Semi-pneumatic tire for mine service

A semi-pneumatic tire assembly including a tire casing 22 and a lining 26 is provided. The lining 26 includes a contoured inward surface 30 defining an inflation chamber 18 about an associated wheel rim. The tire assembly is formed by injecting a curable, lining-forming material 96 into a cavity 57 defmed between the tire casing 22 and a molding member 50. The molding member 50 includes a contoured outer surface 54 which molds the inward surface of the lining 26. The molding member 50 may be an inflatable airbag 100 retained in the tire assembly during service. Alternately, the molding member 50 may be a solid core 114 which is removed prior to mounting the tire casing 22 and lining 26 on the associated rim.

TECHNICAL FIELD 
This invention pertains to methods and apparatuses for forming 
semi-pneumatic tires, and more specifically to methods and apparatuses for 
forming semi-pneumatic tires having a lining member that includes a 
contoured inward surface to provide a pneumatic cavity of predetermined 
dimensions between the lining member and an associated wheel rim. 
BACKGROUND ART 
Tires for use in off-road applications, such as mine service tires, are 
subjected to conditions which require the tires to withstand punctures, 
especially in the tread regions. Solid-fill tires have been used in such 
applications. However, disadvantages of solid-fill tires include the facts 
that they generally run hotter than pneumatic tires and do not provide the 
cushioned ride of pneumatic tires. 
Alternatives to solid-fill tires have been proposed in the art. For 
example, U.S. Pat. No. 3,022,810 to Lambe discloses a tire and rim 
combination wherein the cavity between an inner surface of the tire and 
the rim may be partially filled with a resilient foam. Generally, the 
resilient foam is said to adhere to the wheel rim to form an air-tight 
seal. The foam may allegedly be prevented from adhering to the wheel rim 
at certain points to allow the introduction of compressed air through the 
wheel rim. The foam is compressed in the presence of introduced air or 
expanded to fill the cavity in the absence of air. 
U.S. Pat. No. 4,197,893 to O'Coin discloses a reusable shield for use 
within a tire casing. The outer surface of the shield mates with the 
inside surface of the casing and the inner surface of the shield is 
contoured to minimize the thickness at a flex point of the tire in order 
to purportedly reduce heat build-up and fatigue. A base ring fills the 
space between the wheel rim and the shield. Alternately, a pneumatic tube 
can be used in place of the ring. The outer surface of the shield does not 
adhere to the inside surface of the casing in order to allow removal and 
reuse of the shield. The shield is molded by fitting the base ring between 
a casing and a wheel by cutting a slit in the ring. The ring is also 
equipped with pull tabs to assist removal. An opening passage is formed 
through either the ring or the casing. Liquid urethane is then injected 
between the ring and the casing under pressure and allowed to harden. 
There still exists a need in the art for a tire and method of producing 
such for use in off-road applications which provides puncture-resistance, 
especially in the tread region, which provides better performance than 
solid-fill tires. 
DISCLOSURE OF THE INVENTION 
The inventive semi-pneumatic tire 10 includes a tire assembly 12 for 
mounting on an associated rim 14. The tire assembly 12 includes a tire 
casing 22 and a lining 26. Tire casing 22 encloses a predetermined volume 
between an inner surface 38 thereof and the associated rim 14. The lining 
26 occupies a portion of the enclosed volume with the remainder of the 
enclosed volume being an inflation chamber 18. 
The lining 26 comprises a radially inward surface 30 and a radially outward 
surface 32. The radially outward surface 32 conforms to the shape of the 
inner surface 38 of a tire casing 22. The inward surface 30 of the lining 
26 cooperates with associated wheel rim 14 to define boundaries for 
inflation chamber 18. 
