Patent Publication Number: US-11035352-B2

Title: Method and system for enhancing performance in a reciprocating compressor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application claims the priority benefit under 35 U.S.C. § 371 of international patent application no. PCT/EP2016/059905, file May 6, 2016, which claims the priority benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application No. 62/157,183, filed on May 5, 2015, the contents of which are herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present disclosure pertains to methods and systems for enhancing performance in a reciprocating compressor. 
     2. Description of the Related Art 
     Typically, a compressor receives a supply of fluid, such as a liquid or gas, at a first pressure and increases the pressure of the fluid by forcing a given quantity of the received fluid having a first volume into a smaller second volume using a piston. Some compressors have a reciprocating piston that reciprocates within the cylinder to compress the fluid. The piston includes a reciprocating rod assembly. The rod assembly may be coupled to a crank shaft housed in a crank shaft housing. The crank shaft may be operated by a motor housed in a motor housing. Typical rod assemblies include input and output valves to intake and exhaust the fluid. The rod assembly may include a cup seal to provide a seal between the pressurized and non-pressurized sides of the rod assembly. The cup seal flexes during movement of the rod assembly within the cylinder and the frictional engagement creates wear on the cup seal. The cup seal is expected to wear over time due to pressurization of gas on the pressurized side of the rod assembly, the frictional engagement of the cup seal with the cylinder, and/or other operating conditions in the compressor. As a result, performance of the compressor may diminish because of the loss of contact between the cup seal and the cylinder which may require a cup seal replacement. 
     In current practice, the replacement of the cup seal requires removing multiple screws on the reciprocating rod assembly to disassemble and replace the cup seal. This process includes removing valves as well. The valve alignment is usually needed for performance and long term life of the compressor. In the event there are reassembly errors, such as bending of valve or misalignment can result in compromised compressor performance (fluid flow, pressure, clearance volume, noise, etc.) and/or reduction in valve life. These factors may make service/replacement of cup seal labor intensive and/ or expansive. 
     SUMMARY OF THE INVENTION 
     Accordingly, one or more aspects of the present disclosure relate to a system configured to enhance performance in a reciprocating compressor. The compressor includes a first cylinder that forms a first space for compressing a fluid; a first crank shaft housing operatively coupled with the first cylinder; a first crank shaft housed within the first crank shaft housing; a motor housing operatively coupled with the first crank shaft housing; a motor housed within the motor housing and configured to drive the first crank shaft; and a first rod assembly configured to reciprocate within the first cylinder so as to compress the fluid within the first space, and is configured to be driven by the first crank shaft. The first rod assembly includes a first connecting rod portion configured to couple the first rod assembly to the first crank shaft; a first head portion operatively coupled to the first coupling rod; a first cup seal configured to provide a movable seal between the first cylinder and the first rod assembly; a first cap removably coupled with the first rod assembly and configured to hold the cup seal in place on the first head portion; and one or more valves configured to control air across the head portion. The one or more valves are removably coupled to the first head portion. The one or more valves are constructed and arranged to remain coupled to the first head portion when the first cap is detached from the first rod assembly. 
     Another aspect of the present disclosure relates to a method for enhancing performance in a reciprocating compressor. The compressor includes a first cylinder, a first crank shaft housing, a first crank shaft, a motor housing, a motor, and a first rod assembly. The first rod assembly includes a first connecting rod portion, a first head portion, a first cup seal, a first cap, and one or more valves. The method includes forming, with the first cylinder, a first space for compressing a fluid; operatively coupling the first crank shaft housing with the first cylinder; housing the first crank shaft within the first crank shaft housing; operatively coupling the motor housing with the first crank shaft housing; housing the motor within the motor housing, the motor being configured to drive the first crank shaft; reciprocating the first rod assembly within the first cylinder so as to compress the fluid within the first space, the first rod assembly being driven by the first crank shaft; coupling, with the first connecting rod portion, the first rod assembly to the first crank shaft; operatively coupling the first head portion to the first connecting rod; providing, with the first cup seal a movable seal between the first cylinder and the first rod assembly; holding, with the first cap, the cup seal in place on the first head portion; and controlling air across the head portion, with the one or more valves, the one or more valves constructed and arranged to remain coupled to the first head portion when the first cap is detached from the first connecting rod assembly. 
