FIELD OF THE INVENTION

The present invention relates to a hub assembly with a reduction gear, which is suitable for use in steering systems for marine vessels. Embodiments of the present invention relate to a steering hub assembly for a marine steering system.

BACKGROUND TO THE INVENTION

Steering systems for marine vessels may comprise a helm wheel mounted on a pedestal in a cockpit of the vessel. The wheel is coupled to a rudder by a transmission mechanism such that turning movement of the wheel causes pivoting of the rudder in order to steer the vessel. These systems may be used in larger vessels in preference to a tiller since they can afford a greater mechanical advantage to a helmsman.

In some known transmission mechanisms, commonly known as chain and wire mechanisms, the wheel turns a sprocket which is engaged with a length of roller chain. Ends of a cable are connected to each end of the chain, and the cable is wrapped around part of a wheel or quadrant connected to the rudder, such that movement of the cable transmits drive to pivot the rudder.

In other transmission mechanisms, the wheel is coupled to a shaft or torque tube by way of a rack and pinion or bevel gears. Typically, the lower end of the shaft is connected to the rudder by a lever and draglink arrangement.

These transmission mechanisms may include a gearing mechanism, to provide greater mechanical advantage to a helmsman.

The reduction ratio of the gearing mechanism may be chosen in accordance with the size and intended use of the vessel. For example, a heavier yacht used mainly for cruising may use a larger ratio to provide lighter, albeit slower steering, whilst a smaller racing vessel may use a smaller ratio to provide faster, more responsive steering, but which may require greater force from the helmsman. Accordingly, the ratio between rudder torque and the force required at the helm can be modified by varying gear ratios, and/or by varying the geometry of other parts of the steering system. Steering systems may also include drive units, such as electric or hydraulic motors, as part of an autopilot system, and/or to provide power assisted steering.

It is also known to provide more than one gear ratio that is selectable during use. For example, such a steering system may be switchable between a low ratio, permitting faster steering for low speed manoeuvres, and a high ratio for use under greater rudder loads, for example at higher speeds. To this end, in some steering systems the wheel is connected to a two-speed gearbox mounted in the pedestal, which allows the reduction ratio to be adjusted whilst sailing. However, such gearboxes may be bulky and inconvenient to install and maintain.

It is against this background that the present invention has been devised.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a hub assembly for coupling a rotational input to a rotational output. The hub assembly comprises an input shaft for connection to the input, an output shaft for connection to the output, a coupler for transmitting drive from the input shaft to the output shaft, and a reduction gear assembly. The reduction gear assembly comprises a plurality of layshafts, each layshaft carrying an input planetary gear and an output planetary gear, a carrier for supporting the layshafts, an input sun gear for coupling the input shaft to the input planetary gears, and an output sun gear for coupling the output planetary gears to the output shaft. The coupler is movable between a first position and a second position to switch the hub assembly from a first configuration in which the coupler is directly engaged with both the input shaft and the output shaft and a second configuration in which the coupler is engaged with the reduction gear assembly to transmit drive from the input shaft to the output shaft through the reduction gear assembly.

The present invention therefore provides a hub assembly which is switchable in use between a first, direct drive configuration, and a second, reduced ratio configuration. The reduced ratio configuration provides a greater mechanical advantage such that greater output torque can be achieved for a given input torque. The use of planetary gears provides a smaller, more compact arrangement than would otherwise be possible.

The input sun gear may be provided on the input shaft and the output sun gear may be provided on the coupler. In this case, when the coupler is in the first position, the output sun gear may be disengaged from the output planetary gears and, when the coupler is in the second position, the coupler may be disengaged from the input shaft and the output sun gear may be engaged with the output planetary gears.

In another arrangement, the output sun gear is provided on the output shaft and the input sun gear is provided on the coupler. In this arrangement, when the coupler is in the first position, the input sun gear may be disengaged from the input planetary gears, and when the coupler is in the second position, the coupler may be disengaged from the output shaft and the input sun gear may be engaged with the input planetary gears.

Movement of the coupler between the first position and the second position may comprise linear movement along a rotation axis of the input shaft and/or the output shaft. Preferably, the input shaft and the output shaft are splined for engagement with a splined bore of the coupler.

