Patent Publication Number: US-2022213939-A1

Title: Planar ratchet assembly for human-powered vehicle

Description:
BACKGROUND 
     Technical Field 
     This disclosure generally relates to a planar ratchet assembly for a human-powered vehicle. 
     Background Information 
     Generally, bicycle wheels have a hub, a plurality of spokes and an annular rim. The hub has a hub axle that is non-rotatably mounted to a frame of the bicycle. The hub has a hub shell that is coaxially coupled to the hub axle so that the hub shell is disposed radially outwardly with respect to the hub axle. The bearings are configured and arranged to support the hub shell so that the hub shell can freely rotate around the hub axle. In almost all types of bicycles except fixed gear and track racers, a wheel of the bicycle, typically the rear wheel, is provided with a bicycle freewheel that is arranged on a hub of the wheel. The bicycle freewheel usually has a one-way clutch function whereby it only transfers torque in one direction. Thus, freewheels are used so that the bicycle can advance freely without any rotation of the pedals (i.e., during coasting). During coasting, the bicycle freewheel is considered to be in a state of freewheeling in which the bicycle wheel can freely rotate while the sprockets remain stationary. 
     SUMMARY 
     Generally, the present disclosure is directed to various features of a planar ratchet assembly for a human-powered vehicle. The term “human-powered vehicle” as used herein refers to a vehicle that can be driven by at least human driving force, but does not include a vehicle using only a driving power other than human power. In particular, a vehicle solely using an internal combustion engine as a driving power is not included in the human-powered vehicle. The human-powered vehicle is generally assumed to be a compact, light vehicle that sometimes does not require a license for driving on a public road. The number of wheels on the human-powered vehicle is not limited. The human-powered vehicle includes, for example, a monocycle and a vehicle having three or more wheels. The human-powered vehicle includes, for example, various types of bicycles such as a mountain bike, a road bike, a city bike, a cargo bike, and a recumbent bike, and an electric assist bicycle (E-bike). 
     In view of the state of the known technology and in accordance with a first aspect of the present disclosure, a planar ratchet assembly is provided for a human-powered vehicle. The planar ratchet assembly basically comprises a first ratchet member and a second ratchet member. The first ratchet member includes a first axial surface defining a plurality of first serrated teeth. The first serrated teeth has a first driving surface, a first non-driving surface and a first tooth tip. The first tooth tips connect corresponding ones of the first driving surfaces and the first non-driving surfaces. At least one of the first non-driving surfaces includes a first convex curved surface that has a first radius of curvature of at least 0.5 mm. The second ratchet member includes a second axial surface defining a plurality of second serrated teeth. The second serrated teeth has a second driving surface, a second non-driving surface and a second tooth tip. The second tooth tips connects corresponding ones of the second driving surfaces and the second non-driving surfaces. The first ratchet member and the second ratchet member are configured to rotate together about a rotational axis in a driving direction where the first driving surfaces contact the second driving surfaces. At least one of the first ratchet member and the second ratchet member is movable in an axial direction of the rotational axis to permit relative rotation between the first ratchet member and the second ratchet member about the rotational axis in a non-driving direction where the first non-driving surfaces and the second non-driving surfaces slidably contact each other. 
     With the planar ratchet assembly according to the first aspect, it is possible to suppress the noise that the non-driving surfaces hit each other when the first non-driving surfaces and the second non-driving surfaces slidably contact each other. 
     In accordance with a second aspect of the present disclosure, the planar ratchet assembly according to the first aspect is configured so that the first radius of curvature is at least 1.0 mm. 
     With the planar ratchet assembly according to the second aspect, it is possible to further suppress the noise that the non-driving surfaces hit each other when the first non-driving surfaces and the second non-driving surfaces slidably contact each other. 
     In accordance with a third aspect of the present disclosure, the planar ratchet assembly according to the second aspect is configured so that the first radius of curvature is at least 1.5 mm. 
     With the planar ratchet assembly according to the third aspect, it is possible to even further suppress the noise that the non-driving surfaces hit each other when the first non-driving surfaces and the second non-driving surfaces slidably contact each other. 
     In accordance with a fourth aspect of the present disclosure, the planar ratchet assembly according to any one of the first to third aspects is configured so that the at least one of the first non-driving surfaces further include a first planar surface. 
     With the planar ratchet assembly according to the fourth aspect, it is possible to ensure smooth sliding along the at least one of the first non-driving surfaces. 
     In accordance with a fifth aspect of the present disclosure, the planar ratchet assembly according to any one of the first to fourth aspects is configured so that the at least one the first non-driving surfaces further include a first concave curved surface. 
     With the planar ratchet assembly according to the fifth aspect, it is possible to ensure smooth sliding along the at least one of the first non-driving surfaces. 
     In accordance with a sixth aspect of the present disclosure, the planar ratchet assembly according to the fifth aspect is configured so that the first convex curved surface is located between the first tooth tip and the first concave curved surface of the at least one the first non-driving surfaces. 
     With the planar ratchet assembly according to the sixth aspect, it is possible to minimize contact of the first tooth tip by the second non-driving surfaces. 
     In accordance with a seventh aspect of the present disclosure, the planar ratchet assembly according to the fifth aspect is configured so that the at least one of the first non-driving surfaces further include a first planar surface connecting the first convex curved surface and the first concave curved surface. 
     With the planar ratchet assembly according to the seventh aspect, it is possible to ensure smooth sliding along the at least one of the first non-driving surfaces. 
     In accordance with an eighth aspect of the present disclosure, the planar ratchet assembly according to the fifth aspect is configured so that the first convex curved surface and the first concave curved surface for the at least one of the first non-driving surfaces are continuous without a planar surface therebetween. 
     With the planar ratchet assembly according to the eighth aspect, it is possible to ensure smooth sliding along the at least one of the first non-driving surfaces. 
     In accordance with a ninth aspect of the present disclosure, the planar ratchet assembly according to any one of the first to eighth aspects is configured so that the at least one of the first non-driving surfaces has a first tilt angle with respect to a plane perpendicular to the rotational axis that is greater than zero degrees and that is twenty-five degrees or less. 
     With the planar ratchet assembly according to the ninth aspect, it is possible to reduce the force of the non-driving surfaces hitting each other since the non-driving surfaces slide easily. Therefore, the impact when the non-driving surfaces hit each other can be reduced and the noise generated can be reduced. 
     In accordance with a tenth aspect of the present disclosure, the planar ratchet assembly according to the eighth aspect is configured so that the first tilt angles are twenty degrees or less. 
     With the planar ratchet assembly according to the tenth aspect, it is possible to further reduce the impact and reduce the noise generated when the non-driving surfaces hit each other. 
     In accordance with an eleventh aspect of the present disclosure, the planar ratchet assembly according to the eighth aspect is configured so that the first tilt angles are sixteen degrees or less. 
     With the planar ratchet assembly according to the eleventh aspect, it is possible to even further reduce the impact and reduce the noise generated when the non-driving surfaces hit each other. 
     In accordance with a twelfth aspect of the present disclosure, the planar ratchet assembly according to any one of the first to eleventh aspects is configured so that at least one of the first tooth tips includes a first flat surface. 
     With the planar ratchet assembly according to the twelfth aspect, it is possible to improve a shearing force of the at least one of the first tooth tips. 
     In accordance with a thirteenth aspect of the present disclosure, the planar ratchet assembly according to any one of the first to twelfth aspects is configured so that the first ratchet member further includes a first root surface between adjacent ones of the first serrated teeth. 
     With the planar ratchet assembly according to the thirteenth aspect, it is possible to avoid contact of the non-driving surfaces at the tooth tips of the teeth to minimize damage to the tooth tips where the planar ratchet assembly is rotating at a very high speed. 
