20, while the liquid impermeable portion 40 defines a second tubular portion 40" of the barrier wall 20. The first and second tubular portions 30', 40" extend in collinear series relation along the axis X. As illustrated, the second tubular portion 40" may be arranged between the first tubular portion 30' and the sealing portion 10.

[0090] The barrier wall 20 of the first filter assembly 1 further includes a liquid impermeable portion 40 which includes or consists of a liquid impermeable material 41, which may be a rubber or other elastomer. For example, the liquid impermeable portion 40 and the sealing portion 10 may be respective parts of a unitary rubber or elastomeric moulding, optionally having a fibrous reinforcement.

[0091] In the use position, the liquid impermeable portion 40 extends within the headspace 112 and defines a liquid impermeable barrier 40' to prevent the liquid 150 from sloshing, in use, through the liquid impermeable barrier 40' between the first and second parts 111', 111" of the internal space.

[0092] Referring also to Fig. 2, a flowpath 42 is formed through the liquid impermeable barrier 40'. The flowpath 42 has a smallest total cross-sectional area A through which, in the use position, gas 160 in the headspace 112 can flow between the first and second parts 111', 111" of the internal space.

[0093] By the "smallest total cross-sectional area A" of the flowpath is meant the total or aggregate cross-sectional area A of the flowpath when considered at its narrowest point, i.e. where its cross-section is smallest.

[0094] That is to say, if the cross-sectional area of the flowpath changes along its length then the smallest cross-sectional area is identified at the narrowest point along the length of the flowpath. If the flowpath is divided into more than one vent hole, or into multiple interstices 63 between the fibres 62 of a structured fabric 61 that screens a discrete vent hole, then the smallest total cross- sectional area A of the flowpath will be the aggregate cross-sectional areas A of all of those discrete vent holes or interstices 63, each at its narrowest point.

[0095] The first and second parts 111', 111" of the internal space are not in fluid communication through the liquid impermeable barrier 40' except via the flowpath 42.

[0096] As illustrated, the first permeable material of the first filter assembly 1 may be a non-woven fabric 31 as defined above, although it could alternatively be a structured fabric depending on the filtering efficiency required.

[0097] The first permeable material 31 may be connected to the liquid impermeable portion 40 by stitching, welding, bonding, or moulding.

[0098] The stitching may comprise a thread made from the same material as the first permeable material 31, which may be a synthetic fibre and may be selected to resist chemical attack from the DEF or other liquid 150. It is found that the threads do not create leakage paths through the impermeable portion 40 of the barrier wall, particularly when it is made from a rubber or other elastomer.

[0099] In this specification, "welding" means any suitable welding technique, for example: ultrasonic welding, high frequency welding, thermal welding (using heat or a combination of heat and pressure), or solvent welding. "Bonding" means any suitable bonding technique, e.g. bonding with adhesive, e.g. cyanoacrylate or epoxy.

[0100] The liquid impermeable material 41 may be a rubber or elastomer and may define an internal wall 43 of the flowpath 42.

[0101] As illustrated, both the sealing portion 10 and the liquid impermeable portion 40 may include the liquid impermeable material 41, e.g., as parts of a unitary moulding.

[0102] The sealing portion 10 may be configured as a flange 11 that extends radially outwardly from an axis X of the barrier wall 20, as further discussed below with reference to the third aspect of the disclosure.

[0103] As best seen in Figs. 2 and 3, the area A may be a total cross- sectional area of at least one discrete vent hole 42' formed directly in the liquid impermeable material 41 and extending through a thickness T1 of said liquid impermeable barrier 40' between the first and second parts 111', 111" of the internal space.

[0104] The at least one discrete vent hole 42' may consist of a single discrete vent hole 42' as shown in Fig. 2, or may consist of not more than four discrete vent holes 42', for example, exactly two discrete vent holes 42', which may be diametrically opposed across the central axis X of the barrier wall 20 as shown in Fig. 4.

[0105] The or each vent hole 42' may be linear, which is to say, it may extend straight through the barrier wall 20 from one side to the other.

[0106] Surprisingly, in tests, further described below, it is found that this simple configuration can allow gas 160 to flow through the barrier wall to rapidly equalise the pressure across the barrier wall while also effectively excluding all but a negligible quantity of the liquid 150. Since the liquid outlet 131 may be protected by a further outlet filter 133, a negligible leakage through the vent hole 42' has no effect on the operation of the exhaust treatment system when the tank is used for DEF. This makes it possible to make the first permeable material 31 of the first filter assembly 1 a non-woven fabric without introducing unacceptable hysteresis into the level sensing system.

