U.S. patent application number 11/060133 was filed with the patent office on 2005-09-15 for composite solid tire and method of producing same.
This patent application is currently assigned to Maeda Shell Service Co., Ltd.. Invention is credited to Maeda, Sadao.
Application Number | 20050199327 11/060133 |
Document ID | / |
Family ID | 34824560 |
Filed Date | 2005-09-15 |
United States Patent
Application |
20050199327 |
Kind Code |
A1 |
Maeda, Sadao |
September 15, 2005 |
Composite solid tire and method of producing same
Abstract
A composite solid tire, including a worn solid rubber tire
having a remaining rubber layer, and a thermo-setting polyurethane
elastomer layer which is provided on an outer circumferential
surface of the rubber layer.
Inventors: |
Maeda, Sadao; (Okazaki-Shi,
JP) |
Correspondence
Address: |
BURR & BROWN
PO BOX 7068
SYRACUSE
NY
13261-7068
US
|
Assignee: |
Maeda Shell Service Co.,
Ltd.
Okazaki-Shi
JP
|
Family ID: |
34824560 |
Appl. No.: |
11/060133 |
Filed: |
February 17, 2005 |
Current U.S.
Class: |
152/323 ;
152/302; 264/36.14 |
Current CPC
Class: |
B29D 30/02 20130101;
B29D 30/54 20130101; B29D 30/06 20130101; B60C 7/00 20130101; B60C
7/102 20130101; Y10T 152/10306 20150115; B60C 11/02 20130101; B60C
2007/005 20130101 |
Class at
Publication: |
152/323 ;
152/302; 264/036.14 |
International
Class: |
B60C 007/00; B29D
030/54 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 9, 2004 |
JP |
2004-066104 |
Claims
What is claimed is:
1. A composite solid tire, comprising: an inner layer of a rubber
layer; and an outer layer made of a thermo-setting polyurethane
elastomer which is provided on an outer circumferential surface of
the rubber layer.
2. The composite solid tire according to claim 1, wherein said
rubber layer is formed of a worn solid rubber tire, and the rubber
layer has a pre-determined thickness.
3. The composite solid tire according to claim 1, wherein said
rubber layer is formed of at least one rubber material, which is
softer than the thermo-setting polyurethane elastomer of the outer
layer.
4. The composite solid tire according to claim 1, wherein a
characteristic value of the thermo-setting polyurethane elastomer
according to Taber Abrasion Test is 90 mm.sup.3 or less.
5. The composite solid tire according to claim 1, wherein a
percentage of a thickness of the outer layer relative to a whole
thickness of said composite solid tire in a radial direction
thereof is not more than 40%.
6. The composite solid tire according to claim 1, wherein said
outer layer is formed by reacting and setting of at least one
polyisocyanate component selected from the group consisting of
tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI),
and naphthalene diisocyanate (NDI), and at least one polyol
component selected from the group consisting of
poly(oxybutylene)glycol, polyester polyol, and polyethylene adipate
glycol.
7. The composite solid tire according to claim 6, wherein said at
least one polyisocyanate component and said at least one polyol
component are reacted and set at a temperature of 70.degree. C. to
115.degree. C.
8. A method of producing a composite solid tire according to claim
1, the method comprising the steps of providing a rubber layer to
be the inner layer of said tire; applying a primer and an adhesive
to the outer circumferential surface of said rubber layer; and
forming an outer layer by causing raw materials of a thermo-setting
polyurethane elastomer to react and cure by die-casting.
9. A method of producing a composite solid tire, the method
comprising the steps of cutting an outer circumferential surface of
a remaining rubber layer of a worn solid rubber tire; applying a
primer and an adhesive to the cut outer circumferential surface of
the rubber layer; and forming an outer layer which is formed by
causing raw materials of a thermo-setting polyurethane elastomer to
react and cure by die-casting.
10. The method of producing a composite solid tire according to
claim 8, wherein said die-casting is implemented by introducing
said raw material of the thermo-setting polyurethane elastomer into
a space in a die-casting device, said space is formed between an
inner circumferential surface of an outer die and an outer
circumferential surface of said rubber layer, wherein said inner
circumferential surface and said outer circumferential surface are
heated in a way that a temperature of said outer circumferential
surface is higher than that of said inner circumferential
surface.
