WO2013175363A1

WO2013175363A1 - Radial free-travel vibration damper, and household appliance with a dampening system comprising said radial damper

Info

Publication number: WO2013175363A1
Application number: PCT/IB2013/054030
Authority: WO
Inventors: Ismael Gracia Bobed; Roberto Latre Abadia; Gerardo Martinez Perez; Eduardo Recio Ferrer
Original assignee: BSH Bosch und Siemens Hausgeräte GmbH
Priority date: 2012-05-23
Filing date: 2013-05-17
Publication date: 2013-11-28
Also published as: CN104541082B; EP2852776B1; ES2431464A2; RU2599307C2; EP2852776A1; RU2014148154A; PL2852776T3; ES2431464R1; CN104541082A; ES2431464B1

Abstract

The invention relates to a radial vibration damper comprising a cylindrical outer bushing 2, a rota table inner bushing 4 housed in the outer bushing 2, inner bushing 4 comprising an axial inner passage 4b in which internal friction means 5 are provided that exert frictional force at least on the inner bushing 4. The rotation between the inner bushing 4 and the outer bushing 2 is limited by a rotation-delimiting system 2b, 4c, 7, 8 comprising at least one axial channel 7 located between the inner bushing 4 and the outer bushing 2, and at least one rotation-delimiting element 2b, 4c, 6 moveable within the corresponding channel 7 in such a manner that when the outer bushing 2 and the inner bushing 4 rotate with respect to one another, each protruding element 2b, 4c has free travel in the axial channel 7 limited by said stop surfaces 8.

Description

RADIAL FREE-TRAVEL VIBRATION DAMPER, AND HOUSEHOLD APPLIANCE WITH A DAMPENING SYSTEM COMPRISING SAID

RADIAL DAMPER The present invention relates to the technical field of vibration dampening devices, particularly radial dampers, and has particular utility in household electrical appliances such as washing machines and dryers.

Washing machines and dryers with a wash drum housed rotatably in a wash tub usually have a vibration dampening device that joins the wash tub or the wash tank to the housing. The vibrations and noise produced by the rotational movement of the drum are dampened by means of a vibration dampening device.

Vibrations are transmitted through dampening elements to avoid having the movements of the oscillating unit (assembly: wash tub, drum, and motor) directly transmitted to the frame of washing machines to produce vibrations and noise therein. Linear damper systems for absorbing these vibrations are known that include piston type dampers such as, for example, the free-travel damper described in application EP 1754908 A2, which has a short path (from 5 mm to 8 mm) with little or no frictional force. These dampers essentially function 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 braking 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 transmitted 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 large, especially in length. Also known are radial dampers for which the design is different from that of linear dampers. In radial dampers, for example, such as those described in prior art document WO 201 1/070092 A1 , the necessary frictional force is achieved radially with 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. Nevertheless, known radial damper systems do not have free travel, and thus have the disadvantage of being engaged continuously, and of transmitting vibrations at all times, which can cause the vibration damper to wear out prematurely.

The present invention has the object of overcoming the disadvantages of the state of the art described above by means of a radial free-travel vibration damper, and a household appliance with a dampening system comprising the radial damper.

The radial vibration damper according to the invention comprises, connectable to a first element, a cylindrical outer bushing having an inner wall able to house an inner shaft that is connectable to a second element, so that the inner shaft and the cylindrical outer bushing are capable of angular movement relative to one another, and a friction means to radially grasp the inner shaft exerting a frictional force to dampen rotational movement, wherein the damper comprises an inner bushing rotatably housed within an outer bushing, with the inner bushing comprising an outer wall facing the inner wall of the outer bushing and an inner axial passage within which the inner shaft is located; and a rotation-delimiting system between the inner bushing and the outer bushing that permits rotation between the outer bushing and the inner bushing over a determined free-travel angle of rotation within which the friction means does not engage, and which rotationally locks the inner bushing and the outer bushing together by engaging the friction means.

