EP2917396A2

EP2917396A2 - Oscillation damper for a household appliance with rotating drum, and household appliance comprising the damper

Info

Publication number: EP2917396A2
Application number: EP13821971.2A
Authority: EP
Inventors: Ismael Gracia Bobed; Roberto Latre Abadia; Gerardo Martinez Perez; Eduardo Recio Ferrer
Original assignee: BSH Hausgeraete GmbH
Current assignee: BSH Hausgeraete GmbH
Priority date: 2012-11-09
Filing date: 2013-10-24
Publication date: 2015-09-16
Anticipated expiration: 2033-10-24
Also published as: ES2460393R1; WO2014072860A2; RU2015118325A; EP2917396B1; ES2460393B1; ES2460393A2; PL2917396T3; CN104769177A; RU2613779C2; CN104769177B; WO2014072860A3

Abstract

The invention relates to an oscillation damper 1 for a household appliance 9, in particular a washing machine 9 or dryer 9, with a fixed support 2 mountable on a lower part of the housing 10 of the household appliance 9 in which is housed an oscillating group comprising a tub 15, a drum 13, and a motor 21, a pivot shaft 3 mounted on a support 2 and in which is mounted a radial friction element 4, a swiveling lever 5 associated with the radial damper 4, and articulable 5a to a support element 24 simultaneously articulated to a lower part of the tub 15, and an elastic element with at least a helical spring 6, 6' with windings arranged around the pivot shaft 3 and connected to the swiveling lever 5 and the fixed support 2, opposing a torsional force to the rotation of the swiveling lever 5, and designed such that the torsional force corresponds to a proportional part of the load of the oscillating group transmitted by the support element 24.

Description

OSCILLATION DAMPER FOR A HOUSEHOLD APPLIANCE WITH ROTATING DRUM, AND HOUSEHOLD APPLIANCE COMPRISING

THE DAMPER

The present invention relates to an oscillation damper for a household appliance, with a fixed support fixedly mountable on a lower part of the housing of the household appliance in which is housed an oscillating group comprising a tub in which a drum rotates around a rotation shaft, a pivot shaft mounted on the support, a radial friction element mounted on the pivot shaft, and a swiveling lever associated with the radial friction element, with a free end articu- lable to a support element simultaneously articulated to a lower part of the tub receiving a load from the oscillating group. The invention also relates to a household appliance, comprising a housing that houses an oscillating group comprising a tub in which a drum rotates, driven by a motor, the tub being connected at the top with the housing by means of at least a pair of sustaining springs and at the bottom by means of at least two support elements con- nected to an oscillation damping system, the support element being articulated to the housing with the intercalation of at least one articulation comprising a radial friction element. The invention has particular utility in household electrical appliances such as washing machines and dryers. Washing machines and dryers with a wash drum rotatably accommodated in a wash tub usually have a vibration damping device that joins the wash tub to the housing. The vibrations and noise produced by the rotational movement of the drum are damped by means of a vibration damping device. Vibrations are transmitted through damping elements to avoid having the movements of the oscillating group (assembly: wash tub, drum, and motor) directly transmitted to the frame of washing machines to produce vibrations and noise therein.

Practically all commercially available washers have their own arrangement of systems for equilibrating and suspending their oscillating groups, that is two or three springs above that are intended to support a load of, for example, 42 kg to 48 kg (weight of the oscillating groups). Being suspended from the upper part of the frame, they logically transmit vibrations and reactions to the machine that are converted into vibrations and noise. In the lower part, the movement is damped by two or three dampers. Linear damper systems for absorbing these vibrations are known that include piston type dampers such as, for example, the free-travel damper described in EP 1 754 908 A1 , which has a short path (from 5 mm to 8 mm) with little or no frictional force. Such damper essentially functions during the periods when the machine motor is accelerating or decelerating the rotational speed of the drum, that is, when oscillating movements are longer due to greater inertia and exceed the amplitude of the frictionless free travel path of the damper, which then exerts a damping action. When the load in the washer drum stabilizes as higher rotational speeds are reached, the oscillating movements are of lower amplitude and piston movement is reduced so as to move within the range of free travel without exerting frictional force. In this way, it is possible to reduce or eliminate the force trans- mitted to the frame, the vibrations and hence the noise, since frictional force is not exerted due the tub hardly moving at all, and the slight movement produced is not limited by the damper so that forces are not transmitted to the frame. However, these linear free-travel vibration dampers are relatively complicated and costly. A radial damper and its application to a washing machine are known, for example, from document WO 201 1/070092 A1 . In such damper, the necessary frictional force is achieved radially by means of friction applied by rotation of a shaft driven by a rigid arm attached to the tub. It is an example of a connecting rod-crankshaft unit, and friction is applied to the shaft radially so that the crossbar supporting the mounts is not directly affected and bending is not transmitted.