11. The method of producing a composite solid tire according to
claim 9, wherein said die-casting is implemented by introducing
said raw material of the thermo-setting polyurethane elastomer into
a space in a die-casting device, said space is formed between an
inner circumferential surface of an outer die and an outer
circumferential surface of said rubber layer, wherein said inner
circumferential surface and said outer circumferential surface are
heated in a way that a temperature of said outer circumferential
surface is higher than that of said inner circumferential surface.
Description
[0001] This application is based on Japanese Patent Application No.
2004-066104 filed on Mar. 9, 2004, the contents of which are
incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a composite solid tire and
a method of producing the same, and particularly to advantageous
techniques for renewing worn solid rubber tires.
[0004] 2. Discussion of Related Art
[0005] As a tire that supports, in a vehicle such as an automotive
vehicle or an industrial vehicle, a load and has the function of
smoothly transmitting forces between the vehicle and road surface,
there have conventionally been known two sorts of tires, i.e., a
pneumatic tire having a hollow structure in which air is charged,
and a solid tire having a solid structure constituted by a
rubber-based annular body. In particular, the solid tire enjoys, as
tire's functions, a load supporting property, a cushioning
property, and a rubber elasticity, and is widely used in low-speed
and high-load vehicles such as a forklift truck, an industrial
tractor, a battery carrier, or a trailer. As predominant sorts of
the solid tire, there are known a tire that is constituted by a
single tread rubber and is directly bonded to a wheel, a tire that
is constituted by a rubber adhered, by vulcanization, to a base
band and is press-fitted onto a wheel, and a tire that is
constituted by an annular tread rubber and is fitted on an outer
circumferential portion of a wheel.
[0006] Generally, the solid tire is known as a solid rubber tire
that is constituted by a tread rubber formed of, e.g., NR or SBR.
Since the solid rubber tire contacts the road surface and produces
a frictional force to allow movement of the vehicle, a surface of
contact of the tire with the road surface is worn little by little
as the tire is used for a long time and, if a life expectancy of
the tire is fulfilled, the tire should be disposed of. Recently,
however, the disposal of waste tires has become a serious social
problem. In particular, since the solid rubber tires are heavier
than pneumatic tires used in, e.g., passenger cars, the solid
rubber tires are more difficult to handle. In addition, the solid
rubber tires are hard to burn or find other applications. Thus, the
solid rubber tires are very difficult to dispose of.
[0007] In the above-indicated technical background, Patent Document
1 (Japanese Patent Application Publication No. 5-31822) has
proposed a pneumatic-type solid tire having a structure in which a
surface of a tread portion of a worn tire is subjected to buffing
as a sort of polishing and a renewing tread rubber is adhered to
the thus polished tread portion. According to this technique, worn
tires that have conventionally been difficult to dispose of can be
effectively utilized, tire materials can be saved, and times needed
to produce tires can be reduced.
[0008] However, even though the renewing tread rubber may be
adhered to the tread portion of the worn tire, so as to produce a
renewed tire, the tread portion of the renewed tire is easily worn
again as it is used. Thus, the durability of the tread portion of
the renewed tire is not satisfactorily improved. In addition, since
rubber materials used to form the renewed tread rubber contain
carbon black as a reinforcing agent and accordingly have a black
color, black marks of the tire are left on the road surface because
frictions are produced between the tread rubber and the road
surface. The black tire marks left on the road surface may damage
an aesthetic appearance of the road surface and, in a work field
where a forklift truck or an industrial tractor is used, not only
the black tire marks but also black rubber powder resulting from
wearing of tires may damage a work environment.
[0009] In addition, Patent Document 2 (Japanese Patent Application
Publication No. 2002-144442) discloses a wheel renewing method in
which urethane rubber is used. More specifically described, this
document discloses a renewed wheel obtaining technique in which,
after a rubber portion is removed from a base band of a waste tire,
an ether-based urethane rubber layer is formed on an outer
circumferential surface of the base band.
