PATENT ABSTRACT
A hub-bearing assembly for rotatably mounting a tilling disc about an axis of rotation. The hub-bearing assembly includes an annular hub providing an axially extending tubular portion, comprising a housing and a radially outer flange for mounting a disc. A bearing unit is mounted within the housing. An elastic damping body axially is fitted between the radially outer flange and the disc.

PATENT DESCRIPTION
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a Non-Provisional Patent Application, filed under the Paris Convention, claims the benefit of Italy Patent (IT) Application Number TO2014A000393 filed on 19 May 2014, which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present invention is related to a hub-bearing assembly for an agricultural tilling disc. 
     As known, discs for agricultural use are usually rotatably assembled on corresponding spindle, projecting from the frame of a plough or other agricultural machine. 
     BACKGROUND ART 
     From document WO 2002/019791 A is known a hub-bearing assembly for rotatably mounting a tilling disc for agricultural use, around an axis of rotation. The assembly comprises an annular hub, having a tubular portion axially extending, which defines a substantially cylindrical housing and a radially outer flange for fixing the disc. In the housing a bearing unit is located, the bearing unit comprising an outer ring, one or two inner rings and one or two set of rolling bodies, interposed between inner and outer rings. In other solutions, the outer ring is in one piece with the flanged hub. 
     During the working life, impacts of the disc against stones and similar bodies damage the bearing raceways, reducing the bearing lifetime. 
     BRIEF SUMMARY OF THE INVENTION 
     Aim of the present invention is to realize a hub-bearing assembly for an agricultural tilling disc, which overcomes the above mentioned inconveniences. 
     This and other purposes and advantages, which will be better hereafter understood, are obtained according to an aspect of the invention by a hub-bearing assembly as defined in the enclosed independent claim. 
     Further embodiments of the invention, preferred and/or particularly advantageous, are described according to the characteristics as in the enclosed dependent claims. 
     In practice, the hub-bearing assembly comprises an elastic damping body coupled to the hub flange and facing the disc for agricultural use. The elastic damping body absorbs part of dynamic loads, due to the impacts of the disc against the stones. Therefore, the dynamic loads no more fully transmitted to the bearing and its rolling bodies, do not remarkably damage the bearing raceways. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be now described by reference to the enclosed drawings, which show some non-limitative embodiments, namely: 
         FIG. 1  is an axial cross section of a disc for agricultural use, the disc being rotatably assembled around a spindle by a hub-bearing assembly, according to an embodiment of the invention; 
         FIG. 2  is a perspective view of the disc with hub-bearing assembly and spindle of  FIG. 1 ; 
         FIG. 3  is an enlarged view, partly in cross section, of the hub-bearing assembly and the spindle of  FIG. 1 ; and 
         FIG. 4  is an enlarged detail of the cross section in  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to the above figures, a hub-bearing assembly according to an embodiment of the invention, referenced as a whole with  10 , is used for mounting a tilling disc A in a freely rotatable way around an axis of rotation x, which is defined by a spindle B projecting from an agricultural machine or tool (not shown), as an example, a plow, a harrow or other similar tools. Features of disc A, which can be a whatever known disc, for example a disc for plowing or a disc for seeding (suitable for opening furrows in a previously plowed land), are not relevant for the invention understanding and therefore will not be described in further details. 
     With reference to  FIG. 3 , the hub-bearing assembly  10  comprises a hub  20 , a bearing unit  30  housed in the hub  20  and an elastic damping body  40 , axially interposed between the hub and the disc A. 
     In particular, the hub  20  has a substantially annular shape and presents a main tubular portion  21  axially extended, which internally defines a substantially cylindrical housing  22  for the bearing unit  30 . The housing is radially confined by an inner wall  22   a  substantially cylindrical. Throughout the present description and in the claims, the terms and expressions indicating positions and orientations such as “radial” and “axial” are to be taken to refer to the axis of rotation x of the bearing unit  30 . 
     From a first axial end of the tubular portion  21  of the hub, a radially outer flange  23  extends, the flange having a plurality of axial holes for mounting the disc A by means of suitable fastening means, for example screws  24 . From a second axial end of the tubular portion  21  a radially inner flange  25  extends, axially confining the housing  22  on the very far side with respect to the disc. 
     The bearing unit  30  is a so called first generation unit, without radially projecting flanges. The bearing unit  30  comprises a rotatable outer ring  31 , a pair of inner rings  32 ,  33  side by side assembled on the spindle B and a dual set of rolling bodies  34 ,  35 , for example spheres, interposed between the outer ring  31  and the inner rings  32 ,  33 . The rotatable outer ring  31  presents a radially outer wall  31   c  substantially cylindrical, which is coupled with the inner wall  22   a  of the tubular portion  21  of the hub  20 . 