[0107] In each arrangement (whether formed from one or more than one discrete vent hole, or as multiple intersticial spaces 63 in a fabric screen over a discrete vent hole), the area A may be not greater than the area of a circle of diameter D, wherein D is 3mm, more preferably 2.5mm.

[0108] As shown in Fig. 3, where single discrete vent hole 42' is formed as a circular hole with a cylindrical inner wall passing straight through the liquid impermeable portion 40, the total smallest cross-sectional area A of the flowpath 42 will be the area of the circular section at the opening 44 of the flowpath through the surface 45 of the liquid impermeable portion 40 of the barrier wall.

[0109] Alternatively or additionally, where the flowpath is formed as one or more discrete vent holes 42', each of the discrete vent holes 42' may have, individually, a smallest cross-sectional area A that is not greater than the area of a circle of diameter D, wherein D is 3mm, more preferably 2.5mm.

[0110] As best seen in Fig. 2, the flowpath 42 or discrete vent hole 42' may define an opening 44 in a surface 45 of the liquid impermeable portion 40, wherein the tank assembly 100 defines a confronting surface 114 proximate the header assembly 130. The opening 44 faces the confronting surface 114 so that the opening 44 is spaced apart from the confronting surface 114 by a gap 46. The gap 46 opens into the headspace 112 within the second part 111" of the internal space in the use position.

[0111] As illustrated, the confronting surface 114 may be a surface of the thickened portion 141 of the upper wall of the tank.

[0112] In the use position as shown, the gap 46 may open into the headspace 112 downwardly and not sidewardly. This creates an air pocket in the gap 46 that resists liquid ingress.

[0113] The opening 44 may be spaced apart from the confronting surface 114 by a distance DI across the gap 46 (i.e. the width of the gap 46) not greater than, or less than, the diameter of a circle having said area A of the flowpath or individual discrete vent hole.

[0114] So for example, where the flowpath consists of a single, cylindrical, discrete vent hole 42', or two or more such discrete vent holes 42', the distance DI across the gap 46 may be equal to or less than the diameter of the or each vent hole 42'.

[0115] For example, where the respective individual smallest cross- sectional area A of the or each discrete vent hole 42' is equal to the area of a circle 2.5mm in diameter, the distance DI across the or each respective gap 46 facing the or each respective vent hole 42' may be not more than 2mm.

[0116] Figs. 5, 7, 8 and 9 illustrate various ways in which the flowpath 42 can be further protected against liquid ingress.

[0117] Referring to Fig. 5, the flowpath 42 may be screened by a structured fabric 61 as defined above. Here, the flowpath is formed as a window through the impermeable portion 40. The cross-sectional area A is defined as the smallest total cross-sectional area of the intersticial spaces 63. The fabric screen may be fixed for example by bonding to the liquid impermeable portion 40, e.g. with a cyanoacrylate adhesive.

[0118] Fig. 7 illustrates how a check valve 50 may be arranged to allow fluid to flow through the flowpath 42 from the first part 111' to the second part 111" of the internal space, and to prevent fluid from flowing through the flowpath 42 from the second part 111" to the first part 111' of the internal space. The check valve 50 may be a simple flap, e.g. as shown.

[0119] Fig. 8 illustrates how a semipermeable membrane 51 may be arranged to allow a flow of gas 160 while inhibiting a flow of liquid 150 through the flowpath 42.

[0120] Fig. 9 illustrates how liquid ingress may be suppressed by making the flowpath 42 nonlinear, which is to say, tortuous, twisting, indirect, or labyrinthine. The Second Filter Assembly 1’ (Second Aspect)

[0121] Referring now to Fig. 10, the second filter assembly 1' generally corresponds to the first filter assembly 1, including a sealing portion 10 and a first permeable portion 30 of the barrier wall 20 including a first permeable material 31 as described above. Unlike the first filter assembly 1, the barrier wall 20 of the second filter assembly 1' includes a second permeable portion 60 including a second permeable material 61 different from the first permeable material 31.

[0122] The second permeable portion 60 extends within the headspace 112 and defines a permeable barrier 60' between the first and second parts 111', 111" of the internal space within the headspace 112.

[0123] In the second filter assembly 1' the first permeable material 31 is a non-woven fabric, while the second permeable material 61 is a structured fabric, as defined above. The first and second parts 111', 111" of the internal space within the headspace 112 are in fluid communication via the intersticial spaces 63 of the structured fabric, through which gases 160 can pass to equalise the pressure on either side of the barrier wall 20.

