The present invention refers to an improved kind of water circulating pump, as used in particular as a drain pump in a clothes washing machine, preferably of the type for use in households, which is capable of doing away with the risk of lint causing it to run into a stalled condition.

The general requirement for household appliancesâ€”and particularly clothes washing machines, which, among these appliances, are certainly most affected by this kind of considerations, i.e. most susceptible in this particular connection, owing to the peculiar manner in which they are used and operatedâ€”to be simplified as far as possible in the use and maintenance thereof.

A chore that users of such washing machines have quite frequently, i.e. periodically to grapple with is cleaning the so-called lint filter provided upstream of the drain pump.

The need for such filter to be used is generally known in the art, so that it shall not be dealt with any further here. On the other hand, the type of filter to be used can vary most widely depending on the actual needs that have to be complied with. Again, most varied resultsâ€”from a practical point of viewâ€”are to be expected to derive from the use of different kinds of filters, i.e. different filter design options.

Ifâ€”as this is increasingly the case nowadaysâ€”a design target is to as much as possible reduce, i.e. minimize the frequency of maintenance operations to clean and service the filter, the latter tends to be provided in the form of an almost â€œnon-filterâ€ , i.e. more in the form of a sieve than an actual filter, in the sense that it is designed so as to be able to only intercept and retain the coarser and more sizeable matters that may be unintentionally end up in the washing tub of the machine along with the clothes to be washed and eventually in the flow of washing liquor being let out. These coarser or more sizeable matters may for instance be comprised of brooches, hairpins and the like, toothpicks, coins, small handkerchiefs, and the like. These matters, owing to their not really negligible consistency and size, may prove quite dangerous if allowed to reach the drain pump of the machine, since they can quite easily cause it to run into a stalled condition and, possibly, even damage it, thereby giving rise to a number of negative after-effectsâ€”even of an economic natureâ€”as this can be most easily figured out.

If use is made on the contrary of very fine-meshed strainers, so as to cause also most of the lint carried away by the flow of washing liquor being let out to be intercepted and retained, a rapid clogging of the filter will be the obvious result, accompanied by a considerable increase in the frequency of operations needed to be normally performed in order to unclog and clean the filter.

On the other hand, the large amount of lint of various kind that separates from the washload, i.e. from the clothes during the washing process, and passes then through filters of the afore-cited â€œnon-filterâ€ , i.e. sieve kind provided to only retain the coarser of more sizeable matters in the flow of the washing liquor being let out, is not really dangerous for the drain pump, since it is generally capable of being let out with the washing liquor without giving rise to clogging or similar problems.

This is actually the reason why filters used in currently produced washing machines are generally provided with quite large meshes, holes or other kinds of passages that are adapted to retain only the largest matters and bodies that may accidentally end up in the washing tub of the machine with the clothes to be washed, while enabling lint to pass therethrough.

However, although this lint is unable to cause the pump impeller to get locked, since they do not get entangled on the impeller, it has been nevertheless found that it may well roll up round the shaft that rotatably drives the same impeller, in the section thereof lying between the impeller vanes and the point at which it penetrates the wall of the drain manifold, whichâ€”owing to its having a much smaller diameter than the impellerâ€”is unable to bring about any whirling water stream that would move away such lint.

The ultimate result is that the impeller is still likely to be braked, i.e. slowed down, or even locked by lint rolling up and getting entangled round the driving shaft thereof.

This occurrence is much more manifest ifâ€”as this is quite often the caseâ€”part of said driving shaft comes to lie freely extended and accessible between the vanes of the impeller and the inner wall of the drain manifold, in which said impeller is housed and from which said driving shaft comes out to reach the impeller.

It would therefore be desirable, and it is actually a main object of the present invention, to provide a drain pump for a clothes washing machine, which is capable of ensuring an adequate extent of inherent protection against lint, or other minute matters that may equally be carried away in the flow of washing liquor being let out, accidentally rolling up/getting entangled around the portion of the impeller driving shaft that extends from the vanes of said impeller to the wall from out it comes out.

According to the present invention, these aims, along with further ones that will become apparent further on in the following description, are reached in a drain pump for a clothes washing machine incorporating the features and characteristics as recited in the appended claims. Anyway, features and advantages of the present invention will be more readily and clearly understood from the description that is given below by way of non-limiting example with reference to the accompanying drawings, in which:

FIG. 1 is a schematical view illustrating the operating principles of a washing machine according to an embodiment of the present invention;

FIG. 2 is a schematical see-through view of a drain pump according to the present invention;

FIG. 3 is a an axially cross-sectional view of an embodiment of the drain pump according to the present invention;

FIGS. 4 and 5 are a perspective view and a front elevational view, respectively, of the impeller of the pump shown in FIG. 3;

FIG. 6 is a an axially cross-sectional view of a second embodiment of a drain pump according to the present invention;

FIGS. 7 and 8 are a perspective view and a front elevational view, respectively, of the impeller of the pump shown in FIG. 3.

