AU2020220813A1 - Disc plough accessory - Google Patents

Abstract

The invention is directed to a bearing hub protector for a disc plough having one or more discs rotatably supported on an axle by a bearing housed in a bearing hub, the bearing hub being fastened to at least one of the discs and having an access face on a side opposite to the disc, wherein the protector is formed: (a) to extend at least partly about the bearing hub and axle; and (b) to provide a space between the protector and the disc fastened to the bearing hub such that the space is off-set along the axle from the access face of the bearing hub.

Description

DISC PLOUGH ACCESSORY

TECHNICAL FIELD

The present invention relates to ploughs for agriculture. More particularly, the invention relates to ploughs that have tilling instruments in the forms of discs which are rotatably linked to a support frame.

BACKGROUND ART

Disc ploughs are often used to turn over a significant amount of soil during preparation of a field for planting. The discs have a slightly concave profile which facilitates turning over the soil as the disc moves through the soil. The discs are rotatably mounted on an axle that is fixed to a support frame and the support frame is a pulled behind a prime move to effect ploughing of the soil. However, the weight of the support frame is carried on the discs to ensure adequate penetration into the soil. That can involve the discs cutting to a depth where the axle and the hub components that secure the disc to the axle are exposed to soil and other matter that is turned over by the discs. In some soil conditions that soil can become clogged between two adjacent discs so that the soil is forcibly push against the axle and the hub components. In other cases, the discs may cut to such a depth that the axle touches the ground or slightly above where it is also exposed to soil being forcibly rammed against the axle and the hub components.

An embodiment of a disc mounted on an axle is shown in Figure 1. Specifically, an annular bearing hub is fixed to a disc by a series of bolts. In countries where the soil is harder, the discs are fixed by six bolts because of the higher forces required to advance the disc through the soil. The bearing hub further has a radially-inner rim which traps a ring bearing (comprising an annular race and a series of ball bearings) on an axle. A gap exists between the inner and outer bearing race parts (between which the ball bearings are held) to enable free rotation of the inner part (which is fixed on the axle) relative to the outer part (which is fixed relative to the bearing hub). The gap, however, is large enough for soil particles to enter the race and cause significant damage to the bearing. While small amounts of soil in the bearing are tolerable, larger mounts tend to reduce the amount of lubricant available for the bearings, thereby causing significant wear to the ball bearings and the race. If, in these circumstances, the soil is not cleaned out, the bearing may be destroyed within a few hours of operation. To avoid this, more frequent maintenance is required to clear soil out of the bearings.

There is a need to reduce the amount of soil to which the bearings are exposed. It is anticipated that reduced exposure will prolong the operational lifespan of the bearings and/or will reduce the frequency of maintenance to remove soil from the bearings.

The current way of dealing with soil exposure involves an annular dust cover that fits over the axle to cover the central opening of the bearing hub, thereby shielding the bearing from soil (as shown in Figure 1). The cover is pressed against the bearing hub by a coil spring which also abuts an axle housing (Figure 2) opposite the bearing hub. The spring constant of the coil spring is selected to enable a worker to pull the dust cover along the axle and free of the bearing hub by hand, thereby enabling manual cleaning of the bearing. This spring constant is relatively low, so the force required to shift the dust cover is much lower than the ramming force of soil against the dust cover with the consequence that the dust cover provides limited protection from soil and mud working it was way into the bearing. This means that the bearing must be cleaned at least every time after the plough is used and sometimes cleaned more frequently. This maintenance is labour intensive, frequent and, even with such maintenance activities, the service life of the bearings is limited to 1 to 2 years on account of the wear caused by soil and mud working its way into the bearing in such conditions.