[0124] As illustrated, the barrier wall 20 may extend along the axis X so that the first permeable portion 30 defines a first tubular portion 30' of the barrier wall 20, and the second permeable portion 60 defines a second tubular portion 60" of the barrier wall 20, with the first and second tubular portions 30', 60" extending in collinear series relation along the axis X.

[0125] As illustrated, the second tubular portion 60" may be arranged between the first tubular portion 30' and the sealing portion 10.

[0126] The first and second permeable portions 30, 60 may be connected together, e.g. by stitching, welding, bonding, or moulding, either directly or indirectly via an intermediate supporting frame or other portion of the barrier wall.

[0127] As illustrated, the sealing portion 10 of the second filter assembly 1' may include a collar that extends along the axis X of the barrier wall, providing a convenient surface for attachment of the permeable portion. The collar may define a liquid impermeable portion 40 forming a liquid impermeable barrier 40' similar to that of the first filter assembly 1. Although the second permeable portion 60 forms a flowpath for gases, which is the same function as the flowpath 42 of the first filter assembly 1, in alternative embodiments (not shown) a flowpath 42 may also be formed through the liquid impermeable portion 40 of the second filter assembly T.

[0128] Third Aspect

[0129] Turning now to the third aspect of the disclosure, and as exemplified by each of the first and second filter assemblies 1, T, in embodiments in accordance with the third aspect the sealing portion 10 includes a flange 11 extending radially outwardly, with respect to the axis X of the barrier wall 20, from an upper end 21 of the barrier wall 20 in the use position.

[0130] The flange 11 is configured to be interposed, in the use position, between the mounting surface 132 of the header assembly 130, and the upper wall 116 of the tank 110 which in accordance with the third aspect defines the sealing surface 113 of the tank assembly. This simplifies assembly and, where the flange 11 is formed from a suitable material such as a rubber or elastomer, also allows the flange 11 to form a sealing gasket between the header assembly 130 and the upper wall 116 of the tank, which further simplifies assembly.

[0131] The fixing screws 140 or other fixings may pass through holes or recesses in the flange 11.

[0132] Optionally in embodiments in accordance with the third aspect, the filter assembly may further include any or all of the features particular to either or both of the first and second aspects, as described above.

[0133] The first permeable portion 30 of the filter assembly in accordance with the third aspect may include or consist of a non-woven fabric 31, although it could alternatively be a structured fabric 61 depending on the filtering efficiency required. In embodiments in accordance with the third aspect, and as exemplified by the first filter assembly 1, the barrier wall 20 may include a liquid impermeable portion 40 including a liquid impermeable material 41 and defining a second tubular portion 40" of the barrier wall 20. The first and second tubular portions 30', 40" extend in collinear series relation along the axis X. The second tubular portion 40" is arranged between the first tubular portion 30' and the sealing portion 10. In the use position, the liquid impermeable portion 40 extends within the headspace 112 and defines a liquid impermeable barrier 40' to prevent the liquid 150 from sloshing, in use, through the liquid impermeable barrier 40' between the first and second parts 111', 111" of the internal space.

[0134] Optionally, both the liquid impermeable portion 40 and the flange 11 include the liquid impermeable material 41, which may be a rubber or elastomer.

[0135] Optionally, a flowpath 42 may be formed through the liquid impermeable barrier 40', as described above. The liquid impermeable material 41 may define an internal wall 43 of the flowpath 42.

[0136] Alternatively or additionally in embodiments in accordance with the third aspect, as exemplified by the second filter assembly 1', the barrier wall 20 may include a second permeable portion 60 including a second permeable material 61 different from the first permeable material 31 and defining a second tubular portion 60" of the barrier wall 20. The first and second tubular portions 30', 60" extend in collinear series relation along the axis X. The second tubular portion 60" is arranged between the first tubular portion 30' and the sealing portion 10. In the use position, the second permeable portion 60 extends within the headspace 112 and defines a permeable barrier 60' between the first and second parts 111', 111" of the internal space within the headspace 112. The first permeable material 31 is a non-woven fabric, and the second permeable material 61 is a structured fabric, as described above.

[0137] Tests In tests 1 and 2, a 46 litre tank was configured and fitted with a filter assembly 1 similar to that shown in Fig. 1 and filled with DEF to the fill line 151. The first permeable portion 30 of the filter was made from a non-woven fabric 31, and the liquid impermeable portion 40 and flange 11 were moulded from rubber. The non-woven fabric 31 was connected to the liquid impermeable portion 40 by stitching.

