Continously variable gear system

Abstract

A variable gear system (100), comprising an input shaft (110) configured to receive an input torque; an outer drive mechanism (120) comprising a recess (121), wherein the outer drive mechanism is configured to rotate in response to rotation of the input shaft; an inner drive mechanism (130), the inner drive mechanism comprising a projection (131), wherein the projection is disposed within the recess of the outer drive mechanism. The variable gear system comprises a hydraulic controller (140) and a plurality of fluid pathways, wherein each fluid pathway provides a continuous fluid path extending from the hydraulic controller, through the input shaft, into the recess of the outer drive mechanism, and wherein the fluid pathways are fluidly isolated from each other. The hydraulic controller is adjustable between (i) a first configuration in which hydraulic fluid is free to travel between the fluid pathways and the hydraulic controller without restriction from the hydraulic controller, and in which the inner drive mechanism does not rotate in response to rotation of the outer drive mechanism; and (ii) a second configuration in which hydraulic fluid is restricted from travelling between the fluid pathways and the hydraulic controller by the hydraulic controller, and in which the inner drive mechanism rotates in response to rotation of the outer drive mechanism.

Description

[0001] CONTINOUSLY VARIABLE GEAR SYSTEM

[0002] The invention relates generally to a continuously variable gear system. More particularly, but not exclusively, the invention relates to a continuously variable gear system in which hydraulic fluid is restricted to adjust gear ratios.

[0003] Background

[0004] Continuously variable transmissions (CVTs) are widely used in a variety of industries due to their ability to provide smooth transitions between a wide range of desired gear ratios.

[0005] Traditional CVTs rely on belt-and-pulley systems, toroidal mechanisms, or hydrostatic designs, all of which introduce mechanical complexity and multiple points of potential failure. These designs often require a large number of moving parts which can suffer from wear and degradation over time. As a result, maintenance costs and reliability concerns remain key limitations for conventional CVTs. Efforts to improve CVT reliability have led to innovations in materials, lubrication, and control systems, but challenges persist due to the fundamentals of current designs.

[0006] Further, as a result of the large number of complicated moving parts, CVTs are typically large and heavy. This is often undesirable for the final implementation, such as in vehicles, wherein is it desirable to minimise weight and the space occupied by the CVT. The effects of reduced weight and space for a transmission can be particularly beneficial in electric vehicles, as their range could be dramatically improved and / or the size of their batteries could be reduced.

[0007] The present invention was devised with the foregoing in mind.

[0008] Summary of Invention

[0009] According to a first aspect of the invention, there is provided a variable gear system.

[0010] The variable gear system may comprise an input shaft configured to receive an input torque.The variable gear system may comprise an outer drive mechanism comprising a recess. The outer drive mechanism may be configured to rotate in response to rotation of the input shaft.

[0011] The variable gear system may comprise an inner drive mechanism. The inner drive mechanism may comprise a projection, wherein the projection is disposed within the recess of the outer drive mechanism.

[0012] The variable gear system may comprise a hydraulic controller.

[0013] The variable gear system may comprise a single fluid pathway. The single fluid pathway may provide a continuous fluid path extending from the hydraulic controller, through the input shaft, into the recess of the outer drive mechanism.

[0014] The variable gear system may comprise a plurality of fluid pathways. Each fluid pathway may provide a continuous fluid path extending from the hydraulic controller, through the input shaft, into the recess of the outer drive mechanism. The fluid pathways may be fluidly isolated from each other.

[0015] The hydraulic controller may be adjustable between:

[0016] (i) a first configuration in which hydraulic fluid is free to travel between the fluid pathways and the hydraulic controller without restriction from the hydraulic controller, and in which the inner drive mechanism does not rotate is response to rotation of the outer drive mechanism; and

[0017] (ii) a second configuration in which hydraulic fluid is restricted, or partially restricted, from travelling between the fluid circuits (pathways) and the hydraulic controller by the hydraulic controller, and in which the inner drive mechanism rotates in response to rotation of the outer drive mechanism.

[0018] Having a variable gear system which utilises a hydraulic controller to switch between different configurations, rather than moving meshing gears, reduces the likelihood of components becoming misaligned and / or damaged.The variable gear system may comprise an output shaft configured to provide an output torque. The output shaft may be coupled to the inner drive mechanism such that rotation of the inner drive mechanism drives rotation of the output shaft.

[0019] The hydraulic controller may be continuously adjustable between a range of intermediate configurations in which the hydraulic fluid is partially restricted, by the hydraulic controller, from travelling between the fluid circuits (one or more fluid pathway(s)) and the hydraulic controller.

[0020] Having a continuously adjustable variable gear system enable the gear system to provide an exact desired gear ratio, rather than having to rely on one of a preset number of gear ratios.

[0021] The input shaft may rotate about a first axis and the outer drive mechanism may rotate about a second axis parallel with the first axis. The second axis may be offset from the first axis. The second axis may follow a circular path around the first axis during rotation of the input shaft.

[0022] The input shaft may comprise an open pocket. The outer drive mechanism may be disposed within the open pocket.

[0023] The recess of the outer drive mechanism may comprise a plurality of lobes. The projection of the inner drive mechanism may act as a fluid barrier to prevent hydraulic fluid from passing between lobes within the recess.

[0024] When the hydraulic controller is in the first configuration, the outer drive mechanism may rotate such that the projection consecutively enters each lobe of the recess, without driving rotation of the projection, by displacing fluid from the lobe being entered into the hydraulic circuits and the hydraulic controller.

[0025] When the hydraulic controller is in the second configuration, the outer drive mechanism may rotate and drives rotation of the inner drive mechanism via the hydraulic fluid, which cannot be displaced into the hydraulic circuits and the hydraulic controller.The variable gear system may comprise a shell configured to at least partially surround the input drive shaft. The shell may be configured to remain stationary whilst the input drive shaft rotates.

[0026] The hydraulic controller may comprise a body configured to retain hydraulic fluid. The body may comprise a plurality of body openings configured to enable the passage of hydraulic fluid therethrough. The hydraulic controller may comprise a housing surrounding the body. The housing may comprise one or more housing openings configured to enable the passage of hydraulic fluid therethrough. The body may be adjustable relative to the housing so as to enable alignment and misalignment between the body openings and the housing openings.

[0027] In the first configuration of the hydraulic controller, the body openings and the housing openings may be aligned. In the second configuration of the hydraulic controller, the body openings and the housing openings maybe misaligned such that fluid cannot travel into or out of the body.

[0028] The body may comprise a leg protruding through the housing. The leg may enable movement of the body relative to the housing.

[0029] Each fluid pathway may comprise a conduit extending between the hydraulic controller and the shell.

[0030] Each fluid pathway may comprise a first circumferential channel disposed between the shell and the input drive shaft.

[0031] Each fluid pathway may comprise a second circumferential channel disposed between the input drive shaft and the outer drive mechanism.

[0032] Each fluid pathway may comprise openings to provide fluid connections between:

[0033] (i) the conduit and the first circumferential channel;

[0034] (ii) the first circumferential channel and the second circumferential channel; and

[0035] (iii) the second circumferential channel and the recess of the outer drive mechanism.The recess may comprise three lobes, the plurality of fluid pathways may comprise three fluid pathways, and each fluid pathway may provide a fluid connection between a respective lobe of the recess and the hydraulic controller.

[0036] The term “hydraulic fluid” used herein is not intended to limit the invention for use with any specific type of fluid. Instead, any fluid suitable for use in the invention, such as oil, or a specialised hydraulic fluid, can be used.

[0037] According to second aspect of the invention, there is provided a rotary system. The rotary system of the second aspect may be used in the gear system of the first aspect.

