Support assembly

Abstract

Support assembly (10) for movable rotating shafts (50), having a bearing unit (30), a housing (20) and a cover (60); the bearing unit (30) is provided with a radially outer ring (31), which is stationary, a radially inner ring (33), which is rotatable, and a row of rolling elements (32) between the radially outer ring (31) and the radially inner ring (34); the support assembly (10) is also provided with a sealing device (70), located on the opposite side to the cover (60) with respect to the bearing unit (30) and stably fixed to the housing (20) where the sealing device (70) is provided with: - a metallic shaped shield (71); - an elastomer lining (72) co-moulded onto the shaped shield (71); - two radially inner sealing lips (73, 74), wherein a first axially outer lip (73) and a second axially inner lip (74) are in sliding contact with a radially outer cylindrical surface (33a) of the radially inner ring (33).

Description

[0001] SUPPORT ASSEMBLY

[0002] DESCRIPTION

[0003] Technical field of the invention

[0004] The present invention relates to a support assembly comprising a bearing unit with rolling members. The support assembly and the associated thus-formed bearing unit are suitable in particular for applications in the food industry, referred to below also as the F&B (food and beverage) industry.

[0005] Prior art

[0006] In the food industry the support assemblies of the known type are formed by a housing provided with a flange for fixing to the frame of a machine, and a bearing unit, which is located inside the housing in order to support a movable shaft and is provided with a system for spherical coupling with the said housing in order to compensate for possible static mounting misalignment of the movable shaft with respect to the fixed frame.

[0007] The machinery used in the food industry has numerous moving parts supported by rotating shafts, for example conveyor belts, kneading machines, machines for washing fresh food.

[0008] The assemblies for supporting movable shafts may be of the end-mounting type, where a terminal end of the shaft is housed, or of the through-mounting type. These support assemblies are formed by a housing, generally ring-shaped, provided with a base or flange for fixing to the machinery, by a bearing unit, which is located inside the housing and which is coupled with the movable shaft, and by a cover, normally cup-shaped, which is force-fitted onto the housing so that a connecting portion of the cover forms a fluid-tight seal with a radially outer side surface of the housing.

[0009] On the opposite side to the cover a rear sealing device is also provided, said sealing device comprising a metal shield onto which a vulcanized rubber provided with a plurality of sealing lips is co-moulded. The rear sealing device is stably fixed to the housing and, by means of its lips, forms a sliding contact with the shaft of the machinery.

[0010] The bearing unit, in turn, comprises a first component, for example a radially inner ring, which is fixed to a rotating element (for example the shaft), and a second component, for example a radially outer ring, which is fixed to a stationary element (for example the housing). In rolling bearing units, the rotation of one ring with respect to the other ring is allowed by a plurality of rolling elements which are positioned between the cylindrical surface of one component and the cylindrical surface of the second component, normally called raceways. The rolling elements may be balls, cylindrical or tapered rollers, needle rollers or similar rolling elements.

[0011] The bearing unit also has two sealing devices, located on opposite sides of the rolling elements, for providing protection against external contaminants and for forming a seal for the lubrication grease. The sealing devices are formed by a shaped shield which is mounted by means of an interference fit in suitable seats of the rings of the bearing unit, for example the radially outer ring, and provided with an elastomer lining comprising one or more sealing lips. The latter may form, during use, a sliding contact with other components of the bearing unit, for example, with the rotating radially inner ring. In particular, the sealing device located on the same side as the cover, namely axially inner side, could be provided with a pair of shields, the sealing lips of which may be in the form of a “gutter”, namely arranged axially on the outside and substantially parallel to each other, so as to form “labyrinth” seals.

[0012] As mentioned, the rear sealing device of the support assembly forms a sliding contact with the rotating shaft of the machinery. In order to provide an effective seal, the shaft should be of optimum quality, namely be heat-treated so as not to be subject to wear. In the food industry, however, it is necessary for the components to be corrosion-resistant and therefore the material of the shaft must of the same class as that of stainless steels. As is known, stainless steels are the best material in terms of corrosion-resistance, but cannot be heat- treated. Therefore, it is difficult to ensure a contact between the rear sealing device and the shaft which does not wear the shaft itself. This wear negatively affects the performance of the sealing device and, in addition, gives rise to metal particles which circulate inside the bearing unit.

