SK152197A3 - Shock absorber for washing machine, particularly for home laundry washing machines - Google Patents

Description

Technical field

BACKGROUND OF THE INVENTION The present invention relates to a shock absorber in a washing machine, and more particularly to a household laundry washing machine, adapted to support the drum tank units of the washing machine and effectively dampen mechanical stress during the operation of the washing machine.

BACKGROUND OF THE INVENTION

Various types of shock absorbers for washing machines are known, in particular for household washing machines, adapted to dampen the mechanical stress of the combined washing units (tank and drum) of the washing machines during operation and are connected between the bottom of each washing unit and the washing machine base. .

These shock absorbers consist essentially of a hollow cylinder and a cylindrical rod movable on both sides within the cylinder, the rod being provided with braking surfaces made of a suitable material interacting with the inner surface of the cylinder moving linearly and reversibly inside the cylinder during rotation. washing and spinning speeds, thereby producing a braking effect adapted to the braking of the created mechanical stress.

However, these types of shock absorbers, which are essentially made of metal materials or sometimes also of components made of plastic in part, have some disadvantages, especially if they have to be installed on clothes washing machines whose drum rotates at too high a centrifugal speed. (higher than 1000 rpm), under these conditions, the washing unit generates high mechanical stresses on the washing machine design. In fact, in such cases, it has been found that on each impact of the wash drum movements at different shock absorbers, the bar movable with a reciprocating linear movement within the cylinder also moves radially within its engagement, so that the braking surfaces of such a bar no longer exert braking effects. distributed almost equally to the entire inner surface of the cylinder, they rather apply irregular and variable braking effects on the inner surface, which tend to concentrate in predetermined positions on the inner surface, causing both premature and unwanted wear and thus shorter lifetime for each shock absorber and insufficient braking effects for mechanical loading of the washing unit.

SUMMARY OF THE INVENTION

The main object of the present invention is to overcome the disadvantages associated with the use of current shock absorbers, with a new type of shock absorber adapted to provide effective braking effects distributed almost equally to the shock absorber, in any operating condition of clothes washing machines consisting of simple components that may be assembled together quickly and capable of operating with a long life in a satisfactory and reliable manner.

In addition, according to the invention, the shock absorber has a powerful structure and therefore its use is satisfactory.

The shock absorber according to the invention is manufactured with the constructional features which are described in detail and claimed in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated in more detail by the following description, in particular by way of non-limiting examples, with reference to the accompanying drawings in which:

Fig. 1 schematically shows a washing machine equipped with an impact absorber according to the invention,

Fig. Figures 2, 3 and 4 show, in front, side and schematic perspective views, a shock absorber according to a first embodiment of the invention,

Figure 5 schematically shows a side view of two main components of the shock absorber which are inserted into one another,

Fig. 6 and 7 schematically show front and side views of the two main components of FIG. 5, which are disassembled,

Fig. 8, 9 and 10 show a cross-sectional view along the lines A-A, B-B and C-C of the shock absorber shown in FIG. 5

Fig. 11 a, b, c show diagrams of the distribution of braking effects in a conventional shock absorber,

Fig. 12 a, b, c show diagrams of the distribution of the braking effects in the shock absorber according to the invention,

Fig. 13 is a front view of other components of the shock absorber of the present invention;

Fig. 14 and 15 show the component of FIG. section along the D-D and E-E lines,

Fig. 16 is a front view of another member of the shock absorber of the present invention;

Fig. 17 shows the component of FIG. 16 in section along the line F-F, FIG. 18 is a front view of a shock absorber in a second embodiment of the invention;

Fig. 19 is a side view of the shock absorber of FIG. 18, in section along the line H-H,

Fig. 20 is a side view of the impact absorber half of FIG. 18, in section along line I-I,

Fig. 21 is a front view of a shock absorber in a third embodiment of the invention;

Fig. 22 is a side view of half of the shock absorber of FIG. 21, in section along the L-L line,

Fig. 23 is a side view of a portion of the shock absorber of FIG. 21, in section along the line M-M,

Fig. 24 and 25 show a perspective view of the shock absorber of FIG. 21 and its displacement in two different working positions,

Fig. 26 is a schematic perspective view of the shock absorber absorber of FIG. 21st

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1 schematically illustrates a washing machine 20, in particular a household washing machine, designated 20, comprising a substantially metal cabinet housing 21 in which the washing unit 22 comprises a washing tank 23 and a rotating drum 24 for inserting clothing into the tank 23 is attached by means of upper suspension springs 25 and supported by the lower shock absorbers 26, which are located between the lower part of the wash tank 23 and the base 27 of the washing machine housing 20. The impact absorbers 26 reduce the mechanical stresses caused by the swinging movement of the washing unit during drum operation at different washing speeds; spinning.

