Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to pneumatic tires and in
particular to a composite, high mobility tire ~or off-road
vehicles, and to the method of making the tire.
BACKGROUND OF THE INVENTION
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In my co-pending Canadian application S~rial
No. 244,775 filed February 2, 1976, there is disclosed an
8 X 8 off-road vehicle in the form of a tree harvesting machine.
The requlremen~s for tires for a vehicle of this nature cannot
be fulfilled in an appropriate way if one turns to the products
presently available from tire manufacturers. Tire construction
and design concepts presently available would not be
satisactory from the standpoints of performance, reliability
and stability. Examples of the presently available tires for
off~road vehicle applications are the high-load,rough road
tire of radial construction used for earth movers and the
like as well as the terra tire or high floatation off-road
conventional constructed tire used on agricultural and
recreational type vehicles. These examples of the presently
available art would be unsatisfactory in use due to excessive
ground contact pressure in the case of earth mover type tires
and by insuf~icient resistance to sidewall damage in the case
of terra tires. Both of these types of tires are unsatisfactory
from the standpoint of stability due to a lack of torsional
and lateral rigidity when operated at the low inflation
pressures required for mobility in a machine for tree
harvesting operations.
SUMMARY OF T~E INVENTION
The tire construction according to the present
invention results in a radially reinforced, composite
construction, inner torus in combination with an integrated torus
support in the form of a tread belt bonded to the torus, the
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txead belt being provided with a pair of hollow annular
chambers on the peripheral side edges of the beltr the
chambers being bonded to the periphery of the inner torus.
The inner torus incorporates an integrally formed pair of
rigid metal flanges rather than a conventional bead
construction whereby the tire can be mechanically, detachably
secured to a vehicle wheel.
There are numerous advantages to be derived from
using a tire constructed in accordance with the present
lQ invention on large off-road vehicles such as that described
in the abovementioned corresponding Canadian application. ~-
A higher inflation pressure for relatively low yround pressure
results in greater tire rigidity with enhanced stability over
known tire constructions. The manner in which the belt
structure is fabricated and secured to th~ inner torus ensures
that the tire is extremely flexible for operation over stumps,
rocks, etc. and for absorbing pressure peaks thererom.
Furthermore, the tire has greater lateral stability during
vehicle maneuvering on horizontal ground or on slopes and
greater resistance to sidewall buckling under heavy traction
load conditions.
Adequate floatation under soft ground operating
conditions requires tire deflection rates in the oxder of
25~. This operation condition necessitates the use of radial
reinforcement in the construction of the inner torus and
results in yreater bulging under load and increased
vulnerability of the sidewall of a tire to damage from ground
obstacles such as stumps, rocks, etc.
The flexibility of the belt loops permi~ each such
section to fold up under load in a manner that provides for
protection to the sidewalls of the torus section. As adequate
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protection to the undertread area of a tire can be obtained
by the steel cord belts of conventional tire construction,
this novel approach in the present invention to sidewall
protection ensures that all parts of the tire can now have
the same level of reliability as that experienced by the
undertread portion.
According to one broad aspect, the invention relates
to a high mobility tire for off-road vehicles, the tire
comprising an inner torus having a pair of rigid flanges
integrally formed therewith for mechanically, detachably ~ -
securing the tire to a base wheel. A tread belt is bonded
to the inner torus, the belt including a pair of hollow
annular chambers on the peripheral side edges thereof.
The belt is substantially wider than the torus with the latter
nesting between the hollow annular chambers. A fillet of
tough, flexible rubber material is bonded into the area ~'
hetween the inner curvature of the annular chambers and the
outer curvature of the torus.
In accoraance with a further aspect, the inner torus
consists of two half toruses secured together, each torus
half comprising layers of rubber having one of the rigid
flanges integrally molded therein. An inteqrally positioned,
rubber sheathed steel cable is threaded through apertures in
the flanye and provides exposed loops which extend beyond the
terminal edge of the half torus remote from its associated
flange. The cables are evenly tensioned and spaced apart to
terminate at a position adjacent to the flange to form a
radial reinforcement cord mat. The exposed loops of each half
torus are subsequently laced together and-th,e gap between the
two half toruses is filled with rubber compound to form a
complete inner torus.
