MXPA97008732A - Shock absorber for machines for washing, in particular machines for washing domest clothing - Google Patents

Abstract

Shock absorber for the oscillations of the tub-drum unit of domestic laundry washing machines, comprising a tubular housing (28) and a bar (33) that reciprocates slidably therein, which is made with profiles in polygonal shape, having sides of number and shape equal to each other, so as to coincide reciprocally in any operative state of the shock absorber, to allow friction means (56) fixed to the bar (33) to always firmly and uniformly exercise braking actions distributed on the housing ( 28) tubular. The shock absorber is also made with a removable and self-lubricating structure and in different embodiments

Description

SHOCK ABSORBER FOR WASHING MACHINES. IN PARTICULAR MAQUINAS TO WASH DOMESTIC CLOTHES D E SCR I PC ION The present invention relates to a shock absorber for washing machines and in particular for washing machines, adapted to support the drum units of those machines and to effectively cushion the mechanical stresses produced during the operation of the referred machines.

Different dampers are known for washing machines and in particular domestic laundry washing machines, adapted to withstand and damp the mechanical efforts of the washing units (tub and drum) of those machines during their operation and connected between the lower portion of each washing unit. and the lower base of the same machines.

These shock absorbers are generally formed by a hollow cylinder and a cylindrical bar that slides reciprocally inside that cylinder, that bar is provided with braking surfaces made of appropriate material, which cooperate with the inner surface of the cylinder and which, during the operation of the respective machine moves linearly and reciprocally inside the cylinder, due to the movements of the washing unit that are caused by the rotation of the drum at its different washing and centrifugation speeds, with which a braking action is produced adapted to cushion the mechanical stresses generated.

However, this kind of shock absorbers, which are generally made of metallic materials or sometimes also made with component parts made of plastic, have some drawbacks, especially when they have to be mounted on clothes washers, whose drum is rotated with very high centrifugation speeds (greater than 1000 rpm), under which conditions high mechanical stresses are produced by the washing unit on the structure of the machine. In fact, in those cases, it has been found that on each damper the sliding bar with a rectilinear reciprocating movement inside the cylinder, moves during its stroke also radially, so that the braking surfaces of that bar no longer exert more brakes distributed almost uniformly over the entire inner surface of the cylinder, instead they exert irregular and variable braking actions on that inner surface, which tends to concentrate in pre-established positions on the same internal surface, thereby causing both Premature wear as undesirable and therefore a shorter life of each shock absorber and braking actions unsatisfactory for the mechanical efforts of the washing unit.

The main object of the present invention is to eliminate the drawbacks associated with the use of the present shock absorber, by means of a shock absorber of a new class adapted to ensure effective braking actions, distributed almost uniformly on the same shock absorber, in any operating state of the machines. clothes washers, shock absorber that is composed of simple component parts that can be quickly assembled together and can operate for large life durations in a satisfactory and reliable manner.

In addition, the invention also provides a shock absorber with a strong structure that makes it convenient in use.

The damper in accordance with the present invention is made with the constructive features substantially described, with particular reference to the accompanying patent claims.

The invention will be better understood with the following description, given only as a non-limiting example, with reference to the appended drawings, in which: Figure 1 schematically shows a washing machine provided with at least one shock absorber made in accordance with the present invention.

Figures 2, 3 and 4 show, in front, side and exploded perspective views, a damper made in accordance with the present invention, in a first mode.

Figure 5 shows schematically in a side view the two main component parts of the present damper, inserted one into the other.

Figures 6 and 7, schematically show in front and side views, the two main component parts of Figure 5, extracted from each other.

Figures 8, 9 and 10 show, in plan views, sections respectively along the lines A-A, B-B and C-C the damper shown in Figure 5.

Figure 11 a, b and c show a diagram of distribution of braking actions in a conventional shock absorber.

Figure 12 a, b and c shows a distribution diagram of braking actions in the present damper.

Figure 13 shows in a front view another component part of the shock absorber according to the present invention.

Figures 14 and 15 show the component part of Figure 13 respectively, in sections along the lines D-D and E-E.

Figure 16 shows in a front view another component part of the shock absorber according to the present invention.

Figure 17 shows the component part of figure 16 cut along the line F-F.

Figure 18 shows a front view of the shock absorber according to the present invention, in a second embodiment.

