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 radially inner ring (34), axially external with respect to the first shield (60) and which cooperates with the first shield (60) and the flange portion (23) of the pinion (20) 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 202400133

[0002] PINION BEARING UNIT

[0003] D E S C RI Z I O N E

[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. 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, requires solutions that are in principle 2 202400133 incompatible with each other: for example, the need for low friction and highspeed 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.

[0012] These technical problems require further development of the known solutions of sealing devices.

[0013] Summary of the Invention

[0014] The object of the present invention is to provide a bearing pinion unit which is free from the above-described drawbacks.

[0015] 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.

[0016] Further embodiments of the invention, preferred and / or particularly advantageous, are described according to the characteristics set out in the attached dependent claims.

[0017] Brief Description of the Drawings

[0018] The invention will now be described with reference to the attached drawings, which illustrate a non-limiting example of implementation, in which :

[0019] - Figure 1 illustrates a cross-section of a pinion bearing unit in a preferred embodiment of the present invention, and

[0020] - Figure 2 illustrates a detail of the assembly of Figure 1.

[0021] Detailed Description

[0022] 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.

[0023] The pinion bearing unit 10 has a central rotation axis X, and comprises:

[0024] - a bearing unit 30; and

[0025] - a pinion 20, rotatable with respect to the X axis, which is provided with a radially internal cylindrical seat 21 to house the bearing unit 30, a pair of side 3 202400133 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'.

[0026] The bearing unit 30 comprises, in turn :

[0027] - a radially outer ring 31, rotatable as it is stably connected to the pinion 20,

[0028] - a radially inner ring 34, stationary, and

[0029] - a row 32 of rolling bodies 33, in this case balls, interposed between the radially outer ring 31 and the radially inner ring 34.

[0030] 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".

[0031] 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.

[0032] Both sealing devices 40, 50 comprise:

[0033] - a shaped, metallic shield 60, stably anchored in a seat 31a for housing the radially outer ring 31 and therefore rotatable, and

[0034] - 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 the radially inner ring 34, opposing the entry of contaminants as well as the escape 4 202400133 of lubricating grease.

[0035] In greater detail, the shield 60 comprises:

[0036] - an anchoring portion 61, shaped and radially external, which is housed in the seat 31a of the radially outer ring 31,

[0037] - a flange portion 62, radially external, and

[0038] - an intermediate portion 63, oblique and interposed between the anchoring portion 61 and the flange portion 62.

[0039] 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.

[0040] 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 radially inner ring 34 and therefore stationary, axially external with respect to the shield 60 and which cooperates with the flange portion 23 of the pinion 20 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. The shield 80 is a metal shield without contact sealing elements and, therefore, its introduction does not involve any increase in friction losses.

[0041] 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.

[0042] 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 the second shield 80.

[0043] The second shield 80 comprises: 5 202400133

[0044] - a first flange portion 81, radially external and axially internal with respect to the flange portion 23 of the pinion 20,

[0045] - a second flange portion 82, radially internal and which does not protrude from the axial dimensions of the bearing unit, in particular of the radially inner ring 34,

[0046] - an intermediate portion 83, oblique and interposed between the first 81 and the second flange portion 82, and

[0047] - a sleeve portion 84, stably connected to the second flange portion 82 and mounted with interference on the radially inner ring 34.

[0048] In particular, the sleeve portion 84 protrudes 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.

[0049] The second shield 80 allows for 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 sliding contact with the radially inner ring 34, the geometry of the whole sealing device 50 drastically reduces the quantity of contaminants that may reach the sealing lip 75.

[0050] This is due to a tortuous path P that the geometry of the sealing device 50 imposes on the contaminants thanks to the cooperation of three elements: flange portion 23 of the pinion 20, first shield 60 and second shield 80. It is between these three components that the obligatory tortuous path P, that the contaminants must follow, develops. This tortuous path is full of distributed and localized resistances to motion : distributed, because it is a sufficiently long path, whose overall length is approximately 10 mm; localized because the components that define the tortuous path also define narrow passages and frequent changes in 6 202400133 direction. For example, following the direction of travel of the tortuous path P by the contaminants, at the beginning of the tortuous path the entry of the contaminants must occur through a narrow passage G defined by the intermediate portion 83 of the second shield 80 and the flange portion 23 of the pinion 20, whose minimum distance dm is only 0.45 mm. This narrow passage G is very important because it creates a very effective filter that opposes the entry of the contaminants into the tortuous path P, which in any case has a limited width, the average value of which is approximately 0.7 mm. Conveniently, in order to avoid contact between the first flange portion 81 of the second shield 80 and the flange portion 23 of the pinion 20, as well as between the first flange portion 81 and the radially outer ring 31, it is appropriate that the corresponding axial distances d between these components are not less than 0.7 mm. This requirement is due to the fact that, normally, the risk of unwanted contact between components is always linked to the axial gap of the bearing unit which is, in the case of ball bearing units, approximately 10 times the radial gap. Therefore, it is clear that the minimum distances to be respected must always be taken in the axial direction.