The problem with the dust cover described above is evident in Figure 2 which shows a permanently deformed dust cover that no longer protects the bearing. While this is a relatively extreme example, it will be appreciated that the ramming force is sufficient to push the cover away from the hub such that mud and soil can work its way into the bearing. In soft, moist soil, this occurs by mud caking on the leading (concave) surface of the disc such that, with each rotation of the disc, the mud that is picked up at the perimeter pushes radially adjacent caked mud closer to the bearing hub. The mud already at the bearing hub is pushed over the surface of the bearing hub (which is away from the surface of the disc) so that its direction includes a component that is parallel to the axle and works against the coil spring. Furthermore, the mud directed over the surface of the hub is directed toward the dust cover, and particularly toward the point where the dust cover contacts the bearing hub. It is understood that such deflection of the mud over the bearing hub pushes back the dust cover such that some of the mud will be directed into the gap between the bearing and the dust cover and will enter the bearing. As shown in Figure 2, the force of h mud has pushed the dust cover back from the bearing hub to the extent that the dust cover has been deformed by the force of the mud. As a result, it no longer functions to protect the bearing from soil and mud. This situation requires frequent maintenance otherwise the bearing will be destroyed by use over as little as an hour.

In other circumstances, the disc penetration depth into the soil results in the bearing hub and axle are in contact with un-ploughed ground owing to the angle of attack or are in contact with ploughed soil. The dust cover provides little protection in that circumstance.

Adopting a coil spring that resists the ramming force of the mud and soil is not a viable alternative because it would become too hard to manually pull the dust cover back from contacting the bearing hub. Accordingly, the manual inspection and maintenance couldn’t be undertaken

SUMMARY OF THE DISCLOSURE

In one aspect there is disclosed a bearing hub protector for a disc plough having one or more discs rotatably supported on an axle by a bearing housed in a bearing hub, the bearing hub being fastened to at least one of the discs and having an access face on a side opposite to the disc, wherein the protector is formed:

(a) to extend at least partly about the bearing hub and axle; and

(b) to provide a space between the protector and the disc fastened to the bearing hub such that the space is off-set along the axle from the access face of the bearing hub.

The term“off-set” in this context means that the space or gap is not aligned and does not overlap with the access face of the bearing hub in a direction that is parallel to the axle.

With this form, the mud and soil accumulating on the disc is deflected mainly by the protector, so the extent to which the nip between the dust cover and the bearing hub is exposed to soil and mud being rammed towards the bearing is significantly reduced compared to the extent of exposure without the protector. This, of itself, is expected to very considerably reduce the maintenance required to keep bearings clean and to prolong the service life of the bearings.

Furthermore, forming the protector to provide the axially off-set space ensures that soil and mud which is forced through the space is directed away from the disc by a circumferential perimeter of the bearing hub. The applicant recognises that the axial thickness of the bearing hub can be used to cause the rammed soil and mud to change direction. The change of direction results in the soil and mud being pushed in a direction away from the nip so that the nip is exposed to only some of the mud that is rammed through the space.

Even then, this arrangement takes advantage of the effect that the ramming force is largely borne by the protector and, for soil and mud passing through the space, is borne by the circumferential perimeter of the bearing hub. The result is that the redirected soil and mud is subject to only a small ramming force (which is directed away from the nip), so that the soil and mud that does reach the nip is unlikely to unseat the dust cover and work its way into the bearings.

It is anticipated that, in view of the effects outlined above, the protector may prolong the life-span of bearings in the disc plough due to reduced ingress of mud and soil. The protector may otherwise or additionally reduce the extent of daily

maintenance required to keep the bearings in a serviceable condition. It is also anticipated that the protector may cause less mud and soil to accumulate around bolts that secure the bearing hub to the disc. This means that the daily maintenance to check the tension on those bolts may be reduced because less time may be required to clear mud and soil from the bolts to make them accessible with a spanner.

The protector may comprise a shaped panel that wraps at least partly about the bearing hub and the axle, the shaped panel includes a leading portion and an open rear such that the access face is accessible via the open rear.

The protector may include a leading portion that transitions to rearwardly extending upper and lower portions and therein the leading, upper and lower portions define a volume between them which can receive the axle and the bearing hub such that the protector wraps at least partly about the bearing hub and the axle.

The protector has a c-shaped profile that extends about 120° to 270° of the bearing hub.

The protector has an internal radius that is slightly greater than the external radius of the bearing hub.

The protector includes at least one spacer that facilitates mounting of the protector to the plough at a location with the internal faces spaced radially outwardly from the bearing hub.

The at least one spacer extends from an internal face of the leading portion.

The spacer may be a boss. In some embodiments the spacer or boss may form part of the bearing shield. In some embodiments the spacer or boss may be welded to the bearing shield.

