Abstract:
A common rail single fluid injection system including fuel injectors with the ability to produce multiple injection rate shapes. This is accomplished by including auxiliary filling orifices which selectively provide pressurized fluid to the check needle control chamber during injection events. In so doing, the speed and movement of the check needle is manipulated and differing injection rates may be achieved.

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to a single fluid fuel injection system, and more particularly to fuel injection systems with an auxiliary filling orifice. 
     BACKGROUND 
     Engines, including diesel engines, gasoline engines, natural gas engines, and other engines known in the art, exhaust a complex mixture of combustion related constituents. The constituents may be gaseous and solid material, which include nitrous oxides (NOx) and particulate matter. Due to increased attention on the environment, exhaust emission standards have become more stringent and the amount of NOx and particulate matter emitted from an engine may be regulated depending on the type of engine, size of engine, and/or class of engine. 
     Engineers have come to recognize that undesirable engine emissions, such as NOx, particulate matter, and unburnt hydrocarbons, can be reduced across an engine&#39;s operating range with fuel injection systems with maximum flexibility in controlling injection timing, flow rate, injection quantity, injection rate shapes, end of injection characteristics and other factors known in the art. However, it has also been observed that an injection strategy at one engine operating condition may decrease emissions at that particular operating condition, but actually produce an excessive amount of undesirable emissions at a different operating condition. Thus, for a fuel injection system to effectively reduce emissions across an engine&#39;s operating range, it must have the ability to produce several different rate shapes, have the ability to produce multiple injections, and produce injection timings and quantities with relatively high accuracy. Providing a fuel injection system that can perform well with regard to all of these different parameters over an entire engine&#39;s operating range has proven to be elusive. 
     In order to reduce hydrocarbon emissions, one strategy has been to seek an abrupt end to each injection event. This strategy flows from the wisdom that reducing poorly atomized fuel spray into the combustion chamber toward the end of an injection event can reduce the production of undesirable hydrocarbon and smoke emissions. In the case of fuel injectors equipped with direct control needle valves, an abrupt end of injection is often accomplished by applying high-pressure fluid to the back side of a direct control needle valve member to quickly move it toward a closed position while fuel pressure within the injection remains relatively high. 
     In one example common rail fuel injector disclosed in U.S. Pat. No. 6,814,302 to Stoecklein et al, a needle control chamber has one outlet and one inlet. At the end of injection the inlet fills the needle control chamber. A bypass conduit, which feeds first into a valve chamber and then into the outlet, may provide additional fuel flow to the needle control chamber. The use of a bypass conduit that feeds into the valve chamber and then the needle control chamber outlet has a drawback of inevitably affecting the start of injection. Moreover, the valve and valve chamber required to facilitate the bypass conduit add cost and variability to the operation of the injector. 
     The disclosed fuel injector with auxiliary filling orifice is directed to overcoming one or more of the problems set forth above. 
     SUMMARY OF THE DISCLOSURE 
     In one aspect, a fluid injector including an injector body defining a high pressure inlet, a fuel supply passage, a low pressure drain, and at least one nozzle outlet. Also included is a check needle movable within the fluid injector between a first position at which the check needle blocks the at least one nozzle outlet and a second position at which the check needle at least partially opens the at least one nozzle outlet, the check needle including at least one opening hydraulic surface exposed to a fluid pressure of the fuel supply passage and at least one closing hydraulic surface exposed to a fluid pressure of a check needle control chamber, wherein said check needle control chamber is in selective fluid communication with the low pressure drain via a first orifice, and said check control chamber is in fluid communication with the nozzle supply passage via a second orifice, and said check needle control chamber is in selective fluid communication with the nozzle supply passage via a third orifice. The fluid injector also includes a control valve assembly having a valve member configured to selectively allow fluid communication via the first orifice between the low pressure drain and check control chamber. 