[0138] The flowpath 42 was formed as a pair of discrete vent holes 42', diametrically opposed across the central axis X and each having a smallest section area A of 2.5mm, giving a total (aggregate) smallest section area A of the flowpath of 5mm.

[0139] Test 1

[0140] In test 1, the tank was mounted far from the centre of gravity of a work vehicle (configured for digging on a construction site) in the worst possible position, so that it experienced the maximum amount of movement of the vehicle.

[0141] The vehicle was operated continuously over very rough ground for 60 hours.

[0142] The first permeable portion 30 of the filter was covered with a protective sheath leaving only the two vent holes 42' exposed. The total quantity of DEF that passed through the vent holes into the first part 111' of the internal space was measured at the end of the test and found to be a negligible volume, from about 10g to 20g, which is to say, about a teaspoonful.

[0143] Test 2

[0144] Fig. 11 shows the results of a fill test on the same tank as used in Test 1.

[0145] The tank was filled progressively from time zero to the line tF which indicates when the level of DEF in the second part 111" of the tank outside reached the fill line 151. The level L of the tank as indicated by the level sensor 142 in the header assembly is plotted against time t in seconds, from 0% (indicating the sensor float 143 was at its lowest point corresponding to an empty tank) to 100% (indicating that the sensor float 143 was at its highest point, corresponding to a liquid level at the fill line 151 in the first part 111' of the interior space of the tank within the barrier wall 20.)

[0146] Plot A shows the sensor output. It can be seen that the level sensor 142 indicated a full tank approximately three seconds after the liquid level in the second part 111" of the interior space reached the fill line 151.

[0147] Plot B shows the sensor output for the same test but with the flowpath 42 closed. It can be seen that the liquid level across the non-woven filter fabric 31 equalised around ten minutes after filling started.

[0148] The test demonstrates the effective seal obtained by the stitched connection between the filter fabric 31 and the liquid impermeable portion 40, and by the flange 11 which formed a seal between the mounting surface 132 of the header assembly 130 and the upper wall 116 of the tank, as well as the rapid pressure equalisation provided by the small diameter vent holes 42'.

[0149] Industrial Applicability

[0150] The novel filter assembly 1, T can be used in liquid storage tanks in vehicular and non-vehicular applications, and particularly in DEF tanks on vehicles, including work vehicles.

[0151] By providing a flowpath 42 through which gas in the headspace 112 can pass between the first and second parts 111', 111" of the internal space, the novel filter assembly 1, 1' allows the liquid level to equalise rapidly across the barrier wall 20 of the filter. Where the header assembly 130 includes a level sensor 142, this allows the level sensor 142 to respond rapidly to the changing level of DEF when the tank 110 is filled.

[0152] A non-woven fabric 31 has relatively high filtration efficiency and so more effectively excludes particulate contaminants from the header assembly 130, compared with a structured (e.g. woven) fabric 61.

[0153] However, it has been found that a non-woven fabric 31 will tend to wick DEF or other liquid 150 in the tank, which can quickly saturate the entire body of fabric 31 even if the level of liquid 150 in the tank is only just enough to wet the bottom of the filter. Moreover, when saturated, the permeability of the non-woven fabric 31 to gas in the headspace 112 is greatly reduced. In consequence, a prior art bag filter made entirely from non-woven fabric 31 and tightly sealed to the tank assembly 100 will effectively prevent the flow of gas 160 through the filter in the headspace 112. This can cause a delay of several minutes before the liquid level inside the filter rises to match the level in the rest of the tank 110 when the tank is filled.

[0154] It has further been observed that this problem is less evident when a prior art bag filter is mounted over the neck of the header assembly 130 using a band clamp, since pleating of the fabric 31 beneath the band clamp gives rise to leakage paths that allow gas to flow across the filter in the headspace 112, even when the filter fabric 31 is saturated.

[0155] A more satisfactory seal is obtained when the permeable fabric 31 of the prior art filter is connected to the sealing portion by stitching, welding, bonding, or moulding, since all these methods obviate leakage paths.

[0156] However, when a more satisfactory method is used to seal the filter to the tank assembly 100, the problem of reduced gas flow through the saturated, nonwoven fabric 31 in the headspace 112 is more apparent.

