Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
  • B60C5/00—Inflatable pneumatic tyres or inner tubes
  • B60C5/002—Inflatable pneumatic tyres or inner tubes filled at least partially with foam material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
  • B60C17/00—Tyres characterised by means enabling restricted operation in damaged or deflated condition; Accessories therefor
  • B60C17/04—Tyres characterised by means enabling restricted operation in damaged or deflated condition; Accessories therefor utilising additional non-inflatable supports which become load-supporting in emergency
  • B60C17/06—Tyres characterised by means enabling restricted operation in damaged or deflated condition; Accessories therefor utilising additional non-inflatable supports which become load-supporting in emergency resilient
  • B60C17/065—Tyres characterised by means enabling restricted operation in damaged or deflated condition; Accessories therefor utilising additional non-inflatable supports which become load-supporting in emergency resilient made-up of foam inserts
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
  • B60C7/00—Non-inflatable or solid tyres
  • B60C7/10—Non-inflatable or solid tyres characterised by means for increasing resiliency
  • B60C7/101—Tyre casings enclosing a distinct core, e.g. foam
  • B60C7/1015—Tyre casings enclosing a distinct core, e.g. foam using foam material
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/04—Homopolymers or copolymers of ethene
  • C08L23/08—Copolymers of ethene
  • C08L23/0846—Copolymers of ethene with unsaturated hydrocarbons containing other atoms than carbon or hydrogen atoms
  • C08L23/0853—Vinylacetate

Definitions

• the present invention relates to tyres, and in particular but not exclusively to tyres for vehicles such as cycles, wheelchairs and the like.
• One aspect of the invention relates to a tyre core intended to replace the inner tube of conventional pneumatic tyres, and to the composition and method of manufacture thereof.
• Other aspects of the invention relate to other features and elements of tyre construction, composition and fitting.
• Pneumatic tyres provide excellent load support and shock absorbing properties in many applications.
• many vehicles such as automobiles, aircraft, military vehicles, motorcycles, bicycles, wheelchairs and the like are provided with pneumatic tyres.
• Pneumatic tyres generally comprise an outer tyre casing and an inner tube which is located between the wheel rim and the tyre casing and which is inflated with gas, typically air, to fill the rim-tyre casing space; the inflated inner tube provides the means for pneumatic support of the vehicle and retains the tyre casing on the rim.
• tyres known as "tubeless" tyres
• tubeless tyres comprise a gas impermeable tyre casing the bead of which is sealed to the wheel rim.
• tubeless tyres are now used in the great majority of automobile applications, such tyres are unsuitable for application in which the wheel rim is not readily sealable, for example, in spoked wheels as commonly used on bicycles.
• pneumatic tyres provide excellent support and cushioning they have some drawbacks .
• the tyre material must have a low permeability to the gas contained therein but remain flexible to maintain the cushioning effect of the tyre. The number of materials which fulfil these requirements tends to be rather limited.
• Such materials include butyl rubbers and halogenated butyl rubbers. These materials are expensive compared to conventional rubbers, which do not possess the required degree of gas impermeability. The valves of such inner tyres are also required to seal sufficiently well so that leakage is kept to a minimum.
• a major drawback, however, of certain foam filled tyres or cores is that the foam is readily flexed or deformed. In certain materials, this may result in excessive heat build-up in the tyre in use, which may lead to a breakdown of the foam material resulting in reduced support, increased rolling contact and subsequent tyre damage.
• a certain degree of flexibility however is necessary to provide the desired cushioning properties as provided by the conventional gas- filled pneumatic tyre.
• Harder, or less flexible tyre filling materials, such as the non- foam material of Gomberg (US Reissue 29,890) are claimed to have reduced heat build-up properties.
• a reduction in cushioning may occur, and such tyres may be relatively expensive as more material is required than those employing foam cores.
• US 4,416,844, US 4, 683,929 and US Re 29,890 describe foam- filled deflation-proof pneumatic tyres which are produced by injecting the filling material into the outer tyre casing and wheel rim cavity, to create an integral arrangement as described above .
• US 3,348,597 describes a polyurethane foamed rubber tyre which is formed directly on the axle.
• US 3,987,832 describes a solid wheel which comprises a hard radially extending core enclosing a hub sleeve.
• US 4,033,395 describes a tyre wherein the outer tyre casing and core are integral.
• foam cores have a skin covering the surface of the core which is intended to reduce abrasion and damage to the core.
• the skin also protects the open-cell core from filling with water in wet conditions.
• This document describes the core as being 10% larger in cross section than the tube cavity in which it is housed, it is believed this would make the fitting of such a tyre difficult.
