DESCRIPTION:

Technical field of the invention

This invention relates to a freewheeling bicycle hub including a force closed type one way clutch configuration.

Background of the invention

One-way clutches for bicycle wheel hubs are well known. These can be classified into form and force closed one-way clutches. Most one-way clutches are of the form-closed type. The main limitations of this design are the finite number of engagement points and the relatively high resistance during coasting.

However, there are also a number of hubs on the market with a force closed oneway clutch. The best known is the hub from Christianson Systems Inc as described in US 10,113,597 B2. The main disadvantage of the force closed type is that it cannot transmit as much torque as a form-closed coupling at the same system weight.

Summary of the invention

An object of the present invention is to provide a bicycle hub assembly that can transmit more torque than the known bicycle hub assembly and keeping the weight limited. To this end the bicycle hub assembly according to the invention is characterized in that it comprises: a hub shell body, having an internal cavity and defining a longitudinal rotational axis, provided with spoke mounting elements present in two axially spaced rows spaced around the circumference of the wheel hub, each spoke mounting element is provided with at least one spoke mounting hole into which a wheel spoke can be inserted, an axle including a first end portion and a second end portion, the axle extending through the internal cavity of the hub body shell in a coaxial arrangement, a freewheel body on which the sprocket(s) are mounted, four bearings that allow for a relative rotational displacement between the axle and the freewheel body and the axle and the hub shell body, but prevent the axial relative displacement between these components, a force closed one-way clutch with an infinite amount of engagement points such as a sprag clutch or a one-way roller clutch, comprising at least an inner ring, an outer ring and elements that generate a clamping force between the inner and the outer ring when a torque is applied to the inner or the outer ring, such that, on the one hand, the driving torque exerted by the cyclist on the sprockets is transferred to the wheel hub and, on the other hand, a relative rotation between freewheel body and hub is allowed during coasting, a means of introducing a permanently present radial force, at the same axial location of the one way clutch, to the hub shell body that is opposite to a radial expansion force that the elements of the force closed one-way clutch exert to the hub shell when the one way clutch is to transmit a torque applied by the cyclist.

For embodiments of the bicycle hub assembly according to the invention is referred to the attached claims.

The present disclosure eliminates the weight disadvantage of the previously known force-closed one-way clutch bicycle hub and even further reduces drag during coasting. This is achieved by applying a permanently present uniformly distributed radial force to the circumference, of the hub body shell at the location of the one-way clutch. This radial force is directed towards the centre of the hub body shell, such that it acts against the outward directing radial forces of the one way clutch elements. This significantly limits the radial expansion of the outer ring of the one-way clutch when a driving torque is applied to the inner ring of the one-way clutch. The invention provides thereto a cycle hub assembly with for example a compression ring press fitted over the circumference of the hub body shell or a pre-tensioned high-strength low density wire wound around the hub body shell, a clamp or a strapping band put around the circumference of the hub body shell.

The form-closed one-way clutch could for example be of the sprag or roller type. When the cyclist pedals, a drive torque is thereby applied to the inner ring of the one way clutch. This drive torque causes the sprag elements or rollers to be clamped between the outer and inner ring of the one way clutch. At this point, the tangential component of the clamping force between the sprag elements respectively roller elements on the one hand and the inner and outer ring on the other hand can transfer a driving torque from the inner ring to the outer ring. The outer ring is rigidly connected to the hub body shell. As a result, a pedal motion is converted into a rotational movement of the hub body shell.

The tangential component of the clamping force is the product of the clamping force itself and the coefficient of friction between the sprag elements respectively roller elements and the inner and outer ring of the one way clutch. These components are all made of hardened steel. The friction coefficient for steel on steel lubricated with grease is typically around 0.1 .

This means that the clamping force is typically a factor of 10 greater than the tangential component. This clamping force acts almost radially on both the inner and outer ring. For the inner ring this is a force directed inward, for the outer ring it is a force directed outward (see Figures 1A and IB). These radial forces place high demands on the strength and rigidity of the inner and outer ring as well as on the hub body shell in which the outer ring is installed and the freewheel body on which the inner ring is installed. The larger the torque applied, the larger the clamping force. This clamping force causes the clamping gap between the inner and outer ring to elastically expand. If this gap becomes too large, the sprag or the roller elements can no longer transfer the required torque and the freewheel body will begin to slip relative to the hub body shell. In order to transfer sufficient torque, the wall thickness of the outer ring and/or the hub body shell would have to be so great that the bicycle wheel hub assembly would become much too heavy.

With the earlier mentioned hub from Christianson Systems Inc, this has been solved by installing two sprag clutches in series, hence reducing the radial stress on the inner and outer rings as well as on the hub body shell. This bicycle wheel hub assembly is still about 60% heavier though than an equivalent bicycle hub assembly with a form closed one way clutch.

The bicycle hub assembly according to the present invention benefits of applying a compressive radial force on the hub body shell. In order to realize the greatest weight reduction the material of this compression ring, clamp, strapping bandor wire has a greater specific yield strength and greater specific young’s modulus than the material for the outer one-way clutch ring and hub body shell. Suitable materials for the compression ring and wire are, for example, titanium and carbon fibre composites. A high specific yield strength allows for a thin walled (and therefore lightweight) compression ring, clamp or strapping band or few windings in case a wire is wound around the hub body shell. The compression stress is acting on the hub body shell in a direction opposite to the expansion stress that the sprag or roller elements exert on the outer ring. As a result the outer ring of the one way clutch only expands when a drive torque, at which the radial expansion stress is greater than the static compression stress caused by the compression ring, is exceeded. In addition, the compression ring, clamp, strapping band or pre-tension wound wire increase the radial stiffness of the hub body shell at the location of the one way clutch. This allows a greater drive torque to be transmitted before, the one-way clutch begins to slip. For given materials, the joint stress that occurs between the compression ring and the hub body shell depends on the press fit and wall thicknesses. This enables one to calculate the required press fit and wall thickness of the compression ring to ensure that the gap between the inner and outer ring at the maximum torque to be transmitted does not become too large. The same applies for a clamp, tension band and a pre-tension wound wire.

The application of a compression ring, a clamp, a tension band or a pre-tension wound wire allows the use of a single sprag clutch as opposed to two units as used in currently known bicycle hub assemblies. Since the sprag clutch elements and the inner and outer rings are made from steel this leads to a significant weight reduction of the cycle hub assembly. The result is a hub that has a similar weight than an equivalent hub with a form closed one-way clutch. Another advantage of a single sprag clutch versus two is the reduced dragwhile coasting.

Brief description of the drawings

The invention will be further elucidated by means of non-limiting exemplary embodiments illustrated in the following figures, wherein:

Figures 1A and IB show the clamping force on both the inner and outer ring; Figure 2 is an isometric view of a first embodiment of a hub according to the principles of the present disclosure;

Figure 3 is a longitudinal cross-sectional view of the hub of Figure 2;

Figure 4 is an isometric view of a second embodiment of a hub according to the principles of the present disclosure;

Figure 5 is a longitudinal cross-sectional view of the hub of Figure 4;

Detailed description of the drawings

Referring to Fig. 2, a first embodiment of a cycle hub assembly according to the present disclosure is shown. In the depicted embodiment, the cycle hub assembly (1) includes a hub body shell (2), an axle (3) and a freewheel body (25). In the depicted embodiment, the cycle hub assembly (1) is configured to freewheel. In other words, a freewheel body (25) rotates with the hub body shell (2) when the wheel is driven by the freewheel body (25) and the freewheel body (25) rotates relative to the hub body shell (2) when the wheel is coasting (rotating and not being driven by the cyclist).

Referring to Figs. 3-5, the configuration of the cycle hub assembly (1) is described in greater detail. In the depicted embodiment the cycle hub assembly (1) is configured for use with multiple speed bicycles (e.g. road bikes, mountain bikes, gravel bikes, cyclo-cross bikes etc.) that utilize an external cassette driven by a chain. In the depicted embodiment the axle (3) is co-axially arranged within the hub body shell (2). In particular, the axle (3) extends through the hub body shell. The axle (3) includes a first end portion (4) that extends outwardly from the first end portion of the hub body shell (2) and a second opposed end portion (6) that extends outwardly from the freewheel body (25).

In the depicted embodiment, the axle (3) includes a shoulder (7) located approximately half way along the axle (3). This shoulder and an adjustable threaded bearing retainer (8) cooperatively prevent the relative axial movement of a first bearing set (9), and a second bearing set (10) on the axle (3). The first bearing set (9) engages an exterior surface of the axle (3) and an interior surface of the sprag clutch inner ring (11). The second bearing set (10) engages an exterior surface of the axle (3) and an interior surface of the internal cavity (12) located at the second end portion of the freewheel body (25). The first and second bearing sets (9, 10) enable a relative rotational movement between the axle (3) and the freewheel body (25) yet prevent the axial movement of the freewheel body (25) on the axle (3). In the depicted embodiment the position of the adjustable bearing retainer (8) is secured through a lock-nut (13) that is threaded onto the axle (3).

A seal (14) between the adjustable bearing retainer (8), located at the second end portion of the axle (3), and the freewheel body (25) seals the interface between axle and freewheel body (25).

The inner ring has one integrated ball raceway and is threaded onto the freewheel body (25), forming a unilateral rigid connection with the freewheel body.

The axle (3), the first bearing set (9), the second bearing set (10), the seal (14), the adjustable bearing retainer (8), the locknut (13) together form a separate subassembly. A main bearing set (15) engages an exterior surface of the freewheel body and an interior surface of an internal cavity (16) located at extreme of the second end portion of the hub body shell (2). This main bearing set (15) is located about halfway between the first and second bearing set (9,10) and thus evenly distributing the load between the two bearing sets (9, 10) in the freewheel body (25). Another main bearing set (17) engages an exterior surface of the axle (3) and an interior surface of an internal cavity (18) located at the first end portion of the hub body shell. The first and second main bearing sets (16, 17) enable a relative rotational movement between the axle - freewheel body sub assembly and the hub body shell (2) yet prevent a relative axial movement. A second adjustable threaded bearing retainer (19) takes the clearance out of these main bearing sets (16, 17). The position of the adjustable bearing retainer (19) is secured through a second lock-nut (20) that is threaded onto the axle (3).

A seal (21) between the adjustable bearing retainer (19) and the hub body shell (2) seals the interface between axle (3) and hub body shell (2). A labyrinth ring (22) pressed onto the freewheel body (25) seals the interface between the freewheel body and the hub body shell (2).

In the depicted embodiment, the hub body shell (2) defines a longitudinal rotational axis A-A. The hub body shell (2) includes an internal cavity (23) that receives the axle-freewheel body subassembly. The hub body shell includes spoke mounting elements. These spoke mounting elements are a set of radially extending tabs (24) coaxial with the rotational axis A-A. This set of radially extending tabs (24) is located at the first end portion of the hub body shell (2). A second set of radially extending tabs is located at the second end of the hub body shell. Each of the radially extending tabs (24) includes 2 spaced apart through apertures (26) that are configured to secure spokes. Adjacent the first set of radially extending tabs (24) is a disk brake mount flange (27) to support a disk of a disk brake system.

