TECHNICAL FIELD The present disclosure relates to valves and, in particular, to control valves that control the pressure reduction of high pressure fluids. Specifically, the disclosure relates to trims disposed in the valves and through which the fluid flows. The disclosure also relates to method of forming the trims in a cost effective manner. BACKGROUND ART

Control valves act as a variable resistance within a pipeline, and it is this function that differentiates them from shut off valves, which are normally in either the closed or full open positions. On the basis of this function, control valves are a mechanism for dissipating energy; when the pressure is dropped across the system and the excess fluid energy is dissipated through noise, heat and vibration.

Owing to the applications in which control valves are used, considerable design work goes in to configuring trims with the aim of being able to:

• Reduce erosion - for example in flashing liquids and in multi-phase

applications (such as wet gases or fluids with entrained solids);

• Reduce or avoid cavitation - when the pressure drops below the vapour

pressure of the liquid, vapour bubbles are formed which collapse and reduces valve's remaining useful life; and

• Reducing noise - typically gases, or cavitating fluids. The solution to these problems has been to divide the flow of high pressure fluid through the control valve into multiple separate streams, each of which is in the form of a tortuous path. The fluid pressure and energy of the fluid is partially dissipated along such paths as a result of losses caused by friction between walls of the path, rapid changes in fluid direction and as a result of flowing through a series of expansion or contraction chambers.

In one form, the trim comprises multiple concentric cylindrical sleeves and is known as a cage. Specifically, the sleeves are radially perforated with the perforations of adjacent sleeves being offset to cause the fluid to flow in a tortuous path. The sleeves may be separated by intermediate annular passages which allow the fluid passing therethrough to expand before it then has to contract to pass through the perforations of the next sleeve. The specific geometric arrangement of such designs can be configured as desired to allow the pressure of the fluid of each stream to drop in relatively small increments and in many stages. In another form, the trim takes the form of a stack of discs where the fluid path is machined into one or both facing surfaces of adjacent discs. An example of a disc stack is disclosed in PCT/GBOl/01124 (Morton - published as WO01/69114) in the name of the Hopkinsons Limited (which is the same entity as the present applicant, following a name change). As shown in Figures 3 and in Figures 5 to 7, each disc in the stack is formed as an annulus and includes four independent channels that permit fluid to flow from an outer perimeter of the plate to an interior cavity where fluid from each of the four channels (and the channels of all of the stacked plates) combines into a single outflow from the control valve. Each channel on each disc is formed with a series of concentrically disposed arrays of columnar obstructions. As a consequence, the fluid has several alternative flow paths through the channel. Morton states that the separate and discrete flow obstructions (i.e. obstructing members) "serve to separate incident fluid into separate streams that then pass around the obstructing member and recombine downstream before being separated again when incident on an obstructing member in a subsequent row. The separation and convergence of the flow together with the usual frictional drag effects cause a smooth pressure drop and therefore energy reduction in the fluid. By increasing the number of rows the repeated separation and convergence imparts a greater pressure reduction. In a preferred embodiment the flow obstructing members of one row are offset laterally from those of an adjacent row in the direction of fluid flow. This arrangement is designed to ensure that the downstream flows of fluid from one row are directed to be incident directly on the obstructing members of the subsequent row. The separation and convergence of the flow together with the usual frictional drag effects causes a smooth pressure drop and therefore energy reduction in the fluid. By increasing the number of rows, the repeated separation and convergence imparts a greater pressure reduction."

Although the discs disclosed in Morton provide a number of functional advantages in terms of reducing erosion, cavitation and noise, the plates are manufactured by EDM (electric discharge machining) which is a thermal erosion process where metal is removed by a series of electric discharges between an electrode and a conductive work piece, all in the presence of a dielectric liquid. The discharge results due to a voltage gap between the electrode and the work piece. Heat from the spark erodes small particles of the piece of material, which are then removed by flushing the liquid.

EDM allows discs to be prepared to a high degree of specificity as required by industry for specific valve conditions and applications. In that sense, the designs of the discs in Morton is adaptable for those conditions and applications and the EDM process is versatile for providing custom design solutions. However, EDM can be quite costly, especially when increasing the number of stages or the capacity of the disc. Furthermore, EDM has relatively long lead times (of up to 10 weeks per disc), limiting the delivery times for original equipment, and also spares replacements.

