WO2024028665A1

WO2024028665A1 - Rotary feedthrough arrangement

Info

Publication number: WO2024028665A1
Application number: PCT/IB2023/056215
Authority: WO
Inventors: Felix SODERMANNS
Original assignee: Agco International Gmbh
Priority date: 2022-08-04
Filing date: 2023-06-15
Publication date: 2024-02-08
Also published as: GB202211397D0

Abstract

A Rotary Feedthrough A rotary feedthrough (22) between first (12) and second (11) relatively rotatable components includes a fluid seal (31, 32) having a body (31a, 32a) comprising an elastomeric material mounted to a supporting surface (50) of one of the components (11). The body has a pair of spaced sealing members (31c, 32c) for engagement with a sealing surface (30) on the other component to define a high-pressure area (40, 41) between them. Said one of the components includes a pressurised fluid passage (25, 28) fluidly connected with the high– pressure area which comprises an annular recess (25a, 28a) which opens at the supporting surface and extends radially outwardly of the supporting surface and a bore (25b, 28b) which opens into the recess at a position offset radially outwardly from the supporting surface. The elastomeric body (31a, 32a) of the seal engages with the supporting surface (50) either side of the recess. The rotary feedthrough (22) enables the seal to be pressed into position without passing over splinters or bores formed when the bore is produced.

Description

ROTARY FEEDTHROUGH ARRANGEMENT

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] Not applicable.

FIELD

[0002] Embodiments of the present disclosure relate generally to a rotary feedthrough which enables a fluid under pressure to be passed between two relatively rotatable components. The rotary feedthrough may be part of a tyre pressure control system.

BACKGROUND

[0003] Tyre pressure control systems (also referred to as central tire inflation systems) have been developed which allow tyre pressures on apparatus, such as a mobile machine or vehicle, to be monitored and adjusted centrally. For agricultural applications in particular, it is desirable to be able to optimise tyre inflation pressures for use in different environments. For example, for use in a field it is often desirable to use lower tyre inflation pressures. This helps to spread the weight of the apparatus, reducing soil compaction, and maximises grip. Whereas, for use on a road or other hard surface higher tyre pressures are required to provide stability, increased fuel efficiency, and minimise tire wear. Accordingly, tyre pressure control systems have been adopted for use on various agricultural apparatus, such as tractors, combined harvesters, forage harvesters, trailers, sprayers, and towed implements including planters, and the like, which can be used to adjust tyre pressures, e.g., when transitioning between road and field use. An example of a known tyre pressure control system is described in US patent application publication No. 2015/0231937 Al, published 20 August 2015, by Hbldrich et al., to which the reader should refer for further details

[0004] Tyre pressure control systems generally include a rotary feedthrough which enables pressurised air to be passed between two components which rotate relative to one another. In some embodiments, the rotary feed through is provided between a rotatable component, such as an axle shaft or hub shaft, and a non-rotatable component, such as a housing, in which the rotatable component is mounted. A rotary seal arrangement is operative between the components to seal off a high-pressure area between them through which pressurised air may be passed from an air passage in one of the components to enter a corresponding air passage in the other of the components. The seal arrangement prevents pressurised air escaping from the high-pressure area and also prevents oil and other contaminants which may be present outside of the high- pressure area from entering the air passages.

[0005] An example of a seal arrangement for a rotary feedthrough for a tyre pressure control system is described in International patent application publication no. WO 2012/084412 Al, published 28 June 2012, by Honzek et al. The sealing arrangement includes seal cartridge having a metallic casing which supports spaced sealing members. The casing is mounted to a housing and the spaced sealing members contact a rotatable component in the housing to define the high pressure area between themselves. The seal cartridge is pre-assembled and can be easily mounted to the housing about the rotatable component. The metallic casing holds the sealing members in position and protects them from damage during assembly but increases the overall number of parts and so adds to the cost of the sealing arrangement.

BRIEF SUMMARY

[0006] Aspects of the disclosure relate to a rotary feedthrough, an apparatus having a rotary feedthrough, and to a method of manufacturing a rotary feedthrough.

[0007] An aspect of the invention provides a rotary feedthrough comprising a first component and a second component mounted for rotation relative to one another, and a rotary feedthrough seal arrangement operative to seal off a high-pressure area between the first and second components, the rotary feedthrough seal arrangement comprising a fluid seal having a body comprising an elastomeric material mounted to a supporting surface of the second component, the body carrying a pair of spaced sealing members for engagement with a sealing surface on the first component to define the high-pressure area between them, wherein second component includes a pressurised fluid passage fluidly connected with the high-pressure area, the pressurised fluid passage including an annular recess defined in the second component which opens at the supporting surface and extends radially outwardly of the supporting surface and a bore which opens into the recess at a position offset radially outwardly from the supporting surface, the elastomeric body of the seal engaging with the supporting surface either side of the recess.

[0008] As the bore enters the recess at a position off-set from the supporting surface, the elastomeric body of the fluid seal does not engage with any splinters, burrs, or other manufacturing defects arising during production of the bore as the fluid seal is pressed into position along the supporting surface.

[0009] In an embodiment, a second fluid seal is arranged in line with the first mentioned fluid seal in an axial direction, the second component comprising a second pressurised fluid passage fluidly connected with a high-pressure area defined between spaced sealing members of the second fluid seal, the second pressurised fluid passage including a second annular recess defined in the second component which opens at the supporting surface and extends radially outwardly of the supporting surface and a second bore which opens into the second recess at a position offset radially outwardly from the supporting surface, the elastomeric body of the second seal engaging with the supporting surface either side of the second recess.

