GB2047736A

GB2047736A - Lubricant-containing pneumatic tires

Info

Publication number: GB2047736A
Application number: GB8011117A
Authority: GB
Original assignee: General Tire and Rubber Co
Current assignee: Aerojet Rocketdyne Holdings Inc
Priority date: 1979-04-26
Filing date: 1980-04-02
Publication date: 1980-12-03
Also published as: IT1130355B; JPS55145011A; CA1104474A; FR2454918A1; DE3004723A1; IT8019139A0

Abstract

To facilitate relative movement between the internal surfaces of a pneumatic tire which come into contact when the tire is run in a deflated condition, the interior of the tire is coated with a lubricant and solid micro- beads of diameter 32-1,000 microns are added to the lubricant. When the tire is run flat, the balls and lubricant reduce rubbing friction and temperature rise which would otherwise occur by rubber- to-rubber contact. The lubricated ball containing tire can be run flat to a service station.

Description

SPECIFICATION Pneumatic tires This invention relates to pneumatic tires.

A number of designs have been proposed to increase the stability and rideability of the tire when deflated or flat.

U.S. Patent 4,057,092 relates to a circumferential locking lug. Other proposals, such as U.S. Patent Nos.

2,040,645; 3,392,722 and 3,610,308 have special units in the interior of the tire. Other proposals include liquid lubricants within the tire (U.S. Patent 4,045,362) and solid lubricants which liquify on the addition of chemicals (U.S. Patent 3,931,843).

To reduce the friction generated by tires running flat, the inclusion of either liquid or solid lubricants on the tire interiors has been proposed. U.S. Patent 2,040,645, for instance suggest a graphite lubricant; U.S. Patent 3,610,308 mentions the use of liquid silicone and U.S. Patents 3,739,829; 3,850,217 and 4,045,362 describe the use of polyalkylene glycols, glycerol, propylene glycol, silicone and other lubricants. The liquid lubricants, however, are not evenly distributed in the operating tire and can adversely effect balance and tire performance. Solid lubricants which liquify at flat tire temperature are also known but they require a chemical reagent for liquification (U.S. Patent 3,931,843).While the use of lubricants has significantly reduced the friction and heat generated by running a tire flat, the prior art has not provided a complete remedy to the heat and friction problem.

The present invention comprises using lubricated rolling microbeads (balls) as the lubricating medium.

The employment of the rolling microbeads can then have the same effect as the use of ball bearings in ball races where the rolling mode greatly minimizes friction and wear. When applied to the run flat tires or similar types of applications involving sliding between rubber surfaces, the surfaces should be partially or totally separated in the presence of the rolling elements. Rubber-to-rubber sliding may then be replaced by the desired mode of rolling, thus reducing friction and the associated heat build-up.

Any of the prior art lubricants may be used in combination with the microbeads. The microbeads can have a diameter of from 32 to 1,000 microns (0.001 to 0.039 in.) and preferably from 120 to 800 microns (0.005 to 0.031 in.). They must also be strong enough not to break when the tire is run flat. Suitable microbeads are available from the Microbeads Division of Cataphote Corporation, Jackson 5, Mississippi.

The preferred microbeads are manufactured from high-grade, optical crown glass. The composition is of a type designed to resist wear and fracture upon impact. The microbeads are annealed in their spherical shape to equalize internal stresses and resist fracture.

The preferred microbeads are spherical in shape, containing not more than 15% irregularly shaped particles. They are reasonably free of sharp angular particles, the quantity of which does not exceed 1%; particles showing milkiness or surface scoring or scratching, the quantity of which does not exceed 2%, and foreign matter, the quantity of which does not exceed 1/2%, including iron particles, the quantity of which does not exceed 1/10%.

Microbeads are available in the following size ranges: Micron Range 710 - 350 210 - 105 590 - 297 149 - 74 500 - 250 105 - 53 420 - 210 74 - 44 297 - 177 53 - 10 250 - 149 Any of the lubricants disclosed in the above discussion of the prior art can be used in the practice of the present invention.

Examples The A-1 lubricant which was used in the examples was prepared by mixing the following ingredients: Ingredients Parts by weight Ethylene glycol 70 Water 30 Polyethylene oxides WSR 301 (Union Carbide) m.w. 4 x 106 0.05 WSR 205 (Union Carbide) m.w. 6 x 105 0.03 Polyssaccharide Kelzan (Kelco Co.) xanthane gum m.n. > 106 0.15 100.23 The microbeads used were solid spheres and had a diameter of 350 to 710 microns (0.0138 to 0.0280 in.).

The significant effect of microbeads in friction reduction between rubber surfaces which slide over one another is shwon in Table I below with the following test conditions: Sliding speed = 20 inches/minute (0.85 cm/sec) Temperature = ambient Normal load = 22.1 pounds (10.05 kg) Approximate cross-sectional area of sliding surface = 3.75 sq. in. (88.7 sq. cm.) TABLE I Dry and lubricated friction between sliding rubbers Friction Coefficient Lubricant Static Kinetic None (rubber-to-rubber) 2.89 2.17 A-1 lubricant 0.41 0.34 Microbeads* 0.18 0.12 Microbeads plus A-1 lubricant 0.14 0.065 *Microbeads Class Ill, MS-XPX; Cataphote, Division of Ferro Corp.

The results are self evident, showing the effectiveness of the microbeads as a lubricating medium for sliding rubber surfaces. A thirty-fold reduction in kinetic friction was achieved when the microbeads were combined wih the ethylene glycol/water based lubricant A-l.

Similar results are also found in the case of a radial tire innerliner sliding on a bead wrapping compound as shown in Table II.

Table il Sliding between an innerliner and a bead wrapping compound Sliding speed = 50 inches/minute (2.12 cm/sec) room temp.

Normal load = 5.4 Ibs. (2.5 kilograms) Approximate cross-sectional area of sliding surface = 6.25 sq. in. (40.3 sq. cm.) Friction Coefficient Lubricant Static Kinetic None (rubber-to-rubber) 1.8 1.75 Paraffin wax 0.83 0.5 Microbeads plus paraffin wax (No. 155), International wax and Refining Co. 0.21 0.15

Claims

1. A pneumatic tire having an interior surface and mounted on a rim to define an inflation chamber, the rim having means to prevent the tire beads from becoming dislodged from the rim where the tire is operated in a deflated condition and having a coating of a lubricant on the interior surface of the tire, wherein solid microbeads having diameters in the range from 32 to 1000 microns (0.005 to 0.031 in.) are present in the tire to reduce the friction generated when the tire is running flat by rolling between rubber surfaces.

2. A tire according to claim 1 wherein from 100 to 500 grams of microbeads are present.

3. A tire according to claim 1 or claim 2 wherein the microbeads have a diameter of from 120 to 800 microns (0.005 to 0.031 in.).

4. A pneumatic tire having in its inflation chamber a lubricant comprising a flowable lubricant and microbeads substantially as any such lubricant herein described in the Examples.