The inner bushing either can be joined solidly to the inner shaft in which case the friction means is located within the rota table connection between the inner shaft and the second element, or else the inner bushing can be rota table with respect to the inner shaft with the friction element placed between the two with the inner shaft not rota table with respect to the second element. in a more detailed embodiment, the radiai vibration damper comprises a cylindrical outer bushing with an inner wall, connectabie to a first element and able to house an inner shaft connectabie to a second element, in such a way that the inner shaft and the cylindrical outer bushing are capable of angular movement relative to one another, and the internal friction means for radially grasping the inner shaft exerts a frictional force for dampen rotational movement, with the radial damper being characterized in

comprising an inner bushing rotatably housed within the outer bushing, the inner bushing comprising an outer wall facing the inner wall of the outer bushing and an inner axial passage within which the friction means is arranged radially, exerting a frictional force at least on the inner bushing;

rotation between the inner bushing and the outer bushing being limited by a rotation- delimiting system (comprising at least one axial channel located between the inner bushing and the outer bushing, and at least one rotation-delimiting element) located in the axial channel;

the axial channel having a cross section in the shape of a circular ring segment delimited by two radial end stop surfaces;

each rotation-delimiting element being selected from among, protrusions arising from the inner wall of the outer bushing, projections arising from the outer wall of the inner bushing, and sliding blocks; and

each protruding element being moveable in the corresponding channel such that for the inner bushing and the external bushing to rotate with respect to one another each protruding element has a free path in the axial channel limited by said stop surfaces, which can correspond to a 1 to 4° arch. The radial damper can comprise at least one rotation-delimiting element designed to move in the channel opposing a friction force when the external bushing and the inner bushing rotate with respect to one another so as to dampen the rotation between the inner bushing and the external bushing. The internal friction means can comprise at least one tubular element interposed between the inner shaft and the inner bushing, or a plurality of internal friction means spaced away from one another by respective axial gaps; and the inner passage of the inner bushing comprises at least one axial internal projection fitting into one of the axial gaps. In this latter case, the internal friction means can have a cross-section in the shape of a circular ring segment, and can be pads of an elastic material inserted under pressure between the inner shaft and the inner bushing. The inner shaft can comprise at least one outer axial rib inserted into one of the axial gaps. According to a preferred embodiment of the invention, the radial damper comprises at least one axial channel formed by an internal recess in the inner wall of the outer bushing, while the rotation-delimiting element located in the internal recess is an external protrusion that arises from the outer wall of the inner bushing. Alternatively, the radial damper comprises at least one axial channel that is formed by an external recess in the outer wall of the inner bushing. According to this embodiment, the rotation-delimiting element located in said external recess is an internal protrusion that arises from the inner wall of the outer bushing. According to this embodiment, the stop surfaces of said axial channel are formed by respective radial steps that delimit the axial channel formed by the internal recess of the outer bushing.

According to another preferred embodiment, the radial damper comprises at least one axial channel that is formed by an internal recess in the inner wall of the outer bushing or by an external recess in the outer wall of the inner bushing; and at least one of the rotation- delimiting elements is a sliding block arranged in the axial channel that is moveable along the length of same free path between the stop surfaces.

According to a further preferred embodiment of the invention, the radial damper can comprise a plurality of sliding blocks each of which is arranged in an axial channel. In this case, the outer wall of the inner bushing can be provided with a plurality of external projections, while the external projections comprise respective radially opposed axial sides, which form the respective stop surfaces delimiting the free paths of the respective sliding blocks. Alternatively, the inner wall of the outer bushing can be provided with a plurality of internal projections, in which case the internal projections comprise respective radially opposed axial sides, which form the respective stop surfaces delimiting the free paths of the respective sliding blocks. According to yet another preferred embodiment of the invention, when the radiai damper comprises a plurality of sliding blocks each arranged in an axial channel, the outer wall of the inner bushing can be provided with at least one external protrusion that comprises respective radially opposed axial sides, in which case the inner wall of the outer bushing can be provided with at least one internal protrusion that comprises respective radially opposed axial sides, such that at least one of the axial channels will be delimited between an internal protrusion and an external protrusion and the opposed axial sides of the projections form the respective stop surfaces that limit the free travel of the sliding block located in said axial channel.

