Pinion bearing unit

Abstract

Pinion bearing unit (10) having a pinion (20), provided with a seat (21), cylindrical and radially internal, and a bearing unit (30) housed inside the seat (21), in which - the pinion (20) is provided with a flange portion (23), radially internal and axially external, - the bearing unit (30) is provided with a radially outer ring (31) connected to the pinion (20), a radially inner ring (34) and a sealing device (50), in turn having a first shield (60), metallic and shaped, stably anchored in a housing seat (31a) of the radially outer ring (31), and - the sealing device (50) is provided with a second shield (80), metallic and shaped, stably connected to the flange portion (23) of the pinion (20), axially external with respect to the first shield (60) and which cooperates with the first shield (60) and the radially inner ring (34) to prevent the entry of contaminants into the bearing unit (30), as well as the leakage of lubricating grease from the bearing unit itself.

Description

[0001] 1 202400134

[0002] PINION BEARING UNIT

[0003] D E S C RI PTI O N

[0004] Technical Field of the Invention

[0005] The present invention is related to a pinion bearing unit used preferably, but not exclusively, in motion transmission units of industrial machinery, to which the following description will make explicit reference without losing its generality.

[0006] Background Art

[0007] In industrial machinery, known pinion bearing units are predominantly used as chain tensioners in motion transmission units, and comprise:

[0008] - a pinion provided with a radially internal cylindrical seat, and

[0009] - a bearing unit housed in the cylindrical seat.

[0010] The bearing unit typically comprises a radially inner ring, normally mounted on a central axis of the motion transmission unit, and a radially outer ring, integrally connected to the pinion. The relative rotation of the outer ring with respect to the inner ring is ensured by a plurality of rolling bodies, typically balls. The balls are designed to roll inside a radially external raceway formed on the inner ring and a corresponding radially internal raceway formed on the outer ring.

[0011] The bearing unit has sealing devices to protect the raceways and rolling bodies from external contaminants and to seal against the lubricating grease. Typically, the sealing devices consist of an elastomer gasket co-molded onto a shaped metal shield mounted by interference or caulking in a seat of the bearing unit rings, for example the radially outer ring. The gasket is provided with at least one contacting sealing lip which, by means of sliding contact with the other ring of the bearing unit, performs its sealing function.

[0012] Typically, the bearing unit must be able to operate at high speed, develop low friction losses and, of course, offer good resistance to external contaminants. Each of these three requirements, as far as the sealing devices are concerned, 2 202400134 requires solutions that are in principle incompatible with each other: for example, the need for low friction and high-speed means that it is not possible to use multiple contact lips or to increase the pressure of the lips themselves. Conversely, to achieve a good sealing capacity, the presence of one or more contact lips is certainly important.

[0013] These technical problems require further development of the known solutions of sealing devices.

[0014] Summary of the Invention

[0015] The object of the present invention is to provide a bearing pinion unit which is free from the above-described drawbacks.

[0016] Therefore, according to the present invention, a bearing pinion unit is provided having the characteristics set forth in the independent claim, attached to this description.

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

[0018] Brief Description of the Drawings

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

[0020] - Figure 1 illustrates a cross-section of a pinion bearing unit in a preferred embodiment of the present invention, and

[0021] - Figure 2 illustrates a detail of the unit of Figure 1.

[0022] Detailed Description

[0023] With reference to figures 1 and 2, it is illustrated as a whole a pinion bearing unit 10 applied to the frame 100 (illustrated only schematically) of a machine, of a known type, for the transmission of motion.

[0024] The pinion bearing unit 10 has a central rotation axis X, and comprises:

[0025] - a bearing unit 30; and

[0026] - a pinion 20, rotatable with respect to the X axis, which is provided with 3 202400134 a radially internal cylindrical seat 21 to house the bearing unit 30, a pair of side walls in which a first annular wall 22 faces the frame 100 and a second annular wall 22' is on the opposite side, and a flange portion 23, radially internal and obtained from the same opposite side to the frame 100, i.e., from the side of the second annular wall 22'.

