Rotary transmission joint for a tyre pressure control system

Abstract

The present invention relates to a rotary transmission joint for a tyre pressure control system for guiding a flow of pressurized fluid between an axle of a vehicle and a rotary hub of the vehicle, the rotary transmission joint comprising: a hollow axle insert, a hub fitment, and a rotary seal assembly between the insert and the fitment, comprising a mechanical seal with a stationary seal member and a rotary seal member that contact each other and slide against each other upon mutual rotation between them, further comprising an elastic element pretensioned in between the axle insert and the stationary seal member, in order to hold the stationary seal member substantially stationary relative to the axle insert.

Description

[0001] Title: Rotary transmission joint for a tyre pressure control system

[0002] Field of the invention

[0003] The present invention relates to a rotary transmission joint for a tyre pressure control system. The present invention further relates to an axle assembly of a vehicle and to a method of assembling such an axle assembly.

[0004] State of the art

[0005] Tyre pressure control systems are known for, for example, agricultural vehicles to inflate or deflate their tyres while driving, depending on the subsoil the vehicle is driving on. To realise this, there must be a minimum of one airline per wheel connecting a pressurised fluid from a source of pressurized fluid attached to the body of the vehicle towards the tyres that are arranged on the vehicle’s wheels. Depending on the axle type, there are different limitations of realising the airline, to change from a stationary airline on the vehicle body into a rotating airline on the rotating wheel.

[0006] At present, airlines are brought to the outside of the vehicle and lowered to a rotary transmission joint mounted in-line with the axle at the outside thereof, and rotating at the same speed as the tyre. These outward airlines increase the width of the vehicle, for example above a maximum width allowed on the public road, and is prone to damages. An example of such a rotary transmission joint is disclosed in EP 3 341 225 B1

[0007] The present invention is intended for axle types that can be provided hollow for supplying pressurized fluids internally through the axle towards a rotary hub at the outer ends of the axle. From there, an internal rotary transmission joint between the axle and the hub can be utilized to further guide the pressurized fluid towards the wheel.

[0008] An example of such an internal rotary transmission joint is disclosed in US 7,207,365 B2. This system comprises a seal with a stationary portion and a rotary portion, wherein the stationary portion extends into the hub via a bearing. A flexible coupling sleeve is provided between the axle and the stationary seal portion in order to compensate for misalignments between the axle and the hub due to wear and re-adjustments of the hub bearing. This known system, however, has the drawback that it contains various bearings, due to the occurring mutual rotations between stationary parts arranged inside rotary parts and vice versa, which may increase complexity of the rotary transmission joint.

[0009] Object of the invention In view of the above drawbacks, it is an object of the invention to provide a rotary transmission joint that is less complicated compared to the rotary transmission joints that are known in the art, or at least to provide an alternative rotary transmission joint.

[0010] Detailed description

[0011] According to a first aspect, the present invention provides a rotary transmission joint for a tyre pressure control system for guiding a flow of pressurized fluid between an axle, for example a stationary non-driven axle of a vehicle and a rotary hub of the vehicle, the rotary transmission joint comprising: a hollow axle insert, configured to be connected to the axle, for example inserted, in particular press-fitted or screwed, along an axle centreline into a cavity in the axle and configured to receive a flow of fluid from a source of pressurized fluid, a hub fitment, which is configured to be connected to the hub, to be rotated along with the hub relative to the axle insert about a hub rotation axis and to supply the flow of fluid, obtained from the axle insert, towards a wheel of the vehicle, and a rotary seal assembly, which is functionally arranged in between the axle insert and the hub fitment to define a fluid transfer channel for sealingly guiding the flow of fluid between the axle insert and the hub fitment whilst enabling mutual rotation between them, characterized in that the rotary seal assembly comprises, e.g. a mechanical seal with, a stationary seal member attached to the axle insert to remain substantially stationary, and a rotary seal member attached to the hub fitment to be rotated therewith relative to the stationary seal member, wherein the seal members each comprise a through passage, which together define the fluid transfer channel, and an annular seal plane surrounding the respective through passage, wherein the seal planes contact each other to seal-off the fluid transfer channel and slide against each other upon mutual rotation between them, wherein the rotary seal assembly further comprises an elastic element, which is functionally arranged in between the axle insert and the stationary seal member, in order to: hold the stationary seal member substantially stationary relative to the axle insert, and / or accommodate an angular offset between the seal plane of the stationary seal member and the seal plane of the rotary seal member, and / or press the stationary seal member and the rotary seal member against each other with their seal planes, and / or align the seal members to compensate for an offset between the axle centreline and the hub rotation axis.

[0012] The present rotary transmission joint is adapted for mounting in a cavity of an axle.

[0013] Such a cavity is generally provided at a head end of such an axle and extends into the axle along the centreline, preferably concentrically with the centreline. The axle may be nondriven. The axle may possess a hollow channel inside, which may extend along the centreline as well. A feed line for the pressurized fluid may be provided in the hollow channel, extending from a source of pressurized fluid towards the rotary transmission joint. The feed line is thereby configured to supply the pressurized fluid towards the rotary transmission joint.

[0014] Throughout the present application, the wording of rotary and stationary is used to indicate components that are configured to rotate with respect to a reference object, that is for example arranged stationary, or rotatable at a lower rotational velocity, relative to the rotary component.

[0015] The rotary transmission joint thus needs to form a substantially fluid tight transfer for the flow of pressurized fluid from the stationary axle towards the rotary hub. To this effect, the rotary transmission joint comprises the axle insert that is configured to be connected to the axle to remain stationary therewith. In particular, the axle may be provided with the cavity at its head end in which the axle insert is inserted. The axle insert may be secured to the axle by means of a press-fit connection, although other connections, such as threaded connections, may also be envisaged. The rotary transmission joint is, during use, configured to receive the pressurized fluid at the stationary axle insert.

[0016] The vehicle may further comprise a hub, to which a wheel of the vehicle is connected, which is rotatable relative to the axle, in order to allow for rotation of the wheel. The hub may be associated to the axle via conical hub bearings, which are configured to guide the rotations of the hub. The hub bearings may wear over time, during use of the vehicle, which may require re-adjustment of the bearings, which could possibly result in that the alignment between the hub and the axle may vary over time. Initially, for example in a newly built axle assembly, a hub rotation axis may be aligned concentrically with the centreline of the axle.

[0017] Furthermore, the wear of the hub bearings may give the effect that, after re-adjustment of the hub bearings, the hub becomes located somewhat closer to the axle, due to axial adjustments. Alternatively or additionally, the hub may end up being tilted relative to the axle to a small extent after re-adjustment of the hub bearings.

[0018] The hub fitment of the rotary transmission joint is connectable to the hub, for example by means of a threaded connection or a press-fit connection, which implies that the hub fitment rotates along with the hub when the vehicle is driving. Likewise, the hub fitment continues to rotate about the hub rotation axis over time, which could potentially give rise to a rotational offset between the hub fitment and the axle insert. The hub fitment may be connected to further fitments and airlines of the tyre pressure control system, for example towards a wheel valve thereof. As such, the hub fitment receives the flow of pressurized fluid from the axle insert, during use, and further guides the fluid towards the wheel. The rotary transmission joint comprises the rotary seal assembly in between the hub fitment and the axle insert, through which the pressurized fluid can be guided between them. The rotary seal assembly forms the transition between the stationary axle insert and the rotary hub fitment, whereby the rotary seal assembly is able to safeguard the transfer of fluid between a stationary part of the rotary seal assembly and a rotary part thereof. Likewise, the rotary seal assembly is able to compensate for possible offsets in between the hub rotation axis and the axle centreline whilst maintaining the fluid connection. To this effect, the rotary seal assembly comprises the fluid transfer channel of which an interior is sealed-off from the surroundings of the rotary transmission joint, i.e. from the interior of the hub, where contaminants, such as bearing grease for the hub bearings, may be present.

[0019] The present rotary seal assembly differs from that in existing rotary transmission joints in that it comprises a seal, e.g. a mechanical seal between the stationary part and the rotary part, by which the fluid transfer channel is sealed in rotation. The rotary seal assembly comprises a stationary seal member that is associated with the axle insert and thus configured to remain substantially stationary with the axle, i.e. at least not rotating along with the hub fitment. Likewise, the rotary seal assembly comprises the rotary seal member that is attached to the hub fitment, so that it will rotate when the vehicle’s wheel attached to the hub is rotated. This yields that a mutual rotation will be present between stationary seal member and the rotary seal member.

[0020] The stationary seal member and the rotary seal member each comprise a through passage, which are arranged substantially in-line, so that they are fluidly interconnected and that they together define the fluid transfer channel between the axle insert and the hub fitment. The stationary seal member and the rotary seal member further each comprise an annular seal plane, which extend around the through passage in an annular manner.

