TYRE CONSTRUCTION

Abstract: A non-pneumatic tyre (10) comprising an annular body (15) of resilient construction having a radially outer peripheral portion (19) and a radially inner peripheral portion (17). A circumferential web extends between, and is connected to, the radially inner and outer portions. To each side of the circumferential web there is a set of circumferentially spaced ribs (45, 49). Each rib extends between and is connected to the radially inner and outer portions of the tyre. Each rib is also connected to the web. A characterising feature of the tyre is that the circumferential web comprises consecutive web sections (53) extending in alternate directions.

Description: "Tyre Construction" FIELD OF THE INVENTION THIS INVENTION relates to a tyre construction and in particular to a tyre construction which is non-pneumatic. BACKGROUND OF THE INVENTION There are various proposals for construction of tyres which are non-pneumatic so as to avoid the problem of puncturing and which provide acceptable cushioning and performance characteristics. Where the proposals are concerned with solid tyres constructed predominantly from elasto eric material, a difficulty arises in dissipating heat generated in the tyres, and resultant accumulation of heat may lead to degradation of the tyre material. Other proposals overcome or avoid the problem of heat accumulation by providing cavities in the body of the tyre. The cavities not only reduce the overall mass of the tyre so as to reduce the extent of heat generated but also enhance heat dissipation. In certain proposals, the cavities are so arranged as to result in the formation of a load carrying and supporting structure within the tyre between its inner and outer peripheries. Such a structure within the tyre is arranged to have load bearing capabilities while also being capable of deformation to provide cushioning. Several such proposals are disclosed in European Patent Application Nos. 0159880 and 0245789 and each comprises a structure in the form of circumferentially spaced apart ribs interconnected by a central web which is generally planar and extends circumferentially around the rotational axis of the tyre. With this structure, each section of the central web between neibouring ribs has a longitudinal extent aligned with the direction of rotation of the tyre and consequently may be vulnerable to collapsing when the tyre is subjected to lateral forces, particularly during cornering. SUMMARY OF THE INVENTION The present invention seeks to provide a novel and useful tyre construction which improves the stability of the tyre. In one form the invention resides in a tyre construction comprising an annular body of resilient construction having a radially outer peripheral portion, a radially inner peripheral portion, a circumferential web extending between and connected to the radially inner and outer portions, and two sets of circumferentially spaced apart ribs one set to each side of the circumferential web, each rib extending between and connected to the radially inner and outer portions and being connected to the " web, characterised in that the circumferential web comprises consecutive web sections extending in alternate directions. Preferably, said consecutive sections of the web define a zig-zag formation. Preferably, the ribs of one set are circumferentially offset from the ribs of the other set. Preferably, the ribs are connected to the web at the ends of said web sections. Where the consecutive web sections define a zig-zag formation as aforesaid, the ribs are connected to the web at the junctions between consecutive straight sections of the zig-zag formation. Preferably each rib is configured so as to be somewhat angular in profile to define a zone at which the rib can resiliently flex. Preferably, each web section is also configured so as to be somewhat angular in profile to define a zone at which the web section can resiliently flex. Conveniently, the arrangement of the web and circumferentially spaced ribs to each side of the web is produced by providing two sets of passageways in the tyre one corresponding to each side of the tyre, the passageways of each set opening onto their corresponding side of the tyre and extending across the tyre towards the other side to terminate inwardly of said other side, the two sets of passageways being circumferentially offset in relation to each other such that each passageway of one set extends into the region between neighbouring passageways of the other set. In another form the invention resides in a tyre construction comprising an annular body of resilient construction having a radially outer peripheral portion, a radially inner peripheral portion and an intermediate portion between the radially outer and inner portions, the intermediate portion being provided with two sets of circumferentially spaced apart passages one set corresponding to each side of the tyre, the passageways of each set opening onto their corresponding side of the tyre and extending across the tyre towards the other side to terminate inwardly of said other side, said two sets of passageways being offset in relation to each other such that each passageway of one set extends into the region between neighbouring passageways of the other set. Preferably, the inner portion of each passageway converges in the inward direction. , - _ * ■ r With such a construction, a rib is defined by the partition between neighbouring passageways of each set and a web section is defined by a further partition between each passageway in one set and a neighbouring passageway in the other set wherein consecutive web sections extend in alternate directions. Preferably, said web sections co-operate to define a circumferentially extending web of zig-zag formation. The tyre may be of unitary construction or segmental construction. The radially inner portion of the tyre may encase reinforcing means. Preferably, the reinforcing means extends across the radially inner portion for a substantial part of the width thereof. The reinforcing means is preferably in the form of an annular band concentric with the tyre. The annular band may be perforated to facilitate bonding of the tyre material to the annular band. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood by reference to the following description of one specific embodiment thereof as shown in the accompanying drawings in which:- Fig. 1 is a side view of the tyre according to the embodiment; Fig. 2 is a cross-sectional view of the tyre according to the embodiment; Fig. 3 is a fragmentary side view of the tyre, on an enlarged scale; Fig. 4 is a section along the line 4-4 of Fig. 2 , on an enlarged scale; Fig. 5 is a section along the line 5-5 of Fig. 2, on an enlarged scale; Fig. 6 is an elevational view of the tyre with various parts cut away to reveal the internal construction of the tyre; Fig. 7 is a schematic view showing the tyre according to the embodiment fitted onto a support rim with a portion of an outer part of the support rim cut away to reveal an inner part of the rim; and Fig. 8 is a section along the line 8-8 of Fig. 7. DESCRIPTION OF PREFERRED EMBODIMENT The embodiment shown in the drawings is directed to a non-pneumatic tyre 10 which is to be mounted onto a support rim 11. The support rim is shown in Figs. 7 and 8 and is constructed in two parts being an inner part 12 and an outer part 13. The two parts 12 and 13 can be separated to facilitate mounting of the tyre onto the rim and thereafter secured together by any suitable means, such as circumferentially spaced apart bolts 14, to maintain the tyre on the rim. The tyre 10 comprises an annular body 15 of composite construction having a radially inner portion 17, a radially outer portion 19 and an intermediate portion 21 between the inner and outer portions. The radially inner portion 17 is adapted to be mounted on the support rim 11, as best shown in Fig. 7 of the drawings. The radially outer portion 19 defines a running surface 23 having a tread formation 25 for gripping engagement with the ground. The outer portion 19 is also provided with a zone which is reinforced with breaker elements 27 of known type. The radially inner portion 17 of the body is provided with reinforcing means 29 in the form of an annular band which is concentric with the tyre and which extends a substantial part across the width of the radially inner portion. The annular band 29 is constructed of metal and in turned back on itself at its sides in an arcuate fashion to provide circumferential ribs 31 which serve to reinforce circumferential beads 33 provided at the sides of the radially inner portion 17 of the tyre. The beads 33 are adapted for engagement with the support rim 11, as best seen in Fig. 7 of the drawings. The annular band 29 is provided with a plurality of holes 35, as shown in Fig. 6 to facilitate bonding of the elastomeric material to the band. The band 29 serves to reinforce the radially inner portion 17 of the tyre so that it can be securely fixed to the rim. The body 15 of the' tyre is of composite construction, being formed predominantly of an elastomeric material (such as rubber) which is firm yet resiliently flexible and having the breaker elements 27 and the reinforcing means 29 encased therein. The intermediate portion 21 of the tyre is provided with two sets of passageways 37 and 39, one corresponding to each side of the tyre. The passageways in each set open onto their corresponding sides of the tyre at respective openings 40 and 41 and extend across the tyre towards the other side, terminating at 43 inwardly of said other side. The set of passageways 37 are circumferentially spaced apart around the tyre whereby a partition 45 is defined between neighbouring passageways. Similarly, the passageways 39 are circumferentially spaced apart around the tyre whereby a partition 49 is defined between neighbouring passageways. The partitions 45 and 49 define rib members which extend between the radially inner and outer portions 17 and 19. The two sets of passageways are circumferentially offset in relation to each other such that each passageway in one set extends into the region between neighbouring passageways in the other set and vice versa, as best seen in Fig. 6 of . the drawings. The inner portions of the passageways converge in the inward direction to 43, also as best seen in Fig. 6. With such a construction, there is defined a further partition 53 between each passageway in one set and a neighbouring passageway in the other set. The partitions 53 constitute web sections which co-operate to define a web which extends circumferentially around the tyre and which extends between the radially inner and outer portions of the tyre. In this embodiment, the web sections define a web which is of zig-zag formation. Also with this arrangement, the ribs defined by partitions 45 and 49 are integrally connected to the web defined by partitions 53 at the ends of the partitions 53. Because of the resiliently flexible nature of the elastomeric material from which the body is predominantly constructed, the ribs and web sections are capable of flexing and this feature assists in providing cushioning to the tyre. The zig-zag formation of the web sections 53 enhances the stability of the tyre and resists uncontrolled collapse of the web defined by such web sections. To enhance the flexing action, the ribs defined by partitions 45 and 49 between neighbouring passageways in each set are configured so as to be somewhat angular in profile to define a zone 59 at which the ribs can resiliently flex. Similarly, the web sections defined by partitions 53 are configured so as to be somewhat angular in profile to define a zone 61 at which the web sections can resiliently flex. From the foregoing, it is evident that the present invention provides a tyre which is non-pneumatic but which is capable of flexing to provide a cushioned ride. It should be appreciated that the scope of the invention is not limited to the scope of the embodiment described. For instance, rather than being of unitary construction, the body may be constructed as a plurality of segments which can be positioned around and affixed to the support rim. With this arrangement, segments can be replaced on an individual basis in the event of damage.

