WO2000078560A1

WO2000078560A1 - Wheel structure

Info

Publication number: WO2000078560A1
Application number: PCT/GB2000/002388
Authority: WO
Inventors: Gavin Reay; Simon David Heap
Original assignee: IMAGE AUDIT DESIGN CONSULTANCY Ltd
Current assignee: IMAGE AUDIT DESIGN CONSULTANCY Ltd
Priority date: 1999-06-21
Filing date: 2000-06-21
Publication date: 2000-12-28
Anticipated expiration: 2001-12-21
Also published as: AU5549100A; GB9914473D0

Abstract

A wheel structure having a rim (2) and a hub (1) linked by a number of generally radially extending spokes (3). Each spoke (3) has substantially the same construction and includes a free end (3B) spaced from the hub (1) when the rim (2) is in its rest position, and a flexible spur (3C) connection attached to the hub (1), whereby as the rim (2) is compressed towards the hub (1), the spur (3C) will flex until the free end of the spoke engages the hub.

Description

WHEEL STRUCTURE

The invention relates to a wheel structure and in particular an internally sprung wheel structure, that is to say, of the type in which a suspension is provided between the hub and a continuous rim.

Examples of such structures are described in GB-A- 1292928 and EP-A-0051996.

In EP-A-0051996, each spoke has a spur or extension which, as the rim is compressed towards the hub, engages an adjacent spoke thereby limiting the degree of compression.

This is a relatively complex construction and there is a need to reduce the complexity in order to make the structure more suitable for mass production. In accordance with one aspect of the present invention, a wheel structure has a rim and a hub linked by a number of generally radially extending spokes, each spoke having substantially the same construction and including a free end spaced from the hub when the rim is in its rest position and a flexible spur connection attached to the hub, whereby as the rim is compressed towards the hub, the spur will flex until the free end of the spoke engages the hub.

We have devised a much simpler construction in which compression movement of the rim is limited primarily by engagement between the spoke and the hub. It is possible that the spoke will have some flexure so that further compression of the rim would be allowed although this would need to overcome a much stronger reaction force due to the spoke resilience.

Preferably, the spur is attached to the rest of the spoke at a point spaced from the free end of the spoke. In this way, the free end of the spoke forms a stop member. In accordance with a second aspect of the present invention, a wheel structure has a rim and a hub linked by a number of pairs of generally radially extending spokes extending between the hub and the rim, each pair of spokes being constructed so as to flex in an opposed manner when the rim is compressed towards the hub; and means linking the two spokes to oppose the said flexure.

In this aspect of the invention, the compression of the rim towards the hub is controlled not only by the inherent resilience of the spokes but in addition by the presence of the additional means. This will result in a more controlled compression movement and a smoother operation. The means can take a variety of forms including, for example, a tension or compression spring or a flexible member. In particular, the pair of spokes could be integrally moulded together with the means linking the two spokes together. Typically, each spoke has a section which is curved in an opposite sense to that of the other spoke of the pair. In this way, the spokes will flex away from each other during the compression movement.

Preferably, each spoke of the pair further includes an abutment portion, the abutment portions of the pairs moving towards each other during compression movement so that they engage after a predetermined degree of compression movement and thus limit further the compression achievable. This will effectively lock the spokes against further significant flexure.

The number of spokes which can be used can vary depending upon the strength of the materials used and the degree of compression to be allowed but there will be an upper limit to that number since all the spokes must fit within the circumference of the wheel.

In accordance with a third aspect of the present invention, a wheel structure comprises two wheel sub- assemblies, each sub-assembly having a rim and a hub linked by a number of generally radially extending spokes, the spokes being resilient so as to allow the rim to compress towards the hub, the sub-assemblies being mounted coaxially together to form the wheel structure. With this aspect of the invention, it is possible to increase the number of spokes over the number which can be achieved in the more simple wheel structures described above by utilizing two sub-assemblies. The spokes could have any conventional form as, for example, described in the prior art mentioned above but in the preferred arrangement, each sub-assembly is in the form of a wheel structure according to either the first or second aspect of the invention. One of the advantages of this aspect of the invention is that the compressible nature of the wheel structure can be tuned by setting an appropriate circumferential offset between the spokes of the two sub-assemblies. In one extreme, they could be aligned with each other and in the other extreme fully offset. Offsetting the spokes increases the resistance to compression of the rim.

