Patent Publication Number: US-11384753-B1

Title: Gas operated unloader valve

Description:
BACKGROUND 
     Gas compressors and in particular reciprocating gas compressors often include an unloader valve that controls the flow of gas to be compressed into the compressor. Due to flow and operating constraints, these unloader valves often include a number of smaller valves that are each opened and closed simultaneously. A complex mechanical system performs the actuation and is controlled or driven by a separate electric, hydraulic, or pneumatic system. These separate systems can be costly to operate and maintain and add significant complexity to the gas compression system employing the reciprocating gas compressor. 
     BRIEF SUMMARY 
     In one aspect, an unloader valve includes a seat including a plurality of inlet apertures, each inlet aperture spaced apart from the other inlet apertures and extending through the seat along one of a plurality of parallel inlet axes. A manifold plate is fixedly connected to the seat and includes a plurality of outlet apertures, each spaced apart from the other outlet apertures and extending through the manifold plate along one of a plurality of parallel outlet axes. The unloader valve also includes a plurality of blind plug holes, each centrally aligned along one of the plurality of parallel inlet axes, a control chamber formed in the manifold plate, and a control space fully defined by the manifold plate and arranged to fluidly connect the control chamber and each of the blind plug holes to one another. The unloader valve also includes a control member disposed within the control chamber and movable between a first position in which the control space is exposed to a pressure source, and a second position in which the control space is isolated and a plurality of plugs, each plug positioned within one of the blind plug holes and movable between a closed position in which each plug closes one of the inlet apertures and an open position in which the plurality of inlet openings are in fluid communication with the plurality of outlet openings. 
     In another aspect, an unloader valve for use with a reciprocating gas compressor having a compression space defined by a piston and a cylinder includes a seat including a plurality of inlet apertures, and a manifold plate fixedly connected to the seat. The manifold plate includes a plurality of outlet apertures, a plurality of plug holes, a control chamber formed in the manifold plate, and a control space fully defined by the manifold plate and arranged to fluidly connect the control chamber and each of the plug holes to one another. The unloader valve also includes a control member disposed within the control chamber and movable between a first position in which the control space is exposed to the compression space, and a second position in which the control space is isolated from the compression space. The unloader valve for use also includes a plurality of plugs, each plug positioned within one of the plug holes, each plug movable from a closed position in which each plug closes one of the inlet apertures to an open position in response to the control member being disposed in the first position and a pressure within the control space being below a predetermined pressure, and where each plug is maintained in the open position in response to the control member being in the second position. 
     In another aspect, an unloader valve for use with a reciprocating gas compressor having a compression space defined by a piston and a cylinder includes a seat including a plurality of inlet apertures, a manifold plate including a plurality of outlet apertures and a plurality of attachment apertures, a control seat threadably coupled to the manifold plate to fixedly attach the seat and the manifold plate, and an interface plate positioned between the seat and the manifold plate and cooperating with the manifold plate to define a control space. A plurality of valve cups are arranged with each valve cup threadably connected to the manifold plate and operable to sandwich the interface plate between the valve cups and the manifold plate. A control member is disposed within the control seat and is movable between a first position in which the control space is exposed to the compression space, and a second position in which the control space is isolated from the compression space. A plurality of plugs is arranged with each plug positioned within one of the valve cups and movable from a closed position in which each plug closes one of the inlet apertures to an open position in response to the control member being disposed in the first position and a pressure within the control space being below a predetermined pressure, and where each plug is maintained in the open position in response to the control member being in the second position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced. 
         FIG. 1  is a section view of a portion of a reciprocating gas compressor. 
         FIG. 2  is a perspective view of a portion of the reciprocating gas compressor of  FIG. 1  including an unloader valve. 
         FIG. 3  is a perspective view of the unloader valve of  FIG. 2 . 
         FIG. 4  is a perspective view of a portion of the unloader valve of  FIG. 3 . 
         FIG. 5  is a schematic illustration of a portion of the reciprocating gas compressor and the unloader valve of  FIG. 4 . 
         FIG. 6  is a perspective view of a manifold plate of the unloader valve of  FIG. 4 . 
         FIG. 7  is a cross-sectional view of the unloader valve of  FIG. 4  taken along line  6 - 6  of  FIG. 6 . 
