RUN-FLAT TIRE CONTAINING SMALL FRICTION REDUCING BALLS AND A LUBRICANT

PNEU RENFERMANT DE PETITES ANTIFRICTION ET UN LUBRIFIANT POUR L'USAGE A L'ETAT DEGONFLE

English Abstract

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 small loose round
balls 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.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In 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, the improve-
ment characterized by the presence of solid microbeads having a
diameter of from 32 to 1000 microns being present in the tire to
reduce the friction generated when the tire is running flat by
rolling between rubber surfaces.
2. The tire of claim 1 wherein from 100 to 500 grams of
microbeads are present.
3. The tire of claim 2 wherein the microbeads have a diameter
of from 120 to 800 microns (0.005 to 0.031 in.).

Description

_ GT-1600
P4~74
A run-rlat tlre contalnin~ small frictlon
reduclng balls and a lubr cant ___
This lnvention relates to rrictlon reducers for pneu-
matlc tires runnlng whlle de~lated.
A number of designs have been proposed to increase the
stability and rideablllty of the tlre when deflated or flat.
U.S. Patent 4,057,092 relates to a circumferentlal
locking lug. Other proposals, such as U.S. Patent Nos.
2,040,645; 3,392,722 and 3,610,308 have special units ln
the interlor of the tlre. Other proposals lnclude liquid
lubricants wlthin the tlre (U.S. Patent 4,045,362) and
solld lubrlcants which llquify on the addltion of chemi-
cals (U.S. Patent 3,931,843).
To reduce the frlctlon generated by tlres runnlng
~lat, the lnclusion o~ elther llquid or solld lubrlcants
on the tire lnterlors has been proposed. U.S. Patent
2,040,645, ~or lnstance suggests a graphlte lubrlcant;
U.S. Patent 3,610,308 mentlons the use Or liquld silicone
and U.S. Patents 3,739,829; 3,850,217 and 4,045,362
20 descrlbe the use o~ polyalkylene glycols, glycerol,
propylene glycol, slllcone and other lubricants. The
llquld lubricants, however, are not evenly dlstrlbuted ln
the operatlng tire and can adversely er~ect balance and
tlre per~ormance. Solid lubrlcànts whlch llqulfy at ~lat
tlre temperature are also known but they require a cheml-
cal reagent for liquificatlon (U.S. Patent 3,931,843).
Whlle the use of lubrlcants has slgnlflcantly reduced the
frictlon and heat generated by runnlng a tlre ~lat, the
prior art has not provlded a complete remedy to the heat
30 and ~riction problem.
The present inventlon comprlses uslng lubrlcated rol-
ling mlcrobeads (balls) as the lubrlcatlng medium. The
employment o~ the rolllng mlcrobeads would have the same
effect as the use of ball bearlngs ln ball race~ where the
35 rolllng mode greatly minimlze~ friction and wear. When
applled to the run ~lat tires or slmllar type~ of appll-
cations lnvolvlng slldlng between rubber surfaces, the
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74
surfaces should be partially or totally separated in the presence
of the rolling elements. Rubber-to-rubber sliding would then be
replaced by the desired mode of rolling, thus reducing friction
and the associated heat build-up.
Thus, the invention provides in 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 be-
coming dislodged from the rim where the tire is operated in a de-
flated condition and having a coating of a lubricant on the
interior surface of the tire, the improvement characterized by
the presence of solid microbeads having a diameter of from 32 to
lO00 microns being present in the tire to reduce the friction
generated when the tire is running flat by rolling between rubber
surfaces.
Basically, any of the prior art lubricants can 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. The micro-
beads are available from the Microbeads Division of CataphoteCorporation, 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 reason-
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ably 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 - 297149 - 74
500 - 250105 - 53
420 - 21074 - 44
297 - 17753 - 10
250 - 149
Any of the lubricants disclosed in the above
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dlscussion of the prlor art can be used ln the practice o~
the present lnvention.
The A-l lubricant whlch was used in the examples was
prepare~ by mixing the rollowing lngredients:
Ingredients Parts by Weight
Ethylene glycol 70
Water 30
Polyethylene oxldes
WSR 301 (Union Carblde) m.w. 4 x 106 0.05
WSR 205 (Unlon Carbide) m.w. 6 x 105 0.03
Polyssaccharide
Kelzan (Kelco Co.) xanthane gum m.w. ~106 0.15
100.23
The microbeads used were solid spheres and had a dla-
meter Or 350 to 7io microns (0.0138 to 0.0280 in.).
The signiricant effect Or mlcrobeads ln friction re-
ductlon between rubber surraces whlch sllde o~er one
another ls shown ln Table I below wlth the followlng test
conditlons:
Sllding speed ~ 20 lnches/mlnute (0.85 cm/sec)
Temperature ~ amblen~
Normal load ~ 22.1 pounds (10.05 kg)
Approxlmate cros~-sectlonal area Or sllding surface =
3.75 sq. ln. (88.7 sq. cm.)

- 4 - 11&~
Table I
Dry and Lubricated Friction
Between Slidlng Rubbers
Friction Coe~lcient
Lùbrlcant Statlc Kinetlc
None (rubber-to-rubber) 2.89 2.17
A-l lubrlcant 0.41 0.34
Mlcrobeads* 0.18 0.12
Mlcrobeads plus A-l lubrlcant 0.14 0.065
*Mlcrobeads Class III, MS-XPX; Cataphote, Dlvlsion o~
Ferro Corp.
The results are self-evident, showlng the effectlve-
ness o~ the microbeads as a lubricating medlum for slldlng
rubber surfaces. A thirty-fold reductlon in klnetic
- frlction wa~ achleved when the mlcrobeads were comblned
wlth the ethylene glycol~water based lubrlcant A-l.
Slmllar results are also found ln the case of a radlal
tlre lnnerllner slldlng on a bead wrapplng compound as
shown ln Table Il.
Table II
Slldlng Between An Innerllner
And A Bead Wrapplng Compound
Slldlng speed = 50 lnches/mlnute (2.12 cm/sec) room temp.
Normal load - 5.4 lbs. (2.5 kllograms)
Approximate cross-sectlonal area Or slidlng surrace 3
6.25 sq. ln. (40.3 sq. cm.)
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Table II (Cont'd)
Friction Coe~rlcient
Lubrlcant Static Kinetic
5 None (rubber-to-rubber) 1.8 1.75
Paraffin wax 0.83 0.5
Microbeads plus paraffln wax
(No. 155), Internatlonal Wax and
Refinlng Co. 0.21 0.15
.