Wheel substitutes for land vehicles – Endless belt having nonmetallic track or tread – Track formed of endless flexible belt
Reexamination Certificate
2002-07-11
2004-08-03
Morano, S. Joseph (Department: 3617)
Wheel substitutes for land vehicles
Endless belt having nonmetallic track or tread
Track formed of endless flexible belt
C305S165000, C305S178000
Reexamination Certificate
active
06769746
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a two part endless vehicular rubber track comprised of a polyurethane based tread component and a rubber carcass component. In one aspect, the tread component may be comprised of a sulfur curable polyurethane or blend of sulfur curable polyurethane and sulfur curable elastomer. The invention includes a vehicle containing such track.
BACKGROUND OF THE INVENTION
Endless rubber tractor tracks are increasingly being used for propelling various vehicles over the ground such as, for example, various tractors and other agricultural vehicles including, for example, combines and spreaders, as well as various earth moving machines.
In particular, such track is conventionally positioned over at least two wheels, normally a drive wheel for engaging an inner surface of the track and driving the track and at least one driven wheel to control the path of the track as it moves to propel the associated vehicle. The outer surface of the peripheral tread configuration of the track typically contains a plurality of raised lugs designed for engaging the ground and assisting the propelling of the associated vehicle such as, for example, a tractor over an agricultural ground.
In practice, the tread of such rubber tracks provide a considerably wider footprint than conventional pneumatic tires and are, thereby, more adaptable to agricultural fields in that they offer better flotation and less soil compaction than rubber tires, which may result in better crop yield. In addition, use of rubber tracks instead of pneumatic tires may permit a farmer to get out into a field earlier in the planting season and plant crops sooner in point of time and may permit a harvesting of a crop on a more timely basis as compared to conventional pneumatic rubber tire equipped agricultural vehicles. Such use and advantages of rubber tractor tracks are well known to those having skill in such art.
Such rubber tracks are conventionally in a form of an endless rubber belt composed of a rubber carcass reinforced with continuous steel cables molded into the carcass rubber composition itself to add dimensional stability for the track and an integral outer rubber tread with raised lugs for ground-contacting purposes.
Polyurethane treads have sometimes been suggested for rubber tires. Such polyurethanes are typically a reaction product of a polyisocyanate (e.g. diisocyanate) and one or more polymeric polyols such as for example polyether polyols and/or polyester polyols. For example, rubber tires, pneumatic and solid, have been heretofore been proposed having a rubber carcass bonded to a polyurethane tread. For example, see U.S. Pat. Nos. 4,669,517 and 4,095,637.
Sulfur curable polyurethanes have been proposed as a reaction product of a polyisocyanate (e.g. diisocyanate) and polymeric polyols which contain a degree of unsaturation, particularly carbon-to-carbon double bond unsaturation. Such polyisocyanate may be, for example, a methylene bis(4-phenylisocyanate), or MDI, and the polymeric polyol may be a trifunctional active hydrogen compound-initiated polyoxyalkylene polyether polyol having a degree of unsaturation which may also include a polytetramethylene ether glycol. (For example see U.S. Pat. No. 6,255,431 where a trifunctional agent is used with a polyol with an imparted unsaturation is used to promote physical properties of the polyurethane).
Sulfur curable millable thermoplastic polyurethanes may also be used alone or as a blend with sulfur curable diene-based elastomers as a product of relatively equivalent amounts of polymeric polyol (e.g. polyester and/or polyether polyols) and a polyisocyanate (e.g. a diisocyanate such as for example MDI) which, in adding certain unsaturated carbon-to-carbon double bonds, usually in the polymeric polyol component of the polyurethane. Representative examples are, for example, polyether polyurethane rubber such as Millathane E34® and polyester polyurethane such as Millathane 76® from TSE Industries of Rheim Chemie, a Bayer Company.
Sulfur vulcanizable polyurethanes such as a product of a polyisocyanate (e.g. diisocyanate) and a liquid diene prepolymer and particularly a functional liquid diene prepolymer, which may be described in U.S. Pat. No. 4,104,265.
The purpose of this invention relates to a vehicular track comprised of two parts, namely a polyurethane based tread component designed to be ground-contacting (ground-engaging particularly for a farm implement) namely a tread component containing spaced apart lugs and an underlying rubber carcass component for supporting the tread component. For this invention, said track tread portion may be a polyurethane tread chemically bonded and/or physically interlocked to a rubber carcass.
It is contemplated that such a rubber track with a polyurethane tread configured with extended lugs, which is non-pneumatic, not intended for extensive highway use, intended for slow speed operation with minimal internal heat buildup within the polyurethane tread and where traction of the tread over the ground is primarily derived from its extended ground-engaging lugs rather than being primarily derived from the polyurethane composition itself has merit.
Most all of such above properties are not normally experienced by pneumatic passenger tires so that application of a polyurethane tread to the rubber carcass of a vehicular track is believed to be unique.
In the description of this invention the terms “cured” and “vulcanized” if used are used interchangeably. The term “phr” relates to parts by weight of a material per 100 parts by weight of rubber. The terms “rubber” and “elastomer” are used interchangeably unless otherwise noted.
SUMMARY AND PRACTICE OF THE INVENTION
In accordance with this invention, an endless rubber track designed to encompass at least one drive wheel and at least one driven wheel of an associated vehicle is provided wherein said track is a two part track comprised of a polyurethane based outer tread component having an outer surface and an opposing inner surface and an underlying rubber carcass component having an inner surface and an opposing outer surface, wherein said tread outer surface is configured with raised, spaced apart lugs designed to be ground engaging, wherein said tread inner surface is chemically bonded to and/or physically interlocked with, said carcass inner surface and wherein said carcass outer surface is designed to engage at least one of said drive wheels and/or driven wheels of said vehicle.
In one aspect of the invention, said polyurethane tread is chemically bonded to said underlying rubber carcass by an adhesive layer positioned between said tread inner surface and said carcass inner surface to bond said polyurethane tread and said rubber carcass together.
In practice, said diene-based rubber for said polyurethane tread blend can be, for example, a elastomeric polymer of isoprene and/or 1,3-butadiene and/or elastomeric copolymer of styrene with isoprene and/or 1,3-butadiene.
Representative examples of such rubbers are, for example, cis 1,4-polyisoprene cis 1,4-butadiene, styrene/butadiene copolymers isoprene/butadiene copolymers, styrene/isoprene copolymers and styrene/isoprene/butadiene terpolymer.
While various polyurethanes may be used, whether prepared by a one shot process or, preferably, by a pre-polymer process, sulfur curable polyurethanes are preferred which can be simple blended with typical rubber compounding ingredients (e.g. sulfur, etc) in an internal mixer in a manner similar to diene-based rubber compositions.
Sulfur curable polyurethanes can be of many forms which usually contain carbon-to-carbon double bonds therein to facilitate the sulfur curing thereof. Usually such double bonds are contained in the polyol component of the polyurethane.
While various diisocyanates might be used for the preparation of the polyurethane, sometimes diisocyanates which are considered to be non-discoloring might be desired, particularly where a colored track tread is desired (particularly if the desired color is other than a black color)
Representative of various
Botts Bina Patel
Krishnan Ram Murthy
Rodgers Michael Brendan
Bellinger Jason R.
Morano S. Joseph
The Goodyear Tire & Rubber Company
Young, Jr. Henry C.
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