Patent Publication Number: US-8985278-B2

Title: Lubrication system having segmented anti-backflow feature

Description:
BACKGROUND 
     The present disclosure relates to a lubrication system for a gas turbine engine and, more particularly, to a lubrication system that remains operable in reduced gravity (reduced-G) conditions. 
     Aircraft gas turbine engines include a lubrication system to supply lubrication to various components. An auxiliary lubrication capability may also be provided so that at least some components can be lubricated under transient conditions. It is also desirable to ensure that at least some components are not starved of lubricant during reduced-G conditions in which acceleration due to gravity, is partially or entirely counteracted by aircraft maneuvers and/or orientation. 
     SUMMARY 
     A lubricant tank according to one disclosed non-limiting embodiment of the present disclosure includes a lubricant tank discharge passageway at least partially within a tank body. A segmented anti-back flow structure mounted adjacent to the lubricant tank body and the lubricant tank discharge passageway. 
     In a further embodiment of the foregoing embodiment, the lubricant tank body and the lubricant tank discharge passageway are defined along a non-linear axis. 
     In a further embodiment of any of the foregoing embodiments, the segmented anti-back flow structure includes a multiple of walls each of which includes an aperture which extends therethrough. 
     In the alternative or additionally thereto, the foregoing embodiment, includes at least one tube which extends though at least one of the multiple of walls, the at least one tube extends toward a bottom of the lubricant tank body 
     In the alternative or additionally thereto, the foregoing embodiment, includes at least one of the multiple of walls surround the lubricant tank discharge passageway. 
     In the alternative or additionally thereto, each of the tubes extends towards an adjacent lower wall. 
     In the alternative or additionally thereto, each of the multiple of walls surround the lubricant tank discharge passageway. 
     In a further embodiment of the foregoing embodiment, the lubricant tank discharge passageway includes an opening to allow lubricant transfer between the lubricant tank discharge passageway and the lubricant tank body. 
     A lubrication system, according to another disclosed non-limiting embodiment of the present disclosure includes a main lubricant tank configured to hold lubricant that is communicated from the main lubricant tank to a component along a first communication path. An auxiliary lubricant tank configured to hold lubricant that is communicated from the component to the auxiliary lubricant tank along a second communication path, the first communication path separate from the second communication path. An auxiliary lubricant tank discharge passageway at least partially within the auxiliary lubricant tank, the auxiliary lubricant tank discharge passageway includes an opening to permit lubricant transfer between the auxiliary lubricant tank and the auxiliary lubricant tank discharge passageway. A segmented anti-back flow structure mounted adjacent to the auxiliary tank and the auxiliary lubricant tank discharge passageway. 
     In a further embodiment of any of the foregoing embodiments, the opening is a multiple of perforations. 
     In the alternative or additionally thereto, each of the multiple perforations have an area that decreases toward a bottom of the auxiliary lubricant tank discharge passageway. 
     In a further embodiment of any of the foregoing embodiments, the auxiliary lubricant tank and the auxiliary lubricant tank discharge passageway are defined along a non-linear axis. 
     In the alternative or additionally thereto, the segmented anti-back flow structure includes a multiple of walls each of which includes a tube which extends therethrough. 
     In the alternative or additionally thereto each of the tubes extends toward a bottom of the auxiliary lubricant tank. 
     In the alternative or additionally thereto, at least one of the tubes extends towards an adjacent lower wall with respect to a bottom of the auxiliary lubricant tank. 
     A method of reducing lubrication starvation from a lubrication system in communication with a geared architecture for a gas turbine engine, according to another disclosed non-limiting embodiment of the present disclosure includes segmenting an auxiliary lubricant tank defined around an auxiliary lubricant tank discharge passageway. 
     In a further embodiment of any of the foregoing embodiments, the method includes segmenting the auxiliary lubricant tank with a multiple of walls each of which includes a tube which extends therefrom. 
     In the alternative or additionally thereto, the multiple of walls are with respect to a bottom of the auxiliary lubricant tank, each of the tubes directed toward the bottom from a respective wall. 
     In a further embodiment of any of the foregoing embodiments, the method includes orienting the auxiliary lubricant tank and the auxiliary lubricant tank discharge passageway along a non-linear axis. 
