Patent Description:
When the valve is actuated, the spool shifts or moves axially within a bore in a valve body of the valve. As the spool moves, a variable area orifice is formed between a metering edge of the spool and the inner surface of the valve body. The size of the area of such variable area orifice depends on the extent of axial motion of the spool and the shape of the metering edge of the spool.

The shape and size of the variable area orifice controls the flow gain of the spool, where the flow gain is the change of fluid flow rate for a given axial movement of the spool. In some applications, it may be desirable to have a substantially-linear flow gain such that movement of the hydraulic actuator controlled by the valve is predictable. <CIT> discloses a valve spool that is described as having pocket like depressions and fluid guide surfaces that form a closed cosine-shaped curve along an outer circumference. <CIT> discloses a spool having sinusoidal notches.

The present disclosure describes implementations that relate to a proportional valve spool with linear flow gain. The invention is as set forth in the appended claims.

The foregoing summary is illustrative only. In addition to the illustrative aspects, implementations, and features described above, further aspects, implementations, and features will become apparent by reference to the figures and the following detailed description.

The illustrative examples, however, as well as a preferred mode of use, further objectives and descriptions thereof, will best be understood by reference to the following detailed description of an illustrative example of the present disclosure when read in conjunction with the accompanying Figures.

Hydraulic fluid flow in a hydraulic machine can be controlled using hydraulic control valves. A valve can include a valve body or housing having internal fluid passages, external ports, and a valve bore with a spool slidably-disposed within the valve bore. The valve is configured to control flow of fluid to and from a hydraulic actuator of the hydraulic machine.

The spool of the valve includes portions of differing diameter, such as a relatively smaller diameter portion (e.g., a neck portion) that acts as a flow area permitting flow of fluid across the spool, and a relatively larger diameter portion referred to as a land that restricts or blocks the flow of fluid across the spool, thereby controlling the flow of fluid through the valve. The spool can have a plurality of lands that interface with inner surfaces of the valve body to control fluid flow.

Particularly, the land can have an edge that can be referred to as a metering edge, and when the valve is actuated and the spool shifts within the spool bore a variable area orifice is formed between the metering edge and the inner surface of the valve body. The variable area orifice allows fluid flow therethrough. As the spool moves axially within the valve bore, the variable area of the orifice changes, thereby changing the fluid flow rate. The flow gain of the valve, i.e., the change in fluid flow rate through the valve for a given axial movement of the spool within the valve bore, is determined based on the change in the area of the orifice as the spool moves axially.

The spool can include one or more metering notches formed in the land, and such metering notches are configured to control fluid flow from a source of fluid into a downstream flow passage. The shape, depth, and number of the metering notches determine the flow gain of the spool.

In some applications, it may be desirable to have a substantially-linear flow gain such that movement of the hydraulic actuator controlled by the valve is predictable. Such substantially-linear flow characteristics may also provide for easier controller tuning. A nonlinear flow gain indicates that a given axial movement distance of the spool corresponds to a different amount of change in fluid flow rate based on where the spool is in its stroke. In other words, the flow rate through the valve versus the axial movement of the spool follows a nonlinear curve. In contrast, a linear flow gain indicates that the change in fluid flow rate versus the axial movement of the spool follows a substantially-straight line. Particularly, for a given axial distance of spool movement, the change in the fluid flow rate is consistent regardless of where the spool is in its stroke. Throughout this disclosure, the term "substantially-linear flow gain" indicates that the fluid flow rate of the valve versus the stroke of the spool follows a substantially-straight line, such that the flow rate can deviate from the line by no more than a threshold value (e.g., between <NUM>% and <NUM>% of maximum flow).

In one example, complex-shaped notches can be formed in the land to achieve a linear flow gain. Such complex notches can be formed in the spool via expensive machining techniques such as electrical discharge machining (EDM). Such manufacturing techniques can be costly. It may thus be desirable to have a spool that can achieve a substantially-linear flow gain using simpler notch shapes that are not complex to machine.

Disclosed herein are spools, valves, and systems that achieve substantially-linear flow gain. Particularly, an example spool has at least one annular metering land comprising one or more sine notches and one or more additional notches that have a different shape (e.g., generally square or triangular notches) from the at least one sine notch. The combination of the sine notch and the additional notch can achieve linear flow characteristics as described below.

