Patent Description:
A substrate for purification of exhaust gases may typically comprise a monolithic substrate that is provided with passages for the through-flow of exhaust gases. The substrate may be provided with a coating, which may be a catalytic coating. The coating may be applied to the substrate as a washcoat that is passed through the passages of the substrate. Various methods for applying the coating to a substrate are known. One such method involves applying washcoat to a first face of the substrate (e.g. an upper face) and subjecting an opposite, second face (e.g. a lower face) of the substrate to at least a partial vacuum to achieve movement of the washcoat through the passages. After coating the substrate may be dried and calcined.

The substrate may be configured as a flow-through substrate wherein each passage is open at both the first and second faces of the substrate and the passage extends through the whole length of the substrate. Consequently, exhaust gases entering through a first face of the substrate into a passage pass through the substrate within the same passage until the exhaust gases exit a second face of the substrate. Alternatively, the substrate may be configured as a filter substrate, in which some passages are plugged at a first face of the substrate and other passages are plugged at a second face of the substrate. In such a configuration, exhaust gases entering through a first face of the substrate into a first passage flow along that first passage part-way along the substrate and then pass through a filtering wall of the substrate into a second passage. The exhaust gases then pass along said second passage and out of the second face of the substrate. Such an arrangement has become known in the art as a wall-flow filter.

The coated flow-through substrate may comprise a three way catalyst (TWC), a selective catalytic reduction (SCR) catalyst, a diesel oxidation catalyst (DOC), a lean NOx trap catalyst (LNT), an ammonia slip catalyst (ASC), a combined selective catalytic reduction catalyst and ammonia slip catalyst (SCR/ASC), or a passive NOx adsorber (PNA).

The coated filter substrate, for example, be a catalysed soot filter (CSF) comprising an oxidation catalyst, a selective catalytic reduction filter (SCRF) comprising a selective catalytic reduction (SCR) catalyst, a lean NOx trap filter (LNTF) comprising a NOx adsorber composition, a gasoline particulate filter (GPF) comprising a three-way catalyst composition, or a filter substrate comprising a selective catalytic reduction (SCR) catalyst and an ammonia slip catalyst (ASC).

The substrate may be made or composed of a ceramic material or a metallic material. For example, the substrate may be made or composed of aluminium titanate, cordierite (SiO2-Al2O3-MgO), silicon carbide (SiC), Fe-Cr-Al alloy, Ni-Cr-Al alloy, or a stainless steel alloy.

The substrate will commonly have a substrate body which has a uniform cross-sectional shape along its longitudinal length. Typically, the substrate body may have a circular or near circular shape in cross-section, although other cross-sectional shapes are possible, for example square and rectangular. An upper surface of the substrate body may be defined as the face that is positioned uppermost during coating and likewise a lower surface of the substrate body may be defined as the face that is positioned lowermost during coating. Commonly, the upper face and lower face are planar and orthogonal to the longitudinal axis of the substrate body.

When coating substrates it may typically be desirable to achieve a substantially 'flat' washcoat profile - i.e. achieving a leading 'front' or 'edge' of the washcoat (marking the boundary interface between the coated and uncoated portions of the substrate) that is substantially flat or perpendicular to the longitudinal axis of the passages.

An uneven washcoat profile can result in a detrimental effect to the operational efficiency of the substrate. For example, uneven profiles may lead to portions of the substrate being uncoated (which reduces the catalytic efficiency of the substrate) or portions of the substrate being unintentionally coated more than once - where multiple doses of washcoat are applied (which can deleteriously increase the back pressure of the substrate). In some circumstances washcoat may be fully pulled through the substrate body and emerge from the lower surface.

To achieve an even washcoat profile it may be desirable to achieve an even depth of the washcoat over the upper surface of the substrate before the substrate is drawn through the substrate. Factors including the evenness of the depositing of the washcoat onto the upper surface and the rate of spread of the washcoat when on the upper surface may affect the depth of the washcoat across the upper surface.

Another factor that can affect performance is dripping or leakage of washcoat from the washcoat showerhead. The showerhead is described, for example, in <CIT>. Such leakage or dripping (after the desired volume of washcoat has been discharged from the washcoat showerhead) may lead to excess washcoat on the upper surface. This may result in a reduced economy of operation due to wastage of washcoat. It may also lead to washcoat being fully pulled through portions of the substrate body so as to emerge from the lower surface. This can lead to potential blocking of the passage openings on the lower face of the substrate. Such leakage and dripping can also lead to deposits being left on the upper surface which may block passage openings on the upper face of the substrate and may result in visual degradation of the substrate which is found undesirable by customers.

<CIT> describes, according to its abstract, a nozzle that is configured to discharge a fluid containing a raw material of a catalytic layer to a substrate having first and second end faces and provided with holes each extending from the first end face to the second end face. The nozzle is provided with discharge ports each discharging the fluid toward the first end face of the substrate. <CIT> discloses a method of coating a substrate with a washcoat according to the preamble of claim <NUM> and a substrate coating apparatus according to the preamble of claim <NUM>.

<CIT> describes, according to its abstract, a multi-port application system for applying or dispensing fluids such as adhesives to a substrate at relatively high pressures. The dispensing system includes a manifold chamber and a plurality of nozzles in which the inner end of each nozzle is spaced inwardly of the inner manifold chamber wall. The method includes applying the fluid at a pressure of at least <NUM> psi.

In a first aspect the present disclosure provides a method of coating a substrate with a washcoat according to claim <NUM>.

