Patent Description:
Valves are located and configured to control a flow of fluid through a conduit. Valves are coupled into the conduit and include various forms of obstruction to block the fluid flow through the conduit that passes through the valve. The obstruction may be moveable to regulate and manage the amount of fluid that passes through the valve. Various obstructions may include a gate, a knife, a piston, or other blocking members, and may be powered by an actuator. One type of actuator is a linear actuator. Opening and closing of the valve obstruction, particularly at high speeds, can cause internal components of the valve to contact each other and result in damage. It is sometimes desirable to slow down the actuation speed of the internal, moveable components of the valve such as the obstruction member and the actuator before these components reach a full stop. A mechanical or electrical control system may be used to slow down these components before full stop contact is achieved.

<CIT> describes a valve comprising a body having a casing adapted for mounting in a container, and a housing adapted for communication with an outlet line communicating with the container, the housing being shaped to form a valve seat at one end thereof. A valve head assembly is mounted in a support secured to the casing and is configured for movement toward and away from the valve seat. A spring is operatively connected to the support and the head assembly to cause the valve head to assume a position spaced from the valve seat, the strength of the spring being adjusted so that an excess flow of fluid from the casing to the housing causes the valve head to move into engagement with the valve seat against the force of the spring. A pressure-receiving member is operatively connected to the valve head assembly, the cross-sectional area of said member being greater than that of the valve head. When the housing pressure becomes excessive, a force is developed urging the valve head against the valve seat.

<CIT> describes an actuator having a piston disposed within a master chamber, the piston being slidable upstream and downstream within the master chamber having a seal that forms a seal surface with a complementary interior surface of the master chamber, the seal surface forming opposing upstream and downstream fluid drive chambers. A bleed port extends through the interior surface of the master chamber and is disposed immediately downstream of the complementary interior surface of the master chamber and in communication with the downstream fluid drive chamber when the piston is in a fully upstream position, or immediately upstream of the complementary interior surface of the master chamber and in communication with an upstream fluid drive chamber when the piston is in a fully downstream position.

The present invention resides in a valve actuator as defined in claim <NUM>. Preferred embodiments of the actuator are defined in claims <NUM> to <NUM>.

The present invention further resides in a valve for stopping and starting the flow of a process fluid as defined in claim <NUM>.

Thus, embodiments described herein include a combination of features and characteristics intended to address various shortcomings associated with certain prior devices, systems, and methods. The various features and characteristics described above, as well as others, will be readily apparent to those of ordinary skill in the art upon reading the following detailed description, and by referring to the accompanying drawings.

For a detailed description of the disclosed exemplary embodiments, reference will now be made to the accompanying drawings, wherein:.

The following description is exemplary of certain embodiments of the disclosure. One of ordinary skill in the art will understand that the following description has broad application, and the discussion of any embodiment is meant to be exemplary of that embodiment, and is not intended to suggest in any way that the scope of the disclosure, including the claims, is limited to that embodiment.

The drawing figures are not necessarily to scale. Certain features and components disclosed herein may be shown exaggerated in scale or in somewhat schematic form, and some details of conventional elements may not be shown in the interest of clarity and conciseness. In some of the figures, in order to improve clarity and conciseness, one or more components or aspects of a component may be omitted or may not have reference numerals identifying the features or components. In addition, within the specification, including the drawings, like or identical reference numerals may be used to identify common or similar elements.

As used herein, including in the claims, the following definitions and ideas will apply:.

The terms "including" and "comprising," as well as derivations of these, are used in an open-ended fashion, and thus should be interpreted to mean "including, but not limited to. " Also, the term "couple" or "couples" means either an indirect or direct connection. Thus, if a first component couples or is coupled to a second component, the connection between the components may be through a direct engagement of the two components, or through an indirect connection that is accomplished via other intermediate components, devices and/or connections. The recitation "based on" means "based at least in part on. " Therefore, if X is based on Y, then X may be based on Y and any number of other factors. The word "or" is used in an inclusive manner. For example, "A or B" means any of the following: "A" alone, "B" alone, or both "A" and "B.