[0010] In an embodiment, the seal arrangement further comprising an oil seal adjacent the fluid seal, the oil seal having an oil seal body mounted to the supporting surface and an oil sealing member for engagement with a sealing surface of the first component, the oil sealing member and a first one of the sealing members of the fluid seal defining a pressure control area between themselves, the second component may include a pressure control fluid passage which is fluidly connected with the pressure control area, the pressure control fluid passage including an annular recess defined in the second component which opens at the supporting surface and extends radially outwardly of the supporting surface and a bore which opens into the annular recess at a position offset radially outwardly from the supporting surface, the body of the fluid seal and the body of the oil seal engaging with the supporting surface either side of the annular recess of the pressure control fluid passage.

[0011] In an embodiment where there are two fluid seals, the seal arrangement further comprising a second oil seal adjacent the second fluid seal, the second oil seal including an oil seal body mounted to the supporting surface and an oil sealing member for engagement with a sealing surface of the first component, the oil sealing member and a first one of the sealing members of the second fluid seal defining a second pressure control area between themselves, the second component may include a second pressure control fluid passage which is fluidly connected with the pressure control area defined by the second fluid seal and the second oil seal, the second pressure control fluid passage including an annular recess defined in the second component which opens at the supporting surface and extends radially outwardly of the supporting surface and a bore which opens into the annular recess at a position offset radially outwardly from the supporting surface, the body of the second fluid seal and the body of the second oil seal engaging with the supporting surface either side of the annular recess of the second pressure control fluid passage.

[0012] In an embodiment, the annular recess of the, or each, pressurised fluid passage is defined by annular base wall region in the second component spaced radially outboard of the supporting surface and which extends generally parallel to the supporting surface, and inclined end wall regions which extend between the base wall region and the supporting surface, the bore opening into the recess through the base wall region.

[0013] In an embodiment, the annular recess of the, or each, pressure control fluid passage is defined by a pair of surfaces in the second component that are inclined relative to one another and to the supporting surface, the inclined surfaces meeting at an apex substantially at a mid-point of the respective annular recess when considered in an axial direction of the first component.

[0014] In an embodiment, the, or each, fluid seal is annular having spaced engagement regions for contact with the supporting surface either side of the annular recess of the respective pressurised fluid passage, the engagement regions having a first outer diameter, the, or each, fluid seal having a region between the spaced engagement regions with an outer diameter which is smaller than the first diameter, such that an outer surface of a portion of the fluid seal between the engagement regions is offset radially inwardly from the supporting surface.

[0015] In an embodiment, the, or each, bore is a drilling.

[0016] In an embodiment, a pressurised fluid passage is defined in the first component which opens into the high-pressure area defined by the fluid seal.

[0017] In an embodiment where there are two fluid seals, a second pressurised fluid passage is defined in the first component which opens into the high-pressure area defined by the second fluid seal.

[0018] The, or each, fluid seal may be an air seal.

[0019] In an embodiment the rotary feedthrough forms part of a tyre pressure control system.

[0020] In an embodiment, the rotary feedthrough is provided a part of a rear axle assembly, the first component comprising a drive shaft and the second component comprising an axle housing in which the drive shaft is rotatably mounted.

[0021] In an embodiment, the rotary feed through is provided as part of a final drive assembly for a steerable wheel, the final drive assembly comprising a steering knuckle housing, a wheel hub mounted for rotation about the steering knuckle housing, and a planetary gear train for transmitting drive to the wheel hub, the planetary gear train including a sun gear mounted for rotation within a bore of the steering knuckle housing, a ring gear rotational fast with the steering knuckle housing, planetary gears, and a planetary gear carrier rotationally fast with the wheel hub, wherein: a. the first component is the steering knuckle and the second component is the wheel hub; b. the first component is the sun gear and the second component is the steering knuckle housing, or c. the first component is the sun gear and the second component is planetary gear carrier.

[0022] In an embodiment, the final drive assembly includes two rotary feedthroughs according to the invention, a first rotary feedthrough in which the first component is the sun wheel and the second component is the steering knuckle housing, and a second rotary feedthrough in which the first component is the sun gear and the second component is the planetary gear carrier.

[0023] In an embodiment, the final drive assembly is part of a front axle.

[0024] According to a further aspect of the invention, there is provided apparatus having at least one inflatable tyre and a tyre pressure control system including the rotary feedthrough according to the previous aspect set out above. The apparatus may be an agricultural machine such as a tractor.

[0025] According to a still further aspect of the invention, there is provided a method of manufacturing the rotary feedthrough according to the aspect first mentioned above, the method comprising, for the, or each, fluid passage, forming the respective annular recess in the second component prior to forming the respective bore.

[0026] Within the scope of this application it should be understood that the various aspects, embodiments, examples and alternatives set out herein, and individual features thereof may be taken independently or in any possible and compatible combination. Where features are described with reference to a single aspect or embodiment, it should be understood that such features are applicable to all aspects and embodiments unless otherwise stated or where such features are incompatible.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] One or more embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0028] FIG. 1 is a sectional view through part of a tractor rear axle showing a rotary hub mounted in an axle housing and fitted with a rotary feedthrough arrangement in accordance with an aspect of the present disclosure, the view taken on an axis of the rotary hub;

[0029] FIG. 2 is an enlarged view of detail A in FIG. 2;

[0030] FIG. 3 is an enlarged view of detail B in FIG. 2;

[0031] FIG. 4 is a cross sectional view through a rotary feedthrough seal arrangement forming part of the rotary feedthrough of FIG. 2

[0032] FIG. 5 is an enlarged view of detail C in FIG 3, illustrating details of a pressurised fluid passage forming part of the rotary feedthrough;

[0033] FIG. 6 is an enlarged view of detail D in FIG. 3, illustrating details of a pressure control fluid passage forming part of the rotary feedthrough; and,

[0034] FIG. 7 is a schematic cross sectional view through a final drive for a steerable wheel illustrating first and second alternative embodiments of a rotary feedthrough arrangement in accordance with an aspect of the present disclosure.

