| 1. | A loadbearing deformable nonpneumatic tyre [10] adapted to be mounted on an annular wheel hub [14] having an axis of rotation [Y], the tyre [10] comprising an outer annular band [12] to which a tread [26] is fitted; and at least two resilient tensioning members [16a and 16b] having outer and inner annularly disposed ends [16 (i) and 16 (ii) ], the outer ends [16 (i) ] of the tensioning members [16a and 16b] being annularly disposed on the outer annular band [12], the tensioning members [16a and 16b] extending inwardly from the outer annular band [12] towards the axis of rotation [Y], the inner ends [16 (ii) ] of the tensioning members [16a and 16b] being adapted to be secured to the wheel hub [14], the tensioning members [16a and 16b] at least in part being angularly disposed relative to the tread [26] and relative to a circumferential plane [X] bisecting the annular band [12] and which is perpendicular to the axis of rotation [Y]. |
| 2. | The tyre [10] according to claim 1 wherein the annular band [12] has two opposite parallel edges [12.1 and 12.2], the tyre [10] being characterised therein that the tensioning members [16a and 16b] each comprise of two sections, namely an outer section [16.1] and an inner section [16. 2] wherein each section has an outer and an inner end [16 (i) and 16 (ii) ], the outer section [16.1] being disposed at its outer end<BR> [16 (i) ] proximate an edge [12.1 or 12.2] of the annular band [12] and extending inwardly, at a first angle, towards the circumferential plane [X] and towards an annular intermediate zone [18] defined radially between and coaxially with the annular band [12] and the wheel hub [14]; the inner section [16.2] extending outwardly, at a second angle, away from the circumferential plane [X] and from the annular intermediate zone [18] to the wheel hub [14]. |
| 3. | The tyre [10] according to claim 2 characterised therein that the tensioning members [16a and 16b] have a substantially curvilinear profile so as to reduce the incidence of material stresses in the tensioning members [16a and 16b], the tyre [10] in particular being characterised therein that the outer section [16.1] of each tensioning member at least in part has an Sshaped profile between the annular band [12] and the intermediate zone [18]. |
| 4. | The tyre [10] according to claim 2 characterised therein that two opposing tensioning members [16a and 16b] are connected to each other by means of an intermediate spacer [22] arranged proximate the intermediate zone [18] and orientated in a direction substantially parallel to the axis of rotation [Y], the intermediate spacer [22] being adapted to maintain the two opposing tensioning members [16a and 16b] at a predetermined distance from each other so as to manipulate compression characteristics of the tyre [10], and particularly to limit displacement of the tensioning members [16a and 16b] towards each other when the tyre [10] is under radial compression. |
| 5. | The tyre [10] according to claim 4 characterised therein that the intermediate spacer [22] is an annular spacer [22] arranged radially between and coaxially with the annular band [12] and the wheel hub [14]. |
| 6. | The tyre [10] according to claim 4 characterised therein that the tyre [10] comprise a number of distinct and circumferentially spacedapart spacers [22], preferably located at opposing radial positions on the tyre [10]. |
| 7. | The tyre [10] according to claim 4 characterised therein that the intermediate spacer [22] is selected from a group including, but not limited to, a plate, having two opposing edges and connected at either side thereof to the opposing tensioning members [16a and 16b]; a rubber or the like resiliently deformable spacer [22] connected at either side thereof to the opposing tensioning members [16a and 16b]; or an extendable spacer [22], such as an extender screw cylinder. |
| 8. | The tyre [10] according to claim 2 characterised therein that each tensioning member [16a and 16b] is a substantially continuous member between the annular band [12] and the wheel hub [14] such that the inner and outer sections [16.1 and 16. 2] are integral with one another. |
| 9. | The tyre [10] according to claim 2 characterised therein that the inner and outer sections [16.1 and 16.2] of each tensioning member [16a and 16b] are two separate sections of material whose opposing ends [16 (i) and 16 (ii)] meet and are secured to each other within the intermediate zone [18]. |
| 10. | The tyre [10] according to claim 9 characterised therein that the outer section [16. 1] <BR> <BR> of the tensioning member [16a and 16b] is welded at its outer end [16 (i) ] to an edge<BR> [12.1 or 12.2] of the annular band [12], and secured at its inner end [16 (ii) ], within the intermediate zone [18], to an outer end [16 (i) ] of the inner section [16.2] of the tensioning member, the inner section [16.2] in turn being connected at its inner end [16 (ii) ] to a periphery of the wheel hub [14]. |