The protector may include a reinforcing partition that connects the leading portion with at least one of the upper or lower potions.

The upper and/or lower portions may include a slot for receiving a support member of the plough.

In another aspect, there is a disclosed a disc plough having one or more discs supported on a frame, wherein at least one disc is rotatably supported on an axle by a bearing housed in a bearing hub, the bearing hub being fastened to at least one of the discs and having an access face on a side opposite to the disc, wherein the protector is formed in accordance with the aspect described above.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of the protector as set forth in the Summary, a specific embodiment will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a photograph of a disc rotatably mounted on a disc plough with a dust cover positioned over bearings of that are housed in a bearing hub to which the disc is fastened;

Figure 2 is a photograph of another disc that is rotatably mounted in the same configuration as shown in Figure 1 after use in soil conditions that cause fouling of the bearings;

Figure 3 is a photograph of the same portion of a disc plough shown in Figure 1 with a protector according to an embodiment of the invention fitted to the plough;

Figure 4 is a photograph of the rear view of the portion of the disc plough shown in Figure 3;

Figure 5A is an oblique isometric view of a disc plough showing the locations of protectors;

Figure 5B is a magnified view of the portion of the disc plough that is inside the circle marked B in Figure 5A;

Figure 6 is a horizontal cross-sectional view of the axle, bearing hub, disc and a portion of the protector;

Figure 7 A is a rear perspective view of a handed embodiment of the protector;

Figure 7B is a front perspective view of the handed shield of Figure 7A;

Figure 8A is a rear perspective view of the protector of Figure 7 A installed between two adjacent discs of a gang of discs; and

Figure 8B is a front perspective view of the handed protector installed between two adjacent discs of a gang of discs. DESCRIPTION OF EMBODIMENT

A disk plough 10 incorporating a protector, in the form of a shield 40, is shown in Figures 5A and 5B. The disc plough 10 includes a central frame 12 from which depends a series of support beams 14 that rotatably link to the frame to enable the support beams 14 to rotate from a compact transport position to an expanded ploughing position (Figure 5A). Each support beam 14 includes a series of downwardly extending support arms 16 which terminate in an axel mount 18 that houses a fixed axle 20.

Groups of discs 17, termed gangs, are rotatably mounted between adjacent supports 16 and each disc 17 in the gang comprises a concave dish which may include a scalloped perimeter. In other forms, the discs 17 may have a circular perimeter. In the ploughing position, the concave surface of the disks so that the perimeter edge of the disc 17 cuts into the soil and the concavity lifts and turns the soil as the disc 17 rotates. The extent to which each disc 17 cuts and lifts the soil depends on the angle of attack, i.e. the angle of the discs relative to the direction of travel of the disk plough 10, when the discs are in the ploughing position. As explained in the“Background” section above with reference to Figure 2, one disc 17 in the gang is fastened to a bearing hub 26 which has an upstanding perimeter portion 28 and an access face 30 which is generally frusto-conical and extends from the perimeter portion toward a central rim 32. The access face 30 includes six circumferentially-spaced recesses which seat bolts 36 that fasten the disc 17 to the bearing hub 26. The profile of the bearing hub 26 (as shown in Figure 6) includes a volume for receiving a bearing 38 which fits onto the axle 20. Accordingly, when the bearing 38 is fitted to the axle 20 and the bolts fasten the disc 17 to the bearing 38, the bearing 38 is clamped between the disc 17 and the bearing hub 26 such that the disc 17 freely rotates around the axle.

As also explained in the“Background” section above, the disc plough 10 includes a compression coil 22 about the axle which abuts the axle mount 18 at one end and a dust cover 24 at the other end such that a compressive force is constantly exerted against the dust cover 24 to keep it in contact with the bearing hub 26. The dust cover 24 has a central opening through which the axel 20 passes, but which has only a small spacing between the axle 20 and the dust cover 24 so that very little dust or soil is able to work its way into the bearing 38 through the gap. The dust cover 24 has a generally planar body extending radially from the central opening that extends about the axle 20 and has an outer rim 25 which extends a short distance perpendicular to the body in a direction away from that the coil 22. The radial spacing of the rim 25 is selected to overlap with the rim 32 of the bearing hub 26 so that, with the force applied by the coil, a nip is formed between the rim 25 of the dust cover and the bearing hub 26.