In the known damper systems, a substantial portion of the weight of the oscillating group is being supported by the springs from which the oscillating group is suspended, and despite the presence of the dampers that support the bottom of the oscillating group, a portion of the oscillations from the oscillating group can be transmitted to the household appliance housing through these springs. An object of the present invention is to overcome the inconveniences of the state of the art described above by means of an oscillation damper for a household appliance, particularly for a washing machine or dryer, and a household appliance comprising at least one oscillation damper of this type.

The oscillation damper according to the present invention comprises a fixed support fixedly mountable on a lower part of the housing of the household appliance in which is housed an oscillating group comprising a tub in which a drum rotates around a rotation shaft, a pivot shaft mounted on a support, a radial friction element mounted on the pivot shaft, a swiveling lever associated with the radial damper, with a free end articulable to a support element simultaneously articulated to a lower part of the tub receiving a load from the oscillating group. Further, the oscillation damper comprises an elastic element that comprises at least a at least a metallic helical spring with windings arranged around the pivot shaft and with a first end connected to the swiveling lever and a second end connected to the fixed support, such that it opposes a torsional force to the rotation of the swiveling lever, and the elastic element is designed so that the torsional force it opposes to the rotation of the swiveling lever corresponds to a proportional part of the load of the oscillating group transmitted by the support element to which the swiveling lever is articulable. Meanwhile, the household appliance, particularly the washing machine or dryer, according to the present invention comprises a housing that encloses the oscillating group that in its turn comprises a tub in which rotates a drum driven by a motor. The tub is connected with the housing at the top by means of at least one pair of sustaining springs and at the bottom through at least two support elements connected to an oscillation damping system. The sup- port element is articulated to the housing by intercalation of at least one joint comprising a radial vibration damper. This household appliance is further characterized in that at least one of the swiveling levers is joined to an oscillation damper that features at least the previously described characteristics, although it can also feature one or more of the characteristics of preferred embodiments of oscillation dampers as described below.

The oscillation damper is designed to oppose a torsional force to the load of the oscillating group received by the support element articulated to the swiveling lever. The load of the oscillating group is based on the weight of the assembly formed by the tub, the drum, and the motor that form the oscillating group plus the weight of the maximum volume of wash water present in the tub and the maximum possible weight of laundry present in the drum that, during the drum rotation during the washing and centrifuging processes, exerts forces that afford the mentioned oscillations, the transmission of which to the washing machine housing can be mitigated by means of employing the oscillation damper of the present invention. In a washing machine with a capacity of 7 kg of laundry, this oscillating group usually has a weight of 42 kg to 48 kg and the maximum total weight of the water and laundry is usually about 15 kg.

In a preferred embodiment of the oscillation damper, the fixed support comprises a first end socket and a second end socket in which is mounted the pivot shaft, and the radial friction element is mounted on one intermediate part of the pivot shaft. According to this embodiment, the elastic element comprises a first helical spring with windings arranged around the pivot shaft between the first end socket and the radial damper and a second helical spring with windings arranged around the pivot shaft between the second end socket and the radial damper.

The swiveling lever can comprise two lugs articulable to the support element, in which case the first helical spring is connected by its first end to one of the lugs and by its second end to first end socket, and the second helical spring is connected by its first end to the other lug and by its second end to second end socket.

Preferably, the first end of each helical spring is connected to the swiveling lever near to the pivot shaft. This first end of each helical spring can be connected to the swiveling lever permitting a limited rotation of the swiveling lever without opposing the torsional force, which prevents oscillations that are below a certain threshold value that do not result in substantial vibrations in the household appliance housing, thus activating the oscillation damper unnecessarily, which reduces wear on the oscillation damper.

