Valve assembly including pressure relief mechanism

1. A valve assembly comprising:

a housing having a first chamber, a second chamber, and a valve seat disposed between said first chamber and said second chamber;

a valve head disposed in said housing and moveable relative to said housing between an open position spaced from said valve seat and a closed position engaged with said valve seat, said valve head defining a bore therethrough along an axis;

a valve stem operatively coupled to said valve head and being rotatably and reciprocally movable along a stem axis for moving said valve head between said open position and said closed position;

a pressure relief mechanism including a plug coupled to said valve stem and extending along a plug axis in said bore of said valve head, said plug being moveable relative to said valve head from a sealed position preventing fluid communication through said bore to an unsealed position allowing fluid communication through said bore for relieving pressure differences between said first chamber and said second chamber when said valve head is in said closed position;

a link disposed within and pivotably connected to said housing and coupled to said valve stem and said plug to transmit movement from said valve stem to said plug;

one of said valve head and said plug defining a groove elongated along said plug axis; and

an intermediate member separate from said plug and said valve head and retained in said groove between said plug and said valve head wherein said groove is sized larger than said intermediate member along said plug axis for allowing selective movement of said plug relative to said valve head between said sealed position and said unsealed position.

2. A valve assembly as set forth in claim 1 wherein one of said valve head and said plug includes a first wall and the other of said valve head and said plug includes a second wall defining said groove, said first wall and said second wall are spaced radially from each other and oppose each other radially.

3. A valve assembly as set forth in claim 2 wherein said intermediate member is spaced from said second wall when said valve stem is in said sealed position and is spaced from said first wall when said valve stem is in said unsealed position.

4. A valve assembly as set forth in claim 1 wherein said valve head defines a ledge in said bore.

5. A valve assembly as set forth in claim 4 including a bore seal disposed in said bore and abutting said ledge for contact with said plug when said valve stem is in said sealed position.

6. A valve assembly as set forth in claim 5 wherein a first wall engages said intermediate member when said plug contacts said bore seal.

7. A valve assembly as set forth in claim 5 wherein said plug and said valve head include opposing shoulders.

8. A valve assembly as set forth in claim 1 wherein said valve head defines a recess with said intermediate member fixed along said plug axis in said recess.

9. A valve assembly as set forth in claim 1 wherein said valve head includes a tube that defines said bore.

10. A valve assembly comprising:

a housing having a first chamber, a second chamber, and a valve seat disposed between said first chamber and said second chamber;

a valve head disposed in said housing and moveable relative to said housing between an open position spaced from said valve seat and a closed position engaged with said valve seat, said valve head defining a bore therethrough along an axis;

a valve stem operatively coupled to said valve head for moving said valve head between said open position and said closed position;

a pressure relief mechanism including a plug coupled to said valve stem and extending along a plug axis in said bore of said valve head, said plug being moveable relative to said valve head from a sealed position preventing fluid communication through said bore to an unsealed position allowing fluid communication through said bore for relieving pressure differences between said first chamber and said second chamber when said valve head is in said closed position;

one of said valve head and said plug defining a groove elongated along said plug axis;

an intermediate member separate from said plug and said valve head and retained in said groove between said plug and said valve head wherein said groove is sized larger than said intermediate member along said plug axis for allowing selective movement of said plug relative to said valve head between said sealed position and said unsealed position;

a link pivotably connected to said housing and coupled to said valve stem and said plug to transmit movement from said valve stem to said plug;

wherein said valve head includes a tube that defines said bore; and

wherein said link defines a cup to receive said plug and said link receives said tube of said valve head between said cup and said plug.

11. A valve assembly as set forth in claim 10 wherein said plug includes a threaded surface and a fastener threadably engages said threaded surface for attaching said plug to said cup.

12. A valve assembly as set forth in claim 10 including a pin engaging said link and said valve stem to pivotably connect said link to said valve stem.

13. A valve assembly comprising:

a housing having a first chamber, a second chamber, and a valve seat disposed between said first chamber and said second chamber;

a valve head disposed in said housing and moveable relative to said housing between an open position spaced from said valve seat and a closed position engaged with said valve seat, said valve head defining a bore therethrough along an axis;

a valve stem operatively coupled to said valve head for moving said valve head between said open position and said closed position;

a pressure relief mechanism including a plug coupled to said valve stem and extending along a plug axis in said bore of said valve head, said plug being moveable relative to said valve head from a sealed position preventing fluid communication through said bore to an unsealed position allowing fluid communication through said bore for relieving pressure differences between said first chamber and said second chamber when said valve head is in said closed position;

one of said valve head and said plug defining a groove elongated along said plug axis; and

an intermediate member separate from said plug and said valve head and retained in said groove between said plug and said valve head wherein said groove is sized larger than said intermediate member along said plug axis for allowing selective movement of said plug relative to said valve head between said sealed position and said unsealed position;

a link pivotably connected to said housing and coupled to said valve stem and said plug to transmit movement from said valve stem to said plug; and

wherein said link defines a cam slot and including a pin engaging said valve stem and said cam slot.

