Abstract:
The present disclosure provides a bicycle hub that provides improved drive line efficiency and bike-to-rider torque feedback. The drive line efficiencies are due to lower rolling resistance resulting from a novel bearing and sprag clutch configuration, a lightweight design, and immediate torque transfer from the cassette drive to the hub body. The bike-to-rider feedback has been improved as the torque transfer is smooth, predictable, and immediate.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation of application Ser. No. 14/798,977 filed Jul. 14, 2015, which is a continuation of application Ser. No. 13/763,848 filed Feb. 11, 2013, issued as U.S. Pat. No. 9,102,197 on Aug. 11, 2015, both entire disclosures of which are incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    A freewheeling bicycle hub including a sprag type clutch configuration. 
       BACKGROUND 
       [0003]    Freewheeling bicycle hubs are generally known. For example, U.S. Pat. No. 2,211,548 to Frank W. Schwinn issued on Jun. 24, 1940 is directed to a freewheeling bicycle hub configuration. Freewheeling bicycle hubs are configured to enable rotation of the pedals to drive the rotation of the wheels while also allowing the wheels to rotate independent of the rotation of the pedals. This functionality enables the pedals of the bike to be held stationary while the wheels rotate as the bike coasts. Freewheeling bicycle hubs are also commonly referred to as coaster hubs. 
       SUMMARY 
       [0004]    The present disclosure provides a bicycle hub that provides improved drive line efficiency and bike-to-rider torque feedback. The drive line efficiencies are due to lower rolling resistance resulting from a novel bearing and sprag clutch configuration, a lightweight design, and immediate torque transfer from the cassette drive to the hub body. The bike-to-rider feedback has been improved as the torque transfer is smooth, predictable, and immediate. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is an isometric view of a hub according to the principles of the present disclosure; 
           [0006]      FIG. 2  is a longitudinal cross-sectional view of the hub of  FIG. 1 ; 
           [0007]      FIG. 3  is a cross-sectional view of the hub along line  3 - 3  of  FIG. 2 ; 
           [0008]      FIG. 4  is a cross-sectional view of the hub along line  4 - 4  of  FIG. 2 ; 
           [0009]      FIG. 5  is an exploded assembly view of the hub of  FIG. 1 ; 
           [0010]      FIG. 6  is an isometric view of an alternative embodiment of the hub of  FIG. 1 ; 
           [0011]      FIG. 7  is a longitudinal cross-sectional view of the hub of  FIG. 6 ; 
           [0012]      FIG. 8  is an exploded assembly view of the hub of  FIG. 6 ; and 
           [0013]      FIG. 9  is an enlarged view of a portion of  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Referring to  FIG. 1 , a first embodiment of a hub according to the present disclosure is shown. In the depicted embodiment, the hub  10  includes a hub body  12 , an axle  14 , and cassette driver  16 . In the depicted embodiment, the hub  10  is configured to freewheel. In other words, a cassette driver  16  rotates with the hub body  12  when the wheel is driven by the cassette driver  16  and the cassette driver  16  rotates relative to the hub body  12  when the wheel is coasting (rotating and not being driven). 
         [0015]    Referring to  FIGS. 2-5 and 9 , the configuration of hub  10  is described in greater detail. In the depicted embodiment the hub  10  is configured for use with multiple speed bicycles (e.g., road bikes, mountain bikes, etc.) that utilize an external cassette driven by a chain. In the depicted embodiment the axle  14  is co-axially arranged within the hub body  12 . In particular, the axle  14  extends through the hub body  12 . The axle  14  includes a first end portion  18  that is positioned within the first end portion  22  of the hub body  12  and a second opposed end portion  24  that includes a portion that extend outwardly from the second end  26  of the hub body  12 . 
         [0016]    In the depicted embodiment, the first end portion  18  of the axle includes a shoulder  28 . The hub body  12  includes a snap ring groove  30  aligned with the shoulder  28  in a radial direction such that a snap ring  32  and the shoulder  28  cooperatively limit the axial movement of a bearing set  34  in a direction toward the second end  26  of the hub body  12 . The bearing set  34  engages an exterior surface of the axle and an interior surface of the internal cavity  56  of the hub body  12 . In the depicted embodiment a spacer  36  covers the first end  38  of the axle. In the depicted embodiment a first o-ring  44  seals the interface between the spacer  36  and the axle, and a second o-ring  46  seals the interface between the bearing set  34  and the axle. 
         [0017]    In the depicted embodiment, the second end portion  24  of the axle  14  is co-axially arranged within both the hub body  12  and drive end portion  48  of the cassette driver  16 . In the depicted embodiment a portion of the second end portion  24  of the axle  14  extends into the driven end of the cassette driver and is connected to a spacer  50 . In the depicted embodiment, the second end of portion  24  of the axle  14  interfaces with the cassette driver  16  via bearing set  52 . The spacer  50 , which is secured to the axle  14 , interfaces with the cassette driver  16  via bearing set  54 . 