Advantageously, the method may mitigate dripping and or leakage of washcoat from the washcoat showerhead after the valve assembly has been closed. The pressure drop within the interior of the washcoat showerhead may act to create a suction force which reduces or prevents dripping or leakage of the washcoat.

The outlet valve comprises a valve stem that reciprocates relative to a valve seat.

The valve stem, or a valve seal provided on the valve stem, may sealingly engage the valve seat in the closed state of the outlet valve. Optionally, the valve stem, or the valve seal provided on the valve stem, may sealingly engage a downstream face of the valve seat in the closed state of the outlet valve.

The valve stem or the valve seal may be pulled into sealing engagement with the valve seat in the closed state of the outlet valve.

The valve stem may extend through the valve seat in both the open state and the closed state.

The valve assembly creates a pressure drop within a valve chamber of the valve assembly when moving from the open state to the closed state.

The valve stem functions as a piston within the valve chamber and creates a pressure drop within the valve chamber when moving from the open state to the closed state.

The valve stem may extend towards the outlet when the outlet valve moves into its open state and retract away from the outlet when the outlet valve moves into its closed state.

A capacity of the valve chamber able to accommodate washcoat may be greater in the closed state of the outlet valve than in the open state of the outlet valve.

The valve stem may be moved by a valve stem actuator. The valve stem actuator may be a pneumatic, hydraulic or electro-mechanical actuator.

Within the washcoat showerhead, the washcoat may enter centrally into an upper portion of the interior, then flow towards a periphery of the interior, and may then be directed down into a lower portion of the interior and then be directed to flow inwards within the lower portion towards a centre of the washcoat showerhead.

The washcoat may be discharged from the lower portion of the interior through an array of apertures arranged in a lower layer of the washcoat showerhead. The pressure drop within the interior of the washcoat showerhead may act to create a suction force at the array of apertures which reduces or prevents dripping or leakage of the washcoat.

In a second aspect the present disclosure provides a substrate coating apparatus according to claim <NUM>.

Advantageously, the substrate coating apparatus may mitigate dripping and or leakage of washcoat from the washcoat showerhead after the valve assembly has been closed. The pressure drop within the interior of the washcoat showerhead may act to create a suction force which reduces or prevents dripping or leakage of the washcoat.

The outlet valve comprises a valve stem configured for reciprocating movement relative to a valve seat.

The valve stem, or a valve seal provided on the valve stem, may be configured to sealingly engage the valve seat in the closed state of the outlet valve. The valve stem, or the valve seal provided on the valve stem, may be configured to sealingly engage a downstream face of the valve seat in the closed state of the outlet valve.

The valve stem or the valve seal may be configured to be pulled into sealing engagement with the valve seat in the closed state of the outlet valve by a valve stem actuator.

The valve assembly further comprises a valve chamber.

The valve assembly is configured to create a pressure drop within the valve chamber when moving from the open state to the closed state.

The valve stem is configured to function as a piston within the valve chamber to create a pressure drop within the valve chamber when moving from the open state to the closed state.

The valve chamber of the valve assembly may be sealed in a fluid-tight manner to the interior of the washcoat showerhead.

The valve stem may be extended towards the outlet when the outlet valve moves into its open state and be retracted away from the outlet when the outlet valve moves into its closed state.

The valve assembly may be configured such that a capacity of the valve chamber able to accommodate washcoat is greater in the closed state of the outlet valve than in the open state of the outlet valve.

The valve stem may comprise an enlarged valve stem head and comprise a valve stem seal located adjacent a proximal face of the enlarged valve stem head.

The enlarged valve stem head may be located downstream of the valve seat in both the open state and the closed state.

The valve stem seal may comprise an O-ring, optionally an EPDM O-ring.

The substrate coating apparatus may further comprise a valve stem actuator. The valve stem actuator may be a pneumatic, hydraulic or electro-mechanical actuator.

The washcoat showerhead may comprise a housing comprising an upper layer having a fluid connection to the outlet of the valve assembly and a lower layer comprising an array of apertures for discharging the washcoat towards the upper surface of a substrate. The pressure drop within the interior of the washcoat showerhead may act to create a suction force at the array of apertures which reduces or prevents dripping or leakage of the washcoat.

The array of apertures may comprise a plurality of equi-spaced apertures.

An inner diameter of the or each aperture may be <NUM> to <NUM>, optionally about <NUM>, optionally <NUM>. The sizing of the inner diameter of each aperture may be particularly beneficial for creating the suction force at the array of apertures which reduces or prevents dripping or leakage of the washcoat.

The or each of the apertures may be defined by a tubular insert.

The tubular insert of the or each of the apertures may extend below a lower face of the lower layer by at least <NUM>, more preferably by at least <NUM>, most preferably by at least <NUM>, or by about <NUM> or by <NUM>.

The washcoat showerhead may further comprise a baffle layer, which may be configured to direct washcoat that flows centrally into an upper portion of the interior to flow towards a periphery of the interior.

The baffle layer may be configured to convey the washcoat into a lower portion of the interior at or near the periphery of the interior such that the washcoat may be subsequently directed to flow inwards across an upper face of the lower layer towards a centre of the lower layer.

The upper layer and the baffle layer may be separated by a first gap, and optionally the first gap may be <NUM> to <NUM>, optionally about <NUM>, optionally <NUM>.

The baffle layer and the lower layer may be separated by a second gap, and optionally the second gap may be <NUM> to <NUM>, optionally about <NUM>, optionally <NUM>.

The upper layer, baffle layer and lower layer may be sealed together, and optionally may comprise at least a first O-ring seal between the upper layer and the baffle layer and a second O-ring seal between the baffle layer and the lower layer.