| 11. | The tyre [10] according to claim 1 characterised therein that the tensioning members [16a and 16b] are disposed at their respective outer ends [16 (i)] proximate opposing edges [12.1 and 12.2] of the annular band [12] and extend inwardly, at a first angle, towards the circumferential plane [X] and towards the annular intermediate zone [18], and extending at the same first angle away from the circumferential plane [X] and from the annular intermediate zone [18] to the wheel hub [14], such that in a radial plane [Z] the tensioning members [16a and 16b] intersect each other so as to form a crosswise Xconfiguration. |
| 12. | 12 The tyre [10] according to claim 11 characterised therein that the tensioning members [16a and 16b] extend substantially tangentially between the annular band [12] and the annular wheel hub [14]. |
| 13. | The tyre [10] according to claim 1 characterised therein that the tensioning members [16a and 16b] are disposed at their respective outer ends [16 (i)] proximate opposing edges [12.1 and 12.2] of the annular band [12] and extend inwardly, at a first angle, towards the circumferential plane [X] and towards the wheel hub [14], such that in a radial plane [Z] the tensioning members [16a and 16b] meet each other at the wheel hub [14] so as to form a Vconfiguration. |
| 14. | The tyre [10] according to claim 13 characterised therein that each tensioning member [16a and 16b] is a substantially continuous annular member such that the two tensioning members [16a and 16b] together define two opposing annular diaphragms between the annular band [12] and the wheel hub [14]. |
| 15. | The tyre [10] according to claim 14 characterised therein that the two opposing tensioning members [16a and 16b] define opposing sidewalls of the tyre [10]. |
| 16. | The tyre [10] according to claims 11 or 13 characterised therein that the tyre [10] comprises a plurality of independent tensioning members [16a and 16b], circumferentially spacedapart in substantially twobytwo configuration so that every pair of tensioning members [16a and 16b] are connected at their respective outer ends [16 (i) ] to opposing edges [12.1 and 12. 2] of the annular band [12] and extend inwardly towards the circumferential plane [X]. |
| 17. | The tyre [10] according to claim 16 characterised therein that every two opposing tensioning members [16a and 16b] are offset from one another in a radial plane [Z]. |
| 18. | The tyre [10] according to claim 1 characterised therein that the tensioning members [16a and 16b] are angularly disposed, not only to a circumferential plane [X] of the tyre [10], but also to a radial crosssectional plane [Z] of the tyre [10] and relative to each other. |
| 19. | The tyre [10] according to claim 1 characterised therein that the tensioning members [16a and 16b] are resiliently deformable under compression so as to provide shock absorbing characteristics to the tyre [10], the tensioning members [16a and 16b] being comprised of a material characterised therein that it exhibits relatively greater strength when a tensional force is applied thereto as opposed to when a compression force is exerted thereon. |
| 20. | The tyre [10] according to claim 19 characterised therein that the tensioning members [16a and 16b] is of a material selected from a group including, but not limited to, flexible, woven mesh, such as a canvas material ; canvas material impregnated with a resiliently deformable material, such as a polymer or elastomeric composition; canvas material having rubber fibres interwoven therein; vulcanised tensioning members [16a and 16b]; and spring steel or the like metallic material. |
| 21. | The tyre [10] according to claim 1 characterised therein that it is releasably mounted on a split rim [24] having outer and inner rim sections [24.1 and 24.2] that are releasably connectable to each other to form a wheel rim, such that the split rim [24] defines the wheel hub [14]. |
| 22. | The tyre [10] according to claim 21 characterised therein that the tensioning members [16a and 16b] are bolted to, clamped between or otherwise connected to the outer and inner rim sections [24.1 and 24.2] of the split rim [24]. |
| 23. | A wheel comprising a tyre [10] according to anyone of claims 1 to 22, mounted on a wheel hub [14]. |
| 24. | A nonpneumatic tyre [10] substantially as herein illustrated and exemplified with reference to the accompanying drawings. |
| 25. | A wheel substantially as herein illustrated and exemplified with reference to the accompanying drawings. |
BACKGROUND ART Various categories of tyres are known in the art, including tubeless solid tyres, tubeless pneumatic tyres and pneumatic tyres conventionally comprising an inner tube.