     In accordance with a fourteenth aspect of the present disclosure, the planar ratchet assembly according to the thirteenth aspect is configured so that the second ratchet member further includes a second root surface between adjacent ones of the second serrated teeth, and at least one of the first tooth tips is spaced from the second root surfaces where the first driving surfaces are engaged with the second driving surfaces. 
     With the planar ratchet assembly according to the fourteenth aspect, it is possible to avoid contact the tooth tips of the teeth from contacting the mating ratchet to minimize damage to the tooth tips. 
     In accordance with a fifteenth aspect of the present disclosure, the planar ratchet assembly according to any one of the first to fourteenth aspects is configured so that the first serrated teeth include an outer surface having an aluminum alloy. 
     With the planar ratchet assembly according to the fifteenth aspect, it is possible to the impact when the non-driving surfaces hit each other can be reduced by using a soft material such as an aluminum alloy. 
     In accordance with a sixteenth aspect of the present disclosure, the planar ratchet assembly according to any one of the first to fifteenth aspects is configured so that at least one of the second non-driving surfaces including a second convex curved surface that has a second radius of curvature of at least 0.5 mm. 
     With the planar ratchet assembly according to the sixteenth aspect, it is possible to further suppress the noise that the non-driving surfaces hit each other when the first non-driving surfaces and the second non-driving surfaces slidably contact each other. 
     In accordance with a seventeenth aspect of the present disclosure, the planar ratchet assembly according to the sixteenth aspect is configured so that the second radius of curvature is at least 1.0 mm. 
     With the planar ratchet assembly according to the seventeenth aspect, it is possible to even further suppress the noise that the non-driving surfaces hit each other when the first non-driving surfaces and the second non-driving surfaces slidably contact each other. 
     In accordance with an eighteenth aspect of the present disclosure, the planar ratchet assembly according to the seventeenth aspect is configured so that the second radius of curvature is at least 1.5 mm. 
     With the planar ratchet assembly according to the eighteenth aspect, it is possible to even further suppress the noise that the non-driving surfaces hit each other when the first non-driving surfaces and the second non-driving surfaces slidably contact each other. 
     In accordance with a nineteenth aspect of the present disclosure, the planar ratchet assembly according to the sixteenth aspect is configured so that the at least one of the second non-driving surfaces further includes a second planar surface. 
     With the planar ratchet assembly according to the nineteenth aspect, it is possible to ensure smooth sliding along the at least one of the second non-driving surfaces. 
     In accordance with a twentieth aspect of the present disclosure, the planar ratchet assembly according to the sixteenth aspect is configured so that the at least one of the second non-driving surfaces further includes a second concave curved surface. 
     With the planar ratchet assembly according to the twentieth aspect, is possible to ensure smooth sliding along the at least one of the second non-driving surfaces. 
     In accordance with a twenty-first aspect of the present disclosure, the planar ratchet assembly according to the twentieth aspect is configured so that the second curved convex surface is located between the second tooth tip and the second concave curved surface of the at least one the second non-driving surfaces. 
     With the planar ratchet assembly according to the twenty-first aspect, it is possible to minimize contact of the second tooth tip by the first non-driving surfaces. 
     In accordance with a twenty-second aspect of the present disclosure, the planar ratchet assembly according to the twentieth aspect is configured so that the at least one of the second non-driving surfaces further includes a second planar surface connecting the second convex curved surface and the second concave curved surface. 
     With the planar ratchet assembly according to the twenty-second aspect, it is possible to ensure smooth sliding along the at least one of the second non-driving surfaces. 
     In accordance with a twenty-third aspect of the present disclosure, the planar ratchet assembly according to the twentieth aspect is configured so that the second convex curved surface and the second concave curved surface for the at least one of the second non-driving surfaces are continuous without a planar surface therebetween. 
     With the planar ratchet assembly according to the twenty-third aspect, it is possible to ensure smooth sliding along the at least one of the second non-driving surfaces. 
     In accordance with a twenty-fourth aspect of the present disclosure, the planar ratchet assembly according to the sixteenth aspect is configured so that the at least one of the second non-driving surfaces has a second tilt angle with respect to a plane perpendicular to the rotational axis that is greater than zero degrees and that is twenty-five degrees or less. 
     With the planar ratchet assembly according to the twenty-fourth aspect, it is possible to reduce the force of the non-driving surfaces hitting each other since the non-driving surfaces slide easily. Therefore, the impact when the non-driving surfaces hit each other can be reduced and the noise generated can be reduced. 
     In accordance with a twenty-fifth aspect of the present disclosure, the planar ratchet assembly according to the twenty-fourth aspect is configured so that the second tilt angles are twenty degrees or less. 
     With the planar ratchet assembly according to the twenty-fifth aspect, it is possible to further reduce the impact and reduce the noise generated when the non-driving surfaces hit each other. 
     In accordance with a twenty-sixth aspect of the present disclosure, the planar ratchet assembly according to the twenty-fourth aspect is configured so that the second tilt angles are sixteen degrees or less. 
     With the planar ratchet assembly according to the twenty-sixth aspect, it is possible to even further reduce the impact and reduce the noise generated when the non-driving surfaces hit each other. 
     In accordance with a twenty-seventh aspect of the present disclosure, the planar ratchet assembly according to the sixteenth aspect is configured so that at least one of the second tooth tips includes a second flat surface. 
     With the planar ratchet assembly according to the twenty-seventh aspect, it is possible to improve a shearing force of the at least one of the second tooth tips. 
     In accordance with a twenty-eighth aspect of the present disclosure, the planar ratchet assembly according to the sixteenth aspect is configured so that the second ratchet member further includes a second root surface between adjacent ones of the second serrated teeth. 
     With the planar ratchet assembly according to the twenty-eighth aspect, it is possible to avoid contact of the non-driving surfaces at the tooth tips of the teeth to minimize damage to the tooth tips where the planar ratchet assembly is rotating at a very high speed. 
     In accordance with a twenty-ninth aspect of the present disclosure, the planar ratchet assembly according to the twenty-eighth aspect is configured so that the first ratchet member further includes a first root surface between adjacent ones of the first serrated teeth, and at least one of the second tooth tips is spaced from the first root surfaces where the first driving surfaces are engaged with the second driving surfaces. 
     With the planar ratchet assembly according to the twenty-ninth aspect, it is possible to avoid contact the tooth tips of the teeth from contacting the mating ratchet to minimize damage to the tooth tips. 
     In accordance with a thirtieth aspect of the present disclosure, the planar ratchet assembly according to the sixteenth aspect is configured so that the second serrated teeth include an outer surface having an aluminum alloy. 
     With the planar ratchet assembly according to the thirtieth aspect, it is possible to the impact when the non-driving surfaces hit each other can be reduced by using a soft material such as an aluminum alloy. 
     In accordance with a thirty-first aspect of the present disclosure, the planar ratchet assembly according to any one of the first to thirtieth aspects is configured so that the first ratchet member has a total number of the first serrated teeth arranged in a first ring having a first outer ratchet diameter such that a first ratio of the total number of the first serrated teeth divided by the first outer ratchet diameter is 0.7 or more. 
     With the planar ratchet assembly according to the thirty-first aspect, it is possible to reduce noise generated by the non-driving surfaces of the serrated teeth hitting each other because the number of sounds generated is reduced. 
     In accordance with a thirty-second aspect of the present disclosure, the planar ratchet assembly according to the thirty-first aspect is configured so that the first ratio is 1.5 or less. 
     With the planar ratchet assembly according to the thirty-second aspect, it is possible to further reduce noise generated by the non-driving surfaces of the serrated teeth hitting each other because the number of sounds generated is reduced. 
     In accordance with a thirty-third aspect of the present disclosure, a hub comprises the planar ratchet assembly according to any one of the first to thirty-second aspects, and further comprises a hub axle, a hub body and a sprocket support. The hub axle defines the rotational axis. The hub body is rotatably disposed around the hub axle. The sprocket support is rotatably coupled to the hub axle via the planar ratchet assembly to transmit a driving force from the sprocket support to the hub body while the sprocket support rotates in the driving direction. 
