Abstract:
A bearing assembly is for a washing machine, the washing machine including a tub and a drum rotatable about a central axis. The bearing assembly comprises two bearings spaced axially apart along the central axis, a spacer disposed generally between the two bearings, and a polymeric housing. The housing includes a box-type frame molded to the bearings and to the spacer and configured to provide stiffness to the bearing assembly.

Description:
CROSS-REFERENCE 
       [0001]    This application claims priority to Italian Patent Application No. TO2010A000230 filed on Mar. 25, 2010, the contents of which are incorporated fully herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to bearing assemblies, and more particularly to bearing assemblies for washing machine drums. 
         [0003]    Bearing assemblies for rotatably supporting washing machine drums are known. In certain applications, the bearing assembly can be “co-molded” with, i.e., molded onto or together with, the washing machine tub so as to become an integral part of the tub itself, which facilitates the washing machine assembly operations. Such a bearing assembly typically includes two roller bearings arranged along an axis of rotation of a washing machine drum, a spacer interposed between the two bearings, and a cylindrical housing sleeve. The sleeve is often made of a plastic material and is co-molded around the two bearings and the spacer. 
         [0004]    With bearing assemblies of the type described above, the spacer is typically formed of a metallic material, which sometimes causes technical problems due to the environment in which the bearing assembly operates. Specifically, although the spacer is housed within an environment protected from direct contact with the washing machine liquids, water vapour and condensate are typically formed on the sleeve during most washing cycles, which gives rise to the possible formation of ferrous oxides (i.e., rust) on the inner surface of the spacer. 
       SUMMARY OF THE INVENTION 
       [0005]    The object of this invention is to provide a bearing assembly for a washing machine drum. 
         [0006]    In one aspect, the present invention is a bearing assembly for a washing machine, the washing machine including a tub and a drum rotatable about a central axis. The bearing assembly comprises two bearings spaced axially apart along the central axis, a spacer disposed generally between the two bearings, and a polymeric housing. The housing includes a box-type frame molded to the bearings and to the spacer and configured to provide stiffness to the bearing assembly. 
     
    
     
