Thin cross-section bearing unit

Abstract

A bearing unit having a thin cross-section with a central rotation axis, the bearing unit being provided with: an inner ring including a shaped groove for each side of the bearing unit; an outer ring defining a cylindrical gap with the inner ring; a plurality of rolling elements disposed within the gap and interposed between the inner ring and the outer ring so as to be relatively rotatable about an axis; sealing means mounted on both sides of the bearing unit to protect the gap from contaminants and dirt and to prevent grease leakage within the gap itself, and in that, for each side, two sealing lips arranged in the groove, flexible support arms for the two sealing lips, and intrinsic control elements are arranged in sequence, an intrinsic control element is used to control the bending of the arm to individually and specifically control the flexibility of the arm and the frictional force exerted on the inner ring by a contact of the two sealing lips.

Description

Technical Field

[0001] The present invention relates to a bearing unit of thin section ( / thin-wall bearing unit). Background Art

[0002] Known thin section bearing units have a relatively large corresponding diameter and reduced axial thickness, and are designed to reduce weight, size and friction, to increase structural flexibility and to ensure high rotational accuracy. These bearing units must meet specific demanding requirements and are often used in aerospace applications, medical systems, robotics, astronomical instruments and machine tools, as well as in racing engine design and agriculture. The efficiency of their design can lead to significant savings in space, weight and cost, and requires the application of particularly complex technical solutions to ensure consistent high performance.

[0003] The bearing unit has a central axis of rotation and comprises:

[0004] - an inner ring, delimited axially by a corresponding annular surface transverse to the axis A and also radially on the outside by an outer raceway,

[0005] an outer ring delimited radially on the inside by an inner cylindrical surface and defining a cylindrical gap with the inner ring, and

[0006] - A plurality of rolling elements are arranged in the gap and between the inner ring and the outer ring so that the inner ring and the outer ring can rotate relative to each other around the axis.

[0007] The above-mentioned known thin-section bearing units must be capable of being used in applications where contaminants and dirt could damage the bearing unit itself and enter the gap, significantly reducing not only the performance but also the service life. In order to protect the gap (i.e. the rolling elements and the grease therein), known bearing units (e.g. the bearing unit described in Italian patent application 102019000011646 filed by the same applicant) comprise two sealing shields (shields) arranged on opposite sides of the bearing unit in the axial direction and between the inner ring and the outer ring to prevent contaminants and dirt from entering the gap and to prevent the internal grease from leaking out.

[0008] In Italian patent application 102019000011646, the inner ring (in this case stationary) has two annular shaped grooves formed in the annular surface, and the sealing shield is a formed metal shield (i.e., essentially rigid) formed by pressing, which is assembled in the inner cylindrical surface of the outer ring and has corresponding free cylindrical ends, which are inserted into the corresponding formed annular grooves to form corresponding multi-stage labyrinth seals.

[0009] Although on the one hand these multi-stage labyrinth seals are particularly effective in preventing contaminants and dirt from entering the gaps and preventing internal grease from leaking out, their specific "open" shape allows certain types of contaminants to accumulate at least at the entrance to the labyrinth seal, slowly forming a sediment that tends to become denser over time, increasing the rolling resistance of the bearing and increasingly hindering the free relative rotation of the inner and outer rings. Summary of the invention

[0010] The present invention aims to provide a thin-section bearing unit which achieves the same performance level in terms of rolling resistance but has improved resistance to contaminants and dirt, thereby increasing its service life.

[0011] The present invention provides a thin-section bearing unit having the features set out in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The invention is described below with reference to the accompanying drawings, which show non-limiting example embodiments of the invention, in which:

[0013] - Figure 1 is a cross-sectional view of a preferred embodiment of a thin-section bearing unit according to the present invention, and

[0014] - Figure 2 yes Figure 1 Magnified detail of a thin-section bearing unit. DETAILED DESCRIPTION

[0015] exist Figure 1In the present invention, a bearing unit of thin cross-section (and therefore of very limited axial dimension and at the same time of slightly large diameter) is designated as a whole by reference numeral 10. In particular, although the present description applies generally, the present description explicitly refers to a bearing unit 10 having a cross-section or more precisely a thickness of the cross-section which is very small and predominantly square and, as better described below, having a particularly large shaft diameter and seat diameter, even 8 to 11 times or more greater than the thickness of the cross-section.