14. A valve assembly comprising:

a housing having a first chamber, a second chamber, and a valve seat disposed between said first chamber and said second chamber;

a valve head disposed in said housing and moveable relative to said housing between an open position spaced from said valve seat and a closed position engaged with said valve seat, said valve head defining a bore therethrough along an axis;

a valve stem operatively coupled to said valve head and being rotatably and reciprocally movable along a stem axis for moving said valve head between said open position and said closed position;

a pressure relief mechanism including a plug coupled to said valve stem and extending along a plug axis in said bore of said valve head, said plug being moveable relative to said valve head from a sealed position preventing fluid communication through said bore to an unsealed position allowing fluid communication through said bore for relieving pressure differences between said first chamber and said second chamber when said valve head is in said closed position;

a link disposed within and pivotably connected to said housing and coupled to said valve stem and said plug to transmit movement from said valve stem to said plug;

wherein one of said valve head and said plug includes a first wall and the other of said valve head and said plug includes a second wall defining a groove, said first wall and said second wall are spaced from each other radially and oppose each other radially;

an intermediate member separate from said plug and said valve head and retained in said groove between said plug and said valve head wherein said groove is sized larger than said intermediate member along said plug axis for allowing selective movement of said plug relative to said valve head between said sealed position and said unsealed position;

wherein said first wall engages said intermediate member when the end of said plug contacts a bore seal; and

wherein said intermediate member is spaced from said second wall when said valve stem is in said sealed position and is spaced from said first wall when said valve stem is in said unsealed position.

15. A valve assembly as set forth in claim 14 wherein said valve head includes a tube that defines said bore.

16. A valve assembly as set forth in claim 15 wherein said link defines a cup to receive said plug and said link receives said tube of said valve head between said cup and said plug.

17. A valve assembly as set forth in claim 14 including a pin engaging said link and said valve stem to pivotably couple said link to said valve stem.

18. A valve assembly comprising:

a housing having a first chamber, a second chamber, and a valve seat disposed between said first chamber and said second chamber;

a valve head disposed in said housing and moveable relative to said housing between an open position spaced from said valve seat and a closed position engaged with said valve seat, said valve head defining a bore therethrough along an axis;

a valve stem operatively coupled to said valve head for moving said valve head between said open position and said closed position;

a pressure relief mechanism including a plug coupled to said valve stem and extending along a plug axis in said bore of said valve head, said plug being moveable relative to said valve head from a sealed position preventing fluid communication through said bore to an unsealed position allowing fluid communication through said bore for relieving pressure differences between said first chamber and said second chamber when said valve head is in said closed position;

a link pivotably connected to said housing and coupled to said valve stem and said plug to transmit movement from said valve stem to said plug;

wherein one of said valve head and said plug includes a first wall and the other of said valve head and said plug includes a second wall defining a groove, said first wall and said second wall are spaced from each other radially and oppose each other radially;

an intermediate member separate from said plug and said valve head and retained in said groove between said plug and said valve head wherein said groove is sized larger than said intermediate member along said plug axis for allowing selective movement of said plug relative to said valve head between said sealed position and said unsealed position;

wherein said first wall engages said intermediate member when the end of said plug contacts a bore seal;

wherein said intermediate member is spaced from said second wall when said valve stem is in said sealed position and is spaced from said first wall when said valve stem is in said unsealed position; and

wherein said link defines a cam slot and including a pin engaging said valve stem and said cam slot.

19. A valve assembly comprising:

a housing having a first chamber, a second chamber, and a valve seat disposed between said first chamber and said second chamber;

a valve head disposed in said housing and moveable relative to said housing between an open position spaced from said valve seat and a closed position engaged with said valve seat, said valve head defining a bore therethrough along an axis;

a valve stem operatively coupled to said valve head and being rotatably and reciprocally movable along a stem axis for moving said valve head between said open position and said closed position;

a pressure relief mechanism including a plug coupled to said valve stem and extending along a plug axis in said bore of said valve head, said plug being moveable relative to said valve head from a sealed position preventing fluid communication through said bore to an unsealed position allowing fluid communication through said bore for relieving pressure differences between said first chamber and said second chamber when said valve head is in said closed position;

a link disposed within and pivotably connected to said housing and coupled to said valve stem and said plug to transmit movement from said valve stem to said plug;

wherein said valve head includes a first wall and said plug includes a second wall defining a groove, said first wall and said second wall are spaced from each other radially and oppose each other radially; and

an intermediate member separate from said plug and said valve head and retained in said groove between said plug and said valve head wherein said groove is sized larger than said intermediate member along said plug axis for allowing selective movement of said plug relative to said valve head between said sealed position and said unsealed position.

20. A valve assembly comprising:

a housing having a first chamber, a second chamber, and a valve seat disposed between said first chamber and said second chamber;

a valve head disposed in said housing and moveable relative to said housing between an open position spaced from said valve seat and a closed position engaged with said valve seat, said valve head defining a bore therethrough along an axis;

a threaded actuator operatively coupled to said valve head for moving said valve head between said open position and said closed position;

a pressure relief mechanism including a plug coupled to said threaded actuator and extending along a plug axis in said bore of said valve head, said plug being moveable relative to said valve head from a sealed position preventing fluid communication through said bore to an unsealed position allowing fluid communication through said bore for relieving pressure differences between said first chamber and said second chamber when said valve head is in said closed position;

a link pivotably connected to said threaded actuator and said plug to transmit movement from said valve stem to said plug;

one of said valve head and said plug defining a groove elongated along said plug axis; and

an intermediate member separate from said plug and said valve head and retained in said groove between said plug and said valve head wherein said groove is sized larger than said intermediate member along said plug axis for allowing selective movement of said plug relative to said valve head between said sealed position and said unsealed position.