         [0018]    In the depicted embodiment, the hub body  12  includes a one-piece construction. The hub body  12  is machined from a single piece of aluminum (e.g., aluminum 7075TC51). The hub body  12  defines a longitudinal rotational axis A-A. The hub body  12  includes an internal cavity  56  that receives the axle  14  as well as the drive end portion  48  of the cassette driver  16 . The hub body  12  includes a first radially extending flange  58  located at the first end portion  22  of the hub body  12 , and a second radially extending flange  60  located at the second end of the hub body. Each of the radially extending flanges  58 ,  60  includes a plurality of spaced apart through apertures  62  that are configured to secure spokes. Adjacent the first radially extending flange  58  is a disk brake mount flange  64  configured to support a disk of a disk brake system. The external cylindrical body of the hub body  12  tapers from the second flange  60  towards the first flange  58 . In other words, the exterior diameter of the hub body  12  adjacent the second flange  60  is greater than the exterior diameter of the hub body  12  adjacent the first flange  58 . 
         [0019]    In the depicted embodiment, the wall thickness of the hub body  12  is greater in the portion that radially overlaps the drive end portion  48  of the cassette driver  16  as compared to the portion that does not overlap the cassette driver  16 . In the depicted embodiment the internal cavity  56  of the second end portion  26  of the hub body defines two internal cylindrical surfaces. A first cylindrical surface  66  is defined as being a distance D 1  from the longitudinal rotational axis A-A, and a second cylindrical surface  68  is defined as being a distance D 2  from the longitudinal rotational axis A-A. In the depicted embodiment D 2  is greater than D 1  and the first surface  66  is closer to the first end portion  22  of the hub body  12  than the second cylindrical surface  68 . In the depicted embodiment, the hub body is machined in a process whereby the hub body is not removed from a spindle until both the first and second cylindrical surfaces  66 ,  68  are drilled. 
         [0020]    In the depicted embodiment the cassette driver  16  includes an internal cavity  70  that extends from a drive end portion  48  to an opposed driven end portion  72 . The cavity receives the axle  14 , which extends into the drive end portion  48  of the cassette driver  16 . The cassette driver  16  defines a longitudinal axis of rotation that is coaxial and coincident with the axis of rotation A-A of the hub body  12 . In the depicted embodiment, the driven end  72  includes a cylindrical body with a plurality of axially extending grooves  74 , which are configured to engage cassette comprised of sprockets and spacers. 
         [0021]    In the depicted embodiment the drive end  48  of the cassette driver  16  includes a plurality of coaxial cylindrical surfaces that are positioned within the hub body  12  opposite the internal cylindrical surfaces  66 ,  68  of the hub body  12 . In the depicted embodiment an annular snap ring groove  76  is located in the first cylindrical surface  66  of the inner cavity  56  of the hub body  12  opposite an end face  78  of the drive end portion  48  of the cassette driver  16 . A first cylindrical surface  80  extends from the end face  78  of the cassette driver towards the driven end  72  of the cassette driver  16 . The first cylindrical surface  80  of the drive end  48  together with the first cylindrical surface  66  defines a first annular cavity that receives bearing set  82  that interfaces between the drive end  48  of the cassette driver  16  and the hub body  12 . 
         [0022]    In the depicted embodiment a second cylindrical surface  84  having a larger diameter than the first cylindrical surface  80  extends from the first cylindrical surface  80  towards the driven end  72  of the cassette driver  16 . The second cylindrical surface  84  of the drive end  48  together with the second cylindrical surface  68  defines an annular cavity that receives a sprag clutch assembly. In the depicted embodiment the surface finish of the second cylindrical surface  84  is less than or equal to Rz of 2.5 micrometers and has a HRC hardness of 60. In the depicted embodiment, the second cylindrical surface  84  has a diameter of greater than 22 mm (e.g., 29 mm). In the depicted embodiment the second cylindrical surface is constructed of a 5210 bearing race type steel. In the depicted embodiment the drive end portion  48  of the drive cassette  16  is precision ground and subsequently hardened, thereby enabling it to act as a force bearing surface for the sprags. 
         [0023]    In the depicted embodiment the sprag clutch assembly includes a sprag sleeve  86 , a sprag retaining cage  88 , sprags  90 , and a tensioning band  92 . In the depicted embodiment the surface finish of the inside surface of the sprag sleeve is less than or equal to Rz of 2.5 micrometers and the inside surface of the sprag sleeve has a HRC hardness of 60. In the depicted embodiment, the sprag sleeve  86  has a diameter of less than 40 mm (e.g., 37 mm). The sprag sleeve has a height dimension that is greater than the height dimension of the sprag retaining cage  88 . The sprag sleeve  86  includes a snap ring groove that receives a snap ring that limits the axial movement of the sprag cage  88  in the axial direction towards the driven end  72  of the cassette driver. Axial movement of the sprag cage  88  in the direction towards the first cylindrical surface  80  of the driven end  48  of the cassette driver  16  is limited by contact with the bearing set  82 . In the depicted embodiment the sprag sleeve is constructed of a 5210 bearing race type steel which is pressed fit/interference fit into the second cylindrical surface  68  of the hub body  12 . In the depicted embodiment the sprag sleeve  86  overlaps the second flange  60  in the radial direction. The construction of the sprag sleeve  86  and the hub body  12  cooperatively provide the structural stiffness needed for reliable and long lasting operation of the hub despite the strong radial forces that are generated by the sprags  90 . The sprags and sprag cages used in the depicted embodiment are currently available commercially from GMN Paul Müller Industrie GmbH &amp; Co. KG. 