[0157] Surprisingly, in accordance with the first aspect of the disclosure, it is found that a flowpath 42 with a small cross-sectional area and formed though an impermeable portion 40 of the barrier wall 20 can mitigate this problem by effectively preventing any significant flow of liquids 150 sloshing in the headspace 112, even in a vehicular tank 110 operating under severe off-road use conditions, while providing an effective gaseous flowpath for pressure equalisation in the headspace 112. The flowpath 42 can be in the form of one or a few discrete vent holes 42'. Optionally, the flowpath 42 may be further protected against liquid flow by a confronting surface 114 of the tank assembly or by providing it with a non-linear configuration, a non-return valve 50, a semipermeable membrane 51, or a structured fabric 61 which remains gas permeable even when wet.

[0158] In contrast to a non-woven fabric, a structured fabric 61 will tend to remain permeable to gases in the headspace even when saturated, due to its regular pattern of intersticial spaces which extend through the thickness of the fabric.

[0159] Accordingly, in an alternative approach in accordance with the second aspect of the disclosure, the upper portion of the filter in the headspace 112 is made from a structured fabric 61 while the lower portion below the fill line 151 is made from a non-woven fabric 31. Again, it is found that the structured fabric can exclude contaminants to a sufficient extent if arranged in the headspace 112, where it need only resist flow due to sloshing of the liquid 150, while remaining permeable to gases 160.

[0160] Although these approaches of the first and second aspects of the disclosure can be used as alternative ways to provide better gaseous pressure equalisation in the headspace, it is conceivable also to combine them in the same filter which then would include an impermeable portion defining a flowpath, and an upper portion of structured fabric in the headspace, and a lower portion of non-woven fabric below the fill line. The structure fabric of the upper portion may be arranged to screen a vent hole in the impermeable portion, as illustrated, or in other arrangements, not illustrated, could extend between the impermeable portion and the lower, non-woven portion of the filter.

[0161] Where the filter includes an impermeable portion, the impermeable portion can include or consist of a rubber or elastomer which can also form the sealing portion of the filter. In the first aspect of the disclosure, by forming the flowpath through the rubber or elastomer, it is found that as the filter vibrates in service (especially when mounted in a tank on a vehicle, e.g. a DEF tank), the walls of the flowpath will flex as the tank vibrates in use, and so will tend to dislodge any particles (e.g. particles of dirt, or crystals of DEF or ice) that enter the flowpath. In accordance with the third aspect of the disclosure, the sealing portion of the filter is configured to form a flange that extends radially outwardly from the upper end of the barrier wall to be interposed between the mounting surface of the header assembly, and the upper wall of the tank defining said sealing surface. This makes it easy to mount the filter in the use position while effectively sealing it to the tank and the header assembly.

[0162] The novel filter assembly of the third aspect may be combined with the features of the novel filter assembly of either or both of the second or third aspects, providing simpler assembly with improved sealing while also mitigating the effect of improved sealing by providing a pressure equalising flowpath, via an impermeable portion of the filter assembly and / or a structured fabric arranged in the headspace.

[0163] Advantageously, by making the flange from a rubber or elastomer, the flange can also function as a gasket that provides the seal between the upper wall of tank and the mounting surface of the header assembly, which further simplifies assembly and further improves sealing between those three parts of the tank assembly. By providing for the rubber or elastomer also to form a liquid impermeable portion of the filter, it is possible to provide a flowpath in that liquid impermeable portion that benefits from the flexing of the rubber or elastomer as discussed above.

[0164] Alternative Embodiments

[0165] In summary, in embodiments, a filter assembly includes a sealing portion and a barrier wall having a first permeable portion that extends below the liquid fill line in a tank, e.g. a DEF tank. The sealing portion is connected to a sealing surface of the tank assembly so that the barrier wall divides a first part of the internal space of the tank containing a header assembly from a second part external to the first part. In a first aspect, the filter assembly includes a liquid impermeable portion defining a flowpath. In a second aspect, the first permeable portion is made from a non-woven fabric, and the barrier wall includes a second permeable portion made from a structured fabric, also providing a flowpath. The flowpath is arranged to allow gas to flow in the headspace of the tank to equalise pressure across the barrier wall. In a third aspect, the filter assembly is tubular and the sealing portion is configured as a flange that is interposed between respective sealing surfaces of the header assembly and the upper wall of the tank, e.g. to form a gasket.

[0166] In alternative embodiments the liquid in the tank may be diesel exhaust fluid (DEF) or any other liquid. The header assembly need not include a pump, which could be arranged externally of the tank, e.g. elsewhere on a vehicle. The level sensor if present need not include a float, and could be of any other suitable type as known in the art.