Pneumatic tyres are commonly used in commercial applications, such as long distance road haulage. An obvious disadvantage of pneumatic tyres is that they are vulnerable to punctures and valve leakages, the hazards and inconvenience of which are well known.
More particularly, where a pneumatic tyre used on a long-haulage vehicle is punctured it may be difficult or even impossible for a driver to replace the punctured tyre himself and the consequent downtime may result in penalties for the carrier. Furthermore, puncture of a tyre on a driving wheel of an articulated vehicle may cause such a vehicle to jack-knife dangerously and/or spill its load. Moreover, puncture of any pneumatic tyre on a driving wheel of any vehicle can result in a driver losing control of the vehicle, often with tragic results.
Non-pneumatic tyres are also well known in the art and have routinely been used on vehicles where neither handling, nor cushioning of a load, is a prime consideration, as for example in fork lift trucks, carts, wheelbarrows, tricycles and the like. Such tyres are also particularly useful on rough terrain and in harsh conditions, such as in mining environments
or in military applications, where tyres are prone to damage. A considerable advantage associated with non-pneumatic tyres is of course their resistance to fail when punctured.
One such deformable non-pneumatic tyre is disclosed in European patent number EP 1,112. 1 and 12.2, 544 B1, which discloses a non-pneumatic tyre having an inner annulus and an outer annulus, being interconnected by means of a plurality of radial spokes. The spokes are capable of opposing radial compression stresses and are shaped and arranged between the inner and outer annuli such that their flexibility in a meridian plane is substantially less than their flexibility in a circumferential plane. Stabilising means in the form of cables, connecting the inner and outer annuli, is provided in order to minimise the amplitude of relative circumferential rotation between the outer and inner annuli.
EP 0 ; 399,383 discloses another non-pneumatic tyre. In this patent, the non-pneumatic tyre comprises of generally cylindrical inner and outer annular members, the two members being connected by a plurality of axially extending, circumferentially spaced ribs (forming a trapezoidal shape with the inner and outer members) which have certain characteristics in compression, giving the tyre unique handling characteristics.
A further non-pneumatic resilient tyre is described in EP 0,420, 033, wherein the inner volume of the tyre contains a resiliently deformable honeycomb structure. The tyre deforms under compression to give the tyre certain compressive qualities, which influence the tyre's handling.
US 5,050, 656 discloses a wheel having a circumferentially extending shock-absorbing element that is curvilinear in cross-section extending radially from the hub underneath a conventional pneumatic tyre. The shock-absorbing element provides a resilient spring force under compression from inside the tyre. Radial slots are provided in C-shaped sidewalls to allow for resilient deformation in compression.
In US 1,388, 350 a non-pneumatic tyre incorporates V-shaped spring members, wherein the bottom of the V is attached to the rim of a wheel, and the two free ends of the V abut the inner circumference of the tyre-wall. When force is applied to the tyre the outer wall is displaced towards the rim, and the V-shaped spring members oppose such displacement.
The V-shaped spring members allow the tyre to deform resiliently under compression, for example when a vehicle's weight is supported on it.
Prior art non-pneumatic tyres, and certainly those mentioned above, generally all suffer from one of more of the following substantial disadvantages, namely (i) excessive heat build-up within the tyre, (ii) excessive weight of the tyre, (iii) lack of tyre deformability, (iv) lack of tyre stability, especially during turning and hard braking, (v) poor shock-absorbing characteristics, (vi) as well as complicated manufacturing technologies and resultant excessive manufacturing costs. The use of non-pneumatic tyres in general automotive applications is often less than satisfactory because of undesirable handling characteristics.
Also, it is often not possible to provide a variable spring rate in prior art non-pneumatic tyres without changing the tyre's structural configuration or the materials of its construction.
OBJECT OF THE INVENTION It is an object of this invention to provide a novel non-pneumatic tyre, which at least partially alleviates some of the disadvantages associated with the prior art and/or provides a useful alternative to known non-pneumatic tyres.
More particularly, it is an object of the present invention to provide a non-pneumatic tyre that is able to deform locally, that is, near the point where the tyre contacts a surface, yet performs its load-bearing and cushioning functions in a manner analogous to that in which a pneumatic tyre does.