     With the hub according to the thirty-third aspect, it is possible to provide a hub in which the noise that is generated by the non-driving surfaces hitting each other is suppress when the first non-driving surfaces and the second non-driving surfaces slidably contact each other during coasting. 
     Also, other objects, features, aspects and advantages of the disclosed planar ratchet assembly will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the planar ratchet assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the attached drawings which form a part of this original disclosure: 
         FIG. 1  is a side elevational view of a human-powered vehicle (e.g., a bicycle) equipped with a rear wheel having a hub having a planar ratchet assembly in accordance with one embodiment; 
         FIG. 2  is a perspective view of the hub of the rear wheel of the human-powered vehicle illustrated in  FIG. 1 ; 
         FIG. 3  is a longitudinal cross sectional view of the hub illustrated in  FIG. 2  with the frame securing device omitted; 
         FIG. 4  is an enlarged cross sectional view of a portion of the hub illustrated in  FIG. 3  showing the first ratchet member and the second ratchet member of the planar ratchet assembly in an engaged position for driving a hub body of the hub; 
         FIG. 5  is an enlarged cross sectional view of the portion of the hub illustrated in  FIG. 4  showing the first ratchet member and the second ratchet member in a disengaged position for coasting; 
         FIG. 6  is an exploded perspective view of selected parts of the freewheel of the hub illustrated in  FIGS. 1 to 5 ; 
         FIG. 7  is an exploded perspective view of other selected parts of the freewheel of the hub illustrated in  FIGS. 1 to 5 ; 
         FIG. 8  is an exploded perspective view of other selected parts of the freewheel of the hub illustrated in  FIGS. 1 to 5 ; 
         FIG. 9  is an exploded perspective view of other selected parts of the freewheel of the hub illustrated in  FIGS. 1 to 5 ; 
         FIG. 10  is a perspective view of the sprocket support of the freewheel of the hub illustrated in  FIGS. 1 to 5 ; 
         FIG. 11  is a perspective view of the first ratchet member of the hub illustrated in  FIGS. 1 to 5 ; 
         FIG. 12  is a side elevational view of the first ratchet member illustrated in  FIG. 11  for the hub illustrated in  FIGS. 1 to 5 ; 
         FIG. 13  is a perspective view of the second ratchet member of the hub illustrated in  FIGS. 1 to 5 ; 
         FIG. 14  is a side elevational view of the second ratchet member illustrated in  FIG. 11  for the hub illustrated in  FIGS. 1 to 5 ; 
         FIG. 15  is an enlarged diagrammatic profile view the first serrated teeth of the first ratchet member for the hub illustrated in  FIGS. 1 to 5 ; 
         FIG. 16  is an enlarged diagrammatic profile view the second serrated teeth of the second ratchet member for the hub illustrated in  FIGS. 1 to 5 ; 
         FIG. 17  is an enlarged diagrammatic profile view the first serrated teeth of the first ratchet member and the second serrated teeth of the second ratchet member for the hub illustrated in  FIGS. 1 to 5  in which the first serrated teeth are engaged with the second serrated teeth for driving the hub body of the hub as the sprocket support rotates in a driving direction; 
         FIGS. 18 to 22  are a series of enlarged diagrammatic profile view, similar to  FIG. 17 , but in which the first serrated teeth are sliding relative to second serrated teeth as the hub body rotates while the sprocket support remains stationary; 
         FIG. 23  is an enlarged diagrammatic profile view modified first serrated teeth of a first ratchet member and modified second serrated teeth of a second ratchet member for the hub illustrated in  FIGS. 1 to 5  in which the first serrated teeth are engaged with the second serrated teeth for driving the hub body of the hub as the sprocket support rotates in a driving direction; 
         FIG. 24  is an enlarged diagrammatic profile view modified first serrated teeth of a first ratchet member and modified second serrated teeth of a second ratchet member for the hub illustrated in  FIGS. 1 to 5  in which the first serrated teeth are engaged with the second serrated teeth for driving the hub body of the hub as the sprocket support rotates in a driving direction; and 
         FIG. 25  is an enlarged diagrammatic profile view modified first serrated teeth of a first ratchet member and modified second serrated teeth of a second ratchet member for the hub illustrated in  FIGS. 1 to 5  in which the first serrated teeth are engaged with the second serrated teeth for driving the hub body of the hub as the sprocket support rotates in a driving direction. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Selected embodiments will now be explained with reference to the drawings. It will be apparent to those skilled in the human-powered vehicle field (e.g., the bicycle field) from this disclosure that the following descriptions of the embodiments are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. 
     Referring initially to  FIG. 1 , a human-powered vehicle V is illustrated that is equipped with a hub  10  in accordance with one illustrated embodiment. In this embodiment, the human-powered vehicle V is a bicycle and the hub  10  is a bicycle hub. The human-powered vehicle V includes a front wheel FW and a rear wheel RW rotatably attached to a vehicle body VB. Here, the hub  10  is provided to the rear wheel RW. The vehicle body VB is also provided with a handlebar H and a front fork FF for steering the front wheel FW. The vehicle body VB is also provided with a saddle S for a rider to sit on while riding the human-powered vehicle V. 
     As seen in  FIG. 1 , the human-powered vehicle V further comprises a drive assembly  12 . The drive assembly  12  comprises the hub  10 . Here, for example, the drive assembly  12  is a chain-drive type. The drive assembly  12  further comprises a crank  14 , a chain  16  (i.e., a force transmission member), a plurality of front sprockets  18  (i.e., a front rotatable body) and plurality of rear sprockets  20  (i.e., a rear rotatable body). The chain  16  provides mechanical communication between the crank  14  and the hub  10 . Thus, a rotational force caused by rotation of the crank  14  in a forward traveling direction R can be transmitted to the hub  10  via the chain  16 . The crank  14  includes a crank axle  14 A and a pair of crank arms  14 B. A pedal PD is rotatably coupled to the distal end of each of the crank arms  14 B. The crank arms  14 B are provided on opposite ends of the crank axle  14 A. The chain  16  can provide a mechanical connection between the front sprockets  18  and the rear sprockets  20  provided on the hub  10 . 
     Here, the human-powered vehicle V further includes a front derailleur FD that is attached to the vehicle body VB for shifting the chain  16  between the sprockets  18  that are provided to the crank  14 . Also, here, the human-powered vehicle V further includes a rear derailleur RD that is attached to the rear of the vehicle body VB for shifting the chain  16  between the rear sprockets  20  that are provided to the hub  10 . The front derailleur FD and the rear derailleur RD are one type of gear changing device. Here, for example, the front derailleur FD and the rear derailleur RD are electric derailleurs (i.e., electric gear changing devices). The front derailleur FD and the rear derailleur RD are operated when a rider of the human-powered vehicle V manually operates a gear shift operating device or shifter SL. The front derailleur FD and the rear derailleur RD can also be automatically operated based on traveling conditions and/or operating conditions of the human-powered vehicle V. 
     The structure of the hub  10  will now be described with particular reference to  FIGS. 2 to 4 . The hub  10  basically comprises a hub axle  30 , a hub body  32  and a sprocket support  34 . The hub axle  30  defines the rotational axis CA. The hub body  32  is rotatably disposed around the hub axle  30 . The sprocket support  34  is rotatably coupled to the hub axle  30  to transmit a driving force from the sprocket support  34  to the hub body  32  while the sprocket support  34  rotates in a driving direction D 1  as explained later. Basically, the hub axle  30  is non-rotatably attached to the vehicle body VB, and the hub body  32  is rotatably mounted around the hub axle  30 . As indicated in  FIG. 1 , the hub body  32  rotates relative to the hub axle  30  in a driving direction D 1  which corresponds to a forward traveling direction R of the rear wheel RW. The sprocket support  34  is configured to support the rear sprockets  22 . 