     In another aspect, an internal combustion engine including an engine housing defining a plurality of engine cylinders, and including a plurality of pistons each being movable within a corresponding one of the engine cylinders. Also included is a fuel system having a plurality of fuel injectors associated one with each of the plurality of engine cylinders, each of the fuel injectors including an injector body defining a high pressure inlet, a fuel supply passage, a low pressure drain, and at least one nozzle outlet. Also included is a check needle movable within the fluid injector between a first position at which the check needle blocks the at least one nozzle outlet and a second position at which the check needle at least partially opens the at least one nozzle outlet, the check needle including at least one opening hydraulic surface exposed to a fluid pressure of the fuel supply passage and at least one closing hydraulic surface exposed to a fluid pressure of a check needle control chamber, wherein said check needle control chamber is in selective fluid communication with the low pressure drain via a first orifice, and said check control chamber is in fluid communication with the nozzle supply passage via a second orifice, and said check needle control chamber is in selective fluid communication with the nozzle supply passage via a third orifice. The fluid injector also includes a control valve assembly having a valve member configured to selectively allow fluid communication via the first orifice between the low pressure drain and check control chamber. 
     In yet another aspect, a method of operating a fuel injector having a check needle, including the steps of supplying high pressure fuel to a nozzle chamber via a fuel supply passage. The method further includes the step of supplying high pressure fuel to a check needle control chamber via the fuel supply line and a z-orifice. Also included is a step of selectively supplying high pressure fuel to the check needle control chamber via the fuel supply line and an f-orifice. The method further includes a step of moving the check needle from its said first position to its said second position, wherein the check needle prevents fuel injection at the first position, and allows fuel injection at the second position; said moving step is accomplished by allowing fluid communication between the check needle control chamber and a low pressure drain via an a-orifice. The method also includes the step of moving the check needle from its second position to its first position by blocking fluid communication between the check needle control chamber and the low pressure drain via the a-orifice. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic schematic of a fuel system using a common rail fuel injector; 
         FIG. 2  is a cross section of an exemplary common rail fuel injector utilizing auxiliary filling orifices; 
         FIG. 3  is a detail of a first embodiment of the check needle and auxiliary filling orifice; 
         FIG. 4  is a detail of an alternate embodiment of the check needle and auxiliary filling orifice; 
         FIG. 5  is a comparison graph showing fuel delivery rates of an injector using and not using the disclosed embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , an example diesel engine  10  includes six cylinders  12  and a common rail fuel injection system  14 . The system includes an individual fuel injector  16  for each engine cylinder  12 , a single common rail  18 , and a fuel tank  20 . Those skilled in the art will appreciate that in other applications there may be two or more separate common rails, such as a separate rail for each side of a V8 engine. An electronic control module  22  controls the operation of fuel injection system  14 . The electronic control module  22  preferably utilizes advanced strategies to improve accuracy and consistency among the fuel injectors  16  as well as pressure control in common rail  18 . For instance, the electronic control module  22  might employ electronic trimming strategies individualized to each fuel injector  16  to perform more consistently. Consistent performance is desirable in the presence of the inevitable performance variability responses due to such causes as realistic machining tolerances associated with the various components that make up the fuel injectors  16 . In another strategy, the electronic control module  22  might employ a model based rail pressure control issue into one of open loop flow control coupled with closed loop error and pressure control. 
     When fuel injection system  14  is in operation, a transfer pump  24  draws low-pressure fuel through fuel supply line  26  and provides it to high-pressure pump  28 . High-pressure pump  28  then pressurizes the fuel to desired fuel injection pressure levels and delivers the fuel to the common rail  18 . The pressure in common rail  18  is controlled in part by safety valve  30 , which spills fuel to the fuel return line  32  if the pressure in the common rail  18  is above a desired pressure. The fuel return line  32  returns fuel to the fuel tank  20 . 
     Fuel injector  16  draws fuel from common rail  18  and injects it into a combustion cylinder  12  of the engine  10 . Fuel not injected by fuel injector  16  is spilled to fuel return line  32 . Electronic Control Module (ECM)  22  provides general control for the system. ECM  22  receives various input signals, such as from pressure sensor  34  and a temperature sensor  36  connected to common rail  18 , to determine operational conditions. ECM  22  then sends out various control signals to various components including the transfer pump  24 , high-pressure pump  28 , and fuel injector  16 . 
