Patent Publication Number: US-2015078694-A1

Title: Tubular bushing co-moldable with tubs of washing machines

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Italian Patent Application No. TO2013A000745 filed Sep. 13, 2014, the contents of which are herein fully incorporated by reference. 
     FIELD OF THE INVENTION 
     The present invention is related to a tubular bushing co-moldable with tubs of washing machines. 
     BACKGROUND OF THE INVENTION 
     In general, known co-moldable tubular bushings are co-molded in a bottom wall of the tub of washing machines, in order to support embossed drums of said washing machines and are passed through by a drum drive shaft. Such tubular bushings include two rolling bearings, located along a central axis of the bushing, to allow a rotation of the drive shaft with respect to the tub. The bushing also comprises a spacer, axially interposed between the two bearings, to make stiffer the bushing, and a sealing element, axially alongside the bearing, the one of the two bearings located on the drum side. Finally, the bushing comprises a containing sleeve, which is which is made of plastic, by means of co-molding around the two bearings and the spacer, and defining a housing for the sealing element. 
     The assembly position of the above described tubular bushings forces the related components to temperature and humidity gradients, which are remarkable (for example, in the tub temperature over 90° C. are reachable) and also time dependent. Only as an example, such gradients can influence the good performance of the sealing element, which can be submitted to different working conditions at its opposite sides. Such different working conditions can deteriorate the sealing of the contacting lips on the drive shaft. 
     SUMMARY OF THE INVENTION 
     One aim of the present invention is to realize a tubular bushing co-moldable with tubs of washing machines, the tubular bushing avoiding the above described inconveniences. 
     According to the present invention, a tubular bushing co-moldable with tubs of washing machines is realized, the tubular bushing having the characteristics as 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 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A preferred embodiment of the invention will be now described, in an exemplifying and not limitative way, by reference to the enclosed drawing, in which: 
         FIG. 1  is a perspective view, with some parts taken away for clarity, of a preferred embodiment of the tubular bushing according to the present invention; and 
         FIG. 2  is an axial section, of the tubular bushing of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIGS. 1 and 2 , with  10  is referenced as a whole a tubular bushing co-moldable with tubs of washing machines. 
     The tubular bushing  10  is co-moldable with a tub, schematized in  FIG. 2  and referenced with  11 , of a washing machine, to define a one-piece component with said tub  11 , so as to reduce the washing machine production time. 
     The tubular bushing  10  has a central axis A and comprises:
         two rolling bearings  20  and  30 , located along the axis A;   a spacer  40  preferably made of plastic material or, for specific applications, metal material and axially interposed between the two bearings  20  and  30 ;   a containing sleeve  50 , which is preferably made of plastic material and is co-molded around the two bearings  20 ,  30  and the spacer  40 ; and   a sealing element  53 , which is located inside the sleeve  50 , axially alongside the bearing  30 .       