       BRIEF SUMMARY OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0007]    The invention will now be described with reference to the attached drawings which illustrate a non-limiting exemplary embodiment, in which: 
           [0008]      FIG. 1  is a front elevational view of a preferred embodiment of the bearing assembly of this invention; and 
           [0009]      FIG. 2  is a cross-section of the bearing assembly of  FIG. 1  along the line A-A. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0010]    With reference to the attached drawing figures, a bearing assembly  10  in accordance with the present invention is co-moldable (i.e., moldable to or together with) with a washing machine tub, or with any other fixed structural element, and is configured or adapted to support a washing machine drum, or any other part that rotates with a structural element. 
         [0011]    For simplicity, the description that follows will make express reference to the case in which the bearing assembly  10  is co-molded with a tub, schematically designated  11  in the drawings, of a washing machine in order to constitute a single component with the tub  11  in such a way as to reduce the washing machine production time. 
         [0012]    The bearing assembly  10  basically comprises two rolling bearings  20  and  30  spaced axially along an axis A of rotation of a drum (known and not shown) of the washing machine, a polymeric or plastic spacer  40  disposed generally between the two bearings  20  and  30 , and a housing sleeve  50 . In order to optimize production costs and times, the housing sleeve  50  is preferably formed of a polymeric or plastic material molded (or co-molded or over-molded) around the two bearings  20  and  30  and the spacer  40 . 
         [0013]    When it has been co-molded with the tub  11 , the bearing assembly  10  defines a sort of pipe  12  communicating between a wet side  13  inside the tub  11  and a dry side  14  outside the tub  11 , and is capable of being engaged internally by a support shaft (known and not illustrated) which supports the abovementioned drum and is arranged inside the pipe  12  so as to protrude at least partly from the dry side  14 . 
         [0014]    In order to further reduce both the washing machine production costs and times, and also to increase the reliability of the watertight seal of the tub  11 , the housing sleeve  50  comprises an annular rim  51 , which faces the wet side  13 , and projects axially from the sleeve  50  proximal to the bearing  30 . The rim  51  is generally coaxial with the axis A of rotation and is configured to define a seat  52  for a sealing element, schematically indicated in  FIG. 2  at  53 . The direct manufacturing of the seat  52  during the co-molding of the sleeve  50  with the bearings  20  and  30 , instead of during co-molding of the tub  11  with the bearing assembly  10 , not only makes the production of the tub  11  simpler, but also allows to control the geometry of the seat  52  with greater accuracy and increase the reliability of the sealing element  53 . Furthermore, due to the precision of the shape with which the seat  52  is made as described herein, this could also be advantageously used for housing an encoder or any other precision measurement instruments. 
         [0015]    Further, during the process of molding the tub  11  with the bearing assembly  10 , both the injection pressure and temperature can attain values that are particularly high and critical for the materials involved. In view of this and the importance of maintaining the geometrical characteristics of the seat  52  identical to those obtained during co-molding of the bearing assembly  10 , the housing rim  51  has a generally annular frontal groove  54  extending axially inwardly from a front surface of the rim  51 , which is open axially toward the wet side  13  of the bearing assembly  10 . The groove  54  is configured for engagement by a cylindrical stiffening body, the body having a form that is complementary to the form of the groove  54  itself, during molding of the bearing assembly  10  to the tub  11 . 
         [0016]    More specifically, the annular groove  54  extends axially inside the rim  51  with an axial depth that is lesser than an axial dimension of the rim  51 . Further, the groove  54  defines a cylindrical bracket  55  having radial thickness which is lesser than an overall radial thickness of the rim  51 . The bracket  55  is radially delimited or bounded radially inwardly by the seat  52 . During co-molding of the tub  11  with the bearing assembly  10 , the abovementioned cylindrical stiffening body (not shown) is inserted into the groove  54  in order to prevent any deformation of the bracket  55  while protecting the seat  52  from any possible deformation at the same time. 
         [0017]    The seat  52 , which is preferably generally cylindrical, is delimited axially on the wet side  13  by an inlet bevel  56  adapted to facilitate the insertion of the sealing element  53  inside the seat  52 , and is axially delimited on the side of the bearing  30  by a shoulder  57  which is interposed between the bearing  30  and the seat  52 , and also defines an axial shouldering element for fitting the sealing element  53 . 
         [0018]    The spacer  40  is formed of a polymeric or a plastic material, preferably but not necessarily of polypropylene reinforced with glass fiber, and if both the sleeve  50  and the spacer  40  are made of the same plastic material, the co-molding process of the former on the latter can also give rise to an intrinsic union between a surface portion of the spacer  40  and the sleeve  50 , making the entire structure of the bearing assembly  10  even stiffer. According to further embodiments not shown herein, but clearly deducible from this disclosure by one skilled in the relevant art, the spacer  40  can also be made of polybutylenterephthalate reinforced with glass fibers or, in any case, with similar plastic or polymeric materials and capable of being injected in a semi-liquid state into a mold in order to give the spacer  40  a structure described herein after. 
         [0019]    The spacer  40  has a box-type structure and comprises an internal cylindrical body  41 , a shaped external body  42  coaxial with the body  41 , and an intermediate radial partition wall  43  which is arranged transversally to the axis A and extends radially from the body  41  to the body  42  in a substantially intermediate position along the spacer  40  in order to render the body  41  integral with the body  42 . The bodies  41  and  42  with the partition wall  43  define two annular spaces  44 , so that the overall weight of the spacer  40  is lower than the weight of a solid spacer with the same stiffness characteristics. 
         [0020]    The spacer  40  also comprises two axial ribs  43   a  which are arranged inside the spaces  44  parallel to the axis A and on opposite sides of the A axis, and are made in one piece and with the same material as the partition wall  43  and with the bodies  41  and  42 . In the example illustrated in  FIG. 2 , there are two ribs  43   a  which subdivide each space  44  into two sectors but, in order to increase the stiffness of the spacer  40 , the latter can also be made with several ribs  43   a  uniformly distributed around the A axis. 
         [0021]    On the side axially facing the outside of the bearing assembly  10 , the ribs  43   a  have respective shaped frontal surfaces  43   s  which are arranged axially recessed compared to the respective tubular end portions  42   a  of the body  42 , while they are arranged axially flush vis-à-vis the body  41 . 
         [0022]    The spacer  40  has two housing seats  46  and  47  which respectively house the bearing  20  and the bearing  30  in such a way that the outer rings  22  and  32  are axially blocked to one another and are also radially blocked in the seats  46  and  47 . 
         [0023]    Each seat  46  and  47  is radially delimited by an associated tubular portion  42   a  which radially envelops the associated outer rings  22  and  32  from the outside, and is axially delimited towards the inside of the bearing assembly  10  by the surfaces  43   s  which are in axial contact with the outer rings  22  and  32  and are axially separated by the inner rings  21  and  31 . In this way, each tubular portion  42   a  of the body  42  is arranged radially around and in contact with a portion of the outer rings  22  and  32  and the associated surfaces  43   s  act as an axial reference for the rings  22  and  32  with the univocal definition of an axial distance between the bearings  20  and  30 , while allowing the bearings  20  and  30  to be blocked in position when they are arranged in the mold for co-molding the sleeve  50 . 
         [0024]    As the radial dimensions of the bearing  30  are greater than the radial dimensions of the bearing  20 , because it has to support a greater load as it is positioned closer to the aforementioned drum, the body  42 , which is maintained parallel to the body  41  on the bearing  20  side, has, on the bearing  20  side, a conical portion  45  with an increasingly wider outer diameter. 
         [0025]    Furthermore, both the outer rings  22  and  32  are provided with respective pairs of external grooves  23  and  33  which, during co-molding of the sleeve  50 , are filled with the same material as the sleeve  50  in such a way as to increase the axial sealing between the sleeve  50  and the bearings  20  and  30 . 
         [0026]    Finally, the sleeve  50  comprises one or more radial anti-rotational teeth  61 , each of which extends outside an external surface  62  of the sleeve  50  to prevent any rotation between the bearing assembly  10  and the tub  11 . There could also be only one of these radial teeth  61 , but in order to give the entire bearing assembly  10  a symmetrical shape it is preferable to provide two teeth  61  arranged in symmetrical positions vis-à-vis the axis A. 
         [0027]    The box-type structure of the spacer  40  gives the spacer not only such a stiffness as to support the mechanical and vibrational stresses to which the bearing assembly  10  is subject during its use, but also such a form and stiffness as to render the spacer  40  substantially unresponsive to the thermal stresses to which it is subjected during co-molding with the sleeve  50 . 
         [0028]    It is intended that the invention not be limited to the embodiment described and illustrated here, which is to be considered as an exemplary embodiment of the bearing assembly which is, instead, open to further modifications as regards shapes and arrangements of parts, and construction and assembly details. In fact, as has been reiterated several times, the hose is not only suitable for being used in applications that are not strictly linked to washing machines and the associated tubs, but is advantageously usable in other applications in which the bearing assembly  10 , for production simplicity reasons, must be co-molded with a fixed support and must support a part that rotates relative to the fixed support, while the whole always guarantees adequate stiffness characteristics at the same time as well as a sealing capacity against atmospheric agents such as humidity, water vapour and the like.