[0027] The bearing unit 30 comprises, in turn :

[0028] - a radially outer ring 31, rotatable as it is stably connected to the pinion 20,

[0029] - a radially inner ring 34, stationary, and

[0030] - a row 32 of rolling bodies 33, in this case balls, interposed between the radially outer ring 31 and the radially inner ring 34.

[0031] Throughout this description and in the claims, the terms and expressions indicating positions and orientations such as "radial" and "axial" are intended to refer to the central rotation axis X of the bearing unit 30. Furthermore, the term "axially internal" is to be understood as an axial direction towards the frame 100 of the machine on which the bearing pinion unit 10 is applied. The opposite direction will be indicated with the term "axially external".

[0032] The bearing unit 30 is also provided with a first 40 and a second sealing device 50, arranged on opposite sides with respect to the rings and rolling bodies of the bearing unit and between the radially inner ring 34 and the radially outer ring 31, for the protection of the bearing unit 30 from external contaminants. In particular, the first sealing device 40 is axially internal, i.e. it is housed towards the frame 100, while the second sealing device 50 is axially external, i.e. it is housed on the free end of the bearing unit 30.

[0033] Both sealing devices 40, 50 comprise:

[0034] - a shaped, metallic shield 60, stably anchored in a seat 31a for housing the radially outer ring 31 and therefore rotatable, and

[0035] - a sealing element 70 in elastomeric material overmolded on the metallic shield 60 and provided with a contacting lip 75 which makes sliding contact with 4 202400134 the radially inner ring 34, opposing the entry of contaminants as well as the escape of lubricating grease.

[0036] In greater detail, the shield 60 comprises:

[0037] - an anchoring portion 61, shaped and radially external, which is housed in the seat 31a of the radially outer ring 31,

[0038] - a flange portion 62, radially external, and

[0039] - an intermediate portion 63, oblique and interposed between the anchoring portion 61 and the flange portion 62.

[0040] Evidently, the frame 100 still ensures good protection for the bearing unit 30 since the space between the pinion 20 and the frame is very narrow and in itself makes it difficult for external contaminants to enter. The axially external sealing device 50 is more exposed to contaminants since it is not supported by the barrier offered by the frame 100 to the axially internal sealing device 40.

[0041] Therefore, according to the present invention, the sealing device 50, axially external, comprises an additional shield 80, metallic and shaped, the shield being stably connected to the flange portion 23 of the pinion 20 and therefore rotatable, axially external with respect to the shield 60 and which cooperates with the first shield 60 and the radially inner ring 34 to increase the performance of the sealing device, preventing contaminants from entering the bearing unit, as well as the lubricating grease from leaking from the bearing unit itself. It is a metal shield without contact sealing elements and, therefore, its introduction does not lead to any increase in friction losses as no contact with the inner ring occurs.

[0042] This additional shield 80, as will be better explained below, does not require any modification to the geometry of the bearing unit 30 and therefore its introduction does not involve any increase in the production process of the unit itself or in the related costs.

[0043] For the sake of clarity, in the following description the pre-existing shield will be defined as the first shield 60, while the additional shield will be defined as 5 202400134 the second shield 80.

[0044] The second shield 80 comprises:

[0045] - a sleeve portion 81, radially external and mounted with interference in the flange portion 23 of the pinion 20,

[0046] - a first flange portion 82, stably connected to the sleeve portion 81 and, with respect to it, radially internal. The first flange portion 82 does not protrude from the axial dimensions of the bearing unit, in particular of the radially inner ring 34, and from the axial dimensions of the flange portion 23 of the pinion 20,

[0047] - a second flange portion 83, radially internal and axially internal with respect to the first flange portion 82, which protrudes towards the radially inner ring 34 without however having any contact with it, and

[0048] - an intermediate portion 84, oblique and connecting between the first 82 and the second flange portion 83.

[0049] In particular, the sleeve portion 81 extends axially inwards, i.e. towards the row 32 of rolling bodies 33: with this measure it is possible to design the second shield 80 so that it does not protrude from the axial dimensions of the radially inner ring 34 and the flange portion 23 of the pinion 20. Therefore, the introduction of this second shield 80 does not alter the geometry of the bearing unit 30 and, in particular, does not require an increase in the axial dimensions of the radially inner ring 34 and the flange portion 23 of the pinion 20.