In regard to increasing capacity, the applicant has been investigating trim design that expand the width of the flow paths in each disc. However, the applicant is cognizant that expanding the width of the flow paths add the amount of material that must be removed from each disc and, therefore, the increasing in production times and production costs if EDM is used to produce the discs.

There is a need, therefore, to reduce the production time for manufacturing trims in order to better meet industry demand. It would be desirable to produce trims more cost effectively than EDM.

SUMMARY OF THE DISCLOSURE

The applicant has identified additive layer manufacturing (ALM - also known as 3D printing) as an option for reducing production times. However, the applicant has further identified that ALM can be used to print entire stacks of discs in a unitary construction. This means that, in addition to reducing production times, the trim can be produced as a single unit in a form ready for service or in a form close to the final form ready for service. In other words, the more costly and time consuming process of preparing the trim via EDM can be replaced with considerably faster production techniques.

The applicant anticipates that production times of approximately 10 weeks for a single disc using EDM can be reduced to less than two weeks for an entire trim. The bulk of the production process, being the raw production of the entire trim, is expected to be less than 48 hours, and in some cases may be less than 20 hours. While finishing steps may be required to take the raw trim to a final form ready for service, the finishing steps are expected to take less than 2 weeks and most likely less than 1 week.

The particular ALM technique identified by the applicant is selective laser melting (SLM). It will be appreciate, however, that alternative ALM techniques may be used in place of SLM to achieve the same result. Accordingly, this disclosure is not limited to SLM and, therefore, other ALM techniques should be understood as being applicable to the concepts and trim designs disclosed or otherwise contemplated by the disclosure. Adopting SLM to prepare trims is not straightforward because of the problem of printing levels of the trim over the flow paths. Specifically, the flow paths are vacant spaces in the final trim, but in the production process metallic powder must be deposited onto a surface so that it can be melted by a laser and thereby extend the surface. Forming a new level between flow paths (i.e. the equivalent of a floor of a disc in a trim comprising a stack of discs) requires a modified approach to SLM.

To deal with this problem, it has been identified that printing the trim by SLM can be achieved by printing the trim on an angle. In other words, the normal operating orientation of the trim is inclined to horizontal so that the levels are printed gradually from one side the trim to the other side of the trim.

It has further been identified that printing on the angle is facilitated by adopting a non-flat floor to each level of the trim. More specifically, it has been identified that a ripple profile comprising a sinusoidal form, a concertina form or a scalloped form extending through the flow channel facilitates printing by SLM. More specifically, the ripple profile is selected to be hydrodynamically smooth and to provide sufficient gaps between floors such that flow is not restricted in certain paths. If flow is restricted, then the flow is preferentially directed to larger flow paths through which lower pressure drops and lower flow velocities occur. While preferential flow paths have a lower potential for cavitation and erosion, the trim has a reduced overall flow capacity.

Accordingly, in a first aspect, the present disclosure provides a trim or a trim segment for a control valve, the trim or the trim segment having:

(a) an inlet and an outlet,

(b) a fluid flow passage extending between the inlet and the outlet and divided by a series of vertically spaced platforms, and

(c) flow obstruction members extending generally vertically within the flow

passage between adjacent platforms so as to define a series of fluid flow paths that change the condition of a fluid flowing through the trim or trim segment; and wherein the platforms have a non-flat profile so that the flow paths include lateral and vertical changes of direction.

As a result of designing trim and trim segments that are suitable for production by SLM, the applicant arrived at a trim and trim segment design that has a non-flat profile for the platform that divides the flow passage. The applicant understands that the non-flat platform profile is advantageous because it provides a smoother flow for fluid, thereby reducing cavitation and erosion and increasing the fluid flow capacity of the trim.

The non-flat platform profile may be a ripple profile extending from the outlet of the flow passage to the inlet of the flow passage.

The ripple profile may be a concertina profile, a sinusoidal wave profile or a scalloped profile.