The tread belt consists of a plurality of uniform
layers of rubber in which a mat of overlaid or loosely woven
cylindrical steel cables is incorporated. In addition, a
circumferentially wound steel cable is provided on the outside
of the plurality of rubber layers and a further rubber layer
is provided over the circumferential cable. Tread bars on the
belt are positioned transverse to the circumferential cable, the
tread bars havin~ steel cables integrally positioned therein.
In a further aspect, one or more annular hoops can be
positioned on the outer sidewall of the torus in the area
between the annular chamber of the belt and the wheel
construction of the vehicle. These hoops can be pressurized
or filled with foam rubber and if necessary can be reinforced
with wire or steel cord as required by a specific application.
These hoops provide increased resistance to sidewall deflection
as well as increased protection to the base wheel and sidewall
of the inner torus from ground obstacles and debris.
In accordance with a still further aspect, the
in~ention relates to a method of fabricating a tire comprising
the steps of laying a uniform layer of any appropriate rubber
gum stock over the surface of a half torus mold; positioning a
rigid tire flange on supports that loca-te the tire flanye on
the inner diameter of the half torus mold and on the surface of
the first layer of gum stock; threading a rubber sheathed steel
cable through peripheral apertures in the tire flange and
looping the cable over retractable pins located on the outer
diameter of the half torus mold and retaining the ends evenly
tensioned and spaced apart to a position adjacent to the tire
flange thereby to form a radial reinforcement cord mat;
applying a second uniform layer of appropriate g~m stock over
the radial reinforcement cord mat; placing a cover mold on the
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assembly and curing the assembly to produce a hal tire section
having a rigid tire flange therein on its inner diameter and
a frill of uniformly spaced reinforcement cord loops extending
beyond the edge of the cured gum stock on the outer diameter
thereof.
In accordance with a still further aspect, the
invention provides a method of fabricating a tire as described
above and further comprising the steps of joining two cured
half tire sections by lacing reinforcement cords through
alternate loops of those extending from each half section on
their outer diameters thereby tying the half sections together
mechanically with an apprcpriate gap between them and which is
subsequently filled with green rubber and cured to complete a
torus section.
In accordance with an additional aspect, the invention
provides a method of fabricating a tire as described above and
further comprising the steps of applying at least one flexible
hoop of circular cross section on the outer sidewall of the
torus intermediate the tread hollow chambers and the vehicle
wheel.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is illustrated by way of example in the
accompanying drawings in which: -
Figure 1 is a sectional view through the tire and
related wheel construction;
Figure 2 is a sectional view through the tire-base
wheel interface;
Figure 3 is an elevation view of a segment of the
tire flange shown in cross section in Figure 2;
Figure 4 shows the radial cord pattern as laid down
in each half torus;
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Figure 5 is a sectional view taken along the lines
5-5 in Figure l; ..
Figure 5a is a plan view of a mat of reinforcing cable;
Figure 6 is a further sectional view through the
tread of the tire of Figure l and viewed at 90 to the
sectional view of Figure 5 or as seen in the direction of
arrow 6-6 in Figura 5;
Figure 7 is a sectional view through the half torus
mold;
Figure 8 is an elevation view of a segment of the
outer surface of the half torus mold;
Figure 9 is a perspective view of segments of the
half toruses;
Figure lO is a perspective view of the manner of
forming the elements making up the tread portion of the tire;
Figure 11 is a cross-sectional view of the tread .
portion of the tire showing the method of applying the tread
bars thereto;
Figure 12 is an end view of the tread bar being
applied to the tread in Figure 11 and illustrating the positions
of the reinforcing cables therein;
Figure 13 is a perspective view of the tread portion
of the tire in its completed form;
Figure 14 is a cross-sectional view showing the
placement of the formed inner torus into engagement with the
tread belt; and
Figure 15 is a cross sectional view of a tire similar
to that shown in Figure 1 but including a plurality of buffer
hoops and sealing skirt on the sidewall of the torus.