The outlet valve may comprise a reverse poppet valve.

In a third aspect described herein but not claimed the present disclosure provides a valve assembly for a substrate coating apparatus comprising:.

Advantageously, the valve assembly may mitigate dripping and or leakage of washcoat from a washcoat showerhead (when assembled therewith) after the valve assembly has been closed. The pressure drop within the interior of the valve chamber may act to create a suction force which reduces or prevents dripping or leakage of the washcoat.

The valve assembly may further comprise a valve stem actuator, and optionally the valve stem actuator may be a pneumatic, hydraulic or electro-mechanical actuator.

In any of the above aspects the substrate maybe selected from a flow-through substrate (e.g. a monolithic flow-through substrate) or a filter substrate (e.g. a wall-flow filter substrate).

In any of the above aspects the washcoat may comprise a catalytic coating selected from a three way catalyst (TWC), a selective catalytic reduction (SCR) catalyst, a diesel oxidation catalyst (DOC), a lean NOx trap catalyst (LNT), an ammonia slip catalyst (ASC), a combined selective catalytic reduction catalyst and ammonia slip catalyst (SCR/ASC), and a passive NOx adsorber (PNA).

In any of the above aspects the washcoat may have a viscosity of <NUM> to <NUM> cP, optionally <NUM> to <NUM> cP, optionally <NUM> to <NUM> cP, optionally <NUM> to <NUM> cP, optionally <NUM> to <NUM> cP, optionally <NUM> to <NUM> cP.

In the present specification all references to viscosity refer to the viscosity of the fluid as measured using a Brookfield Rotational Viscometer fitted with a Small Sample Adaptor and link hanging spindle with the sample temperature controlled at <NUM>. Such viscometers are available from Brookfield Engineering Laboratories, Inc. , Middleboro, MA, USA.

All measurements were taken at a shear rate of <NUM>-<NUM>. As will be common general knowledge to the skilled person, the spindle, rotational speed and viscometer model were chosen in dependence on the viscosity of the fluid in order to ensure the % viscometer torque has a minimum measurement greater than <NUM> % and a maximum measurement less than <NUM> %, where this is not possible the % viscometer torque may have a minimum measurement greater than <NUM> % and a maximum measurement of less than <NUM> %. For the viscosity measurements in the present specification the following spindles were used:.

Aspects and embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:.

As used in this specification and the appended claims, the singular forms "a", "an" and "the" include plural referents unless the context clearly indicates otherwise. Thus, for example, reference to a "catalyst" includes a mixture of two or more catalysts, and the like.

As used in this specification the term "about" also includes the specific value. For example, "about <NUM>%" includes about <NUM>% and also <NUM>% within its meaning.

The skilled reader will recognise that one or more features of one aspect or embodiment of the present disclosure may be combined with one or more features of any other aspect or embodiment of the present disclosure unless the immediate context teaches otherwise.

<FIG> shows a schematic view of a non-limiting example of a substrate coating apparatus <NUM> that may be used for coating a substrate <NUM> with a washcoat. The substrate coating apparatus <NUM> comprises a source <NUM> of a washcoat, a valve assembly <NUM>, a washcoat showerhead <NUM>, a headset <NUM>, and a vacuum generator <NUM>.

The substrate <NUM> may, for example, be of a type that comprises a substrate body <NUM> that has a uniform cross-sectional shape along its longitudinal length. Typically, the substrate body <NUM> may have a circular or near circular shape in cross-section. The substrate body <NUM> may be positioned in the substrate coating apparatus <NUM> such that an upper surface <NUM> of the substrate body <NUM> is uppermost and a lower surface <NUM> of the substrate body <NUM> is lowermost. The upper surface <NUM> and lower surface <NUM> may be planar and orthogonal to a longitudinal axis of the substrate body <NUM>.

The source <NUM> of washcoat may supply in use washcoat to the valve assembly <NUM> via a conduit <NUM>. The source <NUM> may take various forms. In one, non-limiting, example the source <NUM> may comprise a hopper reservoir of washcoat and a dispensing mechanism for feeding controlled volumes of the washcoat to the valve assembly <NUM> from the hopper reservoir. The dispensing mechanism may comprise, for example, a piston which is axially moveable within a bore for providing a motive force to displace washcoat into and or along the conduit <NUM> towards the valve assembly <NUM>. The source <NUM> may comprise an on/off valve (such as a ball valve or diaphragm valve) located in between the hopper reservoir (or equivalent) and the valve assembly <NUM>.

The substrate <NUM> may be located and positioned between the headset <NUM> and a pallet insert9 or other substrate tooling. The pallet insert <NUM> or other substrate tooling may be mounted to a rotary table <NUM>. The pallet insert <NUM> or other substrate tooling may be vertically movable relative to the rotary table <NUM> and headset <NUM>. The rotary table <NUM> may enable the pallet insert <NUM> or other substrate tooling to be moved laterally relative to the headset <NUM>.

The washcoat showerhead <NUM> is configured for discharging the washcoat towards the upper surface <NUM> of the substrate <NUM>. The washcoat showerhead <NUM> may be located above the headset <NUM> and may be aligned with the headset <NUM> and substrate <NUM> such that a central longitudinal axis of the washcoat showerhead <NUM> is coincident with a central longitudinal axis of both the headset <NUM> and substrate body <NUM>.

The headset <NUM> is configured for engaging the substrate <NUM> to locate the upper surface <NUM> of the substrate <NUM> below the washcoat showerhead <NUM>. The headset <NUM> may comprise a headset seal <NUM> that may engage an upper edge circumscribing the upper surface <NUM> of the substrate body <NUM>. The headset seal <NUM> may comprise an annular ring that extends fully around the headset <NUM>.