     Here, the hub axle  30  is a conventional member having a shaft portion  30   a  with a first end cap  30   b  screwed on a first threaded end of the hub axle  30  and a second end cap  30   c  screwed on a second threaded end of the hub axle  30 . The hub axle  30  defines a rotational axis CA. The hub body  32  is rotatably mounted on the hub axle  30  to rotate around the rotational axis CA. The hub body  32  has a center tubular body  32   a  and a pair of spoke attachment flanges  32   b  and  32   c  extending outwardly in a radial direction from the center tubular body  32   a.    
     As shown in  FIG. 2 , a frame securing device  36  is provided for attaching the hub  10  to a bicycle frame F (See  FIG. 1 ) in a conventional manner. In the first illustrated embodiment, the frame securing device  36  includes a skewer or spindle  36   a  that has a cam lever mechanism  36   b  mounted at one end of the spindle  36   a . Thus, the hub  10  can be mounted onto a rear section of the vehicle body VB of the human-powered vehicle V as seen in  FIG. 1 . 
     As shown in  FIG. 3 , the hub  10  further comprises at least one bearing assembly for rotatably supporting the hub body  32  on the hub axle  30 . In the illustrated embodiment, the hub body  32  is rotatably mounted on the hub axle  30  by a pair of bearing assemblies  38 A and  38 B. The bearing assemblies  38 A and  38 B are conventional parts that are well known in the bicycle field, and thus, the bearing assemblies  38 A and  38 B will not be discussed any or illustrated in detail herein. Also, other bearing arrangements can be used as needed and/or desired. 
     Referring to  FIGS. 3 and 6 , the hub  10  further comprises at least one bearing assembly for rotatably supporting the sprocket support  34  on the hub axle  30 . In the illustrated embodiment, the sprocket support  34  is rotatably coupled to the hub axle  30  by a pair of bearing assemblies  40 A and  40 B as seen in  FIG. 3 . The sprocket support  34  is axially retained on the hub axle  30  by the second end cap  30   c . The second end cap  30   c  is screwed on the shaft portion  30   a  of the hub axle  30  to contact an inner race of the bearing assembly  40 B. An O-ring  44  is provided between the second end cap  30   c  and the hub axle  30  for sealing the interface therebetween. Also, a first sealing ring  46  is provided to the interior of the sprocket support  34  and a second sealing ring  48  is provided to the exterior of the second end cap  30   c  for sealing the space between the interior of the sprocket support  34  and the exterior of the second end cap  30   c.    
     Referring to  FIGS. 3 to 7 , a planar ratchet assembly  50  is provided for the human-powered vehicle V. More specifically, the hub  10  comprises the planar ratchet assembly  50 . The planar ratchet assembly  50  is configured to transmit a driving force from the sprocket support  34  to the hub body  32  while the sprocket support  34  rotates in the driving direction D 1 . In other words, the sprocket support  34  is rotatably coupled to the hub axle  30  via the planar ratchet assembly  50  to transmit a driving force from the sprocket support  34  to the hub body  32  while the sprocket support  34  rotates in the driving direction D 1 . 
     The planar ratchet assembly  50  functions as a one-way clutch between the hub body  32  and the sprocket support  34  to permit coasting or freewheeling of the sprocket support  34  with respect to the hub body  32 . In particular, coasting or freewheeling occurs when the sprocket support  34  is stopped from rotating in the driving direction D 1  (i.e., clockwise about the rotational axis CA as viewed from the freewheel side of the hub  10 ) by a chain  16 , while the hub body  32  rotates in the forward traveling direction R. Additionally, coasting or freewheeling occurs when the hub body  32  rotates faster in the forward traveling direction R than the sprocket support  34  rotates in the driving direction D 1  by the chain  16 . Also, coasting or freewheeling occurs when the sprocket support  34  rotates in a non-driving direction D 2  by the chain  16  due to the rider pedaling backwards. 
     Basically, the planar ratchet assembly  50  comprises a first ratchet member  51  and a second ratchet member  52 . The planar ratchet assembly  50  further comprises a biasing element  53 . As shown in  FIGS. 4 and 5 , the biasing element  53  is disposed between the hub body  32  and the second ratchet member  52 . The biasing element  53  biases the second ratchet member  52  in the axial direction A toward the first ratchet member  51  into the engagement position. Preferably, the biasing element  53  is configured to rotate with the hub body  32 . In the illustrated embodiment, the biasing element  53  has a protrusion that is disposed in a recess of the hub body  32  so that the biasing element  53  rotates together with the hub body  32 . With the sprocket support  34  in a rest position (i.e., no torque being applied thereto), the biasing element  53  maintains the second ratchet member  52  in driving engagement with the first ratchet member  51 . The biasing element  53  includes, for example, a compression spring in the illustrated embodiment and the friction member  54 . In other words, in the illustrated embodiment, the friction member  54  is provided as a separate piece that is fixed on the end of the compression spring of the biasing element  53  that faces the second ratchet member  52 . Alternatively, the friction member  54  can be omitted such that an end coil of the biasing element  53  forms a friction member. 
     The first ratchet member  51  and the second ratchet member  52  move relative to each other in the axial direction as shown in  FIG. 5 . In particular, the second ratchet member  52  is biased in a first axial direction A 1  towards the first ratchet member  51  into an engaged position by the biasing element  53  as seen in  FIG. 4 . During coasting, the sprocket support  34  stops rotating in the driving direction D 1  and the hub body  32  continues to rotate in the forward traveling direction R. As a result of the sprocket support  34  stop rotating in the driving direction D 1 , the second ratchet member  52  is moved in the second axial direction A 2  away from the first ratchet member  51  against the force of the biasing element  53 . In this way, the first ratchet member  51  and the second ratchet member  52  can slide relative to each other as seen in  FIG. 5 . 
     As seen in  FIGS. 4 and 5 , a dust shield  56  is provided for covering annular gap between the sprocket support  34  and the hub body  32 . A support retaining assembly retains the dust shield  56  to the hub body  32 . The support retaining assembly includes an outer cap  58  and a retaining ring or clip  60 . The outer cap  58  is disposed between the sprocket support  34  and the hub body  32 . The retaining ring or clip  60  disposed in a recess in the sprocket support  34  to retain on the retaining ring  60  on the sprocket support  34  and to limit outward axial movement of the outer cap  58 . 
     The hub  10  further includes a circumferential spacer  62  and an axial spacer  64 . The circumferential spacer  62  is disposed between the hub body  32  and the first ratchet member  51  to take up the circumferential space between the first ratchet member  51  and the hub body  32 . The axial spacer  64  is disposed between the sprocket support  34  and the first ratchet member  51  to take up the axial space between the sprocket support  34  and the first ratchet member  51 . 
     Referring to  FIGS. 6, 7 and 10 , the sprocket support  34  constitutes a driving member that has a tubular shape. The sprocket support  34  is rotatably mounted on the hub axle  30  to rotate around the rotational axis CA. The sprocket support  34  has an outer peripheral surface  66 . The outer peripheral surface  66  is provided with a plurality of axially extending splines  68  for non-rotatably engaging the rear sprockets  20  in a conventional manner. The splines  68  are parallel to each other, and extend parallel to the rotational axis CA. As seen in  FIG. 2 , the rear sprockets  20  are held on the sprocket support  34  in a conventional manner such as a conventional nut that screws into the sprocket support  34 . The sprocket support  34  has another outer peripheral surface  70  having a plurality of helical splines  72  that is helically arranged with respect to the rotational axis CA. 
