Fail safe valve actuator

• US 5,195,721 A
• Filed: 03/28/1991
• Issued: 03/23/1993
• Est. Priority Date: 05/04/1990
• Status: Expired due to Term

• Current Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Original Assignee: AVA International Corp (Halliburton Company)
• Inventors: Akkerman, Neil H.
• Primary Examiner(s): Rosenthal, Arnold
• Application Number:
  US07/676,841
• Time in Patent Office: 726 Days
• Field of Search: 251/69, 251/129.13, 192/56 R, 192/81 C, 192/56 C, 74/424.8 VA, 464/40, 464/30
• US Class Current: 251/129.13
• CPC Class Codes: F16D 27/105 with a helical band or equivalent member co-operating with a cylindrical coupling surface
• CPC Class Codes: F16D 41/206 having axially adjacent coils, e.g. helical wrap-springs
• CPC Class Codes: F16D 43/04 controlled by angular speed F16D43/24 takes precedence; clutches in which the drive is transmitted through a medium consisting of small particles F16D37/00
• CPC Class Codes: F16D 43/2024 the axially moving part being coaxial with the rotation, e.g. a gear with face teeth
• CPC Class Codes: F16D 43/2028 with at least one part moving radially between engagement and disengagement F16D43/208 takes precedence
• CPC Class Codes: F16D 43/22 controlled by both speed and torque
• 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 31/04 using a motor
• CPC Class Codes: Y10T 74/18592 Auxiliary drive [e.g., fluid piston, etc.] for load
• CPC Class Codes: Y10T 74/19749 Recirculating rolling elements

Abstract

A fail safe valve actuator is disclosed that is powered by an electric motor. A valve stem with a helical groove is moved in one direction by a ball nut rotated by the electric motor to move a valve member to its operating position. The valve member is held in operating position by a solenoid. When power fails, a spring moves the valve stem in the other direction to move the valve member to its fail safe position. A torque limiting device protects the electric motor from the high torque created when the valve stem abruptly stops moving when the valve member reaches its operating position. A centrifugal brake absorbs a portion of the energy released when the power fails and the valve stem is moved rapidly to its fail safe position by the spring.

Claims

1. A fail safe valve actuator comprising a housing for mounting on a valve body, a valve stem having one portion adapted to be connected to the valve member of a valve and another portion having an elongated helical groove in its outer surface, means mounting the valve stem in the housing to reciprocate and thereby move the valve member between valve open and valve closed positions, compressible means for urging the valve stem toward one position, means for moving the valve member to its other position including a ball nut in engagement with the helical groove on the valve stem and mounted in the housing for rotation relative to the valve stem, an electric motor having an output shaft, a centrifugal clutch connected to the output shaft of the electric motor that will engage and transmit torque when the motor reaches a preselected speed of rotation, means for transmitting the torque from the centrifugal clutch to the ball nut to rotate the nut and move the valve stem and valve member to one position, and electrically powered means for holding the stem and valve member in said one position and then releasing the valve stem and valve member for movement by the compressible means to the other position when the electrical power fails.

2. The fail safe valve actuator of claim 1 in which the means for transmitting the torque from the centrifugal clutch to the ball nut includes a torque limiting device that will disconnect the centrifugal clutch from the ball nut when the valve member reaches the other position and the output torque of the electric motor increases to a preselected amount.

3. The fail safe valve of claims 1 or 2 in which the torque transmitting means includes an output shaft, a roller clutch on the shaft, a centrifugal brake having a cylindrical shell, and a plurality of brake shoes positioned between the roller clutch and the shell for rotation with the roller clutch, said roller clutch allowing free rotation of the shaft when moving the valve stem to the one position while rotating the brake shoes when the output shaft rotates in the other direction causes the brake shoes to engage the shell and retard the speed of rotation of the output shaft when the compressible means is urging the valve stem to the other position.

