Abstract:
A fan section for a gas turbine engine includes a fan hub having blade slots for receiving a root of a fan blade. A lock ring is configured to move rotatably from an unlocked position to a locked position for securing the blade root in the blade slot. A nose cone is secured to the lock ring, and thereby secured to the fan section.

Description:
BACKGROUND 
       [0001]    This disclosure relates to a nose cone of a gas turbine engine fan section and, in particular, attaching the nose cone relative to a fan hub. 
         [0002]    A gas turbine engine typically includes a fan section, a compressor section, a combustor section and a turbine section. Air entering the compressor section is compressed and delivered into the combustor section where it is mixed with fuel and ignited to generate a high-speed exhaust gas flow. The high-speed exhaust gas flow expands through the turbine section to drive the compressor and the fan section. The compressor section typically includes low and high pressure compressors, and the turbine section includes low and high pressure turbines. 
         [0003]    One type of gas turbine engine includes a fan drive gear system having a fan section with relatively large fan blades. The fan blades are mounted to a fan hub, and a blade lock assembly is used to axially retain the fan blades within corresponding fan hub slots. One example blade lock assembly includes a lock ring that is axially slid onto the fan hub in an unlocked position and rotated to a locked position. In the locked position, fan hub and lock ring tabs are aligned with one another to prevent axial movement of the lock ring with respect to the fan blades. A retaining ring, or pilot ring, having circumferentially spaced prongs is mounted to the fan hub with the prongs received in spaces between the lock ring and fan hub. The retaining ring is bolted to the fan hub. A nose cone is located by the retaining ring. 
       SUMMARY 
       [0004]    In one exemplary embodiment, a fan section for a gas turbine engine, includes a fan hub having blade slots for receiving a root of a fan blade. A lock ring is configured to move rotatably from an unlocked position to a locked position for securing the blade root in the blade slot. A nose cone is secured to the lock ring, and thereby secured to the fan section. 
         [0005]    In a further embodiment of any of the above, the fan hub includes circumferentially spaced first slots. The lock ring includes circumferentially spaced second slots aligned with the first slots in the locked position. The fan section comprises a plurality of discrete locating elements, each configured to be slidably received in paired first and second slots in the locked position to prevent rotational movement of the lock ring relative the fan hub. 
         [0006]    In a further embodiment of any of the above, the first and second slots are arcuate in shape, and each locating element includes a pin engaging the first and second slots in an interference fit. 
         [0007]    In a further embodiment of any of the above, the pin includes an end retained by the spinner. 
         [0008]    In a further embodiment of any of the above, the first and second fastening elements cooperate with one another to secure the spinner directly to the lock ring. 
         [0009]    In a further embodiment of any of the above, the second fastening element is a nut secured to the first fastening element. 
         [0010]    In a further embodiment of any of the above, the first fastening element is carried by the lock ring. 
         [0011]    In a further embodiment of any of the above, the first fastening element includes a head cooperating with a corresponding locating feature in the lock ring to prevent rotation of the first fastening element. 
         [0012]    In a further embodiment of any of the above, the corresponding locating feature is a notch in a back side of the lock ring. 
         [0013]    In a further embodiment of any of the above, the fan hub provides a shoulder. The spinner includes a flange having an inner diameter radially located with respect to the shoulder to concentrically align the nose cone with the fan hub. 
         [0014]    In a further embodiment of any of the above, the nose cone includes a spinner that provides the flange. A cap is secured to the spinner to enclose a cavity of the spinner. 
         [0015]    In one exemplary embodiment, a method of assembling a fan section of a gas turbine engine includes the steps of mounting fan blades into a fan hub, sliding a lock ring onto the fan hub, rotating the lock ring to axially retain the fan blades within the fan hub, and securing a nose cone directly to the lock ring. 
         [0016]    In a further embodiment of any of the above, the mounting step includes sliding roots of the fan blades into the corresponding slots in the fan hub, whereby the lock ring axially blocks the axial movement of the fan blade roots. 