[0021] The annular seal plane may imply that the seal planes may form end surfaces of the stationary seal member and the rotary seal member, which are aligned perpendicular to the hub rotation axis, optionally aligned perpendicular to the axle centreline as well. The seal planes of the stationary seal member and the rotary seal member oppose each other and contact each other, as they are clamped against each other in a direction parallel to the hub rotation axis, in order to obtain the desired sealing between the seal planes. During rotation of the hub fitment relative to the axle insert, the seal plane of the rotary seal member slides over the seal plane of the stationary seal member.

[0022] Alternatively, the term annular may imply that the seal planes encircle the through passage, such that they are aligned tangentially relative to the hub rotation axis and / or axle centreline. In the latter example, the stationary seal member may comprise an outer annular seal plane and the rotary seal member may comprise an inner annular seal plane, whereby the outer annular seal plane and the inner annular seal plane face each other, preferably contacting each other to define a cylindrical sealing interface between them. The cylindrical sealing interface may form a slide bearing between the stationary seal member and the rotary seal member, in order to assist with the alignment between them.

[0023] The elastic element of the rotary seal assembly is arranged in between the axle insert and the stationary seal member and is thus intended to remain substantially stationary with the axle as well. The elastic element thereby serves to hold the stationary seal member in place, while the rotary seal member rotates during use. This means that of the entire rotary transmission joint, only the hub fitment and the rotary seal member rotate, whereas the other components remain stationary. This may allow that no bearings, e.g. roller bearings, may be needed in the present rotary transmission joint, since the hub fitment and the rotary seal member are fixedly attached to the hub and since the other components of the rotary seal assembly are held stationary.

[0024] The elastic element may further be configured to accommodate an angular offset between the seal plane of the stationary seal member and the seal plane of the rotary seal member. Such angular offsets may appear over time and may, for example, occur as a misalignment between the hub rotation axis and the axle centreline. The elastic element may deform elastically to accommodate the misalignment, so that it may remain attached to the axle insert on one end, being aligned with the axle centreline, while the stationary seal member on the other end of the elastic element may remain aligned with the hub rotation axis.

[0025] The elastic element may be pretensioned in between the axle insert and the stationary seal member, so that the elastic element forces the stationary seal member away from the axle insert, for example in a pretension direction parallel to the axle centreline. The pretension may contribute in pressing the seal planes of the stationary seal member and the rotary seal member against each other. As such, the elastic element may have a double function of both holding the stationary seal member stationary relative to the axle insert and of pressing the stationary seal member and the rotary seal member against each other with their seal planes, in order to improve the sealing.

[0026] Finally, the elasticity of the elastic element may provide that it is able to bridge an offset between the axle centreline with which the axle insert is aligned and the hub rotation axis with which the hub fitment is aligned. The elastic element may thereby be configured to hold the stationary seal member at the offset position relative to the axle insert, in order to align the stationary seal member with the rotary seal member and to safeguard the sealing between them.

[0027] In view of the above, the present rotary transmission joint allows for a less complicated design, e.g. due to the absence of bearings, thus offering a reduced manufacturing complexity and reduced costs, whilst still allowing desirable sealing between stationary parts and rotary parts and enabling compensation of offsets between the axle centreline and the hub rotation axis.

[0028] In an embodiment, the stationary seal member and the rotary seal member are aligned coaxially with each other, so that a centreline of the stationary seal member is coaxial with the hub rotation axis. According to this embodiment, the stationary seal member may be offset relative to the axle centreline in order to compensate for the offset between the axle centreline and the hub rotation axis. The stationary seal member may thereby be positioned coaxially with the rotary seal member under influence of the elastic element.

[0029] In an alternative embodiment, the stationary seal member and the rotary seal member may be offset, so that the centreline of the stationary seal member is offset relative to the hub rotation axis. The rotary seal member may thereby not describe a fully rotational movement relative to the stationary seal member, but rather an orbital movement instead.

[0030] To this effect, a width of the annular seal planes of the rotary seal member and the stationary seal member, i.e. a width of the annular rim in a direction radial to the hub rotation axis, may be relatively large compared to the offset between the axle centreline and the hub rotation axis. Additionally or alternatively, the width of the annular seal plane of the stationary seal member may be selected relatively large compared to the width of the annular seal plane of the rotary seal member, or vice versa. As such, it may be achieved that the seal planes of the stationary seal member and the rotary seal member will remain in contact with each other over their entire perimeter, i.e. irrespective of the offset between the axle centreline and the hub rotation axis, in order to maintain the sealing of the fluid transfer channel.

[0031] In an embodiment, the elastic element may be fixedly connected to the stationary seal member, for example being unitary or integral therewith, so that deformations of the elastic element will be directly converted into displacements of the stationary seal member.

[0032] In an embodiment, the rotary seal assembly, for example the rotary seal member comprises a polymeric material, for example comprising PTFE. According to this embodiment, the polymeric material may provide for a desirable balance between a strong wear resistance and a low degree of friction. Polytetrafluoroethylene (PTFE) is an advantageous material to meet these objectives.

[0033] In an embodiment, the rotary seal member comprises a lip seal, for example a spring- loaded lip seal, comprising the inner sealing plane that faces, and that is for example spring- loaded against, the outer sealing plane. The lip seal is thereby provided between the stationary seal member and the rotary seal member, e.g. embodied as annular lip seal in between the opposed annular seal planes of the seal members, to seal of the fluid transfer channel. The lip seal may be able to accommodate the misalignment between the stationary seal member and the rotary seal member in an improved manner, that the sealing of the fluid transfer channel may be improved.

[0034] The lip seal forms the rotary seal member and may surround the stationary seal member, or vice versa, to guide mutual rotations between them. The stationary seal member may thereby be embodied as a cylindrical tube that defines the fluid transfer channel and that is received in the lip seal.

[0035] The lip seal may be spring-loaded in order to be pretensioned against the stationary seal member when forming the rotary seal member or vice versa. The spring-loading may provide for a further improved sealing of the lip seal, e.g. against the cylindrical tube.

[0036] In an embodiment, the elastic element comprises a compression spring. The compression spring may comprise a plurality of annular windings, defining a central passage through which the pressurized fluid may be guided, for example through a fluid duct extending through the central passage of the spring.

[0037] The compression spring may be pretensioned in compression in between the axle insert and the stationary seal member, in order to force the stationary seal member away from the axle insert. The compression spring may further be able to flex in a sideward direction, for example sideward relative to the axle centreline, in order to compensate for the potential offset between the axle centreline and the hub rotation axis.

[0038] In an embodiment, the elastic element comprises an elastic fluid duct, for example an elastic hose, extending between the axle insert and the through passage of the stationary seal member, for example extending through the central passage of the compression spring. The elastic fluid duct is able to deform to follow a possible offset between the axle insert and the stationary seal member, whilst safeguarding a fluid-tight connection between them.

[0039] The elastic fluid duct may comprise an elastic hose, for example made of a rubber, metallic, elastomeric or polymeric material, that extends between a central aperture in the axle insert and the through passage in the stationary seal member. Such an elastic hose may be sufficiently flexible to compensate for the offset between the axle centreline and the hub rotation axis over a relatively long lifespan, i.e. not being prone to fatigue failure.

[0040] For example, the central aperture of the axle insert may be defined by a neck that faces towards the stationary seal member, around which the elastic hose can be disposed. Likewise, the through passage of the stationary seal member may be defined by a similar neck that faces towards the axle insert, around which the elastic hose can be secured to the stationary seal member.

[0041] In a further embodiment, the elastic element further comprises a shielding sleeve, which is arranged radially inside the compression spring and which surrounds the elastic fluid duct to radially confine the elastic fluid duct inside the compression spring.

[0042] The shielding sleeve is located in between the compression spring and the elastic fluid duct and may serve to prevent damaging of the elastic fluid duct under influence of the compression spring, as it may form a barrier in between the spring windings and the fluid duct.

[0043] Equally, the shielding sleeve may form an outer confinement for the elastic fluid duct and may thereby serve, in conjunction with the surrounding windings of the compression spring, to strengthen the elastic fluid duct in withstanding the pressure levels of the pressurized fluid inside it, during use. This may allow the fluid duct itself to be provided relatively thin and flexible, whereas additional strength for the fluid duct is provided by the spring surrounding the shielding sleeve.

[0044] In an embodiment, the elastic element comprises a hollow bellow, for example a bellow with a corrugated outer wall. The bellow may have an interior that is fluidly connected to the through passage in the stationary seal member and the central aperture in the axle insert. Furthermore, the bellow may be dimensioned such, that it is elastically compressed when arranged in between the axle insert and the stationary seal member, so that its elastic compression force applies the pretension force between the axle insert and the stationary seal member.