DISCLOSURE OF THE INVENTION According to the invention there is provided a load-bearing deformable non-pneumatic tyre adapted to be mounted on an annular wheel hub having an axis of rotation, the tyre comprising an outer annular band to which a tread is fitted; and at least two resilient tensioning members having outer and inner annularly disposed ends, the outer ends of the tensioning members being annularly disposed on the outer annular band, the tensioning members extending inwardly from the outer annular band towards the axis of rotation, the inner ends of the tensioning members being adapted to be secured to the wheel hub, the tensioning members at least in part being angularly disposed relative to the tread and relative to a circumferential plane bisecting the annular band and which is perpendicular to the axis of rotation.
For the purposes of this specification, a circumferential plane is defined as being a plane extending through the circumference of the tyre and being orientated transversely
perpendicular to the axis of rotation of the tyre. A radial cross-section is a cross section through a radius of the tyre in the direction of the axis of rotation and orientated transversely perpendicular to the circumferential plane, and radial plane has the same meaning. The axis of rotation should be interpreted as the axis about which the wheel, and hence the tyre, rotates in use.
The annular band may have two opposite parallel edges.
According to a first aspect of the invention the tensioning members each may comprise of two sections, namely an outer section and an inner section wherein each section has an outer and an inner end, the outer section being disposed at its outer end proximate an edge of the annular band and extending inwardly, at a first angle, towards the circumferential plane and towards an annular intermediate zone defined radially between and coaxially with the annular band and the wheel hub; the inner section extending outwardly, at a second angle, away from the circumferential plane and from the annular intermediate zone to the wheel hub.
The tensioning members may have a substantially curvilinear profile so as to reduce the incidence of material stresses in the tensioning members. In particular, the outer section of each tensioning member may at least in part have an S-shaped profile between the annular band and the intermediate zone.
Two opposing tensioning members may be connected to each other by means of an intermediate spacer arranged proximate the intermediate zone and orientated in a direction
substantially parallel to the axis of rotation. The intermediate spacer may be adapted to maintain the two opposing tensioning members at a predetermined distance from each other so as to manipulate compression characteristics of the tyre. More particularly, the intermediate spacer may be adapted to limit displacement of the tensioning members towards each other when the tyre is under radial compression.
The intermediate spacer may be an annular spacer arranged radially between and coaxially with the annular band and the wheel hub. In an alternative embodiment of the invention the tyre may comprise a number of distinct and circumferentially spaced-apart spacers, preferably located at opposing radial positions on the tyre.
The intermediate spacer may be a plate having two opposing edges and connected at either side thereof to the opposing tensioning members. Alternatively, the intermediate spacer may be a rubber or the like resiliently deformable spacer connected at either side thereof to the opposing tensioning members. In yet a further alternative, the spacer may be an extendable spacer, such as an extender screw cylinder.
Each tensioning member may be a substantially continuous member between the annular band and the wheel hub such that the inner and outer sections are integral with one another.
Alternatively, the inner and outer sections of each tensioning member may be two separate sections of material whose opposing ends meet and are secured to each other within the intermediate zone. More particularly, in this embodiment of the invention the outer section
of the tensioning member may be welded at its outer end to an edge of the annular band, and secured at its inner end, within the intermediate zone, to an outer end of the inner section of the tensioning member, the inner section in turn being connected at its inner end to a periphery of the wheel hub.
According to a second aspect of the invention the tensioning members may be disposed at their respective outer ends proximate opposing edges of the annular band and extend inwardly, at a first angle, towards the circumferential plane and towards the annular intermediate zone, and extending at the same first angle away from the circumferential plane and from the annular intermediate zone to the wheel hub, such that in a radial plane the tensioning members intersect each other so as to form a cross-wise X-configuration.
In this embodiment of the invention the tensioning members may extend substantially tangentially between the annular band and the annular wheel hub.
According to a third aspect of the invention the tensioning members may be disposed at their respective outer ends proximate opposing edges of the annular band and extend inwardly, at a first angle, towards the circumferential plane and towards the wheel hub, such that in a radial plane the tensioning members meet each other at the wheel hub so as to form a V-configuration.