The hub assembly may comprise an actuator operable to move the coupler between the first position and the second position. Preferably the coupler is biased into the first position and the actuator is operable to move the coupler against the bias into the second position. The hub may comprise a coupler spring for biasing the coupler into the first position. The coupler spring may be received in a bore of the input shaft or the output shaft. In this way, the coupler spring can be accommodated in a compact arrangement.

The actuator may comprise an elongate actuating member connected at a first end to the coupler, and may extend through a bore of the input shaft or the output shaft and/or through the coupler spring when provided. The actuator may comprise a flexible line such as a cable or chain and/or a rigid member such as a rod.

Preferably, the hub assembly comprises a sprocket connected to the output shaft for engagement with a chain for driving the output. Alternatively, the output shaft may be connected to a drive shaft, a gear, a pulley, or any other suitable mechanism for driving the output.

Preferably, the carrier includes a central aperture for receiving the coupler. By accommodating the coupler in this way, a compact arrangement of the gear assembly is achieved.

The hub assembly may comprise an output bearing for supporting the output shaft and an output bearing retainer mounted to the carrier for retaining the output bearing. The output bearing may be provided between the sprocket and the output bearing retainer. The hub assembly may comprise an input bearing for supporting the input shaft and an input bearing retainer mounted to the carrier for retaining the input bearing.

Preferably, the hub assembly comprises an input drive shaft connected to the input shaft. The input bearing may be provided between the input drive shaft and the input bearing retainer.

The hub assembly may comprise a drive adaptor for connecting the input drive shaft to the input shaft and an adaptor bearing. The adaptor bearing may be provided between the drive adaptor and the input bearing retainer. One or more of the bearings may be a rolling element bearing. In this case, for example, an inner race of the output bearing, when provided, may be carried by a drive portion of the sprocket and an outer race of the output bearing may be retained by the output bearing retainer. Similarly, an inner race of the input bearing, when provided, may be carried by an enlarged head of the input drive shaft. An inner race of the adaptor bearing, when provided, may be carried by the drive adaptor. An outer race of the input bearing and/or an outer race of the adaptor bearing may be retained by the input bearing retainer.

Preferably, the input shaft and the output shaft are coaxially aligned. The layshafts are preferably disposed around the carrier in an equiangular arrangement. In this way, loads on the input shaft, layshafts, planetary gears and output shaft may be evenly distributed.

The coupler may be movable to a third position to switch the hub assembly to a neutral configuration in which the input shaft is decoupled from the output shaft. In this way, the output shaft may be rotated independently of the input shaft.

The hub may comprise a keying arrangement for matching angular positions of the input shaft and the output shaft.

The input may comprise a manually-operated control. In this case, the hub assembly allows a user to selectively switch the hub assembly from a direct-drive configuration to a geared configuration in which the user is provided with greater mechanical advantage.

The hub assembly is particularly suitable for use as a steering hub assembly for coupling a helm wheel to a steering mechanism in a marine vessel. To this end, the input may comprise a helm wheel for a marine vessel and the output may comprise a steering mechanism of the marine vessel. In this application, the reduced ratio configuration provides a user with greater mechanical advantage such that higher rudder torque can be achieved for a given force applied to the helm. The compact arrangement of the hub assembly allows the steering hub to be fitted conveniently into a pedestal.

When used as a steering hub assembly, a chain of the steering mechanism may be coupled to a sprocket driven by the output shaft. The input drive shaft may comprise a helm shaft to which the helm wheel can be connected.

When the hub assembly is switchable to a neutral configuration, the steering mechanism may be operated without rotating the input shaft, for example by an autopilot system.

