Patent Publication Number: US-2020284158-A1

Title: Device for cleaning turbine blades of a jet engine

Description:
CROSS-REFERENCE TO PRIOR APPLICATIONS 
     This application is a U.S. National Phase Application under 35 U.S.C. § 371 of International Application No. PCT/EP2018/078204, filed on Oct. 16, 2018, and claims benefit to German Patent Application No. DE 10 2017 218 425.6, filed on Oct. 16, 2017. The International Application was published in German on Apr. 25, 2019 as WO 2019/076875 under PCT Article 21(2). 
    
    
     FIELD 
     The invention relates to a device for cleaning turbine blades of a turbine stage of a jet engine. 
     BACKGROUND 
     Aircraft jet engines have one or more compressor stages, a combustion chamber, and one or more turbine stages. In the turbine stages, the hot combustion gases, which originate from the combustion chamber, discharge a portion of their thermal and mechanical energy, which is used to drive the compressor stages. A contamination of an aircraft jet engine may lead to a reduction of the degree of efficiency, which results in increased fuel consumption and consequently increased environmental pollution. This applies particularly when the contamination forms a coating on the components of a jet engine through which air flows and thereby impairs the surface quality. 
     Particularly in aircraft that are used in desert regions, there is further the problem that the desert sand (CMAS) which is in the air is drawn in by the engine and, as a result of the high temperatures in the combustion chamber, becomes molten. When striking the high-pressure turbine blades (HPT blades), which are arranged in the flow direction downstream of the combustion chamber, the molten sand solidifies again. In addition, extremely fine sand reaches the cooling air, which is drawn off in the high-pressure compressor from the inner side into the internal cooling channels of the high-pressure turbine blades, which open at the profile projection of the blades in order to form a film cooling, and is deposited at that location. Both effects leads to a narrowing or blockage of the cooling air channels of the high-pressure turbine blades so that they are no longer sufficiently cooled. In connection with erosion effects and oxidation effects, the high-pressure turbine blades become worn substantially more quickly and the period of use and service-life is drastically reduced, in particular in comparison with use outside desert regions. 
     In order to clean the high-pressure turbine blades, the affected engine is removed from the aircraft and engine maintenance is undertaken in order, in this instance, to subject the high-pressure turbine blades to a repair cycle, which involves cleaning. This engine maintenance is complex and cost-intensive. 
     DE 10 2012 002 275 A1 discloses a method in which the aircraft engine can remain on the aircraft in order to clean the high-pressure turbine blades. To this end, via a lateral opening of the engine a cleaning device, where applicable using an auxiliary introduction means, is introduced into the combustion chamber and has a jet nozzle for producing a pressure fluid jet, by means of which deposits on the high-pressure turbine blades are intended to be removed. After the introduction, the cleaning device is freely movable and only slightly limited by any auxiliary introduction means, which may be provided. The orientation of the cleaning device with respect to the high-pressure turbine blades can be verified by means of a borescope which is guided through the cleaning device. The results of such a method are, however, not always satisfactory. 
     SUMMARY 
     An embodiment of the present invention provides a device that cleans turbine blades of a turbine stage of a jet engine. The device includes a cleaning lance. The cleaning lance is configured to be introduced into the jet engine through a through-opening. The cleaning lance has an outlet opening at one end thereof and a supply connection for supplying cleaning media at an other end thereof. The cleaning lance includes a guide configured to guide the cleaning lance for clear and reproducible positioning and orientation of the cleaning lance; and a securing device configured to releasably secure the guide to an outer side of the jet engine. The securing device is configured to adjustably orient the guide to a predetermined orientation with respect to the outer side of the jet engine. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be described in even greater detail below based on the exemplary figures. The invention is not limited to the exemplary embodiments. Other features and advantages of various embodiments of the present invention will become apparent by reading the following detailed description with reference to the attached drawings which illustrate the following: 
         FIG. 1  shows an embodiment of a device according to the invention; 
         FIGS. 2 a - c    are schematic illustrations of a use of the device from  FIG. 1 ; 
         FIG. 3  is a switch valve for the device according to  FIGS. 1 and 2 ; and 
         FIGS. 4 and 5  are sectioned illustrations of the switch valve according to  FIG. 3  in different switching positions. 