     Referring to  FIG. 2 , the internal structure and fluid circuitry of each fuel injector  16  is illustrated. In particular, an injector body  38  defines a high-pressure fuel supply inlet  40  and a fuel supply passage  42 , which are interconnected. Fuel supply passage  42  is in fluid communication with nozzle chamber  44 . A control valve assembly  46  is partially disposed within injector body  38 . The operation of the fuel injector  16  is controlled, at least partially, by control valve assembly  46 . Control valve assembly  46  may include a rod member  48  that controls a valve member  50 . The valve member  50  disclosed in  FIG. 2  is a ball valve having a flat. However, those skilled in the art will recognized that any myriad of shapes/geometries of valve members may be utilized without departing from the scope of this disclosure. In the embodiment shown, rod member  48  is coupled to an armature  52 , which is disposed within an armature guide member  54 . Control valve assembly  46  also includes an electrical actuator  56 . When electrical actuator  56  is de-energized, a biasing spring  58  biases armature  52 , rod member  48  and valve member  50  downward. In this de-energized state, valve member  50  rests atop an orifice plate  60  and seals a first orifice  62 , which is defined by the orifice plate  60 . This first orifice  62  is also known as the a-orifice. As will be discussed, below, orifice plate  60  may also include a second orifice (z-orifice)  64  and a third orifice (f-orifice)  66 . However, in the embodiment shown in  FIG. 2 , the orifice plate only has a first orifice  62  and second orifice  64 . The third orifice is found within an upper check guide  68  of check needle  70 . When the electrical actuator  56  is energized, an electromagnetic field is generated. The electromagnetic field causes armature  52  and rod member  48  to lift by overcoming the downward force applied by biasing spring  58 . When this happens, valve member  50  is no longer in sealing contact with first orifice  62 . It will be appreciated by those skilled in the art that control valve assembly  46  could have many alternate embodiments without deviating from the scope and spirit of this disclosure. These alternate embodiments may include piezo actuation, a needle valve and other armature, spring, control rod and valve member configurations. 
     Check needle  70  is disposed within nozzle chamber  44 . Check needle  70  may have a first end  72  and a second end  74 . The first end  72  may be disposed within a lower check guide  76  and the second end  74  may be disposed within the upper check guide  68 . A biasing spring  78 , which is also disposed within the nozzle chamber  44 , biases check member downward in a first position. In this first position, first end  72  of check needle  70  rests on seat  80  and blocks at least one tip orifice  82  disposed within injector tip  84 . Check needle  70  is also movable to a second position wherein the first end  72  is at least partially out of contact with seat  80  and the at least one tip orifice  82  is partially unblocked. 
     Referring now to  FIG. 3 , a detail (not to scale) of a first embodiment is shown. A check needle control chamber  86  is defined by a lower surface  88  of orifice plate  60 , a distal surface  90  of the second end of check needle  70  and a portion  92  an interior surface of the upper check guide  68 . First orifice  62 , which may also be called an a-orifice, is in direct fluid communication with check needle control chamber  86 . When injector  16  is not injecting fluid, valve member  50  rests atop orifice plate  60  and blocks first orifice  62 . As will be explained in greater detail below, during injection, valve member  50  is at least partially out of contact with orifice plate  60  and fluid from check needle control chamber  86  is allowed to drain out of the first orifice  62  and ultimately out of injector  16 . 
     In the embodiment shown in  FIG. 3 , orifice plate  60  also has a second orifice  64 , which may also be called a z-orifice. Second orifice  64  is in direct fluid communication with check needle control chamber  86 . Additionally, second orifice  64  is in fluid communication with high-pressure fuel supply passage  42 . 
     An auxiliary, or third orifice  66  is in the upper check guide  68 . The third orifice  66 , which may also be called an f-orifice, is also in fluid communication with high-pressure fuel supply passage  42  in parallel with the second orifice  64 . The third orifice  66  may selectively be in fluid communication with check needle control chamber  86  via a check groove  94  and a check orifice  96 . When check needle  70  is in its downward first position, third orifice  66  is out of fluid communication with check needle control chamber  86 . In this position, third orifice  66  is blocked by a portion of check needle  70  known as a groove offset  98 . When check needle  70  is in a second position, the third orifice  66  is no longer blocked by groove offset  98 . In this position, third orifice  66  is in fluid communication with check needle control chamber  86 . 