The trim may be an annulus and the ripple profile may radiate through the platforms from a central vertical axis of the trim. The trim segment may be a segment of an annular trim and the ripple profile may radiate through the platforms from a central vertical axis of the trim.

The obstruction members may be arranged in arrays between the inlet and the outlet and each array may have a size and shape selected so that the condition of the fluid is gradually changed as it flows through the flow paths.

Adjacent arrays may be offset so that, in the flow direction, the obstruction members are alternately located at peaks and troughs of the ripple profile. The profile of one or more of the flow obstruction members may be selected to enhance the flow of fluid through the flow paths. The selection may be based on smoothing flow paths so that the trim has higher pressure drops and lower potential for cavitation and erosion.

One or more obstruction members may have a profile that includes a portion that is shaped to reduce recirculation of fluid at the surface of the obstruction members.

The portion may be a tapered portion extending from the or each obstruction member on an upstream side or downstream side of the obstruction member. The profile of the or each obstruction member with the portion may have a teardrop shape.

There is also provided in another aspect a control valve having an inlet and an outlet, a central chamber that links the inlet and the outlet, and a trim according to the first aspect that is located in the central chamber such that fluid flowing through the control valve enter the central chamber and flows radially through the trim to the outlet and a plunger that is operable to control the flow of fluid through the trim. The applicant has found that SLM can be used for manufacturing entire trims according to existing trim designs and still derive advantages associated with reduced production times and reduced costs. The same applies to manufacturing individual discs for a trim that comprises a stack of discs. Accordingly, a third aspect provides a method of forming a trim or a trim segment for a control valve, the method comprising forming the trim or trim segment as an integral body by additive layer manufacturing (ALM). The ALM may be selective laser melting (SLM). The method may include forming the trim or the trim segment at an inclination from its normal operating orientation so that powder used in the ALM process is always supported on an underlying surface. The method may include forming the trim with non-flat platforms which divide a flow passage through the trim into a series of flow paths and wherein the profile may be a ripple profile extending from an outlet of the flow passage to an inlet of the flow passage.

The method may include forming the ripple profile as a concertina profile, a sinusoidal wave profile or a scalloped profile. The method may further include controlling conditions of the ALM to reduce residual internal stress in the trim or the trim segment.

The conditions may include hatch distance, point distance, powder layer thickness, powder size, powder material, laser spot size, exposure time and laser power.

Other aspects, features, and advantages will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, which are a part of this disclosure and which illustrate, by way of example, principles of inventions disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of the disclosure as set forth in the Summary, specific embodiments will now be described by way of example and with reference to the accompanying drawings in which:

Figure 1 is a cut-away vertical cross-section through a control valve that

incorporates a trim. Figure 2 is an isometric view of a trim with a portion cut-away to show the arrangement of obstruction members on a platform. Figure 3 is a side view of a trim formed on an angle by SLM and having an outer supporting jacket to reduce manufacturing defects.

Figure 4 is an isomeric view of a trim that is designed for production by SLM.

Figure 5 is a horizontal section (equivalent to a disc of a disc stack trim) of the trim in Figure 4.

Figure 6 is an enlarged view of the section shown in Figure 5.

DESCRIPTION OF PREFERRED EMBODIMENTS

A control valve 1 that incorporates a trim is shown in Figure 1. The control valve 1 comprises a valve body 10 defining inlet and outlet conduits 11, 12 that in use are connected to pipes (not shown) that transport the fluid to and from the valve 1. The fluid flow is shown by arrows marked F in Figure 1. The valve 1 is intended to be bi-directional, such that the direction of fluid flow can be the reverse of that shown in Figure 1, and as described hereinbelow. The choice of fluid flow direction is dependent on the particular application.

Between the inlet and outlet conduits 11, 12 the valve body 10 defines a generally circular central chamber 8 into which a trim 13 is removably received. The trim 13 is disposed on a generally circular disc or valve seat 14, and the trim 13 comprises an integrally formed body having a central circular aperture 19. A valve cover 17 (also known as a bonnet) is fixed to the valve body 10 by bolts 18 (or other suitable means) so as to close the chamber 8 and retain the trim 13 in place.

