WO1995014130A1

WO1995014130A1 - Imrpovement in a shock absorber for clothes washing machines

Info

Publication number: WO1995014130A1
Application number: PCT/EP1994/003481
Authority: WO
Inventors: Silvio Battistella; Lucio Valent; Riccardo Quaroni
Original assignee: Zanussi Elettrodomestici S.P.A.
Priority date: 1993-11-17
Filing date: 1994-10-22
Publication date: 1995-05-26
Also published as: ITPN930033V0; IT231986Y1; ITPN930033U1

Abstract

Clothes washing machine, in particular of the household type, provided with an outer casing, an inner wash tub, a plurality of shock-absorbing means connected between said tub and said outer casing, said shock-absorbing means substantially consisting of an inner (1) sliding part and an outer (2) hollow part, said parts being engaged with each other by the action of one or more first braking means (8) interposed between said outer and said inner part, wherein said inner part comprises an extension (4) inserted in its side facing the inner side of the outer part, an assembly (6) being fitted on said extension and said first braking means being applied externally on said assembly, whereas said assembly is capable of sliding on said extension and comprises internally at least a second braking means (9) engaging with the outer surface of said extension.

Description

IMPROVEMENT IN A SHOCK-ABSORBER FOR CLOTHES WASHING

MACHINES

DESCRIPTION

Technical Field

The present invention refers to a clothes washing machine, in particular of the household type, provided with an improved type of shock-absorber for dampening the oscillations of the washing subassembly of the machine.

Although the present invention relates particularly to a front-loading clothes washing machine which is provided with a washing subassembly that is rigidly connected with the washing tub, and although for a greater exemplification effectiveness the following description is in fact referred to such a type of clothes washing machine, it will be appreciated that the invention itself may as well be advantageously applied to other types of clothes washing machines, in particular top- loading ones provided with a drum rotating about a horizontal axis.

Background Art

Clothes washing machines are largely known to include a washing tub containing a perforated drum in which the clothes, ie. the washload is introduced, and which rotates within said washing tub, the rotation shaft of said drum being journalled by means of bearings against a wall of said tub. As a consequence, all of the oscillations that are imparted to the inner drum are fully transmitted to the outer tub that contains said drum.

And it is exactly for that reason that during spin- extraction phases, ie. when owing to the high speed at which the drum is caused to rotate more or less marked unbalances occur in the distribution of the washload within the same drum, such unbalances due to uneven washload distribution cause the drum to oscillate to even a considerable extent, ie. give rise to excursions of considerable amplitude in the movement of the drum which transmits them directly to the washing tub.

In order to dampen said oscillations, which may be also very violent in their nature, various devices and techniques aimed at minimizing or doing away with such an undesired occurrence have been implemented.

One of these techniques involves reducing washload unbalance at the source through a sequence of phases of gradual increase in the rotation speed of the drum, possibly alternated with slowing-down phases, so as to promote a more uniform distribution of the washload and, as a result, minimize unbalance.

Another widely used technique involves applying ballast masses to the tub, by adding inert loads thereto, so as to increase overall inertia of the washing subassembly and, therefore, make it less subject to the centrifugal oscillations coming from the drum rotating under washload unbalance conditions.

A third measure taken in this connection consists in providing the tub, which is normally hanged by means of elastic tie-rods to appropriate spots located in the upper inside portion of the outer shell of the washing machine, with appropriate shock-absorbing means that are normally arranged between attachment spots in the lower portion of the tub and zones, located thereunder, of the machine outer shell resting on the floor, so that oscillations, albeit dampened by the action of said shock-absorbers, are unloaded into the machine base lying firmly against the floor, which is in turn effectively isolated with respect to the structure of the building, so that said oscillations are ultimately fully neutralized.

All such solutions have normally proven adequate in meeting the requirement of effectively neutralizing oscillations generated by a rotating drum containing an unbalanced washload. However, more recently a problem has become increasingly apparent following the implementation of new building construction techniques: in certain types of private dwellings, floor coverings are not rigid, but elastic, and they are further substantially connected with the bearing structure of the building, structure which in turn is of a "hyperstatic" type, ie. with the structural elements that are in practice mutually tensioned.