         FIG. 8  is a perspective view of the various spaces that define a control space formed in the manifold plate of  FIG. 6 . 
         FIG. 9  is a cross-sectional view of another unloader valve taken through a centerline of the unloader valve. 
         FIG. 10  is a perspective view of an interface plate suitable for use with the unloader valve of  FIG. 9 . 
         FIG. 11  is an enlarged view of a portion of the unloader valve of  FIG. 10  including an attachable valve cup. 
         FIG. 12  illustrates several arrangements of a seal positioned between the attachable valve cup of  FIG. 11  and a plug. 
         FIG. 13  is a perspective view of another arrangement of a portion of an unloader valve. 
         FIG. 14  is a section view of a valve cylinder of the arrangement of  FIG. 13 . 
         FIG. 15  is a perspective view of a manifold plate of the arrangement of  FIG. 13 . 
         FIG. 16  is a perspective view of an interface plate of the arrangement of  FIG. 13 . 
         FIG. 17  is a section view of the arrangement of  FIG. 13  taken through a centerline of the manifold plate. 
     
    
    
     DETAILED DESCRIPTION 
     As used herein, the terms “component” and “system” are intended to encompass hardware, software, or a combination of hardware and software. Thus, for example, a system or component may be a process, a process executing on a processor, or a processor. Additionally, a component or system may be localized on a single device or distributed across several devices. 
     Further the phrase “at least one” before an element (e.g., a processor) that is configured to carry out more than one function/process may correspond to one or more elements (e.g., processors) that each carry out the functions/processes and may also correspond to two or more of the elements (e.g., processors) that respectively carry out different ones of the one or more different functions/processes 
     Also, it should be understood that the words or phrases used herein should be construed broadly, unless expressly limited in some examples. For example, the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation. The singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Further, the term “and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. The term “or” is inclusive, meaning and/or, unless the context clearly indicates otherwise. The phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like. 
     Also, although the terms “first”, “second”, “third” and so forth may be used herein to refer to various elements, information, functions, or acts, these elements, information, functions, or acts should not be limited by these terms. Rather these numeral adjectives are used to distinguish different elements, information, functions or acts from each other. For example, a first element, information, function, or act could be termed a second element, information, function, or act, and, similarly, a second element, information, function, or act could be termed a first element, information, function, or act, without departing from the scope of the present disclosure. 
     In addition, the term “adjacent to” may mean that an element is relatively near to but not in contact with a further element or that the element is in contact with the further portion, unless the context clearly indicates otherwise. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise. 
       FIG. 1  illustrates a portion of a reciprocating gas compressor  100  that is driven by a prime mover, such as an electric motor or other engine to produce a compressed gas. The reciprocating gas compressor  100  includes one or more casings  106  that each define a cylinder  114  that supports a piston  110  for reciprocating movement. The piston  110  and the casing  106  cooperate to define a compression space  108  that has a volume that various with the reciprocating motion of the piston  110  to draw in gas to be compressed and to compress the gas as is well known. 
     A gas inlet  102  is provided in the casing  106  to receive a supply of gas to be compressed and a gas outlet  104  is formed in the casing to collect the compressed gas produced by the reciprocating gas compressor  100 . As will be discussed in greater detail, a number of unloader valves  300  are coupled to the casing  106  and are positioned between the gas inlet  102  and the compression space  108  to control the admission of uncompressed gas into the compression space  108 . Similarly, a number of discharge valves  112  are provided between the compression space  108  and the gas outlet  104  to control the outflow of compressed gas. 
       FIG. 2  illustrates a portion of the reciprocating gas compressor  100  that includes the casing  106  and defines a number of inlet/outlet bores  202 . One unloader valve  300  is attached to each of four of the inlet/outlet bores  202  with four discharge valves  112  (not shown) attached to the remaining four inlet/outlet bores  202 . Of course, other arrangements could have more or fewer unloader valves  300  and discharge valves  112  as may be required for the particular design. 
       FIG. 3  illustrates one of the unloader valves  300  of  FIG. 2  with all the unloader valves  300  being substantially the same. The unloader valve  300  includes a valve housing  302  that supports the remaining components in their desired operating positions and a flange  304  that is arranged to facilitate the attachment of the unloader valve  300  to the casing  106 . In the illustrated construction, the flange  304  includes a plurality of apertures arranged to receive fasteners that attach the unloader valve  300  to the casing  106 . 
