"Ground-Engaging Means"

TECHNICAL FIELD

This invention relates to a ground-engaging means and more particularly to a ground-engaging structure for a vehicle, and to ground-engaging segments which can be assembled to provide such a ground engaging structure.

BACKGROUND

The invention is concerned with ground-engaging structures in the form of wheels and endless tracks which are of non-pneumatic character.

There have been various proposals for wheels having non-pneumatic tyres. The non-pneumatic tyres take the form of a resiliently flexible covering fitted around a wheel rim. Typical examples of such wheels are disclosed in various patents including US 1421029 (Roe), US 1414252 (Brubaker), US 1458844 (Lang), US 1553018 (Barth), US 5078454 (Burns), US 5139066 (Jar an), US 5154490 (Burns), and GB 207632 (Blakey) .

The resiliently flexible coverings in some cases are of one-piece construction and in other cases are formed of an assembly of elements positioned circumferentially around a wheel rim.

Such resiliently flexible coverings have advantages over pneumatic tyres in that they are not susceptible in puncturing. However, as the flexible coverings are formed

of resiliently flexible material such as rubber, they are to some extent vulnerable to damage when operating in harsh environments such as rocky terrain, demolition sites and waste disposal sites. Furthermore, as the surface over which the tyres operate when in such environments is often unstable, difficulties can be encountered in maintaining traction between the tyres and the unstable surface.

SUMMARY OF THE INVENTION

The present invention seeks to provide a ground-engaging structure of non-pneumatic character which can operate in harsh environments.

According to one aspect of the invention there is provided a ground-engaging structure for a vehicle, comprising a load-bearing inner zone of resilient compressible construction and an outer zone around the inner zone for contacting the ground, the outer zone comprising a plurality of traction members positioned around the inner zone, the traction members being of more rigid construction than the inner zone.

The feature whereby the traction members are of more rigid construction than the inner zone provides the ground-engaging structure with the ability to operate in harsher environments than would be the case if the structure was devoid of the traction members. The traction members also facilitate traction between the ground-engaging structure and the surface on which it is intended to operate.

In one arrangement, the ground-engaging structure may comprise a wheel in which case the inner zone may be mounted onto a support surface defined by a rotatable support such as a rim.

In another arrangement, the ground-engaging structure may comprise an endless track in which case the inner zone may be mounted onto a support surface defined by a cyclically movable support such as an endless band of flexible construction movable around track rollers. In an alternative arrangement, the inner zone may comprise a resiliently flexible band movable around track rollers.

The inner zone may present an outer peripheral face against which the traction members are positioned.

The traction members may be substantially rigid or may have at least some resilient flexibility. On the one hand, traction members formed of rigid material such as, for example, metal have the advantage of being more robust in harsh working conditions. On the other hand, traction members with at least some resilient flexibility have the advantage of providing further cushioning and are less aggressive to paved surfaces.

While the traction members may be permanently mounted onto the inner zone, it is preferable that they are releasably fastened thereto. Releasably fastening the traction members onto the inner zone facilitates easy repair of either the inner zone or the traction members in the event of damage. Additionally, releasable fastening of the traction members to the inner zone allows the traction members to be changed in certain circumstances. In this regard, it is possible to have a range of different styles of traction members which can be employed according to the nature of the terrain in which the wheel or endless track is operating. It may be that one particular style of traction member is more suitable in certain terrain than other styles.

The traction members may each comprise a plate with at least one traction element projecting outwardly thereof for engagement with the ground. The traction element may take any suitable form such as a lug or a stud. Conveniently, each plate would be provided with a plurality of such lugs or studs, or possibly a combination thereof.

The traction elements may be arranged in any suitable configuration. Where the traction elements comprise lugs, they may extent circumferentially with respect to the direction of cyclical movement of the wheel or endless track, transversely of such direction, or indeed in any other suitable arrangement.

In one arrangement, the traction members may extend beyond the opposed sides of the inner zone to enhance the extent of protection afforded to the inner zone.

In another arrangement, the traction members may turn inwardly at the outer ends thereof and extend alongside the opposed sides of the inner zone to enhance extent of protection afforded to the inner zone.

The inner zone may comprise a body of resiliently flexible material having a plurality of spaced apart cavities formed therein, the spacing between neighbouring cavities providing load-bearing walls or ribs which resiliently deflect under load.

The inner zone may be of one-piece construction or it may comprise a plurality of elements. Where there are a plurality of elements, they may be positioned in abutting relationship, spaced apart relationship or a combination thereof.

Where the inner zone comprises a plurality of elements, the elements may be, in one arrangement, configured for assembly in a simple side-by-side arrangement or, in another arrangement, configured for positioning in an interfitting disposition. In the former arrangement, the elements may be elongated and generally straight in the longitudinal direction such that the elements simply but one against another at their longitudinal sides. In the latter arrangement, the elements may comprise two sections arranged symmetrically about the midpoint of the element in a V-formation such that when assembled together the elements interfit one with respect to another in a chevron formation. Other arrangements are, of course, also possible.