Figure 19 shows a side view of the shock absorber of figure 18, cut along the line H- H.

Figure 20 shows a side view of a half portion of the shock absorber according to Figure 18, cut along the line I-I.

Figure 21 shows a front view of the shock absorber according to the present invention, in a third embodiment.

Figure 22 shows a side view of a half portion of the shock absorber of Figure 21, cut along the line L-L Figure 23 shows a side view of a portion of the damper of Figure 21, cut along the line M-M.

Figures 24 and 25 show a perspective view of the shock absorber of Figure 21, displaced on two different operative positions.

Figure 26 shows an exploded perspective view of the shock absorber of Figure 21.

In figure 1, a washing machine is represented schematically, in particular a washing machine for domestic laundry, that is to say house washing, marked with reference numeral 20, which substantially comprises a housing 21 in the form of a metal box, in which washing unit 22, formed by the washing tub 23 and a drum 24 for rotating to hold the laundry, housed in the tub, is supported by means of upper suspension springs 25 and lower shock absorbers 26, fixed between the lower portion of the tub 23 and the lower base 27 of the machine housing and provided to dampen the mechanical stresses caused by the balancing of the washing unit during operation of the drum at its washing and centrifugation speeds.

In Figures 2-7, one of the dampers 26 made in accordance with the present invention is now schematically shown, in a first embodiment, which is constituted substantially by two main component parts, namely a metallic tubular housing 28 having a elongated shape, which is internally hollow and provided respectively with an open end portion 29 and a closed bottom portion 30, which is attached to an end zone 31 provided with a through hole 32 in which a short sleeve is inserted. rubber and then a bolt (none shown), for its articulated and vibration-damped connection to the base 27 of the machine and by an elongated rectilinear bar 33 made of plastic material, which is dimensioned in such a way that it is capable of being inserted and adapted in the interior cavity 34 of the tubular housing 28, in such a way that it slides reciprocally and rectilinearly therein, with the end zone 35 xternal being provided with a through hole 36 opposite the hole 32 of the tubular housing 28, and in which first a rubber sleeve and then a pin (none shown) is inserted for its articulated and vibration-damped connection to the lower portion of the tub of the machine.

As is particularly evident from Figures 2, 3, 4 and 8-10, the metallic tubular housing 28 is constituted by two semi-helmets 37 and 38 identical and symmetrical with respect to each other, each of which is configured in the manner described below and is obtained by drawing and stretching processes. cut from a corresponding sheet metal part and are respectively provided with two flattened edges 39 and 40 rectilinear, opposite one another, adapted to be aligned and mutually superimposed and finally joined by means of resistant welding or by means known per se.

In particular, each half shell is formed by an elongated rectilinear box 41 having a contour of polygonal shape, with sides of equal or different dimensions, extending from the open end portion 29 to near the closed lower portion 30, attached to the end zone 31, for which the rectilinear box 41 is connected with a set of conical steps 42 and 43.

In the present embodiment, each half shell is configured with a rhombus-shaped exterior contour and is provided with a central planar side 44 and two flat and inclined sides 45 and 46, which are almost the same size as the central side 44 towards the axis of longitudinal AA symmetry passing centrally in the tubular housing 28. Obviously, the shape and sides of the rectilinear box 41 of each half-hull 37 and 38 may vary with respect to the present embodiment, provided that flat sides are always obtained capable of performing the damping functions of the oscillations of the washing unit of washing machines with the criteria described in the following. In turn, the elongated rectilinear bar 33, preferably, is integrally formed of molded plastic material and is constituted by two portions 47 and 48 with ribs joined together and configured with an identical external contour and having slightly smaller dimensions than those of the inner cavity 34 of the tubular housing 28, in order to be able to be adapted and slide rectilinearly and reciprocally in the same housing, wherein the portions are provided with respective longitudinal ribs 49, 50 and 51, 52, orthogonally joined between them and that they extend respectively along the largest and smallest portion of the cross section of the tubular housing 28, these ribs are limited at their ends by plates 53, 54 and 55 having the same contour of the internal cavity 34, whose plate 53 is larger than that interior cavity and is attached to the outer end zone 35 of the bar 33, and plates 54 and 55 so n slightly smaller than the inner cavity, in order to be able to slide therein and are respectively arranged in an interposed position between the portions 47 and 48 with ribs and an end position of the bar 33, opposite to that where the plate 53 is located. In this way, when the bar 33 is inserted or withdrawn with respect to the interior cavity 34 of the tubular housing 28, as is evident from Figs. 5, 6 and 7, the plates 54 and 55 fit exactly into said tubular housing, while whereas, on the contrary, the plate 53, by means of the support of the end of the tubular housing, prevents the rod from being completely inserted in the same tubular housing.

