GB1583185A

GB1583185A - Tyre and wheel rim assembly incorporating an elastically deformable structure

Info

Publication number: GB1583185A
Application number: GB25205/77A
Authority: GB
Original assignee: Industrie Pirelli SpA; Pirelli SpA
Current assignee: Industrie Pirelli SpA; Pirelli and C SpA
Priority date: 1976-06-28
Filing date: 1977-06-16
Publication date: 1981-01-21
Also published as: JPS532805A; ES229675U; AR212271A1; FI771561A; IT1079133B; ATA460477A; NL7706006A; CA1063915A; DK286477A; BR7704118A; LU77634A1; DE2728117A1; TR19902A; SE7707463L; AU2633077A; NO772260L; FR2356529A1; ZA773704B; ES229675Y; BE856149A

Description

(54) TYRE AND WHEEL RIM ASSEMBLY INCORPORATING AN ELASTICALLY DEFORMABLE STRUCTURE (71) We, INDUSTRIE PIRELLI SpA, an Italian Company of Centro Pirelli, Piazza Duca d'Aosta No 3, Milan 20100, Italy, do thereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention concerns a tyre and wheel rim assembly incorporating an elastically deformable structure, and in particular, a safety tyre and wheel rim assembly, that is to say comprising a tubeless tyre inside which is disposed such a structure suitable for supporting the tyre in the event of a puncture, so guaranteeing to the tyre a continued service even in a situation of emergency.

Formerly, there have been safety tyres conceived, based on the principle of the tyre containing a tube having the form of a toroidal ring which totally occupies the inside of the casing: this ring being subdivided internally by means of radial walls, into numerous compartments, each one independent of the other.

Once the tube is placed inside the tyre, each of these compartments is inflated by air under pressure and admitted through a series of valves, each valve being connected with a respective compartment, and the valves all being connected to a main valve.

Successively. the valves of these compartments are shut, in order to guarantee an individual sealing for each of the compartments themselves. Consequently, in case the tyre should puncture, the aforesaid tube would adequately be able to support the tyre for at least a certain run - until the first service station, even though the foreign body which caused the puncture should extend far enough as to pierce the tube surface lying in contact with the casing. In such cases. as a matter of fact. the foreign body would only penetrate into a single compartment, causing it to become deflated, but obviously leaving the other remaining compartments of the tube completely unaffected, so much so, that these other compartments would still be able to carry on functioning well.

Although the principle described above is, in theory, perfectly valid, in reality it has not till now been successful in obtaining any practical achievement on an industrial level.

Its greatest drawbacks were its undeniable complexity - both, as regards the manufacture of the tube described above, as well as for the step of introducing it inside the casing. Moreover, the weight of the tube itself - due to the numerous valves it contains, quite easily generates unbalanced forces of such a considerable amount as to clearly limit the performance of this tyre in question.

Another type of known expedient for obtaining safety tyres, consists of an inflatable structure which once introduced inside the tubeless tyre, substantially defines two cavities. one on its inside, and the other between it and the casing. Both these cavities can be filled with air having the very same pressure or even with air having different pressures.

According to the type of operation foreseen by said structure, it can, in the case of a punctured tyre. simply support the deflated casing with which it comes into contact in correspondence with its internal surface underlying the tread; otherwise, this inflatable structure passes from its original at rest position, where - as has been stated before, it only partially occupies the casing cavity, to a second working position, where it is inflated, at a higher pressure, and it comes into contact with the internal surface of the tyre casing so as to support it.

Neither has the type of inflated structure just described, achieved any outstanding success in actual practice. As a matter of fact, if conceived for carrying out the first type of action, it normally has to comprise two or more layers of rubberized fabric, covered with other further layers of rubber in order to guarantee an adequate support to the deflated tyre, and to furnish, should the foreign body causing the puncture penetrate into the interior of the casing, still another thickness of material. If it is conceived for carrying out the second type of action, there would, beside the manufacturing complexity of the type of structure indicated above, also be the drawback that the inflation of the tube in a working position, would, in general, not take place, neither would it take place during the deflation phase of the tyre, but it would require the actual direct intervention on the part of the car driver himself, for feeding the pressurized air, or gas, into the structure once the tyre is completely deflated.