[0013] Furthermore, the bearing units present on the food industry market almost all use a system for eccentrically locking the inner ring on the shaft (locking screw or eccentric locking system). This results from the requirements of the F&B applications. The solutions with a concentric locking system are more complex and require further components (sleeves, bushes, fixing rings) which increase the assembly time, but in particular create many small holes inside which contaminants may become lodged and make a good washing process practically impossible. Nevertheless, even when an eccentric solution is used, the external contaminating agents may in any case penetrate inside, for example via the end cover, and reach the rear part of the bearing unit, bypassing the rear sealing device which is therefore completely ineffective.

[0014] From experimental tests it has been seen that water and metal particles (for example due to wear of the shaft) manage to pass from one side to the other of the bearing unit. Furthermore, a further risk of infiltration of contaminants is associated with the procedure for disassembly and reassembly of the end cover which might not be performed correctly. Finally, the washing procedure, if not performed at the correct pressure, but at higher pressures, results in the entry of water inside the bearing unit. Basically, there exist numerous situations which lead to the contamination of the inside of the bearing unit.

[0015] Summary of the invention

[0016] The object of the present invention is to provide a support assembly for applications in the food industry which does not have the aforementioned drawbacks.

[0017] According to the present invention a support assembly for the food industry having the characteristic features described in the accompanying claims is provided.

[0018] Brief description of the drawings

[0019] The invention will now be described with reference to the attached drawings which illustrate a number of non-limiting examples of embodiment of the housing element, in which:

[0020] - Figure 1 shows a cross-sectional view of a preferred embodiment of a support assembly provided in accordance with the present invention;

[0021] - Figure 2 shows, on a larger scale and cross-sectioned, a detail of Figure 1; and

[0022] - Figure 3 shows, on an even larger scale and cross-sectioned, another detail of Figure 1.

[0023] Detailed description With reference now to Figure 1, the reference number 10 denotes overall a support assembly for movable rotating shafts, which are not shown for simpler illustration.

[0024] The support assembly 10 comprises a bearing unit 30, for example a rolling bearing of the known type, adapted to receive in a known manner a movable shaft 50, for example rotating shaft, in order to support it, and a housing 20 having a through-seat 40 inside which the bearing unit 30 is housed in a stable and known manner. The support assembly 10 further comprises an end cover 60 adapted to close in a fluid-tight manner the bearing unit 30, and a sealing device 70 situated at the rear, in other words located on the opposite side to the cover 60 with respect to the bearing unit 30.

[0025] The bearing unit 30 for applications in the food sector comprises:

[0026] - a radially outer ring 31, which is preferably stationary;

[0027] - a radially inner ring 33, which is preferably rotatable about a central axis of rotation X of the bearing unit 30;

[0028] - a row of rolling elements 32, in this example balls, interposed between the radially outer ring 31 and the radially inner ring 33;

[0029] - a cage 34 for containing the rolling elements so as to keep the rolling elements of the row of rolling elements 32 in position;

[0030] - a device 36 for fixing the bearing unit 30, in particular the radially inner ring 33 to a machine shaft, formed for example by means of a pair of hexagon socket screws 36a.

[0031] In all of the present description and in the claims, the terms and the expressions indicating positions and orientations such as "radial" and "axial" are understood as being in relation to the central axis of rotation X of the bearing unit 30.

[0032] For the sake of simpler graphical illustration, the reference number 32 will be attributed both to the individual balls and to the row of balls. Again for the sake of simplicity, the term "ball" may be used by way of example in the present description and in the attached drawings instead of the more generic term "rolling element" (and likewise the same reference numbers will be used). Some examples of embodiment and the associated drawings may envisage the use of rolling elements other than balls (for example rollers) without thereby departing from the scope of the present invention. The bearing unit 30 is also provided with two sealing devices 35, 35’ for sealing off the bearing unit from the external environment. The two sealing devices are located on opposite sides of the rolling elements 32, in particular a first sealing device 35’, on the same side as the cover 60, namely the axially inner side, and a second sealing device 35, on the opposite side, namely the axially outer side. The second sealing device 35 is in any case situated axially inner with respect to the rear sealing device 70.