     The second ratchet member  52  is movably supported on the outer peripheral surface  70  of the sprocket support  34  via the helical splines  72 . The sprocket support  34  also includes an abutment  74  that abuts the first ratchet member  51  to restrict axial movement of the first ratchet member  51  away from the hub body  32 . In an axial direction of the rotational axis CA, the first ratchet member  51  is disposed between the abutment  74  and the second ratchet member  52 . 
     Referring to  FIGS. 11 and 12 , the first ratchet member  51  will now be discussed in more detail. The first ratchet member  51  is an annular member. The first ratchet member  51  includes a first axial surface  80  defining a plurality of first serrated teeth  82 . The first axial surface  80  axially faces the second ratchet member  52 . The first serrated teeth  82  are configured to engage the second ratchet member  52  so that the first ratchet member  51  and the second ratchet member  52  rotate together in the driving direction D 1  and rotate relative to each other in the non-driving direction D 2 . 
     Referring to  FIGS. 8 and 9 , the first ratchet member  51  is a ring-shaped member that is concentrically disposed around the hub axle  30 . The first ratchet member  51  is configured to rotate with the hub body  32 . In particular, the first ratchet member  51  also includes an outer peripheral surface  84  having a plurality of protrusions  86 . The protrusions  86  form a hub shell engagement portion that engages plurality of protrusions  88  of the hub body  32 . More specifically, the spacer  62  is disposed between the protrusions  86  of the first ratchet member  51  and the protrusions  88  of the hub body  32  to take up the circumferential spaces between the protrusions  86  of the first ratchet member  51  and the protrusions  88  of the hub body  32 . In this way, torque applied from the sprocket support  34  via the second ratchet member  52  is transferred from the first ratchet member  51  to the hub body  32 . The first ratchet member  51  is sandwiched between the abutment  74  of the sprocket support  34  and the second ratchet member  52 . Here, the spacer  64  is disposed between the first ratchet member  51  and the abutment  74  of the sprocket support  34 . In this way, movement of the first ratchet member  51  in the first axial direction A 1  is restricted. 
     Referring to  FIGS. 13 and 14 , the second ratchet member  52  will now be discussed in more detail. The second ratchet member  52  is an annular member that is concentrically disposed around the hub axle  30 . The second ratchet member  52  includes a second axial surface  90  defining a plurality of second serrated teeth  92 . The second axial surface  90  axially faces the first axial surface  80  of the first ratchet member  51 . The second serrated teeth  92  are configured to engage the first serrated teeth  82  of the first ratchet member  51  so that the first ratchet member  51  and the second ratchet member  52  rotate together in the driving direction D 1  and rotate relative to each other in the non-driving direction D 2 . In other words, the first ratchet member  51  and the second ratchet member  52  are configured to rotate together about the rotational axis CA in the driving direction D 1  where the first driving surfaces  82   a  contact the second driving surfaces  92   a . Also, at least one of the first ratchet member  51  and the second ratchet member  52  is movable in the axial direction A 1  or A 2  of the rotational axis CA to permit relative rotation between the first ratchet member  51  and the second ratchet member  52  about the rotational axis CA in the non-driving direction D 2  where the first non-driving surfaces  82   b  and the second non-driving surfaces  92   b  slidably contact each other. Here, the second ratchet member  52  is movable in the second axial direction A 2  to permit relative rotation between the first ratchet member  51  and the second ratchet member  52  about the rotational axis CA in the non-driving direction D 2  where the first non-driving surfaces  82   b  and the second non-driving surfaces  92   b  slidably contact each other. 
     Referring to  FIGS. 10, 13 and 14 , the second ratchet member  52  is a ring-shaped member that is concentrically disposed around the hub axle  30 . The second ratchet member  52  is configured to rotate with the sprocket support  34  as the sprocket support  34  rotates about the rotational axis CA. However, the second ratchet member  52  is configured to move both axially and circumferentially with respect to the sprocket support  34  for limited range of movement. In particular, the second ratchet member  52  also includes an inner peripheral surface  94  having a plurality of helical splines  96  that are helically arranged with respect to the rotational axis CA. The helical splines  96  mates with the helical spline  72  of the sprocket support  34 . In this way, the second ratchet member  52  is movably mounted in the axial direction A 1  or A 2  with respect to the sprocket support  34  via the helical splines  96  engaging the helical splines  72 . 
     Referring to  FIGS. 11, 12 and 15 , the first serrated teeth  82  of the first ratchet member  51  will now be discussed in more detail. In the illustrated embodiment, the first ratchet member  51  has a total number of the first serrated teeth  82  that are arranged in a first ring TR 1 . The first ring TR 1  has a first outer ratchet diameter OD 1  and a first inner ratchet diameter ID 1 . In other words, the first ring TR 1  is defined by an area between the first outer ratchet diameter OD 1  and the first inner ratchet diameter ID 1  of the first serrated teeth  82 . The first ring TR 1  is configured such that a first ratio of the total number of the first serrated teeth  82  divided by the first outer ratchet diameter OD 1  is 0.7 or more. Preferably, the first ratio is 1.5 or less. Also, preferably, the first serrated teeth  82  include an outer surface OS 1  having an aluminum alloy. For example, the outer surface OS 1  can have aluminum alloy coating, or the first serrated teeth  82  can be made of partly or entirely of aluminum alloy. 
     Basically, the first serrated teeth  82  has a first driving surface  82   a , a first non-driving surface  82   b  and a first tooth tip  82   c . In the illustrated embodiment, all of the first serrated teeth  82  have the same shape. However, it will be apparent from this disclosure that the first serrated teeth  82  can have different shapes. In any case, at least one of the first non-driving surfaces  82   b  includes a first convex curved surface  82   b   1  that has a first radius of curvature X 1  of at least 0.5 mm. Preferably, the first radius of curvature X 1  is at least 1.0 mm. More preferably, the first radius of curvature X 1  is at least 1.5 mm. An upper limit of the first radius of curvature X 1  is preferably one hundred millimeters. However, at the upper limit of the first radius of curvature X 1 , the first convex curved surface  82   b   1  can be any curved surface that close to a flat plane. Thus, the first radius of curvature X 1  can be, for example, five millimeters, ten millimeters, twenty millimeters, thirty millimeters, fifty millimeters or seventy millimeters. In the illustrated embodiment, all of the first serrated teeth  82  have the first convex curved surface  82   b   1 . However, only one or some of the first serrated teeth  82  can have the first convex curved surface  82   b   1 . In the illustrated embodiment, the first ratchet member  51  further includes a first root surface  82   d  between adjacent ones of the first serrated teeth  82 . 
     In the illustrated embodiment, the at least one of the first non-driving surfaces  82   b  has a first tilt angle θ 1  with respect to a plane perpendicular to the rotational axis CA that is greater than zero degrees and that is twenty-five degrees or less. Here, the first tilt angle θ 1  is the same for all of the first serrated teeth  82 . However, all or some of the first serrated teeth  82  can have different tilt angles. Preferably, the first tilt angles θ 1  are twenty degrees or less. More preferably, the first tilt angles θ 1  are sixteen degrees or less. In the illustrated embodiment, the first tilt angles θ 1  are sixteen degrees. In the case where the first non-driving surface  82   b  includes a planar surface, the first tilt angle θ 1  can be measured as an angle between the planar surface and the plane perpendicular to the rotational axis CA. In the case the first non-driving surface  82   b  does not includes a planar surface, the first tilt angle θ 1  can be measured as an angle between a straight line connecting the end points of the first non-driving surface  82   b  and the plane perpendicular to the rotational axis CA. In the case the first non-driving surface  82   b  does not includes a planar surface, the first tilt angle θ 1  can be measured as an angle between an approximate plane of the first non-driving surface  82   b  and the plane perpendicular to the rotational axis CA. 