The vacuum generator <NUM> is configured for drawing the washcoat discharged from the washcoat showerhead <NUM> through the substrate <NUM>. The vacuum generator <NUM> may comprise a vacuum cone that may be located beneath the substrate <NUM>. The vacuum generator <NUM> may be configured to apply a suction force to a lower surface <NUM> of the substrate <NUM>. The vacuum generator <NUM> may comprise an apparatus or combination of apparatus that function to produce a pressure reduction. Non-limiting examples of suitable apparatus include vacuum generators that operate on the venturi principle, vacuum pumps, for example rotary vane and liquid ring vacuum pumps, and regenerative blowers.

The valve assembly <NUM> is configured for controlling flow of the washcoat into the washcoat showerhead <NUM>.

A first example of a valve assembly <NUM> according to the present disclosure is shown in <FIG> and <FIG>. The valve assembly <NUM> may comprise a valve body housing <NUM>, a valve stem actuator <NUM>, a valve stem <NUM>, and a valve seat <NUM>.

The valve assembly <NUM> comprises an inlet <NUM> for receiving the washcoat supplied from the source <NUM> of washcoat, an outlet <NUM> for supplying the washcoat to the washcoat showerhead <NUM>, and a valve chamber <NUM>.

The valve body housing <NUM> may, for example, have a T-shaped configuration comprising a longitudinal portion <NUM> and a lateral portion <NUM>. It will be understood that such a configuration is merely one possible example and other configurations for the valve body housing <NUM> may be used.

The longitudinal portion may extend between an upper end <NUM>, provided for coupling directly or indirectly to the valve stem actuator <NUM>, and a lower end <NUM>, provided for coupling directly or indirectly to the washcoat showerhead <NUM>.

The upper end <NUM> may be directly coupled to the valve stem actuator <NUM>. Alternatively, as shown in <FIG>, the coupling may be indirect with an actuator coupling <NUM> provided that is interposed between the upper end <NUM> and the valve stem actuator <NUM>. The valve stem actuator <NUM> may be coupled to the valve body housing <NUM> by fixatives, for example by bolts, that pass through the actuator coupling <NUM>.

The lower end <NUM> may be directly coupled to the washcoat showerhead <NUM> and therefore define the outlet <NUM>. Alternatively, as shown in <FIG>, the coupling may be indirect with the valve seat <NUM> and an outlet coupling <NUM> provided that are interposed between the lower end <NUM> and the washcoat showerhead <NUM>. In this example the outlet coupling <NUM> defines the outlet <NUM>. The outlet coupling <NUM> may be coupled to the valve body housing <NUM> by fixatives, for example by bolts that pass through the outlet coupling <NUM>. A first gasket seal <NUM>, shown in <FIG>, may be interposed between the valve body housing <NUM> and the valve seat <NUM>, and a second gasket seal <NUM>, also shown in <FIG>, may be interposed between the valve seat <NUM> and the outlet coupling <NUM> to ensure a fluid-tight coupling of the washcoat showerhead <NUM> to the valve assembly <NUM>.

The outlet coupling <NUM> may comprise a flange <NUM> that may be sized and shaped to couple to a flange <NUM> of the washcoat showerhead <NUM>, shown in <FIG>.

The lateral portion <NUM> may extend between the longitudinal portion <NUM> and the inlet <NUM>. A mounting <NUM> may be provided at the inlet end of the lateral portion <NUM> for coupling directly or indirectly the valve body housing <NUM>, and hence the valve assembly <NUM>, to the conduit <NUM>. The mounting <NUM> may comprise a flange, screw fitting or other means for coupling the conduit <NUM> in a fluid-tight manner to the valve assembly <NUM>.

The longitudinal portion <NUM> and the lateral portion <NUM> may each comprise a hollow bore that are interconnected where they intersect one another such that washcoat is free to flow from the lateral portion <NUM> into the longitudinal portion <NUM> during use.

The valve stem actuator <NUM> may comprises an actuator body <NUM> and an actuator stem <NUM>. The actuator stem <NUM> may be configured to engage an upper end <NUM> of the valve stem <NUM>. The actuator stem <NUM> and upper end <NUM> may be fixedly attached or releasable attached together. The actuator stem <NUM> and the upper end <NUM> may be mutually shaped to form an interlocking formation. The interlocking formation may comprise mutual projections and undercuts that can interlock with one another.

The valve stem actuator <NUM> may be a pneumatic, hydraulic or electro-mechanical actuator. The actuator body <NUM> may comprise inlet and or outlet connections for coupling to a pneumatic, hydraulic or electrical source of power.

The valve stem <NUM> may comprise an elongate member. The elongate member may comprise a single component or multiple components that are assembled together.

The valve stem <NUM> may comprises an upper portion <NUM> and a lower portion <NUM>. The upper portion <NUM> may be a cylindrical portion of a first diameter. The upper end <NUM> may be provided at an upper end of the upper portion <NUM>. The lower portion <NUM> may be a cylindrical portion of a second diameter. The first diameter may be greater than the second diameter.

The valve stem <NUM> may comprise an enlarged valve stem head <NUM>. The enlarged valve stem head <NUM> may be provided at a lower end of the enlarged valve stem head <NUM>, optionally at a lower end of the lower portion <NUM>.