In FIG. Figures 2 to 7 show schematically a first embodiment of an impact absorber 26 according to the invention, which consists essentially of two main components, namely a metal tubular cover 28 having an elongated shape and hollow inside. It is provided with an open end portion 29 and a closed lower portion 30 connected to an end zone 31 with a through hole 32 in which a rubber insert and a pin (both not shown) are inserted for articulation and vibration-damping connections to the base of the washing machine 27. the linear rod 33 made of plastic material is sized so that it can be retracted directly into the interior recess 34 of the tubular cover 28. The outer end zone 35 is provided with a through hole 3.6 which is opposite to the through hole 32 of the tubular cover 28 into which the rubber insert and then the pin (both not shown) are inserted first and serve for articulated and vibration dampening connections to the bottom of the tank 23 of the washing machine 20.

As shown in FIG. 2,3,4 and 8 to 10, the metal tubular cover 28 comprises two half-shells 37 and 38 which are identical and symmetrical to each other. Each is shaped in the manner described below and is obtained by the drawing and shearing process of the respective portions of the sheet and is provided with two linearly straight cuts of the edges 39 and 40, which are opposed and arranged to be aligned coaxially and overlapping. They are connected by resistance welding or by means of conventional means.

In particular, each half-shell 37 and 38 consists of an elongated flat shell 41 having a polygonally shaped profile, with sides of the same or different size, extending from the open end portion 29 and extending to the closed bottom portion 30 connected to the end zone 31, to which a flat shell 41 with a plurality of tapered steps 42 and 43 is attached.

In the present embodiment, each half-sleeve is shaped with a rhombus-shaped outer profile with a central flat side 44 and two adjacent flat and oblique sides 45 and 46. having nearly the same size as the central flat side 44 and facing each other symmetrically opposite and oriented from the respective corner Of course, the shape and sides of the flat shell 41 of each half-shell 37 and 38 may vary with respect to the respective embodiment, provided that the flat sides 44 having the function of damping the washing machine oscillations with the criteria described above. The elongated linear rod 33 is preferably made of a molded plastic material and consists of two ribbed portions 47 and 48 connected to each other and shaped with an identical outer profile, their size being slightly smaller than the size of the inner recess 34 of the tubular housing 28 to be capable of sliding rectilinearly and bilaterally within the housing, the rib portions 47 and 48 being provided with longitudinal rectilinear ribs 49, 50 and 51, 52 which are mutually rectangularly connected to one another and extend along a larger portion and a smaller portion of the section plane of the tubular housing 28. The ribs 49, 50, 51 and 52 are delimited at the ends by plates 53, 54 and 55 having the same contour as the inner recess 34, the plate 53 being larger than the inner recess 34 and connected to the outer end of the zone 35 of the rod 33. The plates 54 and 55 are slightly smaller than the inner recess 34 so that they can be inserted therein and are individually disposed in the retracted position between the rib portions 47 and 48 and the end position of the rod 33 in the opposite direction to the placement of the plate 53.

When the rod 33 is inserted or withdrawn, with respect to the inner recess 34 of the tubular housing 28, as shown in FIG. 5, 6 and 7, the plates 54 and 55 are precisely matched within the tubular housing 28, while the plate 53 adjacent the free edge of the tubular housing 28 protects the rod 33 from being fully inserted into the tubular housing 28.