[0045] As such, the bellow has a combined functionality of sealing the fluid transfer channel and of positioning the stationary seal member against the rotary seal member, e.g. of pretensioning the stationary seal member against the rotary seal member. Especially a bellow with a corrugated outer wall may allow for desirable deformation and pretension properties, whilst still offering adequate sealing over time, i.e. offering desirable fatigue properties.

[0046] The hollow bellow may comprise a metallic material and / or an elastomeric material. A metallic material may, for example, provide for a desirable balance between sufficient stiffness for pretensioning, whilst till being sufficiently deformable.

[0047] In a further embodiment, the elastic element, e.g. the hollow bellow, is integrally connected to the stationary seal member. This integral or unitary connection may provide for a strong and reliable connection, also being sufficiently leak tight. The stationary seal member may thereby be provided as the cylindrical tube that is connected to the hollow bellow end-to- end. The bellow and the tube may be unitary, being made from the same material. The fluid transfer channel may thereby be continuous through the hollow bellow and the cylindrical tube.

[0048] In an embodiment, the axle insert defines an inner chamber, in which the rotary seal assembly is substantially entirely accommodated. The inner chamber protrudes towards the rotary seal assembly in an installed configuration and, for example, also surrounds the neck of the axle insert. The inner chamber may, for example, serve to shield substantially the entire rotary seal assembly, for example from contaminants inside the hub, such as bearing grease or the like.

[0049] Furthermore, the inner chamber may provide that the rotary transmission joint can be pre-assembled to a large extent, prior to inserting the axle insert in the cavity in the axle. For example, the rotary seal assembly can be connected to the axle insert, for example allowing the elastic fluid duct to be connected to the neck of the axle insert. Similarly, the stationary seal member and the rotary seal member can be positioned in the inner chamber to face each other, optionally even with the hub fitment attached to the rotary seal member.

[0050] Finally, the incorporation of the stationary seal member, the rotary seal member and the elastic element inside the inner chamber may provide for an improved stability of the rotary seal assembly. As such, it may no longer be required to provide a bearing for the stationary seal member inside the hub, thus improving robustness and reliability of the rotary transmission joint.

[0051] In a further embodiment, the rotary seal assembly further comprises an annular ring, which is arranged in the inner chamber and which surrounds the stationary seal member and the rotary seal member. The annular ring may serve to shield off an interior of the inner chamber of the axle insert from the surroundings inside the hub. As such, the annular ring may contribute in avoiding entry of contaminants towards the stationary seal member and the rotary seal member.

[0052] The annular ring may serve to confine the stationary seal member, in order to position the stationary seal member at a certain alignment relative the axle centreline or the hub rotation axis. Similarly, the annular ring may also serve such a purpose for the rotary seal member and, optionally, for both the stationary seal member and the rotary seal member in order to hold those aligned with each other.

[0053] The annular ring may be provided relatively rigid, for example made of a metallic material, in case it is desired to accurately define an intended position for the stationary seal member and / or the rotary seal member. However, in case it is desired for the stationary seal member and / or rotary seal member to navigate towards a beneficial mutual sealing position in presence of an offset between the axle centreline and the hub rotation axis, the annular ring may instead be provided relatively weak, in order to allow such offsets for the stationary seal member and the rotary seal member.

[0054] In a further embodiment, the annular ring is clamped in the inner chamber. The annular ring is thereby held in place inside the inner chamber under influence of clamping forces, which may allow for convenient assembly of the rotary transmission joint. Furthermore, such clamping may be desirable in preventing displacements of the annular ring under influence of contacting by the stationary seal member and the rotary seal member.

[0055] In an alternative or additional embodiment, the stationary seal member and / or the rotary seal member abut the annular ring. The stationary seal member and / or the rotary seal member may thereby be tightly surrounded by the annular ring, so that the annular ring may form an annular bearing at least for the rotary seal member and that it may form a sideward confinement against offsets of the stationary seal member, for example offsets relative to the axle centreline. Furthermore, the tight surrounding of the annular ring may be beneficial for the sealing against the stationary seal member and the rotary seal member.

[0056] In an embodiment, the annular ring is made of an elastic material, configured to deform in dependence of the offset between the axle centreline and the hub rotation axis. This may provide the benefit that the annular ring is able to follow displacements of the stationary seal member and the rotary seal member, which may occur over time. With the annular ring being elastic, the tight surrounding of the stationary seal member and the rotary seal member may be maintained even with the offset the stationary seal member and the rotary seal member or between the stationary seal member and the axle insert.

[0057] In an embodiment, the annular ring is made of a porous material and / or configured to hold a lubricant configured to hold a lubricant for lubricating the contact between the seal planes of the seal members. Such lubrication may be desirable for the mechanical seal in the rotary seal assembly, i.e. between the stationary seal member and the rotary seal member, since they slide against each other upon mutual rotation between them.

[0058] The lubrication with lubricant held in the annular ring, for example a viscous oil lubricant, may reduce friction and thus wear between the stationary seal member and the rotary seal member, which may increase the lifespan of the rotary seal assembly. Furthermore, the lubrication may contribute to the airtight sealing between the stationary seal member and the rotary seal member. The optional use of a porous material for the annular ring may be beneficial to absorb fluids, in particular to absorb liquid lubricants.

[0059] It is to be understood, however, that the rotary transmission joint according to the present invention not necessarily needs to rely on lubrication between the stationary seal member and the rotary seal member. For example in applications where relatively low rotational velocities are reached by the wheels, such as for agricultural vehicles, the low speeds may provide that lubrication is not essential.

[0060] In an embodiment, the annular ring comprises a felt material, e.g. a felt material with a lubrication fluid absorbed in it, for example drenched with the lubrication fluid. It was found by the present inventor that such a felt material may have desirable mechanical properties, for example in elasticity and strength, whilst also being porous and therefore suitable to soak fluids.

[0061] As such, an annular ring made of felt material that contains lubrication fluid may be able to meet the required demands for the annular ring in terms of strength and elasticity, whilst also being able to soak a sufficient amount of lubrication fluid to safeguard lubrication between the stationary seal member and the rotary seal member for a sufficiently long period of time, e.g. for the lifespan of the rotary transmission joint.

[0062] In an embodiment, the inner chamber is substantially shielded from the surroundings of the rotary transmission joint, e.g. by the annular ring and / or the rotary seal member. The inner chamber may, for example, serve to shield substantially the entire rotary seal assembly, for example from contaminants inside the hub, such as bearing grease or the like. This may ensure reliable operation of the rotary seal assembly over time, as it minimizes disadvantageous influences of foreign contaminants inside the hub.

[0063] In an embodiment, the rotary seal assembly is substantially free of a bearing between the stationary seal member and the hub fitment and / or free of a bearing between the rotary seal member and the axle insert. This absence of bearings may reduce the number of parts in the rotary transmission joint and thus reduces complexity of the rotary transmission joint, as well as that it may improve reliability over time.

[0064] Compared to existing rotary transmission joints, the present rotary transmission joint can now be provided without ball bearings or without bearings in general, because all stationary parts of the rotary seal assembly, i.e. the stationary seal member and the elastic element, are attached to the axle insert in close proximity thereof. Hence, in various embodiments, the stationary seal member and the rotary seal member are even arranged inside an inner chamber of the axle insert. This placement may allow for an improved stability of the rotary seal assembly. As such, it may no longer be required to provide a bearing for the stationary seal member inside the hub, thus improving robustness and reliability of the rotary transmission joint.

[0065] In an embodiment, the stationary seal member and / or the rotary seal member may comprise an annular seal plane that comprises a ceramic material, a carbon and / or graphite material and / or a hard metallic material or other suitable material. It was found by the present inventor that such materials may provide desirable properties in terms of wear resistance, especially if lubricated from the surrounding annular ring, as well as offering desirable sealing properties.

[0066] In an embodiment, the rotary seal assembly comprises a slide bearing between the stationary seal member and the rotary seal member. Such a slide bearing may be beneficial in accommodating misalignments between the stationary seal member and the rotary seal member, whilst still enabling sufficient leak tightness of the fluid transfer channel.

[0067] According to a second aspect, the present invention provides an axle assembly of a vehicle, comprising: an axle, for example a stationary non-driven axle, comprising a cavity extending along an axle centreline, a rotary hub that is rotatable relative to the axle about a hub rotation axis, and the rotary transmission joint as disclosed herein, wherein the hollow axle insert of the rotary transmission joint is inserted, for example press-fitted or screwed, into the cavity along the axle centreline, and wherein the hub fitment of the rotary transmission joint connected to the hub.

[0068] The axle assembly according to the second aspect of the invention may comprise one or more of the features and / or benefits disclosed herein in relation to the rotary transmission joint according to the first aspect of the invention, for example as recited in the appended claims.

