Methods and apparatus to assemble actuators

Methods and apparatus to assemble actuators are described. An example method includes positioning a biasing element in a cavity defined by a housing of an actuator such that the biasing element is in an uncompressed state and at least a portion of the biasing element is to extend outside of the cavity beyond an end defined by the housing; compressing the biasing element to a compressed state until the portion of the biasing element extending outside of the cavity is positioned inside the cavity; coupling a cover to the end of the housing to capture the biasing element in the cavity; and maintaining the biasing element in the compressed state during the coupling such that the biasing element does not engage the cover.

FIELD OF THE DISCLOSURE

This patent relates generally to actuators and, more specifically, to methods and apparatus to assemble actuators.

BACKGROUND

Control valves are commonly used in process control systems to control the flow of process fluids. A control valve typically includes an actuator (e.g., a pneumatic actuator, a hydraulic actuator, etc.) operatively coupled to a flow control member to automate the control valve. In operation, a control fluid (e.g., air) is supplied to the actuator to position the flow control member relative to a valve seat to regulate fluid flow through the control valve.

Many process control applications require actuators (e.g., valve actuators) to include fail-safe systems. A fail-safe system provides protection to a process control system by causing the actuator and, thus, the flow control member to move to either a fully-closed position or a fully-opened position during emergency situations, power failures, and/or if the control fluid (e.g., air) supply to an actuator (e.g., a pneumatic actuator) is shut down.

To provide a fail-safe system, some actuators include a biasing member disposed in a cylinder of the actuator. However, in some instances, including a biasing member may significantly increase a dimensional envelope (e.g., length) of the actuator. In other instances, including a biasing member may require complex assembly or tools if the cylinder of the actuator has a smaller dimensional length than the biasing element.

SUMMARY

An example method includes positioning a biasing element in a cavity defined by a housing of an actuator such that the biasing element is in an uncompressed state and at least a portion of the biasing element is to extend outside of the cavity beyond an end defined by the housing; compressing the biasing element to a compressed state until the portion of the biasing element extending outside of the cavity is positioned inside the cavity; coupling a cover to the end of the housing to capture the biasing element in the cavity; and maintaining the biasing element in the compressed state during the coupling such that the biasing element does not engage the cover.

An example actuator includes a housing defining a cavity having a first dimensional length and a spring positioned in the cavity in a relaxed state. The spring in the relaxed state has a second dimensional length that is greater than the first dimensional length of the cavity such that at least a portion of the spring extends from the housing. A compression assembly is coupled to the spring and compresses the spring to a compressed state. The spring in the compressed state has a third dimensional length that is less than the first dimensional length of the cavity. A cover is coupled to the housing and at least a portion of the compression assembly being accessible via the cover when the cover is coupled to the housing.

Another example actuator includes means for actuating a means for controlling fluid flow through a valve, where the means for actuating is positioned in a cavity defined by a housing. A means for biasing is positioned in the cavity in an uncompressed state. A means for compressing compresses the means for biasing to a compressed state such that the means for biasing is positioned inside the cavity and away from an edge of the housing. A means for covering the cavity couples to the edge of the housing when the means for biasing is in the compressed state such that the means for biasing does not impart a force to the means for covering during assembly of the means for covering to the housing.

DETAILED DESCRIPTION

Some known actuators (e.g. spring-return actuators) provide a mechanical fail-safe return. For example, to provide a mechanical fail-safe return, some such known actuators employ a spring disposed in a cylinder of the actuator and in direct contact with a loading member (e.g., a diaphragm or a piston) of the actuator. The spring urges the loading member to one end of a stroke travel (e.g. a fully-opened or a fully-closed position) when a control fluid supply to the actuator fails and/or is otherwise removed.

To facilitate assembly of an actuator employing a spring-return mechanism, a cylinder is often provided with a dimensional profile (e.g., a length or a height) to contain the spring inside (e.g., fully inside) a cavity of the cylinder when the spring is in a relaxed state or an uncompressed condition. In this manner, the spring does not impart a significant force to the cover when the cover is attached to the cylinder.