The rib portion 48 is shorter than the portion 47 of the elongated rectilinear bar 33. The ribs are sized in such a way as to allow the outer bearing of the friction pad 56 made of a suitable bearing material adapted to produce a braking effect by rubberizing against the inner recess 34 of the tubular cover 28. the movement of the rod 33 within the tubular housing 28 caused by the oscillations of the drum unit of the drum unit of each washing machine during operation, followed by damping of the mechanical stress caused by the oscillations. Preferably, the friction pad is made with separate components, each having the shape of an elongated flat plate 59 having the same contour and a slightly larger size than the inner recess 34 of the tubular cover 28 to allow such components to adapt and slide into the inner recess 34. In the present case, the friction pad 56 consists of two components 60 and 61, each having two equal sides 62 and 63, symmetrically angled in their entirety, having the same slope as the respective adjacent sides 45 and 46 of the two half-shells 37, and 38 of the tubular cover 28. These elongated plates 59 of the friction pad 56, which are shown in detail in FIG. 16 and 17 in a front view and in cross-section, they are provided with a plurality of through holes 64 distributed regularly on the surface so as to ensure the passage of lubricant and other suitable lubricating materials to maintain all shock absorber components always greased during operating cycles. Externally, they are overlapped by the rectilinear ribs 51, 52 of the rib portion 43 of the elongated rod 33 of the intermediate position of the elastic elements in the form of two metal springs 65 and 66 shown in FIG. 4, 8 to 10, each of which is sized and shaped to fit on one side with its surfaces to each elongated plate 59 of the friction pad 56 and the opposite side of the surface to the outer contour of the rectilinear ribs 51, 52 of the rib portion 48.

Preferably, each metal leaf spring 65 and 66 is shaped so as to have one or more slots for the passage of lubricant and other suitable lubricating materials that keep all of the shock absorber components always greased. In this case, such leaf spring 65 and 66 is rectangular in shape and comprises a central slot 67 along its longitudinal edge 68 and two slots 69 and 70 along its other longitudinal edge 71, the slots 69 and 70 being displaced relative to the central slot 67 and being provided with central laminates 72 and 73 which are angled relative to the plane of the respective leaf springs 65 and 66 and rotated relative to the ribs 51 and 52 of the ribbed portion 48 so as to react flexibly thereto so as to stably guide each leaf spring 65 and 66 to the attached the elongated plate 59 of the friction pad 56, so that they always keep it in sliding contact with the surface of the inner recess 34 of the tubular cover 28. In FIG. 11 and 12 are diagrams of brake force distribution of a conventional shock absorber and a shock absorber according to the invention. In FIG. 11a is a schematic illustration of a conventional cylindrical shock absorber 74 comprising a cylindrical rod 75 within a cylindrical housing 76 adapted to be rectilinear and reciprocating.

In this case, the shock absorber is shown in its idle state, with the drum of the washing machine at rest and therefore the rod 75 does not exhibit braking effects and can be practically applied in a coaxial (coaxial) relationship to the cylindrical housing 76. In contrast, in FIG. 11b, in which the shock absorber 74 is schematically shown in working condition, when the drum has been moved, it has been noted that the rod 75 tends to move reciprocally in the housing 76 not only axially but also radially, thereby contacting the inner surface of the housing. In this case, the zone is indicated by the reference numeral 77.

In the operating state, the rod 75 operates eccentrically with respect to the housing 76, thereby applying irregular braking effects to the inner surface of the housing 76, which are larger in particular in the contact zone and gradually drop from this zone to the remaining portions of the inner surface as shown. a set of force vectors 78 in FIG. llc. In FIG. 12a is a schematic illustration of the shock absorber 26 of the present invention in a stationary state in which it can be seen that the rod 33 is coaxially covered within the tubular housing 28 and the braking effects are not applied. In contrast, FIG. 12b, the shock absorber 26 is shown in a working state in which it is. the rod 33 is always radially displaced by the eccentric displacement inside the tubular housing 28. It can be observed that in this case the friction pad 56 of the rod 33 is positioned with two surfaces of its two adjacent sides 62 and 63 opposite the respective sides 45 and 46 of the tubular cover 28 on its contact zone 77 so as to reciprocate the friction pad 56 into the interior. tubular cover no more applied than before. The irregular braking action against the inner surface of the tubular housing 28 is still applied and the braking action against the inner surface is uniform, due to the fact that the friction pad sides 62 and 63 are always parallel to the opposite sides 45 and 46 of the tubular housing 28. state. In the operating state, mutual friction of the sides is achieved in any of their contact positions in accordance with different eccentricities between the rod 33 and the tubular cover 28, the braking effects forming having the same intensity on the same sides and schematically shown in FIG. 12c using a set of force vectors 78 having the same intensity. In this way, the shock absorber 26 according to the invention makes it possible to obtain braking effects which are distributed almost equally at every operating condition of the washing machines due to the fact that during operation of the washing machines the friction pad 56 is steadily and equally pressed against the tubular cover 28 by leaf springs 65 and 66, which for this purpose are preferably made of harmonious steel and shaped so as to conform completely to the contour of the two plates 59 of the friction pad 56 and the ribs 51, 52 of the rib portion 48. In this way, effective and targeted damping of the mechanical the stresses generated by the oscillations of the drum unit tank during the movement of the drum, in particular at high centrifugal speeds and, on the other hand, reducing the wear of the shock absorber 26 and its longer life. Furthermore, each impact absorber 26 of this kind is structurally simple and is made up of several components which can be assembled and disassembled easily and easily, these parts being made of metal materials and allowing the heat generated by the friction of these parts to be well distributed. . Finally, the presence of the fins of finned portions 47 and 48 of the shock absorber 26 _f which are longitudinal to the direction and oriented in the same direction of application of the mechanical stress on the wash unit to the base 27 of the washer 20 allows the shock absorber 26 effectively resists the mechanical stresses of the washing unit , in both its states, in a state of rest and in a working state.