[0167] In alternative embodiments in accordance with the first or second aspect of the disclosure, the filter assembly need not have a tubular configuration, and the sealing surface need not be formed on the upper wall of the tank. In such alternative embodiments, the sealing portion of the filter assembly could be sealingly connected to a sealing surface elsewhere on the tank or on the header assembly or on another component of the tank assembly. For example, if the filter assembly is installed via an aperture in a lower wall of the tank then the sealing surface could be a surface of the lower wall of the tank. The sealing portion of the filter assembly may then be sealed to the sealing surface at the bottom of the tank to support the barrier wall in an upright position extending up into the internal space of the tank. For example, if the barrier wall is tubular, a closed end of the barrier wall may extend into the headspace.

[0168] Many further adaptations are possible within the scope of the claims.

[0169] In the claims, reference numerals and characters are provided in parentheses, purely for ease of reference, and should not be construed as limiting features.

Claims

Claims1. A filter assembly (1) for use as part of a tank assembly (100); the tank assembly (100) further including a tank (110), and a header assembly (130) extending into an internal space (111) of the tank (110); the internal space (111) containing a liquid (150) in use, and including a headspace (112) above a maximum fill level (151) of the liquid (150); the header assembly (130) including an outlet (131) for the liquid (150) to flow out of the tank (110); the filter assembly (1) including: a sealing portion (10), and a barrier wall (20); the barrier wall (20) including: a first permeable portion (30) including a first permeable material (31), and a liquid impermeable portion (40) including a liquid impermeable material (41); the sealing portion (10) being sealingly connected or connectable to a sealing surface (113) of the tank assembly (100) to locate the filter assembly (1) in a use position; wherein, in the use position: the barrier wall (20) is arranged in the internal space (111) of the tank (110) to enclose a first part (111') of the internal space containing the header assembly (130), and to separate the first part (111') of the internal space from a second part (111") of the internal space external to the first part; the first permeable portion (30) extends below the maximum fill level (151) of the liquid (150) to filter the liquid (150) flowing, in use, through the first permeable portion (30) from the secondpart (111") of the internal space to the first part (1111) of the internal space; and the liquid impermeable portion (40) extends within the headspace (112) and defines a liquid impermeable barrier (40') to prevent the liquid (150) from sloshing, in use, through the liquid impermeable barrier (40') between the first and second parts (111', 111") of the internal space; wherein a flowpath (42) is formed through said liquid impermeable barrier (40'), the flowpath (42) having a smallest total cross-sectional area (A) through which, in the use position, gas (160) in the headspace (112) can flow between the first and second parts (111', 111") of the internal space, wherein the first and second parts (111', 111") of the internal space are not in fluid communication through the liquid impermeable barrier (40') except via the flowpath (42).

2. A filter assembly (1) according to claim 1, wherein the first permeable material (31) is a non-woven fabric made from randomly interconnected fibres (32) without a regular structured pattern.

3. A filter assembly (1) according to claim 2, wherein the first permeable material (31) is connected to the liquid impermeable portion (40) by stitching, welding, bonding, or moulding.

4. A filter assembly (1) according to claim 1, wherein the liquid impermeable material (41) is a rubber or elastomer and defines an internal wall (43) of the flowpath (42).

5. A filter assembly (1) according to claim 1, wherein: the barrier wall (20) extends along an axis (X), andthe first permeable portion (30) defines a first tubular portion (30') of the barrier wall (20), and the liquid impermeable portion (40) defines a second tubular portion (40") of the barrier wall (20), and the first and second tubular portions (30', 40") extend in collinear series relation along the axis (X), and the second tubular portion (40") is arranged between the first tubular portion (30') and the sealing portion (10).

6. A filter assembly (1) according to claim 5, wherein both the sealing portion (10) and the liquid impermeable portion (40) include said liquid impermeable material (41), wherein the liquid impermeable material (41) is a rubber or elastomer and defines an internal wall (43) of the flowpath (42).

7. A filter assembly (1) according to claim 1, wherein the area (A) is a total cross-sectional area of at least one discrete vent hole (42') formed directly in said liquid impermeable material (41) and extending through a thickness (Tl) of said liquid impermeable barrier (40') between the first and second parts (111', 111") of the internal space.

8. A filter assembly (1) according to claim 7, wherein the at least one discrete vent hole (42') consists of not more than four discrete vent holes (42').