[0069] The present axle assembly comprises the stationary axle and the rotary hub, which are rotatable relative to each other. The rotary hub is configured to rotate about the hub rotation axis, which may coincide with an axle centreline, e.g. with a centreline of the cavity therein, or which may be disposed at an offset relative to the axle centreline.

[0070] The rotary transmission joint is mounted in the cavity of the axle. Such a cavity is generally provided at a head end of such an axle and extends into the axle along the centreline, preferably concentrically with the centreline. The axle may be non-driven. The axle may possess a hollow channel inside, which may extend along the centreline as well. A feed line for the pressurized fluid may be provided in the hollow channel, extending from a source of pressurized fluid towards the rotary transmission joint.

[0071] The axle assembly further comprises the hub, to which a wheel of the vehicle is connected, which is rotatable relative to the axle, in order to allow for rotation of the wheel. The hub may be associated to the axle via conical hub bearings, which are configured to guide the rotations of the hub. The hub bearings may wear over time, during use of the vehicle, which may require re-adjustment of the bearings, which could possibly result in that the alignment between the hub and the axle may vary over time. Initially, for example in a newly built axle assembly, a hub rotation axis may be aligned concentrically with the centreline of the axle.

[0072] The hub fitment of the rotary transmission joint is connected to the hub, for example by means of a threaded connection or a press-fit connection, which implies that the hub fitment rotates along with the hub when the vehicle is driving. Likewise, the hub fitment continues to rotate about the hub rotation axis over time, which could potentially give rise to a rotational offset between the hub fitment and the axle insert. The hub fitment may be connected to further fitments and airlines of the tyre pressure control system, for example towards a wheel valve thereof. As such, the hub fitment receives the flow of pressurized fluid from the axle insert, during use, and further guides the fluid towards the wheel.

[0073] The rotary transmission joint comprises the rotary seal assembly in between the hub fitment and the axle insert, through which the pressurized fluid can be guided between them. The rotary seal assembly forms the transition between the stationary axle insert and the rotary hub fitment, whereby the rotary seal assembly is able to safeguard the transfer of fluid between a stationary part of the rotary seal assembly and a rotary part thereof. Likewise, the rotary seal assembly is able to compensate for possible offsets in between the hub rotation axis and the axle centreline whilst maintaining the fluid connection. To this effect, the rotary seal assembly comprises the fluid transfer channel of which an interior is sealed-off from the surroundings of the rotary transmission joint, i.e. from the interior of the hub, where contaminants, such as bearing grease for the hub bearings, may be present.

[0074] The axle assembly with the present rotary transmission joint allows for a less complicated design, e.g. due to the absence of bearings, thus offering a reduced manufacturing complexity and reduced costs, whilst still allowing desirable sealing between stationary parts and rotary parts and enabling compensation of offsets between the axle centreline and the hub rotation axis.

[0075] In an embodiment, the hollow axle insert of the rotary transmission joint, e.g. the inner chamber thereof, substantially protrudes towards the hub. This means that the hub may be located in close proximity to the axle insert, which may allow the axle insert to define an inner chamber that is substantially shielded from the surroundings of the rotary transmission joint, e.g. by the annular ring and / or the rotary seal member.

[0076] The inner chamber may, for example, serve to shield substantially the entire rotary seal assembly, for example from contaminants inside the hub, such as bearing grease or the like. This may ensure reliable operation of the rotary seal assembly over time, as it minimizes disadvantageous influences of foreign contaminants inside the hub.

[0077] In an embodiment, the axle assembly further comprises a sealing device in between the hub and the axle, for example in between the hub fitment and the axle insert. The sealing device is intended to further contribute in preventing contaminants inside the hub, such as bearing grease or the like, from reaching the rotary transmission joint, in particular from entering the rotary seal assembly.

[0078] In an embodiment, the axle assembly further comprises venting device in the hub fitment and / or in the hub, which is configured to vent pressurized air out of an interior of the hub in case of leakage of the fluid transfer channel, in order to prevent undesired removal of bearing grease through the hub bearings. The venting device may be provided as a one-way check valve, configured to open in case a pressure level inside the hub interior is larger than a pressure level outside the hub.

[0079] According to a third aspect, the present invention provides a method of assembling an axle assembly of a vehicle, comprising the steps of: providing the rotary transmission joint as disclosed herein, inserting, for example press-fitting or screwing, the rotary seal assembly with the hollow axle insert thereof along an axle centreline into a cavity in an axle, attaching a rotary hub to the axle, which is rotatable relative to the axle about a hub rotation axis, and connecting the hub fitment to the hub.

[0080] The method according to the third aspect of the invention may comprise one or more of the features and / or benefits disclosed herein in relation to the rotary transmission joint according to the first aspect of the invention and / or in relation to the axle assembly according to the second aspect of the invention, for example as recited in the appended claims.

[0081] The method according to the present invention allows the rotary transmission joint to be at least partly included in the axle assembly during initial manufacturing thereof. As such, it may no longer be necessary to disassemble an original axle assembly when a rotary transmission joint needs to be retrofitted inside it. This may allow for reduce assembling costs and reduced complexity, compared to existing ways of installing rotary transmission joint in existing axle assemblies.

[0082] According to the present method, the axle assembly can furthermore be pre-assembled to a large extent, prior to inserting the axle insert in the cavity in the axle. For example, the rotary seal assembly can be connected to the axle insert, for example allowing the elastic fluid duct to be connected to the neck of the axle insert. Similarly, the stationary seal member and the rotary seal member can be positioned in the inner chamber to face each other, optionally even with the hub fitment attached to the rotary seal member.

[0083] According to a fourth aspect, the present invention provides a rotary transmission joint for a tyre pressure control system for guiding a flow of pressurized fluid between an axle, for example a stationary non-driven axle of a vehicle and a rotary hub of the vehicle, the rotary transmission joint comprising: a hollow axle insert, configured to be connected to the axle, for example inserted, in particular press-fitted or screwed, along an axle centreline into a cavity in the axle and configured to receive a flow of fluid from a source of pressurized fluid, a hub fitment, which is configured to be connected to the hub, to be rotated along with the hub relative to the axle insert about a hub rotation axis and to supply the flow of fluid, obtained from the axle insert, towards a wheel of the vehicle, and a rotary seal assembly, which is functionally arranged in between the axle insert and the hub fitment to define a fluid transfer channel for sealingly guiding the flow of fluid between the axle insert and the hub fitment whilst enabling mutual rotation between them, characterized in that the rotary transmission joint further comprises a wheel valve for the tyre pressure control system that is associated with the hub fitment and that is configured to be associated with a rim of a vehicle wheel and for inflating or deflating a tyre mounted on the rim by means of a pressurized fluid, the valve comprising: a valve housing, comprising: a fluid inlet that is connected to the fluid transfer channel, and an inflation opening, which is configured to be fluidly connected to an interior of the tyre mounted on the rim, a deflation piston arranged in the valve housing, which comprises a deflation piston surface and which defines an inflation passage extending between the fluid inlet and the inflation opening, a first pretension device configured to exert a first pretension force onto the deflation piston relative to the valve housing, in order to bias the deflation piston towards the fluid inlet into a closed position, an inflation piston arranged in the inflation passage, which comprises an inflation piston surface, a second pretension device configured to exert a second pretension force onto the inflation piston relative to the deflation piston, in order to bias the inflation piston towards the fluid inlet into a closed position against an inflation seat provided on the deflation piston, an deflation opening, which is configured to be fluidly connected to the interior of the tyre and which is separate and located at a distance from the inflation opening, an exhaust port, which projects into the ambient for discharging fluid out of the tyre to deflate the tyre, and a deflation passage, which extends between the deflation opening and the exhaust port and which is separate from the inflation passage, and wherein the deflation piston, in its closed position, closes the deflation passage between the deflation opening and the exhaust port.

[0084] The rotary transmission joint according to the fourth aspect of the invention may comprise one or more of the features and / or benefits disclosed herein in relation to the rotary transmission joint according to the first aspect of the invention and / or in relation to the axle assembly according to the second aspect of the invention, for example as recited in the appended claims.

[0085] The present rotary transmission joint comprises the wheel valve, with which a tyre can be selectively inflated or deflated. The wheel valve thereto comprises two passages through which the fluid can be guided. An inflation passage is used to guide pressurized fluid from the fluid inlet to the wheel inflation opening, thereby allowing inflation of the tyre by increasing the pressure level in the interior of the tyre. A separate deflation passage extends between the deflation opening, which is provided separate from the inflation opening, and the exhaust port. The deflation passage is used to guide fluid out of the interior of the tyre during deflation thereof. This allows the tyre to be deflated through a separate passage and will prevent that possible contaminations can accumulate in the inflation passage during deflation, thus avoiding the risk of blockage of the inflation passage and the inflation piston arranged therein.