DETAILED DESCRIPTION

[0035] While the disclosure will be described in connection with these drawings there is no intent to limit to the embodiment or embodiments disclosed herein. Although the description identifies or describes specifics of one or more embodiments, such specifics are not necessarily part of every embodiment, nor are all various stated advantages necessarily associated with a single embodiment or all embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents included within the scope of the disclosure as defined by the appended claims. Further, it should be appreciated in the context of the present disclosure that the claims are not necessarily limited to the particular embodiments set out in the description.

Overview of Tyre Pressure Control System

[0036] Referring to FIG. 1, a tractor rear axle 10, one end region of which is shown in cross-section, has an outer trumpet housing 11 having an inner bore within which a driveshaft 12 is rotatably supported by bearings 13. Driveshaft 12 terminates in a hub flange 14 to which a wheel disc 15a of a wheel 15 is clamped by bolts 16 and a clamping ring 17. The wheel disc 15a carries a wheel rim 18 on which a pneumatic tire 19 is mounted. A corresponding arrangement for mounting a second wheel and tyre is provided at the other end of the rear axle 10.

[0037] The driveshaft 12 rotates about an axis X and terms used herein in relation to the embodiment described below with reference to FIGs. 1 to 6 which imply a direction relative to an axis such as "axial", "axially", "radial", or "radially" and the like, should be understood as relating to the axis X of the driveshaft 12 even if made in reference to components other than the driveshaft 12, unless the context requires otherwise.

[0038] A tyre pressure control system 20 is provided for selectively conveying compressed air from a tractor air supply system 4 to the tyre 19 to inflate the tyre, or for conveying air from the tyre 19 to atmosphere to deflate the tyre. Air supply system 4 provides compressed air for a control circuit 230 and a supply circuit 220. Control circuit 230 and supply circuit 220 may comprise valve arrangements to control air flow from tractor air supply system 4 to tyre 19 or in the reverse direction. These are not described herein in detail but the tyre pressure control system may be generally similar to that described in published US patent application US2015/231937, published 20 August 2015, by AGCO International GmbH, to which the reader should refer for further details, except for any differences in the embodiments describe below.

[0039] Supply circuit 220 is connected with the interior of the tyre 19 via a supply air passage 28 in the trumpet housing 11, a supply air passage 24 in the driveshaft 12, a supply air line 47, a supply valve 223, and a further supply air line 48. With the supply valve 223 open, the supply circuit 220 and is actuatable to connect the interior of tyre with a source of pressurised air to inflate the tyre 19 or to connect the interior of the tyre 19 to atmosphere to deflate the tyre.

[0040] Operation of the air supply valve 223 is controlled by a pilot air pressure forwarded by the control circuit 230 to the air supply valve 223 via a pilot control air passage 25 in the trumpet housing 11, a pilot control air passage 21 in the driveshaft 12, and a pilot control air line 49.

Rotary Feedthrough

[0041] The tyre pressure control system includes a rotary feedthrough 22 according to an aspect of the disclosure to enable pressurised air to be fed between the air passages 25, 28 in the trumpet housing 11 and the corresponding air passages 21, 24 in the driveshaft 12. The rotary feedthrough 22 is shown in more detail in in FIG. 2. In this embodiment of a rotary feedthrough, the driveshaft 12 can be considered a first component and the trumpet housing a second component.

[0042] The pilot control air passage 21 in the driveshaft 12 has at least one radial portion 21a which opens at one end at the outer peripheral surface of the driveshaft 12 in a first axial zone 12a. The corresponding pilot control air passage 25 in the trumpet housing 11 extends radially through the housing 11 to open into the gap between the housing 11 and the driveshaft 12 opposite the first axial zone 12a of the driveshaft 12. The pilot control air passage 21 in the driveshaft 12 has an axial portion 21b extending axially from an inner end of the at least one radial portion 21a to the outer end of the driveshaft 12 where it is connected with the pilot control air line 49.

[0043] The supply air passage 24 in the driveshaft 12 has at least one radial portion 24a which opens at one end at the outer peripheral surface of the driveshaft 12 in a second axial zone 12b. The corresponding supply air passage 28 in the trumpet housing 11 extends radially through the housing 11 to open into the gap between the housing 11 and the driveshaft 12 opposite the second axial zone 12b. The supply air passage 24 in the driveshaft 12 has an axial portion 24b extending axially from an inner end of the at least one radial portion 24a to the outer end of the driveshaft 12 where it is connected with the supply air line 47.

[0044] A rotary feedthrough seal arrangement 23 is provided between the trumpet housing 11 and the driveshaft 12. The seal arrangement includes two fluid seals 31 and 32 located between a cylindrical supporting surface 50 which forms part of a central bore of the trumpet housing 11 and an outer peripheral sealing surface 30 of the driveshaft 12. In the present embodiment for use as part of a tyre pressure control system, the first and second fluid 31, 32 seals are air seals and will be referred to as such. However, in other embodiments, the rotary feedthrough can be adapted to feedthrough a fluid other than air and the fluid seals adapted accordingly. The sealing surface 30 may be provided on a separate member mounted to the driveshaft, in which case the radial portions of the air passages 21, 24 in the driveshaft 12 extend through the member.