In addition, the portion 48 with ribs, which is shorter than the remaining portion 47 of the elongated rectilinear bar 33, has the ribs dimensioned in such a way that it allows to house externally at least one friction bearing 56 made of a suitable antifriction material, adapted to exert a braking action by friction against the surface of the interior cavity 34 of the tubular housing 28, during the reciprocating movement of the bar 33 within that tubular housing, caused by the oscillations of the tub-drum unit in the operation of each machine, with the consequent damping of the mechanical efforts produced by these oscillations. In particular, the friction bearing is made with separate component parts each configured as an elongated plate 59, provided with flat sides having the same contour and dimensions slightly larger than the internal cavity 34 of the tubular housing 28, so as to allow those component parts to adapt and slide inside the interior cavity. In the present case, the friction bearing comprises two component parts 60 and 61, each of which is provided with two equal sides 62 and 63, inclined symmetrically throughout its extension, having the same inclination of the adjacent sides 45 and 46 corresponding to the two half-shells 37 and 38 of the tubular housing 28. These elongated plates of friction bearings, also evident in detail in Figures 16 and 17, respectively in a front view and a plan view in section, are provided with a plurality of through holes 64 uniformly distributed over their surface, for the purpose to ensure passage of the grease and other suitable lubricating materials therethrough, which are adapted to keep all the component parts of the damper always lubricated during its operating cycles and which are externally housed against the ribs 51, 52 rectilinear of the orifice 48 with ribs of the elongate bar 33, with interposition of elastic elements configured as two springs 65 and 66 metal planes, in particular evident of figures 4, 8-10, each of which is dimensioned and configured in such a way that it adapts with a surface against the outer contour of the rectilinear ribs 51, 52 of the portion 48 with ribs.

Each metal planar spring, in particular, is configured in such a way that it has one or more grooves for the passage of grease or other suitable lubricating materials to keep the different component parts always lubricated and in the present case, that planar spring is shaped in such a way that rectangular and comprises a central groove 67 along the longitudinal edge 68 and two grooves 69 and 70 along its other longitudinal edge, these grooves are offset with respect to the previous ones and in which a sheet 72 and 73 is provided. respective central, which is bent with respect to the plane of the corresponding planar spring and rotates towards the ribs 51 and 52 of the portion 48 with ribs, in order to act resiliently against it, in a manner to push consequently tightly each flat spring against the elongated plate of the associated friction bearing, with which it is always pushed with a sliding contact against the surface of the cavity 34 inside housing 28 tubular. Now examining FIGS. 11 and 12, shown are the distribution diagrams of the braking forces respectively on a conventional damper and a damper according to the present invention. With particular reference to FIG. 1A, a conventional cylindrical damper 74 is shown schematically, comprising a cylindrical bar 75 internally housed in a housing 76 in the form of a cylindrical box and adapted to slide rectilinearly and reciprocally therein.

In this case, the shock absorber is represented in the idle state, when the drum of the washing machine is immobile and therefore the bar 75 does not exert braking actions and can be considered practically in a coaxial relationship with the housing 76 in the form of box. In figure 11b, on the other hand, where the damper is schematically represented in the operating state, with the drum of the machine set in motion, it is observed that the bar 75 tends to move reciprocally in the housing 76 in the form of a box not only axially but also radially, whereby it comes into contact with the inner surface of the same housing in the form of a box, in this case over the area marked with the numeral 77 of reference.