     
    
    
     DETAILED DESCRIPTION 
     An embodiment of the present invention provides a device for cleaning turbine blades of a turbine stage of a jet engine, which is improved compared with the prior art. 
     The invention relates to a device for cleaning turbine blades of a turbine stage of a jet engine. The device includes a cleaning lance for introducing into a jet engine having an outlet opening at one end thereof and a supply connection for supplying cleaning medium at the other end thereof. The device includes a guide for the cleaning lance for clear and reproducible positioning and orientation of the cleaning lance with respect to the guide, and a securing device for releasably securing the guide to the outer side of the jet engine. The securing device has an orientation unit, by means of which the guide can be adjusted to a predetermined orientation with respect to the outer side of the jet engine. 
     The turbine blades, which are intended to be cleaned, may in particular be the high-pressure turbine blades of a high-pressure turbine stage, for example, the first high-pressure turbine stage. 
     The invention has recognized that for a continuously satisfactory cleaning of the turbine blades the cleaning medium should strike the surface of each turbine blade which is intended to be cleaned at a predetermined angle and—if the cleaning jet does not directly cover the entire surface which is intended to be cleaned—it is ensured that the cleaning jet is guided over the entire surface which is intended to be cleaned. The position and orientation of the outlet opening of the cleaning lance required for a good cleaning effect with respect to the turbine blades which are intended to be cleaned may be defined as specifications in this instance. 
     In order to comply in a reproducible manner with the specifications with respect to the position and orientation of the outlet opening of the cleaning lance with respect to the turbine blades, which are intended to be cleaned, there is first provision according to the invention for the cleaning lance to be guided through a guide in a securing device for clear and reproducible positioning and orientation of the cleaning lance. So that a guide is suitable “for clear and reproducible positioning and orientation of the cleaning lance”, the cleaning lance and/or guide has/have means, via which the relative movement with respect to each other can be determined in defined positions of the cleaning lance in the guide and/or the number of degrees of freedom of the cleaning lance in the guide is limited. In both cases, the guiding is carried out without play to the greatest possible extent. 
     For example, there may be provided locking elements and/or securing screws by means of which the cleaning lance can be adjusted selectively in positions with respect to the guide determined by the locking elements and/or securing screws. The locking elements and/or securing screws may in this instance be arranged in the guide or the cleaning lance The respective other component then has, for example, corresponding indentations or recesses for engagement of the locking elements and/or securing screws. 
     In order to limit the number of degrees of freedom of the cleaning lance in the guide, there may be provided, for example, groove, rail or linear guides that limit the degrees of freedom of the relative contact of the cleaning lance with respect to the guide to the direction predetermined by the groove and/or rail. The movability of the cleaning lance in the guide can thus be limited, for example, to an individual linear movement without degrees of freedom of rotation existing. 
     It is preferable for the guide to be constructed to limit the movability of the cleaning lance with respect to the guide to one degree of freedom. The degree of freedom may in this instance represent a rotational movement, a linear movement, and/or any, also partial, combination thereof. It is preferable for the single degree of freedom to which the movement is limited to be a rectilinear translation degree of freedom. It is preferable for the single degree of freedom to be configured in such a manner that—in the mounted state of the device—as a result of movement along the single degree of freedom, the outlet end of the cleaning lance is moved in a direction radial relative to the axis of the rotor of the jet engine, preferably in a linear manner. 
     So that the specifications that exist for a good cleaning action are also actually complied with regard to the position and orientation of the cleaning lance with respect to the turbine blades, which are intended to be processed, in addition to the described guiding of the cleaning lance it is further necessary for the guide itself to be arranged in a predetermined position and orientation with respect to the turbine blades which are intended to be cleaned. The position of the guide is in this instance substantially predetermined by the through-opening for the cleaning lance in the jet engine. 
     However, the invention has recognized that directly securing the guide to the outer side of the jet engine in the region of the through-opening without further adjustment possibilities cannot safely ensure a position and orientation of the cleaning lance in accordance with the specifications. 
     In order to enable this, the device according to the invention includes a securing device with an orientation unit, by means of which the orientation of the guide can be adjusted. As a result of the orientation unit of the securing device, orientation errors can be prevented. 
