Earing unit provided with a sealing device

Abstract

Bearing unit (30) having a central axis of rotation (X) and having: - a radially outer ring (31), - a radially inner ring (34), a sealing device (50) provided with a shaped annular shield (60) mounted on the radially outer ring (31), and an annular sealing element (70) made of elastomeric material, which is integrally supported by the shield (60), wherein the shield (60) has: - a thickness between 0.25 mm and 0.35 mm, - a radially external anchoring portion (61), which is housed with interference in the groove (31a) and has an external mounting surface (62a, 69a, 63a) provided with a plurality of surface reliefs (80), - a radially internal flange portion (65) provided with a plurality of circumferentially distributed circular sector-shaped recesses (68), and - an elbow (66) provided with a plurality of circumferentially distributed hollows (67).

Description

[0001] BEARING UNIT PROVIDED WITH A SEALING DEVICE DESCRI PTIO N

[0002] Technical Field of the Invention

[0003] The present invention relates to a bearing unit provided with a sealing device and preferably, but not exclusively, applicable in all agricultural applications that may involve relatively high stresses.

[0004] Prior Art

[0005] Known bearing units comprise an outer ring and an inner ring that rotate relative to each other by virtue of the interposition of a ring of rolling bodies, and are also provided with a respective sealing device interposed between the two rings to protect the bearing units from the entry of external contaminants.

[0006] According to the prior art, the sealing device comprises, for each side of the bearing unit, a metal shield anchored to the outer ring, and an elastomeric body connected to the shield by vulcanization so as to form a single body with the shield itself. The shield is interference-fitted into a housing groove formed internally in the radially outer ring, while the elastomeric body is provided with at least one radially inner lip, which can be in contact to provide a sliding contact on the radially inner ring of the bearing unit, ensuring sealing with respect to the latter.

[0007] Another important function of a sealing device is to prevent the leakage of lubricants present inside the bearing unit. Lubricating grease retention is a very important feature of bearing units for agricultural applications: sufficient lubrication must be ensured even in environments where very severe contaminants are present.

[0008] In addition, as already mentioned, bearing units for agricultural applications which are subjected to high loads are designed to operate in the presence of dust, mud and in any case in highly contaminated environments. Due to the high loads, the shields of known sealing devices do not have the ability to remain firmly anchored in the bearing unit seat, compromising their sealing performance. However, highly contaminated environments make it essential for the seals of bearing units for agricultural applications to have optimum performance.

[0009] Known sealing devices can ensure good performance if provided with multiple contacting lips. However, this type of solution leads to an increase in friction losses and consequent power dissipation.

[0010] Ultimately, the technical problems to be solved are:

[0011] - the anchoring capacity of the shield of the sealing device in its anchoring seat in the bearing unit,

[0012] - sealing with respect to external contaminants so as not to reduce the service life of the bearing units and sealing of the lubricating grease inside the bearing unit,

[0013] - friction losses due to the contacting lips.

[0014] Summary of the Invention

[0015] To substantially solve the technical problems presented above, the present invention discloses a bearing unit provided with a high-performance sealing device with optimized shape and geometry.

[0016] Thus, according to the present invention, a bearing unit is provided that is equipped with a sealing device and has the characteristics laid out in the independent claim.

[0017] Further preferred and / or particularly advantageous embodiments of the invention are described according to the characteristics laid out in the attached dependent claims.

[0018] Brief Description of the Drawings

[0019] The invention will now be described with reference to the appended drawings, which illustrate a non-limiting implementation example thereof, in which:

[0020] - Figure 1 is a schematic representation of a bearing unit provided with a sealing device, according to a preferred embodiment of the present invention, - Figure 2 illustrates the sealing device shown in Figure 1,

[0021] - Figure 3 is an axonometric detail view of the shield of the sealing device shown in Figure 1, and

[0022] - Figure 4 is a detail illustrating a sealing lip of the sealing device shown in Figure 1.