The external cylindrical body of the hub body shell (2) is of a constant diameter between the first set of radially expanding tabs (24) and the second end portion of the hub body shell (2) that axially overlaps the sprag clutch outer ring (28). The external diameter of the second end portion of the hub body shell (2) that axially overlaps the sprag clutch outer ring (28) is bigger than the circular outer face of the first set of radially extending tabs (24) such that a titanium compression ring can be slid over the tabs located at the first end portion and pressed onto the second end portion of the hub body shell. In the depicted embodiment, the wall thickness of the hub body shell (2) is greater in the portion that axially overlaps the clutch outer ring (28). In the depicted embodiment the internal cavity (16) of the second end portion of the hub body shell (2) defines two internal cylindrical surfaces. A first cylindrical surface is threaded to accommodate for the outer ring (28) which is threaded into the hub body shell thus forming a unilateral rigid connection with the hub body shell (2). The thread outer diameter D _ou t is equal or smaller than the diameter of the second cylindrical surface that interfaces between the hub body shell (2) and the main bearing set (15).

In the depicted embodiment the internal cylindrical surface of the outer ring (28), together with the external cylindrical surface of the inner ring (11) define an annular cavity that receives the sprag clutch assembly (29). The sprag clutch assembly includes a sprag retaining cage, sprag elements and a tension spring.

Axial movement of the sprag assembly (29) is limited by shoulder (30) in the hub body shell (2) on one side and by the main bearing set (15) on the other side. In the depicted embodiment the outer ring (28) is located at the second end portion of the hub body shell (2) with increased wall thickness onto which the titanium compression ring (31) is pressed. The construction of the outer ring (28), the hub body shell (2) and the titanium compression ring (31) cooperatively provide the structural stiffness and a radial compressive force needed for the torque transfer as encountered on multi gear bicycles such as road bikes, mountain bikes, gravel bikes, cyclo-cross etc. Therefore only one sprag assembly is required as opposed to 2 sprag assemblies in the hub from Christianson systems described in US 10,113,591 B2. Apart from a significant weight reduction this results in a 50% reduction of the drag during coasting caused by the sprag assembly (29).

Referring to Fig. 4, a second embodiment of a cycle hub assembly according to the present disclosure is shown. In the depicted embodiment, the cycle hub assembly (1) includes a hub body shell (2), an axle (3) and a freewheel body (25). In the depicted embodiment, the cycle hub assembly (1) is configured to freewheel. In other words, a freewheel body (25) rotates with the hub body shell (2) when the wheel is driven by the freewheel body (25) and the freewheel body (25) rotates relative to the hub body shell (2) when the wheel is coasting (rotating and not being driven by the cyclist).

Referring to Fig. 5, the configuration of the cycle hub assembly (1) is described in greater detail. In the depicted embodiment the cycle hub assembly (1) is configured for use with multiple speed bicycles (e.g. road bikes, mountain bikes, gravel bikes, cyclo-cross bikes etc.) that utilize an external cassette driven by a chain. In the depicted embodiment the axle (3) is co-axially arranged within the hub body shell (2). In particular, the axle (3) extends through the hub body shell. The axle (3) includes a first end portion (4) that extends outwardly from the first end portion of the hub body shell (2) and a second opposed end portion (6) that extends outwardly from the freewheel body (25).

In the depicted embodiment, the axle (3) includes a shoulder (7) located approximately half way along the axle (3). This shoulder and an adjustable threaded bearing retainer (8) cooperatively prevent the relative axial movement of a first bearing set (9) , and a second bearing set (10) on the axle (3). The first bearing set (9) engages an exterior surface of the axle (3) and an interior surface of the sprag clutch inner ring (11). The second bearing set (10) engages an exterior surface of the axle (3) and an interior surface of the internal cavity (12) located at the second end portion of the freewheel body (25). The first and second bearing sets (9, 10) enable a relative rotational movement between the axle (3) and the freewheel body (25) yet prevent the axial movement of the freewheel body (25) on the axle (3). In the depicted embodiment the position of the adjustable bearing retainer (8) is secured through a lock-nut (13) that is threaded onto the axle (3).

A seal (14) between the adjustable bearing retainer (8), located at the second end portion of the axle, and the freewheel body (25) seals the interface between axle (3) and the freewheel body (25). The inner ring has two integrated ball race ways and is threaded onto the freewheel body (25), forming a unilateral rigid connection with the freewheel body.