In accordance with a fourth aspect of the present invention, a wheel structure comprises a rim and a hub linked by a number of generally radially extending resilient spokes which allow the rim to be compressed towards the hub, circumferentially adjacent spokes being axially offset but including an axially extending portion which will interfere with flexure of an adjacent spoke upon compression of the rim towards the hub so as to limit flexure of both spokes.

This aspect of the invention provides a further alternative way of limiting flexure of the spokes in a particularly simple manner.

Preferably, a wheel structure according to the fourth aspect of the invention is also constructed in accordance with a third aspect of the invention. Thus, two sub- assemblies could be used and typically these will have an identical construction and then one is reversed relative to the other when they are coupled together. The two sub-assemblies could be coupled together in a variety of ways, either by using an additional shaft member or the like or by utilizing corresponding connection elements on the two sub-assemblies such as screw threads or snap fit formations.

The wheel structures could be manufactured using a variety of materials but they are particularly suited for use with plastics and in particular can be moulded in a one-piece construction.

Wheel structures according to all the aspects of the invention can be used in a number of different applications but are particularly suited for use in shopping trolleys and the like.

Some examples of wheel structures according to the invention will now be described with reference to the accompanying drawings, in which: -

Figure 1 is a plan of a first example; Figure 2 is a plan of a second example;

Figures 3A and 3B illustrate two versions of a third example in perspective view; and,

Figure 4 is a perspective view of a fourth example. The wheel structure shown in Figure 1 is formed as a one-piece plastics moulding and comprises a cylindrical hub 1 which is surrounded by a cylindrical rim 2. The rim 2 is connected to the hub 1 by a set of six spokes 3. Although six spokes 3 have been shown in the drawings, other numbers of spokes could be used. Each spoke 3 has a main section 3A extending from the rim 2 to a free end 3B just spaced from the hub 1. The spoke also includes a spur section 3C which extends from adjacent the free end 3B to the hub 1.

In use, the hub 1 is mounted on an axle (not shown) so as to either rotate with the axle or about the axle. The rim 2 will be periodically compressed towards the hub 1 as the wheel rotates. This compression is initially taken up by flexure of the spurs 3C of the spokes until the free ends 3B of the relevant spokes contact the surface of the hub 1. At that point, further compression movement of the rim 2 towards the hub 1 is substantially prevented although a small amount of movement will be permitted by flexure of the sections 3A of the spokes.

In the Figure 2 example, a one-piece plastics moulding is used to form a hub 5 and surrounding rim 6 together with a set of spokes 7. Each spoke 7 has a generally arcuate section 7A extending from the rim 6 towards the hub 5 and a thinner, V-shaped section 7B extending from the inner end of the section 7A to the hub 5.

Each spoke 7 also includes an extension 7C which terminates in an anchorage point 7D . It will be seen in Figure 2 that the spokes 7 are arranged in pairs with the extensions 7C of each pair extending towards each other. A tension spring 8 is mounted about the pairs of anchorage points 7D. As the rim 6 is compressed towards the hub 5, the arcuate sections 7A of the spokes 7 will flex outwardly against the force of the tension spring 8 so that this force will limit the outward movement and hence inward movement of the rim 6. This outward movement of the spokes will continue, however, until adjacent portions of the sections 7B of each pair contact one another so that, as in the Figure 1 example, the rim 6 will then be generally locked in position relative to the hub 5.