According to yet a further preferred embodiment of the invention, the radial damper comprises a plurality of sliding blocks each of which is arranged in an axial channel. According to this preferred embodiment, the outer wall of the inner bushing is provided with a plurality of external projections that comprise respective radially opposed axial sides that form the respective stop surfaces that delimit the free travel of the respective sliding blocks, while the inner wall of the outer bushing is provided with a plurality of internal projections that comprise respective radially opposed axial sides that form the respective stop surfaces that delimit the free travel of the respective sliding blocks. In this way, each axial channel is delimited between an internal protrusion and an external protrusion.

According to still another preferred embodiment of the invention, at least one of and preferably all of the sliding blocks can comprise a pad of an elastic material inserted under pressure into one of the axial channels. Moreover, at least one and preferably all of the rotation-delimiting elements can have a cross-section in the shape of a circular ring segment.

The household appliance, especially a washing machine or dryer according to the invention comprises a housing that houses a wash tub in which a wash drum rotates being driven by a motor, the tub being connected with the housing through at least one support element from a dampening system. The support element articulated to the housing with interposition of a swiveling lever and at least one articulation that comprises a radial vibration damper, at least one articulation comprising the radial damper described earlier. As can be observed, a radial damper according to the present invention can achieve, in a certain type of oscillation, the shortest and most frequent, that is produced in a stabilized machine at a constant speed, a reduction in friction so that no vibrations are transmitted to the frame in phase with the greater number of revolutions and oscillations. In addition, these radial dampers offer the advantages of: reducing the stresses transmitted to the base of the frame, greater ease of assembly such that in fact the installation onto the frame can be accomplished on an assembly line with the connection to the tub becoming easier, requiring less space for assembly, and packaging as a standard part. According to what is apparent from the foregoing, the present invention achieves its object by means of a radial vibration damper of simple and robust construction, easy and economical in its manufacture, and additionally simple to install in household appliances such as washers and dryers, offering an efficient vibration dampening effect. Aspects and embodiments of the invention are described below with reference to the accompanying drawing, based in several figures, wherein

Figure 1 is a cross-sectional view of a first embodiment of a radial vibration damper;

Figure 1 a is a cross-sectional view of a fifth embodiment of a radial vibration dampen

Figure 1 b is an anterior perspective view of a radial vibration damper;

Figure 2 is a cross-sectional view of a second embodiment of a radial vibration damper;

Figure 3 is a cross-sectional view of a third embodiment of a radial vibration damper;

Figure 4 is an anterior perspective view of a radial vibration dampen Figure 5 is a cross-sectional view of the radial damper along line A-A shown in Figure 4;

Figure 6 is an exploded view of the radial damper shown in Figures 4 and 5;

Figure 7 is a frontal perspective view of a washing machine suitable for incorporation of a dampening system with at least one radial damper;

Figure 8 is a sectional view along line B-B shown in Figure 7.

In the embodiments illustrated in Figures 1 through 6, the subject radial vibration damper 1 comprises cylindrical outer bushing 2 with inner wall 2a, connectable to a first element and capable of housing inner shaft 3 connectable to a second element, in such a way that inner shaft 3 and cylindrical outer bushing 2 can move rotatably with respect to one another, and internal friction means 5 to radially enclose inner shaft 3 exerting a friction force for dampening the rotational movement. Rota table inner bushing 4 is housed in outer bushing 2. Inner bushing 4 exhibits outer wall 4a opposite to inner wall 2a of outer bushing 2 and inner axial passage 4b wherein friction means 5 are radially arranged to exert frictional force at least against inner bushing 4.

The rotation between inner bushing 4 and outer bushing 2 is limited by rotation-delimiting system 2b, 4c, 7, 8 that comprises at least one axial channel 7 located between inner bushing 4 and outer bushing 2, and at least one rotation-delimiting element 2b, 4c, 6 located in axial channel 7. Axial channel 7 has a cross section in the shape of a circular ring segment delimited between two radial end stop surfaces 8. Each rotation-delimiting element 2b, 4c, 6 is selected among protrusions 2b arising from inner wall 2a of outer bushing 2, projections 4c arising from outer wall 4a of inner bushing 2 and sliding blocks 6. Each protruding element 2b is moveable in corresponding channel 7 such that for outer bushing 2 and inner bushing 4 to rotate with respect to one another each protruding element 2b, 4c has a free path in axial channel 7 limited by stop surfaces 8, which can correspond to a 1 to 4° arch.