Even despite the dust cover 24 being installed on the disc plough 10, soil or mud are able to work their way into the bearing 38 due to the soil and mud being forced across the inclined access face 30 of the bearing hub 26 and into the nip 34, thereby pushing the dust cover 24 away from the bearing hub 26. The gap created between them allows mud and soil to penetrate the bearing, leading to the excessive wearing of the bearing 38 and, therefore, frequent maintenance to remove the soil and mud.

The shield 40 shown in Figures 5A and 5B is shown also in Figures 3 and 4. Figure 3 shows the front of the shield 40, having regard to the direction of travel of the disc plough 10, and figure 4 shows a rear-side of the shield when it is fitted to a disk plough.

The shield 40 includes a leading face 42, a top wall 44, a bottom wall 46 and upper and lower transition panels 48, 50 which connect with the leading face 42 with the respective top and bottom walls 44, 46. Accordingly, the shield has a generally c- shaped profile formed from 5 distinguishable panel sections (see Figure 5B). It will be appreciated, however, that the shield may be formed from 4 distinguishable panel sections (see Figure 7A) or may be formed to have a continuously curved profile from the top to the bottom without distinguishable panel sections (not illustrated). In an alternative embodiment, the shield may have more than five panel sections, or less than five panel sections. In some embodiments the bottom wall 46 may be eliminated.

Furthermore, while the embodiment shown in Figures 3 and 4 extends approximately 180° around the bearing hub, it will be appreciated that the shield 40 may extend around more than 180° of the bearing hub 26, or less than 180° of the bearing shield. The same applies to an embodiment which is continuously curved. In each alternative embodiment the shield 40 may cover up to 270° of the bearing hub 26. In each case, the extent of coverage may vary depending upon the embodiment, but the open rear to the shield 40 is important to provide access to the access face 30 of the bearing hub for maintenance activities. This includes access to the bolts 36 and to the dust cover 24 and bearing 38. As shown in Figure 4, the open rear of the shield 40 enables access to three of the circumferentially-spaced bolts 36 and clear access to the dust cover 24.

As shown in Figure 3, the shield 40 is dimensioned to provide spacing, in the form of a space or gap 56, between the disc 17 and the edge of the shield 40. The size of the gap 56 varies depending on the radial distance of the shield 40 from the axle 20. More specifically, the gap 56 varies due to the planar sections (42, 44, 46, 48, 50) of the shield 40 and the curvature of the concave disc 17. As a result, the gap is narrowest where the shield 40 transitions from one panel section to another panel section and is widest between those transitions points. If the shield 40 had a constant radius of curvature, the gap 56 would be constant as well. The embodiment shown in Figures 3 and 4 has a gap 56 that varies in width within the range of 0.5 to 2 cm.

It will be appreciated, however, that the size of the gap 56 may vary or may be constant provided that the gap 56 is offset from the access face 30 of the bearing hub. That is, the shield 40 must be formed such that the gap 56 aligns with the perimeter portion 28 of the bearing hub 26 and is large enough for the disc 17 to rotate freely without interference from the shield 40. The offset from the access face 30, as shown in Figure 6, causes the soil or mud passing through the gap 56 to change direction as shown by the arrow A. This change of direction forces the soil and mud to travel in a direction away from the nip 34, rather than along the access face 30 in the direction of the nip 34. This means that the ramming force applied through the soil and mud deflects mud and soil passing through the gap 56 in a direction away from the nip 34 so that the dust cover 24 is protected from the ramming force of the mud and soil.

While the above description explains what happens to soil and mud that is rammed across the surface of the disc 17 and through the gap 56, the bulk of the soil and mud will be forced into the panel sections 42, 44, 46, 48 and 50. The shield 40 is formed as a substantially rigid structure so that the mud and soil is deflected from the shield without deforming it. This is represented by the arrows marked B in Figure 6. The shield 40, therefore, forms a direct barrier to soil and mud that would otherwise reach the bearing hub 26 and axle 20. The protection afforded by the shield 40 substantially reduces the exposure of the bearing hub 26 and to bearing 38 to soil and mud. The applicant anticipates that the shield will significantly reduce the need for maintenance work on the bearing 38, thereby improving its service life compared to disc ploughs 10 without such a shield 40 protecting the bearing hub 26.

