Bearing arrangement with integrated electrical insulation, in particular for electric motor or machine
By designing insulating sleeves and insulating liners in the bearing assembly, the problem of separation between current-damaged components and insulating liners in electric motors is solved, achieving economical and reliable electrical insulation effects and reducing machining time and weight.
Patent Information
- Application Number
- CN202510963522.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-07-22
- Filing Date
- 2025-07-14
- Publication Date
- 2026-01-23
AI Technical Summary
Existing rolling bearings in electric motors or machines suffer from damage and vibration problems due to current flow caused by potential differences. Furthermore, hybrid rolling bearings are costly and carry the risk of separation between the insulating liner and the outer ring, resulting in designs that are neither economical nor reliable.
Design a bearing assembly including an insulating sleeve and an insulating liner, the insulating liner being overmolded onto a second ring and a housing, a strong bond being ensured by end face offset and locking structure, using synthetic or elastomeric materials to reduce temperature sensitivity, and the housing being made of a metal material for easy machining.
This achieves a robust bond between the insulating liner and the second ring in the bearing assembly, reducing machining time and weight, lowering costs, and simultaneously improving the reliability and resistance to temperature changes of the assembly.
Smart Images
Figure CN121382797A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present invention relates to the field of bearings, in particular bearings used in electric motors, electric machines and associated equipment. BACKGROUND
[0002] In an electric motor or machine, at least one rolling bearing is mounted between the housing of the electric motor or electric machine and a rotating shaft, in order to support this shaft.
[0003] During operation, when the shaft rotates, a potential difference can appear between the shaft and the housing of the electric motor or electric machine, thus creating an electric current between the inner ring (rigidly fixed to the shaft) and the outer ring (rigidly fixed to the housing) of the rolling bearing.
[0004] The electric current flowing through the constituent parts of the rolling bearing can damage these constituent parts, in particular the rolling elements and the raceways formed on the inner and outer rings. Discharges can also cause vibrations.
[0005] To remedy these drawbacks, it is known in practice to replace the rolling elements of the bearing, initially made of the same steel as the inner and outer rings, with rolling elements made of ceramic. This type of bearing is generally referred to as a hybrid rolling bearing.
[0006] However, this type of hybrid rolling bearing is relatively expensive.
[0007] To further remedy the aforementioned drawbacks, it is also known in practice to equip the outer ring of the rolling bearing with an insulating sleeve comprising a socket and an insulating liner made of electrically insulating material and interposed radially between the outer ring and the socket.
[0008] In order to fix the insulating liner to the outer ring and the socket without the need for additional constituent parts or specific machining of the outer ring, the insulating liner can be overmoulded.
[0009] However, with this type of solution, relative separation of the insulating liner from the outer ring can occur during operation.
[0010] The present invention therefore aims to remedy the aforementioned drawbacks by providing a bearing device that is simple and economical to design. SUMMARY
[0011] The present invention relates to a bearing device comprising a bearing provided with a first ring and a second ring that can rotate relative to each other.
[0012] The device also comprises at least one insulating sleeve mounted on the second ring of the bearing. The insulating sleeve has a socket and an insulating liner interposed radially between the second ring of the bearing and the socket. The insulating liner is made of an electrically insulating material.
[0013] The socket comprises an outer surface delimiting a radial thickness of the socket and an inner surface opposite the outer surface. The socket also comprises a first end face and a second end face delimiting an axial length of the socket.
[0014] The second ring comprises an outer surface delimiting a radial thickness of the second ring and an inner surface opposite the outer surface. The second ring also comprises a first end face and a second end face delimiting an axial length of the second ring.
[0015] The insulating liner is overmolded on at least one of the outer surface and the inner surface of the second ring and on at least one of the outer surface and the inner surface of the socket.
[0016] The first end face of the second ring and the first end face of the socket are axially offset on a first side relative to a median radial plane of the device. The second end face of the second ring and the second end face of the socket are axially offset on a second side relative to the median radial plane.