     Still another aspect of the present disclosure relates to a system configured to enhance performance in a reciprocating compressor. The system includes first means for forming a first space for compressing a fluid; first means for housing a crank shaft operatively coupled with the first means for forming a first space; means for housing a motor for driving the crank shaft such that the means for housing the means for driving are operatively coupled with the first means for housing the crank shaft ; and first means for reciprocating within the first means for forming a first space so as to compress the fluid within the first space and such that the means for reciprocating are driven by the crankshaft. The first means for reciprocating includes first means for coupling the first means for reciprocating to the crankshaft; first means for forming a head portion of the first means for reciprocating operatively coupled to the first means for reciprocating; first means for providing a movable seal between the first means for forming a first space and the first means for reciprocating; first means for holding the cup seal in place on the first means for forming a head portion; and first means for controlling air across the head portion, the first means for controlling air being removably coupled to the first means for forming a head portion, the first means for controlling air constructed and arranged to remain coupled to the first means for forming a head portion when the first means for holding is detached from the first means for reciprocating. 
     These and other objects, features, and characteristics of the present disclosure, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of a cross-sectional view of a compressor; 
         FIG. 2  illustrates an exemplary rod assembly, in accordance with one or more embodiments; 
         FIG. 3  illustrates an exemplary head portion of a rod assembly, in accordance with one or more embodiments; 
         FIG. 4  illustrates an exemplary cross-sectional view of a head portion of a rod assembly, in accordance with one or more embodiments; 
         FIG. 5  illustrates an exemplary cup seal, in accordance with one or more embodiments; 
         FIG. 6  illustrates an example of a cap, in accordance with one or more embodiments; 
         FIG. 7  illustrates another example of a cap, in accordance with one or more embodiments; and 
         FIG. 8  illustrates a method for enhancing performance in a reciprocating compressor. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     As used herein, the singular form of “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. As used herein, the statement that two or more parts or components are “coupled” shall mean that the parts are joined or operate together either directly or indirectly, i.e., through one or more intermediate parts or components, so long as a link occurs. As used herein, “directly coupled” means that two elements are directly in contact with each other. As used herein, “fixedly coupled” or “fixed” means that two components are coupled so as to move as one while maintaining a constant orientation relative to each other. 
     As used herein, the word “unitary” means a component is created as a single piece or unit. That is, a component that includes pieces that are created separately and then coupled together as a unit is not a “unitary” component or body. As employed herein, the statement that two or more parts or components “engage” one another shall mean that the parts exert a force against one another either directly or through one or more intermediate parts or components. As employed herein, the term “number” shall mean one or an integer greater than one (i.e., a plurality). 
     Directional phrases used herein, such as, for example and without limitation, top, bottom, left, right, upper, lower, front, back, and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting upon the claims unless expressly recited therein. 
       FIG. 1  illustrates a compressor  10 . In some embodiments, compressor  10  includes cylinders  12   a ,  12   b  (two are shown in this embodiment) for compressing a fluid, such as a liquid or gas, rod assemblies  14   a ,  14   b , crank shafts  72   a ,  72   b , and/or other components. Rod assemblies  14   a ,  14   b  are configured to reciprocate in cylinders  12   a ,  12   b , respectively, so as to compress the fluid. Crank shafts  72   a  and  72   b  are configured to drive the rod assemblies  14   a  and  14   b  within cylinders  12   a  and  12   b  respectively. Rod assemblies  14   a  and  14   b  include one or more valves  52   a  and  52   b  and cup seals  60   a  and  60   b  (described herein). Compressor  10  may be configured to reduce the possibility of damage and/or misalignment to the valves in the compressor when a cup seal needs replacement. The configuration of compressor  10  may help minimize overall replacement time of the cup seal, minimize costs associated with replacing the cup seal, enhance volume clearance in compressor  10 , and reduce noise of compressor  10 . Volume clearance is the space remaining within cylinders  12   a  and  12   b  when the rod assemblies  14   a  and  14   b  are at the most advanced position in their travel within cylinders  12   a  and  12   b . Managing clearance volume may enhance the compressor&#39;s performance. Compressor  10  may be used in oil-less applications where service is performed to replace worn-out cup seals after a given number of hours of operation (e.g., medical oxygen concentrator compressors) and/or in other applications. 