[0038] The rotary system may comprise:

[0039] an input shaft configured to receive an input torque;

[0040] an outer drive mechanism comprising a recess, wherein the outer drive mechanism is configured to rotate in response to rotation of the input shaft;

[0041] an inner drive mechanism, the inner drive mechanism comprising a projection, wherein the projection is disposed within the recess of the outer drive mechanism; wherein rotation of the input shaft is configured to drive rotation of the outer drive mechanism, and wherein the outer drive mechanism is configured to rotate about the inner drive mechanism.

[0042] Features described in relation to the first aspect of the invention may equally apply to the second aspect of the invention, and vice versa.

[0043] Brief description of the drawings

[0044] The invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0045] Figure 1 shows an exploded front-perspective view of a gear system;

[0046] Figure 2(a) and 2(b) respectively show front and side views of the input shaft of the gear system of Figure 1, and Figure 2(c) shows a perspective view of axes within the gear system;Figure 3 shows an exploded rear-perspective view of the gear system of Figure 1;

[0047] Figures 4(a) and (b) show front views of the gear system when assembled;

[0048] Figure 5 shows an enlarged perspective view of the outer drive mechanism and the input shaft during assembly;

[0049] Figures 6(a) and (b) respectively show front and rear cross-sectional perspective views of the input shaft, the outer drive mechanism, and a shell, of the gear system;

[0050] Figure 7 shows an enlarged perspective view of the shell and the input shaft during assembly;

[0051] Figures 8(a)-(d) show perspective views of a gear system as it operates in a neutral configuration;

[0052] Figures 9(a)-(d) show perspective views of a gear system as it operates in a fully engaged configuration;

[0053] Figures 10(a)-(d) show perspective views of a gear system as it operates in an engaged configuration;

[0054] Figure 11(a) shows a perspective exploded view of a hydraulic controller according to one example; and Figure 11(b) shows a sectional perspective view of the assembled hydraulic controller;

[0055] Figures 12(a)-(c) show enlarged sectional side views of the alignment between the body and the housing of the hydraulic controller of Figures 11(a) and 11(b);

[0056] Figure 13 shows a front perspective view of a transmission system comprising the gear system of Figure 1;

[0057] Figure 14 shows a front perspective view of the transmission system of Figure 13;Figures 15(a) and 15(b) show front and rear perspective views of the transmission system of Figure 13 when assembled;

[0058] Figure 16 shows an exploded perspective view of part of a transmission system which is configured to enable reverse gearing; and

[0059] Figures 17(a) and (b) respectively show side views of forward and reverse gear components of the transmission system of Figure 16 in a forward configuration and a reverse configuration.

[0060] Detailed description

[0061] Figure 1 shows an exploded front-perspective view of a gear system 100.

[0062] The gear system 100 comprises an input shaft 110, an outer drive mechanism 120, and an inner drive mechanism 130. In use, the gear system 100 can comprise, or be used in conjunction with, additional components, but the input shaft 110, outer drive mechanism 120, and inner drive mechanism 130 are essential and common to all embodiments of a gear system of the present invention.

[0063] The input shaft 110 comprises a base 112. In the examples shown herein, the base 112 is circular but, in other examples, non-circular bases can be used.

[0064] The input shaft 110 comprises an input rod 118. The input rod 118 extends from the base 112 perpendicular to the plane of the base 112. The input rod 118 is configured to receive an input torque. The input rod 118 has a circumference comprising a plurality of grooves. In use, an external component can engage the grooves of the input rod 118 to exert a torque upon the input rod 118 to drive rotation of the input shaft 110.

[0065] The input shaft 110 comprises a sidewall 111 extending around the circumference of the base 112. The sidewall 111 extends perpendicularly from the base 112 in an opposing direction to the input rod 118. The sidewall 111 defines an open pocket with the base 112. The open pocket is disc-shaped (i.e., cylindrical, with a diameter greater than its length) with sides defined by the sidewall 111 and a face of the base 112.In the examples shown herein, the sidewall 111 is non-uniform, such that the thickness of the sidewall 111 varies around the circumference of the base 112. As a result of the non-unform thickness of the sidewall 111, the open pocket is off-centre relative to the centre of the base 112. In other examples, the sidewall 111 is uniform such that the thickness of the sidewall 111 is constant around the entire circumference of the base. In other examples, the open pocket is disposed centrally relative to the base 112.

[0066] The sidewall 111 comprises a hollow portion 113. The hollow portion 113 is disposed within the thickest region of the sidewall 111 and is configured to reduce the weight of the input shaft 110. In other examples, such as in those with a uniform sidewall 111, the hollow portion 113 is not present. In some examples, a counterbalance can be added to the outer drive mechanism 120 to offset any imbalance of centrifugal forces about its central axis. In some examples, a counterbalance can be added to the input shaft as well as to the outer drive mechanism 120 to offset any imbalance of centrifugal forces.

[0067] The base 112 comprises two faces. The first face of the base 112 is referred to as the “front face” and is the face visible in Figure 1. The second face of the base 112 is referred to as the “rear face”. The rear face of the base 112 is not visible in Figure 1 but is visible in Figure 3. The rear face of the base 112 is the face from which the input rod 118 extends.

[0068] The input shaft 110 comprises a set of front face grooves 114. The front face grooves 114 extend perpendicularly into the front face of the base 112. In the examples shown herein, the front face grooves 114 comprise four concentric circular grooves but, in other examples, the shape and / or number of grooves can change.

[0069] Figure 2(a) shows a front view of the input shaft 110 of the gear system 100. Figure 2(b) shows a side view of the input shaft 110 of the gear system 100.

[0070] The four front face grooves 114 define projections 117. Each projection 117 is ringshaped, having an inner radius and outer radius defined by consecutive front face grooves 114. Each projection 117 comprises an opening 115 configured to enable the passage of fluid through the base 112.Figure 2(b) shows a first axis (A) and a second axis (B). The first axis (A) is the axis about which the input rod 118 is centred and rotates. The first axis (A) is referred to herein as the “input axis”. The second axis (B) is the parallel with the input axis but is offset along the plane of the base 112. The second axis (B) is referred to herein as the “drive axis”. As explained later in the description, the outer drive mechanism 120 is centred on, and rotates about, the drive axis (B).

[0071] In the example of Figure 2, the input axis (A) is aligned with the centre of the input shaft 110 and the drive axis (B) is off-centre from centre of the input shaft 110.

[0072] Figure 2(c) shows a perspective view of axes within the gear system 100. Axis (B) is offset relative to the input axis (A) and follows a circular path around the input axis (A) as a result of the open pocket of the input shaft 110 (in which the outer drive mechanism 120 is disposed) being off-centre relative to the centre of the base 112.

[0073] The outer drive mechanism 120 rotates about axis (B) and, because of its placement within the open pocket of the input shaft 110, it also rotates about axis (A). The only exception is when the gear system 100 is in a fully engaged configuration (described in greater detail below), in which case the outer drive mechanism does not rotate about axis (B).

[0074] Figure 3 shows an exploded rear-perspective view of the gear system 100 of Figure 1.

[0075] The rear face of the base 112 of the input shaft 110 is visible in Figure 3.

[0076] The base 112 comprises a set of rear face grooves 116. The rear face grooves 116 extend perpendicularly from the rear face of the base 112 into the base in the opposite direction to the input rod 118. In the examples shown herein, the rear face grooves 116 comprise four concentric circular grooves but, in other examples, the shape and / or number of grooves can change. The rear face grooves 116 are centred about the input axis (A).