     In the alternative or additionally thereto, the method includes forming an opening in the auxiliary lubricant tank discharge passageway along an inner radius thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiment. The drawings that accompany the detailed description can be briefly described as follows: 
         FIG. 1  is a schematic cross-section of a gas turbine engine; 
         FIG. 2  is a cross sectional side elevation view of a gear train configured as a star system and useful in an aircraft gas turbine engine; 
         FIG. 3  is a schematic diagram showing a lubrication system in a normal state of operation, i.e. with the lubricant pressure at a normal level; 
         FIG. 4  is a schematic diagram showing the lubrication system of  FIG. 3  shortly after the onset of an abnormal state of operation, i.e. with the lubricant pressure lower than a normal level; 
         FIG. 5  is a schematic diagram showing the lubrication system at a later time than that shown in  FIG. 4 ; 
         FIG. 6  is a schematic view showing an auxiliary lubricant tank mounted adjacent to a Fan Drive Gear System of a geared turbofan engine according to one non-limiting embodiment; 
         FIG. 7  is an expanded schematic view showing the auxiliary lubricant tank with a segmented anti-back flow structure; 
         FIG. 8  is an expanded schematic view showing the auxiliary lubricant tank with a segmented anti-back flow structure during an example normal operation; 
         FIG. 9  is an expanded schematic view showing the auxiliary lubricant tank with a segmented anti-back flow structure during an example reduced-G operation; and 
         FIG. 10  is an expanded schematic view showing the auxiliary lubricant tank with a segmented anti-back flow structure according to another non-limiting embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  schematically illustrates a gas turbine engine  20 . The gas turbine engine  20  is disclosed herein as a two-spool turbofan that generally incorporates a fan section  22 , a compressor section  24 , a combustor section  26  and a turbine section  28 . Alternative engines might include an augmentor section (not shown) among other systems or features. The fan section  22  drives air along a bypass flowpath while the compressor section  24  drives air along a core flowpath for compression and communication into the combustor section  26  then expansion through the turbine section  28 . Although depicted as a turbofan gas turbine engine in the disclosed non-limiting embodiment, it should be understood that the concepts described herein are not limited to use with turbofans as the teachings may be applied to other types of turbine engines such as a three-spool (plus fan) engine wherein an intermediate spool includes an intermediate pressure compressor (IPC) between the LPC and HPC and an intermediate pressure turbine (IPT) between the HPT and LPT. 
     The engine  20  generally includes a low spool  30  and a high spool  32  mounted for rotation about an engine central longitudinal axis A relative to an engine static structure  36  via several bearing structures  38 . The low spool  30  generally includes an inner shaft  40  that interconnects a fan  42 , a low pressure compressor  44  (“LPC”) and a low pressure turbine  46  (“LPT”). The inner shaft  40  drives the fan  42  through a geared architecture  48  to drive the fan  42  at a lower speed than the low spool  30 . An exemplary reduction transmission is an epicyclic transmission, namely a planetary or star gear system. 
     The high spool  32  includes an outer shaft  50  that interconnects a high pressure compressor  52  (“HPC”) and high pressure turbine  54  (“HPT”). A combustor  56  is arranged between the high pressure compressor  52  and the high pressure turbine  54 . The inner shaft  40  and the outer shaft  50  are concentric and rotate about the engine central longitudinal axis A which is collinear with their longitudinal axes. 
     Core airflow is compressed by the low pressure compressor  44  then the high pressure compressor  52 , mixed with the fuel and burned in the combustor  56 , then expanded over the high pressure turbine  54  and low pressure turbine  46 . The turbines  54 ,  46  rotationally drive the respective low spool  30  and high spool  32  in response to the expansion. 
     The main engine shafts  40 ,  50  are supported at a plurality of points by bearing structures  38  within the static structure  36 . It should be understood that various bearing systems  38  at various locations may alternatively or additionally be provided. 