However, in certain applications (e.g., sanitary markets), space may be limited and, thus, providing an actuator having a dimensional profile substantially equal to a dimensional length of the spring when the spring is in the relaxed state may not be practical or feasible. Thus, in such instances, a cylinder of an actuator if often provided with a dimensional profile that is smaller than a dimensional profile of spring when the spring is in a relaxed state. As a result, in such instances, the spring imparts a load or force to the cover when the cover is being coupled to the cylinder. A load imparted to the cover during assembly and/or disassembly of the cover and a cylinder may cause the cover and/or the cylinder to wear and/or become damaged due to, for example, galling. Galling refers to wear and/or transfer of material between metallic surfaces in contact with each other due to, for example, increased compressive stress during dynamic contact and/or sliding between metallic surfaces.

In sanitary applications, for example, a cover and/or a cylinder of an actuator may be composed of a material providing anti-corrosive or cleanliness characteristics (e.g., stainless steel, 300 series stainless steel, etc.). However, materials such as stainless steel are relatively malleable. As a result, actuator components (e.g., a housing and/or a cover) composed of stainless steel material may be susceptible to galling during assembly.

The example apparatus and related methods disclosed herein prevent damage (e.g., due to galling) to actuator components during assembly. More specifically, the apparatus and related methods disclosed herein operatively decouple or remove a force (e.g., a vertical force) of a biasing element from some components (e.g., a cover, a base, etc.) of an actuator during assembly and/or disassembly of the actuator.

As a result, the example apparatus and related methods disclosed herein enable actuators to have relatively small dimensional envelope. Additionally or alternatively, the example apparatus and related methods disclosed herein enable an actuator composed of malleable material to be assembled and/or disassembled without significant damage (e.g., due to galling) while enabling the actuator to have a relatively small dimensional envelope or profile. In particular, an example actuator disclosed herein may have a profile or dimensional length that is less than a profile or dimensional length of a spring or biasing element. In this manner, the example actuators disclosed herein may be employed in applications (e.g., sanitary applications) having relatively small or limited space, but requiring use of anti-corrosive materials such as, for example, stainless steel.

To operatively decouple or effectively remove a force of the biasing element during assembly and/or disassembly of the actuator, the example actuator apparatus and related methods disclosed herein employ a compression apparatus. More specifically, the example compression apparatus disclosed herein positions or compresses a portion of a biasing element inside of the cavity and away from an edge of the cylinder. Thus, any portion of the biasing element extending from the cavity is compressed inside the cavity. In this manner, an example cover may be coupled to the end of the cylinder without influence of a force that would otherwise be imparted to the cover by the biasing element. As a result, the force of the biasing element is effectively removed from the cover as the cover is being attached to the cylinder. Removal of the force from the cover significantly prevents galling during assembly and/or disassembly of the cover relative to the cylinder when the cover and/or the cylinder are composed of, for example, stainless steel. Further, at least a portion of the compression assembly is accessible via the cover when the cover is coupled to the actuator and/or at least a portion of the compression assembly may remain in the housing during operation without interference to the operation of the actuator.

FIG. 1illustrates an example control valve assembly100having an example actuator102constructed in accordance with the teachings disclosed herein. In this example, the actuator102is coupled to a valve104via a bonnet106. The valve104has a valve body108defining a fluid flow passageway110between an inlet112and an outlet114. A flow control member116is interposed in the fluid flow passageway110and is operatively coupled to the actuator102via a valve stem118. The actuator102causes the flow control member116to move relative to a valve seat120(e.g., a valve body or seat ring) disposed in the passageway110to control the flow of fluid between the inlet112and the outlet114. Thus, the flow rate permitted through the valve104is controlled by the position of the flow control member116relative to the valve seat120.

More specifically, the flow control member116moves away from the valve seat120in a first rectilinear direction122along a longitudinal axis124of the actuator102to allow fluid flow between the inlet112and the outlet114and moves toward the valve seat120in a second rectilinear direction126along the longitudinal axis124of the actuator102to restrict or prevent fluid flow between the inlet112and the outlet114. Additionally, movement of the flow control member116in the first rectilinear direction122is limited by a first stop128(e.g., defined by a wall130of the valve body108) and movement of the flow control member116in the second rectilinear direction126is limited by a second stop132(e.g., defined or provided by the valve seat120of the valve body108).