     First crank shaft housing  18   a  encloses first crank shaft  72   a , is operatively coupled to first rod assembly  14   a , and is configured to drive first rod assembly  14   a . In some embodiments first crank shaft  72   a  is operatively coupled with motor shaft  16  that provides torsional energy from the motor (not shown) housed within motor housing  22 . As illustrated in  FIG. 1 , motor shaft  16  is operatively coupled with second crank shaft  72   b  housed within second crank shaft housing  18   b  located at third side  44  along fourth side  46  of compressor assembly  10 . 
     Second crank shaft  72   b  is configured to drive second rod assembly  14   b  to compress gas within second reciprocating space  11   b . Second space  11   b  is defined by second rod assembly  14   b , second cylinder  12   b , and second cap seal  13   b  on along fourth side  46  of compressor assembly  10 . The components along fourth side  46  of compressor assembly  10  may be the same and/or similar to the components located along second side  42  of the compressor assembly  10 . For example, first cap seal  13   a  located along second side  42  may be the same and/or similar to second cap seal  60   b  located along fourth side  46 . 
     In some embodiments, compressor  10  has a tandem arrangement with two cylinders  12   a ,  12   b , having a rod assembly  14   a ,  14   b  received therein. A motor shaft  16  is configured to couple the motor to crankshafts  72   a  and  72   b , which are coupled with one of the two rod assemblies  14   a ,  14   b , so that the movement of the rod assemblies  14   a ,  14   b  oppose each other. However, this embodiment is not intended to be limiting, and it is contemplated that the compressor  10  may have other arrangements and numbers of cylinders  12   a ,  12   b . For example, compressor  10  may be of single or dual acting designs. Compressor  10  may also include more than two cylinders. 
     In some embodiments, rod assemblies  14   a  and  14   b  are configured to alternately reciprocate within cylinders  12   a  and  12   b  respectively so as to compress the fluid. Crank shafts  72   a  and  72   b  are configured to drive pistons  14   a ,  14   b  within cylinders  12   a  and  12   b . In some embodiments, rod assemblies  14   a  and  14   b  are wobble (or WOB-L) rod assemblies. However it is contemplated that other types of rod assembly may be used. Crank shafts  72   a  and  72   b  are housed in crankcases or crank shaft housings  18   a ,  18   b  that are operatively coupled with cylinders  12   a ,  12   b . In some embodiments, two crankcases  18   a ,  18   b  are provided. The crankcases  18   a ,  18   b  are associated with one of the cylinders  12   a ,  12   b . A motor (not shown) is operatively coupled with the crank shafts  72   a  and  72   b  and is configured to drive the crank shafts  72   a  and  72   b . The motor is housed in a motor housing  22  that is operatively coupled with crankcases  18   a ,  18   b.    
     As shown in  FIG. 1 , rod assemblies  14   a  and  14   b  having lower ends  68   a  and  68   b  with bearing centers  71   a  and  71   b  configured to receive a portion of the crank shafts  72   a  and  72   b . Crank shafts  72   a  and  72   b  are offset and not in linear correlation to the axis of motor shaft  16 . In this configuration, motor shaft  16  and rod assemblies  14   a  and  14   b  are configured to be eccentric. The eccentric crank shafts  72   a  and  72   b  are connected to motor shaft  16  such that the axis defined by motor shaft  16  is offset from the axis defined by the center of the bearings. 
     In some embodiments, motor housing  22  includes a motor (not shown) configured to drive crank shafts  72   a  and  72   b . Motor shaft  16  rotates crank shafts  72   a  and  72   b , which in turn causes rod assemblies  14   a  and  14   b , to reciprocate upwardly and downwardly within cylinders  12   a ,  12   b . This configuration enables rod assemblies  14   a  and  14   b  to tilt relative to cylinders  12   a ,  12   b  at all positions (except when rod assemblies  14   a  and  14   b  are positioned such that they are located nearest a first side  40  and a third side  44  of  FIG. 1 ) due to the eccentricity of crank shaft  72 . It is contemplated that crank shaft  72  does not need to be eccentric and may have other configurations or arrangements. As an example, rod assembly  14   a  shown in  FIG. 2  is in the bottom most position and rod assembly  14   b  shown in  FIG. 2  is in the top most position. This configuration of rod assemblies  14   a  and  14   ba  and  14   b  and crank shafts  72  converts the rotary energy from the motor (not shown) into linear motion of rod assemblies  14   a  and  14   ba ,  14   b  within cylinders  12   a ,  12   b . This configuration enables compressor assembly  10  to increase the pressure of the fluid. 
