GB2120181A - Wheels for domestic appliances - Google Patents

Abstract

A wheel, especially for a washing machine, comprises an inner disc 4 of a resilient material, such as rubber, sandwiched between two outer discs 1,2 of harder more rigid material, such as nylon, and of smaller diameter than the inner disc. The inner disc 4 has on each side a plurality of angularly spaced ribs 5 each extending to the peripheral region of the disc, the inner parts of the ribs being accommodated in co- operating slots 3 in the two outer discs. The projecting part of the inner disc, with the outer ends of the ribs, forms a resilient tread which between adjoining ribs is more readily compressed than at the ribs themselves, this tending to resist "walking", but at the same time the outer discs impart a degree of stiffness which assists in suppressing vibrations. <IMAGE>

Description

SPECIFICATION Wheels This invention relates to wheels, more especially, though not exclusively, for domestic appliances such as washing machines and spin dryers.

In such appliances, as well as other equipment fitted with wheels and subject to vibration in use, the wheels can play an important part in reducing the degree of vibration. Thus hard, stiff wheels have usually been found to be the most suitable for achieving this. However for many purposes it is desirable that the wheels should be sufficiently soft and resilient to prevent damage to floors on which the equipment is used. Such requirements are obviously contradictory, and the common solution to the problem is to make the wheels with a hard solid core and to provide, around the core, a tyre in the form of a ring of rubber or like resilient material.

However in the use of such wheels the tyres can in some cases peel off the cores, which is obviously undesirable.

An object of the present invention is to provide an alternative form of wheel which is not subject to this drawback, and has a number of other advantages over such conventional wheels, as will be apparent from the following description.

According to the invention a wheel comprises an inner disc of resilient material sandwiched coaxially between two outer discs of harder more rigid material and of smaller diameter than the inner disc, the latter having on each side a plurality of angularly spaced ribs each extending outwards to the peripheral region of the disc.

The peripherial region of the inner disc which projects beyond the edges of the outer discs provides, with the radially outer ends of the ribs, a resilient tread pattern which is presented to the floor in use of the wheel but, at the same time, the harder, more rigid outer discs impart to the wheel a degree of stiffness which assists in suppressing vibration of equipment to which it is fitted.

It is frequently necessary to apply a degree of friction to the wheels of washing machines and spin dryers in order to counteract the tendency of the machine to "walk" across smooth floors in use.

We have found that the resuitant tread pattern of a wheel in accordance with the invention itself provides a measure of resistance to this tendency to "walk". Thus, in use, the wheel tends to stabilise itself with a region of its periphery between adjacent ribs in contact with the floor. This is because the volume of resilient material in such a region is smaller than at the ribbed region themselves, and as a result the compression of material at this region when it contacts the floor is greater, resulting in a marked flattening of the tread between the adjacent ribs which tends to resist rotation.

In one form of wheel in accordance with the invention the radially inner parts of the ribs are accommodated in co-operating slots in the respective outer discs.

However the ribs may simply be in the form of shallow radially extending ridges which are compressed by adjacent planar surfaces of the outer discs when the wheel is assembled. In a further arrangement the ribs may be formed as projections lying wholly on the region of the inner disc which projects beyond the peripheries of the outer discs.

Thus it will be understood that the ribs can be in the form of projections of any convenient configuration, and that the word 'rib' does not imply any particular shape or dimensions, these being readily chosen to suit the size of the wheel and the use to which it is to be put. Similarly the number and disposition of the ribs, and also slots where provided, the thickness of the inner disc and the amount by which it projects beyond the periphery of the outer discs, can readily be selected to give the most satisfactory performance for any particular application of the invention.

It is not necessary for the ribs on opposite sides of the inner disc to be aligned with each other, and the ribs on one side of the disc can in some cases be rotationally staggered with respect to those on the other side.

Conventionally the inner disc projects beyond the peripheries of the outer discs a distance of between 2% and 6% of the diameter of the outer discs, and in the case of a washing machine we have found the use of an inner disc having a diameter of between 30mm and 40mm, and a thickness of between 3mm and 5mm, with eight ribs spaced uniformly around each side and having a width in the circumferential direction where they join the main part of the disc of between 3mm and 5mm, to be effective in suppressing vibration and restricting "walking" of the washing machine in use. However the most satisfactory dimensions of a wheel in accordance with the invention, for any particular application of the invention may readily be found by trial.

