Coupling apparatus for use with electric actuators

Coupling apparatus for use with electric actuators are described herein. An example coupling apparatus described herein includes a coupling assembly to operatively couple a fluid flow control member of a fluid valve and a drive system of the electric actuator. Rotation of the drive system in a first rotational direction causes the coupling assembly to move in a first rectilinear direction and rotation of the drive system in a second rotational direction causes the coupling assembly to move in a second rectilinear direction opposite the first direction. The coupling assembly includes a biasing element that is to be deflected to provide a seat load to the fluid flow control member when the fluid flow control member is in sealing engagement with a valve seat of the fluid valve and electric power to the electric actuator is removed.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to electric actuators and, more particularly, to coupling apparatus for use with electric actuators.

BACKGROUND

Control valves (e.g., sliding stem valves) are commonly used in process control systems to control the flow of process fluids. A control valve typically includes an actuator (e.g., an electric actuator, a hydraulic actuator, etc.) that automates operation of the control valve. Sliding stem valves such as gate, globe, diaphragm, pinch, and angle valves typically have a valve stem (e.g., a sliding stem) that drives a fluid flow control member (e.g., a valve plug) between an open position and a closed position.

Electric actuators often employ a motor operatively coupled to a flow control member via a drive system (e.g., one or more gears). During operation, when electric power is supplied to the motor, the electric actuator moves the flow control member between a closed position and an open position to regulate fluid flowing through a valve. When the valve is closed, the flow control member is typically configured to sealingly engage an annular or circumferential seal (e.g., a valve seat) disposed within the flow path to prevent the flow of fluid between an inlet and an outlet of the valve.

When the valve is in the closed position and electric power is provided to the motor, the motor typically provides sufficient seat load to the fluid flow control member to ensure that the fluid flow control member is in sealing engagement with a valve seat of the valve. When electric power is removed from the motor, the drive system (e.g., worm gears) may maintain the position of the fluid flow control member relative to the valve seat and prevent substantial movement of the fluid flow control member in a reverse or opposite direction (e.g., away from the valve seat). However, the drive system may not provide an adequate or sufficient seat load to the fluid flow control member to ensure the fluid flow control member is in sealing engagement with the valve seat. As a result, fluid may leak through the valve between the inlet and the outlet of the valve.

SUMMARY

In one example, a coupling apparatus includes a coupling assembly to operatively couple a fluid flow control member of a fluid valve and a drive system of the electric actuator. Rotation of the drive system in a first rotational direction causes the coupling assembly to move in a first rectilinear direction and rotation of the drive system in a second rotational direction causes the coupling assembly to move in a second rectilinear direction opposite the first direction. The coupling assembly includes a biasing element that is to be deflected to provide a seat load to the fluid flow control member when the fluid flow control member is in sealing engagement with a valve seat of the fluid valve and electric power to the electric actuator is removed.

In another example, a coupling assembly includes a drive member to be operatively coupled to a drive system of the electric actuator. The drive system is to move the drive member between a first position, a second position, and a third position. A housing slidably receives at least a portion of the drive member. A biasing element is disposed between a surface and the drive member such that when the drive member is in the third position, the biasing element deflects to apply a seat load to a fluid flow control member sealingly engaged with a valve seat of a fluid valve when electric power to the electric actuator is removed.

In yet another example, a coupling apparatus includes means for converting rotational motion of a drive system to rectilinear motion of a coupling assembly. The coupling assembly includes means for coupling the means for converting to a valve stem. The means for coupling includes an opening to slidably receive the means for converting via a first end of the means for coupling and to receive the valve stem via a second end of the means for coupling. The coupling assembly also includes means to provide a seat load to a fluid flow control member of a fluid valve coupled to the valve stem when the flow control member is in sealing engagement with a valve seat of the fluid valve, the means to provide a seat load is deflected, and electric power to the electric actuator is removed.

DETAILED DESCRIPTION

In general, the example electric actuators described herein provide a seat load to a fluid valve when electric power to a drive motor of the actuators is removed. The example electric actuators described herein provide a seat load without consuming electric power. More specifically, the example electric actuators may include a biasing element to provide a seat load to a fluid flow control member of a valve when the fluid flow control member is in sealing engagement with a valve seat and the electric actuator (e.g., an electric motor) is not receiving electric power. For example, the biasing element may be implemented as one or more springs that exert a force to provide a seat load to a fluid flow control member (e.g., a valve plug) operatively coupled to the electric actuator when the fluid flow control member is sealingly engaged with the valve seat (e.g., a closed position) and a power supply source fails to provide power to a motor of the electric actuator.