[0050] Furthermore, the fact that the second additional shield is anchored to the pinion and not to the bearing unit, allows the assembly process of the bearing unit not to be altered.

[0051] The second shield 80 allows to obtain a notable synergistic effect of opposition to the entry of contaminants into the bearing unit. In fact, in addition to the contaminant blocking effect exerted by the sealing lip 75 through the sliding contact with the radially inner ring 34, the geometry of the entire sealing device 50 drastically reduces the quantity of contaminants that can reach the sealing lip 75. 6 202400134

[0052] This is due to a path P that the geometry of the sealing device 50 imposes on the contaminants thanks to the cooperation of three elements: radially inner ring 34, first shield 60 and second shield 80. It is between these three components that the obligatory path P that the contaminants must follow develops. In particular, following the direction of travel of the path P by the contaminants, the entry of the contaminants must occur through a narrow passage G defined by the second flange portion 83 of the second shield 80 and the radially inner ring 34. Therefore, the contaminants continue along two directions: an axial direction along a first branch Pl of the path P at the end of which the contaminants are blocked by the lip 75 of the sealing element 70 and an oblique direction along a second branch P2, axially internal and radially external, at the end of which the contaminants are blocked by the anchoring portion 61 of the first shield 60. The second branch P2 is certainly the path that collects the majority of the contaminant, due to the centrifugal forces to which it is subjected during the operation of the pinion bearing unit.

[0053] Conveniently, between the first 60 and the second shield 80 an internal volume V is defined that can be filled with lubricating grease. In this way, the grease itself creates an additional barrier that opposes the passage of contaminants towards the inside of the bearing unit. In particular, in the rest conditions of the pinion bearing unit, that is when the pinion does not rotate, the grease, due to the effect of the gravitational force, naturally tends to move in a radially internal direction to position itself in correspondence with the narrow passage G, creating a further barrier to contaminants when the unit returns to operation.

[0054] The path P is full of distributed and localized resistances to motion: distributed, because it is a sufficiently long path, whose overall length is about 10 mm; localized because the components that define the path P also define narrow passages and frequent changes in direction.

[0055] An example of localized leakage is precisely the narrow passage G, 7 202400134 through which the contaminants enter. The radial dimension drof the narrow passage G is only 0.35 mm, since this type of bearing unit can tolerate a very low radial clearance, without risk of the two components (second shield and inner ring) coming into contact with each other. This narrow passage G is very important because it creates a very effective filter that opposes the entry of contaminants into the path P.

[0056] The second shield 80 is positioned so that the axial distance dabetween the first 60 and the second shield 80 (in particular between the flange portion 62 of the first shield 60 and the second flange portion 83 of the second shield 80) is still sufficient to ensure the absence of contact between the two components but, at the same time, to prevent the grease from leaking out from inside the sealing device 50 in a short time. The axial distance must ensure that the grease remains almost entirely inside the sealing device ensuring a continuous barrier effect. The minimum dimension of the axial distance from must be no less than 0.35 mm with a positive tolerance of +0.2 mm. In this way, it is taken into account that, in a bearing unit having balls as rolling bodies, the play in the axial direction between the components is greater than the play in the radial direction.

[0057] Advantageously, the flange portion 23 of the pinion 20 is provided with an entry chamfer 23a, axially external and radially internal, which facilitates the insertion of the second shield 80, more precisely, of its sleeve portion 81, inside the flange portion 23 during the assembly process.

[0058] Preferably, the flange portion 23 of the pinion 20 is provided with an annular surface 23b, axially internal, which acts as a stop surface for the sleeve portion 81 of the second shield 80. This stop allows the second shield 80 to be aligned with the flange portion 23 and with the radially inner ring 34. In particular, the alignment occurs in the axial direction between an annular surface 82', axially external surface of the first flange portion 82 of the second shield 80, an annular surface 34', axially external, of the radially inner ring 34 and an annular surface 23c, axially external of the flange portion 23. By doing so, any 8 202400134 contact between the first 60 and the second shield 80 is avoided, as well as any contact between the second shield 80 and other external components. Finally, as already mentioned, the result is obtained of not altering the limit dimensions of the bearing unit 30 with the insertion of the second shield 80.