[0010] In the above-indicated renewed wheel, the urethane rubber
layer contacts road surface. The urethane rubber has a higher wear
resistance than that of a common tread rubber formed of, e.g., NR
or SBR. Thus, the renewed wheel can enjoy a significantly improved
durability or life expectancy. On the other hand, the renewed wheel
suffers a lower cushioning property than that of a wheel having the
common tread rubber. Therefore, when an operator operates a
vehicle, such as a forklift truck or an industrial tractor, in
which the renewed wheel is used, uncomfortable shocks may be
transmitted to the operator. The cushioning property of the renewed
wheel might be improved by forming the urethane rubber layer to
have a foamed structure or largely lowering the hardness (or
increasing the softness) of the urethane rubber layer. In this
case, however, the urethane elastomer may lose its proper wear
resistance and accordingly its durability.
SUMMARY OF THE INVENTION
[0011] It is therefore an object of the present invention to
provide a composite solid tire that has not only an excellent wear
resistance but also an excellent shock-absorbing or -damping
property, and a method of advantageously producing the same. It is
another object of the present invention to provide advantageous
techniques for renewing a waste solid rubber tire that has been
worn to such a degree that its life expectancy has been
fulfilled.
[0012] According to the present invention, there is provided a
composite solid tire, wherein an inner layer of the solid tire is
formed of a rubber layer, and an outer layer of the solid tire is
formed of a thermo-setting polyurethane elastomer layer.
[0013] According to a preferred feature of the present invention,
the rubber layer is formed of a worn solid rubber tire, wherein the
remaining rubber layer of the worn solid rubber tire has a
pre-determined thickness.
[0014] According to another preferred feature of the present
invention, the rubber layer is formed of at least one material,
which is softer than the thermo-setting polyurethane elastomer.
[0015] According to a first aspect of the method of the present
invention, there is provided a method of producing a composite
solid tire comprising the steps of providing a rubber layer to be
the inner layer of said tire; applying a primer and an adhesive to
an outer circumferential surface of the rubber layer; and forming
an outer layer by causing raw materials of a thermo-setting
polyurethane elastomer to react and cure by die-casting.
[0016] According to a second aspect of the method of the present
invention, there is provided a method of producing a composite
solid tire comprising the steps of cutting an outer circumferential
surface of a remaining rubber layer of a worn solid rubber tire;
applying an adhesive to the cut outer circumferential surface of
the rubber layer; and providing, on the outer circumferential
surface of the rubber layer, a thermo-setting polyurethane
elastomer layer by causing raw materials of a thermo-setting
polyurethane to react and cure.
[0017] According to another preferred feature of the present
invention, the composite solid tire producing method is embodied by
introducing the raw materials of the thermo-setting polyurethane
elastomer into a space in a die-casting device, wherein the space
is formed between an inner circumferential surface of an outer die
and an outer circumferential surface of the rubber layer, and the
inner circumferential surface and the outer circumferential surface
are heated in a way that a temperature of the outer circumferential
surface is higher than that of the inner circumferential
surface.
[0018] In addition, the polyurethane elastomer layer as the outer
layer of the tread portion of the renewed solid tire does not
contain, unlike common rubber layers, any amounts of carbon black.
Therefore, unlike conventional solid rubber tires, no black marks
of the renewed solid tire (i.e., the tread rubber) are left on the
road surface the tire contacts. Thus, the renewed solid tire is
freed of the problems that the black marks may damage the aesthetic
appearance of the road surface and that scattering of black rubber
powder resulting from wearing of tires may damage a work
environment. Moreover, the rubber layer as the remaining portion of
the worn solid rubber tire is utilized, substantially as it is, as
the inner layer of the tread portion of the renewed solid tire.
Therefore, an amount of consumption of the raw materials of the
polyurethane elastomer can be significantly reduced as compared
with the case where an entirety of the tread portion is constituted
by a polyurethane elastomer layer only. This advantageously
prevents or restrains the cost of the manufacture of the composite
solid tire, which has the above-mentioned excellent features, from
increasing.