To achieve this effect, the swiveling lever can be provided with a guide slot in which the first end of the helical spring slides during the limited rotation of the swiveling lever, and which extends perpendicularly to the pivot shaft. This guide slot comprises an upper guide, a lower guide, and a supporting wall that is arranged between first ends of the upper guide and of the lower guide, an on which the first end of the helical spring is supported when the swiveling lever is subjected to the load of the oscillating group received by the support element to which the swiveling lever is articulable. The guide slot can be provided with a retaining wall arranged between the second ends of the upper and lower guides opposite to the supporting wall. Alternatively, the guide slot can be a recess that, instead of the retaining wall, comprises an access opening between the second ends of the upper and lower guides opposite to the supporting wall. When the swiveling lever comprises both lugs, each one of same comprises such a guide slot.

In one embodiment of the invention, the radial friction element comprises outer bushing associated with the swiveling lever rotatably arranged with respect to the pivot shaft, and moreover comprising internal friction means that radially encircle the pivot shaft exerting a frictional force to damp rotational movement between the pivot shaft and the outer bushing. The purpose of the radial friction element is to reduce a certain type of oscillation, namely the shortest and most frequent that is produced in a stabilized machine at a constant speed, such that it can reduce the friction and transmission of vibrations to the household appliance housing in phase with the greater number of revolutions and oscillations.

This radial friction element can comprise an inner bushing rotatably enclosed in the outer bushing. The inner bushing comprises an outer wall opposite to an inner wall of the outer bushing and an inner axial passage wherein the internal friction means is radially arranged to exert a frictional force at least against the inner bushing. The rotation between the inner bushing and the outer bushing is limited by a rotation limiting system comprising at least an axial channel placed between the inner bushing and the outer bushing and at least a rotation limiting system situated in the axial channel, which has a cross section in the shape of a circular ring segment delimited by two radial end stop surfaces. Each rotation limiting element is selected from among projections emerging from the inner wall of the outer bushing, protrusions emerging from the outer wall of the inner bushing, sliding locking elements, and combinations thereof. Each protruding element is moveable in the corresponding axial channel such that for the inner bushing and the outer bushing to rotate with respect to one another each protruding element has a free path in the axial channel limited by said stop surfaces. The free rotation path between the outer bushing and the inner bushing can, for example, correspond to a 1° to 4° arch. By means of this free path, it can be achieved that only the oscillations produced by oscillations transmitted by the support element having an intensity greater than a predetermined threshold value corresponding to an intensity below which these oscillations result in a transmission of vibrations of an acceptable level to the house- hold appliance housing, causing the sliding locking elements to be displaced by the free path until stopped by the respective stop surfaces and pushed to a greater or lesser degree, causing the rotation of the inner bushing in one direction and another. These rotational movements will be damped by the resistance to rotation afforded by the internal friction elements from the surface of inner axial passage of inner bushing with respect to the peripheral surface of the pivot shaft. By contrast, if the vibrations transmitted by the support element are below said threshold value, the sliding locking elements move along the length of the free path without stopping at the stop surfaces. Preferably, the elastic element is designed so that the torsional force that opposes the rotation of the swiveling lever corresponds to 80% to 90% of the load of the oscillating group transmitted by the support element to which the swiveling lever is articulable. When provided with more than one elastic element, each one of these is designed to oppose a portion of the torsional force proportional to the oscillating group load.

In accordance with what can be deduced from the foregoing, the present invention enables a reduction in the level of vibrations and noise induced by the oscillations of the oscillating group by means of a damper with a simple and robust configuration which is very easily assembled.

Aspects and embodiments of the invention are described below with reference to preferred embodiments shown in the figures of the attached drawing, wherein:

Figure 1 is a frontal perspective view of a washing machine suitable for incorporation of a damping system with an oscillation damper;

Figure 2 is a sectional view along line A-A shown in Figure 1 ;

Figure 3 is a top perspective view of an embodiment of an oscillation damper;

Figure 4 is an elevated posterior view corresponding to a first embodiment of the oscillation damper shown in Figure 3; Figure 5 is an elevated iaterai view of the left swive!ing lever present in the oscillation damper shown in Figure 4;

Figure 6 is an elevated lateral view of the right swivelling lever present in the oscilla- tion damper shown in Figure 4;

Figure 7 is an elevated posterior view corresponding to a first embodiment of the oscillation damper shown in Figure 3; Figure 8 is an elevated lateral view of the left swiveling lever present in the oscillation damper shown in Figure 7;

Figure 9 is an elevated lateral view of the right swiveling lever present in the oscillation damper shown in Figure 7;

Figure 10 is a lateral perspective view of an embodiment of a radial friction element present in the oscillation damper shown in Figure 3; and

Figure 1 1 is a cross-sectional view of the radial damper along line B-B shown in Fig- ure 4.