<FIG> illustrates a partial, schematic representation of a hydraulic system <NUM>, in accordance with an example implementation. <FIG> particularly illustrates a partial, perspective cross-sectional view of a valve <NUM> that is configured to control movement of a hydraulic actuator <NUM> by controlling fluid flow to and from the hydraulic actuator <NUM>.

The hydraulic system <NUM> includes a source <NUM> of fluid. The source <NUM> of fluid can be a pump (e.g., fixed displacement, variable displacement pump, a load-sense variable displacement pump, etc.), or an accumulator, as examples. A pump can receive fluid from a fluid tank or fluid reservoir <NUM> of the hydraulic system <NUM>, and the source <NUM> then pushes the fluid to the valve <NUM>.

The valve <NUM> has a valve body <NUM> that defines multiple fluid passages, cavities, and bores therein. Such fluid passages, cavities, and bores are fluidly coupled to various components of the hydraulic system <NUM> such as the source <NUM>, the fluid reservoir <NUM>, and the hydraulic actuator <NUM>.

In the example implementation of <FIG>, the hydraulic actuator <NUM> includes a cylinder <NUM> and a piston <NUM> slidably accommodated within the cylinder <NUM>. The term "slidably accommodated" is used throughout herein to indicate that a first component (e.g., the piston <NUM>) is positioned relative to a second component (e.g., the cylinder <NUM>) such that the first component is able to move relative to the second component.

The piston <NUM> includes a piston head <NUM> and a piston rod <NUM> extending from the piston head <NUM> along a central longitudinal axis direction of the cylinder <NUM>. The piston head <NUM> divides the inside or internal space of the cylinder <NUM> into a chamber <NUM> and a chamber <NUM>. The chamber <NUM> can be referred to as a cap chamber or head chamber, whereas the chamber <NUM> can be referred to as a rod chamber.

The valve <NUM> includes a workport <NUM> that is fluidly coupled (e.g., via a fluid lines such as a hose or tube) to the chamber <NUM> of the hydraulic actuator <NUM>, and the valve <NUM> also includes a workport <NUM> that is fluidly coupled to the chamber <NUM> of the hydraulic actuator <NUM>. Fluid lines are represented in <FIG> with dashed arrows. The valve <NUM> is configured to control supply fluid flow from the source <NUM> to the workports <NUM>, <NUM>, and control return fluid flow from the workports <NUM>, <NUM> to the fluid reservoir <NUM>.

The valve <NUM> has a spool <NUM> slidably accommodated (i.e., axially movable) in a longitudinal bore <NUM> formed in the valve body <NUM>. The spool <NUM> can be configured to be biased to a neutral or centered position by springs (not shown) disposed at the ends of the spool <NUM>.

<FIG> illustrates a cross-sectional view of the valve <NUM> shown in <FIG>, in accordance with an example implementation. <FIG> shows the spool <NUM> in a neutral position. When the spool <NUM> is in a neutral position, the spool <NUM> blocks fluid flow from the source <NUM> to the workports <NUM>, <NUM>. The term "block" is used throughout herein to indicate substantially preventing fluid flow except for minimal or leakage flow of drops per minute, for example.

The spool <NUM> can be actuated in either direction from the neutral position via various types of mechanisms. As an example for illustration, the spool <NUM> can be controlled by pilot valves such as pilot valves <NUM>, <NUM> shown as blocks in <FIG>.

In an example, the pilot valves <NUM>, <NUM> are solenoid-operated. In one example, the pilot valves <NUM>, <NUM> can be configured as pressure reducing valves that receive pressurized fluid from the source <NUM> then generate a pilot fluid signal that is proportional to a magnitude of an electric command provided to a respective solenoid of the pilot valves <NUM>, <NUM>. In another example, the pilot valves <NUM>, <NUM> are hydro-mechanical valves that are manually controlled by joysticks or levers to provide the pilot fluid signal.

When actuated, the pilot valve <NUM> provides the pilot fluid signal to a pilot fluid passage <NUM> that communicates the pilot fluid signal to a first pilot cavity <NUM> at a first end of the spool <NUM>. The pilot fluid signal in the first pilot cavity <NUM> applies a fluid force on a pilot land <NUM> of the spool <NUM> to shift the spool <NUM> in a first direction (to the left in <FIG>).