[0019] According to the preferred features of the present
invention, the rubber layer as the remaining portion of the worn
solid rubber tire is utilized, substantially as it is, as the inner
layer of the tread portion of the renewed solid tire. Therefore, an
amount of consumption of the raw materials of the polyurethane
elastomer can be significantly reduced as compared with the case
where an entirety of the tread portion is constituted by a
polyurethane elastomer layer only. This leads to largely saving the
amount of materials used to renew the worn tread portion of the
solid tire. Moreover, according to the present invention, worn
solid rubber tires can be utilized again as renewed solid tires,
the worn solid rubber tires need not be disposed of, so that the
present invention contributes to overcome the social problem with
the disposal of waste tires.
[0020] In the renewed solid tire in accordance with the present
invention, an annular tread portion to be attached to an outer
circumferential portion of a wheel is constituted by the rubber
layer that is a remaining portion of the worn solid rubber tire and
has an appropriate thickness, and the room temperature-setting
polyurethane elastomer layer that is integrally formed on the
rubber layer. Therefore, impacts exerted from road surface to the
tread portion can be effectively absorbed or damped by the rubber
layer as an inner layer of the tread portion, and the outer
polyurethane elastomer layer that provides a contact surface of the
tread portion that contacts the road surface enjoys a proper
excellent wear resistance of the polyurethane elastomer, and
accordingly a significantly improved durability. Thus, the renewed
solid tire can enjoy a significantly increased life expectancy.
[0021] In addition, according to the present method of
manufacturing the composite solid tire, the inner layer formed of
the rubber layer and the outer layer formed of the thermo-setting
polyurethane elastomer layer are effectively integrated with each
other. Moreover, by cutting an outer surface of a remaining rubber
layer of a worn solid rubber tire, in which the remaining rubber
layer has a pre-determined thickness, and applying the
thermo-setting polyurethane elastomer to the rubber layer, the worn
solid rubber tire can be advantageously utilized. It is also
assured that the thermo-setting polyurethane elastomer layer and
the rubber layer can be more effectively formed into an integral
structure.
[0022] In particular, in the above-mentioned preferred features of
the present invention, the raw materials of the thermo-setting
polyurethane elastomer, which are introduced into the die-casting
device, react and cure from a side of the rubber layer, whose
temperature is higher than that of the other side of the rubber
layer. Therefore, the feature, in which the thermo-setting
polyurethane elastomer layer formed on the rubber layer is further
firmly integrated with the rubber layer, is exhibited.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The above and other objects, features, advantages and
technical and industrial significance of the present invention will
be better understood by reading the following detailed description
of presently preferred embodiments of the invention, when
considered in connection with the accompanying drawings, in
which:
[0024] FIG. 1 is a side elevational view of a portion of a solid
rubber tire, for explaining respective states of the tire before
and after it is worn;
[0025] FIG. 2 is a cross-sectional view of a portion of a worn
solid rubber tire, and a portion of a composite solid rubber tire
in which a thermo-setting polyurethane elastomer layer is formed
integrally with the worn solid rubber tire according to the present
invention;
[0026] FIG. 3 is a cross-sectional view for explaining steps of a
first half portion of a composite solid tire producing method in
accordance with the present invention; and
[0027] FIG. 4 is a cross-sectional view for explaining steps of a
second half portion of the composite solid tire producing method
that follows the first half portion shown in FIG. 3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] Hereinafter, there will be described in detail preferred
embodiments of the present invention by reference to the
drawings.
[0029] FIG. 1 is a side elevation view of a portion of a solid
rubber tire 10 that is attached to a vehicle, not shown, and has
not been worn, and a side elevation view of a portion of the same
solid rubber tire 10 whose tread portion 14 has been used and worn.
FIG. 1 shows the worn solid tire, which provides an annular rubber
layer, and which is suitably used for the present invention. More
specifically described, the solid rubber tire 10 is formed, as
known in the art, of a single sort of rubber, or a blend of two or
more sorts of rubbers, that is or are selected from NR, IR, SBR,
BR, EPM, EPDM, IIR, and the like. Generally, the solid rubber tire
10 is formed of a blend of rubbers including NR or IR as a main
component, and is vulcanized. The solid rubber tire 10 is
commercially available as a so-called solid tire. The solid rubber
tire 10 has a generally annular shape, and an outer circumferential
surface of a wheel 18 fixed to an axle shaft of the vehicle is
attached to an inner circumferential portion of the tire 10, by a
well known method, such as bonding, press-fitting, or fitting.
