Abstract:
A hub-bearing assembly is disclosed, wherein the hub-bearing assembly is used for rotatably mounting a tilling disc about an axis of rotation is disclosed. The hub-bearing assembly comprises an annular hub comprising an axially extending tubular portion defining a cylindrical housing and an outer flange for mounting a disc, a bearing unit mounted in the housing, and an elastic damping body arranged in the housing and radially interposed between the hub and an outer ring of the bearing unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a United States Non-Provisional Utility Patent Application claiming the benefit of Italian Patent Application Number TO2012A000651 filed on 25 Jul. 2012, which is incorporated herein in its entirety. 
     TECHNICAL FIELD 
     The present invention relates to a hub-bearing assembly for a tilling disc. 
     BACKGROUND ART 
     As is well known, tilling discs are usually mounted rotatably on respective spindles projecting from the frame of a plough or other agricultural machine. 
     WO 2002/019791 A discloses a hub-bearing assembly for rotatably mounting a tilling disc about an axis of rotation. The assembly comprises an annular hub having an axially extended tubular portion defining a generally cylindrical housing and a radially outer flange for fixing to a disc. In the housing is mounted a bearing unit comprising an outer ring, one or two inner rings and a dual set of rolling elements interposed between the outer and inner rings. In other solutions, the outer ring of the bearing is integrated into the flanged hub, forming therewith a single piece. 
     During use, impacts suffered by the disc against stones and similar damage the raceways of the bearing and shorten its working life. 
     It is therefore an object of the invention to create a hub-bearing assembly for a tilling disc capable of remedying the above-mentioned disadvantage. 
     DISCLOSURE OF INVENTION 
     It is therefore an object of the invention to create a hub-bearing assembly for a tilling disc capable of remedying the above-mentioned disadvantage. 
     This and other objects and advantages, which will be better understood hereafter, are achieved according to an aspect of the invention by a hub-bearing assembly for rotatably mounting a tilling disc about an axis of rotation, the hub-bearing assembly comprising:
         an annular hub including:
           an axially extending tubular portion defining a generally cylindrical housing, and   a radially outer flange for mounting a disc;   
           a bearing unit mounted within the housing and comprising an outer ring, a pair of inner rings and a dual set of rolling elements, interposed between the outer ring and the inner rings; and   an elastic damping body arranged in the housing and radially interposed between the hub and the outer ring of the bearing unit.       

     Other advantageous features are defined in the dependent claims. 
     Briefly, the hub-bearing assembly comprises an elastic damping body radially interposed between the hub and the outer ring of the bearing unit. The elastic damping body absorbs part of the dynamic stresses coming from impacts of the disc against stones. These stresses, no longer being fully transferred to the bearing and its rolling elements, do not noticeably damage the raceways. According to some preferred embodiments, the relative movements between the bearing unit and the housing formed from the hub for the bearing are limited due to the forced mounting of the elastic body between the bearing and the hub and owing to particular shapes taken by the outer surface of the outer bearing ring and by the housing of the hub in which the bearing unit is accommodated by means of the interposition of the elastic damping body. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       A description will now be given of a few preferred, but not limiting, embodiments of the invention. Reference is made to the attached drawings, in which: 
         FIG. 1  is a view in axial section of a tilling disc mounted rotatably about a spindle by means of a hub-bearing assembly according to an embodiment of the invention; 
         FIG. 2  is a perspective view of the disc with the hub-bearing assembly and spindle of  FIG. 1 ; and 
         FIG. 3  is an enlarged view, in partial axial section, of the hub-bearing assembly and spindle of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Making reference now to the drawings, a hub-bearing assembly according to an embodiment of the invention, indicated in its entirety  10 , serves for mounting a disc A in freely rotatable manner about an axis of rotation x defined by a spindle B projecting in cantilever from a machine or an agricultural implement (not illustrated), such as for example a plough, a harrow or similar. The characteristics of the disc A, which may be of any known type, for example a disc for ploughing or a disc for sowing (suitable for opening furrows in a previously ploughed terrain), are not significant for the purposes of understanding the present invention and will therefore not be described here in detail. 
     The assembly  10  comprises a hub  20 , a bearing unit  30  housed in the hub  20  and an elastic damping body  40  interposed between the hub and the bearing unit. 
     The hub  20 , of overall annular form, has an axially extended principal tubular portion  21 , which defines within itself a generally cylindrical housing  22  for the bearing unit  30 . The housing  22  is delimited radially by a substantially cylindrical inner wall  22   a , described below. 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 central axis of rotation x of the bearing unit  30 . 
     From a first axial end of the tubular portion  21  of the hub there extends a radially outer flange  23  having a plurality of axial bores  24  for mounting the disc A. From a second axial end of the tubular portion  21  there extends a radially inner flange  25  which axially delimits the housing  22  on the side further from the disc. 
     The bearing unit  30  is a bearing unit of the so-called first generation, i.e. without radially projecting flanges. The bearing unit  30  comprises a rotatable outer ring  31 , a pair of inner rings  32 ,  33  mounted side by side on the spindle B and a dual set of rolling elements  34 ,  35 , in this example balls, interposed between the outer ring  31  and the inner rings  34 ,  35 . The rotatable outer ring  31  has a substantially cylindrical radially outer wall  31   a , more fully described below. Referring to  FIG. 3 , the first axial end of the outer ring  31  is the end closest to the disc  10 , and, the second axial end of the outer ring  31  is the end furthest from the disc  10 . 