The present invention aims at a tyre and wheel rim assembly incorporating a structure capable of bearing out an efficient anti-puncture function for a tubeless tyre in the sense that a puncture does not cause the tyre to collapse, said structure having an extremely simplified construction, being suitable for introduction into a tyre, and mounted together with it, onto a rim without involving any particular or complex operations; and which furthermore does not interfere with the behaviour characteristics of the tyre when it is being run under normal service, and even at higher speeds.

The present invention provides a tyre and wheel rim assembly comprising a tyre mounted on a wheel rim to define an inflation chamber and an elastically deformable structure located in the inflation chamber, the structure comprising an annular band which is circumferentially stretched when the structure is surrounded by air at atmospheric pressure, said structure having a plurality of sealed hollow bodies on the radially outer surface of the annular band, said sealed hollow bodies containing a gas at a pressure greater than atmospheric pressure but not greater than the design inflation pressure of the inflation chamber. whereby the structure will support the tyre if the latter is punctured.

In this specification. the expression "sealed hollow body" means a hollow body that is permanently sealed during manufacture so as to be free of apertures (unless punctured or ruptured).

Preferably. the stretched condition of the said annular band varies. as the pressure surrounding said structure varies from atmospheric pressure to the value of the inflation pressure of the tyre. so that the circumference of this band is comprised between a maximum value. corresponding at least to the maximum circumference of the said rim, and a minimum value which is equal at least to the minimum circumference of the said rim.

In the present disclosure, the term "maximum circumference" of the rim is intended to mean the circumference corresponding to the extremity of the rim flange; and the term "minimum circumference" is intended to mean the circumference of the base of the rim well.

In particular, the sealed hollow bodies are the means which are able to vary the stretched condition of the annular band of the structure, in consequence of the variations in the ambient pressure surrounding the structure.

In a preferred embodiment, the annular band has a width which is equal substantially to the axial distance between the tyre beads, when the tyre is mounted onto the rim.

The sealed hollow bodies preferably have an axial width which is equal at least to the width of the said annular band. The bodies are preferably disposed on this band at regular intervals.

For the purpose of efficiently fulfilling their function with respect to the annular band, and so as to be capable of supporting the tyre, should it become accidently deflated (which function shall be dealt with further on in more detail), the walls of the sealed hollow bodies, are made of elastomeric, air-impermeable material, which will ensure that the gas pressure contained inside these bodies is maintained as stable as possible with the passage of time. Preferably, these walls are made of a vulcanized elastomeric compound based on natural rubber, or a synthetic rubber such as butyl rubber, either halogenated or not.

Preferably, the sealed hollow bodies are integral with the annular band; that is to say, the wall portion of each sealed hollow body where in contact with the annular band, consists of a length of the said band.

The latter, which as aforesaid, can be made of any elastically deformable material, is then constituted by an air-impermeable elastomeric material as indicated above.

In order to ensure that during the variations in the ambient pressure. the sealed hollow bodies can perform their function as regards the said annular band - so that the latter is able to vary its circumference, appropriate thicknesses are selected for the band and for the body walls respectively.

For example. by employing one single elastomeric compound. having a modulus of 0.128 Kg/mm. at elongation of 10%. the wall thickness of the bodies is 3mm, while the thickness of the band is 13 mm. On the contrary. by adopting a constant thickness of the body wall and of the band. equal to 3 mm, the elastomeric compound utilized for the body walls, will have a modulus at elongation of 10%, equal to 0.128 kg/mm2 while the elastomeric compound utilized for the annular band has a modulus at elongation of 10% equal to 6 kg/mm2.

The annular band of the structure when surrounded by air at atmospheric pressure, has a circumference equal at least to the maximum circumference of the rim onto which the structure is mounted.

The volume of the sealed hollow bodies on said band is preferably such that their radial extension when atmospheric pressure surrounds them, gives the entire structure a radial thickness comprised between 60% and 85% of the section height of the tyre casing in which it is located; besides this, the ideal circumference circumscribing the said sealed hollow bodies is either equal to, or exceeds by 10%- at the most the internal circumference of the tyre in its tread region.