[0045] The first air seal 31 is located in the first axial zone 12a and defines together with the trumpet housing 11 and the driveshaft 12 a first feedthrough chamber or high pressure area 40 through which pressurised air forming a pilot control signal for the supply valve 223 can be passed from the pilot control air passage 25 in the trumpet housing 11 to the pilot control air passage 21 in the driveshaft. Similarly, the second air seal 32 is located in the second axial zone 12b and defines together with the trumpet housing 11 and the driveshaft 12 a second feedthrough chamber or high pressure area 41 through which pressurised air can be passed between the supply air passage 28 in the trumpet housing 11 and the supply air passage 24 in the driveshaft to inflate or deflate the tyre 19. The two air seals 31, 32 are arranged inline in an axial direction of the driveshaft and may be positioned with their bodies 31a, 32a contacting each other as shown. However, this is not essential.

[0046] Each of the air seals 31, 32 are substantially the same and so only a first one of the air seals 31 will be described in detail with reference in particular to FIGs. 2, 3, and 4. The air seal 31 is annular to encircle the driveshaft. The air seal 31 comprises a seal body 31a made of an elastomeric material, which may be a polymeric material. A radially outer surface of the body is profiled to define two axially spaced engagement regions 31b which sealingly engage with the supporting surface 50 of the trumpet housing 11 on either side axially of the pilot control air passage 25. First and second axially spaced sealing members 31c project radially inwardly from the seal body 31a to resiliently and sealingly engage with the sealing surface 30 of the driveshaft on either side axially of the entrance to the radial portion 21a of the pilot control air passage 21 in the driveshaft 12. At least one air passage 31d extends radially through a central region of the seal body 31a between the engagement regions 31b and the sealing members 31c. The first feedthrough chamber 40 is defined between the trumpet housing 11 and the driveshaft 12 in-between the engagement regions 31b of the seal body and the sealing members 31c. In operation, pressurised air can flow from the pilot control air passage 25 through the trumpet housing

11 into the first feedthrough chamber 40 between the engagement regions 31b, through the at least one air passage 31d into the region of the first feedthrough chamber 40 between the first and second sealing members 31c to enter the pilot control air passage 21 in the driveshaft 12. This is possible regardless of the rotary position of the driveshaft

12 and even when the driveshaft 12 is rotating. The engagement regions 31b and the first and second sealing members 31c prevent the pressurised air from escaping from the first feedthrough chamber 40 axially between the trumpet housing 11 and the driveshaft 12.

[0047] The first and second sealing members 31c may be in the form of sealing lips which extend radially inwardly from the seal body 31a. The sealing lips may be made of the same material as the seal body 31a or a different material. In an embodiment the sealing lips are made of PTFE. Each of the sealing members 31c may be supported by a respective supporting ring 31e located axially to the outside of the sealing member 31c to resist the sealing member being deflected outwardly (in an axial direction of the driveshaft) when the first feedthrough chamber 40 is pressurised. The supporting rings 31e may be made of a metallic material.

[0048] The radially outer surface of the seal body 31a may be recessed radially inwardly of the engagement regions 31b in a central region so as not to contact the supporting surface 50 of the trumpet housing 11. This reduces the force required to inset the seal into the trumpet housing during assembly. Accordingly, the outer dimeter of the seal body 31a may be smaller in an axially central region than it is in the engagement regions 31b.

[0049] The second air seal 32 is substantially identical to the first air seal 31 and so will not be described in detail. Briefly, the second air seal 32 has seal body 32a with axially spaced engagement regions 32b, axially spaced sealing members 32c, and at least one radial air passage 32d. The second seal 32 can be made of the same materials and in a similar manner as the first air seal 31. Each of the sealing members 32c may be supported by a respective supporting ring 32e located axially to the outside of the sealing member 32c similar to first air seal 31.

[0050] The second air seal 32 is located in the second axial zone 12b so that the engagement regions 32b sealingly engage the supporting surface 50 of the trumpet housing 11 on either side axially of the supply air passage 28 with the axially spaced sealing members 32c engaging the sealing surface 30 of the driveshaft on either side axially of the entrance to the radial portion 24a of the supply air passage 24 in the driveshaft 12. Accordingly, the second feedthrough chamber 41 is defined between the trumpet housing 11 and the driveshaft 12 in-between the engagement regions 32b and the sealing members 32c of the second air seal 32. In operation, pressurised air can flow from the supply air passage 28 through the trumpet housing 11 into the second feedthrough chamber 41 between the engagement regions 32b, through the at least one radial air passage 32d into the region of the second feedthrough chamber 41 between the first and second sealing members 32c to enter the supply air passage 24 in the driveshaft 12 to enable the tyre 19 to be inflated. When the tyre 19 is being deflated, pressurised air from the tyre may flow through the second feedthrough chamber 41 in the opposite direction. The engagement regions 32b and the first and second sealing members 32c prevent the pressurised air from escaping from the second feedthrough chamber 41 axially between the trumpet housing 11 and the driveshaft 12.

[0051] The seal arrangement 23 includes a pair of oil seals 33, 34. A first oil seal 33 is located adjacent an axially inner end of the first air seal 31 and a second oil seal 34 is located adjacent an axially outer end of the second air seal 32. The first and second oil seals 33, 34 prevent oil and other debris which may be present in the trumpet housing 11 entering the first and second feedthrough chambers 40, 41. The first and second oil seals are similar to one another, and which in this embodiment are mirror images of each other. Accordingly, only the first oil seal 33 will be described in detail. [0052] The first oil seal 33 has an elastomeric body 33a which abuts the axially inner end of the first air seal 31. The oil seal body 33a defines an engagement region 33b which engages in a sealing manner with the supporting surface 50 of the trumpet housing 11. The first oil seal 33 has an oil sealing member 33c which resiliently engages the sealing surface 30 of the driveshaft 12. In a manner known in the art, a circular spring 33d may be provided to clamp at least a part of the oil sealing member 33c onto the sealing surface 30 of the driveshaft 12.