The valve stem <NUM> may comprise a valve stem seal <NUM>. The valve stem seal may be located adjacent a proximal face of the enlarged valve stem head <NUM>. The valve stem seal <NUM> may comprise an O-ring, for example an EPDM O-ring.

The valve seat <NUM> may define a sealing surface <NUM> to be engaged by the valve stem <NUM> and or valve stem seal <NUM>. The sealing surface <NUM> may be on a downstream face of the valve seat <NUM> facing the outlet <NUM>. The valve seat <NUM> may define an aperture <NUM>. The valve seat <NUM> may be annular with the aperture <NUM> arranged as a central passage surrounded by the sealing surface <NUM>.

The valve seat <NUM> may be formed integrally with the valve body housing <NUM>. Alternatively, as shown in <FIG> the valve seat <NUM> may be formed as a separate component that is coupled to the valve body housing <NUM>. In the illustrated example the bolts that couple the outlet coupling <NUM> to the valve body housing <NUM> also pass through the valve seat <NUM>. As noted above, the first gasket seal <NUM> may be interposed between the valve body housing <NUM> and the valve seat <NUM> and the second gasket seal <NUM> may be interposed between the valve seat <NUM> and the outlet coupling <NUM> to ensure a fluid-tight coupling of the washcoat showerhead <NUM> to the valve assembly <NUM>.

The enlarged valve stem head <NUM> may be located downstream of the valve seat <NUM>, i.e. the valve stem <NUM> may project through the aperture <NUM>. The valve stem <NUM> may extend through the valve seat <NUM> in both the open state and the closed state of the valve assembly <NUM>.

The valve stem <NUM> may be mounted to be reciprocally movable relative to the valve seat <NUM>. As shown in <FIG>, the upper portion <NUM> of the valve stem <NUM> may project through the upper end <NUM> of the longitudinal portion <NUM> and the actuator coupling <NUM> to be engaged with the actuator stem <NUM> of the valve stem actuator <NUM>.

A rod seal or bushing <NUM> may be provided between the actuator coupling <NUM> and the valve stem <NUM>. The rod seal or bushing <NUM> may function to provide lateral support to the valve stem <NUM> to assist in maintaining the alignment of the valve stem <NUM> relative to the longitudinal portion <NUM> of the valve body housing <NUM>.

A wiper seal <NUM> may be provided between the upper end <NUM> and the valve stem <NUM>. The wiper seal <NUM> may function to provide a fluid seal between the valve stem <NUM> and the valve body housing <NUM> to prevent leakage of washcoat in use out of the upper end <NUM>. The wiper seal <NUM> may be configured as a slidable seal able to maintain a fluid-tight seal during reciprocal movement of the valve stem <NUM> relative to the wiper seal <NUM>.

The functions of the rod seal or bushing <NUM> and the wiper seal <NUM> may be combined in a single seal component.

The rod seal or bushing <NUM> and or the wiper seal <NUM> and or the single seal component may be formed, for example, from EPDM, a fluoroelastomer (e.g. Viton®) or polyurethane.

The valve chamber <NUM> may comprise at least a portion of an interior of the valve body housing <NUM>. The valve chamber <NUM> may comprise at least a portion of the hollow bores of the longitudinal portion <NUM> and the lateral portion <NUM>.

In some examples a portion of a boundary of the valve chamber <NUM> may be demarcated by the valve body housing <NUM>. Another portion of the boundary of the valve chamber <NUM> may be demarcated by the intersection of the seal <NUM> with the valve stem <NUM>. Another portion of the boundary of the valve chamber <NUM> may be demarcated by the intersection of the valve stem seal <NUM> with the valve seat <NUM>. Another portion of the boundary of the valve chamber <NUM> may be demarcated by an inlet valve provided for sealing the inlet <NUM>. Such an inlet valve may form a part of the valve assembly <NUM>. Alternatively, the inlet valve may be provided in a component coupled to the inlet <NUM> of the valve assembly <NUM> or be provided within the conduit <NUM> or source <NUM> itself.

The valve stem <NUM> and the valve seat <NUM> may together function as an outlet valve movable between a closed state and an open state to control flow of washcoat out of the outlet <NUM>. The outlet valve may comprise a reverse poppet valve.

In the closed state of the outlet valve the valve stem seal <NUM> may seal against the sealing surface <NUM> to close off the aperture <NUM>. In the open state of the outlet valve the valve stem seal <NUM> may be disengaged from the sealing surface <NUM> to open the aperture <NUM>.

The valve assembly <NUM> is configured to create a pressure drop within the valve chamber <NUM> when the outlet valve moves from its open state to its closed state, with the valve stem <NUM> functioning as a piston within the valve chamber <NUM>. Thus, the valve stem <NUM> may be considered a valve piston.

For example, <FIG> illustrates the outlet valve in the closed state. In order to discharge washcoat out of the outlet <NUM> (in the direction of arrow B) into the washcoat showerhead <NUM> the valve stem <NUM> must be moved downwards relative to the valve seat <NUM> to disengage the valve stem seal <NUM> from the sealing surface <NUM>. During this movement the valve stem <NUM> is extended towards the outlet <NUM>. In addition, the inlet valve must be in an open state to permit washcoat to enter the valve body housing <NUM> through the inlet <NUM>. The source <NUM> may then be activated to transfer washcoat along the conduit <NUM>, into the valve chamber <NUM> through inlet <NUM> (in the direction of arrow A), through the aperture <NUM> in the valve seat <NUM> and out of the outlet <NUM> into the washcoat showerhead <NUM> located downstream of the valve assembly <NUM>.