The number of sealed hollow bodies containing pressurized gas preferably varies according to the size of the tyre. Taking into account that in order to perform an efficient function which shall be explained further on - the sealed hollow bodies have to be in contact with each other, and at the same time, their volume has to be such as to allow for a space within the cavity of the tyre casing into which the structure is mounted, these sealed hollow bodies will preferably number between 8 and 360.

In an alternative, embodiment of the present invention, the elastically deformable structure also comprises a second annular band which is placed in contact with the radially outward portions of the sealed hollow bodies; also this second annular band is in a stretched condition when the structure is surrounded by air at atmospher ic pressure and the second band has a circumference which is equal at least to the aforesaid ideal circumference circumscribing the said sealed hollow bodies.

Similarly to the first annular band, the second band can also be integral with the sealed hollow bodies underlying it; in other words, the radially outward portion of the wall of each said sealed hollow bodies consists of a length of said second annular band.

It is evident that the aforesaid structure in elastomeric material, has a very simplified construction. and does not present any particular difficulty as to its manufacture.

The sealed hollow bodies containing pressurized gas can be obtained by moulding, either along with the single. or the two, annular bands or even apart from these bands, by employing any suitable manufacturing process known to technicians of the field, which is suitable for obtaining hollow bodies containing pressurized gas. - such as for instance, by utilizing a pellet of a substance which releases gas through its decomposition in consequence of a raising in the-temperature.

Inside each of the sealed hollow bodies to be manufactured, constituted by two symmetrical halves, a pellet is inserted; after the two half surfaces have been placed in contact together, the moulding process takes place - followed, as needed, by a curing treatment of the whole article.

As an alternative, recourse can be taken to the-process according to which the two symmetrical halves of all the hollow bodies either separately or with the single annular band or the two annular bands, are moulded simultaneously into a series of cavities of the mould which is contained within a case, into which is admitted either air or nitrogen having a pressure value equal to the desired value for the hollow bodies; there the halves are welded together and cured.

No matter which moulding technique is followed, the first annular band is formed inside the mould with a slightly lesser diameter than the minimum diameter of the rim onto which the structure will have to be mounted. Once the structure is extracted from the mould and brought into surround inns at atmospheric pressure, the sealed hollow bodies containing pressurized gas, which were originally slightly spaced apart, one away from the other, now expand so that the facing wall portions of adjacent hollow bodies now come into contact with each other, and their cross-section, which was previously substantially circular, now becomes ovoidal. In the meanwhile, an action of reciprocal repulsion is generated between these closed hollow bodies in contact with each other, thus giving rise to radial forces which cause a further expansion of the sealed hollow bodies in the outward direction, and the stretching of the underlying annular band; so taking the latter to a circumference greater than that in the moulding. In the imposed conditions of band thickness and of the sealed hollow body wall thickness, of the gas pressure inside the said bodies and/or of the modulus of the elastomeric compound selected for the annular -band and the sealed hollow bodies, the interal circumference of the stretched annular band is at least equal to the maximum external circumference of the rim flange over which the structure is to be fitted.

Should the structure also comprise the second annular band, this will be moulded with a diameter equal to that of the aforesaid ideal circumference by appropriately selecting the modulus of the elastomeric compound and/or its thickness, so that this second band can follow, by getting into a stretched condition and varying its circumference, the expansion of the sealed hollow bodies when extracted from the mould.

As said before, the structure in elastically deformable material, according to the present invention, has been conceived for being inserted and mounted together with a tubeless tyre onto a rim, and for carrying out the effective function of supporting the tyre, should it become accidently deflated due to a puncture.

More particularly, said structure, when inserted into the tyre and wheel rim assembly and with the tyre at normal inflation pressure, is in a first position, where the stretching of the annular band facing the rim is reduced, and it preferably has a circumference equal at least to the minimum circumference of the rim, while the sealed hollow bodies are contracted by the inflation pressure and lateral portions of the walls of said bodies are pushed towards the rim, without necessarily touching the tyre beads. In a working condition (that is to say, when the tyre is punctured and the inflation air consequently escapes) as a result of the expansion of the hollow bodies caused by the pressure of the gas inside them, the aforesaid structure is able to move into a second position, according to which the stretching condition of said annular band increases and the latter assumes a greater circumference than the circumference when the structure is in the first position, while the external surfaces of all the sealed hollow bodies comes into contact with the internal surface of the casing which is underlying the tread. Should the structure also have the second annular band around the sealed 'hollow bodies, this second band will come into contact with the internal surface of the casing. Hence, in the punctured condition of the tyre (that is, when the tyre is without inflation pressure) in the portion of the tyre which, during its rotation, is subjected to squeezing under load, the hollow bodies will be compressed against the rim, and will contemporaneously undergo an axial expansion which will taken them into contact with the tyre beads so as to guarantee the correct positioning of the tyre on the rim flange even when the tyre is subjected to forces tending to dislodge the beads.

