Patent GB-1359467-A (GB)
Title: Pneumatic tyre and wheel rim assemblies
IPC: B60C15/02
Filed: 1971-04-03
Abstract: 1359467 Lubricating contacting interior surfaces of a tyre on deflation DUNLOP HOLDINGS Ltd 9 June 1971 [20 June 1970 3 April 1971] 30033/70 and 8592/71 Heading B7C A pneumatic tyre and wheel assembly with a single inflation chamber comprises a wheel rim with a pair of tyre bead retaining flanges, a tyre with a tread width greater than the distance between the rim flanges, means to prevent the tyre from being dislodged from the rim when running deflated, and a flowable liquid lubricating compound for lubricating those interior surfaces of the tyre which contact when the tyre deflates under load, to thereby prevent destruction of the tyre due to frictionally generated heat and enable continued running of the tyre in the deflated state. The lubricating compound may be thixotropic with a viscosity in the range 10,000-200,000 centistokes at 38 C., may be miscible with water, may contain a liquid component with a vapour pressure at 140 C. of less than 50 mm. of mercury, and may have a boiling-point of at least 90 C., a freezing point below - 20 C., and a specific gravity less than 1À4. The lubricating compound may comprise a volatile liquid component, e.g. an aqueous gel, which serves to volatilize and partially re-inflate the deflated tyre, in combination with a lubricating component, e.g. glycerol, with a boiling-point sufficiently high to ensure that all the component does not boil off when the tyre is run deflated. The volatile liquid component may have a vapour pressure at 80 C. of above 200 mm. of mercury and a boiling point in the range 70-110 C., and there may be sufficient of the volatile liquid component to generate in a volume of at least 4 times that of the inflation chamber a pressure of 1 p.s.i. at 68 C. Other components which the lubricating compound may contain are a puncture sealant, e.g. chopped cotton, wool, asbestos or synthetic fibres; a freezing point lowering agent, e.g. ethylene glycol; an agent to increase the lubricating qualities, e.g. molybdenum disulphide; a wetting agent; a foaming agent, e.g. a detergent, together with a defoamer to control the extent of foaming; an antioxidant; a bactericide; and a viscosity index improver. Numerous examples of suitable materials for use in the lubricating compound are given in the Specification in addition to those mentioned above, and specific examples of suitable formulations for the compound are also disclosed. The amount of lubricating compound provided may be between 105 and 1300 millilitres per square meter of tyre interior surface. The tyre may have an aspect ratio of between 30 and 75%. The means to prevent the tyre from being dislodged from the rim may comprise a bead spacer ring, or removable studs on the rim, and/or a flat base rim, i.e. a rim without a well into which the tyre beads can fall. The flat base rim may be divisible to permit tyre mounting and demounting, or may be a "crimped" rim, i.e. a rim initially formed with a well which is then closed up after a tyre has been mounted on the rim. The tyre may be secured to the rim by swaging the rim over the tyre beads. Specifications 1,359,461, 1,359,462, 1,359,463, 1,359,464, 1,359,465, 1,359,466 and Application No. 7024/71 are referred to.