[0051] Consequently, to avoid contact between the sleeve portion 84 of the second shield 80 and the flange portion 62 of the first shield 60, since this is a potential contact in the radial direction, it is not risky to create, at the end of the tortuous path P, a narrow passage G' that is decidedly limited in the radial direction, for example with a radial distance drof only 0.2 mm between the first 60 and the second shield 80.

[0052] Preferably, in order to ensure good anchoring of the second shield 80 to the radially inner ring 34, the sleeve portion 84 does not develop in the axial direction but in a slightly inclined direction, radially outwards: the sleeve portion 84 therefore forms with the radially inner ring 34 an angle a between 2° and 7° (for example 4°, in figure 2). This simplifies the assembly process, as, due to the slight inclination of the sleeve portion 84, during the assembly process the second shield 80 is not blocked by possible imperfections in the roundness of the radially 7 202400133 inner ring 34.

[0053] Advantageously, during the assembly process of the second shield 80 it is very important to maintain an annular surface 82', the axially outer surface of the second flange portion 82 of the second shield 80, aligned in the axial direction with an annular surface 34', the axially outer surface, of the radially inner ring 34. In this way, any contact between the sleeve portion 84 of the second shield 80 and the lip 75 of the elastomeric sealing element 70 is avoided. To avoid any contact that could damage the sealing lip 75, a minimum distance de of 0.7 mm must be maintained to account for the possible axial gap of the bearing unit.

[0054] Maintaining the axial alignment between the second shield 80 and the radially inner ring 34 allows, at the same time, to avoid any possible contact with other components external to the pinion bearing unit 10, in addition, obviously, to avoid any variation in the axial dimensions of the bearing unit 30.

[0055] Finally, between the first 60 and the second shield 80 an internal volume V is defined which, conveniently, 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.

[0056] Ultimately, the solution relating to the pinion bearing 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 life 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.

[0057] 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 neitherthe 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 8 202400133 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 202400133C LA I M S1. Pinion bearing unit (10) comprising:- a pinion (20), provided with a cylindrical and radially internal seat (21),- a bearing unit (30) housed inside the seat (21) and provided with a radially outer ring (31) connected to the pinion (20) and 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 connected to the radially inner ring (34), axially external with respect to the first shield (60) and which cooperates with the first shield (60) and with the flange portion (23) of the pinion (20) 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 first flange portion (81), radially external and axially internal with respect to the flange portion (23) of the pinion (20),- a second flange portion (82), radially internal and which does not protrude from the axial bulk of the radially inner ring (34),- an intermediate portion (83), oblique and interposed between the first (81) and the second flange portion (82), and- a sleeve portion (84), stably connected to the second flange portion (82)10 202400133 and mounted with interference on the radially inner ring (34).

3. Unit (10) according to claim 2, wherein the sleeve portion (84) extends axially towards the inside of the bearing unit (30).

4. Unit (10) according to claim 3, wherein the sleeve portion (84) forms an angle (a) between 2° and 7° with the radially inner ring (34).

5. Unit (10) according to anyone of the preceding claims, wherein the flange portion (23) of the pinion (20), the first shield (60) and the second shield (80) define a tortuous path (P) that hinders the entry of contaminants into the bearing unit (30).

6. Unit (10) according to claim 5, wherein the intermediate portion (83) of the second shield (80) and the flange portion (23) of the pinion (20) define a narrow passage (G) at the beginning of the tortuous path (P).

7. Unit (10) according to claim 5 or 6, wherein the sleeve portion (84) of the second shield (80) and a flange portion (62) of the first shield (60) define a narrow passage (G') at the end of the tortuous path (P).

8. Unit (10) according to claim 2, wherein an axially external annular surface (82') of the second flange portion (82) is aligned in the axial direction with an axially external annular surface (34') of the radially inner ring (34).

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

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