A reciprocal plug 20 is slidably disposed within the central circular aperture 19. The plug 20 is attached to one end of an elongate stem 21 that extends upwardly through a bore 22 in the cover 17 via a guide seal 23 and is reciprocal by means of an actuator (not shown) connected to the other (uppermost) end of the stem 21 and to the exterior of the valve cover 17. The plug 20 is selectively moveable in an axial direction between a fully open position in which fluid flowing through the valve from the inlet to outlet conduits 11, 12 passes through the trim 13, and a closed position where the plug 20 is in abutment with the valve seat 14 and thereby blocks flow through the trim 13. Between these two positions, the plug 20 acts as a throttle by permitting only a predetermined volume of fluid flow, thereby determining the characteristics of the valve performance.

An example of a trim 13 based on existing trim designs is shown in Figure 2.

However, the trim 13 is formed as an integral body by using selective laser melting (SLM). For the purposes of this specification, this trim design is denoted as Trim A.

The trim 13 comprises upper and lower end plates 24, 25 that are configured to fit the corresponding mating surfaces of the valve seat 14 and the valve body 10. Between the end plates 24, 25 are four radial flow passages 26 which are equi- angularly spaced around the trim 13 and separated by walls 29 (which extend between the outer and inner peripheries of the trim 13) so that the radial flow passages 25 correspond roughly with the four quadrants of the trim 13. In other embodiments, the flow passages 26 comprise other equally sized portions of the trim, such as fifths, thirds or halves of the trim separated by walls. In some embodiments, there is a single flow passage that extends around the entire trim, i.e. there are no walls.

Each passage 26 is divided into a series of vertically separate flow paths 31 by a series of vertically spaced apart platforms 32. Projecting between the platforms 32 and terminating at each of the end plates 24, 25 are a plurality of discretely spaced columns 27 which are arranged in concentric annular circular rows. In the embodiment shown in Figure 2, the columns 27 are circular in cross section and reduce in individual cross sectional area from an inlet 33 of the flow path 31 which is located at the outer perimeter region of the trim 13 to an outlet 34 which is located at the inner perimeter of the trim 13. The columns 27 are staggered in such a way that those of any particular annular circular row are circumferentially offset from those in the preceding and subsequent annular circular rows. The fluid flow into the trim stack 13 is incident on the first (outermost) row of columns 27 (moving in the direction from the inlet 33 to the outlet 34) in each passage 26, and is divided into a plurality of smaller flow paths that pass between adjacent columns 27. As the fluid progresses to subsequent rows, it is again forced to divide as it passes around the front of each column 27. However, there is a convergence of the smaller flows downstream of the column 27. The staggering of the columns 27 between adjacent annular circular rows is designed to direct the downstream fluid flow from between the columns of one row directly into the path of a column of the next row. This constant fluid flow separation, the subsequent recombination and the frictional drag between the fluid and the curved surfaces of the columns 27 serves to reduce the energy and therefore the pressure of the fluid in stages, thereby providing a smooth pressure drop across the trim 13. It is to be appreciated that the specific design of the trim 13 can be varied according to the particular application, the flow direction and the flow characteristics that are required. For example, the spacing between columns 27 may increase from row to row in applications where it is necessary to increase the fluid flow area through the flow passage 26. Additionally, the size and the shape of the columns 27 may be varied depending on the nature of the fluid and the extent of change required in the fluid condition. Furthermore, the number of annular rows may be increased or decreased as required to meet the intended effect of the control valve.

In order to print the trim 13 by SLM, the trim is printed on an angle as shown in Figure 3. This enables metallic powder to be supported in position, such as the position of platforms 32 above flow paths 31, on surfaces in anticipation of melting by a laser. The end result is a trim 13 integrally formed with a stem 15 and inclined to horizontal. To reduce defects that can arise during the SLM process, the trim is formed with an outer support jacket 3 that covers the inlets 33 and an inner support jacket 5 that covers the outlets 34. More specifically, these jackets 3 and 5 provide mechanical support to the trim 13 during production to reduce slumping of SLM formed components. Manufacturing the trim 13 by SLM provides advantages in terms of reduced production times and reduced production cost. Accordingly, it is anticipated that using SLM to produce trims based on existing designs will resolve the problems of using EDM as the manufacturing method. However, the applicant tested the performance of the same trim 13 when produced by SLM and EDM. The results are shown in Table 1 below where Cv (according to Equation 1 below) is a measure of flow performance and is typically used by purchasers of trims as an indication of effectiveness.