[0017] According to one general feature, the first end face of the second ring is axially offset relative to the first end face of the socket towards an inner side of the device.
[0018] According to another general feature, the second end face of the second ring is axially offset relative to the second end face of the socket towards an inner side of the device.
[0019] According to yet another general feature, the insulating liner is also overmolded on the first end face and the second end face of the second ring.
[0020] The overmolding of the insulating liner on these first and second end faces ensures a secure coupling with the second ring. The risk of relative movement between the insulating liner and the second ring in the axial direction, in particular in the event of temperature variations, is avoided. The term "axial direction" refers to a direction parallel to the axis of the bearing device.
[0021] Moreover, making the first and second end faces of the second ring each axially set back with respect to the first and second end faces of the seat reduces the machining time of the device, since only the end faces of the seat need to be ground. This also reduces the overall weight of the device, considering that the axial length of the second ring is shorter compared to the axial length of the seat.
[0022] The insulating liner is provided with first and second end faces delimiting the axial length of the liner.
[0023] According to a first design, at least one of the first and second end faces of the seat can be axially flush with one of the end faces of the insulating liner.
[0024] According to a second design, each of the first and second end faces of the seat is axially flush with one of the end faces of the insulating liner.
[0025] Alternatively, one or each of the end faces of the seat can be axially offset, either inwardly or outwardly, with respect to the associated end face of the insulating liner.
[0026] The first ring comprises first and second end faces delimiting the axial length of the first ring.
[0027] In one particular embodiment, the first and second end faces of the first ring can be respectively coplanar with the first and second end faces of the seat.
[0028] In one embodiment, the surface of the seat comprises at least one protuberance protruding radially on one side of the second ring.
[0029] In another embodiment, the seat is monobloc and comprises an axial portion delimiting the surface of the seat on which the insulating liner is overmoulded, and first and second flanges extending radially on one side of the second ring from the axial portion.
[0030] By "monobloc socket" is meant that the socket is made from one continuous piece. The socket is formed in one single part.
[0031] The insulating liner also covers the inner face of each of the first and second flanges of the seat. The second flange of the seat may extend radially beyond the second ring and cover the surface on which the insulating liner is formed. The first flange of the seat may be set back radially relative to the outer surface of the second ring.
[0032] In another embodiment, the seat is made of at least two separate parts. The two parts together define an axial portion that forms the surface of the seat overlying the insulating liner, and each part includes a flange extending radially from the axial portion on one side of the second ring. The insulating liner also overlying the inner surface of each flange of each of the two parts of the seat.
[0033] According to a particular design, the surface of the seat is provided with at least one groove extending in the circumferential direction, and locking ribs of the insulating liner having complementary shapes extend within the groove.
[0034] Therefore, the axial locking of the insulating liner on the socket is further enhanced.
[0035] "Circumferential direction" refers to the direction perpendicular to the axial direction and the radius of the bearing assembly; in other words, it is tangential to the circle centered on the axis of the bearing assembly.
[0036] If the insulating liner is made of synthetic or elastomeric materials, this makes the device less sensitive to temperature changes.
[0037] In one particular embodiment, the seat is made of a metallic material. Therefore, the seat can be easily machined to a predetermined radial tolerance. The seat is advantageously obtained from sheet metal blanks by cutting, pressing, and rolling.
[0038] In one embodiment, the insulating liner covers the entire surface of the seat. In this case, the insulating liner completely covers the surface of the seat in both the axial and circumferential directions.
[0039] According to the first design, the seat defines the outer surface of the device. In this case, the second ring is the outer ring of the bearing.
[0040] According to the second alternative design, the seat defines the inner surface of the device. In this case, the second ring is the inner ring of the bearing.
[0041] In one particular embodiment, the bearing comprises at least one row of rolling elements arranged between the raceway of the first ring and the raceway of the second ring. The rolling elements can be made of a metallic material.
