A TIGHT BEARING SUITABLE FOR EXCEPTIONALLY HEAVY DUTY CONDITIONS

Abstract: A tight bearing suitable for exceptionally heavy duty condi­ tions is supplied with side screens (14) made of a plate com­ position (16) which is restrained to the external ring (10) of the bearing and forms a labyrinth seal against the inter­ nal ring (11), and of plastic and elastomer materials (15) supplied with a lip (17) which creates friction on the inter­ nal ring (11); other plates (18) are assembled externally with respect to the screens (14) and are integral on the in­ ternal ring (11) and form a labyrinth seal (23) with the ex­ ternal ring (10) of the bearing; the internal face of the external plates (28) is lined with a layer of plastic and elastomer material (19) from which at least one lip (20) ex­ tends and forms an essentially axial seal against the external face of the plate (16) of the internal adjacent screen (14); the lip (20) of the layer (19) which lines the internal face of the external plates (18) slips and seals along a certain length (21) of bent conical converging internal plate (16) towards the internal ring (11) and towards the external part of the bearing.

Description: The invention refers to a tight bearing suitable for particularly heavy duty conditions of the type known from the US-A-4376541. The bearings appointed to heavy duty operations are those ― as an example ― assembled on the rotating parts of earthworks machines. In these applications some elements like sand, stones, pebble gravel, mud, vegetable fibres are very hard on the resistance and tightness of the bearing during all its operating life. At present, the bearings appointed to particularly heavy duty conditions are generally of the type having a multi-contact rubber seal, that is consisting of a central body restrained to the plate that acts as a screen, from which several abreast lips extend and form a seal on the rotating element. Alternatively, several abreast rubber rings are assembled in the respective housings of the screen-plate instead of a central rubber body. These realizations having several sealing lips have the purpose of creating barriers to stop the entrance of external agents into the body of the bearing. Obviously, the more are the contact surfaces (lips) on the rotating part, the higher is the friction produced by the bearing: consequently, a reduction of the rotation speed takes places and/or a shorter life of the bearing. Furthermore, the above solutions require a high precision of the parts assembly, and this may be difficult to realize; a violent crash of the element on which the bearing is assembled or a strong hit against a stone is sufficient to cancel the optimum assembly conditions and consequently a quick wear of the bearing takes place. Document US-A-4376541 discloses a seal assembly used in rolling bearings whereby a sealing is held in a cavity formed by two side screens respectively fitted to the outer race and to the inner race. The sealing ring is mounted on the screen fixed to the outer race and it is designed so that its outer radial surface flatly engages the internal surface of the opposite screen. A drawback of such sealing is that it creates a great deal of friction and that consequently it is going to wear out quite quickly. Document EP-A-0198324 discloses a sealing unit with two rigid shields fitted, one on each race. The shield mounted on the outer race is fitted with an elastomeric sealing member having an annular rib that is extended prependicularly towards the shield fixed on the inner race, but without touching it. In very heavy conditions, a hard impact may cause misalignment between the inner and the outer races of the bearing: consequently, the two shields are moved away from each other, allowing contaminating agents to enter the bearing. In order to remove the above mentioned troubles, the invention proposes the realization of a bearing supplied with at least a rubber lip applied on a protection plate assembled on the rotating part and slidding on a conical surface of the plate of the immovable part of the bearing, so to guarantee contact between rubber lip and the conical surface of the plate, even in case some misalignment between the races may occur. This solution allows a sensible reduction of friction as it is less responsive to axial variations both during assembly and if crashes occur. The possibility to operate at higher speed and lower operative temperature derives from the above statement and the result is a longer operating life of the bearing. For these purposes and for further ones that will be understood better as the description follows, the invention proposes to realize a tight bearing suitable for exceptionally heavy duty conditions, of the type supplied with side screens made of a plate composition, which is restrained to the external ring of the bearing and which forms a labyrinth seal against the internal ring, and of a plastic or elastomer material supplied with a lip which creates friction on the internal ring; other plates are assembled externally with respect to the screens and are integral on the internal ring; the plates and the screens form a labyrinth seal with the external ring of the bearing; the internal face of the external plates is lined with a layer of plastic or elastomer material; characterized in that at least one lip extends from the plastic or elastomeric material and slips and forms an essentially axial seal against the external face of the plate of the internal adjacent screen, along a certain lenght of the plate which is bent, conical towards the internal ring and the external part of the bearing. A description of two types of the bearing follows and reference must be made to the enclosed drawings; the two types are meant to be examples of the realization of the invention, but not limits to it. Figure 1 is the part section view of the bearing according to fhe first realization of the invention. Figure 2 represents the view as in Figure 1 of the bearing according to the second realization of the invention. As it is well known, a revolving element consists of an external ring (10), an internal ring (11), balls (12) and screens (14) made of a composition of elastomer or plastic materials (15) and plate (16). The screens (14) are forced into grooves (13) of the external ring (10) and create a labyrinth seal with the internal one (11), while the lip (17) of the elastomer or plastic portion (15) creates a seal by pressing directly on the ring (11). A plate (18) is assembled on the internal ring (11); this plate operates as a rotating centrifuge with same internal ring. The plate (18) is also supplied with a plastic or elastomer materials lining (19) from which a slipping lip extends on the bent length (21) of the plate (16). The upper portion of the lining (19) creates a labyrinth seal (23) having a reduced port with the external ring (10) which is appointed for avoiding that coarse particles (stones, sand, mud, vegetable fibres) enter in contact with the seal lips (17 and 20). The chamber (22) located between the lips (17 and 20) and the plate screens (16 and 18) may be advantageously filled with grease in order to keep out eventual impurities and maintain the lubrication of the main lip (17). However, the main element of this bearing is lip (20) which slips on the conical surface (21) of the screen (16). This is an axial type of seal; for this reason the lip (20) will always find its own setting on the surface (21) either in case of faulty assembly or in case of crashes or blows on the bearing, so as to ensure the sealing without increasing the friction among the parts in contact. Furthermore, the rubber portion (19) of the external plate (18) will avoid the contact between metal and metal of the plates (16 and 18) still allowing a good operation of the bearing in case of crashes and damages to it. It is possible to realize a second lip (24, Fig. 2) if a further increase of the safety of the seal is wanted. This lip extends from the rubber portion (19) and slips on the plate (16) thus forming a further barrier against impurities towards the lip (17) in case a part of them should come over the labyrinth (23) and the seal (20-21).