Where the inner zone comprises a plurality of elements, it is preferable that there is one traction member associated with each element. Other arrangements are, however, possible including traction members arranged to bridge several elements. Furthermore, the traction members can be of a configuration different to that of the elements; for example, the elements may be formed in a generally straight arrangement and the traction members may be of a V-formation , or vice versa.

Where the inner zone comprises a plurality of elements in abutting relationship, the traction members may be arranged to overlie the regions at which neighbouring segments abut for the purposes of inhibiting the ingress of foreign matter such as dirt. This may be accomplished by providing each traction member with a formation extending along one longitudinal side thereof, the arrangement being such that the traction member is fitted onto a respective one of the elements such that the formation overlies the corresponding longitudinal side of the element.

Each element may comprise an outer wall and a pair of longitudinal side walls on opposed sides of the outer wall, with a longitudinal rebate being provided at the junction between each outer wall and side wall. When the elements are assembled together, adjacent longitudinal rebates of neighbouring elements co-operate to form a groove in the region above the junction between the abutting elements. The longitudinal formation provided on the traction member may be configured to be received in the groove, preferably in a snug manner.

Where the inner zone is comprised of a plurality of elements in spaced apart relationship, the traction members may have portions which are receivable in the gaps between neighbouring elements. Such portions may enhance the stability of the elements by providing lateral support for them.

Where each traction member is releasably attachable to at least one of the load-bearing element, attachment means are provided for such purpose.

In one arrangement, the attachment means may comprise one or more fasteners such as bolts for securing the traction member onto the load-bearing element. With such an arrangement, the attachment means may further comprise a mounting plate for engagement with the outer portion of the load-bearing element on a face thereof inwardly of the outer face.

The outer portion of the load-bearing element may be clamped between the traction member and the mounting plate in such a way as to resist flexing of the outer portion when the element is under load.

In another arrangement, the attachment means may comprise a base embedded in or otherwise secured to the load-bearing element and engaging means for releasably engaging the traction member. The engaging means may provide for sliding engagement between the traction member and the base.

In still another arrangement, the traction member may be embedded directly into the load-bearing element. This avoids the need for attachment means although it does not facilitate selective detachment of the traction member.

Preferably the load-bearing elements are individually and removably mounted on a support surface which may comprise a rim of a wheel or an inner band forming part of an endless track. This may be achieved in any suitable manner such as by the provision of mounting bolts extending between the support and a further rigid plate positioned within the hollow element. Other mounting arrangements are, of course, also possible.

According to another aspect of the invention there is provided a ground-engaging segment for a ground-engaging structure, the ground-engaging segment comprising a resiliently compressible load-bearing element of hollow construction having an interior open to atmosphere, and a traction member for attachment to the element, the traction member being of more rigid construction than the element.

The load-bearing element may comprise an elongated, tubular body having at least one longitudinally extending aperture providing interior access to the hollow element, the body having a longitudinal inner face for engagement with a support surface, a longitudinal outer face for carrying at least a portion of at least of one the traction members,

and longitudinal side faces extending between the inner and outer faces, and a longitudinal rebate extending along the junction between each side face and outer face.

Preferably, each traction member is adapted to be supported on the outer face of a respective one of the elements, the traction member being provided with a longitudinal formation on one side thereof which overlies the corresponding longitudinal side face of the element.

Preferably the longitudinal formation is configured to be received in a groove formed by co-operation between the adjacent longitudinal rebates of two elements positioned in side-by-side arrangement.

According to another aspect of the invention there is provided a traction member for use with a load-bearing segment as set out hereinbefore.

Preferably the traction member includes a base having a longitudinal inner face for confronting the longitudinal outer face of the load-bearing element.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood by reference to the following description of several specific embodiments thereof. The description will be made with reference to the accompanying drawings in which:-

Fig. 1 is an isometric view of a wheel according to the first embodiment having a tyre defined by a plurality of ground engaging segments; Fig. 2 is a fragmentary side view of the wheel of Fig. 1, showing one of the ground engaging segments;

Fig. 3 is a view similar to Fig. 2 with the exception that it is in cross-section to reveal mounting bolts;

Fig. 4 is an isometric view showing the traction member and the load-bearing element of the ground engaging segment;

Fig. 5 is an isometric view of a mounting plate employed in the wheel;

Fig. 6 is a schematic view of a segment according to a second embodiment;

Fig. 7 is a schematic view of a wheel according to a further embodiment, with one of the segments removed; and

Fig. 8 is a fragmentary side view of the wheel of Fig.