Each tensioning member may be a substantially continuous annular member such that the two tensioning members together define two opposing annular diaphragms between the annular band and the wheel hub. In this form of the invention the two opposing tensioning
members may define opposing sidewalls of the tyre, although it should be understood that, in addition to the tensioning members, sidewalls may be provided between the annular band and the wheel hub, primarily for aesthetic purposes and to prevent unauthorised access to and tampering with the tensioning members.
In an alternative form of the invention, the tyre may comprise a plurality of independent tensioning members, circumferentially spaced-apart in substantially two-by-two configuration so that every pair of tensioning members are connected at their respective outer ends to opposing edges of the annular band and extend inwardly towards the circumferential plane. In this form of the invention, two opposing tensioning members may be offset from one another in a radial plane.
The tensioning members may be angularly disposed, not only to a circumferential plane of the tyre, but also to a radial cross-sectional plane of the tyre and relative to each other.
The tensioning members may be resiliently deformable under compression so as to provide shock-absorbing characteristics to the tyre. The tensioning members may be comprised of a material characterised therein that it exhibits relatively greater strength when a tensional force is applied thereto as opposed to when a compression force is exerted thereon. In one embodiment of the invention, the tensioning members may be of a flexible, woven mesh, such as a canvas material. In another embodiment, the tensioning members may be of a canvas material impregnated with a resiliently deformable material, such as a polymer or elastomeric composition. The tensioning members may be of canvas material having rubber fibres interwoven therein. The tensioning members may be
vulcanised. The tensioning members alternately may be of spring steel or the like metallic material.
The non-pneumatic tyre according to the invention may releasably be mounted, in use, on a split rim having outer and inner rim sections that are releasably connectable to each other to form a wheel rim. The split rim may define the wheel hub. In particular, the tensioning members may be bolted to, clamped between or otherwise connected to the outer and inner rim sections of the split rim.
The invention extends to a wheel fitted with the non-pneumatic tyre according to the invention.
These and other features of the invention are described in more detail below.
SPECIFIC EMBODIMENT OF THE INVENTION In order more clearly to illustrate the invention, embodiments thereof are described hereunder purely for the purposes of illustration, without limiting the scope of the invention, wherein- Figure 1 is a first perspective view of a tyre, according to the invention, fitted to a rim and illustrating a continuous annular tensioning member; Figure 2 is a partial schematic radial cross-sectional view of a wheel comprising a first embodiment of a non-pneumatic tyre according to the invention, fitted to a split rim, and illustrating the outer and inner sections of the tensioning
members, wherein the tyre includes a flexible spacer plate, typically suitable for use on motor vehicles, for connecting the tensioning members to each other; <BR> <BR> . Figure 3 is a partial schematic radial cross-sectional view of a tyre, illustrating a more<BR> "f rigid spacer plate suitable for use on more heavy vehicles, such as trucks; Figure 4 is a partial schematic radial cross-sectional view of an alternative embodiment of the tyre, illustrating the S-shaped profile of the outer section of the tensioning member; Figure 5 illustrates an alternative spacer in the form of an extension screw cylinder between the opposing tensioning members; Figure 6 illustrates a rubber spacer located between the tensioning members; Figure 7 is a partial schematic radial cross-sectional view of a wheel comprising yet another embodiment of a non-pneumatic tyre according to the invention, the tyre being fitted to a split rim and including two tensioning members that intersect each other to form an X-configuration, and bolted to a split-rim ; Figure 8 is a cut-away perspective view of the wheel and tyre arrangement of Figure 7, illustrating the offset configuration of the tensioning members; Figure 9 is a side view of the wheel and tyre arrangement of Figures 7 and 8; Figure 10 is a partial radial cross-sectional view of yet a further embodiment of the invention wherein the tyre includes two tensioning members extending between the annular band and the wheel hub in a V-configuration; Figure 11 is a partial radial cross-sectional view of the wheel and tyre arrangement of Figure 10, illustrating the manner in which the annular band and the tensioning members deform when the tyre is under radial compression;
Figure 12 is a cut-away perspective view of the wheel of Figures 10 and 11; Figure 13 illustrates a tyre that includes two tensioning members, extending between the band and the wheel hub in an alternative embodiment of the X- configuration; and Figure 14 is a stress analysis model of the tyre of Figure 13 shown under loading.
