Sealing device for a rolling bearing and associated rolling bearing

Abstract

Sealing device (5) for a rolling bearing (1), including an annular support (15) and a sealing element (16) made of an elastomeric material and integral with the support; a radially outer annular portion (18) of the sealing element is shaped to mate fluid-tightly with the outer ring (2) of the bearing, and a radially inner annular portion (19) is provided with a first annular sealing lip (20) extending radially in cantilever from the support and mating with an exclusively radial sliding fluid-tight seal with a sealing surface (11) of a second annular seat (9) of the inner ring (3), with radial interference of between 1 and 3 hundredths of a mm; the first annular sealing lip having a constant axial thickness (S) and a radial cantilever length (L) from the support of between five and ten times its axial thickness.

Description

[0001] 1 202400206

[0002] SEALING DEVICE FOR A ROLLING BEARING AND ASSOCIATED ROLLING BEARING DESCRI PTIO N

[0003] Technical field of the invention

[0004] The present invention relates to a low-friction sealing device with high lubricating-grease retention for a rolling bearing, in particular for a high-speed optical encoder for machine tools. The invention also relates to an associated rolling bearing, equipped with such a sealing device.

[0005] Prior art

[0006] In the field of machine tools, and beyond, a rolling bearing can be used as part of a device for detecting the rotational speed (encoder) of a component of the machine tool, such as a spindle. The precision encoders normally used are optical encoders, which include at least one lens and one radiation emitter, such as a laser. Even a slight loss of lubricating grease from the rolling bearing can impair the functionality of the encoder, as it can be detrimental to the performance of the optical lenses. Furthermore, the encoder operates at high speed and therefore requires a rolling bearing with very low operating friction.

[0007] Similar requirements may also apply to other rolling bearing applications.

[0008] There is therefore a need in the sector for a sealing device for a rolling bearing, and an associated rolling bearing, in which the sealing device is shaped such that losses due to potential leaks are substantially zero and that operates with very low friction, for example 50% less than the known sealing devices commonly used in rolling bearings.

[0009] A further problem with the described rolling bearings is that unpredictable relative axial displacements of the order of tenths of a millimetre can occur between the inner and outer rings of the rolling bearing, which reduce sealing efficiency and reliability in known sealing devices.2 202400206

[0010] Summary of the invention

[0011] The purpose of the present invention is to provide a sealing device for a rolling bearing and an associated rolling bearing, in particular for use with a high-speed optical encoder for machine tools, are free from the technical problems in the prior art, and in particular exhibit low friction and high lubricating grease retention.

[0012] According to the present invention, a sealing device for a rolling bearing and an associated rolling bearing are provided with the features set out in the attached claims.

[0013] In particular, a sealing device with a single sliding annular sealing lip ensuring exclusively radial contact, making it insensitive to any axial movements of the inner ring of the bearing that may occur when in use, is provided. The lip also mates with a machined, preferably ground, surface of the inner ring of the bearing and has a constant thickness or axial width and a length of 5 to 10 times the axial width of the lip.

[0014] This provides a sealing lip that exhibits low deformation under all conditions and has linear contact, which minimizes the contact surface.

[0015] There may also be a second, non-contacting annular sealing lip which projects towards a shoulder of the sealing seat formed on the inner rings of the bearing.

[0016] Brief description of the drawings

[0017] The invention is described below with reference to the attached drawings showing a non-limiting example embodiment thereof, in which:

[0018] - Figure 1 schematically illustrates an elevation view in radial section of a rolling bearing according to the invention; and

[0019] - Figure 2 schematically illustrates, on an enlarged scale, a detail of figure 1 showing the shape and structure of the sealing device according to the invention, details of which are illustrated not to scale and for purely illustrative3 202400206

[0020] purposes.

[0021] Detailed description

[0022] With reference to figures 1 and 2, reference number 1 denotes as a whole a rolling bearing, in particular for use with an optical encoder for machine tools, which is known and not shown for simplicity.

[0023] The rolling bearing 1 (figure 1) comprises a radially outer ring 2, a radially inner ring 3, a plurality of rolling bodies 4 between the inner ring 3 and the outer ring 2 to make them relatively rotatable with low friction, and at least one sealing device 5 interposed between the inner ring 3 and the outer ring 2 (figure 1) at corresponding axial ends 6, 7 of the inner ring 3 and of the outer ring 2.