[0077] The four rear face grooves 116 define three projections 119. Each projection 119 is ringshaped, having an inner radius and outer radius defined by consecutive rear face grooves 116. The openings 115 in the projections 117 extend through the base 112 of the input shaft 110 into the projections 119 on the rear face of the input shaft 110. The openings115 are therefore configured to enable the passage of fluid through the base 112 between the front face projections 117 and rear face projections 119.

[0078] The outer drive mechanism 120 comprises a front face, as shown in Figure 1, and a rear face, as shown in Figure 3.

[0079] The outer drive mechanism 120 is disk-shaped. In use, the outer drive mechanism 120 is parallel with the input shaft 110 such that the plane defined by the base 112 of the input shaft 110 is parallel with the plane defined by the outer drive mechanism 120.

[0080] The outer drive mechanism 120 comprises a recess 121 formed in its front face. The recess 121 extends at least partially into the outer drive mechanism. The recess 121 does not extend fully between the front and rear faces of the outer drive mechanism. The centre of the recess 121 is aligned with the centre of the outer drive mechanism.

[0081] The recess 121 is shaped to comprise three lobes. The three lobes are spread evenly about the centre of the outer drive mechanism such that the angle between consecutive lobes is 120°. In other examples, the recess 121 can be shaped differently to in the present examples and, for example, can comprise additional lobes.

[0082] The outer drive mechanism 120 comprises open portions 122 surrounding the recess 121. The open portions 122 are configured to reduce the weight of the outer drive mechanism 120 and the overall gear system 100.

[0083] The outer drive mechanism 120 comprises a set of rear face walls 123. The rear face walls 123 extend perpendicularly from the rear face of the outer drive mechanism 120. In the examples shown herein, the rear face walls 123 comprise four concentric circular walls but, in other examples, the shape and / or number of walls can change. The rear face walls 123 are centred about the centre of the outer drive mechanism 120.

[0084] The four rear face walls 123 define three channels 124. Each channel 124 is ring-shaped, having an inner radius and outer radius defined by consecutive rear face channel walls 123.Each channel 124 comprises an opening 125 which extends through the outer drive mechanism 120 from a rear face to a front face. Each opening 125 fluidly connects a channel 124 with a lobe of the recess 121.

[0085] The inner drive mechanism 130 comprises a projection 131 and a face plate 132. In use, the projection 131 is inserted into the recess 121 of the outer drive mechanism.

[0086] The face plate 132 comprises connectors 133 which extending from a peripheral edge of the face plate 132. As explained later in the description, the connectors 133 enable the face plate 132 to connect with additional components.

[0087] Figures 4(a) and (b) show front views of the gear system 100 when assembled, such that the input shaft 110, outer drive mechanism 120, and inner drive mechanism 130 are brought together. In Figure 4(a), the face plate 132 of the inner drive mechanism 130 is removed for clarity.

[0088] The depth of the projection 131 is equal to the depth of the recess 121 of the outer drive mechanism. As shown in Figure 4(a), the projection 131 is shaped such that, when inserted into the recess 121, it occupies / fills one lobe whilst fluidly isolating the remaining two lobes from each other.

[0089] The outer drive mechanism 120 is disposed within the open pocket of the input shaft 110. The radius of the outer drive mechanism 120 is substantially equal to the radius of the open pocket of the input shaft 110 such that there is contact between an outer wall of the outer drive mechanism 120 and an inner surface of the sidewall 111. In some examples, there may be a clearance between the inner surface of the sidewall 111 and the outer wall of the outer drive mechanism 120, wherein the clearance is filled with a lubricating fluid. The outer drive mechanism 120 fits inside the open pocket of the input shaft 110 such that it is rotatable within the open pocket relative to the input shaft 110 but that frictional forces oppose the rotation.

[0090] Figure 5 shows an enlarged perspective view of the outer drive mechanism 120 and the input shaft 110 during assembly.As the outer drive mechanism 120 is disposed within the open pocket of the input shaft 110, the rear face channel walls 123 of the outer drive mechanism 120 are inserted into the front face grooves 114 of the input shaft 110. The projections 117 of the input shaft 110 partially extend into the channels 124 of the outer drive mechanism 120 such that the channels 117 are sealed. The channels 124 are sealed (i.e., fluid tight) except for the openings 125 in the outer drive mechanism and the openings 115 in the input shaft 110.

[0091] Although the present example shows an input shaft 110 comprising groves 114 and an outer drive mechanism 120 comprising walls, in other examples the reverse can be true, such that the input shaft 110 comprises walls and the outer drive mechanism 120 comprises grooves. In other examples, any other features can be formed on the relevant faces of the input shaft 110 and outer drive mechanism 120 so as to formed sealed channels therebetween.

[0092] Figures 6(a) and (b) respectively show front and rear cross-sectional perspective views of the input shaft 110, the outer drive mechanism 120, and a shell 140, of the gear system 100.

[0093] In use, the shell 140 acts as a housing for the input shaft 110, outer drive mechanism 120, and inner drive mechanism 130.

[0094] The shell 140 is a substantially hollow cylinder. The shell 140 comprises a rear wall 144, a sidewall 145, and a front wall 147 (not shown in Figure 6, but visible in Figures 13 and 14).

[0095] The rear wall 144 comprises a central aperture 142. In use, the input rod 118 of the input shaft 110 extends through the central aperture 142. The input shaft 110 is free to rotate relative to the shell 140 via the input rod 118.

[0096] The rear wall 144 comprises a front face comprising a set of walls 141. The walls 141 extend perpendicularly from the front face of the rear wall 144 of the shell 140. In the examples shown herein, the walls 141 comprise four concentric circular walls but, in other examples, the shape and / or number of walls can change. The walls 141 are centred about the central aperture 142.The four walls 141 define three channels 148. Each channel 148 is ring-shaped, having an inner radius and outer radius defined by consecutive walls 141.

[0097] The rear wall 144 comprises a rear face. The rear face comprises inlets 143. The inlets 143 are openings which extend through the rear wall 144. There are three inlets 143, and each inlet 143 provides an opening into one of the three channels. In other examples wherein there are a different number of channels 148, there will be a corresponding number of inlets 143.

[0098] Figure 7 shows an enlarged perspective view of the shell 140 and the input shaft 110 during assembly.

[0099] As the input shaft 110 is disposed within the shell 140 and the input rod 118 is inserted through the central aperture 142, the walls 141 of the rear wall 144 of the shell 140 extend into the rear face grooves 116 of the input shaft 110. The projections 119 of the input shaft 110 partially extend into the channels 148 of the shell 140 such that the channels 148 are sealed. The channels 148 are sealed (i.e., fluid tight) except for the inlets 143 on the rear face of the rear wall 144 of the shell 140, and the openings 115.

[0100] Although the present example shows an input shaft 110 comprising groves 114 and a shell 140 comprising walls, in other examples the reverse can be true, such that the input shaft 110 comprises walls and the shell 140 comprises grooves. In other examples, any other features can be formed on the relevant faces of the input shaft 110 and shell 140 so as to formed sealed channels therebetween.

[0101] Considering the features described above, there are continuous fluid pathways provided between the inlets 143 of the shell 140 and the lobes of the recess 121 of the outer drive mechanism 120. Fluid can enter / exit the sealed channels 148 formed between the shell 140 and the input shaft 110 via the inlets 143. Fluid can travel from the channels 148, into the channels 124 formed between the input shaft 110 and the outer drive mechanism 120, and vice versa, via the openings 115. Fluid can travel from the channels 124 into the recess 121, and vice versa, via the openings 125. In the present example, there are three fluid pathways but, in other examples, other numbers of fluid pathways can be used in conjunction with a corresponding number of lobes in the recess 121. For example, the number of channels between the input shaft 110 and the shell 140 shouldbe the same as the number of channels between the input shaft 100 and the outer drive mechanism 120 and the number of lobes in the recess 121. Each of the fluid pathways are isolated from each other. Each fluid pathway opens into the recess 121 of the outer drive mechanism 120, but the projection 131 of the inner drive mechanism ensures that the fluid pathway remains fluidly isolated.

[0102] As will be described below, each fluid pathway is connected to a hydraulic controller when in use. The hydraulic controller regulates the input and output of fluid into the fluid pathways via the inlets 143. The hydraulic controller pressurises the hydraulic fluid within the fluid pathways.

[0103] The working principle of the invention is now described, with reference to Figures 8-10, which respectively show the gear system operating in a neutral configuration, a fully engaged configuration, and an engaged configuration.

[0104] Figures 8(a)-(d) show perspective views of a gear system 100 as it operates in a neutral configuration. The gear system progresses from the position shown 8(a), through each of Figures 8(b)-(d) in turn.

[0105] In the neutral configuration, each of the three fluid pathways are unrestricted by the hydraulic controller. Hydraulic fluid fills each of the three fluid pathways initially, and hydraulic fluid is free to exit / enter the fluid pathways via the inlets 143 unrestricted by the hydraulic controller.

[0106] In Figure 8(a), the projection 131 of the inner drive mechanism 130 is disposed in the recess 121 of the outer drive mechanism 120 such that the projection 131 fills / occupies a first lobe 121a, whilst abutting an edge of the recess 121 to fluidly isolate the other two lobes 121b, c from each other. In the position of Figure 8(a), hydraulic fluid fills both of the lobes 121b, c which are not occupied by the projection 131.

[0107] The input shaft 110 rotates under the influence of a torque exerted upon the input rod 118. As the input shaft 110 rotates, there is friction between the inner surface of the side wall 111 and an outer surface of the outer drive mechanism 120. This friction exerts a torque upon the outer drive mechanism 120 such that the outer drive mechanism 120 rotates in the same direction as the input shaft 110. In the example of Figures 8(a)-(d),the input shaft 110 and outer drive mechanism 120 rotate anticlockwise. The skilled person will recognise that the anticlockwise direction is shown merely for example, and the input shaft 110 and outer drive mechanism 120 could equally rotate clockwise.

[0108] As the outer drive mechanism 120 rotates, the position of the lobes 121a, b, c of the recess 121 change relative to the projection 131. As shown from Figures 8(a) to 8(b), the lobe 121a filled by the projection 131 begins to move away from the projection 131, and a next lobe 121b becomes partially filled by the projection 131. In the position of Figure 8(b), the projection 131 partially fills two lobes 121a, b.

[0109] As the outer drive mechanism 120 rotates further, the initially occupied lobe 12 la moves further from the projection 131, and the formerly unoccupied lobe 121b becomes increasingly occupied by the projection 131. This process continues (as shown in Figures 8(c) and (d)) until the initially occupied lobe 121a becomes entirely unoccupied by the projection 131 and the next lobe 121b becomes fully occupied by the projection 131. This process repeats and the projection 131 repeatedly occupies each lobe 121a, b, c of the recess 121 in turn.

[0110] As a result of the shape of the edge of the recess 121 and the shape of the projection 131, the lobes 121a, b, c remain fluidly isolated from each other as the relative position of the projection 131 changes with respect to the recess 121. The lobes 121a, b, c remain fluidly isolated from each other for all possible arrangements of the projection 131 within the recess 121.

[0111] It will be appreciated that the shape of the recess 121 and the shape of the projection 131 are complementary to one another and are defined by their relative rotational motion during operation. In particular, rotational motion of the projection 131 within the recess 121 defines the shape of the recess 121, and rotational motion of the recess 121 about the projection 131 defines the shape of the projection 131. The recess 121 and the projection 131 therefore have a symbiotic geometry which is determined by their tight-fitting interactive motion relative to one another. This complementary geometry enables the projection 131 to remain in sealing engagement with the recess 121 throughout relative rotation, thereby maintaining fluid isolation between adjacent lobes and enabling the tight tolerances required to prevent fluid leakage between lobes.During rotation, as an occupied lobe (e.g., lobe 121a in Figure 8(a) or lobe 121b in Figure 8(d)) moves away from the projection 131 and gradually becomes unoccupied, hydraulic fluid enters the lobe via the corresponding fluid pathway as a result of the pressure redistribution applied by the hydraulic controller. Simultaneously, as the formerly unoccupied lobe begins to receive the projection 131, fluid is forced out of that lobe into its respective fluid channel. In the example described above via Figures 8(a)-(d), hydraulic fluid enters lobe 121a via a hydraulic fluid pathway, and hydraulic fluid is forced out of lobe 121b into a hydraulic fluid pathway by the projection 131.

[0112] Because the hydraulic fluid pathways are unrestricted by the hydraulic controller in the neutral configuration, there is minimal (ideally none) force exerted upon the projection 131 of the inner drive mechanism 130 by the hydraulic fluid. As a result, there is insufficient torque exerted upon the projection 131 of the inner drive mechanism 130 via the hydraulic fluid to overcome the starting torque (i.e., the minimum torque required to overcome static friction to begin rotation), so the inner drive mechanism 130 does not rotate. Therefore, in the neutral configuration, there is no rotation of the inner drive mechanism 130, regardless of the input torque applied to the input shaft 110.

[0113] In practice, the hydraulic fluid experiences some resistance due to drag and viscosity. As a result of these resistive forces, the hydraulic fluid exerts a small force upon the projection 131 and the outer drive mechanism 120. In order for the process explained in the paragraph above to work, it is essential that the starting torque (i.e., the minimum torque required to overcome static friction to begin rotation) of the inner drive mechanism 130 is greater than the force exerted upon the inner drive mechanism 130 by the hydraulic fluid.

[0114] The friction between the input shaft 110 and the outer drive mechanism 120 causes the outer drive mechanism 120 to rotate, as explained above, but the stationary projection 131 forces the outer drive mechanism to follow a path which prevents one-to-one rotation between the input shaft 110 and the outer drive mechanism 120. The projection 131 exerts a torque on the outer drive mechanism 120 (via the hydraulic fluid) which causes “slipping” between the outer drive mechanism 120 and the input shaft 110 as the outer drive mechanism 120 winds around the projection 131. For every complete rotation of the input shaft 110 about axis (A), there is one third of a rotation of the outer drive mechanism 120 about axis (B). In other embodiments wherein the recess 121 hasa different shape and / or a different number of lobes, the ratio of rotational speeds between the input shaft and the outer drive mechanism may be different to 3:1.

[0115] Figures 9(a)-(d) show perspective views of a gear system 100 as it operates in a fully engaged configuration. The gear system progresses from the position shown 9(a), through each of Figures 9(b)-(d) in turn.

[0116] In the fully engaged configuration, each of the three fluid pathways are completely restricted by the hydraulic controller. Hydraulic fluid fills each of the three fluid pathways, and fluid is restricted such that it cannot exit / enter the fluid pathways.

[0117] In Figure 9(a), the projection 131 of the inner drive mechanism 13 is disposed in the recess 121 of the outer drive mechanism 120 such that the projection 131 fills / occupies a first lobe 121a, whilst abutting an edge of the recess to fluidly isolate the other two lobes 121b, c from each other. In the position of Figure 9(a), hydraulic fluid fills both of the lobes 121b, c which are not occupied by the projection 131.