3~ Referring to Figure 1, the tire 10 comprises a torus
12 mechanically connected to a vehicle base wheel 14 by means
of a pair of rigid flanges 16 integrally formed with the torus
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as will be explained relative to Figure 2. The left hand
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portion of Figure 1 shows the torus 12 in its inflated but
unloaded condition while the right hand side of Figure 1
shows the torus deflected under load. A tread belt
illustrated generally at 18 is bonded to the torus 12, the
belt 18 including a pair of hollow annular chambers 20 on the
peripheral side edges of the tire 10, the belt 18 together with
the chambers 20 being substantially wider than the torus 12
with the latter nesting between the chambers 20. A fillet 22
of tough, flexible material, preferably rubber, is bonded into
the area between the inner curvature of the annular chambers
20 and the outer curvature of the sidewall o the torus 12 to
prevent dirt and debris from entering this area. As shown
in Figure 1, the tread belt 18 includes tread or traction bars
24 which extend across the width o the belt and up into the
shoulder portion thereof adjacent the chambers 20. The base
wheel 14 includes an annular cavity 11 opening into the interior
of the torus 12 and which can be used for inflation of the torus
by means of an appropriate valve arrangement- 13 which could for
example be connected to one of the walls of the cavity 11 at
one end and to the outer surface of the base wheel at the
other end.
Referring now to Figure 2 as well as to ~igure 1, the
rigid flanges 16 (only one of which is illustrated) are secured
by bolts 26 of appropriate configuration and strength to the
flange 28 of the base wheel 14, flange 28 being a part of the
angulated base collar 30 as seen in Figure 1, the surface of
which provides support to the upper sidewall of the torus when
the latter is in its deflected position as shown on the right
hand side of Figure 1. Additionally, the collar 30 provides
means for mechanically connecting the torus to the base wheel
as illustratedO The tapered working surface of collar 30 and
opposite annular chamber 20 act as opposing wedge-like members
to deform torus 12 under wheel side-loading conditions thus
providing increased la~eral stif~ness characteristics for the
tire/wheel assembly.
As seen în Figures 2 and 3, the flanye 16 has an
L-shaped leg 36 conforming to the configuration of the base
collar 30 and base wheel 14. An anchoring lip 32 of the
flange is embedded in the upper terminal edge 34 of the torus.
The L-shaped leg 36 is provided with threaded apertures 38 in
individual boss portions 39 for receiving sealing plugs
37 and mounting bolts 26 while the lip 32 is provided with a
plurality of equally spaced apertures 40 for anchoring the
loops in the individual radial cords. The torus air chamber
is sealed on assembly of base collar 30 and torus flange 16 to
base wheel 14 by O-ring seal 27.
As shown in Figure 1, the torus 12 comprises two half
toruses 12a and 12b which are assembled prior to bonding to the
tread belt. Each torus half, such as the segment of half 12a
as shown in Figure 4, comprises a layer of rubber 44 to which
one o~ the flanges 16 will be integrally molded therein. As
seen in Figures 3 and 4, rubber sheathed steel cable such as a
strand 46 thereof is threaded through the aperture 40 and the
lip 32 of the flange 16 and, in the return run, a loop 48 is
left exposed to extend beyond the terminal edge 50 of the
section of the half tor~s 12a with the inner terminal end of
the cable being retained in a position such as 52 adjacent to
the tire flange or at any point appropriate to the strength and
continuity of the torus. As shown in Figure 4, the cables 46
are maintained in uniform, spaced relationship to form a radial
reinforc~ment cord mat 42, the neutral axis of which is the
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same as in ~he inflated tire.