As can be seen in Figure 2, there is a limit to the number of spokes which can be incorporated within the allowable space. Figure 3 illustrates a further example in which more spokes can be accommodated. In this example, the wheel structure is split into two sub-assemblies 20,21 having identical forms. Again, one-piece plastics mouldings are preferred. Each sub-assembly, and we will describe the sub-assembly 20, has a rim 22 and a hub 23 with a set of spokes 24 extending from the rim to the hub. Each spoke has an outer, arcuate portion 24A and an inner linear portion 24B. These portions are resilient so that the rim 22 can be compressed towards the hub 23. That compression movement will be stopped when adjacent shoulders 26 of adjacent spokes 24 contact one another. The two sub-assemblies 20,21 can be connected together in any conventional form, for example via a third shaft member (not shown) or by screw threads provided on one or both of the hubs 23 and rims 22, or by a snap fit engagement between these components .

One of the advantages of this aspect of the invention is that both sub-assemblies have an identical construction so that only one type of sub-assembly has to be manufactured. These can then be joined together in pairs as shown in the drawings. Furthermore, the circumferential offset between the spokes 24 in one sub-assembly and the spokes in the other sub-assembly can be adjusted as required to tune the compressibility of the overall wheel structure. In Figure 3A, the spokes 24 of the two sub- assemblies 20,21 are shown fully circumferentially offset while in Figure 3B they are shown in alignment.

In the example shown in Figure 4, again a double sub- assembly arrangement is shown (although this is not essential in this case) . The two sub-assemblies are labelled 30,31. Each sub-assembly has a rim 30A,31A and a corresponding hub 30B,31B. The rims are connected to the hubs via spokes 30C,31C. Each spoke has a form similar to the spoke 7 in Figure 2 but instead of having anchorage points, each spoke has an axially extending stop member 30D,31D.

The two sub-assemblies 30,31 are connected together so that the stop members 30D,31D are spaced from the adjacent spokes 31C,30C respectively. When the rims 30A,31A are compressed towards the hubs 30B,31B, the corresponding spokes 30C,31C will flex until they engage the stops 31D,30D at which point further compression is significantly restricted or prevented.

By providing the two sub-assemblies, the distance through which the spokes can flex before they engage the stops can be varied.

Claims

1. A wheel structure having a rim and a hub linked by a number of generally radially extending spokes, each spoke having substantially the same construction and including a free end spaced from the hub when the rim is in its rest position, and a flexible spur connection attached to the hub, whereby as the rim is compressed towards the hub, the spur will flex until the free end of the spoke engages the hub.

2. A structure according to claim 1, wherein the spur is attached to the rest of the spoke at a point spaced from the free end of the spoke.

3. A structure according to claim 1 or claim 2, wherein the spur is more flexible than the rest of the spoke.

4. A wheel structure having a rim and a hub linked by a number of pairs of generally radially extending spokes extending between the hub and the rim, each pair of spokes being constructed so as to flex in an opposed manner when the rim is compressed towards the hub; and means linking the two spokes to oppose the said flexure.

5. A structure according to claim 4, wherein the means linking the two spokes comprises a tension or compression spring.

6. A wheel structure according to claim 4, wherein a pair of spokes are integrally moulded together with the means linking the two spokes.

7. A structure according to any of claims 4 to 6 , wherein each spoke has a section which is curved in an opposite sense to that of the other spoke of the pair.

8. A structure according to any of claims 4 to 7, wherein each spoke of the pair further includes an abutment portion, the abutment portions of the pairs moving towards each other during compression movement so that they engage after a predetermined degree of compression movement and thus limit further the compression achievable.

9. A wheel structure comprising two wheel sub-assemblies, each sub- ssembly having a rim and a hub linked by a number of generally radially extending spokes, the spokes being resilient so as to allow the rim to compress towards the hub, the sub-assemblies being mounted coaxially together to form the wheel structure.

10. A structure according to claim 9, further comprising means for enabling the sub-assemblies to be connected together in more than one relative circumferential position.

11. A wheel structure comprising a rim and a hub linked by a number of generally radially extending resilient spokes which allow the rim to be compressed towards the hub, circumferentially adjacent spokes being axially offset but including an axially extending portion which will interfere with flexure of an adjacent spoke upon compression of the rim towards the hub so as to limit flexure of both spokes.

12. A wheel structure according to claim 11, and claim 9 or claim 10.

13. A wheel structure according to any of the preceding claims, wherein the structure is made from plastics.