     The securing device may have as securing means a threaded portion for engagement in a thread of the through-opening for the cleaning lance and/or screws for releasable securing to the outer side of the jet engine. In particular, the threaded portion may be a portion of a hollow screw with a conically formed head. The cleaning lance may be guided through the hollow screw which in turn can engage in an inner thread of the through-opening. As a result of the conically formed head, with a suitable formation of the corresponding counter-piece of the securing device, it is possible for the counter-piece to be fixed to the through-opening in a position suitable for the desired orientation of the guide and to be secured in this position. 
     The securing device has, between the securing means or a portion of the securing device, which is secured in a fixed manner with respect to the jet engine (for example, the securing means), and the portion of the securing device which comprises the guide a movable and/or deformable portion which enables the orientation of the guide. The orientation device may act directly on this portion, for example, by the position of the two components of the securing device being able to be changed with respect to each other via the orientation device. 
     The orientation unit preferably has one or more stop faces, which are configured to abut defined components of the jet engine and to which the portion of the securing device that includes the guide are connected. In this instance, at least a portion of the stop faces can preferably be adjusted, for example, displaced using adjustment screws or threaded spindles. It is also possible for the free end of an adjustment screw to directly form an adjustable stop face. As a result of the stop faces, the orientation of the guide with respect to the outer side of the jet engine is fixed. The adjustability of the stop faces makes the orientation of the guide adjustable. 
     In the device according to the invention for cleaning turbine blades of a turbine stage of a jet engine, the position and orientation of the outlet opening of the cleaning lance can be reliably adjusted to a specification as a result of the orientability of the guide provided according to the invention and the reproducible positioning of the cleaning lance with respect to the guide. The correct orientation of the guide necessary for this purpose can be achieved by orientation of the guide with respect to components of the engine, the position of which can be used as a reliable reference, for example, by stop faces abutting these components. Alternatively or additionally, it is possible for the correct orientation of the guide to be found by means of measurement, for example, by means of laser, or by means of auxiliary orientation members arranged on the guide, for example, circular levels. 
     It is preferable for the device to include a guide mechanism, by means of which the cleaning lance can be moved along the guide. In this instance, the guide mechanism is preferably configured in such a manner that it moves the outlet end of the cleaning lance in a direction radial relative to the axis of the rotor of the jet engine, preferably in a linear manner. The movement may, for example, be achieved by limiting the movability of the cleaning lance to a corresponding single degree of freedom. In this instance, it is self-evident that the desired movement at the outlet end of the cleaning lance will generally only occur when the guide is orientated in accordance with the respective specifications. 
     The guide mechanism may have a crank drive for introducing the movement along the guide. As a result of a corresponding crank drive, an oscillating movement of the outlet end of the cleaning lance, which is advantageous for uniform cleaning of the turbine blade, can be achieved. This applies in particular to a so-called stochastic cleaning in which the cleaning of all the turbine blades of a stage is carried out together. To this end, the turbine stage is continuously rotated with the turbine blades which are intended to be cleaned and the jet of the cleaning medium discharged from the outlet opening of the cleaning lance is continuously moved back and forth in an oscillating manner in a direction perpendicular to the rotation axis of the turbine stage so that, after a period of time which can be established, the jet of the cleaning medium was guided at least once over all regions of each turbine blade of the turbine stage which are in principle intended to be reached by the jet. By appropriately selecting the rotation speed of the turbine stage and the oscillation speed, a uniform cleaning over the length of the individual turbine blades can also be ensured. 
     So that the device can be used in a variable manner for different engine models, the cleaning lance may be replaceable and/or the crank of the crank drive may be longitudinally adjustable. By means of replacement of the cleaning lance, the device can be adapted to different engine geometries. Via the longitudinal adjustment of the crank drive, the travel range of the device can be adapted to the length of the turbine blades which are intended to be cleaned. 
     Furthermore, other guide mechanisms are also possible, for example, guide mechanisms comprising a helical gear. The travel range of the device can then be freely controlled via the guide mechanism. 
     The guide mechanism can be driven manually, for example, by means of a hand crank. However, it is preferable for the guide mechanism to include a controllable drive, preferably a step motor, for moving the cleaning lance along the guide. If a crank drive is present, the drive can act on the crank drive; in the case of a helical gear, it can act on the threaded spindle. 