In addition, the terms "axial" and "axially" generally mean along or parallel to a given axis, while the terms "radial" and "radially" generally mean perpendicular to the axis. For instance, an axial distance refers to a distance measured along or parallel to a given axis, and a radial distance means a distance measured perpendicular to the axis. Furthermore, any reference to a relative direction or relative position is made for purpose of clarity, with examples including "top," "bottom," "up," "upward," "down," "lower," "clockwise," "left," "leftward," "right" "right-hand," "down", and "lower. " For example, a relative direction or a relative position of an object or feature may pertain to the orientation as shown in a figure or as described. If the object or feature were viewed from another orientation or were implemented in another orientation, it may be appropriate to describe the direction or position using an alternate term.

This disclosure presents various embodiments of an actuator configured to control the opening and closing speeds of various valves before the valve comes to a fully stopped position. Exemplary valves include gate valves, ball valves, and hydraulic piston valves. In the disclosed embodiments, the actuator may include a piston or other drive member driven in at least one direction by a working fluid. The actuator includes a fluid flow area that is configured, during operation of the valve, to restrict the fluid flow area through which the working fluid flows. The restriction causes the speed at which the working fluid exits from the actuator to be lessened or slowed, thereby causing the piston or other drive member to be slowed.

Referring to <FIG>, which illustrates an example that does not fall within the ascope of the present invention, a valve <NUM> includes a valve housing <NUM>, a bonnet <NUM>, a gate <NUM> positioned within housing <NUM>, a flow passage <NUM>, a valve stem <NUM> extending from gate <NUM> into bonnet <NUM>, a pair of valve seats <NUM>, and a valve actuator <NUM>. Flow passage <NUM> extends through housing <NUM> along a flow axis <NUM> from an entry zone 52A to an exit zone 52B and expands into a chamber <NUM> within the central region of housing <NUM>, between zones 52A, 52B. Valve seats <NUM> are located in chamber <NUM>, having flow passages centered on axis <NUM>. Bonnet <NUM> is coupled to housing <NUM> and includes a through-bore <NUM> that intersects the chamber <NUM> and a downward facing shoulder or stop <NUM> that limits the upward travel of stem <NUM> and the attached gate <NUM>. As noted above, the valve <NUM> can take different forms such as a gate valve, a ball valve, or a hydraulic piston valve, among other valves, though a gate valve is used for illustrative purposes in this description.

Gate <NUM> is held between valve seats <NUM> and includes a through-passage <NUM>, a blocking portion <NUM>, and a stem coupling portion <NUM> that couples to valve stem <NUM>. Valve stem <NUM> extends from gate <NUM> through bonnet <NUM> along an actuation axis <NUM>. In <FIG>, axis <NUM> is perpendicular to axis <NUM>. Valve <NUM> is configured so that reciprocal movement of valve stem <NUM> along axis <NUM> slides gate <NUM> so that through-passage <NUM> and blocking portion <NUM> are alternately positioned between valve seats <NUM>, respectively allowing fluid communication through the length of flow passage <NUM> or inhibiting fluid communication through the passage <NUM>. During at least some positions of gate <NUM>, chamber <NUM> is in fluid communication with entry zone 52A, exit zone 52B, or both zones 52B so that fluid pressure from passage <NUM> is exerted within chamber <NUM> during a portion of the reciprocation cycle of gate <NUM>. <FIG> shows valve <NUM> and gate <NUM> in the open position, having through-passage <NUM> aligned with flow passage <NUM>. In the closed position, gate <NUM> is raised so that portion <NUM> blocks flow passage <NUM>. Valve <NUM> and gate <NUM> include intermediate positions that can be referred to as partially open or partially closed.

Valve actuator <NUM> includes an actuator housing <NUM> extending away from bonnet <NUM> along the shared axis <NUM>, a fluid port <NUM>, a piston <NUM> configured for reciprocation within housing <NUM>, and a plug or obstruction <NUM> configured to reciprocate as a result of the reciprocation of the piston and configured to variably block or obstruct port <NUM>.