[0053] The oil sealing member 33c is axially spaced from the adjacent one of the sealing members 31d of the first air seal 21 and the engagement region 33b of the oil seal body is axially spaced from the adjacent engagement region 31b of the first air seal 31. A first pressure control air passage 42 extends radially through the trumpet housing 11 opening into the gap between the housing 11 and the driveshaft 12 in a region axially between the engagement region 33b of the first oil seal 33 and the adjacent engagement region 31b of the first air seal. A first pressure control chamber 43 is defined in the gap between the trumpet housing 11 and the driveshaft 12 in-between the engagement region 33b of the first oil seal, the adjacent engagement region 31b of the first air seal, the oil sealing member 33c of the first oil seal 33 and the adjacent sealing member 31c of the first air seal 31. The first pressure control chamber 43 is connected to ambient air pressure through the first pressure control air passage 42. At least one air passage is provided through the first oil seal 33 or between the first oil seal 33 and the first air seal 31 to enable air to flow between the first pressure control air passage 42 and the first pressure control chamber 43.

[0054] The first oil seal 33 may comprise supporting elements embedded in the body which may be metallic. In an embodiment, the first oil seal 33 is assembled close to the body 31a of the first air seal 31. The body 33a of the first oil seal 33 may have a bendable metallic insert 33e to reinforce the oil seal 33. In alternative embodiments, the first oil seal 33 may be formed integrally with the first air seal 31 or may be connected to the first air seal 31 to form a subassembly prior to assembly of the seal arrangement 23 in the supporting surface 50 in known manner. [0055] As noted the second oil seal 34 is similar to the first oil seal 33 and is constructed and operates in combination with the second air seal 32 substantially as described above for the first oil seal 33 in combination with the first air seal 32, except that the second oil seal 34 and the second air seal 32 are generally mirror images of the first oil seal 33 and the first air seal 31 when considered relative to a radial plane perpendicular to the axis of rotation of the driveshaft. The second oil seal 34 is located adjacent the outer axial end of the second air seal 32 and may be formed integrally with the second air seal or attached to the second air seal. A second pressure control chamber 45 is defined in the gap between the trumpet housing 11 and the driveshaft 12 in-between the engagement region 34b of the second oil seal, the adjacent engagement region 32b of the second air seal, the oil sealing member 34c of the second oil seal 34 and the adjacent sealing member 32c of the second air seal 32. The second pressure control chamber 45 is connected to ambient air pressure through a second pressure control air passage 44 in the trumpet housing. At least one air passage is provided through the second oil seal 34 or between the second oil seal 34 and the second air seal 32 to enable air to flow between the second pressure control air passage 44 and the second pressure control chamber 45.

[0056] Each of the first and second pressure control air passages 42, 44 may exit to the outside of trumpet housing 11 via a screw-in diaphragm valve (not shown) or other means to avoid debris entering the passage but which allows air to exit. The first and second pressure control chambers 43, 45 and corresponding first and second pressure control air passages 42, 44 ensure that when the feedthrough chambers 40, 41 are pressurised, a high pressure differential is maintained between the feedthrough chambers 40, 41 and the adjacent ambient air pressure chambers 43, 45. This ensures that sealing members 31b and 32b of the air seals 31, 32 are pressed hard against the sealing surface 30, thus preventing air leaks. In addition, the pressure control chambers 43, 45 and associated pressure control passages 42, 44 are operative to prevent pressurised air enter the cavity between driveshaft 12 and trumpet housing 11 in the event the air seals fail. Such a leakage of pressurised air might otherwise lead to an increase of pressure in an oil sump in the axle resulting in damage to the bearings 13 supporting the driveshaft 12. Air passages may be provided in the oil seals 33, 34 or between the oil seals 33, 34 and their respective air seals 31, 32 to ensure that air is able to pass between the respective pressure control air passage 42, 44 and the volume contained between the oil sealing member 33c, 34c and the adjacent sealing member 31c, 32c of the respective air seal 31, 32. In alternative embodiments, the pressure control chambers 43, 45 may be connected through their respective pressure control air passages 42, 44 to an evacuation means operative to reduce the pressure in the pressure control chambers 43, 45 below atmospheric. Suitable evacuation means may be a vacuum pump or a source of pressurized air configured to provide a suction effect. Reducing the pressure in the pressure control chambers 43, 45 below atmospheric helps to force sealing members 31c, 32c of air seals 31, 32 into contact with sealing surface 30 of driveshaft 12. Alternatively, the pressure control chambers 43, 45 may be connected through their respective pressure control air passages 42, 44 to a source of pressurised air to enable the pressure control chambers to be pressurised above ambient. This might be desirable in order to lift the sealing members 31b and 32b from the sealing surface 30 to remove debris or to reset the sealing members. Details of such a systems are known in prior art and therefore not explained in detail. Reference is taken to applicant's published patent application EP2 655 101 Bl.

[0057] The inner bore of the trumpet housing is a stepped bore in which the cylindrical supporting surface 50 defines a first region having a first diameter. The stepped bore includes a smaller diameter second region 51 axially outboard of the first region 50. A radial step 52 between the first and second regions 50, 51 forms a stop surface against which the body 34a of the second oil seal 34 is located to position the seal arrangement axially. Working axially inwardly, the second oil seal 34 is followed by the second air seal 32, the first air seal 31, and the first oil seal 33. The seal arrangement or seal assembly 23 is held in position axially by a circlip 71 engaged in a groove defined in the trumpet housing which abuts the axially inner end of the first oil seal body 33a. However, it will be appreciated that the seal arrangement 23 can be located axially within the supporting surface 50 by other arrangements, such as one or more spacers positioned between the first oil seal body 33a and inner bearing 13.