         [0024]    In the depicted embodiment a third cylindrical surface  94  extends coaxially from the second cylindrical surface  84  towards the driven end  72  of the cassette driver  16 . The third cylindrical surface  94  has a diameter that is greater than the diameter of the second cylindrical surface  84 . A shoulder  96  is provided on the cassette driver  16  between the third cylindrical surface  94  and the driven end  72  of the cassette driver  16 . The third cylindrical surface  94  of the drive end  48  of the cassette driver  16  together with the second cylindrical surface  68  defines a first annular cavity that receives bearing set  98  that interfaces between the drive end  48  of the cassette driver  16  and the hub body  12 . The shoulder  96  limits axial movement of the bearing set  98  in the direction towards the driven end  72  of the cassette driver  16 . An end face of the sprag sleeve  86  limits axial movement of the bearing set  98  on the axial direction towards the first cylindrical surface  80  of the drive end  48  of the cassette driver  16 . In the depicted embodiment the third cylindrical surface  94  includes an annular o-ring groove configured to receive an o-ring that seals the interface between the third cylindrical surface  94  and the bearing set  98 . 
         [0025]    In the depicted embodiment the, the internal cavity of the drive end  48  of the of the cassette driver includes a first cylindrical surface  100  defined by a first diameter that is greater than the diameter of the axle, and a second cylindrical surface  102  defined by a second diameter that is greater than the first diameter, the second cylindrical surface being closer to the driven end of the cassette driver than the first cylindrical surface. The configuration results in further weight savings and strength of the cassette driver and facilitates precision manufacturing thereof. 
         [0026]    In the depicted embodiment the configuration results in a high performance hub as it has the strength and durability to withstand intense use while also being lightweight and smooth in operation. The hub body  12  is constructed of lightweight, relatively softer aluminum material and it is designed so that it can be manufactured with high precision as the above-referenced cylindrical surfaces  66 ,  68  can be machined without detaching the hub body  12  from the chuck that holds the part during machining. The hard and robust sprag sleeve  86  is pressed into the softer aluminum. The pressing process creates a tight interference fit between the sprag sleeve  86  and cylindrical surface  68 . This interface allows the hub body  12  to work together to resist the radial forces generated by the sprags. The sprag sleeve  86  provides the hardened surface that interfaces with the sprags and also provides additional structural strength to the hub. The hub of the depicted embodiment does not require rebuilding and can operate in extreme environments including environments as cold as −50 degrees Fahrenheit. 
         [0027]    In the depicted embodiment the sprag cage moves with the cassette driver  16 . The tensioning member (e.g., spring) on the sprag cage biases the individual sprags against the cylindrical surface  84  of the cassette driver  16  resulting in the sprag cage being essentially tension mounted to cassette driver  16 . The internal ends of the sprags contact the second external surface  84  of the cassette driver and are biased radially outwardly against a spring and extend radially slightly beyond the periphery edge of the sprag cage. This configuration results in little and light contact between the sprags and the sprag sleeve  86  during coasting, which results in a very low friction configuration as the clutch configuration is disengaged during coasting. The non-drive forces applied between the hub body  12  and the cassette driver  16  are transferred through the bearing sets  82 ,  98  that sandwich the sprag clutch assembly. 
         [0028]    In the depicted embodiment as soon as the driven end  72  is rotated in the drive direction at a rotational speed that exceeds the rotational speed in the drive direction of the hub body  12 , the sprags engage and lock against the sprag sleeve  86  and transfer torque from the cassette driver  16  to the hub body  12 . In the depicted embodiment the sprag clutch assembly transfers torque to drive the hub forward. However, the sprag clutch assembly is not relied on as a bearing set support the relative rotation between the cassette driver  16  and the hub body  12 . This configuration results in a clutch configuration that immediately engages when the driven end is driven. For example, in the depicted configuration the driven end cannot be rotated relative to the hub body in the drive direction more than a small amount before it fully engages and transfers torque from the cassette driver  16  to the hub body  12 , thereby causing the hub body to rotate with the cassette driver  16 . The amount of relative rotation in the drive direction, commonly referred to as play or slop, can be less than five degrees (e.g., less than two degrees, less than one degree, or one half of a degree). 
         [0029]    Referring to  FIGS. 6-8 , an alternative embodiment of the hub according to the present disclosure is shown. In the depicted embodiment the hub is configured for a single speed bicycle such as a bmx bike. One of ordinary skill in the art would recognized that this embodiment includes many of the same features discussed above, therefore this embodiment will not be described separately detail herein. 
         [0030]    The above specification, examples and data provide a complete description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.