Textiles: fluid treating apparatus – Machines – Tumbling
Patent
1996-04-15
1997-12-23
Coe, Philip R.
Textiles: fluid treating apparatus
Machines
Tumbling
D06F 3704, D06F 3722
Patent
active
056996829
DESCRIPTION:
BRIEF SUMMARY
The present invention refers to a clothes washing machine, particularly of the household type, provided with an improved type of washing tub made of plastic material.
Although the present invention refers specially to a washing machine of the front-loading type, and for greater convenience of exemplification the following description is actually referred to such a type of washing machine, it can in an advantageous manner be applied also to other types of washing machines, in .particular to the ones that are loaded from the top and have their drum rotating about an horizontal axis.
Plastic washing tubs for clothes washing machines are known to substantially comprise a rigid structure forming the peripheral cylindrical envelope and the rear circular wall, and a front wall having a circular shape, too, which is sometimes separated and is capable of being attached to said rigid structure by means of per se known fastening means.
In correspondence of the rear wall, preferably radial ribs are provided in a usually integral way so as to increase the strength of the tub, said ribs being arranged radially from the central portion of said rear wall, as this is for instance illustrated in the Italian patent application no. PN91U000040.
A through-hole, in which the shaft supporting and rotatably driving the drum housed within the tub is inserted, is provided in correspondence of said central portion of the rear wall, said shaft being shrink-fitted, outside the tub, into a pulley on which a belt is acting to transmit the motion needed to rotatably drive the drum.
To support said shaft and enable it to rotate under the lowest possible friction effect, as well as to ensure an adequate sealing effect against washing liquor leaking therethrough, such a hole is usually provided with a coaxially arranged hub carrying the bearings for the shaft and normally locked against the inside wall of the hole with known locking means, such as for instance by means of screws or through a press-fitting arrangement or again by moulding the plastics of the tub directly over said hub. The latter is further joined to an external flange adhering to the wall of the tub, and in particular to the portions in relief thereof, said flange being fastened to said wall using known fastening means, preferably a plurality of through-bolts or screws.
The provision of such a hub, if on the one hand it is required to ensure both the support of the shaft and a water-tight sealing of the tub, has the drawback that the hub itself is directly exposed to the relatively high temperatures to which the washing liquor is usually heated up, said washing liquor touching directly the central portion of the rear wall of the tub.
This fact, owing to the mechanical action exterted by the rotating shaft against said hub, leads to a gradual stressing of the plastic material which, after a certain period, undergoes an aging process with a decay in its overall mechanical properties that may become visible through such failures as a loss of tightness (water leakage) or the hub becoming loose from its plastic seat.
Such a development is not effectively opposed by the external fastening of the afore cited flange, owing to the slack that gruadually builds up in the holes accomodating said through-bolts or screws.
Furthermore, in the case of a replacement of the bearing or any other repair work to be done under removal of the drum, it is absolutely necessary that said screws or bolts be first loosened and this, if performed repeatedly, leads eventually to a permanent deformation of the plastic material around said fastening elements, so that the need arises to ultimately replace the tub itself. Furthermore, it should be emphasized that the assembly of a great number of fastening screws and/or bolts to the tub turns out to be rather expensive due to both the required processing work and the amount of material used.
It therefore is a purpose of the present invention to provide a washing tub having superior structural and functional characteristics with respect to prior-art tubs, wh
Coe Philip R.
Electrolux Zanussi Elettrodomestici S.p.A.
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