When it is desired to stop discharge of the washcoat the inlet valve may be closed to stop conveyance of any additional washcoat into the inlet <NUM>. In addition, closing the inlet valve may also create a fluid-tight seal at or upstream of the inlet <NUM> preventing backflow of washcoat present within the valve chamber <NUM> through the inlet <NUM>.

In addition, simultaneously or subsequently to closing the inlet valve, the valve stem <NUM> may be moved upwards by the valve stem actuator <NUM> to close the outlet valve by engaging the valve stem seal <NUM> against the sealing surface <NUM> of the valve seat <NUM>. In particular, the valve stem <NUM> may be configured to be pulled into sealing engagement with the valve seat <NUM> in the closed state of the outlet valve by the valve stem actuator <NUM>.

The valve stem <NUM> may act as a valve piston such that the upward movement of the valve stem <NUM> causes the pressure drop within the valve chamber <NUM>. The washcoat showerhead <NUM> may be coupled in a fluid-tight manner to the valve assembly <NUM>. Hence, a pressure drop within the valve chamber <NUM> may also cause a pressure drop within the washcoat showerhead <NUM>.

An example of the washcoat showerhead <NUM> according to the present invention is shown in <FIG>. The washcoat showerhead <NUM> may comprise a housing <NUM> comprising an upper layer <NUM> having a fluid connection to the outlet <NUM> of the valve assembly <NUM> and a lower layer <NUM> comprising an array of apertures <NUM> for discharging the washcoat towards the upper surface <NUM> of the substrate <NUM>.

The fluid connection may comprise a conduit <NUM> provided with a flange <NUM> sized and shaped to mate sealingly with the flange <NUM> of the valve assembly <NUM>. The conduit <NUM> may define an inlet to an interior of the washcoat showerhead <NUM> which may be arranged on a central axis of the washcoat showerhead <NUM>.

The upper layer <NUM> may comprise a body <NUM> provided with a central aperture <NUM> which may be aligned with the conduit <NUM>.

The lower layer <NUM> may comprise a body <NUM> that contains the array of apertures <NUM>. The array of apertures <NUM> may comprise a plurality of equi-spaced apertures. The apertures may be arranged in a regular pattern as shown in <FIG>. The regular pattern may be a hexagonal pattern of apertures wherein each aperture is surrounded by six apertures.

An inner diameter of each aperture may be <NUM> to <NUM>, optionally about <NUM>, optionally <NUM>.

Each aperture may be defined by a tubular insert <NUM>. The tubular inserts <NUM> may be formed from stainless steel, for example Grade <NUM> stainless steel. The inner diameter of the tubular insert <NUM> may define the inner diameter of the aperture and may be <NUM> to <NUM>, optionally about <NUM>, optionally <NUM>. The tubular inserts <NUM> may extend below a lower face <NUM> of the lower layer <NUM>. It has been found to be beneficial for the tubular inserts <NUM> to extend below the lower face <NUM> of the lower layer <NUM> as this helps to prevent the washcoat clinging to the surface of the lower face <NUM>. Washcoat clinging to the lower face <NUM> in the vicinity of the apertures may build up and at least partially obstruct the apertures leading to non-uniform deposition of the washcoat onto the upper surface <NUM> of the substrate <NUM>. In addition a build-up of washcoat on the lower face <NUM> may dry and harden and flake off or fall onto the upper surface <NUM> of a substrate <NUM> leading to potential blockage of one or more channels of the substrate <NUM> and or aesthetic degradation of the final product. Preferably the tubular inserts <NUM> extend below the lower face <NUM> of the lower layer <NUM> by at least <NUM>, more preferably by at least <NUM>, most preferably by at least <NUM>, or by about <NUM> or by <NUM>.

The washcoat showerhead <NUM> may further comprise a baffle layer <NUM> which is configured to direct washcoat that flows centrally into an upper portion <NUM> of the interior to flow towards a periphery of the interior. The baffle layer <NUM> may be configured to then convey the washcoat into a lower portion <NUM> of the interior at or near the periphery of the interior such that the washcoat is subsequently directed to flow inwards across an upper face <NUM> of the lower layer <NUM> towards a centre of the lower layer <NUM>. To this end the baffle layer <NUM> may be provided with one or more transfer apertures <NUM> as shown in <FIG>. The one or more transfer apertures <NUM> may be located near the periphery of the baffle layer <NUM>. Each transfer aperture <NUM> may comprise an arcuate aperture. Three, four, five or more transfer apertures <NUM> may be provided.

The upper layer <NUM>, lower layer <NUM> and baffle layer <NUM> may be connected together using fixatives, for example, bolts, that pass through bolt holes provided in each layer as shown in the exploded view of <FIG>. The upper layer <NUM>, baffle layer <NUM> and lower layer <NUM> may be sealed together. Thus, the housing of the washcoat showerhead <NUM> may be fluid-tight except for the inlet defined by conduit <NUM> and the outlets defined by the array of apertures <NUM>. In this way, a pressure drop within the valve chamber <NUM> of the valve assembly <NUM> may also produce a pressure drop within the interior of the housing of the washcoat showerhead <NUM>. In particular, a pressure drop within the valve chamber <NUM> of the valve assembly <NUM> may also produce a pressure drop at the upper ends of each of the apertures of the array of apertures <NUM>. For example, at least a first O-ring seal <NUM> may be provided between the upper layer <NUM> and the baffle layer <NUM> and at least a second O-ring seal <NUM> may be provided between the baffle layer <NUM> and the lower layer <NUM>.

The upper layer <NUM>, lower layer <NUM> and baffle layer <NUM> may be formed from a metal, for example a stainless steel, or an engineering plastic, for example POM (polyoxymethylene).