The axle (3), the first bearing set (9), the second bearing set (10), the seal (14), the adjustable bearing retainer (8), the locknut (13) and the main bearing set (15) together form a separate sub-assembly. A first main bearing set (17) engages an exterior surface of the axle (3) and an interior surface of an internal cavity located at the first end portion of the hub body shell. A second main bearing set (15) engages an exterior surface of the freewheel body and an interior surface of an internal cavity located at the second end portion of the hub body shell. The first and second main bearing sets (15, 17) enable a relative rotational movement between the axle - freewheel body sub assembly and the hub body shell (2) yet prevent a relative axial movement. A second adjustable threaded bearing retainer (19) takes the clearance out of these main bearing sets (15, 17). The position of the adjustable bearing retainer (19) is secured through a second lock-nut (20) that is threaded onto the axle (3).

A seal (21) between the adjustable bearing retainer (19) and the hub body shell (2) seals the interface between axle (3) and hub body shell (2). A second seal (22), seals the interface between the freewheel body (25) and the hub body shell (2).

In the depicted embodiment, the hub body shell (2) defines a longitudinal rotational axis A-A. The hub body shell (2) includes an internal cavity that receives the axle-freewheel body subassembly. The hub body shell (2) comprise a plurality of spoke mounting elements (24) present in a row positioned around the circumference of the wheel hub, wherein each spoke mounting element comprises two spoke mounting holes

(26) for receiving a spoke. The centre line of the spoke mounting holes extend in a direction substantially perpendicular to the axial direction of the hub body shell.

Adjacent the set of spoke mounting elements (24) is a disk brake mount flange

(27) to support a disk of a disk brake system.

The external cylindrical body of the hub body shell (2) is of a constant diameter between the first set of the spoke mounting elements (24) and the second end portion of the hub body shell (2) that axially overlaps the sprag clutch outer ring (28). In the depicted embodiment, the wall thickness of the hub body shell (2) is greater in the portion that axially overlaps the clutch outer ring (28). A titanium compression ring (31) provided with a plurality of spoke mounting elements (24) present in a row positioned around the circumference of the compression ring, wherein each spoke mounting element (24) comprises two spoke mounting holes (26) for receiving a spoke. The centre line of the spoke mounting holes (26) extend in a direction substantially perpendicular to the axial direction of the hub body shell. The hub body shell (2) is provided with external spline elements and the compression ring with internal spline elements, in order to properly position the compression ring (31) and to achieve a form closed connection between the compression ring (31) and the hub body shell (2), such that the required drive torque can be transferred to the spokes that are attached to the spoke mounting elements (24) of the compression ring (31). In the depicted embodiment the internal cavity of the second end portion of the hub body shell (2) defines two internal cylindrical surfaces. A first cylindrical surface accommodates for the outer race of the second main bearing set (16) which is pressed into the hub body shell (2). A second threaded cylindrical surface interfaces between the hub body shell (2) and the threaded one-way clutch outer ring (28) thus forming a unilateral rigid connection with the hub body shell (2). The inner diameter Di _n of the outer ring is larger or equal to the outer diameter of the second main bearing set (15).

In the depicted embodiment the internal cylindrical surface of the outer ring (28), together with the external cylindrical surface of the inner ring (11) define an annular cavity that receives the sprag clutch assembly (29). The sprag clutch assembly includes a sprag retaining cage, sprag elements and a tension spring.

Axial movement of the sprag assembly (29) is limited by the second main bearing set (15) on one side and by the freewheel body (25) on the other side. The construction of the outer ring (28), the hub body shell (2) and the titanium compression ring (31) cooperatively provide the structural stiffness and a radial compressive force needed for the torque transfer as encountered on multi gear bicycles such as road bikes, mountain bikes, gravel bikes, cyclo-cross etc. Therefore only one sprag assembly is required as opposed to 2 sprag assemblies in the hub from Christianson systems described in US 10,113,591 B2. Apart from a significant weight reduction this results in a 50% reduction of the drag during coasting caused by the sprag assembly.