External fuel metering valve with shuttle mechanism

1. An external fuel metering valve, comprising:

a main valve body;

a valve cap coupled to the main valve body;

a chamber, including:

a first portion defined in the main valve body; and

a second portion defined in the valve cap, axially aligned with the first portion;

a control space connected to the chamber; and

a shuttle movably positioned in the chamber, between

a first position, in which a discharge flow path from the control space through the shuttle and an outlet of the valve cap is open; and

a second position, in which a filling flow path from an inlet of the main valve body through the shuttle and into the control space is open.

2. The valve of claim 1 , wherein the shuttle includes:

an inlet flow passage in fluid communication with an inlet of the main valve body;

an outlet flow passage in fluid communication with an outlet of the valve cap; and

a plurality of seals each positioned on a corresponding outer circumferential portion of the shuttle so as to selectively engage a corresponding inner peripheral portion of the chamber.

3. The valve of claim 2 , wherein the plurality of seals includes:

an inlet end seal;

at least one intermediate seal; and

an outlet end seal,

wherein

the inlet end seal, the at least one intermediate seal and the outlet end seal are sequentially arranged on the outer circumferential portion of the shuttle,

the inlet flow passage is positioned between the inlet end seal and the at least one intermediate seal, and

the outlet flow passage is positioned between the at least one intermediate seal and the outlet end seal.

4. The valve of claim 3 , wherein, in a transitional position between the first position and the second position of the shuttle in the chamber, the inlet end seal, the at least one intermediate seal, and the outlet end seal are engaged against the inner peripheral portion of the chamber, to block the filling flow path, and to block the discharge flow path, and to maintain a state of fuel in the control space.

5. The valve of claim 4 , wherein, in the transitional position of the shuttle in the chamber,

the inlet end seal is positioned in the first portion of the chamber corresponding to the main valve body, and is engaged against the inner peripheral portion of the first portion of the chamber,

the outlet end seal is positioned in the second portion of the chamber corresponding to the valve cap and is engaged against the inner peripheral portion of the second portion of the chamber, and

the at least one intermediate seal is positioned between the inlet end seal and the outlet end seal, and is engaged against the inner peripheral portion of a corresponding portion of the chamber.

6. The valve of claim 5 , wherein the inlet flow passage is positioned between the inlet end seal and the at least one intermediate seal, and the outlet flow passage is positioned between the at least one intermediate seal and the outlet end seal.

7. The valve of claim 2 , wherein the plurality of seals includes a first seal, a second seal, a third seal and a fourth seal sequentially arranged on the outer circumferential portion of the shuttle, and

wherein the inlet flow passage is positioned between the first seal and the second seal, and the outlet flow passage is positioned between the third seal and the fourth seal.

8. The valve of claim 7 , wherein in the first position of the shuttle in the chamber, the first seal, the second seal and the fourth seal are engaged against the inner peripheral portion of the chamber, and the third seal is disengaged from the inner peripheral portion of the chamber so as to open the discharge flow path from the control space to the outlet flow passage, and to block the filling flow path.

9. The valve of claim 7 , wherein, in the second position of the shuttle in the chamber, the first seal, the third seal and the fourth seal are engaged against the inner peripheral portion of the chamber corresponding to the valve cap, and the control space is open to the filling flow path from the inlet flow passage through the shuttle, and to block the discharge flow path from the shuttle.

10. The valve of claim 9 , wherein in the second position of the shuttle in the chamber,

the first seal is positioned in the first portion of the chamber corresponding to the main valve body and is engaged against the inner peripheral portion of the first portion of the chamber, and

the third seal and the fourth seal are positioned in the second portion of the chamber corresponding to the valve cap and are engaged against the inner peripheral portion of the second portion of the chamber, and the filling flow path is open to the control space.

11. The valve of claim 1 , wherein the shuttle also includes:

a central inlet passage in fluid communication with an inlet into the main valve body; and

a central outlet passage in fluid communication with an outlet of the valve cap.