Figures 1 and 2 show an embodiment of a household appliance 9 embodied as a washing machine 9 that, in the conventional manner, comprises a housing 10. Housing 10 comprises a frontal wall 1 1 with a loading opening 12 that permits access to a drum 13, and which is closed by means of a loading door 14. Inside housing 10 is enclosed an oscillating group comprising a tub 15 in which rotates a drum 13, and that has a front hatch 14 facing loading opening 12. Drum 13 comprises a driven pulley 23 connected to a driving motor 21 by means of a belt 22. Housing 10 moreover comprises a back wall (not shown in the figures), a cover wall 19, a lower base 20, as well as both side walls 25.

Tub 15 is connected to the top of housing 10 by means of two sustaining springs 17 that are engaged in respective hooks 18 in the sides of covering wall 19 of housing 10, and below through two support elements 24 connected to base 20 of housing 10 in both positions that are close to respective side walls 25 of housing 10. The inner end of each support element 24 is connected to base 20 of housing 10 through a respective oscillation damper 1 comprising a fixed support 2 anchored in base 20, a first joint 26 that comprises a pivot shaft 26 rotatably coupled in fixed support 2, and at least one swiv- eling lever 5 joined to pivot shaft 3 through a friction damper (not shown in Figures 1 and 2). The inner end of support element 24 is joined to swiveling lever 5 by means of second joint 26, during which the upper end of each support element 24 is articulated to tub 15 by means of third joint 29.

The oscillation dampers 1 are designed to oppose torsional forces that collectively correspond to 80% to 90% of the load of the oscillating group transmitted by support elements 24 articulated to swiveling levers 5, during which the rest of the load is supported by sustaining springs 17. The load of the oscillating group is based on the weight of the assembly formed by tub 15, drum 13, and motor 21 that form the oscillating group plus the weight of the maximum volume of wash water present in tub 15 and the maximum possible weight of laundry present in drum 13 that, during the rotation of drum 13 during the washing and cen- trifuging processes, exerts forces that afford the mentioned oscillations, the transmission of which to the washing machine housing can be mitigated by means of employing oscillation dampers 1. In a washing machine with a capacity of 7 kg of laundry, this oscillating group usually has a weight of 42 kg to 48 kg and the maximum total weight of the water and laundry is usually about 15 kg.

In the embodiment shown in Figures 3 through 1 1 , oscillation damper 1 comprises a fixed support 2 fixably mounted to lower base 20 of housing 10, support 2 mounted to pivot shaft 3, radial friction element 4 mounted to an intermediate portion of pivot shaft 3, swiveling lever 5 associated with radial friction element 4 with lugs 5, 5b, 5c with free ends 5a articulable to support element 24, and elastic element 6, 6'. The radial friction element 4 is designed so that the torsional force generated by friction that opposes the rotation of swiveling lever 5 corresponds to a proportional part of the load of the oscillating group received by support element 24 to which swiveling lever 5 is articulable.

The ends of pivot shaft 3 are mounted respectively in first end socket 2a and second end socket 2b from fixed support 2. As can be seen in Figures 3, 4, and 7, an elastic element 6, 6' comprising first helical spring 6 with windings arranged around pivot shaft 3 between first end socket 2a and radial friction element 4 and second helical spring 6' with windings arranged around pivot shaft 3 between second end socket 2b and radial friction element 4 is provided, to generate a torsional elastic force in addition to the said torsional f fictional force. First end 6a of first helical spring 6 is connected to first lug 5b while its second end 6b is con- nected to second end socket 2b. Analogously, second helical spring 6' is connected through its first end 6a' to second lug 5c and through its second end 6b' to second end socket 2b.

Figure 4 shows that first end 6a, 6a' of each helical spring 6, 6' is joined together forming an integrated elastic element to give better stability to the oscillation damper 1. At the same time, first end 6a, 6a' of each helical spring 6, 6' is connected to lugs 5b, 5c near to pivot shaft 3. In this manner, helical springs 6, 6' are capable of opposing a torsional force to the rotation swiveling lever 5 induced by the oscillations transmitted by support element 24. Free ends 6a of lugs 6b, 6c comprise both through holes 8 through which pivot shaft 28 (Figure 2) extends by means of second rotational joint 27 by which support element 24 is articulated to lugs 5b, 5c to form swiveling lever 5.