[0059] Ultimately, the solution relating to the bearing pinion unit, according to the present invention, achieves the intended purposes as it increases the protection from contaminants and the performance of the sealing device. Consequently, it increases the duration of the bearing unit. This is thanks to the use of a single additional component, compatible with the existing ones, a component that does not imply any modification to the geometry of the bearing unit, does not involve additional friction losses and requires a simple assembly procedure.

[0060] In addition to the embodiment of the invention, as described above, it is to be understood that numerous other variants exist. It is also to be understood that such embodiments are exemplary only and limit neither the scope of the invention, nor its applications, nor its possible configurations. On the contrary, although the above description allows the skilled person to carry out the present invention at least according to an exemplary embodiment thereof, it must be understood that many variants of the components described are possible, without thereby 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

9 202400134C LA I M S1. Pinion bearing unit (10) comprising:- a pinion (20), provided with a cylindrical and radially internal seat (21), and- a bearing unit (30) housed inside the seat (21) and provided with a radially outer ring (31) connected to the pinion (20), a radially inner ring (34) and an axially external sealing device (50), in turn comprising a first shaped metal shield (60), stably anchored in a seat (31a) for housing the radially outer ring (31) and a sealing element (70) in elastomeric material overmolded on the first metal shield (60) and provided with a contacting lip (75) which makes sliding contact with the radially inner ring (34), the pinion bearing unit (10) being characterized in that, in combination:- the pinion (20) comprises a flange portion (23), radially internal and axially external, and- the sealing device (50) comprises a second shield (80), metallic and shaped, stably fixed to the flange portion (23) of the pinion (20), axially external with respect to the first shield (60) and which cooperates with the first shield (60) and with the radially inner ring (34) to prevent the entry of contaminants into the bearing unit (30), as well as the leakage of lubricating grease from the bearing unit itself.

2. Unit (10) according to claim 1, wherein the second shield (80) comprises:- a sleeve portion (81), radially external and mounted with interference in the flange portion (23) of the pinion (20),- a first flange portion (82), stably connected to the sleeve portion (81) and, with respect to it, radially internal,- a second flange portion (83), radially internal and axially internal with respect to the first flange portion (82), which protrudes towards the radially inner ring (34) without having any contact with it, and10 202400134- an intermediate portion (84), oblique and connecting between the first(82) and the second flange portion (83).

3. Unit (10) according to claim 2, wherein the sleeve portion (81) protrudes axially towards the inside of the bearing unit (30).

4. Unit (10) according to claim 3, wherein the first flange portion (82) does not protrude from the axial envelope of the radially inner ring (34) and the flange portion (23) of the pinion (20).

5. Unit (10) according to claim 4, wherein an axially external annular surface (82') of the first flange portion (82) of the second shield (80), an axially external annular surface (34') of the radially inner ring (34) and an axially external annular surface (23c) of the flange portion (23) are aligned with each other in the axial direction.

6. Unit (10) according to anyone of the preceding claims, wherein the radially inner ring (34), the first shield (60) and the second shield (80) define a path (P) that prevents the entry of contaminants into the bearing unit (30).

7. Unit (10) according to claim 6, wherein the path (P) comprises:- a narrow passage (G) defined between the second flange portion (83) of the second shield (80) and the radially internal ring (34),- a first branch (Pl) in the axial direction that extends towards the lip (75) of the sealing element (70), and- a second branch (P2), axially internal and radially external, that extends towards an anchoring portion (61) of the first shield (60).

8. Unit (10) according to anyone of the preceding claims, wherein between the first (60) and the second shield (80) an internal volume (V) is defined that contains lubricating grease.

9. Unit (10) according to anyone of the preceding claims, wherein the flange portion (23) of the pinion (20) is provided with an entry chamfer (23a), axially external and radially internal.

10. Unit (10) according to anyone of claims 2 to 9, wherein the flange202400134 portion (23) of the pinion (20) is provided with an annular surface (23b) configured as a stop surface for the sleeve portion (81) of the second shield (80).

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