Embodiments of the invention will now be described by way of example, with reference to the accompanying drawings, where: Figure 1 represents a perspective partial view of an elastically deformable structure according to the invention, Figure 2 represents a length of the structure in Figure 1, in section on a circumferen tial plane, Figure 3 represents a radial section of a portion of a tubeless tyre. of a portion of a rim and a portion of the elastically deformable structure of Figure 1 and 2. during assembly, Figures 4 and 5 represent, respectively in radial section, and in section on the equatorial plane, the tyre and wheel rim assembly, comprising the elastically deformable structure, under normal service conditions, Figures 6 and 7 represent in radial section and in section on the equatorial plane, the assembly of Figure 4, in working conditions.

More particularly, Figure 1 represents in perspective view a length of the elastically deformable structure of the present invention, when surrounded by air at atmospheric pressure. The structure is constituted by an annular band 2, and by a plurality of sealed hollow bodies 3, each one of these bodies 3 containing air at a pressure of 1.3 atm. This structure, destined to be mounted together with a tubeless tyre, size 135 SR 12, onto a rim having a maximum diameter equal to 339 mm, has the annular band 2 in a stretched condition with a diameter equal to 345 mm, the width of said band being 70 mm, and with a thickness of 3.5 mm. The sealed hollow bodies being 32 in number, are distributed at regular intervals along the whole of the outer circumference of the annular band 2, and they are constituted - as in the case of the annular band - of an elastomeric compound based on vulcanized chlorobutyl rubber having its modulus E equal to 0.15 Kg/mm2. Their axial width equals 85 mm. Under their state of maximum expansion, the thickness of the walls of these sealed hollow bodies is equal to 1.5 mm.

In Figure 2 is represented in section on a circumferential plane, a length of the structure 1 where it is evident how each sealed hollow body 3 is integral with the annular band 2, how the mutually facing wall portions between adjacent bodies are in contact with one another, and how by expansion when surrounded by air at atmospheric pressure, the bodies assume an ovoidal section.

The elastically deformable structure 1, with the sealed hollow bodies containing pressurized air, cause the annular band to assume a stretched condition with a circumference which is greater than the maximum circumference of the rim. As a matter of fact, in making the structure according to any manufacturing process known per se, the circumference of the annular band is made to be either equal to or preferably less than the maximum circumference of the rim onto which the structure has to be mounted.

But it must be taken into account that once the structure is manufactured, and is then externally subjected to atmospheric pressure, between each of the bodies 3, having inside them a pressure - which in the given case illustrated by the figures, is 1.3 atm, there is produced an action of mutual repulsion due to the expansion of the bodies already in mutual contact', which results in radial forces which cause the stretched condition i.e. the deformations of the annular band to the extent of a greater circumference than that with which it was manufactured, until the maximum circumference of the rim is reached and exceeded.

This leads to a first advantage in the operation of mounting the tubeless tyre together with the structure, onto the rim - as is evident in Figure 3. In this figure where there is represented in radial section a portion of rim 6, a portion of tyre 7 and a portion 8 of the elastically deformable structure 1, at the time of mounting, it is noted that this structure lies completely inside the tyre 7, and bears against the surface underlying the tread'9, so as to leave the region of.

the tyre beads 10 completely free. In such a way, the mounting of the tyre onto the rim takes place without any impediment on the part of the herein introduced structure, and without there being any need for manual or mechanical intervention, for fixing the structure into the above-indicated position.

In Figures 4 and 5, there is partially represented in a radial section, and in a section in the equatorial plane respectively, the tyre and wheel rim ,assembly containing the structure, under normal service conditions - meaning under a condition in which there is a pressure higher than the atmos pheric pressure encompassing the structure.