First end 6a, 6a' of each helical spring 6, 6' is connected to swiveling lever 5 permitting a limited rotation of swiveling lever 5 without opposing the torsional force. According to what is illustrated in Figures 4 through 9, this is achieved due to first end 6a, 6a' of each helical spring 6, 6' slides in a guide slot in 8, 8' in swiveling lever 5, that is, the first end of first helical spring 6 slides in first guide slot 7 in first lug 5b during the limited rotation of swiveling lever 5, and the first end of second helical spring 6^' slides in second guide slot T in the second lug during the limited rotation of swiveling lever 5. Guide slots 7, T extend perpendicularly with respect to pivot shaft 3.

Each guide slot 7, T comprises upper guide 7a, 7a^', lower guide 7b, 7b' and supporting wall 7c, 7c' that is arranged between first ends of upper guide 7a, 7a) and of lower guide 7b, 7b', an on which first end 6a, 6a' of helical spring 6, 6' is supported when swiveling lever 5 is subjected to the load of the oscillating group received by support element 24 to which swiv- eling lever 5 is articulable. In the embodiment shown in Figures 4 through 6, guide slot 7, T is a recess comprising an access opening 7e, 7e' between the second ends of upper and lower guides 7a, 7a'; 7b, 7b' opposite to supporting wall 7c, 7c'. Meanwhiie, in the embodiment shown in Figures 7 through 19, guide slot 7, T is a notch comprising retaining wall 7b, 7b' arranged between the second ends of upper and lower guides 7a, 7a'; 7b, 7b' opposite to supporting wall 7c, 7c'.

Radial friction element 4 comprises outer bushing 30 with inner passage 4a and associated with swiveling lever 5, and inner bushing 31 rotatably enclosed in outer bushing 30. Inner bushing 31 comprises outer wall 31 a facing inner wall 30a of outer bushing 30 and inner axial passage 31 b in which is radially arranged internal friction means 32 that radially encircle pivot shaft 3 exerting a frictional force to damp the rotational movement between pivot shaft 3 and inner bushing 31 , and therefore between pivot shaft 3 and outer bushing 30. Internal friction means 32 is four pads of an elastic material with a cross-section in the shape of a circular ring segment, each of which is inserted under pressure between four equidistant internal radial projections 31 c that emerge toward the interior of inner passage 4b and pivot shaft 3.

The rotation between inner bushing 31 rotatably enclosed in outer bushing 30 is limited by a rotation limiting system comprising four axial channels 34 with a cross-section in the shape of a limited circular ring segment, each of which is between two radial end stop surfaces 35 placed between inner bushing 31 and outer bushing 30. In axial channels 34 is enclosed two rotation limiting elements 30b, 31 b, 33 in the form of two internal axial protrusions 30b that emerge from opposite sides of inner wall 30a of outer bushing 30, two external axial protrusions 31 b that emerge from opposite sides of outer wall 31 a of inner bushing 31 , and four sliding locking elements 33, each one of which is arranged between one of the internal pro- trusions 30b and one of the external protrusions 31 b. Sliding locking elements 33 are also pads of an elastic material with a cross-section in the shape of a circular ring segment inserted under pressure into corresponding axial channel 34. Stop surfaces 35 are formed by the axial sides opposite to the internal and external protrusions 30b and 31 b. Sliding locking elements 33 have a radial extension less than axial channels 34 so as to be moveable in axial channel 34 along the length of a free path limited by said stop surfaces 35, corresponding to a 1° to 4° arch, that is outer bushing 30 and inner bushing 31 can themselves rotate between 1⁰ to 4° before internal friction elements 32 oppose a frictional force to rotation between pivot shaft 3 and outer bushing 30. It is thus achieved that the oscillations transmitted by support element 24 that have an intensity greater than a predetermined threshold value induce sliding locking elements 33 to move through the free path to bump against the respective stop surfaces 33 and push them to a greater or lesser degree, causing the rotation of the inner bushing 31 in one direction and another. These rotational movements will be damped by the resistance to rotation afforded by internal friction elements 32 from the surface of inner axial passage 4b of inner bushing 31 with respect to the peripheral surface of pivot shaft 3. By contrast, if the vibrations transmitted by support element 24 are below said threshold value, sliding locking elements 33 move along the length of the free path without stopping at stop surfaces 35. A certain limitation of that rotation within damper 1 is also afforded by the elastic element 6, 6' which provides additional torsional force acting against the rotation, where the force is essentially proportional to the angle of rotation. Thus the damper 1 provides for a limitation that is not only provided by hard stops as defined by the system detailed above but that also includes some soft limitation due to the action of the elastic element 6, 6'.