[0033] With reference also to Figure 2, each sealing device 35, 35’ comprises a first shield 35a which is stably fixed to the radially outer ring 31, which is therefore stationary, and a second shield 35b which is axially outer with respect to the first shield 35a and stably fixed to the radially inner ring 33, which is therefore rotatable. The first shield 35a and the second shield 35b axially face each other and are provided with an elastomer lining and a plurality of annular sealing lips. Each lip 35c of the first shield 35a faces axially a respective lip 35d of the second shield 35b, thus defining pairs of sealing lips, wherein the lips of each pair of annular sealing lips are radially and axially superimposed, but also radially and axially separate, namely free from each other without any point of contact.

[0034] According to the invention, the rear sealing device 70 is stably fixed to the housing 20 and is in sliding contact with the rotatable radially inner ring 33. More particularly, the rear sealing device 70 comprises:

[0035] - a metallic shaped shield 71;

[0036] - an elastomer lining 72 co-moulded onto the shaped shield 71;

[0037] - two sealing lips 73, 74 forming the radially inner portions of the elastomer lining 72, wherein a first axially outer lip 73 and a second axially inner lip 74 ensure the seal by means of sliding contact with the radially inner ring 33 and in particular with a radially outer cylindrical surface 33a thereof.

[0038] Preferably, the metallic shaped shield 71, in the direction radially inwards from the housing 20 to the radially inner ring 33, comprises:

[0039] - a cylindrical portion 711 stably fixed inside a seat 20a for mounting the housing 20;

[0040] - a first flange portion 712 connected to the cylindrical portion 711;

[0041] - a first oblique portion 713; - a second flange portion 714, where the first flange portion 712 and the second flange portion 714 are connected together by means of the first oblique portion 713; and

[0042] - a second oblique portion 715, inclined axially inwards and connected to the second flange portion 715.

[0043] The two oblique portions 713, 715 have the function of reinforcing the entire rear sealing device 70.

[0044] In particular and with reference also to Figure 3, the second oblique portion 715 supports and reinforces a root portion 721 of the elastomer lining 72, from which the first sealing lip 73 and the second sealing lip 74 extend.

[0045] Advantageously, the root portion 721 defines a radially inner cylindrical surface 722, from the sides of which the first lip 73 and the second lip 74 extend. This cylindrical surface 722 must be located at a distance of not less than 1.8 mm from the cylindrical surface 33a of the radially inner ring 33, i.e. as mentioned, the surface making contact with the lips 73, 74, so as to ensure sufficient flexibility of the sealing lips 73, 74.

[0046] Preferably, the first axially outer lip 73, in addition to extending radially inwards, extends axially outwards. The lip 73 is defined on the axially inner side by a conical surface 731 and, on the axially outer side, starting from the root portion 721, by a spherical surface 732, by a conical surface 733 and by an annular surface 734. Finally, a radially inner cylindrical surface 735 defines, together with the surface 33a of the radially inner ring 33, the sliding contact between the lip 73 and the inner ring 33.

[0047] The first lip 73, by means of the axially outer surfaces, i.e. spherical surface 732, conical surface 733 and annular surface 734, forms the first and most effective barrier against the contaminants, in particular against any high-pressure washing water. The pressure of the water, in fact, pushes the first lip 73 axially inwards and the first lip, being deformed, increases its interference with the cylindrical sealing surface 33a.