[0016] The bearing unit 10 has a central axis of rotation A and comprises:

[0017] a rotating ( / rotating) inner ring 20 provided radially on the outside with an outer raceway 21 and delimited axially by a respective annular surface 24, wherein the respective annular surface 24 is transverse to the axis A and identifies a respective side L of the bearing unit 10,

[0018] a stationary outer ring 30 , which is provided with an inner raceway 31 on the radial inside and defines a cylindrical gap 11 with the inner ring 20 , and

[0019] A plurality of rolling elements 40 (ie, balls) are arranged in the gap 11 between the inner ring 20 and the outer ring 30 so as to roll in the raceways 21 and 31 and to enable relative rotation of the plurality of rolling elements 40 about the axis A.

[0020] The bearing unit 10 also includes sealing devices 50, which are installed on both sides L of the bearing unit 10 to protect the gap 11 (i.e., the rolling elements 40 and the grease in the gap 11 itself) from the influence of contaminants and dirt and prevent internal grease from leaking out.

[0021] The outer ring 30 is delimited radially outside by an outer cylindrical surface 32 defining the above-mentioned seat diameter, and is provided with two shaped grooves 33, which are predominantly radial (i.e., extend predominantly in the radial direction and are substantially closed in the axial direction) and are arranged on opposite sides of the raceway 31, while the inner ring 20 is delimited radially inside by an inner cylindrical surface 22 defining the above-mentioned shaft diameter, and is delimited radially outside by an inner cylindrical surface 29 forming the raceway 21, and is provided with two shaped grooves 23, which are predominantly axial (i.e., extend predominantly in the axial direction and are substantially closed in the radial direction), are arranged on opposite sides of the raceway 21, and are substantially formed through the relative surface 24.

[0022] like Figure 2As more clearly shown in FIG. 1 , each shaped groove 23 is defined by:

[0023] a cylindrical surface 25 , coaxial with the axis A, extending axially from the relative surface 24 towards the interior of the inner ring 20 and connected to the relative surface 24 itself by a circular entry edge 251 of increasing diameter from the relative surface 24 towards the relative surface 25 ,

[0024] - an annular surface 26, transverse to the cylindrical surface 25 and connected to the cylindrical surface 25 itself,

[0025] a conical surface 27, projecting towards the cylindrical surface 25 and connected to the annular surface 26, and

[0026] A further annular surface 28 connected to both the conical surface 27 and the cylindrical surface 29 and axially offset towards the surface 24 than the annular surface 26 .

[0027] The sealing device 50 is an anchoring sealing device, which is mounted on both sides L of the bearing unit 10, and as a substantially non-rigid device, the sealing device 50 can be Figure 1 ) in an operational ( / working) undeformed pre-assembled state and (as shown by way of example) in an operational ( / working) undeformed pre-assembled state and (as shown by way of example) in Figure 2 (detailed in the figure) operational ( / working) (operational) deformation elastic deformation between assembly states.

[0028] For each side L of the bearing unit 10, the sealing device 50 comprises a shield 51, preferably but not necessarily made of metal and having an inverted "L" shape in the cross section of the bearing unit 10, and an elastomeric coating 52, which is co-molded onto the shield 51. The shield 51 and coating 52 of one side L are arranged as mirror images of the shield 51 and coating 52 of the other side L, and are actually identical to the shield 51 and coating 52 of the other side L. Therefore, the following description relates to the shield 51 and coating 52 on the other side L. Figure 1 The shielding member 51 and the coating 52 on one side L of the left-hand side of the bearing unit 10 in FIG. 1 are shown in FIG. 1 , and should be understood to be completely applicable to the shielding member 51 and the coating 52 on the other side L.