In the first embodiment shown in Figure 1 , radial damper 1 comprises axial channel 7 formed by external recess 4e in outer wall 4a of inner bushing 4. According to this embodiment, the rotation-delimiting element located in said external recess 4e is internal protrusion 2b with a cross-section in the shape of a circular ring segment that arises from inner wall 2a of the outer bushing. Stop surfaces 8 of said axial channel 7 are formed by respective radial steps that delimit axial channel 7 formed by the internal recess of outer bushing 2. The internal friction means are constituted by tubular element 5 that encircles inner shaft 3 and that is formed to be interposed between inner shaft 3 and inner bushing 4.

In this first embodiment, the oscillations produced by low-intensity vibrations cause internal protrusion 2b to be freely moved back and forth between stop surfaces 8 in axial channel 7. In turn, the oscillations produced by vibrations of an intensity higher than a certain threshold value cause external protrusion 2b to stop at respective stop surfaces 8 and push them to a varying extent, causing rotation of inner bushing 4 in one direction or the other. These rotation movements will be dampened by the resistance to rotation afforded by the friction element in the form of tubular element 5, both with respect to the surface of inner axial passage 4b of bushing 4 as well as with respect to the peripheral surface of inner shaft 3.

In Figure 1 a is shown a sectional view of another embodiment of the radial damper wherein inner wall 4b of bushing 4 is joined without rotation to inner shaft 3 such that when outer bushing 2 rotates and the rotation-delimiting system blocks the relative rotation between the two bushings 2 and 4, the outer bushing that carries the inner shaft as shown in Figure 1 b will rotate around lug 32 of the second element for fastening to the housing of the appliance (or of the tub) engaging friction elements 5.

In the second embodiment shown in Figure 2, radial damper 1 also comprises external recess 4e in outer wall 4a of inner bushing 4. According to this second embodiment, the rotation-delimiting element is sliding block 6 arranged in axial channel 7 in a moveable manner along said free path between stop surfaces 8. Sliding block 6 is a pad of an elastic material with a cross-section in the shape of a circular ring segment inserted under pressure into axial channel 7. In this second embodiment, the oscillations produced by low-intensity vibrations cause sliding block 6 to be moved back and forth between stop surfaces 8 in axial channel 7 against the frictional force exerted by friction block 6 in inner wall 2a of the outer bushing and outer wall 4a of inner bushing 4, such that the rotation between outer bushing 2 and inner bushing 4 will be dampened. Oscillations produced by vibrations of an intensity higher than a certain threshold value cause sliding block 6 to stop at respective stop surfaces 8 and push them to a varying extent, causing rotation of inner bushing 4 in one direction or the other. These rotation movements will be dampened by the resistance to rotation afforded by the friction element in the form of tubular element 5, both with respect to the surface of inner axial passage 4b of bushing 4 as well as with respect to the peripheral surface of inner shaft 3.