The actuator102of the illustrated example includes a cylinder or housing134that defines a cavity136between a first end or edge138of the housing134and a second end or edge140of the housing134. A loading member or piston142is positioned in the cavity136to define a pressure chamber144adjacent a first side or face146of the piston142and a spring chamber148adjacent a second side150of the piston142. A biasing element152is positioned in the spring chamber148and imparts a force to the second side150of the piston142when the actuator102is assembled as shown inFIG. 1. In this example, the biasing element152includes two springs. However, in other examples, the biasing element may be one spring or more than two springs.

To capture or encase the biasing element152in the housing134, the actuator102employs a cover154. The cover154of the illustrated example is removably attached to the edge138of the housing134to capture the biasing element152in the spring chamber148between the second side150of the piston142and the cover154. Thus, the cover154at least partially defines the spring chamber148and engages a first end156of the biasing element152to provide a spring seat158when the cover154is attached or coupled to the housing134. As shown, the second side150of the piston142includes an annular wall160(e.g., defined by a recess) adjacent a second end162of the biasing element152to guide or orient the biasing element152in the cavity136.

As shown inFIG. 1, an actuator stem or stem connector164couples the piston142to the valve stem118. As shown, the actuator stem164includes a fastener166that engages an opening168of the valve stem118through an opening170(e.g., a central opening) in the piston142.

Additionally, as described in greater detail below in connection withFIGS. 2-4, the example actuator102employs a compression assembly172coupled to the first end156of the biasing element152to facilitate assembly of the actuator102.

In operation, a pressurized control fluid is provided or supplied to the pressure chamber144to impart a force to the first side146of the piston142. A pressure differential provided across the piston142by a pressure of the control fluid in the pressure chamber144and a pressure provided by the biasing element152to the second side150of the piston142causes the piston142to move the flow control member116in the first and second rectilinear directions122and126. More specifically, a pressure or force provided to the first side146of the piston142that is greater than a pressure or force provided to the second side150causes the flow control member116to move in the first rectilinear direction122. Likewise, a pressure or force provided to the first side146of the piston142that is less than a pressure or force provided by the second side150of the piston142causes the flow control member116to move in the second rectilinear direction126.

For example, the flow control member116sealingly engages the valve seat120to prevent or restrict fluid flow through the valve104when the flow control member116engages the valve seat120(e.g., a fully-closed position) and the flow control member116is spaced away from the valve seat120to allow fluid flow through the valve104(e.g., a fully-opened position). As noted above, the first and second stops128and132limit the travel of the flow control member116and, thus, the piston142in the first and second rectilinear directions122and126, respectively. The compression assembly172does not interfere or affect the operation of the piston142and/or the actuator102when the flow control member moves between the first and second stops128and132.

Further, in this example, the actuator102of the illustrated example provides a fail-to-close fail-safe mechanism. In other words, the biasing element152biases the flow control member116toward the valve seat120to prevent fluid flow through the passageway110of the valve104when a control fluid is removed from the pressure chamber144. However, in other examples, the control valve assembly100may be configured to provide a fail-to-open fail-safe mechanism. For example, the flow control member116may be configured to move away from the valve seat120to an open position when a control fluid is removed from the pressure chamber144.

FIG. 2illustrates the example actuator102ofFIG. 1in a partially assembled state. To assemble the actuator102, the piston142is attached to the actuator stem164and is disposed in the cavity136of the housing134. During assembly, the piston142(e.g., the first side146of the piston142) is positioned adjacent or engages a surface or base200(e.g., a removable base) of the housing134. The valve stem118is attached to the piston142via the actuator stem164.