• such a core is not circumferentially symmetrical - having a portion for extending into the rim and engaging the spoke ends - orientation of such a core on fitting to a wheel would be necessary, which may increase the fitting difficulty.
• compositions for use in the manufacture of a tyre core wherein said composition comprises a copolymer of ethene with a vinyl acetate.
• the copoly ⁇ ner thus formed is known as an ethylene vinyl acetate copolymer
• the vinyl acetate is un-substituted.
• the properties are:
• EVA compositions have been found to possess such properties .
• EVA compositions are preferred because they are relatively light weight, that is of a lower density compared to existing polyurethane compositions.
• EVA tyre cores, tyre inserts and tyres have also been found to provide relatively low rolling resistance which, without
• EVA also provides the required hardness, while retaining the desirable flexural properties of tyre cores, for example memory properties, which ensure good shape recovery following removal of a deforming force. This ensures good replication of the desirable properties of conventional pneumatic tyres.
• EVA also desirably does not, in general, contain ozone depleting substances nor heavy metals, thus conferring additional environmental benefits in EVA product manufacture or disposal .
• materials other than EVA may be utilised to form tyre cores having such desirable properties.
• EPR and EPDM ethylene-propylene rubbers
• low polypropylene in the region of 15%
• Hytel rubber also Hytel rubber
• the amount of vinyl acetate monomer incorporated into the preferred EVA copolymer in relation to the ethene content by weight may be between 30% and 60%.
• the amount of vinyl acetate is between 30% and
• said EVA may be cross-linked EVA, wherein the cross -linking is achieved by any suitable method.
• the composition may be in the form of a foam. Foaming may be achieved by any suitable method in the art, for example mechanical agitation or chemical means .
• the foam is preferably of closed cell construct, the closed cell construct offering the advantage that liquid, typically water, will not be taken up by the tyre, and an outer "skin" is not required. In other embodiments a "skin" may be desirable, for example to protect the core from abrasion or to facilitate fitting, and may be formed as a consequence of the manufacturing or forming method.
• the composition may contain one or more agents independently selected from the following classes: lubricants, cross -linking agents, foaming agents and fillers. It is to be understood that more than one agent may be selected from each of the above classes. Any suitable lubricant may be used. Typical lubricants include long chain carboxylic acids, for example stearic acid.
• Any suitable cross-linking agent commonly known in the art may be used, such as dicumyl peroxide (DCP) .
• Suitable foaming agents include those commonly known in the art such as azodicarbonamide (ADCA) .
• Suitable fillers include any suitable calcium salt and those fillers commonly known in the art such as mica, silica, calcium carbonate, carbon black and clay.
• a preferred formulation has the following constituents :
• a tyre core or insert having a Shore (A) hardness of 30° - 70°, preferably 35° - 60°.
• Shore (A) hardness of 30° - 70°, preferably 35° - 60°.
• the most preferred Shore hardness will depend on the intended use of the core, for example most preferably 38° to 40° for a leisure and commuting cycle, and 48° to 50° for a wheelchair.
• the tyre core may be formed for fitting within a tyre casing, or may be formed within a tyre casing, or the tyre casing formed around the core, or the casing and tyre core formed simultaneously.
• a tyre produced using the composition according to the first aspect is provided.
• the tyre may be of the type which is moulded as a unit piece containing a core made using the composition of the first aspect and an outer, abrasion resistant skin or casing.
• the composition may be used to make a tyre core which may be inserted into a conventional pneumatic tyre casing in place of or in combination with a pneumatic inner tube.
• a core may be any suitable shape, including a torus shaped core.
• Such a torus shaped core has a circular cross-section, however other cross-sectional shapes may be desirable in certain circumstances, such as half -moon or crescent shapes, where a pneumatic tube is to be retained.
• the core may have a smooth, irregular or discontinuous surface or profile; a smooth surface may facilitate fitting while a rougher surface may facilitate grip between the tyre elements and prevent or limit relative movement therebetween.
• the characteristics of different areas or sections of the core may differ, for example the core may include a relatively stiff or hard central element, to minimise rolling resistance, and softer side portions, to provide greater grip when cornering, or a similar effect may be possible by providing a triangular core profile.
• the core may also be configured such that by reversing the core orientation within the tyre casing it is possible to provide the tyre with different characteristics; each half of the core section may be formed from a material having different properties, for example a relatively soft material and a relatively hard material.
• the core may also be configured to facilitate contact with the spoke nuts within the rim, to support the nuts and also to assist in preventing the nuts vibrating loose from the spokes. This may be achieved by providing the core with an appropriate profile, or by forming the inner surface of the core in a softer material which will readily deform to extend into the rim.
