Metering valve

1. A metering valve comprising a valve stem co-axially slidable within a valve body, the metering valve comprising a metering chamber wherein the metering chamber is static and no part of the valve stem defines the metering chamber, and the metering chamber is constructed wholly from rigid components.

2. A metering valve as claimed in claim 1 wherein the metering chamber is constructed wholly from components formed from one or more materials selected from polyester, nylon, acetal, stainless steel, ceramics or glass.

3. A metering valve as claimed in claim 1 further comprising inner and outer seals external to the metering chamber.

4. A metering valve as claimed in claim 1 wherein the metering chamber is constructed from only two rigid components.

5. A metering valve as claimed in claim 1 wherein the components of the metering chamber comprises one or more stops for limiting axial movement of the valve stern therethrough.

6. A metering valve as claimed in claim 1 wherein the metering chamber surrounds the valve stem.

7. A metering valve as claimed in claim 1 wherein the metering chamber is annular.

8. A metering valve as claimed in any preceding claim wherein the valve body defines a radially outermost surface of the metering chamber.

9. A metering valve as claimed in claim 1 wherein the metering chamber has a dosage volume that is designed to correspond with a single dose discharge volume to be discharged by the metering valve when the metering valve is placed in an outlet access state.

10. A metering valve as claimed in claim 1 further comprising an internal sleeve.

11. A metering valve as claimed in claim 10 wherein the internal sleeve is located concentrically within the valve body.

12. A metering valve as claimed in claim 10 wherein the metering chamber is formed between the valve body and the internal sleeve.

13. A metering valve as claimed in claim 10 wherein the internal sleeve defines a radially innermost surface of the metering chamber.

14. A metering chamber as claimed in claim 10 wherein the internal sleeve comprises a cylindrical portion.

15. A metering valve as claimed in claim 10 wherein the inner seal is carried on the valve stem in sliding sealing contact with a radially innermost surface of the internal sleeve, being external the metering chamber.

16. A metering valve as claimed in claim 10 wherein a radially directed flange of the internal sleeve defines an outer end surface of the metering chamber.

17. A metering valve as claimed in claim 10 wherein the valve stem is adjustably received by the internal sleeve such that, when said metering valve is in use, said valve stem moves relative to a more stationary internal sleeve.

18. A metering valve as claimed in claim 10 wherein the internal sleeve surrounds the valve stem.

19. A metering valve as claimed in claim 18 wherein the internal sleeve separates the metering chamber from the valve stem.

20. A metering valve as claimed in claim 10 wherein the internal sleeve comprises one or more ports for passage of a product into or out of the metering chamber.

21. A metering valve as claimed in claim 20 wherein the one or more ports each function as both an inlet to, and an outlet from, the metering chamber in use.

22. A metering valve as claimed in claim 20 wherein the one or more ports are located at an inner end of the metering chamber.

23. A metering valve as claimed in claim 20 wherein the one or more ports are static.

24. A metering valve as claimed in claim 1 wherein the metering chamber has a volume of up to 300 microlitres.

25. A metering valve as claimed in claim 24 wherein the metering chamber has a volume up to 25 microlitres.

26. A metering valve as claimed in claim 25 wherein the metering chamber has a volume of 10 to 25 microlitres.

27. A metering valve comprising a valve stem co-axially slidable within a valve body, the metering valve comprising a metering chamber wherein the metering chamber is static in that it contains no part of the valve stem and is constructed wholly from rigid components, and said metering valve further comprising an internal sleeve, and

wherein a radially directed flange of the valve body defines an inner end surface of the metering chamber.

28. A metering valve comprising a valve stem co-axially slidable within a valve body, the metering valve comprising a metering chamber wherein the metering chamber is static in that it contains no part of the valve stem and is constructed wholly from rigid components; and

wherein the metering chamber is located within the valve stem such that product held in the metering chamber is dischargeable directly into the valve stem.

29. A metering valve as claimed in claim 28 wherein the metering chamber is cylindrical.

30. A metering valve as claimed in claim 28 wherein the metering chamber comprises one or more ports which each function as both an inlet to, and an outlet from, the metering chamber in use.

31. A metering valve as claimed in claim 30 wherein the one or more ports are located at an inner end of the metering chamber.

32. A metering valve as claimed in claim 28 further comprising a seal which is movable relative to the metering chamber to close off said one or more ports, wherein said seal is external to said metering chamber.

33. A metering valve as claimed in claim 32 wherein said seal surrounds said metering chamber.

34. A metering valve as claimed in claim 28 wherein the metering chamber is constructed from an open-ended chamber body and a plug.

35. A metering valve as claimed in claim 34 wherein the chamber body is substantially located within the valve stem.

36. A metering valve comprising a valve stem co-axially slidable within a valve body, the metering valve comprising a metering chamber wherein the metering chamber is static in that it contains no part of the valve stem and is constructed wholly from rigid components; and

wherein the metering chamber has no moving parts therein.

37. A metering valve comprising a valve stem co-axially slidable within a valve body, the metering valve comprising a metering chamber wherein the metering chamber is static in that it contains no part of the valve stem and is constructed wholly from rigid components, and said metering valve further comprising one or more seals, and said metering chamber being arranged as to preclude any seal material from bounding and defining the metering chamber.

38. A metering valve as recited in claim 37 , further comprising a product, which product is contained in said metering chamber, and which product is a pharmaceutical product comprising a propellant.