When assembled together, the upper layer <NUM> and the baffle layer <NUM> may be separated by a first gap, and optionally the first gap may be <NUM> to <NUM>, optionally about <NUM>, optionally <NUM>. The baffle layer <NUM> and the lower layer <NUM> may be separated by a second gap, and optionally the second gap may be <NUM> to <NUM>, optionally about <NUM>, optionally <NUM>.

In use, the substrate <NUM> may first be engaged with the headset <NUM> of the substrate coating apparatus <NUM> so as to locate the upper surface <NUM> of the substrate <NUM> below the washcoat showerhead <NUM>. Washcoat may then be conveyed from the source <NUM> of the washcoat towards the washcoat showerhead <NUM>. The valve assembly <NUM> may be used to control flow of the washcoat from the source <NUM> into the interior of the washcoat showerhead <NUM>. Thus, washcoat may be discharged out of the washcoat showerhead <NUM> onto the upper surface <NUM> of the substrate <NUM>. Thereafter the washcoat may be drawn through the substrate <NUM> by applying a suction force to a lower surface <NUM> of the substrate <NUM>. The outlet valve of the valve assembly <NUM> may be moved between its closed state and its open state to control flow of washcoat into the interior of the washcoat showerhead <NUM>. When the outlet valve is moved from its open state to its closed state a pressure drop is created within an interior of the washcoat showerhead <NUM>. This pressure drop may advantageously act to mitigate dripping and or leakage of washcoat from the apertures of the washcoat showerhead <NUM> by creating a suction force at the upper end of each of the array of apertures <NUM> (or tubular inserts <NUM> where present).

<FIG> shows a second example of a valve assembly <NUM> for the substrate coating apparatus <NUM>. Features of the valve assembly <NUM> that are the same or substantially the same as the valve assembly <NUM> of <FIG> and <FIG> have been referenced with the same reference numerals and will not be described in further detail. Reference should be made to the above description. In addition, this second example of valve assembly <NUM> may be used in the same substrate coating apparatus <NUM> as described above in exchange for the first example of valve assembly <NUM>. As such other parts of the substrate coating apparatus <NUM> will not be described further. Reference should be made to the above description.

As above the second example of valve assembly <NUM> may comprise a valve body housing <NUM>, a valve stem actuator <NUM>, a valve stem <NUM>, and a valve seat <NUM>.

The valve body housing <NUM> may be formed from fewer separate components than in the first example. For example, the flange <NUM> and the valve seat <NUM> may be integrated as part of the longitudinal portion <NUM>. The valve seat <NUM> may comprise an annular surface of the longitudinal portion <NUM>. The annular surface may be forward-facing, i.e. pointing towards the outlet <NUM>.

Additionally or alternatively, the valve stem actuator <NUM> may be directly coupled to the upper end <NUM> of the valve body housing <NUM> without an intervening actuator coupling.

Additionally or alternatively, the actuator stem <NUM> of the valve stem actuator <NUM> may be coupled to the upper portion <NUM> of the valve stem <NUM> by means of fixative, for example a bolt, engaged between bolt holes <NUM> and <NUM> in, respectively, the valve stem actuator <NUM> and the valve stem <NUM>. Use of the fixative may obviate the need for a busing to maintain alignment of the valve stem <NUM> as in the first example.

Additionally or alternatively, the valve stem <NUM> may be provided with one or more sliding seals <NUM>, <NUM> for sealing the upper portion <NUM> to the longitudinal portion <NUM> of the valve body housing <NUM>. Two sliding seals <NUM>, <NUM> may be provided. Each sliding seal <NUM>, <NUM> may be an O-ring seal. Each sliding seal <NUM>, <NUM> may be located in an annular recess <NUM>, <NUM> in the upper portion <NUM>.

Additionally or alternatively, the enlarged valve stem head <NUM> of the valve stem <NUM> may be a separate part that is coupled to a remainder of the valve stem <NUM> by a fixative, for example a bolt, engaged between bolt holes <NUM> and <NUM> in, respectively, the lower portion <NUM> and the enlarged valve stem head <NUM>.

Additionally or alternatively, the valve stem seal <NUM> may be located in an annular recess <NUM> in a backward-facing surface of the enlarged valve stem head <NUM>, i.e. in a surface pointing away from the outlet <NUM>.

The inlet <NUM> may be provided with a gasket seal for sealing engagement with the conduit <NUM>. The outlet <NUM> may be provided with a gasket seal <NUM> for sealing engagement with the washcoat showerhead <NUM>.

Operation of the second example of the valve assembly <NUM> is substantially the same as for the first example as described above.

In the following examples comparison is made between the operation of the valve assembly <NUM> and or the washcoat showerhead <NUM> of the present disclosure as described above and shown in <FIG>, compared to the operation of a valve assembly <NUM>' and or a washcoat showerhead <NUM>' not according to the disclosure described above.

The comparative valve assembly <NUM>' is shown in <FIG>. The design is similar to the valve assembly <NUM> shown in <FIG>. In particular, the valve assembly <NUM>' comprises a valve body housing <NUM>', a valve stem actuator <NUM>', a valve stem <NUM>', and a valve seat <NUM>'. The valve stem <NUM>' carries a valve stem seal <NUM>'. The valve seat <NUM>' defines a sealing surface <NUM>' to be engaged by the valve stem seal <NUM>'. The valve assembly <NUM>' comprises an inlet <NUM>' for receiving the washcoat and an outlet <NUM>' for supplying the washcoat to a washcoat showerhead. In contrast to the valve assembly <NUM> of the present disclosure described above, the valve stem <NUM>' of the valve assembly <NUM>' of <FIG> is moved downwards by the valve stem actuator <NUM>' to engage the valve stem seal <NUM>' against the sealing surface <NUM>' of the valve seat <NUM>'. In particular, the valve stem <NUM>' is pushed into sealing engagement with the valve seat <NUM>' in the closed state of the valve assembly <NUM>'.

