Sealing structure for a CTIS system

Abstract

A sealing structure (1) for sealing an annular space (2) formed between a stator element (3) and a rotor element (4) which is movable relative to the stator element (3) with a rotational movement about an axis (A), wherein the sealing structure (1) is configured to allow the sealed passage of a fluid under pressure between the stator element (3) and the rotor element (4) through the annular space (2) and to prevent the passage of contaminants from an external environment (50) into the annular space (2); wherein the sealing structure (1) comprises: - an annular support bushing (13) configured to be integrally toothed on the stator element (3) and having an inner annular toothing surface (13a) and an outer annular sliding surface (13b); - a pair of annular sealing elements (10) arranged on axially opposite sides of the annular space (2) to seal the annular space (2) in a fluid-tight manner; wherein each sealing element (10) comprises a support portion (11) configured to be integrally coupled to the rotor element (4) and a sealing portion (12) carried by the support portion (11), arranged to bear in a fluid-tight manner against the outer surface (13b) of the support bush (13) and suitable to slide on the outer surface (13b) due to the rotational movement exerted by the rotor element (4) on the support portion (11); wherein the sealing assembly (1) further comprises an annular retaining element (14) securing the sealing elements (10) to one another and to the support bushing (13), thereby defining an assembly of parts coupled to one another in a detachable manner.

Description

TECHNICAL FIELD

[0001] The invention relates to a sealing structure for sealing an annular space formed between a first stator element, in particular a support shaft of a wheel of a vehicle, and a second rotor element movable with respect to the first element, for example a hub of the same wheel.

[0002] In particular, the sealing structure is configured to allow the sealed passage of a fluid (e.g., air under pressure) from a first environment into a second environment located on opposite sides of the space and also to prevent the passage of contaminants (e.g., lubricating oil) from an external environment into the space.

[0003] In particular, the invention relates to a sealing structure of the above-mentioned type which is particularly suitable for being implemented in a CTIS system (“Central Tire Inflating System”). STATE OF THE ART

[0004] CTIS systems are known to be used in vehicles operating in conditions involving frequent transitions from paved roads to dirt roads or, in any case, uneven roads and vice versa (off-road vehicles, firefighting vehicles, tractors, and the like). Specifically, these systems allow the tires to be pressurized and depressurized (inflated and deflated) depending on the various ground conditions while the aforementioned vehicles are moving.

[0005] Specifically, on paved or, in any case, relatively hard and barely uneven terrain, it is necessary to maintain a pressure of around 8-10 bar within the tires. On softer or uneven terrain, such as dirt roads, it is necessary to depressurize the tires until a pressure of around 2 bar is reached. As mentioned above, this pressurization and depressurization process must occur simultaneously while the vehicle is moving.

[0006] For this purpose, the aforementioned vehicles are equipped with a circuit through which compressed air flows. Specifically, the circuit is configured to supply and remove compressed air from the tires. Typically, the circuit has as many branches as the number of wheel centers of the vehicle, encompassing the tires to be supplied.

[0007] In the following description, reference is made to a single branch of the circuit and to the respective wheel body, and the disclosure will be equally applicable to each branch of the circuit and to each respective wheel body.

[0008] It should be noted that in this description and for a single tire, "wheel body" means the structure that includes the wheel support shaft, the wheel hub and all components necessary for their mutual operation, such as bearings.

[0009] Each branch of the circuit typically includes: - a fixed section that receives compressed air from a source, for example a compressor, and extends within the fixed part of the wheel body (shaft); - a movable section receiving compressed air from the fixed section and extending within the rotating part of the wheel body (the hub); and - an annular space formed between the wheel shaft and the respective hub and fluidly inserted between the fixed portion and the movable portion and fluidly connecting the fixed portion to the movable portion.

[0010] In order to seal the fluid connection between the fixed portion and the movable portion of the branch of the circuit, a sealing structure is inserted in the annular space formed between the shaft and the hub.