[0048] In particular, the spherical surface 732 defines a cavity 75 inside which most of the contaminants may be collected. The contaminants in fact collect in the centre of the groove 73. Moreover, in the presence also of water, the contaminants may be driven circumferentially by the water itself and may be expelled by means of gravity once the underlying part of the bearing unit is reached (passing therefore through an angle of about 180 degrees). Moreover, the spherical surface 732 is such that the lip 73 is sufficiently flexible with the aim of:

[0049] - reducing the friction resistance generated by the sliding contact with the inner ring; and

[0050] - ensuring, at the same time, sliding contact with the inner ring, also in the case where static misalignment occurs during mounting of the movable shaft (and therefore the inner ring) with respect to the fixed frame (and therefore the housing).

[0051] In other words, the flexibility ensures that the lip 73 may extend in the event of misalignments which move the surface 33a of the inner ring 33 away from the cylindrical surface 735 of the lip 73, while remaining always in contact and sufficiently compressed by the inner ring, and also that the lip 73 may compress further in the event of misalignments which move the surface 33a of the inner ring 33 towards the cylindrical surface 735 of the lip 73.

[0052] The inclination towards the outside of the first lip 73 may be defined by the angle a formed between the cylindrical surface 33a of the radially inner ring 33 and the axially inner oblique surface 731 of the first lip 73. Preferably, values for the angle a are between 50° and 70°. Higher values would make the above-described action against contaminants (in particular fluids under pressure) less effective, while lower values (lip more open outwards) would weaken the structure of the lip itself and at the same time would require a greater axial length of the radially inner ring.

[0053] The second lip 74 extends from the root portion 721 of the elastomer lining 72 axially towards the inside (as well as radially inwards). The lip 74 is defined on the axially outer side by a conical surface 741 and, on the axially inner side, starting from the root portion 721, by a conical surface 742 and by an annular surface 743. Finally, a radially inner cylindrical surface 744 defines the sliding contact with the surface 33a of the radially inner ring 33.

[0054] The inclination towards the inside of the second lip 74 may be defined by the angle b formed between the cylindrical surface 33a of the radially inner ring 33 and the axially outer conical surface 741 of the first lip 74. Preferably, the values for the angle b range between 50° and 70° and the two angles a and b assume the same value so that there is symmetry with respect to the cylindrical surface 722 of the root portion 721 between the respective conical surfaces 731, 741 of the first lip 73 and the second lip 74.

[0055] The second lip 74, however, should not make contact with the second shield 35b of the sealing device 35 of the bearing unit. This is because the lip 74 would come into sliding contact with a rotating steel element which has a sharp corner edge, with the risk of wear. For this reason, the minimum axial distance D2 between the second lip 74 and the second shield 35b of the sealing device 35 must be not less than 0.5 mm.

[0056] Advantageously, owing to the generally rigid structure of the rear sealing device 70 and, consequently, the rigidity of the two lips, it is possible to reduce also by up to 30% the interference between the said lips 73, 74 and the radially inner ring 33.

[0057] The seal formed by the lips 73, 74 in sliding contact with the radially inner ring 33 offers numerous advantages compared to the known solutions in which the sliding contact of the rear sealing device occurs between lips and rotating shaft.

[0058] First of all, the radially inner ring, which is made of tempered steel, is not subject to wear.

[0059] Moreover, since there is no contact between lips 73, 74 and the rotating shaft, any risk of wear of the shaft and, consequently, any risk of metal particles circulating inside the bearing unit 30 is avoided. By way of a further consequence, the manufacturer of the machinery comprising the support assembly 10 may use a shaft with an outer surface which is not particularly finished, since the seal is formed on the radially inner surface and not on the shaft.

[0060] Finally, the seal is of an excellent quality since the surface 33a of the radially inner ring is finished with extreme precision since it also has the function of being a contact surface for the sealing shields 35 and 35’. Therefore, owing to this high-quality seal, even if the contaminants (for example the pressurised water for washing the components) were to penetrate inside the support assembly 10 on the side where the terminal cover 60 is located, they would be unable to reach the bearing unit 30 from the rear side, namely the side opposite to the cover 60. All of this, without forgetting that the bearing unit 30 is also protected by the sealing devices 35, 35’ which, owing to their geometry, define in any case winding paths, similar to labyrinths, which prevent further the passage of the contaminants.