[0030] The solid rubber tire 10 has, on a side surface thereof, a
tread wear indicator (or a tire wear indicator) 12 that indicates a
limit of use of the tire 10. The tread wear indicator 12 has, e.g.,
a triangular shape and is formed by indent or relief. When the
tread portion 14 of the solid rubber tire 10 is worn little by
little because of repeated friction with road surface and
eventually the outer circumferential surface of the tread portion
14 that contacts the road surface reaches the tread wear indicator
12, the solid rubber tire 10, i.e., a worn solid rubber tire 16
should be changed with a new one, because a life expectancy of the
tire 10 has been fulfilled.
[0031] According to the present invention, however, the worn solid
rubber tire 16 whose life expectancy has been fulfilled is used to
advantage. More specifically described, as shown in FIG. 1, the
worn solid rubber tire 16 has, as a remaining portion of the solid
rubber tire 10, a worn rubber layer 20 that remains along the
entire circumference of the wheel 18 and has a pre-determined
thickness corresponding to the tread wear indicator 12. As shown in
FIG. 2, on an outer circumferential surface of the worn rubber
layer 20, a thermo-curing or -setting polyurethane elastomer layer
24 is integrally formed to have a pre-determined thickness and
thereby provide a new tread portion 14. Thus, the worn solid rubber
tire 16 is renovated into a renewed solid tire (composite solid
rubber tire) 26 that can be used again with the vehicle.
[0032] The above-indicated polyurethane elastomer layer 24 is
integrally formed on the outer circumferential surface of the worn
rubber layer 20, by casting, into the die-casting device,
conventionally known raw materials of a thermo-curing or -setting
polyurethane, so that the renewed solid rubber tire 26 may have a
desired thickness. Generally, the raw materials of the
thermo-setting polyurethane contain, as a polyisocyanate component,
a tolylene diisocyanate (TDI), a diphenylmethane diisocyanate
(MDI), and a naphthalene diisocyanate (NDI) or the like, and
additionally contain, as a polyol component, a
poly(oxybutylene)glycol, polyester polyol, polyethylene adipate
glycol or the like. The raw materials additionally contain a
diamine, a diol or the like, as a catalyst that causes the
polyisocyanate component and the polyol component to react with
each other, and cure, while the raw materials are heated. The
catalyst can be selected, as needed, from various commercially
available products, such as the ones available under commercial
name "Adiprene", "Vibrathane", "Multrathane", "Vulkollan",
Hiprene", or the like.
[0033] The polyurethane elastomer, which forms the layer 24, has an
excellent wear resistance property, as clearly shown in the
following TABLE 1. TABLE 1 compares the comparison of the physical
properties of "Vulkollan", which is an example of the commercially
available elastomers suitable for the present invention, with a
commercially available room temperature-setting polyurethane. In
the present invention, a polyurethane elastomer, whose
characteristic value according to Taber Abrasion Test (DIN 53516)
is 90 mm.sup.3 or less, preferably 70 mm.sup.3 or less, more
preferably 50 mm.sup.3 or less, is advantageously used.
1 TABLE 1 Polyurethane elastomer Room Thermo-setting temperature-
Measuring elastomer setting method (VULKOLLAN) elastomer Hardness
DIN 53505 80 80 (Shore hardness A) Tensile strength (MPa) DIN 53504
35 15 Breaking elongation (%) DIN 53504 800 370 Tear strength
(KN/m) DIN 53515 65 24 Impact resilience (%) DIN 53512 55 35 Wear
resistance (mm.sup.3) DIN 53516 40 102
[0034] As the polyurethane elastomer, which has the excellent wear
resistance and is used for the polyurethane elastomer layer 24, NDI
elastomer is advantageously used. More specifically described,
naphthalene-1,5-diisocyanate (NDI) is used as a polyisocyanate
component, and polyester polyol or the like is used as a polyol
component. After the two components are reacted with each other, in
advance, so as to form an NDI/ester prepolymer, a glycol
cross-linking agent, etc. are mixed with the prepolymer, and the
resultant mixture is heated, so as to form a desired solid
NDI-based elastomer. Thus, the desired layer 24 is formed by a
die-casting method in which the polyurethane raw materials are cast
into the die-casting device. The raw materials of the polyurethane
elastomer having an excellent wear resistance are commercially
available; for example, polyurethane raw materials available under
commercial name "VULKOLLAN" from Bayer AG, Germany, are
advantageously used.