     In the illustrated embodiment, the at least one of the first non-driving surfaces  82   b  further include a first planar surface  82   b   2 . Here, all the first serrated teeth  82  include the first planar surface  82   b   2 . However, some of the first serrated teeth  82  can omit the first planar surface  82   b   2 . In other words, only one or some of the first serrated teeth  82  can include the first planar surface  82   b   2 . The first serrated tooth  82  may not include the first plane  82   b   2 . Also, in the illustrated embodiment, the at least one the first non-driving surfaces  82   b  further include a first concave curved surface  82   b   3 . Here, all the first serrated teeth  82  include the first concave curved surface  82   b   3 . However, some of the first serrated teeth  82  can omit the first concave curved surface  82   b   3 . In other words, only one or some of the first serrated teeth  82  can include the first concave curved surface  82   b   3 . The first serrated tooth  82  may not include the first concave curved surface  82   b   3 . In any case, in the illustrated embodiment, the first planar surface  82   b   2  connects the first convex curved surface  82   b   1  and the first concave curved surface  82   b   3 . Thus, the first convex curved surface  82   b   1  is located between the first tooth tip  82   c  and the first concave curved surface  82   b   3  of the at least one the first non-driving surfaces  82   b . The first convex curved surface  82   b   1  is preferably formed near the first tooth tip  82   c.    
     The first tooth tips  82   c  connect corresponding ones of the first driving surfaces  82   a  and the first non-driving surfaces  82   b . In particular, the first tooth tips  82   c  connect the first driving surfaces  82   a  and the first convex curved surface  82   b   1  of the first non-driving surfaces  82   b . Preferably, at least one of the first tooth tips  82   c  includes a first flat surface  82   c   1 . Here, all the first serrated teeth  82  include the first flat surface  82   c   1 . However, some of the first serrated teeth  82  can omit the first flat surface  82   c   1 . In other words, only one or some of the first serrated teeth  82  can include the first flat surface  82   c   1 . The first serrated tooth  82  may not include the first flat surface  82   c   1 . In the illustrated embodiment, each of the first tooth tips  82   c  further includes a first non-sharp surface  82   c   2  that connects the first flat surface  82   c   1  to the first driving surfaces  82   a . However, some of the first serrated teeth  82  can omit the first non-sharp surface  82   c   2 . In other words, only one or some of the first serrated teeth  82  can include the first non-sharp surface  82   c   2 . The first serrated tooth  82  may not include the first non-sharp surface  82   c   2 . Here, the first non-sharp surface  82   c   2  includes a convex surface, but is not limited to that shape. 
     The first ratchet member  51  can be formed using a pair of straight-pull molds in which the straight-pull molds are separated in a direction parallel to the rotational axis CA. Thus, the first serrated teeth  82  are configured such that the first serrated teeth  82  do not include any undercut surfaces as viewed in the direction parallel to the rotational axis CA. For example, the first convex curved surface  82   b   1  does not undercut in the direction of the rotational axis CA. However, by providing an opening adjacent to the first drive surface  82   a , the first drive surface  82   a  can have an undercut shape. Also, preferably, the first serrated teeth  82  all have the same height at the first tooth tips  82   c  as measured in a direction parallel to the rotational axis CA. 
     Referring to  FIGS. 13, 14 and 16 , the second serrated teeth  92  of the second ratchet member  52  will now be discussed in more detail. In the illustrated embodiment, the second ratchet member  52  has a total number of the second serrated teeth  92  that are arranged in a second ring TR 2 . The second ring TR 2  has a second outer ratchet diameter OD 2  and a second inner ratchet diameter ID 2 . In other words, the second ring TR 2  is defined by an area between the second outer ratchet diameter OD 1  and the second inner ratchet diameter ID 2  of the second serrated teeth  82 . The second ring TR 2  is configured such that a second ratio of the total number of the second serrated teeth  92  divided by the second outer ratchet diameter OD 2  is 0.7 or more. Preferably, the second ratio is 1.5 or less. Also, preferably, the second serrated teeth  92  include an outer surface OS 2  having an aluminum alloy. For example, the outer surface OS 2  can have aluminum alloy coating, or the second serrated teeth  92  can be made of partly or entirely of aluminum alloy. 
     Basically, the second serrated teeth  92  has a second driving surface  92   a , a second non-driving surface  92   b  and a second tooth tip  92   c . In the illustrated embodiment, all of the second serrated teeth  92  have the same shape. However, it will be apparent from this disclosure that the second serrated teeth  92  can have different shapes. In any case, at least one of the second non-driving surfaces  92   b  including a second convex curved surface  92   b   1  that has a second radius of curvature X 2  of at least 0.5 mm. Preferably, the second radius of curvature X 2  is at least 1.0 mm. More preferably, the second radius of curvature X 2  is at least 1.5 mm. An upper limit of the second radius of curvature X 2  is preferably one hundred millimeters. However, at the upper limit of the second radius of curvature X 2 , the second convex curved surface  92   b   1  can be any curved surface that close to a flat plane. Thus, the second radius of curvature X 2  can be, for example, five millimeters, ten millimeters, twenty millimeters, thirty millimeters, fifty millimeters or seventy millimeters. In the illustrated embodiment, all of the second driving surface  92   a  have the second convex curved surface  92   b   1 . However, only one or some of the second serrated teeth  92  can have the second convex curved surface  92   b   1 . In the illustrated embodiment, the second ratchet member  52  further includes a second root surface  92   d  between adjacent ones of the second serrated teeth  92 . 
     In the illustrated embodiment, the at least one of the second non-driving surfaces  92   b  has a second tilt angle θ 2  with respect to a plane perpendicular to the rotational axis CA that is greater than zero degrees and that is twenty-five degrees or less. Here, the second tilt angle θ 2  is the same for all of the second serrated teeth  92 . However, all or some of the second serrated teeth  92  can have different tilt angles. Preferably, the second tilt angles θ 2  are twenty degrees or less. More preferably, the second tilt angles θ 2  are sixteen degrees or less. In the illustrated embodiment, the second tilt angles θ 2  are sixteen degrees. In the case where the first non-driving surface  92   b  includes a planar surface, the second tilt angle  02  can be measured as an angle between the planar surface and the plane perpendicular to the rotational axis CA. In the case the second non-driving surface  92   b  does not includes a planar surface, the second tilt angle θ 2  can be measured as an angle between a straight line connecting the end points of the second non-driving surface  92   b  and the plane perpendicular to the rotational axis CA. In the case the second non-driving surface  92   b  does not includes a planar surface, the second tilt angle θ 2  can be measured as an angle between an approximate plane of the second non-driving surface  82   b  and the plane perpendicular to the rotational axis CA. 
     In the illustrated embodiment, the at least one of the second non-driving surfaces  92   b  further includes a second planar surface  92   b   2 . Here, all the second serrated teeth  92  include the second planar surface  92   b   2 . However, some of the second serrated teeth  92  can omit the second planar surface  92   b   2 . In other words, only one or some of the second serrated teeth  92  can include the second planar surface  92   b   2 . The second serrated tooth  92  may not include the second plane  92   b   2 . Also, in the illustrated embodiment, the at least one of the second non-driving surfaces  92   b  further includes a second concave curved surface  92   b   3 . Here, all the second serrated teeth  92  include the second concave curved surface  92   b   3 . However, some of the second serrated teeth  92  can omit the second concave curved surface  92   b   3 . In other words, only one or some of the second serrated teeth  92  can include the second concave curved surface  92   b   3 . The second serrated tooth  92  may not include the second concave curved surface  92   b   3 . In any case, in the illustrated embodiment, the second planar surface  92   b   2  connects the second convex curved surface  92   b   1  and the second concave curved surface  92   b   3 . Thus, the second convex curved surface  92   b   1  is located between the second tooth tip  92   c  and the second concave curved surface  92   b   3  of the at least one the second non-driving surfaces  92   b . The second convex curved surface  92   b   1  is preferably formed near the second tooth tip  92   c.    