     For simpler handling, the device can preferably be disassembled into sub-assemblies. The device thereby does not have to be secured in a single step and as a whole to the jet engine, which, as a result of the required introduction of the cleaning lance into the opening of the jet engine, may be difficult, but it is instead possible to assemble the components which are combined to form sub-assemblies of the device one after the other. For example, the cleaning lance may form one sub-assembly, whilst the guide is associated with another sub-assembly. As a result of the ability of the device to be disassembled, the capacity of the device for storage and transport can also be improved. 
     The device according to the invention is preferably configured for cleaning with a cleaning medium comprising carbon dioxide. The carbon dioxide may be in the form of pellets, which are conveyed through the cleaning lance using a propellant gas. However, it is also possible to provide liquid carbon dioxide as a pre-stage of the cleaning medium. The liquid carbon dioxide at least partially solidifies when discharged from the cleaning lance and forms a solid component in the form of carbon dioxide flakes. 
     In order to improve the cleaning action with such a cleaning medium, there may be provision for the turbine blades to be heated prior to the cleaning with corresponding cleaning medium. The already good cleaning action of the cleaning medium is thereby further increased. This is because, as a result of previous heating of the turbine blade, the temperature difference between the cleaning medium and cleaning region is increased, which contributes to breaking up and flaking of contamination. 
     In order to heat the turbine blades, hot gas, in particular hot air, can be used. In this instance, the hot gas may be directed through the same cleaning lance to the turbine blades, through which the cleaning medium, for example, pressurized gas with carbon dioxide, is subsequently guided. 
     In order in this instance to prevent mixing of the cleaning medium with the hot gas, the device preferably has a switch valve for selectively supplying two media to the supply connection of the cleaning lance, wherein the switch valve is configured in such a manner that it switches from the second inlet of the switch valve discretely to the first inlet if there is sufficient pressure at the first inlet or a control inlet. The term “discrete switching” is intended to mean in this context that at no time during the switching from one inlet to the other inlet are both inlets even only partially open at the same time. 
     As a result of the switching device, the medium that is present at the second inlet of the switch valve, for example, hot gas, is prevented from coming into contact with the medium present at the first inlet. In the case of cleaning medium comprising solid carbon dioxide at the first inlet, an undesirable sublimation and clumping of the carbon dioxide can thus be prevented. 
     It is preferable for the switch valve to have a restoring element that switches the switch valve discretely from the first inlet to the second inlet if there is no longer sufficient pressure at the first inlet or a control inlet. As a result of a corresponding restoring element, the switch valve is switched to the second inlet if there is no longer sufficient pressure at the first inlet or the control inlet. If the switch valve is controlled directly via the first inlet, this is comparable with a lack of influx through this inlet. In any case, a return flow into the first inlet can be prevented by the switch valve. 
     Of course, the switch valve may also be used with any media other than the combination of cleaning medium comprising carbon dioxide and hot gas as mentioned merely by way of example. 
     The device according to the invention enables cleaning of turbine blades of a turbine stage, whilst the jet engine remains on the aircraft (on-wing). As a through-opening for the cleaning lance, it is possible to use, for example, a spark plug opening, a fuel injection nozzle opening and/or a borescope opening on the housing of the jet engine. 
     The invention is now described by way of example with reference to an advantageous embodiment and the drawings. 
       FIG. 1  shows a first embodiment of a device  1  according to the invention for cleaning turbine blades  82  of a turbine stage  81  of a jet engine  80 . 
     The device  1  has a cleaning lance  2  which can be introduced through a lateral opening  83  into a jet engine  80 . The cleaning lance  2  has at the end thereof which is intended to be introduced into the jet engine  80  an outlet opening  3  from which cleaning medium—for example, air with solid carbon dioxide—can be discharged under high pressure. The cleaning medium is supplied via a supply connection  4  to the other end of the cleaning lance  2 . 
     The cleaning lance  2  is guided in a linear manner in a guide  10 . To this end, the cleaning lance  2  is securely connected to a carrier  5 , which is guided in a play-free manner on a linear guide  11  so that the cleaning lance  2  can be moved exclusively in the direction indicated by the arrow  90 . The cleaning lance  2  therefore has—if guided in the guide  10 —only a purely translational degree of freedom, whereby the cleaning lance  2  can be positioned in a clear and reproducible manner with respect to the guide  10 —that is to say, by means of corresponding displacement along the guide  10 . 