4. The fail safe actuator of claim 2 in which the torque limiting device includes a body rotated by the electric motor around its central axis, said body having a plurality of holes spaced from the central axis, an output shaft, a plate attached to the output shaft for rotation therewith and positioned with one side facing the holes in the body, said plate having a plurality of indentations spaced from its axis of rotation to move along the same general circular path as the holes in the body, and detent means located in the holes for engaging the indentations in the plate and rotating the plate and the output shaft with the body, resilient means for holding the detents in engagement with the indentations and for allowing the detents to move out of engagement with the indentations when the torque reaches a predetermined amount to allow the body to rotate free of the plate and the output shaft, and means to hold the detents out of engagement until the electric motor is turned off.

5. The fail safe actuator of claim 2, wherein the torque limiting device includes a drive shaft connectible to the centrifugal clutch and a driven shaft connectible to the ball nut, one of the shafts having a cylindrical inner portion mounted within a cylindrical portion of the other shaft for relative rotation with respect thereto about an axis which is eccentric to the axis of rotation of the other shaft, a pin carried by the cylindrical outer portion for radial movement with respect thereto, and means yieldably holding the inner end of the pin engaged with the inner portion to allow the drive shaft to rotate the driven shaft until the torque transmitted between them overcomes the yieldable holding means to allow the inner portion of the one shaft portion to rotate relative to the outer portion of the other shaft.

6. The fail safe valve of claim 5, wherein said yieldable holding means comprises a C-spring disposed about the outer cylindrical portion to engage the outer end of the pin.

7. The fail safe valve of claim 2, wherein the torque limiting device comprises first, second and third coaxially disposed and relatively rotatable bodies, one of said first and third bodies being rotated by the centrifugal clutch and the other of the first and third bodies rotating the bolt nut, a wrap spring clutch surrounding portions of the second and third bodies and held at one end by the third body, a coil spring held at its ends between oppositely facing shoulders of the first and second bodies so as to transmit rotation therebetween in one directional sense while yieldably resisting relative rotation therebetween in the opposite directional sense, detent means mounted on the second body for movement between a first, normally assumed position holding the opposite end of the wrap spring clutch so that the third body is rotated with the second body to tighten the wrap spring clutch about said portions of the second and third bodies and thus cause the shafts to rotate with one another in response to rotation of said second body in said one directional sense, rotation to the output shaft, and a second position releasing said opposite end of the wrap spring clutch to permit said third body to rotate relatively to the second body, and means responsive to a predetermined amount of torsion applied to the coil spring, through rotation of the second body in said opposite directional sense with respect to said first body, for moving the holding means to its second position, said holding means remaining in its second position until rotation of said first body is stopped.

8. A fail safe valve actuator comprising a housing for mounting on a valve body, a valve stem having one portion adapted to be connected to the valve member of a valve and another portion having an elongated helical groove in its outer surface, means mounting the valve stem in the housing to reciprocate and thereby move the valve member between valve open and valve closed positions, compressible means for urging the valve stem toward one position, means for moving the valve stem to its other position including a ball nut in engagement with the helical groove on the valve stem and mounted in the housing for rotation relative to the valve stem, an electric motor having an output shaft, means for transmitting the torque from the electric motor to the ball nut to rotate the nut and move the valve stem and valve member to one position, including a torque limiting device to disconnect the electric motor from the torque transmitting means when the torque reaches a preselected amount, and electrically powered means for holding the stem and valve member in said one position and then releasing the valve stem and valve member for movement by the compressible means to the other position when the electrical power fails.

9. The fail safe valve actuator of claim 8 in which the means for transmitting the torque from the motor to the ball nut includes a centrifugal clutch that will engage and transmit torque when the motor reaches a given speed of rotation.

10. The fail safe valve of claim 8 in which the torque transmitting means includes an output shaft, a roller clutch on the shaft, a centrifugal brake having an outer cylindrical shell on the housing, and a plurality of brake shoes positioned between the roller clutch and the shell for rotation with the roller clutch, said roller clutch allowing free rotation of the output shaft when moving the valve stem to the one position while rotating the brake shoes when the output shaft rotates in the other direction causing the brake shoes to engage the housing and retard the speed of rotation of the output shaft when the compressible means is urging the valve stem to the other position.