     In one non-limiting example, the gas turbine engine  20  is a high-bypass geared aircraft engine. In a further example, the gas turbine engine  20  bypass ratio is greater than about six (6:1). The geared architecture  48  can include an epicyclic gear train, such as a planetary gear system or other gear system. The example epicyclic gear train has a gear reduction ratio of greater than about 2.3, and in another example is greater than about 2.5:1. The geared turbofan enables operation of the low spool  30  at higher speeds which can increase the operational efficiency of the low pressure compressor  44  and low pressure turbine  46  and render increased pressure in a fewer number of stages. 
     A pressure ratio associated with the low pressure turbine  46  is pressure measured prior to the inlet of the low pressure turbine  46  as related to the pressure at the outlet of the low pressure turbine  46  prior to an exhaust nozzle of the gas turbine engine  20 . In one non-limiting embodiment, the bypass ratio of the gas turbine engine  20  is greater than about ten (10:1), the fan diameter is significantly larger than that of the low pressure compressor  44 , and the low pressure turbine  46  has a pressure ratio that is greater than about five (5:1). It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present disclosure is applicable to other gas turbine engines including direct drive turbofans. 
     In one embodiment, a significant amount of thrust is provided by the bypass flow path B due to the high bypass ratio. The fan section  22  of the gas turbine engine  20  is designed for a particular flight condition—typically cruise at about 0.8 Mach and about 35,000 feet. This flight condition, with the gas turbine engine  20  at its best fuel consumption, is also known as bucket cruise Thrust Specific Fuel Consumption (TSFC). TSFC is an industry standard parameter of fuel consumption per unit of thrust. 
     Fan Pressure Ratio is the pressure ratio across a blade of the fan section  22  without the use of a Fan Exit Guide Vane system. The low Fan Pressure Ratio according to one non-limiting embodiment of the example gas turbine engine  20  is less than 1.45. Low Corrected Fan Tip Speed is the actual fan tip speed divided by an industry standard temperature correction of “T”/518.7 0.5 . in which “T” represents the ambient temperature in degrees Rankine. The Low Corrected Fan Tip Speed according to one non-limiting embodiment of the example gas turbine engine  20  is less than about 1150 fps (351 m/s). 
     With reference to  FIG. 2 , the geared architecture  48  includes a sun gear  60  driven by a sun gear input shaft  62  from the low speed spool  30 , a ring gear  64  connected to a ring gear output shaft  66  to drive the fan  42 , and a set of intermediate gears  68  in meshing engagement with the sun gear  60  and ring gear  64 . Each intermediate gear  68  is mounted about a journal pin  70  which are each respectively supported by a carrier  74 . A replenishable film of lubricant, not shown, is supplied to an annular space  72  between each intermediate gear  68  and the respective journal pin  70 . 
     A lubricant recovery gutter  76  is located around the ring gear  64 . The lubricant recovery gutter  76  may be radially arranged with respect to the engine central longitudinal axis A. Lubricant is supplied thru the carrier  74  and into each journal pin  70  to lubricate and cool the gears  60 ,  64 ,  68  of the geared architecture  48 . Once communicated through the geared architecture the lubricant is radially expelled thru the lubricant recovery gutter  76  in the ring gear  64  by various paths such as lubricant passage  78 . 
     The input shaft  62  and the output shaft  66  counter-rotate as the sun gear  60  and the ring gear  64  are rotatable about the engine central longitudinal axis A. The carrier  74  is grounded and non-rotatable even though the individual intermediate gears  68  are each rotatable about their respective axes  80 . Such a system may be referred to as a star system. It should be appreciated that various alternative and additional configurations of gear trains such as planetary systems may also benefit herefrom. 
     Many gear train components are able to tolerate lubricant starvation for various intervals of time, however the journal pins  70  may be less tolerant of lubricant starvation. Accordingly, whether the gear system is configured as a star, a planetary or other relationship, it is desirable to ensure that lubricant flows to the journal pins  70 , at least temporarily under all conditions inclusive of reduced-G conditions which may arise from aircraft maneuvers and/or aircraft orientation. As defined herein, reduced-G conditions include negative-G, zero-G, and positive-G conditions materially less than 9.8 meters/sec./sec., particularly when such conditions result in an inability of the main lubricant system to satisfy the lubrication requirements of the gears, journal pins and other components requiring lubrication. 