     The device  1  further has a hollow screw  21  with a conically formed head  22 , which together with a counter-piece  23  forms a securing device  20 , via which the device  1  can be secured to the outer side of a jet engine  80 . As will be further explained below with reference to  FIGS. 2 a - c   , the conically formed head  22  of the hollow screw  21  allows a securing of the device  1  in the desired orientation of the guide  10  since between the hollow screw  21  acting as a portion of the securing device  20  and the counter-piece  23 , a movable portion is provided as an additional portion of the securing device  20 . 
     Furthermore, with the device  1 , an orientation unit  30  is further provided as a portion of the securing device  20 . The orientation unit  30  is securely connected to the counter-piece  23  of the securing device  20  and has a plurality of stop faces  31  in the form of the free ends  32  of adjustment screws  33 . Furthermore, the adjustment screws  33  are further arranged on a carriage  35  which can be displaced along a linear guide  34 , wherein the carriage  35  can be fixed in any position along the linear guide  34 . 
     The device  1  also comprises a guide mechanism  40 , by means of which the cleaning lance  2  can be moved along the guide  10 , whereby the outlet end  3  of the cleaning lance  2  can ultimately also be linearly moved parallel with the direction  90 . 
     The guide mechanism  40  includes a crank drive  41 , the connecting rod  42  of which is pivotably secured at one end thereof to the carrier  5 . At the other end thereof, the connection rod  42  is rotatably connected to a crank journal, which is arranged remotely from the crank axis on a crank  43 , wherein the crank  43  is in turn rotatably supported about the crank axis. Via the adjustment screw  44 , the spacing between the crank journal and crank axis can be changed, whereby the travel carried out by the carrier  5  can be adjusted in terms of its length. 
     In order to actuate the crank drive  41 , a hand crank  45  is provided. However, it is also possible in place of the hand crank  45  to provide a controllable drive. 
     As can be seen below from the explanation of  FIGS. 2 a - c   , the device  1  according to  FIG. 1  can be disassembled into individual sub-assemblies, whereby the use of the device  1  is facilitated. A first sub-assembly includes the securing device  20  with an orientation unit  30 , a second sub-assembly comprises the cleaning lance  2  including the carrier  5 . The third sub-assembly comprises the guide  10 , whilst the guide mechanism  40  forms the fourth sub-assembly. 
       FIGS. 2 a - c    schematically illustrate a typical use of the device  1  from  FIG. 1 . 
     Beginning with  FIG. 2 a   , in a first step the first sub-assembly including the securing device  20  was initially placed on a lateral opening  83  of the jet engine  80  provided for introducing the cleaning lance  2 —in this embodiment, a spark plug retention member, but not yet securely connected thereto. Subsequently, the cleaning lance  2  was guided as the second subassembly through the hollow screw  21  of the securing device  2  and subsequently through the opening  83  in the jet engine  80  so that the outlet opening  3  of the cleaning lance  2  is already in principle arranged in front of the turbine blades  82  to be cleaned, but without actually being orientated toward the inlet edges of the turbine blades  82 . 
     Afterwards, the securing device  20  is orientated and the guide  10  is securely connected to the securing device  20  so that the orientation of the guide  10  is clearly defined by the orientation of the securing device  20 . In  FIG. 2 b   , the result of the steps which are described in greater detail below is illustrated. 
     Initially, the hollow screw  21  is screwed into the thread of the opening  82  in the jet engine  80 , but not tightened so that, although the position of the securing device  20  with respect to the jet engine  80  and in particular the opening  83  is substantially fixed, the position of the securing device  20  can certainly still be changed. 
     Subsequently, the carriage  35  of the orientation unit  30  is displaced into a predetermined position and fixed at that location. In this position of the carriage  35 , the stop faces  31  adjoin the free ends  32  of the screws  33  on a component of the jet engine  80 —in this instance, a flange of the housing. This abutment ensures the correct orientation of the securing device  20 , in which the securing device  20  is subsequently ultimately secured by tightening the hollow screw  21  on the jet engine  80 . 