A deformable non-pneumatic tyre according to the invention is generally designated by reference numeral [10]. The tyre [10] is adapted to be mounted on an annular wheel hub [14] having an axis of rotation [Y]. The tyre comprises an outer annular band [12], which carries a rubber tread [26]. The annular band [12] has two opposite parallel edges [12.1 and 12. 2].
The tyre [10] also comprises at least two resilient tensioning members [16a and 16b] <BR> <BR> having outer and inner annularly disposed ends [16 (i) and 16 (ii) ]. The outer ends [16 (i) ] of the tensioning members [16a and 16b] are annularly disposed on the outer annular band [12]. The tensioning members [16a and 16b] extend inwardly from the outer annular band <BR> <BR> [12] towards the axis of rotation [Y]. The inner ends [16 (ii) ] of the tensioning members are adapted to be secured to the wheel hub [14]. The tensioning members [16a and 16b] are characterised therein that they are at least in part angularly disposed relative to the tread [26] and relative to a circumferential plane [X] bisecting the annular band [12] and which is perpendicular to the axis of rotation [Y].
In the embodiments of the invention illustrated in Figures 1 to 6, the tensioning members [16a and 16b] comprise of two sections, namely an outer section [16.1] and inner section
[16.2], which each has an outer end [16 (i) ] and an inner end [16 (ii) ]. Each of the outer<BR> sections [16 (1)] is disposed at its outer end [16 (i) ] proximate an edge [12. 1 or 12.2] of the annular band [12] and extend inwardly, at a first angle, towards the circumferential plane [X] and towards an annular intermediate zone [18] defined radially between and coaxially with the annular band [12] and the wheel hub [14]. The inner section [16.2] extends outwardly, at a second angle, away from the circumferential plane [X] and from the annular intermediate zone [18] to the wheel hub [14]. The arrangement may be such that the opposing tensioning members [16a and 16b] define the opposing sidewalls of the tyre [10].
This is the case, for example, in Figures 1 to 6 and Figure 14. However, it will be appreciated that the tyre may include additional sidewalls [15a and 15b], such as are illustrated in Figures 7,10, 11 and 12, to prevent visual access to and unauthorised tampering with the tensioning members [16a and 16b].
As can best be seen in Figures 1,12 and 14, the tensioning members [16a and 16b] may comprise a continuous annular member extending between the annular band [12] and the wheel hub [14] about the circumference of the tyre [10]. However, the tensioning members [16a and 16b] alternatively may be defined by a plurality of tensioning members, wherein each tensioning member extends between the annular band [12] and the wheel hub [14] and wherein the tensioning members [16a and 16b] are interruptedly arranged in circumferentially spaced-apart configuration. This is best illustrated in Figures 8 and 9.
In the embodiments illustrated in Figures 2 to 6, the inner and outer sections [16.1 and 16.2] of each tensioning member [16a and 16b] are two separate sections of material <BR> <BR> whose opposing ends [16 (i) and 16 (ii) ] meet and are secured to each other within the
intermediate zone [18]. More particularly, in this embodiment of the invention the outer section [16.1] of the tensioning member [16a and 16b] is welded at its outer end [16 (i) ] to an edge [12.1 or 12.2] of the annular band [12], and is secured at its inner end [16 (ii)], within the intermediate zone [18], to an outer end [16 (i) ] of the inner section [16.2] of the tensioning member [16a and 16b], the inner section [16.2] in turn being connected at its inner end [16 (ii) ] to a periphery of the wheel hub [14].
Two opposing tensioning members [16a and 16b] are connected to each other by means of an intermediate spacer [22] arranged proximate the intermediate zone [18] and orientated in a direction substantially parallel to the axis of rotation [Y]. The intermediate spacer [22] is adapted to maintain the two opposing tensioning members [16a and 16b] at a predetermined distance from each other so as to manipulate compression characteristics of the tyre [10], and particularly to limit displacement of the tensioning members [16] towards each other when the tyre [10] is under radial compression.
In one embodiment of the invention, illustrated in Figures 2,3 and 4, the intermediate spacer [22] is a plate connected at either side thereof to the engaging points [20] of the opposing tensioning members [16a and 16b]. In Figure 5 the intermediate spacer [22] is an extender screw cylinder, whereas Figure 6 illustrates the spacer [22] as being a rubber or the like resiliently deformable spacer connected to the opposing tensioning members [16a and 16b].