     With Reference to  FIGS. 3-5 , a lubrication system  80  is schematically illustrated in block diagram form for the geared architecture  48  as well as other components  84  (illustrated schematically) which require lubrication. It should be appreciated that the lubrication system is but a schematic illustration and is simplified in comparison to an actual lubrication system. The lubrication system  80  generally includes a main system  86 , an auxiliary system  88  and a pressure responsive valve  90 . 
     The main system  86  generally includes a sump  92 , a scavenge pump, a main lubricant tank  96 , a main pump  98  and various lubricant reconditioning components such as chip detectors, heat exchangers and deaerators, collectively designated as a reconditioning system  100 . The scavenge pump  94  scavenges lubricant from the sump  92 , the main lubricant tank  96  receives lubricant from the scavenge pump  94  and the main pump  98  pumps lubricant from the main lubricant tank  96 . The main pump  98  is in fluid communication with the pressure responsive valve  90  through the reconditioning system  100 . 
     The auxiliary system  88  generally includes an auxiliary lubricant tank  102  and an auxiliary pump  104 . The auxiliary pump  104  is in fluid communication with the pressure responsive valve  90 . 
     Downstream of the gears of the geared architecture  48 , lubricant is communicated to the lubricant recovery gutter  76  as rotation of the gears of the geared architecture  48  ejects lubricant radially outwardly into the lubricant recovery gutter  76 . An auxiliary lubricant tank supply passageway  106  extends from the lubricant recovery gutter  76  to the auxiliary lubricant tank  102  such that the lubricant recovery gutter  76  serves as a source of lubricant for the auxiliary lubricant tank  102 . A bypass passageway  108  branches from the auxiliary lubricant tank supply passageway  106  at a junction  107  and extends to the sump  92  for lubricant which backs up from filled auxiliary lubricant tank  102 . 
     An auxiliary lubricant tank discharge passageway  110  extends from the auxiliary lubricant tank  102  to the auxiliary pump  104  and an auxiliary pump discharge passageway  112  extends from the auxiliary pump  104  to the pressure responsive valve  90 . A main lubricant tank return passageway  114  extends from the pressure responsive valve  90  to the main lubricant tank  96  and a lubricant delivery passageway  116  extends from the main pump  98  to the lubricant reconditioning system  100 . A lubricant return passageway  118  communicates lubricant from the components  84  to the sump  92 . 
     Downstream of the lubricant reconditioning system  100 , a conditioned lubricant passageway  120  branches to the pressure responsive valve  90  through a first conditioned lubricant passageway  122  to the gears of the geared architecture  48  as well as the other components  84  through a second conditioned lubricant passageway  124 . A journal lubricant passageway  126  communicates lubricant directly to the journal pins  70  downstream of the pressure responsive valve  90 . 
     The lubrication system  80  is operable in both normal and abnormal states of operation. Those skilled in the art will appreciate that normal operation refers to an expected state of operation in which the lubrication system substantially meets design specification. For example, the normal state is a state of operation in which the system delivers lubricant at the rates, temperatures, pressures, etc. determined by the designer so that the lubricated components, including the gears and journal pins, receive a quantity of lubricant enabling them to operate as intended. Abnormal operation refers to a state of operation other than the normal state. 
     During normal operation, rotation of the gears of the geared architecture  48  ejects lubricant radially outwardly into the lubricant recovery gutter  76  which communicates lubricant into the auxiliary lubricant tank supply passageway  106  which branches substantially tangentially off the lubricant recovery gutter  76  ( FIG. 6 ) to capture the ejected lubricant. A portion of the lubricant flows through the bypass passageway  108  and returns to the sump  92  while a relatively smaller portion of the lubricant flows into the auxiliary lubricant tank  102  to establish or replenish a reserve quantity of lubricant therein. That is, the lubricant is cycled by the main system  86 , and the lubricant in the auxiliary system  88  is continually refreshed. 
     The auxiliary pump  104  pumps lubricant from the auxiliary lubricant tank  102  to the pressure responsive valve  90  while the scavenge pump  94  extracts lubricant from the sump  92  for delivery to the main lubricant tank  96 . The main pump  98  pumps the lubricant from the main lubricant tank  96  to the reconditioning system  100 . A majority of the conditioned lubricant flows to the geared architecture  48  and other components  84 . The remainder of the conditioned lubricant flows to the pressure responsive valve  90  which, in response to normal pressure in the lubrication system  80 , directs this remainder of lubricant to the journal pins  70  through the journal pins lubricant passageway  126  and directs reserve lubricant received from the auxiliary pump  104  back to the main lubricant tank  96  through the main lubricant tank return passageway  114 . 
