U.S. patent application number 11/743968 was filed with the patent office on 2007-08-30 for non-pneumatic tire and method of making same.
This patent application is currently assigned to CARLISLE INTANGIBLE COMPANY. Invention is credited to Jacob Charles III Forney, Zhang Qing Hua.
Application Number | 20070200265 11/743968 |
Document ID | / |
Family ID | 34984930 |
Filed Date | 2007-08-30 |
United States Patent
Application |
20070200265 |
Kind Code |
A1 |
Forney; Jacob Charles III ;
et al. |
August 30, 2007 |
NON-PNEUMATIC TIRE AND METHOD OF MAKING SAME
Abstract
A method of making a non-pneumatic tire comprising a
toroidal-shaped tube having inner and outer circumferential
surfaces and opposite side surfaces collectively forming a hollow
chamber therebetween, the tube having at least two openings
proximate the inner circumferential surface, and a solid fill
composition disposed in the hollow chamber of the tube. The
non-pneumatic tire provides the benefits of a smooth, comfortable
ride, durability, and lightweight with good load-carrying
capability.
Inventors: |
Forney; Jacob Charles III;
(Carlisle, PA) ; Hua; Zhang Qing; (Shenzhen,
CN) |
Correspondence
Address: |
WOOD, HERRON & EVANS, LLP
2700 CAREW TOWER
441 VINE STREET
CINCINNATI
OH
45202
US
|
Assignee: |
CARLISLE INTANGIBLE COMPANY
250 South Clinton Street Suite 201
Syracuse
NY
13202
|
Family ID: |
34984930 |
Appl. No.: |
11/743968 |
Filed: |
May 3, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10803753 |
Mar 18, 2004 |
7231948 |
|
|
11743968 |
May 3, 2007 |
|
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Current U.S.
Class: |
264/45.7 ;
156/112; 264/46.6 |
Current CPC
Class: |
B29C 39/08 20130101;
B60C 7/105 20130101; B29D 30/04 20130101; Y10T 152/10378 20150115;
B29C 70/745 20130101 |
Class at
Publication: |
264/045.7 ;
156/112; 264/046.6 |
International
Class: |
B29C 67/00 20060101
B29C067/00 |
Claims
1. A method of making a non-pneumatic tire, the method comprising:
extruding a toroidal-shaped tube having inner and outer
circumferential surfaces interconnected by opposite side surfaces
to collectively form a hollow chamber therebetween; cutting at
least two openings in the extruded tube at spaced locations
proximate the inner circumferential surface; and filling the hollow
chamber of the tube with a fill composition through the at least
two cut openings to make a non-pneumatic tire.
2. The method of claim 1 further comprising curing the fill
composition in the hollow chamber of the tube to form a hardened
core therein.
3. The method of claim 2 wherein curing comprises exposing the fill
composition to at least one of heat and pressure.
4. The method of claim 1 wherein filling the hollow chamber of the
tube comprises centrifugally dispersing the fill composition into
the hollow chamber of the tube.
5. The method of claim 1 wherein filling the hollow chamber of the
tube comprises injecting the fill composition into the hollow
chamber of the tube.
6. The method of claim 5 wherein the fill composition is injected
into the hollow chamber of the tube while the tube is rotating at
about 500 rpm.
7. The method of claim 1 further comprising mounting the tire onto
a rim.
8. The method of claim 1 wherein filling the hollow chamber of the
tube comprises injecting the fill composition through cut openings
in a number in a range from 4 to 12.
9. The method of claim 1 wherein filling the hollow chamber of the
tube comprises injecting the fill composition through 8 cut
openings.
10. The method of claim 1 wherein filling the hollow chamber
comprises filling the hollow chamber with a fill composition having
a surface Durometer hardness in a range from about 68 to about 75,
as measured by Shore A.
11. The method of claim 1 wherein filling the hollow chamber
comprises filling the hollow chamber with a fill composition
comprising a polyurethane-based foam.
12. The method of claim 1 wherein extruding the tube comprises
extruding a tube having a Durometer hardness of greater than about
50, as measured by Shore A.
13. A method of making a non-pneumatic tire, the method comprising:
extruding a rubber material into a toroidal-shaped tube having an
outer diameter ranging from about 8 inches to about 20 inches, an
outer circumferential surface with a width ranging from about 2
inches to about 6 inches, an inner diameter ranging from about 2
inches to about 16 inches, an inner circumferential surface, and a
hollow chamber between the inner and outer circumferential surfaces
and having a height ranging from about 2 inches to about 6 inches;
cutting at least 4 independent rectangular openings at
substantially equidistant locations along the interior
circumferential surface of the tube, each opening having a width
ranging from about 0.3 inches to about 0.5 inches and a length
ranging from about 0.6 inches to about 0.8 inches; injecting a
liquid fill composition into the hollow chamber of the tube through
one or more of the cut openings; and curing the fill composition to
form a solid core filling the hollow chamber of the tube, the core
having a surface Durometer hardness in the range from about 68 to
about 75, as measured by Shore A.
14. The method of claim 13 wherein filling the hollow chamber of
the tube comprises centrifugally dispersing the fill composition
into the hollow chamber of the tube.
15. The method of claim 14 wherein the fill composition is injected
into the hollow chamber of the tube while the tube is rotating at
about 500 rpm.
16. The method of claim 14 further comprising mounting the tire
onto a rim.
17. The method of claim 13 wherein cutting of the independent
rectangular openings comprises cutting 8 rectangular openings.
18. The method of claim 13 wherein filling the hollow chamber
comprises filling the hollow chamber with a fill composition
comprising a polyurethane-based foam.
19. The method of claim 13 wherein extruding the tube comprises
extruding a tube having a Durometer hardness of greater than about
50, as measured by Shore A.
20. A method of making a non-pneumatic tire, the method comprising:
extruding a rubber material into a toroidal-shaped tube having an
outer diameter ranging from about 8 inches to about 20 inches, an
outer circumferential surface with a width ranging from about 2
inches to about 6 inches, an inner diameter ranging from about 2
inches to about 16 inches, an inner circumferential surface, and a
hollow chamber between the inner and outer circumferential surfaces
and having a height ranging from about 2 inches to about 6 inches;
cutting 8 independent rectangular openings at substantially
equidistant locations along the interior circumferential surface of
the tube, each opening having a width ranging from about 0.3 inches
to about 0.5 inches and a length ranging from about 0.6 inches to
about 0.8 inches; injecting a liquid fill composition into the
hollow chamber of the tube through one or more of the cut openings;
and curing the fill composition to form a solid core filling the
hollow chamber of the tube, the core having a surface Durometer
hardness in the range from about 68 to about 75, as measured by
Shore A.
Description
CROSS-REFERENCE
[0001] This is a divisional application of and claims priority to
pending U.S. patent application Ser. No. 10/803,753, filed Mar. 18,
2004, the disclosure of which is hereby incorporated by reference
in its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to non-pneumatic tires and, in
particular, to foam-filled non-pneumatic tires.
BACKGROUND OF THE INVENTION
[0003] Pneumatic tires, which are pressurized air-filled tires,
have proven value in providing a comfortable ride with optimal
load-carrying capabilities for a variety of vehicles. Consequently,
pneumatic tires have become the standard in virtually all passenger
tire and high speed wheel applications, and more specifically, in
almost every aircraft, automobile, truck, van, bicycle and the
like, where ride quality and comfort is an important part of the
performance of the vehicle. Pneumatic tires have also been
successful in low speed applications, such as on tractors, carts,
and the like, where load carrying capability is important. However,
the tire carcass in pneumatic tires is susceptible to cracks,
punctures and/or other damage causing release of the air trapped
inside and resulting in the tire going flat. A flat tire may simply
cause inconvenience, by requiring a repair and/or loss of use of
the vehicle, or may render the tire unusable and cause more of a
financial burden, particularly in industrial applications, by
requiring costly tire replacement. The consequences of a flat tire
might also be far more dire. For example, a tire suddenly going
flat, such as a blow out, can be life threatening, particularly to
passengers traveling in the vehicle at high speeds.
[0004] As an optional substitute to pneumatic tires, non-pneumatic
tires have been developed and utilized in a wide variety of
applications. Non-pneumatic tires are typically solid tires having
no hollow or air-pressurized cavities or chamber(s) therein, as
opposed to semi-pneumatic tires, which are partially filled with
air. Being of zero pressure, a non-pneumatic tire is generally
deflation-proof, due to the lack of air pressure. The first
non-pneumatic tires developed were solid tires formed generally
from natural rubber. However, rubber tires require thick walls and
thick tread regions to provide load carrying capability comparable
to pneumatic tires, and such added rubber results in an undesirable
increase in the weight of the tire and a compromise in its ride
quality.
[0005] More technically advanced non-pneumatic tires have been
proposed utilizing various materials having greater performance
characteristics then the previously developed rubbers.
Particularly, solid non-pneumatic tires formed from polymeric
materials, such as polyurethane, have been developed. However,
while solid polyurethane tires are capable of carrying higher loads
with a smoother ride, they are generally heavier and prone to
faster wear and breakdown than pneumatic tires. In addition, solid
polyurethane tires are subject to "chunking" (sections separating
from the tire body) and are easily cut when used in aggressive
applications and/or on rugged terrain. Further, solid polyurethane
tires also have reduced traction characteristics as well as UV and
ozone resistance when compared to pneumatic tires.
[0006] More recently, conventional pneumatic tire shells or casings
have been filled with a solid composition, such as a polyurethane
elastomer, to produce deflation-proof, non-pneumatic tires in an
attempt to overcome the weaknesses of previously developed
non-pneumatic tires. For example, U.S. Pat. Nos. 4,943,233,
4,855,096, and 5,906,836 all disclose the use of polyurethane foams
as filling materials for a conventional pneumatic tire to produce a
non-pneumatic tire, such as a bicycle tire.
[0007] In conjunction with producing such non-pneumatic tires, new
methods and fill compositions have been proposed. For example, U.S.