Housing <NUM> includes tubular wall <NUM> that extends from a proximal end <NUM> adjacent bonnet <NUM> to a distal end <NUM> with an inner surface <NUM>. Housing <NUM> also includes a cap <NUM> at distal end <NUM>. A shoulder <NUM> is positioned along surface <NUM> between ends <NUM>, <NUM>, facing the end <NUM> such that inner surface <NUM> has a larger diameter at distal end <NUM>. In this embodiment, proximal end <NUM> is directly attached to an upper end of bonnet <NUM> and shoulder <NUM> is closer to housing end <NUM> than to housing end <NUM>. Cap <NUM> seals the distal end <NUM> of wall <NUM>, forming a head portion of housing <NUM>. Cap <NUM> includes an internal end surface <NUM>, an external end surface <NUM> separated from surface <NUM> along axis <NUM>, and a through-hole <NUM> extending through the surfaces <NUM>, <NUM> and centered on axis <NUM>. Alternatively, the upward travel of stem <NUM> and gate <NUM> can be stopped or limited by surface <NUM> rather than or in addition to shoulder.

Continuing to reference <FIG>, piston <NUM> is cylindrical and extends along an axis <NUM> from a proximal end <NUM> to a distal end <NUM> and includes a sidewall <NUM> slidingly engaged with surface <NUM> of housing <NUM>. Piston <NUM> is configured for reciprocation between shoulder <NUM> and cap <NUM> at end <NUM>. A seal <NUM> surrounds and is seated within piston sidewall <NUM> and, consequently, also slidingly engages wall <NUM>. Piston <NUM> is rigidly coupled to valve stem <NUM> at piston end <NUM>, and a second stem <NUM> is rigidly coupled to the opposite end <NUM> and extends through hole <NUM> in cap <NUM>. In other embodiments, stems <NUM>, <NUM> are a single piece or member that connects to piston <NUM>.

The location of piston <NUM> within housing <NUM> defines two chambers <NUM>, <NUM> having variable volumes. A proximal chamber <NUM> is located between bonnet <NUM> and piston proximal end <NUM>. A distal chamber <NUM> is located between piston distal end <NUM> and cap internal surface <NUM>. A resilient member, which in this embodiment is a compression spring <NUM>, is disposed within chamber <NUM> extending between bonnet <NUM> and piston <NUM> to bias piston <NUM> away from valve body <NUM>, which biases gate <NUM> to the closed position. A vent <NUM> provides fluid communication into chamber <NUM> to allow air, ambient fluid, or another fluid to enter and exit as piston <NUM> moves. Vent <NUM> extends through wall <NUM>.

Port <NUM> extends through the surfaces <NUM>, <NUM> of cap <NUM> along a port axis <NUM> parallel to actuation axis <NUM>. In other embodiments, port <NUM> and port axis <NUM> are offset from or not parallel to actuation axis <NUM>. As best shown in <FIG>, port <NUM> has an inner flow area <NUM> extending perpendicular to port axis <NUM> adjacent surface <NUM>. Plug <NUM> of actuator <NUM> is attached to piston <NUM> and includes a head <NUM> and a body <NUM> that extend along a plug axis <NUM> aligned with port axis <NUM>. In at least this embodiment port <NUM>, head <NUM>, and body <NUM> are cylindrical, centered on axis <NUM>, <NUM>.

Referring again to <FIG>, port <NUM> provides fluid communication into distal chamber <NUM> for a control fluid to enter chamber <NUM>. In some embodiments, the control fluid is pressurized to push piston <NUM> toward valve body <NUM>, opening valve gate <NUM>. A three-port control valve <NUM> supplied by a source of pressurized fluid governs the flow of fluid into port <NUM>. In other embodiments, the control valve <NUM> is a two-by-two port valve or other control valves known in the industry. To hold gate <NUM> open, control valve <NUM> remains closed, keeping fluid within chamber <NUM>. Port area <NUM> provides a fluid flow path for the control fluid to leave chamber <NUM> when an operator or a control system decides that valve <NUM> needs to close, switching valve <NUM> to exhaust the fluid to a reservoir. With valve <NUM> exhausting the control fluid, the closing of valve <NUM>, i.e., the upward movement of gate <NUM> along axis <NUM>, is driven by the pressure of the process fluid in flow passage <NUM> including chamber <NUM> and in gate passage <NUM>. Stem <NUM> pushes piston <NUM> in the same direction, and piston <NUM> drives the control fluid from chamber <NUM> along the fluid flow path of port area <NUM>, thereby shrinking or making smaller chamber <NUM>. The upward movement of gate <NUM> is also driven by spring <NUM> pushing on piston <NUM> and stem <NUM>.