The inventive method can be summarized by the following steps: 
positioning a molding member 50 relative to a tire casing 22, the tire 
casing including a pair of spaced beads 120,122; 
mounting the tire casing 22 and the molding member 50 on an associated 
rim-like member 56; 
seating the beads 120,122 on bead-receiving areas of the rim-like member by 
introducing air through a rim valve 106; 
introducing flowable, curable fill material 96 into a cavity 57 between the 
outer surface 54 of the molding member 50 and an inner surface 38 of the 
tire casing through the rim valve 106; 
curing the material so that the material solidifies to fill the cavity and 
forms an inward surface 30; and 
leaving the molding member inside the wheel tire assembly for the 
introduction of variable air pressure to control ride characteristics. 
The molding member 50 is generally ring-shaped having a first contoured 
surface 54. The first contoured surface 54 of the molding member 50 
includes a tread-underlying portion, shoulder-underlying portions, and 
bead-underlying portions. The shape of the molding member 50 determines 
the contour of inward surface 30 of lining 26 and also the shape of the 
inflation chamber 18. The tread-underlying portion 58 of first surface 54 
is substantially parallel to the tread region 42 as indicated by the 
straight line between points 62,64. The shoulder-underlying portions 68 of 
the first surface 54 are convex in cros-section and symmetric about the 
circumferential centerline 76. The mating lining inward surface 30 
therefore is concave in cross-section near the shoulder regions 78 of the 
tire casing 22. Points 82,84 indicate flex points on the first surface 54. 
The bead-underlying portions 90 of the first surface 54 are concave in 
cross-section and also symmetric about the circumferential centerline 76. 
After curing, the tire assembly 12 is ready for in-service operation. In a 
preferred embodiment, the molding member 50 remains in the tire assembly 
12 to produce an enclosed inflation chamber 18.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to the drawings wherein the showings are for purposes of 
illustrating a preferred embodiment of the invention only and not for 
purposes of limiting the same, FIG. 1 shows a semi-pneumatic tire 10 
according to the present invention. The semi-pneumatic tire 10 includes a 
tire assembly 12 mounted on an associated wheel rim 14. The tire assembly 
12 cooperates with the associated rim 14 to form an inflation chamber 18 
for containing inflation fluid, such as air. The tire assembly 12 includes 
a tire casing 22, beads 120,122 and a lining 26. Tire casing 22 encloses a 
predetermined volume between an inner surface 38 and the associated rim 
14. The lining 26 occupies a portion of the enclosed volume with the 
remainder of the enclosed volume being the inflation chamber 18. 
With reference to FIG. 2, the lining 26 comprises an inward surface 30 and 
an outward surface 32. In a preferred embodiment, the lining 26 comprises 
soft urethane or other rubber-like material. The contour of the lining 26 
is an important aspect of the present invention. The radially outward 
surface 32 conforms to the shape of the inner surface 38 of a tire casing 
22. In one embodiment, the outward surface 32 of the lining 26 is adhered 
to the inner surface of tire casing 22. As shown in FIG. 2, the inward 
surface 30 comprises a different contour than outward surface 32. 
Therefore, the thickness of the lining 26 is not consistent throughout but 
includes a first thickness T.sub.1 near the tread region 42 of the tire 
casing 22 and a second thickness T.sub.1 near the bead region 44 of the 
tire casing 22. The thickness of the lining 26 is varied to match the need 
for puncture protection. In a preferred embodiment the first thickness 
T.sub.2 is greater than a second thickness T.sub.2. In one preferred 
embodiment T.sub.1 is a maximum thickness of the lining 26. 
The preferred methods for producing a semi-pneumatic tire 10 according to 
the invention will now be described with reference to FIGS. 1-6. According 
to one preferred method, and with particular reference to FIG. 3, an 
annular molding member 50 is mounted about the rim band 104 of rim-like 
member 56. The molding member 50 includes a first contoured surface 54. As 
is evident from FIG. 3, a first annular cavity 57 is defined between the 
inner surface 38 of the tire casing 22 and first surface 54 of the molding 
member 50 when the bead regions 44 of casing 22 are seated on rim-like 
member 56 by introduction of air through rim valve 106. The first cavity 
57 will be occupied by the lining 26 as shown in FIG. 2 and described 
later in this specification. 