[0024] Since the rolling bearing 1 is symmetrical, only the half containing the ends 6 and 7 is shown, but it also comprises an opposite axial end (not illustrated) defined by the corresponding axial ends (not illustrated) of the inner ring 3 and the outer ring 2 opposite the ends 6 and 7, and is preferably provided with a second sealing device (not illustrated) mirror-symmetrical to the sealing device 5.

[0025] The axial end 7 of the outer ring 2 is provided with a first annular seat 8, which is known as a whole and shaped to receive, by means of static fluid-tight snap-fitting, the sealing device 5, which is constrained to rotate with the outer ring 2.

[0026] The axial end 6 (figures 1 and 2) is provided with a radial step consisting of a second annular seat 9 arranged in a position corresponding to the annular seat 8 and shaped, precisely, as a step.

[0027] The annular seat 9 is directly formed on a radially outer lateral surface 10 of the inner ring 3 and comprises an annular sealing surface 11, which is defined by a radially inner bottom lateral wall 12 of the annular seat 9, which is step-shaped, and an axial shoulder 13 defined by a terminal radial front face4 202400206

[0028] 13c of the seat 9. The axial shoulder 13 is therefore arranged substantially perpendicular to the annular sealing surface 11.

[0029] The sealing device 5 comprises a substantially rigid annular support 15, for example made of a metal, such as steel, suitably pressed, and an annular sealing element 16 made of an elastomeric material and that is integral with the metal support 15.

[0030] For example, the annular sealing element 16 may be joined to the support 15 by adhesive bonding during vulcanization and, in any case, the support 15 is at least partially embedded in the elastomeric annular sealing element 16.

[0031] The annular sealing element 16 comprises a radially outer annular portion 18 (figure 1) shaped to be fluid-tightly snap-fitted, in a substantially known manner, into the first annular seat 8 of the outer ring 2 of the bearing 1, and a radially inner annular portion 19 provided with a first annular sealing lip 20, said lip 20 extending radially in cantilever from and radially inside the support 15.

[0032] The radially outer portion 18 of the annular sealing element 16 forms a known static seal system with the seat 8 that seals the front of the outer ring 2.

[0033] The first annular sealing lip 20 is shaped to mate in use, fluid-tightly and in sliding contact, with the second annular seat 9 of the inner ring 3 of the bearing 1, in this case with the lateral annular sealing surface 11.

[0034] According to one aspect of the invention, the first annular sealing lip 20 is shaped to exert an exclusively radial sealing action on the second annular seat 9, in particular on the lateral annular surface 11, and is sized to achieve in use exclusively a predetermined radial interference I with an annular sealing surface 11 of the second annular seat 9.

[0035] The interference I is represented schematically and not to scale, for5 202400206

[0036] illustrative purposes only and for greater clarity, in figure 2, where the annular lip 20, which is elastically deformable, is shown in an undeformed state.

[0037] In combination with this first feature, the annular sealing lip 20 has a constant axial thickness or width S (figure 2) along the entire radial cantilever length L from the support 15.

[0038] According to a further aspect of the invention and in combination with the foregoing, the first annular sealing lip 20 has a radial cantilever length L from the support 15 which is much greater than its axial width or thickness S and which is equal to a multiple of the axial width or thickness S of the sealing lip 20 itself.

[0039] According to a preferred aspect of the invention, the annular sealing lip 20 has a radial cantilever length L from the support 15 which is approximately five to ten times greater than the axial width or thickness S of the lip 20 itself; in other words the following applies:

[0040] [1] L = 5-10 S

[0041] According to another significant aspect of the invention, the sealing device 5 also comprises a second annular sealing lip 21, shaped as a noncontacting lip that projects axially and radially in cantilever from the support 15 and, in use, towards the shoulder 13 of the second annular seat 9 formed on the inner ring 3 of the bearing 1.

[0042] The second annular sealing lip 21 extends obliquely in cantilever from an axially inner front face 22 of the annular support 15, which in use faces the inside of the rolling bearing 1 and therefore the rolling bodies 4, and forms an acute angle with the first annular lip 20 on the opposite side to the axially inner face 22 of the support 15.