     The operation of injector  16  will now be explained. The opening and closing of check needle  70  is controlled in part by the presence of high-pressure fuel in fuel supply passage  42 . When an injection event is not desired, the electrical actuator  56  of control valve assembly  46  is not energized. High-pressure fuel enters fuel injector  16  through high-pressure fuel supply inlet  40 . High-pressure fuel is supplied to nozzle chamber  44  via the high-pressure fuel supply passage  42 . High pressure fuel is also supplied to the check needle control chamber  86  via high pressure fuel supply passage  42  and the second orifice  64 . The high pressure fuel within check needle control chamber  86  is prevented from escaping through the first orifice  62  by the valve member  50 , which is blocking the same. The high-pressure fuel within the check needle control chamber  86  provides a hydraulic load on the distal surface  90  of check needle  70 . This hydraulic load coupled with the downward force of biasing spring  78 , holds check needle  70  in its first position wherein it rests on seat  80  and blocks the at least one tip orifice  82 . 
     The high-pressure fuel that is provided to nozzle chamber  44  seeks to unseat check needle  70  by applying hydraulic pressure to various surfaces to the check needle  70 . These forces seek to lift check needle  70  off of its seat  80 . However, when the electrical actuator  56  control valve assembly  46  is deenergized, check needle  70  remains seated because the hydraulic forces applied to the check are countered by hydraulic load applied in the check needle control chamber  86  and the downward force of biasing spring  78 . 
     When injection is desired, the electrical actuator  56  of control valve assembly  46  is energized. The electrical actuator  56  thus creates an electromagnetic field causing armature  52  and rod member  48  to overcome the force of biasing spring  58  and lift. When rod member  48  lifts, the downward force that was holding valve member  50  in place is removed. Thus, valve member  50  also lifts and the high pressure fuel within check needle control chamber  86  is allowed to drain out of the first orifice  62 . This fuel ultimately drains out of the injector  16 . 
     When the high pressure fuel drains out of the check needle control chamber  86  through the first orifice  62 , the hydraulic load that was on top of the distal surface  90  of check needle  70  decays. At the same time, pressurized fuel is still being provided to nozzle chamber  44  via high pressure fuel supply passage  42 . Because of the decay in the hydraulic load in the check needle control chamber  86 , there is a pressure imbalance between the nozzle chamber  44  and the check needle control chamber. The higher pressure in the nozzle chamber  44  now applies hydraulic forces to the various surfaces of the check needle  70  causing it to lift off of seat  80 . As the check needle  70  is unseated, pressurized fuel is injected into an engine cylinder  12  through the at least one tip orifice  82 . 
     As the check needle  70  moves from its first position to its second position wherein it is out of contact with seat  80 , it eventually travels a distance equal to that of the groove offset  98 . When the check needle  70  moves a distance equal to that of the groove offset  98 , the third orifice  66 , which was heretofore blocked, comes into fluid communication with the check needle control chamber  86 . In the embodiment shown in  FIG. 3 , the groove offset  98  is sized such that it is approximately 60% to 80% of the total distance traveled by check needle  70  during an injection event. Preferably, the groove offset  98  is sized such that it is 65% to 75% of the total distance traveled by a check needle during an injection event. Because the third orifice  66  is blocked from fluid communication with check needle control chamber  86  while check needle  70  travels a distance equal to the groove offset  98 , the high pressure fuel, which comes through the third orifice  66  does not substantially interfere with the opening of check needle  70 . (See  FIG. 5 .). 
     When it is desirable to stop injection, electrical actuator  56  is deenergized. As the electromagnetic field generated by electrical actuator  56  dissipates, the force of biasing spring  58  acts on rod member  48  and armature  52 . As rod member  48  and biasing spring  58  apply a downward force on valve member  50 , it in turn returns to its position on orifice plate  60 , wherein it blocks first orifice  62 . When the first orifice  62  is blocked, check needle control chamber  86  begins to fill with high-pressure fuel. Initially, both the second orifice  64  and third orifice  66  provide high-pressure fuel to fill the check needle control chamber  86 . However, as the high pressure fuel within check needle control chamber  86  begins to apply a hydraulic load on the distal surface  90  of check needle  70 , check needle  70  begins to move downward toward seat  80 . As check needle  70  moves downward, third orifice  66  will subsequently become blocked by groove offset  98 . When this happens, third orifice  66  is no longer in fluid communication with check needle control chamber  86 . The second orifice  64  then continues to fill the check needle control chamber  86  until the hydraulic load caused by the high pressure fluid in the check needle control chamber  86  and the downward force of biasing spring  78  cause check needle  70  to return to its first position. When check needle  70  returns to its seat  80 , the tip orifice  82  is blocked and injection ends. 
