GB1586854A - Frictional damping device particularly for the tanks of washing machines and washing machines incorporating such a device - Google Patents

Description

(54) A. Fk4CTI0.NAL DAMPING DEVICE PARTICUiAk.L"Y FOR THE TANKS Og WASHING MACH S AND WASHING MACE S INCORPORATING SUCH A DEVICE.

(k71) Wev EssweIN S.A., a French Body Corporate, of 67, Quai Paul Doumer 92 Courbevoiej France,. do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to a frictional damping device of the kind intended for suspending a mechanically oscillating assembly, such as the tank of a machine for washing laundry..

Frictional damping devices are known in which the friction is obtained by moving a piston. within a tube. When such devices are in operation, a large amount of heat is generally released inside the said tube and it is difficult for this heat to escape. This large amount of heat raises the temperature of the said devices and causes an undesirable alteration in the frictional characteristics of their moving parts and thus affects their efficiency as dampers. In laundry washing machines, the tank is suspended by means of damping devices of this kind which are attached either to the frame of the said machines or to their base. When the machines are operating, the tank often oscillates with a movement of greater or lesser amplitude depending upon whether or not there is an imbalance in the laundry drum to which the tank is connected mechanically. If the damping provided by the suspension devices is effective, the duration of the oscillations of the tank is lessened. In cases where the damping characteristics of the devices alter and their damping ability is reduced, the amplitude of the oscillations of the tank of the machine may become excessive and may unfortunately result in violent collisions between the tank and the outer shell of the machine..

These known damping devices also require the damping tube to be accurately machined in the process of manufacture and this results in a increase in their manufacturing cost.

The present invention, which has as an object substantially to reduce these disad vantage, makes it possible to produce an improved frictional damping device which is economical and whose damping efficiency is relatively constant.

According to the invention, a frictional damping device comprises an inner cylindrical member disposed co-axially within an outer tubular member and such that said members can slide one relative to the other under friction between said members, wherein said outer tubular member is apertured so as to assist in the dissipation to atmosphere' of heat produced by friction when the damping device is in operation, and wherein the inner cylindrical member is tubular and the inner face of the outer tubular member is provided with material having a high. coefficient of friction.

The invention will now be further described by way of example, with reference to the accompanying drawings, in which:- Fig. 1 is a perspective view of one embodiment of damping device according to the invention, Fig. 2 is a cross-sectional view on line II-II of the device of Figure 1, to a different scale, Fig. 3 is a side view, partly cut away, of a resilient sleeve for the device of Figure 1, to a different scale, Fig. 4 is a perspective view, partly in section, of a ferrule for the device of Figure 1, to a different scale, Fig. 5 is a view from below of a modified embodiment of the device of Figure 1, to a different scale, showing a resilient sleeve and a spring which co-operates with it; and Fig. 6 is a side view, partly in section of the sleeve and the spring df Figure 5..

Referring to Figures 1 to 4, a frictional dam- ing device comprises a gripping apertured resilient sleeve 1 provided with an end wall 2 at one extrernity,. a guide rod 3 fixed coaxially in the sleeve 1., a tube 4, which on the one hand slides freely on' this guide rod 3 and which on the other hand slides under friction in the said gripping,. apertured resilient sleeve 1, and a spring 5 mounted on the guide rod 3 which tends to force the tube 4 away from the end wall 2 of the sleeve 1.

The stamped or added end wall 2 is formed with a central hole 6 intended for the passage and securing of the guide rod 3, and the sleeve 1 has, in its side wall, running for part of its length from its open end, two wide, diametrically opposed generally omega-shaped longitudinal slots 7. These slots 7, which give the sleeve 1 its apertured form to promote the rapid dissipation. of the heat which is released by friction when the damping device is operating, divide the side wall of the sleeve 1 into two substantially semi-cylindrical arms 8 and 9. The ends 10 (Figure 3) of these arms 8 and 9 which are connected to the end wall of the sleeve 1, are smaller in size than the other ends of the arms. The smaller size of the ends 10 endows the arms 8 and 9 with resilience which enables the sleeve 1 to grip the tube 4 resiliently. To tighten the grip of the sleeve 1 on the tube 4, two substantially semi-cylindrical leaf springs 11 are mounted between the free ends of the arms 8 and 9. These springs 11 draw the arms 8 and 9 towards one another resiliently. The ends of the springs 11 are held in place either by ridges 12 (Figure 2) or by sunken stamped areas (not shown) formed in the free ends of the arms 8 and 9. On the inner faces of their free ends, the arms 8 and 9 of the sleeve 1 are provided with pads 13 made of a material having a high coefficient of friction. The grip of the arms 8 and 9, plus the clamping effect of the springs 11 and the high coefficient of friction of the pads 13 all play a part in effectively braking the axial movement of the tube 4 in the gripping apertured resilient sleeve 1.

The co-axial guide rod 3 has a smoothsurface which helps the tube 4 to slide, and a threaded end 14 which enables it to be attached to the sleeve 1 and which enables the said sleeve 1 to be connected mechanically to another mechanical part, such as the base or frame of a washing machine, when the damping device is in use.

The tube 4 is closed at one end by a solid cap 22 and has in its second end an added ferrule 15. The ferrule 15 which is shown inverted in Figure 4, has on the one hand, in its central region, a shoulder 16 which acts as an abutment to restrict the extent to which it enters the tube 4 and to support one of the ends of the coil spring 5, and on the other hand, in the portion of its side wall which enters the said tube 4 and in the surface of the shoulder 16 in contact with the end of this tube 4, one or more continuous longitudinal grooves 17 which allow free inter-communication between the interior of the tube 4 and the exterior. The ferrule 15 also has a smooth axial bore 18 which, when the ferrule is mounted on the rod 3, enables the movement of the tube 4 to be guided.