• the core may contain one or more cavities of gas such as air, or such cavities may be filled with gels, foams or other materials possessing particular desirable properties. For example a torus shaped core having a central cavity may be provided, resulting in a tubular configuration.
• the core may not necessarily fill the entire wheel rim - tyre casing cavity, for example a pneumatic tube or element may be provided, or separate elements may be provided to engage and support the spoke nuts .
• a core is used in conjunction with a pneumatic inner tube it may be preferred that the core is located directly beneath the tyre casing, with the inner tube sandwiched between the wheel rim and the core. Tyres of this arrangement have been found to retain the desirable properties of solely pneumatic tyres while being effectively puncture proof. This mode of construction may be particularly applicable to half-moon or crescent shaped cores.
• a method of producing a tyre core comprising the steps of : providing an EVA composition; mixing said composition; moulding said mixed composition under pressure; and shaping said moulded composition to form a tyre core.
• any suitable mixing method may be used and the components of the EVA composition may be mixed in any suitable order.
• a preferred mixing apparatus is a two roll mill which is commonly known in the art.
• the EVA composition is introduced into the mill in the order of: EVA, lubricant, cross-linking agent, foaming agent, filler.
• the roll mixing may be conducted at any suitable temperature conveniently provided by controlling the temperature of the rolls. It has been conveniently found that good mixing is achieved with one roll set at a temperature in the region of 100°C and the other roll at the
• Moulding may be achieved using any suitable method. Conveniently this is achieved by injection moulding.
• the moulded composition once removed from the mould may then be shaped using any suitable method to form a tyre core.
• pieces of the moulded composition may be cut to form rods of the composition.
• the offcuts may be used for other purposes, for example for location in a tyre rim adjacent to the spoke nuts.
• the ends of the rods may then be joined to form the tyre core. Joining may be accomplished using adhesive applied to each end of the rod.
• the rod ends are preferably flat cut, however other profiles suitable for bonding may be used.
• the ends of the rods remain free, to facilitate fitting; this may allow a rod to be fitted to, for example, a bicycle wheel without having to remove the wheel from the bicycle.
• an apparatus for forming a puncture resistant tyre core comprising means for shaping an EVA composition into a rod configuration.
• tyre core is relatively rough and therefore grips the wheel rim and inside tyre surface, thus reducing slippage and disengagement of the tyre from the wheel.
• a tyre core for location in the volume defined between a tyre casing and a wheel rim, the tyre core comprising a resilient rod having free ends, the rod length being selected to conform to the length of the volume between the casing and rim.
• the invention also relates to a method of fitting such a core to a tyre.
• tyre cores may be fitted in rod form.
• stock keeping, and production of tyre cores may be simplified, as a retailer may be supplied with long lengths of rod which may be cut to size in accordance with individual customers' requirements.
• Such tyre cores also facilitate accommodation of variations in rim and tyre casing dimensions; rims and tyre casings tend to be provided in a range of "standard" diameters and widths, however different manufacturers tend to produce different rim and tyre configurations, and the ends of tyre cores in accordance with this aspect of the invention may be trimmed or shortened accordingly to provide a "perfect" fit.
• Figure 1 is a sectional view of a tyre core in accordance with an embodiment of an aspect of the present invention
• Figure 2 is a sectional view of a tyre core in accordance with a further embodiment of the present invention.
• Figure 3 is a sectional view of a tyre core in accordance with a still further embodiment of the present invention .
• the core 10 is circular in cross section and is intended to replace a conventional pneumatic inner tube, that is the core 10 is located between a tyre rim and the tyre casing.
• the core is of an EVA foam composition, as will be described in due course .
• FIG. 2 of the drawings illustrates a section of an EVA tyre core or insert 20 in accordance with a further embodiment of the present invention.
• the core 20 is part- circular in section and is intended to be inserted in the crown of a tyre, between an existing pneumatic tube and tyre casing. It has been found that, when the tube is inflated to its normal recommended pressure, as used in the absence of the core 20, the tyre retains the desirable properties of a solely pneumatic tyre, but is effectively puncture proof. It has also been found that the core 20 is easier to fit than the core 10 described above.
• Figure 3 of the drawings illustrates a section of an EVA tyre core or insert 20 in accordance with a further embodiment of the present invention.
• the core 20 is part- circular in section and is intended to be inserted in the crown of a tyre, between an existing pneumatic tube and tyre casing. It has been found that, when the tube is inflated to its normal recommended pressure, as
• EVA tyre core 30 in accordance with a still further embodiment of the present invention.
• the core 30 is rectangular in section and is intended to be inserted in the crown of a relatively small diameter "balloon" tyre, such as utilised in electrically-powered wheelchairs, between an existing pneumatic tube and tyre casing.