Preferred and/or optional features of each aspect and embodiment of the invention may be used, alone or in appropriate combination, in the other aspects and embodiments also.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which like reference numerals are used for like features and in which:

Figure 1 is a perspective view of a steering hub according to a first embodiment of the present invention;

Figure 2 is a side view of the steering hub of Figure 1 ;

Figure 3 is a cross-sectional view of the steering hub of Figure 1 ;

Figure 4 is a perspective view of a helm shaft assembly of the steering hub of Figure

1 ; Figure 5 is a rear perspective view of part of the steering hub of Figure 1 , including a gear assembly;

Figure 6 is a front perspective view of part of the steering hub of Figure 1 , including the gear assembly;

Figure 7 is a perspective view showing components of the steering hub in a first configuration;

Figure 8 is a perspective view of a coupler of the steering hub of Figure 1 ;

Figure 9 is a perspective view of a sprocket of the steering hub of Figure 1 ;

Figure 10 is cross-sectional view of the steering hub of Figure 1 in a second configuration; and

Figure 11 is a perspective view of the components of Figure 7, with the steering hub in the second configuration.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a hub assembly for coupling an input to an output. In the following example, the hub assembly is a steering hub assembly for coupling a helm wheel to a steering mechanism in a steering system of a marine vessel.

In the following, the terms rearward, aft and related terms refer to an input end of the steering hub that is connected to a wheel or other steering input device (i.e. to the left in Figures 1 to 3), whilst the terms forward, front, fore and related terms refer to an opposite, output end of the steering hub that is connected to a steering mechanism (i.e. to the right in Figures 1 to 3). These terms refer to the most common orientation of the steering hub when installed in a vessel, where the input end of the steering hub faces rearward (towards the stern) and is connected to a wheel, and the steering hub extends forward (towards the bow) from the wheel such that the output end of the hub faces forward and away from the helm. It will be appreciated however, that these terms are for reference only, and the present invention could be used in any suitable orientation.

Figures 1 to 3 show a steering hub 10 according to a first embodiment of the invention. In this embodiment, the steering hub 10 is arranged to couple a helm wheel to a chain (not shown) forming part of a chain and cable steering mechanism. The steering hub 10 is arranged to be mounted in a cockpit pedestal of the vessel.

The steering hub 10 comprises a helm shaft assembly 12, a gear assembly 14, and a sprocket 16. The helm shaft assembly 12 extends rearward from the gear assembly 14 to a rearward end 18 of the hub 10, and the sprocket 16 extends forward from the gear assembly 14 towards a forward end 20 of the hub. The helm shaft assembly 12, gear assembly 14 and sprocket 16 lie along a hub axis (indicated by the dashed line marked “A” in Figure 1 ).

Referring additionally to Figure 4, the helm shaft assembly 12 comprises an input drive shaft or helm shaft 22 and a drive adaptor 24. The helm shaft 22 is generally cylindrical and extends coaxially along the hub axis A. A rearward part of the helm shaft 22 provides a wheel mounting portion 25, which is arranged to connect to a helm wheel (not shown).

The wheel mounting portion 25 comprises a securing portion 26 and a mounting shaft 27. The mounting shaft 27 may be splined or keyed to engage with the helm wheel in order to transmit torque form the wheel to the helm shaft 22. The securing portion 26 may be threaded to engage with a fastener for securing the wheel to the helm shaft 22.

A forward part of the helm shaft 22 forms an enlarged diameter head portion 28 provided with an annular flange 30. The drive adaptor 24 comprises an annular body mounted to the end of the head portion 28 of the helm shaft 22. The drive adaptor 24 carries an annular end flange 32, disposed adjacent a forward end of the drive adaptor 24. In this embodiment, the drive adaptor 24 is connected to the helm shaft 22 by a plurality of angularly spaced fasteners 34 which engage with corresponding angularly spaced holes (not visible in Figure 4) in the end of the head portion 28 of the helm shaft 22.

A central bore 36 of the drive adaptor 24 extends coaxially with the hub axis A. The bore 36 is splined to engage with an input shaft 52 to connect the helm shaft assembly 12 to the gear assembly 14, as will be described further below. The input shaft 52 is retained by a retaining circlip and an annular spacer 40 disposed adjacent a rear end of the input shaft 52. The annular spacer 40 abuts a shoulder in the bore 36 of the drive adaptor. The annular spacer 40 helps to align the drive adaptor 24 with the input shaft 52. In some embodiments, the drive adaptor is not present, and the input shaft 52 is instead engaged directly with a forward end of the helm shaft.