Under this operating state, then, the bar 75 operates eccentrically with respect to the box-shaped housing 76 and therefore exerts irregular braking actions against the inner surface of the box-shaped housing, namely that they are larger in their area of contact and progressively decrease from that zone towards the remaining parts of the inner surface, as represented by a set of force vectors 78 in Fig. 11c. Referring now to Figure 12a, a damper 26 according to the present invention is shown schematically in a state of rest, in which it will be seen that the bar 33 is housed coaxially within the tubular housing 28 and does not exert braking actions. . On the other hand, in FIG. 12b, where the damper is shown in the operational state, in which the rod is always radially displaced, with which it slides eccentrically inside the tubular housing 28, it will be observed that in this case the bearing the friction bar arranged in itself with the surfaces of its two adjacent sides 62 and 63 against the corresponding sides 45 and 46 of the tubular housing 28, in its contact zone 77, so that the reciprocating sliding of the friction bearing within the housing Tubular no longer exerts, as previously, irregular braking actions against the inner surface of the tubular housing, instead, braking actions distributed against that internal surface are exerted firmly and uniformly, thanks to the fact that the sides 62 and 63 of the Friction bearings are always arranged parallel to opposite sides 45 and 46 of the tubular housing 28, both in the resting state and in the operating state and therefore, in the latter state the reciprocal friction of these sides is achieved in any contact position, in correspondence with different eccentricities between the bar and the tubular housing, with which braking actions always have the same intensity on the same sides, which is represented schematically in Figure 12c by a set of force vectors 78 having the same intensity. In this way, the damper according to the invention allows to obtain braking actions that are distributed almost uniformly in any operational state of the washing machines, thanks to the fact that during the operation of these machines the friction bearing is firmly and uniformly maintained presined against the tubular housing, by means of the flat springs 65 and 66, which for this purpose are advantageously made of harmonic steel and configured in such a way that they adapt to the entire profile of both the plates 59 of the friction bearing and ribs 51, 52 of the portion 48 with ribs, thereby providing, on the one hand, an effective and certain damping of the mechanical stresses produced by the oscillations of the tub-drum unit during the drum movement, in particular at high centrifugal speeds, and another part, a reduced wear of that shock absorber and a longer life Saint. In addition, each shock absorber of this class is simple in its construction and consists of few component parts that can be assembled and disassembled quickly and easily, with parts made of metallic materials and therefore allow to dissipate the heat produced by the reciprocal friction of the Same parts very well. Finally, the presence of the ribs of the portions 47 and 48 with ribs of the shock absorber, which are longitudinal and directed in the same direction of the mechanical stresses exerted by the washing unit on the basis of the machine, allows the shock absorber to effectively support all the mechanical efforts of the washing unit, in both resting and operating states.

Another important advantage obtained by the use of the present shock absorber is that an effective and firm lubrication of the different component parts of the same shock absorber is always ensured, thanks to the fact that it provides, on the inner surface of the respective elongated rectilinear box 41 of the two semi - housings 37 and 38 of the tubular housing 28, a plurality of recesses 79 and 80, respectively aligned and inclined to each other with opposite inclined directions with respect to the longitudinal extension of that elongated box (Figure 2 shows a recess 79 cut along of the GG line).

In this way, before each shock absorber is mounted on the washing machine, some grease or other suitable lubricant material is introduced, which is therefore collected and concentrated by itself in rows 79 and 80 and then firmly removed by the friction bearing, during the reciprocal sliding in the tubular housing 28 and distributed over all the component parts of the shock absorber, it passes through the holes 64 of the plates of that friction bearing and the recesses 67, 69 and 70 of the springs planes 65 and 66. In addition, each absorber obtained allows the contaminated air to be vented effectively inside during the reciprocal travel of the bar 33 in the tubular housing 28, thanks to the presence of a plurality of through holes 81 provided on the two semi-hulls 37 and 38 of the tubular housing, and provided in this case for the entire length of the respective central flat sides 44 of the half-hulls. Finally, in accordance with the present invention, it is also possible to change the shape of the friction bearing 56 and tubular housing 28, by providing them with a polygonal shape having a number of equal sides to each other and different to those previously described only by way of example , provided that the sides of that bearing and the tubular housing are always parallel and correspond to each other in any operating state of the washing machine and can always be in contact with each other, causing uniform and firm braking actions at any position of the machine. contact between the friction bearing and the tubular housing. With reference to Figure 18, in which the shock absorber according to the present invention is shown in a second embodiment, it is noted that also in this case the shock absorber is constituted as that previously described and its respective free end portions of the housing 28. tubular and the bar 33, are also provided with a corresponding through hole 32 and 36, in which are inserted the two relative friction bushings 82, 83 and 84, 85, which are concentric with each other (see Figure 26) for the passage of a corresponding articulated bolt (not shown), which bolt is respectively mounted to the base 27 of the machine and unit 22 of the machine. As is particularly evident from FIGS. 19 and 26, the bushings 82, 83 and 84, 85 are made respectively of rubber and metal and are dimensioned so that they fit together and then assembled in the corresponding through hole and each bushing is composed of two identical half-parts marked with the relative reference numerals 82 ', 82", 83', 83" and 84 •, 84", 85 ', 85", which are assembled and disassembled reciprocally in an easy and fast manner without the use of tools. Furthermore, as is evident from Figure 18 again, the half-shells 37 and 38 along their contiguous longitudinal straight edges, adapted to be joined together, are configured with a respective set of projecting teeth 86, 87 and 88, 89 provided in those reciprocally displaced positions in order to allow the teeth and slots of a half-hull to be engaged by coupling with the slots and teeth of the other half-hull, such that the areas of attachment of those teeth and grooves be perfectly continuous and aligned with each other. The previous union thus achieved of the semi-helmets allows to ensure a high dimensional stability and mechanical resistance as well as an effective assembly safety of the same half-helmets, which will be obtained with difficulty in the case of sewing or conventional electric welding of the two semi-helmets configured as male-female connectors.