7;

Fig. 9 is an isometric view of a traction member forming part of the wheel of Fig. 7;

Fig. 10 is a fragmentary wheel of a wheel according to a still further embodiment, with several traction members removed to more fully reveal the load-bearing elements; and

Fig. 11 is a fragmentary side view of an endless track according to a still further embodiment.

BEST MODES OF PERFORMING INVENTION

The various embodiments shown in the drawings are directed to ground engaging structures for vehicles which are intended for operation in conditions where the ground is aggressive and so unstable as not to be conducive to good traction. A typical example of such a vehicle would be a bulldozer operating at a waste disposal site.

The first embodiment, which is shown in Figs. 1 to 5, is directed to a ground engaging structure in the form of a wheel comprising a rigid rim 11 and a plurality of ground

engaging segments 13 each individually and removably mounted onto the rim. The ground engaging segments 13 are positioned so that they abut one another.

Each ground engaging segment 13 comprises a load-bearing cushioning element 15 of tubular construction and a rigid traction member 17. The cushioning element 15 may be formed of elastomeric material such as rubber and the traction member 17 may be formed of metal.

The assembly of cushioning elements 17 provides a cushioning inner zone 18 and the traction members 17 provide a protective outer zone 19 about the inner zone.

Each cushioning element 15 comprises an inner wall 21, an outer wall 23, and two side walls 25 extending between the inner and outer walls. The inner wall 21 defines an inner face 22 which is configured for engagement against the curved outer surface of the rim 11. The outer wall 23 defines an outer face 24 against which the traction member 17 locates, as will be explained in more detail later. The two side walls 25 each define longitudinal side faces 26. A longitudinal rebate 27 extends between the two ends 28 of the cushioning element 15, at the junction between the outer face 24 and each side face 26.

When the cushioning elements 15 are in abutting relationship, the rebates 27 of neighbouring elements co-operate to form grooves 29.

The two side walls 25 of each cushioning element are greater in thickness than the inner wall 21 and the outer wall 23. The relative proportions of the various walls and the longitudinal rebates 27 are selected so that the side walls 25 of abutting cushioning elements deflect in unison

rather than independently of each other. In other words, abutting side faces 26 of neighbouring cushioning elements remain in face to face engagement during deflection of the ground engaging means rather than separating from each other.

The rigid traction member 17 comprises a base 31 and a plurality of traction lugs 33 formed integrally with the base. The base 31 defines an inner face 35 and the traction lugs 33 extend in the direction away from the face 35.

The traction lugs 33 are elongated and extend along the full length of the base. One lug 33 extends along each longitudinal side of the base 31 and together with the base defines a longitudinal side face 37 of the traction member. The longitudinal side faces 37 are inclined inwardly with respect to the traction member in the direction away from the inner face 35.

The width of the traction member 17 corresponds to the width of the outer face 24 of the cushioning element 15 as defined by spacing between the rebates 27. As a result of this, the inner face 35 on the traction member is co-terminus in the lateral direction with the outer face 24 of cushioning element 15. The longitudinal recesses 27 on the cushioning element 15 and the longitudinal side faces 37 on the traction member are configured to provide a smooth transition between themselves, as best seen in Figs. 2 and 3 of the drawings. This ensures that there are no exposed edges at the longitudinal junction between the cushioning element 15 and the traction member 17.

The traction member 17 is removably mounted onto the cushioning element 15. For this purpose, corresponding mounting holes 41 and 43 are provided in the top wall 23 of

the cushioning element 15 and the base 31 of the traction member 17 respectively. When the traction member 17 is in position on the cushioning element 15 with the face 35 of the traction member in engagement with the face 24 of the cushioning element, the holes 41 and 43 are in alignment to receive mounting bolts 45. A mounting plate 47 is provided within the interior of the cushioning element in engagement with the inner face of the upper wall 23. The mounting plate is of rigid construction.

The mounting plate 47 not only assists in anchoring the traction member 17 to the cushioning element 15 but together with the rigid traction member 17 serves to resist flexing of the top wall 23 of the tubular element 15. As a consequence of this, effectively all of the flexing of the cushioning element under load occurs in the side walls 25 and the regions where each side wall merges with the top and bottom walls 23 and 24 respectively.

As previously mentioned, the ground engaging segments 13 are individually and removably mounted onto the rim 11. This is achieved by way of mounting bolts 49 which extend through aligned apertures 51 and 53 in the bottom wall 21 of each cushioning 15 element and the rim 11 respectively. A mounting plate 55 locates against the inner face of the inner wall 21 so that the inner wall can be clamped between the mounting plate and the rim. The mounting plate 55 together with the rim 11 serve to resist flexing of the inner wall 21 in much the same way as the traction member 17 and the mounting plate 47 serves to resist flexing of the upper wall 23.