     An actuator  306  is positioned adjacent the flange in a position that ultimately is outside of the casing  106  during operation. As will be discussed in greater detail, the actuator  306  can be an electrical, hydraulic, pneumatic or any other type of actuator desired. A control member  308  (better illustrated in  FIG. 4 ) is coupled to the actuator  306  for movement as will be discussed in greater detail. 
     The unloader valve  300  also includes a seat  310  and a manifold plate  312  positioned at one end of the valve housing  302  such that when the unloader valve  300  is attached to the casing  106  in its operating position, the manifold plate  312  is positioned nearest to the piston  110 . 
       FIG. 4  illustrates the manifold plate  312 , the seat  310 , and the control member  308  with the remainder of the unloader valve  300  omitted. The control member  308  includes an elongated shaft that extends from the seat  310  to a position within the actuator  306  to allow the actuator  306  to move the control member  308  between a first position and a second position. A control seat  402  is coupled to one of the seat  310  and the manifold plate  312  and cooperates with the control member  308  during operation of the control member  308 . 
     The seat  310  includes a plurality of inlet apertures  404  with each inlet aperture  404  passing through the seat  310 . The inlet apertures  404  are arranged in a series of rows and columns with other arrangements being possible. In the illustrated construction, forty-eight inlet apertures  404  are employed with typical applications including twenty or more. Of course, any suitable number of inlet apertures  404  could be employed as required. 
       FIG. 6  illustrates one possible embodiment of a manifold plate  312 . In the illustrated construction, the manifold plate  312  includes a central bore  602 , a series of outlet apertures  502 , and a series of plug bores  504 . The central bore  602  is sized to receive the control seat  402  which, as illustrated in  FIG. 7  also serves to attach the seat  310  to the manifold plate  312 . Specifically, the control seat  402  threadably engages the manifold plate  312  and includes a collar  702  that retains the seat  310  in the desired position. 
     The outlet apertures  502  and the plug bores  504  are arranged adjacent one another in a series of rows and columns. With this arrangement, each outlet aperture  502  is most closely surrounded by four plug bores  504 . Similarly, each plug bore  504  is most closely surrounded by four outlet apertures  502 . Each of the plug bores  504  is aligned with and coaxial with an inlet aperture  404  of the seat  310  while the outlet apertures  502  are arranged parallel to the inlet apertures  404  but are offset or misaligned. 
       FIG. 7  is a section view taken through the rows or columns described with regard to  FIG. 6 . Each of the plug bores  504  is a blind plug bore  504  (closed at one end) and receives a biasing member  704  and a plug  506 . Each plug bore  504  is aligned coaxially with one of the inlet apertures  404  such that the biasing member  704  operates to bias the plug  506  toward a closed position in which the plug  506  contacts a plug seat  708  formed as part of the seat  310 . In the closed position, each plug  506  closes the inlet aperture  404  with which it is aligned, thereby inhibiting flow through the seat  310 . Each plug  506  is further movable from the closed position to an open position in which the plug  506  is retracted from the plug seat  708  and flow can pass through the inlet apertures  404  and through the outlet apertures  502  to enter the compression space  108 . 
     The manifold plate  312  includes a control space  508 , a control seat  706 , and a control opening  510  formed as part of the manifold plate  312 . In preferred constructions, these features are formed as part of a one-piece or unitary manifold plate  312  and cannot be separated without destroying the manifold plate  312 . Due to the preferred shape of these features, the most viable method of forming the manifold plate  312  is an additive manufacturing process. Conventional manufacturing processes are generally not capable of forming the desired shapes of these features, with the desired surface finishes, and in particular are not capable of forming the control space  508 . 
     The control opening  510  provides for fluid communication between the compression space  108  and the control space  508 . The control seat  706  is positioned such that the control member  308  is movable into a position that blocks fluid communication between the compression space  108  and the control space  508  such that the control space  508  is effectively sealed and isolated. Thus, when the control member  308  moves to the second position and isolates the control space  508 , the pressure within the control space  508  becomes fixed at whatever point it was at just prior to the movement of the control member  308  into the second position. 
