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An apparatus and method for manual operation of an actuator is disclosed. A mechanical override includes a housing coupled to the actuator, a drive ring, and a shaft extending through a bore of the housing. The drive ring rotationally keys to the bore such that the drive ring is capable of axial mov

An apparatus and method for manual operation of an actuator is disclosed. A mechanical override includes a housing coupled to the actuator, a drive ring, and a shaft extending through a bore of the housing. The drive ring rotationally keys to the bore such that the drive ring is capable of axial movement within the bore in response to automatic operation of the actuator. A backstop limits axial movement of the drive ring during manual operation. A thread located on an external portion of the shaft threads to the drive ring. In the manual operation, the shaft rotates through the drive ring imparting axial movement to the shaft capable of moving a valve between a first position and a second position. The override provides visual indication of the valve position during both automatic and manual operation. The backstop may be an insert that selectively permits movement of the shaft to a failsafe position in response to a temperature or pressure change.

대표청구항 ▼

What is claimed is: 1. A mechanical override for a valve actuator, comprising: an outer housing coupled to the valve actuator, the outer housing having a longitudinal bore therethrough; an internally threaded drive ring, wherein the drive ring is rotationally locked and axially moveable within the

What is claimed is: 1. A mechanical override for a valve actuator, comprising: an outer housing coupled to the valve actuator, the outer housing having a longitudinal bore therethrough; an internally threaded drive ring, wherein the drive ring is rotationally locked and axially moveable within the longitudinal bore in response to an automatic operation of the actuator, and wherein the drive ring keys to the longitudinal bore by an elongated pin member that provides a mechanical interference with a longitudinal recess of the bore and a profile along the length of the drive ring; a backstop for limiting axial movement of the drive ring; and a shaft extending through the longitudinal bore, wherein a thread is located on an external portion of the shaft for rotation through the drive ring to impart axial movement to the drive shaft capable of moving a valve between a first position and a second position. 2. The mechanical override of claim 1, wherein the mechanical override is integral with the valve actuator. 3. The mechanical override of claim 1, wherein the backstop is a fusible member. 4. The mechanical override of claim 1, wherein the backstop is a fusible member blocking a sufficient length of the bore such that the drive ring traverses the length in a failsafe operation to move the valve between the second position and the first position. 5. The mechanical override of claim 4, wherein the first position is a closed position and the second position is an open position. 6. The mechanical override of claim 1, wherein the backstop is a fusible member having a smaller inside diameter than an outside diameter of the drive ring, thereby selectively preventing the drive ring from passing through an end portion of the longitudinal bore. 7. The mechanical override of claim 1, wherein the backstop is a shoulder formed in the longitudinal bore. 8. The mechanical override of claim 1, wherein the thread is an Acme thread. 9. The mechanical override of claim 1, wherein the thread is an Acme thread having less than eight threads per inch. 10. The mechanical override of claim 1, further comprising a coupling assembly that couples the shaft to an operator member of the actuator. 11. The mechanical override of claim 1, further comprising a coupling assembly that couples the shaft to a member of the actuator, the coupling assembly capable of isolating rotational movement of the shaft from the member. 12. The mechanical override of claim 1, further comprising a coupling assembly coupling the shaft to a member of the actuator, the coupling assembly capable of isolating rotational movement of the shaft from the member and preventing longitudinal separation between the shaft and the member. 13. A mechanical override for a valve actuator, comprising: a retainer ring disposed in the longitudinal bore for retaining the seal cartridge, the retainer ring externally removable from the longitudinal bore. 14. A mechanical override for a valve actuator, comprising: an outer housing coupled to the valve actuator, the outer housing having a longitudinal bore therethrough; an internally threaded drive ring, wherein the drive ring is rotationally locked and axially moveable within the longitudinal bore in response to an automatic operation of the actuator; a backstop for limiting axial movement of the drive ring; a shaft extending through the longitudinal bore, wherein a thread is located on an external portion of the shaft for rotation through the drive ring to impart axial movement to the drive shaft capable of moving a valve between a first position and a second position; a seal cartridge disposed in an annular area between the shaft and the longitudinal bore; and a retainer ring disposed in the longitudinal bore for retaining the seal cartridge, the retainer ring externally removable from the longitudinal bore. 15. The mechanical override of claim 1, wherein the drive ring keys to the longitudinal bore by a rotational locking assembly comprising an inner sleeve and the elongated pin member disposed in a slot of the inner sleeve. 16. The mechanical override of claim 1, wherein the backstop limits axial movement of the drive ring during manual operation of the mechanical override. 17. A mechanical override for a valve actuator, comprising: an outer housing coupled to the valve actuator, the outer housing having a longitudinal bore therethrough; an internally threaded drive ring; a rotational locking assembly that prevents rotation of the drive ring and permits axial movement of the drive ring within the longitudinal bore; a backstop for limiting axial movement of the drive ring; and a rotatable drive shaft extending through the longitudinal bore, wherein a thread is located on an external portion of the shaft, the shaft configured to be manually rotated through the drive ring that is prevented from rotation to impart axial movement to the drive shaft capable of moving a valve between a first position and a second position. 18. The mechanical override of claim 17, wherein the mechanical override is integral with the valve actuator. 19. A mechanical override for a valve actuator, comprising: an outer housing coupled to the valve actuator, the outer housing having a longitudinal bore therethrough, wherein the longitudinal bore has a shoulder formed by an interface between a first inside diameter portion and a larger second inside diameter portion; a fusible insert positioned in the second inside diameter portion adjacent the shoulder, wherein an outside diameter of the fusible insert is larger than the first inside diameter portion; a shaft extending through the longitudinal bore, wherein a thread is located on an external portion of the shaft; a drive ring threaded to the thread of the shaft, wherein an outside diameter of the drive ring is larger than an inside diameter of the fusible insert and smaller than the first inside diameter; and a rotational locking assembly that prevents rotation of the drive ring and permits axial movement of the drive ring within the longitudinal bore. 20. The mechanical override of claim 19, wherein the rotational locking assembly comprises an inner sleeve and an elongated pin member disposed in a slot of the inner sleeve, the pin member providing a mechanical interference with a longitudinal recess of the bore and a profile along the length of the drive ring. 21. The mechanical override of claim 19, further comprising a coupling assembly that couples the shaft to an operator member of the actuator. 22. The mechanical override of claim 19, further comprising a coupling assembly that couples the shaft to a member of the actuator, the coupling assembly capable of isolating rotational movement of the shaft from the member. 23. The mechanical override of claim 19, further comprising a coupling assembly coupling the shaft to a member of the actuator, the coupling assembly capable of isolating rotational movement of the shaft from the member and preventing longitudinal separation between the shaft and the member. 24. The mechanical override of claim 19, further comprising a coupling assembly, the coupling assembly comprising: an intermediate shaft coupled to an operator member of the actuator; ball bearings positioned between a bottom load surface of the shaft and a top surface of the intermediate shaft; and a coupler connecting the intermediate shaft to the shaft, wherein the coupler is capable of rotation about the intermediate shaft. 25. The mechanical override of claim 17, wherein the backstop is a fusible member selected to melt at a respectively lower temperature than parts of the valve actuator capable of maintaining the valve actuator in a fail safe position.