Referring again to <FIG>, a cylindrical fluid flow area <NUM> can be defined that extends vertically from the circumference of plug <NUM> to the circumference of port <NUM>. Fluid leaving chamber <NUM> first travels through fluid flow area <NUM> or the volume that it defines, and then the exiting fluid flows through fluid flow area <NUM> of port <NUM>. The relative fluid flow areas between fluid flow area <NUM> and port flow area <NUM> will determine the speed or volumetric flow rate of fluid leaving port <NUM>. In other words, whichever of the flow areas <NUM>, <NUM> is smaller than the other will dictate the speed or the volumetric flow rate of fluid leaving port <NUM>.

In certain embodiments, initially, port flow area <NUM> is smaller than cylindrical flow area <NUM>, as shown in the valve open condition of <FIG>. But as piston <NUM> rises, flow area <NUM> becomes smaller than port flow area <NUM>, as shown in the successive piston <NUM> positions of <FIG>, thereby restricting the flow of fluid into port <NUM>. First, the restriction of shrinking flow area <NUM> increases the velocity of fluid passing through that area. Then, the continuing shrinking of flow area <NUM> reduces the volumetric flow rate of fluid entering port <NUM>, which slows the speed of piston <NUM>. For example, <FIG> shows plug <NUM> and its top or upper surface very close to port <NUM> so that flow area <NUM> is much smaller than port flow area <NUM>. Thus, the upward movement of piston <NUM> and plug <NUM> reduces a flow area through which fluid from chamber <NUM> passes to reach port <NUM> as it exits chamber <NUM>. By the time piston <NUM> has reached its top-dead-center location, plug <NUM> blocks port <NUM> entirely or nearly entirely. In some embodiments, as shown in <FIG>, plug <NUM> extends into port <NUM>, extending through the port flow area <NUM>.

The blockage of port <NUM> and resulting stoppage of fluid flow first slows and ultimately stops the upward movement of piston <NUM>. In some embodiments, the stoppage of piston <NUM> is augmented by a trapped portion of the working fluid held within a residual pocket of chamber <NUM>. Furthermore, the stop-shoulder <NUM> in bonnet <NUM> and a shoulder on stem <NUM> may assist or cause the stopping of piston <NUM>, stem <NUM>, and gate <NUM>. In some embodiments, other movement limiting features in valve <NUM> may assist with stopping piston <NUM>. With actuator <NUM>, the stopping of piston <NUM>, stem <NUM>, and gate <NUM> is smoother or less abrupt than if port <NUM> was not variably restricted, or no fluid was trapped. In this manner, the fluid flow path along the areas <NUM>, <NUM> is variable or adjustable such that the volumetric flow rate along this flow path is correspondingly variable or adjustable to provide fluid dampening of the speed of piston <NUM>.

The opening of valve <NUM> is driven by working fluid pushing on plug <NUM> and eventually pushing on piston <NUM>. In some embodiments, plug <NUM> does not entirely restrict port <NUM> when the valve is closed. Rather, plug <NUM> leaves a clearance for fluid flow when seated within port <NUM>. The clearance provides a path for returning fluid to immediately pressurize both plug <NUM> and piston <NUM>, providing a greater initial force due to the larger, combined surface area that promptly experiences the renewed pressure.

The partial view of <FIG> presents an example that does not fall within the scope of the present invention, namely, a valve actuator <NUM> that is compatible with valve <NUM> (<FIG>) to replace actuator <NUM>. Valve actuator <NUM> includes an actuation axis <NUM>, a housing <NUM>, a port <NUM> in housing <NUM>, a piston <NUM>, and a plug <NUM>.