The pilot valve <NUM> can be configured similar to the pilot valve <NUM> and is configured to provide, when actuated, a pilot fluid signal to a pilot fluid passage <NUM> that communicates the pilot fluid signal to a second pilot cavity <NUM> at a second end of the spool <NUM>. The pilot fluid signal in the second pilot cavity <NUM> applies a fluid force on a pilot land <NUM> the spool <NUM> to shift the spool <NUM> in a second direction (to the right left in <FIG>) opposite the first direction.

Supply fluid provided from the source <NUM> is provided through an inlet port of the valve <NUM> to a supply cavity <NUM> formed within the valve body <NUM> of the valve <NUM>. When the spool <NUM> moves axially in either direction, a variable metering orifice is formed as described below to allow fluid to flow from the supply cavity <NUM> to one of the workports <NUM>, <NUM>.

The spool <NUM> varies in diameter along its length to form annular metering lands separated by respective reduced diameter annular neck portions (also referred to as undercuts), thereby selectively interconnecting the various passages intercepting the longitudinal bore <NUM> to control flow of fluid to and from the workports <NUM>, <NUM> as the spool <NUM> shifts axially. The term "annular metering land" is used herein to indicate a generally cylindrical spool body portion having a larger diameter compared to the reduced diameter annular neck portions that separate the lands from each other. The annular metering lands of the spool <NUM> cooperate with internal surfaces of the valve body <NUM> to define variable metering orifices that allow fluid flow therethrough. For example, the spool <NUM> has annular metering land <NUM>, annular metering land <NUM>, annular metering land <NUM>, and annular metering land <NUM> configured to cooperate with the internal surfaces of the valve body <NUM> to form the variable metering orifices and control the fluid flow rate and direction through the valve <NUM>. The annular metering lands <NUM>-<NUM> each has a first diameter, and they are separated from each other by reduced diameter annular neck portions having a second diameter that is smaller than the first diameter. With this configuration, annular grooves are formed between each two adjacent annular metering lands of the annular metering lands <NUM>-<NUM>.

Each land of the annular metering lands <NUM>-<NUM> can block a respective fluid passage in the valve body <NUM> when the spool <NUM> is in the neutral position shown in <FIG>. As the spool <NUM> shifts, a metering edge of a subset of the annular metering lands <NUM>-<NUM> moves past an edge of a respective internal surface bounding a fluid passage in the valve body <NUM> to form a variable metering orifice. The term "variable metering orifice" is used herein to indicate a spool-to-bore cylindrical area opening that forms between an annular metering land of the spool <NUM> and the internal surfaces of the valve body <NUM> when the spool <NUM> shifts axially therein. Thus, the variable metering orifice is a flow area that forms between the spool <NUM> and the internal surface of the valve body <NUM>, and the flow area varies in size based on the axial position of the spool <NUM> within the longitudinal bore <NUM>, e.g., the farther the spool <NUM> shifts axially, the larger the flow area.

The valve <NUM> has a return cavity <NUM> and a return cavity <NUM> that are fluidly coupled to each other via fluid passage <NUM> and are both fluidly coupled to the fluid reservoir <NUM>. The fluid reservoir <NUM> is drawn in two locations on <FIG> to reduce visual clutter but it should be understood that the return cavities <NUM>, <NUM> are fluidly coupled to an outlet port of the valve <NUM>, and the outlet port is fluidly coupled to the fluid reservoir <NUM>.

The valve <NUM> has a workport passage <NUM> that is fluidly coupled to the workport <NUM>. The valve <NUM> also has a workport passage <NUM> that is fluidly coupled to the workport <NUM>. When the spool <NUM> is in the neutral position shown in <FIG>, fluid flow to the various cavities and passages can be blocked. Particularly, the annular metering land <NUM> blocks fluid flow from the supply cavity <NUM> to the workport passage <NUM>, the annular metering land <NUM> blocks fluid flow from the supply cavity <NUM> to the workport passage <NUM>, the annular metering land <NUM> blocks fluid flow from the workport passage <NUM> to the return cavity <NUM>, and the annular metering land <NUM> blocks fluid flow from the workport passage <NUM> to the return cavity <NUM>. As such, the piston <NUM> of the hydraulic actuator <NUM> might not move when the spool <NUM> is in the neutral position.

