Electrically driven actuator with failsafe feature

• US 5,984,260 A
• Filed: 10/15/1996
• Issued: 11/16/1999
• Est. Priority Date: 10/15/1996
• Status: Expired due to Term

• Current Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Original Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Inventors: Tompkins, Charles Mark, Trott, Doug, Rawson, Michael S.
• Primary Examiner(s): RIVELL, JOHN A
• Application Number:
  US08/734,783
• Time in Patent Office: 1,127 Days
• Field of Search: 251/69, 251/70, 251/71, 251/129.11, 251/129.12, 251/266, 251/267, 74/424.8 VA
• US Class Current: 251/71
• CPC Class Codes: F16H 2025/2068 Means for returning linear actuator to zero position, e.g. upon occurrence of failure by using a spring
• CPC Class Codes: F16K 31/047 characterised by mechanical means between the motor and the valve, e.g. lost motion means reducing backlash, clutches, brakes or return means F16K31/043 takes precedence
• CPC Class Codes: Y10T 74/18592 Auxiliary drive [e.g., fluid piston, etc.] for load

Abstract

A valve actuator preferably driven by an electric motor is disclosed. The valve actuator is useful with surface safety valves and uses power input from an electric motor to position the valve in its normal position. A mechanism is provided to allow the valve to shift positions to a failsafe position upon failure of electrical power to the motor connected to the actuator. A screw drive is provided with the motor, with a latch mechanism holding a nut against rotation. The nut can advance longitudinally upon rotation of the drive to move a valve stem. Upon failure of electrical power, the latch mechanism releases the nut from a coupling in the actuator which is connected to the valve stem, and the main return springs in the actuator allow the nut to rotate with respect to the screw drive so that the valve can assume its failed position. Normal applications allow the valve to fail closed; however, the valve can be configured so that failure results in opening of the valve if the application requires it.

Claims

1. An actuator for a valve having a valve stem, comprising:

a housing;

a coupling movably mounted in said housing and adapted to be connected to said valve stem;

an electrically powered drive assembly for selective actuation of said coupling in a first direction;

a return mechanism in said housing operably connected to said coupling to selectively move said coupling in a second direction opposite said first direction;

said drive assembly further comprising a mechanical latch mechanism to selectively engage said drive assembly to said coupling;

a threaded shaft;

a nut mounted to said threaded shaft, said latch mechanism selectively retaining said nut rotationally with respect to said coupling;

whereupon with said nut retained by said coupling against rotation, said coupling is translated in response to a rotation of said shaft which translates said nut.

2. The actuator of claim 1, wherein:

said latch mechanism is electrically actuated.

11. The actuator of claim 2, wherein:

said return mechanism comprises at least one spring, said spring translating said coupling in said second direction as said nut becomes free to rotate about said shaft due to an electrical power outage to said solenoid.

12. The actuator of claim 11, further comprising:

an electric motor as a part of said drive assembly;

a speed reducer connecting said motor and said threaded shaft.

13. The actuator of claim 11, wherein:

said nut is engaged to said threaded shaft by at least one ball movably mounted in said nut and extending into contact with a thread forming said threaded shaft.

3. An actuator for a valve having a valve stem, comprising:

a housing;

a coupling in said housing movably mounted therein and adapted to be connected to said valve stem;

an actuating shaft rotatably mounted to said housing and selectively engageable to said coupling to drive said coupling in a first direction;

a biasing member in said housing acting on said coupling to move it in a second direction opposite said first direction when said actuating shaft is selectively disengaged from said coupling;

a nut mounted to a thread on said actuating shaft, said nut selectively rotationally secured to said coupling;

said coupling further comprises a mechanical latch to selectively secure said nut against relative rotation with respect to said coupling;

whereupon when said latch is mechanically engaged, rotation of said actuating shaft translates said coupling against said biasing member due to translation of said nut, and when said latch is mechanically released, said biasing member translates said coupling as said nut rotates with respect to said shaft.

4. The actuator of claim 3, wherein:

said coupling further comprises a latch to selectively secure said nut against relative rotation with respect to said coupling;

whereupon when said latch is engaged, rotation of said actuating shaft translates said coupling against said biasing member due to translation of said nut, and when said latch is released, said biasing member translates said coupling as said nut rotates with respect to said shaft.

5. The actuator of claim 3, wherein:

said nut also rotates with respect to said coupling, with said latch disengaged and said biasing member translating said coupling.

6. The actuator of claim 5, wherein:

said latch is electrically actuated.

7. The actuator of claim 6, wherein:

said latch retains said nut against rotation with respect to said coupling by virtue of a solenoid which, when de-energized, allows said latch to be biased in order to allow relative rotation between said nut and said coupling.

8. A surface safety valve, comprising:

a valve body having a gate attached to a stem;

a valve actuator further comprising;

a housing;

a coupling in said housing movably mounted therein and adapted to be connected to said valve stem;

an actuating shaft rotatably mounted to said housing and selectively engageable to said coupling to drive said coupling in a first direction.

9. The valve of claim 8, wherein:

said coupling further comprises a latch to selectively secure said nut against relative rotation with respect to said coupling;

whereupon when said latch is engaged, rotation of said actuating shaft translates said coupling against said biasing member due to translation of said nut, and when said latch is released, said biasing member translates said coupling as said nut rotates with respect to said shaft.

10. An actuator for a valve having a valve stem, comprising:

a housing;

a coupling movably mounted in said housing and adapted to be connected to said valve stem;

an electrically powered drive assembly for selective actuation of said coupling in a first direction;

a return mechanism in said housing operably connected to said coupling to selectively move said coupling in a second direction opposite said first direction;

said drive assembly further comprising a latch mechanism to selectively engage said drive assembly to said coupling, said latch mechanism comprises a lever and is electrically actuated by a solenoid;

a threaded shaft;

a nut mounted to said threaded shaft, said latch mechanism selectively retaining said nut rotationally with respect to said coupling;

whereupon with said nut retained by said coupling against rotation, said coupling is translated in response to a rotation of said shaft which translates said nut;

said solenoid, upon loss of power, allows said lever mounted to said coupling to be biased, whereupon a tab on said lever disengages from a stop on said nut.

14. An actuator for a valve having a valve stem, comprising:

a housing;

a coupling in said housing movably mounted therein and adapted to be connected to said valve stem;

an actuating shaft rotatably mounted to said housing and selectively engageable to said coupling to drive said coupling in a first direction;

a biasing member in said housing acting on said coupling to move it in a second direction opposite said first direction when said actuating shaft is selectively disengaged from said coupling;

a nut mounted to a thread on said actuating shaft, said nut selectively rotationally secured to said coupling;

said coupling further comprises a latch to selectively secure said nut against relative rotation with respect to said coupling;

whereupon when said latch is engaged, rotation of said actuating shaft translates said coupling against said biasing member due to translation of said nut, and when said latch is released, said biasing member translates said coupling as said nut rotates with respect to said shaft;

said nut also rotates with respect to said coupling, with said latch disengaged and said biasing member translating said coupling;

said latch is electrically actuated;

said latch retains said nut against rotation with respect to said coupling by virtue of a solenoid which, when de-energized, allows said latch to be biased in order to allow relative rotation between said nut and said coupling;

said latch is pivotally mounted to said coupling with a coiled spring rotating a tab out of engagement with a detent on said nut when said solenoid is de-energized.

15. The actuator of claim 14, wherein:

said shaft is driven by an electric motor.