9. A filter assembly (1) according to claim 1, wherein either: (a) the flowpath (42) is screened by a structured fabric (61), the structured fabric (61) being made from strands or fibres (62) arranged in a regular structured pattern to define a regular pattern of inter sti ci al spaces (63) extending through a thickness (T2) of the structured fabric (61) between adjacent ones orgroups of the strands or fibres (62), wherein the area (A) is defined as a smallest total cross-sectional area of said intersticial spaces (63); or(b) a check valve (50) is arranged to allow fluid to flow through the flowpath (42) from the first part (111') to the second part (111") of the internal space, and to prevent fluid from flowing through the flowpath (42) from the second part (111") to the first part (111') of the internal space; or(c) a semipermeable membrane (51) is arranged to allow a flow of gas (160) while inhibiting a flow of liquid (150) through the flowpath (42); or(d) the flowpath (42) is nonlinear.

10. A tank assembly (100) including : a tank (110) having an internal space (111), wherein in use the internal space (111) contains a liquid (150) and includes a headspace (112) above a maximum fill level (151) of the liquid (150); a header assembly (130) extending into the internal space (111) and including an outlet (131) for the liquid (150) to flow out of the tank (110); and a filter assembly (1) according to claim 1, the sealing portion (10) being sealingly connected to a sealing surface (113) of the tank assembly (100) in the use position; wherein the flowpath (42) defines an opening (44) in a surface(45) of the liquid impermeable portion (40), and the tank assembly (100) defines a confronting surface (114) proximate the header assembly (130); the opening (44) facing the confronting surface (114) so that the opening (44) is spaced apart from the confronting surface (114) by a gap (46); the gap (46) opening into the headspace (112) within the second part (111") of the internal space in the use position.

11. A filter assembly (!') for use as part of a tank assembly(100); the tank assembly (100) further including a tank (110), and a header assembly (130) extending into an internal space (111) of the tank (110); the internal space (111) containing a liquid (150) in use, and including a headspace (112) above a maximum fill level (151) of the liquid (150); the header assembly (130) including an outlet (131) for the liquid (150) to flow out of the tank (110); the filter assembly (1') including: a sealing portion (10), and a barrier wall (20); the barrier wall (20) including: a first permeable portion (30) including a first permeable material (31), and a second permeable portion (60) including a second permeable material (61) different from the first permeable material (31); the sealing portion (10) being sealingly connected or connectable to a sealing surface (113) of the tank assembly (100) to locate the filter assembly (1) in a use position; wherein, in the use position: the barrier wall (20) is arranged in the internal space (111) of the tank (110) to enclose a first part (111') of the internal space containing the header assembly (130), and to separate the first part (111') of the internal space from a second part (111") of the internal space external to the first part; the first permeable portion (30) extends below the maximum fill level (151) of the liquid (150) to filter the liquid (150) flowing, in use, through the first permeable portion (30) from the second part (111") of the internal space to the first part (111') of the internal space; andthe second permeable portion (60) extends within the headspace (112) and defines a permeable barrier (60') between the first and second parts (1111, 111") of the internal space within the headspace (H2); wherein the first permeable material (31) is a non-woven fabric made from randomly interconnected fibres (32) without a regular structured pattern, and the second permeable material (61) is a structured fabric made from strands or fibres (62) arranged in a regular structured pattern to define a regular pattern of intersticial spaces (63) extending through a thickness (T2) of the structured fabric (61) between adjacent ones or groups of the strands or fibres (62), the first and second parts (1111, 111") of the internal space within the headspace (112) being in fluid communication via said intersticial spaces (63).

12. A filter assembly (1') according to claim 11, wherein the barrier wall (20) extends along an axis (X), the first permeable portion (30) defining a first tubular portion (30') of the barrier wall (20), the second permeable portion (60) defining a second tubular portion (60") of the barrier wall (20), the first and second tubular portions (30', 60") extending in collinear series relation along the axis (X).

13. A filter assembly (1') according to claim 12, wherein the second tubular portion (60") is arranged between the first tubular portion (30') and the sealing portion (10).