As shown inFIG. 2, the biasing element152is then positioned in the cavity136of the housing134in a relaxed state or uncompressed condition. In the relaxed state, the biasing element152imparts a force that is significantly less than a force imparted by the biasing element152when the biasing element152is in a compressed state or condition. As shown inFIG. 2, the first end156of the biasing element152extends or protrudes outside of the cavity136away from the edge138of the housing134by a distance202when the biasing element152is positioned in the cavity136in the relaxed state. In other words, a dimensional profile (e.g., a length or height) of the biasing element152is greater than a dimensional profile (e.g., a height or length) of the cavity136and/or the housing134when the biasing element152is disposed in the cavity136in the relaxed state.

Prior to attachment or coupling the cover154to the housing134, the biasing element152is compressed via the compression assembly172. The compression assembly172is coupled to the first end156of the biasing element152. In the illustrated example, the compression assembly172includes a plate204and a fastener206. The plate204is positioned or coupled to the first end156of the biasing element152and the fastener206couples the plate204to the actuator stem164. As shown, the fastener206is positioned through an opening208of the plate204. A first surface210of the plate204engages the first end156of the biasing element152and a head212of the fastener206engages a second surface214of the plate204opposite the first surface210. The plate204of the illustrated example includes an annular wall or lip216to guide or orient the biasing element152in the cavity136. Additionally or alternatively, the plate204overlaps or engages an entire surface area or diameter of the biasing element152(e.g., engages the springs) to evenly distribute a load to the biasing element152when the biasing element152is compressed or decompressed during assembly. Further, the fastener206includes a threaded portion218to threadably engage a threaded opening220of the actuator stem164and an unthreaded portion222to slide relative to the opening208of the plate204. In the position shown inFIG. 2, the fastener206is partially threaded into the threaded opening220of the actuator stem162.

FIG. 3illustrates the example actuator102in another partially assembly state. Referring toFIG. 3, after the compression assembly172is attached to the biasing element152, the compression assembly172compresses the biasing element152inside the cavity136. More specifically, the compression assembly172positions or moves the portion of the biasing element152extending outside of the cavity136shown inFIG. 2toward the inside of the cavity136and away from the edge138of the housing134.

To compress the biasing element152, the fastener206is rotated (e.g., via a tool or wrench) in a first rotational direction300(e.g., a clockwise direction) about the longitudinal axis124. More specifically, the fastener206is screwed into the threaded opening220. As the fastener206is threaded into the threaded opening220of the actuator stem164, the fastener206initially draws the piston142toward the edge138of the housing134in the first rectilinear direction122(e.g., an upward direction in the orientation ofFIG. 3) until the flow control member116engages the first stop128, which prevents further movement of the piston142toward the edge138of the housing134.

Further rotation of the fastener206in the first rotational direction300causes the plate204to move in the second rectilinear direction126along the longitudinal axis124toward the second side150of the piston142(e.g., a downward direction toward the flow control member116in the orientation ofFIG. 3). Movement of the plate204in the second rectilinear direction126causes the biasing element152to compress. In other words, the dimensional profile (e.g., the length or height) of the biasing element152in the compressed position is less than the dimensional profile (e.g., the length or height) of the biasing element152when the biasing element152is in the relaxed state as shown inFIG. 2. The biasing element152is compressed to a dimensional profile that is less than the dimensional profile of cavity136so that the biasing element152is disposed or positioned inside of the cavity136and spaced away from the edge138of the housing134. For example, the first end156of the biasing element152may be compressed by a distance302relative to the edge138of the housing134.

Further, the compression assembly172maintains the biasing element152in the compressed position or state inside the cavity136. With the biasing element152compressed inside of the cavity136as shown inFIG. 3, the cover154is attached or coupled to the edge138of the housing134. In this example, the cover154is threadably coupled to the edge138of the housing134. In other examples, the cover154may be coupled to the housing134via a clamp, welding, or any other fastening mechanism(s) or technique(s). With the biasing element152spaced away from the edge138of the housing134, the cover154is attached to the edge138of the housing134without influence of a spring force of the biasing element152. In other words, because the biasing element152is compressed inside of the cavity136and spaced away from the edge138of the housing134, the biasing element152does not engage the cover154as the cover154is being coupled to the housing134. As a result, a spring force of the biasing element152(e.g., an upward vertical force in the orientation ofFIG. 3) is operatively decoupled or effectively removed from the cover154during assembly of the cover154to the housing134.