Pat. No. 6,187,125, issued to Rustad, discloses a fill composition
and method for producing a non-pneumatic tire filled with the cured
composition. The fill composition is a mixture of a polyisocyanate
having an average functionality of at least 2.3; a high molecular
weight polyol having a hydroxyol number in the range of about 20 to
about 31 and having an actual functionality of greater than 2.1; 6
to 65 weight percent of a polar plasticizing extender oil; and
optionally a polyamine in an amount less than 0.5 weight percent.
The mixture is cured in the presence of a catalyst to form a
resilient polyurethane elastomer having a vertical rebound of
greater than about 60% based on ASTM D2632 and Durometer hardness
in the range of about 5 to 60 (as measured by the Shore A
method).
[0008] U.S. Pat. No. 6,450,222, issued to Fleming, discloses a
non-pneumatic tire having an elastomeric portion encompassing the
tread and a radially inward foam portion. The non-pneumatic tire
may be formed from a multi-shot process in a spin cast
procedure.
[0009] U.S. Pat. No. 5,080,737, issued to Shoner, discloses a
method of filling a tire with a composite foam to eliminate rapid
deflation "blow-outs". The composite foam tire filling is comprised
of a multiplicity of preconstructed, hollow, pressurized
elastomeric, one-piece, seamless cells bonded together into a
configuration whereby substantially all of the exterior cell wall
surface of all cells in the filling is engaged with portions of the
exterior cell wall surfaces of the surrounding cells.
[0010] U.S. Pat. No. 5,229,047, issued to Becker, discloses a
method and apparatus for producing foam elastomer tires for various
uses including bicycles and wheel chairs. The method involves spin
casting the tires in a mold and filling the mold with a preblended
liquid foamable material that is poured directly into the mold or
onto a surface immediately adjacent to the mold, prior to entry
into the mold.
[0011] U.S. Pat. No. 4,094,353, issued to Ford, discloses a process
for puncture-proofing a pneumatic tire mounted on a wheel rim
comprising filling the tire with a cross-linked mixture of
polyoxypropylene polyether polyol and diphenylmethane diisocyanate
to form a resilient solid polyurethane fill material inside the
tire.
[0012] U.S. Pat. No. 4,909,972, issued to Britz, discloses a method
of making a solid core locatable between a wheel rim and a tire
fitted to the rim, the core formed by introducing a foamable
composition into a mold cavity having a substantially inflexible
mold surface, and allowing the composition to foam and fill the
cavity, prior to removal for placement in a standard tire
carcass.
[0013] U.S. Publication No. 2002/0129883, issued to O'Coin,
discloses a tire including a tread region, a rim region, and a
further region between the tread and the rim region containing a
foamed rubber.
[0014] U.S. Pat. No. 5,605,657, issued to Nybakken, discloses an
industrial solid tire for heavy-load, off-road use having a
heat-cured, silicone containing polyurethane therein, produced by a
batch method.
[0015] U.S. Pat. No. 5,073,444, issued to Shanelec, discloses a
molded polypropylene foam tire core suitable for all types of
wheels. The core may be inserted, in one or more sections, into a
pneumatic-type tire casing and mounted on a wheel rim to provide
puncture-proof and rupture-proof internal support for said tire
casing.
[0016] U.S. Pat. No. 5,681,411, issued to O'Coin, discloses a
pneumatic tire having a plurality of layers of high density foam
rubber formed therein and methods of manufacturing and installing
the layers in the tire.
[0017] Despite generally having a harder ride and, in some cases,
adding more weight to the vehicle in comparison to a pneumatic
tire, the availability of deflation proof non-pneumatic tires is
generally more economical and practical, relative to pneumatic
tires, for many uses and applications in various industries
including mining, scrap yards, military, and heavy construction.
Non-pneumatic tires eliminate the problem of a flat and/or blowout
by eliminating the need for pressurized air. Thus, non-pneumatic
tires overcome the inherent problems with pneumatic tires, as
discussed above.
[0018] However, many of the desirable performance characteristics
found in pneumatic tires have not been duplicated in the previously
proposed non-pneumatic tires. In particular, the performance
characteristics of cushioning ability, roll ability, noise and
vibration reductions have not been equaled. Thus, there is a desire
to replicate the pneumatic tire characteristics and properties in a
non-pneumatic tire. In addition, many of the compositions and
methods previously proposed for producing non-pneumatic tires
involve polymers which provide an advantage in one property while
suffering from a weakness in another property. For example, one
polymer may exhibit superior vibration and noise characteristics
while possessing an inferior load carrying capacity. Further, the
overall costs of previously proposed non-pneumatic tires by methods
of producing same has generally increased with the added step of
filling, containing and curing the fill material within a pneumatic
tire shell. Also, many of the methods previously proposed are
unreliable in that they fail to ensure a complete fill without
voids, are relatively expensive, and/or raise various safety and/or
environmental concerns.
[0019] Thus, there exists a need to provide non-pneumatic tires
having performance characteristics similar to those of pneumatic
tires without the disadvantage of flats and blow-outs. There is
also a need to provide a high quality, zero pressure, air-free
non-pneumatic tire with improved load handling capacity and without
a significant compromise in ride quality. There is a further need
to provide non-pneumatic tires having beneficial qualities in a
more simplistic, convenient and cost effective manner than
previously proposed methods.