Referring to <FIG>, actuating the pilot valve <NUM> or pilot valve <NUM> causes the spool <NUM> to move axially, thereby providing fluid flow to the hydraulic actuator <NUM> to move the piston <NUM>. For instance, if the pilot valve <NUM> is actuated and the spool <NUM> shifts axially to the left in <FIG>, the annular metering land <NUM> can move to the extent that it moves past an edge of the internal surface of the valve body <NUM> interfacing therewith. As a result, a metering orifice is formed (as depicted in <FIG>), allowing fluid flow from supply cavity <NUM> to the workport passage <NUM>.

The workport passage <NUM> is fluidly coupled to the workport <NUM>, and thus fluid flows through the workport passage <NUM> to the workport <NUM>, and then to the chamber <NUM> of the hydraulic actuator <NUM> to retract the piston <NUM> (e.g., move the piston <NUM> to the right in <FIG>). Fluid discharged from the chamber <NUM> of the hydraulic actuator <NUM> flows through the workport <NUM> and the workport passage <NUM>, then through another metering orifice formed between the annular metering land <NUM> and the internal surface of the valve body <NUM> (as depicted in <FIG>) to the return cavity <NUM>, which is fluidly coupled to the fluid reservoir <NUM>.

On the other hand, if the pilot valve <NUM> is actuated and the spool <NUM> shifts axially to the right in <FIG>, the annular metering land <NUM> can move to the extent that it moves past an edge of the internal surface of the valve body <NUM> interfacing therewith. As a result, a metering orifice is formed, allowing fluid flow from the supply cavity <NUM> to the workport passage <NUM>. The workport passage <NUM> is fluidly coupled to the workport <NUM>, and thus fluid flows through the workport passage <NUM> to the workport <NUM>, and then to the chamber <NUM> of the hydraulic actuator <NUM> to extend the piston <NUM> (e.g., move the piston <NUM> to the left in <FIG>). Fluid discharged from the chamber <NUM> of the hydraulic actuator <NUM> flows through the workport <NUM> and the workport passage <NUM>, then through another metering orifice formed between the annular metering land <NUM> and the internal surface of the valve body <NUM> to the return cavity <NUM>, which is fluidly coupled to the fluid reservoir <NUM>.

In some applications, it may be desirable to have a linear relationship between axial movement of the spool <NUM> and the amount of fluid flow rate provided to or from a workport of the workports <NUM>, <NUM>. Such linearity may render the performance of the valve <NUM> predictable. It may thus be desirable to configure the spool <NUM> to provide such linear relationship between its axial movement and the amount of fluid flow rate provided to and from the workports <NUM>, <NUM>. It may also be desirable to configure the spool <NUM> as such in a cost-effective way that does not involve expensive manufacturing techniques such as EDM.

<FIG> illustrates a perspective view of the spool <NUM>, <FIG> illustrates a side elevational view of the spool <NUM>, <FIG> illustrates a cross-sectional view of the spool <NUM> taken along section line A-A shown in <FIG>, in accordance with an example implementation. The spool <NUM> has a cylindrical spool body or shaft <NUM> that varies in diameter along its length to form the pilot lands <NUM>, <NUM> and the annular metering lands <NUM>-<NUM> separated by reduced diameter neck portions as described above. Particularly, the annular metering lands <NUM>, <NUM> form a first pair of opposed annular lands formed on the shaft <NUM> and spaced-apart by a first reduced diameter annular neck portion <NUM>. Similarly, the annular metering lands <NUM>, <NUM> form a second pair of opposed annular lands formed on the shaft <NUM> and spaced-apart by a second reduced diameter annular neck portion <NUM>.

Each of the annular metering lands <NUM>-<NUM> has a first plurality of notches formed as a portion of a sine wave and a second plurality of notches having a different shape disposed in a circular array about a circumference of the annular metering land. The first plurality of notches are interleaved with the second plurality of notches about a circumference of the respective annular land. As a particular example, each annular land can have a pair of sine notches and a pair of notches that have a different shape, e.g., having a generally square-shaped notch.

The term "plurality of notches" is used herein to indicate one or more notches. The term "sine notch" is used herein to refer to notch shaped as a portion of a geometric sine waveform formed along a portion of a meter edge of an annular metering land. Also, the term "interleaved" is used here to indicate that one of the sine notches is circumferentially-interposed between two notches having a different shape (i.e., are not shaped as sine notches), and similarly, each of the notches having the different shape is circumferentially-interposed between two sine notches.