[0058] In use, the feedthrough chambers 40, 41 are only pressurised when the tyre 19 is being inflated or deflated. At other times, the control circuit 230, the supply circuit 220, and supply valve 223 are closed so that the feedthrough chambers are not pressurised. This helps to reduce wear of the sealing members 31c, 32c of the first and second air seals.

[0059] The seals 31, 32, 34, 34 are pressed into the cylindrical supporting surface 50 and the engagement regions are a tight fit against the supporting surface 50. At least the engagement regions 31b, 32b, 33b, 34b of the seals are made of a relatively soft elastomeric material to form a seal against the supporting surface 50. Accordingly, there is a risk that the engagement regions could be damaged as the seals are pressed into position if there are any splinters, burrs, or other manufacturing defects over which they are moved. A particular issue has been found in relation to the air passages 25, 28, 42, 44 in the trumpet housing which are typically bored (e.g., drilled) after the supporting surface 50 has been machine finished. This can result in splinters or burrs where the air passages break through the supporting surface 50 which are difficult to remove. Pressing the elastomeric seals in to the supporting surface 50 in these circumstances can cause the splinters or burrs to damage and possibly score the engagement regions, preventing an effective seal being formed.

[0060] To address this issue, and in accordance with an aspect of the disclosure, at least one of the air passages in the trumpet housing 11 includes an annular recess defined in the trumpet housing which opens at the supporting surface 50 and a bore which opens into the recess at a position offset radially outwardly from the supporting surface 50. With this arrangement, any splinters or burrs which are formed when the bore is produced are located in a position offset radially outwardly from the supporting surface 50 and so are not contacted by the engagement regions of the seals 31, 21, 33, 34 when the seals are pressed into position over the supporting surface 50. Typically, when manufacturing the trumpet housing 11, it is expected that the recess would be produced before the bore, though this need not be the case. This aspect of the disclosure will be described in more detail with relation to FIGS. 3, 5, and 6.

[0061] FIGs. 3 and 5 which shows on enlarged scale a portion of the pilot control air passage 25 where it enters the bore of the trumpet housing 11. The pilot control air passage 25 includes an annular recess 25a formed in trumpet housing which opens at the supporting surface 50 and a bore 25b. The recess extends radially outwardly from the supporting surface 50 and includes an annular base wall region 25a' which extends axially generally parallel to the supporting surface and a pair of inclined end wall regions 25a" which extend between the base wall region 25a' and the supporting surface 50. The bore 25b opens into the recess 25a through the base wall region 25a'. The bore 25b in this embodiment extends radially through the trumpet housing 11 for connection to the control circuit 230. Since the bore 25b breaks through the base wall region 25a' of the recess at a position spaced radially outwardly of the supporting surface 50 any splinters or burrs 66 formed when producing the bore 25b are also spaced radially outwardly of the supporting surface and so are not contacted by the engagement regions of the 31b of the first air seal 31, or indeed the engagement regions of the second air seal 32 and the second oil seal 33 which must be pressed past the pilot control air passage 25 when being assembled. Once assembled, the engagement regions 31b of the first air seal 31 contact the supporting surface 50, either side of the annular recess 25a in the axial direction of the driveshaft to form an effective seal.

[0062] The supply air passage 28 may be formed in a similar manner to the pilot control air passage 25, having an annular recess 28a and a bore 28b which are similar to the recess 25a and bore 25b of the control air passage 25.

[0063] The first and second pressure control passages 42, 44 may also be formed with an annular recess in the trumpet housing 11 and a bore which opens into the recess at a position offset radially outwardly from the supporting surface 50. An embodiment is illustrated in FIG. 6 which shows the first pressure control air passage 42 having an annular recess 42a and a bore 42b. In this case, the annular recess 42a has an inverted V shape in cross section as shown in FIG. 6, with a pair of angled surfaces 42a', 42a" inclined to one another and to the supporting surface 50 and which meet at an apex radially outboard of the supporting surface 50 and at a position substantially in line with a radial plane extending through the centre of the bore 42b. This profile of recess is adopted due to the limited axial space available for the recess 42a whilst ensuring that the engagement region 33b of the first oil seal 33 and the adjacent engagement region 31b of the first air seal are able to contact the supporting surface either axial side of the recess 42a to form an effective seal.

[0064] The second pressure control air passage 44 is formed with an annular recess 44a and a bore 44b in a similar manner to the first pressure control air passage as illustrated in FIG. 6.

[0065] It should be appreciated that the annular recesses 25a, 28a, 42a, 44a for the various air passages through the trumpet housing 11 can take any suitable shape or profile so long as the objective of spacing the location at which the bore breaks through into the recess radially away from the supporting surface 50.

[0066] The embodiment described above in which a driveshaft 12 rotatably supported in a trumpet housing 11 is particularly suited for use in a rear axle of a tractor or other agricultural vehicle. However, in other alternative embodiments, a rotary feedthrough according to the disclosure can be provided in a final drive for a steerable axle, such as may be used in a front tractor axle.