SUMMARY OF THE INVENTION
[0020] The present invention provides non-pneumatic tires, and
methods of making the same, which are configured to be mounted on
rims and used as wheels for a variety of vehicular applications.
The tires address the weaknesses and drawbacks of previously
proposed and utilized non-pneumatic tires by providing the benefits
of smooth ride, good durability and excellent traction
characteristics, similar to that of a comparable pneumatic tire,
while remaining light weight, ozone and UV resistant,
characteristics not otherwise found with traditional non-pneumatic
tires, and providing these properties without a compromise in load
carrying capacity and/or ride comfort. The tires accomplish these
advantages while eliminating the hazards and costs associated with
deflation and/or flats, which can occur with pneumatic tires.
[0021] In one embodiment, the present invention provides
non-pneumatic tires comprising (1) a toroidal-shaped tube having an
inner circumferential surface, an outer circumferential surface and
a hollow chamber therebetween, with the tube having at least two
openings independently located proximate the inner circumferential
surface, and (2) a solid fill composition disposed in the hollow
chamber of the tube.
[0022] The enclosed, annular tube forms the outer toroidal-shaped
tire casing and is generally formed of conventional elastomeric
material, such as rubber. The tube, however, may be formed from one
or more layers of desired elastomers. Rubber, and other similar
elastomeric materials, generally provide good traction, are
generally amenable to desirable tread patterns, and are typically
cheap and lightweight. Further, it provides a protective layer over
the fill composition conferring UV and ozone resistant properties
to the tire.
[0023] The inner circumferential section of the tube includes two
or more circumferentially spaced openings or slots cut therein. The
location, relative the inner circumference, and dimension of each
opening may vary as desired. In one embodiment, the openings are
rectangular with the length extending in the direction parallel to
the tire's circumference. In another embodiment, the tube includes
between 4 and 12 openings evenly spaced along its inner diameter. A
larger number of openings, particularly openings having large
dimensions, generally compromise the integrity and/or durability of
the tire.
[0024] Enclosed within the hollow interior cavity of the tube is a
solid foam fill composition. This composition forms the core of the
tire. In one embodiment, the composition is a foam material, such
as a polyurethane. The composition may further include desirable
additives, such as a blending agent. Where the desired composition
is a liquid, it can be injected, for example, into the tube,
advantageously through the cut openings and cured or hardened
therein to form the core.
[0025] The core composition generally influences the overall
physical properties of the tire. For example, the composition can
be modified as desired to adjust the hardness, softness of the
tire, thereby affecting the ride quality, comfort, and/or load
capacity. In one embodiment, the composition has a Durometer
hardness of greater than about 60 as measured by Shore A. In
another, a Durometer hardness in the range of about 68-75.
[0026] In another embodiment of the invention, there is provided a
non-pneumatic tire comprising (1) a toroidal-shaped tube having an
inner circumferential surface, an outer circumferential surface and
a hollow chamber therebetween, with the tube having a number of
independent openings ranging from 4 to 12 with each opening at
spaced locations proximate the inner circumferential surface; and
(2) a solid fill composition disposed in the hollow chamber of the
tube, the composition having a surface Durometer hardness of
greater than about 60, as measured by Shore A.
[0027] In yet another embodiment, there is provided a non-pneumatic
tire compromising (1) a toroidal-shaped rubber tube having an inner
circumferential surface, an outer circumferential surface, and a
hollow chamber therebetween, with the tube comprising 8 rectangular
openings, each opening having a width ranging from about 0.3 inches
to about 0.5 inches and a length ranging from about 0.6 inches to
about 0.8 inches, the 8 openings being equidistantly spaced along
the interior circumferential surface; an outer diameter ranging
from about 8 inches to about 20 inches, an inner diameter ranging
from about 2 inches to about 16 inches; an outer circumferential
surface having a width ranging from about 2 inches to about 6
inches; and a height between the outer and inner circumferential
surfaces ranging from about 2 inches to about 6 inches; and (2) a
solid polyurethane foam fill composition disposed in the hollow
chamber of the tube, with the composition having a surface
Durometer hardness in the range from about 68 to about 75, as
measured by Shore A.
[0028] The non-pneumatic tires provided herein may be made by
various different methods. In one embodiment of the invention,
there is provided a method of making a non-pneumatic tire
comprising extruding a toroidal-shaped tube having an inner
circumferential surface, an outer circumferential surface, and a
hollow chamber therebetween; cutting at least two openings in the
extruded tube at spaced locations proximate the inner
circumferential surface; and filling the hollow chamber of the tube
with a fill composition through the at least two cut openings to
make a non-pneumatic tire.
[0029] Such methods may generally be carried out utilizing various
molds. For example, the elastomeric material, or rubber, may be
extruded from a die and formed into a tube of desired dimension. As
such, the rubber is then cured, in or outside of a mold, and the
desired number of slots or openings are cut along the inner
circumferential section or diameter of the extruded tube.
Conventional methods and instruments may be utilized to cut
sections of the tube once formed.