Referring additionally to Figures 5 to 7, the gear assembly 14 includes a gear arrangement having a planetary configuration. The gear assembly 14 comprises a gear carrier 38, an input sun gear 54, an output sun gear 74, three input planet gears 56 and three output planet gears 66. The gear assembly 14 is arranged to transfer drive from the helm shaft assembly 12 to the sprocket 16, as will be described in more detail below.

The gear carrier 38 comprises a generally annular body having a rear side 44, a front side 46, and a central opening 48.

As can be seen most clearly in Figures 3 and 5, the input shaft 52 is generally tubular and has a splined forward end part 53. A forward end of the input shaft 52 is received in the central opening 48 of the gear carrier 38, and the rear end of the input shaft 52 projects rearwardly from the gear carrier 38 along the hub axis. The input shaft 52 is arranged to rotate about the hub axis A, and the splined forward part 53 engages with a splined central aperture of the input sun gear 54. In this way, the input sun gear 54 is mounted for rotation with the input shaft 52. As can be seen in Figure 3, forward axial movement of the input sun gear 54 along the input shaft 52 is blocked by a securing circlip 58 fixed on the input shaft 52 and rearward axial movement of the input sun gear 54 is blocked by the drive adaptor 24. The input sun gear 54 is spaced from the rear side 44 of the gear carrier 38 so as to be outside of the central opening 48. The rear end of the input shaft 52 engages with the splined bore 36 in the drive adaptor 24.

Three angularly spaced layshaft holes 50 extend through the gear carrier 38 between the rear side 44 and the front side 46 in an equiangular arrangement around the hub axis A. Each input planet gear 56 is mounted, with a suitable fastener, on a corresponding splined layshaft 60 which extends through a corresponding one of the layshaft holes 50 in the gear carrier 38. Each layshaft 60 is provided with a sleeve, and the layshafts 60 rotate with the input planet gears 56.

As can be seen in Figure 5, the input sun gear 54 and input planet gears 56 are mounted in substantially the same plane, adjacent the rear side 44 of the gear carrier 38, such that the teeth of the input sun gear 54 mesh with the teeth of the input planet gears 56. In this way, the input sun gear 54 drives each of the input planet gears 56 simultaneously.

As shown most clearly in Figures 3 and 6, an output shaft 62 is connected to the gear assembly 14 adjacent the front side 46 of the gear carrier 38. The output shaft 62 is arranged to rotate about the hub axis A. A rear end of the output shaft 62 is disposed in the central opening 48 and a forward end projects forwards from the gear carrier 38 along the hub axis A.

As shown in Figure 3, the output shaft 62 is generally tubular, having a central bore 70 which extends longitudinally through the output shaft 62 along the hub axis A. An elongate actuating member 68 passes from the forward end 20 of the steering hub 10 through the central bore 70 towards the input shaft 52. An enlarged head 72 is provided at a rearward end of the actuating member 68. The actuating member may be in the form of a flexible line such as a cable or a rigid member such as a rod.

As most clearly shown in Figures 7 and 8, the output sun gear 74 is formed on a coupler 64. The coupler 64 is generally tubular, and includes a coupler tube 76 which extends rearwards from the output sun gear 74. The coupler 64 is received in the central opening 48 of the gear carrier 38. A central bore 78 extends through the coupler 64, and is splined to engage with a splined rearward part 63 of the output shaft 62. In this way, the coupler 64 is mounted for rotation with the output shaft 62.

The coupler 64 is arranged to slide axially with respect to the output shaft 62 from a first, rearward position, shown in Figures 3 and 5 to 7, to a second, forward position, shown in Figures 10 and 11. Forward movement of the coupler 64 is limited by a retaining circlip 80 mounted on the output shaft 62.

The coupler 64 is arranged to engage with the input shaft 52 when the coupler 64 is in the rearward position. In particular, the coupler tube 76 extends rearwards so that the splined central bore 78 can engage with the splined forward part 53 of the input shaft 52.