For example, the annular metering land <NUM> has two sine notches and two additional notches having a different shape. Particularly, the annular metering land <NUM> has a first sine notch <NUM> formed in a proximal metering edge <NUM> of the annular metering land <NUM> and has a second sine notch <NUM> formed in the proximal metering edge <NUM> diametrically-opposite from the first sine notch <NUM>.

The annular metering land <NUM> further has a first square notch <NUM> circumferentially-interposed between the first sine notch <NUM> and the second sine notch <NUM>. The annular metering land <NUM> also has a second square notch <NUM> diametrically-opposite from the first square notch <NUM> and interposed circumferentially between the first sine notch <NUM> and the second sine notch <NUM>.

The annular metering land <NUM> is configured similar to the annular metering land <NUM>, with the respective sine notches being formed in the distal metering edge rather than a proximal metering edge. In other words, the notches of the annular metering land <NUM> face in an opposite direction compared to the notches of the annular metering land <NUM>. For example, the annular land <NUM> has a first sine notch <NUM>, a second sine notch <NUM>, a first square notch <NUM>, and a second square notch <NUM> (shown in <FIG>). The other pair of annular metering lands, i.e., the annular metering lands <NUM>, <NUM>, is configured similar to the annular metering lands <NUM>, <NUM>.

Advantageously, sine notches can be formed in a cost-effective manner, e.g., via milling. Further, sine notches are characterized by having a large flow area gradient versus axial movement of the spool <NUM>. In other words, a small stroke or axial movement of the spool <NUM> exposes a large flow metering area due to the geometric shape of a sine notch. However, having the sine notches by themselves, i.e., the sine notches <NUM>, <NUM> without the square notches <NUM>, <NUM>, might not be sufficient to provide linear flow relationship.

<FIG> illustrates a graph <NUM> showing flow area characteristics of a spool with sine notches compared to substantially-linear flow area characteristics. The y-axis in the graph <NUM> represents flow area through a spool and the x-axis represents axial movement or stroke of the spool as a percentage of maximum stroke. Line <NUM> represents variation in flow area versus stroke of the spool. As an example, the line <NUM> may represents variation in flow area formed between sine notches similar to the sine notches <NUM>, <NUM> and the internal surfaces of the valve body <NUM> (assuming the annular metering land <NUM> only has the sine notches <NUM>, <NUM> without the square notches <NUM>, <NUM>) as the spool <NUM> moves axially in the distal direction. Line <NUM> represents substantially-linear variation in a flow area versus the stroke of a spool and is used to benchmark linearity of the spool associated with the line <NUM>.

As depicted, a spool with just sine notches as represented by the line <NUM> does not provide linear flow characteristics as represented by the line <NUM>. Vertical dashed arrows depicted in the graph <NUM> represent the additional flow area required to make up for the difference between the line <NUM> and the line <NUM>. Advantageously, while some conventional spools have many notches disposed about the entire circumference of a land of the spool to provide a particular flow area, a sine notch can provide the same flow area without occupying the entire circumference of the land. As such, there is enough room along a circumference of the land to form additional notches, such as the square notches <NUM>, <NUM>, and provide additional flow area that can make up for the flow area difference between the line <NUM> and the line <NUM>. Particularly, the geometry of the additional notches, e.g., the square notches <NUM>, <NUM>, can be adjusted in a "tuning" process to provide the appropriate amount of additional flow area such that the spool <NUM> provides a linear flow gain as the spool <NUM> moves axially within the valve body <NUM>.

<FIG> illustrates a graph <NUM> showing flow characteristics of different spools. The y-axis in the graph <NUM> represents flow rate as a percentage of maximum flow rate for a particular pump flow capacity and the x-axis represents commanded voltage to a solenoid that actuates the spool as a percentage of maximum command. A positive voltage indicates a voltage to a first solenoid that, when actuated, moves the spool in a given direction allowing flow from an actuator to the fluid reservoir through the valve (i.e., negative flow), whereas and a negative voltage indicates a voltage to a second solenoid that, when actuated, moves the spool in an opposite direction allowing flow from the source of fluid to the actuator through the valve (i.e., positive flow).