Housing <NUM> includes a side wall <NUM>, a head portion <NUM>, and the port <NUM> extending through head portion <NUM> parallel to axis <NUM> (or non-parallel in some examples). Piston <NUM> is disposed within housing <NUM> and configured for reciprocation. Piston <NUM> is coupled to a valve stem <NUM> as previously described regarding valve <NUM> and actuator <NUM>. Piston <NUM> lacks a second stem <NUM> extending opposite valve stem <NUM> and head portion <NUM> lacks a through-hole <NUM> (<FIG>), but other examples of actuator <NUM> include a second stem and a cap <NUM> like those of actuator <NUM>. Plug <NUM> is mounted or coupled adjacent port <NUM> and is biased away from port <NUM> by a spring <NUM> or another resilient or biasing member. Plug <NUM> is mounted or coupled independently of piston <NUM>. In some embodiments, plug <NUM> is mounted by a stem or other elongate member that extends to head portion <NUM> or through port <NUM>. Plug <NUM> is configured to reciprocate with piston <NUM> when piston <NUM> is adjacent port <NUM> and presses against plug <NUM>. The movement of plug <NUM> with respect to port <NUM> is parallel to axis <NUM> and is the same or similar to the movement described above (including not being parallel in some examples). A variable volume chamber <NUM> is formed between piston <NUM>, sidewall <NUM>, and head portion <NUM>. Chamber <NUM> is in fluid communication with port <NUM>, dependent on the position of plug <NUM>. The movement of piston <NUM> or plug <NUM> toward or into port <NUM> reduces at least one flow area that feeds exiting fluid to port <NUM>. In this manner, piston <NUM> or plug <NUM> reduces or stops fluid communication from chamber <NUM> to port <NUM>, thereby reducing or dampening the speed of piston <NUM>.

The partial view of <FIG> presents an embodiment of the present invention, namely, a valve actuator <NUM>. Various embodiments of valve actuator <NUM> are compatible with valve <NUM> (<FIG>) to replace actuator <NUM>. Like actuator <NUM>, valve actuator <NUM> includes an actuation axis <NUM>, a housing <NUM>, a fluid port <NUM> in housing <NUM> and a piston <NUM>. Valve <NUM> also includes a conical or frustoconical plug <NUM>.

Housing <NUM> includes a side wall <NUM>, a head portion <NUM>, and the port <NUM> extending through head portion <NUM> parallel to axis <NUM> (or non-parallel in some embodiments). Piston <NUM> is disposed within housing <NUM> and configured for reciprocation along axis <NUM>. Piston <NUM> is coupled to a valve stem <NUM> as previously described. Plug <NUM> includes a cylindrical head <NUM> and a frustoconical body <NUM> that extend along a plug axis <NUM> centered with port <NUM>. Body <NUM> tapers in diameter as it extends away from head <NUM> and toward or into port <NUM>, and to the mounting mechanism in head portion <NUM> or further into port <NUM> (not shown). Plug <NUM> is mounted adjacent port <NUM> and is biased away from port <NUM> by a spring <NUM> or another resilient member. Plug <NUM> is mounted independently of piston <NUM>. Plug <NUM> is configured to reciprocate with piston <NUM> when piston <NUM> is adjacent port <NUM> and presses against plug <NUM>. The movement of plug <NUM> with respect to port <NUM> is parallel, or non-parallel, to axis <NUM> and is the same or similar to the movement described above for plugs <NUM>. A variable volume chamber <NUM> is formed between piston <NUM>, sidewall <NUM>, and head portion <NUM>. Chamber <NUM> is in fluid communication with port <NUM>, dependent on the position of plug <NUM>. As described above regarding area <NUM> in <FIG>, similarly, a flow area <NUM> extending between the perimeter of plug <NUM> and head portion <NUM> is reduced as plug <NUM> moves upward in <FIG>. Flow area <NUM> is located within chamber <NUM> and surrounds port area <NUM>. For convenience, flow area <NUM> may be considered to be cylindrical; although, any area between plug <NUM> and head portion <NUM> may be used. As shown in <FIG>, frustoconical body <NUM> is partially extends into port <NUM> and blocks a portion of flow area <NUM> even before piston <NUM> contacts or pushes plug <NUM>. When piston <NUM> pushes plug upward, body <NUM> blocks more and more of area <NUM>, also reducing this area. Eventually, plug <NUM> reaches its uppermost position, and head <NUM> contacts head portion <NUM> and may block entirely the flow area <NUM>. Thus, like the embodiments described above, the movement of piston <NUM> or plug <NUM> toward or into port <NUM> reduces a flow area that feeds exiting fluid to port <NUM>. More specifically, similar to the previous embodiments, the areas <NUM>, <NUM> are each reduced by the movement of piston <NUM> or plug <NUM>. In this manner, plug <NUM> is configured to reduce or stop fluid communication from chamber <NUM> to port <NUM>, thereby reducing or dampening the speed of piston <NUM>. In some embodiments of valve actuator <NUM>, flow area <NUM> is not entirely blocked when plug <NUM> is in its uppermost position. In some embodiments, during a portion of the cycle of actuator <NUM>, all of plug <NUM> is offset downward from area port <NUM>, and no portion of plug <NUM> blocks area <NUM> until piston <NUM> pushes plug <NUM> into area <NUM>.