[0118] The input shaft 110 rotates under the influence of a torque exerted upon the input rod 118. As the input shaft 110 rotates, there is friction between the inner surface of the side wall 111 and an outer surface of the outer drive mechanism 120. This friction exerts a torque upon the outer drive mechanism 120 such that the outer drive mechanism 120 rotates in the same direction as the input shaft 110. In the example of Figures 9(a)-(d), the input shaft 110 and outer drive mechanism 120 rotate anticlockwise.

[0119] Because the fluid pathways are restricted, the projection 131 cannot move within the recess 121, as it cannot displace the hydraulic fluid within the unoccupied lobes 121b, c. As a result, as the outer drive mechanism 120 rotates, the position of the lobes of the recess 121 remain stationary relative to the projection 131.

[0120] As a result of the hydraulic fluid being trapped within the unoccupied lobes 121b, c, torque is exerted upon the projection 131 of the inner drive mechanism 130 by the hydraulic fluid. The torque exerted upon the projection 131 of the inner drive mechanism via the hydraulic fluid is sufficiently large to overcome the starting torque (i.e., the minimum torque required to overcome static friction to begin rotation) to drive rotation of the inner drive mechanism 130. Therefore, in the fully engagedconfiguration, there is rotation of the inner drive mechanism 130 in response to application of an input torque to the input shaft 110. The inner drive mechanism 130 rotates at the same angular speed as the outer drive mechanism 120 because the hydraulic fluid cannot be displaced from the unoccupied lobes.

[0121] In order for the process explained in the paragraph above to work, it is essential that the starting torque (i.e., the minimum torque required to overcome static friction to begin rotation) of the inner drive mechanism 131 is less than the frictional force exerted upon the outer drive mechanism 120 by the input shaft 110.

[0122] In the fully engaged configuration, for every complete rotation of the input shaft 110, there is one complete rotation of the outer drive mechanism 120, such that the ratio between rotation of the input shaft 110 about axis (A) and rotation of outer drive mechanism 120 about axis (B) is 1:1.

[0123] Figures 10(a)-(d) show perspective views of a gear system as it operates in an engaged configuration. The gear system progresses from the position shown 10(a), through each of Figures 10(b)-(d) in turn.

[0124] In the engaged configuration, each of the three fluid pathways are partially restricted by the hydraulic controller. The partial restriction increases the resistance against hydraulic fluid as it enters or exits the fluid pathways but does not prevent it completely. Hydraulic fluid fills each of the three fluid pathways, and fluid is free to exit / enter the fluid pathways under some restriction applied by the hydraulic controller.

[0125] In Figure 10(a), the projection 131 of the inner drive mechanism 130 is disposed in the recess 121 of the outer drive mechanism 120 such that the projection 131 fills / occupies one lobe 121a, whilst abutting an edge of the recess to fluidly isolate the other two lobes 121b, c from each other. In the position of Figure 10(a), hydraulic fluid fills both of the lobes 121b, c which are not occupied by the projection 131.

[0126] As with the examples shown in Figures 8(a)-(d) and 9(a)-(d), the input shaft 110 and the outer drive mechanism 120 rotate anticlockwise.As the outer drive mechanism 120 rotates, the position of the lobes 121 a, b, c of the recess 121 change relative to the projection 131. As shown from Figures 10(a) to 10(b), the lobe 121a filled by the projection 131 begins to move away from the projection 131, and a next lobe 121b becomes partially filled by the projection 131. In the position of Figure 10(b), the projection 131 partially fills two 121a, b out of the three lobes. As the outer drive mechanism 120 rotates further, the initially occupied lobe 121a moves further from the projection 131, and the formerly unoccupied lobe 121b becomes increasingly occupied by the projection 131. This process continues (as shown in Figures 10(c) and (d)) until the initially occupied lobe 121a becomes entirely unoccupied by the projection 131 and the next lobe 121b becomes fully occupied by the projection 131. This process repeats and each lobe 121a, b, c is occupied by the projection 131 in turn.

[0127] As the lobe 121a originally filled by the projection 131 begins to move away from the projection 131, hydraulic fluid enters the lobe 121a via the corresponding fluid pathway. Simultaneously, as the formerly unoccupied lobe 121b begins to receive the projection 131, fluid is forced out of that lobe 121b into its respective fluid channel.

[0128] Because the fluid channels are partially restricted by the hydraulic controller in the neutral configuration, there is some resistive force exerted upon the projection 131 of the inner drive mechanism 130 by the hydraulic fluid. Unlike in the examples of Figures 8(a)-(d), there is sufficient torque (due to the partial restriction by the hydraulic controller) exerted upon the projection 131 of the inner drive mechanism 130 via the hydraulic fluid to overcome the starting torque (i.e., the minimum torque required to overcome static friction to begin rotation), so the inner drive mechanism 130 rotates. Therefore, in the engaged configuration, there is rotation of the inner drive mechanism 130 in response to input torque applied to the input shaft 110.

[0129] In the engaged configuration, for every complete rotation of the input shaft 110 about axis (A), there is between one to three complete rotations of the outer drive mechanism 120 about axis (B), such that the ratio between rotation of the input shaft 110 about axis (A) and rotation of outer drive mechanism 120 about axis (B) is between 1:1 and 3:1. As the fluid restriction is increased and the gear system approaches the fully engaged configuration, the ratio approaches 1:1. As the fluid restriction lessens and the gear system approaches the neutral configuration, the ratio approaches 3:1.Figure 11(a) shows a perspective exploded view of a hydraulic controller 150 according to one example. Figure 11(b) shows a sectional perspective view of the assembled hydraulic controller 150. In other examples, alternative hydraulic controllers can be used.

[0130] The hydraulic controller 150 comprises a body 151. The body 151 is configured to retain hydraulic fluid therein. The body 151 comprises a plurality of body openings 151-2 configured to enable the passage of hydraulic fluid therethrough. The body openings 151-2 are apertures in the examples of Figure 11.

[0131] The hydraulic controller 150 comprises a housing 152 surrounding the body 151. The housing 152 comprises one or more housing openings 152-1 configured to enable the passage of hydraulic fluid therethrough.

[0132] In the example of Figures 11(a) and (b), both the body 151 and the housing 152 are cylindrical, and the body 151 fits within the housing 152. In other examples, the body 151 and housing 152 can have different shapes whilst enabling the body 151 to fit inside the housing 152.

[0133] The body 151 is adjustable relative to the housing 152 so as to enable alignment and misalignment between the body openings 151-2 and the housing openings 152-1. The body 151 and the housing 152 are both centred on the same longitudinal axis, and the body 151 is configured to slide parallel with the longitudinal axis relative to the housing 152.

[0134] The hydraulic controller 150 comprises a cap 156 configured to seal an open end of the housing 152. The cap 156 is configured to retain the body 151 (and other components of the hydraulic controller 150) within the housing 156. The cap 156 comprises a central aperture 156-1.

[0135] The body 151 comprises a leg 151-1. The leg 151-1 is an elongated protrusion extending from the body 151 along the longitudinal axis of the body 151. When assembled, the leg 151-1 extends through the cap 156 so as to enable translation of the body 151 relative to the housing 152.The body 151 comprises a pair of grooves 151-3. The grooves 151-3 engage with notches (not shown) of the housing 152 to prevent rotation of the body 151 relative to the housing 152 whilst enabling displacement along their longitudinal axis.

[0136] The hydraulic controller comprises a first resilient member 153 and a second resilient member 155. In the present example the resilient members 153, 155 are springs, but the skilled person will recognise that alternatives, such as elastic components, could be used instead. The springs 153, 155 are disposed either side of the body 151 within the housing 152. The springs 153, 155 are configured to bias the body 151 towards a default position when no force is applied via the leg 151-1.