As can be seen, once the pressurized air has been admitted into the tyre - which in this case is at 2 atm pressure, the air pressure acts on each body 3, and consequently uniformly reduces the volume of each sealed hollow ' body.

Hence, the stretched condition of the annular band tends to be annulled, and the band returns practically to the same circumference as in the moulding.

If this circumference was designed to be equal to the minimum circumference of the rim, the band comes into contact with the base of the well 4 of the rim 6.

But preferably, the moulded circumference is designed to be less than the minimum circumference of the rim. Therefore, consequent to the action of the inflation pressure exerted on the sealed hollow bodies 3 tending to reduce them to their original as-moulded dimensions. the band 2 abuts against the base of the well 4 of the rim. In this way. even under tyre service conditions at the highest speeds. due to the residual elastic tension of the band. and due also to the direct action of the pressure which holds the structure against the rim.

the structure does not shift from its position, and no unbalance rises which could adversely affect the performance of the tyre.

For facilitating this action of the sealed hollow bodies by means of inflated airpressure, a hole (not represented in the figure) is provided in the rim base; said hole although stopped both at the time of tyre inflation as well as during the normal functioning of the tyre, is opened for permitting the escape of air which may have remained entrapped between the rim base and the annular band 2.

In Figure 6, there is represented in radial section, the assembly of Figure 4- i.e. the rim 6, the tyre 7, and the elastically deformable structure. For showing the working condition of structure 1 which takes place in case of tyre deflation due to a puncture, it was considered preferable to show the assembly as a whole here. More particularly, the rotation axis A-A divides the lower part B of the assembly, including the part of the tyre which is squeezed against the ground under load, from the upper part C of the assembly.

Once there occurs an accidental puncture to the tyre 7, the inflation air contained in the cavity 12 (see Figure 4) escapes through the opening incurred, and hence the pressure which originally acted under tyre operation conditions on the bodies 8 of the structure 1, reduces to atmospheric. As can be seen in Figure 6, as a consequence of the diminishing of the inflation pressure, the sealed hollow bodies are expanded by their own internal pressure, and therefore in similar manner to what occurs in the mounting phase illustrated in Figure 3, tend to regain contact with the tyre internal surface 9, which underlies the tread, causing the annular band 2 to being stretched, and deforming it to a greater circumference than the circumference when the structure was in the first position in the base of ,the well (Figure 4) and tending to a maximum value, corresponding to the value which it had in the mounting stage. Obviously, when the tyre is rolling, the tyre is squeezed in the zone which comes into contact with the ground under load of the vehicle on which the tyre is mounted. However, the tyre is efficiently supported in this state by the radially external surface of the bodies 8, and at the same time. even the tyre beads 10 remain fixed in their position on the rim.

Figure 7 is an equatorial planar section of the structure 1 represented in a working condition in the radial section of Figure 6 to illustrate the conditions of the sealed hollow bodies 8 along the entire circumferential extent of the structure 1. In particular, it can be noticed that the bodies 8' which are in the tyre zone in contact with the ground are expanded with respect to their dimensions in Figure 5. and their radially external surfaces are pressed against the tyre internal surface 9 underlying the tread, whilst the respective portion of the annular band is pressed against the corresponding part of the base of the well of the rim 4. As one gradually moves away from the squeezed tyre zone towards the zone diametrically opposite it, the sealed hollow bodies 8" become more freely subject to the action of their own internal pressure, and hence, owing to their increasingly un-opposed expansion, they put the underlying band into a stretched condition and they gradually pull it away from the base of the well of the rim.

This stage of operation is repeated cyclically, as the tyre rolls along; and whereas on one hand, the vehicle driver is in a position to be warned if a puncture has occurred to the tyre, on the other hand he may continue driving the vehicle - even for long distances, without causing any further damage to the tyre. So as to facilitate the movements of the elastically deformable structure within the tyre cavity, the latter may contain a known lubricant. It is to be noted that even in the case of a tyre having become punctured owing to a sharp foreign body having a length such as to penetrate right inside the tyre, the elastically deformable structure of the present invention is nonetheless still able to carry on functioning in an efficient manner.