<FIG> illustrates an example that does not fall within the scope of the present invention, namely, a valve actuator <NUM>. The valve actuator <NUM> is compatible with valve <NUM> to replace actuator <NUM>. Like various examples and embodiments of the invention described above, valve actuator <NUM> includes an actuation axis <NUM>, a housing <NUM>, and a piston <NUM>. Actuator <NUM> also includes a fluid port <NUM> in housing <NUM>, but port <NUM> is oriented differently than the port <NUM> described above. In the embodiment shown, actuator <NUM> lacks a plug to restrict flow into fluid port <NUM>.

Housing <NUM> includes a side wall <NUM>, a head portion <NUM>, and the port <NUM> extending through side wall <NUM> along a port axis <NUM> that is not parallel to axis <NUM>. In <FIG>, port axis <NUM> is perpendicular or generally tangential to axis <NUM>. Actuator <NUM> also includes a piston <NUM> that serves a similar purpose to piston <NUM> and is disposed within housing <NUM> and configured for reciprocation along axis <NUM>. Piston <NUM> includes a side wall comprising two portions. A lower, cylindrical sidewall portion <NUM>, and an upper, cylindrical sidewall portion <NUM> extends from portion <NUM> toward head portion <NUM>. Lower portion <NUM> slidingly engages housing sidewall <NUM> along with an embedded seal <NUM>. Upper portion <NUM> has a smaller diameter than lower portion <NUM>. Piston <NUM> at lower portion <NUM> is coupled to a valve stem <NUM> located opposite head portion <NUM>. A variable volume chamber <NUM> is formed between piston <NUM>, sidewall <NUM>, and head portion <NUM>. Chamber <NUM> is in fluid communication with port <NUM> through an inner flow area <NUM> extending generally perpendicular to port axis <NUM>, adjacent the inner surface of sidewall <NUM>. The extent of fluid communication between chamber <NUM> and port <NUM> depends on the position of piston <NUM>. Like the examples and embodiments of the invention described above, while piston <NUM> moves upward, toward head portion <NUM>, it reduces a flow area through which fluid from chamber <NUM> passes to reach port <NUM>. This reducing of flow area eventually reduces the volumetric flow rate of control fluid exiting chamber <NUM> through port <NUM>. The gradual blockage of port <NUM> and decline in volumetric flow rate slows and may ultimately stop the upward movement of piston <NUM>. By the time that piston <NUM> reaches its top-dead-center location, piston upper portion <NUM> faces a portion, a majority, or all of the port area <NUM>. Due to the smaller diameter of piston upper portion <NUM>, port <NUM> continues to have fluid communication with chamber <NUM> above piston <NUM> even when piston <NUM> reaches its top-dead-center. This state of continued fluid communication while piston <NUM> is at top-dead-center facilitates the reentry of working fluid into chamber <NUM> when an operator or a machine controller decides to push piston <NUM> down, as may be done to re-open a gate <NUM> that may be attached to piston <NUM> via stem <NUM>, for example.