The third embodiment illustrated in Figure 3 differs from the first embodiment only in that in the case of Figure 3, the internal friction means comprise two symmetrical pads 5 with a cross-section in the shape of a circular ring segment, which are spaced apart by respective axial gaps into which respectively fit axial rib 3a that arises from the periphery of inner shaft 3 and internal projection 4d that arises to the inside of inner passage 4b of the inner bushing, such that the inner shaft 3 cannot rotate about inner bushing 4. Also in this third embodiment, the oscillations produced by low-intensity vibrations cause internal protrusion 2b to be moved freely back and forth between stop surfaces 8 in axial channel 7, while the oscillations produced by vibrations of an intensity higher than a certain threshold value cause external protrusion 2b to stop at respective stop surfaces 8 and push them to a varying extent, causing rotation of inner bushing 4 in one direction or the other. These rotation movements will be dampened by the resistance to rotation afforded by the friction element in the form of tubular element 5 only with respect to the surface of inner axial passage 4b of bushing 4. Radial damper 1 of the fourth embodiment shown in Figures 4 through 6 comprises a plurality of sliding blocks 6 with a cross-section in the shape of a circular ring segment, each one inserted under pressure into an axial channel 7. Outer wall 4a of inner bushing 4 is provided with a plurality of external projections 4c that comprise respective radially opposed axial sides that form respective stop surfaces 8 delimiting the free paths of respective sliding blocks 6 on the one hand, while inner wall 2a of outer bushing 2 is provided with a plurality of internal projections 2b that comprise respective radially opposed axial sides that form the respective stop surfaces 8 delimiting the free travel of respective sliding blocks on the other hand, such that each axial channel 7 is delimited between internal protrusion 2b and external protrusion 4b. Projections 2b, 4c have a cross-section in the shape of a circular ring segment. From outer bushing 2 arise two coupling lugs 2d provided from respective through holes 2e that permit coupling of radial damper 1 to the household appliance. In this fourth embodiment, the internal friction means comprise a plurality of internal friction elements 5 spaced apart from one another by respective axial gaps into which respectively fit internal projections 4d. Internal friction means 5 have a cross-section in the shape of a circular ring segment, while internal friction means 5 can be pads of an elastic material inserted under pressure between inner shaft 3 and inner bushing 4. The operation of radial damper 1 shown in Figure 1 is analogous to that of the radial damper of the second embodiment described earlier with reference to Figure 2. Thus, oscillations produced by vibrations of an intensity higher than a certain threshold value cause sliding blocks 6 to stop at respective stop surfaces 8 and push them to varying extents, causing rotation of inner bushing 4 in one direction or the other. These rotational movements will be dampened by the resistance to rotation afforded by internal friction elements 5 with respect to the surface of inner axial passage 4b of bushing 4 as well as with respect to the peripheral surface of inner shaft 3.

In Figures 7 and 8 can be seen an example of a household appliance, namely washing machine 9 that incorporates radial dampers 1 according to the invention. As can be seen, washing machine 9 comprises housing 10 that comprises front loading wall 1 1 , upper base 19, lower base 20, and respective side walls 26. Front loading wall 1 1 comprises loading opening 12 through which is accessed wash drum 13, and loading door 14 to close loading opening 12.

In housing 9 is housed wash tub 15 in which wash drum 13 rotates being driven by motor 21 connected by fan belt 22 to driven pulley 23 coupled to wash drum 15.

The upper portion of tub 15 is connected to upper base 19 of housing 20 by means of springs 17, the respective lower ends of which are coupled to respective hooks 18 provided in tub 15 and the upper ends of which are coupled to upper base 19 of housing 9.

The lower portion of tub 15 is connected with lower base 20 of housing 10 through support elements 24 of a dampening system. Each support element 24 is articulated to housing 10 with interposition of swiveling lever 25, for example, constituted of coupling lugs 2d described earlier with reference to radial damper 1 of Figure 4, and articulations 27, 29, 31 that comprise radial damper 1 as described earlier. In particular, radial damper 1 is connected to first pivoting shaft 28, for example, as in axial shaft 3 described with reference to radial damper 1 according to the embodiments shown in Figures 1 through 6, which pivots on fastening lugs 32 mounted on base 20 of housing 10 so as to form first swivel joint 27. Swiveling lever 25 is articulated to one of the ends of support element 24 by means of second pivoting shaft 29 such that swiveling lever 25 and support element 24 are connected through second swivel joint 29. In turn, support element 24 is articulated through its other end to wash tub 15 by means of third swivel joint 31.