       FIG. 2  illustrates an example of a rod assembly  14  that is similar to rod assemblies  14   a  and  14   b  described above, in accordance with one or more embodiments. Rod assembly  14  includes a connecting rod portion  56 , a head portion  54 , a cup seal  60 , a cap  53 , one or more valves  52 , and/or other components. Connecting rod  56  has a lower end with a bearing  70 . Bearing  70  has a center area  71  configured to receive a portion of a crank shaft (not shown in  FIG. 2 ). Head portion  54  may be the same as and/or similar to head portions  54   a  and  54   b  described in  FIG. 1 . Head portion  54  is operatively coupled to connecting rod portion  56 . In this embodiment, head portion  54  and connecting rod portion  56  are integral. In some embodiments, head portion  54  may be removably coupled to connecting rod portion  56 , and/or head portion  54  and connecting rod portion  56  may be separate from each other in other embodiments. Head portion  54  and/or connecting rod portion  56  may be cast from a strong lightweight material such as aluminum alloy and/or formed in other ways with other materials. In some embodiments, head portion  54  and/or connecting rod portion  56  may be made of steel (e.g., for production engines), made of titanium for a combination of lightness with strength at higher cost (e.g., for high performance engines), cast iron for applications such as motor scooters, and/or a combination of other materials. 
       FIG. 3  illustrates an exemplary head portion  54  of a rod assembly  14 , in accordance with one or more embodiments. Head portion  54  shown in  FIG. 3  may have a receiving surface  51  configured to receive a cup seal (not shown), receive other components of connecting rod assembly  56 , and/or receive other components of compressor  10 . Head portion  54  may have a flat substantially circular configuration with an annular groove  58  defined by an edge  66  of the head portion  54  for receiving the cup seal (described herein). Orifices  39  may be configured to receive one or more screws configured to couple a cap (described herein) with head portion  54 , thereby coupling the cup seal with head portion  54 . In some embodiments, the cup seal may be coupled with head portion  54  using a cap. The cap may be coupled with head portion using one or more screws, and/or other coupling devices. In some embodiments, head portion  54  may have an elevated portion  59 , located on receiving surface  51  of head portion  54 . Elevated portion  59  is defined by an edge  67  and a surface  69 . Surface  69  may be configured such that one or more valves may be removably connected to elevated portion  59  at surface  69  of elevated portion  59 . In some embodiments the one or more valves may be coupled to elevated portion  59  at surface  69  by one or more screws and/or other coupling mechanisms. For example, orifice  79  may be configured to receive a screw for coupling a valve to elevated portion  59  at surface  69 . In some embodiments, orifices  49  located on elevated portion  59  may be configured to receive the one or more valves. 
     Elevated portion  59  may be of different sizes and shapes. In some embodiments, elevated portion  59  may be square shaped, annular shaped, kidney shaped, oval shaped, and/or other shapes. Elevated portion  59  may be of different sizes. For example, elevated portion may be of a size that will allow elevated portion  59  to receive one valve, or may be of a size that will allow elevated portion  59  to receive one or more valves and/or other components. In some embodiments, elevated portion  59  may be an integral part of head portion  54 , may be coupled to head portion  54 , or removably coupled with portion  54 . In some embodiments, elevated portion  59  may be made of the same material as head portion  54 , made of a different material, and/or a combination thereof. 
       FIG. 4  is a cross sectional view of a rod assembly of compressor  10 , in accordance with one or more embodiments.  FIG. 4  shows connecting rod  56 , head portion  54 , groove  58 , and elevated portion  59 . As shown in  FIG. 4 , edge  66  defines groove  58  and elevated portion  59  is defined by surface  69  and edge  67 . Orifices  49  for receiving one or more valves (not shown) and orifice  79  for receiving a coupling device (for example a screw) for securing the one or more valves on elevated portion  59  of head portion  54 . 