It will be appreciated from Figures 2 to 4 and 6 that the intermediate spacer [22] can be an annular spacer [22] arranged radially intermediate and coaxial with the annular band [12]
and inner annular wheel hub [14]. Alternatively, the spacer [22] can comprise of a number of distinct spacers located at opposing radial positions on the tyre [10]. This would typically be the case where the spacer [22] is an extender screw cylinder or a rubber member, as illustrated in Figures 5 and 6 respectively. In such cases, spacers [22] would typically be arranged at radially opposing positions on the tyre, for example in the 12 o'clock, 6 o'clock, 3 o'clock and 9 o'clock positions.
In the embodiments of the invention illustrated in Figures 4 to 6, the outer section [16. 1] of the tensioning member [16a and 16b] has a substantially curvilinear profile so as to reduce the incidence of material stresses in the tensioning member. In particular, it has a partly S- shaped profile between the annular band [12] and the intermediate zone [18].
The tensioning members [16] in Figures 2 to 6 are typically of high quality spring steel or the like resiliently deformable metallic material. Spring steel exhibits relatively greater strength when a tensional force is applied thereto as opposed to when a compression force is exerted thereon.
It is envisaged that the non-pneumatic tyre [10] according to the invention will releasably be connected in use to a split rim [24], characterised in having outer and inner rim sections [24.1 and 24. 2] that are releasably connectable to each other, such that when connected, the inner and outer rim sections [24. 1 and 24.2] together form the split rim [24]. In such a case, and as illustrated in the accompanying embodiments, the split rim [24] would define <BR> <BR> the wheel hub [14]. In particular, the inner ends [16 (ii) ] of the inner sections [16. 2] of the tensioning members [16a and 16b] are bolted or otherwise connected to the split rim [24].
Reference is now made particularly to Figures 7 to 13, which illustrate the tyre [10] fitted on a split rim 24 comprising an inner rim section 24.1 and an outer rim section 24.2.
In these embodiments of the invention the tensioning members [16a and 16b] typically comprise of spring steel that is approximately 2mm in diameter. In the embodiments of Figures 7 to 9 and 13 the two tensioning members [16a and 16b] are disposed at their <BR> <BR> respective outer ends [16 (i) and 16 (ii) ] proximate opposing edges [12.1 and 12.2] of the annular band [12] and extend inwardly, at a first angle, towards the circumferential plane [X] and towards the annular intermediate zone [18]. They then extend further, at the same first angle, away from the circumferential plane [X] and from the annular intermediate zone [18] to the wheel hub [14], such that in a radial plane [Z] the tensioning members [16a and 16b] intersect each other so as to form a cross-wise X-configuration. in particular, the <BR> <BR> inner ends [16 (ii) ] of the tensioning members [16a and 16b] are bolted to opposing peripheral flanges of the inner and outer rim sections [24.1 and 24.2] of the split rim [24]. It will be appreciated that in this embodiment of the invention the tensioning members [16a and 16b] extend substantially tangentially between the annular band [12] and the annular wheel hub [14].
In the embodiments illustrated in Figures 7,10, 11 and 12, the tyre [10] includes sidewalls [15a and 15b] that are comprised of approximately 0.5mm spring steel. The sidewalls [15a and 15b] are spot-welded to the annular band [12] and extend from the annular band [12] to the split rim [24], where they are bolted at [13] to peripheral flanges of the inner and outer rim sections [24.1 and 24.2] of the split rim [24].
Figure 8 best illustrates the embodiment wherein the tyre [10] includes a plurality of independent tensioning members [16a and 16b], circumferentially spaced-apart in substantially two-by-two configuration so that every pair of tensioning members [16a and 16b] is connected at their respective outer ends to opposing edges [12.1 and 12.2] of the annular band [12] and extend inwardly towards the circumferential plane [X]. The two opposing tensioning members [16a and 16b] are angularly disposed relative to the circumferential plane [X] and are also offset from one another in a radial plane [Z].