In contrast, some known electric actuators use a complex combination of biasing elements, clutches and brake systems that provide a sufficient seat load when the electric actuator is in a fail-safe condition. In other words, known electric actuators may include a biasing element to move a flow control member of a valve to a closed position during, for example, a power failure. Thus, if the fluid valve is in the open position when a power failure occurs, the biasing element moves the fluid flow control member to the closed position. However, these known actuators often include complex assemblies. Additionally, some of these known actuation systems having fail-safe apparatus typically include a declutchable gear box to enable operation of the fail-safe apparatus. In other words, a drive assembly must typically be operatively decoupled from, for example, a gear transmission to enable operation of the fail-safe apparatus. However, declutchable gearboxes are relatively expensive, difficult to operate, enlarge the dimensional envelope of a valve and actuator assembly, and involve complex assemblies with the actuator. Additionally, such fail-safe apparatus may not be required and/or desired for some applications, thereby unnecessarily increasing the costs of a control valve assembly.

FIG. 1illustrates an example control valve assembly100described herein. The control valve assembly100includes an electric actuator102operatively coupled to a fluid valve104via a coupling assembly106. The fluid valve104includes a valve body108that defines a fluid flow passageway110between an inlet112and an outlet114. A fluid flow control member116(e.g., a valve plug) is disposed within the fluid flow passageway110and includes a seating surface118that sealingly engages with a valve seat120to control fluid flow through a port area or orifice122between the inlet112and the outlet114. A valve stem124is coupled (e.g., threadably coupled) to the fluid flow control member116at a first end126and is operatively coupled to the electric actuator102at a second end128via the coupling assembly106. A bonnet130is coupled to the valve body108and includes a bore132to slidably receive the valve stem124. The bonnet130houses a valve packing assembly134that provides a seal to oppose the pressure of the process fluid flowing through the fluid valve104to prevent leakage of process fluid past the valve stem124and/or protect the environment against the emission of hazardous or polluting fluids.

In this example, the electric actuator102includes a motor136coupled to a housing138of the electric actuator102via, for example, fasteners140and/or any other suitable fastening mechanism(s). The motor136may be any motor such as, for example, an alternating current (AC) motor, a direct current (DC) motor, a variable frequency motor, a stepper motor, a servo motor, or any other suitable motor or drive member.

The motor136is operatively coupled to a drive system142. The drive system142includes a drive member or output shaft144operatively coupled to the motor136via a transmission (not shown) (e.g., a gear transmission) disposed within the housing138of the electric actuator102. As shown, the output shaft144is a screw. However, in other examples, the output shaft144may be a gear system, a ball screw system, a leadscrew system, and/or any other suitable transmission system to convert rotational motion of the motor136to rectilinear motion of the valve stem124.

Although not shown, the transmission may be a gear transmission or gearbox having a spur gear, a planetary gear, or any other suitable transmission. The transmission may be configured to amplify the torque generated by the motor136and transmit the amplified torque to the output shaft144. The amplified torque transmitted to the output shaft144enables the flow control member116to engage the valve seat120with a greater force and, thus, provide a tighter sealing engagement with the valve seat120to prevent the flow of fluid through the valve body108when the flow control member116is sealingly engaged with the valve seat120and electric power is provided to the motor136. Also, a relatively smaller sized motor136may be used to drive the flow control member116with a transmission configured to amplify the torque generated by the motor136. For example, the amount of torque amplification provided by the transmission can vary based on the size (e.g., the diameter, number of gear teeth, etc.) of a gear. In yet other examples, the motor136may be directly coupled to the output shaft144or the second end128of the valve stem124. In such a direct-drive configuration, the motor136directly drives the output shaft144or the valve stem124without any other interposing mechanism or device such as a transmission or the like.

As shown inFIG. 2, the coupling assembly106includes a housing202, a drive coupler or drive member204slidably coupled to the housing202, and a biasing element206. The housing202includes a body207(e.g., a cylindrically-shaped body, a rectangular-shaped body, etc.) having an aperture or opening208therethrough between a first end210of the housing202and a second end212of the housing202opposite the first end210. As shown, the opening208adjacent the first end210has a diameter that is smaller than the diameter of the opening208adjacent the second end212to provide a stepped surface or shoulder214(e.g., integrally formed with the housing202). In other examples, a flange (not shown) may be coupled to the housing202to provide the stepped surface or shoulder214. Also, as shown, the opening208adjacent the second end212includes a threaded portion216to threadably receive an insert218(e.g., a fastener, a nut, etc.). The insert218includes a body portion220having an internally threaded aperture to receive a threaded portion222of the valve stem124and an externally threaded outer portion224. The externally threaded outer portion224threadably couples the insert218to the housing202via the threaded portion216of the opening208, thereby coupling the valve stem124to the housing202.