     Returning to  FIG. 2 , cup seal  60  is disposed on the head portion  54 . Cup seal  60  is configured to provide a movable seal between first cylinder  12   a  and first rod assembly  14  described in  FIG. 1 . Cup seal  60  may have an outward bias relative to head portion  54  such that it compressively engages inner walls  13   a  of cylinder  12   a  (shown in  FIG. 1 ), throughout rod assembly  14  strokes. Cup seal  60  may adopt an upwardly flexed position with respect to space  11   a  of cylinder  12   a . An example of cup seal  60  is shown in  FIG. 5 . Cup seal  60  may be of annular shape with a hole  65 , a lip  63 , and groove  67 . Dimensions of cup seal  60  may correspond to a compressor type of compressor  10 , dimensions of head portion  54 , dimensions of cap  53 , and/or dimensions of other components of compressor  10 . For example, a height  33  of lip  63 , a width  37  of groove  67 , a cup seal  60  thickness  35 , a diameter  32  of hole  65 , and or other dimensions of cup seal  60  may correspond to a type of compressor  10 , dimensions of head portion  54 , dimensions of cap  53 , and/or dimensions of other components of compressor  10 . 
     Cap  53  is removably coupled with rod assembly  14 . Cap  53  is configured to hold cup seal  60  in place on head portion  54 . One or more screws  62  may be used to secure cap  53  to head portion  54 , thereby also retaining cup seal  60  within groove  58 . In some embodiments, cap  53  may have a substantially circular configuration. In some embodiments, cap  53  may have different configurations and be formed indifferent shapes. In some embodiments, cap  53  may be configured to have a hole  19  to accommodate the shape of elevated portion  59  of head portion  54 . Hole  19  is configured such that when cap  53  is placed on top of head  54 , cap  53  engages head portion  54  such that elevated portion  59  is surrounded by cap  53 . 
       FIGS. 6 and 7  show examples of cap  53  according to one or more embodiments. In the examples shown in  FIG. 6-7 , cap  53  includes four holes  29  configured to receive four screws to be used to secure first cap  53  to head portion  54 , thereby also retaining cup seal  60  within groove  58  of head portion  54  (described above). Also shown in  FIGS. 6-7  is hole  19  configured to receive elevated portion  59  of head portion  54 . Hole  19  may be of different sizes and shapes so as to accommodate elevated portion  59 . For example, hole  19  of cap  53  may be square shaped, annular shaped, kidney shaped, oval shaped, and/or have other shapes. 
     Returning to  FIG. 2 , one or more valves  52  are configured to control air across the head portion  54 . In some embodiments, the one or more valves  52  may be constructed and arranged such that the one or more valves  52  allow air through when rod assembly  14  is moving downwards. In some embodiments, the one or move valves  52  may be constructed and arranged such that the one or more valve  52  allow air through when rod assembly  14  is moving downwards, and/or in other directions. In some embodiments, the one or more valves may be removably coupled to head portion  54 , such that the one or more valves remain coupled to head portion  54  when the cap  53  is detached from the connecting rod assembly  14  (e.g., when cup seal  60  needs to be replaced). 
     In some embodiments, the one or more valves  52  are removably coupled to the elevated portion  59  by one or more screws. In this example, screw  57  may be configured to be inserted through opening  79  (shown in  FIG. 3 ) to couple the one or more valves  52  to head portion  54 . In some embodiments, the one or more valves  52  may be removably coupled to the elevated portion  59  of head portion  54  by other coupling means. 
     Replacing cup seal  60   a , for example, may be performed by removing screws ( 62  shown in  FIG. 2 ), detaching cap  53   a  from head portion  54   a , and removing cup seal from head portion  54   a . The one or more valves  52   a  remain attached to head portion  54   a  while cup seal  60  is removed. A new cup seal  60   a  may be placed on head portion  54 , and held down in place by cap  53   a  that will be coupled to head portion  54   a  using screws  62 . The one or more valves remain attached to head portion  54   a  while the new cup seal  60  is put in place. A configuration of compressor  10  according to one or more embodiments may help reduce the possibility of damage and/or misalignment to the valves which may help reduce noise resulting from misaligned valves and helps managing volume clearance in compressor  10 . 