[0042] The application also relates to an electric motor comprising a housing, a shaft and at least one bearing arrangement as defined above mounted radially between the housing and the shaft. BRIEF DESCRIPTION OF DRAWINGS
[0043] The application will be better understood by studying the detailed description of embodiments, provided by way of non-limiting example and illustrated by the attached drawings in which:
[0044] Figure 1 is an axial half-section view of a bearing arrangement according to an exemplary embodiment of the application, and
[0045] Figure 2 , Figure 3 , Figure 4 , Figure 5 is an axial half-section view of a bearing arrangement according to other exemplary embodiments of the application. DETAILED DESCRIPTION
[0046] Figure 1 The bearing arrangement shown comprises a bearing 10 provided with a first ring 12 and a second ring 14 able to rotate relative to each other about the axis X-X’ of the bearing. In the exemplary embodiment shown, the first ring 12 is the inner ring of the bearing and the second ring 14 is the outer ring.
[0047] The bearing arrangement is designed in a manner that does not conduct electric current. The bearing arrangement has integrated electrical insulation.
[0048] The inner ring 12 and the outer ring 14 of the bearing are concentric and extend in the axial direction along the axis X-X’ of the bearing. The rings are made of solid steel. The rings are solid.
[0049] In the embodiment shown, the bearing 10 also comprises a row of rolling elements 16, in this case balls, radially interposed between the inner ring 12 and the outer ring 14. The rolling elements 16 are made of steel. The bearing 10 also comprises a cage 17 for maintaining a regular circumferential spacing between the rolling elements 16. The bearing 10 can also be equipped with seals or sealing flanges.
[0050] The inner ring 12 comprises a cylindrical bore 12a, a cylindrical axial outer surface 12b opposite the bore in the radial direction, and first and second end faces 12c and 12d axially delimiting the bore and the outer surface in the radial direction. The bore 12a and the outer surface 12b delimit a radial thickness of the inner ring 12. The bore 12a forms an inner surface of the inner ring. The first and second end faces 12c and 12d delimit an axial length of the inner ring 12.
[0051] The inner ring 12 further comprises an inner raceway 18 for the rolling elements 16 formed on the outer surface 12b. The raceway 18 points radially outwards.
[0052] The outer ring 14 comprises a cylindrical axial outer surface 14a, a cylindrical bore 14b opposite the outer surface 14a in the radial direction, and first and second radial end faces 14c and 14d axially delimiting the bore 14b and the outer surface 14a. The outer surface 14a and the bore 14b delimit a radial thickness of the outer ring 14. The first and second faces 14c and 14d delimit an axial length of the outer ring 14.
[0053] The outer ring 14 further comprises an outer raceway 20 for the rolling elements 16 formed on the bore 14b. The raceway 20 points radially inwards.
[0054] The bearing arrangement further comprises an electrically insulating sleeve 26 mounted on the outer ring 14. The insulating sleeve 26 is mounted on the outer surface 14a of the outer ring 14. The insulating sleeve 26 is rigidly fixed to the outer ring 14.
[0055] The insulating sleeve 26 comprises a seat 28 and an insulating lining 30 radially interposed between the outer ring 14 and the seat 28. The insulating lining 30 is overmoulded on the outer ring 14 and the seat 28.
[0056] The seat 28 is annular. The seat 28 is monobloc. In the present case, the seat 28 is made in one piece. The seat 28 is preferably made of steel. Advantageously, the seat 28 can be obtained from a tube or from forged and / or rolled blanks, or also by stamping.
[0057] The seat 28 comprises a cylindrical annular axial outer surface 28a and a cylindrical annular axial bore 28b opposite the outer surface 28a in the radial direction. The bore 28b forms an inner surface of the seat 28. The bore 28b is oriented radially inwards, i.e. on the side of the outer ring 14 and of the insulating lining 30. The axis 25 of the bore 28b is coaxial with the axis X-X’.
[0058] The outer surface 28a and the bore 28b delimit a radial thickness of the seat 28. The outer surface 28a of the seat delimits an outer surface of the bearing arrangement 10. In other words, the outer surface 28a defines an outer diameter of the bearing arrangement 10.