[0011] This sealing structure is configured to prevent compressed air from flowing out of the circuit and at the same time prevent external contaminants (for example, lubricants) from entering the circuit.

[0012] The sealing assemblies commonly used comprise two seals or gaskets inserted radially with respect to the axis of the shaft (and therefore to the axis of rotation of the hub) between the shaft and the hub and positioned in the area of ​​the aforementioned space.

[0013] In detail, the two seals are arranged symmetrically with respect to the space itself to have corresponding parts facing each other through the space.

[0014] Each seal is attached to the wheel hub for integral rotation and includes at least one sealing lip, which operates under dynamic conditions when required to seal a space between fixed and moving components. Essentially, each sealing lip slides on the surface of the wheel shaft while the respective seal is caused to rotate by the hub.

[0015] In this way, the fluid connection between the fixed section and the movable section of the circuit can be created.

[0016] The applicant has observed how the sealing structures of the above-mentioned type can be improved with regard to assembly and attachment to the respective wheel body.

[0017] To apply a sealing assembly of the type mentioned above to the respective wheel center, it is necessary, at a minimum, to: precisely mesh the first seal (internal side of the wheel center) with the respective seat provided on the shaft; maintain this first seal in position; precisely mesh the second seal (external side of the wheel center) with the respective seat provided on the shaft; maintain this second seal in position. These phases are particularly complicated to manage, given the dimensions of the pre-existing parts and the assembly conditions, as well as the fact that the meshing also requires the wheel hub to support the seals.

[0018] In addition, additional components such as retaining rings (e.g. Seeger rings) are provided, which must be perfectly positioned.

[0019] Additional components such as wear or support bushings and various sealing rings, such as O-rings, may also be provided, which significantly complicates the assembly of the sealing structure and its attachment to the respective wheel body.

[0020] Since the correct assembly of the seals and all auxiliary components mentioned above is necessary to ensure the nominal operation of the pressurization and depressurization circuit, it is necessary to simplify the architecture, reduce the number of components and simplify the assembly of known sealing assemblies. SUBJECT AND SUMMARY OF THE INVENTION

[0021] The invention is based on the object of creating a sealing structure for CTIS systems that is very reliable and cost-effective, and that solves at least some of the disadvantages of known sealing structures discussed above.

[0022] According to the invention, this object is achieved by a sealing structure according to claim 1. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The invention may best be understood from the following description of a preferred non-limiting embodiment, provided by way of example only, with reference to the accompanying drawings. - Fig. 1 is a perspective sectional view of a sealing structure according to the invention; - Fig. Figure 2 is a sectional view of a wheel body of a vehicle defining an annular space into which the sealing structure of Fig. 1 is inserted; - Fig. 3 is an enlarged view of the sealing structure inserted into the wheel body; and - Fig. 4 is an exploded perspective view of the sealing structure of Fig. 1. DETAILED DESCRIPTION

[0024] With reference to the attached figures, the reference numeral 1 designates as a whole a sealing structure arranged in the region of an annular space 2 formed between a stator element 3 and a rotor element 4 which moves with respect to the stator element 3 with a rotational movement about an axis A.

[0025] In particular, the stator element 3 is annular and defines the end part (or shaft) of an axle of a wheel of a vehicle; the rotor element 4 is also annular, defines the hub of the wheel, and extends in a radially outer position than the stator element 3.

[0026] In particular, the structure 1 is suitable to be implemented in a CTIS system of a vehicle and is configured to seal the space 2 in a fluid-tight manner.

[0027] In detail, the structure 1 is configured to allow the sealed passage of a pressurized fluid, in particular pressurized air, through the space 2. In detail, the pressurized fluid flows, in use, from a first environment 5 of a circuit (not shown) to a second environment 6 of the same circuit and vice versa; the environments 5 and 6 are arranged on radially opposite sides of the space 2 in the region of the stator element 3 and the rotor element 4, respectively.