[0023] Detailed description

[0024] With reference to Figure 1, 30 indicates a bearing unit as a whole, having an axis of rotation X and comprising:

[0025] - a radially outer ring 31, provided internally and towards the axis X with at least one annular, shaped anchoring groove 31a,

[0026] - a radially inner ring 34,

[0027] - a plurality of rolling bodies 32, in this example balls, interposed between the outer ring 31 and the inner ring 34,

[0028] - a cage 38 for containing and retaining the rolling bodies 32.

[0029] According to the preferred embodiment of the present invention described herein, the outer ring 31 is a stationary ring, while the inner ring 34 is a ring rotating about the axis X.

[0030] Throughout the present description and in the claims, terms and expressions indicating positions and orientations such as "radial" and "axial" are understood to refer to the central axis of rotation X of the bearing unit 30.

[0031] Expressions such as "axially external" and "axially internal" refer, rather, to the mounted condition of the sealing device in the bearing unit and, in this case, preferably refer to one side of insertion of the sealing device into the housing groove of the outer ring and, respectively, to a side opposite the insertion side.

[0032] The outer ring 31 and the inner ring 34 define between them a cavity 35 which, if not shielded, would allow contaminants and impurities to enter the bearing unit 30.

[0033] The sealing device 50 is shown in Figure 1 in a deformed state, i.e. after being mounted in the housing groove 31a of the outer ring 31, while in Figure 2 it is shown in its undeformed state, isolated from the bearing.

[0034] The housing groove 31a is provided with a toroidal bottom surface 31c and two side surfaces 31d, 31e, respectively axially internal and axially external.

[0035] The sealing device 50 comprises, for each side of the bearing unit: - a shaped annular shield 60, which is preferably made of sheet metal, with a standard thickness of about 0.5 mm so as to be sufficiently rigid, and is mounted in the outer ring 31. Thus, the shield 60 and, consequently, the sealing device 50 are stationary;

[0036] - an annular sealing element 70, made of elastomeric material, integral with the shield 60 and axially internal with respect thereto.

[0037] The shield 60 comprises:

[0038] - a radially external anchoring portion 61 for interference fitting into groove 31a of the radially outer ring 31,

[0039] - a radially internal flange portion 65, and

[0040] - an intermediate conical portion 64,

[0041] - an elbow 66 connecting the intermediate portion 64 to the flange portion 65.

[0042] According to the present invention, the thickness of the metal sheet of the shield 60 is reduced by 40% relative to known solutions: from a thickness of 0.5 mm to a thickness of between 0.25 mm and 0.35 mm, preferably equal to 0.3 mm. The reduction in thickness makes the shield more flexible and therefore facilitates anchoring in the groove of the outer ring. Finally, the reduction in shield thickness means that there is more volume available for lubricating grease between the rings and the sealing device.

[0043] To simultaneously ensure optimum rigidity, the shield 60 has additional features that compensate for the reduction in thickness by increasing its rigidity.

[0044] With reference to Figure 3, a first feature is that the flange portion 65 has a plurality of recesses 68 in the form of circular sectors arranged in a circumferential direction. In particular, the recesses 68 are made by plastic deformation of the flange portion 65 and are uniformly distributed around the axis X, each of which being delimited by an upper radial edge 681, a lower radial edge 682 and two lateral edges 683. The upper radial edges 681 are arranged on the same circumference Cl, centred on the axis X, and the lower radial edges are arranged on the same circumference C2, also centred on the axis X, but with a smaller diameter than circumference Cl. The recesses 68 also have a back wall 684, which define circular sectors in relief on side 65a, opposite the side on which the recesses 68 themselves open, i.e. on the side of the shield on which the sealing element 70 is applied. By virtue of the formation of the edges 681, 682, 683, the recesses 68 make the shield 60 more rigid, compensating for the reduction in thickness.

[0045] Alternatively, the plurality of recesses 68 can be made:

[0046] - with circular sectors in relief axially inwards, i.e. on the side of the sealing element 70, as in the example shown in Figure 3,

[0047] - with circular sectors in relief axially outwards, i.e. on the side opposite the sealing element 70,

[0048] - with alternating circular sectors in relief on the side of the sealing element 70 and on the opposite side.