[0086] According to the present aspect of the invention, the wheel valve is connected directly to the hub fitment, so that the fluid inlet is in fluid communication with the fluid transfer channel and the source of pressurized fluid located upstream of the rotary transmission joint. The wheel valve is thereby configured to receive pressurized fluid from the source of pressurized fluid. The wheel valve may further be free of other fluid inlets.

[0087] The valve comprises the valve housing, which is attached to the hub fitment, for example being fastened therein by means of a threaded connection. The valve housing may be a single one-piece housing, but may also be assembled of multiple pieces that together form the valve housing. The inflation opening in the valve housing is intended to be in fluid communication with the interior of the tyre, for example through a dedicated wheel fluid line.

[0088] The valve housing may comprise a hollow interior in between the fluid inlet and the inflation opening, in which interior the deflation piston can be arranged. The deflation piston is thereby provided in between the fluid inlet and the inflation opening, in order to close off a passage, e.g. the inflation passage, between the fluid inlet and the inflation opening. According to the present invention, this passage is closed off irrespective of the position of the deflation piston, since the deflation piston is only configured to be operated for deflation of the tyre, which is carried out through the deflation passage and for which the inflation passage has no role.

[0089] The deflation piston comprises the deflation piston surface, which faces towards the fluid inlet. The pressurized fluid supplied into the valve at the fluid inlet thus acts against the piston surface of the deflation piston. The pressure level of the pressurized fluid at the piston surface of the deflation piston may thereby determine the position or state in which the deflation piston is arranged. The deflation piston is arranged in the valve housing and is thus configured to move in relation to the valve housing when moving between its closed position and an opened position.

[0090] The first pretension device is provided, for example embodied as a first compression spring, to move the deflation piston in its closed position. The first pretension device is aligned to act on the deflation piston in a direction towards the fluid inlet, so that the deflation piston is moved towards the fluid inlet under influence of the biasing first pretension force from the first pretension device. The net force acting on the deflation piston may thus be formed by the pressurized fluid acting on the piston surface of the deflation piston on the one hand and the first pretension force by the first pretension device on the other hand. Additionally, a further contribution may be provided by a pressure level of the fluid in the interior of the tyre acting on the deflation piston, i.e. on a counter surface opposite to the piston surface thereof, thus acting alongside the first pretension device towards the fluid inlet.

[0091] The deflation piston comprises the inflation passage through which the pressurized fluid is passed upon inflation of the tyre. The inflation passage extends through the deflation piston, for example along a centreline of the deflation piston. As such, the inflation passage does form a channel for the fluid between the fluid inlet and the inflation opening, irrespective of the position of the deflation piston.

[0092] The inflation passage, in turn, can be selectively closed off by means of the inflation piston that is provided in the inflation passage. The inflation piston comprises, in a manner similar to the deflation piston, a piston surface that faces towards the fluid inlet. Any pressurized fluid at the fluid inlet, during use of the valve, thus acts against the piston surface of the inflation piston. This inflation piston is arranged in the deflation piston and is thus configured to move in relation to the deflation piston when moving between its closed position and an opened position.

[0093] The valve comprises a second pretension device, which acts against the inflation piston to bias the inflation piston towards the fluid inlet under influence of the second pretension force. The second pretension device may be a second compression spring, which is functionally arranged in between the inflation piston and the deflation piston, so that the second compression spring is configured to move the inflation piston in relation to the deflation piston. Any movement of the deflation piston relative to the housing may therefore not have any influence on the position of the inflation piston inside the deflation piston.

[0094] The deflation piston comprises the inflation seat inside the inflation passage, against which the inflation piston is pushed under influence of the second pretension device when the inflation piston is biased in the closed position. In this closed position, the inflation passage is closed off, thereby preventing passage of pressurized fluid from the fluid inlet towards the wheel inflation opening, and vice versa.

[0095] The second pretension device is aligned to act on the inflation piston in a direction towards the fluid inlet, so that the inflation piston is moved towards the fluid inlet under influence of the biasing second pretension force from the second pretension device. The net force acting on the inflation piston may thus be formed by the pressurized fluid acting on the piston surface of the inflation piston on the one hand and the second pretension force by the second pretension device on the other hand. Additionally, a further contribution may be provided by a pressure level of the fluid in the interior of the tyre acting on the inflation piston, i.e. on a counter surface opposite to the piston surface thereof, thus acting alongside the second pretension device towards the fluid inlet.

[0096] The working principle of the present valve is contributed by the mutual relationship between the piston surfaces of the deflation piston and of the inflation piston, as well as between the first pretension device and the second pretension device, in particular the pretension forces exerted therewith. These may be selected such that both the deflation piston and the inflation piston may be arranged in their closed positions when the pressure level at the fluid inlet is below an inflation pressure level. The inflation piston may be moved out of its closed position when the pressure level at the fluid inlet is above the inflation pressure level, but below a deflation pressure level, in order to allow fluid to pass from the fluid inlet towards the wheel inflation opening. Finally, the deflation piston may be moved out of its closed position when the pressure level at the fluid inlet is above the deflation pressure level, so that the tyre can be deflated through the deflation passage.

[0097] To this effect, the surface area of the inflation piston surface may be smaller than the surface area of the deflation piston surface. This may provide that a resulting force acting on the inflation piston, for a certain pressure level at the fluid inlet, may be smaller than a resulting force acting on the deflation piston.

[0098] In the closed position of the inflation piston and in the closed position of the deflation piston, the pressure level in the tyre, i.e. the tyre pressure, may also be present in the inflation passage, opposite to the piston surface that faces the fluid inlet. As such, the tyre pressure may contribute, together with the second pretension device, to bias the inflation piston in the closed position.

[0099] Likewise, the second pretension force may be selected smaller than the first pretension force, for example by embodying the first pretension device as a stronger compression spring compared to the second pretension device. This may enable that the first pretension force is overcome later than the second pretension force, so that the inflation piston is moved out of its closed position at a fluid inlet pressure level lower than the fluid inlet pressure level at which the deflation piston is moved out of its closed position.

[0100] The present valve further comprises the deflation passage, which is provided separate from the inflation passage. This allows the deflation of the tyre to be carried out through a passage different from the passage through which inflation takes place. The deflation passage extends between the deflation opening and the exhaust port. With the deflation passage separate from the inflation passage, it may be provided that deflation will not influence the inflation passage, for example preventing that possible contaminations inside the tyre will end up in the inflation passage during deflation of the tyre

[0101] The exhaust port is configured to discharge fluids out of the tyre into the ambient of the wheel during deflation. This allows the deflated fluid to bypass the inflation passage. As such, the exhaust port may be provided remote from the fluid inlet as well. For example, the fluid inlet may be provided as a single opening at a head end of the valve housing that projects outside the tyre. The exhaust port may be formed by a plurality of exhaust ports that are located around the circumference of the portion of the valve housing projecting outside the tyre.

[0102] The deflation passage may be defined in between the valve housing and the deflation piston, so that the fluid deflated from the tyre during deflation can be guided around the outside of the deflation piston. The deflation piston thereby forms the separation between the inflation passage and the deflation passage. The deflation passage may be formed by one or more passages around the outer surface of the deflation piston, for example a number of deflation passages corresponding to the number of wheel deflation openings and / or the number of exhaust ports. The multiple deflation passages may be spaced around an outer perimeter of the deflation piston.

[0103] In the closed position, the deflation piston closes the deflation passage between the deflation opening and the exhaust port. As such, it can be prevented that the tyre is deflated, both when the inflation piston is closed, i.e. to maintain a pressure level in the tyre, and when the inflation piston is moved out of its closed position, i.e. during inflation of the tyre. The movement of the deflation piston will thus influence the deflation passage that surrounds the deflation piston, in order to allow or prevent pressurized fluid from passing through the deflation passage, i.e. in between the deflation piston and the valve housing.

[0104] According to this aspect of the invention, the valve housing will typically be mounted remotely from the interior of the tyre. As such, the wheel valve may further comprise a wheel fluid line, extending from the inflation opening and the deflation opening towards the interior of the tyre. As such, the wheel valve may be located closer to the centre of the wheels, only requiring the wheel fluid line to extend towards the rim and the tyre. The wheel fluid line may be conveniently connected to the rim in a manner similar to conventional tyre valves.

[0105] With this rotary transmission joint having the wheel valve, existing vehicle wheels can be easily retrofitted with a tyre pressure control system, e.g. by simply replacing a conventional tyre valve with the current wheel fluid line, therefore not requiring complicated modifications to the wheels. Furthermore, with the wheel valve being located closer to the axis of rotation of the wheel and remote of the rim, the eccentricity of the wheel may be reduced, so that its degree of imbalance can be reduced. Furthermore, it may provide that the wheel valve is positioned at a location where it is less prone to damaging, i.e. away from the tyre.

[0106] In an embodiment, the valve housing further comprises a cap member, which is connected to the wheel fluid line and which comprises a cap interior that faces the inflation opening and the deflation opening, in order to fluidly connect the inflation opening and the deflation opening with the wheel fluid line. The cap interior is therefore subjected to the same pressure level as the interior of the tyre, i.e. as a result of the fluid communication through the wheel fluid line, so that the valve, despite the valve housing being located away from the interior of the tyre, may still operate in a manner similar to when the inflation opening and the deflation opening directly project into the interior of the tyre. The cap member may thereby serve to surround all of the deflation openings, e.g. around the perimeter of the valve housing, so that a large number of smaller deflation openings may be provided around a single inflation opening. As such, this embodiment of the wheel valve may also allow a number of exhaust ports spread around the perimeter of the valve housing.

[0107] In a further embodiment, for example in a wheel valve comprising multiple of the deflation openings and / or exhaust ports, spread over a perimeter of the valve housing, the cap member is an annular cap member, which surrounds all of the deflation openings. The annular shape may allow the wheel fluid line to be located at one side of the annular cap member, wherein the annular cap member serves to assure a substantially constant pressure level at all of the deflation openings.

[0108] The annular cap member may, for example, be attached to the other parts of the valve housing by means of a threaded connection. The annular cap member may include the flexible closure element, embodied as an annular elastic ring, located in a fluid path between the inflation opening and the wheel fluid line, in order to allow pressurized fluid to flow from the inflation opening towards the wheel fluid line and to inhibit a return flow of fluid from the wheel fluid line back into the inflation opening.

[0109] In an embodiment, e.g. in a wheel valve comprising an inflation passage closure, the cap member comprises the inflation passage closure. This may allow cap member and the inflation passage closure to be mounted to the rest of the valve housing as a unitary component, thereby improving the manufacturability of the wheel valve.

[0110] In an alternative or additional embodiment, the cap member forms a seat for the first pretension device, so that the deflation piston is pretensioned by the first pretension device against the cap member. The first pretension device may thereby be provided around the inflation passage closure to secure a sideward position of the first pretension device vis-a-vis the cap member.

[0111] Brief description of drawings

[0112] Further characteristics of the invention will be explained below, with reference to embodiments, which are displayed in the appended drawings, in which:

[0113] Figure 1 schematically depicts an embodiment of an axle assembly according to the present invention,

[0114] Figure 2 shows a magnification of figure 1,

[0115] Figure 3 shows the rotary transmission joint of the axle assembly in figure 1 in isolation,

[0116] Figure 4 shows an alternative embodiment of the axle assembly according to the present invention,

[0117] Figure 5 shows an embodiment of the rotary transmission joint according to the present invention including a wheel valve, and

[0118] Figure 6 shows another embodiment of the rotary transmission joint with wheel valve.

[0119] Throughout the figures, the same reference numerals are used to refer to corresponding components or to components that have a corresponding function.

[0120] Detailed description of embodiments Figure 1 schematically depicts an embodiment of an axle assembly according to the present invention, to which is referred with reference numeral 100. The axle assembly 100 comprises an axle 110, which is a stationary non-driven axle in the present example, but which may alternatively be driven and which may then comprise a hollow channel for guiding pressurized fluid. The axle 110 comprises a cavity 111 extending along an axle centreline C.

[0121] The axle assembly 100 further comprises a rotary hub that is rotatable relative to the axle 110 about a hub rotation axis H. In the figures, a hub cap 120 of the hub is displayed. For the sake of clarity, reference numeral 120 is used in the figures to refer to the rotary hub in general. The hub 120 is connected to the axle 110 via conical hub bearings 130, which are configured to guide the rotations of the hub 120. The hub bearings 130 may wear over time, which may require re-adjustment of the bearings 130. This means that the alignment between the hub 120 and the axle 110 may vary over time. Initially, for example in a newly built axle assembly 100 as it is shown in figure 1 , the hub rotation axis H is aligned concentrically with the axle centreline C, whereas over time, an offset may occur between the hub rotation axis H and the axle centreline C.

[0122] The axle assembly 100 further comprises the rotary transmission joint according to the present invention, to which is referred to with reference numeral 1 in the figures. Further details of the rotary transmission joint 1 are discussed in the following with reference to figures 2 and 3.

[0123] The rotary transmission joint 1 is adapted for mounting in axle cavity 111 and is connected to a feed line 101 for pressurized fluid channel, extending from a source of pressurized fluid towards the rotary transmission joint 1. The rotary transmission joint 1 forms a substantially fluid tight transfer for the flow of pressurized fluid from the stationary axle 110 towards the rotary hub 120. To this effect, the rotary transmission joint 1 comprises the axle insert 10 that is configured to be connected to the axle 110 to remain stationary therewith. The axle insert 10 is inserted, in particular press-fitted, into the cavity 111 along the axle centreline C.

[0124] The rotary transmission joint 1 further comprises the hub fitment 20, which is connected to the hub 120 by means of a threaded connection via a plurality of bolts 121. As such, the hub fitment 20 rotates along with the hub 120 when the vehicle is driving. Likewise, the hub fitment 20 continues to rotate about the hub rotation axis H over time, which could potentially give rise to a rotational offset between the hub fitment 20 and the axle insert 10.

[0125] The rotary transmission joint 1 comprises a rotary seal assembly 30 in between the hub fitment 20 and the axle insert 10, through which the pressurized fluid can be guided between them. The rotary seal assembly 30 forms the transition between the stationary axle insert 10 and the rotary hub fitment 20, whereby the rotary seal assembly 30 is able to safeguard the transfer of fluid between a stationary part of the rotary seal assembly 30 and a rotary part thereof. Likewise, the rotary seal assembly 30 is able to compensate for possible offsets in between the hub rotation axis H and the axle centreline C whilst maintaining the fluid connection. To this effect, the rotary seal assembly 30 comprises the fluid transfer channel 50 of which an interior is sealed-off from the surroundings of the rotary transmission joint 1, i.e. from the interior of the hub 120, where contaminants, such as bearing grease for the hub bearings 130, may be present.

[0126] It is shown on the left in figure 1 that the hub fitment 20 is connected to a further fitment 21 of the tyre pressure control system, which extends towards a wheel valve. As such, the hub fitment 20 receives the flow of pressurized fluid from the axle insert 10, during use, and further guides the fluid towards the wheel.

[0127] The hollow axle insert 10 of the rotary transmission joint 1 substantially protrudes towards the hub 120. This means that the hub 120 is located in close proximity to the axle insert 10, which allows the axle insert 10 to define an inner chamber 11 that is substantially shielded from the surroundings of the rotary transmission joint 1.

[0128] Furthermore, the axle assembly 100 comprises a sealing device 140 in between the hub 120 and the axle 110. Alternatively, such a sealing device may be arranged in between the hub and the axle insert and / or between the hub fitment and the axle and / or between the hub fitment and the axle insert. In the present embodiment, the sealing device 140 comprises an annular lip seal, which extends around an outer perimeter of the hub fitment 20, towards the axle 110. The sealing device 140 contributes in preventing contaminants inside the hub 120, such as bearing grease or the like, from reaching the rotary transmission joint 1 , in particular from reaching the rotary seal assembly 30.

[0129] The axle assembly 100 further comprises venting device 150, which is arranged in the hub fitment 20 and which projects through the hub 120. The venting device 150 is provided as may be provided as a one-way check valve, being configured to vent pressurized air out of an interior of the hub 120 in case of leakage of the fluid transfer channel 50, in order to prevent undesired removal of bearing grease through the hub bearings 130. The venting device 150 is configured to open in case a pressure level inside the interior of the hub 120 is higher than a pressure level outside the hub 120.

[0130] The present rotary seal assembly 30 differs from that in existing rotary transmission joints in that it comprises a mechanical seal between the stationary part and the rotary part, by which the fluid transfer channel 50 is sealed in rotation. The rotary seal assembly 30 comprises a stationary seal member 31 that is associated with the axle insert 10 and thus configured to remain substantially stationary with the axle 110, i.e. at least not rotating along with the hub fitment 20. Likewise, the rotary seal assembly 30 comprises the rotary seal member 32 that is attached to the hub fitment 20, so that it will rotate when the hub 120 is rotated. This yields that a mutual rotation will be present between stationary seal member 31 and the rotary seal member 32.

[0131] The stationary seal member 31 comprises a stationary through passage 33 and the rotary seal member 32 comprises a rotary through passage 34, which are arranged substantially in-line, so that they are fluidly interconnected and that they together define the fluid transfer channel 50 between the axle insert 10 and the hub fitment 20.