[0028] Thus, the structure 1 is configured to allow the sealed passage of the fluid under pressure between the stator element 3 and the rotor element 4 through the space 2 and to prevent the passage of contaminants from an external environment into the space 2.

[0029] The above-mentioned circuit is configured to supply the fluid under pressure to the environment 6 and, conversely, to selectively convey the fluid from the environment 6 to the environment 5.

[0030] For this purpose, the cycle includes: - a fixed portion 7 arranged in the environment region 5 and, in use, receiving the fluid under pressure from a source, for example a compressor, and extending within the stator element 3; - a movable portion 8 arranged in the environment region 6 and rotating about the axis A, which, in use, receives the fluid under pressure from the fixed portion 7 and extends inside the rotor element 4; and - the space 2 configured to fluidly connect the fixed section 7 to the movable section 8.

[0031] In detail, the fixed section 7, the movable section 8 and the space 2 constantly absorb the fluid under pressure during use.

[0032] As mentioned above, the structure 1 is also configured to prevent the passage of contaminants (for example, lubricating oil) from an external environment 50 into the space 2.

[0033] For this purpose, the structure 1 comprises a pair of annular sealing elements or seals 10.

[0034] The seals 10 have an annular configuration about the axis A and are arranged (suitably symmetrically) on axially opposite sides of the space 2 in order to seal the space 2 in a fluid-tight manner.

[0035] Since the seals 10 have the same structure, only one of them will be described in detail below; of course, the properties described with reference to the selected seal 10 also apply in a completely equivalent manner to the other seal 10 of the sealing assembly 1.

[0036] According to Fig. 3 includes the seal 10: - a support portion 11 configured to be coupled to the rotor element 4 in an integral manner and therefore capable of rotating about the axis A due to the rotation imparted by the rotor element 4; - a sealing section 12 carried by the support section.

[0037] In detail, seal 10 includes: - an annular body 31, preferably made of a rigid material (for example metal or rigid plastic), which defines the support portion 11; and - Sealing elements, conveniently made of an elastomeric material (for example EPDM rubber), carried by the annular body 31 and defining the sealing portion 12.

[0038] The sealing section 12 advantageously comprises: - a first sealing lip 12a designed to define a fluid seal to prevent contaminants present in the external environment 50 from entering the space 2; - a second sealing lip 12b designed to define a fluid seal to prevent the fluid under pressure from escaping from the space 2 towards the external environment 10.

[0039] The first sealing lip 12a is arranged in a suitable manner in an axially outer position than the second sealing lip 12b with respect to the space 2 and faces the external environment 50.

[0040] The second sealing lip 12b faces the space 2.

[0041] Given the symmetrical arrangement of the seals 10 with respect to the space 2, the second sealing lips 12b are arranged in use so that they face each other through the space 2.

[0042] Preferably, the seal 10 is of the type described in Italian patent application No. 102017000129950 filed by the Applicant. In particular, the structure, shape, and parts constituting each seal 10 are preferably considered to be equivalent to those of the seal described in the patent application.

[0043] The sealing structure 1 advantageously comprises a support bushing 13 having an annular shape around the axis A, which is configured to be toothed on the stator element 3 to be integral therewith, and having an inner annular toothing surface 13a and an outer annular sliding surface 13b.

[0044] The sealing portion 12 is arranged to abut in a fluid-tight manner on the outer surface 13b and is designed to slide on the outer surface 13b due to the rotational movement exerted by the rotor element 4 on the support portion 11.

[0045] Due to the above, both the first sealing lip 12a and the second sealing lip 12b rest in a sliding manner on the outer surface 13b.

[0046] In other words, the first sealing lip 12a and the second sealing lip 12b cooperate in a fluid-tight manner with the outer surface 13b of the bushing 13.

[0047] According to one aspect of the invention, the sealing assembly 1 further comprises an annular retaining element 14 that secures the seals 10 to each other and to the support bushing 13, thereby defining an assembly of parts that are coupled to each other in a detachable manner.