Additional advantages of this solution are that it is possible to have only one mold available to manufacture each semi-hull, instead of two different molds, as is the case with semi-molds of male-female connectors and that less sewing equipment is necessary that an electrical welding machine and its associated control device.

With reference to Figure 18 again, it will be noted that in one of the half-hulls of the tubular housing 28 in the present case the half-shells 37, at least one slightly re-indent 90 is provided to the cushion cavity, which interacts with the slide bar 33 so as to allow the latter to be inserted with a slight force into the interior cavity and to prevent the bar from being casually removed from the tubular housing 28 during the operation of the machine.

This constructive characteristic of the present shock absorber also ensures that it can be disassembled only by exerting a greater and pre-established stress, such as to overcome the coupling action of the indentation 90 with the bar 33 and thereby prevent the shock absorber from accidentally dismounting and incorrectly, when it is removed from the machine.

With reference to Figure 21, where the damper according to the invention is shown in a third embodiment, it will be noted that the shock absorber is made with the same characteristics described above, it will also be noted that the semi-shells of material are provided by pressing. metallic and slightly reentrant in the inner cavity of the tubular housing 28 in the manner and for the purpose described hereinbefore. As is evident from Figure 23, the impressions are configured slightly inclined with respect to the bar 33 and in particular the two impressions 91 are slightly inclined with respect to the bar 33 and in particular the two impressions 91 are slightly inclined converging one to the other. another from the midline of the half shell 37 towards its free end portion, which is provided with the bushings 82, 83, whereby the corresponding inclined surfaces 94 are defined, while the remaining two impressions 92 are configured slightly converging to each other in the opposite direction to the preceding one, namely from the midline of the half-shell 37 towards the other end portion of the latter where the rod 33 is inserted, thereby defining the corresponding inclined surfaces 95, said corresponding inclined surfaces 94 and 95 interact with the friction bearing 56 of the bar 33 during sliding of the latter within the tubular housing 28, so as to produce variable intensity braking actions which increase when the bar is sliding in correspondence with the surfaces 94 and 95 respectively in the N or O direction and decreases when that bar is sliding in the opposite direction. These braking actions of variable intensity are proportional to the intensity of the mechanical stress and serve to improve the shock absorbing capacity of the shock absorber.

Turning now to Figures 24 and 25, it will be noted that the present shock absorber, respectively in the condition in which the suitably shaped bar 33 is removed and inserted with respect to the tubular housing 8, while in Figure 26 the different parts are observed components of the same shock absorber, and in particular it is also observed that the plates 59 of the friction bearing 56, are fixed by means of elastic elements (not shown) against the outer surface of the non-linked end portion 96, which is inserted into the inner cavity of the tubular housing 28 and the coupling of the plates on the bar is made easy by the presence of the teeth 97 provided raised from that outer surface and engaging with the corresponding surfaces of the same plates.

Therefore, the shock absorber thus made, is composed of several component parts that can be easily assembled and disassembled without using tools, in such a way that it allows different kinds of materials to be separated and consequently can be recirculated in accordance with the special rules on this matter.