         [0017]    In a further embodiment of any of the above, the method includes the step of inserting the first fastening elements into the lock ring prior to sliding the lock ring onto fan hub. 
         [0018]    In a further embodiment of any of the above, the method includes the step of inserting discrete locating elements into aligned slots in the fan hub and lock ring to prevent relative rotational movement between the lock ring and fan hub prior to the securing step. 
         [0019]    In a further embodiment of any of the above, the nose cone retains the locating elements axially. 
         [0020]    In a further embodiment of any of the above, the securing step includes fastening a spinner to the lock ring, and securing a cap to the spinner. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The disclosure can be further understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
           [0022]      FIG. 1  schematically illustrates a gas turbine engine embodiment. 
           [0023]      FIG. 2A  is a perspective view of a portion of a fan section having fan blades and discrete platforms. 
           [0024]      FIG. 2B  is a schematic cross-sectional view through a portion of the fan section shown in  FIG. 2A . 
           [0025]      FIG. 2C  is a schematic perspective view of the fan section with a nose cone removed. 
           [0026]      FIG. 3  is a cross-sectional perspective view through a fan hub and a spinner using a single lock ring. 
           [0027]      FIG. 4A  is a partial perspective view of the lock ring in an unlocked position with respect to the fan hub. 
           [0028]      FIG. 4B  is an enlarged cross-sectional perspective view of the lock ring in the locked position, as shown in  FIG. 3 . 
           [0029]      FIG. 5  is a perspective view of a back side of the lock ring with the spinner secured thereto. 
           [0030]      FIG. 6  is a perspective view of the lock ring in the locked position and pins used to circumferentially retain the lock ring relative to the fan hub. 
           [0031]      FIG. 7  is a cross-sectional perspective view through the lock pins. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]      FIG. 1  schematically illustrates an example gas turbine engine  20  that includes a fan section  22 , a compressor section  24 , a combustor section  26  and a turbine section  28 . Alternative engines might include an augmenter section (not shown) among other systems or features. The fan section  22  drives air along a bypass flow path B while the compressor section  24  draws air in along a core flow path C where air is compressed and communicated to a combustor section  26 . In the combustor section  26 , air is mixed with fuel and ignited to generate a high pressure exhaust gas stream that expands through the turbine section  28  where energy is extracted and utilized to drive the fan section  22  and the compressor section  24 . 
         [0033]    Although the disclosed non-limiting embodiment depicts a turbofan gas turbine engine, 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; for example a turbine engine including a three-spool architecture in which three spools concentrically rotate about a common axis and where a low spool enables a low pressure turbine to drive a fan via a gearbox, an intermediate spool that enables an intermediate pressure turbine to drive a first compressor of the compressor section, and a high spool that enables a high pressure turbine to drive a high pressure compressor of the compressor section. 
         [0034]    The example engine  20  generally includes a low speed spool  30  and a high speed spool  32  mounted for rotation about an engine central longitudinal axis A relative to an engine static structure  36  via several bearing systems  38 . It should be understood that various bearing systems  38  at various locations may alternatively or additionally be provided. 
         [0035]    The low speed spool  30  generally includes an inner shaft  40  that connects a fan having fan blades  42  and a low pressure (or first) compressor section  44  to a low pressure (or first) turbine section  46 . The inner shaft  40  drives the fan blades  42  through a speed change device, such as a geared architecture  48 , to drive the fan blades  42  at a lower speed than the low speed spool  30 . The high-speed spool  32  includes an outer shaft  50  that interconnects a high pressure (or second) compressor section  52  and a high pressure (or second) turbine section  54 . The inner shaft  40  and the outer shaft  50  are concentric and rotate via the bearing systems  38  about the engine central longitudinal axis A. 
         [0036]    A combustor  56  is arranged between the high pressure compressor  52  and the high pressure turbine  54 . In one example, the high pressure turbine  54  includes at least two stages to provide a double stage high pressure turbine  54 . In another example, the high pressure turbine  54  includes only a single stage. As used herein, a “high pressure” compressor or turbine experiences a higher pressure than a corresponding “low pressure” compressor or turbine. 