Another important advantage achieved by the use of the shock absorber 26 of the present invention is that effective and permanent lubrication of the various components of the shock absorber 26, due to the fact that it comprises, on the inner surface of the elongated flat shell 41 two half sleeves 37 and 38 of the tube cover 28 , a plurality of depressions 79 and 80 disposed and inclined relative to each other in the opposite direction of inclination relative to the longitudinal direction of the elongated housing (FIG. 2 shows the depression 79 in cross section along the GG line).

In this way, before each shock absorber 26 is installed on the washing machine, a lubricant or other suitable lubricant material is deposited and collected in this manner and centered in the recesses 79 and 80 and then stably withdrawn therefrom by a friction pad during each movement and distributed to all of the shock absorber components 26 by passing through the through holes 64 of the friction pad plates 56 and the slots 67, 69 and 70 of the leaf springs 65 and 66. In addition, each such shock absorber 26 allows the air contained therein to effectively During the reciprocal engagement of the rod 33 in the tubular housing 28, due to the presence of through holes 81 located on the semiconductors 37 and 38 of the tubular housing 28 and along the entire length of the individual central flat sides 44 of the semiconductors 37 and 38. friction pad 56 and tubular cover 28 in a polygonal form having a plurality of mutually identical sides and different from the above-described molds, provided that the sides of such a washer and the tubular cover are always parallel and correspond to each other in each operating condition of the washing machine and can always come into contact with each other continuous braking effects in each contact position between said friction pad and the tube cover. According to FIG. 18, in which the shock absorber according to the invention is shown in its second embodiment, it can also be observed that in this case the shock absorber 26 is made as described above and the individual parts of the free ends of the tubular housing 28 and the rods 33 are provided with respective an opening 32 and 26 in which two rubber inserts 82, 83 and 84.85 are inserted, which are coaxially positioned relative to one another (see FIG. 26) to pass the respective articulated pin (not shown), the pin being aligned with the base 27 of the washer 20; As can be seen in particular from FIG. 19 and 26, the inserts 82, 83 and 84, 85 are made of rubber and metal and sized in such a way that they are aligned with each other and then installed in the respective through hole. Each insert 82, 52 / la. and 85 consists of two equal halves, indicated by 82 ¹ . 82 ^{1 1} . 83 ¹ . 83 ^{1 1} and 84 ¹ . 84 ¹¹ . 85 ', 85'', which can be assembled and disassembled in a quick and easy way without tools. Moreover, as again seen in FIG. 18, the half-shells 37 and 38 along adjacent longitudinal straight edges adapted to engage with each other are shaped by a set of radially designed gears 86, 87 and 88, 89 disposed in such relative sliding positions to allow the teeth and slots of the half-shells 37 to connect to the slot and the teeth so that the connection zones of the gearing and the slots are absolutely continuous and coaxial to one another. The thus achieved connection of the half-shells 37 and 38 makes it possible to ensure high bulk stability and mechanical strength, as well as efficient safe assembly of the half-shells 37 and 38, which is difficult to achieve in conventional electrical welding or splicing of two half-shells .