11. The fail safe actuator of claim 8 in which the torque limiting device includes a body rotated by the electric motor around its central axis, said body having a plurality of holes spaced from the central axis, an output shaft, a plate attached to the output shaft for rotation therewith and positioned with one side facing the holes in the body, said plate having a plurality of indentations spaced from its axis of rotation to move along the same general circular path as the holes in the body, and detent means located in the holes for engaging the indentations in the plate and rotating the plate and the output shaft with the body, resilient means for holding the detents in engagement with the indentations and for allowing the detents to move out of engagement with the indentations when the torque reaches a predetermined amount to allow the body to rotate free of the plate and the output shaft and means to hold the detents out of engagement until the electric motor is turned off.

12. The fail safe actuator of claim 8, wherein the torque limiting device includes a drive shaft rotatable by the electric motor and a driven shaft for rotating the ball nut, one of the shafts having a cylindrical inner portion mounted within a cylindrical portion of the other shaft for relative rotation with respect thereto about an axis which is eccentric to the axis of rotation of the other shaft, a pin carried by the cylindrical outer portion for radial movement with respect thereto, and means yieldably holding the inner end of the pin engaged with the inner portion to allow the drive shaft to rotate the driven shaft until the torque transmitted between them overcomes the yieldable holding means to allow the inner portion of the one shaft portion to rotate relative to the outer portion of the other shaft.

13. The fail safe actuator of claim 12, wherein said yieldable holding means comprises a C-spring disposed about the outer cylindrical portion to engage the outer end of the pin.

14. The fail safe actuator of claim 8, wherein the torque limiting device comprises first, second and third coaxially disposed and relatively rotatable bodies, one of said first and third bodies being rotated by the electrical motor and the other of the first and third bodies rotating the bolt nut, a wrap spring clutch surrounding portions of the second and third bodies and held at one end by the third body, a coil spring held at its ends between oppositely facing shoulders of the first and second bodies so as to transmit rotation therebetween in one directional sense while yieldably resisting relative rotation therebetween in the opposite directional sense, detent means mounted on the second body for movement between a first, normally assumed position holding the opposite end of the wrap spring clutch so that the third body is rotated with the second body to tighten the wrap spring clutch about said portions of the second and third bodies and thus cause the shafts to rotate with one another in response to rotation of said second body in said one directional sense, and a second position releasing said opposite end of the wrap spring clutch to permit said third body to rotate relatively to the second body, and means responsive to a predetermined amount of torsion applied to the coil spring, through rotation of the second body in said opposite directional sense with respect to said first body, for moving the holding means to its second position, said holding means remaining in its second position until rotation of said first body is stopped.

15. The fail safe valve of claim 8 in which the means for transmitting the torque from the electric motor to the ball nut includes a drive shaft, a gear train connected to the output shaft of the electric motor and the drive shaft to transmit torque from the electric motor to the drive shaft to rotate the drive shaft, a driven shaft connected to the ball nut, and an electrically operated clutch for connecting the drive shaft to the driven shaft to allow the electric motor to rotate the ball nut.

16. The fail safe valve actuator of claims 8 in which the means for holding the stem and valve member in said position includes a one-way clutch for holding the output shaft of the electric motor from rotating in a direction opposite the direction it rotated when driving the ball nut to move the valve member to said one position as long as the clutch is engaged.

17. The fail safe valve operator of claim 8 further provided with brake means for controlling the speed of rotation of the ball nut when the holding means of the valve is released and the resilient means is moving the valve member to its other position.

18. The fail safe valve operator of claim 17 in which the brake means includes a plurality of brake shoes carried by the driven shaft, resilient means resisting the outward movement of the brake shoes due to centrifugal force as the driven shaft and ball nut are rotated by the moving valve stem, and clutch means that is engaged by the outward movement of the brake shoes to slow the rotation of the driven shaft.

19. The fail safe valve operator of claim 18 in which the clutch includes a wrap spring that will grip the housing and the driven shaft and slow the rotation of the ball nut when actuated by the outward movement of the brake shoes.