Moving ahead to Figure 9, the exposed loops 48 on :~
half torus 12a lie between the loops 49 from half torus 12b
and one or more lacing cables 54 are threaded between the loops
48 and 49 thereby tying ths two half toruses together
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mechanically with an appropriate gap 56 between the half
toruses to permit subsequent sealing and bonding operations.
As shown in Figure 1, the tread belt 18 has its
terminal side edges folded inwardly to fonm the chambers 20
with the terminal ends 58 of the belt as well as the
immediately adjacent poxtions, being bonded to the juxtaposed
portions of the outer wall of the torus 12~ the tread bar 24
extending somewhat into the shoulder at 60 as illustrated.
P~eferring now to the cross-sectlonal views of
Figures 5 and 6, the tread area of the tire 10 comprises a)
the layers of rubber constituting the torus 12 with b) the
radial cords 46 therein together with c) two layers of loosely
woven or overlaid belt cords 62 tFigure 5a) and d) a circum- !
ferenti~ally and helically wound steel cable 64 positioned
adjacent the outer surface of the tire, with e) a further
rubber layer of rubber of appropriate toughness over the top
O~ that outer cable. The tread bars 24 are positioned
transverse to the circumferential cable 64, the bars 24 having
steel reinforcing cables 66 therein.
It will be appreciated from Figure 5 that the
arrangements of a plurality of layers of steel cables and
patterns thereof spaced throughout the thickness of the tread
area of the ti.re 10 provides a high degree of strength, foot-print
flexibility and penetration resistance needed for the vehicle
mentioned above.
Looking now at the method of making the tire, Figure
7 illustrates a half torus mold 70 of suitable configuration
which serves as a base for mounting thereon a uniform layer
44 of any appropriate ru~ber gum stock as previously described
with respect to Figure 4. This layer 44 of gum stock constitutes
the inner surface of the half torus 12a or 12b shown in Figures
1 and 4. One of the rigid tire flanges 16 is detachably
secured such as by locking pins or bolts 72 on a support
flange 74, pins 72 locating the flange 15 on the inner
diameter of the half torus mold 70 ~ith the lip 32 of the
flange being located on the surface of the first layer of
gum stock 44. The mold 70 is also provided with spring loaded
pins 76 on the outer surface of the half torus mold 70, the
pins prvjecting outwardly as shown in Figure 7 so as to provide
anchor means for the looping of the steel cables 46, the outer
portion of the pin cooperating with cable guide channels 78
(Figure 8) to provide a pathway for looping the cable 46 around
the body of the pins. As shown in greater detail in the
pattern of Figure 4, the rubber sheathed steel cable 46 is
threaded through the peripheral apertures 40 in the tire flange
16 and is looped over the ends of the retractable pins 76,
the ends of the cables being evenly tensioned and spaced apart
to positions such as 52 and 80 in Figure 4 adjacent to the tire
flange 16 to form the radial reinforcement cord mat.
As seen in Figure 7, the second layer of appropriate
gum rubber stock 82 is then placed over the radial reinforcement
cord mat 42, a cover mold (not shown) is then placed on the
assembly and the torus assembly is cured to produce a half
tire section such as the half torus 12a of Figure 1 which has
the rigid flange 16 integrated therein on its inner diameter.
As previously described and as shown in Figure 9, the half
tire section has a frill of uniformly spaced reinforcement cord
loops 48 which extend beyond the cured gum stock on its outer
diameter 50. Two cured half tire sections 12a and 12b are
assembled and placPd so that the loops 48 from half torus 12a
3~ mesh with the loops 49 from half torus 12b and these loops are
laced together by reinforcement cords 54 to tie the half sections
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together leaving a gap 56 be~ween them ~o permit subsequent
filling and sealing operations. This completas the formation
of the torus 12 shown in Figure 1.