However, in other examples, the housing202may be configured to receive the threaded portion222of the valve stem124. In yet other examples, the insert member218may be fastened to the housing202(e.g., to the second end212of the housing202) via a fastener (e.g., a bolt, a rivet, a pin, etc.), interference fit, press fit, and/or any other suitable fastening mechanism(s).

The drive member204includes a body portion226(e.g., a cylindrically-shaped body portion) and a flanged portion228. The body portion226includes a threaded bore230to threadably receive a threaded portion232of the output shaft144. The flanged portion228is disposed or captured within the opening208of the housing202between the biasing element206and the shoulder214of the housing202. The flange portion228retains the drive member204to operatively couple the drive member204to the housing202.

The biasing element206is disposed within the housing202between the insert member218(or the valve stem) and the flange portion228of the drive member204. In this example, the biasing element206includes a stack of Belleville springs. In general, a Belleville spring provides a relatively high loading relative to the travel or deflection imparted on the Belleville spring. Thus, as a result, the example coupling assembly106may be configured to have a relatively small footprint, thereby reducing the overall envelope or footprint of the control valve assembly100. In other examples, the biasing element206may be a coil spring, spring washers and/or any other suitable biasing element(s).

In other examples, the biasing element206may be disposed within the housing202between the flange228and the shoulder214. In yet another example, a biasing element (e.g., a spring) may be disposed between an end234of the housing138and the drive member204. In yet other examples, the coupling assembly106and/or the biasing element206may be configured to provide a seat load in a direction opposite to the direction of the seat load provided in the example coupling assembly106shown inFIG. 2. Such a configuration enables the coupling assembly106to be used with a fluid valve having a fluid control member and a valve seat in a configuration opposite that shown inFIG. 1(e.g., a push-to-open fluid valve).

Referring toFIG. 3, the fluid valve104is depicted in an open position300and the biasing element206of the coupling assembly106is in a first or a substantially non-deflected condition302.FIG. 4illustrates the fluid valve in a closed position400, but showing the biasing element206of the coupling assembly106in a substantially non-deflected condition402.FIG. 5illustrates the fluid valve in a closed position500and shows the biasing element206in a substantially deflected condition502to provide a seat load504to the flow control member116.

Referring toFIGS. 3-5, in operation, the motor136drives or rotates the output shaft144in a first direction304(e.g., a clockwise direction) about an axis306to move the fluid valve104toward the open position300as shown inFIG. 3and a second direction404(e.g., a counterclockwise direction) opposite the first direction304about the axis306to move the fluid valve104toward the closed positions400and500as shown inFIGS. 4 and 5.

To move the fluid valve104toward the open position300, electric power is provided to the motor136. The transmission (not shown) causes the output shaft144to rotate in the first direction304(e.g., a clockwise direction) about the axis306. Rotation of the output shaft144in the first direction304causes the coupling assembly106to move in a rectilinear motion along the axis306in a direction away from the fluid valve104. More specifically, as the output shaft144rotates in the first direction304, the threaded portion232of the output shaft144rotates within the threaded bore230of the drive member204to cause the drive member204to move rectilinearly in a direction along the axis306such that the flange portion228engages the shoulder214of the housing202. The flange portion228of the drive member204engages the shoulder214of the housing202to cause the housing202to move in a rectilinear direction away from the fluid valve104. In turn, the housing202causes the flow control member116to move away from the valve seat120to allow or increase fluid flow through the fluid flow pathway110between the inlet112and the outlet114.

To move the fluid valve104toward the closed position400as shown inFIG. 4, electrical power is provided to the motor136to cause the output shaft114to rotate in the second direction404(e.g., a counterclockwise direction) via the transmission. Rotation of the output shaft144in the second direction404causes the coupling assembly106to move rectilinearly along the axis306in a direction toward the valve body108. More specifically, the threaded portion232of the output shaft144rotates within the threaded bore230of the drive member204to cause the drive member204to move rectilinearly in a direction along the axis306. In turn, the coupling assembly106causes the flow control member116to move toward the valve seat120to restrict or prevent fluid flow between the inlet112and the outlet114.