Claims: THE CLAIMS defining the invention are as follows :- # 1. A tyre construction comprising an annular body of resilient construction having a radially outer peripheral portion, a radially inner peripheral portion, a circumferential web extending between and connected to the radially inner and outer portions, and two sets of circumferentially spaced apart ribs one set to each side of the circumferential web, each rib extending between and connected to the radially inner and outer portions and being connected to the web, characterised in that the circumferential web comprises consecutive web sections extending in alternate directions. 2. A tyre construction according to claim 1 wherein the ribs of one set are circumferentially offset from the ribs of the other set. 3. A tyre construction according to claim 1 or 2 wherein the ribs are connected to the web at the ends of said web sections. 4. A tyre construction according to claim 1, 2 or 3 wherein said consecutive sections of the web define a zig¬ zag formation. 5. A tyre construction according to claim 4 wherein the ribs are connected to the web at the junctions between consecutive straight sections of the zig-zag formation. 6. A tyre construction according to any one of the preceding claims wherein each rib is configured so as to be angular in profile to define a zone at which the rib can resiliently flex. 7. A tyre construction according to any one of the preceding claims wherein each web section is configured so as to be angular in profile to define a zone at which the _ έj# web section can resiliently flex. 8. A tyre construction comprising an annular body of resilient construction having a radially outer peripheral portion, a radially inner peripheral portion and an intermediate portion between the radially outer and inner portions, the intermediate portion being provided with two sets of circumferentially spaced apart passages one set corresponding to each side of the tyre, the passageways of each set opening onto their corresponding side of the tyre and extending across the tyre towards the other side to terminate inwardly of said other side, said two sets of passageways being offset in relation to each other such that each passageway of one set extends into the region between neighbouring passageways of the other set wherein a rib is defined by the partition between neighbouring passageways of each set and a web section is defined by a further partition between each passageway in one set and a neighbouring passageway in the other set wherein consecutive web sections extend in alternate directions. 9. A tyre construction according to claim 8 wherein the inner portion of each passageway converges in the inward direction. 10. A tyre construction according to claim 8 or 9 wherein said web sections co-operate to define a circumferentially extending web of zig-zag formation. 11. A tyre construction according to any one of the preceding claims wherein the radially inner portion of the tyre encases reinforcing means. 12. A tyre construction according to claim 11 wherein the reinforcing means extends across the radially inner portion for a substantial.jjDart of the width thereof. 13. A tyre construction according to claim 12 wherein the reinforcing means comprises an annular band concentric with the tyre. 14. A tyre construction according to claim 13 wherein the annular band is perforated to facilitate bonding of the tyre material to the annular band. 15. A tyre construction according to claim 13 or 14 wherein circumferential beads are provided at the sides of said radially inner portion, the circumferential beads being adapted to be releasably engaged by a support rim for the tyre and wherein the sides of the annular band are profiled to provide reinforcement for said circumferential beads. 16. A tyre construction according to any one of the preceding claims wherein the annular body is of unitary construction. 17. A tyre construction according to any one of claims 1 to 15 wherein the annular body comprises a plurality of segments. 18. A tyre construction substantially as herein described with reference to the accompanying drawings.

Inventors: JARMAN BRIAN, JARMAN, BRIAN
Applicants: ALTRACK LTD, ALTRACK LIMITED
Application year: 1988
Main classification: B60C7
IPC codes: B60C7, B60C17