[0030] The hollow cavity within the tube is generally filled by
conventional methods known in the art. For example, in one
embodiment the tube is filled by injecting the fill composition
through the openings previously cut. Desirable foam compositions,
such as a liquid polyurethane compositions, may be injected into
the tube using a spin casting method, also referred to as a spin
rotational method, through the slots of the rotating tube. The
centrifugal force, due to rotation generally disperses the
composition evenly throughout the interior cavity of the tube until
the entire chamber is filled. The composition is then allowed to
cure, generally at ambient conditions, and the foam begins to set
or harden after as little as ten minutes. The filled tire may then
be removed from the mold and allowed to sit for additional time
such as 24 hours to allow the composition to fully cure. The
non-pneumatic tire may then be mounted on a rim to form a wheel
useful for various vehicle applications including, without
limitation, low speed carts, wheel barrows, hand carts, golf carts,
material carts, construction carts, lawn mowers,
motorized/non-motorized wheel chairs and the like, and agricultural
implements and machinery including, without limitation, planters,
grain drills, cultivators, and many other applications.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] The accompanying drawings, which are incorporated in and
constitute a portion of this specification, illustrate embodiments
of the invention and together with the general description of the
invention given above and the detailed description of the
embodiments given below serve to explain the principles of the
invention.
[0032] FIG. 1 is perspective view of one embodiment of the present
invention;
[0033] FIG. 2 is a cross-sectional view of the embodiment
illustrated in FIG. 1; and
[0034] FIGS. 3A-3C are schematic cross-sectional views of an
exemplary method of making the non-pneumatic tires of the present
invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0035] The present invention provides non-pneumatic tires for use
as wheels in a variety of vehicles and related tire applications.
The tires generally include an outer tire casing or a tubular shell
and an inner solid fill composition inside the casing. Such a
combination results in tires having a comfortable ride with good
durability and traction, similar to that of a comparable pneumatic
tire. In addition, this combination provide tires that are fairly
light in weight with greater ozone and UV resistance, relative
traditional non-pneumatic tires, and provide these benefits while
eliminating the risks and costs associated with flat tires, which
can occur with pneumatic tires.
[0036] With reference to FIG. 1, there is shown a non-pneumatic
tire 10 including an outer tube 12 and a solid fill composition 26
(FIG. 2) inside tube 12. Tube 12 forms the outer casing or shell
for tire 10 and is a hollow toroid shaped shell, such as an inner
tube. The elastomeric outer tube provides a soft flexible and
durable surface. Tube 12 is formed generally of one or more layers
of rubber or other elastomeric material, or combinations thereof.
For example, shell 12 may be formed from a variety of acceptable
rubber type materials commonly utilized in tires. The term "rubber"
as used herein, is used generically and includes a whole host of
conventionally known and utilized polymeric and elastomeric
compositions. Examples of rubbers that are suitable for the outer
tire shell include, without limitation, natural rubbers (NR), and
synthetic rubbers such as NBR and SBR. Examples of synthetic
rubbers include polyisoprene, polybutadiene, polychloroprene, butyl
rubber, styrene-butadiene co-polymers,
acrylonitrile-butadiene-styrene co-polymers, EPDM
(ethylene-propylene-diene) terpolymers, and the like. These rubbers
may be cross-linked, for instance, under the action of sulfur,
peroxides, or bis-maleimides, with or without sulfur. The rubber
composition may comprise a single rubber compound or a mixture of
two or more rubber compounds of the same type or different types.
The rubber, or layers thereof, forming tube 12 may further include
known additives common to rubber compositions, such as: reinforcing
carbon blacks; inactive fillers such as calcium carbonates, chalks,
talcs, or metal oxides; accelerator systems; vulcanization
retarders; promoters such as zinc oxide or stearic acid;
plasticizers such as aromatic, paraffinic, naphthenic and synthetic
mineral oils; aging, light-protecting ozone-protecting, fatigue,
coloration, and processing auxiliaries; and sulfur. These additives
may be used in a quantity of about 0.1 parts to about 80 parts by
weight per 100 parts by weight of the rubber composition, as
appreciated by those of ordinary skill in the art.
[0037] Tube 12 is generally in the form of a toroidal-shaped hollow
tube, such as an inner tube, and includes an inner circumferential
surface 14 and an outer circumferential surface 16 and a hollow
chamber 18 or cavity therebetween. As shown, hollow chamber 18 is
filled with a solid fill composition 26. As appreciated by those of
ordinary skill in the art, tube 12 also includes opposing side
walls 20 connecting inner and outer circumferential surfaces 14,
16, respectively. Outer circumferential surface 16 may further
include a raised section 22, typically included and generally
referred to on tires as a tread pattern or area. The design of such
tread may be as any design desired by the maker of the tire. The
tread provides traction as well as cushion and ride qualities for
the tire, depending upon the tread depth, thickness and particular
pattern.
[0038] Tube 12 further includes two or more circumferentially
spaced openings 24 or slots cut along inner circumferential surface
14, or proximate the interior diameter of tire 10. As illustrated
in FIG. 1, tire 10 includes 8 rectangular-shaped openings 24 (only
3 are shown) longitudinally extending in the direction generally
parallel to the circumference of tire 10. While so illustrated,
however, the invention is not so limited and tube 12 may include as
few as 2 separate, independent openings 24 or as many as desired.