The graph <NUM> illustrates experimental results of flow gain characteristics for various spool configurations. Particularly, the graph <NUM> has four line plots corresponding to four different spool configurations. Line <NUM> represents a benchmark spool having substantially-linear flow characteristics. For example, the benchmark spool may be an expensive spool that can provide substantially-linear flow. Line <NUM> represents a spool that has sine notches only, without additional notches, and providing non-linear flow characteristics. For example, the line <NUM> can correspond to the spool associated with the line <NUM> of <FIG>.

Lines <NUM>, <NUM> represent respective spools that having sine notches as well as additional notches to make up for the flow difference between the line <NUM> and the line <NUM>. <FIG> illustrates a partial view of a spool <NUM> associated with line <NUM>, and <FIG> illustrates a partial view of a spool <NUM> associated with line <NUM>, in accordance with example implementations. The spools <NUM>, <NUM> are variations of the spool <NUM>. Notably, in the graph <NUM>, flow rate tapers off near the end of stroke (i.e., at maximum command) due to the maximum available pump flow used in the experiments, and is not due to the geometry of the spools. Flow rates would be expected to continue with a greater pump flow.

Referring to <FIG>, in addition to respective sine notches, the spool <NUM> has an annular metering land <NUM> (e.g., representing the annular metering land <NUM>) having a square notch <NUM> with a width Y, whereas the spool <NUM> has an annular metering land <NUM> (e.g., representing the annular metering land <NUM>) having a square notch <NUM> with a width X. As illustrated by <FIG>, Y is greater than X.

As illustrated by the lines <NUM>, <NUM> in <FIG>, the spools <NUM>, <NUM> provide make up flow relative to the spool associated with the line <NUM>. However, the line <NUM> indicates that the width Y is larger than required and the make-up flow rate of the spool <NUM> is larger than the amount required to match the benchmark spool represented by the line <NUM>. The line <NUM> of the spool <NUM> with the smaller width X is closer to the line <NUM> of the benchmark spool. As such, the graph <NUM> illustrates that the width or other geometric characteristics of the square notch can be "tuned" to provide substantially-linear flow characteristics similar to the line <NUM>. For instance, a third width Z that is smaller than X might move the flow curve even closer to the line <NUM> of the benchmark spool.

The square notches <NUM>, <NUM>, <NUM>, <NUM>, <NUM> described above can be referred to as "generally" square notches as they may have radiuses at respective corners. For example, as shown in <FIG>, the square notch <NUM> has corners with radii <NUM>, <NUM> as opposed to sharp corners. Further, while the notches added to the sine spool to make up for the flow difference and achieve substantially-linear flow characteristics are shown and described as square notches, other geometries can be used to provide a linear flow gain.

<FIG> illustrates a perspective view of a spool <NUM> having sine notches and triangular notches, in accordance with an example implementation. The spool <NUM> is similar to the spool <NUM> in that it has four annular metering lands having sine notches. The spool <NUM> differs from the spool <NUM> in that the metering lands have additional notches that are generally triangular as opposed to being generally square.

For example, annular metering land <NUM> has a sine notch <NUM> (and a corresponding sine notch diametrically-opposite from the sine notch <NUM>) and has a triangular notch <NUM>. In an example, the annular metering land <NUM> has another triangular notch <NUM> diametrically-opposite from the triangular notch <NUM>.

Other shapes and configuration (e.g., geometries) of additional notches (other than the sine notches) can be used. For example, an additional notch can comprise a first portion have a first depth followed by, or contiguous to, a second portion have a second depth. Each portion may have a different geometric shape.

In another example, the additional notches (other than the sine notches) are not shaped similarly. For instance, the shape of the additional notches of the same annular metering land may differ (e.g., one notch is generally square, while another is generally triangular). In one example, the additional notches can be same on one metering land, but differ from additional notches of another metering land.

Further, although the four annular metering lands of the spools <NUM>, <NUM> are configured in the same manner, in other example implementations, not all metering lands are configured similarly. For example, at least one metering land may be configured to have sine notches and additional notches to achieve a linear flow gain, while other metering lands are not configured in that manner.

<FIG> is a flowchart of a method <NUM> for making a spool of a valve, in accordance with an example implementation. For example, the method <NUM> can be implemented to make the spool <NUM> or the spool <NUM>.