[0043] Preferably, the face 22 is bare, not being embedded in the elastomeric sealing element 16, and the opposing radial end portions 18 and 19 of the sealing element 16 are radially cantilevered from opposing radially peripheral6 202400206

[0044] edges 23 of the annular support 15, so that the radial portions 18 and 19 are free of the support 15, which is not embedded therein, and are made only from elastomeric material. The radial portions 18 and 19 are thus partially free to undergo small elastic deformations when in use, for example caused by possible relative axial displacements of the rings 2 and 3, which may have an axial play of up to 1 / 10 millimetre between each other.

[0045] The first annular sealing lip 20 is V-shaped in radial section with its vertex turned towards the second annular lip 21, and is formed by a pair of annular radial arms 24 (figure 2) forming an obtuse angle with each other, so that the V formed by the lip 20 is very open.

[0046] A further aspect of the invention is that the radially inner annular portion 19 of the annular sealing element 16 is delimited, on the opposite side to the first annular sealing lip 20, by a front annular surface 25 arranged obliquely to the annular support 15 and projecting obliquely in cantilever from the annular support 15.

[0047] From the annular surface 25, the second annular sealing lip 21 projects axially and radially in cantilever from the annular support 15, and at substantially the same angle as the surface 25, forming said acute angle with the annular lip 20 immediately adjacent thereto.

[0048] According to a significant aspect of the invention, the annular surface 25 of the radially inner annular portion 19 of the annular sealing element 16 is provided with a plurality of annular undulations 26, specifically at least two or three, arranged axially in series between the annular support 15 and the second annular sealing lip 21.

[0049] According to an important aspect of the invention, the annular sealing surface 11 is a machined surface, preferably ground, and is shaped to mate slidingly with the first annular lip 20 resulting in an exclusively radial hydraulic seal therewith.7 202400206

[0050] According to one aspect of the invention, the first annular lip 20 and the annular sealing surface 11 of the second annular seat 9 are mated with each other with a predetermined radial interference I of between 4 and 7 hundredths of a millimetre.

[0051] Furthermore, the second annular lip 21 of the annular sealing element 16 extends to an edge 27 (figure 2) of the second annular seat 9 which separates the axial shoulder 13 from the radially outer surface 10 of the inner ring 3.

[0052] The lateral surface 10 is connected to the axial shoulder 13 by the edge 27, which is preferably rounded.

[0053] As a result, the second annular lip 21 is a non-contacting lip and defines with the edge 27 a labyrinth seal arranged downstream of a lubricating grease trap defined by the annular surface 25 of the radially inner annular portion 19 of the annular sealing element 16 provided with the plurality of annular undulations 26, which, when in use, trap and hold the lubricating grease present between the rings 2 and 3 of the bearing 1 to hinder the movement of the lubricating grease towards the lip 21 and the labyrinth seal it forms with the edge 27.

[0054] It is evident from the foregoing that the lip 21 is designed to minimize the gap or clearance with the inner ring 3. The grease trap formed by the surface 25 with the undulations (or alternatively grooves) 26 on the lip (2 or 3) has the function of keeping the grease attached to the rubber surface of the annular sealing element 16. This prevents lubricating grease from leaking out of the rolling bearing 1 and, at the same time, provides a hydraulic seal with low friction due to the limited interference between the lip 20 and the surface 11.

[0055] Finally, the sealing action of the lip 20 is not affected by any small relative axial movements between the rings 2 and 3, as the seal according to8 202400206

[0056] the invention is provided exclusively in a radial direction.

[0057] All the objectives of the invention are therefore achieved.

Claims

9 202400206CLAIMS1. A sealing device (5) for a rolling bearing (1), of the type comprising a substantially rigid annular support (15) and an annular sealing element (16) made of an elastomeric material and integrally with the support; the annular sealing element (16) comprising a radially outer annular portion (18) configured to snap and fluid-tightly mate with a first annular seat (8) of a bearing outer ring (2), and a radially inner annular portion (19) provided with a first annular sealing lip (20) extending radially cantilevered from the support (15), radially on the inside thereof, the first annular sealing lip (20) being configured to mate in use, fluid-tightly and with sliding contact, with a second annular seat (9) of a bearing inner ring (3) characterized in that, in combination:(a) the first annular sealing lip (20) is configured to exert on the second annular seat (9) an exclusively radial sealing action being sized to achieve in use only a predetermined radial interference (I) with an annular sealing surface (11) of the second annular seat (9);(b) the first annular sealing lip (20) has a constant axial thickness or width (S) throughout its entire radial cantilever length (L) from the support (15);(c) the first annular sealing lip (20) has a radial cantilever length from the support (L) that is much greater than its axial width or thickness (S).