[0035] Generally, it is preferred that the materials of the
heat-curing polyurethane elastomer used to form the polyurethane
elastomer layer 24 be reacted, and cured, at a low heating
temperature of, e.g., from 70.degree. C. to 115.degree. C. This
assures that the curing of polyurethane materials does not need to
subject the rubber layer 20 of the worn solid rubber tire 16 to
high temperatures, thereby effectively preventing the properties of
the rubber layer 20 from being changed by heat. Therefore, the
composite solid rubber tire 26 in which the polyurethane elastomer
layer 24 is integrally formed on the rubber layer 20 can
advantageously exhibit, against shocks or impacts exerted thereto,
the cushioning property of the rubber layer 20. In addition, the
durability of the rubber layer 20 and accordingly the life
expectancy of the renewed solid rubber tire 26 as a whole can be
advantageously improved.
[0036] Also, in the renewed solid rubber tire 26 constructed as
described above, an outer circumferential surface of the
polyurethane elastomer layer 24 provides a contact surface that
contacts the road surface. Therefore, the polyurethane elastomer
can exhibit its proper wear resistance, and accordingly the renewed
solid rubber tire 26 can enjoy a significantly improved life
expectancy. In addition, since the rubber layer 20 is present under
the polyurethane elastomer layer 24 having the excellent wear
resistance, the rubber layer 20 can effectively absorb or damp the
impacts transmitted from the road surface to the vehicle, even if a
hardness of the rubber layer 24 may be such a level of Shore
hardness 80 A or over, while an ordinary rubber layer has a Shore
hardness less than 70 A and an ordinary room temperature-setting
elastomer has a Shore hardness less than 80 A. Thus, the rubber
layer 20 largely contributes to improving, e.g., a driving comfort
of the vehicle. In order to advantageously exhibit the effect of
presence of the rubber layer 20, it is preferred that a percentage
of a thickness of the polyurethane elastomer layer 24 relative to a
whole thickness of the renewed solid rubber tire 26 in a radial
direction thereof be not more than 40%, more preferably, not more
than 30%, and that a percentage of a thickness of the rubber layer
20 relative to the whole thickness of the renewed solid rubber tire
26 be not less than 60%.
[0037] Moreover, the polyurethane elastomer layer 24 does not
contain, unlike the rubber layer 20, any amounts of carbon black as
a reinforcing material. Therefore, although the renewed solid
rubber tire 26 is rolled and moved on the road surface, no black
marks of the tire 26 are left on the road surface. Thus, the
polyurethane elastomer layer 24 contributes to keeping the
environment clean. In addition, the elastomer layer 24 has no
possibilities of damaging a work environment where the renewed
solid rubber tires 26 are produced.
[0038] The renewed solid rubber tire 26 constructed as described
above according to the present invention is produced by a composite
solid tire producing method also according to the present
invention. The composite solid tire producing method is based on a
known method, e.g., a die-casting method. In the composite solid
tire producing method, before the desired thermo-setting
polyurethane elastomer layer 24 is formed, the outer
circumferential surface 22 of the rubber layer 20 of the worn solid
rubber tire 16 is worked, i.e., cut or machined using, e.g., a
lathe so as to remove, from the rubber layer 20, a superficial
portion thereof having a pre-determined thickness. Thus, oil
adhered to the outer surface, and/or impregnated into, the inner
mass, of the rubber layer 20, and/or particles biting into the
outer surface of the same 20 are removed to assure that the
polyurethane elastomer layer 24 can be more effectively bonded to
the clean outer surface 22 of the rubber layer 20. On the clean
outer surface 22 of the rubber layer 20, a primer layer is formed
using a known primer to improve a degree of bonding of the outer
surface 22, and additionally an adhesive layer is formed, on the
primer layer, using a known adhesive suitable for polyurethanes.