Further advantages of the solution according to the invention are that one mold is sufficient for the manufacture of each half-sleeve, instead of two different forms, as is the case with the half-sleeves of the inner and thrust connection pieces. Less expensive crimping machine is required than electric welding equipment and associated inspection equipment.

FIG. 18, it is also apparent that one of the half-shells of the tubular cover 28. in this case, the half-sheath 37 is provided with at least one notch 90 slightly deepening the inner recess 34 of the shock absorber 26, which interacts with the sliding bar 33 to an inner recess and prevents the rod 33 from accidentally sliding out of the tubular cover 28 during operation of the washing machine.

This characteristic of the design of the shock absorber 26 of the invention ensures that the shock absorber 26 can be disassembled only in such a way that greater and predetermined effort is applied to overcome the connection of the notch 90 with the rod 33, thereby preventing the absorber impact accidentally and improperly disassembled when installed on the washing machine.

As shown in FIG. 21 showing the shock absorber 26 of the present invention in a third structure. The Ab12 shock absorber 26 is manufactured with the same characteristics as described above, but is provided with different matrices 91 and 92 on at least one half-sheath. In the case shown in Figure 22 on the half-sleeve 37. The matrices 91 and 92 are formed by pressing the half-sleeves of metal material and slightly deepen the inner depression of the tubular cover 28 for the purposes described below. As shown in FIG. 23, the dies are shaped at a slight inclination with respect to the rod 33, and in particular the two dies 91 are tapered slightly convergent with respect to each other from the center line of the semi-housing 37 to the portion of the free end 93 provided with inserts 82, 83 defining respective inclined surfaces 94. whereas the two matrices 92 are mutually shaped slightly convergent in the opposite direction to the previous one from the center line of the semi-housing 37 to the portion of the other end of the semi-housing in which the rod 33 is inserted thereby defining respective inclined surfaces 95. The inclined surfaces 94 and 95 interact with the friction washer 56 of the rod 33 as the rod 33 is moved into the tubular housing 28 in such a way as to produce braking effects of varying intensity which increase as the rod slides in accordance with surfaces 94 and 95 in the N or O direction and sink when the rod 33 moves in the opposite direction. Such braking effects of varying intensity are proportional to the intensity of mechanical stress and serve to improve the damping properties of the shock absorber 26.

In FIG. 24 and 25, the shock absorber 26 is shown in a state in which the suitably shaped bar 33 extends and retracts with respect to the tubular housing 28. FIG. 26, two different components of the shock absorber 26 are shown, and in particular it is also shown that the friction pad plates 59 are fastened by means of resilient elements (not shown) to the outer surface of the non-articulated end portion 96 of the rod 33 which is inserted into the inner recess 34 of the tubular cover 28. The joining of the plates to the rod 33 is effected simply by means of a toothing 97, provided that the outer surface is raised and the respective surface of the plates is joined.

The shock absorber 26 thus formed is comprised of a plurality of components which can be easily assembled and disassembled without the use of tools, so as to allow separation and subsequent recycling of the various materials in accordance with special standards relating to this problem.

List of reference marks

- washing machine

- box cover

- washing unit

- washing tank

- rotary drum

- upper suspension springs

- impact absorber

- base

- tubular cover

- upper part

- lower part

- end zone

- through hole

- rod

- depression

- the outer end zone

- through hole

- polopuzdro

- polopuzdro

- edge

- edge

- flat coat

- degree

- degree

- flat side

- oblique side

- oblique side

- ribbed part

- ribbed part

- rectilinear rib

- rectilinear rib

- rectilinear rib

- rectilinear rib

- pltňa

- plate

- plate

- friction pad

- extended plate

- component

- component

- page

- page

- hole

- leaf spring

- leaf spring

- center slit

- longitudinal edge

- slot

- slot

- longitudinal edge

- central laminate

- central laminate

- a conventional cylindrical shock absorber

- a cylindrical rod of a conventional shock absorber

- housing of a conventional shock absorber

- zone

- force vectors

- depression

- depression

81 - through hole 82 - rubber insert 83 - rubber insert ⁸⁴ - rubber insert 85 - rubber insert 86 - rack 87 - rack 88 - rack 89 - rack 90 - notch 91 - nut 92 - nut 93 - free end 94 - inclined surface 95 - inclined surface 96 - uncouple trailing 97 - rack