Referring again to Figure 3, the actuating member 68 is connected to the coupler 64 to control the position of the coupler 64. To this end, the enlarged head 72 of the actuating member 68 is disposed in the central bore 78 in the coupler 64, and engages with a stop washer 82 held in place by two circlips in the central bore 78. The stop washer 82 has an internal diameter smaller than an external diameter of the enlarged head 72 so that the head 72 is retained in the coupler 64. A compression spring 84 is disposed between the stop washer 82 and an annular shoulder 86 in the bore 70 of the output shaft 62. The compression spring 84 biases the coupler 64 rearwards towards the input shaft 52, into its rearward position. Rearward movement of the coupler 64 is limited by abutment of the rearward circlip holding the stop washer 82, against the forward end of the input shaft 52. Rearward movement of the coupler 64 is also limited by the abutment of a rear end of the coupler tube 76 against the securing circlip 58 on the input shaft. The actuating member 68 can be pulled in the forward direction to move the coupler 64 against the bias of the spring 84 and into the forward position.

As shown in Figures 10 and 11 , when the coupler 64 is in the forward position, the teeth of the output sun gear 74 mesh with the teeth of the output planet gears 66, and the coupler 64 disengages from the input shaft 52.

The output planet gears 66 are mounted for rotation on the layshafts 60 using suitable fasteners. In this way, each output planet gear 66 is rotationally coupled, by its layshaft 60, to one of the input planet gears 56.

Referring to Figure 9, the sprocket 16 comprises a sprocket wheel 88 and a sprocket hub 90, which are integrally formed in this example. The sprocket hub 90 is generally tubular and extends along the steering hub axis A. A drive portion 94 of the sprocket hub 90 extends rearward from the sprocket wheel 88, and the bore 92 of the hub 90 is splined in the drive portion 94 to engage with a forward part of the output shaft 62. The sprocket 16 rotates with the output shaft about the hub axis A, as will be described in more detail below. The sprocket wheel 88 comprises a plurality of radially spaced teeth for engagement with a roller chain (not shown).

The sprocket 16 is retained on the output shaft 62 by a retaining circlip and an annular spacer 42 disposed adjacent a forward end of the output shaft 62. The spacer 42 abuts a shoulder in the bore 92. The spacer 42 helps to align the output shaft 62 with the sprocket 16.

A bearing portion 96 of the sprocket hub 90 extends forward from the sprocket wheel 88. A forward end part of the bearing portion 96 has a reduced outer diameter which provides an annular bearing surface 98.

When the coupler is in the rearward position, the coupler 64 is engaged with both the input shaft 52 and the output shaft 62, as can be seen most clearly in Figure 3. In this way, the coupler 64 directly couples the input shaft 52 to the output shaft 62. The output shaft 62, and thus the sprocket 16, therefore rotate with the helm shaft 22 and input shaft 52 in a 1 :1 , or direct drive ratio. The head 72 of the actuating member 68 locates in the forward end part of the input shaft 52. The rearward position of the coupler 64 therefore defines a first, direct drive configuration of the steering hub 10.

When the coupler 64 is in the forward position, as shown in Figures 10 and 11 , the coupler tube 76 is disengaged from the input shaft 52 and the output sun gear 74 is engaged with the output planet gears 66. In this arrangement, torque is transmitted indirectly from the input shaft 52 to the output shaft 62 by the gear assembly 14. Rotation of the input shaft 52 and input sun gear 54 drives rotation of the input planet gears 56 and layshafts 60, which rotates the output planet gears 66. The output planet gears 66 drive the output sun gear 74 and thus the output shaft 62.

A gearing ratio (i.e. a rate of rotation of the output shaft 62 relative to a rate of rotation of the input shaft 52) is determined by the relative dimensions of the components of the gear assembly 14.

As can be seen in Figure 7, the input sun gear 54 has a smaller pitch circle diameter than the output sun gear 74. Correspondingly, the input planet gears 56 have a larger pitch circle diameter than the output planet gears 66. In this way, with the coupler 64 in the forward position, the gear assembly 14 provides a reduction gearing mechanism such that the output shaft rotates at a reduced rate relative to the input shaft. The forward position of the coupler 64 therefore defines a second, reduced ratio configuration of the steering hub 10. In one example, the gear assembly provides a reduction ratio of 4:3. In other embodiments, the second configuration may provide a different reduction ratio, which may be chosen in accordance with the intended use of the steering hub.