     Referring now to  FIG. 5 , which depicts three curves showing fuel injector fluid delivery rate versus time. Curve  100  is an exemplary delivery rate of an injector that does not employ the techniques disclosed in the present application. Curve  102  is an exemplary delivery rate of an injector that does employ the techniques disclosed in the present application. Generally speaking, curves  100  and  102  are virtually identical from point  104 , which is the start of injection, until point  106 . On curve  102 , point  106  represents the point where check needle  70  moves beyond the groove offset  98 . At point  106 , the delivery rates begin to differ. On curve  102 , the delivery rate begins to slow down. However, engineers have learned that this slowing down is of negligible effect on start of injection events. The reason that this slowing has a negligible effect is because by the time point  106  occurs, most of the fuel that will be delivered to the an engine cylinder has already been delivered. In other words, because of the placing of the third orifice  66  within the upper check guide  68  and the groove offset  98 , the effect of the third orifice  66  in the embodiment of  FIG. 3  is essentially masked until the end of injection where it assists in providing a faster closing of check needle  70 . 
     Point  108  represents the time at which the electrical actuator of a control valve assembly is deenergized. This point represents the beginning of the end of injection. As can be clearly seen, curve  102  moves to a zero fluid delivery rate significantly faster than curve  100 . The reason for this is because on curve  102 , the second and third orifices together (Curve  102 ) fill the check needle control chamber faster than the second orifice can on its own (Curve  100 ). Improved speed in filling the check needle control chamber leads directly to a faster closing of check needle and end of injection. 
     Referring now to  FIG. 4 , a detail (not to scale) of a second embodiment is shown. A check needle control chamber  186  is defined, at least partially, by a lower surface  188  of orifice plate  160 , a distal surface  190  of a second end  174  of check needle  170  and a portion  192  of an interior surface of the upper check guide  168 . First orifice  162 , which may also be called an a-orifice, is in direct fluid communication with check needle control chamber  186 . In the embodiment shown, in  FIG. 4 , the orifice plate  160  includes a counter bore  167 , which may further facilitate fluid communication between the first orifice  162  and the check needle control chamber  186 . When fuel injector  16  is not injecting fluid, valve member  150  rests atop orifice plate  160  and blocks first orifice  162 . During injection, valve member  150  is at least partially out of contact with orifice plate  160  and fluid from check needle control chamber  186  is allowed to drain through counter bore  167  and the first orifice  162  and ultimately out of the fuel injector  16 . 
     In the embodiment shown in  FIG. 4 , orifice plate  160  also has a second orifice  164 , which may also be called a z-orifice. Second orifice  164  is in direct fluid communication with check needle control chamber  186 . Additionally, second orifice  164  is in fluid communication with high-pressure fuel supply passage  42  in parallel with second orifice  164 . An auxiliary, or third orifice  166  is also in the orifice plate  160 . The third orifice  166 , which may also be called an f-orifice, is also in fluid communication with high-pressure fuel supply passage  42 . The third orifice  166  is also in direct fluid communication with check needle control chamber  186  via counter bore  167 . 
     In operation, the embodiment shown in  FIG. 4  operates in much the same way as that of the embodiment in  FIG. 3 . The differences relate to the manner in which the third orifice  166  comes into play at the very beginning of an injection event. The third orifice  166  in  FIG. 4  is always in direct fluid communication with the check needle control chamber  186  via counter bore  167 . Thus, at the very beginning of an injection event, the unseating of check needle  170  is manipulable. The speed in which check needle  170  unseats will be slowed depending on the sizing of the counter bore  167 , the second orifice  164  and the third orifice  166 . This slowing is caused because high-pressure fluid supplied to the check needle control chamber  186  from both the second orifice  164  and third orifice  166  must drain out of the first orifice  162 . Alternatively, in the embodiment shown in  FIG. 3 , the third orifice  66  is not in fluid communication with the check needle control chamber  86  until after the check needle  70  has moved a distance equal to the groove offset  98 . Thus, the effect of the sizing of the second orifice  64  and third orifice  66  is minimized as compared to that of the embodiment in  FIG. 4 . 