Claims: 1. A tight bearing suitable for exceptionally heavy duty conditions, of the type supplied with side screens (14) made of a plate composition (16), which is restrained to the external ring (10) of the bearing and which forms a labyrinth seal against the internal ring (11), and of a plastic or elastomeric material (15) supplied with a lip (17) which creates friction on the internal ring (11); other plates (18) are assembled externally with respect to the screens (14) and are integral on the internal ring (11); the plates (18) and the screens (14) form a labyrinth seal (23) with the external ring (10) of the bearing; the internal face of the external plates (18) is lined with a layer of plastic or elastomer material (19); characterized in that at least one lip (20) extends from the plastic or elastomeric material (19) and slips and forms an essentially axial seal against the external face of the plate (16) of the internal adjacent screen (14), along a certain lenght (21) of the plate (16) which is bent, conical towards the internal ring (11) and the external part of the bearing. 2. Bearing according to claim 1 characterized in that besides the lip (20) which slips along the conical lenght (21), there is a second one (24) which also extends from the same layer of plastic or elastomer material (19) between the first lip (20) and the internal ring (11) which slips along the external face of the internal plate (16). 3. Bearing according to claim 1 characterized in that the layer of plastic or elastomer material (19) lines also the upper part of the external plate (18) and forms said labyrinth seal (23) with the external ring (10) of the bearing. 4. Bearing according to claim 1 characterized in that the chamber, located between lips (17 and 20) and the plates (16, 18), is filled with grease.

Inventors: COLANZI, FRANCO, VIGNOTTO, ANGELO
Applicants: RIV-SKF OFFICINE DI VILLAR PEROSA S.P.A
Application year: 1988
Main classification: F16C33
IPC codes: F16C33, F16J15