       FIG. 8  is a reverse image of a portion of the manifold plate  312  such that the spaces that define the control space  508  are shown as solid and the solid areas are removed. As can be seen, the control seat  402  and the control opening  510  define a large control chamber  802  that is capable of receiving fluid. Four distribution channels  804  connect the control chamber  802  to a series of runners  808  that interconnect each of the plug bores  504  to the control space  508  such that a plug space  806  is in fluid communication with the control space  508 . 
     To operate the construction of  FIG. 7  and  FIG. 8 , the unloader valve  300  is first assembled into a reciprocating gas compressor  100  as is schematically illustrated in  FIG. 5 . Specifically, the manifold plate  312  is in fluid communication with the compression space  108  and the seat  310  is positioned in fluid communication with a source of gas to be compressed. The actuator  306  is coupled to a controller  512  that operates to move the control member  308  between the first position and the second position. In some constructions a digital control such as a programmable logic controller (PLC) is employed to drive an electronic actuator  306  that ultimately moves the control member  308 . 
     With the control member  308  in the first position (shown in  FIG. 5 ), the control space  508  is exposed to the compression space  108  which acts as a pressure source. As the piston  110  retracts (note that the piston  110  is shown rotated 90 degrees as compared to the piston of  FIG. 1 ), the compression space  108  becomes larger and the pressure drops. When the pressure within the control space  508  reaches a predetermined point, the biasing force of the biasing members  704  is overcome and the plugs  506  are pulled into an open position. As gas to be compressed flows into the compression space  108 , the pressure could increase which would allow the biasing members  704  to return the plugs  506  to a closed position. To stop this, once the plugs  506  move to the open position, the control member  308  is moved via the controller  512  and the actuator  306  to the second position to seal and isolate the control space  508 . This effectively holds the plugs  506  in the open position regardless of the pressure within the compression space  108 . At some point just before, as, or just after the piston  110  begins its compression stroke, the controller  512  moves the control member  308  back to the first position and the control space  508  fills with higher pressure gas which allows the plugs  506  to return to the closed position during the compression stroke. This process is repeated with each rotational cycle and for each individual inlet/outlet bore  202  and unloader valve  300  to compress the gas as desired. 
       FIG. 9  through  FIG. 12  illustrate an alternative construction of an unloader valve  900 . The unloader valve  900  includes a manifold plate  902 , an interface plate  910 , a control seat  904 , and a seat  310  that is very similar to the prior described seat  310 . The manifold plate  902  includes a plurality of outlet apertures  502  similar to those described earlier. In addition, the manifold plate  902  includes a series of attachment apertures  1106  (best illustrated in  FIG. 11 ) that are threaded to receive one of a plurality of valve cups  908 . 
     The control seat  904  is similar to the control seat  402  and attaches to and retains the seat  310  and the manifold plate  902  as previously described. The control seat  904  includes one or more control passages  906  that are arranged to selectively provide fluid communication between the control opening  510  and a control space  912 . 
     The control space  912  is formed between the manifold plate  902  and the interface plate  910 . The interface plate  910 , better illustrated in  FIG. 10  engages the manifold plate  902  and is held in place by the plurality of valve cups  908  that are threaded into the manifold plate  902  with the interface plate  910  sandwiched therebetween. The manifold plate  902  and the interface plate  910  define spaces that correspond with the valve cups  908  such that fluid can enter the valve cups  908  via cup holes  1102  formed therein and positioned in the control space  912  between the manifold plate  902  and the interface plate  910 . 
     As illustrated in  FIG. 10 , the interface plate  910  includes a plate portion  1004 , a central bore  1002 , a series of cup openings  1006 , and a series of outlet bores  1008 . The plate portion  1004  is substantially planar and is shaped to fit within the manifold plate  902 . The central bore  1002  is formed at or near the center of the plate portion  1004  and is sized to allow for the passage of the control seat  904  therethrough. 
     The outlet bores  1008  are bores that pass through the plate portion  1004 . The outlet bores  1008  could include threads that are sized and arranged to threadably receive the valve cups  908 . Alternatively, the outlet bores  1008  are through bores and the attachment apertures  1106  in the manifold plate  902  are threaded. The outlet bores  1008  are arranged in a series of rows and columns that extend around the central bore  1002 . 