For example, in one embodiment, tube 12 includes between 4 and 12
openings 24 evenly spaced along inner diameter 14. Further, the
specific dimensions of openings 24 may vary, as desired. For
example, and in one embodiment, each opening 24 is rectangular in
shape having a width ranging from about 0.2 inches to about 0.8
inches and a length ranging from about 0.5 inches to about 1 inch.
Each opening 24 illustrated in FIG. 1 is generally about 0.5 inches
in width and about 0.75 inches in length. The specific dimension of
openings 24 in general, as well as the number of openings 24,
effect the properties of the tire. For example, larger dimensioned
openings 24, as well as a larger number of openings 24, will
generally reduce the integrity and/or the durability of tube 12. It
has been found that about 8 openings 24, each having the dimensions
described in connection with FIG. 1 has produced good durability
relative traditional non-pneumatic tires. Openings 24 may also be
sized as needed based upon the method of filling the fill
composition 26 in tube 12, as will be described herein with respect
to FIG. 2.
[0039] With reference to FIG. 2 there is shown, in cross-sectional
view, the non-pneumatic tire illustrated in FIG. 1. As shown, the
hollow interior chamber 18 in tube 12 is completely filled with a
solid fill composition 26. Fill composition 26 may be selected
depending upon properties and tire characteristics desired. In one
embodiment, fill composition is a foam-like material, such as
polyurethane. Polyurethanes are generally formed from a reaction
between a mixture or combination of a diisocyanate and a polyol.
Any number of polymeric diisocyanates alone or blended with other
diisocynates may be utilized as appreciated. Suitable examples
include polymeric diphenylmethane diisocyanate (MDI) such as those
commercially available including PAPI 2027, PAPI 2901, PAPI 2094
supplied by Dow; RUBINATE M, RUBINATE1820, and RUBINATE 9041
supplied by ICI; MONDUR MR, MONDUR MR-5, MONDUR MRS, MONDUR MRS-5,
MONDUR MRS-4 supplied by Bayer; and LUPRANATE-20 and LUPRANATE-10
supplied by BASF.
[0040] The polyol component may include any one or a combination of
conventional polyols. Examples of suitable polyols include ethylene
glycol, diethylene glycol, and dipropylene glycol, phenyl
dienthanolamine, and REZOL EPO 225 sold by Witco, MP, diol,
neopentyl glycol, trimethylol propane, glycerine, VORANOL 230-660
sold by Dow Chemical, PLURACOL TP440 sold by BASF and POLY-G 20-265
sold by Olin Chemical. Polyols may also be synthetically produced
or modified as desired. Particularly, the molecular weight of the
polyol and the number of terminal hydroxyl groups available to
react with the diisocyanate may vary as desired. The hydroxyl
number of the polyol is defined as the amount of KOH, in milligrams
equivalent to the free hydroxyl groups present in 1 gram of the
polymer. Polyethers suitable for use in fill composition 26 may be
obtained by the action of a triol or higher polyol such as a
glycerine, trimethylol, trimethylol propane, and
pentaerythritol.
[0041] Fill composition 26 may further include other desirable
components to convey the desired properties and/or durability as
well as hardness to the final non-pneumatic tire. For example,
ingredients such as foaming agents including, without limitation,
water; hydrocarbons such as cyclopentane, pentane, hexane, heptane,
pentene, heptene; azo compounds such as azohexahydrobenzodinitrile,
azodicarbonamide; CFC halogenated hydrocarbons such as
dichlorodifluoromethane, trichlorofluoromethane,
dichlorodifluoroethane, HCFC hydrocarbons, HFC hydrocarbons and
methoylene chloride, as well as plasticizing extender oils and oil
blends may be used. Plasticizing extender oils or any other process
oils commonly used to extend polymers should be compatible with the
cured polyurethane elastomers. If the extender oil is removed from
the formulation, the hardness of the elastomer may increase,
sometimes as high as by a factor of four. Suitable extender oils
are substantially aromatic, contain polar compounds and are
designated as aromatic extract oils. Less polar extender oils,
those that contain lesser amounts of an aromatic and polar
compounds, or even non-polar extender oils, can be blended with the
polar extender oils so that the resulting blend has at least a
slight polarity and is compatible with the cured polyurethane
elastomer. Suitable examples include naphthenic and paraffinic
process oils with high levels of aromatic and polar compounds such
as those sold by Witco Corporation, Sun Company, Shell Oil Company,
BP Oil Company, and Crowley Chemical Company.
[0042] The advantageous properties of the tires of the present
invention including ride quality, light weight, load carrying
capacity and resistance to elements of the environment, such as UV
from sunlight and ozone from the atmosphere, render the present
tires more useful than previously utilized non-pneumatic tires.
Particularly, the fill composition 26 conveys various advantages.