20. A fail safe valve actuator comprising a housing for mounting on a valve body, a valve stem having one portion adapted to be connected to a valve member of the valve and another portion having an elongated helical groove in its outer surface, means mounting the valve stem in the housing to reciprocate and thereby move the valve member between valve open and valve closed positions, compressible means for urging the valve stem toward one position, means for moving the valve stem to its other position including a ball nut in the housing in engagement with the helical groove on the valve stem and mounted in the housing for rotation relative to the valve stem, an electric motor having an output shaft, a centrifugal clutch connected to the output shaft of the electric motor that will engage and transmit torque when the motor reaches a preselected speed of rotation, means for transmitting the torque from the centrifugal clutch to the ball nut to rotate the nut and move the valve stem and valve member to one position including a torque limiting device that will disconnect the centrifugal clutch from the ball nut when the torque reaches a preselected amount, electrically powered means for holding the stem and valve member in one position and then releasing the valve stem and valve member for movement by the compressible means to the other position when the electrical power fails.

21. The fail safe valve of claim 20 in which the torque transmitting means includes a shaft and is further provided with a roller clutch on the shaft, a centrifugal brake having an outer cylindrical shell on the housing, and a plurality of brake shoes positioned between the roller clutch and the shell for rotation with the roller clutch, said roller clutch allowing free rotation of the output shaft when moving the valve stem to the one position while rotating the brake shoes when the output shaft rotates in the other direction causing the brake shoes to engage the shell and retard the speed of rotation of the output shaft when the compressible means is urging the valve stem to the other position.

22. The fail safe actuator of claim 20 in which the torque limiting device includes a body rotated by the electric motor around its central axis, said body having a plurality of holes spaced from the central axis, an output shaft, a plate attached to the output shaft for rotation therewith and positioned with one side facing the holes in the body, said plate having a plurality of indentations spaced from its axis of rotation to move along the same general circular path as the holes in the body and detent means located in the holes for engaging the indentations in the plate and rotating the plate and the output shaft with the body, resilient means for holding the detents in engagement with the indentations and for allowing the detents to move out of engagement with the indentations when the torque reaches a predetermined amount to allow the body to rotate free of the plate and the output shaft, and means to hold the detents out of engagement until the electric motor is turned off.

23. An actuator for a valve having a body and a closure member movable between alternate positions within the body, comprising

a housing for mounting on the valve body,

a reversible drive mechanism comprising a first drive part supported for rotation in the housing and a second drive part engageable with the first drive part, and connectible to the closure member for moving it to one of its positions upon rotation of the first part in one direction,

an electric motor for rotating the first drive part in one direction,

means yieldably urging the second drive part in a direction to move the closure member to its other position,

electrically powered means for preventing said first drive part from rotating in said opposite direction and thus holding the closure member in its one position,

means for releasing said rotation preventing means to permit said closure member to be moved by said urging means to its other position in response to the loss of the supply of electrical power to said, rotation preventing means, and

a torque limiting device for disconnecting the motor shaft and said first drive part in response to the transmission of a predetermined torque therebetween.

24. An actuator of the character defined in claim 23, including

means for rotating first drive part in said one direction in response to rotation of the motor shaft but enabling said first drive part to rotate in the opposite direction without rotating the motor shaft.

25. An actuator of the character defined in claim 23, wherein

the valve is a gate valve and the gate has a rising stem to which the second drive part is connectible, and

means are provided for dissipating the energy due to fluid pressure in the valve body acting over the stem and the means with which said other drive part is urged to its other position upon release of said rotating preventing means.

26. An actuator of the character defined in claim 25, including

means rotating first drive part in said one direction in response to rotation of the motor shaft but enabling said first drive part to rotate in the opposite direction without rotating the motor shaft.

27. An actuator of the character defined in claim 23, wherein

said rotation preventing means comprises

a first member having a first cylindrical surface which is rotatable with the first drive part,

a second member having a second cylindrical surface aligned with the first cylindrical surface of the first member and rotatable in response to the rotation of motor shaft,

a wrap spring surrounding the first and second cylindrical surfaces with one end connected to the second member, and

stop means engageable with the other end for causing the spring to be wrapped tightly about the surfaces to rotate the first member with the second member, and

said releasing means comprises

means for removing said stop means to permit the spring to expand and thus permit said first member to rotate relative to said second member.

28. An actuator of the character defined in claim 23, wherein

one of said drive parts is a nut having helical grooves therein,

the other drive part is a screw having helical grooves thereabout and extending through the nut, and

anti-friction elements are disposed between them for rolling within the helical grooves of both.