     In some embodiments, instead of having an elevated portion  59 , head portion  54  may have an indented portion. The indented portion may be configured to receive one or more valves such that the one or more valves remain attached to head portion  54  when cap  53  is detached from head portion  54 . The indented portion of head portion  54  may be of different sizes and shapes. In some embodiments, the indented portion of head portion  54  may be square shaped, round shaped, annular shaped, kidney shaped, oval shaped, and/or other shapes. The indented portion of head portion  54  may be of different sizes. For example, the indented portion may be of a size that will allow it to receive one valve, or may be of a size that will allow it to receive one or more valves and/or other components. 
       FIG. 8  illustrates a method  800  for increasing pressure of a fluid with a compressor. The compressor includes a first cylinder, a first crank shaft housing, a first crank shaft, a motor housing, a motor, and a first rod assembly, and/or other components. The first rod assembly includes a first connecting rod portion, a first head portion, a first cup seal, a first cap, one or more valves, and/or other components. 
     The operations of method  800  presented below are intended to be illustrative. In some embodiments, method  800  may be accomplished with one or more additional operations not described, and/or without one or more of the operations discussed. Additionally, the order in which the operations of method  800  are illustrated in  FIG. 8  and described below is not intended to be limiting. 
     At an operation  802 , a first space for compressing a fluid is formed with the first cylinder. In some embodiments, operation  802  is performed by a first cylinder the same as or similar to first cylinder  12   a  (shown in  FIG. 1  and described herein). 
     At an operation  804 , the first crank shaft housing is operatively coupled with the first cylinder. In some embodiments, operation  804  is performed by first crank shaft housing the same as or similar to connector ( 18   a ) (shown in  FIG. 1  and described herein). 
     At an operation  806 , the first crank shaft is housed within the first crank shaft housing. In some embodiments, operation  806  is performed by first crank shaft the same as or similar to first crank shaft  72   a  (shown in  FIG. 1  and described herein). 
     At an operation  808 , the motor housing is operatively coupled with the first crank shaft housing. In some embodiments, operation  808  is performed by a motor housing the same as or similar to motor housing  22  (shown in  FIG. 1  and described herein). 
     At operation  810 , the motor is housed within the motor housing. The motor is configured to drive the first crank shaft. In some embodiments, operation  810  is performed by a motor the same as or similar to motor  20  (shown in  FIG. 1  and described herein). 
     At operation  812 , the first rod assembly is reciprocated within the first cylinder so as to compress the fluid within the first space. The first rod assembly is driven by the first crank shaft. In some embodiments, operation  812  is performed by a first rod assembly the same as or similar to first rod assembly  14   a  (shown in  FIG. 1  and described herein). 
     At operation  814 , the first rod assembly is coupled to the first crank shaft with the first connecting rod portion. In some embodiments, operation  814  is performed by a first connecting rod portion the same as or similar to the first connecting rod portion  56   a  (shown in  FIG. 1  and described herein). 
     At operation  816 , the first head portion is operatively coupled to the first connecting rod. In some embodiments, operation  816  is performed by a first head portion the same as or similar to first head portion  54   a  (shown in  FIG. 1  and described herein). 
     At operation  818 , a movable seal is provided between the first cylinder and the first rod assembly by the first cup seal. In some embodiments, operation  818  is performed by a first cup seal the same as or similar to first cup seal  60   a  (shown in  FIG. 1  and described herein). 
     At operation  820 , the cup seal is held on place on the first head portion by the first cap. In some embodiments, operation  820  is performed by a first cap the same as or similar to first cap  53   a  (shown in  FIG. 1  and described herein). 
     At operation  822 , the one or more valves are constructed and arranged to remain coupled to the first head portion when the first cap is detached from the first connecting rod assembly. The one or more valves are configured to control air across the head portion. In some embodiments, operation  822  is performed by one or more valves the same as or similar to one or more valves  52   a  (shown in  FIG. 1  and described herein). 
     In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word “comprising” or “including” does not exclude the presence of elements or steps other than those listed in a claim. In a device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. In any device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain elements are recited in mutually different dependent claims does not indicate that these elements cannot be used in combination. 
     Although the description provided above provides detail for the purpose of illustration based on what is currently considered to be the most practical and preferred embodiments, it is to be understood that such detail is solely for that purpose and that the disclosure is not limited to the expressly disclosed embodiments, but, on the contrary, is intended to cover modifications and equivalent arrangements that are within the spirit and scope of the appended claims. For example, it is to be understood that the present disclosure contemplates that, to the extent possible, one or more features of any embodiment can be combined with one or more features of any other embodiment.