The shield 40 is fastened to the axle mount via a pair of bolts which provide a substantially rigid connection. This ensures that the tolerance of the gap 56 remains basically the same throughout use of the disc plough 10, thereby avoiding instances where the shield 40 might contact the disc 17 and impede its rotational movement. To provide the correct location of the shield relative to the disc 17, the shield 40 includes a pair of spaced bosses 54 (Figure 5A) through which the bolts extend. The length of the bosses 54 is selected to provide the correct spacing of the gap 56 so that it is offset from the access face 30. The bosses 54 extend from a rear side of the leading face 42. The size of the bosses 54 and the bolts is selected so that they can withstand the ramming force from the mud and soil.

The shield includes at slot 58 which receives a support arm 16 (shown in Figure 5B). In the embodiment shown in Figures 3 to 6, the slot 58 is offset from the centre of the shield to account for a slight inclination of the arm 16 from vertical and to account for extra space provided on the side of the axle mount 18 on which the coil is located (which coincides with a concave side of the disc). A further slot 58 is located on the vertically opposing side of the shield 40 so that it may be used interchangeably with gangs of discs 17 on other support beams 14. Specifically, the support beam 14 in Figure 5B is one of two leading support beams at a forward end of the disc plough 10.

The discs on that support beam 14 all have the concave surfaces of the discs facing outwardly from the frame 12. To balance the drag on the plough so that the disc plough 10 tracks truly behind a prime mover, the discs 17 on the other leading support beam 14 have their concave surfaces facing also away from the frame. This means that the slot 58 needs to be offset from the centre of the shield 40 on the opposite side. This can be achieved by rotating the shield 40 through 180° about a horizontal axis that passes through the centre of the leading face. The same issue applies with the trailing support beams 40 where the discs 17 on each beam face inwardly toward the frame 12.

In one embodiment, the shield 40 can be a handed shield 40’, i.e. a left-handed shield or a right-handed shield. When the shield 40’ is handed, only a single slot 58 is required, as there is no need to be able to rotate and reverse the shield 40’. This embodiment of the shield is illustrated in Figures 7 A and 7B. Where Figure 7 A illustrates a rear perspective view of the shield 40’ and Figure 7B illustrates a front perspective view of the shield 40’. In the non-handed embodiments of the shield 40, the slot 58 is provided in each of the (i) top and upper portions of the shield; and (ii) the lower and bottom portions of the shield. In some embodiments the slot 58 is centrally located and in some embodiments the slot 58 may be offset either towards the left or right-hand side of the shield 40.

The shield 40’ in Figure 7B illustrates hexagonal openings 60 for receiving and housing hexagon bolt heads therein. This can assist in resisting rotation of the bolts 52 during use of the disc plough and also provides a countersink to the bolt heads so they don’t protrude from the leading face 42’ of the shield 40’.

From the rear of the handed shield 40’ (shown in Figure 7 A) a pair of reinforcing partitions illustrated as webs 59 support a pair of mountings bosses 54 for receiving a pair of fasteners 52 for securing the shield 40’ to the arm 16. These same mounting bosses 54 and support webs 59 can be used in the non-handed shield 40 for securing the shield 40 to the arm 16. Additional webs (not illustrated) can be incorporated into the rear of the shield for additional structural reinforcement, in the form of additional vertical webs 59 or in the form of horizontal webs, disposed perpendicularly to webs 59 to reinforce across the leading portion 42,42’ of the shield 40,40’.

Figure 8A illustrates a rear perspective view of the handed shield 40’ installed between two adjacent discs 17 of a gang of discs. Figure 8B illustrates a front perspective view of the handed shield 40’ installed between the two adjacent discs 17.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country. In addition, the foregoing describes only some embodiments of the invention(s), and alterations, modifications, additions and/or changes can be made thereto without departing from the scope and spirit of the disclosed embodiments, the embodiments being illustrative and not restrictive.