14. A filter assembly (1, 1') for use as part of a tank assembly(100); the tank assembly (100) further including a tank (110), and a header assembly (130) extending through an aperture (115) in an upper wall (116) of the tank (110) into an internal space (111) of the tank (110); the internal space (111) containing a liquid (150) in use, and including a headspace (112) above a maximum fill level (151) of the liquid (150); the header assembly (130) including an outlet (131) for the liquid (150) to flow out of the tank (110), and a mounting surface (132), the mounting surface (132) being sealingly mounted to the upper wall (116) of the tank (110) to seal the header assembly (130) in the aperture (115); the filter assembly (1, 1') including: a sealing portion (10), and a barrier wall (20); the barrier wall (20) extending along an axis (X) and including a first permeable portion (30); the first permeable portion (30) including a first permeable material (31) and extending along the axis (X) to define a first tubular portion (30') of the barrier wall (20); the sealing portion (10) being sealingly connectable to a sealing surface (113) of the tank assembly (100) to locate the filter assembly (1, 1') in a use position; wherein, in the use position: the barrier wall (20) is arranged in the internal space (111) of the tank (110) to enclose a first part (111') of the internal space containing the header assembly (130), and to separate the first part (111') of the internal space from a second part (111") of the internal space external to the first part, and the first permeable portion (30) extends below the maximum fill level (151) of the liquid (150) to filter the liquid (150)flowing, in use, through the first permeable portion (30) from the second part (111") of the internal space to the first part (1111) of the internal space; wherein the sealing portion (10) includes a flange (11) extending radially outwardly, with respect to the axis (X), from an upper end (21) of the barrier wall (20) in the use position, the flange (11) being configured to be interposed, in the use position, between the mounting surface (132) of the header assembly (130), and the upper wall (116) of the tank (110) defining said sealing surface (113).

15. A filter assembly (1) according to claim 14, wherein the barrier wall (20) includes a liquid impermeable portion (40) including a liquid impermeable material (41) and defining a second tubular portion (40") of the barrier wall (20); the first and second tubular portions (30', 40") extending in collinear series relation along the axis (X); the second tubular portion (40") being arranged between the first tubular portion (30') and the sealing portion (10); wherein, in the use position, the liquid impermeable portion (40) extends within the headspace (112) and defines a liquid impermeable barrier (40') to prevent the liquid (150) from sloshing, in use, through the liquid impermeable barrier (40') between the first and second parts (111', 111") of the internal space.

16. A filter assembly (1) according to claim 15, wherein both the liquid impermeable portion (40) and the flange (11) include said liquid impermeable material (41), wherein the liquid impermeable material (41) is a rubber or elastomer.

17. A filter assembly (1) according to claim 15, wherein a flowpath (42) is formed through said liquid impermeable barrier (40'), the flowpath (42) having a smallest total cross-sectional area (A) through which, in the use position, gas (160) in the headspace (112) can flow between the first and second parts (1111, 111") of the internal space, wherein the first and second parts (111', 111") of the internal space are not in fluid communication through the liquid impermeable barrier (40') except via the flowpath (42).

18. A filter assembly (1, 1') according to claim 17, wherein both the liquid impermeable portion (40) and the flange (11) include said liquid impermeable material (41), wherein the liquid impermeable material (41) is a rubber or elastomer and defines an internal wall (43) of the flowpath (42).

19. A filter assembly (1') according to claim 14, wherein the barrier wall (20) includes a second permeable portion (60), the second permeable portion (60) including a second permeable material (61) different from the first permeable material (31) and defining a second tubular portion (60") of the barrier wall (20); the first and second tubular portions (30', 60") extending in collinear series relation along the axis (X); the second tubular portion (60") being arranged between the first tubular portion (30') and the sealing portion (10); wherein, in the use position, the second permeable portion (60) extends within the headspace (112) and defines a permeable barrier (60') between the first and second parts (111', 111") of the internal space within the headspace (H2); wherein the first permeable material (31) is a non-woven fabric made from randomly interconnected fibres (32) without a regular structured pattern, andthe second permeable material (61) is a structured fabric made from strands or fibres (62) arranged in a regular structured pattern to define a regular pattern of intersticial spaces (63) extending through a thickness (T2) of the structured fabric between adjacent ones or groups of the strands or fibres (62), the first and second parts (1111, 111") of the internal space within the headspace (112) being in fluid communication via said intersticial spaces (63).

20. A tank assembly (100) including: a tank (110) having an internal space (111), wherein in use the internal space (111) contains a liquid (150) and includes a headspace (112) above a maximum fill level (151) of the liquid (150); a header assembly (130) extending through an aperture (115) in an upper wall (116) of the tank (110) into the internal space (111) and including an outlet (131) for the liquid (150) to flow out of the tank (110), and a mounting surface (132), the mounting surface (132) being sealingly mounted to the upper wall (116) of the tank (110) to seal the header assembly (130) in the aperture (115); and a filter assembly (1, 1') according to claim 14, the flange (11) being interposed in the use position between the mounting surface (132) of the header assembly (130), and the upper wall (116) of the tank (110) defining said sealing surface (113).

Images