[0059] The seat 28 also comprises opposite first and second radial end faces 28c, 28d which axially bound the bore and the outer surface of the seat. The end faces 28c, 28d bound the axial length of the seat.
[0060] The end face 14c of the outer ring and the end face 28c of the seat are axially located on a first side with respect to a median radial plane P of the device, and the end face 14d of the outer ring and the end face 28d of the seat are axially located on a second side, opposite the first side, with respect to said median radial plane P. Here, the median radial plane P passes through the center of the rolling element 16.
[0061] The end face 14c of the outer ring is axially offset towards the inside with respect to the end face 28c of the seat. The end face 14d of the outer ring is axially offset towards the inside with respect to the end face 28d of the seat. In other words, the end faces 14c and 14d of the outer ring are axially set back from the end faces 28c, 28d of the seat. The axial dimension of the outer ring 14 is less than the axial dimension of the seat 28.
[0062] The end face 14c of the outer ring is axially offset towards the inside with respect to the end face 12c of the inner ring. The end face 14d of the outer ring is axially offset towards the inside with respect to the end face 12d of the inner ring.
[0063] The insulating liner 30 is made of an electrically insulating material. The insulating liner 30 can for example be made of a synthetic material such as PEEK or PA46, or also of an elastomeric material, for example rubber.
[0064] The insulating liner 30 is interposed radially between the outer surface 14a of the outer ring and the bore 28b of the seat. The insulating liner 30 covers the outer surface 14a of the outer ring. In the present case, the insulating liner 30 covers the outer surface 14a of the outer ring with respect to the axial and circumferential directions. The insulating liner 30 also covers the end faces 14c, 14d of the outer ring.
[0065] The insulating liner 30 also covers the bore 28b of the seat. In this case ( / in the present case), the insulating liner 30 also completely covers the bore 28b, taking into account the axial and circumferential directions.
[0066] The insulating liner 30 is annular. The insulating liner 30 extends axially. The insulating liner 30 comprises a cylindrical axial outer surface 30a, a cylindrical bore 30b opposite the outer surface 30a in the radial direction, and first and second radial end faces 30c, 30d which axially bound the bore and the outer surface. The radial end faces 30c, 30d bound the insulating liner 30 in the axial direction. The outer surface 30a and the bore 30b bound the radial thickness of the insulating liner 30. The outer surface 30a is in radial contact with the bore 28b of the seat. The bore 30b is in radial contact with the outer surface 14a and the end faces 14c, 14d of the outer ring. The bore 30b has a stepped configuration.
[0067] The end face 14c of the outer ring is axially offset towards the inside with respect to the end face 30c of the insulating liner. The end face 14d of the outer ring is axially offset towards the inside with respect to the end face 30d of the insulating liner.
[0068] In the exemplary embodiment shown, the faces 30c, 28c and the faces 30d, 28d of the insulating liner and of the seat are respectively coplanar. Other configurations can be envisaged alternatively. For example, the seat 28 can axially protrude beyond the insulating liner 30 with respect to the faces 30c and 30d, or remain axially recessed from these faces.
[0069] In the exemplary embodiment shown, the faces 12c, 28c and the faces 12d, 28d of the inner ring and of the seat are respectively coplanar. Other configurations can be envisaged alternatively. For example, the seat 28 can axially protrude beyond the faces 12c and 12d of the inner ring, or remain axially recessed from these faces.
[0070] To manufacture the bearing device, the following procedure is followed.
[0071] In a first step, the seat 28 and the outer ring 14 of the bearing are installed inside a mold provided for overmolding the insulating liner 30.
[0072] Next, in a second step, the insulating liner 30 is overmolded on the outer ring 14 and on the seat 28.
[0073] Then, in a third successive step, the unitary assembly made of the outer ring 14, the seat 28 and the insulating liner 30 is extracted from the mold.
[0074] Next, in a fourth step, the end faces 28c, 28d of the seat are ground. At this stage, the outer surface 28a of the seat and the raceway 20 of the outer ring can also be ground.