<FIG> presents another example that does not fall within the scope of the present invention, namely, a valve actuator <NUM>. The valve actuator <NUM> is compatible with valve <NUM> to replace actuator <NUM>. Like actuator <NUM>, valve actuator <NUM> includes an actuation axis <NUM>, a housing <NUM>, and port <NUM> extending through housing sidewall <NUM> along a port axis <NUM> that is not parallel to axis <NUM>. Actuator <NUM> also includes a piston <NUM> that serves a similar purpose to piston <NUM>. In the example shown, actuator <NUM> lacks a plug to restrict flow into fluid port <NUM>.

Piston <NUM> extends along an axis <NUM> from a proximal end <NUM> (proximal relative to the location where bonnet <NUM> and valve body <NUM> would be attached) to a distal end <NUM> and includes a side wall comprising two portions. A lower, cylindrical sidewall portion <NUM> starts at end <NUM>, and an upper, frustoconical sidewall portion <NUM> extends from portion <NUM> to distal end <NUM>. Cylindrical portion <NUM> slidingly engages housing sidewall <NUM> along with an embedded seal <NUM>. Piston <NUM> is disposed within housing <NUM> and configured for reciprocation along axis <NUM>. Piston <NUM> is coupled to a valve stem <NUM> located opposite head portion <NUM> of housing <NUM>. A variable volume chamber <NUM> is formed between piston <NUM>, sidewall <NUM>, and head portion <NUM>. Chamber <NUM> is in fluid communication with port <NUM> through an inner flow area <NUM> extending generally perpendicular to port axis <NUM>, adjacent the inner surface of sidewall <NUM>. The extent of fluid communication between chamber <NUM> and port <NUM> depends on the position of piston <NUM>. While piston <NUM> moves upward, toward head portion <NUM>, frustoconical portion <NUM> reduces a flow area through which fluid from chamber <NUM> passes to reach port <NUM>. The reducing of flow area eventually reduces the volumetric flow rate of control fluid exiting chamber <NUM> through port <NUM>. The gradual blockage of port <NUM> and decline in volumetric flow rate slows the upward movement of piston <NUM>. In at least some embodiments, cylindrical portion <NUM> blocks some portion of port flow area <NUM> as piston <NUM> travels toward head portion <NUM>. When piston <NUM> comes to a stop adjacent head portion <NUM>, frustoconical portion <NUM> faces at least a portion of flow area <NUM> so that the recess allows fluid communication between chamber <NUM> and port <NUM>, and fluid communication is not entirely blocked. Even while piston <NUM> is at its top-dead-center location, this state of continued fluid communication exists between chamber <NUM> and port <NUM> due to the tapered side of frustoconical portion <NUM>. This state of continued fluid communication at top-dead-center facilitates the reentry of working fluid into chamber <NUM> when an operator or a machine controller decides to push piston <NUM> down.

<FIG> presents another example that does not fall within the scope of the present invention, namely, a valve actuator <NUM>. The valve actuator <NUM> is compatible with valve <NUM> to replace actuator <NUM>. Valve actuator <NUM> includes an actuation axis <NUM>, a housing <NUM>, a port <NUM> in housing <NUM>, a piston <NUM>, and a second stem <NUM>.

Housing <NUM> includes a side wall <NUM>, a head portion <NUM>, and the port <NUM> extending through head portion <NUM>, and a pocket structure or pocket <NUM> extending upward from portion <NUM>. Pocket <NUM> includes an inlet port <NUM> at proximal end and port <NUM> has a selected port diameter. Piston <NUM> is disposed within housing <NUM> and configured for reciprocation. A valve stem <NUM> is coupled to the proximal end <NUM> of piston <NUM> as previously described regarding valve <NUM> and actuator <NUM>. The second stem <NUM> is coupled to the distal end <NUM> of piston <NUM> and is aligned to reciprocate into and out from pocket <NUM>. Stem <NUM> includes a lower portion <NUM> extending from piston <NUM>, a tapered, central portion <NUM>, extending from portion <NUM>, and an upper portion <NUM> extending from central portion <NUM>.