The biasing element206provides a biasing force and is in the substantially non-deflected condition402as the drive member204moves toward the fluid valve104. The biasing force provided by the biasing element206enables drive member204to move the housing202in linear direction toward the fluid valve104. Additionally, the biasing force provided by the biasing element206substantially reduces or eliminates lost motion that may otherwise occur between the drive member204, the housing202, the valve stem124, etc. In other words, the biasing force provided by the biasing element206enables the coupling assembly106to move as a substantially unitary structure when the coupling assembly106moves between the position shown inFIG. 3and the position shown inFIG. 4. Of course, in other examples, the biasing element206may be configured to deflect prior to the drive member204moving the housing202toward the valve body108, which will also substantially reduce or prevent lost motion between the housing202, the drive member204, the valve stem124or any other component of the control valve assembly100.

When the valve102is in the closed position400, the seating surface118of the fluid flow control member116sealingly engages the valve seat120to prevent fluid flow through the valve102. At this position, the housing202no longer move further toward the valve seat120because the valve stem124is rigidly coupled to the housing202via the insert member218and the fluid flow control member116is in engagement with the valve seat120(e.g., an end of travel or stroke position). However, the motor136continues to drive the drive member204in a rectilinear direction toward the valve seat120to cause the biasing element206to deflect or compress as shown inFIG. 5because the drive member204is slidably coupled to the housing202. In other words, the housing202remains in the position as shown inFIG. 4and the flange portion228of the drive member204moves in a rectilinear direction away from the shoulder214of the housing202to deflect or compress the biasing element206as shown inFIG. 5.

When in the closed position500as shown inFIG. 5, the motor136provides a seat load to the fluid flow control member116when electric power is provided to the motor136. However, when electric power is removed from the motor136, the flow control member116may lack adequate or sufficient seat load to sealingly engage the valve seat120. Although a backdrive resistance of the motor136and/or the transmission maintains the position or prevents rectilinear motion of the drive member204, the backdrive resistance of the motor136and/or the transmission may not be adequate to maintain or provide a seat load to the flow control member116when electric power is removed from the motor136. An adequate or sufficient seat load prevents fluid leakage through the orifice122when the flow control member116is sealingly engaged with the valve seat120. In other words, an adequate or sufficient seat load maintains the fluid flow control member116in sealing engagement the valve seat120to substantially prevent fluid flow through the passageway210of the fluid valve104. Absent such a seat load, fluid may leak past the orifice122even when the sealing surface118of the fluid flow control member116engages the valve seat120.

The coupling assembly106provides the mechanical seat load504to maintain or keep the fluid flow control member116in sealing engagement with the valve seat120if electric power is removed from the motor136while the flow control member116is sealingly engaged with the valve seat120. For example, it may be necessary to keep or retain the fluid valve104in the closed position400to prevent a spill (e.g., a chemical spill) during emergency situations, power failures, or if the electric power supply to the electric actuator102(e.g., the motor136) is removed or shut down. Otherwise, failing to provide an adequate or sufficient seat load to the fluid flow control member116during, for example, a power outage may cause fluid flow to pass through the orifice122of the valve104between the inlet112and the outlet114. For example, the pressure of the pressurized fluid at the inlet112may provide a force against the fluid flow control member116(e.g., in a direction toward the bonnet130in the orientation ofFIG. 5) to cause the sealing surface118of the fluid flow control member116to move away from the valve seat120and allow fluid to flow or leak toward the outlet114.

Thus, the example coupling assembly106provides the seat load504to the fluid flow control member116to prevent fluid flow through the fluid flow pathway110when the fluid valve104is in the closed position500and electric power is removed from the electric actuator102. In particular, the coupling assembly106provides a seat load for an indefinite period of time. Additionally or alternatively, the coupling assembly106provides a seat load (e.g., the seat load504) without consumption of electric power (i.e., with substantially zero electric power consumption). Thus, in some examples, when the valve104is in the closed position500, electric power to the motor136may be removed to conserve energy, thereby improving the performance and/or the efficiency of the electric actuator102.

Additionally, the example electric actuator102reduces manufacturing costs and simplifies maintenance of the control valve assembly100because the coupling assembly106does not require a clutching mechanism, a complex combination of biasing elements and/or brake systems to provide a seat load when the electric power to the electric actuator102is removed.