     With reference to  FIG. 4 , the lubricant pressure has dropped such that an unsatisfactorily reduced quantity of lubricant flows through the second conditioned passageway  124  after the onset of abnormal operations (e.g. due to a severe leak, clog or malfunction of a system component). In response to the abnormally low pressure, the pressure responsive valve  90  shunts the reserve lubricant received from the auxiliary pump  104  to the journal pins  70  to ensure that the journal pins  70  receive lubricant. 
     The gears of the geared architecture  48  continue to expel lubricant into the lubricant recovery gutter  76 . As with normal operation, a relatively large portion of lubricant flows through the bypass passageway  108  and returns to the sump  92 . A relatively smaller portion of the lubricant flows to the auxiliary lubricant tank  102  to at least partially replenish the lubricant that is withdrawn by the auxiliary pump  104 . 
     If the abnormally low lubricant pressure persists, the system reaches the state shown in  FIG. 5  in which the quantity of lubricant that circulates through the lubrication system  80  has been reduced to the point that little or no lubricant backs up from the auxiliary lubricant tank  102  and enters the bypass passageway  108 . Instead, nearly all of the limited quantity of lubricant flows to the auxiliary pump  104  and eventually back to the journal pins  70 . This state of operation persists until the auxiliary lubricant tank  102  is depleted and the flow rate from the lubricant recovery gutter  76  is insufficient for replenishment. 
     Although effective during normal-G operation, it may be desirable to extend such operability to reduced-G conditions irrespective of whether the lubricant pressure is normal ( FIG. 3 ) or abnormal ( FIGS. 4 and 5 ). 
     With reference to  FIG. 6 , the auxiliary lubricant tank  102  is mounted to a non-rotatable mechanical ground. The auxiliary lubricant tank  102  has an auxiliary lubricant tank body  130  that is generally defined by a top  132 , a bottom  134  and a wall  136  which extends therebetween. In one disclosed non-limiting embodiment, the wall  136  may define a cylinder with an arcuate profile to fit at least partially around the lubricant recovery gutter  76 . That is, the auxiliary lubricant tank body  130  is defined along an axis T which is non-linear. Alternatively, the auxiliary lubricant tank  102  is generally rectilinear in cross-section or other cross-sectional shapes. 
     The auxiliary lubricant tank  102  contains an auxiliary lubricant tank discharge passageway  138  often referred to as a “piccolo tube” defined along the axis T. The auxiliary lubricant tank discharge passageway  138  may be a component physically distinct from the auxiliary lubricant tank supply passageway  106  and connected thereto by a fitting or other appropriate connection as shown. Alternatively, the discharge passageway may be an extension of the auxiliary lubricant tank supply passageway  106 . 
     In one disclosed non-limiting embodiment, the auxiliary lubricant tank discharge passageway  138  may define a cylinder with an arcuate profile which generally conforms to the arcuate profile of the auxiliary lubricant tank  102 . Alternatively, the auxiliary lubricant tank discharge passageway  138  is generally rectilinear in cross-section or of other cross-sectional shapes either generally equivalent or different than the auxiliary lubricant tank  102 . At least a portion of the auxiliary lubricant tank discharge passageway  138  is contained within the auxiliary lubricant tank  102  and communicates with the auxiliary pump  104 . 
     The portion of the auxiliary lubricant tank discharge passageway  138  contained within the auxiliary lubricant tank  102  has an opening  140  along an inner radial boundary of the wall  136  to permit lubricant transfer between the auxiliary lubricant tank  102  and the auxiliary lubricant tank discharge passageway  138 . The opening may be of various forms, for example, the opening  140  may be a single opening such as a hole or a slot. In the disclosed, non-limiting embodiment, the opening is a multiple of perforations which decrease in area with a decrease in elevation to at least partially counteract the tendency for the auxiliary pump  104  to extract air from the bottom of the auxiliary lubricant tank  102  during reduced-G operations. It should be appreciated that other baffles or structure may alternatively or additionally be provided. 