List of Reference Symbols

1 Radial damper

2 Outer bushing

2a Inner wall of the outer bushing

2b Internal protrusion from the outer bushing

2c Internal recess

2d Coupling lug

2e Through hole

3 Inner shaft

3a Axial rib

4 Inner bushing

4a Outer wall of the inner bushing

4b Axial inner passage of the inner bushing

4c External projection from the inner bushing

4d Internal projection from the inner bushing

4e External recess

5 Internal friction element

6 Sliding block element

7 Axial channel

8 Stop surface

9 Washing machine

10 Housing

1 1 Front wall of the housing

12 Loading opening

13 Wash drum

14 Loading door

15 Wash tub

16 Drum rotation shaft

17 Springs

18 Hooks from the springs to the tub Cover wall

Housing base

Drive motor

Fan belt

Driven pulley

Support elements

Swiveling lever

Side walls of the housing

First swivel joint

First pivoting shaft

Second swivel joint

Second pivoting shaft

Third swivel joint

Fastening lugs

Claims

Radial vibration damper comprising a cylindrical external bushing (2) which comprises an internal wall (2a), connectable to a first element and capable of housing an internal axis (3) connectable to a second element, in such a way that the internal axis (3) and the cylindrical external bushing (2) have rotatory movement capacity one respect to the other, and friction means (5) to radially enclose the internal axis (3) exerting a friction force for dampening the rotatory movement, characterized in that it comprises:

an internal bushing (4) housed in the external bushing (2) with a rotation capacity, the internal bushing (4) comprising an external wall (4a) opposite to the internal wall (2a) of the external bushing (2) and an internal axial passage (4b) in which the internal axis (3) is arranged; and

a rotation-delimiting system (2b, 4c, 7, 8) between the internal bushing (4) and the external bushing (2) such that it allows the rotation between the external bushing (2) and the internal bushing (4) in a determined free path, therefore the friction means (5) do not act and it blocks rotation between the external bushing (2) and the internal bushing (4) by actuating the friction means.

Radial vibration damper according to claim 1 , characterized in that:

the internal friction means (5) are arranged radially in the internal axial passage (4b) exerting a friction force at least on the internal bushing (4);

the rotation-delimiting system (2b, 4c, 7, 8) comprises at least an axial channel (7) located between the internal bushing (4) and the external bushing (2), and at least a rotation-delimiting element (2b, 4c, 6) located in the axial channel (7);

the axial channel (7) has a cross section in the shape of a circular ring segment delimited between two radial end stop surfaces (8);

each rotation-delimiting element (2b, 4c, 6) being selected among projections (2b) emerging from the internal wall (2a) of the external bushing (2), protrusions (4c) emerging from the external wall (4a) of the internal bushing (2) and sliding blocks (6); and

each projecting element (2b, 4c) is displaceable within the corresponding channel (7) in such a manner that, when the external bushing (2) and the internal bushing (4) rotate one respect to the other, each projecting element (2b, 4c) has a free path in the axial channel (7) limited by said stop surfaces (8).

3. Radial damper according to claim 2, characterized in that at least one rotation- delimiting element (2b, 4c, 6) is designed to be displaced in the channel (7) opposing a friction force when the external bushing (2) and the internal bushing (4) rotate one respect to the other so as to dampen the rotation between the internal bushing (4) and the external bushing (2). 4. Radial damper according to claim 2 or 3, characterized in that

- at least one axial channel (7) is formed by an internal recess on the internal wall (2a) of the external bushing (2);

the rotation-delimiting element placed in the internal recess is an external protrusion (4c) emerging from the external wall (4a) of the internal bushing (4); and

the stop surfaces (8) of said axial channel (7) are formed by respective radial steps that delimit the axial channel (7) formed by the internal recess of the external bushing (2).

Radial damper according to claim 2 or 3, characterized in that

at least one axial channel (7) is formed by an external recess (4e) on the external wall (4a) of the internal bushing (4);

the rotation-delimiting element placed in said external recess (4e) is an internal projection (2b) emerging from the internal wall (2a) of the external bushing (2); and

the stop surfaces (8) of said axial channel (7) are formed by respective radial steps that delimit the axial channel (7) formed by the internal recess (4e) of the internal bushing (4). Radial damper according to claim 2 or 3, characterized in that

at least one axial channel (7) is formed by an internal recess on the internal wall (2a) of the external bushing (2), or by an external recess (4e) on the external wall (4a) of the internal bushing (4); and

at least one of the rotation-delimiting elements is a sliding block (6) arranged in the axial channel (7) in a displaceable manner along said free path between the stop surfaces (8).