Since the primer layer and the adhesive layer are formed on the
outer surface 22 of the rubber layer 20, the polyurethane elastomer
layer 24 can be more firmly bonded to the rubber layer 20.
[0039] After the primer and then the adhesive are applied to the
rubber layer 20, the worn solid rubber tire 16 including the worn
rubber layer 20 is set in an appropriate die-casting device 32.
Subsequently, as shown in FIG. 3, raw materials of a thermo-setting
polyurethane are cast in the die-casting device 32.
[0040] More specifically described, as shown in FIG. 3, the
die-casting device 32 includes an outer die 34 having a cylindrical
shape and including a bottom wall, and a core-like inner die 36
that is provided in an inner space of the outer die 34 such that
the inner die 36 is concentric with the outer die 34. The worn
solid rubber tire 16 is set in the die-casting device 32 such that
the inner die 36 fits in an inner bore of the tire 16. It is
desirable that at least the outer die 34 is pre-heated in a
suitable furnace at a pre-determined temperature, for example, at
about 100 to 110.degree. C. In this case, it is desirable that the
rubber layer 20 of the solid rubber tire 16 is also pre-heated at a
temperature higher than that of the pre-heated outer die 34. For
example, it is preferable that the temperature of the pre-heated
solid rubber tire 16 is at least about 5.degree. C. higher than
that of the pre-heated outer die 34. Adaptation of the
above-mentioned relationship between the temperature of the outer
layer die 34 and that of the lubber layer 20 effectively causes the
raw materials of the thermo-setting polyurethane elastomer to react
and cure from the side of the rubber layer 20. As a result, thus
formed polyurethane elastomer layer 24 and the rubber 20 are fixed
to each other, much firmer than layers obtained without the
adaptation of the above-mentioned relationship. Therefore, the
solid tire of the present invention has an advantageously
integrated structure.
[0041] In this state, a known material casting device 40 casts raw
materials 42 of a room temperature-setting polyurethane, into an
annular space (i.e., a molding space) 38 located between the outer
circumferential surface of the rubber layer 20 of the worn solid
rubber tire 16 and the inner circumferential surface of the outer
die 34, till the annular space 38 is filled with the raw materials.
The material casting device 40 may be one that has a well known
construction; such as a mixing head or a gun-type injector. The
material casting device 40 is supplied with the polyisocynate
component: A, and the polyol component: B, mixed with the curing
agent (i.e., the catalyst) and, after the two components are mixed
uniformly using an appropriate dynamic or static mixer, the mixture
is cast in the die-casting device 32. The polyisocynate component:
A and the polyol component: B may be previously reacted to form a
pre-polymer before being supplied to the material casting device
40. In this case, the material casting device 40 is supplied with
the pre-polymer and the curing agent, and after the two components
are mixed, the mixture is cast in the die-casting device 32.
[0042] The polyurethane raw materials 42 cast in the die-casting
device 32 react and cure, while they are heated. Thus, the
polyurethane elastomer layer 24 is integrally formed on the outer
surface of the rubber layer 20. Subsequently, as shown in FIG. 4,
an integral mold product 44 including the rubber layer 20 and the
polyurethane elastomer layer 24 is removed from the die-casting
device 32, and is subjected to a finishing operation. More
specifically described, widthwise opposite ends of an outer
circumferential surface of the polyurethane elastomer layer 24 are
rounded to provide rounded portions 46, and are thereby prevented
from being chipped off in use. Thus, a desired renewed solid tire
48 is produced.
[0043] In the above-described method of producing the composite
solid tire 48, the polyurethane raw materials 42 are just cast in
the die-casting device 32, so as to integrally form the
polyurethane elastomer layer 24 on the outer circumferential
surface of the rubber layer 20. Thus, the composite solid tire 48
can be very easily produced. In addition, not all portions of the
composite solid tire 48 are formed of the polyurethane elastomer,
but just the polyurethane elastomer layer 24 is integrally formed
on the outer surface of the worn rubber layer 20 remaining with the
pre-determined thickness along the entire circumference of the
wheel 18. Thus, the present composite solid tire producing method
is economical since the amount of use of the polyurethane raw
materials 42 is considerably small.