29. An actuator for a gate valve having a body and a rising stem for moving the gate between alternate positions within the body, comprising

a housing for mounting on the valve body,

a reversible drive comprising a first drive part supported for rotation in the housing and a second drive part engageable with the first drive part and connectible to the stem for moving the gate to one of its positions upon rotation of the first part in one direction,

an electric motor for rotating the first drive part in one direction,

means yieldably urging the second drive part in a direction to move gate to its other position,

electrically powered means for preventing said drive part from rotating in said opposite direction and thus holding the gate in its one position,

means for releasing aid rotation preventing means to permit said gate to be moved by said urging means to its other position in response to the loss of the supply of electrical power to said rotation preventing means and

means which is independent of the rotation preventing means for dissipating the energy due to line fluid in the valve body acting over the stem and the means with which said second drive part is urged to its other position upon release of said rotating preventing means in proportion to the velocity with which said second part is moved toward its other position.

30. An actuator of the character defined in claim 29, wherein

the energy dissipating means includes

a brake housing,

a plurality of brake shoes carried by the second drive part for rotation within a brake housing,

resilient means resisting the outward movement of the brake shoes due to centrifugal force as the second drive part is rotated with the first drive part, and

means engageable responsive to outward movement of the brake shoes against the brake housing for slowing the rotation of the second drive part.

31. An actuator of the character defined in claim 30, wherein

the means for slowing rotation of the second drive part includes a spring wrapped about aligned cylindrical surfaces of the brake housing and the second drive part and adapted to be tightened thereabout to slow rotation of the first drive part in response to rotation of the brake housing with the shoes.

33. An actuator of the character defined in claim 29, wherein

one of said drive parts is a nut having helical grooves therein,

the other drive part is a screw having helical grooves thereabout and extending through the nut,

and anti-friction elements are disposed between them for rolling within the helical grooves of both.

32. An actuator of the character defined in 30, wherein

said rotation preventing means comprises

a first member having a first cylindrical surface which is rotatable with the first drive part,

a second member having a second cylindrical surface aligned with the first cylindrical surface of the first member and rotatable in response to the rotation of motor shaft,

a wrap spring surrounding the first and second cylindrical surfaces with one end connected to the second member, and

stop means engageable with the other end for causing the spring to be wrapped tightly about the surfaces to rotate the first member with the second member, and

said releasing means comprises

means for removing said stop means to permit the spring to expand and thus permit said first member to rotate relative to said second member.

34. An actuator for a valve that is opened and closed by the reciprocation of a valve member comprising a housing for mounting on the valve, a valve stem in the housing for connecting to a valve member, a portion of the valve stem having an external helical groove, a ball nut housing balls in engagement with the helical groove on the valve stem, means mounting the ball nut for rotation relative to the valve stem to move the stem longitudinally in one direction to a first position to open or close the valve, resilient means positioned in the housing to be compressed by the movement of the stem in said one direction, and electrically powered means for rotating the ball nut to move the stem to said first position including an electric motor having a first output shaft, a centrifugal clutch mounted on the first output shaft that will engage and drive a second output shaft when the output shaft of the motor reaches a preselected speed of rotation to provide a soft starting torque to the second shaft, a torque limiting device having a third output shaft and connected to the second shaft, and means for transmitting the torque from a third output shaft to the ball nut to rotate the nut and move the valve stem longitudinally to move the valve member to one of said positions, said torque limiting device disconnecting the third shaft from the second shaft when the torque reaches a preselected amount, and electrically powered means for holding the valve member in said position and then releasing the valve member for movement by the resilient means to the other position should the electricity supplied to the holding means be shut off.

35. The fail safe valve of claim 34 in which the torque transmitting means includes a shaft and is further provided with a roller clutch on the shaft, a centrifugal brake having an outer shell on the housing, and a plurality of brake shoes positioned between the roller clutch and the shell for rotation with the roller clutch, said roller clutch allowing free rotation of the output shaft when moving the valve stem to the one position while rotating the brake shoes when the output shaft rotates in the other direction causing the brake shoes to engage the shell and retard the speed of rotation of the output shaft when the compressible means is urging the valve stem to the other position.