[0029] The shielding member 51 basically comprises a cylindrical portion 511 and a flange portion 512, wherein the cylindrical portion 511 is arranged in the groove 33, the flange portion 512 extends from the portion 511 transversely to the axis A toward the inner ring 20, is basically flush with the surface 24, and terminates at a cylindrical free edge 513, which is basically aligned with the surface 29 in the radial direction, or at least does not extend radially inward beyond the surface 29.

[0030] The shield 51 serves as a stiffening element for the elastomeric coating 52, which in turn comprises:

[0031] an anchoring lip 53 integral with the cylindrical portion 511 and fitted into the groove 33 to anchor the shield 51 and the coating 52 to the outer ring 30, ie to anchor the sealing device 50 to the bearing unit 10,

[0032] two sealing lips 54 , 55 , arranged in the groove 23 and in substantially opposite directions with respect to the axis A,

[0033] a flexible support arm 56 extending radially from the free cylindrical edge 513 of the flange portion 512 to support the two lips 54 and 55 and having a substantially central centre axis F, and

[0034] A deflector baffle 57 extending laterally from the flange portion 512 to the edge 513 in a position radially outside the arm 56 and towards the gap 11 and having a corresponding front annular surface 571 substantially axially aligned with the surface 28 .

[0035] The two sealing lips 54 and 55, the flexible arm ( / flexible arm) 56 and the deflection baffle 57 together with the groove 23 (that is, together with the surfaces 25, 26, 27 and 28 of the groove 23 itself) define a multi-stage labyrinth seal ( / seal) 70. Figure 1 In the operational, undeformed, pre-assembled state shown, since the elastomeric coating 52 will be arranged to have an axis F orthogonal to the axis A, i.e., having an arm 56, the multi-stage labyrinth seal 70 has a constant aperture from the lip 54 (also in an undeformed configuration) to the surface 571, where the labyrinth seal 70 opens into the gap 11.

[0036] According to the present invention, in the operational ( / working) (operational) deformed assembly state, such as Figure 2 As shown in detail in FIG. 1 , the arm 56 and its axis F are deformed and, more specifically, curved or bent, and as a result the bore of the multi-stage labyrinth seal ( / seal) 70 is no longer constant.

[0037] The bend or curvature of the arm 56 is determined by the specific shape of the sealing lip 54 and the sealing lip 55, wherein the lip 54 extends from the arm 56 axially toward the outside of the bearing unit 10 and radially toward the surface 25 and has a contact edge 541 with an inner diameter φ 541 , inner diameter φ 541 The size is smaller than the outer diameter φ of the surface 25 25 of dimensions, and the contact edge 541 is arranged against the surface 25 itself in the operational deformed assembly condition, while closing the multi-stage labyrinth seal 70 and bending the arm 56. In fact, in the operational non-deformed pre-assembly condition, the sealing lip 54 is arranged in front of the inner ring 20, the edge 541 of the sealing lip 54 is radially inside the axial projection of the surface 25, and when the sealing device 50 is assembled in the bearing unit 10, this edge 541 intercepts the inlet edge 251 and gradually converges to the same diameter φ25 as the surface 25 to reach the operational deformed assembly condition, thereby forcing the lip 54 to gradually open to fit the surface 25, but also causing the arm 56 to bend to accompany the opening of the lip 54. In other words, the sealing lip 54 of the two sealing lips 54 and 55 is a contact sealing lip arranged against the surface 25, so that the surface 25 is a sliding surface.