Although not shown, the example coupling assembly106may be implemented with control valve assemblies having a fail-safe mechanism. For example, the example control valve assembly100may be implemented with a biasing element or system that causes the flow control member116to move to the closed position400ofFIG. 4during, for example, a power failure or when power is not provided to the motor136. Such fail-safe mechanism may be implemented via, for example, a clutch mechanism.

The example electric actuator102may be used to implement other types of valves or control devices. For example,FIGS. 6A-6Cillustrate an example control valve assembly600having the example electric actuator102ofFIGS. 1-5coupled to a rotary valve602. The rotary valve602includes a valve body604having a disk or flow control member606interposed in a fluid flow path608between an inlet610and an outlet612. The flow control member606is rotatably coupled relative to the valve body604via a valve shaft614. A portion616(e.g., a splined end) of the valve shaft614extends from the rotary valve602and is received by a lever618. In turn, the lever618operatively couples the drive member204of the electric actuator102and the flow control member606. A rod end bearing620is coupled (e.g., threadably coupled) to the first end126(FIG. 1A) of the valve stem124and couples to a lever arm622of the lever618via a fastener624to operatively couple the lever618and the drive member204. The lever618converts a rectilinear displacement of the drive member204into a rotational displacement of the valve shaft614.

In operation, the motor136rotates the output shaft144in a first direction626(e.g., a clockwise direction) about an axis628. Rotation of the output shaft144in the first direction626causes the coupling assembly106to move in a rectilinear motion630along the axis628. More specifically, as the output shaft144rotates in the first direction626, the threaded portion232of the output shaft144rotates within the threaded bore230of the drive member204to cause the drive member204to move rectilinearly in the first direction630along the axis628such that the flange portion228engages the shoulder214of the housing202. The flange portion228of the drive member204engages the shoulder214of the housing202to cause the housing202to move in the first rectilinear direction630. In turn, the drive member204causes the lever618to rotate in a first direction632about an axis634. Rotation of the valve shaft614in the first direction632about the axis634causes the flow control member606to rotate away from a sealing surface636(e.g., an open position) to allow fluid flow through the valve body604between the inlet610and the outlet612.

When the motor136rotates the output shaft144in a second direction638(e.g., a counterclockwise direction) about the axis628, the threaded portion232of the output shaft144rotates within the threaded bore230of the drive member204to cause the drive member204to move in a second rectilinear direction640. When the drive member204moves in the second rectilinear direction640, the coupling assembly106causes the lever614to rotate in a second direction642about the axis634. Rotation of the valve shaft614in the second direction642about the axis634causes the flow control member606to rotate toward the sealing surface636(e.g., a closed position) to prevent or restrict fluid flow through the valve body604between the inlet610and the outlet612. When in the closed position, the motor136continues to rotate the output shaft144in the second direction638. However, the housing202cannot move further in the second rectilinear direction640(i.e., the housing reached an end of stroke position) when the flow control member606sealingly engages the sealing surface636. As a result, the motor136continues to rotate the output shaft144in the second direction638relative to the drive member204and causes the drive member204to move in the second rectilinear direction640along the axis628toward the biasing element206to compress or deflect the biasing element206of the coupling assembly106. In other words, in this example, the shoulder228of the drive member204moves away from the shoulder214of the housing202to compress the biasing element206and provide a seat load to the flow control member606when the flow control member606is in sealing engagement with the sealing surface636and the motor136continues to drive the drive member204in the second rectilinear direction640.

Although the backdrive resistance of the transmission and/or the motor136prevents the lever618from rotating in the first direction632about the axis634when electric power to the motor136is removed, the backdrive resistance of the transmission and/or motor136may not provide an adequate or sufficient seat load to prevent leakage of fluid through the pathway608when the rotary valve602is in the closed position. For example, the pressure of the fluid at the inlet610may cause fluid leakage between the flow control member606and the sealing surface636if an insufficient seat load is provided to the flow control member606. However, when the biasing element206is in the deflected or compressed condition, the biasing element206exerts a force to provide an adequate or sufficient mechanical seat load to maintain or keep the fluid flow control member606in sealing engagement with the sealing surface636when electric power is removed from the motor136and the flow control member606is sealingly engaged with the sealing surface636. In other words, for example, the biasing element206, when deflected or compressed, provides a force that substantially restricts or prevents a relatively high pressure fluid at the inlet610from leaking between the flow control member606and the sealing surface636and through the pathway608when the fluid flow control member606sealingly engages the sealing surface636and electric power to the motor136is removed.

Although certain example apparatus have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all apparatus and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.