     The second tooth tips  92   c  connects corresponding ones of the second driving surfaces  92   a  and the second non-driving surfaces  92   b . In particular, the second tooth tips  92   c  connect the second driving surfaces  92   a  and the second convex curved surface  92   b   1  of the second non-driving surfaces  92   b . Preferably, at least one of the second tooth tips  92   c  includes a second flat surface  92   c   1 . Here, all the second serrated teeth  92  include the second flat surface  92   c   1 . However, some of the second serrated teeth  92  can omit the second flat surface  92   c   1 . In other words, only one or some of the second serrated teeth  92  can include the second flat surface  92   c   1 . The second serrated tooth  92  may not include the second flat surface  92   c   1 . In the illustrated embodiment, each of the second tooth tips  92   c  further includes a second non-sharp surface  92   c   2  that connects the second flat surface  92   c   1  to the second driving surfaces  92   a . However, some of the second serrated teeth  92  can omit the second non-sharp surface  92   c   2 . In other words, only one or some of the second serrated teeth  92  can include the second non-sharp surface  92   c   2 . The second serrated tooth  92  may not include the second non-sharp surface  92   c   2 . Here, the first non-sharp surface  92   c   2  includes a convex surface, but is not limited to that shape. 
     The second ratchet member  52  can be formed using a pair of straight-pull molds in which the straight-pull molds are separated in a direction parallel to the rotational axis CA. Thus, the second serrated teeth  92  are configured such that the second serrated teeth  92  do not include any undercut surfaces as viewed in the direction parallel to the rotational axis CA. For example, the second convex curved surface  92   b   1  does not undercut in the direction of the rotational axis CA. However, by providing an opening adjacent to the second drive surface  92   a , the second drive surface  92   a  can have an undercut shape. Also, preferably, the second serrated teeth  92  all have the same height at the second tooth tips  92   c  as measured in a direction parallel to the rotational axis CA. 
     Referring to  FIGS. 17 to 18 , a coasting situation is illustrated. In  FIG. 17 , the first serrated teeth  82  of the first ratchet member  51  and the second serrated teeth  92  of the second ratchet member  52  are engaged for driving the hub body  32  of the hub  10  as the sprocket support  34  rotates in the driving direction D 1 . In  FIGS. 18 to 22 , the first serrated teeth  82  are sliding relative to each other as the sprocket support rotates in a non-driving direction. 
     With the sprocket support  34  rotates in the driving direction D 1 , at least one of the second tooth tips  92   c  is spaced from the first root surfaces  82   d  where the first driving surfaces  82   a  are engaged with the second driving surfaces  92   a . Here, all of the second tooth tips  92   c  are spaced from the first root surfaces  82   d  where the first driving surfaces  82   a  are engaged with the second driving surfaces  92   a . However, one or some of the second tooth tips  92   c  spaced can be spaced from the first root surfaces  82   d.    
     Referring now to  FIG. 23 , a portion of a first ratchet member  151  and a portion of a second ratchet member  152  are partly illustrated in accordance with a first modification. The first ratchet member  151  and the second ratchet member  152  can be used in the hub  10  instead of the first ratchet member  51  and the second ratchet member  52  discussed above. The first ratchet member  151  includes a first axial surface  180  defining a plurality of first serrated teeth  182 . The second ratchet member  152  includes a second axial surface  190  defining a plurality of second serrated teeth  192 . The first ratchet member  151  and the second ratchet member  152  are identical to the first ratchet member  51  and the second ratchet member  52 , discussed above, except that shapes the first serrated teeth  182  and shapes the second serrated teeth  192  are modified. 
     In this first modification, each of the first serrated teeth  182  has a first driving surface  182   a , a first non-driving surface  182   b , a first tooth tip  182   c  and a first root surface  182   d . Alternatively, only one or some of the first serrated teeth  182  can have the same configuration. The first driving surface  182   a , the first tooth tip  182   c  and the first root surface  182   d  have the same shape as the first driving surface  82   a , the first tooth tip  82   c  and the first root surface  82   d . In other words, only the first non-driving surfaces  182   b  of the first serrated teeth  182  are different from the first serrated teeth  82 . Here, each of the first non-driving surfaces  182   b  includes a first convex curved surface  182   b   1  and a first concave curved surface  182   b   3 . Alternatively, only one or some of the first serrated teeth  182  can have both the first convex curved surface  182   b   1  and the first concave curved surface  182   b   3 . In any case, at least one of the first serrated teeth  182  has the first convex curved surface  182   b   1 . 
     Here, the first non-driving surfaces  182   b  do not include a first planar surface. Rather, the first convex curved surface  182   b   1  and the first concave curved surface  182   b   3  for the at least one of the first non-driving surfaces  182   b  are continuous without a planar surface therebetween. The first convex curved surface  182   b   1  has a radius of curvature that is identical to the first convex curved surface  82   b   1 , discussed above. However, for example, the first convex curved surface  182   b   1  is longer than the first convex curved surface  82   b   1  such that the first convex curved surface  182   b   1  is contiguous with the first concave curved surface  182   b   3 . Also, for example, the first concave curved surface  182   b   3  is longer than the first concave curved surface  82   b   3  so that the first convex curved surface  182   b   1  and the first concave curved surface  182   b   3  are contiguous with each other. 
     Likewise, in this first modification, each of the second serrated teeth  192  has a second driving surface  192   a , a second non-driving surface  192   b , a second tooth tip  192   c  and a second root surface  192   d . Alternatively, only one or some of the second serrated teeth  192  can have the same configuration. The second driving surface  192   a , the second tooth tip  192   c  and the second root surface  192   d  have the same shape as the second driving surface  92   a , the second tooth tip  92   c  and the second root surface  92   d . In other words, only the second non-driving surfaces  192   b  of the second serrated teeth  192  are different from the second serrated teeth  92 . Here, each of the second non-driving surfaces  192   b  includes a second convex curved surface  192   b   1  and a second concave curved surface  192   b   3 . Alternatively, only one or some of the second serrated teeth  192  can have both the second convex curved surface  192   b   1  and the second concave curved surface  192   b   3 . In any case, at least one of the second serrated teeth  192  has the second convex curved surface  192   b   1 . 
     Here, the second non-driving surfaces  192   b  do not include a second planar surface. Rather, the second convex curved surface  92   b   1  and the second concave curved surface for the at least one of the second non-driving surfaces  92   b  are continuous without a planar surface therebetween. The second convex curved surface  192   b   1  has a radius of curvature that is identical to the second convex curved surface  92   b   1 , discussed above. However, for example, the second convex curved surface  192   b   1  is longer than the second convex curved surface  92   b   1  such that the second convex curved surface  192   b   1  is contiguous with the second concave curved surface  192   b   3 . Also, for example, the second concave curved surface  192   b   3  is longer than the second concave curved surface  92   b   3  so that the second convex curved surface  192   b   1  and the second concave curved surface  192   b   3  are contiguous with each other. 
     Referring now to  FIG. 24 , a portion of a first ratchet member  251  and a portion of a second ratchet member  252  are partly illustrated in accordance with a second modification. The first ratchet member  251  and the second ratchet member  252  can be used in the hub  10  instead of the first ratchet member  51  and the second ratchet member  52  discussed above. The first ratchet member  251  includes a first axial surface  280  defining a plurality of first serrated teeth  282 . The second ratchet member  252  includes a second axial surface  290  defining a plurality of second serrated teeth  292 . The first ratchet member  251  and the second ratchet member  252  are identical to the first ratchet member  51  and the second ratchet member  52 , discussed above, except that shapes the first serrated teeth  282  and shapes the second serrated teeth  292  are modified. 