Radial damper according to claim 6, characterized in that

it comprises a plurality of sliding blocks (6), each being arranged in an axial channel (7);

the external wall (4a) of the internal bushing (4) is provided with a plurality of external protrusions (4c); and

the external protrusions (4c) comprise corresponding radially opposed axial sides, which form respective stop surfaces (8) delimiting the free paths of the respective sliding blocks (6).

Radial damper according to claim 6, characterized in that

the internal wall (2a) of the external bushing (2) is provided with a plurality of internal projections (2b); and

the internal projections (2b) comprise corresponding radially opposed axial sides, which form respective stop surfaces (8) delimiting the free paths of the respective sliding blocks (6).

Radial damper according to any of claims 6, characterized in that

the external wall (4a) of the internal bushing (4) is provided with at least an external protrusion (4c) comprising respective radially opposed axial sides;

the internal wall (2a) of the external bushing (2) is provided with at least an internal projection (2b) comprising respective radially opposed axial sides;

at least one of the axial channels (7) is delimited between an internal projection (2b) and an external protrusion (4c); and

the opposed axial sides of the projections (2b, 4c) form the respective stop surfaces (8) limiting the free path of the sliding block (6) placed in said axial channel (8).

Radial damper according to claim 6, characterized in that

the external wall (4a) of the internal bushing (4) is provided with a plurality of external protrusions (4c);

the external protrusions (4c) comprise respective radially opposed axial sides, which form the respective stop surfaces (8) delimiting the free paths of the respective sliding blocks (6);

the internal wall (2a) of the external bushing (2) is provided with a plurality of internal projections (2b);

the internal projections (2b) comprise respective radially opposed axial sides, which form the respective stop surfaces (8) delimiting the free paths of the respective sliding blocks (6); and

each axial channel (7) is delimited between an internal projection (2b) and an external protrusion (4c).

Radial damper according to any of claims 2 to 10, characterized in that at least one of the sliding blocks (6) is comprised by a pad of an elastic material inserted under pressure in one of the axial channels (7).

Radial damper according to any of the preceding claims, characterized in that at least one of the rotation-delimiting elements (6) has a cross section in the shape of a circular ring segment. 13. Radial damper according to any of the preceding claims, characterized in that the free path of each rotation-delimiting element (2b, 4c, 6) corresponds to a 1 to 4° arch.

14. Radial damper according to any of the claims 2 to 13, characterized in that the internal friction means (5) comprise at least a tubular element interposed between the internal axis (3) and the internal bushing (4).

15. Radial damper according to any of the preceding claims, characterized in that the internal friction means (5) are arranged interposed between the internal axis (3) and the second element (4).

16. Radial damper according to any of claims 2 to 13, characterized in that the internal friction means (5) comprise a plurality of internal friction elements (5) spaced away one from the other by respective axial gaps; and the internal passage (4b) of the internal bushing (4) comprises at least an axial internal projection (4d) fitting into one the axial gaps.

17. Radial damper according to claim 16, characterized in that the internal friction means (5) have a cross section in the shape of a circular ring segment.

18. Radial damper according to one of claims 16 and 17, characterized in that internal friction means (5) are pads of an elastic material inserted under pressure between the internal axis (3) and the internal bushing (4).

19. Radial damper according to one of claims 16, 17 and 18, characterized in that the internal axis (3) comprises at least an external axial rib (3a) fitting into one of the axial gaps.

20. Household appliance, in particular washing machine or dryer (9), comprising a housing (10) which houses a washing tub (15) in which a washing drum (13) rotates being driven by a motor (21 ), the tub (15) being connected to the housing (10) by means of at least a supporting element (24) of a dampening system, the supporting element (24) being articulated to the housing (10) with intercalation of a swivelling lever (25) and at least one articulation (27, 29, 31 ) comprising a radial vibration damper, characterized in that at least one articulation (27) comprises the radial damper (1 ) which is defined in any of the preceding claims.