The cap 22 has a threaded end 19 which, when the damping device is in use, enables the tube 4 to be mechanically connected to part of a mechanically oscillating assembly such as the tank of a laundry washing machine.

When the damping device described above is in operation with the sleeve 1 and the coaxial guide rod 3 fixed, for example, and the tube 4 connected to a mechanically oscillating assembly, the tube performs a reciprocating movement between the friction pads 13 of the sleeve 1. The pads 13, which have a high coefficient of friction and whose action is combined with the opposing force from the spring 5, have a powerful braking effect on the oscillatory sliding of the tube 4. The heat which is released as the tube 4 rubs against the pads 13 can quickly be dissipated by virtue of the direct contact between the tube 4 and surrounding medium and in particular by virtue of the ease with which it is able to escape from the tube 4 to the external surroundings through the grooves 17 in the ferrule 15 and the slots 7 in the sleeve 1.

In a modified embodiment of the invention which is illustrated in Figure 5 and 6, the semicylindrical leaf springs 11 on the sleeve 1 are replaced by a spring 20 of hairpin shape whose parallel sides are bent at right angles to the common semi-circular central part 21 of the said spring. When the spring 20 is fitted to the sleeve 1 (Figure 6) itssemi-circularpart 21 clasps the body of the sleeve 1, whilst the free ends of the sides of the spring 20 bear against the free ends of the arms 8 and 9 of the sleeve 1 to force then towards one another.

By virtue of its simple and improved structure the damping device which is described above is a device which is not only economical but also effective in damping mechanical oscillations. The direct contact between its tube 4 and the surrounding medium and the easy intercommunication between the interior of the tube 4 and the exterior via the grooves 17 in the ferrule 15 and the slots 7 in the sleeve 1 assist in rapid dissipation of the heat which is released by friction and thus make it possible to avoid the disadvantages attendant on changes in characteristics due to variations in temperature such as are normally encountered in known damping devices. As regards its application the damping device according to the invention as described above may, with advantage, be used in suspending a mechanically oscillating assembly such as the tank of a laundry-washing machine.

In the various applications of the damping device according to the invention, the requisite damping characteristics may easily be obtained simply by altering the resilient characteristics of the springs 11 mounted on the sleeve 1.

As an example, which is not illustrated, a laundry washing machine according to the invention, has, inside its shell, a tank which is suspended by means of a plurality of frictional damping devices, four for example. The upper ends of these damping devices are connected, in such a way as to pivot, to the outer wall of the said tank, whilst the lower ends of the devices are secured to the base of the machine.

When the laundry drum turns, it imparts a certain amount of oscillatory motion to the tank of the machine. The amplitude of this oscillation depends upon the size of any imbalance which exists in the laundry drum.

When the amplitude of the oscillation is large, the tank may strike the shell of the machine and cause serious mechanical damage. The damping devices according to the invention as described above are intended to brake such oscillation. The constant nature of their damping characteristics is an advantage in that it effectively enables this undesirable oscillation by the tank of the said washing machine to be cut down and quickly suppressed.

WHAT WE CLAIM IS: 1. A frictional damping device comprising an inner cylindrical member disposed co-axially within an outer tubular member and such that said members can slide one relative to the other under friction between said members, wherein said outer tubular member is apertured so as to assist in the dissipation to atmosphere of heat produced by friction when the damping device is in operation, and wherein the inner cylindrical member is tubular and the inner face of the outer tubular member is provided with material having a high coefficient of friction.

2. A device as claimed in claim 1, wherein one or more openings are provided at one end of the inner tubular member, which openings provide a path between the interior of the inner tubular member and the apertures in the outer tubular member to allow heat to dissipate to atmosphere.

3. A device as claimed in claim 1 or 2, wherein a guide rod is fixed to the outer tubular member and a ferrule is provided in said one end of the inner tubular member, said ferrule having a bore surrounding said guide rod such as to allow relative sliding movement therebetween, and said ferrule being provided with one or more grooves on its outer surface to permit intercommunication between the interior of the inner tubular member and the apertures in the outer tubular member.

4. A device as claimed in any one of claims 1 to 3, wherein the outer tubular member is apertured by means of a plurality of slots which extend over a major part of the length of the outer tubular member and which extend generally in the direction of the axis of the outer tubular member.

5. A device as claimed in claim 4, wherein the slots are open at one end of the outer tubular member to provide the latter with a plurality of arms, and means are provided which urge the arms radially inwards towards the inner cylindrical member.

6. A device as claimed in claim 5, wherein the urging means comprise spring means.

7. A device as claimed in claim 6, wherein the spring means comprise leaf springs.

8. A device as claimed in claim 6, wherein the spring means comprises a hairpin spring having generally parallel sides which are bent substantially at right angles to the semicircular central part of the hairpin.

9. A device as claimed in any one of the preceding claims, wherein the outer tubular member is in the form of a sleeve having resilient properties in the radial direction which resiliently urge the sleeve towards the inner cylindrical member.

10. A device as claimed in any one of the preceding claims, wherein a spring is provided for urging the two members apart in the axial direction.

11. Damping devices substantially as hereinbefore described with reference to the accompanying drawings.

12. Tank of a laundry-washing machine, characterised in that it has, to suspend it in the said machine, a plurality of frictional damping devices according to any one of

Claims (1)

1. claims 1 to 11.

   13. Laundry washing machine, including a tank as claimed in claim 12.