• a relatively small diameter "balloon" tyre such as utilised in electrically-powered wheelchairs
• the rectangular form of the core 30 does not have an adverse effect on the tyre performance; it appears that the properties of the preferred EVA composition, as described below, are such that the core 30 may deform to fill the tyre casing, and in doing so does not lose the advantageous properties of the composition.
• the manufacture and testing of the core 10 will now be described in some detail, and it will be apparent to those of skill in the art that the manufacturing process may be adapted as required in order to produce the other cores 20, 30 described above.
• the ethylene monomer content was added to a two roll mill.
• Stearic acid 1 part (w/w) , DCP 1 part (w/w) , ADCA 2 parts (w/w) and calcium carbonate 40 - 50 parts (w/w) were then added to the mill in that order.
• the formulation was then removed from the mill and then introduced into a 6 ounce - 150 ton injection moulding machine.
• the material contained within the mould was cooled by cooling the mould with water.
• the cooling water had a temperature of 20°C on input to the mould.
• cylinder temperatures of the injection moulding machine were 140 °C and 180 °C.
• the moulding timing was as follows:
• the resultant moulded EVA composition was removed from the mould.
• the dimensions of the sheet depended on the mould used, but typically were 40 - 41" x 64 - 65" x 40 mm and 42 - 43" x 65 - 66" x 50 mm.
• the moulded EVA composition following removal from the mould, was then cut into strips using a band saw. The strips were then fed into a cutting machine to produce cylindrical rods.
• Typical sizes of rod could be made by using different cutting heads in the cutting machine. Typical sizes of rod have the following diameters: 1 . 75 “ - 1 . 95 “ ; 2 . 0 “ - 2 . 10 “ ; 1 . 25 “ - 1 . 375 “ .
• a rod was then cut to the required length for the particular wheel to which it was to be fitted, and the ends glued together using impact glue containing Tolvene and Polene R.C. to form a torus shape.
• the torus could then be inserted directly into a conventional wheel, for example a bicycle wheel in place of the inner tube therein.
• the tyre core had a shore hardness of 50° (ASTM D2240) .
• a company based on a large site uses a fleet of 24 bicycles to facilitate movement of personnel around the site.
• Half of the fleet of bicycles were fitted with tyre cores 10 as described above and used over a 12 month trial period. Users found that the 12 test cycles performed in a similar manner to the bicycles fitted with conventional pneumatic tubes, providing comparable rider comfort, handling capabilities and tyre casing wear, and of course did not experience any punctures or other tyre failures.
• the company selected to abandon pneumatic tubes and fitted the tyre cores 10 to the remainder of their fleet of bicycles.
• Example 2 A wheel builder, who builds wheels by hand for cycles and wheelchairs, was supplied with a number of 26" tyre cores 10. Over a six month period cycles fitted with the tyre core were ridden over a variety of terrain, giving a comfortable ride, and exhibiting no problems. In particular, it was noted that no tyres were forced off the rim, even under extreme pressure and stress, in contrast to the behaviour of existing "solid" polyurethane tyres. Further, the wheels to which the cores were fitted experienced no adverse effects, notably no hub damage, no loosening of spokes, and no effect on the trueness of the wheels .
• a number of tyre cores 10 were supplied to a cycle road racing team, who carried out a number of tests and comparisons with existing products, as described below.
• the tyre insert was fitted to a 26" ATB wheel, with a payload of 72.5 kg and run continuously for 100 hours, at a continuous speed of 15 mph therefore covering 1,500 miles non-stop .
• the hardness of the final composition may be chosen for particular applications such that simulation of differing conventional tyre pressures is achieved.
• a shore hardness of 48 to 50° has been found to be particularly suitable for wheelchair use, whereas a shore hardness of 38 to 40° has been found to be particularly suitable for leisure and commuting bicycles.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Tires In General (AREA)
• Compositions Of Macromolecular Compounds (AREA)

Applications Claiming Priority (5)

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• 1999
  • 1999-11-22 CA CA002351826A patent/CA2351826A1/en not_active Abandoned
  • 1999-11-22 WO PCT/GB1999/003886 patent/WO2000030873A1/en not_active Application Discontinuation
  • 1999-11-22 AU AU15101/00A patent/AU1510100A/en not_active Abandoned
  • 1999-11-22 EP EP99957377A patent/EP1131215A1/de not_active Withdrawn
  • 1999-11-22 CN CN99814155A patent/CN1367741A/zh active Pending
• 2002
  • 2002-03-11 HK HK02101831.9A patent/HK1040071A1/zh unknown

Non-Patent Citations (1)

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