     With reference to  FIGS. 6 and 7 , a segmented anti-back flow structure  142  is located in the auxiliary lubricant tank  102  to surround the auxiliary lubricant tank discharge passageway  138  and still further counteract the tendency for the auxiliary pump  104  to extract air from the bottom of the auxiliary lubricant tank  102  during reduced-G operations. The segmented anti-back flow structure  142  generally includes a multiple of walls  144 A- 144   n  transverse to the auxiliary lubricant tank discharge passageway  138 . It should be understood that although a particular number of walls  144 A- 144   n  are disclosed in the illustrated embodiment, essentially any number may be utilized. 
     At least one tube  146 A- 146   n  extends from each wall  144 A- 144   n  downward toward the lower wall, such as the next lower wall  144 B- 144   n  to be close, but not blocked, by that lower wall  144 B- 144   n . As used herein, “lower” is with respect to the bottom  134  of the auxiliary lubricant tank  102  and “elevation” refers to distance or height above the bottom  134  of the auxiliary lubricant tank  102  when the system is in the orientation of  FIG. 7 , i.e. an orientation representative of the engine or aircraft being on level ground or in straight and level flight. 
     The walls  144 A- 144   n  create a multiple of separate compartments  148 A- 148   n  from which the respective tube  146 A- 146   n  provides fluid communication between compartments  148 A- 148   n . The separate compartments  148 A- 148   n  permit lubricant flow to fill the compartments  148 A- 148   n  in normal operation ( FIG. 8 ) yet prevent lubricant from being violently agitated in reduced-G conditions ( FIG. 9 ). That is, for normal operations, lubricant will flow freely from top down and fill the separate compartments  148 A- 148   n  bottom up. At reduced-G, the walls  144 A- 144   n  minimize lubricant back flow such that the filled compartments  148 A- 148   n  remain filled to the level of the multiple of tubes  146 A- 146   n  ( FIG. 9 ) and the auxiliary lubricant tank discharge passageway  138  may draw lubricant for such that, for example only, the journal pins  70  are prevented from oil starvation at reduced-G conditions ( FIGS. 4 and 5 ). 
     With reference to  FIG. 10 , in another disclosed, non-limiting embodiment, a multiple of apertures  150 A- 150   n  may alternatively be utilized within one or more walls  144 A- 144   n  to slow flow of the lubricant between the multiple of separate compartments  148 A- 148   n . The multiple of apertures  150 A- 150   n  may be provided either alone or in combination with one or more tubes  146 A- 146   n  to define the compartments  148 A- 148   n . The apertures  150 A- 150   n  facilitate simplification of manufacture as well as reduced lubricant agitation. 
     The lubricant is encouraged to enter the auxiliary lubricant tank discharge passageway  138  partly due to the decrease in area of the perforations of opening  140  toward the bottom  134 , partly due to suction created by the auxiliary pump  104  and partly due to the segmented anti-back flow structure  142 . In other words, the separate compartments  148 A- 148   n  maintain a supply of lubricant within the auxiliary lubricant tank  102  such that the auxiliary lubricant tank discharge passageway  138  is much less likely to “pull air” which may result in lubricant starvation at reduced-G conditions. 
     For further understanding of other aspects of the auxiliary lubrication system, attention is directed to U.S. Pat. No. 8,020,665, entitled Lubrication System with Extended Emergency Operability which is assigned to the assignee of the instant disclosure and which is hereby incorporated herein in its entirety. 
     It should be understood that relative positional terms such as “forward,” “aft,” “upper,” “lower,” “above,” “below,” “bottom”, “top”, and the like are with reference to the normal operational attitude of the vehicle and should not be considered otherwise limiting. 
     It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom. 
     Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present disclosure. 
     The foregoing description is exemplary rather than defined by the limitations within. Various non-limiting embodiments are disclosed herein, however, one of ordinary skill in the art would recognize that various modifications and variations in light of the above teachings will fall within the scope of the appended claims. It is therefore to be understood that within the scope of the appended claims, the disclosure may be practiced other than as specifically described. For that reason the appended claims should be studied to determine true scope and content.