With particular reference to FIG. 6, a vent hole 110 is drilled through the 
tire casing 22 at the centerline of the tire casing 22 at a position 
aligned with the location of the rim valve 106. Preferably, the vent hole 
110 has a diameter of at least 0.25 inches (0.635 cm). The tire casing 22 
is then vertically positioned, tread surface down, so that the exposed end 
126 of the rim valve 106 projects directly downward and a centerline of 
the vent hole 110 is perpendicular and 90.degree. to the floor. A 
flowable, curable fill material 96 is introduced into first cavity 57 to 
form lining 26 through the rim valve 106 until it begins to flow out 
through the vent hole 110. A plug or screw 112 is then inserted into the 
vent hole 110 and pressure of the flowable material 96 is increased to 
approximately 9 pounds per square inch. The filled assembly is then laid 
horizontally while the material cures. Preferably, the curable material 96 
cures in approximately 24 hours at room temperature. It is believed that 
acceptable cures can be had with cures between 12 hours and 36 hours. 
The contour of the first surface 54 of the molding member 50, and the 
inward surface 30 of the lining 26 will now be described in detail with 
reference to FIGS. 2 and 3. The tread-underlying portion 58 of first 
surface 54 is substantially parallel to the tread region 42 as indicated 
by the straight line between points 62,64. The cross-sectional height H of 
the molding member 50 cooperates with inner surface 38 to determine the 
eventual thickness T.sub.1 of the lining 26 near the tread region 42 of 
the tire casing 22. In a preferred embodiment, the molding member 50 has a 
height H which yields a thickness T.sub.1 of at least 2.0 inches (5.1 cm). 
The shoulder-underlying portions 68 of the first surface 54 are convex in 
cross-section and symmetric about a circumferential centerline 76. The 
mating lining inward surface 30 therefore is concave in cross-section near 
the shoulder regions 78 of the tire casing 22. Points 82,84 indicate flex 
points on the first surface 54. The bead-underlying portions 90 of the 
first surface 54 are concave in cross-section and also symmetric about the 
circumferential centerline 76. Flex points 82,84 allows the lining to flex 
with the tire casing 22 during operation. In this way, lining 26 operates 
as an integral part of the tire. As is readily apparent, the inward 
surface 30 of the lining 26 is therefore convex near the bead regions 44 
of the tire casing 22. The cross-sectional width W of the molding member 
50 near the rim-like member 56 cooperates with inner surface 38 to 
determine the eventual thickness T.sub.2 of the lining 26 near the bead 
regions 44 of the tire casing 22. In a preferred embodiment T.sub.2 is 
between 0.5 inches and 0.8 inches. The thickness T.sub.1 is at least 2.5 
T.sub.2. 
As the material 96 cures, first cavity 57 is filled and lining 26 is 
formed. Lining 26 therefore has an inward surface 30 which mates with the 
first surface 54 of the molding member 50. The lining 26 also has an 
outward surface 32 which mates with the inner surface 38 of tire casing 
22. In one embodiment, the lining 26 adheres to the inner surface 38 of 
the tire casing 22. The adherence of the lining 26 with inner surface 38 
may be accomplished by a curing reaction of the material 96 with tire 
casing 22. Alternately, an adhesive may be applied to the inner surface 38 
of the tire casing 22 before introduction of material 96. The lining 26 
and the tire casing 22 together form a tire assembly 12. The adhesive can 
be chosen with sound engineering judgement. 
With reference to FIG. 4, in one embodiment, the molding member 50 
comprises a generally hollow ring-shaped, toroidal airbag 100, having an 
airbag valve 102. Rim-like member 56 is adapted to receive airbag valve 
102. Airbag 100 is inserted into the tire casing 22. The tire casing 22 
and airbag 100 are then mounted about rim-like member 56. The airbag 100 
is designed to have a stretch fit over the rim band 104. The bead regions 
44 of the tire casing 22 are seated on rim-like member 56 by introducing 
air through a rim valve 106 by methods common and known in the art. 