A consequence of this is that even vibrations of a moderate intensity that may be imparted to the floor are transmitted to the structure of the building, thereby giving rise to disturbing vibrations throughout the living area around the place where the washing machine is operating. As a matter of fact, shock-absorbers of the currently used type are not capable of absorbing in a differentiated manner vibrations having different amplitudes, so that all vibrations, even vibrations of moderate intensity, but occurring at a higher frequency, ie. such as the ones that occur during steady-state rotation of the drum at its highest speed in the spin- extraction phase, are transferred through said shock-absorbers to the base structure of the washing machine and, from here. to the entire structure of the building when the latter is built according to the above mentioned construction techniques.

As a consequence, undesired vibrations of an entire living area around the washing machine are in all these cases unavoidably experienced whenever a spin-extraction cycle is performed, and throughout the entire duration thereof, even if during the steady-state operation of such a cycle the amplitude of the oscillations is limited as compared to the amplitudes that typically prevail during spin-extraction starting and braking transients.

Disclosure of Invention

It would therefore be desirable, and it is actually a main purpose of the present invention, to provide a type of shock- absorber which, apart from being able to effectively dampen wide-amplitude oscillations, as currently used shock-absorbers normally do, is also able, by isolating them, to effectively prevent vibrations having amplitudes below a certain pre¬ determined value from being passed on, said shock-absorbers being adapted to be installed in current-type washing machines without requiring them to undergo any design modification.

The present invention will be more clearly understood on the basis of the description which is given below by way of non-limiting example with reference to the accompanying drawings in which:

- Figure 1 is a schematical view of the cross-section of a shock-absorber according to the invention;

- Figure 2 is a partially cut-away view of the same shock- absorber shown in Figure 1.

Referring now to Figures 1 and 2, which illustrate a preferred embodiment of the present invention, a shock- absorber according to the present invention is described and the operating principle thereof is explained.

Since the real problem arises from the transmission of all of the vibrations generated inside the washing tub, and entirely transmitted to the outside environment also through the shock-absorbers of the known type, the solution lies in identifying a means that is effective in eliminating also the transmission of higher-frequency, moderate-amplitude vibrations. It is therefore necessary that a means be identified that is able to at least partially neutralize the dampening effect for those oscillations whose excursion is limited to a pre-determined value, and that is at the same time able to operate in a normal way as for the oscillations whose excursion exceeds said value.

The invention therefore consists of a shock-absorbing means that is formed by two separate inner and outer parts 1 and 2, respectively. The latter part, ie. the outer one, is the same as used in shock-absorbers of the known type, so that it is not concerned by the present invention.

The inner part 1 is formed by a first element 3 sliding within said outer part, a rod-shaped extension means 4 inserted in the outermost side 5 of the inner part facing the inner side of the cavity of the outer part, said extension 4 and said first element 3 being fastened together.

On the extension 3 there is arranged by shrink-fitting or similar method an assembly 6 that is constituted by a central body 7, a plurality of outer braking elements 8 and at least an inner braking element 9 which is provided with a through- opening inside it, so that said extension 4 can be inserted through it and said inner braking element 9 can engaged said extension 4 by friction.

Said outer braking elements 8 are arranged on the outside of the central body 7 in such a way that, when the first element 3, on the extension 4 of which said assembly 6 is shrink-fitted, is inserted in said second hollow part 2, said braking elements 8 engage by friction against the smooth inner surface of said second hollow part 2.

Conclusively it can be said that a constructive configuration is in this way obtained so that the assembly 6 may slide both with respect to the extension 4, due to the friction effect of the inner braking element 9, and with respect to the inner surface of the second hollow part 2 owing to the friction effect of said outer braking elements 8.