[0038] In contrast, the sealing lip 55 extends from the arm 56 axially toward the interior of the bearing unit 10 and radially toward the surface 25 to be positioned in front of the surfaces 25, 26 and 27 of the groove 23, forming an inverted "V" shape with the lip 54 that is open toward the axis A, and has a free end edge 551, which has a corresponding inner diameter φ in both the operational ( / working) deformed assembly state and the operational undeformed pre-assembly state. 551 , the inner diameter φ 551 The size is always greater than the size of the inner diameter of the edge 541, in particular, greater than the diameter φ of the surface 25. 25The dimension of the free length of the sealing lip 55 is smaller than the dimension of the free length of the lip 54, and if the sealing lip 54 is a contact lip, the sealing lip 55 cannot contact any of the surfaces 25, 26 and 27 of the groove 23, but is carried by the arm 56 and follows the bending of the arm 56, and the sealing lip 55 is inclined relative to the axis A, so that the edge 551 of the sealing lip 55 is closer to the surface 25, and causes the multi-stage labyrinth seal 70 to be widened relative to the surfaces 26 and 27, and the narrowing portion ( / narrowing portion) ( / narrowing portion) (71) of the multi-stage labyrinth seal ( / seal) 70 relative to the surface 25 itself.

[0039] The narrowing portion 71 of the multi-stage labyrinth seal 70 has a radial dimension that is always smaller than the diameter φ 551 Size and diameter φ 25 The difference between the sizes of , but never equals zero, so that the sealing lip 55 of the two sealing lips 54 , 55 is a non-contact sealing lip which is simply arranged in front of the surface 25 .

[0040] As mentioned above, the bearing unit 10 must always meet specific requirements and the related design always requires the use of particularly complex technical solutions. Therefore, the arm 56 must have a specific shape and characteristics so that the curvature of the arm 56, that is, the bending of the axis F of the arm 56, can be controlled with absolute precision.

[0041] In particular, according to the present invention, the arm 56 is anchored to the flange portion 512 by a root portion 58, which is part of the elastomeric coating 52 and, despite being formed of the same elastomeric material as the arm 56, has a stiffness greater than that of the arm 56 because the root portion 58 is directly connected to the flange portion 512 and also has an axial thickness that is greater than the axial thickness of the arm 56. In other words, the root portion 58 is neutral and is not affected by any bending of the arm 56, and this neutrality is further reinforced by the fact that the root portion 58 is substantially contiguous with the baffle 57.

[0042] Reference again Figure 2, the arm 56 is delimited axially by two annular surfaces 561 and 562, wherein the surface 561 is oriented toward the outside of the gap 11 and has a radial extension that is smaller than the radial extension of the surface 562, which is not only oriented axially toward the gap 11, but is also directly in front of the surface 28. The surface 561 is identified along the portion of the elastomeric coating 52 oriented toward the outside of the bearing unit 10, i.e. also delimited radially by two annular angular edges 563 and 565, which define a structural discontinuity in the elastomeric coating 52 itself and constrain the arm 56 to essentially a specific rotation about it, essentially acting as an annular hinge. Corner edge 563 specifically defines a structural discontinuity between arm 56 and root portion 58, allowing arm 56 to rotate relative to root portion 58, while corner edge 565 specifically defines a structural discontinuity between arm 56 and lip 54, and allowing lip 54 to rotate relative to arm 56, reducing the impact of rotation of lip 54 on arm 56 after lip 54 contacts surface 25, but edge 563 is a substantially stationary edge when structurally connected to root portion 58, while edge 565 is a movable edge relative to edge 563, and edge 565 has an oscillation determined by the bending of arm 56.

[0043] Again, in order to obtain a close control of the bending of the arm 56, along the portion of the elastomeric coating 52 oriented towards the inside of the bearing unit 10, the surface 562 is marked by two annular arcuate edges 564 and 566, which define respective toroidal connection surfaces between the arm 56 and the baffle 57 and between the arm 56 and the lip 55, respectively. If the two annular angular edges 563 and 565 force the arm 56 to bend substantially towards the outside of the bearing unit 10, thereby substantially rotating around the edges 563 and 565 themselves, and substantially compressing the surface 561, the arcuate edges 564 and 566 tend to open, conversely providing the arm 56 with the elasticity necessary to enable the surface 562 to stretch, in particular always in a fully controlled manner. The arcuate edge 566 also facilitates the actual rotation of the lip 55 around the edge 565 under the opening stress of the lip 54.