The inner fill composition 26 being a foam or similar
polyurethane-based material provides a light weight, yet durable
and structurally strong, composition suitable for preventing
deflation and failure of the tire. Polyurethanes are known to be a
light weight material. In addition, polyurethanes are generally
hard and durable, sufficient to provide good load carrying
capability. In one embodiment, fill composition 26 has a surface
Durometer hardness of at least about 60 (as measured by Shore A).
In another embodiment, fill composition 26 has a surface Durometer
hardness in the range from about 68 to about 75 (Shore A).
Similarly, fill compositions 26, in accordance with the invention,
have Asker hardness of about greater than 60. Such a high level of
hardness provides the advantage of increasing the load or weight
carrying capability of the tire without a corresponding increase in
overall tire weight, as seen with previously proposed non-pneumatic
tires or filled pneumatic tires. It should be understood, as with
all solid polyurethane materials, the surface Durameter is
important for it contributes to the overall hardness of the solid,
while the interior hardness (core of polyurethane solid) generally
has a hardness less than that of the surface.
[0043] Various methods may be used to make the non-pneumatic tires
of the present invention. For example, methods involving the use of
one or more molds such as the rotating mold illustrated in FIGS.
3A-3C, may be used to make the non-pneumatic tires. In one
embodiment, the method generally includes extruding an elastomeric
material such as rubber to form the outer tire casing. The extruded
material is then shaped and spliced into a circle and cured in a
mold (not shown) to form a completely enclosed, toroidal-shaped
tube 12 or tire skin having a hollow, interior chamber or cavity
18. The mold may also provide a tread pattern 22 on the outer
circumferential surface 16 of tube 12. After removing the cured
tube from the mold, a desired number of elongated openings 24 or
slots are cut at spaced locations proximate the inner
circumferential surface 14. Each opening 24 exposes the interior
chamber 18. With reference to FIG. 3A, slit tube 12 is then placed
in a second mold 50 and filled with the fill composition 26 in an
open "spin casting method". In one embodiment, mold 50 has upper
and lower mold plates pivotally coupled to each other and
collectively define a recess therein for supporting tube 12.
Moreover, the upper mold plate cooperates with the bottom mold
plate to form channels 52 that extend radially toward the recess.
In this method, a premixed liquid fill composition 26, such as the
polyurethane based foam, is injected into the interior cavity of
the casing via channels 52 through one or more of the cut openings
24 during rotation, as shown in FIG. 3B. Alternatively, the machine
or instrument utilized in the spin casting method may have
individual fill components A (desired diisocyanate) and (desired
polyol) in separate areas and mix them in desired amounts and
ratios just prior to injection into the tire casing. The mold is
rotated at a desired speed during injection or filling of the tube.
In one embodiment, the mold is rotated at a speed of about 500 rpm
while the interior cavity of the tire is filled by injecting with a
liquid polyurethane fill composition. Centrifugal force, due to the
rotation of the tire, disperses composition 26 evenly throughout
the interior cavity of the tire casing, as illustrated in FIG. 3B,
and ensures that the filling occurs radially inward until the
entire cavity 18 is full (FIG. 3C). The rate and time required to
completely fill tube 12 will generally depend on the rate of
rotation or the rotational force generated by the rotation speed of
the tire.
[0044] Composition 26 is allowed to cure in ambient conditions,
such as at room temperature, and the fill begins to set or harden
shortly thereafter. Curing times for the fill composition will vary
in accordance with the components and the constituency of the
components of the fill therein. For example, while the polyurethane
formation from a reaction between the diisocyanate and the poylol
component is quick, depending on concentration of these components
and concentrations of other desirable recipients in the fill
composition, curing may occur at room temperature or with the
addition of heat and/or pressure to fully set or harden.
Polyurethane compositions generally cure in as little as about ten
minutes. The tire is then removed from the mold and allowed to set
for additional time, such as from about 2 hours to about 24 hours,
to allow the composition to fully cure and harden.
[0045] The fully cured and ready tire may then be mounted onto a
rim suitable to the inner circumference of the tire by conventional
mounting methods. For example, the tire may be mounted utilizing a
machine with fingers that stretch the tire over the rim flange and
then retracts. Another conventional mounting technique involves the
use of a plastic cone that is driven hydraulicly through the tire,
thereby expanding the tire to allow insertion of the tire onto the
rim. Once mounted, the tire assembly can be installed and used in
the normal fashion as would a normal pneumatic, semi-pneumatic or
other non-pneumatic tire. Accordingly, the wheels so formed by the
rim and tire, may be utilized on a variety of vehicles including,
without limitation, a golf cart, a wheel barrow, a hand cart, a
construction cart, a lawnmower, a motorized/non-motorized wheel
chair, a material cart, a farm machine, and on other low speed
vehicles.
[0046] The foregoing advantages or benefits of the present
invention will be further appreciated and made more apparent in
light of the following examples.