         [0037]    The example low pressure turbine  46  has a pressure ratio that is greater than about  5 . The pressure ratio of the example low pressure turbine  46  is measured prior to an inlet of the low pressure turbine  46  as related to the pressure measured at the outlet of the low pressure turbine  46  prior to an exhaust nozzle. 
         [0038]    A mid-turbine frame  57  of the engine static structure  36  is arranged generally between the high pressure turbine  54  and the low pressure turbine  46 . The mid-turbine frame  57  further supports bearing systems  38  in the turbine section  28  as well as setting airflow entering the low pressure turbine  46 . 
         [0039]    The core airflow C is compressed by the low pressure compressor  44  then by the high pressure compressor  52  mixed with fuel and ignited in the combustor  56  to produce high speed exhaust gases that are then expanded through the high pressure turbine  54  and low pressure turbine  46 . The mid-turbine frame  57  includes vanes  59 , which are in the core airflow path and function as an inlet guide vane for the low pressure turbine  46 . Utilizing the vane  59  of the mid-turbine frame  57  as the inlet guide vane for low pressure turbine  46  decreases the length of the low pressure turbine  46  without increasing the axial length of the mid-turbine frame  57 . Reducing or eliminating the number of vanes in the low pressure turbine  46  shortens the axial length of the turbine section  28 . Thus, the compactness of the gas turbine engine  20  is increased and a higher power density may be achieved. 
         [0040]    The disclosed gas turbine engine  20  in one example is a high-bypass geared aircraft engine. In a further example, the gas turbine engine  20  includes a bypass ratio greater than about six (6), with an example embodiment being greater than about ten (10). The example geared architecture  48  is an epicyclical gear train, such as a planetary gear system, star gear system or other known gear system, with a gear reduction ratio of greater than about 2.3. 
         [0041]    In one disclosed embodiment, the gas turbine engine  20  includes a bypass ratio greater than about ten (10:1) and the fan diameter is significantly larger than an outer diameter of the low pressure compressor  44 . It should be understood, however, that the above parameters are only exemplary of one embodiment of a gas turbine engine including a geared architecture and that the present disclosure is applicable to other gas turbine engines. 
         [0042]    A significant amount of thrust is provided by the bypass flow B due to the high bypass ratio. The fan section  22  of the engine  20  is designed for a particular flight condition—typically cruise at about 0.8 Mach and about 35,000 feet. The flight condition of 0.8 Mach and 35,000 ft., with the engine at its best fuel consumption—also known as “bucket cruise Thrust Specific Fuel Consumption (‘TSFC’)”—is the industry standard parameter of pound-mass (lbm) of fuel per hour being burned divided by pound-force (lbf) of thrust the engine produces at that minimum point. 
         [0043]    “Low fan pressure ratio” is the pressure ratio across the fan blade alone, without a Fan Exit Guide Vane (“FEGV”) system. The low fan pressure ratio as disclosed herein according to one non-limiting embodiment is less than about 1.50. In another non-limiting embodiment the low fan pressure ratio is less than about 1.45. 
         [0044]    “Low corrected fan tip speed” is the actual fan tip speed in ft/sec divided by an industry standard temperature correction of [(Tram° R)/(518.7° R)] 0.5 . The “Low corrected fan tip speed”, as disclosed herein according to one non-limiting embodiment, is less than about 1150 ft/second. 
         [0045]    The fan section  22  is shown in more detail in  FIGS. 2A-2C . The fan section  22  includes multiple circumferentially arranged fan blades  42 . Platforms  60 , or spacers, are arranged between adjacent fan blades  42  and may be integral with or discrete from the fan blades  42 . Referring to  FIGS. 2A and 2B , the fan blades  42  are mounted to a fan hub  62 . A nose cone  64  is arranged forward of the fan blades  42  to provide an aerodynamic inner flowpath through the fan section  22  along with the platforms  60 . The nose cone  64  is provided by a spinner  66  and a cap  70 . The nose cone  66  is secured to the fan hub  62 , via a lock ring  96  ( FIG. 2B ), by fasteners  68 . The cap  70  is secured to the spinner  66  by fasteners  72 . A one-piece nose cone may also be used in which the cap  70  is integrated with the spinner  66 . 