[0137] The hydraulic controller 150 comprises a flange 154 disposed on the leg 151-1, separating the spring 155 from the body 151. The flange 154 seals hydraulic fluid within the hydraulic controller 150. The flange 154 abuts spring 155 such that the pressure within the hydraulic controller 150 remains constant.

[0138] Body 151 comprises overflows 151-4. The overflows 151-4 enable hydraulic fluid to exit the body 151, when necessary, due to an increase of fluid entering through the openings 151-2. The fluid passes through the overflows 151-4 into the space between the body 151 and the flange 154.

[0139] In use, hydraulic fluid is stored within the centre of the body 151. The hydraulic controller 150 is configured such that the hydraulic fluid can travel from the body 151, through the body openings 151-2 and housing openings 152-1, to the inlets 143 of the shell 140. Conduits (e.g., flexible or rigid pipes, tubes, etc) can be positioned between the inlets 143 and the body openings 152-1.

[0140] The hydraulic controller 150 is adjustable between different configurations in which the restriction against hydraulic fluid flow varies. Figures 12(a)-(c) show enlarged sectional side views of the alignment between the body 151 and the housing 152.

[0141] In Figure 12(a), the body openings 151-1 are fully aligned with the housing openings 152-1. In such a configuration, there is no restriction to fluid flow between the body 151 and the inlets 143 of the shell. In this configuration, the gear system 100 is in theneutral configuration, as explained above with reference to Figures 8(a)-(d). Fluid is free to flow into and out of the fluid pathways of the gear system 100 with the hydraulic controller 150 restricting the fluid.

[0142] In Figure 12(b), the body 151 is offset along the longitudinal axis of the housing 152 such that the overlap between the body openings 151-2 and the housing openings 152-1 is reduced (i.e., they are only partially aligned). In this configuration, fluid can transfer between the body 151 and the fluid pathways of the gear system 100, but there is resistance against the fluid flow as it passes through the join between the body openings 151-2 and the housing openings 152-1. In this configuration, the gear system 100 is in the engaged configuration, as explained above with reference to Figures 10(a)-(d).

[0143] In Figure 12(c) the body 151 is further offset along the longitudinal axis of the housing 152 such that there is no overlap between the body openings 151-2 and the housing openings 152-1 (i.e., they are misaligned). In this configuration, fluid cannot transfer between the body 151 and the fluid pathways of the gear system 100. In this configuration, the gear system 100 is in the fully engaged configuration, as explained above with reference to Figures 9(a)-(d).

[0144] To switch between the different configurations, force is applied to the leg 151-2 in order to move the body 151 relative to the housing 152. The leg 151-2 can be controlled via any suitable means. In some examples, a processor is configured to control an apparatus to adjust the body 151 position via the leg 151-2.

[0145] Although Figures 12(a)-(c) only show three configurations, there are an infinite number of possible configurations due to the continuous adjustment of the body 151 position. For example, the body 151 can be translated greater than, or less than, shown in Figure 12(b) in order to provide greater or lesser resistance against fluid flow between the body 151 and the gear system 100. As a result, the gear ratio between the input shaft 110 and the inner drive mechanism 130 is continuously variable.

[0146] Although the hydraulic controller 150 is configured such that the body 151 is translatable along its longitudinal axis relative to the housing 152 in order to adjustalignment between the body openings 151-2 and the housing openings 152-2, in other examples the body 151 can be rotatable about its longitudinal axis.

[0147] In an alternative example, the gear system can comprise a single fluid pathway configured to provide a continuous fluid path extending between the hydraulic controller and each of the lobes of the recess of the outer drive mechanism. In such an example, the features which define multiple isolated circumferential channels in earlier examples (for example, the front-face grooves 114, the rear-face grooves 116, the rear-face walls 123, and the walls 141 of the shell) may be omitted such that the individual fluid pathway become a single fluid pathway. Instead, the input shaft, the outer drive mechanism, and the shell may comprise simplified internal surfaces which collectively form the single fluid pathway. Each opening 125 from the respective lobes of the recess may be arranged in fluid communication with this single pathway.

[0148] In this example, the projection 131 of the inner drive mechanism 130 can continue to act as a fluid barrier between lobes, preventing direct fluid transfer between adjacent lobes within the recess. However, indirect fluid communication between lobes can be permitted via the single fluid pathway. As the outer drive mechanism 120 rotates, the lobe vacated by the projection 131 draws hydraulic fluid from the single fluid pathway, whilst the hydraulic fluid is forced from the lobe receiving the projection into the single fluid pathway. As a result, the volume of hydraulic fluid within each lobe varies dynamically during operation, establishing a continuous “give-and-take” interaction between the lobes.

[0149] In some examples of this alternative example comprising a single fluid pathway, the hydraulic controller performs a different function to that described in relation to embodiments having multiple isolated fluid pathways. In some examples, the hydraulic controller is not configured to provide adjustable restriction of fluid flow between the lobes. Instead, the hydraulic controller serves as a volume-accommodating chamber which remains in fluid communication with the single fluid pathway and accommodates increases and decreases in fluid volume within the closed hydraulic system formed by the fluid pathway and hydraulic controller.

[0150] In the single fluid pathway embodiment, the respective lobes of the recess are fluidly connected to one another via the single fluid pathway during “neutral” operation. Asthe outer drive mechanism rotates relative to the projection of the inner drive mechanism, hydraulic fluid displaced from a lobe receiving the projection is free to flow through the single fluid pathway and into one or more other lobes which are being vacated by the projection. In this state, hydraulic forces acting on the projection are insufficient to drive rotation of the inner drive mechanism, and the gear system operates in a neutral configuration.

[0151] An adjustable restriction mechanism is provided and is configured to act directly on the single fluid pathway. In some examples, the restriction mechanism is separate and distinct from the hydraulic controller. The adjustable restriction mechanism is adjustable between a first condition in which fluid communication between the lobes via the single fluid pathway is substantially unrestricted, and a second condition in which fluid communication between the lobes is substantially restricted / prevented. Intermediate conditions may partially restrict fluid flow between the lobes via the single fluid pathway.

[0152] The adjustable restriction mechanism can be, for example, one or more valves within the single fluid pathway. In another examples, the adjustable resistance mechanism can be a valve controlling fluid access to the hydraulic controller. The adjustable restriction mechanism can be formed in, or as part of, another part of the gear system. For example, the adjustable restriction mechanism can be part of the outer drive mechanism. The adjustable restriction mechanism can be any means configured to restrict movement of hydraulic fluid.

[0153] As the adjustable restriction mechanism progressively closes the single fluid pathway, the ability of hydraulic fluid to transfer between the lobes is reduced. This causes hydraulic pressure to increase within one or more lobes thereby exerting an increasing torque on the projection of the inner drive mechanism. When the restriction mechanism substantially prevents fluid exchange between the lobes, the outer drive mechanism and inner drive mechanism become hydraulically locked together and rotate in unison.

[0154] In this embodiment, the hydraulic controller is not required to be adjustable and may comprise a chamber in continuous fluid communication with the single fluid pathway. One or more resilient members, such as springs acting on plungers, may be associated with the chamber to maintain a substantially constant hydraulic pressure and toaccommodate volumetric changes within the closed fluid system. The hydraulic controller may therefore accommodate increasing and decreasing fluid volumes within the single fluid pathway during operation.

[0155] In some examples, the hydraulic controller compensates for fluctuations in the volume of hydraulic fluid within the fluid pathway as fluid is displaced from lobes of the recess. The hydraulic controller compensates by receiving and temporarily accommodating the additional fluid.

