Apparatus and method for coating substrates with washcoats
An apparatus and a method for coating substrates with washcoats in which a substrate ( 10 ) is engaged with a headset ( 6 ) of a substrate coating apparatus ( 1 ) below a washcoat showerhead ( 5 ) are disclosed. The washcoat is discharged from the washcoat showerhead ( 5 ) onto an upper surface ( 12 ) of the substrate under control of a valve assembly ( 4 ) before being drawn through the substrate by use of a vacuum generator ( 7 ). The valve assembly ( 4 ) comprises an outlet valve movable between a closed state and an open state. The valve assembly ( 4 ) creates a pressure drop within an interior of the washcoat showerhead ( 5 ) when the outlet valve moves from its open state to its closed state.
1. A method of coating a substrate with a washcoat, comprising the steps of:
engaging the substrate with a headset of a substrate coating apparatus so as to locate an upper surface of the substrate below a washcoat showerhead of the substrate coating apparatus;
conveying washcoat from a source of the washcoat towards the washcoat showerhead;
using a valve assembly to control flow of the washcoat from the source into an interior of the washcoat showerhead;
discharging the washcoat out of the washcoat showerhead onto the upper surface of the substrate; and
drawing the washcoat through the substrate by applying a suction force to a lower surface of the substrate;
wherein the valve assembly comprises an outlet valve movable between a closed state and an open state to control flow of washcoat into the interior of the washcoat showerhead and the valve assembly creates a pressure drop within an interior of the washcoat showerhead when the outlet valve moves from its open state to its closed state.
2. The method of claim 1 , wherein the outlet valve comprises a valve stem that reciprocates relative to a valve seat.
3. The method of claim 2 , wherein the valve stem or a valve seal provided on the valve stem is pulled into sealing engagement with the valve seat in the closed state of the outlet valve.
4. The method of claims 2 , wherein 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.
5. The method of claim 4 , wherein 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.
6. The method of claim 1 , wherein, within the washcoat showerhead, the washcoat enters centrally into an upper portion of the interior, then flows towards a periphery of the interior, is then directed down into a lower portion of the interior and is then directed to flow inwards within the lower portion towards a centre of the washcoat showerhead.