With reference to FIGS. 1 and 2, in a clothes washing machine that uses a drain pump according to the present invention there is provided a perforated rotating drum 1, a washing tub 2 accommodating said drum rotatably, and under this washing tubâ€”as connected therewith via an appropriate conduit 3 opening at the bottom thereofâ€”there is provided a related drain manifold 4 to collect the liquor being let off the tub.

In a manner that is generally known as such in the art, this drain manifold is associated to, and sometimes even includes, a drain pump 5, the driving or revolving shaft 6 of which extends into the interior of the pumping chamber of said drain manifold and terminates in an impeller, which is in turn provided with a plurality of vanes 7 arranged on respective planes that are regularly angled relative to each other, but passing in all cases through the axis X of said shaft 6.

With reference to FIGS. 3, 4 and 5, the wall 9, from which said shaft extends to enter said pumping chamber, is a planar wall. Moreover, said pumping chamber has two access apertures, or mouths, of which a first inflow aperture 10 is provided to connect said conduit 3 with said pumping chamber, whereas a second aperture 11 acts as an outflow aperture connecting the same pumping chamber with an outlet or drain pipe 12.

The first aperture 10 is so situated and oriented in the wall of said pumping chamber as to come to lie in front of the vanes of said impeller, where it substantially corresponds to, i.e. agrees with a plane lying orthogonally to the axis X of the shaft 6 used to rotatably drive the vanes 7.

The second aperture 11 is on the contrary situated laterally relative to said shaft, and is positioned in the substantially cylindrical wall of the pumping chamber, so that, when the impeller rotates, the vanes thereof successively expose all of their faces to said second aperture 11.

In a conventional manner, said vanes 7 are separated from the drive motor of the pump 5 by said planar wall 9, from which said shaft 6 comes out, and a hollow space or gap 20, which, if no adequate measure is taken, allows in fact for said lint to reach and settle on said shaft, as favoured by said first inflow mouth or aperture 10 being practically located in front of said shaft.

In view of avoiding such circumstance, according to the present invention provision is made of a plurality of members 22 that come to be arranged inside said hollow space, integral with or, anyway, firmly joined to the portion of said shaft 6 that extends therethrough.

Therefore, as it rotates to drive the impeller, the shaft 6 clearly causes even said members 22 to similarly rotate, so that they are able to bring about a moderate whirling effectâ€”somewhat apart from the shaft itselfâ€”that is effective in preventing lint and other foreign matters from reaching the same shaft and, ultimately, braking or even locking it.

As broadly explained above, this solution has enough scope to further accommodate a number of improvements and modified embodiments. So, for instance,

- a first such improvement may rely on providing said members 22 in the form of planar members arranged on respective planes that are regularly angled relative to each other, but passing in all cases through the axis X of said shaft;
- a second improvement, whichâ€”as best illustrated in FIGS. 6, 7 and 8â€”is basically aimed at making it easier to manufacture said planar members 22, provides for the latter to be made in a co-planar arrangement with the respective vanes 7, wherein they are preferably made integral with said vanes as a unitary-piece construction requiring just a single manufacturing step, preferably an injection-moulding operation;
- a third improvement lies in sizing said planar members in their length â€œlâ€ â€”as measured parallel to said axis Xâ€”so that they are able to extend throughout the widthâ€”or the depthâ€”of said hollow space so as to minimize the possibility for any lint or foreign body whatsoever to actually reach the shaft (see FIG. 3);
- finally, a last improvement lies in sizing said planar members 22 in their height â€œaâ€ so that they are able to extend above, i.e. are greater than the radius â€œrâ€ of the central hub 6A of the shaft 6, to thereby generate a marked whirling effect, while at the same time being significantly lower than the radial dimension R of said vanes 7, so as to avoid interfering with the effectiveness of the pumping action thereof.

In fact, since said outflow aperture or mouth 11 is only aligned with and projects towards said vanes 7, and not also towards said hollow space 20, and since said vanes 7â€”on construction-related considerationsâ€”must be separated from said planar wall 9 by said hollow space 20, the volume defined by said hollow space 20 might therefore prove unable to be effectively drained by the action of the whirling effect produced by the contiguous vanes 7.