[0067] A final drive 100 for a steerable axle is illustrated somewhat schematically in FIG. 7 and includes a steering knuckle housing 102, a wheel hub 103 rotatably mounted to the steering knuckle housing 102 by bearings 104 and a planetary gear train 105 for transmitting drive to the wheel hub 103. The wheel hub 103 provides a first portion 103a of a hub flange to which a wheel disc 15a of a wheel 15 is clamped by bolts 16. The wheel disc 15a carries a wheel rim 18 on which a pneumatic tire 19 is mounted. The steering knuckle housing can be pivoted about an axis Y to provide steering movement of the wheel.

[0068] The planetary gear train 105 includes a sun gear 106, a ring gear 107, planetary gears 108 and a planetary gear carrier 109. The sun gear 106 has a shaft portion 106a mounted within a central bore 110 in the steering knuckle housing 102 for rotation about an axis Z. The sun gear 106 provides an input to the final drive and is drivingly connected with a front axle power train which in turn is coupled by a transmission to a combustion engine or other prime mover. The ring gear 107 is mounted rotationally fixed to the steering knuckle housing 102. The planetary gears 108 rotate between the sun gear 106 and the ring gear 107. The planetary gear carrier 109 is coupled to the wheel hub 103 to form a second portion 109a of the hub flange and provides an output from the planetary gear train 105. In addition, planetary gear carrier 109 and wheel hub 103 form a housing which protects the planetary gear train 105 and provides an oil sump for lubrication. The planetary gear train 105 provides speed reduction to the wheel 15.

[0069] Examples of final drives for a steerable axle of the type shown in FIG. 7 are shown in WO 2013/056988 Al, published 15^th April 2013, by AGCO International GmbH, and WO 2017/174646 Al, published 12 October 2017, by CNH Industrial Italia S.P.A., to which the reader should refer for further details.

[0070] In a first alternative embodiment, a rotary feedthrough 22' according to an aspect of the disclosure is provided between the steering knuckle housing 102 and the wheel hub 103 to enable air to be transferred between fluid passages 25, 28 in the steering knuckle housing and fluid passages 21, 24 in the wheel hub 103. The fluid passages 25, 28 in the steering knuckle housing may be connected with a control circuit 230 and a supply circuit 220 of a tyre pressure control system 20 with the fluid passages 21, 24 in the wheel hub connected with a supply valve 223 for the tyre 19 in a similar manner to that shown in FIG. 1. The rotary feedthrough 22' is similar to the rotary feedthrough illustrated in FIGs. 2 to 6 and as described above, with the seal bodies mounted to a supporting surface 50 formed in the wheel hub 103. In this embodiment, the wheel hub 103 can be considered a second component and the steering knuckle housing 102 a first component. The fluid passages 21, 24 in the wheel hub 103 are each provided with an annular recess opening at the supporting surface and a bore opening into the recess at a location radially offset from the supporting surface 50. The seal assembly 23 will rotate with the wheel hub 103 but otherwise the fluid feedthrough 22' is constructed and operates in a manner similar to the rotary feedthrough 22 in the embodiment described above.

[0071] In a second alternative embodiment also illustrated in FIG. 7, the fluid passages for the tyre pressure control system are routed through a first rotary feedthrough 22" from the steering knuckle housing 103 into the sun wheel 106 and through a second rotary feedthrough 22"' from the sun wheel 106 into the planetary gear carrier 107, which rotates with the wheel hub 103 and the wheel 15. In this embodiment, either one or both of the first and second rotary feedthroughs 22", 22"' can be formed as a rotary feedthrough according to the present disclosure. Where the first rotary feedthrough 22" is configured in accordance with the present disclosure, the supporting surface 50 against which the bodies of the seals are mounted is provided in the steering knuckle housing 103, which can be considered the second component and the sun wheel the first component. The fluid passages 25, 28 in the knuckle housing 103 are each formed with an annular recess opening at the supporting surface and a bore opening into the recess at a location offset radially from the supporting surface. In this case the seals do not rotate. Where the second rotary feedthrough 22'" is formed in accordance with the disclosure, the supporting surface 50 against which the seal bodies are mounted is provided in the planetary carrier 109 so that the fluid passages in the planetary carrier are each formed with an annular recess opening at the supporting surface and a bore opening into the recess at a location radially spaced from the supporting surface. In this example, the planetary carrier 109 can be considered the second component and the sun wheel 106 the first component and the seal arrangement rotates with the planetary carrier.

[0072] In the second alternative embodiment, the sun gear 106 can be provided with a spigot 111 which locates in a bore 112 in an annular extension 113 of the planetary carrier with the second rotary feedthrough 22'" operative between the spigot and the annular extension 113. However, the spigot 111, the extension 113, and the bore 112 are not required for the first alternative embodiment and so can be omitted in this case.

[0073] The rotary feedthroughs 22', 22", 22'" in either of the first and second alternative embodiments may or may not define pressure control chambers 40, 41 between the air seals and the oil seals and so may or may not be provided with corresponding pressure control air passages.

[0074] In relation to either of the first and second alternative embodiments, terms used herein which imply a direction relative to an axis such as "axial", "axially", "radial", or "radially" and the like, should be understood as relating to the axis Z of the sun gear 106 even if made in reference to components other than the sun gear, unless the context requires otherwise.

[0075] Aspects of the disclosure can be applied in rotary feedthroughs for a wide range of tyre pressure control systems and are not limited to application with tyre pressure control systems in accordance with the embodiments described above. For example, the tyre pressure control system may not use a pilot air pressure to control a supply valve and so the rotary feedthrough 22, 22', 22", 22'" may only have a single air seal. In other embodiments, the rotary feedthrough may have three or more air seals. Further, alternative embodiments may not include pressure control chambers 40, 41 and/or pressure control air passages 42, 44. Thus in a simple embodiment, there may be only one air seal and there may or may not be an oil seal either side of the air seal. The air passage or passages the second component, need not be radial or at least not wholly radial.