In this way, the steering hub 10 allows a user to select the degree of mechanical advantage provided in a steering system by pulling the actuating member 68 to switch the hub 10 from the first configuration to the second configuration. A force acting forwardly on the actuating member 68 must be maintained to keep the steering hub in the second configuration. For example, if the actuator is a flexible line, the line may be cleated or tied off. Alternatively, the actuating member may be connected to a lever mechanism, a hydraulic mechanism, an electrically operated mechanism (e.g. a solenoid), or other suitable securing mechanism for pulling the actuator and releasably retaining the actuator in a forward position. Releasing the actuating member 86 returns the hub 10 to the first configuration. In the first configuration, the steering hub 10 provides a direct drive which may be used, for example, at lower vessel speeds where faster steering may be required. In the second configuration, the steering hub 10 provides a reduced ratio which provides greater mechanical advantage to the helmsman, which may be used, for example, at higher vessel speeds which may involve greater rudder torque.

The steering hub 10 may be mounted in a helm pedestal of a vessel. The steering hub may be incorporated in the pedestal before installation, or may be mounted in an installed pedestal, either in a new build or by retrofitting to replace an existing steering hub. To this end, the hub 10 includes a rear bearing cup 100 and a forward bearing cup 111 , that can be mounted in the pedestal, and which together support the other components of the hub 10.

The helm shaft assembly 12 is mounted for rotation in the rear bearing cup 100 which is mounted on the rear side 44 of the gear carrier 38 via a plurality of mounting lugs 102. In this embodiment, three mounting lugs 102 extend forwards and radially outwards from the rear bearing cup 100 and connect to the rear side 44 of the gear carrier 38 in between the input planet gears 56. The head portion 28 and drive adaptor 24 are sized to be retained for rotation in the rear bearing cup 100.

A first annular bearing 104 is disposed between the enlarged head portion 28 and an inner surface 106 of the rear bearing cup 100, and is retained by the annular flange 30. In this way, the first annular bearing 104 provides an input bearing which supports the helm shaft 22 and the input shaft 52 and the rear bearing cup 100 provides an input bearing retainer. A second annular bearing 108 or adaptor bearing is disposed between the drive adaptor 24 and the inner surface 106 of the rear bearing cup 100, and is retained by the annular end flange 32. The helm shaft 22 extends through a rear end opening 110 in the rear bearing cup 100.

The sprocket 16 is mounted for rotation in an output bearing retainer and the forward bearing cup 111. The output bearing retainer comprises a bearing ring 112 having a plurality of ring mounting lugs 114 which are mounted to the front side 46 of the gear carrier 38. In this embodiment, three mounting lugs 114 attach to the front side 46 of the gear carrier 38 in between the output planet gears 66.

In this way, the gear carrier 38 is fixed to the rear bearing cup 100 and the bearing ring 112, such that the carrier 38 does not rotate around the hub axis A. The sun gears 54, 74 and planet gears 56, 66 are arranged to rotate with respect to the gear carrier 38.

The drive portion 94 of the sprocket 16 is mounted in the bearing ring 112. A third annular bearing 116 is disposed between an outer surface of the drive portion 94 and an inner surface 118 of the bearing ring 112. In this way, the third annular bearing 116 provides an output bearing which supports the sprocket 16 and the output shaft 62. The bearing portion 96 of the sprocket is mounted for rotation in the forward bearing cup 111. A fourth annular bearing 120 is disposed between the annular bearing surface 98 of the bearing portion 96 and an inner surface 122 of the forward bearing cup 111. The reduced diameter of the annular bearing surface provides an annular shoulder 124 against which the fourth annular bearing 120 is retained. The actuating member 68 extends through the bearing portion 96 and through a forward end opening 126 provided in the forward bearing cup 111.

The splined connections between the drive adaptor 24, input shaft 52, coupler 64, output shaft 62 and sprocket 16 may include a master spline or other suitable keying arrangement, such that these components may only be engaged when they are in a predetermined rotational orientation about the hub axis A. In this way, whenever the steering hub 10 is in the first configuration, a rotational position of the input shaft 52 is aligned with a corresponding rotational position of the output shaft 62. With this arrangement, a steering system may be configured such that an angle of a wheel corresponds to a rotational orientation of the output shaft 62 and therefore to an angle of a rudder.