[0156] Accordingly, in the single fluid pathway embodiment, control of engagement and gear ratio is achieved primarily by the adjustable restriction mechanism acting on the single fluid pathway.

[0157] Features described in relation to examples of the gear system comprising a plurality of fluid pathways can be equally applicable to examples of the gear system comprising a single fluid pathway.

[0158] Figure 13 shows a front perspective view of a transmission system 1000 comprising the gear system 100. Figure 14 shows a rear perspective view of the transmission system 1000. Figures 15(a) and 15(b) show front and rear perspective views of the transmission system 1000 when assembled.

[0159] The transmission system 1000 is provided by way of example to demonstrate how the gear system 100 can be utilised. In other examples, alternative and / or additional components can be used in conjunction with the gear system 100.

[0160] The skilled person will recognise that lubricating fluid can be disposed between various components (e.g., within the shell 140) of the transmission system 1000 which are in direct contract so as to prevent wear and / or excessive frictional heating.

[0161] The transmission system 1000 comprises an input shaft 110, outer drive mechanism 120, inner drive mechanism 130, shell 140, and hydraulic controller 150, as described in greater detail above.The transmission system 1000 also comprises a planetary ring gear 160, a guide 170, and an output shaft 180.

[0162] The planetary ring gear 160 comprises a receiving portion 161 on its face. The receiving portion 161 has a corresponding shape to the face plate 132 of the inner drive mechanism 130. In use, the plate 132 is inserted into the receiving portion 162 such that the planetary ring gear 160 rotates in unison with the inner drive mechanism. The connectors 133 of the face plate 132 engage with the receiving portion 161.

[0163] The planetary ring gear 160 comprises a sidewall 162 on its front face. The sidewall 162 comprises teeth on an inner surface extending radially towards the centre of the planetary ring gear 160.

[0164] The output shaft 180 is an elongate rod comprising a first set of teeth around its circumference at a first end and a second set of teeth around its circumference at a second end. The teeth on the inner surface of the sidewall 162 are configured to engage with the first set of teeth of the output shaft 180, such that the output shaft rotation of the planetary ring gear 160 causes rotation of the output shaft 180.

[0165] The guide 170 is positioned between the planetary ring gear 160 and the front wall 147 of the shell 140. The guide 170 is configured to maintain correct positioning and alignment between the output shaft 180 and the planetary ring gear 160.

[0166] The ratio between the diameter of the planetary ring gear 160 and the output shaft 180 determines the gear ratio between them, but the skilled person will recognise that any suitable ratio can be used depending on the requirements of the final system.

[0167] In transmission system 1000, an input torque applied to the input shaft 110 creates rotation of the inner drive mechanism 130, and the gear ratio between them depends on the configuration of the hydraulic controller, as discussed above. The rotation of the inner drive mechanism 130 (which occurs unless the hydraulic controller is in a “neutral” configuration) causes rotation of the output shaft, which can be used to provide a force / torque as desired. As the gear ratio between the input shaft 110 and inner drive mechanism 130 is continuously variable, via the hydraulic controller, the gear ratio of the overall transmission system 1000 is also continuously variable.Figure 16 shows an exploded perspective view of part of a transmission system 1000’ which is configured to enable reverse gearing.

[0168] Similarly to the transmission system 1000 of Figures 13-15, the transmission system 1000’ comprises a planetary ring gear 160, a guide 170, and an output shaft 180.

[0169] However, the transmission system 1000’ also comprises first 192 and second 194 forward gear components and first 196 and second 198 reverse gear components.

[0170] The transmission system 1000’ is configurable in a forward configuration and a reverse configuration. The transmission system 1000’ can switch between these configurations by adjusting the alignment between the forward 192, 194 and reverse 196, 198 gear components, as explained below with reference to Figures 17a, b.

[0171] In use, the planetary ring gear 160 rotates in conjunction with the inner drive mechanism 130, as for the transmission system 1000 described above.

[0172] The first forward gear component 192 is cylindrical. The first forward gear component 192 comprises a first set of radial grooves 192-1 on its circumference which engage with the teeth on the inner surface of the sidewall 162 of the planetary ring gear 160, thereby causing the first forward gear component 192 to rotate.

[0173] The first forward gear component 192 also comprises a second set of radial grooves 192-2 adjacent the first set of radial grooves 192-1.

[0174] The second forward gear component 194 is ring-shaped. It comprises an outer set of radial grooves 194-1 on its outer circumference and an inner set of radial grooves 194-2 on its inner circumference. The inner set of radial grooves 194-2 is configured to engage with (i.e., mesh with) the second set of radial grooves 192-2 of the first forward gear component 192.

[0175] The first and second forward gear components 192, 194 are aligned such that their longitudinal axes align.The first reverse gear component 196 comprises a set of radial grooves 196-1 on its outer surface.

[0176] The second reverse gear component 198 comprises a set of radial grooves 198-1 on its outer surface.

[0177] The first and second reverse gear components 196, 198 are cylindrical and are aligned such that their longitudinal axes align.

[0178] The output shaft 180 comprises a set of radial grooves 180-1 which are configured to engage with the inner set of radial grooves 194-2 of the second forward gear component 194.

[0179] Figures 17(a) and (b) respectively show side views of the forward 192, 194 and reverse 196, 198 gear components of transmission system 1000’ in a forward configuration and a reverse configuration. To switch between the forward and reverse configurations, the second forward gear component 194 is shifted relative to the other components.

[0180] In Figure 17(a), the first forward gear component 192 is brought sufficiently close to the second forward gear component 194 to engage the second set of radial grooves 192-2 of the first forward gear component 192 with the inner set of radial grooves 194-2 of the second forward gear component 194. As a result, the second forward gear component 194 rotates in unison with the first forward gear component 192.

[0181] The second forward gear component 194 is sufficiently deep to receive both the second set of radial grooves 192-2 of the first forward gear component 192 and the set of radial grooves 180-1 of the output shaft 180 simultaneously. This is shown in Figure 17(a). As a result of the engagement between the first and second forward gear components 192, 194 and the output shaft 180, the output shaft 180 rotates in unison with the first forward gear component 192. This is referred to as the forward direction.

[0182] In Figure 17(b), the second forward gear component 194 is moved along its longitudinal axis away from the first forward gear component 192 relative to in Figure 17(a).As a result of the movement of the second forward gear component 194, it no longer engages directly with the first forward gear component 192. Instead, the outer set of radial grooves 194-1 of the second forward gear component 194 engage with the radial grooves 198-1 of the second reverse gear component 198.

[0183] The first reverse gear component 196 rotates in the same direction as the first forward gear component 192, as the radial grooves 196-1 engage with the teeth of the planetary ring gear 160. The second reverse gear component 198 is joined to the first reverse gear component 196 such that they rotate in unison. In some examples, the first 196 and second 198 reverse gear components are a single component such that the first and second parts are permanently connected.

[0184] The outer set of radial grooves 194-1 of the second forward gear component 194 engage with the radial grooves 198-1 of the second reverse gear component 198, causing the second forward gear component 194 to rotate in an opposing direction to the second reverse gear component 198.

[0185] The inner radial grooves 194-2 of the second forward gear component 194 engage with the set of radial grooves 180-1 of the output shaft 180, thereby causing the output shaft 180 to rotate in unison with the second forward gear component 194.

[0186] Therefore, in the reverse configuration, the output shaft 180 rotates in an opposing direction to in the forward direction.