The wheel is conveniently mounted in a carrier of dimensions such that the inner disc is held in compression, thereby pressing the outer surfaces of the two outer discs into frictional contact with co-operating surfaces of the carrier. This imparts a measure of friction, which provides an additional resistance to rotation without the use of additional members such as spring star washers commonly employed with conventional washing machine wheels.

The inner disc is preferably of rubber and the outer discs of hard plastics material such as nylon, both the inner and outer discs being conveniently formed by moulding.

For facilitating the moulding process of the inner disc the thickness of the ribs, that is to say as measured in a circumferential direction, preferably decreases towards their axially outer edges. The width of the slots preferably also decreases towards the outer faces of the discs.

Instead of being of hard plastics the outer discs can alternatively be of metai and can be fabricated in any convenient manner.

Where the ribs are accommodated in slots in the outer discs the depth of the ribs, that is as measured in an axial direction, is preferably such that the ribs do not project beyond the outer faces of the outer discs, and although the slots in the latter may extend completely through the thickness of the discs, they need not do so, and the outer surfaces of the discs can then be substantially smooth and unbroken.

One wheel in accordance with the invention for a washing machine and some modifications thereof will now be described by way of example with reference to Figures 1 to 6 of the accompanying schematic drawings, in which Figure 1 illustrates the different components of the wheel; Figure 2 represents a perspective view of the wheel; Figure 3 shows an end view of the wheel in a wheel carrier of a washing machine; Figure 4 illustrates an end view of part of a modified form of the wheel shown in Figures 1 to 3; and Figures Sand 6 show two further modifications.

Referring first to Figure 1,thewheel comprises a pair of comparatively rigid side members 1,2, for example of hard moulded plastics material, in the form of discs each having a plurality of radially extending slots 3, in this case eight, disposed at a uniform angular spacing around the disc, and on one surface a centrally disposed boss 11. The members 1, 2 are arranged, bosses outwards, on opposite sides of an inner member 4 of a resilient flexible material, for example rubber, also in the form of a disc, having on each side eight radially extending ribs 5 which are positioned so as to lie within the slots 3 in the side members 1,2 when the member is sandwiched between them as shown in Figures 2 and 3. Central holes 6 in the side and inner members are provided for receiving an axle 7.

The diameter of the inner member 4 is slightly greater than that of the side members 1, 2 so that it projects slightly beyond them in a radial direction as at 8, the ribs 5 extending to the edge of the member 4 and, with the projecting peripheral region 8 of the members 4, they provide a resilient tread. At the same time the side members 1, 2 impart stiffness to the wheel which is desirable to reduce the effect of vibration in operation of the washing machine as above described. In use the wheel is fitted into a wheel carrier 9 (Figure 3) having side supports 10 between which the axle 7 extends, the supports 10 bearing against the bosses 11 of the wheel side members 1, 2 thereby compressing the inner member 4 slightly. The compression of the inner member 4 provides an outward force which keeps the bosses of the side members 1, 2 pressed into frictional contact with the wheel carrier.This obviates the need for additional spring star washers commonly employed with conventional washing machine wheels to provide a degree of friction for resisting rotation, and consequent walking of the washing machine, in use.

In addition the wheel has a tendency to stabilise itself with a peripheral section of the inner member 4, lying between two pairs of ribs 5, in contact with the floor. As the volume of rubber under compression is smaller at this peripheral section the deflection is higher, effectively causing a small flat on the rubber tread which tends to resist rotation of the wheel.

The inner member 4 as well as the side members 1,2 are conveniently formed by moulding processes, and to facilitate this each of the ribs 5 and the co-operating slots 3 are preferably formed with a slight taper as shown.

In this embodiment the depth of the ribs 5 is about 7/8ths of the thickness of the side members 1,2 so that they do not project beyond the outer faces of the latter. In some cases therefore the slots 3 which accommodate the ribs 5 need not extend to the outer faces of the side members, which can then provide a smooth unbroken surface. However in certain instances, where additional friction may be beneficial, for further retarding movement of the wheels, the ribs 5 can project beyond the outer surfaces of the side members and make frictional contact with co-operating surfaces of the wheel carrier.