[0075] Finally, in a fifth step, the unitary assembly made of the outer ring 14, the seat 28 and the insulating liner 30 is assembled with the row of rolling elements 16, the cage 17 and the inner ring 12.
[0076] Figure 2 The exemplary embodiment shown, in which identical elements have the same reference numerals, differs from the first example in that the hole 28b of the seat comprises a first protrusion 32 which protrudes towards the inside, i.e. in the direction of the insulating liner 30. The protrusion 32 protrudes with respect to the hole 28b. The protrusion 32 extends radially.
[0077] The protrusion 32 is located at one axial end of the hole 28b of the seat. The protrusion 32 extends radially inwards from the end face 28c of the seat. The outer face of the protrusion 32 is coplanar with the end face 28c.
[0078] In the illustrated embodiment, the bore 28b of the bushing further comprises, at the other axial end thereof, a second protrusion 34 protruding towards the inside, i.e. in the direction of the insulating liner 30. The protrusion 34 protrudes with respect to the bore 28b. The protrusion 34 extends radially. The protrusion 34 extends radially inwards from the end face 28d of the seat. The outer face of the protrusion 34 is coplanar with the end face 28d.
[0079] Figure 3 The illustrated exemplary embodiment, in which identical elements have identical reference numerals, differs from the preceding example in that the seat 28 is obtained from a sheet metal blank by cutting, pressing and rolling. The seat 28 is monobloc.
[0080] In this example, the seat 32 comprises an axial portion 36a and a first annular radial flange 36b and a second annular radial flange 36c each extending radially inwards from the axial portion. Each flange 36b, 36c extends radially. Each flange 36b, 36c extends from an axial end of the axial portion 36a. In the illustrated exemplary embodiment, the flanges 36b, 36c are annular. Alternatively, at least one of the flanges 36b, 36c can be implemented as sectors spaced apart from each other in the circumferential direction.
[0081] The end face 28c of the seat is delimited by the flange 36b, and the end face 28d is delimited by the flange 36c. More precisely, the end face 28c is delimited by the outer face of the flange 36b, and the end face 28d is delimited by the outer face of the flange 36c. The insulating liner 30 also covers the inner face of each flange 36b, 36c of the seat. The inner and outer faces opposite each other in the axial direction delimit the axial thickness of each flange 36b and 36c. For each flange 36b and 36c, the inner face is oriented in the axial direction towards the inside of the device, and the outer face is oriented in the axial direction towards the outside of the device. The insulating liner 30 also covers the free end of each flange 36b, 36c of the seat.
[0082] The flange 36b of the seat extends radially beyond the outer surface 14a of the outer ring, i.e. the flange 36b of the seat protrudes radially inwards with respect to the outer surface 14a. In other words, the free end of the flange 36b is offset radially inwards with respect to the outer surface 14a of the outer ring.
[0083] The flange 36c of the seat recedes radially from the outer surface 14a of the outer ring. In other words, the free end of the flange 36b is offset radially outwards with respect to the outer surface 14a of the outer ring. The flanges 36b, 36c are axially spaced apart from the outer ring 14.
[0084] Figure 4The exemplary embodiment shown, in which identical elements have identical reference numerals, differs from the preceding example mainly in that the seat 28 is made of two distinct parts 38 and 40. These two separate parts 38, 40 form half-flanges bearing against each other (in this case, bearing against each other in the axial direction). In the exemplary embodiment shown, the parts 38 and 40 of the seat are identical and symmetrical with respect to the median radial plane P of the device, in order to reduce manufacturing costs. Alternatively, of course, asymmetrical parts 38 and 40 can be envisaged. In another variant, it can be envisaged that the seat 28 is made of more than two parts. The parts 38, 40 of the seat 28 are preferably made of steel. Advantageously, the parts 38, 40 can be obtained from sheet metal by cutting, stamping and rolling. Each part 38 or 40 of the seat delimits a portion of the axial portion 36a and comprises one of the flanges 36b or 36c.