     Once co-molded with the tub  11 , the tubular bushing  10  defines a communication duct  12  between a humid side  13 , inside the tub  11 , and a dry side  14 , outside said tub  11 , and is suitable to be internally and completely engaged by a drive shaft  15 , in order to support a drum of the washing machine. 
     On one end, towards the humid side  13 , the containing sleeve  50  comprises a cylindrical seat  30   a,  formed, during co-molding, by the bearing  30 , and an annular edge  51 , which extends coaxially to the axis A from the seat  30   a  towards the humid side  13  and internally defines a cylindrical housing  52 , to accommodate the sealing element  53 , so as to seal the inside of the duct  12  from the humid side  13 . The housing  52  is located axially alongside and outside the seat  30   a  and has a diameter, whose dimension is greater than the dimension of the diameter of the seat  30   a.    
     The bearing  30  comprises an outer ring  301  located axially close to the spacer  40 , an inner ring  302  engaged and crossed by the drive shaft  15  and a plurality of rolling bodies  303 , interposed between the rings  301  and  302 , to allow the drive shaft  15  rotation with respect to the sleeve  50 , in other words, to the tub  11 . The rings  301  and  302  define, between them and for each side of the bearing  30 , a cavity  304 , which is sealed by a correspondent gasket  305 . 
     The spacer  40  has a closed body structure nevertheless, according to the use of the tubular bushing  10 , the spacer  40  could also have a box-type structure. 
     The sealing element  53  comprises a shaped insert  54 , assembled inside the housing  52 , in a position axially exposed to the bearing  30  and, in the shown embodiment, two sealing lips  55 , which radially extend towards the inside of the insert  54  and have a slide contact with the drive shaft  15  to seal the duct  12  with respect to the humid side  13 . 
     The sealing element  53  and the bearing  30  confine and axially enclose an annular chamber  56 , which is further closed in a radial direction by the drive shaft  15  and is completely sealed with respect to the external environment: in fact, if towards outside, in other words, towards the humid side  13 , the chamber  56  is sealed both thanks to the sealing element  53  and the slide contact of the lips  55  on the drive shaft  15 , towards inside, in other words, towards the duct  12 , the chamber  56  is sealed thanks to the bearing  30  and its gaskets  305 . In fact, the ring  302  of the bearing  30  is directly assembled on the drive shaft  15  and the ring  301  is located inside the seat  30   a  and is also provided with a pair of external grooves  306 , which, while the sleeve  50  co-molding, are filled of the same material of the sleeve  50 . The grooves  306 , in addition to improve the sealing of the tubular bushing  10 , avoiding liquid infiltration between the ring  301  and the seat  30   a,  also allow to lock the ring  301  inside the seat  30   a:  such a locking is for sure against the axial direction and, according to the grooves  306  shape, could also be against the rotation, above all in a case the grooves  306  were eccentric with respect to the axis A, in other words, had a variable depth around said axis A. 
     The containing sleeve  50 , which, as mentioned, is co-molded around the bearings  20 ,  30  and the spacer  40 , comprises a stiffening ring  70 , which extends around the annular chamber  56 , the bearing  30  and the sealing element  53 . The stiffening ring  70 , in addition to improve, together with the spacer  40 , the stiffness of the tubular bushing  10  structure, above all on the tub  11  side where the said bushing  10  is mainly stressed, also presents a radially outer surface  71 , which, whenever the tubular bushing  10  is co-molded with the tub  11 , however remains free and exposed to the external environment, in other words is not drown inside the plastic material of the tub  11 , as happen at the remaining parts of the tubular bushing  10 . 
     The tubular bushing  10  further comprises two ducts  200  and  201 , which directly extend through the containing sleeve  50  and having corresponding inner openings  202 ,  203  formed in the annular chamber  56  and corresponding outer openings  204 ,  205  formed through the surface  71 , to fluid connect the annular chamber  56  with the external environment, eliminating whatever pressure and/or temperature gradient between the annular chamber  56  and the external environment. In fact, during working conditions, the almost high temperatures, which are reached at the humid side  13 , can determine different temperature and pressure conditions at the opposite sides of the sealing element  53 , causing in a worst case also a detachment of the lips  52  from the drive shaft  15 , thus worsening the performance of the sealing element  53 . 
     The two ducts  200 ,  201  are completely and internally obtained through the sleeve  50  and the corresponding openings  202 ,  203  are located over the seat  30   a  and the housing  52 . In the described embodiment, the two ducts  200 ,  201  are arranged in diametrically opposite positions to each other and are substantially equal each other, having same dimensions and same inclination with respect to the axis A. In particular, the outer openings  204 ,  205  are axially offset towards the dry side  14  with respect to the associated inner openings  202 ,  203 , so that the ducts  200 ,  201  are inclined with respect to the dry side  14 . 
     The ducts  200 ,  201  work as supply duct and evacuation duct, thus allowing both the incoming of the air into the chamber  56  and the exiting of the air from said chamber  56 . In other words, the ducts allow the chamber  56  to get an internal pressure substantially equal to the pressure of the external environment, thus eliminating whatever pressure gradient between the chamber  56  and said external environment. Therefore, the availability of two ducts  200 ,  201  is needed to contemporary allow the air evacuation and incoming inside the chamber  56 , thus creating a continuous flow, which cannot be realized by using only one duct. Moreover, in the case some liquid coming from the washing machine were able to overcome the sealing of the lips  52  and penetrate the chamber  56 , such a liquid would be drained outside through the duct  201 , which, in the shown embodiment, is the lower one. 
     The inclination of the ducts  200 ,  201  allow to locate the openings  202 ,  203  as close as possible to the sealing element  53  and, at the same time, to locate the openings  204 ,  205  as far as possible from the annular edge  51 , thus obtaining an axial space outside the sleeve  50 , which is optimized for the co-molding with the tub  11 . 
     Finally, the containing sleeve  50  comprises one or more anti-rotational teeth  61 , each of them extends out of an external surface  62  of said sleeve  50 , to avoid any rotation between the tubular bushing  10  and the tub  11 . It is sufficient to have only one radial tooth  61 , but, to create a symmetrical shape to the whole tubular bushing  10 , preferably such teeth  61  are more than one and are reciprocally symmetric with respect to the axis A. 
     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.