The steering system may be configured such that the steering hub 10 may only be switched between the first and second configurations when the wheel and/or rudder are turned to a particular angle or rotational orientation. For example, the steering system may be configured such that the steering hub 10 may only be switched between the first and second configurations when the wheel and/or rudder is at an angle of zero degrees, or steering straight ahead.

In that connection, the splined connections between the layshafts 60, the input planet gears 56 and the output planet gears 66 may include a master spline arrangement, such that each input planet gear 56 is coupled to its respective output planet gear 66 in a specific rotational orientation. In this way, the output planet gears 66 are phased, such that the output sun gear 74 may mesh with the output planet gears 66 only when the output planet gears 66 are in one or more predefined orientations. With this arrangement, the coupler 64 may only be movable into the forward position when the input shaft 52 is in one or more predefined rotational orientations with respect to the output shaft 62.

With the arrangement described above, the steering hub 10 is particularly compact and lightweight. The central opening 48 in the gear carrier 38 provides space for coupling of the input and output shafts 52, 62 by the coupler 64 and access to the coupler 64 by the actuating member 68 is facilitated by the bore 70 in the output shaft 62. The arrangement of the planet gears 56, 66 around the hub axis A evenly distributes loads on the sun gears 54, 74 and planet gears 56, 66 so as to help reduce wear and damage to parts of the steering hub 10 and to provide angularly symmetric support to the input and output shafts 52, 62, reducing load on the bearings. In this embodiment, the gear assembly 14 has a smaller outer diameter than the sprocket 16, such that the outer diameter of the steering hub 10 is determined by the diameter of the sprocket 16, allowing the steering hub to 10 to be accommodated in pedestals designed for direct-drive (i.e. non-switchable) steering hubs.

Advantageously, the compact and lightweight arrangement of the steering hub allows the steering hub to be mounted in compact pedestals, such as pedestals having an aerodynamic design, as may be installed in racing vessels. It will be appreciated that the steering hub need not be installed in a pedestal, and may instead be installed in a different part of the vessel, such as in a dashboard or other parts of a cabin.

Several modifications and variations of the arrangement described above are possible.

For example, the coupler may be provided on the input shaft and be arranged to engage and disengage with the output shaft. In this case the input sun gear may be provided on the coupler.

In some embodiments, the steering hub may be switchable to a third, neutral configuration, in which rotation of the output shaft is fully uncoupled from rotation of the input shaft such that a helm wheel is disconnected from the remainder of the steering system. For example, the spacing between the input and output planet gears could be increased, so that the coupler can adopt a neutral position intermediate the rearward and forward positions in which the coupler is disconnected from the input shaft, but the gearwheel is not meshed with the output planet gears. Advantageously, this may allow an autopilot system to pivot the rudder without turning the helm.

It will be appreciated that the steering hub may be mounted in any suitable orientation in a vessel. For example, the orientation of the steering hub could be reversed, such that the input end faces forward. Alternatively, in some steering systems, the steering hub could be mounted to extend vertically. Also, the input and output ends of the steering hub need not extend in opposite directions. For example, in some embodiments, the steering hub may comprise a suitable additional drive mechanism (e.g. a countershaft) for coupling the helm to the steering hub, such that the input and output ends extend in substantially the same direction.

In other embodiments, the output shaft may not be connected to a sprocket, but may instead be connected to another component of a steering system, such as a rack and pinion, or a drive shaft. In the illustrated example, three pairs of planetary gears are provided in the gear assembly. It will be understood that fewer or more pairs of planetary gears could be provided.

In the example described above, the hub is used as a steering hub in a marine vessel. It will be appreciated, however, that the hub may be used in other applications in which a compact, lightweight, in-line, reduction ratio gearing arrangement is required. For example, the hub may be used in other marine applications, for instance as part of a pulley block or other mechanism for adjusting sheets or lines.

Further modifications and variations not explicitly described above are also possible without departing from the scope of the invention as defined in the appended claims.