LIST OF REFERENCE NUMERALS

1 Oscillation damper

2 Fixed support

2a First end socket

2b Second end socket

3 Pivot shaft

4 Radial friction element

4a Inner passage

5 Swiveling lever

5a Free end

5b, 5c Lugs

5d, 5e Passage opening

6 Elastic element, First helical spring

6' Elastic Element, Second helical spring

6b, 6b' Second end

6a, 6a' First end

7, 7' Guide slot

7a, 7a' Upper guide

7b, 7b' Lower guide

7c, 7c' Supporting wall

7d, 7d' Retaining wall

7e. 7e' Access opening

8 Through hole

9 Household appliance, Washing machine, Dryer

10 Housing

1 1 Front wall of the housing

12 Loading opening

13 Drum

14 Loading door

15 Tub 16 Drum rotation shaft

17 Sustaining springs

18 Hooks from the springs to the tub

19 Cover wall

20 Housing base

21 Motor

22 Belt

23 Pulley

24 Support element

25 Side walls of the housing

26 First swivel joint

27 Second swivel joint

28 Pivot shaft

29 Third swivel joint

30 Outer bushing

30a Inner wall of the outer bushing

30b internal protrusion from the outer bushing

31 Inner bushing

31a Outer wall of the inner bushing

31 b External projection from the inner bushing

31 c Internal projection from the inner bushing

32 Internal friction element

33 Sliding locking element

34 Axial channel

35 Stop surface

Claims

An osciliation damper (1 ) for a household appliance (9), with:

a fixed support (2) fixedly mountable on a lower part of the housing (10) of the household appliance (9) in which is housed an oscillating group comprising a tub (15) in which a drum (13) rotates around a rotation shaft (16);

a pivot shaft (3) mounted on the support (2);

a radial friction element (4) mounted on the pivot shaft (3);

a swiveling lever (5) associated with the radial friction element (4), with a free end (5a) articulable to a support element (24) simultaneously articulated to a lower part of the tub (15) receiving a load from the oscillating group;

characterized in that

it comprises an elastic element (6, 6') with a first end (6a, 6a') connected to the swiveling lever (5), and a second end (6b, 6b') connected to the fixed support (2) such that it opposes a torsional force to the rotation of the swiveling lever (5).

The oscillation damper (1 ) according to claim 1 , characterized in that:

the radial friction element (4) is mounted on an intermediate part of the pivot shaft (3); the fixed support

(2) comprises a first end socket (2a) and a second end socket (2b) in which the pivot shaft (3) is mounted;

the elastic element (6, 6') comprises at least a metallic helical spring (6, 6') with windings arranged around the pivot shaft (3) and comprises a first helical spring (6) with windings arranged around the pivot shaft (3) between the first end socket (2a) and the radial friction element (4) and a second helical spring (6') with windings arranged around the pivot shaft (3) between the second end socket (2b) and the radial friction element (4).

3. The oscillation damper (1 ) according to claim 2, characterized in that: the swiveling lever (5) comprises two lugs (5b, 5c) articulable to the support element (24);

the first helical spring (6) is connected at its first end (6a) to one (5b) of the lugs and at its second end (6b) to the first end socket (2a); and

the second helical spring (6') is connected at its first end (6a') to the other lug (5c) and at its second end (6b') to the second end socket (2b).

4. The oscillation damper (1 ) according to any of claims 1 to 3, characterized in that the first end (6a, 6a') of each helical spring (6, 6') is connected to the swiveling lever (5) near the pivot shaft (3).

5. The oscillation damper (1 ) according to any of claims 1 to 4, characterized in that the first end (6a, 6a') of each helical spring (6, 6') is connected to the swiveling lever (5) allowing a limited rotation of the swiveling lever (5) without opposing the torsional force.