In Figures 10 to 12 the tensioning members [16a and 16b] are arranged in a V- configuration. In this form of the invention the tensioning members [16a and 16b] are <BR> <BR> disposed at their respective outer ends [16 (i) ] proximate opposing edges [12.1 and 12.2] of the annular band [12] and extend inwardly, at a first angle, towards the circumferential plane [X] and towards the wheel hub [14], such that in a radial plane [Z] the tensioning members [16a and 16b] meet each other at the wheel hub [14] so as to form the V- configuration. In particular, the tensioning members [16a and 16b] each comprise of an annular diaphragm, extending between the annular band [12] and the wheel hub [14]. The tensioning members [16a and 16b] are comprised of a woven mesh, in this case a canvas material, having threads of a resiliently deformable material, such as a polymer or elastomeric composition, embedded in the canvas.
The inner ends [16 (ii) ] of the tensioning members [16a and 16b] are sandwiched between two plates [28a and 28b], which in turn are clamped between inner and outer rim sections [24.1 and 24.2] of a split rim [24] with a bolt arrangement [13].
The outer ends [16 (i) ] of the tensioning members [16a and 16b] engage the annular band [12] in such a manner that they are positioned around the edges [12.1 and 12. 2] of the annular band [12] and are clamped respectively between the sidewalls [15a and 15b] and the band [12]. In this arrangement the tyre [10] includes an annular O-ring [30] having a radial slot for accommodating an edge [12.1 and 12.2] of the annular band [12]. It is envisaged that the O-ring [30] will prevent the edge [12.1 and 12.2] of the annular band [12] from cutting into the tensioning members [16a and 16b] when the same are clamped between the sidewalls [15a and 15b] and the annular band [12].
Figure 11 illustrates the manner in which the annular band [12] and the tensioning members [16a and 16b] deform when the tyre [10] is under radial compression. As pressure is exerted on the tyre [10], the annular band [12] deflects towards to the axis of rotation [Y] for a distance [Q]. It will be appreciated that such deflection [Q] should not be more than what is achieved with conventional tyres in the art. As the annular band [12] deflects radially inwardly towards the axis of rotation [Y], the tensioning members [16a and 16b] become relaxed. It will be appreciated that the tyre [10] and the weight of a vehicle is supported not by outward pressure of those tensioning members [16a and 16b] proximate the ground-engaging zone, but instead because the axis of rotation [Y] and tyre [10] effectively hangs from and is suspended by those tensioning members [16a and 16b] that are disposed radially opposite from the ground-engaging zone.
In the embodiment illustrated in Figure 13, the tensioning members [16a and 16b] are again angularly disposed so as to intersect each other in an X-configuration. However, in
this embodiment the tensioning members [16a and 16b] each has an inner skeletal portion [32], comprised of a canvas material, extending between two steel cables [34], and a rubber outer portion [36] which encloses the canvas skeleton [32] and steel cables [34].
The tensioning members [16a and 16b] are substantially continuous or annular in shape and X-shaped in a radial plane [Z].
The annular band [12] typically comprises of approximately 2mm spring steel, which is capable of deforming when operatively compressed against a surface on which it rolls, but will resume its original form in the absence of any force exerted thereon. It is envisaged that this will enable the tyre [10] to accommodate unevenness in a road surface, thereby to provide shock-absorbing characteristics to the tyre [10]. Figure 14, which is a stress analysis model of the tyre of Figure 13 under loading, illustrates this point better.
The applicant believes that the weight of a vehicle will be supported on the wheel axes, which, in turn, will exert a downward force on the tyre. The downward forces on the tyre [10] are balanced by tensional forces in the tensioning members [16a and 16b] extending between the annular band [12] and the wheel hub [14] at an operatively upper of portion of the tyre. In effect, the weight of the vehicle is suspended from an operatively upper portion of the annular band [12] by the tensioning members [16a and 16b].
The applicant further believes that the tensioning members [16a and 16b], which extend angularly relative to both the circumferential plane [X], a radial cross-sectional plane [Z] and relative to each other, will provide resistance to axial movement of the annular band [12] relative to the wheel hub [14]. It is anticipated that this will increase tyre stability and
enable the tyre to resist lateral forces exerted on the tyre during cornering. At the same time, the particular angular orientation of the tensioning members [16a and 16b] reduces moment of inertia of the annular band [12] relative to the wheel axis and thus prevents relative circumferential movement of the annular band [12] relative to the split rim [24] as and when the wheel axis is turned.
It will be appreciated that numerus embodiments of the invention may be possible without departing from the spirit or scope of the invention as defined in the claims.