12. The valve of claim 11 , wherein

the central inlet passage and the central outlet passage extend axially in the shuttle,

an inlet flow passage extends radially outward from the central inlet passage of the shuttle to a corresponding outer circumferential portion of the shuttle; and

the outlet flow passage extends radially outward from the central outlet passage to a corresponding outer circumferential portion of the shuttle.

13. The valve of claim 1 , wherein the chamber is substantially cylindrical, the chamber including:

an inlet at a first axial end of the chamber, wherein the inlet connects a central inlet passage of the shuttle to a pressurized source of fuel; and

an outlet at a second axial end of the chamber, wherein the outlet is connected with an outlet flow passage of the shuttle, and wherein

the control space is defined by a void surrounding the chamber, and

a volume of fuel metered by the valve is defined by an internal geometry of the void.

14. A fuel delivery system for a combustion-powered tool, comprising:

a fuel canister; and

an external fuel metering valve externally coupled to the fuel canister, the external fuel metering valve including:

a main valve body;

a valve cap coupled to the main valve body;

a chamber defined within the main valve body and the valve cap;

a control space defined in at least one of the main valve body or the valve cap, the control space being in fluid communication with the chamber; and

a shuttle movably installed in the chamber, wherein

in a first position of the shuttle in the chamber, a discharge flow path from the control space through the shuttle and an outlet of the valve cap is opened in response to an external force; and

in a second position of the shuttle in the chamber, a filling flow path is opened to the control space.

15. The fuel delivery system of claim 14 , further comprising:

an inlet flow passage at a first end portion of the shuttle, the inlet flow passage providing for fluid communication between the fuel canister and the control space; and

an outlet flow passage at a second end portion of the shuttle, the outlet flow passage providing for fluid communication between the control space and an outlet of the valve.

16. The fuel delivery system of claim 15 , wherein,

in the first position of the shuttle in the chamber, the filling flow path from an inlet of the main valve, through the inlet flow path, and into the control space is closed; and

in the second position of the shuttle in the chamber, the discharge flow path is closed in response to a differential between pressure exerted on the shuttle and a lack of pressure at an outlet stem of the valve.

17. The fuel delivery system of claim 16 , wherein

the shuttle is biased into the second position in response to a pressure differential between an inlet pressure at an inlet of the valve and an outlet pressure at an outlet of the valve, and

the shuttle is moved from the second position in response to an actuation force on the valve.

18. The fuel delivery system of claim 14 , wherein the fuel metering system further comprises:

a coupling device that selectively couples and de-couples the external fuel metering valve to the fuel canister, the coupling device including:

a first coupler fixedly coupled to the fuel canister; and

a second coupler fixedly coupled to the external fuel metering valve, and configured to selectively engage the first coupler so as to couple the external fuel metering valve to an exterior of the fuel canister, wherein

engagement of the first coupler and the second coupler allows fuel to flow from the fuel canister into the external fuel metering valve, and

disengagement of the first coupler and the second coupler restricts the flow of fuel from the fuel canister.

19. The fuel delivery system of claim 14 , wherein the chamber is substantially cylindrical, the chamber including:

an inlet at a first axial end of the chamber, wherein the inlet connects a central inlet passage of the shuttle to a pressurized source of fuel; and

an outlet at a second axial end of the chamber, wherein the outlet is connected with an outlet flow passage of the shuttle, and wherein

the control space is defined by a void surrounding the chamber, and

a volume of fuel metered by the valve is defined by an internal geometry of the void.

20. The fuel delivery system of claim 19 , wherein

the central inlet passage is oriented axially in the shuttle,

a central outlet passage oriented axially n the shuttle is in fluid communication with the outlet of the valve cap,

an inlet flow passage extends radially outward from the central inlet passage to a corresponding outer circumferential portion of the shuttle, and

the outlet flow passage extends radially outward from the central outlet passage to a corresponding outer circumferential portion of the shuttle.