The comparative washcoat showerhead <NUM>' is shown in <FIG>. The washcoat showerhead <NUM>' comprises a housing <NUM>' comprising an upper layer <NUM>' having a fluid connection for receiving washcoat and a lower layer <NUM>' comprising an array of apertures <NUM>' for discharging the washcoat. Each aperture <NUM>' is defined by a tubular insert <NUM>'. The tubular inserts <NUM>' extend below a lower face <NUM>' of the lower layer <NUM>' by a distance of <NUM> to <NUM>.

In the following examples a series of predetermined shots of three examples of washcoat were dispensed onto the upper surface of a series of substrates, each substrate receiving one shot of washcoat. A first washcoat had a solids content of <NUM>% and a viscosity of <NUM>-<NUM> cP. A second washcoat had a solids content of <NUM>% and a viscosity of <NUM>-<NUM> cP. A third washcoat had a solids content of <<NUM>% and a viscosity of <NUM>-<NUM> cP.

A combination of the comparative valve assembly <NUM>' and the comparative washcoat showerhead <NUM>' was tested. Following discharge of each shot of washcoat the number of drips was observed. A total of <NUM> drips of washcoat was observed to drip from the apertures <NUM>' when the third washcoat was used, having a viscosity of <NUM>-<NUM> cPs. A total of <NUM> drips of washcoat was observed to drip from the apertures <NUM>' when the first washcoat was used having a viscosity of <NUM>-<NUM> cPs. When the second washcoat having a viscosity of <NUM>-<NUM> cPs was used the number of drips observed was between <NUM> and <NUM>.

A combination of the comparative valve assembly <NUM>' and the washcoat showerhead <NUM> of the present disclosure was tested. Following discharge of each shot of washcoat the number of drips was observed. A total of <NUM> drips of washcoat was observed to drip from the apertures <NUM> when the third washcoat was used, having a viscosity of <NUM>-<NUM> cPs. A total of <NUM> drips of washcoat was observed to drip from the apertures <NUM> when the first washcoat was used having a viscosity of <NUM>-<NUM> cPs. When the second washcoat having a viscosity of <NUM>-<NUM> cPs was used the number of drips observed was between <NUM> and <NUM>.

A combination of the valve assembly <NUM> of the present disclosure and the comparative washcoat showerhead <NUM>' was tested. Following discharge of each shot of washcoat the number of drips was observed. A total of <NUM> drips of washcoat was observed to drip from the apertures <NUM>' when the third washcoat was used, having a viscosity of <NUM>-<NUM> cPs. A total of <NUM> drips of washcoat was observed to drip from the apertures <NUM>' when the first washcoat was used having a viscosity of <NUM>-<NUM> cPs. When the second washcoat having a viscosity of <NUM>-<NUM> cPs was used the number of drips observed was between <NUM> and <NUM>.

A combination of the valve assembly <NUM> of the present disclosure and the washcoat showerhead <NUM> of the present disclosure was tested. Following discharge of each shot of washcoat a total of <NUM> to <NUM> drips of washcoat were observed to drip from the apertures <NUM> for each of the first, second and third washcoats.

As can be seen when comparing Examples <NUM> and <NUM>, the use of the washcoat showerhead <NUM> of the present disclosure was found to have some limited benefit in reducing the amount of dripping when combined with the comparative valve assembly <NUM>'.

Claim 1:
A method of coating a substrate (<NUM>) with a washcoat, comprising the steps of:
engaging the substrate (<NUM>) with a headset (<NUM>) of a substrate coating apparatus (<NUM>) so as to locate an upper surface (<NUM>) of the substrate (<NUM>) below a washcoat showerhead (<NUM>) of the substrate coating apparatus (<NUM>);
conveying washcoat from a source (<NUM>) of the washcoat towards the washcoat showerhead (<NUM>);
using a valve assembly (<NUM>) to control flow of the washcoat from the source (<NUM>) into an interior of the washcoat showerhead (<NUM>);
discharging the washcoat out of the washcoat showerhead (<NUM>) onto the upper surface (<NUM>) of the substrate (<NUM>); and
drawing the washcoat through the substrate (<NUM>) by applying a suction force to a lower surface (<NUM>) of the substrate (<NUM>);
wherein:
the valve assembly (<NUM>) comprises an outlet valve (<NUM>, <NUM>) movable between a closed state and an open state to control flow of washcoat into the interior of the washcoat showerhead, the method being characterised in that the valve assembly (<NUM>) creates a pressure drop within an interior of the washcoat showerhead (<NUM>) when the outlet valve (<NUM>, <NUM>) moves from its open state to its closed state;
the outlet valve (<NUM>, <NUM>) comprises a valve stem (<NUM>) that reciprocates relative to a valve seat (<NUM>);
the valve assembly (<NUM>) creates a pressure drop within a valve chamber (<NUM>) of the valve assembly (<NUM>) when the outlet valve (<NUM>,<NUM>) moves from the open state to the closed state; and
the valve stem (<NUM>) functions as a piston within the valve chamber (<NUM>) and creates a pressure drop within the valve chamber (<NUM>) when moving from the open state to the closed state.