36. An actuator for a valve having a body and a closure member movable between alternate positions within the body, comprising

a housing for mounting a valve body,

a reversible drive mechanism comprising a first drive part supported for rotation in the housing and a second drive part engageable with the first drive part, and connectible to the closure member for moving it to one of its positions upon rotation of the first part in one direction,

an electric motor having a rotary shaft,

clutch means for rotating first drive part in said one direction in response to rotation of the motor shaft but enabling said first drive part to rotate in the opposite direction without rotating the motor shaft,

means yieldably urging the second drive part in a direction to move the closure member to its other position,

electrically powered means for preventing said first drive part from rotating in said opposite direction and thus holding the closure member in its one position,

means for releasing said rotation preventing means to permit said closure member to be moved by said urging means to its other position in response to loss of the supply of electrical power to said rotation preventing means, and

means for reducing the speed of the motor shaft which is transmitted to the first drive part including a gear train connected between the clutch means and said first drive part.

37. An actuator for a valve having a body and a closure member movable between alternate positions within the body, comprising

a housing for mounting a valve body,

a reversible drive mechanism comprising a first drive part supported for rotation in the housing and a second drive part engageable with the first drive part, and connectible to the closure member for moving it to one of its positions upon rotation of the first part in one direction,

an electric motor having a rotary shaft,

clutch means for rotating first drive part in said one direction in response to rotation of the motor shaft but enabling said first drive part to rotate in the opposite direction without rotating the motor shaft,

means yieldably urging the second drive part in a direction to move the closure member to its other position,

electrically powered means for preventing said first drive part from rotating in said opposite direction and thus holding the closure member in its one position, and

means for releasing said rotation preventing means to permit said closure member to be moved by said urging means to its other position in response to loss of the supply of electrical power to said rotation preventing means,

said clutch means including means which is responsive to centrifugal force so as to connect the motor shaft to said first drive part only when the motor shaft attains a given speed.

38. An actuator for a valve having a body and a closure member movable between alternate positions within the body, comprising

a housing for mounting a valve body,

a reversible drive mechanism comprising a first drive part supported for rotation in the housing and a second drive part engageable with the first drive part, and connectible to the closure member for moving it to one of its positions upon rotation of the first part in one direction,

an electric motor having a rotary shaft,

clutch means for rotating first drive part in said one direction in response to rotation of the motor shaft but enabling said first drive part to rotate in the opposite direction without rotating the motor shaft,

means yieldably urging the second drive part in a direction to move the closure member to its other position,

electrically powered means for preventing said first drive part from rotating in said opposite direction and thus holding the closure member in its one position, and

means for releasing said rotation preventing means to permit said closure member to be moved by said urging means to its other position in response to loss of the supply of electrical power to said rotation preventing means,

said rotation preventing means including

a first member having a first cylindrical surface which is rotatable with the first drive part,

a second member having a second cylindrical surface aligned with the first cylindrical surface of the first member and rotatable in response to the rotation of motor shaft,

a wrap spring surrounding the first and second cylindrical surface with one end connected to the second member, and

stop means engageable with the other end for causing the spring to be wrapped tightly about the surfaces to rotate the first member with the second member, and

said releasing means comprises

means for removing said stop means to permit the spring to expand and thus permit said first member to rotate relative to said second member.

39. An actuator for a valve having a body and a closure member movable between alternate positions within the body, comprising

a housing for mounting a valve body,

a reversible drive mechanism comprising a first drive part supported for rotation in the housing and a second drive part engageable with the first drive part, and connectible to the closure member for moving it to one of its positions upon rotation of the first part in one direction,

an electric motor having a rotary shaft,

clutch means for rotating first drive part in said one direction in response to rotation of the motor shaft but enabling said first drive part to rotate in the opposite direction without rotating the motor shaft,

means yieldably urging the second drive part in a direction to move the closure member to its other position,

electrically powered means for preventing said first drive part from rotating in said opposite direction and thus holding the closure member in its one position, and

means for releasing said rotation preventing means to permit said closure member to be moved by said urging means to its other position in response to loss of the supply of electrical power to said rotation preventing means,

one of said drive parts being a nut having helical grooves therein,

the other drive part being a screw having helical grooves thereabout and extending through the nut, and

anti-friction elements being disposed between them for rolling within the helical grooves of both.