     The inner rings  32 ,  33  are axially locked in position against a shoulder C on the spindle by means of a spacer D forcefully fitted onto the spindle, which is preloaded through a ring-nut (not illustrated) according to a per se known arrangement. Preferably, inner ring  32  extends axially outwardly past the first axial end of the outer ring. 
     The inner flange  25  extends radially towards the spindle, and provides a radial surface  25   a  for abutting a radial surface  31   c  of the outer ring  31  of the bearing. In the embodiment illustrated, the flange  25  further forms an annular recess  26 , facing towards the bearing, suitable for accommodating a sealing device schematically indicated E, designed to slide against the spacer D or against another element integral with the spindle B in order to hermetically seal the housing  22  of the bearing towards the outside. The annular recess  26  of the inner flange  25  may extend over the entire radial side of the sealing device. 
     The elastic damping body  40  allows the disc A to elastically absorb the impacts which it receives during use, and to limit damage, undesired movements and the appearance of play which the bearing unit may undergo as a result of impacts transmitted by the disc. 
     The elastic damping body  40  is comprised of a tubular sleeve of elastomeric material, radially interposed between the substantially cylindrical wall  22   a  of the housing  22  and the radially outer surface  31   a  of the outer ring  31  of the bearing. 
     In a preferred embodiment, the elastic body  40  is fabricated at a preliminary stage, for example by extrusion or hot forming, and is then forcibly introduced (cold pressed) into a cylindrical gap located between the surfaces  22   a  and  31   a , after the bearing unit has been introduced into the housing  22 . 
     The elastic body  40  has a tubular wall  41  having a radial thickness which, in the undeformed condition, i.e. before the introduction of the body  40  between the walls  22   a  and  31   a , is preferably greater than a dimension or radial distance which separates the surface  31   a  from the wall  22   a . Due to this arrangement, the elastic body  40  remains elastically compressed in radial directions between the housing  22  of the hub and the outer bearing ring  31 . 
     According to an alternative embodiment, the elastic body  40  is fabricated by injecting elastomeric material in the fluid state into the cylindrical gap located between the surfaces  22   a  and  31   a , after the bearing unit has been introduced into the housing  22 . 
     In the illustrated embodiment, the elastic body  40  has an axial length greater than the axial length of the outer ring  31  of the bearing, so as to ensure an elastic damping effect on the bearing unit for stresses transmitted thereto by the hub according to any direction or angle. Preferably, the elastic body  40  extends axially outwardly past the first and second axial ends of the outer ring. 
     To allow a uniform elastic response, the radial thickness of the tubular wall  41  is preferably constant. In order to guarantee correct positioning of the elastic body  40 , an annular groove  27  is formed in the housing  22 . The annular groove  27  extends into the inner flange  25  at the axial end of the wall  22   a  located, in use, further from the disc A. The annular groove  27  steadily accommodates an edge  42  of the elastic body  40 . One axial end of the elastic damping body  40  may be free of abutment. 
     Preferably, the wall  22   a  is not perfectly cylindrical but has a protrusion projecting in a radially inner direction, in this example a protrusion  22   b  in the form of an annular ridge, suitable for favoring a steady axial positioning of the elastic body  40  with respect to the housing  22  and the hub  20 . In this example, the protrusion  22   b  is shaped as an annular ridge which extends circumferentially around the substantially cylindrical inner wall  22   a . In the particular embodiment illustrated, also the radially outer surface  31   a  of the outer ring  31  is not perfectly cylindrical but provides a radial recess  31   b  preferably in the form of an annular channel or groove extending circumferentially, with the object of favoring a stable relative axial positioning of the elastic body  40  with respect to the bearing unit. In order to maintain a uniform level of compression in the body  40 , it is preferable that the radial protrusion  22   b  and the radial recess  31   b  should be aligned in a same radial plane, so as to maintain a constant radial distance between the facing surfaces  22   a  and  31   a . Advantageously, the protrusion  22   b  is located in an axially intermediate position between two radial planes P 1 , P 2  in which lie the two sets of rolling elements  34 ,  35 . 
     In a preferred embodiment, the annular groove  31   b  is formed in a particularly convenient manner if the outer ring  31  is fabricated starting from steel tube cut and subjected to cold rolling so as to form the annular groove  31   b . The specific form illustrated of the annular groove  31   b  is not to be considered limiting, since grooves of different profile, for example of square profile, can also be effective for axially locking the outer ring  31 . The material of the damping body  40 , being elastically deformable, makes it possible to adapt the shape of the body  40  to that of the annular groove  31   b.    
     In a preferred embodiment, the elastic damping body  40  is axially retained between the hub and the outer ring of the bearing simply as a result of the elastic compression to which the body  40  is subjected, without necessitating further retaining means, such as for example the application of adhesive. The elastic damping body  40  is held even more stably as a result of the protrusion  22   b , which generates a further radial compression stress, favoring the axial retention of the elastic body  40 . 
     It is to be understood that the invention is not limited to the embodiments here described and illustrated, which are to be considered examples of the assembly; it will be clear to experts in the field that various changes may be made to the functions and configuration of the elements described in the exemplary embodiment, without departing from the scope of the invention as defined in the attached claims and their equivalents.