[0048] In other words, according to the invention, the seal 10, the support bushing 13 and the retaining element 14 define parts that are connected to each other in a detachable manner and form a compact sealing assembly 100 that can be mounted between the stator element 3 and the rotor element 4 to seal the annular space 2 defined between them.

[0049] This particular and advantageous configuration therefore makes it possible to define a type of sealing "cartridge" or, in other words, a sealing assembly 1 consisting of a single piece made up of parts coupled together, which can be implemented in the relative wheel body by means of a single gearing operation.

[0050] In fact, it is sufficient to mesh the support bushing 13 (which, as mentioned above, already supports the seals 10 coupled thereto by means of the retaining element 14) on the stator element 3; during this meshing, the support portions 11 of the seals 10 are inserted with a fit into the radial annular space between the stator element 3 and the rotor element 4, sliding on the inner surface 4a of the rotor element 4 until the space 2 is reached.

[0051] Once the predetermined axial position, namely the seat of the sealing structure 1, is reached, the support portions 11 are internally toothed in a rigid manner on the rotor element 4, whereas the sealing portions are free to slide in a fluid-tight manner on the bushing 13.

[0052] Therefore, the installation of assembly 1 takes place in a single gearing movement, rather than requiring multiple assembly operations for various separate parts, as is the case with known sealing assemblies for CTIS systems.

[0053] This results in significant savings in terms of time and costs, both during assembly and during maintenance and / or replacement of the structure or individual parts thereof.

[0054] Preferably, the support bushing 13 is configured to be toothed in the region of its inner surface 13a on the stator element 3 directly and without the interposition of parts.

[0055] Similarly, each support portion 11 is configured to be coupled in a toothed manner to the inner annular surface 4a of the rotor element 4 directly and without the interposition of any parts.

[0056] These solutions underline a significant simplification of the architecture and a reduction of the components of the structure 1.

[0057] Advantageously, the support bush 13 comprises: - a rigid section 15 supporting the outer surface 13b and defining a sliding bearing track for each sealing section 12; and - an elastomeric portion 16 supporting the inner surface 13a and adapted to be mounted on the stator element 3 in a fluid-tight manner.

[0058] The rigid portion 15 is preferably made of a metal material.

[0059] In this way, an optimal rigidity of the support bush 13 (ensured by the rigid portion 15) is ensured, while ensuring sufficient adhesion thereof to the stator element 3, without the use of screws or other connecting elements between the two bodies, and also ensuring fluid tightness (by means of the elastomer portion 16).

[0060] The holding element 14 is arranged in the area of ​​the space 2 and is inserted axially between the seals 10.

[0061] In detail, the holding element 14 has at least two and in particular a multiple number of two holding projections 17 which extend from axially opposite sides of the holding element 14 in the axial direction.

[0062] Each projection 17 engages a respective seal 10 to keep the seal axially restricted with or without play on the retaining element 14 itself.

[0063] In detail, the annular body 31 and the sealing elements of the seal 10, namely the support portion 11 and the sealing portion 12, cooperate to define an annular chamber 18 fluidly connected to the space 2 by means of at least one through-hole 19 (the function of the annular chamber 18 is described in the above-mentioned Italian patent application No. 102017000129950); each projection 17 engages a respective through-hole 19 to reach the annular body 11 of the relative seal 10.

[0064] Preferably, the support bushing 13 comprises two annular half-profiles 20 which are arranged axially next to one another and are held by the holding element 14 to abut one another.

[0065] Each half-profile 20 receives, by radial sliding engagement and on its own part of the outer surface 13b, the sealing portion 12 of a respective seal 10.

[0066] More specifically, each half-profile 20 has an L-shaped cross-section and comprises a first axially oriented portion 21 and a second radially oriented portion 22.

[0067] The second section 22 defines an axial support for the other half-profile 20.

[0068] Each half-profile 20 is pushed or pressed axially towards the axial abutment 22 of the other half-profile 20 by the engagement of an above-mentioned projection 17 in the respective through-hole 19 and by the axial thrust exerted by the sealing portion 12 sliding on the half-profile 20.