[0049] A second feature intended to compensate for the reduction in thickness of the shield 60 and to increase its rigidity is found in the fact that the elbow 66 of the shield 60 has a plurality of hollows 67 positioned in the circumferential direction. In particular, the plurality of hollows 67 is formed on an axially external surface 66a of the elbow 66, i.e. on the side opposite to the sealing element.

[0050] Advantageously, the hollows 67 are arranged in an intermediate position between the side edges 683 of two contiguous recesses 68.

[0051] The presence of the recesses 68 and hollows 67 improves the adhesion of the sealing element 70 material, as recesses and hollows increase the contact surface between the shield and the rubber. Preferably, the shield 60 is coated with adhesive material and, therefore, this increase in contact surface is beneficial to the stability of the connection between the elastomer and the metal.

[0052] Regarding Figure 2 once again, the anchoring portion 61 in turn comprises a conical annular portion 62, a flange portion 63 and a curvilinear portion 69, connecting the annular portion 62 and the flange portion 63. An elbow 64' connects the flange portion 63 to the intermediate portion 64. The housing groove 31a is shaped so that, when the shield 60 is inserted into the housing groove 31a, the shield itself deforms and its anchoring portion 61 adopts a substantially "hook"-like configuration, complementary to the shape of the anchoring groove 31a. In this "hook" configuration, the annular portion 62 is adjacent to the flange portion 63, also adopting a substantially flange-like configuration. When the shield 60 is inserted into the groove 31a, the curvilinear portion 69 and the elbow 64' undergo elastic deformation that would tend to return the annular portion 62 and the flange portion 63 to their undeformed state. This does not occur due to the blocking of the housing groove 31a by the lateral surface 31d which is axially internal with respect to the annular portion 62 and by the lateral surface 31e which is axially internal with respect to the flange portion 63.

[0053] Both the annular portion 62 and the flange portion 63 and the curvilinear connecting portion 69 have respective surfaces 62a, 63a, 69a which, when in use, together form a mounting surface in contact with the bottom surface 31c of the groove 31a. More precisely: surface 62a is the radially external surface of annular portion 62 and extends in the axial and tangential directions over the entire annular portion 62; surface 63a is the axially internal surface of flange portion 63 and extends in the radial and tangential directions over the entire flange portion 63; similarly, surface 69a is the radially external and axially internal surface of connecting portion 69 and extends in the axial, radial and tangential directions over the entire connecting portion 69. These surfaces 62a, 63a and 69a are provided with surface reliefs 80 of a specific shape to increase the friction coefficient of the surface and to enhance the anti-slip properties of the shield inside the housing groove 31a. These surface reliefs 80 are thus made over the entire mounting surface of the anchoring portion 61 of the shield 60 in the "hook" configuration described above, thus forming part of the means for anchoring the shield 60 in the housing groove. Preferably, the reliefs 80 have an axial development, thus being even more effective in preventing accidental rotation between the shield and the housing groove of the outer ring as they are transverse to the direction of potential relative movement between the shield and the housing groove.

[0054] To ensure greater adhesion of the sealing element 70 to the shield 60, the surface reliefs 80 also extend beyond the anchoring portion 61, in an internal radial direction, affecting an annular and axially external surface 60' of the shield 60, in contact with the sealing element 70. The covering by the reliefs 80 of the interface area between the shield 60 and the sealing element 70 has the effect of increasing the contact surface between the two components. As already mentioned, the shield 60 is, in fact, completely coated with adhesive material to allow it to bond with the elastomeric sealing element 70 during the vulcanization process inside the mould.

[0055] Preferably, the reliefs 80 are made by stamping, a metal compression moulding operation that generates different thicknesses and shapes on the worked object.

[0056] Still for the purpose of improving the anchoring in the groove 31a of the outer ring 31, the annular portion 62 has, under undeformed conditions and unlike known solutions, a taper angle a relative to the axial direction of the axis of rotation X. The angle a is at least 30° so as to allow a better grip on the surface 62a of the annular portion 62 by the tool dedicated to inserting the shield 60 into the housing groove 31a.

[0057] The annular portion 62 and the connecting portion 69 also have an overall length L in the axial direction to avoid interference with the intermediate portion 64 of the shield 60 after the sealing device has been anchored in the groove 31a of the outer ring 31.