2. Sealing device according to claim 1, characterized in that the annular sealing lip (20) has a radial cantilever length (L) from the support (15) equal to a multiple of the axial width or thickness (S) of the sealing lip itself.

3. Sealing device according to claim 1 or 2, characterized in that the annular sealing lip (20) has a radial cantilever length (L) from the support (15) about five to ten times greater than the axial width or thickness (S) of the sealing lip.

4. Sealing device according to one of the preceding claims,10 202400206characterized in that it also comprises a second annular sealing lip (21), configured as a non-contacting lip that projects axially and radially cantilevered from the support (15) and, in use, towards a shoulder (13) of the second annular seat (9) formed on the inner ring (3) of the bearing.

5. Sealing device according to claim 4, characterized in that the second annular sealing lip (21) extends cantilevered from an axially inner face (22) of the annular support (15), in use facing the inside of the rolling bearing (1), and forms with the first annular lip (20), on the opposite side to said axially inner face (22) of the support (15), an acute angle.

6. Sealing device according to one of claims 4 or 5, characterized in that the first annular sealing lip (20) is configured in radial section as a V having a vertex facing the second annular lip (21) and formed by a pair of radial annular arms (24) forming an obtuse angle between them.

7. Sealing device according to one of the preceding claims, characterized in that said radially inner annular portion (19) of the annular sealing element (16) is bounded, on the side opposite to the first annular sealing lip (20), by an annular surface (25) disposed obliquely to the annular support (15) and projecting obliquely in cantilever from the annular support, from which surface (25) a second annular sealing lip (21) projects axially and radially cantilevered from the annular support, the second annular sealing lip forming with the first annular sealing lip (20), immediately adjacent thereto, an acute angle; said annular surface (25) of the radially inner annular portion (19) of the annular sealing element (16) being provided with a plurality of annular undulations (26), specifically at least two or three, arranged axially in series with each other between the annular support (15) and the second annular sealing lip (21).

8. A rolling bearing (1), in particular for an optical encoder, comprising a radially outer ring (2), a radially inner ring (3), a plurality of rolling bodies (4)11 202400206interposed between the inner and outer rings to make them relatively rotatable with low friction, and at least one sealing device (5) according to any one of claims 1 to 7 interposed between the inner and outer rings (3,2) at a corresponding axial end (6,7) of the inner and outer rings; said axial end (7) of the outer ring (2) being provided with a first annular seat (8) configured to receive by snap coupling and with a static fluid-tight sealing action said radially outer portion (18) of the annular sealing element (16); and said corresponding axial end (6) of the inner ring (3) being provided with a second annular seat (9) configured as a step and comprising an annular sealing surface (11), which is defined by a bottom wall (12) of the second annular seat conformed as a step, and by an axial shoulder (13) arranged substantially perpendicular to the annular sealing surface (11); characterized in that the annular sealing surface (11) is a machined surface, preferably ground, and is configured to couple by sliding with the first annular lip (20) resulting in an exclusively radial hydraulic seal therewith.

9. Rolling bearing according to claim 8, characterized in that said first annular lip (20) and said annular sealing surface (11) of the second annular seat (9) are coupled together with a radial interference (I) between 4 and 7 hundredths of a mm.

10. Rolling bearing according to claim 8 or 9, characterized in that said second annular lip (21) of the annular sealing element (16) extends up to an edge (27) of the second annular seat (9) separating said axial shoulder (13) from a radially outer surface (10) of the inner ring (3), which is connected with the axial shoulder (13) by means of said edge (27); the second annular lip (21) being a non-contacting lip and defining with said edge (27) a labyrinth seal arranged downstream of a lubricating grease trap defined by said annular surface (25) of the radially inner annular portion (19) of the annular sealing element (16) provided with said plurality of annular undulations (26).

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