[0132] In the configuration shown in the figures, the stationary seal member 31 and the rotary seal member 32 are aligned coaxially with each other, so that a centreline of the stationary seal member 31 is coaxial with the hub rotation axis H. The stationary seal member 31 may end up being offset relative to the axle centreline C over time, in order to compensate for the offset between the axle centreline C and the hub rotation axis H.

[0133] The stationary seal member 31 and the rotary seal member 32 are provided with an interlocking annular ridge and annular grooves, surrounding the respective through passages 33, 34, which interlocking provides for the concentric alignment between the stationary seal member 31 and the rotary seal member 32.

[0134] Alternatively, in an embodiment not shown in the figures, the stationary seal member and the rotary seal member may be offset with each other, so that the centreline of the stationary seal member is offset relative to the hub rotation axis H. The rotary seal member may thereby not describe a fully rotational movement relative to the stationary seal member, but rather an orbital movement instead.

[0135] The stationary seal member 31 further comprises a stationary annular seal plane 35 and the rotary seal member 32 further comprises a rotary annular seal plane 36, which extend around the through passages 33, 34 in an annular manner. The seal planes 35, 36 form end surfaces of the stationary seal member 31 and the rotary seal member 32 and are aligned perpendicular to the hub rotation axis H. The seal planes 35, 36 oppose each other and contact each other, as they are clamped against each other in a direction parallel to the hub rotation axis H, in order to obtain the desired sealing between the seal planes 35, 36. During rotation of the hub fitment 20 relative to the axle insert 10, the seal plane 36 of the rotary seal member 32 slides over the seal plane 35 of the stationary seal member 31. The annular seal planes 35, 36 comprise a ceramic material, which was found to provide desirable properties in terms of wear resistance, as well as offering desirable sealing properties. Alternatively, the seal planes may comprise a carbon and / or graphite material and / or a hard metallic material or other suitable materials.

[0136] It is best shown in figure 3 that a width of the annular seal plane 36 of the rotary seal member 32 is relatively large compared to the width of the annular seal plane 35 of the stationary seal member 31. As such, it is achieved that the seal planes 35, 36 of the stationary seal member 31 and the rotary seal member 32 will remain in contact with each other over their entire perimeter, i.e. irrespective of the offset between the axle centreline C and the hub rotation axis H, in order to maintain the sealing of the fluid transfer channel 50.

[0137] The rotary seal assembly 30 comprises an elastic element that is arranged in between the axle insert 10 and the stationary seal member 31, which is thus intended to remain substantially stationary with the axle 110. The elastic element comprises a compression spring 40 that is composed of a plurality of spring windings. The compression spring 40 is pretensioned in compression in between the axle insert 10 and the stationary seal member 31, in order to force the stationary seal member 31 away from the axle insert 10. As such, the compression spring 40 serves to hold the stationary seal member 31 in place, while the rotary seal member 32 rotates during use. The pretension contributes in pressing the seal planes 35, 36 of the stationary seal member 31 and the rotary seal member 32 against each other. The elasticity of the compression spring 40 further provides that it is able to bridge an offset between the axle centreline C with which the axle insert 10 is aligned and the hub rotation axis H with which the hub fitment 20 is aligned.

[0138] The compression spring 40 defines a central passage with an elastic fluid duct 41 arranged therein, through which the pressurized fluid may be guided. The fluid duct 41 extends between the axle insert 10 and the through passage 33 of the stationary seal member 31 and is able to deform to follow a possible offset between the axle insert 10 and the stationary seal member 31, whilst safeguarding a fluid-tight connection between them. The elastic fluid duct 41 is made of a metallic, elastomeric or polymeric material and is, as such, sufficiently flexible to compensate for the offset between the axle centreline C and the hub rotation axis H. The fluid duct 41 extends around a neck 12 of the axle insert 10 that faces towards the stationary seal member 31. Likewise, the stationary seal member 31 comprises a similar neck 37 that faces towards the axle insert 10, around which the fluid duct 41 is secured at the other side.

[0139] A shielding sleeve 42 is provided at the axle insert 10 and the stationary seal member 31, which is arranged radially inside the compression spring 40 and which surrounds the fluid duct 41 to radially confine the elastic fluid duct 41 inside the compression spring 40. The shielding sleeve 42 serves to prevent damaging of the elastic fluid duct 41 under influence of the compression spring 40, as it forms a barrier in between the spring windings and the fluid duct 40.

[0140] The rotary seal assembly 30 is substantially entirely accommodated in the inner chamber 11. The inner chamber 11 surrounds the rotary seal assembly 30 in the installed configuration shown in the figures and also surrounds the neck 12 of the axle insert 10. The inner chamber 11 further provides that the rotary transmission joint 1 can be pre-assembled to a large extent, prior to inserting the axle insert 10 in the cavity 111 in the axle 110. Hence, the rotary seal assembly 30 is connected to the axle insert 10, allowing the elastic fluid duct 41 to be connected to the neck 12 of the axle insert 10. Similarly, the stationary seal member 31 and the rotary seal member 32 can be positioned in the inner chamber 11 to face each other with the hub fitment 20 attached to the rotary seal member 32.

[0141] The rotary seal assembly 30 is substantially free of a bearing between the stationary seal member 31 and the hub fitment 20 and free of a bearing between the rotary seal member 32 and the axle insert 10. This absence of bearings is now possible, because all stationary parts of the rotary seal assembly 30, i.e. the stationary seal member 31 and the compression spring 40, are attached to the axle insert 10 in close proximity thereof. Hence, the stationary seal member 31 and the rotary seal member 32 are even arranged inside the inner chamber 11. This placement allows for an improved stability of the rotary seal assembly 30.

[0142] The rotary seal assembly 30 further comprises an annular ring 38, which is arranged in the inner chamber 11 and which surrounds the stationary seal member 31 and the rotary seal member 32. The annular ring 38 serves to shield off the interior of the inner chamber 11 of the axle insert 10 from the surroundings inside the hub 120. As such, the annular ring 38 contributes in avoiding entry of contaminants, such as bearing grease or the like, towards the stationary seal member 31 and the rotary seal member 32.

[0143] The annular ring 38 is clamped in the inner chamber 11 and serves to confine the stationary seal member 31 and the rotary seal member 32 and may serve to hold those aligned with each other. The stationary seal member 31 and the rotary seal member 32 abut the annular ring 38. The annular ring 38 is thereby made of an elastic and relatively weak and porous material, in order to allow for rotational offsets between the stationary seal member 31 and the rotary seal member 32.

[0144] In the present embodiment, the annular ring 38 is made of a felt material, which is configured to easily deform in dependence of the offset between the axle centreline C and the hub rotation axis H. The felt annular ring 38 further holds a liquid lubricant absorbed in the felt material for lubricating the contact between the seal planes 35, 36 of the seal members 31 , 32. The lubricant is a viscous oil lubricant, which may reduce friction and thus wear between the stationary seal member 31 and the rotary seal member 32, which may increase the lifespan of the rotary seal assembly 30 and which may contribute to the airtight sealing between the stationary seal member 31 and the rotary seal member 32.

[0145] Figure 4 depicts an alternative embodiment of the axle assembly 100, of which the rotary transmission joint is similar as in figures 1 - 3. The axle assembly 100 in figure 4 comprises a hollow bellow 43 with a corrugated outer wall made of a metallic material, which is provided instead of the compression spring, elastic fluid duct and shielding sleeve in the embodiment of figures 1 - 3. The hollow bellow 43 may be elastically compressed when arranged in between the axle insert 10 and the stationary seal member 31 , so that its elastic compression force applies the pretension force between the axle insert 10 and the stationary seal member 31. As such, the bellow 43 may has a combined functionality of sealing the fluid transfer channel 50 and of positioning the stationary seal member 31 inside the rotary seal member 32, in particular for accommodating misalignments between the axle centreline C and the hub rotation axis H during rotation of the hub 20.

[0146] As a further difference compared to figures 1 - 3, the axle assembly 100 in figure 4 comprises seal members that are made of a polymeric material, e.g. polytetrafluoroethylene (PTFE). The rotary seal member comprises a spring-loaded lip seal 32, having an inner annular seal plane that bears against the stationary seal member that comprises a cylindrical tube 31. The cylindrical tube 31 protrudes through the lip seal 32 so that the lip seal 32 seals against an outer annular seal plane of the cylindrical tube 31.

[0147] Figure 5 shows an embodiment of the rotary transmission joint 1 that comprises the wheel valve, to which is referred with reference numeral 201. The wheel valve 201 is mounted to remotely from the tyres, being provided at a hub 200 to which the rim is attached. In the current example, the wheel valve 201 is provided adjacent to the rotary transmission joint inside the hub 200.