[0061] From the design point of view, this solution does not involve any drawback, it being sufficient to lengthen the radially inner ring 33 axially. Incidentally, it may be pointed out that, owing to the axial lengthening of the radially inner ring 33, it is possible to locate also on the opposite side to the cover 60, a sealing device (the second sealing device 35) which is identical and a mirror image of the first sealing device 35’, namely also provided both with the first shield 35a and the second shield 35b.

[0062] Therefore, the solution according to the present invention, overall, is undoubtedly suitable for increasing the protection of the bearing unit. In addition to the embodiments of the invention, as described above, it is to be understood that numerous further variants exist. It must also be understood that said embodiments are only examples and do not limit either the scope of the invention, nor its applications, nor its possible configurations. On the contrary, although the description provided above enables the person skilled in the art to implement the present invention at least in one of its examples of configuration, it must be understood that numerous variations of the components described are feasible, without thereby departing from the scope of the invention, as defined in the accompanying claims, interpreted literally and / or in accordance with their legal equivalents.

Claims

CLAIMS1. Support assembly (10) for movable rotating shafts (50), comprising a bearing unit (30) adapted to receive the movable shaft, a housing (20) and a fluid-tight cover (60) adapted to seal a first side of the bearing unit (30); the bearing unit (30) comprising a radially outer ring (31), which is stationary and mounted in the housing, a radially inner ring (33), which is rotatable, and a row of rolling elements (32) between the radially outer ring (31) and the radially inner ring (34); the support assembly (10) also comprising a sealing device (70), located on the opposite side to the cover (60) with respect to the bearing unit (30) and stably fixed to the housing (20); the support assembly being characterized in that the sealing device (70) comprises, in combination:- a metallic shaped shield (71),- an elastomer lining (72), co-moulded onto the shaped shield (71),- two single, radially inner, sealing lips (73, 74), wherein a first axially outer lip (73) and a second axially inner lip (74) are in sliding contact with a radially outer cylindrical surface (33a) of the radially inner ring (33) and wherein the first lip (73) projects axially outwards and is defined on an axially outer side by a spherical surface (732).

2. Support assembly (10) according to Claim 1, wherein the first lip (73) is defined on an axially inner side by a conical surface (731) and, on the axially outer side, in addition to the spherical surface (732), by a conical surface (733), by an annular surface (734) and by a radially inner cylindrical surface (735).

3. Support assembly (10) according to Claim 2, wherein an angle (□) between the cylindrical surface (33a) of the radially inner ring (33) and the axially inner conical surface (731) of the first lip (73) ranges between 50° and 70°.

4. Support assembly (10) according to any one of the preceding claims, wherein the shaped shield (71) comprises:- a cylindrical portion (711) stably fixed in a seat (20a) for mounting the housing (20),- a first flange portion (712) connected to the cylindrical portion (711),- a first oblique portion (713),- a second flange portion (714) which connects together the first flange portion (712) and the second flange portion (714), and- a second oblique portion (715) connected to the second flange portion (714).

5. Support assembly (10) according to Claim 4, wherein the second oblique portion (715) supports a root portion (721) of the elastomer lining (72), from which the first sealing lip (73) and second sealing lip (74) extend.

6. Support assembly (10) according to Claim 5, wherein the root portion (721) comprises a radially inner cylindrical surface (722), from the sides of which the first lip (73) and the second lip (74) extend.

7. Support assembly (10) according to Claim 6, wherein the cylindrical surface (722) is situated at a distance of not less than 1.8 mm from the cylindrical surface (33a) of the radially inner ring (33).

8. Support assembly (10) according to any one of the preceding claims, wherein the bearing unit (30) comprises on opposite sides of the row of rolling elements (32) two sealing devices (35, 35'), each of which comprises a second shield (35b) stably fixed to the radially inner ring (33).

9. Support assembly (10) according to any one of the preceding claims, wherein the second lip (74) extends from the root portion (721) of the elastomer lining (72) in an axially inward direction.

10. Support assembly (10) according to Claim 9, wherein the minimum axial distance(D2) between the second lip (74) and the second shield (35b) of the sealing device (35) is not less than 0.5 mm.

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