[0058] The sealing element 70 covers, as described previously, the side of the shield facing the inside of the bearing unit and, proceeding in the radial direction, from the outside towards the inside and towards the axis X, has a mean axial thickness of increasing dimensions. With reference to the shield 60 and starting from the anchoring portion 61, the sealing element 70 comprises a first flange portion 71 arranged on part of the anchoring portion 61 of the shield 60 and extending radially outwards until it protrudes with its radially outer end portion 710 inside the anchoring groove 31a. When in use, the end portion 710 will thus be compressed by the anchoring portion 61 of the shield 60 in the groove 31a so as to create a seal with respect to the lubricating grease. For this purpose, with respect to the axis of rotation X, the radius R.1 of a cylindrical and radially outer surface 71a of the first flange portion 71 must be greater than the radius R.2 of a cylindrical and radially internal surface 31b of the radially outer ring 31.

[0059] Still proceeding in the radial direction, from the outside towards the inside and towards the axis X, the sealing element 70 also comprises a conical portion 72, arranged on the intermediate portion 64 of the shield 60, a second flange portion 73 and a sealing portion 74, both arranged on the second flange portion 65 of the shield 60.

[0060] With reference also to Figure 4, the sealing element 70 also comprises a contacting lip 75 which extends from the sealing portion 74 in a radially inward and axially outward direction and interacts slidably with the inner ring 34 by means of a contact profile 76. The lip 75 is delimited with respect to the sealing portion 74 by an external convex surface 75a having a radius of curvature R.3 and by an internal concave surface 75b having a radius of curvature R.4, and is inclined with respect to the axis of rotation X so as to converge towards the axis X on the side facing the shield 60.

[0061] The contacting lip 75 has the following characteristics:

[0062] - the radius of curvature R.4 must be equal to 2 / 5 of the thickness SI of the lip 75, while the radius of curvature R3 must be equal to the sum of the radius of curvature R4 and the thickness SI of the lip 75;

[0063] - the contact profile 76 of the lip 75 and the interference values between the lip 75 and the radially inner ring 34 have been optimized to ensure that the lip makes sliding contact with the inner ring substantially along a circumference and not along a circular surface, thus developing maximum contact pressure with minimum friction. This affords reduced power losses and improved sealing performance.

[0064] Furthermore, the distance A between an internal conical surface 75c of the lip 75 and an axially internal and radially internal edge V of the flange portion 65 and the distance S between a radially internal cylindrical surface 65a of the flange portion 65 and a radially internal cylindrical surface 74a of the sealing portion 74 should advantageously result in the following relationship:

[0065] A > S

[0066] so as to ensure that the lip 75 does not come into contact with the metal shield 60 when mounted in the bearing unit. In addition, this condition has the effect of increasing the resistant section in the mould, which means less risk of breakage of the forming tool and better technological feasibility.

[0067] Ultimately, the bearing unit provided with the sealing device according to the invention has the following advantages:

[0068] - shield rigidity equal to or greater than that of known solutions of greater thickness, by virtue of the presence of rigid ifying recesses and hollows, - reduced production costs by virtue of the reduced amount of metal material, - a greater volume available for lubricating grease,

[0069] - improved anti-rotation anchoring system by virtue of the introduction of the anti-slip surface reliefs,

[0070] - lower friction losses in the sealing device by virtue of optimization of the sealing lip interference,

[0071] - improved sealing performance by virtue of increased contact pressure of the sealing lip itself,

[0072] - optimized sealing to prevent leakage of grease from the groove of the sealing device of the outer ring.

[0073] In addition to the embodiment of the invention as described above, it should be understood that numerous other variations exist. It should also be understood that these embodiments are merely illustrative and do not limit the scope of the invention, its applications, or its possible configurations. On the contrary, although the above description allows a person skilled in the art to work the present invention at least according to one exemplary embodiment thereof, it should be understood that many variations of the described components are possible without departing from the scope of the invention as defined in the attached claims, which are interpreted literally and / or according to their legal equivalents.