[0187] Although the invention is described above in relation to a gearbox, in other examples the invention can be implemented in alternative ways. The core components to the invention are the input shaft, outer drive mechanism, and inner drive mechanism. These components can be used in conjunction for other applications.

[0188] From reading the present disclosure, other variations and modifications will be apparent to the skilled person. Such variations and modifications may involve equivalent and other features which are already known in the art, and which may be used instead of, or in addition to, features already described herein.Although the appended claims are directed to particular combinations of features, it should be understood that the scope of the disclosure of the present invention also includes any novel feature or any novel combination of features disclosed herein either explicitly or implicitly or any generalisation thereof, whether or not it relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the present invention.

[0189] Features which are described in the context of separate embodiments may also be provided in combination in a single embodiment. Conversely, various features which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.

[0190] For the sake of completeness it is also stated that the term "comprising" does not exclude other elements or steps, the term "a" or "an" does not exclude a plurality, and any reference signs in the claims shall not be construed as limiting the scope of the claims.

Claims

Claims1. A variable gear system, comprising:an input shaft configured to receive an input torque;an outer drive mechanism comprising a recess, wherein the outer drive mechanism is configured to rotate in response to rotation of the input shaft;an inner drive mechanism, the inner drive mechanism comprising a projection, wherein the projection is disposed within the recess of the outer drive mechanism; a hydraulic controller; anda plurality of fluid pathways, wherein each fluid pathway provides a continuous fluid path extending from the hydraulic controller, through the input shaft, into the recess of the outer drive mechanism, and wherein the fluid pathways are fluidly isolated from each other;wherein the hydraulic controller is adjustable between:(i) a first configuration in which hydraulic fluid is free to travel between the fluid pathways and the hydraulic controller without restriction from the hydraulic controller, and in which the inner drive mechanism does not rotate in response to rotation of the outer drive mechanism; and(ii) a second configuration in which hydraulic fluid is restricted from travelling between the fluid pathways and the hydraulic controller by the hydraulic controller, and in which the inner drive mechanism rotates in response to rotation of the outer drive mechanism.

2. The variable gear system of claim 1, further comprising an output shaft configured to provide an output torque, wherein the output shaft is coupled to the inner drive mechanism such that rotation of the inner drive mechanism drives rotation of the output shaft.

3. The variable gear system of claim 1 or claim 2, wherein the hydraulic controller is continuously adjustable between a range of intermediate configurations in which the hydraulic fluid is partially restricted, by the hydraulic controller, from travelling between the fluid pathways and the hydraulic controller.

4. The variable gear system of any preceding claim, wherein the input shaft rotates about a first axis and the outer drive mechanism rotates about a second axis parallelwith the first axis, and wherein the second axis is offset from the first axis and follows a circular path around the first axis during rotation of the input shaft.

5. The variable gear system of any preceding claim, wherein the input shaft comprises an open pocket off-centre from the centre of the input shaft, and wherein the outer drive mechanism is disposed within the open pocket.

6. The variable gear system of any preceding claim, wherein the recess of the outer drive mechanism comprises a plurality of lobes, and wherein the projection of the inner drive mechanism acts as a fluid barrier to prevent hydraulic fluid from passing between lobes within the recess.

7. The variable gear system of claim 6, wherein, when the hydraulic controller is in the first configuration, the outer drive mechanism rotates such that the projection consecutively enters each lobe of the recess, without driving rotation of the projection, by displacing fluid from the lobe being entered into one of the fluid pathways and the hydraulic controller.

8. The variable gear system of claim 6 or claim 7, wherein, when the hydraulic controller is in the second configuration, the outer drive mechanism rotates and drives rotation of the inner drive mechanism via the hydraulic fluid, which cannot be displaced into the fluid pathways and the hydraulic controller.

9. The variable gear system of any preceding claim, wherein the variable gear system comprises a shell configured to at least partially surround the input drive shaft, and wherein the shell is configured to remain stationary whilst the input drive shaft rotates.

10. The variable gear system of any preceding claim, wherein the hydraulic controller comprises:a body configured to retain hydraulic fluid, wherein the body comprises a plurality of body openings configured to enable the passage of hydraulic fluid therethrough; anda housing surrounding the body, wherein the housing comprises one or more housing openings configured to enable the passage of hydraulic fluid therethrough;wherein the body is adjustable relative to the housing so as to enable alignment and misalignment between the body openings and the housing openings.

11. The variable gear system of claim 10, wherein, in the first configuration of the hydraulic controller, the body openings and the housing openings are aligned; and wherein in the second configuration of the hydraulic controller, the body openings and the housing openings are misaligned such that fluid cannot travel into or out of the body.

12. The variable gear system of any preceding claim, wherein the body comprises a leg protruding through the housing, and wherein the leg enables movement of the body relative to the housing.

13. The variable gear system of any preceding claim, wherein each fluid pathway comprises:a conduit extending between the hydraulic controller and the shell;a first circumferential channel disposed between the shell and the input drive shaft;a second circumferential channel disposed between the input drive shaft and the outer drive mechanism; andopenings to provide fluid connections between:(iv) the conduit and the first circumferential channel;(v) the first circumferential channel and the second circumferential channel; and(vi) the second circumferential channel and the recess of the outer drive mechanism.

14. The variable gear system of any preceding claim, wherein the recess comprises three lobes, the plurality of fluid pathways comprises three fluid pathways, and each fluid pathway provides a fluid connection between a respective lobe of the recess and the hydraulic controller.

15. A variable gear system, comprising:an input shaft configured to receive an input torque;an outer drive mechanism comprising a recess, wherein the outer drive mechanism is configured to rotate in response to rotation of the input shaft;an inner drive mechanism, the inner drive mechanism comprising a projection, wherein the projection is disposed within the recess of the outer drive mechanism; a restriction mechanism; anda fluid pathway, wherein the fluid pathway provides a continuous fluid path extending through the input shaft, into the recess of the outer drive mechanism;wherein the restriction mechanism is adjustable between:(i) a first configuration in which hydraulic fluid is free to travel between the recess of the outer drive mechanism and the fluid pathway without restriction from the restriction mechanism, and in which the inner drive mechanism does not rotate in response to rotation of the outer drive mechanism; and(ii) a second configuration in which hydraulic fluid is restricted from travelling between the recess of the outer drive mechanism and the fluid pathway by the restriction mechanism, and in which the inner drive mechanism rotates in response to rotation of the outer drive mechanism.

16. The variable gear system of claim 15, further comprising an output shaft configured to provide an output torque, wherein the output shaft is coupled to the inner drive mechanism such that rotation of the inner drive mechanism drives rotation of the output shaft.

17. The variable gear system of claim 15 or claim 16, wherein the restriction mechanism is continuously adjustable between a range of intermediate configurations in which the hydraulic fluid is partially restricted, by the hydraulic controller, from travelling between the fluid pathway and the hydraulic controller.

18. The variable gear system of any of claims 15-17:wherein the restriction mechanism is a hydraulic controller; andwherein the gear system comprises a plurality of fluid pathways; wherein each fluid pathway provides a continuous fluid path extending from the hydraulic controller, through the input shaft, into the recess of the outer drive mechanism, and wherein the fluid pathways are fluidly isolated from each other.

19. A rotary system, comprising:an input shaft configured to receive an input torque;an outer drive mechanism comprising a recess, wherein the outer drive mechanism is configured to rotate in response to rotation of the input shaft;an inner drive mechanism, the inner drive mechanism comprising a projection, wherein the projection is disposed within the recess of the outer drive mechanism; wherein rotation of the input shaft is configured to drive rotation of the outer drive mechanism, and wherein the outer drive mechanism is configured to rotate about the inner drive mechanism.

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