Claims (10)

R E I V I N D I C A C I O N S

1. Shock absorber for washing machines, in particular domestic laundry washing machines, adapted to be mounted between the washing tub-drum unit and the lower base of the housing of these machines, in order to cushion the mechanical stresses produced during the rotation of the drum at its different washing and centrifugation speeds, the damper is formed by at least one tubular housing and a reciprocating slide-in bar within the tubular housing, provided with friction means cooperating with the tubular housing by friction , in order to obtain braking actions adapted to damp mechanical stresses, this shock absorber is further characterized in that the tubular housing and the friction means of the bar are made removable and provided, in their reciprocal friction contact zones, with contours of polygonal shape that have equal number and shape sides ent re si, in such a way that the corresponding sides of the tubular housing and the friction means co-occur with each other in any operating state, be it the rest state or the operational state of the damper, the friction means are associated with adapted elastic means to keep them always in frictional contact with the tubular housing.

2. - Shock absorber according to claim 1, characterized in that the tubular housing comprises at least first and second separated metal helmets, identical and symmetrical with each other, provided with rectilinear flat edges adapted to reciprocate and remain joined, thereby providing a cavity internal to insert and slide the bar therein, the first and second half-helmets each are constituted by an elongated rectilinear box whose outline is of polygonal shape, having sides with equal or different dimensions, extended from its open end portion, wherein the bar is inserted into the interior cavity, to a closed end portion, adapted to be fixed to the washing machine.

3. Shock absorber according to claim 2, characterized in that the first and second half-shells are provided with a plurality of inner recesses to accommodate some grease or other suitable lubricating materials and a plurality of through holes to vent the air contained inside .

4. - Shock absorber according to claim 1, characterized in that the bar preferably is integrally made of molded plastic material and is constituted by portions with first and second ribs joined together and configured with an identical outer contour and having slightly smaller dimensions than those of the interior cavity, as well as comprising longitudinal rectilinear ribs delimited by plates having the same outline of the interior cavity, whose plate is larger than the interior cavity and the plates are slightly smaller than the same interior cavity, in order to be able to slide in it.

5. Shock absorber according to claim 4, characterized in that the friction means comprise a friction bearing made of a suitable anti-icing material, provided with separate first and second component parts configured as an elongated plate, one of which is provided with sides which coincide with those of the inner cavity of the tubular housing and cooperate by friction; each plate is received externally against the second portion with ribs of the bar, with the interposition of the elastic means and provided with a plurality of through holes in communication with the inner recesses, for the passage of the grease or other suitable lubricating materials.

6. Shock absorber according to claim 5, characterized in that the elastic means comprise first and second metallic flat springs made of harmonic steel, which are configured in such a way that they adapt to the contour of both respective plates and the corresponding ribs of the second portion with ribs; the first and second flat springs are provided with respective sheet, bent with respect to the plane of the corresponding flat spring and rotated towards the ribs, in order to act elastically against them and being further provided with grooves for the passage of grease or other suitable lubricant materials.

7. Shock absorber according to the preceding claims, characterized in that the first and second half-shells are configured, along their contiguous longitudinal rectilinear edges, with a respective set of projecting radial teeth and grooves, displaced from each other to allow the teeth and the slots of a half-hull are coupled by joining the slots and the teeth of the other half-hull, as well as being provided with trapping means that interact with bars in order to prevent them from being casually removed from the interior cavity.

8. - Shock absorber according to claim 7, characterized in that the trapping means are constituted by at least one indentation that slightly re-enters the interior cavity.

9. Shock absorber according to claim 7, characterized in that at least one of the half-shells is provided with impressions provided by pressing and slightly reentering the inner cavity, and defining corresponding inclined surfaces with different inclination directions, interacting with the bearing friction in order to produce braking actions of varying intensity during the sliding of the bar in the two opposite directions of sliding within the tubular housing.

10. - Shock absorber according to claim 1, characterized in that the friction bearing is fixed against the bar by means of teeth that rise from the same bar. SUMMARY Shock absorber for the oscillations of the tub-drum unit of domestic laundry washing machines, comprising a tubular housing (28) and a bar (33) that reciprocates slidably therein, which are made with profiles of polygonal shape, having sides of equal number and shape, so as to coincide reciprocally in any operative state of the damper, to allow friction means (56) fixed to the bar (33) to always firmly and uniformly exert braking actions distributed on the housing (28) tubular. The shock absorber is also made with a removable and self-lubricating structure and in different embodiments.