Method for enshrouding an actuator

1. A method for enshrouding an actuator for use in a fuel injector, comprising the steps of:

providing an actuator having a body section, a first end piece, and a second end piece;

providing a flexible shroud having first and second ends;

applying a sealant material to at least one portion of an exterior surface of the end pieces, and/or to at least one corresponding part of the shroud such that the sealant material is disposed only between the shroud and the end pieces; and

enshrouding the actuator with the shroud, such that the shroud extends along the length of the actuator from the first end piece to the second end piece and is conformed to the contours of the actuator and such that the sealant material provides an intermediate layer between the end pieces and the shroud and forms a fluid-tight seal between them.

2. A method according to claim 1 , wherein the shroud comprises a material selected from a fluoropolymer and a thermoplastic polymer.

3. A method according to claim 1 , wherein the sealant material is an adhesive.

4. A method according to claim 3 , wherein the adhesive is selected from the group consisting of silicones, fluorosilicones, fluorocarbon polymers, epoxies and cyanurates.

5. A method according to claim 3 , wherein the adhesive is a toughened epoxy.

6. A method according to claim 5 , wherein the adhesive is a core-shell toughened epoxy.

7. A method according to claim 1 , wherein the method comprises the additional step of applying a coupling agent to at least one surface that will contact the sealant material, prior to application of the sealant material.

8. A method according to claim 7 , wherein the coupling agent comprises an adhesion promoter.

9. A method according to claim 8 , wherein the adhesion promoter comprises a silane.

10. A method according to claim 9 , wherein the adhesion promoter comprises a functional silane adapted to react with the surface of the end pieces and/or the sleeve, and with the sealant material of the intermediate layer.

11. A method according to claim 8 , wherein the adhesion promoter is selected from the following:

(3-acryloxypropyl)trimethoxysilane;

3-aminopropyltriethoxysilane;

3-aminopropyltrimethoxysilane;

aminopropylsilanetriol;

N-(2-aminoethyl)-3-aminopropyltrimethoxysilane;

(3-glycidoxypropyl)trimethoxysilane;

(3-glycidoxypropyl)methyldiethoxysilane;

3-chloropropyltrimethoxysilane;

3-isocyanatopropyltriethoxysilane;

vinyltriethoxysilane;

vinyltrimethoxysilane;

bis(trimethoxysilylpropyl)amine; and

bis [3-trimethoxysilyl)propyl]-ethylenediamine.

12. A method according to claim 7 , wherein the coupling agent comprises a mixture of one or more adhesion promoters.

13. A method according to claim 7 , further including the step of applying a gas plasma treatment process to the at least one surface prior to the application of the coupling agent.

14. A method according to claim 7 , further including the step of applying an amorphous silicate layer to the at least one surface by way of a combustion driven chemical vapour deposition process prior to the application of the coupling agent.

15. A method according to claim 1 , wherein the shroud comprises a plurality of layers or coatings.

16. A method according to claim 15 , wherein at least one of the plurality of layers or coatings comprises a fluoropolymer.

17. A method according to claim 15 , wherein at least one of the plurality of layers or coatings comprises a material adapted to regulate the permeation of ionic species through the shroud.

18. A method according to claim 1 , wherein the method comprises the additional step of applying a clip externally to the shroud, the clip being adapted to apply a constrictive force to the shroud and urge the shroud towards the underlying intermediate layer.