The tread belt 18 is then formed as a sleeve as
shown in Figure 10 by positioning a first uniform layer of
gum stock 84 on a cylindrical dxum 85 of appropriate
diametex and length and then applying the steel mat 62 of
eith~r loo~ely woven or layered construction on the first
layer of gum stock. Subsequently, a second uniform layer of
gum stock 86 is placed on the cylindrical drum over the steel
mat 62 and to completely cover the same to form a thin
flexible steel based sleeve. Over the central portion o the
sleeve that will s~ubsequently become the undertread section
o~ belt 18 (Figure 6~ a rubber sheathed steel cable 64 is wound
circumferentially and helical~y around the sleeve in uniformly
spaced rows across the surface of the undertread area as shown in
Figure 10, the cable layer being suitably anchored to the sleeve
at each end and a final layer of rubber 87 is applied thereover.
Turning to Figure ll, the tread bars 24 are then
made up in a steel mold 88 by means of a preformed first layer
of yum stock 90 over which a series of spaced steel cables 66
(Figure 5) are laid and which extend partially up the sides
of the mold segment 88 in a pattern shown in Figure 12. A
further layer 92 of preformed gum stock is laid over the
cables 66, the mold segments 88 are then locked up to bond
the tread bar 24 to the tread belt 18, the terminal ends 94
of the belt being folded inwardly and bonded to the posi~ion
shown in Figure 11 to complete the belt structure as illustrated
in Figure 13. The formed central torus 12 made up of the
half toruses 12a and 12b laced together, is then placed into
central position on the tread belt as shown in Figure 14 between
the free terminal portlons of the sleeve which are then bonded
to the outer surface of the torus. The preformed fillet 22
(Figure 1) of tough flexible rubber material is subsequently
bonded into the area between the curvature of the now formed
peripheral chambers 20 and the outer surface of the torus to
seal the portion therebetween.
As shown in Figure 15, the reliability characteristics
of the tire may be further increased by adding pro~ection to the
exposed sidewall of the torus 12 through the addition of one
or more circumferential tubular hoops 96. Preferably, a first
hoop 96 would be resiliently secured by means o a flexible
skirt 98 having its upper terminal edge attached to the vehicle
wheel between the outer terminal end 100 of the collar 30 and
a lip 102 of the collar cover-plate. Skirt 98 encircles the
hoop 96 and would be bonded at its inner end to the adjacent
surface of the ~orus 12. A series of additional hoops could
be provided on the exposed sidewall of the torus 12 between the
collar 30 and the belt chamber 20 as shown in Figure 15 and
these additional hoops such as 104 could be bonded to the
adjacent surfaces by means of fillets 106 and 108. If necessary,
chamber 20 could incorporate one or more hoops such as 110.
As described above, the tire of the present invention
comprises three subassemhlies bonded together to form a
composite construction tire having unusual and novel undertread
and sidewall characteristics. The tire so formed is intended
to be mounted on a base wheel support assembly for large
off-road vehicles. It would be in excess of 4 feet in width
and is intended to operate at a torus inflation pressure of
approximately 16 lbs. per square inch but with half that ground-
contact pressuxe as a consequence of its ability to spread
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wheel loads from the torus through its flexible belt to ground.
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This is achieved by the circumferential flexibility of the
torus-belt construction combined with appropriate lateral
stiffness in the belt as a result of the beam effect created
by its tread bars.
The present invention has been described in connection
with a specific embodiment of the tire and in xelation to a
specific use. However, those skilled in the art will appreciate
that a vaxiety of designs are possible for the tire mounting
structure keeping in mind the essential requirement which is a
means of mechanically locking the tire beads between the wheel
proper and the tire supporting structure. For example, while
the location of the beads ox tire flanges are shown near the
center of the assembly, they may be located anywhere out to the
point of support of the undeflected tire. Furthermore, they ~ :
may be oriented as shown or moved into the plane of the torusO
The terms and expressions which have been employed
in this disclosure are used as terms of description and not of
limitation and there is no intention in the use of such terms
and expressions to exclude any equivalents of the features
shown and described or portions thereof but it is recogniæed
that various modifications are possible within the scope of
the invention claimed.
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