     The inner rings  32 ,  33  are axially tightened against a shoulder C of the spindle, by means of a spacer D, mounted on the spindle, which is pre-loaded by means of a nut not shown), according to a known embodiment. 
     The inner flange  25  radially extends towards the spindle and presents a radial surface  25   a  for locking a radial surface  31   c  of the bearing outer ring  31 . Moreover, in the shown embodiment the flange  25  forms an annular groove  26  towards the bearing and suitable to accommodate a sealing device, schematically shown and referenced with E, being the seal deputed to slide against the spacer D or other component steadily connected to the spindle B, with the aim to hermetically seal the bearing housing  22  towards outside. 
     The elastic damping body  40  allows the disc A to elastically absorb impacts, received during use, and reduce damages, undesired movements and arising clearances, due to impacts transmitted by the disc. 
     The elastic damping body  40  is made of an elastomeric and plastic material and is located on the side facing the tilling disc A, more precisely, is located on a substantially annular surface  23   a  of the flange  23 , in an axially external position. As a consequence, the elastic damping body faces the disc A and in particular a substantially circular surface Aa, in an axially internal position. 
     According to a preferred embodiment, the elastic damping body  40  is shaped as a cap, having a substantially annular wall  41 , which is steadily connected to a substantially cylindrical wall  42 , the cylindrical wall  42  being in a radially external position respect to the annular wall  41 . 
     The annular wall  41  of the elastic damping body  40  is axially interposed between the flange  23  of the hub  20  and the disc A. More in detail, the annular wall is located on the annular surface  23   a  of the flange  23 , or when the disc A is mounted, is axially interposed between the annular surface  23   a  of the flange  23  and the circular and axially internal surface Aa of the disc A. 
     The cylindrical wall  42  of the elastic damping body  40  is radially coupled with the flange  23 , by means of a substantially cylindrical surface  42   a  of the cylindrical wall  42 , in a radially internal position, and a corresponding substantially cylindrical surface  23   b  of the flange  23 , in a radially external position. 
     The elastic damping body  40  is coupled to the flange  23  by means of known processes. As an example, the coupling between the two components can be realized co-molding the elastic damping body  40  on the flange  23  or gluing them or connecting them by mechanical fastening means. 
     Preferably, the substantially cylindrical surface  23   b  of the flange  23  is stepwise shaped, in other words is formed by a plurality of cylindrical portions  23   b ′,  23   b ″,  23   b ″′, having decreasing diameters and each other connected by annular surfaces  23   c ′,  23   c ″. As a consequence, also the surface  42   a  of the cylindrical wall  42  of the elastic damping body  40  is stepwise shaped as well. In this way, the coupling surface between elastic damping body and flange increases; moreover, the stepwise shape of the two coupling surfaces improves the grip between elastic body and flange and consequently a more stable coupling between them is obtained. 
     Advantageously, the flange  23  is provided with an annular groove  23   d , located along the substantially annular surface  23   a  and consequently the annular wall  41  of the elastic damping body  40  has an annular protrusion  41   a , which is coupled with the annular groove  23   d . In this way, the thickness of the elastic damping body can be increased, obtaining at the same time a greater damping effect and a better grip in the coupling elastic body-flange. 
     In definitive, the elastic body  40  interposed between the disc and the flange can absorb vibrations and hits, which derive by the impact of the disc against stone materials on the agricultural land. In practice, the elastic damping body works as a shock absorber. In fact, all impulsive load due to impacts against stones are not completely transmitted to the bearing and in particular to its rolling bodies, because of the damping effect of the elastic damping body. This effect avoids damages to the raceways and consequently increases the bearing lifetime. The improved bearing lifetime means a cost reduction of the whole device for agricultural use. 
     Finally, it has to be remarked that the proposed solution does not bring any manufacturing difficulty for realizing the whole bearing-hub assembly. In fact, according to this solution, standard dimensions and shapes can be used for the bearings. Just one component requires further machining operations, the flange of the hub. Anyway, being the flange made of a not hardened metal, such further machining operations do not require special processes or tools. Moreover, the interposition of the elastic damping body between the flange and the disc make simpler the production process of both the bearing and the whole bearing-hub assembly, provided with the damping body. At the same time, this solution does not influence at all the desired pre-stress conditions of the bearing, being the bearing direct interfaces made of metallic components. 
     Other than the embodiments of the invention, as above disclosed, it is to be understood that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents.