CA1056284A - Run flat tire safety device on a drop center rim - Google Patents

Abstract

Abstract of the Disclosure A run flat pneumatic tire on a drop center wheel rim containing an annular support tube in the wheel rim which, in the event the tire goes flat, maintains the beads on their seats and supports the load sufficiently to prevent loss of control and to permit continued operation of the vehicle for a reasonable period. The support tube includes at least on its surface a lubricating composition to reduce friction where the collapsed tire contacts the support tube. The support tube itself can be made resistant to failure from punctures by, for example, having incorporated therein belt reinforcement, and/or having puncture-sealing means such as a puncture sealant layer or particulate puncture sealant, or by having a foamed or solid elastomer filling.

Description

The invention relates to a run flat tire safety device on a drop center wheel rim comprising in particular a single-piece drop-center wheel rim and preferably a tubeless pneumatic tire whose beads are capable of being pressed by the inside pressure in the pneumatic tire against the seats accommodating the beads in the drop-center wheel rim and are supported and secured against slippage from their seats by an inflatable annular hollow support body which, in its inflated state, is limited in axial direction substan-tlally to the width of the drop-center wheel rim. The annular support body, in its radially outwardly pointing wall area, is preferably provided with a radially ex-ternally situated thickening of the wall or an additional ply of material extending down to and into the axially oriented wall areas by diminishing there gradually in radially inwardly oriented direction.
Accordingly, the invention involves a run flat tire with a modified hollow safety body on a drop center wheel rim for supporting the beads and to serve as a bearing means during a run flat condition and being itself puncture-proof. In one aspect, the invention features a tubelike safety body including an anti-friction (wall or cap or layer) and therein a cross angled, thin, steel cord double ply belt reinforcement, at least in the crown. Said body may include therein a puncture sealant material and/or a foam or solid filling arrange-ment.
It is a well-known fact that traffic accidents are fequently caused by the puncturing or becoming de-- . . . ~.................... -. . . ~ .
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~- -2- 1056284 - fective of a pneumatic tire. Upon the occurrence o~
a tire failure, the pneumatic tire alters its con-~iguration. In the case of a sudden escape of all of the air, it is possible that one and/or both beads quickly slip off their seat on the rim. In the case of slow escape ofthe air, the one and/or both beads are gradually forced o~f their seats on the rim as a result of increasing tangential stresses with the tire becoming gradually flattened on the continuingly moving vehicle. There are great differences among drivers in noticing either one of these conditions and only highly experienced drivers succeed in avoiding accidents~
; Apart from the rapid escape o~the balance o~ the air, the stable connection between the tire and the rim is el~inated thereby impairing the controllability of the vehicle to a large extent. Moreover, as a result o~ the slippage of the tire beads into the drop-center 2~' wheel rim, the tire is subjected to extensive damage.
A number of arrangements and safety devices are known which are intended to remedy or at least to alleviate such vehicular problems. It is for instance know~ in the art to dimension the inflatable hollow body in its inflated state in such a way as to limit same axially substantially to the width of the drop-center of the wheel rim and, radially, to a (maximum) diameter totaling the sum of the diameter of the wheel flange plus twice the thickness of the tire bead (cf.
German Patent Disclosure 24 14 588, Oct. 16, 1975, Uniroyal AG). It is the ob~ect of -3- ~ ~56Z84 .
this prior arrangement reliably to prevent that, wlthout any hazard of the formation of imbalances and without an increase in wear phenomena, it is possible to prevent in the event of tire puncture a slipping of the pneumatic tire beads down into the drop-center of the wheel rim without requiring a multisectional rim or a complicated or costly cons-truction. In the case of this safety device known in the art, the hollow body does not bear or absorb any load in the event of tire failure because, with the tire being completely flattened, the load is being transferred to the rim via the wheel ~langes. However, as a result of its axial dimensions, it supports and maintains the beads firmly on their seats thereby maintaining the firm connection between the tire and the rim even in the event the tire has been completely flattened thereby providing the driver also with adequate controllability.
It was found that it is in many instances desirable that, in the event of tire puncture, the load of the vehicle be transferred not only via the rim flanges in view of the fact that this is attended by substantial friction and may result in a very rapid destruction of the tire. However, in the case of an excessively rapid destruction of the tire, even the emergency mileage reserve, that is to say, the distance over which the vehicle is capable of travelllng slowly but with adequate controllability inthe event of tire fallure, does frequently not suffice to attain the closest repairshop in this ma~ner.

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lOS6~84 In U. S. patent 2,987,093, Urbon, June 6, 1961, there 1~ shown a dual compar1;ment tire containing a ~lexible diaphragm; the assembIy includes rubber stock containlng a lubricant to prevent frictlon between the inner surface of the tire and the dlaphragm. Unllke the present lnvention, the di~phragm in the Urbon patent does not serve as a means ~or supporting the beads and further itself . i8 not puncture-proof.
It ls the obJect o~ the instant invention to lmprove a safety device of the type described above ln greater detail ln such a way that a vehlcle pro-vlded with such a safety device can, even in the case of tlre fallure, contlnue to travel over substantial dlstances wlthout the occurrence of inadmlssible frlction ratlos and, as a result, a premature destruc-tlon of the flat tire by guaranteeing at the same tlme t~at the sa~ety devlce proper is extraordinarily in-~ensitive to damage or destruction.
In accordance with the invention, this obJect i8 achle~ed in that the inflatable hollow body itself i8 designed to bé reslstant to puncture or dlscharge-proo~ and, at least when the hollow body is ln its in-flated state, has a wall section or a corresponding additional antl-frlction material ply (made for example~
of a silicone oil-conta'ning or wax-containing rubber ;~
compound or made of a silicone rubber which is itself .
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inherently anti-~riction) extending up to a radial spread capable of bearing or absorbing a load in the event of tire puncture or failure and of supporting the load.
In the case of this design, the inflatable hollow body bears in its operating state adJoining the wheel flanges a substantial portion of the load if its tlre has been flattened as a result of tire failure such . as a puncture. The load transfer in the area of the wheel rim flanges becomes thus substantially reduced and, - ai~ a result, the marked friction in this area in the course of travel with a flattened tire is likewise being reduced substantially. In the flattened state, the friction in the area of the inflatable hollow body is additionally substantlally reduced during the absorption of the load by the anti-friction rubber compound (e.g.
silicone rubber or rubber containing a substance that endows a favorable sliding property). Moreover, the inflatable hollow body itsel~ is designed to be discharge-proof.
mis ob~ect can be achieved in a variety of ways.
Accordingly, the inflatable hollow body rein-forced by the tire cord in such a way that its radial extension is limited can be provided in its exposed area, in other words, the area pointing toward the inslde Gf the tire, with a belt cGmprising two or more than two thin steel "cord" plies. Said plies ci~n be arranged at identical or different angles, running however in opposite directions. The belt should laterally extend down into the area of the well base, thereby protecting the hollow body reliably against , lOS6284 destruction, especially against the penetration by outside elements into any sensitive surface areas.
Another possibility for designing the safety device to be itself puncture-proof resides in that the inflatable hollo~:! body, which can in turn be reinforced by tire cord, is provided with a puncture sealant sub-stance, whether a semi-plastic puncture sealant layer or a loose particulate sealant, or with a foam or solid filling per se known in the tire art as a protection 7 against penetrating foreign bodies. By using a sealant or a protective filling (foam or solid), one avoids that, upon penetration of pointed ob~ects into the safety device, the hollow body becomes damaged to such an extent that it loses its support function in the case of a tire failure.
Contrary to the many proposals to fill a tire completely with foam, the new safety device offers the advantage that, in the course of normal travel and in the normal operating state of the tire, it is in con-tact with same only in the area of the bead toes and does therefore not exert any effect on the behavior of the tire during travel. Moreover, as a result of the limiting of the foam or solid filling and of the safety device to a relatively small radial area one guarantees against the occurrence of practically an~
imbalance. Rather, the safety device is firmly and immovably seated on the rim and is capable of con- ~
tributing significantly and frequently decisively in ~;
the event of a tire failure to permit the vehicle to continue travelling at moderate speed with good con-trollability.
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7 , 1056Z84 .
A particularly reliable protection of the safety device against impairment can be ob~ained if one protects the inflatable hollow body as described above with a steel cord belt and, on its inside, with a foam ~illing.
Another possibility for designing ~he inflated hollow body to be sure against puncture resides in that one applies at a suitable point of the hollow body a - layer o~ material having a self-sealing ef~ect. Particu-larly suitable for this purpose is a layer essentially composed of adhesive plastic material of a partially vulcanized elastomer or a mixture with same. Such a material is capable of reliably closing a perforation produced through a puncture o~ the hollow body.
Another possibility for achieving ~he self-se~ing o~ the hollow body resides in that small plug-or stopper-like particles made of natural or synthetic rubber are provided on its inside. As a result of suction created by ~e escaping air, the one or the other of the particles comes to be carried along and ls capable of providing a hermetic seal of the resultant perforation (see, ror example, Canadian patent 649,236, Reinowski et al.~ September 25,1962.
m e inventlon is explained in greater detail by means of schematic drawings~relating to an exempli~ed embodiment:
Fig. 1 represents a cross-section ~hrough a vehicle run ~lat pneumatic tire having a s~fety device in accordance with the invention and illus~rates the tire in its partially ~lattened state, and Fig. 2 represents, on a larger scale, a cross-section of a modified exemplified embodiment of such a safety device.
The pneumatic tire 1 illustrated in Fig. 1 has a tread 2 and sidewalls 3 terminating in beads 4 and 5 maintained on seats ad~oinlng the rim flanges of a drop-center wheel rim 6.
It is assumed that the tire has been damaged by a foreign body and, in its condition illustrated in the drawing, has already lost a substantial portion of its lnflation air. Upon further escape of air, the tire applies with its inside surface under load onto the areas of the sidewalls ad~oining the beads 4 and 5 so that the tire comes to be substantially braced on the wheel flanges. Upon continued travel there would occur, ln the absence of the invention, as a result of the attendant squeezing and compressing, a substantial friction between the tire portions lying on one another and, as a result, a premature destruction that would rapidly call an end to any continued travel of the vehicie even at moderate speeds.
me controllability of a vehicle travelling with flattened tires is preserved sufficiently as long as the firm connection between the tire and the rim can be preserved, that is to say, as long as the beads 4 and 5 retain their position on the rim even in the case of a flattened tire.
To achieve this ob~ect there is provided an inflatable hollow body 7 which, in its operating condi-tlon as illustrated in Fig. 1, has an axial width sub--9- lOS6Z84 stantially corresponding to the width of the drop-center wheel rim and protruding radially outwardly out of the bed of thP rim by a predetermined value above the wheel flanges. ~Iowever, unlike the diaphragm in typical dual compartment tire constructions (e.g., U. S. patent 2,987,og3 referred to above) the present inflatable hollow body pro~ects radially outwardly above the wheel flanges by only a minor amount of the total radial distance between the wheel flanges and the plane of the interior cro m of the tire (e.g. less than a quarter of said distance, preferably not more than about one or two tenths of said dlstance). mis is in contrast to a diaphragm which projects radially outwardly for more than half of the distance to the crownO Whereas the diaphragm of the dual chamber tube encloses a ma~or proportion o~ the air volume defined between the tire and wheel rim, the present inflatable tube takes up only a very minor fraction (usually less than 25%) of the total available volume.
The inflatable hollow body consists of an elastomer material 8 that is curable and into which there is embedded a tire cord ply 9 defining the dimension of the cross-section of the hollow body in its inflated state.
mis arrangement guarantees that the outside diameter of the hollow body 7 is by that much greater than the rim flange diameter that, in the event of a tire failure, the hollow body can assume a portion of the load. In the absence of this arrangement, the lower portion of the tread 2 of the tire shown in Fig. 1 would, in the ever.t of cont~nued decrease of the inflation pressure, come to be braced against the tire segments r-at the elevation Or the dash-and-dot line 13, which are supported in turn by the wheel flanges. As a result of the improvement in accordance with the in-stant invention as illustrated in the drawing, the inside o~ the tread section 2 attains in the event of a flattening of the tire a load-bracening support al-ready the moment the tread section inside has attained the dash-and dot line 12. In the process, the tire applies centrally onto the inflatable hollow body that is therefore capable of absorbing a substantial portion of the load and of substantially reducing the the transfer of load in the area of the wheel flanges. -In order to reduce friction occurring upon the mutual contacting of tire components under load and during travel, the hollow body elastomer mass 8 itself or else a special outer ply of the hollow body can consist of a material guaranteeing favorable sliding under certain conditions. A material that proved to be particularly suitable for this purpose is rubber containing silicone oil. However, materials containing wax or other substances are likewise suited for this purpose.
Preferably, one covers not the entire hollow body, rather, one applies a special layer 10 made for instance of silicone oil-containing rubber so as to cover completely only the exposed area of the hollow body. In the event of tire puncture or failure, this layer guarantees that a lubrication becomes ef~ective --10_ . . .. . ~ . . . . . . . .

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-ll- 1056284 between the superpositioned layers of rubber, which reduces substantially friction and generation of heat and, consequentl~, prevents to a large extent premature tire destruction during trave] on a flat.
The rubber into which a lubricating substance is compounded to provide the desired anti-friction properties may be any suitable conventional rubber normally used in the construction of tires, whether natural rubber or a synthetic rubber (e.g., SBR, NBR, polychloroprene, or other elastomer based on conjugated - diene [e.g., butadiene, isoprene~ homopolymers or copolymers ~e.g., copolymers with copolymerizable monoethylenically unsaturated monomers such as styrene, acrylonitrile, vinylpyridine, etc.~, as well as rubbers - 15 with little or no unsaturation such as ethylene-propylene copolymer, ethylene-propylene-non-conjugated diene terpolymers ['IEPDM"l, polyurethane elastomers, thermo-plastic rubbers, etc.). Any suitable known lubricating or anti-friction substance may be compounded into the elastomer in amount sufficient to provide the desired low ~riction properties. As indicated, silicone oil is a preferred anti-friction additive for the rubber but other lubricating substances can also be used such as waxes (animal, vegetable, mineral or synthetic wax), various softeners or plasticizers (e.g. high boiling phthalate, adipate or sebacate esters of such alcohols a~ octyl alcohol, cyclohexanol, etc.), or lubricants such as erucyl amide, oleyl amide, sodium stearate, aluminum stearate, oleyl palmitamide, stearyl eurcamide, oleæmide, etnylene bis stearamide, and the like. More than one such anti-friction additive may be incor-porated in the rubber compound if desired. Instead of employing a rubber into which an anti-friction sub-stance is compounded prior to vulcanization, one may employ, as the special layer 10 (or as the inflatable body 7 in the event that the special layer 10 is omitted), an elastomer which is in itself inherently anti-friction, notably silicone rubber curable to an elastomeric state, or a polytetrafluoroethylene composition.
An example of an anti-friction rubber stock containing silicone oil is (by weight) 50 parts natural rubber smoked sheet, 50 parts cis-polybutadiene rubber, 45 parts furnace carbon black, 4 parts process oil (petroleum hydrocarbon oil of aromatlc type), 5-15 parts dimethyl silicone oil (viscosity 60,000 cp), parts tackifier (hydrogenated rosin), 2 parts paraffin wax, 2.5 parts antioxidant (acetone-diphenylamine con-densatinn product), 4 parts zinc oxide, 1.5 parts stearic acid, o.8 part accelerator (tetramethyl thiuram disulfide) and 2.1 parts sulfur.
The safety device can most reliably perform its duty when it has itself been rendered largely immune to destruction or failure even in those instances in which a forelgn body in the damaged tire comes in direct con-tact with the safety aevice with the flattening of the tire.
In the case of the example according to Fig. 1, this ob~ect is materialized in that, following the in-troduction of the hollow body into the drop-center rim, the hollow body is being filled out with a foam 11 (e.g., polyurethane elastomer foam) so as to attain the desired shape and cross-sectional dimension, with said foam guaranteeing, even in the event of penetration of the hollow body by a pointed element, that the hollow body substantially retains its supporting function.
In the normal state of operation of the tire, nelther the foam filling nor the hollow body 7 as a whole (which ls in contact with the tire in the area . of the bead toes only and which, having small radial dimensions, is firmly embedded in the drop-center rim) can impair the travel properties of the tire. Alter-natively, in place of a foam filling, suitable solid ; filling may be used (see, for example, U. S. patent 3,866,651, Gomberg3 Feb. 18, 1975) to prevent collapse of the hollow body even if punctured.
In the case of the exemplified embodiment ac-cording to Fig. 2, the inflatable tube-shaped hollow body ` 24 is fitted into the drop-center wheel rim 23 in the ` identical manner as in the case of the exemplified em-bodiment according to Fig. 1, with the hollow body re-liably supporting and securing the beads 21 and 22 of the tire 20 in the condition shown in the drawing.
Likewise in this case, the hollow body 24 can consist o~ a curable elastomer material 25 designed, if indicated, to have its shape retained by means of a tire cord. The hollow body is reliably protected against damage by foreign bodies or the like by means of a belt 26 preferably consisting of two or more than two thin plies 27, 28 of steel cords arranged at the identical or a different slope but oriented in any event in opposite directions. As a result, the belt forms a dense net of steel on the exposed areas of the inflatable hose-shaped hollow body, with the steel netting reliably preventing a piercing of the hollow body by foreign elements. For this purpose, the belt 26 extends with its edges preferably down into the drop-center rim, an area in which the inflatable hollow body is reliably protected by the rim itself.
Likewise in the case of this exemplified em-bodiment, the hollow body itself can be made of an elastomer composition containing a silicone oil,wax, or similar substances as described above. Preferably, however, there is provided a special ply made for in-stance of such rubber composition and designated by the reference 29.
It is of c`ourse understood that, even in the case of the exemplified embodiment according to Fig. 2, the inflatable hollow body can be provided in addition also with a foam filling similar to the foam filling 11 of the exemplified embodiment according to Fig. 1, or wlth a solid filling~ in order to reinforce even further the unimpairability of the safety device under all circumstances.
Even though it is known that silicone oil con-taining rubber compounds or rubber compounds exuding for instance wax do have a friction-reducing effect, thls arrangement, in combination with the new safety device, plays a special part as a result of its applica-tion on the safety device itself in view of the fact that this arrangement guarantees not only against a premature destruction of the tlre itself but, above all , . ~ . -. . - ;

-15- ~056Z84 else, assures also the maintenance of the operating capacity of the safet~ device. The moment the tire has ~ssumed a sufficiently flat state follo~ing a tire failure, the sliding agent f~om the special rubber ply o~ the safety device enters into action under the effect of the compression o~ the sur~ace pressure and the in-creased temperature caused by friction so that, as in the case of an elastic bearing, a rolling motion under load becomes possible. For operability purposes, this arrangement is just as decisive as the arrangements relating to the indestructability of the safet~ device itselr.
A further possibilit~ to design the safety device to be itself ~ailure-proof resides in that the inflatable hollow body provided -lith cord fabric and/or a thin steel cord comprises in addi~ion or in the alternative a self-sealing means, notably a layer made o~ a self-sealing substance. ~aid layer can be arra~ged at a suitable site of the hollo~r body or instance on its inside or else between the hollow elementary body and the sliding-promoting ply ~ else inside or at the belt ply. Any suitable conventional self-sealant or puncture-sealant ~or pneumatic tires or inner tubes may be used ~or this purpose, such as for example those disclosed in U. S. patents 2,782,829, Peterson et al., February 26, 1957; 2,802,505, PeterYon et al., August 13, 1957, 3,903,947, Emerson, September 9, 1975; 3,935,893, Strang et al., February 3, 1976; 3,952,787, Okado et al., April 27, 1976; Canadian patent 572,799, Iknayan et 3o al., March 24, 1959; or Canadian Serial No. 246,948, Farber et al., M~rch 2, 1976. As is well known, such sealant com~ositions are usually semi-plastic materials, frequently based on a cured or partially cured elastomeric component in combination with a permanently plastic or tacky component. Alternatively, free particulate solid type of sealant may be used, as in Canadian patent 649,236 re~erred to pre~lously.
In this case, one can preferably use partially vulcanized elastomers, in particular rubber compounds a~ailable in their tacky, plastic state.
Self-seallng tire failure sealing materials such as, for ~nstance, depolymerized natural rubber or high-molecular rubbers or unsaturated elastomers con-taining titanium ester and that are partially vulcanizable can llkewlse be used (see Canadlan Sab~ No. 246,948, referred to above).
Moreover, mixtures made up of butyl rubber and ` polychloroprene or else neoprene or mixtures made up of polyisobutylene and chloroprene or neoprene are suitable for this purpose.
The various forms of manufacturing a tubelike body ha~ing included a belt reinforcement are well knol~n to those skilled in the art. For example, a tubelike body, i.e. which consists of a silicone oil containing rubber stock ~Jall, may be built up on a mandrel. An inner liner tape may be wound up on the mandrel in order to have an overlapped bandage. Thereon applied 1s a puncture sealant layer and thereupon applied is a cross angled, thin, steel cord double ply belt rein-forcement. Then a silicone oil compounded rubber tape may be wound up to a helical lined tube covering all , -17- 1056Z~4 the other elements and forms an endless body. This green tube with a valve may then be vulcanized in a mold to receive a safety body as described above.
Preferably, it is appropriate to use separate valves for inflating the main chamber of the tire and the tubelike body chamber. The preferred mounting of the body onto the rim is: first, one of the beads of the tire is put on the rim; second, the reinforced tubelike body is stripped over the free rim flange to put it into the rim, and third, the other bead of the tlre is put on the rim, and thereafter, the finishing mounting of the tire.
It is only thanks to all of the arrangements referred to above that the intended object is materialized, i.e., reliably to guarantee under all circumstances that a vehicle can, in the case of tire punctu~e or failure, reach at moderate speed a repairshop or service station that is still miles away. One prevents the dropping down of one of the beads or the slippage of same into the drop-center ~rheel rim and that, owing to the high friction e~fect, the tire, in particular however the safety device, become unusable as a result of bared points and, finally, one prevents the hazard that the safety device becomes inoperational as a result of other occurrences, in par-ticular as a result of penetrating pointed foreign bodies.
In the embedded reinforcing plies 9, the cord angles described in Canadian patent 782,351, MosRhart et al., lssued Aprll 9, 1968, may be employed.

Claims (6)

What is claimed is:

1. Safety device on vehicles comprising a single-piece drop-center rim and a tubeless pneumatic tire whose beads, owing to the pressure prevailing inside the pneumatic tire, can be forced against the bead seats of the drop-center rim and are secured against slippage from their seats by means of an inflatable, annular hollow body reinforced with tire cord material, with the hollow body being axially limited in its inflated state substantially to the width of the drop-center rim and having in a radially outwardly directed wall area a radially ex-ternally positioned thickening of the wall extending down into the axially oriented wall areas, gradually radially diminishing toward the inside, characterized in that the inflatable hollow body is itself designed to be discharge-proof and is provided at least on its surface with lu-bricating material made out of an anti-friction rubber compound and attaining in the case of a tire failure an at least load-absorbing radial expansion, the radially out-ward projection of the said hollow body above the rim flanges amounting to less than a quarter of the radial distance be-tween the rim flange and the plane of the interior crown of the tire.

2. Safety device according to claim 1, characterized in that the inflatable hollow body is filled with foam.

3. Safety device according to claim 1, characterized in that the hollow body is reinforced along its exposed wall area by a belt consisting of at least two intersecting plies made of thin steel cord.

4. Safety device according to claim 3, characterized in that the belt edges extend down into the area of the drop-center rim.

5. Safety device according to claim 1, character-ized in that there is provided in addition a layer made of self-sealing material incorporated in the hollow body.

6. Safety device according to claim 1, character-ized in that in the free inside space of the hollow body there is present, loosely scattered around, a number of plug-like small elements made of natural or synthetic rubber.