Such possible distinct sliding movements of the assembly 6, as described above, are however of a different extent: as a matter of fact, the assembly 6 slides between two outermost positions that are defined by the central body 7 abutting against said inner side 5 of the inner part 1, on one side, and said, on the other side, central body 7 interfering with an appropriate catch means 10 provided in correspondence of the free end of th _*e extension 4.

With respect to the inner surface of said second hollow part 2, the assembly 6 slides either when the inner part 1 is pulled out by force until said catch means 10 comes to interfere with said central body 7, after that, said pulling- out force being still imposed to said part 1, the catch means 10 provided on the extension 4 starts to drag said assembly jointly with said inner part to cover the further length of movement imparted to said inner part or to move until the penetration of said inner part is such as to push said assembly up to the point at which said penetration has to stop, ie. when said catch means 10 abuts against the bottom wall 11 that closes the cavity of said outer part 2.

The outer braking elements 8 and the inner braking element 9 produce a differentiated braking action, in the sense that the outer braking element 8 develops against the inner surface of the outer part 2 a significantly much more effective braking action than the inner braking element 9 actually does against said extension 4.

This practically means that each stress or load that is applied between the two opposite ends of said shock-absorber is initially absorbed by said assembly 6 sliding under braked conditions against the extension 4 and only upon conclusion of such a braked sliding movement will the residual stress or load start to be absorbed in a traditional way by such an assembly 6 sliding under braked conditions against the inner surface of the outer part 2 through the outer braking elements 8.

The ultimate result of the present invention is that the oscillations of the tub of the washing machine during spin- extraction, which occur at a high frequency, but are of a moderate amplitude, are almost entirely absorbed by the assembly 6 sliding against said extension 4 and, as a consequence, are not transmitted to the other end of the shoch-absorber and, from here, to the bearing base of the machine, whereby the desired effect is achieved of partially disengaging the movement of the tub from the outer casing of the washing machine.

A further improvement of the present invention is possible if the inner braking element 9 is totally eliminated, so that the assembly 6 may slide freely with respect to the extension 4. In such a way, in fact, the tub is entirely disengaged from the shock-absorbers as far as stresses or oscillations of a moderate extent are concerned, although this may give rise to other drawbacks, such as for instance a slight increase of the noise generated by the appliance.

It will be appreciated that, although the invention has been described here on the example of preferred embodiments using a generally known terminology, the same invention shall not be considered as being limited by such a description, since anyone skilled in the art will now be capable of introducing various changes and variations. It is therefore intended that the appended claims include all of such obvious modifications or variants that are at the reach of those skilled in the art and fall within the real meaning and scope of the present invention.

Claims

1. Clothes washing machine, in particular of the household type, provided with an outer casing, an inner wash tub, a plurality of shock-absorbing means connected between said tub and said outer casing, said shock-absorbing means substantially consisting of an inner part (1) and an outer hollow part (2) in which said inner part is capable of sliding, said parts being engaged with each other by the action of one or more braking means interposed between said outer and said inner part, characterized in that:

- said inner part (1) comprises an extension (4) inserted in its side (5) facing the inner side of the outer part (2),

- on said extension there is fitted an assembly (6) consisting of a central body (7), a plurality of outer braking elements (8) adapted to engage by friction against the inner surface of said outer part (2), and at least an inner braking element (9) adapted to engage by friction against said extension (4) .

2. Clothes washing machine according to claim 1, characterized in that said inner braking element (9) is capable of braking the sliding movement of said assembly (6) against said extension with a force that is considerably smaller than the force with which said outer braking elements brake the sliding movement of said assembly against the inner surface of said outer hollow part (2).

3. Clothes washing machine according to claim 2, characterized in that the travel of said assembly (6) is limited on one side by the inner side (5) of said inner part (1) and, on the other side, by an appropriate catch (10) arranged in correspondence of the free end of said extension (4).

4. Clothes washing machine according to claim 2 or 3, characterized in that it is deprived of said inner braking element (9), and that said assembly is capable of sliding freely along said extension (4).

5. Clothes washing machine according to any of the preceding claims, characterized in that said first and said second part, said extension and said assembly have a cylindrical configuration and are arranged coaxially.