[0076] It should also be understood that the teachings in this disclosure can be applied to rotary feedthroughs for applications other than a tyre pressure control system wherever there is a need to mount an elastomeric seal in a bore where a fluid passage enters the bore and where damage to the seal may occur if formation of the passage leaves splinters, burrs or other imperfections that may be contacted by the elastomeric body of the seal during assembly.

[0077] All references cited herein are incorporated herein in their entireties. If there is a conflict between definitions herein and in an incorporated reference, the definition herein shall control.

Claims

CLAIMS What is claimed is:

1. A rotary feedthrough comprising a first component and a second component mounted for rotation relative to one another, and a rotary feedthrough seal arrangement operative to seal off a high-pressure area between the first and second components, the rotary feedthrough seal arrangement comprising a fluid seal having a body comprising an elastomeric material mounted to a supporting surface of the second component, the body carrying a pair of spaced sealing members for engagement with a sealing surface on the first component to define the high-pressure area between them, wherein second component includes a pressurised fluid passage fluidly connected with the high-pressure area, the pressurised fluid passage including an annular recess defined in the second component which opens at the supporting surface and extends radially outwardly of the supporting surface and a bore which opens into the recess at a position offset radially outwardly from the supporting surface, the elastomeric body of the seal engaging with the supporting surface either side of the recess.

2. The rotary feedthrough of claim 1, the seal arrangement comprising a second fluid seal arranged in line with the first mentioned fluid seal in an axial direction, the second component comprising a second pressurised fluid passage fluidly connected with a high-pressure area defined between spaced sealing members of the second fluid seal, the second pressurised fluid passage including a second annular recess defined in the second component which opens at the supporting surface and extends radially outwardly of the supporting surface and a second bore which opens into the second recess at a position offset radially outwardly from the supporting surface, the elastomeric body of the second seal engaging with the supporting surface either side of the second recess.

3. The rotary feedthrough of claim 1 or claim 2, the seal arrangement further comprising an oil seal adjacent the fluid seal, the oil seal having an oil seal body mounted to the supporting surface and an oil sealing member for engagement with a sealing surface of the first component, the oil sealing member and a first one of the sealing members of the fluid seal defining a pressure control area between themselves, the second component may include a pressure control fluid passage which is fluidly connected with a pressure control arrangement to regulate the pressure in the pressure control area, the pressure control fluid passage including an annular recess defined in the second component which opens at the supporting surface and extends radially outwardly of the supporting surface and a bore which opens into the annular recess at a position offset radially outwardly from the supporting surface, the body of the fluid seal and the body of the oil seal engaging with the supporting surface either side of the annular recess of the pressure control fluid passage.

4. The rotary feedthrough of claim 3, when dependent on claim 2, the seal arrangement further comprising a second oil seal adjacent the second fluid seal, the second oil seal including an oil seal body mounted to the supporting surface and an oil sealing member for engagement with a sealing surface of the first component, the oil sealing member and a first one of the sealing members of the second fluid seal defining a pressure control area between themselves, the second component may include a second pressure control fluid passage which is fluidly connected with the pressure control area defined by the second fluid seal and the second oil seal, the second pressure control fluid passage including an annular recess defined in the second component which opens at the supporting surface and extends radially outwardly of the supporting surface and a bore which opens into the annular recess at a position offset radially outwardly from the supporting surface, the body of the second fluid seal and the body of the second oil seal engaging with the supporting surface either side of the annular recess of the second pressure control fluid passage.

5. The rotary feedthrough of any one of claims 1 to 4, wherein the annular recess of the, or each, pressurised fluid passage is defined by annular base wall region in the second component spaced radially outboard of the supporting surface and which extends generally parallel to the supporting surface, and inclined end wall regions which extend between the base wall region and the supporting surface, the bore opening into the recess through the base wall region.

6. The rotary feedthrough of any one of claims 1 to 5, wherein the, the annular recess of the, or each, pressure control fluid passage is defined by a pair of surfaces in the second component that are inclined relative to one another and to the supporting surface, the inclined surfaces meeting at an apex substantially at a mid-point of the respective annular recess when considered in an axial direction of the first component.

7. The rotary feedthrough of any one of claims 1 to 6, wherein the, or each, fluid seal is annular, the, or each, fluid seal having spaced engagement regions for contact with the supporting surface either side of the annular recess of the respective pressurised fluid passage, the engagement regions having a first outer diameter, the, or each, fluid seal having a region between the spaced engagement regions with an outer diameter which is smaller than the first diameter, such that an outer surface of a portion of the fluid seal between the engagement regions is offset radially inwardly from the supporting surface.

8. The rotary feedthrough of any one of claims 1 to 7, wherein the, or each, bore is a drilling.

9. The rotary feedthrough of any one of claims 1 to 8, wherein a pressurised fluid passage is defined in the first component which opens into the high-pressure area defined by the fluid seal.

10. The rotary feedthrough of claim 2, or any one of claims 3 to 9 when dependent on claim 2, wherein a second pressurised fluid passage is defined in the first component which opens into the high-pressure area defined by the second fluid seal.

11. The rotary feedthrough of any one of claims 1 to 10, wherein the rotary feedthrough forms part of a tyre pressure control system.

12. Apparatus having at least one inflatable tyre and a tyre pressure control system including the rotary feedthrough of any one of claims 1 to 11, wherein optionally the apparatus is an agricultural machine such as a tractor.

13. A method of manufacturing the rotary feedthrough of any one of claims 1 to 11, the method comprising, for the, or each, fluid passage, forming the respective annular recess in the second component prior to forming the respective bore.