In a preferred embodiment, annular spacers 128 which are positioned 
adjacent rimlike member 56 may be used to separate the first surface 54 of 
the molding member 50 from the bead regions 44. The preferred 
configuration of the spacers 128 includes alternating protrusions, such as 
stand-off buttons 130, as shown in FIG. 4A. The stand-off buttons 130 
provide the spacing effect needed while the gaps 132 between the buttons 
130 allow flexibility of the spacer 128 and reduce the volume occupied by 
a comparable solid spacer. 
Air is introduced into the interior 108 of the airbag 100 through airbag 
valve 102 until the first contoured surface 54 assumes the molding 
configuration as described above with reference to FIG. 3. 
In this preferred method, the molding member 50, in this case airbag 100, 
is retained in the tire assembly 12 during service. Therefore, rim-like 
member 56 is actually the service rim 14 for the tire 10. 
With reference to FIG. 5, in another preferred method, a flexible solid 
core 114 is used as molding member 50 rather than airbag 100. Solid core 
114 preferably comprises a rubber-like polymer outer shell 116 with a foam 
rubber interior 118. The solid core 114 is positioned in tire casing 22. 
Tire casing 22 is then mounted onto rim-like member 56. The solid core 114 
is designed to have a stretch fit over the rim band 104. The method of 
producing a semi-pneumatic tire 10 proceeds as described above, including 
the steps of seating the bead regions 44, drilling the vent hole 110, and 
introducing and curing the curable material 96. 
After lining 26 is formed, the tire assembly 12 is dismounted from rim-like 
member 56 and the solid core 114 is removed. A heavy duty tube with or 
without a flap (not shown) is then inserted into the tire assembly before 
the tire is mounted onto service rim 14. The tube is then inflated to 
provide a pneumatic feel to the ride. 
For the embodiment which utilizes solid core 114 for molding member 50, 
prior to the introduction of material 96, the first surface 54 of the 
molding member 50 is treated with a mold release to facilitate removal 
from the tire assembly 12 after curing. The mold release can be of any 
type known in the art and chosen with sound engineering judgement. After 
curing, the tire assembly 12 is dismounted from the rim-like member 56 and 
molding member 50. For use in operation, as shown in FIG. 1, the tire 
assembly 12 is mounted onto an associated rim 14. The inward surface 30 of 
the lining 26 cooperates with the rim 14 to form inflation chamber 18. It 
is apparent then that the void due to the absence of the molding member 50 
becomes the inflation chamber 18 of the semi-pneumatic tire 10 according 
to the invention. 
In the embodiment which utilizes airbag 100 as molding member 50, the 
airbag 100 defines inflation chamber 18. 
The molding member 50 preferably comprises rubber when airbag 100 is 
employed. When solid core 114 is utilized, molding core 50 preferably 
comprises a composite of rubber-like polymer around a foam rubber 
interior. 
The curable fill material 96 may be any type of solidifiable, liquid 
material which fills the first cavity 57 upon curing. Preferred materials 
include a product available from the Goodyear Tire and Rubber Company and 
sold under the trade name "Wingfil.TM.". 
In a preferred embodiment, the lining 26 comprises approximately sixty 
percent (60%) of the volume enclosed by casing 22. It is believed the 
lining should be between forty percent and eighty percent. 
In a preferred embodiment, the tire 10 is inflated with air at a pressure 
up to 150 pounds per square inch. It is believed that the lining 26 
compresses slightly in response to the introduction of air. 
The semi-pneumatic tire 10 of the present invention may be advantageously 
used as a mine service tire or in other heavy-use off-road applications. 
The preferred embodiments have been described, hereinabove. It will be 
apparent to those skilled in the art that the above methods may 
incorporate changes and modifications without departing from the general 
scope of this invention. It is intended to include all such modifications 
and alterations in so far as they come within the scope of the appended 
claims or the equivalents thereof.