For example, the shield 40 described above is formed as a unitary structure from the single piece of material. In an alternative embodiment, the shield 40 may be formed from multiple panel sections or multiple curved sections that are assembled together.

Furthermore, inventions have been described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention(s). Also, the various embodiments described above may be implemented in conjunction with other embodiments, for example, aspects of one embodiment may be combined with aspects of another embodiment to realize yet other embodiments.

In the foregoing description of preferred embodiments, specific terminology has been resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar technical purpose. Terms such as "front" and "rear", "inner" and "outer", "above", "below", "upper" and "lower" and the like are used as words of convenience to provide reference points and are not to be construed as limiting terms. The terms “vertical” and“horizontal” when used in reference to the impeller throughout the specification, including the claims, refer to orientations relative to the normal operating orientation of a disc plough.

In the claims which follow, and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word “comprise” and variations such as“comprises” or“comprising” are used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the apparatus and method as disclosed herein.

LEGEND

Claims (19)

1. A bearing hub protector for a disc plough having one or more discs rotatably supported on an axle by a bearing housed in a bearing hub, the bearing hub being fastened to at least one of the discs and having an access face on a side opposite to the disc, wherein the protector is formed:

(a) to extend at least partly about the bearing hub and axle; and

(b) to provide a space between the protector and the disc fastened to the bearing hub such that the space is off-set along the axle from the access face of the bearing hub.

2. The bearing hub protector according to claim 1 , where the space is radially off set from the bearing hub.

3. The bearing hub protector according to claim 1 or claim 2, wherein the bearing hub protector comprises a shaped panel that wraps at least partly about the bearing hub and the axle.

4. The bearing hub protector according to claim 3, wherein the shaped panel includes a leading portion and an open rear such that the access face is accessible via the open rear.

5. The bearing hub protector according to claim 3 or claim 4, wherein the shaped panel includes a leading portion that transitions into rearwardly extending upper and lower portions, such that the leading, upper and lower portions define a volume therebetween configured to receive the axle and the bearing hub.

6. The bearing hub protector according to claim 5, wherein the protector wraps at least partially about both the bearing hub and the axle.

7. The bearing hub protector according to claim 6, wherein the protector has a c- shaped profile that extends around 120° to 270° of the bearing hub.

8. The bearing hub protector according to any one of claims 5-7, wherein the protector includes a reinforcing partition that connects the leading portion with at least one of the upper or lower potions.

9. The bearing hub protector according to claim 8, wherein a reinforcing web extends across the leading portion perpendicularly oriented to the reinforcing partition.

10. The bearing hub protector according to any one of claims 5-9, wherein at least one of the upper and lower portions includes a slot for receiving a support member of the disc plough.

11. The bearing hub protector according to any one of claims 1-10, wherein the protector has an internal radius that is slightly greater than an external radius of the bearing hub.

12. The bearing hub protector according to any one of claims 1-11 , wherein the protector comprises at least one spacer configured to mount the protector to the disc plough.

13. The bearing hub protector according to claim 12, wherein the at least one spacer is mountable to the disc plough to locate internal faces of the protector spaced radially outwardly from the bearing hub.

14. The bearing hub protector according to claim 12 or claim 13, wherein the at least one spacer extends from an internal face of the leading portion.

15. The bearing hub protector according to any one of claims 12-14, wherein the spacer is a boss.

16. The bearing hub protector according to any one of claims 12-15, wherein the spacer or boss is integrally formed with the bearing shield.

17. The bearing hub protector according to any one of claims 12-15, wherein the spacer or boss is welded to the bearing shield.

18. A disc plough comprising one or more discs supported on a frame, wherein at least one disc is rotatably supported on an axle by a bearing housed in a bearing hub, the bearing hub being fastened to at least one of the discs and having an access face on a side opposite to the disc, wherein a protector according to any one of claims 1 to 17 at least partially encircles the bearing hub and the axle.

19. A disc plough disc plough having one or more discs supported on a frame, wherein at least one disc is rotatably supported on an axle by a bearing housed in a bearing hub, the bearing hub being fastened to at least one of the discs and having an access face on a side opposite to the disc, wherein the protector is formed in accordance with the protector defined in any one of claims 1 to 17.