As a matter of fact, in a case such as the above, the foreign body can only damage one - or at most, two of the sealed hollow bodies which, by expanding, have come into contact with the internal surface of the tyre, thus preventing any relative movement between the casing and the structure. But this occurrence does not prevent the remaining closed hollow bodies of the structure from continuing to act as a tyre support.

The structure of this present invention, comprising - as it has already been stated, sealed hollow bodies containing a pressurized gas, can be produced and then stored even for long period of time, before being utilized.

For this purpose, it besides being constituted - at least as far as the walls of the sealed hollow bodies are concerned. by elastomeric material having a high airimpermeability. they can also be stored to advantage. in a way per se known. in a container or box made of metal or of plastics material designed in such a way as to produce, on being shut, an internal pressure equal to that of the gas contained inside the sealed hollow bodies of the elastically deformable structure enclosed in said container. In this way if the structure remains in the container. it does not allow the sealed hollow bodies to deflate. As a matter of fact, owing to the equilibrium between the pressure inside the container and the pressure inside the sealed hollow bodies. there is no outward gas diffusion from the bodies.

Should the pressure within the container exceed that inside the sealed hollow bodies of the structure, the inversion of the phenomena can be obtained with diffusion of air into the bodies, and the consequent "regeneration" of deflated sealed hollow bodies.

A container of the tyre described above, is disclosed in the Italian Patent No. 445,260 by the same Applicant.

It is to be understood that the present invention is not limited to what is indicated above, but that it includes other alternative embodiments, for instance the abovedescribed structure modified by the provision of one or two annular bands in contact with the axially external portions of the sealed hollow bodies of the structure, having a width and circumference such as not to oppose the variations of the dimensions of the structure during its operation.

WHAT WE CLAIM IS: 1. A tyre and wheel rim assembly comprising a tyre mounted on a wheel rim to define an inflation chamber and an elastically deformable structure located in the inflation chamber, the structure comprising an annular band which is circumferentially stretched when the structure is surrounded by air at atmospheric pressure, said structure having a plurality of sealed hollow bodies on the radially outer surface of the annular band, said sealed hollow bodies containing a gas at a pressure greater than atmospheric pressure but not greater than the design inflation pressure of the inflation chamber, whereb

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the base of the well of the rim 4. As one gradually moves away from the squeezed tyre zone towards the zone diametrically opposite it, the sealed hollow bodies 8" become more freely subject to the action of their own internal pressure, and hence, owing to their increasingly un-opposed expansion, they put the underlying band into a stretched condition and they gradually pull it away from the base of the well of the rim. This stage of operation is repeated cyclically, as the tyre rolls along; and whereas on one hand, the vehicle driver is in a position to be warned if a puncture has occurred to the tyre, on the other hand he may continue driving the vehicle - even for long distances, without causing any further damage to the tyre. So as to facilitate the movements of the elastically deformable structure within the tyre cavity, the latter may contain a known lubricant. It is to be noted that even in the case of a tyre having become punctured owing to a sharp foreign body having a length such as to penetrate right inside the tyre, the elastically deformable structure of the present invention is nonetheless still able to carry on functioning in an efficient manner. As a matter of fact, in a case such as the above, the foreign body can only damage one - or at most, two of the sealed hollow bodies which, by expanding, have come into contact with the internal surface of the tyre, thus preventing any relative movement between the casing and the structure. But this occurrence does not prevent the remaining closed hollow bodies of the structure from continuing to act as a tyre support. The structure of this present invention, comprising - as it has already been stated, sealed hollow bodies containing a pressurized gas, can be produced and then stored even for long period of time, before being utilized. For this purpose, it besides being constituted - at least as far as the walls of the sealed hollow bodies are concerned. by elastomeric material having a high airimpermeability. they can also be stored to advantage. in a way per se known. in a container or box made of metal or of plastics material designed in such a way as to produce, on being shut, an internal pressure equal to that of the gas contained inside the sealed hollow bodies of the elastically deformable structure enclosed in said container. In this way if the structure remains in the container. it does not allow the sealed hollow bodies to deflate. As a matter of fact, owing to the equilibrium between the pressure inside the container and the pressure inside the sealed hollow bodies. there is no outward gas diffusion from the bodies. Should the pressure within the container exceed that inside the sealed hollow bodies of the structure, the inversion of the phenomena can be obtained with diffusion of air into the bodies, and the consequent "regeneration" of deflated sealed hollow bodies. A container of the tyre described above, is disclosed in the Italian Patent No. 445,260 by the same Applicant. It is to be understood that the present invention is not limited to what is indicated above, but that it includes other alternative embodiments, for instance the abovedescribed structure modified by the provision of one or two annular bands in contact with the axially external portions of the sealed hollow bodies of the structure, having a width and circumference such as not to oppose the variations of the dimensions of the structure during its operation. WHAT WE CLAIM IS:

1. A tyre and wheel rim assembly comprising a tyre mounted on a wheel rim to define an inflation chamber and an elastically deformable structure located in the inflation chamber, the structure comprising an annular band which is circumferentially stretched when the structure is surrounded by air at atmospheric pressure, said structure having a plurality of sealed hollow bodies on the radially outer surface of the annular band, said sealed hollow bodies containing a gas at a pressure greater than atmospheric pressure but not greater than the design inflation pressure of the inflation chamber, whereby the structure will support the tyre if the latter is punctured.

2. A tyre and wheel rim assembly as claimed in claim 1 in which the circumference of the annular band varies between the maximum and minimum values of the rim circumference as the tyre inflation pressure varies from atmospheric up to maximum inflation pressure respectively.

3. A tyre and wheel rim assembly as claimed in claim 1 or claim 2 in which the annular band has a width which is at least equal to the distance between the beads of the tyre.

4. A tyre and wheel rim assembly as claimed in any one of the preceding claims in which the sealed hollow bodies have an axial width which is at least equal to the width of the annular band.

5. A tyre and wheel rim assembly as claimed in any one of the preceding claims in which the sealed hollow bodies are disposed on the annular band at regular intervals.

6. A tyre and wheel rim assembly as claimed in any preceding claim, wherein when said hollow bodies are expanded under the action of the pressure inside the hollow bodies, the walls thereof have a thickness comprised between 03 and 2.5 mm. the thicknes of said annular band being

comprised between 2 and 13 mm, the modulus E of the elastomeric composition or compositions constituting said annular band and said walls being comprising between 0.05 and 0.5 Kg/mm2.

7. A tyre and wheel rim assembly as claimed in any preceding claim, wherein said sealed hollow bodies are integral with said annular band.

8. A tyre and wheel rim assembly as claimed in any preceding claim, wherein said sealed hollow bodies have a volume such that said structure has a radial thickness comprised between 60 and 85% of the section height of the tyre cavity.

9. A tyre and wheel rim assembly as claimed in any preceding claim, wherein the structure comprises a second annular band disposed in contact with the radially outer portion of each of said sealed hollow bodies, said second band being in a stretched condition when said structure is surrounded by air at atmospheric pressure, said second band having an external circumference which equals or is not more than 10% greater than the internal circumference of the tyre in its tread region.

10. A tyre and wheel rim assembly as claimed in claim 9, wherein said second annular band is integral with said sealed hollow bodies.

11. A tyre and wheel rim assembly as claimed in any preceding claim, wherein the number of said sealed hollow bodies is between 8 and 360.

12. A tyre and wheel rim assembly as claimed in any preceding claim, wherein said structure is so disposed that the first said annular band lies on the rim when the remaining part of the tyre cavity contains air at the normal inflation pressure.

13. A tyre and wheel rim assembly as claimed in claim 12, wherein under the design tyre inflation pressure conditions, said structure is displaced to a first position in which the stretched condition of the first said annular band is reduced and it has a circumference at least equal to the minimum circumference of said rim, the axially outward portion of the walls of each sealed hollow body bearing against the internal surface of said tyre, said structure being able, under working conditions when the tyre is punctured and has lost its inflation, to move into a second position in which the respective length of said annular band is greater than that corresponding to the first position, the surface radially outside the totality of the sealed hollow bodies being in contact with at least the tyre internal surface underlying the tread. in such a way as to support said tyre.

14. A tyre and wheel rim assembly as claimed in any preceding claim. wherein said tyre has a lubricant inside its cavity.

15. A tyre and wheel rim assembly, substantially as hereinbefore described with reference to the accompanying drawings.