     In this second modification, each of the first serrated teeth  282  has a first driving surface  282   a , a first non-driving surface  282   b , a first tooth tip  282   c  and a first root surface  282   d . Alternatively, only one or some of the first serrated teeth  282  can have the same configuration. The first driving surface  282   a , the first tooth tip  282   c  and the first root surface  282   d  have the same shape as the first driving surface  82   a , the first tooth tip  82   c  and the first root surface  82   d . In other words, only the first non-driving surfaces  282   b  of the first serrated teeth  282  are different from the first serrated teeth  82 . Here, each of the first non-driving surfaces  282   b  includes a first convex curved surface  282   b   1  and a first planar surface  282   b   2 . Alternatively, only one or some of the first serrated teeth  282  can have both the first convex curved surface  282   b   1  and the first planar surface  282   b   2 . In any case, at least one of the first serrated teeth  282  has the first convex curved surface  282   b   1 . 
     Here, the first non-driving surfaces  282   b  do not include a first concave curved surface. Rather, the first planar surface  282   b   2  extends contiguous between the first convex curved surface  282   b   1  and first root surface  282   d  for the at least one of the first non-driving surfaces  282   b  without a concave curved surface therebetween. The first convex curved surface  282   b   1  has a radius of curvature that is identical to the first convex curved surface  82   b   1 , discussed above. 
     Likewise, in this second modification, each of the second serrated teeth  292  has a second driving surface  292   a , a second non-driving surface  292   b , a second tooth tip  292   c  and a second root surface  292   d . Alternatively, only one or some of the second serrated teeth  292  can have the same configuration. The second driving surface  292   a , the second tooth tip  292   c  and the second root surface  292   d  have the same shape as the second driving surface  92   a , the second tooth tip  92   c  and the second root surface  92   d . In other words, only the second non-driving surfaces  292   b  of the second serrated teeth  292  are different from the second serrated teeth  92 . Here, each of the second non-driving surfaces  292   b  includes a second convex curved surface  292   b   1  and a second planar surface  292   b   2 . Alternatively, only one or some of the second serrated teeth  292  can have both the second convex curved surface  292   b   1  and the second planar surface  292   b   2 . In any case, at least one of the second serrated teeth  292  has the second convex curved surface  292   b   1 . 
     Here, the second non-driving surfaces  292   b  do not include a second concave curved surface. Rather, the second planar surface  292   b   2  extends contiguous between the second convex curved surface  292   b   1  and second root surface  292   d  for the at least one of the second non-driving surfaces  292   b  without a concave curved surface therebetween. The second convex curved surface  292   b   1  has a radius of curvature that is identical to the second convex curved surface  92   b   1 , discussed above. 
     Referring now to  FIG. 25 , a portion of a first ratchet member  351  and a portion of a second ratchet member  352  are partly illustrated in accordance with a third modification. The first ratchet member  351  and the second ratchet member  352  can be used in the hub  10  instead of the first ratchet member  51  and the second ratchet member  52  discussed above. The first ratchet member  351  includes a first axial surface  380  defining a plurality of first serrated teeth  382 . The second ratchet member  352  includes a second axial surface  390  defining a plurality of second serrated teeth  392 . The first ratchet member  351  and the second ratchet member  352  are identical to the first ratchet member  51  and the second ratchet member  52 , discussed above, except that shapes the first serrated teeth  282  and shapes the second serrated teeth  392  are modified. 
     In this third modification, each of the first serrated teeth  382  has a first driving surface  382   a , a first non-driving surface  382   b , a first tooth tip  382   c  and a first root surface  382   d . Alternatively, only one or some of the first serrated teeth  382  can have the same configuration. Likewise, in this second modification, each of the second serrated teeth  392  has a second driving surface  392   a , a second non-driving surface  392   b , a second tooth tip  392   c  and a second root surface  392   d . Alternatively, only one or some of the second serrated teeth  392  can have the same configuration. 
     Here, the first serrated teeth  382  have the same shape as the second serrated teeth  92 , while the second serrated teeth  392  have the same shape as the first serrated teeth  82 . However, the direction of the first serrated teeth  382  are inverted relative to the second serrated teeth  92 , and the direction of the second serrated teeth  392  relative to the first serrated teeth  82 . In this way, the first serrated teeth  382  can engage the second serrated teeth  392  to drive the sprocket support  34  in the driving direction. As a result of this configuration of the first serrated teeth  382  and the second serrated teeth  392 , the first tooth tips  382   c  are spaced from the second root surfaces  392   d  where the first driving surfaces  382   a  are engaged with the second driving surfaces  392   a . As mentioned above, the first ratchet member  351  and the second ratchet member  352  can be configured as that only one or some of the first serrated teeth  382  and only one or some of the second serrated teeth  392  have this configuration. In other words, the at least one of the first tooth tips  382   c  is spaced from the second root surfaces  392   d  where the first driving surfaces  382   a  are engaged with the second driving surfaces  392   a.    
     In understanding the scope of the present invention, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, “including”, “having” and their derivatives. Also, the terms “part,” “section,” “portion,” “member” or “element” when used in the singular can have the dual meaning of a single part or a plurality of parts unless otherwise stated. 
     As used herein, the following directional terms “frame facing side”, “non-frame facing side”, “forward”, “rearward”, “front”, “rear”, “up”, “down”, “above”, “below”, “upward”, “downward”, “top”, “bottom”, “side”, “vertical”, “horizontal”, “perpendicular” and “transverse” as well as any other similar directional terms refer to those directions of a human-powered vehicle field (e.g., bicycle) in an upright, riding position and equipped with the planar ratchet assembly. Accordingly, these directional terms, as utilized to describe the planar ratchet assembly should be interpreted relative to a human-powered vehicle field (e.g., bicycle) in an upright riding position on a horizontal surface and that is equipped with the planar ratchet assembly. The terms “left” and “right” are used to indicate the “right” when referencing from the right side as viewed from the rear of the human-powered vehicle field (e.g., bicycle), and the “left” when referencing from the left side as viewed from the rear of the human-powered vehicle field (e.g., bicycle). 
     The phrase “at least one of” as used in this disclosure means “one or more” of a desired choice. For one example, the phrase “at least one of” as used in this disclosure means “only one single choice” or “both of two choices” if the number of its choices is two. For another example, the phrase “at least one of” as used in this disclosure means “only one single choice” or “any combination of equal to or more than two choices” if the number of its choices is equal to or more than three. 
     Also, it will be understood that although the terms “first” and “second” may be used herein to describe various components, these components should not be limited by these terms. These terms are only used to distinguish one component from another. Thus, for example, a first component discussed above could be termed a second component and vice versa without departing from the teachings of the present invention. 
     The term “attached” or “attaching”, as used herein, encompasses configurations in which an element is directly secured to another element by affixing the element directly to the other element; configurations in which the element is indirectly secured to the other element by affixing the element to the intermediate member(s) which in turn are affixed to the other element; and configurations in which one element is integral with another element, i.e. one element is essentially part of the other element. This definition also applies to words of similar meaning, for example, “joined”, “connected”, “coupled”, “mounted”, “bonded”, “fixed” and their derivatives. Finally, terms of degree such as “substantially”, “about” and “approximately” as used herein mean an amount of deviation of the modified term such that the end result is not significantly changed. 
     While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. For example, unless specifically stated otherwise, the size, shape, location or orientation of the various components can be changed as needed and/or desired so long as the changes do not substantially affect their intended function. Unless specifically stated otherwise, components that are shown directly connected or contacting each other can have intermediate structures disposed between them so long as the changes do not substantially affect their intended function. The functions of one element can be performed by two, and vice versa unless specifically stated otherwise. The structures and functions of one embodiment can be adopted in another embodiment. It is not necessary for all advantages to be present in a particular embodiment at the same time. Every feature which is unique from the prior art, alone or in combination with other features, also should be considered a separate description of further inventions by the applicant, including the structural and/or functional concepts embodied by such feature(s). Thus, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.