Equation 1

Where:

Q = Volumetric flow rate through the valve in US Gallons per minute

Pi = Density of the working fluid in kg/m3

po = Relative density of Water at 15°C in kg/m3

PI = Inlet pressure to the valve in psi

P2 = Outlet pressure from the valve in psi

The Cvjotai of a control valve comprises the Cv of the trim, the valve body and the valve seat. Given that the valve body and the valve seat remain the same for the purposes of testing, changes in Cv are attributable to changes in the trim 13 from EDM manufacture to SLM manufacture. Trim type Valve opening Water temp (°C) rotal

Trim A (EDM manufacture) 100% 16 32.3

Trim A (SLM manufacture) 100% 16 24.5

Trim B (SLM manufacture) 100% 16 28.3

Table 1

The test results show a reduction in Cv _To tai of roughly 25% when the same trim 13 is manufactured using SLM. This is believed to be a result of increased surface roughness in the flow paths and also as a result of non-uniformity in the surface roughness on the flow paths. The latter is considered to be more important in terms of affecting the performance of the trim 13. It is thought that the nonuniform surface roughness causes preferred flow paths through the trim, thereby decreasing performance, rather than distributing fluid flow evenly through the trim 13.

Although the performance drop suggests that SLM is unsuitable for use in forming trims of unitary construction (that is, formed as an integral body), the same trim produced by SLM was found to take 16 hours to manufacture. This compares favourably with 10 weeks for preparing one disc for a trim comprising a stack of discs. There was also a considerable reduction in the production cost. It follows that SLM is still an advantageous method for forming trims for control valves. Despite the decrease in performance, the performance losses can be offset by redesigning the trim to increase the effective flow area in the flow paths. In other words, the design changes involve adopting smoother flow paths. An example of such a trim re-designed by the applicant is shown in Figures 4 to 6, shown as trim 40 and denoted as Trim B in Table 1. Like features are denoted by like reference numerals used for the trim 13, except as specified below.

The trim 40 (Trim B) differs from the earlier design trim 13 by incorporating profiled platforms 52. The profiled platforms 52 provide a two-fold advantage in that they facilitate manufacture of the trim 40 by SLM by providing support surfaces for powder, and they also increase the effective flow area of the flow paths. The profile of the platform 52 itself is that of a sinusoidal wave. The wave peaks and troughs radiate from a central vertical axis of the trim 40 so that the frequency of the wave is higher at the outlet 34 and lower at the inlet 33. The amplitude of the wave remains the same throughout the platform 52 (see Figure 5).

In this trim 40, the rows of columns 27 are disposed alternatively at the peaks 54 and the troughs 56 of the wave profile. This means that fluid entering the trim first encounters columns 58 located in troughs 56. As the fluid passes around such a column it is forced to flow upwardly from the trough 56 to the adjacent peak 54 located between adjacent columns 58. The flow then encounters the second row of columns 27 which are located on the peaks 54 so that the flow is forced to travel around these columns 27 and into an adjacent trough 56 where the flow then encounters the next row of columns 27. The profile of the platforms 52, therefore, imparts vertical changes in direction to the fluid flow in additional to lateral changes to direction caused by the columns 27 and 58. These changes result in more of the area of the flow paths being taken up by fluid flow. In other words, the flow paths are smoother. It is for this reason that the applicant believes that the profiled platforms 52 of this trim 40 provide a more evenly staged conditioning of fluids as they flow through the trim 40.

Although the trim 40 includes platforms 52 having a sinusoidal wave profile, it will be appreciated that alterative profiles may be adopted to have a similar effect. For example, the platforms may have a concertina profile or a scalloped profile in cross sectional shape. In each case, the profile radiates from a central vertical axis of the trim 40 and the columns 27 and 58 are arranged in the same manner as described above, that is in annular arrays which are offset so that adjacent arrays are respectively located in peaks and troughs.