     The cup openings  1006  are through bores that extend through the plate portion  1004  and that each include a wall portion  1010  that surrounds the cup opening  1006  and extends away from the plate portion  1004  in a direction away from the manifold plate  902 . The cup openings  1006  are arranged in a series of rows and columns that extend around the central bore  1002 . 
     While  FIG. 10  illustrates the rows of cup openings  1006  and the rows of outlet bores  1008  arranged in an alternating fashion, other arrangements such as rows and columns that include both cup openings  1006  and outlet bores  1008  could be employed. The arrangement of the cup openings  1006  and the outlet bores  1008  should not limit the invention in any way. 
       FIG. 11  is an enlarged section view of a portion of the unloader valve  900  of  FIG. 9 . The interface plate  910  is positioned on the inner surface of the manifold plate  902  to define the control space  912  that includes the spaces between the wall portions  1010  and the manifold plate  902 . Each of the valve cups  908  includes a threaded cup stem  1104  that threadably engages one of the cup openings  1006 . As the valve cup  908  is installed, it eventually contacts the wall portion  1010  surrounding its respective cup opening  1006  to form a seal between the valve cup  908  and the wall portion  1010 . Each cup stem  1104  includes one or more cup holes  1102  that provide fluid communication between the control space  912  and the interior of the valve cup  908 . Each valve cup  908  contains a plug  506  that seals the control space  912  behind the plug  506 . Thus, the valve cups  908 , the interface plate  910 , and the manifold plate  902  cooperate to fully enclose the control space  912  with the only opening, the control opening  510  being selectively opened or closed by the control member  308 . 
     The unloader valve  900  operates in much the same way as the unloader valve  300  with the main difference being in how the control space  912  is formed and shaped. 
     As illustrated in  FIG. 12 , a seal can be formed between a mushroom plug  1204  or a cylindrical plug  1206  and the valve cups  908  to reduce the likelihood of unwanted leakage.  FIG. 12  illustrates alternatives for forming this seal with the two different shaped plugs. The first two images include a mushroom plug  1204  that includes a cylindrical body that moves within the valve cup  908  and an enlarged cylindrical head. This arrangement allows for the use of a smaller diameter valve cup  908  with a larger head. The next two images include a uniform cylindrical plug  1206  that moves within the valve cup  908 . 
     A first seal member  1202   a  is positioned within a seal groove formed in the mushroom plug  1204 . The first seal member  1202   a  is relatively short when compared to the length of the plug  506  within the valve cup  908 . The first seal member  1202   a  could be formed from a resilient material such as rubber, or a more rigid material such as TEFLON, brass, or bronze with these more rigid materials also enhancing the ability of the plug  506  to slide within the valve cup  908 . A fourth seal member  1202   d  is similar to the first seal member  1202   a  but is applied to the cylindrical plug  1206  rather than the mushroom plug  1204 . 
     A second seal member  1202   b  is positioned within a seal groove formed in the valve cup  908  rather than in the mushroom plug  1204  or the cylindrical plug  1206 . The second seal member  1202   b  is much longer than the first seal member  1202   a  but can be made using the same materials as the first seal member  1202   a  if desired. A third seal member  1202   c  is similar to the second seal member  1202   b  but is applied to the valve cup  908  for use with a cylindrical plug  1206  rather than the mushroom plug  1204 . 
       FIG. 13  illustrates an alternative arrangement of a manifold plate  1500  and interface plate  1600  suitable for use with any of the prior embodiments described that employ an interface plate. The manifold plate  1500  includes a manifold base  1302  that is surrounded by a manifold wall  1304  to define a manifold interior  1306 . The interface plate  1600  is positioned on top of and in direct contact with the manifold base  1302 . A valve cylinder  1400  is positioned on top of the interface plate  1600  such that it too is disposed within the manifold interior  1306  and so that a portion of the interface plate  1600  is sandwiched between the manifold plate  1500  and the valve cylinder  1400 . 
     Each of the manifold plate  1500  and the interface plate  1600  includes a number of plug bores  1308  and a number of outlet apertures  1310  that are aligned with one another when the interface plate  1600  is positioned within the manifold interior  1306 . The plug bores  1308  and the outlet apertures  1310  can be arranged in any pattern desired, including those arrangements already described. 