6. The oscillation damper (1 ) according to claim 5, characterized in that the swiveling lever (5) comprises a guide slot (7, 7') in which the first end (6a, 6a') of the helical spring (6, 6') slides during the limited rotation of the swiveling lever (5), and which extends perpendicularly to the pivot shaft (3); and

the guide slot (7, 7^') comprises an upper guide (7a, 7a'), a lower guide (7b, 7b') and a supporting wall (7c, 7c') that is arranged between first ends of the upper guide (7a, 7a') and of the lower guide (7b, 7b'), an on which the first end (6a, 6a') of the helical spring (6, 6') is supported when the swiveling lever (5) is subjected to the load of the oscillating group received by the support element (24) to which the swiveling lever (5) is articulable.

7. The oscillation damper (1 ) according to claim 6, characterized in that the guide slot (7, 7') comprises a retaining wall (7d, 7d') arranged between the second ends of the upper and lower guides (7a, 7a'; 7b, 7b') opposite to the supporting wall (7c, 7c').

8. The oscillation damper (1 ) according to claim 6, characterized in that the guide slot (7, 7') is a recess comprising an access opening (7e, 7e') between the second ends of the upper or lower guides (7a, 7a'; 7b, 7b') opposite to the supporting wall (7c, 7c').

9. The oscillation damper (1 ) according to any of claims 1 through 8, characterized in that the elastic element is designed so that the torsional force it opposes to the rotation of the swiveling lever (5) amounts to 80-90% of the load of the oscillating group transmitted by the support element (24) to which the swiveling lever (5) is articulable.

10. The oscillation damper (1 ) according to any of the preceding claims, characterized in that:

the radial friction element (4) comprises an outer bushing (30) associated with the swiveling lever (5);

the outer bushing (30) is capable of rotational movement in relation to the pivot shaft (3) and;

the radial friction element (4) also comprises an internal friction means (32) that radially encircles the pivot shaft (3) exerting a friction force to damp the rotational movement between the pivot shaft (3) and the outer bushing (30).

11. The oscillation damper (1 ) according to claim 10, characterized in that

the radial friction element (4) comprises an inner bushing (31 ) housed in the outer bushing (30) being capable of rotating, the inner bushing (31 ) comprising an outer wall (31 a) opposite to an inner wall (30a) of the outer bushing (30) and an inner axial passage (31 b) in which the internal friction means (32) are radially arranged exerting a friction force at least on the inner bushing (31 );

rotation between the inner bushing (31 ) and the outer bushing (30) is limited by a rotation limiting system comprising at least an axial channel (34) placed between the inner bushing (31 ) and the outer bushing (30) and at least a rotation limiting element (30b, 31 b, 33) arranged in the axial channel (34);

the axial channel (34) has a cross-section in the form of a circular ring segment delimited between two end radial stop surfaces (35);

each rotation limiting element (30b, 31 b, 33) is selected from among projections (30b) emerging from the inner wall of the outer bushing, protrusions (31 b) emerging from the outer wall of the inner bushing, sliding locking elements (33), and combinations thereof; and

each protruding element (30b, 31 b) is displaceable inside the corresponding channel (34) in such a manner that, when the outer bushing (30) and the inner bushing (31 ) rotate in relation to each other, each protruding element (30b, 31 b) has a free path in the axial channel (34) limited by said stop surfaces (35).

The oscillation damper (1 ) according to claim 1 1 , characterized in that the free path of rotation between the outer bushing (30) and the inner bushing (31 ) corresponds to an arch of from 1⁰ to 4°.

A household appliance (9), comprising a housing (10) that houses an oscillating group comprising a tub (15) in which a drum (13) rotates, driven by a motor (21 ), the tub (15) being connected at the top with the housing (10) by means of at least a pair of sustaining springs (17) and at the bottom by means of at least two support elements (24) connected to an oscillation damping system, the support element (24) being articulated to the housing (10) with the intercalation of at least one articulation (26, 27, 29) comprising a radial friction element (4), characterized in that at least one of the swiveling levers (5) is articulated to the oscillation damper (1 ) as defined in one of claims 1 to 12.

The household appliance (9) according to claim 13, characterized in that the damping system comprises a plurality of oscillation dampers (1 ) mounted on opposite sides of the housing (10) and in that the oscillation dampers (1 ) are designed to oppose torsional forces that jointly amount to 80-90% of the load of the oscillating group received by the support elements (24) articulated to the swiveling levers (5).

The household appliance (9) according to one of claims 13 and 14, which is embodied as a washing machine (9) or a laundry dryer (9).