The trim 40 further differs from the trim 13 by having columns 58, which are located adjacent the inlet 33 and the outlet 34, formed with portions 60 that reduce recirculation of fluid at the surface of the columns 58. The portions 60 take the form of tapered extensions on the upstream side of the columns 58 adjacent the inlet 33 and on the downstream side of the columns 58 adjacent the outlet 34. To be more specific, the portions 60 results in the columns having a tear-drop shape.

Numerical analysis by the applicant shows that the portions 60 assist with splitting the fluid flow into the various paths around the first array of columns. In this way, the presence of low flow regions, where the fluid typically recirculates at the surface of the columns, is substantially avoided. The same applies with the fluid flows when they recombine on the downstream side of the columns 58 adjacent to the outlet 34. The effect is that the area of the flow paths around the columns is increased so that the fluid flow is smoothed.

The portions 60 additionally assist with supporting areas of the platforms 52 that extend outside the arrays of columns 58 adjacent to the inlet 33 and the outlet 34.

The improved flow performance of the trim 40 is evident in the Cv measurement shown in Table 1. Specifically, the Cv _To tai value is 28.3 which is a considerable improvement over trim 13 when produced by SLM. Although this is still less than the value for the trim 13 when produced by EDM, the lower Cv _To tai value is understood to result primarily from the non-uniformity of the surface roughness.

For this reason, control over the SLM conditions is important for producing a trim with desirable Cv values. Those conditions include hatch distance, point distance, powder layer thickness, powder size, powder material, laser spot size, exposure time and laser power.

Examples of various SLM conditions are set out below in Table 2. It is relevant to note that the SLM conditions for preparing the trim 13 (denoted Trim A (SLM manufacture) in Table 1) are set out in the column marked "Original SLM Trim Test". Additionally, the SLM conditions for preparing the trim 40 (denoted Trim B (SLM manufacture) in Table 1) are set out in the column marked "Version 5.2".

The SLM conditions chosen for "Original design - New Process" in Table 2 resulted in a trim that increased the Cv _To tai value by almost 10% compared to the Cv _To tai for "Original SLM Trim Test". The compromise was, however, a more than doubling of the production time from 16 hours to 35 hours. Nevertheless, this indicates that controlling the SLM conditions is an important aspect of the forming trims by SLM. It also shows that improved trim performance can be derived from selecting appropriate SLM conditions.

Although the above description concerns producing an entire trim by SLM, it will be appreciated that SLM may be used to produce aspects of a trim. For example, limitations on SLM machines limit the size of entire trims that may be produced. Accordingly, the methods described above may be used to produce a segment of a larger trim, which when combined with complementary segments, forms an entire trim. For example, SLM may be used to produce a quadrant of a trim which can be combined with other trim quadrants also produced by SLM to form an entire trim. Similarly, SLM may be used to produce a disc for a trim formed by a stack of discs. The trim may have the same profiled platform 52 of the trim 40 and may also have the tear-drop shaped columns 58 of the trim 40. However, the disc may have different profiles that provide the benefits outlined above in terms of smoothing fluid flow and, thereby improving trim performance. In the claims which follow, and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word "comprise" and variations such as "comprises" or "comprising" are used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the apparatus and method as disclosed herein.

Table 2

In the foregoing description of preferred embodiments, specific terminology has been resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar technical purpose. Terms such as "front" and "rear", "inner" and "outer", "above", "below", "upper" and "lower" and the like are used as words of convenience to provide reference points and are not to be construed as limiting terms. The terms "vertical" and "horizontal" when used in reference to the trim throughout the specification, including the claims, refer to orientations relative to the normal operating orientation of a trim in a control valve.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as, an acknowledgement or admission or any form of suggestion that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

In addition, the foregoing describes only some embodiments of the invention(s), and alterations, modifications, additions and/or changes can be made thereto without departing from the scope and spirit of the disclosed embodiments, the embodiments being illustrative and not restrictive.

Furthermore, invention(s) have been described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention(s). Also, the various embodiments described above may be implemented in conjunction with other embodiments, for example, aspects of one embodiment may be combined with aspects of another embodiment to realize yet other embodiments. Further, each independent feature or component of any given assembly may constitute an additional embodiment.