[0069] In this way, the parts of the bushing-seal assembly are held together axially and radially by means of the holding element 14.

[0070] Preferably, as particularly in Fig. 3, the axial contact 22 is defined by the elastomeric portion 16 of the bushing 13.

[0071] In other words, the engagement between the two half-profiles 20 is achieved by their respective elastomeric parts 16.

[0072] In this way, a certain axial compressibility of the structure is ensured, which helps during the toothing / insertion of the structure 1 into the respective wheel body.

[0073] Conveniently, the holding element 14 comprises a series of axial ribs 23 which are angularly distributed around the axis A and project from axially opposite sides of the holding element 14 ( Fig. 4).

[0074] In detail, some ribs 23 face one seal 10, whereas other ribs 23 face the other seal 10.

[0075] Advantageously, the support section 11 of each seal 10 lies axially against the respective ribs 23.

[0076] In this way, correct positioning of the seals 10 with respect to the bushing 13 is ensured.

[0077] Preferably, the holding element 14 is made of a rigid plastic material.

[0078] This provides greater rigidity to the entire assembly. Since the retaining element 14 does not compress during installation of the assembly 1 in the relative wheel body, i.e., between the relative stator element 3 and the rotor element 4, it does not alter the final position of the parts, regardless of the load required for installation. This ensures a better and more secure arrangement of the various parts of the assembly.

[0079] The features of the sealing structure 1 according to the invention lead to obvious advantages that can be achieved with it.

[0080] In particular, the particular and advantageous compact "cartridge"-like configuration of the sealing assembly 1 makes it possible, in other words, to define a sealing kit consisting of a single assembly made up of parts coupled together and which can be implemented in the relative wheel body by means of a single gearing operation.

[0081] In fact, it is sufficient to mesh the entire sealing assembly 1 (which, as mentioned above, already comprises the support bushing 13, the seals 10 and the retaining element 14 coupled to each other) on the stator element 3 or between the stator element 3 and the rotor element 4; during this meshing, the support portions 11 of the seals 10 are inserted with a fit into the radial annular space between the stator element 3 and the rotor element 4, sliding on the inner surface 4a of the rotor element 4 until the space 2 is reached.

[0082] In other words, once the predetermined axial position, namely the seat of the sealing structure 1, is reached, the support portions 11 are internally toothed in a rigid manner on the rotor element 4, whereas the sealing portions are free to slide in a fluid-tight manner on the bushing 13.

[0083] Therefore, the installation of assembly 1 takes place in a single gearing movement, rather than requiring multiple assembly operations for various separate parts, as is the case with known sealing assemblies for CTIS systems.

[0084] This results in significant savings in terms of time and costs, both during assembly and during maintenance and / or replacement of the structure or individual parts thereof.

[0085] Furthermore, the risk of installation errors is significantly reduced since operators only have to perform a single insertion of the entire structure 1, with the various elements already well positioned with respect to each other in their respective mutual nominal positions.

[0086] Finally, the seal 1 described and shown here may be subject to modifications and variations without, for this reason, going beyond the scope of protection set out in the appended claims.

[0087] In particular, a single sealing structure 1 could be implemented for a pair of “twin” wheel bodies on the same axle, namely sharing a hub (rotor element 4).

[0088] In this case, it is sufficient to provide a division of the conduit downstream of the sealing structure 1 (namely the movable portion 8 of the aforementioned circuit), for example by means of known valve means.