[0044] In other words, edges 563 to 566 and surfaces 561 and 562 together define an intrinsic control element 100 to control the bending of arm 56 and its dimensions, i.e., the dimensions of the angle subtended by edge 563 and edge 565, the dimensions of the arc subtended by edge 564 and edge 566 and the radial extensions of surfaces 561 and 562, so that the flexibility of arm 56 can be individually and specifically controlled.

[0045] Furthermore, the edge 564, which is also formed essentially in the root portion 58, makes the baffle 57 even more practically neutral with respect to the bending of the arm 56, so that the sealing device 50 can maintain a constant distance between the baffle 57 and the surfaces 28, 29, thereby also ensuring permanent and precise control of the hole of the multi-stage labyrinth seal ( / seal) 70 itself, at which the labyrinth seal 70 opens into the gap 11.

[0046] It is apparent from the foregoing that the sealing device 50 of the bearing unit 10 according to the present invention provides a contact barrier for the labyrinth seal 70 mainly through the seal 54, thereby preventing contaminants and dirt from entering the labyrinth seal 70 itself, and thus provides a narrowing portion of the labyrinth seal 70 through the lip 55, which not only helps to further prevent contaminants and dirt from entering the labyrinth seal 70 (i.e. towards the gap 11), but also prevents grease from coming out of the gap 11 itself.

[0047] Furthermore, since the bending of the arm 56 is completely controlled by the novel geometry of the arm 56 itself, i.e. due to the inherent control element 100, it is also possible to control the total friction force exerted by the edge 541, i.e. the lip 54, on the surface 25 with great precision and again due to the inherent control element 100, thereby improving the performance of the bearing unit 10, i.e. its high precision, its quietness and its high load-bearing capacity. In particular, the novel geometry of the arm 56 itself enables the lip 54 to spontaneously and automatically adapt to the operating stresses of the bearing unit 10, thereby ensuring constant efficiency of the sealing capacity of the sealing device 50, as well as minimal wear and moderate intensity of friction of the lip 54 itself. Similarly, again due to the inherent control element 100, it is also possible to control the radial dimensions of the narrowing 71 of the multi-stage labyrinth seal 70 with great precision, including by adapting it to the type of grease used and the type of application, thereby making the range of use of the bearing unit 10 even more flexible and wider.

[0048] Finally, it should also be emphasized that the presence of the two annular angular edges 563 and 565 creates a concave area 80 in the elastomeric coating 52 which is oriented towards the outside of the bearing unit 10 and which, due to its shape, is able to move contaminants away from the labyrinth seal 70, thus enhancing the sealing capacity of the sealing device 50 itself. Similarly, the baffle 57, due to its shape and its cooperation with the groove 23, helps to return the grease towards the inside of the gap 11, thus preventing the grease from entering the labyrinth seal 70.

[0049] Finally, it should be recalled that, as described above with particular reference to the cross section of the bearing unit 10, the sealing lips 54 and 55 and the flexible support arm 56 are in each case constrained to rotate about the axis A. In particular, the lips 54 and 55 are essentially conical solids of revolution with divergent tapering, their sealing action being provided by 360° about the axis A and also emphasized by the fact that their two facing surfaces 25, 26 and 27 rotate together with the inner ring 20 about the axis A itself. The relative rotation of the surfaces 25, 26 and 27 and of the two lips 54 and 55 generates a swirling motion in any element found inside the labyrinth seal 70, typically a fluid element or in any case a somewhat dense element. Due to the shape and reciprocal orientation of the two lips 54 and 55 , this vortical motion tends to expel any contaminants that have accidentally entered the labyrinth seal 70 and tends to return any grease that has entered the labyrinth seal itself 70 to the gap 11 .