The wheel according to the embodiment has good traction capabilities in soft ground conditions owing to the presence of the traction lugs 33 on the traction member 17. Because of the rigid characteristics of the traction

member, it is less likely to be damaged when operating in adverse conditions where damage to elastomeric materials may occur. The wheel has some cushioning characteristics owing to the presence of the cushioning elements 15 which support the traction members 17. In the event of damage to one of the traction members, it can be removed and replaced quite easily. Similarly, in the event that of damage to one of the cushioning elements 15, it too can be removed and replaced quite readily.

Referring now to Fig. 6 of the drawings, the segment 13 according to the second embodiment is similar to that of the first embodiment with the exception as to the manner of attachment of the traction member 17 onto the cushioning element 15. In this embodiment, the means of attachment comprises a base 51 which is detachably secured to the cushioning element 15 and which is adapted to releasably engage the traction member 17. The base 51 is provided with a longitudinal track 53 having an open end 54 for εlidably receiving an attachment plate 56 provided on the traction member 17. When the plate 56 of the traction member is slidably received in the track 53, the traction member is restrained against lateral separation from the load-bearing element.

The attachment plate 56 may be of metal or other rigid material, or of a resilient material to provide further cushioning and afford some protection to paved surfaces.

Referring now to Figs. 7, 8 and 9, the wheel according to the third embodiment is similar to that according to the first embodiment with the exception of the provision of a longitudinal formation 61 on one side of each traction member 17. The longitudinal formation 61 extends beyond the adjacent side wall of the corresponding cushioning element 15 and is snugly received in the groove 29 provided

by the rebates 27 of the two neighbouring segments. The longitudinal formation 61 overlies the junction between the two abutting cushioning elements to inhibit the ingress of foreign matter such as dirt. The longitudinal formation 61 has a curved undersurface 63 which conforms to the curvature of the groove 29 to provide the snug fit as described. The curvature also ensures that there is clearance between the formation 61 and the adjacent edge of the neighbouring traction member 17 when the two traction members move angularly with respect to each other thereby to avoid any interference between them.

With this arrangement, neighbouring traction members 17 are in close proximity with respect to each other. This facilitates the linking of neighbouring traction members together to form an articulated structure if so desired. The linking may be achieved in any suitable way such as a hinge operating between neighbouring members. The linking can also be employed in other embodiments without the need for the longitudinal formations 61 occupying the grooves 29.

In the embodiments which have been described, the cushioning elements 15 and the traction members 17 have been described and illustrated as being of straight formation. It will be appreciated that the elements and/or the traction members may take other configurations such as a V-formation to provide a chevron pattern on the wheel. One such arrangement is illustrated in the embodiment of Fig. 10 where each cushioning element comprises two integral sections arranged symmetrically about the midpoint of the element in a V-formation. With this arrangement the neighbouring cushioning elements are in an interfitting disposition. In this embodiment the traction members are straight and extend across the rim, generally parallel to the axis of rotation. In this way, each traction member extends across several cushioning elements as shown in the drawing.

In various of the embodiments which have been described, the cushioning elements extend across the rim so as to be parallel to the axis of rotation of the wheel. In other embodiments, the cushioning elements may be disposed angularly with respect to the axis of rotation of the wheel or indeed in other arrangements.

In still another embodiment (which is also not shown) the cushioning elements are of increased width in the circumferential direction of the wheel so as to reduce the number of segments which must be fitted onto a wheel rim to form an assembled tyre. In this arrangement, the cushioning elements may each have a plurality of longitudinal passageways extending therethrough in spaced apart relationship. Thus, the wider cushioning elements each have the appearance somewhat of several elements of the tyre described in the earlier embodiments positioned in side-by-side relationship but formed integrally together.

In the various embodiments described, the traction members have been releasably attached to the cushioning elements. It is, of course, possible for the traction members may be embedded into, or otherwise bonded directly onto, the cushioning elements.

While in the embodiments the wheel has been described in an arrangement where the cushioning elements 15 abut one another around the circumference of the rim, in other arrangements the cushioning elements could be in spaced relationship. Indeed, the traction members may be provided with portions which are received in the gaps between such spaced apart elements. This arrangement may enhance the lateral stability of the cushioning elements by providing lateral support for them.

The cushioning elements may be closed at their ends to resist the ingress of dirt and other foreign matter. In some cases at least one ventilation aperture may be provided in each element to open the interior of the element to atmosphere. In other cases, the interiors of the cushioning elements may be closed to the exterior.

The various embodiments which have been described have been directed to ground-engaging structures in the form of wheels. It is possible for ground-engaging structures according to the invention to be in the form of endless tracks. One such arrangement is illustrated in Fig. 11 where a flexible band 71 provides the inner zone 18, the flexible band being arranged for cyclical movement about a pair of track rollers 73, one of which appears in the drawings.

It should be appreciated that the scope of the invention is not limited to the scope of the various embodiments described.