Claims

[1] Sealing structure (1) for sealing an annular space (2) formed between a stator element (3) and a rotor element (4) which is movable with respect to the stator element (3) with a rotational movement about an axis (A), wherein the sealing structure (1) is configured to allow the sealed passage of a fluid under pressure between the stator element (3) and the rotor element (4) through the annular space (2) and to prevent the passage of contaminants from an external environment (50) into the annular space (2); wherein the sealing structure (1) comprises: - an annular support bushing (13) configured to be integrally toothed on the stator element (3) and having an inner annular toothing surface (13a) and an outer annular sliding surface (13b); - a pair of annular sealing elements (10) arranged on axially opposite sides of the annular space (2) to seal the annular space (2) in a fluid-tight manner; wherein each sealing element (10) comprises a support portion (11) configured to be integrally coupled to the rotor element (4) and a sealing portion (12) carried by the support portion (11), arranged to bear in a fluid-tight manner against the outer surface (13b) of the support bush (13) and suitable to slide on the outer surface (13b) due to the rotational movement exerted by the rotor element (4) on the support portion (11); wherein the sealing assembly (1) further comprises an annular retaining element (14) securing the sealing elements (10) to one another and to the support bushing (13), thereby defining an assembly of parts coupled to one another in a detachable manner. [2] A sealing structure according to claim 1, wherein the support bushing (13) is configured to be toothed on the stator element (3) at its inner surface (13a) directly and without the interposition of parts. [3] A sealing structure according to claim 1 or 2, wherein each support portion (11) is configured to be coupled in a toothed manner to an inner annular surface (4a) of the rotor element (4) directly and without the interposition of parts. [4] Sealing structure according to one of the preceding claims, wherein the support bushing (13) comprises: - a rigid section (15) supporting the outer surface (13b) and defining a sliding bearing track for each sealing section (12); - an elastomeric portion (16) supporting the inner surface (13a) and mountable in a fluid-tight manner on the stator element (3). [5] Sealing structure according to one of the preceding claims, wherein the retaining element (14) is arranged on the annular space (2) and is arranged axially between the sealing elements (10); wherein the retaining element (14) has at least two retaining projections (17) extending in the axial direction from axially opposite sides of the retaining element (14) and each engaging a respective sealing element (10) to hold the sealing element (10) axially constrained with or without play on the retaining element (14). [6] Sealing structure according to claim 5, wherein each sealing element (10) comprises: - an annular support body (31) defining the support section (11); and - at least one sealing element (12a, 12b) defining the sealing section (12); wherein the annular body (31) and the sealing element (12a, 12b) cooperate to define an annular chamber (18) which is in fluid communication with the annular space (2) by means of at least one through-hole (19); wherein each retaining projection (17) engages with a respective through hole (19) to enclose the annular body (31) of the relative sealing element (10). [7] Sealing structure according to one of the preceding claims, wherein the support bush (13) comprises two annular half-profiles (20) which are axially adjacent to one another and are held in contact with one another by the holding element (14), each half-profile (20) receiving in radial sliding contact and on a part of the outer surface (13b) thereof the sealing portion (12) of a respective sealing element (10). [8] Sealing structure according to claim 5 or 6 and according to claim 7, wherein each half-profile (20) has an L-shaped cross-section and comprises a first axially aligned portion (21) and a second radially aligned portion (22), the second portion (22) defining an axial abutment for the other half-profile (20), each half-profile (20) being pushed axially towards the axial abutment of the other half-profile (20) by engagement of the retaining projection (17) in the respective through-hole (19) and by the axial thrust exerted by the sealing portion (12) sliding on the half-profile (20). [9] Sealing structure according to one of the preceding claims, wherein the retaining element (14) is arranged on the annular space (2) and is arranged axially between the sealing elements (10); and wherein the retaining element (14) comprises a series of axial ribs (23) angularly distributed around the axis (A) and projecting from axially opposite sides of the retaining element (14) to respectively face one of the sealing elements (10) or the other sealing element (10); wherein the support portion (11) of each sealing element (10) is arranged to abut axially against respective ribs (23). [10] Sealing assembly according to any one of the preceding claims, wherein the sealing elements (10), the support bushing (13) and the retaining element (14) define parts, which are connected to one another in a detachable manner, of a sealing assembly (100) which is attachable by means of a single gearing operation between the stator element (3) and the rotor element (4) in order to seal the annular space (2) defined between them.

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