     The valve cylinder  1400 , illustrated in  FIG. 14  is a cylindrical component having an annular cross-section that defines a central bore  1402 . A first end of the valve cylinder  1400  includes a shoulder  1404  and an extension  1406  that are arranged to sandwich the interface plate  1600  between the manifold plate  1500  and the valve cylinder  1400  as will be described in greater detail with regard to  FIG. 17   
     Turning to  FIG. 15 , the manifold interior  1306  is illustrated with the valve cylinder  1400  and the interface plate  1600  removed. As illustrated, the manifold base  1302  includes a number of plug bores  1308  and a number of outlet apertures  1310  arranged in a pattern that matches the pattern of the interface plate  1600  to assure the desired level of alignment. The number of plug bores  1308  and the number of outlet apertures  1310  need not exactly match the quantity in the interface plate  1600 . However, in preferred embodiments, the number of plug bores  1308  in the manifold base  1302  matches the number of plug bores  1308  in the interface plate  1600 . 
     A castellated spacer  1502  is positioned at the center of the manifold plate  1500  within the manifold interior  1306 . In the illustrated construction, the castellated spacer  1502  is formed as a single component with the manifold plate  1500  and includes a number of wedge bosses  1504  that extend from the manifold base  1302 . The wedge bosses  1504  are wedge-shaped bosses that are positioned in a circular pattern in a manner that defines gaps between the individual wedge bosses  1504 . The wedge bosses  1504  are arranged to define an inner diameter that is sized to receive the extension  1406  of the valve cylinder  1400  adjacent the shoulder  1404  as will be described with regard to  FIG. 17 . The term “castellated” refers to the appearance of the castellated spacer  1502  which includes alternating high features (wedge bosses  1504 ) with alternating low spaces (the gaps) therebetween. 
       FIG. 16  illustrates the contact side of the interface plate  1600  in greater detail. Each of the plug bores  1308  is defined by a wall that contacts the manifold base  1302 . The walls also cooperate to form a control space between the manifold base  1302  and the interface plate  1600  to allow for a flow of fluid. A plate bore  1602  is formed in the interface plate  1600  and is sized to receive the extension  1406  of the valve cylinder  1400  as will be described with reference to  FIG. 17 . 
       FIG. 17  is a cross-section of the valve cylinder  1400 , manifold plate  1500 , and the interface plate  1600  in the assembled or operating position. As illustrated, the interface plate  1600  is positioned on the manifold base  1302  with each of the plug bores  1308  of the manifold plate  1500  aligned with a corresponding plug bore  1308  of the interface plate  1600 . 
     The plate bore  1602  is sized such that a portion of the interface plate  1600  rests on the castellated spacer  1502  and specifically contacts each of the wedge bosses  1504 . However, the plate bore  1602  has a larger diameter then the inner diameter of the castellated spacer  1502  such that a portion of each of the wedge bosses  1504  remains uncovered when the interface plate  1600  is in place. 
     The valve cylinder  1400  is positioned on top of the interface plate  1600  such that the shoulder  1404  contacts the interface plate  1600  and the extension  1406  defined by the shoulder  1404  contacts the exposed portions of the wedge bosses  1504 . The valve cylinder  1400  can be biased or pushed toward the manifold base  1302  to sandwich the interface plate  1600  between the shoulder  1404  and the wedge bosses  1504 . With this arrangement, the shoulder  1404  and the interface plate  1600  cooperate to define a seal therebetween. In addition, the interface plate  1600  is held in place due to its contact with the shoulder  1404  and the wedge bosses  1504 . However, there is no seal formed between the castellated spacer  1502  and the interface plate  1600  due to the gaps between the wedge bosses  1504 . This arrangement provides a flow path into the control space formed between the interface plate  1600  and the manifold plate  1500 . The control space functions much like the control spaces  508 ,  912  previously described. 
     Although an exemplary embodiment of the present disclosure has been described in detail, those skilled in the art will understand that various changes, substitutions, variations, and improvements disclosed herein may be made without departing from the spirit and scope of the disclosure in its broadest form. 
     None of the description in the present application should be read as implying that any particular element, step, act, or function is an essential element, which must be included in the claim scope. The scope of patented subject matter is defined only by the allowed claims. Moreover, none of these claims are intended to invoke a means plus function claim construction unless the exact words “means for” are followed by a participle.