Removing the force of the biasing element152from the cover154during assembly of the cover154facilitates assembly of the cover154and the housing134because less holding force is needed to rotate the cover154relative to the housing134. Additionally or alternatively, decoupling the spring force of the biasing element152from the cover154during assembly significantly reduces or prevents damage to the cover154and the housing134due to, for example, galling that may otherwise occur if the biasing element152is engaged or in contact with the cover154as the cover154is assembled to the housing134. Therefore, the cover154and/or the housing134(e.g., threads of the cover154and/or the housing134) may be composed of stainless steel and removal of the force of the biasing element152from the cover154during assembly prevents or significantly reduces damage or wear due to galling.

FIG. 4illustrates the example actuator102ofFIGS. 1-3after the cover154has been attached to the housing134. The cover154of the illustrated example includes an opening400to provide access to at least a portion of the compression assembly172when the cover154is attached to the housing134. For example, as shown, the opening400is aligned (e.g., coaxially aligned) with the fastener206such that the head212of the fastener206is accessible and/or protrudes from the opening400when the cover154is attached to the housing134.

FIG. 5illustrates the example actuator102in an assembled state. After the cover154is attached to the housing134as shown inFIG. 4, the compression assembly172is adjusted to at least partially decompress the biasing element152such that the piston142is positioned to a stroke length position of the actuator102(e.g., a full stroke length position). In other words, in the assembled state, the dimensional length or height of the biasing element152is substantially equal to a dimensional length or height of the cavity136as shown inFIG. 5. However, if a greater amount of biasing force is needed, the compression assembly172can adjust or maintain the biasing element152in a compressed state such that the dimensional length or height of the biasing element152is less than the dimensional length or height of the cavity136.

To decompress the biasing element152, the fastener206is rotated (e.g., via a tool or wrench) in a second rotational direction500(e.g., a counterclockwise direction) about to the longitudinal axis124. In particular, movement of compression assembly172or the plate204in the first rectilinear direction122causes the biasing element152to decompress or expand. More specifically, rotation of the fastener206in the second rotational direction500causes the fastener206to unthread and, thus, move away from the threaded opening220of the actuator stem164. As the fastener206is unthreaded from the threaded opening220of the actuator stem164, the compression assembly172or the plate204move in the first rectilinear direction122toward the cover154along the longitudinal axis124due to the force of the biasing element152(e.g., an upward direction toward the flow control member116in the orientation ofFIG. 3) acting on the compression assembly172or the plate204. The fastener206is rotated in the second rotational direction500until the plate204engages the cover154.

When the compression assembly172or the plate204engages the cover154, further rotation of the fastener206in the second rotational direction500causes the piston142to move in the second rectilinear direction126toward the base200(e.g., a downward direction in the orientation ofFIG. 3) until the flow control member116engages the second stop132(e.g., the valve seat120).

As shown inFIG. 5, a cover or cap502may be coupled to an outer surface504of the cover154to prevent contaminates or debris from entering the opening400of the cover154and, thus, the spring chamber148. In operation, the unthreaded portion222of the fastener206slides relative to the opening208of the plate204when the flow control member116moves relative to the valve seat120. The cap502of the illustrated example defines a cavity506to receive a portion of the fastener206(e.g., the head212) during operation of the actuator102. Thus, the fastener206and/or the cap502do not interfere with the operation of the actuator102(e.g., when the valve104is in the fully-open position as shown inFIG. 4). The cap502may include a vent508to allow the spring chamber148to vent to the atmosphere. In some examples, as shown inFIG. 1, the fastener206may be removed and/or decoupled from the actuator stem164via the opening400prior to coupling the cap502to the cover154.

To disassemble the actuator102, the biasing element152is positioned away from the cover154via the compression assembly172and the cover154is decoupled from the housing134.