[0085] In the exemplary embodiment shown, the radial flanges 36b, 36c of the seat extend radially beyond the outer surface 14a of the outer ring.
[0086] The bore of the axial portion 36a of the seat is provided with two slots 42, 44 spaced apart in the axial direction, the slots 42, 44 extending in the circumferential direction around the axis 25 of the bore of the seat. Each slot 42, 44 is oriented radially on one side of the outer ring 14 (i.e. radially towards the inside). The slot 42 is formed on the part 38 of the seat, and the slot 44 is formed on the part 40.
[0087] In the exemplary embodiment shown, each slot 42, 44 is annular. Alternatively, at least one of the two slots 42, 44 can extend by less than 360°, or at least one of the two slots 42, 44 can also be formed by a succession of spiral segments extending in the circumferential direction and spaced apart from each other in the circumferential direction.
[0088] Each slot 42, 44 is delimited in the axial direction by two lateral flanks facing each other, the two lateral flanks having a straight profile in axial section and being connected to each other by an axial base. Alternatively, other shapes can also be envisaged, for example a slot with a cross-section having a circular arc profile oriented towards the inside.
[0089] The insulating liner 30 also comprises two ribs 46 and 48 extending radially outwardly from the outer face 30a, each rib 46 and 48 being housed in one of the slots 42 and 44 in the seat. The ribs 46, 48 are complementary in shape to the corresponding slots 42, 44. Each rib 46, 48 protrudes from the outer face 30a of the insulating liner. Each rib 46, 48 is formed on the outer face 30a during overmolding of the insulating liner 30.
[0090] Figure 5 The exemplary embodiment shown, in which identical elements have identical reference numerals, differs from the preceding example mainly in that the outer ring 14 has an increased axial dimension.
[0091] The axial dimension of the outer ring 14 remains less than the axial dimension of the seat 28. The end face 14c of the outer ring remains offset axially inwardly relative to the end face 28c of the seat. The end face 14d of the outer ring remains offset axially inwardly relative to the end face 28d of the seat.
[0092] In the exemplary embodiment shown, a recess 50 is formed in the end face 14c of the outer ring. The recess 50 is oriented and opened axially outwardly from the outer ring. The recess 50 has a bottom offset axially inwardly relative to the rest of the end face 14c. The bottom of the recess 50 forms a shoulder. In order to facilitate manufacture, in this case the bottom of the recess 50 extends radially. In this embodiment, the recess 50 is annular. The flange 36b of the seat extends partially into the recess 50 while remaining spaced apart from the outer ring 14.
[0093] Likewise, a recess 52 is formed in the end face 14d of the outer ring. The recess 52 is oriented and opened axially outwardly from the outer ring. The recess 52 has a bottom offset axially inwardly relative to the rest of the end face 14d. The bottom of the recess 52 forms a shoulder. In this case, the bottom of the recess 52 extends radially. Here, the recess 52 is annular. The flange 36c of the seat extends partially into the recess 52 while remaining spaced apart from the outer ring 14. The recesses 50 and 52 are symmetrical relative to a radial midplane of the outer ring. The recesses 50, 52 delimit the outer face 14a axially. The insulating liner 30 covers both recesses 50 and 52 of the outer ring.
[0094] In the exemplary embodiment shown, the first ring 12 of the bearing is the inner ring and the second ring 14 on which the insulating liner 30 is overmolded is the outer ring.
[0095] As an alternative, an opposite configuration can be provided, in which the second ring 14, on which the insulating liner 30 is overmoulded, is the inner ring. In this case ( / in this case), the insulating sleeve is located inside the bore 12a of the inner ring. The insulating liner is then radially interposed between the bore 12a of the inner ring and the outer surface of the seat. The insulating liner is overmoulded at least on the inner surface of the inner ring and at least on the outer surface of the seat. The bore of the seat defines the bore of the bearing device.
[0096] In the exemplary embodiments described, the bearing of the device is provided with a single row of rolling elements. As a variant, the bearing can be provided with multiple rows of rolling elements. Furthermore, the rolling bearing can comprise a type of rolling element other than balls, such as for example rollers. In another variant, the bearing can be a sliding bearing without rolling elements.