     Afterwards, the guide  10  is secured to the securing device  20 , where the carrier  5  of the cleaning lance  2  is introduced into the linear guide  11 . Because the securing device  20  is orientated via the orientation unit  30 , the guiding unit  10 , which is securely connected thereto, is also considered to be orientated because the guide unit  10  can be secured in only one predetermined position on the securing device  20 . 
     Finally, the device  1  is completed as in  FIG. 2 c    by the guide mechanism  40  being mounted on the guide  10 . As a result of the guide mechanism  40 , the carrier  5  can be moved in an oscillating movement linearly along the guide rail  11 , whereby the outlet opening  3  of the cleaning lance  2  also makes a corresponding movement. As a result of suitable orientation of the cleaning lance  2  by means of corresponding orientation of the guide  10  or the securing device  20  and suitable adjustment of the stroke travel via the adjustment screw  44  of the crank drive, good cleaning of the turbine blade  82  can be ensured over the entire length thereof. 
     The device  1  according to  FIGS. 1 and 2   a - c  is configured to clean with a cleaning medium comprising carbon dioxide, which forms dry ice flakes at the latest when the cleaning medium is discharged from the cleaning lance, wherein, before the passage of cleaning medium through the cleaning lance  2 , hot air is blown into order to heat the turbine blades  83  which are intended to be cleaned. 
     In order to prevent mixing of cleaning medium and hot air, a switch valve  50  according to  FIGS. 3 and 4  is arranged upstream of the supply connection  4  of the cleaning lance  2  (cf.  FIG. 1 ). 
     The switch valve  50  has a first inlet  51  for the cleaning medium, a second inlet  52  for the hot air, a control inlet  53  and an outlet  54 . The outlet  54  is directly connected to the supply connection  4  of the cleaning lance  2 . 
     The switch valve  50  is constructed for discrete switching between the first inlet and the second inlet  51 ,  52  as a result of a control pressure at the control inlet  53 . In other words, the switch valve  50  is configured in such a manner that media which are supplied via the two inlets  51 ,  52  cannot at any time—not even during a switching operation—mix in the region of the switch valve  50 , nor is there produced any return flow of a medium flowing in from one inlet into the other inlet. 
     In the sectioned illustration according to  FIG. 4 , the inner side of the switch valve  50  is illustrated. The switch valve  50  includes a piston  55  having two line passages  56 ,  57 . One line passage  56  is angled so that the hot air flowing through the inlet  52  in the direction from the blade level in the position of the valve illustrated in  FIG. 4  is redirected toward the outlet  54 . The other line passage  57  in the position shown in  FIG. 5  connects the inlet  51  for the cleaning medium to the outlet  54 . 
     The two line passages  56 ,  57  are configured in such a manner that in no position of the piston  55  between the two end positions shown in  FIGS. 4 and 5  would both inlets  51 ,  52  be connected to the outlet  54  at the same time. Instead, there is an intermediate position of the piston  55 , in which none of the two inlets  51 ,  52  is connected to the outlet. 
     The control of the switch valve  50  is carried out via the control line  53 . If there is not sufficient pressure at the control inlet  53 , the piston  55  is pressed by the spring  58  into the position which is illustrated in  FIG. 4  and in which the second inlet  52  is connected to the outlet  54 . 
     If the control inlet  53  is acted on with pressure which is sufficient to overcome the resilient force of the spring  58 , the piston  55  is displaced into the position shown in  FIG. 5 , whereby the inlet  51  for the cleaning medium is connected to the outlet. 
     The control inlet  53  can be acted on by means of a bypass from the line which is connected to the inlet  51 . In this instance, the switch valve  50  switches to the first inlet  51  as soon as there is sufficient pressure applied thereto to overcome the resilient force of the spring  58  via the bypass to the control inlet  53 . 
     While embodiments of the invention have been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. It will be understood that changes and modifications may be made by those of ordinary skill within the scope of the following claims. In particular, the present invention covers further embodiments with any combination of features from different embodiments described above and below. Additionally, statements made herein characterizing the invention refer to an embodiment of the invention and not necessarily all embodiments. 
     The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B and C” should be interpreted as one or more of a group of elements consisting of A, B and C, and should not be interpreted as requiring at least one of each of the listed elements A, B and C, regardless of whether A, B and C are related as categories or otherwise. Moreover, the recitation of “A, B and/or C” or “at least one of A, B or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B and C.