[0148] The wheel valve 201 in figure 5 is displayed in its holding state and comprises a valve housing 210 with a fluid inlet 211 and inflation opening 212. The valve 201 also comprises the deflation piston 220 and inflation piston 230 inside it. The wheel valve 201 comprises a number of exhaust ports 216 around the perimeter of the valve housing 210, which are closed-off from the surroundings by flexible closure elements 219, as well as a filter element 226 covering the deflation openings 215.

[0149] The valve housing 210 comprises an annular cap member 240, which surrounds the filter element 226 and all of the deflation openings 215, which are spread around the perimeter of the valve housing 210. The cap member 240 defines a cap member interior 241 , inside which the inflation passage closure, e.g. the flexible closure element 214 is provided. The valve 201 further comprises a wheel fluid line 242, of which a fitment 243 it attached to the cap member 240. The wheel fluid line 242 thereby serves to connect the cap member interior 241, and therefore the inflation openings 212 and deflation openings 215 with the tyre.

[0150] The cap member 240 comprises the inflation passage closure 213, embodied as a unitary component. The cap member 240 thereby forms a seat for the first pretension device, e.g. the first compression spring 223, so that the deflation is pretensioned by the first compression spring 223 against the cap member 240, whereby the first compression spring 223 is provided around the inflation passage closure 213 to secure a sideward position of the first compression spring 223 vis-a-vis the cap member 240.

[0151] Figure 6 shows another embodiment of the rotary transmission joint 201 with wheel valve, that is similar to the one shown in figure 5. However, both embodiments differ in that the wheel valve in figure 6 comprises the combined inflation opening and deflation opening, embodied as a common opening 212A that is fluidly connectable to the inflation passage 222, the deflation passage 217 and the interior of the tyre via the wheel fluid line 242. In this situation, a set of common openings 212A is provided in the valve housing 210, which are surrounded by the filter element 226. As such, the inflating and deflating will be performed through the common opening 212A, whereby internally in the valve housing 210, the inflation passage 222 and deflation passage 217 are provided separate from each other.

[0152] During deflation, the inflation passage 222 remains closed, so that pressurized fluid can only travel out of interior of the tyre and from the wheel fluid line 242, through the common opening 212A and into the deflation channel 217.

[0153] The wheel valve 2011 further comprises a deflation piston guide, e.g. located adjacent the inflation passage closure, which is embodied as a number of deflation piston guiding pins 229 around the perimeter of the deflation piston 220 between which apertures are defined and which jointly guide the deflation piston 220. The deflation piston guiding pins 229 are located around the perimeter of the deflation piston 220, in order to prevent the deflation piston 220 from moving sideward, in order to stabilize the position of the deflation piston 220. The apertures in between the deflation piston guiding pins 229 serve to guide a fluid flow out of the inflation passage 222 towards the inflation openings, e.g. common openings 212A when the deflation piston 220 is moved out of its closed position.

Claims

CLAIMS1. Rotary transmission joint for a tyre pressure control system for guiding a flow of pressurized fluid between an axle of a vehicle and a rotary hub of the vehicle, the rotary transmission joint comprising: a hollow axle insert, configured to be connected to the axle, for example inserted, in particular press-fitted or screwed, along an axle centreline into a cavity in the axle, and configured to receive a flow of fluid from a source of pressurized fluid, a hub fitment, which is configured to be connected to the hub, to be rotated along with the hub relative to the axle insert about a hub rotation axis and to supply the flow of fluid, obtained from the axle insert, towards a wheel of the vehicle, and a rotary seal assembly, which is functionally arranged in between the axle insert and the hub fitment to define a fluid transfer channel for sealingly guiding the flow of fluid between the axle insert and the hub fitment whilst enabling mutual rotation between them, characterized in that, the rotary seal assembly comprises a stationary seal member attached to the axle insert to remain substantially stationary, and a rotary seal member attached to the hub fitment to be rotated therewith relative to the stationary seal member, wherein the seal members each comprise a through passage, which together define the fluid transfer channel, and an annular seal plane surrounding the respective through passage, wherein the seal planes contact each other to seal-off the fluid transfer channel and slide against each other upon mutual rotation between them, and wherein the rotary seal assembly further comprises an elastic element, which is functionally arranged in between the axle insert and the stationary seal member, in order to: hold the stationary seal member substantially stationary relative to the axle insert, and / or accommodate an angular offset between the seal plane of the stationary seal member and the seal plane of the rotary seal member.

2. Rotary transmission joint according to claim 1, wherein the seal plane of the stationary sealing member is an outer annular seal plane, wherein the seal plane of the rotary sealing member is an inner annular seal plane, and wherein the outer seal plane and inner seal place are concentric to each other and are aligned tangentially relative to the hub rotation axis.

3. Rotary transmission joint according to any of the preceding claims, wherein the rotary seal assembly, for example the rotary seal member comprises a polymeric material, for example comprising PTFE.

4. Rotary transmission joint according to any of the preceding claims, wherein the rotary seal member comprises a lip seal, for example a spring-loaded lip seal, comprising the inner sealing plane that faces, and that is for example spring-loaded against, the outer sealing plane.

5. Rotary transmission joint according to claim 1, wherein the seal planes are annular seal planes that are aligned perpendicular to the hub rotation axis at opposed head ends of the seal members.

6. Rotary transmission joint according to claim 5, wherein the elastic element is functionally arranged to: press the stationary seal member and the rotary seal member against each other with their seal planes along the hub rotation axis, and / or align the seal members to compensate for an offset between the axle centreline and the hub rotation axis.

7. Rotary transmission joint according to any of the preceding claims, wherein the elastic element comprises a compression spring.

8. Rotary transmission joint according to any of the preceding claims, wherein the elastic element is pretensioned in between the axle insert and the stationary seal member.

9. Rotary transmission joint according to any of the preceding claims, wherein the elastic element comprises an elastic fluid duct, for example an elastic hose, extending between the axle insert and the through passage of the stationary seal member, for example extending through the compression spring.

10. Rotary transmission joint according to any of the preceding claims, wherein the elastic element comprises a hollow bellow, for example a bellow with a corrugated outer wall, for example comprising a metallic material.

11. Rotary transmission joint according to any of the preceding claims, wherein the elastic element, e.g. the hollow bellow, is integrally connected to the stationary seal member.

12. Rotary transmission joint according to any of the preceding claims, wherein the axle insert defines an inner chamber, in which the rotary seal assembly is substantially entirely accommodated.

13. Rotary transmission joint according to claim 12, wherein the rotary seal assembly further comprises an annular ring, which is arranged in the inner chamber and which surrounds the stationary seal member and the rotary seal member.

14. Rotary transmission joint according to claim 13, wherein the annular ring is clamped in the inner chamber and / or wherein the stationary seal member and / or the rotary seal member abut the annular ring.

15. Rotary transmission joint according to claim 13 or 14, wherein the annular ring is made of an elastic material, configured to deform in dependence of the offset between the axle centreline and the hub rotation axis.

16. Rotary transmission joint according to any of the claims 13 - 15, wherein the annular ring is made of a porous material and / or configured to hold a lubricant for lubricating the contact between the seal planes of the seal members.

17. Rotary transmission joint according to any of the claims 13 - 16, wherein the annular ring comprises a felt material, e.g. a felt material with a lubrication fluid absorbed in it, for example drenched with the lubrication fluid.

18. Rotary transmission joint according to any of the claims 12 - 17, wherein the inner chamber is substantially shielded from the surroundings of the rotary transmission joint, e.g. by the annular ring and / or the rotary seal member.

19. Rotary transmission joint according to any of the preceding claims, wherein the rotary seal assembly is substantially free of a bearing between the stationary seal member and the hub fitment and / or free of a bearing between the rotary seal member and the axle insert.

20. Rotary transmission joint according to any of the preceding claims, wherein the rotary seal assembly comprises a slide bearing between the stationary seal member and the rotary seal member.

21. Axle assembly of a vehicle, comprising: an axle, comprising a cavity extending along an axle centreline, a rotary hub that is rotatable relative to the axle about a hub rotation axis, andthe rotary transmission joint according to any of the preceding claims, wherein the hollow axle insert of the rotary transmission joint is inserted, for example press-fitted or screwed, into the cavity along the axle centreline, and wherein the hub fitment of the rotary transmission joint connected to the hub.

22. Axle assembly according to claim 21, wherein the hollow axle insert of the rotary transmission joint, e.g. the inner chamber thereof, substantially protrudes towards the hub.

23. Method of assembling an axle assembly of a vehicle, comprising the steps of: providing the rotary transmission joint according to any of the claims 1 - 20, inserting, for example press-fitting or screwing, the rotary seal assembly with the hollow axle insert thereof along an axle centreline into a cavity in an axle, attaching a rotary hub to the axle, which is rotatable relative to the axle about a hub rotation axis, and connecting the hub fitment to the hub.

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