Claims
1. A bearing assembly comprising a bearing (10) and an insulating sleeve (26), the bearing (10) having a first ring (12) and a second ring (14) rotatable relative to each other, the insulating sleeve (26) being mounted on the second ring (14) of the bearing and having a seat (28) and an insulating liner (30) radially between the second ring (14) and the seat (28), the insulating liner being made of an electrically insulating material, the seat including an outer surface (28a) defining the radial thickness of the seat and an inner surface (28b) opposite to the outer surface, and a first end face (28c) and a second end face (28d) defining the axial length of the seat, the second ring (14) including a radial thickness defining the second ring. The outer surface (14a) and the inner surface (14b) opposite to the outer surface, and the first end face (14c) and the second end face (14b) defining the axial length of the second ring, the insulating liner (30) being overmolded on at least one of the outer and inner surfaces of the second ring (14) and overmolded on at least one of the outer and inner surfaces of the seat (28), the first end face (14c) of the second ring and the first end face (28c) of the seat being axially located on a first side relative to the intermediate radial plane (P) of the device, the second end face (14d) of the second ring and the second end face (28d) of the seat being axially located on a second side relative to the intermediate radial plane (P), characterized in that, The first end face (14c) of the second ring is offset inward relative to the first end face (28c) of the seat in the axial direction, and the second end face (14d) of the second ring is offset inward relative to the second end face (28d) of the seat in the axial direction. The insulating liner (30) is also overmolded on the first end face (14c) and the second end face (14d) of the second ring.
2. The apparatus according to claim 1, characterized in that, The insulating liner (30) is provided with a first end face (30c) and a second end face (30d) defining the axial length of the liner, and at least one of the first end face (28c) and the second end face (28d) of the seat is axially flush with one of the end faces (30c, 30d) of the insulating liner.
3. The apparatus according to claim 2, characterized in that, Each of the first end face (28c) and the second end face (28d) of the seat is axially flush with one of the end faces (30c, 30d) of the insulating liner.
4. The apparatus according to any one of the preceding claims, characterized in that, The first ring (12) includes a first end face (12c) and a second end face (12d) that define the axial length of the first ring, and the surfaces are coplanar with the first end face (28c) and the second end face (28d) of the seat, respectively.
5. The apparatus according to any one of the preceding claims, characterized in that, The surface of the seat (28) includes at least one protrusion (32, 34) that protrudes radially on one side of the second ring (14).
6. The apparatus according to any one of claims 1 to 4, characterized in that, The seat (28) is a single piece and includes an axial portion (36a) and a first flange (36b) and a second flange (36c). The axial portion (36a) defines the surface of the seat over which the insulating liner (30) is formed. The first flange (36b) and the second flange (36c) extend radially from the axial portion on one side of the second ring (14). The insulating liner (30) also over-forms the inner surface of each of the first flange (36b) and the second flange (36c). The second flange (36c) of the seat extends radially beyond the surface of the second ring (14) over which the insulating liner (30) is formed. The first flange (36b) of the seat is radially recessed relative to the outer surface of the second ring.
7. The apparatus according to any one of claims 1 to 4, characterized in that, The seat (28) is made of at least two separate portions (38, 40) that together define an axial portion (36a) that forms the surface of the seat over which the insulating liner (30) is formed, and each portion includes a flange (36b, 36c) extending radially from the axial portion on one side of the second ring (14), the insulating liner (30) also overforming the inner surface of each flange (36b, 36c).
8. The apparatus according to any one of the preceding claims, characterized in that, The seat (28) is made of metal.
9. The apparatus according to any one of the preceding claims, characterized in that, The insulating lining (30) is made of synthetic or elastomeric materials.
10. An electric motor comprising a housing, a shaft, and at least one bearing assembly according to any one of claims 1 to 8, the at least one bearing assembly being radially mounted between the housing and the shaft.