Metered dose inhalers
The present invention addresses the problem of turbophoresis and provides a relatively simple and low cost solution for a metered dose inhaler, in particular, a pressure-actuated metered dose inhaler. A metering valve ( 100 ) comprises a valve body ( 110 ), a valve stem ( 130 ) mounted within the valve body ( 110 ) and a spring element ( 140 ) for biasing the valve stem ( 130 ) in an “at rest” position. A pre-metering region ( 170 ) is formed in the valve stem ( 130 ) which is provided with a miniature valve seal ( 210 ) at its inlet ( 180 ). The miniature valve seal ( 210 ) effectively isolates the pre-metering region ( 170 ) from surrounding bulk formulation ( 4 ) within a canister ( 1 ) in which the metering valve ( 100 ) is mounted when the valve stem ( 130 ) is in the “at rest” position.
1. A metering valve comprising:
a housing;
a valve body mounted in the housing, the valve body having an inlet;
a valve stem moveable within the valve body between at least a first position and a second position with respect to the valve body;
a return member located within the valve body and being operable for biasing the valve stem to the first position;
a pre-metering region formed within a first portion of the valve stem, the pre-metering region including an inlet port and an outlet port, the inlet port being connected to the inlet of the valve body;
a metering chamber formed between the valve stem and the valve housing, the metering chamber being connectable to the outlet port of the pre-metering region;
a first dose retention element positioned in an inlet path to the pre-metering region and being operable for retaining a measured dose within the pre-metering region, the first dose retention element providing fluid transport in both directions therethrough; and
a dispensing channel formed within a second portion of the valve stem, the dispensing channel having a dispensing inlet and a dispensing outlet, the dispensing inlet being connectable to the metering chamber in the second position.
2. A metering valve according to claim 1 , wherein the first dose retention member is located at an entrance to the pre-metering region, the entrance being substantially adjacent the inlet port.
3. A metering valve according to claim 1 , wherein the outlet port comprises an opening in a circumferential wall of the valve stem.
4. A metering valve according to claim 1 , wherein the inlet port comprises an opening at a proximal end of the valve stem.
5. A metering valve according to claim 4 , wherein the first dose retention member has an axis which is substantially aligned with the inlet port.
6. A metering valve according to claim 4 , wherein the first dose retention member has an axis which is aligned to be substantially parallel with the outlet port.
7. A metering valve according to claim 1 , wherein the inlet port comprises an opening in a circumferential wall of the valve stem disposed at a distance from the outlet port.
8. A metering valve according to claim 7 , wherein the first dose retention member has an axis which is substantially aligned with the inlet port.
9. A metering valve according to claim 7 , wherein the first dose retention member has an axis which is aligned to be substantially parallel with the outlet port.
10. A metering valve according to claim 1 , wherein the first dose retention member comprises an elastomeric disc with at least one re-sealable slit located in a central region thereof.
11. A metering valve according to claim 10 , wherein the elastomeric disc has a circumferential region which is thicker than the central region thereof.
12. A metering valve according to claim 1 , further comprising a second dose retention member positioned in an outlet path of the pre-metering region.
13. A metering valve according to claim 12 , wherein the second dose retention member is located at an exit to the pre-metering region.
14. A metering valve according to claim 12 , wherein the second dose second retention member has an axis which is substantially aligned with the outlet port.
15. A metering valve according to claim 12 , wherein the second dose retention member comprises an elastomeric disc with at least one re-sealable slit located in a central region thereof.
16. A metering valve according to claim 15 , wherein the elastomeric disc has a circumferential region which is thicker than the central region thereof.
17. A metering valve according to claim 15 , wherein the second dose retention member is substantially identical to the first dose retention member.