         [0046]    Referring to  FIG. 2B , the platform  60  includes first and second flanges  74 ,  76  secured to corresponding attachment features on the fan hub  62  respectively by fasteners  78 ,  80 . The fasteners  68 ,  72 ,  78 ,  80  are schematically depicted in  FIGS. 2A and 2B  by simple, thickened lines for clarity. The arrangement shown in  FIG. 2B  is exemplary, and other platform configurations may be used, if desired. 
         [0047]    Referring to  FIG. 2C , each fan blade  42  has an airfoil  82 . Each platform  60  has an outer surface  84 , which together form a ring with the other platforms  60 , spaced about axis A to provide an aerodynamic inner flow path surface. Though close fitting, a circumferential gap  86  exists between each platform outer surface  84  and an adjacent fan blade  42 . Each gap  86  is blocked with a seal  88  to minimize a loss of airflow through the gas turbine engine  10 . 
         [0048]    As shown in  FIG. 3 , a single lock ring  96  is used to axially retain the fan blades to the fan hub  62 . The spinner  66  is secured directly to the lock ring  96  using first and second fastening elements  100 ,  108 . In the example shown, an integral flange  110  of the spinner  66  is secured to the lock ring  96 . A separate bracket may be used if desired. Access to the second fastening element  108  is provided through a cavity  109  of the spinner  66  with the cap  70  (illustrated in  FIG. 2A ) removed. 
         [0049]    Referring to  FIGS. 4A and 4B , the fan hub  62  includes an annular recess  92  that receives the lock ring  96  in a locked position. An unlocked position is illustrated in  FIG. 4A . Circumferentially spaced apart hub tabs  94  are provided on the fan hub  62 . In the unlocked position, circumferentially spaced ring tabs  98  are received in the gaps provided between the hub tabs  94  to permit the lock ring  96  to be slid into the annular recess  92 . The lock ring  96  is rotated from this unlocked position to at least partially align the hub tabs  94  and the ring tabs  98 , which prevents axial movement of the lock ring  96  with respect to the fan hub  62 . In this position, a back side of the lock ring  96  abuts the roots  99  of the fan blades  42 , as shown in  FIG. 4B . 
         [0050]    With continuing reference to  FIG. 4B , the first fastening element  100 , which is a bolt in the example, extends through a hole  106  in the lock ring  96 . As best shown in  FIG. 5 , a back side of the lock ring  96  includes a locating feature  104 , such a notch, which cooperates with a head  102  of the first fastening element  100  to prevent rotation of the first fastening element  100  during tightening of the second fastening element  108 . 
         [0051]    Returning to  FIG. 4B , the flange  110  includes an inner diameter  124 , which cooperates with an annular shoulder  122  of the fan hub  62  to precisely locate the spinner  66  relative to the fan hub on the common axis A. The spinner could be radially located with respect to the lock ring  96 , if desired. A corresponding aperture  112  in the flange  110  receives the first fastening element  100 . The flange  110  is secured to the first fastening element  100  by tightening of the second fastening element  108 , which is a nut in the example. 
         [0052]    Multiple circumferentially arranged locating elements, in this example, pins  118  are used to circumferentially lock the lock ring  96  with respect to the fan hub  62 , as shown in  FIG. 6 . First and second slots  114 ,  116 , which are arcuate in shape in one example, are respectively provided in the lock ring  96  and the fan hub  62  to receive discrete pins  118  in an interference fit relationship. In the example, the pins  118  prevent rotational movement of the lock ring  96  relative the fan hub  62 . An end of each pin  120  is generally flush with respect to a front face of the lock ring  96 , as best shown in  FIG. 7 . The flange  110  abuts the ends  120  to prevent the pins  118  from backing out of the first and second slots  114 ,  116 . 
         [0053]    Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of the claims. For that reason, the following claims should be studied to determine their true scope and content.