A variable volume chamber <NUM> is formed between piston <NUM>, sidewall <NUM>, and head portion <NUM>. Chamber <NUM> is in fluid communication with port <NUM> and port <NUM> to provide or remove working fluid. A second chamber <NUM> extends within pocket <NUM>. Chamber <NUM> and chamber <NUM> are in fluid communication through port <NUM>, which includes a flow area <NUM> that extends across port <NUM>. In this exemplary embodiment, area <NUM> is flush with the inner surface of head portion <NUM>. The volume of chamber <NUM> varies depending on the amount of stem <NUM> that is positioned within pocket <NUM> as piston <NUM> reciprocates. As best shown in <FIG>, the diameter of the lower portion <NUM> of stem <NUM> is sized so as to be receivable within port <NUM> of pocket <NUM> while providing an annular flow area that allows, but restricts flow between pocket <NUM> and chamber <NUM>. Portions <NUM> and <NUM> have smaller diameters than lower portion <NUM>. Referring again to <FIG>, the movement of piston <NUM> and stem <NUM> toward head portion <NUM> and pocket <NUM> drives fluid out through port <NUM>. As stem <NUM> reaches and enters pocket <NUM>, some fluid in chamber <NUM> is forced to enter chamber <NUM> and drives fluid out through port <NUM>. In addition, the sequential movement of stem portions <NUM>, <NUM>, <NUM> into pocket <NUM> increasingly reduces the flow area <NUM>. Lower portion <NUM> creates the largest restriction to area <NUM>. The reductions of area <NUM> restrict the flow of fluid from chamber <NUM> to clamber <NUM>, creating a force against stem <NUM>, slowing the movement of piston <NUM>, and reducing the flow rate of fluid exiting through port <NUM>. The slowing movement of piston <NUM> would slow the movement of a valve gate coupled to valve stem <NUM>.

Various embodiments of the invention and other examples have been expressly presented. Multiple additional variations and uses are possible in accordance with the invention as defined in the claims. Additional embodiments may share compatible characteristics of one or more of the previously-described embodiments or those described below.

Although the various plugs <NUM>, <NUM> were described as being configured to close fully an exit port <NUM> and to stop the fluid communication between a chamber and port <NUM>, in some embodiments, a portion of a flow area continues to provide fluid communication between a chamber and port <NUM> even after the selected plug is fully seated against port <NUM>. The flow areas selected for discussion of the various embodiments are representative of many different flow areas that could be analyzed with similar conclusions. While the examples of <FIG> include a second stem <NUM> on piston <NUM> extending opposite valve stem <NUM>, and the embodiments of <FIG> and the examples of <FIG> were shown without a second stem <NUM>, various other embodiments based on any of the previously disclosed embodiments may either include or lack a second stem coupled for motion with the actuator as described above regarding second stem <NUM>. Valve actuator <NUM> of <FIG> is not intended to be fabricated without a second stem <NUM>. While some embodiments of the invention disclosed above were shown with a spring <NUM> biasing the piston upward and a coupled gate toward the open position and other embodiments were shown without such a resilient member, various other embodiments based on any of the previously disclosed embodiments may either include or lack a resilient member configured for biasing the positions of the piston and a gate. Some embodiments may combine multiple flow restrictions from two or more of the described embodiments to restrict flow of the working fluid in an actuator and slow the speed of the piston.

Claim 1:
A valve actuator (<NUM>, <NUM>) comprising:
an actuator housing (<NUM>) with a reciprocation axis (<NUM>);
a piston (<NUM>) configured to reciprocate within the actuator housing (<NUM>) along the reciprocation axis (<NUM>);
a port (<NUM>) in the actuator housing (<NUM>);
a chamber (<NUM>) disposed between the piston (<NUM>) and a portion of the actuator housing (<NUM>) with the port (<NUM>) for fluid communication with the port of a working fluid, the chamber defining a variable flow area; and
a plug (<NUM>, <NUM>) mounted independently of the piston (<NUM>) in the chamber (<NUM>) and biased away from the port (<NUM>) by resilient means , wherein the plug (<NUM>) is configured to reciprocate with the piston (<NUM>) when the piston (<NUM>) is adjacent the port (<NUM>) and pushes against the plug (<NUM>) to reduce the variable flow area (<NUM>, <NUM>) in the chamber (<NUM>) and cause a reduction in speed of the piston (<NUM>) prior to reaching a stop position;
wherein the plug (<NUM>) has a conical or frustoconical profile.