     At the end of injection, the embodiments of  FIG. 4  and  FIG. 3  operate in nearly identical manners. When the valve member  150  is returned to its position atop the orifice plate  160  and the first orifice  162  is blocked, high pressure fluid from fuel supply passage  42  is delivered to the check needle control chamber  186  via both the second orifice  164  and the third orifice  166 . The high pressure fluid provided to the check needle control chamber  186  via the second orifice  164  and third orifice  166  creates a hydraulic load on the distal surface  190  of the second end  174  of check needle  170 . This hydraulic load provides a force that assists in returning the check needle  170  to its seat  80 . As with the embodiment in  FIG. 3 , the embodiment of  FIG. 4  has a faster closing of check needle  170  because the pressure within the check needle control chamber  186  builds faster when two orifices ( 164 ,  166 ) supply high pressure fluid as opposed to just one orifice. 
     Curve  110  on  FIG. 5  shows the fuel delivery rate of an exemplary injector using the auxiliary orifice of embodiment of  FIG. 4 . As can be seen, there is a slight delay in the start of injection because of the presence of the additional orifice  166 . Thus, while a start of current may begin at time point  104 , the actual start of injection may not begin until time point  105 . At point  105 , curve  110  begins to deliver fuel at a rate slower than that of curves  100  and  102 . One reason for this slower delivery is because in addition to the second orifice  164 , a third orifice  166  is providing high-pressure fuel to the check needle control chamber  186 . Another reason for the slower delivery is because in the embodiment depicted in  FIG. 4 , the third orifice  166  is always in fluid communication with the check needle control chamber  186  via counter bore  167 . In other words, there is no groove offset where the third orifice  166  is blocked for a period of time after the start of injection. 
     Although not shown in  FIG. 5 , in some embodiments, the injector of  FIG. 4  may not deliver as much fuel as that of injectors that do not have an additional orifice such as  166 . One reason for this may be because the continuous fluid delivery from the third orifice  166  limits the travel distance of check needle  170 . Thus, curve  110  would not have an apex as high as that of curves  100  and  102 . Notwithstanding, those skilled in the art would readily understand how to adjust the sizes of the first orifice  162 , second orifice  164 , third orifice  166 , and the counter bore  167 , to allow the embodiment shown in  FIG. 4  to deliver a maximum amount of fuel approximately equal to that delivered by  FIG. 3 . This approximately equal amount of fuel delivery is shown in  FIG. 5 . 
     At end of injection time point  108 , curve  110  functions very similarly to that of curve  102 . In other words, after the drain or first orifice  162  is blocked, the high pressure fluid delivered to the check needle control chamber  186  from second orifice  164  and third orifice  166 , acts to quickly close check needle  170 . Here too, there may be a slight delay in end of injection because of the presence of the third orifice  166 . However, even with this slight delay, the end of injection is still faster than injectors that do not use the techniques employed in this application. 
     Industrial Applicability 
     The present disclosure finds a preferred application in common rail fuel injection systems. In addition the present disclosure finds preferred application in single fluid, namely fuel injection, systems. Although the disclosure is illustrated in the context of a compression ignition engine, the disclosure could find application in other engine applications, including but not limited to spark ignited engines. 
     The embodiments of  FIGS. 3 and 4  may provide multiple delivery rates for fuel injectors. The selection of which embodiment is utilized may depend on anticipated engine operating conditions such as engine speed and load. Depending on the desired start of injection characteristics, engineers employing the designs of the disclosed fuel injectors may produce a square or ramp shaped fuel delivery curve (See  FIG. 5 ). However, regardless of which embodiment is selected, the end of injection profile is consistently faster. Specifically, the end of injection profile is faster in injectors that employ the methods and techniques outlined in this application, as opposed to those that do not. The presence of a third orifice ( 66 ,  166 ) supplying high pressure fluid to the check needle control chamber ( 86 ,  186 ) leads to a faster build up of hydraulic load on the distal surface ( 90 ,  190 ) of the second end ( 74 ,  174 ) of the check needle ( 70 ,  170 ). Thus, the check needle ( 70 ,  170 ) returns to its seat  80  faster. 
     The above description is intended for illustrative purposes only and is not intended to limit the scope of the present disclosure in any way. Thus, those skilled in the art will appreciate the various modifications that can be made to the illustrated embodiments without departing from the spirit and scope of the disclosure, which is defined in the terms of the claims set forth below.