ΙΠΜ-Ο - - 17 -

Claims (10)

1. A shock absorber in washing machines, in particular household washing machines, located between the drum of the washing unit and the lower base of the washing machine housing, effectively dampening the mechanical stresses generated during the rotation of the drum at different washing and spin speeds. insertable and displaceable reciprocally in a tubular housing equipped with friction pads interacting with the tubular housing by means of a friction effect such that braking effects reducing mechanical stress are achieved, characterized in that the tubular housing (28) and the friction pads (56) of the rod (33) are replaceable; the rod (33) is formed with a contour of polygonal sides with a number and form identical to the respective sides of the tubular cover (28) and the friction pad (56) in each operating state, whether in rest or in the state of operation of the shock absorber (26), wherein the friction pads (56) are joints The springs (65, 66) are adapted to maintain braking contact with the tubular housing (28). Impact absorber according to claim 1, characterized in that the tubular cover (28) is formed with at least two separate metal half-shells (37, 38) mutually identical and symmetrical, provided with linearly straight cuts of the edges (39, 40) adapted to each other and joining in a manner known per se such that the inner recess (34) provides for the insertion and displacement of the rod (33) in the half-shells (39, 40) formed of an elongated flat shell (41) of polygonal shape with sides (44, 45, 46) of the same or of different size, extending from the open end portion (29) in which the bar (33) is inserted in the inner recess (34), with the closed end portion (30) adapted to be attached to the washing machine. Impact absorber according to claim 2, characterized in that the half-shells (37, 38) are provided with a plurality of depressions (79, 80) for storing lubricant or other suitable lubricating materials and a plurality of through holes (81) for venting the air contained therein. Impact absorber according to claim 3, characterized in that the rod (33) is preferably entirely made of molded plastics material, consisting of two ribbed portions (47, 48) interconnected and shaped in accordance with an identical outer profile of slightly smaller size. such as the size of the inner depression (34) and is provided with longitudinal rectangular ribs (49, 50; 51, 52) bounded by plates (53, 54, 55) with the same outline as the contour of the inner depression (34), the plate 53 being larger than the inner recess (34) and the plates (54, 55) are slightly smaller than the inner recess (34) to be inserted therein. Impact absorber according to claim 4, characterized in that the friction pads (56) are made of a suitable non-slip material with first and second separate parts (60, 61) shaped in the form of an elongate plate (59) and each having sides (62). 63) coincident with the sides of the inner recess (34) of the tubular cover (28) with friction interaction, each plate (59) being covered externally with respect to the second rib portion (48) of the rod (33) by inserting leaf springs (65, 66); is provided with a plurality of through holes (64) connected to the inner recesses (79, 80) for the passage of lubricant or other suitable lubricating materials. Impact absorber according to claim 5, characterized in that it comprises two leaf springs (65, 66) made of harmonic steel adapted to the contour of the individual plates (59) and the respective ribs (51, 52) of the second rib part (48), the first and the second metal leaf spring (65, 66) is provided with laminates (72, 73) inclined to the plane of the respective leaf spring with rotation relative to the ribs (51, 52) so as to respond flexibly thereto and are provided with slots (67, 69, 70) for passing lubricant or other suitable lubricating materials. Impact absorber according to the preceding claims, characterized in that the half-shells (37, 38) are shaped along adjacent longitudinal straight edges with individual sets of radially designed gears (86, 87) and (88, 89) offset from one another. relative to each other so as to allow the teeth and slots of the half-sleeve to be coupled to the slits and the teeth of the second half-sleeve and are provided with gripping slots (90) interacting with the bar (33) to prevent it from accidentally sliding out of the inner cavity. Impact absorber according to claim 7, characterized in that the cuts (90) slightly deepen the inner recess (34). Impact absorber according to claim 7, characterized in that the at least one half-shell (37) is provided with dies (91, 92) formed by pressing with slight deepening of the inner depression (34), defining respective inclined surfaces (94, 95) with different directions of the inclination, interacting with the friction pad (56) in such a way as to produce braking effects of varying intensity as the rod (33) moves in two opposite directions of displacement into the tubular housing (28). Impact absorber according to claim 7, characterized in that said friction washer (56) is fixed to the rod (33) by means of a toothing (97) extending from the rod (33).