[0044] The composite solid tire 48 produced by the method shown in
FIGS. 3 and 4 is attached to the wheel 18, and is used with the
vehicle, such that the wheel 18 is fixed to the inner bore of the
tire 48 by a conventionally known method such as bonding,
press-fitting, or fitting. Thus, the composite solid tire 48 can
enjoy the above-described special advantages of the polyurethane
elastomer layer 24 formed on the rubber layer 20.
[0045] In summary, the renewed solid tire in accordance with the
present invention can enjoy a significantly improved life
expectancy, and can exhibit a significantly improved shock
absorbing or damping effect against shocks exerted from road
surface to a body of a vehicle. In addition, no black marks of the
tire are left on the road surface, which largely contributes to
keeping an aesthetic appearance of the environment and improving a
work environment. In addition, since, according to the present
invention, worn solid rubber tires can be utilized again as renewed
solid tires, the worn solid rubber tires need not be disposed of,
and the social problem with the disposal of waste tires can be
overcome. While the present invention has been described in its
preferred embodiments, it is to be understood that the present
invention is by no means limited to the details of those
embodiments but may be otherwise embodied.
[0046] While the present invention has been described in its
preferred embodiments, it is to be understood that the present
invention is by no means limited to the details of those
embodiments but may be otherwise embodied.
[0047] For example, the worn solid tires 16 employed according to
the present invention may be waste solid tires obtained by recovery
of so-called solid rubber tires, i.e., common rubber-based solid
tires that are widely used in forklift trucks, industrial tractors,
battery carriers, trailers, or the like. In addition, the worn
solid tires 16 may be solid tires that are formed of a common solid
rubber and are used as, e.g., wheels of a cart or casters of a
baggage. Moreover, the worn solid tires 16 may be pneumatic-type
solid tires or cylindrical-base-type solid tires, and the present
invention is applicable to the respective solid-rubber portions of
those tires.
[0048] In the composite solid tire producing method shown in FIGS.
3 and 4, the worn solid rubber tire 16 is detached from the wheel
18, and subsequently is set in the die-casting device 32, and then
the polyurethane elastomer layer 24 is integrally formed on the
outer circumferential surface of the rubber layer 20 of the tire
16. However, it is possible to set, in the die-casting device 32,
the worn solid rubber tire 16 that is not detached from the wheel
18 but remains attached to the wheel 18, and integrally form the
polyurethane elastomer layer 24 on the outer surface of the rubber
layer 20 of the tire 16.
[0049] The polyurethane raw materials 42 used to form the
polyurethane elastomer layer 24 do not contain any amounts of
carbon black as a reinforcing material, but may contain one or more
known additives such as a coloring agent to add a desired color to
the elastomer layer 24; an antibacterial agent to give an
antibacterial activity to the layer 24; a photocatalyst; or an
ultraviolet-ray absorbing agent.
[0050] In each of the illustrated embodiments, the worn solid tire,
to which the present invention is applicable, is used to produce
the renewed solid tire. However, it is to be understood that the
present invention is by no means limited to the details of those
embodiments but may be otherwise embodied. For example, it is
possible to form a new annular rubber layer for an inner
circumferential portion of the solid tire, and form the
thermo-setting polyurethane elastomer layer having an appropriate
thickness on the outer circumferential surface of the rubber layer,
for thereby obtaining the desired composite solid tire.
[0051] It is desirable that the rubber-layer of the above-mentioned
composite solid tire, in which the thermo-setting polyurethane
elastomer layer is formed on the outer circumferential surface of
the rubber layer, is formed of at least one material, which is
softer than the thermo-setting polyurethane elastomer. Generally,
the rubber layer is formed of a rubber, whose hardness (Shore A
hardness) is 70 A or lower. It is also possible to employ a
composite rubber structure, wherein a core is formed of a
relatively soft rubber, and the core is covered by another rubber
layer, which is harder than the core.
[0052] It is to be understood that the present invention may be
embodied with other changes, modifications, and improvements that
may occur to a person skilled in the art, without departing from
the spirit and scope of the present invention.
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