Claims

CLAIMS1. Bearing unit (30) having a central axis of rotation (X) and comprising: - a radially outer ring (31) internally provided with a shaped anchoring groove (31a) ,- a radially inner ring (34) defining, with the radially outer ring (31), a cavity (35),- a plurality of rolling bodies (32) interposed between the radially outer ring (31) and the radially inner ring (34), and- a sealing device (50), which is housed in the cavity (35) and includes, in turn, a shaped annular shield (60) and an annular sealing element (70) made of elastomeric material, integral with the shield (60),the bearing unit (30) being characterized by the fact that the shield (60) has a thickness between 0.25 mm and 0.35 mm, and includes, in turn:- a radially external anchoring portion (61), which is housed with interference in the groove (31a) and is externally delimited by an external mounting surface (62a, 69a, 63a); the external mounting surface (62a, 69a, 63a) being provided with a plurality of surface reliefs (80) to increase a friction coefficient of the external mounting surface itself with the shaped anchoring groove (31a) and to increase the anti-slip properties of the shield (60) inside the shaped anchoring groove (31a),- a radially internal flange portion (65) provided with a plurality of circumferentially distributed recesses (68), andan elbow (66), provided with a plurality of circumferentially distributed hollows (67) to confer structural rigidity to the shield (60) together with the recesses (68) of the flange portion (65).

2. Bearing unit according to claim 1, wherein each recess (68) is delimited by an upper radial edge (681), a lower radial edge (682) and twolateral edges (683) and also has a back wall (684) which defines a circular sector in relief on one side (65a) of the shield (60).

3. Bearing unit according to claim 2, wherein the plurality of recesses (68) is configured to create circular sectors in relief on the side of the sealing element (70).

4. Bearing unit according to claim 2, wherein the plurality of recesses (68) is configured to create circular sectors in relief on the side opposite the sealing element (70).

5. Bearing unit according to claim 2, wherein the plurality of recesses (68) is configured to create circular sectors in relief alternating from the side of the sealing element (70) and from the opposite side.

6. Bearing unit according to claim 1, wherein the plurality of hollows (67) is located on an axially external surface (66a) of the elbow (66).

7. Bearing unit according to claim 6, wherein the hollows (67) are arranged in an intermediate position between the lateral edges (683) of two contiguous recesses (68).

8. Bearing unit according to claim 1, wherein a surface (60') of the shield (60) in contact with the sealing element (70) is also provided with the plurality of surface reliefs (80) to increase the coefficient of friction between the shield (60) and the sealing element (70).

9. Bearing unit according to one of the preceding claims, wherein the anchoring portion (61) includes an annular conical portion (62), a flange portion (63) and a curvilinear portion (69), connecting the annular portion (62) and the flange portion (63).

10. Bearing unit according to one of the preceding claims, wherein the sealing element (70) comprises a radially internal, contacting sealing lip (75), which:- extends from a sealing portion (74) of the sealing element (70) in a radially internal and axially external direction,- is in sliding contact with the radially inner ring (34) by means of a contact profile (76),- is delimited, with respect to the sealing portion (74), by an external convex surface (75a) and an internal concave surface (75b), and- is arranged inclined with respect to the axis (X) of rotation so as to converge towards the axis (X) from the part facing the shield (60).

11. Bearing unit according to claim 9 or 10, wherein the sealing element (70) further has:- a first radially external flange portion (71), arranged on part of the anchoring portion (61) of the shield (60),- a conical portion (72), arranged on an intermediate portion (64) of the shield (60), and- a second flange portion (73) connecting with the sealing portion (74), arranged on a flange portion (65) of the shield (60).

12. Bearing unit according to claim 11, wherein the first flange portion (71) has a cylindrical and radially external surface (71a) having a radius (Rl) relative to the axis (X) of rotation greater than a radius (R2) of a cylindrical and radially internal surface (31b) of the radially outer ring (31).

13. Bearing unit according to claim 10, wherein the internal surface (75b) of the lip (75) has a radius of curvature (R4) equal to 2 / 5 of the thickness (SI) of the lip (75), while the external surface (75a) of the lip (75) has a radius of curvature (R3) equal to the sum of the radius of curvature (R4) and the thickness (SI) of the lip (75).

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