The example actuator100ofFIGS. 1-5is configured as a fail-to-close fail-safe mechanism. Although not shown, the actuator102of the illustrated example may be configured as a fail-to-open fail-safe mechanism. For example, the biasing element152may be disposed in the pressure chamber144instead of the spring chamber148. In such an example, the piston142may be positioned in the cavity136and positioned against the cover154. The compression assembly172may be employed to compress the biasing element152away from the end140of the housing134. For example, an actuator stem or cylindrical body may be coupled to the piston142. The actuator stem may have an internally threaded aperture to receive the fastener206of the compression assembly172and a threaded outer surface to receive the valve stem118. For example, after the biasing element152is compressed to a compressed position inside of the cavity136and away from the end140of the housing134via the compression assembly172, the base200is attached or coupled (e.g., threadably coupled) to the end140of the housing134. The fastener206is then removed from the actuator stem via an opening510of the base200, causing the biasing element152to decompress to engage the base200. The valve stem118may then be coupled to the actuator stem via the threaded outer surface of the actuator stem. In yet another example, the actuator stem does not employ a threaded outer surface. Instead, a double-threaded fastener (e.g., a stud) having a first threaded end to couple to the valve stem118and a second threaded end to couple to the internal threaded opening of the actuator stem after the fastener206is removed from the actuator stem.

FIG. 6is a flowchart of an example method600that may be used to assemble an example actuator disclosed herein such as the example actuator102ofFIGS. 1-5. While the example method600may be used to assemble an example actuator disclosed herein, one or more of the blocks and/or processes illustrated inFIG. 6may be combined, divided, re-arranged, omitted, eliminated and/or implemented in any other way. Further still, the example method ofFIG. 6may include one or more processes and/or blocks in addition to, or instead of, those illustrated inFIG. 6, and/or may include more than one of any or all of the illustrated processes and/or blocks. Although the example method600is described with reference to the flowchart illustrated inFIG. 6, many other methods of assembling an example actuator may alternatively be used.

The example method600begins by positioning a biasing element in a cavity of a housing or cylinder of an actuator (block602). More specifically, the biasing element is positioned in the cavity in a relaxed state or uncompressed condition. In the relaxed state, a portion or an end (e.g., the first end154ofFIG. 1) of the biasing element protrudes from the cavity and past an edge of the housing.

After the biasing element is positioned in the housing, the biasing element is compressed to a compressed position (block604). In the compressed position, the end of the biasing element is positioned inside the cavity and away from the edge of the housing. A compression assembly (e.g., the compression assembly172) may be employed to compress the biasing element to the compressed position. For example, a plate of the compression assembly may be coupled to the end of the biasing element and the plate can be coupled to an actuator stem via a fastener. For example, the compression assembly may cause the biasing element to move or compress in a first rectilinear direction along a longitudinal axis of the biasing element or cavity by rotating the fastener of the compression assembly in a first rotational direction about the longitudinal axis and into a threaded opening of the actuator stem.

The biasing element is then maintained in the compressed position (block606). More specifically, the biasing element is maintained in the compressed position until a cover is coupled or attached to the housing of the actuator. For example, the compression assembly maintains the biasing element in the compressed position via the plate when the fastener of the plate is threaded in the threaded opening of the actuator stem.

A cover is then attached or coupled to the housing134when the biasing element is in the compressed position. (block608). For example, the cover is attached or coupled to the end of the housing while the biasing element is positioned away from the end of the housing. For example, in the compressed position, the biasing element is operatively decoupled or spaced away from the cover as the cover is coupled to the housing of the actuator. As a result, the cover is threadably coupled to the end of the housing while the biasing element is operatively decoupled from the cover.

After the cover is attached to the housing of the actuator, the biasing element is decompressed (block610). For example, the biasing element may be decompressed via the compression assembly. For example, the compression assembly may cause the biasing element to move or decompress in a second rectilinear direction along the longitudinal axis of the biasing element or cavity by rotating the fastener of the compression assembly in a second rotational direction about the longitudinal axis and out of the threaded opening of the actuator stem. For example, the biasing element may be decompressed until the plate of the compression assembly and/or the biasing element engages the cover of the actuator. Additionally, the fastener may be removed from the actuator stem and/or the housing via an aperture in the cover of the actuator.