[0050] In addition to the embodiments of the present invention described above, many other variations exist. The embodiments are provided only as examples and do not limit the scope of the present invention, its application or its possible configurations. In fact, although the description provided above enables those skilled in the art to implement the present invention according to at least one example configuration of the present invention, many variations of the described components may be used without departing from the scope of the present invention as defined in the appended claims as interpreted literally and / or according to their legal equivalents.

Claims

1. A thin-section bearing unit (10) having a central axis (A) of rotation and comprising: - an inner ring (20) provided with an outer raceway (21) on the radial outside and, for each side (L) of the bearing unit (10), provided with a profiled groove (23) extending mainly in the axial direction on the axial outside, - an outer ring (30) defining a cylindrical gap (11) with the inner ring (20) and provided with an outer raceway (31) radially inside and, for each side (L) of the bearing unit (10), provided with a profiled groove (33) extending mainly in the radial direction axially inside, - a plurality of rolling elements (40) arranged in the gap (11) and between the inner ring (20) and the outer ring (30) so as to enable the inner ring (20) and the outer ring (30) to rotate relative to each other around the axis (A); and - sealing means (50) mounted on both sides (L) of the bearing unit (10) to protect the gap (11) from contaminants and dirt and to prevent grease leakage within the gap (11) itself, the sealing means (50) being anchored to the outer ring (30) and defining a multi-stage labyrinth seal (70) with the associated shaped grooves (23) for each side (L) of the bearing unit (10), The bearing unit (10) is characterized in that, for each side (L) of the bearing unit (10), the sealing device (50) comprises: - two sealing lips (54) (55) arranged in the groove (23), - a flexible support arm (56) for the two sealing lips (54)(55), and - Intrinsic control means (100) for controlling the bending of the arm (56) to individually and specifically control both the flexibility of the arm (56) and the friction force exerted on the inner ring (20) by the contacting sealing lip (54) of the two sealing lips (54) (55).

2. The bearing unit according to claim 1, characterized in that: The contact sealing lip (54) closes the multi-stage labyrinth seal (70), thereby substantially preventing the ingress of contaminants and dirt.

3. The bearing unit according to claim 2, characterized in that: The non-contact sealing lip (55) of the two sealing lips (54) (55) defines a narrowing portion (71) of the multi-stage labyrinth seal (70), the narrowing portion having a non-zero radial dimension controlled by the inherent control device (100).

4. The bearing unit according to claim 3, wherein: The sealing device (50) includes a reinforced shield (51) for each side (L) of the bearing unit (10), and the reinforced shield (51) supports the flexible arm (56) and the two sealing lips (54) (55) by means of a rigid root part (58) in between, and the inherent control device (100) for controlling the bending of the arm (56) includes two structural discontinuities (563) (565) arranged between the rigid root part (58) and the flexible arm (56) and between the flexible arm (56) and the contact sealing lip (54), wherein the first structural discontinuity (563) of the two structural discontinuities (563) (565) is a substantially stationary discontinuity, and the second structural discontinuity (565) of the two structural discontinuities (563) (565) is a moving discontinuity.

5. The bearing unit according to claim 4, characterized in that: The inherent control device (100) for controlling the bending of the arm (56) includes two annular arcuate edges (564) (566) arranged between the rigid root portion (58) and the flexible arm (56) and between the flexible arm (56) and the non-contact sealing lip (55), and the annular arcuate edges (564) (566) tend to open to provide the arm (56) with the elasticity required for bending.

6. The bearing unit according to claim 5, characterized in that The inherent control device (100) for controlling the bending of the arm (56) includes a compressible annular surface (561) and an extendable annular surface (562) that define the flexible arm (56) on opposite sides, the compressible annular surface (561) connecting the two structural discontinuities (563) (565) to each other, and the extendable annular surface (562) connecting the annular arc edges (564) (566) to each other.

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