PUMP ASSEMBLY

1 . A pump assembly for use in a selective catalytic reduction system, the pump assembly comprising:

a pump sub-assembly defining a pump axis; and

a housing sub-assembly including a cavity for receiving the pump sub-assembly and comprising an inlet port for receiving a reagent for supply to the pump sub-assembly via a flow path;

wherein at least one seal member is provided to seal the pump sub-assembly within the housing sub-assembly, the seal member being provided in a groove in an outer face of the pump sub-assembly, the seal member providing a fluid tight seal

and wherein the pump sub-assembly comprises a pump core, an outer pole member and a solenoid coil, the core, pole member and coil being provided within a coil over-moulding member.

2 . A pump assembly as claimed in claim 1 , further comprising a compartment defined in part by the pump and housing sub-assemblies wherein the at least one seal member comprises a compartment seal member arranged to separate the compartment and flow path, the compartment seal member being provided in a groove in an outer face of the pump sub-assembly, the compartment seal member providing a fluid tight seal between the compartment and the flow path.

3 . A pump assembly as claimed in claim 1 , wherein the housing sub-assembly comprises a drilling having an opening in an outer surface of the housing sub-assembly, and the pump sub-assembly comprises a neck portion of substantially complementary shape to the drilling wherein the at least one seal member comprises a drilling seal member arranged to seal the neck portion in the drilling, the drilling seal member being provided in a groove in an outer face of the neck portion of the pump sub-assembly and providing a fluid tight seal between the opening of the drilling and the flow path.

4 . A pump assembly as claimed in claim 3 , wherein the neck portion is disposed about the pump axis and defines a bore arranged to receive electrical connector means for connection to a solenoid coil.

5 . A pump assembly as claimed in claim 1 , wherein the over-moulding member is formed from plastic.

6 . A pump assembly as claimed in claim 1 , wherein the flow path comprises one or more flow ports provided through the body of the over-moulding member.

7 . A pump assembly as claimed in claim 6 , wherein a reagent gallery is defined between the housing and pump sub-assemblies, the one or more flow ports being arranged to open into the gallery and the gallery being in fluid communication with the inlet port.

8 . A pump assembly as claimed in claim 7 , wherein the housing sub-assembly defines a reagent passage from the inlet port to the gallery, the flow path being provided by the reagent passage, the gallery and the one or more flow ports.

9 . A pump assembly as claimed in claim 6 , wherein the body of the over-moulding member comprises a plurality of flow ports.

10 . A pump assembly as claimed in claim 9 , wherein the pump sub-assembly comprises a metallic back plate having one or more drillings, each flow port being arranged to align with a drilling.

11 . A pump assembly as claimed in claim 9 , wherein a solenoid coil cable from an electrical connector means for connection to a solenoid coil is routed through the over-moulding member between reagent flow ports to the solenoid coil.

12 . A method of manufacturing a pump assembly comprising manufacturing a pump sub assembly by:

providing a blank disk member of a material having a relatively high magnetic permeability;

deep drawing the blank disk member to form an outer pole piece, the outer pole piece defining an internal volume with an opening;

providing a coil former, the coil former defining an internal volume;

winding coil wire onto the coil former to form a solenoid coil;

inserting the solenoid coil into the internal volume of the outer pole piece;

pressing a back stop plate into the outer pole piece, the back stop plate having at least one drilling through the plate;

injection moulding an over-mould member to encapsulate the outer pole piece and solenoid coil;

forming at least one flow port through the over-moulding member, the at least one flow port aligning with the at least one drilling in the back stop plate;

forming at least one groove in the outer face of the over-mould member.

13 . A method as claimed in claim 12 , further comprising inserting an actuator pump core into the internal volume of the coil former.

14 . A method as claimed in claim 12 comprising placing an O ring sealing member into the at least one groove in the outer face of the over-mould member and inserting the pump sub-assembly into a housing sub-assembly.