EXAMPLE 1
[0047] An exemplary embodiment of the non-pneumatic tire provided
by the present invention and for use on a wheel barrow is made by
the following process. First, a rubber tube was extruded utilizing
conventional extruding techniques and conventional rubber
compositions, and then cut to desired length and then shaped and
spliced into a circle. Once in the circle the rubber was then cured
via external platens and heated to about 320.degree. F. in a
compression mold with about 90 psi internal air pressure. The tube
so formed had the following dimensions: outside diameter was about
14.7 inches; tire section width was about 3.7 inches; tire section
height was about 3.6 inches; tread crown radius was about 2.0
inches; tread crown arc was about 4.1 inches; inside diameter was
about 8 inches, and tire base width was about 2.3 inches. The
rubber tube was then removed from the mold and 8 rectangular slots,
each having a width of about 0.5 inches, and a length of about 0.75
inches, were cut out longitudinally in a circumferential direction
along the inner circumference of the rubber tire. The slotted
rubber tube was then loaded into a second mold which was rotated at
approximately 500 rpm by an electric motor. A premixed polyurethane
foam was then injected at a predetermined, desirable speed and rate
through the cut slots into the inner cavity of the rubber tube. The
fill composition included a liquid polylol component A, containing
a foaming agent, and a liquid polyisocyanate component B that come
together in a mix head which ultimately injected the liquid mixture
through the slots along the inner circumferential surface of the
tube while the tube and the mold were spinning. Once the inner
cavity of the tube was full, the liquid fill composition was then
allowed to cure. The polyurethane partially cured and set at room
temperature after only about ten minutes. The tire was then removed
from the mold and allowed to sit at room temperature for about 24
hours allowing the polyurethane to fully cure. The rubber skin of
the tube was found to have a Durometer hardness of about 62, and
the polyurethane fill composition a surface Durometer hardness of
about 69 with a core Durometer hardness of about 48, as measured by
Shore A. The tire weighed about 7 pounds, and had a load capacity
of about 375 pounds.
EXAMPLE 2
[0048] A non-pneumatic tire was made for use on a wheel barrow, by
the same method described above and had the following dimensions:
outside diameter was about 13.9 inches; tire section width was
about 3.7 inches; tire section height was about 3.1 inches; tread
crown radius was about 3.0 inches; tread crown arc was about 3.5
inches; inside diameter was about 8 inches, and tire base width was
about 2.3 inches. The 8 rectangular slots each had a width of about
0.5 inches, and a length of about 0.75 inches measured
longitudinally in the circumferential direction. The rubber skin of
the tube had a Durometer hardness of about 62, and the polyurethane
fill composition a surface Durometer hardness of about 69 with a
core Durometer hardness of about 48, as measured by Shore A, the
same as in example 1. The tire weighed about 6.2 pounds, and had a
load capacity of about 375 pounds.
EXAMPLE 3
[0049] A non-pneumatic tire was made for use on a material handling
cart, by the same method described above and had the following
dimensions: outside diameter was about 9.9 inches; tire section
width was about 3.0 inches; tire section height was about 3.1
inches; tread crown radius was about 6.7 inches; tread crown arc
was about 2.8 inches; inside diameter was about 4 inches, and tire
base width was about 2.3 inches. The tire had 6 rectangular slots
each having a width of about 0.375 inches and a length of about
0.75 inches measured longitudinally in the circumferential
direction. The rubber skin of the tube had a Durometer hardness of
about 62, and the polyurethane fill composition a surface Durometer
hardness of about 69 with a core Durometer hardness of about 48, as
measured by Shore A, the same as in example 1. The tire weighed
about 3.8 pounds, and had a load capacity of about 280 pounds.
[0050] By virtue of the foregoing, there are provided non-pneumatic
tires and methods for making the same, which can be used as a flat
free equivalent to pneumatic tires. More specifically, the tires
provided herein are used for low speed applications including
without limitation, commercial lawn mowers, motorized/non-motorized
wheel chairs, construction wheelbarrows, construction carts,
material handling equipment, farm implement tires and replacements
for semi-pneumatic and pneumatic tires used on planters, grain
drills, and row crop cultivators. Additional applications and uses
for the tires provided herein, contemplated herewith include use on
golf carts, mobility carts, floor cleaning carts, and other markets
that utilize grey non-marking pneumatic tires. The non-pneumatic
tires provide many advantages and benefits over comparable tires
previously proposed. For example, the elastomeric casing and
polyurethane based foam type fill combines the best features of a
pneumatic tire by providing a smooth ride, durability, and
excellent traction characteristics while maintaining Ozone, UV, cut
and tear resistence and eliminating hazards associated therewith.
Further, the polyurethane tire is lightweight, thereby providing a
pneumatic quality ride, while maintaining a good load carrying
capability. In addition, mounting of the non-pneumatic tire or the
present invention provides an adequate interference fit for
mounting on a rim thereby eliminating the need to include carcass
fabric and/or steel wire beads as necessary for conventional
pneumatic tires.
[0051] While the present invention has been illustrated by the
description of embodiments thereof, and while the embodiments have
been described in considerable detail, it is not intended to
restrict or in any way limit the scope of the appended claims to
such detail. Additional advantages and modifications will be
readily apparent to those skilled in the art. The invention in its
broader aspects is, therefore, not limited to the specific details,
representative apparatus, method, and examples described.
Accordingly, departures may be made from such details without
departing from the scope or spirit of Applicants' general inventive
concept.
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