The method <NUM> may include one or more operations, or actions as illustrated by one or more of blocks <NUM>-<NUM>. Although the blocks are illustrated in a sequential order, these blocks may also be performed in parallel, and/or in a different order than those described herein. Also, the various blocks may be combined into fewer blocks, divided into additional blocks, and/or removed based upon the desired implementation. It should be understood that for this and other processes and methods disclosed herein, flowcharts show functionality and operation of one possible implementation of present examples. Alternative implementations are included within the scope of the examples of the present disclosure in which functions may be executed out of order from that shown or discussed, including substantially concurrent or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art.

At block <NUM>, the method <NUM> includes providing a shaft (e.g., the shaft <NUM>) of the spool (e.g., the spool <NUM>, <NUM>, <NUM>, <NUM>).

At block <NUM>, the method <NUM> includes forming a plurality of annular lands on the shaft such that the plurality of annular lands are spaced-apart by respective reduced diameter annular neck portions, wherein the plurality of annular lands comprise at least one annular metering land (e.g., any of the annular metering lands <NUM>-<NUM>, <NUM>, <NUM>, <NUM>).

At block <NUM>, the method <NUM> includes forming one or more sine notches shaped as a portion of a sine wave (e.g., any of the sine notches <NUM>, <NUM>, <NUM>, <NUM>).

At block <NUM>, the method <NUM> includes forming one or more additional notches (e.g., the square notches <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or the triangular notch <NUM>) having a different shape from the one or more sine notches.

The method <NUM> can further include any of the operations described throughout the disclosure.

The detailed description above describes various features and operations of the disclosed systems with reference to the accompanying figures. The illustrative implementations described herein are not meant to be limiting. Certain aspects of the disclosed systems can be arranged and combined in a wide variety of different configurations, all of which are contemplated herein.

Thus, the figures should be generally viewed as component aspects of one or more overall implementations, with the understanding that not all illustrated features are necessary for each implementation.

Further, devices or systems may be used or configured to perform functions presented in the figures. In some instances, components of the devices and/or systems may be configured to perform the functions such that the components are actually configured and structured (with hardware and/or software) to enable such performance. In other examples, components of the devices and/or systems may be arranged to be adapted to, capable of, or suited for performing the functions, such as when operated in a specific manner.

By the term "substantially" or "about" it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

The arrangements described herein are for purposes of example only. As such, those skilled in the art will appreciate that other arrangements and other elements (e.g., machines, interfaces, operations, orders, and groupings of operations, etc.) can be used instead, and some elements may be omitted altogether according to the desired results. Further, many of the elements that are described are functional entities that may be implemented as discrete or distributed components or in conjunction with other components, in any suitable combination and location.

Claim 1:
A spool (<NUM>, <NUM>, <NUM>, <NUM>) configured to be movable in a longitudinal bore (<NUM>) of a valve (<NUM>), the spool (<NUM>, <NUM>, <NUM>, <NUM>) comprising:
a shaft (<NUM>) varying in diameter along a length of the shaft (<NUM>); and
a plurality of annular lands (<NUM>, <NUM>, <NUM>, <NUM>) formed on the shaft (<NUM>) and spaced-apart by respective reduced diameter annular neck portions (<NUM>, <NUM>), wherein the plurality of annular lands (<NUM>, <NUM>, <NUM>, <NUM>) comprise at least one annular metering land (<NUM>, <NUM>, <NUM>, or <NUM>), and wherein one or more of the the at least one annular metering land (<NUM>, <NUM>, <NUM>, or <NUM>) comprises:
a plurality of sine notches (<NUM>, <NUM> or <NUM>, <NUM>) formed as a portion of a sine wave, and
a plurality of additional notches (<NUM>, <NUM> or <NUM>, <NUM>) having a different shape from the a plurality of sine notches (<NUM>, <NUM> or <NUM>, <NUM>), wherein the plurality of sine notches (<NUM>, <NUM> or <NUM>, <NUM>) and the plurality of additional notches (<NUM>, <NUM> or <NUM>, <NUM>) are disposed in a circular array about a circumference of the at least one annular metering land (<NUM>, <NUM>, <NUM>, or <NUM>), and wherein the plurality of sine notches (<NUM>, <NUM> or <NUM>, <NUM>) are interleaved with the plurality of additional notches (<NUM>, <NUM> or <NUM>, <NUM>), about the circumference of the respective annular metering land, such that each sine notch is circumferentially-interposed between two additional notches (<NUM>, <NUM> or <NUM>, <NUM>).