The wheel shown in part in Figure 4 is generally similar to that illustrated in Figures 1 to 3 except that the ribs 5 on opposite sides of the inner disc 4 are rotationally staggered with respect to each other.

In the wheel illustrated in part in Figure 5 the ribs 5 are in the form of shallow rounded radially extended ridges, and the inner surfaces of the two side members 1,2 are of unbroken planar form, so that in the assembled wheel the ribs are compressed between the members.

Figure 6 shows a wheel similar to that of Figure 5 except that the ribs 5 on opposite sides of the inner disc 4 are rotationally staggered with respect to each other.

In all the embodiments described for use on a particular washing machine the inner disc 4 conveniently has a thickness of 4mm and a diameter of 36mm, and projects about 1 .5mm beyond the peripheries of the side members 1,2, the width of the root portions of the projections 5 in a circumferential direction conveniently being about 4mm.

However it will be appreciated that alternative dimensions and tread patterns could be adopted if desired. For example the frequency of the spacing of the ribs 5 and slots 3 could be reduced or increased according to the wheel diameter, and the ribs could be angled one way or the other were such a condition to be of value in performance.

In addition the number, shape, size and disposition of the ribs, as well as the thickness of the member 4 and the amount by which it projects beyond the peripheries of the side members 1,2 can also be readily selected to give the most satisfactory results depending upon requirements in any particular application ofthe invention.

Whilst the invention is primarily concerned with wheels for washing machines and spin dryers, wheels in accordance with the invention can also be used to advantage in numerous other forms of equipment in place of conventional tyred wheels.

Claims (22)

1. Awheel comprising an inner disc of resilient material sandwiched coaxially between two outer discs of harder more rigid material and of smaller diameter than the inner disc, the latter having on each side a plurality of angularly spaced ribs each extending outwards to the peripheral region of the disc.

2. A wheel according to Claim 1 wherein the radially inner parts of the ribs are accommodated in co-operating slots in the respective outer discs.

3. Awheel according to Claim 2 wherein the slots extend completely through the thickness of the discs.

4. Awheel according to Claim 3 wherein the depth of ribs is less than the thickness of the outer discs.

5. A wheel according to Claim 3 wherein the depth of the ribs is greater than the thickness of the discs such that the ribs project beyond the outer faces of the two outer discs.

6. A wheel according to Claim 2 in which the slots extend only partially through the thickness of the discs.

7. Awheel according to any preceding Claim in which the width of the slots is such that the sides of the slots engage the sides of the ribs.

8. A wheel according to any one of Claims 2 to 6 in which the thickness of the ribs decreases towards their axially outer edges.

9. Awheel according to Claim 8 wherein the width of the slots decreases towards the outer faces of the discs.

10. Awheel according to Claim 1 in which the inner faces of the two outer discs are generally planar and bear against the axially outer surfaces of the ribs.

11. A wheel according to Claim 10 wherein the ribs are in the form of radially extending ridges.

12. Awheel according to any preceding Claim in which the ribs on one side of the inner disc are rotationally staggered with respect to those on the opposite side of the disc.

13. Awheel according to any preceding Claim mounted in a carrier of dimensions such that the inner disc is held in compression.

14. Awheel according to Claims 5 and 13 in which the ribs make frictional contact with cooperating surfaces of the wheel carrier.

15. Awheel according to any preceding Claim wherein the inner disc is of rubber and the outer discs of hard plastics material.

16. A wheel according to any preceding Claim in which the inner disc projects beyond the peripheries of the outer discs a distance of between 2% and 6% of the diameter of the outer discs.

17. Awheel according to any preceding Claim wherein the inner disc has a diameter of from 30mm to 40mm.

18. Awheel according to any preceding Claim wherein the inner disc has a thickness of from 3mm to 5mm.

19. Awheel according to any preceding Claim wherein the inner disc has eight ribs spaced uniformly around each side.

20. Awheel according to any preceding Claim in which the outer face of each outer disc is formed with a centrally disposed boss.

21. A wheel substantially as shown in and as hereinbefore described with reference to Figures 1 to 3 or Figure 4 or Figure 5 or Figure 6 of the accompanying drawings.

22. Awashing machine incorporating at least one wheel according to any preceding Claim.